Shot APPLICATIONS IMPROVEMENT COMPANY A Subsidiary of Curtiss-Wright Corporation

NINTH EDITION

TABLE OF CONTENTS

INTRODUCTION ...... 3 CHAPTER 7: CONTACT FAILURE CHAPTER 1: Fretting Failure...... 25 THEORY Application Case Study: Turbomachinery Blades and Buckets...... 25 The Process...... 4 Pitting ...... 25 Shot Peening Residual ...... 5 Galling ...... 26 Summation of Applied and ...... 6 Application Case Study: NASA Langley Crack Growth Study ...... 6 CHAPTER 8: Depth of Residual Stress...... 7 CORROSION FAILURE Shot Peening Media...... 7 Corrosion Failure...... 27 Effect of Shot ...... 7 Stress Corrosion Cracking...... 27 Application Case Study: Fabrication of Chemical Handling Equipment .... 28 CHAPTER 2: Corrosion ...... 28 RESPONSE OF Application Case Study: Sulfide Stress Cracking...... 28 High Strength Steels ...... 8 Application Case Study: Medical Implants...... 29 Carburized Steels...... 9 Intergranular Corrosion...... 29 Application Case Study: High Performance Crankshafts ...... 9 Decarburization...... 9 Application Case Study: Reduction of Retained Austenite...... 10 CHAPTER 9: Austempered Ductile Iron...... 10 THERMAL FATIGUE & HEAT EFFECTS Cast Iron...... 10 Effects of Heat ...... 30 Aluminum Alloys ...... 11 Thermal Fatigue...... 31 Application Case Study: High Strength Aluminum ...... 11 Application Case Study: Feedwater Heaters ...... 31 Titanium ...... 12 Magnesium...... 12 CHAPTER 10: Powder ...... 12 OTHER APPLICATIONS Application Case Study: High Density Powder Metal Gears...... 13 Peen ...... 32 Contour Correction...... 33 CHAPTER 3: ...... 33 MANUFACTURING PROCESSES Peentexsm ...... 34 Effect on Fatigue Life...... 14 Engineered Surfaces...... 34 ...... 14 Application Case Study: Pneumatic Conveyor Tubing...... 35 Application Case Study: Fatigue of Offshore Steel Structures ...... 15 Application Case Study: Food Industry ...... 35 Application Case Study: Turbine Engine HP Compressor Rotors ...... 15 Exfoliation Corrosion...... 36 Grinding ...... 16 Plating...... 16 Porosity Sealing...... 36 Anodizing ...... 17 Internal Surfaces and Bores...... 36 Application Case Study: Anodized Aluminum Rings...... 17 Dual (Intensity) Peening ...... 37 Plasma Spray...... 17 The C.A.S.E.sm Process...... 38 Electro-Discharge Machining (EDM) ...... 17 On-Site Shot Peening...... 38 Electro-Chemical Machining (ECM)...... 18 Strain Peening ...... 39 Application Case Study: Diaphragm Couplings ...... 18 CHAPTER 11: CHAPTER 4: CONTROLLING THE PROCESS BENDING FATIGUE Controlling the Process...... 40 Bending Fatigue ...... 19 Media Control ...... 40 Gears...... 19 Intensity Control...... 41 Connecting Rods...... 20 Coverage Control ...... 42 Crankshafts ...... 21 Application Case Study: Diesel Engine Crankshafts ...... 21 Automated Shot Peening Equipment ...... 43 Application Case Study: Turbine Engine Disks ...... 21 Application Case Study: CMSP Increases Turbine Engine Service Life ...... 44 Specifying Shot Peening ...... 45 CHAPTER 5: TORSIONAL FATIGUE CHAPTER 12: Torsional Fatigue...... 22 ADDITIONAL CAPABILITIES & SERVICES sm Compression Springs...... 22 Peenstress – Residual Stress Modeling ...... 46 Drive Shafts ...... 23 ...... 46 Torsion Bars...... 23 Coating Services ...... 47 Application Case Study: Automotive Torsion Bars ...... 23 ...... 48 Valve Reeds – Manufacturing...... 48 CHAPTER 6: AXIAL FATIGUE APPENDIX: Axial Fatigue ...... 24 Conversion Tables...... 50-51 Application Case Study: Train Emergency Brake Pin...... 24 MIC Technical Article Reprints...... 52-57 Application Case Study: Auxiliary Power Unit (APU) Exhaust Ducts...... 24 MIC Facilities Listing ...... 58-59 1 NOTES

2 INTRODUCTION

etal Improvement Company (MIC) is a world leader in providing specialized metal treatment MM services that enhance the performance and extend the life of components operating in a wide range of applications. Our services are an integral part of the manufacturing process for producing engineered products for the aerospace, automotive, chemical, medical, power generation and general industrial markets.

Through a network of over 50 facilities in North America and Europe, MIC provides the following metal treatment services: Shot Peening

Shot Peening – MIC has specialized in providing shot peening services to industry since 1945. Shot peening protects components against failure mechanisms such as fatigue, fretting fatigue and stress corrosion cracking. We continue to develop new processing techniques and equipment that help prevent premature part failures and enable designs to achieve their maximum potential.

Laser Peening – MIC is the world’s leading provider of laser peening services. With surgical precision, a unique high energy laser is fired at the surface of a metal part, generating pressure Laser Peening pulses of one million pounds per square inch. Similar to shot peening, the layer of beneficial compressive stress increases the component’s resistance to failure mechanisms, which translates to increased component life and reduced maintenance costs.

Peen Forming – Peen forming is a highly effective process for creating aerodynamic contours in aircraft wing skins and for straightening precision metal parts that have become warped due to prior machining, grinding or heat treating. The imparted residual compressive stresses from the shot peen forming process that shape the wing skins also increase their resistance to flexural bending fatigue and stress corrosion cracking. Peen Forming

Heat Treating – MIC specializes in the thermal processing of metal components used in a wide range of industries. Thermal processing relieves stresses within fabricated metal parts and improves their overall strength, ductility and hardness. By involving MIC at the planning stage of your project, we can recommend the configuration, alloy and thermal process to meet your design requirements.

Coating Services – Our E/M Coating Services Division has over 40 years of experience in applying critical tolerance coatings and is a pioneer in the development and application of solid film lubricant Heat Treating coatings. Selection of the proper coating can facilitate the use of less expensive metals, improve component wear life and reduce maintenance costs.

Each MIC facility maintains quality approvals appropriate to its customer base, such as FAA, CAA, Nadcap, QS 9000, ISO 9001, AS 9100 and TS16949 certifications.

Metal Improvement Company is a wholly-owned subsidiary of the Curtiss-Wright Corporation (NYSE:CW). Curtiss-Wright Corporation is a diversified global company that designs, manufactures Coating Services and overhauls products for motion control and flow control applications in addition to providing metal treatment services. For more information about Curtiss-Wright visit www.curtisswright.com.

Copyright © 2005 By Metal Improvement Company 3 CHAPTER ONE Y R O THE SHOT PEENING PROCESS E Shot peening is a process in which the surface of a part is bombarded with small spherical Impact at high speed H media called shot. Each piece of shot striking the creates a dimple metal acts as a tiny peening hammer imparting a T small indentation or dimple on the surface. In order for the dimple to be created, the surface layer of the metal must in tension (Figure 1-1). Below the surface, the compressed grains try to restore the Impact at high speed Dimple creates a dimple surface to its original shape producing a hemisphere of cold-worked metal highly stressed in compression (Figure 1-2). Overlapping dimples develop a uniform layer of residual compressive stress. Dimple Figure 1-1 Mechanical Yielding at Point of Impact It is well known that cracks will not initiate nor Stretched Surface propagate in a compressively stressed zone. Because nearly all fatigue and stress corrosion failures originate at or near the surface of a part, COMPRESSION compressive stresses induced by shot peening Stretched Surface provide significant increases in part life. The magnitude of residual compressive stress produced COMPRESSION by shot peening is at least as great as half the tensile strength of the material being peened. Figure 1-2 Compression Resists Fatigue Cracking In most modes of long term failure the common denominator is tensile stress. These stresses can result from externally applied loads or be residual stresses from manufacturing processes such as welding, grinding or machining. Tensile stresses attempt to stretch or pull the surface apart and may eventually lead to crack initiation (Figure 1-3). Compressive stress squeezes the surface grain boundaries together and will significantly delay the initiation of fatigue cracking. Because crack growth is slowed significantly in a compressive layer, Figure 1-3 Crack Initiation and Growth Through Tensile Stress increasing the depth of this layer increases crack resistance. Shot peening is the most economical and practical method of ensuring surface residual compressive stresses.

4 www.metalimprovement.com CHAPTER ONE T

Shot peening is primarily used to combat metal fatigue. The following points pertain to metal fatigue and H its application to the Typical Stress versus Load Cycles graph shown in Figure 1-4.

• Fatigue loading E consists of tens of

thousands to millions O of repetitive load cycles. The loads create applied tensile R stress that attempt to

stretch/pull the Y surface of the material apart. • A linear reduction in tensile stress results in an exponential increase in fatigue life (Number of Load Cycles). The graph (Figure 1-4) shows that a 38 ksi (262 Figure 1-4 Typical Stress vs Load Cycles MPa) reduction in stress (32%) results in a 150,000 cycle life increase (300%).

SHOT PEENING RESIDUAL STRESS The residual stress generated by shot peening is of a compressive nature. This compressive stress offsets or lowers applied tensile stress. Quite simply, less (tensile) stress equates to longer part life. A typical shot peening stress profile is depicted in Figure 1-5.

Maximum Compressive Stress – This is the maximum value of compressive stress induced. It is normally just below the surface. As the magnitude of the maximum compressive stress increases so Figure 1-5 Typical Shot Peening Residual Stress Profile does the resistance to fatigue cracking.

Depth of Compressive Layer – This is the depth of the compressive layer resisting crack growth. The layer depth can be increased by increasing the peening impact energy. A deeper layer is generally desired for crack growth resistance.

Surface Stress – This magnitude is usually less than the Maximum Compressive Stress.

5 www.metalimprovement.com CHAPTER ONE 6 THEOR Y SUMMATION OF APPLIED AND RESIDUALSTRESS initial crack of0.050"(1.27mm)wasgenerated. pointfortheabove This wasthestarting results. [Ref 1.1] in fatigueuntil thecrack grew to~ 0.050"(1.27mm).Ifsamples were shotpeened,theywere peenedafterthe Note onsamplepreparation: process. AnotchwasplacedinthesurfaceviaEDM The sampleswere loaded not have initialflawsandshouldrespond withbetterfatiguelifeimprovements atthesestress levels. This testreflects conditionsthatare harsherthan real worldconditions.Real worldconditionswouldgenerally netstressksi (138MPa) conditiontheremaining lifeincreased by 81%. results demonstrate, netstress ata15ksi(104MPa) conditiontheremaining life increased by 237%.Ata20 It wasfoundthatcrack growth wassignificantlydelayed whenshotpeening was included.Asthefollowing should benotedthattheUnitedStates Air Force damagetolerance rogue flawis0.050"(1.27mm). peening. The sampleswere testedwithaninitialcrack of0.050"(1.27mm)andthencycle testedtofailure. It performedastudyoncrack growthEngineers atNASA rates shot of2024-T3aluminumwith andwithout Appli NASA LANGLEY CRACK GROWTH LANGLEY STUDY NASA strain andconsequentlycanstore more residual stress. strength materialshave amore rigidcrystalstructure. This crystallatticecanwithstandgreater degrees of tensile strength. The higherthetensilestrength, themore compressive stress thatcanbeinduced.Higher Shot peeningisidealforhighstrength materials.Compressive stress isdirectly correlated toamaterial’s geometric changes. magnitude, localized compressive stress tooffsetthestress concentration factorcreated from these following twoconditions: Shot peeningishighlyadvantageous forthe significant reduction oftensilestress atthesurface. solid lineisthesummationoftwoshowing a (residual) compressive stress from shotpeening. The from thebendingload. dashed lineisthe The curved The diagonaldashedlineisthetensilestress created stress atthesurface. bar withathree-point loadthatcreates abending shot peeningresidual stress. experiences thenetstress from theappliedloadand an appliedload,thesurfaceofcomponent When acomponentisshotpeenedandsubjectedto S tr N ess risersmayconsistofr Stress Of Tests Life Cycles Life OfTests Stress ON-SHO 5ki275,017 2 15 ksi e ubrAverage Number Net 20 • • • ENDTS RESULTS PEENEDTEST T ca Stress risers 3 ti 26,029 on Case Study on Case • • • adii, notches,cr F F i i g g materials High strength u u r r www.metalimprovement.com e e

1 1 - - 6 6 depicts a oss holes,gr tesO et ieCce Increase Cycles Life OfTests Stress 5ki22312237% 253,142 2 15 ksi e ubrAeaePercent Average Number Net 20 SHO F F oo i i g g v u u T es, keyways,etc.Shotpeeninginducesahigh r r ENDTS RESULTS PEENED TEST e e

3 1 1 - - 6 6 Beam withanE Resultant Stress inaShotPeened 47,177 81% xternal Load Applied

CHAPTER ONE T

DEPTH OF RESIDUAL STRESS H The depth of the compressive layer is influenced by

variations in peening parameters and material hardness [Ref E 1.2]. Figure 1-7 shows the relationship between the depth O of the compressive layer and the shot peening intensity for five materials: steel 30 HRC, steel 50 HRC, steel 60 HRC, R 2024 aluminum and titanium 6Al-4V. Depths for materials

with other hardness values can be interpolated. Y

SHOT PEENING MEDIA Media used for shot peening (also see Chapter 11) consists of small spheres of cast steel, conditioned cut wire (both carbon and ), ceramic or glass materials. Most often cast or wrought carbon steel is employed. Stainless steel media is used in applications where iron contamination on the part surface is of concern. Figure 1-7 Depth of Compression Carbon steel cut wire, conditioned into near round shapes, vs. Almen Arc Height is being specified more frequently due to its uniform, wrought consistency and great durability. It is available in various grades of hardness and in much tighter size ranges than cast steel shot.

Glass beads are also used where iron contamination is of concern. They are generally smaller and lighter than other media and can be used to peen into sharp radii of threads and delicate parts where very low intensities are required.

EFFECT OF SHOT HARDNESS It has been found that the hardness of the shot will influence the magnitude of compressive stress (Figure 1-8). The peening media should be at least as hard or harder than the parts being peened unless surface finish is a critical factor. For a large number of both ferrous and nonferrous parts, this criterion is met with regular hardness steel shot (45-52 HRC).

The increased use of high strength, high hardness steels Figure 1-8 Peening 1045 Steel (Rc 50+) [Ref 1.3] (50 HRC and above) is reflected in the use of special hardness shot (55-62 HRC).

REFERENCES: 1.1 Dubberly, Everett, Matthews, Prabhakaran, Newman; The Effects of Shot and Laser Peening on Crack Growth and Fatigue Life in 2024 Aluminum Alloy and 4340 Steel, US Air Force Structural Integrity Conference, 2000 1.2 Fuchs; Shot Peening Stress Profiles 1.3 Lauchner, WESTEC Presentation March 1974, Northrup Corporation; Hawthorne, California

7 www.metalimprovement.com CHAPTER TWO S L A

T HIGH STRENGTH STEELS The residual compressive stress induced by shot peening is a percentage of the ultimate tensile strength E and this percentage increases as the strength/hardness increases. Higher strength/hardness metals tend to be brittle and sensitive to surface notches. These conditions can be overcome by shot peening M permitting the use of

high strength metals in fatigue prone F applications. Aircraft

O landing gear are often designed to strength

levels of 300 ksi (2068

E MPa) that incorporate

S shot peening. Figure 2- 1 shows the relationship between shot peening N and use of higher

O strength materials.

Without shot peening, P optimal fatigue Figure 2-1 Fatigue Strength vs. Ultimate Tensile Strength S properties for machined

E steel components are obtained at approximately 30 HRC. At higher strength/hardness levels, materials lose fatigue strength due to increased notch sensitivity and brittleness. With the addition of compressive

R stresses, fatigue strength increases proportionately to increasing strength/hardness. At 52 HRC, the fatigue strength of the shot peened specimen is 144 ksi (993 MPa), more than twice the fatigue strength of the unpeened, smooth specimen [Ref 2.1].

Typical applications that take advantage of high strength/hardness and excellent fatigue properties with shot peening are impact wrenches and percussion tools. In addition, the fatigue strength of peened parts is not impaired by shallow scratches that could otherwise be detrimental to unpeened high strength steel [Ref 2.2].

8 www.metalimprovement.com RESPONSE OF METALS 9 CHAPTER TWO CHAPTER ocessing. y during thermal pr ous allo elated to depth. A depth of 0.003 inch Comparison of Shot Peened Comparison of Shot Peened Nitrided and GasPins Crank Carburized 2 2 - - 2 2

e e ticularly r r r u u g g i i www.metalimprovement.com educe the fatigue strength of high strength steels (240 ksi, of high strength educe the fatigue strength F F e e r r u u g g i i F F ( ( able eduction in surface carbon content of a ferr or ed that gas ef 2.3]. v o wn that decarburization can r ated fav Carburizing anomalies resulting from surface intergranular oxidation are reduced. are oxidation surface intergranular from resulting Carburizing anomalies High magnitudes of compressive stress of ~ 200 ksi (1379 MPa) or greater offer (1379 MPa) of ~ 200 ksi or greater stress of compressive High magnitudes benefits fatigue excellent . Results from nitriding from . Results ) ) • • • • •• •• 2 2 - - esting pr 2 2 results over the alternative over results the crankpin to increase diameter [R Crankshafts for 4-cylinder Crankshafts high performance engines failing prematurely were after a few hours running on test at peak engine loads. T and shot peening also demonstr carburizing and shot peening the best gave the crankpins fatigue performance HIGH PERFORMANCE CRANKSHAFTS Application Case Study Application efs 2.4, 2.5 and 2.6]. Shot hardness of 55-62 HRC of 55-62 Shot hardness and carbonitrided parts for fully carburized is recommended if maximum fatigue properties desired. are decarburization can be as detrimental to fatigue strength as a depth of 0.030 inch [Refs 2.4, 2.5 and 2.6]. as a depth of 0.030 inch [Refs decarburization can be as detrimental to fatigue strength Decarburization is the r Decarburization is a surface phenomenon not par It has been sho 45-55% steels (140-150 ksi, 965-1030 MPa)by strength 70-80% and lower by 1650 MPa or above) [R Carburizing and carbonitriding are heat treatment processes that result in very hard surfaces. They are surfaces. hard in very result that processes heat treatment are and carbonitriding Carburizing as follows: are steels 55-62 HRC.commonly carburized benefits of shot peening The DECARBURIZATION CARBURIZED STEELS CARBURIZED CHAPTER TWO 10 RESPONSE OF METALS CAST IRON A Application Study Case USTEMPERED DUCTILEIRON REDUCTION OF RETAINED AUSTENITE - 5120 CARBURIZED STEEL, -5120CARBURIZED AUSTENITE OF RETAINED REDUCTION By coldworkingthesurface,shotpeeningreduces thepercentage ofretained austenite. Decarburization isoftenaccompaniedwiththeundesirable metallurgical conditionofretained austenite. be suspected. exhibitsunusually heavydimplingafterpeening,decarburizationshould surface hardness (58+HRC) ifdecarburizationissuspected.Ifagearthatintended tohaveinsure a high theintegrityofparts tion [Ref peeningcan 2.7].Becausethedecarburized layer isnoteasilydetectableonquantitiesofparts, Shot peeninghasproven tobeeffective inrestoring mostofthefatiguestrength lostduetodecarburiza- depending onthe severity oftheimperfections atthecastingsurface. unmachined pearliticnodular irons. The unnotchedfatiguelimitmaybereduced by asmuch40%, surfaces intheformofpinholes, dross orflakegraphite canconsiderably of reduce thefatigueproperties applications where thecast surfaceissubjecttoloadstresses. The presence ofimperfectionsatcasting withstanding relatively highfatigueloading.Castiron componentsare oftenusedwithoutmachining in There hasbeenanincreased demandinrecent years fornodularcastiron componentsthatare capableof ex weldments insomeengineeringapplications.ADIhasahighstrength-to-weight ratio andthebenefitof Impr least 3timesstr peening compar bending fatiguestrength ofADIcanbeincreased grades upto75%. ofADIwithshot This makescertain HTPEE T0.014"(0.36mm)AINTENSITY AT PEENED SHOT cellent w o v ements inaustempered ductileiron (ADI)have allowed ittoreplace steelforgings, castings,and D D ear capabilities.ADIhasalsor e e p p [Ref 2.8] .0901 510 9 8 7 15 5 15 3 15 14 0.10 14 0.07 0.06 5 0.0055 0.05 0.0039 0.0028 0.0024 0.02 0.0020 0.0016 0.00 0.0012 0.0008 0.0004 0.0000 t t onger andonly2.5timesmor able tocase-carburiz h h

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n n e e d d RESPONSE OF METALS 11 CHAPTER TWO CHAPTER S-N Curves for Shot Peened S-N Curves for Shot Peened 7050-T7651 Aluminum Alloy 3 3 - - 2 2

e e r r u u g g i i F F www.metalimprovement.com . 3 3 - - 2 2

en in e e v r r u u g g i i ef 2.11]. F F oved the oved Aluminum Lithium Alloys (Al-Li) Aluminum Lithium Alloys Composites (MMC) Metal Matrix Isotropic Cast Aluminum (Al-Si) ed from high strength ed from ximately 33%. E o y is shown in in y is shown • • • • • • •• •• •• epar ere shot peened. Fatigue ere Fatigue specimens were Fatigue pr Al 7050-T7651. All four sides of the center test portion w conducted under were tests reversed a four-point The bending mode (R = -1). S-N curvethe shot peened of peened non-shot versus allo It was found that shot peening impr the stress where a regime a factor of by increased the fatigue strength limit, and the endurance the yield strength is between ratio 2.5 to almost 4 [R fatigue endurance limit by fatigue endurance appr Al 7050-T7651 HIGH STRENGTH ALUMINUM Application Case Study Application raditional high strength aluminum alloys (series 2000 and 7000) have been used for decades in the aircraft have (series 2000 and 7000) aluminum alloys high strength raditional T with emerged have aluminum alloys following The ratio. their high strength-to-weight industry because of to shot peening: equally well and respond applications aircraft/aerospace use in critical increasing Shot peening can significantly improve properties when small cast-surface imperfections are present. One properties present. are imperfections small cast-surface when improve significantly peening can Shot the tests, the intensity used in highest shot peening liners. At the is diesel engine cylinder application of 20% reduction to a compares This specimens. machined fatigue that of fully was 6% below fatigue limit has a on the as-cast surface the peening Visually, condition. in the as-cast unpeened for specimens 2.10]. as-cast surface [Ref the rougher of smoothing effect leaving the appearance polishing ALUMINUM ALLOYS ALUMINUM CHAPTER TWO 12 RESPONSE OF METALS POWDER METALLURGY MA TITANIUM components are shotpeenedtoincrease durability. Eachtakeoffandlandingisconsidered oneloadcycle. titanium isther The mostcommonapplicationofLCF for exponential basis. improvements infatiguelifeare onan responded significantlybetter. Note that that initiallyhadmore cycles tofailure shot peeningisapplied,thebaselinecurve thatareload curves notshotpeened. When component [Ref 2.13]. There are twobaseline titanium dovetail slotsonarotating engine compared tosteelconnectingrods [Ref 2.12]. while weight wasreduced by some40%as limit wasincreased by approximately 20% processes. With shotpeening,thefatigue The rods are manufactured usingvarious car.for ahighperformanceEuropean sports capabilities oftitaniumalloy connectingrods High Cycle Fatigue (HCF) sealing andother engineeringapplications. bending. The surface densificationalsoassists intheclosingofsurfaceporosity ofPMcomponents for Surface densificationby shotpeening can increase thefatiguelimitsignificantly, especiallyinthecaseof such asforged powder metalcomponents. rods are candidates for PMwithshotpeening.Shotpeeningismosteffective onhigherdensityPMparts 22% andthefatiguelifeby afactorof 10. [Ref. 2.14] Automotive components suchasgearsandconnecting Optimized peeningparameters have beenshown toraise theendurance limitofsintered steelPMalloys by reduction, specialpeeningtechniquescanbeemployed toachieve 25-35%improvement infatiguestrength. Magnesium allo Low Cycle Fatigue (LCF) Cur This isdemonstr would beassociatedwithhigherstress levels. lower stresses whereas lower cycle fatigue Higher cycle fatiguewouldbeassociatedwith peening increases withhighercycle fatigue. other metals,thefatigueresponse withshot illustrated by F F i i g g GNESIUM u u v r r e e e (

F F 2 2 i i g g - - 5 5 u u r r shows theresults ofshotpeening e e

1 1 F F - - i i 4 g 4 g otating turbineenginehar ys are notcommonlyusedinfatigueapplications.However, whenusedforthebenefitofweight ated gr ) u u and also r r e e

2 2 - - 4 4 aphically intheS-N , whichcompares the - Asistypicalwith - HCFoftitaniumis F F i i g g u u r r e e

2 2 - - www.metalimprovement.com 5 5 . dwar e (discs,spools,andshafts)withtheex F F F F i i i i g g g g u u u u r r r r e e e e

2 2 2 2 - - - - 5 5 4 4 L and ShotPeened Titanium Ti6A14V Comparison ofF CF Benefitsfrom ShotPeening Notched Ti8-1-1 atigue Strengths forPolished ception ofblades. These

RESPONSE OF METALS 13

a P M CHAPTER TWO CHAPTER eening. es Comparing a v Powdered Metal (Fe-3.5Mo) Powdered 3 atigue Life Cur with and without Shot P F to a Steel Wrought (16MnCr5) Reference 7.5 g/cm 6 6 - - 2 2

e e r r

u u

i s k - h t g n e r t S t o o R h t o o T g g i i F F rogress, March 1978, pp. 59-63 1978, pp. March rogress, www.metalimprovement.com d Method, Metal P y Chor aluation b v powdered metal gear. Both gears were 3.5 mm module consisting of 25 teeth and case hardened consisting of 25 teeth 3.5 mm module Both gears were metal gear. powdered the powdered metal gear results are metal gear results the powdered 3 ement Company Memo v 6 6 o - - 2 2

e e Test to Evaluate Effects of Shot Peening on High Heat Treat Steel - Lockheed Report No. 9761 Report No. - Lockheed Steel Treat Heat on High Effects of Shot Peening to Evaluate Test r r u u g g i i atigue F F depicted with the blue curves. The endurance curves.depicted with the blue ~ 35% with the addition of shot limit improved from limit improved The endurance peening. The ~ 95 ksi (650 MPa) MPa). to ~ 128 ksi (880 the shot peened powdered limit of endurance with the non-peened closely very metal compares cost 16MnCr5 material. Due to the significant metal, the shot peened savings of powdered a suitable replacement metal gear may be powder Shot steel gear. wrought expensive to the more mm A) peening was performed at 0.013” A (0.32 2.15]. intensity for all samples [Ref Tooth root bending fatigue studies were performed using pulsator tests to compare a reference wrought gear steel wrought a reference tests to compare using pulsator performed studies were bending fatigue root Tooth to a 7.5 g/cm to 60 HRC. The wrought gear was a 16MnCr5 steel and the powdered metal gear was Fe-3.5Mo alloy content. alloy metal gear was Fe-3.5Mo 16MnCr5 steel and the powdered gear was a to 60 HRC.The wrought In assner; Decarburization and Its E eough, Brandenburg, Hayrynen; Austempered Gears and Shafts: Tough Solutions, Gear Technology March/April 2001, pp. 43-44 2001, pp. March/April Technology Solutions, Gear Tough Gears and Shafts: Hayrynen; Austempered eough, Brandenburg, Center, Solihull, England, July 1986 Center, 45-60 39, pp. Vol. the ASM, of Translations Steel, of Decarburized Strength The Effect of Composition on the Fatigue Jackson and Pochapsky; Bush; F G Internal Metal Impr K 15 - 17, 1985 Volume Metallurgy, in Powder Modern Developments Treatments, Hatano and Namitki; Application of Hard Shot Peening to Automotive Transmission Gears, Special Steel Research Laboratory, Daido Steel Daido Steel Laboratory, Research Gears, Special Steel Transmission to Automotive Shot Peening Hatano and Namitki; Application of Hard Ltd., Japan Company, Cast Surface Imperfections, BCIRA Report #1658, The Casting Development Centre, Alvechurch, Birmingham, UKCast Surface Imperfections, BCIRA Alvechurch, Centre, The Casting Development Report #1658, Engineering, Dept. of Mechanical and Aerospace Aluminum Alloy, High Strength of Shot Peened Damage Evaluation Oshida and Daly; Fatigue NY Syracuse, University, Syracuse HIGH DENSITY POWDER METAL GEARS Application Case Study Application 2.3 Research Lucas Treatments, and Surface Types Steel Pins of Different Engine Crank Between Performance Challenger; Comparison of Fatigue 2.1 1945 Age Reprint – Iron of Shot Peening Advantages Mechanical and Metallurgical Horger; 2.2 2.4 223-224 1, pp. Vol. Properties and Selection, Metals Handbook, Eighth Edition, 2.5 2.6 2.7 Pressed and sintered ferrous powder materials are in increasing demand as the PM industry has grown into has grown demand as the PM industry in increasing materials are powder ferrous and sintered Pressed 1000B with 2% copper and 0.9% graphite components. Ancorsteel stressed highly more involving applications limit of 35 ksi (240 MPa) without shot peening. Shot peening the test specimens when tested had an endurance 2.16]. 40.5 ksi (280 MPa) limit 16% to [Ref the endurance increased 2.10 Specimens Containing Small Iron Nodular Graphite Properties of Unmachined Pearlitic on the Fatigue The Effects of Shot Peening Palmer; 2.11 Ltd., 1998 Motor Co., 2.12Yamaha Engine Components, for Automotive Technology in the Application of Shot-Peening Progress Review, Technical 2.13 Disk Slots Turbine of Shot Peening Benefits from Fatigue Cycle McGann and Smith; Notch Low 2.14Thermal Surface Combined Mechanical and by Steels Properties of Sintered Fatigue the to Improve Muppman; How Sonsino, Schlieper, 2.8 2.9 of Aachen, Germany University Thesis Study, Doctorate Metal Steel,” Powder High Strength Capacity of Gears Made From R., 2001, “Load 2.15 Strehl, 2.16TX. May 1987 Dallas, Conference, Metallurgy P/M Materials, Annual Powder of Selected Ferrous Characterization O’Brian; Impact and Fatigue REFERENCES: CHAPTER THREE S E S

S EFFECT ON FATIGUE LIFE

E Manufacturing processes have significant effects on fatigue properties of metal parts. The effects can be either detrimental or beneficial. Detrimental processes include welding, grinding, abusive machining, metal

C forming, etc. These processes leave the surface in residual tension. The summation of residual tensile stress and applied loading stress accelerates fatigue failure as shown in Figure 1-6. O Beneficial manufacturing processes include surface hardening as it induces some residual compressive stress into the surface. Honing, polishing and burnishing are surface enhancing processes that remove R defects and stress raisers from manufacturing operations. Surface induces compressive stress but is

P primarily limited to cylindrical geometries. Shot peening has no geometry limitations and produces results

that are usually the most economical.

The effect of residual stress on fatigue life is demonstrated in the following example. A test by an airframe G manufacturer on a wing fitting showed the initiation of a crack at just 60% of predicted life. The flaw was removed and the same area of the part shot peened. The fitting was then fatigue tested to over 300% life N without further cracking even with reduced cross sectional thickness [Ref 3.1]. I

R WELDING

U The residual tensile stress from welding is created because the weld consumable is applied in its molten state. This is its hottest, most expanded state. It then bonds to the base material, which is much cooler. The weld

T cools rapidly and attempts to shrink during the cooling. Because it has already bonded to the cooler, stronger base material it is unable to shrink. The net result is a weld that is essentially being "stretched" by the base C material. The heat affected zone is usually most affected by the residual stress and hence where failure will usually occur. Inconsistency in the weld A filler material, chemistry, weld geometry, F porosity, etc., act as stress risers for residual and applied tensile stress to U initiate fatigue failure.

N As shown in Figure 3-1, shot peening is extremely beneficial in reversing the A residual stress from welding that tends to cause failure in the heat affected zone

M from a tensile to a compressive state.

Figure 3-1 demonstrates a number of interesting changes in residual stress from welding, thermal stress relieving and shot peening [Ref 3.2]. Tensile Figure 3-1 Residual Stresses from Welding stresses generated from welding are additive with applied load stresses. This combined stress will accelerate failure at welded connections.

When the weld is stress relieved at 1150 °F (620 °C) for one hour, the tensile stress is reduced to almost zero. This reduction of tensile stress will result in improved fatigue properties. 14 www.metalimprovement.com M ANUFACTURING PROCESSES 15 s s e e h h l l t t c c g g y y n n C C

e e r r 0 0 t t 0 0 S S CHAPTER THREE CHAPTER 0 0

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l l e e e e t t S S cles* Weld Toe Ground (only) Ground Toe Weld (only)Welded As ~ 26 ksi (180MPa) ~ 20 ksi (140MPa) Base Material and Peened Ground Toe Weld ~ 44 ksi (300 MPa) ~ 50 ksi (340 MPa) www.metalimprovement.com ganizations as: osion Engineers [R 16,000 cycles eas of the weldment where cyclic applied stresses are expected". are applied stresses cyclic where eas of the weldment 4,000 cy ations in shot peening contr v espective sign. For this reason, it may be advantageous to induce it may be advantageous this reason, sign. For espective y such or ocess in engine upgrades [Ref 3.8]. [Ref ocess in engine upgrades ed b ocess to improve resistance to fatigue as well as stress corrosion cracking in cracking corrosion as stress to fatigue as well resistance ocess to improve ess in critical ar ecogniz elded W American Society of Mechanical Engineers [R American Society of Mechanical Engineers 3.5] of Shipping [Ref. American Bureau 3.6] Institute [Ref. American Petroleum National Association of Corr esidual str vice, coupled with inno elded and peened essor rotors. Separate pieces are machined from forged titanium (Ti 4Al-6V) titanium (Ti and then welded forged from machined pieces are Separate essor rotors. shows the optimal manufacturing sequence for welding is to stress relieve and then shot relieve is to stress welding sequence for optimal manufacturing the shows As and polishedWelded W 6,000 cycles e r esses depending on their r 1 1 • • • • • • • • •• •• •• •• - - ee ser 3 3

essiv FATIGUE OF OFFSHOREFATIGUE STEEL STRUCTURES program research A Norwegian of concluded that the combination toe grinding and shot peening weld in improvement the largest gave corresponds This life. the structure in than a 100% increase to more at one strength the as-welded shot from fatigue strength in weld that the improvement shows 3.3]. Other research [Ref million cycles metal. in proportion of the parent peening increases to the yield strength as a full manufacturing pr Initially, shot peening was used as additional "insurance" from failure. After many years of failure of failure After many years failure. from shot peening was used as additional "insurance" Initially, fr TURBINE ENGINE HP COMPRESSOR ROTORS high pressure turbine engines jointly manufacture of jet in the manufacture leading companies Two compr results: the following produced Testing together. e e r r u u Application Case Study Application Application Case Study Application g g elding if the fabrication is subject to fatigue loading as described in the follo elding if the fabrication is subject to fatigue elded components is r The American Welding Society (AWS) Handbook cautions readers to consider residual tensile stresses from tensile stresses to consider residual Handbook cautions readers Society (AWS) Welding The American i i F F If the weld is shot peened (rather than stress relieved) there is a significant reversal of residual stress from stress of residual reversal is a significant there relieved) stress than peened (rather is shot weld If the initiation and propagation. to fatigue crack significant resistance This will offer tensile to compressive. w peen. The stress relieving process softens the weld such that inducing a deeper layer of compressive inducing a deeper layer such that the weld softens process relieving stress The peen. becomes possible. stress stresses within a structure may result entirely from external loading, or there may be a combination of or there external loading, from entirely may result within a structure stresses from but they may augment or detract not cyclic, are stresses Residual stresses. applied and residual applied str The use of the shot peening pr w compr CHAPTER THREE 16 M ANUFACTURING PROCESSES PLA GRINDING stress reversal issimilartothatfrom shotpeeningwelded regions in astateoftension. residual stress statefrom tensiletocompressive.the The beneficial reverse will grinding after peening Shot Under fatigueloading,themicr very finecracks thatistypicalofhard chrome plating[Ref 3.10]. without weld) wasground abusively andconventionally. stress generated from various carbonsteel(withand grindingprocesses [Ref 3.9].A1020,150-180BHN dr cr When thebasemetalisshotpeened,potentialforfatigue the basemetalandleadtofatiguefailur Shot peeningprior propagating intothebase material. shows thecompressive layer preventing themicro-cracking from the basematerial. When shotpeened,thegraphic ontheright The graphic ontheleftshows themicro-cracking propagating into assumes dynamicloadingonacomponent. resistance tostress corrosion cracking. will have anegative effectonfatiguelifeand stress. Residual tensilestress ofanymagnitude surrounding metalresulting inresidual tensile contract. This contraction isresisted by the Upon coolingtheyieldedmetalattemptsto surrounding metalandyieldsincompression. expand. The heatedmaterialisweaker thanthe abrasive mediumheatslocally andattemptsto the process. The metalincontactwiththe as aresult oflocalized heatgenerated during Typically, grindinginducesresidual tensilestress or r micro-cracking inthebrittlesurface,hydrogen embrittlement fatigue life.F nickel platingtocounter are shotpeenedpriortochrome andelectrolessMany parts r electrolytic nickelmayalsolower fatigue strength. priortochrome orelectroless nickel-plating.Otherhardshot peeningofsteelparts platingprocesses suchas callfor thatrequire unlimitedlifeunderdynamicloads,federalparts specificationsQQ-C-320andMIL-C-26074 F F F F esulted inhighsurfacetensionwiththeabusiv i i i i g g g g ack pr amatically r TING u u u u esidual tensilestr r r r r e e e e

3 3 3 3 opagation intothebasemetalfr - - - - 3 2 3 2 is a 1200x SEM photograph showing anetworkof is a1200xSEM graphically depictsresidual tensile atigue deficitsfr educed. to plating is recommended on cyclically loaded parts to enhance fatigue properties. For toenhancefatigue properties. to platingisrecommended oncyclically loaded parts esses. F F i i act thepotentialharmfuleffectson g g u u r r e e

om platingmayoccurfr 3 3 o-cr - - 4 4 illustr acks canpr www.metalimprovement.com ates thisconceptand om theplatingis e. opagate into e grindhavingadeeper(detrimental)lay om the F F F F i i g g i i g g u u u u r r r r e e e e

3 3

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3 3

3 3 - - 4 4 - - 3 3 Micro-Crack Growth Compressive Stress Resists Plating Micro-Cracks er ofresidual tension. M ANUFACTURING PROCESSES 17 ) ) e e r r u u l l i i a a F F

% % CHAPTER THREE CHAPTER 0 0 1 1 ( (

d d a a o o L L High Cycle Fatigue Behavior Fatigue High Cycle of Inconel 718 d d e e z z i i 5 5 - - d d 3 3

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g g i i d d F F r r a a H H d d e e n n e e e e P P NoNo No Yes 6744 lb / 30 KN 4496 lb / 20 KN www.metalimprovement.com YesYes No Yes 9218 lb / 41 KN 10,791 lb / 48 KN

ed er t t 5 5 - - o o CHINING (EDM) 3 3 h h

e e S S r r u u g g ecast lay i i o-chemical F F ocess. Shot should be view 5 5 - - 3 3

e e r r elding pr u u g g i i F F anodizing. esults in a solidified r e ef 3.12]. cles. The table shows the The table shows cles. obability at one million cy 3.11]. [Ref results ANODIZED ALUMINUM RINGS purposes with tested for comparison 0.5) rings with external teeth were Aluminum (AlZnMgCu of ~ 24" (612 mm) and a tensile The rings had an outside diameter peening. anodizing and shot (0.02 mm) thick. was ~ 0.0008" layer anodizing The (hard) (490 MPa). of ~ 71 ksi strength were Bending fatigue tests load conducted to find the to cause a 10% failure pr ated during the w wn [R Application Case Study Application DM is essentially a "force-free" spark erosion spark DM is essentially a "force-free" machined (ECM), electro-discharge machined machined (ECM), electro-discharge (EDM) (ELP) and electro-polished surfaces is sho the effect of shot peening on electr E to dischargeThe heat generated process. molten metal r can be brittle This layer on the base material. similar to those and exhibit tensile stresses gener Plasma spray coatings are primarily used in applications that require excellent wear resistance. Shot resistance. wear excellent used in applications that require primarily coatings are Plasma spray applications that are spray prior to plasma as a base material preparation effective peening has proven application to spray fatigue applications. Shot peening has also been used after the plasma used in cyclic surface porosity. surface finish and close improve Hard anodizing is another application in which shot peening improves fatigue resistance of coated fatigue resistance improves in which shot peening application anodizing is another Hard to the base is performed the peening providing to those for plating similar Benefits are materials. material befor in a clockwise format. ECM, EDM and ELP and with compared are fatigue strengths without shot peening. peening is beneficial in restoring the fatigue peening is beneficial in restoring In this process. by debits created ELECTRO-DISCHARGE MA ELECTRO-DISCHARGE PLASMA SPRAY ANODIZING CHAPTER THREE 18 M ANUFACTURING PROCESSES REFERENCES: ELECTRO-CHEMICAL MACHINING (ECM) Application Study Case DIAPHRAGM COUPLINGS DIAPHRAGM 3.14 Calistrat; MetalDiaphragm CouplingPerformance, Hydrocarbon Processing, March 1977 3.13 3.12 InternalMetalImprovement CompanyMemo 3.11 Metallurgical Associates,Inc;"Minutes" Vol.5 No.1, Winter 1999;Milwaukee, WI 3.10 A shot peening posttreatment more thanrestoresA asshown in fatigueproperties softening (therebinder effect)andsurfaceimperfectionsleftby preferential attackongrain boundaries. reagent inthepresence ofanelectriccurrent. isattributedtosurface Areduction infatigueproperties Electro-chemical machiningisthecontrolled dissolutionofmaterialby contactwithastrong chemical 3.9 InternalMetalImprovement CompanyMemo 3.8 N.A.C.EStandard MR-01-75,SulfideStress Cracking ResistantCorrosion MetallicMaterialforOilfieldEquipment,NationalAssociationof Engineers 3.7 Haagensen;Prediction oftheImprovement inFatigue Lifeof Welded JointsDuetoGrinding, Dressing,TIG Weld ShapeControl andShot 3.3 3.2 InternalMetalImprovement CompanyMemo 3.1 3.6 Stern; AmericanBureau ofShipping,Letter toG.Nachman,July1983 3.5 McCulloch;AmericanSocietyofMechanicalEngineers, Letter toH.Kolin, May1975 3.4 improved theendurance limitofthediaphragm couplings[Ref 3.13and3.14]. premature failures. ShotpeeningafterECMwasabletoovercome thisdeficiencyandhassignificantly the surfaceasaresult ofECM. These cavitiesapparently generated stress concentrations thatleadto they foundunderscanningelectron microscope observation thatsmallcavitiessometimesdeveloped on Researchers thatare concludedthattheECMprocess geometrically near-perfect. produces parts However, system misalignmentthrough flexing. This flexing,orcyclic loading,posesconcernsforfatiguefailures. Metal diaphragm couplingsare oftenusedinturbomachineryapplications. These couplingsaccommodate Calistr Bulletin 677-1,June1977 Koster, W.P., ObservationonSurfaceResidual Stress vs.Fatigue Strength, MetcutResearch Associates,Inc.,Cincinnati,Ohio. Milwaukee, July2000 WI; Molz peening." Confer Molz Ubben; AmericanP en, Hornbach;E en, Hornbach;E at; MetalDiaphr ence; Milwaukee, The Norw etr v egian Instituteof v aluation of oleum Institute,L aluation of agm CouplingP WI; July2000 WI; Welding Residual Stress Levels Through ShotPeening andHeat Treating, AWS BasicCracking Conference; W elding R erformance, 5th Turbomachinery Symposium, Texas A&MUniversity, October1976 etter toG.Nachman,F T echnology www.metalimprovement.com esidual S , T rondheim, Norway tress Levels Through ShotPeening andHeat Treating, AWS BasicCracking ebruary 1967 F F i i g g u u r r e e

3 3 - - 5 5 [Ref 3.12]. BENDING FA TIGUE 19 e type of CHAPTER FOUR CHAPTER Ring and Pinion Gear Assembly 2 2 - - 4 4

e e r r u u g g i i F F This is the most destructiv Polarized View of Applied Gear Stresses View Polarized cles. 3 3 - - Highest Stress at Surface Highest Stress 4 4

e e 1 1 r r - - u u 4 4

g g i i e e e load cy F F r r u u g g i i essiv F F www.metalimprovement.com . ) ) . It is 3 3 ) ) dness results in dness results - - 4 4 4 4 - -

e e 4 4

r r e e u u r r RC) when g g u u i i F F g g equire less equire i ( i ( F F ( ( ough tensile and compr eased surface har cle thr ed surfaces r d shot (55-62 H om 170-230 ksi (1170-1600 d shot will induce. shows a cantilever beam a cantilever shows dening. Incr ange fr 1 1 - - ersed bending involves 4 4

ties in the root sections of the tooth profile. The meshing of sections of the tooth profile. ties in the root ev e e r r u u oper g g i i ully r F F disruption of the tooth flank surface. The disruption of the tooth flank surface. will be ~ 50% of stress amount of compressive that which har common to use har gears. However, shot peening carburized shot (45-52 HRC) hardness reduced may be used when carburiz Shot peening of gears is a very common application. Gears of any Shot peening of gears is a very bending fatigue shot peened to improve mainly or design are size pr Bending fatigue is the most Bending fatigue is the This mode. common fatigue failure shot to well mode responds failure highest peening because the at the surface. is (tensile) stress Gears are frequently shot peened after through hardening or hardening through shot peened after frequently Gears are surface har fatigue loading. Fatigue cracks are initiated and propagated from the tensile portion from initiated and propagated the load cycle. of are cracks fatigue loading. Fatigue components that cy F under an applied bending load. under an applied bending causes the The beams deflection putting it in a top surface to stretch or state of tension. Any radii geometry changes along the top risers. surface would act as stress gear teeth is similar to the cantilever beam example. The load beam example. gear teeth is similar to the cantilever in the root a bending stress the tooth contact creates from created the point of contact below area proportional increases in compressive stress. Maximum residual Maximum stress. proportional in compressive increases and shot peened carburized from compression gears can r MPa) depending on the carburizing treatment and shot peening parameters GEARS BENDING FATIGUE BENDING CHAPTER FOUR 20 BENDING FA TIGUE CONNECTING RODS applications. Increases infatiguestrength of30%ormore gearing at1,000,000cycles are commonincertain Chapter 10foradditionalinformationandphotomicrographs onthisprocess. controlled shotpeeningisimplemented: ishing process calledC.A.S.E. offers ashotpeeningandsuperfin- Metal Improvement Company(MIC) area reducing contactstresses. to bedistributedover alarger surface peening dimplesallow thecontactload that refine thesurfacefinishofshot of theshotpeeninglayer. Processes be takentonotremove more than10% isotropic finishingprocess. Care must stress followed by alapping,honingor pitch lineistoinduceacompressive to pittingfatiguenearthegeartooth The optimalwaytoinduceresistance side oftheI-beamsnexttolar r Connecting r that mostpeenedsurfacesdonotr tension (orwithoutresidual stress) such thansmoothsurfaces in properties compr add cost.Rougher surfacesin eliminates maskingoperations that will machining ofthebores orfaces. This or powdered metalrod priortoany peening istopeentheas-forged, as-cast The mosteconomicalmethodofshot maximum stress areas shown inred. prior preparation orpostoperations. ev olution r ession have betterfatigue • • • • • • • • • esults inaloadcy ods are excellent examplesofmetalcomponentssubjectedtofatigue loadingaseachengine ANSI/AGMA 6032-A94MarineGearingSpecification:15% increase ANSI/AGMA Det Norske Lloyds Register ofShipping:20%increase [Ref 4.2] The follo wing or V eritas: 20%incr S cle. M ganizations/specifications allow forincreases intoothbendingloadswhen that hasincreased pittingfatigueresistance ofgearsby 500%. Pleasesee ge bor The criticalfailure areas onmostconnectingrods are theradii oneither www.metalimprovement.com equire e. ease [R F F i i g g u u r r e e ef 4.3]

4 4 F F F F i i - - i i g g 5 5 g g u u

u u sho r r r r e e e e

4 4 ws afiniteelementstr 4 4 - - - - 4 4 5 5 Typical Carburized GearResidual Stress Profile Finite ElementS tress PlotofaConnectingRod ess analysisplotwiththe CHAPTER FOUR B

CRANKSHAFTS E

In most cases, all radii on a crankshaft are shot peened. These N include the main bearing journals and crankpin radii as shown in

Figure 4-6. The most highly stressed area of a crankshaft is the D crank pin bearing fillet. The maximum stress area is the bottom

side of the pin fillet when the engine fires as the pin is in the top I dead center position (Figure 4-6). It is common for fatigue N cracks to initiate in this pin fillet and propagate through the web of the crankshaft to the adjacent main bearing fillet causing G catastrophic failure. Figure 4-6 Crankshaft Schematic

Experience has shown shot peening to be effective on forged steel,

cast steel, nodular iron, and austempered ductile iron crankshafts. Fatigue strength increases of 10 to 30% are F allowed by Norway’s Det Norske Veritas providing fillets are shot peened under controlled conditions [Ref 4.5]. A Application Case Study T DIESEL ENGINE CRANKSHAFTS I Four point bending fatigue tests were carried out on test pieces from a diesel engine crankshaft. The G material was Armco 17-10 Ph stainless steel. The required service of this crankshaft had to exceed one hundred million cycles. Fatigue strength of unpeened and shot peened test pieces were measured at one U billion cycles. The fatigue strength for the unpeened material was 43 ksi (293 MPa) versus 56 ksi (386 MPa) for the peened material. This is an increase of ~ 30% [Ref 4.6]. E

Application Case Study TURBINE ENGINE DISKS

In 1991 the Federal Aviation Authority issued an airworthiness directive that required inspection for cracks in the low pressure fan disk. Over 5,000 engines were in use on business jets in the United States and Europe.

The FAA required that engines that did not have lance (shot) peening following machining in the fan blade dovetail slot be inspected. Those engines having fan disks without lance peening were required to reduce service life from 10,000 to 4,100 cycles (takeoffs and landings). Disks that were reworked with lance peening Figure 4-7 Lance Peening of Fan Disk per AMS 2432 (Computer Monitored Shot Peening) prior to 4,100 cycles were granted a 3,000 cycle extension [Ref 4.7]. A typical lance peening operation of a fan disk is shown in Figure 4-7. See also Chapter 10 – Internal Surfaces and Bores.

REFERENCES: 4.1 Figure 4-2, Unigraphics Solutions, Inc. website (www.ugsolutions / www.solid-edge.com), June 2000 4.2 Letter to W.C. Classon, Lloyds Register of Shipping, May 1990 4.3 Sandberg; Letter to Metal improvement Company, Det Norske Veritas, September 1983 4.4 Figure 4-5, Unigraphics Solutions, Inc. website (www.ugsolutions / www.solid-edge.com), June 2000 4.5 Sandberg; Letter to Metal improvement Company, Det Norske Veritas, September 1983 4.6 Internal Metal Improvement Company Memo 4.7 FAA Issues AD on TFE73, Aviation week & Space Technology; April 22, 1991 21 www.metalimprovement.com CHAPTER FIVE E U G

I TORSIONAL FATIGUE Torsional fatigue is a failure mode that

T responds well to shot peening because the greatest (tensile) stress occurs at A the surface. Torsional loading creates

F stresses in both the longitudinal and

perpendicular directions such that the maximum tensile stress is 45° to L longitudinal axis of the component.

A Figure 5-1 depicts a solid bar loaded in pure torsion with a crack depicting Figure 5-1 Torsional Loading

N reversed torsional loading.

Lower strength materials tend to fail from torsional fatigue in the shear plane perpendicular to the longitudinal O axis. This is because they are weaker in shear than in tension. Higher strength materials tend to fail at 45° to

I the longitudinal axis because they are weaker in tension than in shear. S

R COMPRESSION SPRINGS Compression springs are subject to high cycle fatigue and are one of the

O more common shot peening applications. The spring wire twists allowing the spring to compress creating a torsional stress. In addition to operating T in high cycle fatigue conditions, the coiling process induces detrimental tensile stress at the inner diameter (ID) of the spring. Figure 5-3 demonstrates the residual stress after coiling and shot peening. Figure 5-2 Compression Spring Assembly The spring wire analyzed in Figure 5-3 was a 0.25" (6.35 mm) diameter Chrome-Silicon material with an ultimate tensile strength (UTS) of 260 ksi (1793 MPa). The residual tensile stress at the ID after coiling was ~ 70 ksi (483 MPa) and is the primary reason for failure at 80,000 load cycles [Ref 5.2].

Shot peening induced a reversal of residual stress to a maximum compressive stress of ~ 150 ksi (1035 MPa). This is 60% of UTS of the wire and resulted in fatigue life in excess of 500,000 load cycles without failure.

Figure 5-3 Coil Spring ID Residual Stress With and Without Shot Peen

22 www.metalimprovement.com T O R SIO NAL FA TIGUE 23 CHAPTER FIVE CHAPTER elated . On heavy duty When used in systems Drive Shaft Schematic Shaft Drive 4 4 - - esses occur 5 5

e e r r u u g g i i ehicles, etc.) cracks can also occur on the ehicles, etc.) cracks F F adii and keyways. t utility v esisting twisting motion. cuts, r y r e the highest load str www.metalimprovement.com al members often used in suspensions and other r al members often used in suspensions typical 4 4 - - e splines, under 5 5 e utility trucks, spor e structur

e e r r u u g g i i F F vice life. e shafts ar cellent shot peening wn in e used to maintain stability b The bars ar UTOMOTIVE TORSION TORSION BARS UTOMOTIVE applications (four wheel driv inner diameter (ID), which also experiences torsional loads. MIC necessary is able to shot peen the IDThis provides peening methods. using its lance shot the torsion/anti-sway bar length. throughout stress compressive A savings. Shot peening torsion bars as a means of weight industry has used hollow The automotive was performed on the outer diameter wher e locations for driv Lanke, Hornbach, Breuer; Optimization of Spring Performance Through Understanding and Application of Residual Stress; Wisconsin Coil Spring Wisconsin Stress; Application of Residual Understanding and Through Optimization of Spring Performance Lanke, Hornbach, Breuer; Chicago, IL Symposium; Technical Institute Company; 1999 Spring Manufacturer’s Inc., Metal Improvement Inc., Lambda Research, May 1999 Application Case Study Application orsion bars and anti-sway bars ar failur Other spring designs respond equally well to shot peening. The fatigue failure will occur at the location The fatigue failure to shot peening. equally well respond Other spring designs fail at the springs will generally Torsion stress. and applied tensile of residual of the highest combination of the hook. ODfail at the inner radius Extension near the tangent of the tang. springs will generally flat springs, leaf springs, cantilever peening are shot designs that can benefit from Other potential spring springs, etc. It is quite common to perform a baking operation after shot peening of springs. The baking operation is operation baking The springs. of shot peening after operation a baking to perform common It is quite setting problem used to offset a potential of springs and is in the manufacture stabilizing process used as a °C) for 30 400 °F (205 approximately The baking is peened spring designs. with some shot that may occur above Temperatures of the wire. temperature relief the stress and is below carbon steel springs minutes for shot peening. from stress beneficial residual the °C) will begin to relieve 450 °F (230 5.1 June 2000 / www.solid-edge.com), (www.ugsolutions Solutions, Inc. website 5-2, Unigraphics Figure 5.2 T Shaft applications are used to transmit Shaft applications are one location to another through from power This creates a torsional rotation. of use the Because most member. load on the rotating primary load bearing are shafts drive members, they make ex applications. As sho systems. subjected to repetitive loads such as vehicle suspensions, shot peening offers advantages of weight of suspensions, shot peening offers advantages loads such as vehicle subjected to repetitive savings and extended ser REFERENCES: TORSION BARS BARS TORSION DRIVE SHAFTS DRIVE SHAFTS CHAPTER SIX E U G

I AXIAL FATIGUE Axial fatigue is less common than other (fatigue) failure mechanisms. A smooth test specimen with axial

T loading has uniform stress throughout its cross section. For this reason, fatigue results of smooth, axial loaded shot peened specimens often do not show significant improvements in fatigue life. This is unlike A bending and torsion that have the highest applied stress at the surface. F In most situations, pure axial loading is rare as it is normally accompanied by bending. Shot peening of

axial loaded components is useful when there are geometry changes resulting in stress concentrations. Undercut grooves, tool marks, cross holes and radii are typical examples of potential failure initiation sites. L

A Application Case Study I TRAIN EMERGENCY BRAKE PIN X Figure 6-1 is part of a hydraulic brake

A assembly used in a mass transit system. The undercut sections near the chamfered end were designed to fail in the event of axial overload. During the investigation of premature failures it was found that a Figure 6-1 Brake Pin Schematic bending load was also occurring. The combined axial and bending load when simulated in test caused fatigue failure between 150,000 – 2,600,000 cycles. Shot peening was added to the brake pin and all test specimens exceeded 6,000,000 cycles without failure [Ref 6.1].

Application Case Study AUXILIARY POWER UNIT (APU) EXHAUST DUCTS

This type of APU is used to provide power to aircraft when they are on the ground with the main engines turned off. The tubular exhaust ducts are a high temperature 8009 aluminum alloy welded in an end-to-end design.

Tension-tension fatigue tests measured fatigue strength of 23 ksi (156 MPa) at 3,000 cycles in the as welded condition. Glass bead peening of the welds resulted in a 13% fatigue strength improvement to 26 ksi (180 MPa) [Ref 6.2].

REFERENCES: 6.1 RATP, Cetim; Saint Etienne, France, 1996 6.2 Internal Metal Improvement Company Memo

24 www.metalimprovement.com C O NTACT FAILURE 25 CHAPTER SEVEN CHAPTER Turbine Blade and Turbine Disc Assembly Turbine Engine Turbine Assembly 2 1 2 1 - - - - 7 7 7 7

e e e e r r r r u u u u g g g g i i i i F F F F The discs or wheels www.metalimprovement.com etting. etting. oots have the characteristic fir tree the characteristic oots have e associated with fr t the blades should also be peened. the blade r 2 2 - - 7 7

e e r r ent failur u u ev g g i i F F shape. The tight mating fit coupled with demanding loading The tight mating fit coupled with shape. be shot peened to that the surfaces conditions require pr TURBOMACHINERY BLADES AND BUCKETS of root is the dovetail environment fretting common A very is commonly used turbomachinery blades. Shot peening in As shown of these roots. failures fretting to prevent Many turbine and compressor blade roots are shot peened are blade roots Many turbine and compressor as OEM to restore parts peened upon overhaul and re-shot fatigue debits otherwise lost to fr that suppor Application Case Study Application Resistance to pitting fatigue is of primary concern for those who design gears and other components Resistance is the limiting designed such that contact failure contact. Many gears are with rolling/sliding involved and with less gradually occur more generally pitting failures Though not desirable, factor in gear design. bending failures. consequences than root catastrophic Fretting fatigue can occur when a rotating component is press fit onto a shaft. Vibration or shifting loads Vibration fit onto a shaft. component is press fatigue can occur when a rotating Fretting the producing The exposed surfaces will oxidize fit to bond and tear. may cause the asperities of the press steel. of fretted appearance "rusty powder" Shot peening has been used to prevent fretting and eventual fretting used to prevent Shot peening has been texturing the surface with a non-directional by failures fretting (of certain in surface hardening This results materials) and finish. prevents layer The compressive stress. of compressive a layer of fretting. scoring marks as a result from fatigue cracks of fretting initiation and growth Fretting occurs when two highly loaded members have a common loaded members have occurs when two highly Fretting and sliding take place. Relative surface at which rubbing surface in amplitude result of microscopic movements oxides fatigue. Fine abrasive and eventual pitting discoloration, that furtherdevelop to scoring of the surfaces. Other contribute wear, and fretting corrosion such as fretting mechanisms, failure failures. fretting commonly accompany PITTING FRETTING FAILURE FRETTING CHAPTER SEVEN 26 C O NTACT FAILURE GALLING REFERENCES: gr surface tonotremove more than10%ofthecompressive layer. PleaseseeChapter10forphotomicro- contact area isdistributedover alargerwhenfinishingthe shotpeened surfacearea. Itisimportant follo beneficial incombatingpittingfatiguewhen Shot peeninghasbeenproven tobehighly pitting [Ref 7.2]. flank andthemechanismsthatcause asperities. actual contactoccursbetween the enough toseparate thesurfacesand when thelubricantfilmisnotquitethick susceptible topittingfailure. This occurs A conditionofmixed lubricationisvery separates itselfleavinga"pit". will continueuntiltheasperity micro-crack mayinitiate.Crack growth stresses. With continuedoperation, a from matingsurfacesmakecontact,theloadingisacomplexcombinationofHerzianandtensile andslidingcontactstresses nearthepitchline. Pitting failures initiateduetoHertzian When asperities . Hahlbeck;MilwaukeeGear;Milwaukee, /PowertrainWI Engineers;Pewaukee, WI 7.2 Figure 7-1,Unigraphics Solutions,Inc.website (www.ugsolutions /www.solid-edge.com), June2000 7.1 and 750,MonelK-500alloys ofstainlesssteel,titaniumandaluminum. materials hav hardening. The coldworkedsurfacealsocontainsdimplesthatactaslubricantreservoirs. The following whenthematerialsare capableofwork Shot peeningcanbebeneficialforsurfacesthatgallparticularly andgross transfer offragmentsmetal particles between surfaces. When severe, seizure mayoccur. involved causeplasticdeformationandcoldwelding ofopposingasperities. There isusuallydetachmentof boundary lubrication.Initsearlystagesitissometimesr isanadvancedGalling formofadhesive wear thatcanoccuronmaterialsinslidingcontactwithnooronly aphs ofashotpeenedandisotr w ed b y asurfacefinishimprovement process. Byremoving theasperitiesleftfrom shotpeening,the F F i i g g e demonstr u u r r e e

7 7 - - 3 3 shows agear ated positiv opically finishedsurfaceusingtheC.A.S.E. www.metalimprovement.com e response togallingwiththeassistanceofshotpeening:Inconel718 eferr ed toasscuffing. The adhesive forces F F i i g g u u r r e e

7 7 - - 3 3 SM Pitting F pr ocess. ailure Schematic C O RROSIO N FAILURE 27 CHAPTER EIGHT CHAPTER osion Cracking Triangle osion Cracking ess Corr tr Stress Corrosion Cracking Failure Failure Cracking Corrosion Stress Steel of 300 Series Stainless S 2 2 1 1 - - - - 8 8 8 8

e e e e r r r r u u u u g g g g i i i i evented from ever occurring. The following is a partialThe following list of occurring. ever from evented F F F F www.metalimprovement.com ded or pr etar onment e envir osiv tain alloys (and tain alloys e is significantly r Certain nickel alloys Certain high strength steels Certain brasses Austenitic stainless steels Cer tempers) of series 2000 and 7000 aluminum Corr Tensile stress Tensile Susceptible material depicts a SCC failure. In depicts a SCC failure. shows the stress corrosion triangle in which each leg must be present for SCC to occur. for SCC to occur. triangle in which each leg must be present corrosion the stress shows essive layer from shot peening removes the tensile stress leg of the SCC triangle. Without tensile Without leg of the SCC triangle. the tensile stress shot peening removes from layer essive • • • • • • • • • • • • • • • • •• •• •• •• •• •• •• •• 2 1 2 1 - - - - er branching” pattern is unique er branching” 8 8 8 8

e e e e riv r r r r u u u u ess, SCC failur g g g g i i i i F F F F Stress corrosion cracking (SCC) failure is (SCC) failure cracking corrosion Stress most often associated with static tensile can be from The static stress stress. (such as a bolted flange) or applied stress manufacturing from stress residual SCC to For (such as welding). processes factors must be present: occur three Tensile related corrosion failures can be derived from either static or cyclic tensile stresses. In both types of In both tensile stresses. either static or cyclic from can be derived failures corrosion related Tensile and sour gas wells such as salt water Environments influences contribute to failure. environmental failures, with aggressive become more In most cases, these environments challenges. metallurgical create temperature. increasing to SCC and is often used in failure analysis for identification purposes of this material. austenitic 300 series stainless steel, the “ The compr str alloys that are susceptible to SCC failure: susceptible to SCC failure: that are alloys STRESS CORROSION CRACKING STRESS CORROSION CORROSION FAILURE CORROSION CHAPTER EIGHT 28 C O RROSIO N FAILURE CORROSION FATIGUE Application Study Case Application Study Case str Corrosion fatigueisfailure ofcomponentsincorrosive environments associatedwithcyclic loading.Fatigue pr will experienceasignificantdecrease infatiguestrength. The following testresults illustrate theresponse of strength wasapplied[Ref 8.2]. cracking forthefollowing stainlesssteelalloys. Aloadstress equivalent to70%ofthematerialsyield The following tabledemonstrates theeffectiveness ofshotpeeningincombatingstress corrosion more expensive alloy. material. Even withtheadditionalshotpeeningoperation, constructioncostswere lessthanusingthe SCC susceptiblematerialwasselectedwithshotpeeningrather thanamore expensive non-susceptible equipment. Incaseswhere ammoniaorchloridebasedsolutionswere tobecontained,alower cost Shot peeninghasbeenutilized asacostsavingsmeasure forconstructionofchemicalhandling EQUIPMENT HANDLING FABRICATION OFCHEMICAL Hydrogen sulfide(H S ength canber ecipitation har U LFIDE STRESS CRACKING STRESS LFIDE educed b dened 17-4stainlesssteelexposedtoH 2 % % S) is commonly encountered in sour gas wells. Certain metalalloysS) iscommonlyencountered whenexposedtoH insourgaswells. Certain N.F. =NoFailure M S S M 1 Sys1000N.F. 1000N.F. 11.3 yes yes 321 S no 321 S 318 SS 318 S 316 SS 316 SS Testing DonePer NACE TM-01-77 Test Standard N.F. =NoFailure t t o o a a r r y 50%ormore whensusceptiblealloys are usedincorrosive environments. e t t e f f 03. 561 720N.F. 37.9 29.8 60 50 40 30 e e n n Y Y e 1000N.F. 5.0 3.3 yes no no S S S r r g g i i i i e e a a t t h h l l l l d d www.metalimprovement.com A A ( ( h h s s ( ( r r

P P y y M M s s e e e e . . 15.2 15.4 a a

e e s s t t c c n n / / o o n n h h e e

o o i i f f d d n n a a ) ) e e i i l l 2 d d ) ) S withandwithoutshotpeening[R A A s s S S ( ( M M h h h h T T r r ( ( o o a a e e s s h h t t c c s s . . o o

538 219 h h

t t P P t t u u

i i o o e e L L n n r r

e e i i s s e e f f f f ) n ) n a a d d e e e e i i

l l a a d d ) ) n n d d ef 8.3]. 2 S C O RROSIO N FAILURE 29 CHAPTER EIGHT CHAPTER M Corrosion Photo of Intergranular E Primary and Secondary Cracking from and Secondary Cracking Primary Corrosion Intergranular S b b a a 3 3 3 3 - - - - 8 8 8 8

e e e e r r r r u u u u g g g g i i i i F F F F www.metalimprovement.com . w to the omium ack anular on gr osion to follo andom eased such that granular corrosion. granular to sensitization. No The r prior ough the grain boundaries. ough the grain ecision Mechanics; Warsaw, Poland, 1999 Poland, Warsaw, ecision Mechanics; r shows a primary crack as the a primary crack shows is a scanning electr ea and a secondary cr esistance is decr A B A B ecipitation. 8-3A and 8-3B, http://corrosion.ksc.nasa.gov/html/stresscor.htm, May 2001 8-3A and 8-3B, http://corrosion.ksc.nasa.gov/html/stresscor.htm, 3 3 3 3 - - - - y is susceptible to inter es 8 8 8 8

MEDICAL IMPLANTS body components. and worn out damaged in replacing evolve continues to Medical science In and high strength. must be lightweight fasteners) materials (and associated The implant to engineering metals. corrosive body contains fluids that are addition, the human corrosion for combating both metal fatigue and successfully utilized Shot peening has been steel and titanium. of stainless fatigue in alloys e e e e r r r r oscope image of inter osion r Figure 8-2, http://corrosion.ksc.nasa.gov/html/stresscor.htm, May 2001 8-2, http://corrosion.ksc.nasa.gov/html/stresscor.htm, Figure Institute of P Figur u u u u ecipitation of chromium carbides offers no ecipitation of chromium opagating thr Application Case Study Application g g g g i i i i F F F F When shot peening is performed prior corrosion (sensitized). corrosion benefit is experienced when shot peening is performed after the sensitization process. micr 8.1 During the solution annealing process of process During the solution annealing carbides austenitic stainless steels, chromium This boundaries. to existing grain precipitate in the in a depletion of chromium results boundaries. adjacent to the grain regions Corr the allo Significant improvements in intergranular Significant improvements been documented have resistance corrosion with shot peening continuous path for the corr pr sensitization process, the surface grain sensitization process, This provides up. broken boundaries are many new nucleation sites for chr carbide pr darkened ar pr 8.2 on Shot Peening; 7th International Conference Steels, of Austenitic Stainless Cracking Corrosion on Stress Kritzler; Effect of Shot Peening 8.3 1987 Garmisch-Partenkirchen, on Shot Peening; Germany, Conference Third Corrosion, Stress Can Help Prevent Shot Peening Gillespie; Controlled 8.4 ERENCES: REF INTERGRANULAR CORROSION INTERGRANULAR CHAPTER NINE S T C

E EFFECTS OF HEAT Caution should be exercised when parts are F heated after shot peening. The amount of

F compressive stress that is relieved is a function of temperature, time and material. E Figure 9-1 demonstrates the increasing stress

relief effect of increasing temperature on shot peened Inconel 718 [Ref 9.1]. Inconel 718 is T commonly used in high temperature jet engine

A applications.

E Stress relief temperature is a physical property of the material. Figure 9-2 depicts several

H materials and the temperatures at which

residual stresses will begin to relax. Many shot peened fatigue applications operate

& above these lower temperature limits as

fatigue benefits are still realized providing the operating temperature does not approach the Figure 9-1 Residual Stress Patterns in Shot Peened

E Inconel 718 Alloy after 100-Hour Exposure stress relief temperature of the material. to Elevated Temperatures

U The following are examples where shot peening followed by heat treatment is commonly G incorporated into manufacturing:

I • Springs – It is common to perform a post-bake T operation for improvements in spring performance.

A Please see Chapter 5 – Torsional Fatigue. F • Plated Parts – It is

common for shot peening prior to plating. Peening

L is called out for fatigue benefits and resistance to

A hydrogen embrittlement. Please see Chapter 3 – Manufacturing Processes.

M Plating commonly involves a hydrogen bake operation at Figure 9-2 Approximate Temperature at Which 350-400 °F (175-205 °C) for

R Compressive Stresses Begin to Dissipate several hours. E H T

30 www.metalimprovement.com THERMAL FA TIGUE & HEAT EFFECT S 31 CHAPTER NINE CHAPTER wns of the unit. This wns of the unit. tups and shutdo vice and 747 star www.metalimprovement.com ears of ser emaining life of the units. ossil Power Plants; EPRI, CA; Power Alto, ossil 1994 March Palo echnology for F T acking was attributed to y epair atigue cr The cracked locations were machined and shot peened. Subsequent inspections showed that no additional inspections showed machined and shot peened. Subsequent locations were The cracked of service years 9.2]. after five and 150 startup [Ref cycles developed fatigue cracks and shutdown caused concern about the r FEEDWATER HEATERS FEEDWATER heaters used for power feedwater in eight high pressure discovered were thermal fatigue cracks Large and thermal fatigue environment. temperature in both an elevated These units operate generation. is at 480-660 °F (250-350 °C). state operation Steady cause thermal fatigue. Startups and shut downs the water chamber and tubesheet. between heat affected zone in the weld circumferential were The cracks F elding and R W Application Case Study Application 9.1 Report, Manufacturing Engineering; July 1989 Tech Surface Integrity, 9.2 Follow-Up, Relaxation Thermal Stresses and Shot Peening by Plants Repaired Feedwater Gauchet; EDF on French Feedback Thermal fatigue differs from elevated temperature fatigue that is caused by cyclic mechanical stresses at mechanical stresses cyclic fatigue that is caused by temperature elevated from Thermal fatigue differs many parts Often, both occur simultaneously because high temperatures. both temperature experience loads. and cyclic excursions Thermal fatigue refers to metal failures brought on by uneven heating and cooling during cyclic thermal cooling during cyclic heating and uneven on by brought failures to metal refers Thermal fatigue section, the cross throughout thermal gradients induces large and cooling of metal heating loading. Rapid the metal when to yield generated can be stress Enough expansion and contraction. in uneven resulting of the part. cooler section a thicker, by to expand and is resisted one location attempts ERENCES: REF THERMAL FATIGUE THERMAL CHAPTER TEN S N

O PEEN FORMING I Peen forming is the preferred method of forming aerodynamic

T contours into aircraft wingskins. It is a dieless forming process that is performed at room temperature. The process is ideal for A forming wing and empennage panel shapes for even the largest aircraft. It is best suited for forming curvatures where the radii C are within the elastic range of the metal. These are large bend I radii without abrupt changes in contour.

L Residual compressive stress acts to elastically stretch the peened Figure 10-1

P side as shown in . The surface will bend or "arc" towards the peened side. The resulting curvature will force the

P lower surface into a compressive state. Typically aircraft wingskins have large surface area and thin cross sectional A thickness. Therefore, significant forces are generated from the Figure 10-1 Thin Cross Section Before

shot peening residual stress over this large surface area. The thin and After Shot Peening cross section is able to be manipulated into desired contours R when the peen forming is properly engineered and controlled. E A properly engineered peen forming procedure will compensate for varying curvature requirements, varying wingskin thickness, H cutouts, reinforcements and pre-existing distortion. Figure 10-

T 2 demonstrates a wingskin that has multiple contours along its length. The wingskin is positioned on a checking fixture that

O verifies correct contour.

Peen forming is most often performed on a feed through, gantry Figure 10-2 Checking Fixture for Verifying type machine (Figure 10-3). Peen Forming of Wingskin

Peen forming has the following advantages: • No forming dies are required. • Process is performed at room temperature. • Wingskin design changes are easily accomplished by altering the peen forming procedure. There is no expensive modification of dies required. • All forming is accomplished using residual compressive stress. Peen formed parts exhibit increased resistance to flexural bending fatigue and stress corrosion cracking as a result. • Peen formed skins exhibit compressive Figure 10-3 Wingskin Forming Machine stress on top and bottom surfaces.

32 www.metalimprovement.com O THER APPLICATIO NS 33 e e t t s s n n a a e e e e c c . r r r r ) ) 80 ** c c e e 4 4 CHAPTER TEN CHAPTER - - n n P P 0 0 I I 1 1

e e r r n n u u e e g g C i i r r e e R F F e e ( ( P P t t

f f t t A A o o 45 H h h Computer Modeling of Computer Modeling Operation Forming Peen S S 4 4 - - 0 0 1 1

n n e e e e C e e r r e e RC 55 HRC 139 R r r u u P P o o g g

f f i i t t F F e e 23 H 25 H o o B B h h S S l l y C a a i i r r tainless ought condition ** Cast condition e e r t t www.metalimprovement.com a a W tellite 42 HRC 54 HRC 29 Cartridge Brass304 Stainless 50 HRB316L StainlessMn S 243 HVInconel 625 283 HV 175 HRBS CHastalloy 423 HV 300 HV 250 Hastallo 398 HV* 74 18 HRC 500 HV 41 40 HRC 67 122 * M M ection ys have the potential to work harden through cold working. Shot peening through potential to work harden the ys have tion corr aft wing stiffner adjustment cr elding distor tellite tainless steel Hastelloy Aluminum Manganese stainless steels Inconel S S Air W Driveshaft/crankshaft straightening Driveshaft/crankshaft of ring shaped geometry correction Roundness • • • • • • • • • • • • • • • • • • • • •• •• •• •• •• •• •• •• •• •• This can be of particular value to This can be of particular value parts but that cannot be heat treated on the resistance wear require The table illustrates surface. in surface examples of increases with shot peening. hardness The peen forming process avoids the unfavorable tensile residual stresses produced by other straightening by produced stresses residual tensile the unfavorable avoids The peen forming process stresses. residual inducing beneficial compressive methods by Metal Improvement Company (MIC) computer has developed Metal Improvement feasibility studies of that allow modeling techniques takes three-dimensional particularThe program designs. of compound based on the degree engineering data and, of peen the degree illustrates calculates and curvature, It also exportsforming required. to define the numerical data A to obtain the curvatures. peening that is required of these techniques is that MICsignificant advantage can the desired that These techniques insure designers in the early stages of design. wing assist aircraft manufacturing processes met with economically beneficial are curvatures aerodynamic The majority of aircraft in production with aerodynamically in production aircraft of The majority the peen forming employ wingskins alloy formed aluminum process. A number of materials and allo types of materials: for certain surface hardness in of the following substantial increases alloys can produce Shot peening utilizing peen forming techniques can be used to correct unfavorable geometry conditions. unfavorable can be used to correct Shot peening utilizing peen forming techniques locations of parts the shot peening selective the surface loading from This is accomplished by to utilize Some examples are: requirements. the components to to restore stress induced compressive WORK HARDENING WORK CONTOUR CORRECTION CONTOUR CHAPTER TEN 34 O THER APPLICATIO NS ENGINEERED SURFACES PEENTEX Peentex visual comparison. recommendsdecorative samplingseveral finish,MIC finishesfor numerous otherapplicationsforvisualappeal. When selectinga gateway entrances, buildingfacades,decorative ironwork and Shot peeningfinisheshave beenusedtotexture statues,handrails, damage through workhardening. are consistent,repeatable andmore resistant tomechanical isabletoprovidecontrolled process, MIC architectural finishesthat fine glasstolarge steel(andstainlesssteel)balls.Usingacarefully a great variety ofmediatypesandsizes. These mediarange from stocks of different, aestheticallypleasingsurfacefinishes.MIC Controlled shotpeeningalsocanbeusedtodeliver anumber potential surfaceapplicationsachieved through shotpeening: Engineered surfacesare thosethatare textured toenhancesurfaceperformance. The following are plastic part’s surface. making plasticstohidesurfacedefects. The texture onthemoldsurfacewillbecomeamirror image onthe would otherwisebehighlyvisibleinamachinedorground surface.Itiscommontotexture molds usedfor A textured surfaceisabletohidescratches andflawsthat untextured finish(rightside). sm • • • • • • • • • • • • finish (leftsideof S M sealing applications. in desirable "release" properties. moldapplications,atextured surfacehaslessvacuumIn certain effectresulting dir In someinstances,anon-directional textured surfaceisdesired over auni- retention thatare notpresent inasmoothsurface. In someapplications,the"v the "peaks"ofshotpeeningdimples. a non-textur In mostcases,atextured surfacehasalower coefficientof(sliding)frictionthan ectional machined/gr F F i i g g u u r r e e ed surface. This isbecausethesurfacecontactarea isreduced to

1 1 F F 0 0 i i g g - - 5 5 u u r r is ahandrail utilizingachosen e e

1 1 www.metalimprovement.com 0 0 - - 5 5 ound surface. This hasproven effective incertain ) todulltheglare from the alleys" ofthepeeningdimplesofferlubricant F F i i g g u u r r e e

1 1 0 0 - - 5 5 of Peentex After (left)Comparison Before (right)and sm CHAPTER TEN O

Application Case Study T PNEUMATIC CONVEYOR TUBING H

Pneumatic conveyor tubing can be up to 10 inches in

diameter and is usually a stainless or aluminum alloy. E It is used to transport plastic pellets at facilities R consisting of molding companies or various production, blending and distribution sites.

Transported pellets degrade when contact is made A with internal piping surfaces. The velocity of the

pellets results in friction, heat and lost production. P

sm Using a variation on Peentex that produces P directional dimpling, MIC offers a directionally

Figure 10-6 Manufacturing Plant Utilizing L textured surface that significantly reduces the Directionally Textured Pipe

formation of fines, fluff and streamers that can I account for millions of pounds of lost and/or contaminated production each year. Directional shot peening has C been found to be much superior to other internal treatments of the tubing, often is more economical and can

be applied on-site. The directional surface finish has the A Fines Treatment (grams/100,000 lb added benefit of work hardening (when stainless or

conveyed) T aluminum piping is used), extending the life of the Directional Shot Peened 1,629

surface treatment. I Smooth 4,886

Spiral Groove Pipe 6,518 The table shows test results from six different internal O Sandblasted Pipe 7,145 pipe treatments. A lower value of fines per 100,000 lbs

Polyurethane Coated 7,215 conveyed is desirable. The directional shot peening N Medium Scored Pipe 13,887 resulted in one third of the fines of the next closest

finish [Ref 10.1]. S

Application Case Study FOOD INDUSTRY

The cheese/dairy industry has found that uniform dimples provide a surface that can advantageously replace other surface treatments. The textured surface from shot peening often has a lower coefficient of sliding friction that is necessary for cheese release properties on some food contact surfaces. The dimples act as lubricant reservoirs for fat or other substances allowing the cheese product to slide easier through the mold on the peaks of the shot peening dimples.

Testing has shown that shot peened finishes meet or exceed necessary cleanability requirements in terms of microbial counts. This is due to the Figure 10-7 Single Cavity Cheese Mold rounded dimples that do not allow bacteria to collect and reproduce. Sharp impressions left from grit blasting, sand blasting or broken media have proved to be less cleanable and have a much greater tendency for bacteria to collect and reproduce [Ref 10.2]. Both glass beaded and stainless steel media have been used successfully in this application.

Figure 10-7 depicts a single cavity cheese mold. MIC has successfully textured many geometries and sizes of cheese molds.

35 www.metalimprovement.com CHAPTER TEN S EXFOLIATION CORROSION

N A large number of commercial aircraft are over 20 years old. Ultimately, the safety of older aircraft depends on the quality of the maintenance performed. An aged Boeing 737 explosively depressurized at 24,000 feet

O (7300 m) when 18 feet (6 m) of the fuselage skin ripped away. The cause of the failure was corrosion and

I metal fatigue [Ref 10.3].

MIC has developed a process called Search Peeningsm to T locate surface and slightly sub-surface corrosion. Exfoliation

A corrosion is a form of intergranular corrosion that occurs along aluminum grain boundaries. It is characterized by C delamination of thin layers of aluminum with corrosion

I products between the layers. It is commonly found adjacent to fasteners due to galvanic action between dissimilar metals. L

In exfoliation corrosion, the surface bulges outward P as shown in Figure 10-8. In severe cases, the corrosion Figure 10-8 Exfoliation Corrosion

P is subsurface.

A Once corrosion is present repairmen can manually remove it with sanding or other means. Shot peening is

then applied to compensate for lost fatigue strength as a result of material removal. Additional sub surface corrosion will appear as "blisters" exposed from the shot peening process. If additional corrosion is found,

R it is then removed and the Search Peeningsm process repeated until no more "blistering" occurs.

E MIC is capable of performing the Search Peeningsm on site at aircraft repair hangers. Critical areas of the aircraft are masked off by experienced shot peening technicians before beginning the process. H

T POROSITY SEALING Surface porosity has long been a problem that has plagued the casting and powder metal industries.

O Irregularities in the material consistency at the surface may be improved by impacting the surface with shot peening media. By increasing the intensity (impact energy), peening can also be used to identify large, near-surface voids and delaminations.

INTERNAL SURFACES AND BORES When the depth of an internal bore is greater than the diameter of the hole it cannot be effectively shot peened by an external method. An internal shot peening lance or internal shot deflector (ISD) method must be used under closely controlled conditions (Figure 10-9). Holes as small as 0.096 inch (2.4 mm) in jet engine disks have been peened on a production basis using the ISD method. Potential applications for internal shot Figure 10-9 Lance Peening and Internal Shot Deflector Peening peening include: • Tie wire holes • Propeller blades • Hydraulic cylinders • Shafts with lubrication holes • Helicopter spars • Compressor and turbine disk blade slots 36 • Drill pipes www.metalimprovement.com CHAPTER TEN O

MIC developed an intensity T verification technique for small

holes. Figure 10-10 shows the H results of a study to a jet engine

disk comparing the residual stress E on the external surface (peened R with conventional nozzles) to that on internal surfaces of a small bore

peened with internal shot deflector A methods. Using the same shot size

and intensity, the two residual P stress profiles from these P controlled processes were Figure 10-10 Internal Surface Deflector vs External Shot Peening

essentially the same [Ref 10-4]. L I

DUAL (INTENSITY) PEENING C Dual peening (or Dura Peensm) is used to further enhance the fatigue performance from a single shot peen operation. Fatigue life improvements from shot peening typically exceed 300%, 500%, or more. A

When dual peened, (single) shot peen results can often be doubled, tripled or even more. T

The purpose of dual peening is to I improve the compressive stress at the O outermost surface layer. This is where fatigue crack initiation begins. By N further compressing the surface layer, additional fatigue crack resistance is S

Figure 10-12 SEM Photo of Single Peen Surface Finish Figure 10-11 Single Peen vs Dual Peen

imparted to the surface. Figure 10-11 shows approximately 30 ksi of additional compression at the surface when performing dual peening for a chrome silicon spring wire [Ref 10.5].

Dual peening is usually performed by shot peening the same surface a second time with a smaller media at a reduced intensity. The Figure 10-13 SEM Photo of Dual second peening operation is able to hammer down the asperities Peen Surface Finish from the first peening resulting in an improved surface finish. The effect of driving the asperities into the surface results in additional compressive stress at the surface. Figures 10-12 and 10-13 show the surface finishes from the single and dual peen at 30x magnification recorded in the graph shown in Figure 10-11 [Ref 10.5]. 37 www.metalimprovement.com CHAPTER TEN S

N THE C.A.S.E.SM PROCESS The C.A.S.E.sm process consists of shot peening followed by isotropic finishing. The isotropic finishing

O removes the asperities left from shot peening via vibratory polishing techniques while maintaining the

I integrity of the residual compressive layer. The process is performed in a specially formulated chemical solution to reduce processing time making it feasible for high production components. T C.A.S.E.sm was designed for surfaces that require both excellent fatigue strength and surface finish due to A contact loading. C.A.S.E.sm has proven quite effective in improving resistance to pitting and micro-pitting of gears. Many gear designs are limited by pitting fatigue as the critical factor for load considerations. C Shot peening is performed to both the tooth flanks and roots with isotropic finishing being concentrated I on the flanks. Improvements in surface finish allow for contact loading to be distributed over more L surface area reducing contact stress and extending pitting fatigue life.

P Transmission gears utilized in aerospace, automotive and off-highway applications are ideal applications for the C.A.S.E.sm process. They are expected to run for many years under high root bending loads and P tooth flank contact loads. C.A.S.E.sm has proven successful for applications in all these industries.

sm A Figure 10-14 shows a typical C.A.S.E. finish at a 30x

magnification [Ref 10.5]. The as-shot-peened finish would be similar to Figure 10-12. The process is designed to leave some of the

R "valleys" from the peened finish for lubricant retention.

E Surface finishes of 10 micro-inches (Ra) or better are attainable on carburized gears. Figure 10-15 shows a typical roughness profile of

H Figure 10-14 SEM Photo of C.A.S.E.sm a carburized Surface Finish gear after T shot peening and also after the isotropic finishing portion of O C.A.S.E.sm processing. The "peak to valley" of the shot peened finish is ~ 2.9 microns. After isotropic finishing this improves to ~ 0.6 microns. The Rsk following isotropic finishing can approach –1.1 as Figure 10-15 Surface Roughness After Shot Peening it selectively changes asperities to plateaus leaving and After C.A.S.E.SM Finishing the valleys from the shot peening.

ON-SITE SHOT PEENING Large components that have been installed on their foundations or whose size exceed shipping limitations can be shot peened by certified crews with portable equipment. Field crews perform shot peening worldwide to the same quality standards as MIC’s processing centers. Almen strips, proper coverage and certified peening media are utilized as described in Chapter 11 – Quality Control.

38 www.metalimprovement.com CHAPTER TEN O

Examples of portable shot peening projects that have been successfully performed include: T • Welded fabrications (pressure vessels, crusher bodies, ship hulls,

chemical storage tanks, bridges). H • Aircraft overhaul repair and corrosion removal (wing sections, landing gear, other dynamically loaded components). E • Power plant components (heat exchanger tubing, turbine casings,

rotating components, large fans). R • Plastic pellet transfer facilities for directional peening.

• Miscellaneous processing plants (steel mills, paper mills, mining facilities). A

STRAIN PEENING P Strain (or stress) peening offers the ability P to develop additional residual

compressive stress offering more fatigue L crack resistance. Whereas dual peening I offers improvements at the outermost

surface layer, strain peening develops a C greater amount of compressive stress A throughout the compressive layer.

To perform strain peening, a component T

must be physically loaded in the same I direction that it experiences in service O prior to peening. Extension springs must be stretched, compression springs must N be compressed and drive shafts must be pre-torqued. This will offer maximum Figure 10-16 Figure 10-16 Residual Stress Induced By Strain Peening S (residual) compressive stress opposing the direction of (applied) tensile stress created during cyclic loading.

The additional compressive stress is generated by preloading the part within its elastic limit prior to shot peening. When the peening media impacts the surface, the surface layer is yielded further in tension because of the preloading. The additional yielding results in additional compressive stress when the metal’s surface attempts to restore itself.

Figure 10-16 shows the additional compressive stress that is achieved when strain peening 50CrV4 [Ref 10.7]. The graph demonstrates that more residual compression is achieved when more preload is applied. While the increased compression is desired from strain peening, processing costs are higher due to fabrication of fixtures and additional handling to preload components before shot peening.

REFERENCES: 10.1 Paulson; Effective Means for Reducing Formation of Fines and Streamers in Air Conveying Systems, Regional Technical Conference of the Society of Plastics Engineering; 1978, Flo-Tronics Division of Allied Industries; Houston, TX 10.2 Steiner, Maragos, Bradley; Cleanability of Stainless Steel Surfaces With Various Finishes; Dairy, Food, and Environmental Sanitation, April 2000 10.3 Eckersley; The Aging Aircraft Fleet, IMPACT; Metal Improvement Company 10.4 Happ; Shot Peening Bolt Holes in Aircraft Engine Hardware; 2nd International Conference on Shot Peening; Chicago, IL May 1984 10.5 Lanke, Hornbach, Breuer; Optimization of Spring Performance Through Understanding and Application of Residual Stress; Wisconsin Coil Spring Inc., Lambda Research, Inc., Metal Improvement Company; 1999 Spring Manufacturer’s Institute Technical Symposium; Chicago, IL May 1999 10.6 Metallurgical Associates, Inc; Waukesha, WI 1999 10.7 Muhr; Influence of Compressive Stress on Springs Made of Steel Under Cyclic Loads; Steel and Iron, December 1968 39 www.metalimprovement.com CHAPTER ELEVEN S S E

C CONTROLLING THE PROCESS Controlled shot peening is different than most manufacturing processes in that there is no nondestructive

O method to confirm that it has been performed to the proper specification. Techniques such as X-Ray Diffraction require that a part be sacrificed to generate a full compressive depth profile analysis. To ensure

R peening specifications are being met for production lots, the following process controls must be maintained:

P • Media • Coverage • Intensity • Equipment

• • Metal Improvement Company (MIC) currently meets or exceeds the most stringent quality standards E requested by its industrial, automotive and aerospace customers. Based on local industry requirements, our facilities maintain quality system compliance or registration to ISO9001:2000, TS-16949:2002 and/or H AS9100. Further, MIC facilities that support the aerospace community participate in Nadcap’s rigorous

T accreditation program.

MEDIA CONTROL G Figure 11-1 demonstrates N acceptable and

I unacceptable media shapes. Figure 11-2a Damaged Surface from L Broken Shot Media Peening media

L must be Figure 11-1 Media Shapes predominantly O round. When media breaks down from usage, the broken media must be R removed to prevent surface damage upon impact. Figure 11- Figure 11-2b Typical Surface from Proper Media T 2A (100x magnification) demonstrates the potential for surface damage and crack initiation from using broken down media.

N Figure 11-2B (100x magnification) demonstrates what a properly peened surface should look like.

O Peening media must be of uniform diameter. The impact energy imparted by the media is a function of its mass and C velocity. Larger media has more mass and impact energy. If a mixed size batch of media is used for peening, the larger Figure 11-3a High Quality Shot media will drive a deeper residual compressive layer. This Peening Media results in a non-uniform residual compressive layer and will correlate into inconsistent fatigue results. Figure 11-3A shows a batch of media with proper size and shape characteristics. Figure 11-3B shows unacceptable media.

Figure 11-3b Poor Quality Shot Peening Media

40 www.metalimprovement.com CHAPTER ELEVEN C O To properly remove undersized and oversized media, MIC utilizes a screening system. To properly remove broken media, MIC meters the N shot to a spiral separator consisting of inner and outer flights. The system is based on the rolling velocity of spherical media versus T broken media. Shot will arrive via the channel above the cone near

the top of Figure 11-4. The media will fall to the cone and roll down R the inner flight. Spherical media will gain enough velocity to escape to

the outer flight. This media can be reused. Broken down media rolls O very poorly and will stay on the inner flight where it will be discarded. L

INTENSITY CONTROL L

Shot peening intensity is the measure of the energy of the shot stream. I It is one of the essential means of ensuring process repeatability. The Figure 11-4 Spiral Separation N energy of the shot stream is directly related to the compressive stress System for Shot that is imparted into a part. Intensity can be increased by using larger Media Classification G media and/or increasing the velocity of the shot stream. Other

variables to consider are the impingement angle and peening media.

Intensity is measured using Almen strips. An Almen strip consists of a strip of SAE1070 spring steel that is T peened on one side only. The residual compressive stress from the peening will cause the Almen strip to H bend or arc convexly towards the peened side (Figure 11-5). The Almen strip arc height is a function of the energy of the shot stream and is very repeatable. E There are three Almen strip designations that are used depending on the peening application:

• “N” Strip: Thickness = 0.031" (0.79 mm) P • “A” Strip: Thickness = 0.051" (1.29 mm)

• “C” Strip: Thickness = 0.094" (2.39 mm) R

More aggressive shot peening O utilizes thicker Almen strips.

The Almen intensity is the arc C height (as measured by an Almen E gage) followed by the Almen strip

designation. The proper S designation for a 0.012" (0.30 mm) S arc height using the A strip is 0.012A (0.30A). The usable range of an Almen strip is 0.004"-0.024" (0.10-0.61 mm). The next thicker Almen strip should be called out if Figure 11-5 Almen Strip System intensity is above 0.020" (0.51 mm).

The intensity value achieved on an N strip is approximately one-third the value of an A strip. The intensity value achieved on a C strip is approximately three times the value of an A strip (N ~ 1/3A, C ~ 3A).

41 www.metalimprovement.com CHAPTER ELEVEN S Almen strips are mounted to Almen blocks and are

S processed on a scrap part (Figure 11-6) or similar fixture. Almen blocks should be mounted in locations where E verification of impact energy is crucial. Actual intensity is

C verified and recorded prior to processing the first part. This verifies the peening machine is set up and running according

O to the approved, engineered process. After the production lot of parts has been processed, intensity verification is R repeated to insure processing parameters have not Figure 11-6 Almen Strip Mounting Fixture changed. For long production runs, intensity verifications P will be performed throughout the processing as required.

Saturation (Intensity Verification) – Initial verification of a E process development requires the establishment of a saturation curve. Saturation is defined as the earliest point H on the curve where doubling the exposure time produces no

T more than a 10% increase in arc height. The saturation curve

is developed by shot peening a series of Almen strips in fixed machine settings and determining when the doubling occurs. Figure 11-7 G Saturation Curve Figure 11-7 shows that doubling of the time (2T) from the initial exposure time (T) resulted in less than a 10% increase in N Almen arc height. This would mean that the process reaches saturation at time = T. Saturation establishes

I the actual intensity of the shot stream at a given location for a particular machine setup.

L It is important to not confuse saturation with coverage. Coverage is described in the next section and deals with the percentage of surface area covered with shot peening dimples. Saturation is used to verify the time L to establish intensity. Saturation and coverage will not necessarily occur at the same time interval. This is because coverage is determined on the actual part surface which can range from relatively soft to extremely O hard. Saturation is determined using Almen strips that are SAE1070 spring steel hardened to 44-50 HRC. R

T COVERAGE CONTROL Complete coverage of a shot peened surface is crucial in

N performing high quality shot peening. Coverage is the measure of original surface area that has been obliterated by shot

O peening dimples. Coverage should never be less than 100% as fatigue and stress corrosion cracks can develop in the non- Figure 11-8a Complete Shot C peened area that is not encased in residual compressive stress. Peening Coverage The adjacent pictures demonstrate complete and incomplete coverage. (Figures 11-8a and 11-8b)

If coverage is specified as greater than 100% (i.e. 150%, 200%) this means that the processing time to achieve 100% has been increased by that factor. A coverage of 200% time would have twice the shot peening exposure time as 100% coverage. Figure 11-8b Incomplete Shot Peening Coverage

42 www.metalimprovement.com CHAPTER ELEVEN C

®

PEENSCAN (Coverage Verification) – Determination of shot peening coverage can be fairly easy when O softer materials have been peened because the dimples are quite visible. A 10-power (10x) magnifying

glass is more than adequate for these conditions. In many applications determination of coverage is N more difficult. Internal bores, tight radii, extremely hard materials and large surface areas present

additional challenges in determining coverage. T

MIC has developed the PEENSCAN® process using DYESCAN® fluorescent tracer dyes for this reason. R PEENSCAN® is ideal for measuring uniformity and extent of coverage for difficult conditions. The whitish-

green dye is not visible under normal lighting conditions and must be viewed under a UV (black) light. O

The coating can be applied by dipping, brushing or spraying the part under analysis. As the coated L surface is impacted with peening media, the

impacts remove the fluorescent, elastic coating L at a rate proportional to the actual coverage I rate. When the part is viewed again under a

black light non-uniform coverage is visibly N evident. The shot peening process parameters

can then be adjusted until the PEENSCAN® G procedure verifies complete obliteration of the area of concern. T Figure 11-9a through 11-9c demonstrate the Figure 11-9a Figure 11-9b Figure 11-9c

PEENSCAN® concept. The figures are computer PEENSCAN® Partial Complete H simulations of a turbine blade with the green Coating Prior Removal of Removal of to Shot PEENSCAN® PEENSCAN® representing the whitish-green dye (under black Peening Indicating Indicating E light conditions). As the (green) dye is removed Incomplete Complete

from peening impacts, the (blue) base material Coverage Coverage P is exposed indicating complete coverage. R The PEENSCAN® inspection process has been found to be clearly superior to using a 10-power glass. O AUTOMATED SHOT PEENING EQUIPMENT Throughout the world, MIC service centers are equipped with similar types of automated shot peening C equipment. When required, this network allows for efficient, economic and reliable transfer or duplication E of shot peen processing from one location to another. S MIC also offers Computer Monitored Shot Peening (CMSP), which utilizes additional process controls and

records data during the production shot peening of each part. For components designed to incorporate S shot peening for product life enhancement, customers should request adherence to the computer monitored process specification AMS-2432.

43 www.metalimprovement.com CHAPTER ELEVEN S MIC has developed CMSP equipment that has the

S capability to monitor, control and document the following parameters of the peening process: E • Air pressure and shot flow

C (energy) at each nozzle • Wheel speed and shot flow (energy) of each wheel O • Part rotation and/or translation

R • Nozzle reciprocation • Cycle time P These parameters are continuously monitored and

compared to acceptable limits programmed into the

E computer. If an unacceptable deviation is found, the machine will automatically shut down within one second Figure 11-10a Computer Monitored Lance Shot Peening Machine for

H and report the nature and extent of deviation. The Processing Internal Bores machine will not restart processing until machine T parameters have been corrected.

A printout is available upon completion of the CMSP.

G Any process interruptions are noted on the printout. The process is maintained in MIC quality records and

N is available for review. Figure 11-10a is a CMSP machine used for peening internal bores of aerospace I components. Figure 11-10b is a multi-nozzle CMSP

L machine. Both figures show the central processing unit on the side of the machine. L Figure 11-10b Multi-Nozzle Computer Monitored Shot Peening Machine O

R Application Case Study

T CMSP INCREASES TURBINE ENGINE SERVICE LIFE

CMSP registered significant interest when the FAA allowed a rating increase on a turbine engine from 700 N to 1,500 cycles between overhauls. This increase made it possible for the engine, which was designed for military use, to enter the commercial market. O

There was minimal space for design modifications so the engine manufacturer chose to use shot C peening to improve life limited turbine disks and cooling plates. CMSP ensured that the peening parameters of the critical components were documented and repeated precisely [Ref 11.1].

44 www.metalimprovement.com CHAPTER ELEVEN C

SPECIFYING SHOT PEENING O Figure 11-11 shows a splined shaft (shaded)

installed with two bearings supporting the shaft N inside an assembly. The outboard spline and

adjacent radius would be likely fatigue failure T locations from bending and/or torsional fatigue. In R this case, engineering would specify shot peening

(of the shaft) on the drawing as follows: O • Area "A": Shot peen

• Area "B": Overspray allowed L • Area "C": Masking required Figure 11-11 Assembly Drawing of Spline Shaft L Requiring Shot Peening The details on the print should read: I • Shot peen splined areas and adjacent radius using MI-110H shot; 0.006"-0.009" A intensity. N • Minimum 100% coverage in splined areas ® to be verified by PEENSCAN . G • Overspray acceptable on adjacent larger diameter.

• Mask both bearing surfaces and center shaft area.

• Shot peening per AMS-S-13165. T It is important to note that if Non-Destructive Testing is required, NDT should always be performed before H shot peening. The peening process will obliterate or close up small surface cracks skewing NDT results.

MIC has over five decades of experience engineering shot peening callouts. MIC specializes in the proper E selection of shot size and intensity parameters for fatigue and/or corrosion resistant applications. Our

worldwide service center locations are listed at the back of this manual. P

REFERENCES: R 11.1 Internal Metal Improvement Company Memo O C E S S

45 www.metalimprovement.com CHAPTER TWELVE S E C I PEENSTRESSSM – RESIDUAL STRESS MODELING

V When engineering a proper callout for shot peening, Metal Improvement Company (MIC) considers many factors. One of the most important considerations is predicting the residual compressive stress profile after R shot peening. The following factors influence the resultant residual stress profile: E • Material, heat treatment and hardness

S • Part geometry • Shot (size, material, hardness and intensity) • Single peen, dual peen or strain peen &

In addition to MIC’s over 50 years of experience in selecting proper shot peening parameters, internally

sm S developed Peenstress software is utilized to optimize shot peening results.

E Peenstresssm has an extensive database of materials and heat

I treatment conditions for the user to choose from. Once the appropriate material (and heat treat condition) is selected, T the user then selects shot peening parameters consisting of: I • Shot size L • Shot material and hardness I • Shot intensity

B As shown in Figure 12-1, Peenstresssm graphically plots the

A theoretical curve based on the user inputs. By altering shot peening parameters the user can optimize the shot peening P callout to achieve desired results. Peenstresssm contains a

A large database of x-ray diffraction data that can be called up to verify the theoretical curves. The program is especially C useful when shot peening thin cross sections to determine

Figure 12-1 Typical Peenstresssm anticipated depth of compression to minimize the possibility Residual Stress Profile L of distortion. A

N LASER PEENING MIC developed the laser peening process in conjunction

O with Lawrence Livermore National Laboratory. The process

I uses a unique Nd:glass, high output, high repetition laser in conjunction with precision robotic manipulation of the part T to be laser peened. I During the laser peening process, the laser is fired at the

D surface of a metal part to generate pressure pulses of one million pounds per square inch, which send shock waves

D through the part. Multiple firings of the laser in a pre-defined Figure 12-2 Laser Peening surface pattern will impart a layer of compressive stress on A the surface that is four times deeper than that attainable from conventional peening treatments.

46 www.metalimprovement.com CHAPTER TWELVE A

The primary benefit of laser peening is a very D deep compressive layer with minimal cold working, which increases the component’s D resistance to failure mechanisms such as I fatigue, fretting fatigue and stress corrosion. T Compressive stress layer depths of up to

0.040 inches (1.0 mm) on carburized steels I

and 0.100 inches (2.54 mm) on aluminum O and titanium alloys have been achieved. A

secondary benefit is that thermal relaxation Figure 12-3 Laser Peening of Al 6061-T6 N of the residual stresses of a laser peened

surface is less than a shot peened surface due to the reduced cold work that is involved with the A process. (Ref 12.1). L

The benefits of an exceptionally deep residual compressive layer are shown in Figure 12-3. The S-N

curve shows fatigue test results of a 6061-T6 aluminum. The testing consisted of unpeened, C mechanically shot peened and laser peened specimens (Ref 12.2). A MIC currently operates laser peening facilities in the United States and United Kingdom, and offers a mobile laser peening system in order to bring this unique technology directly to customers on site. P A

COATING SERVICES B

Our E/M Coating Services Division has over 40 years of experience in applying critical tolerance coatings I

and is a pioneer in the development and application of solid film lubricant (SFL) coatings. These coatings L are effective in a broad range of applications, whenever conventional wet lubricants provide insufficient I protection due to high temperatures, extreme loads, corrosion, wear, chemical corrosion and other adverse operating conditions. T

E/M Coating Services can assist you in selecting the right coating to meet your design challenge, lower I

the cost of ownership or enhance the performance and longevity of your products. Selection of the proper E

coating can facilitate the use of less expensive metals, improve part wear life and reduce maintenance costs. S

Among the different categories of coatings E/M Coating Services applies are:

• Solid Film Lubricants – that protect against & adverse operating conditions such as high temperatures, extreme loads, corrosion, wear, galling, seizing, friction, abrasion and S chemical corrosion. E • Impingement Coatings – that provide an ultra

thin, firmly adherent solid film lubricant. R • Conformal Coatings – for sealing more delicate objects — such as medical devices, V satellite components and circuit assemblies

— that operate in hostile environments. I

• Shielding Coatings – that protect electronic C devices from Electro-Magnetic Interference Figure 12-4 Coating Services

(EMI), Radio Frequency Interference (RFI) E and Electro-Static Discharge (ESD). S E/M Coating Services applies all coatings using controlled processes to achieve the highest levels of quality and consistency. Coating engineers and technical service personnel also can help customers determine the right coating process for their application. 47 www.metalimprovement.com CHAPTER TWELVE S

E HEAT TREATING Thermal processing relieves stresses within fabricated metal parts and improves their overall strength,

C ductility and hardness. I MIC specializes in the thermal processing of metal components used in a wide range of industries. Among the

V numerous thermal processes available through our network of facilities are vacuum heat treating, induction hardening, isothermal annealing and atmosphere normalizing. R MIC’s heat treating facilities are located in the Midwest and Eastern U.S. and have capabilities and quality E approvals specific to their local customer base. We have the expertise and equipment to handle demanding S project requirements and materials that include, but are not limited to: • Aluminum • Cast irons

& • Titanium • Tool steels

• Carbon steels • Corrosion resistant steels

S • Alloy steels Each of our facilities uses programmable controllers that set E temperatures and cycle times and monitor the heat treating I process to assure a homogenous correctly treated product.

T Our attention to detail includes an on-going engineering

I review of the process that assures you the most economical Figure 12-5 Heat Treating L approach with the highest standards of quality and delivery. By involving us at the planning stage of your project, we can I use our experience to recommend the optimal alloy and thermal process to meet your design requirements. B A VALVE REEDS – MANUFACTURING P MIC manufactures valve reeds for use in compressors, pump applications and combustion engines. Valve

A reeds are precision stampings that operate in demanding environments. Tight manufacturing tolerances are required to achieve flatness and offer resistance to flexing fatigue and high contact loads. C MIC employs Stress-Litesm finishing techniques that are

designed to provide specific surface finish and edge rounding L requirements for durability. For very demanding applications

sm

A Stress-Lite can be combined with shot peening. The following are results comparing valve reed performance

sm

N using Stress-Lite with and without shot peening [Ref 12.3]: • As Stamped: 47,000 cycles O • Stress-Lite: 62,000

I • Stress-Lite and Shot Peen: 194,000

T Figure 12-6 depicts some of the many complex shapes of Figure 12-6 Valve Reeds

I valve reeds that MIC is capable of manufacturing. D REFERENCES: 12.1 Prevey, Hombach, and Mason; Thermal Residual Stress Relaxation and Distortion in Surface Enhanced Gas Turbine

D Engine Components, Proceedings of ASM/TMS Materials Week, September 1997, Indianapolis, IN 12.2 Thakkar; Tower Automotive fatigue study 1999

A 12.3 Ferrelli, Eckersley; Using Shot Peening to Multiply the Life of Compressor Components; 1992 International Compressor Engineering Conference, Purdue University

48 www.metalimprovement.com NOTES

49 www.metalimprovement.com APPENDIX S E

L Approximate Conversion from Hardness to Tensile Strength of Steels B Rockwell Brinell Vickers Tensile Tensile Hardness Hardness Hardness Strength Strength A HRC BHN HV ksi MPa

T 62 688 746 361 2489 61 668 720 349 2406

60 649 697 337 2324 59 631 674 326 2248

N 58 613 653 315 2172 57 595 633 305 2103

O 56 577 613 295 2034 55 559 595 286 1972 I 54 542 577 277 1910

S 53 525 560 269 1855 52 509 544 261 1800

R 51 494 528 253 1744 50 480 513 245 1689

E 49 467 498 238 1641 48 455 484 231 1593 V 47 444 471 224 1544 46 433 458 217 1496

N 45 422 446 211 1455 44 411 434 206 1420 43 401 423 201 1386 O 42 391 412 196 1351 41 381 402 191 1317 C 40 371 392 186 1282 39 361 382 181 1248 38 352 372 176 1214 37 343 363 171 1179 36 334 354 166 1145 35 325 345 162 1117 34 317 336 158 1089 33 309 327 154 1062 32 301 318 150 1034 31 293 310 146 1007 30 286 302 142 979 29 279 294 138 952 28 272 286 134 924 27 265 279 130 896 26 259 272 127 876 25 253 266 124 855 24 247 260 121 834 23 241 254 118 814 22 235 248 116 800 21 229 243 113 779 20 223 238 111 765

50 www.metalimprovement.comwww.metalimprovement.com APPENDIX C O

Common Conversions Associated with Shot Peening N Metric (SI) to English (US Customary) English to Metric Length 1 mm = 0.0394 in 1 in = 25.4 mm V 1 m = 3.281 ft = 39.37 in 1 ft = 0.3048 m = 304.8 mm E Area 1 mm2 = 1.550 x 10–3 in2 1 in2 = 645.2 mm2 2 2 2 –3 2

1 m = 10.76 ft 1 ft = 92.90 x 10 m R Mass 1 kg = 2.205 lbm 1 lbm = 0.454 kg

Force 1 kN = 224.8 lbf 1 lbf = 4.448 N S Stress 1 MPa = 0.145 ksi = 145 lbf/in2 1 ksi = 6.895 MPa I O Miscellaneous Terms & Constants

lbm = lb (mass) lbf = lb (force) N k = kilo = 103 M = mega = 106 9 –6 G = giga = 10 µ = micro = 10 1 Pa = 1 N/m2 lbf/in2 = psi T ksi = 1000 psi µm = micron = 1/1000 mm A

Young’s Modulus (E) for Steel = 29 x 106 lbf/in2 = 200 GPa B Acceleration of Gravity = 32.17 ft/s2 = 9.81 m/s2 L Density of Steel = 0.283 lbm/in3 = 7.832 x 10–6 kg/mm3 E S

51 www.metalimprovement.com APPENDIX S

T TECHNICAL ARTICLE REPRINTS Metal Improvement Company has on file a large collection of technical resources pertaining to metal N fatigue, corrosion and shot peening. Many of the reprints that are available are listed below. Please I contact your local service center or visit our website www.metalimprovement.com for other specific information on shot peening and our other metal treatment services. R 1. “Shot Peening of Engine Components”; J. L. Wandell, Metal Improvement Company, Paper Nº 97 ICE-45,

P ASME 1997. 2. “The Application of Microstructural Fracture Mechanics to Various Metal Surface States”; K. J. Miller and E R. Akid, University of Sheffield, UK. 3. “Development of a Fracture Mechanics Methodology to Assess the Competing Mechanisms of Beneficial R Residual Stress and Detrimental Plastic Strain Due to Shot Peening”; M. K. Tufft, General Electric

Company, International Conference on Shot Peening 6, 1996. 4. “The Significance of Almen Intensity for the Generation of Shot Peening Residual Stresses”; R. Hertzog, W. E Zinn, B. Scholtes, Braunschweig University and H. Wohlfahrt, University GH Kassel, Germany.

L 5. “Computer Monitored Shot Peening: AMEC Writes New AMS Specification”; Impact: Review of Shot Peening Technology, Metal Improvement Company, 1988.

C 6. “Three Dimensional Dynamic Finite Element Analysis of Shot-Peening Induced Residual Stresses”; S. A. Meguid, G. Shagal and J. C. Stranart, University of Toronto, Canada, and J. Daly, Metal Improvement I Company.

T 7. “Instrumented Single Particle Impact Tests Using Production Shot: The Role of Velocity, Incidence Angle and Shot Size on Impact Response, Induced Plastic Strain and Life Behavior”; M. K. Tufft, GE Aircraft Engines, Cincinnati, OH., 1996. R 8. “Predicting of the Residual Stress Field Created by Internal Peening of Nickel-Based Alloy Tubes”; N. Hamdane, G. Inglebert and L. Castex, Ecole Nationale Supérieure d’Arts et Métiers, France. A

9. “Three Innovations Advance the Science of Shot Peening”; J. S. Eckersley and T. J. Meister, Metal Improvement Company, Technical Paper, AGMA, 1997.

L 10. “Tech Report: Surface Integrity”; Manufacturing Engineering, 1989. 11. “Optimization of Spring Performance Through Understanding and Application of Residual Stresses”; D. A Hornbach, Lambda Research Inc., E. Lanke, Wisconsin Coil Spring Inc., D. Breuer, Metal Improvement Company. C 12. “Plastically Deformed Depth in Shot Peened Magnesium Alloys”; W. T. Ebihara, U. S. Army, N. F. Fiore and

I M. A. Angelini, University of Notre Dame. 13. “Improving the Fatigue Crack Resistance of 2024-T351 Aluminium Alloy by Shot Peening”; E. R. del Rios, University of Sheffield, and M. Trooll and A. Levers, British Aerospace Airbus, England. N 14. “Fatigue Crack Initiation and Propagation on Shot-Peened Surfaces in a 316 Stainless Steel”; E. R. del Rios, A. Walley and M. T. Milan, University of Sheffield, England, and G. Hammersley, Metal Improvement H Company. 15. “Characterization of the Defect Depth Profile of Shot Peened Steels by Transmission Electron C Microscopy”; U. Martin, H. Oettel, Freiberg University of Mining and Technology, and I. Altenberger, B. Scholtes and K. Kramer, University Gh Kassel, Germany. E 16. “Essais Turbomeca Relatifs au Grenaillage de l’Alliage Base Titane TA6V”; A. Bertoli, Turbomeca, France.

T 17. “Effect of Microstrains and Particle Size on the Fatigue Properties of Steel”; W. P. Evans and J. F. Millan, The Shot Peener, Vol. II, Issue 4. 18. “Overcoming Detrimental Residual Stresses in Titanium by the Shot Peening Process”; T. J. Meister, Metal Improvement Company. 19. “The Effect of Shot Peening on Calculated Hydrogen Surface Coverage of AISI 4130 Steel”; I. Chattoraj, National Metallurgical Laboratory, Jamshedspur, India, and B. E. Wilde, The Ohio State University, Columbus, OH. Pergamon Press plc, 1992. 20. “Effect of Shot Peening on Delayed Fracture of Carburized Steel”; N. Hasegawa, Gifu University, and Y. Watanabe, Toyo Seiko Co. Ltd., Japan. 52 www.metalimprovement.com APPENDIX T E

21. “New Studies May Help an Old Problem. Shot Peening: an Answer to Hydrogen Embrittlement?”; J. L. Wandell, Metal Improvement Company. C 22. “The Effects of Shot Peening on the Fatigue Behaviour of the Ni-base Single Crystal Superalloy CMSX- 4”; J. Hou and W. Wei, University of Twente, Netherlands. H 23. “Effect of Shot Peening Parameters on Fatigue Influencing Factors”; A. Niku-Lari, IITT, France. N 24. “Weld Fatigue Life Improvement Techniques” (Book); Ship Structure Committee, Robert C. North, Rear Admiral, U. S. Coast Guard, Chairman. I 25. “Controlled Shot Peening as a Pre-Treatment of Electroless Nickel Plating”; G. Nickel, Metal

Improvement Company, Electroless Nickel ’95. C 26. “Effects of Surface Condition on the Bending Strength of Carburized Gear Teeth”; K. Inoue and M.

Kato, Tohoku University, Japan, S. Lyu, Chonbuk National University, Republic of Korea, M. Onishi and A K. Shimoda, Toyota Motor Corporation, Japan, 1994 International Gearing Conference.

27. “Aircraft Applications for the Controlled Shot Peening Process”; R. Kleppe, MIC, Airframe/Engine L Maintenance and Repair Conference and Exposition, Canada, 1997.

28. “Prediction of the Improvement in Fatigue Life of Weld Joints Due to Grinding, TIG Dressing, Weld Shape Control and Shot Peening”; P. J. Haagensen, The Norwegian Institute of Technology, A. Drigen, T A Slind and J. Orjaseter, SINTEF, Norway.

29. “Increasing Fatigue Strength of Weld Repaired Rotating Elements”; W. Welsch, Metal Improvement R Company. T 30. “B 737 Horizontal Stabilizer Modification and Repair”; Alan McGreal, British Airways and Roger Thompson, Metal Improvement Company. I 31. “Residual Stress Characterization of Welds Using X-Ray Diffraction Techniques”; J. A. Pinault and M. E. Brauss, Proto Manufacturing Ltd., Canada and J. S. Eckersley, Metal Improvement Company. C 32. “Towards a Better Fatigue Strength of Welded Structures”; A. Bignonnet, Fatigue Design, Mechanical Engineering Publications, London, England. L

33. “ABB Bogie Shot-Peening Demonstration: Determination of Residual Stresses in a Weld With and E Without Shot-Peening”; P. S. Whitehead, Stresscraft Limited, England.

34. “The Application of Controlled Shot Peening as a Means of Improving the Fatigue Life of

Intramedullary Nails Used in the Fixation of Tibia Fractures”; M. D. Schafer, State University of New R York at Buffalo.

35. “Improvement in the Fatigue Life of Titanium Alloys”; L. Wagner and J. K. Gregory, Advanced Materials E and Processes, 1997. P 36. “Effet du Grenaillage sur la Tenue en Fatigue Vibratoire du TA6V”; J. Y. Guedou, S.N.E.C.M.A., France.

37. “Fretting Fatigue and Shot Peening”; A. Bignonnet et al., International Conference of Fretting Fatigue, R Sheffield, England, 1993.

38. “Influence of Shot Peening on the Fatigue of Sintered Steels under Constant and Variable Amplitude I Loading”; C. M. Sonsino and M. Koch, Darmstadt, Germany. N 39. “Evaluation of the Role of Shot Peening and Aging Treatments on Residual Stresses and Fatigue Life of an Aluminum Alloy”; H. Allison, Virginia Polytechnic Institute, VA. T 40. “A Survey of Surface Treatments to Improve Fretting Fatigue Resistance of Ti-6Al-4V”; I. Xue, A. K. Koul, W. Wallace and M. Islam, National Research Council, and M. Bibby, Carlton University, Canada, 1995. S 41. “Gearing Up For Higher Loads”; Impact - Review of Shot Peening Technology, Metal Improvement Company. 42. “Belleville Disk Springs”; Product News, Power Transmission Design, 1996. 43. “Improvement in Surface Fatigue Life of Hardened Gears by High-Intensity Shot Peening”; D. P. Townsend, Lewis Research Center, NASA, Sixth International Power Transmission Conference, 1992. 44. “Review of Canadian Aeronautical Fatigue Work 1993-1995”; D. L. Simpson, Institute for Aerospace Research, National Research Council of Canada.

53 www.metalimprovement.com APPENDIX S

T 45. “A Review of Australian and New Zealand Investigations on Aeronautical Fatigue During the Period of April 1993 to March 1995”; J. M. Grandage and G. S. Jost, editors, Department of Defense, Australia and New Zealand. N 46. “Shot Peening to Increase Fatigue Life and Retard Stress Corrosion Cracking”; P. Dixon Jr., Materials I Week, American Society for Metals, 1993. 47. “The Effect of Hole Drilling on Fatigue and Residual Stress Properties of Shot-Peened Aluminum Panels”; R J. Chadhuri, B. S. Donley, V. Gondhalekar, and K. M. Patni, Journal of Materials Engineering and Performance, 1994. P 48. “Shot Peening, a Solution to Vibration Fatigue”; J. L. Wandell, Metal Improvement Company, 19th

E Annual Meeting of The Vibration Institute, USA, 1995. 49. “GE Dovetail Stress Corrosion Cracking Experience and Repair”; C. DeCesare, S. Koenders, D. Lessard

R and J. Nolan, General Electric Company, Schenectady, New York.

50. “Arresting Corrosion Cracks in Steam Turbine Rotors”; R. Chetwynd, Southern California Edison. 51. “Rotor Dovetail Shot Peening”; A. Morson, Turbine Technology Department, General Electric Company, E Schenectady, NY.

L 52. “Stress Corrosion Cracking: Prevention and Cure”; Impact - Review of Shot Peening Technology, Metal Improvement Company, 1989.

C 53. “The Application for Controlled Shot Peening for the Prevention of Stress Corrosion Cracking (SCC)”; J. Daly, Metal Improvement Company, NACE Above Ground Storage Tank Conference, 1996. I 54. “The Use of Shot Peening to Delay Stress Corrosion Crack Initiation on Austenitic 8Mn8Ni4Cr Generator

T End Ring Steel”; G. Wigmore and L. Miles, Central Electricity Generating Board, Bristol, England. 55. “Steam Generator Shot Peening”; B&W Nuclear Service Company, Presentation for Public Service

R Electric & Gas Company, 1991. 56. “The Prevention of Stress Corrosion Cracking by the Application of Controlled Shot Peening”; A P. O’Hara, Metal Improvement Company.

57. “Designing Components Made of High Strength Steel to Resist Stress Corrosion Cracking Through the Application of Controlled Shot Peening”; M. D. Shafer, Department of Mechanical Engineering, Buffalo, L NY, The Shot Peener, Volume 9, Issue 6. 58. “Shot Peening for the Prevention of Stress Corrosion and Fatigue Cracking of Heat Exchangers and A Feedwater Heaters”; C. P. Diepart, Metal Improvement Company. 59. “Shot Peening: a Prevention to Stress Corrosion Cracking – a Case Study”; S. Clare and J. Wolstenholme C 60. “Thermal Residual Stress Relaxation and Distortion in Surface Enhanced Gas Turbine Engine I Components”; P. Prevey, D. Hornbach and P. Mason, Lambda Research, AMS Materials Week, 1997. 61. “EDF Feedback Shot-Peening on Feedwater Plants Working to 360 ºC – Prediction Correlation and N Follow-up of Thermal Stresses Relaxation”; J. P. Gauchet, EDF, J. Barrallier, ENSAM, Y. LeGuernic, Metal Improvement Company, France.

H 62. “EDF Feedback on French Feedwater Plants Repaired by Shot Peening and Thermal Stresses Relaxation Follow-up”; J. P. Gauchet and C. Reversat, EDF, Y. LeGuernic, Metal Improvement Company, J. L. LeBrun, LM# URA CNRS 1219, L. Castex and L. Barrallier, ENSAM, France. C 63. “Effect of Small Artificial Defects and Shot Peening on the Fatigue Strength of Ti-Al-4V Alloys at Elevated

E Temperatures”; Y. Kato, S. Takafuji and N. Hasegawa, Gifu University, Japan. 64. “Investigation on the Effect of Shot Peening on the Elevated Temperature Fatigue Behavior of

T Superalloy”; C. Yaoming and W. Renzhi, Institute of Aeronautical Materials, Beijing, China. 65. “Effect of Shot Peening and Post-Peening Heat Treatments on the Microstructure, the Residual Stresses and Deuterium Uptake Resistance of Zr-2.5Nb Pressure Tube Material”; K. F. Amouzouvi, et al, AECL Research, Canada. 66. “Transmission Components, Gears – CASE Finishing”; Metal Improvement Company. 67. “Steam Generator Peening Techniques”; G. M. Taylor, Nuclear News, 1987. 68. “Shot Peening Versus Laser Shock Processing”; G. Banas, F.V. Lawrence Jr., University of Illinois, IL.

54 www.metalimprovement.com APPENDIX T E

69. “Lasers Apply Shock for Strength”; J. Daly, Metal Improvement Company, The Update, Page 6, Ballistic Missile Defense Organization, 1997. C 70. “Surface Modifications by Means of Laser Melting Combined with Shot Peening: a Novel Approach”; J. Noordhuis and J. TH. M. De Hosson, Acta Metall Mater Vol. 40, Pergamon Press, UK. H 71. “Laser Shock Processing of Aluminium Alloys. Application to High Cycle Fatigue Behaviour”; P. Peyre, R. Fabro, P. Merrien, H. P. Lieurade, Materials Science and Engineering, Elsevier Science S.A. 1996, UK. N 72. “Laser Peening of Metals – Enabling Laser Technology”; C. B. Dane and L. A. Hackel, Lawrence Livermore

National Laboratory, and J. Daly and J. Harrison, Metal Improvement Company. I

73. “Laser Induced Shock Waves as Surface Treatment of 7075-T7351 Aluminium Alloy”; P. Peyre, P. Merrien, H. P. C Lieurade, and R. Fabbro, Surface Engineering, 1995.

74. “Effect of Laser Surface Hardening on Permeability of Hydrogen Through 1045 Steel”; H. Skrzypek, Surface A Engineering, 1996.

75. “Stop Heat from Cracking Brake Drums”; Managers Digest, Construction Equipment, 1995. L

76. “The Ultra-Precision Flappers… Shot Peening of Very Thin Parts”; Valve Division, Impact – a Review of Shot Peening Technology, Metal Improvement Company, 1994. A 77. “The Aging Aircraft Fleet: Shot Peening Plays a Major Role in the Rejuvenation Process”; Impact – Review of Shot Peening Technology, Metal Improvement Company. R 78. “Sterilization and Sanitation of Polished and Shot-Peened Stainless-Steel Surfaces”; D. J. N. Hossack and F. J.

Hooker, Huntingdon Research Centre, Ltd., England. T 79. “Shot Peening Parameters Selection Assisted by Peenstress Software”; Y. LeGuernic, Metal Improvement

Company. I

80. “Process Controls: the Key to Reliability of Shot Peening”; J. Mogul and C. P. Diepart, Metal Improvement C Company, Industrial Heating, 1995.

81. “Innovations in Controlled Shot Peening”; J. L. Wandell, Metal Improvement Company, Springs, 1998. L

82. “Computer Monitored Shot Peening, an Update”; J. R. Harrison, Metal Improvement Company, 1996 USAF E Aircraft Structural Integrity Conference.

83. “Shot Peening of Aircraft Components – NAVAIR Instruction 4870.2”; Naval Air System Command, Department of the Navy, USA. R 84. “A Review of Computer-Enhanced Shot Peening”; J. Daly and J. Mogul, Metal Improvement Company, The

Joint Europe-USA Seminar on Shot Peening, USA, 1992. E 85. “Shot Peening – Process Controls, the Key to Reliability”; J. Mogul and C. P. Diepart, Metal Improvement Company. P

86. “The Implementation of SPC for the Shot Peening Process”; Page 15, Quality Breakthrough, a Publication for R Boeing Suppliers, 1993.

87. “Peenstress Software Selects Shot Peening Parameters”; Y. LeGuernic and J. S. Eckersley, Metal Improvement I Company. N 88. “The Development of New Type Almen Strip for Measurement of Peening Intensity on Hard Shot Peening”; Y. Watanabe et al, Gifu University, Japan. 89. “Interactive Shot Peening Control”; D. Kirk, International Conference on Shot Peening 5, 1993. T

90. “Shot Peening: Techniques and Applications”; (Book) K. J. Marsh, Editor, Engineering Materials Advisory S Services Ltd., England. 91. “Evaluation of Welding Residual Stress Levels Through Shot Peening and Heat Treating”; M. Molzen, Metal Improvement Company, D. Hornbach, Lambda Research, Inc. 92. “Effect of Shot Peening of Stress Corrosion Cracking on Austenitic Stainless Steel”; J. Kritzler, Metal Improvement Company. 93. “An Analytical Comparison of Atmosphere and Vacuum Carburizing Using Residual Stress and Microhardness Measurements”; D. Breuer, Metal Improvement Company, D. Herring, The Herring Group, Inc., G. Lindell, Twin Disc, Inc., B. Matlock, TEC, Inc.

55 www.metalimprovement.com APPENDIX

56 TECHNICAL ARTICLE REPRINTS 117. 116. “Atmosphere vs. Vacuum Carburizing,Heat Treating Progress”, plusPresentation andSAE forASM 115. “Improving GearPerformance by EnhancingtheFatigue ofSteel”; Properties BritishGearAssociation 114. 106. 113. “Pitting Resistance Improvement Through ShotPeening –Renault Experience”; LeGuernic, Y., Jan.2001. 112. “Impactofisotropic superfinishing oncontactandbendingfatigueofcarburized Steel”; Winkelmann, L., 111. 110. “Residual Stress Stability andAlternatingBendingStrength 4140afterShotPeening and ofAISI 109. “Automated SurfaceandSubsurfaceResidual Stress Measurement for QualityAssurance ofShot 108. “X-Ray Diffraction DataonShotPeened Components”;Breuer, D.,3/6/00. 107. 105. “Controlled ShotPeening: Improvements inFatigue LifeandFatigue Characteristics ofPowder 104. “Repair andLifeAssessmentofCriticalFatigue DamagedAluminumAlloy Structure UsingaPeening 103. 102. “BendingFatigue ofCarburized Steels”; Wise, J.,Matlock,D.andKrauss, G.,Heat Treating Progress, 101. EffectofShotPeening on “The the Resistance ofZeron 100toHydrogen Embrittlement”;Francis, R., 100. “MaintenanceofHigh-Strength Alloy Steel Components”;Dickerson,C.andGarber, R.,Aero Magazine, 99. “Optimized Carburized Steel Fatigue Performance asAssessedwithGearandModifiedBrugger Fatigue 98. “Fatigue Crack Growth in Residual Stress Fields”; Wang, J.,Schneider, G.and Vertergaard, L.,American 97. “ShotPeening ofFillet Welded ClosedandOpenFaced Turbo ComImpellers”;Dresser-Rand Turbo 96. “Strength from ShotPeening SpecificationSTD Gained ofCaseHardened3997,1999-2002. Gears”;SAA 95. 9 1.“Development ofShotPeening for Wing Integral SkinforContinental BusinessJets”; Yamada, T., Ikeda, 118. 1.“Cracking Down onCracking(Environmental Cracking ofCarbonSteel)”; Shargay, C.,Chemical 119. .“Strengthening ofCeramics by ShotPeening”; Pfeiffer, W. &Frey, T.,Materials ScienceForum, 2002. 4. Fine ShotPeening Technology”; Yamada, Y., etal, SAE Tech Paper 2002-02-0834, 2001. “Impr Nov. 2002. “Shot P Metallurgy; Lindell,G.,Herring,D.,Breuer, D.andMatlock,B.,Nov. 2001. Oct.2002. Final Report, “F M., E “Surface F Michaud, M.,Sroka, G.andSwiglo, A.,SAE Technical Paper 2002-01-1391,March 2002. Benefit ofHighLoad Gearing”;Breuer, Sept.2003. D.,ASME, “Ulilization ofPowdered MetalandShotPeening Residual Stress toMaximize CostandPerformance Successive Annealing”;Menig,R.,Schulze, V. and Vohringer, O.,MaterialsScienceForum, 2002. Peening”; Diffraction Notes,Spring, 2001. Belassel, M.,Brauss, M.,Pineault,J.andBerkley, S.,MaterialsScienceForum, 2002. S “F Metallurgical Components”;Gray, K. Conference, 2001. Rework Method”;Barter, S.,Molent,L.,Sharp, ASIP K.andClark,G.,USAF “Inspecting Welds toImprove Fatigue Life”; Anderson, T., Practical Welding Today, June2002. August 2001. #TN 1356,July2000. April 2003. Tests”; Spice,J.andMatlock,D.,SAE#2002-01-1003. Helicopter SocietyConference, May2001. Products Spec.015-008,Draft 4/01. M., Ohta, T., Takahashi, T. andSugimoto,S.,MitsubishiHeavyIndustries Ltd.,2002. Processing, May 2000. tr atigue DamageMechanismandS atigue LifeCur ehl, R.,2001. v o ans, H.andSnidle,R.,N v een Forming ofNew_-Dome Tank 5”; Wustefeld, F., SegmentsforARIANE MetalFinishingNews, ement ofFatigue Strength ofNitridedHigh-Strength Valve Springsby ApplicationofaNewSuper atigue Lives ofCase-Carburized Gears withanImproved Surface Finish”; Krantz, T., Alauou, ves Comparinga Wrought Steel toaPowdered Metal With and Without ShotPeening”; www.metalimprovement.com A SA/TM-2000-210044, April2000. tr ess R elaxation inShotPeened andPolished NickelBaseMaterials”; TECHNICAL ARTICLE REPRINTS 57 APPENDIX www.metalimprovement.com am Conference, 2000. am Conference, ogr ., 2003. wain, M., Surface Engineering 2000. wain, M., Surface Engineering r echnology, Jan/Feb. 2001. Jan/Feb. echnology, D T Hornbach, D., SAE Technical Paper #2000-01-25664, Sept. 2000. Sept. #2000-01-25664, Paper Technical D., SAE Hornbach, S M., Halpin, J., Lane, L., Zaleski, T. and Wubbenhorst, W., 2002. W., Wubbenhorst, and T. M., Halpin, J., Lane, L., Zaleski, Dane, C., Specht, R., and A., Demma, A., Hackel, L., Chen, H-L, Hill, M., DeWald, Technology”; “Laser Peening Aug. 2003. and Processes, Materials Advanced Harris, F., Scholtes, B. and Ritchie, R., 2002. Integrity M., USAF Structural and Dubberly, R., Newman,J. Probhakaran, W., R., Matthews, Everett, Steel”; P Halpin, J., Rankin, J., Hill, M. and Chen, H., J., Hill, M. and Halpin, J., Rankin, 2002. Materials Science Forum, 21. Lindell, G. and D., Herring, of Gears”; Breuer, Treatment Method for the Heat the Best Carburizing “Selecting 22. G., Gear Gear Applications”; Link, R. and Kotthoff, Metal Gears for of High Density Powder “Suitability 20. M. and Molzen, Treating”; Heat and Peening Shot Through Levels Stress Residual Welding of “Evaluation 1 1 123. M. and Brandt, V., C., Florea, Montross, Weldments”; 6061-T6 Al Properties “Subsurface Peened of Laser 1 126. 2002. Surface Engineering, Feb. W., Issues”; Reitz, Many Performance Solves Peening “Laser Shock 127.Hill, Specht, R., Jones, D., Hackel, L., Harris, F., of Metals”; for Laser Peening Techniques Control “Process 128. 129. U., I., Noster, Altenberger, Temperatures”; Materials at Elevated Treated of Mechanically Surface “Fatigue 130. and 4340 Alloy Life in 2024 Aluminum and Fatigue “The Growth Crack on Peening Affects of Shot and Laser 124. 2001. Heating, Feb. Aken, D., Industrial Van Processing”; “Laser Shock 125.Hackel, L., Harris, F., Laser Peening”; Induced by Stress on Residual Variations “The of Process Effects APPENDIX S

EUROPEAN CORPORATE OFFICE

E GLOBAL HEADQUARTERS Metal Improvement Company Metal Improvement Company Hambridge Lane I 10 Forest Avenue Newbury, Berkshire RG14 5TU Paramus, NJ 07652 USA England

T Tel: 201-843-7800 Tel: +44 (0) 1635-279621 Fax: 201-843-3460 Fax: +44 (0) 1635-279629 I E-mail: [email protected] E-mail: [email protected] L SHOT PEENING I UNITED STATES KANSAS OHIO Hambridge Lane 440 North West Road 11131 Luschek Drive Newbury, Berkshire RG14 5TU C ARIZONA 103 S. 41st. Avenue Wellington, KS 67152 Blue Ash, OH 45241 England Phoenix, AZ 85009 Tel: 620-326-5509 Tel: 513-489-6484 Tel: +44 (0) 1635-279600 A Tel: 602-278-2811 Fax: 620-326-6043 Fax: 513-489-6499 Fax: +44 (0) 1635-279601 Fax: 602-278-3911 E-mail: wellington-shotpeen@ E-mail: cincinnati-shotpeen@ E-mail: micnewbury@

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SHOT PEENING (continued) LASER PEENING I ITALY Hans-Böckler-Str. 5 UNITED STATES UNITED KINGDOM C Via P. Belizzi 64521 Gross-Gerau CALIFORNIA Barnoldswick 29100 Piacenza Germany 7655 Longard Road West Craven Drive Tel: +49-6152-8577-0 Italy Livermore, CA 94551 West Craven Business Park Tel: +39-0523-590568 Fax: +49-6152-8577-11 Tel: 925-960-1090 Earby, Lancashire BB18 6JZ

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60 www.metalimprovement.com Metal Improvement Company 10 Forest Avenue Paramus, NJ 07652 USA

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