DOCSLIB.ORG

Metallography Specimen Preparation and Examination Objectives 1. To

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Metallography Specimen Preparation and Examination Objectives 1. To Experiment: Metallography Specimen Preparation and Examination Objectives 1. To learn and to gain experience in the preparation of metallographic specimens. 2. To examine and analyze the microstructures of metals and metallic alloys. Abstract Proper preparation of metallographic specimens to determine microstructure and content requires that a rigid step-by-step process be followed. In sequence, the steps include sectioning, mounting, course grinding, fine grinding, polishing, etching and microscopic examination. Specimens must be kept clean and preparation procedure carefully followed in order to reveal accurate microstructures. Each student will prepare and examine a brass, steel or aluminium sample for metallographic examination. Additionally, a brass, steel or aluminiumsample with different composition, a eutectoid steel sample and a eutectoid Pb-Sn sample will be examined under the metallographic microscope. Photographs will be taken of the samples and the ASTM grain size number determined for each of the specimens if applicable. Background Metallography consists of the study of the constitution and structure of metals and alloys. Much can be learned through specimen examination with the naked eye, but more refined techniques require magnification and preparation of the material's surface. Optical microscopy is sufficient for general purpose examination; advanced examination and research laboratories often contain electron microscopes (SEM and TEM), x-ray and electron diffractometers and possibly other scanning devices. Incorrect techniques in preparing a sample may result in altering the true microstructure and will most likely lead to erroneous conclusions. It necessarily follows that the microstructure should not be altered. Hot or cold working can occur during the specimen preparation process if the metallurgist is not careful. Expertise at the methods employed to produce high-quality metallographic samples requires training and practice. The basic techniques can be learned through patient persistence in a matter of hours. This module takes the student through the metallographic sample preparation process step-by-step with demonstrations and explanations of sectioning, mounting, course & fine grinding, polishing, etching and microscopic examination. Sectioning Operations such as shearing produce severe cold work, which can alter the microstructure of a sample. Abrasive cutting (sectioning) offers the best solution to eliminate these undesirable features; the resultant surface is smooth, and the sectioning task is quickly accomplished. Low-speed cut-off wheels are utilized in cases where the heat created by standard abrasive cutters must be avoided. Ample coolant and proper speed control are essential in all sectioning operations. Abrasive Cut-Off Wheels consist of abrasive grains (such as Aluminum Oxide or Silicon Carbide), bonded together with rubber or other materials in the form of a thin wheel. Rubber bonded wheels are most extensively used for wet operation and resin bonds for dry cutting. When sectioning a piece of metal, the abrasive grains on the cutoff wheel become dull, therefore, the bond must be destroyed at the correct rate so that new grains are always at the edge and are still held firmly by the bonding material. The rate at which the bond breaks down is affected by several different factors, including: 1) The hardness of the bond. 2) The hardness and workability of the metal sample. 3) The size and speed of the wheel. 4) The power of the driving motor. 5) The type and amount of coolant and its method of application. 6) The amount of pressure by which the wheel is applied to the sample. 7) The amount of vibration in the machine. Cutoff wheels are indexed from hard to soft and are referred to by "grade". As a rule of thumb, a hard bonded wheel should be selected when sectioning soft stock, and a soft wheel for sectioning harder material. A reasonable amount of wheel pressure must be applied so the abrasive grains will "bite" and remove the metal 1 ME 3701, Materials of Engineering, LSU in fine chips. An experienced operator can tell whether the wheel is cutting or merely "dragging" by the feel of the control arm and monitoring of the power consumption of the cutting equipment. Proper cutting procedures must be followed; abrasive cut-off wheels will crack and become flying projectiles when used improperly. Lab Procedure - Sectioning 1. Place the sample on the slotted Table so that it is at the center of the swing of the head. 2. Place the Locking Lever in the forward position to allow the Control Rod to be moved to the furthest position. Move the Rear Vise section to contact the rear face of the sample. Move the Front Section to a position near the front face of the sample. 3. Tighten the Nuts that secure the Vise sections to the Table. 4. Push the Control Rod in to make firm contact with the sample and pull back the Locking Level to secure the sample. 5. Turn on the coolant; it should flow readily to both cool and clean the cutting area. 6. Apply steady moderate pressure until the specimen is sectioned; avoid jerking motions that may cause the blade to splinter. Mounting Small samples are generally mounted in plastic for convenience in handling and to protect the edges of the specimen being prepared. Compression-type molding is commonly applied to encase specimens in 1 to 1.5 inch diameter plugs of a hard polymer. Compression molding materials are classified as either thermosetting or thermoplastic: 1) Bakelite is a low cost, relatively hard thermosetting polymer that is commonly utilized. 2) Expensive Transoptic Thermoplastics are utilized when transparency is required. Transoptic materials remain molten at maximum temperature and become transparent with an increase in pressure and a decrease in temperature. By definition, thermosetting materials require heat and pressure during the molding cycle. During mounting, the pressure and molding temperature are generally held constant thus time is the only variable. The metal sample is placed in the mounting cylinder which is then encased in a pre-measured amount of powdered polymers. The mounting cylinder is then sealed, pressurized and heated to complete the polymerization process necessary to solidly encase the metal sample. Although inferior in quality to compression-type molding, cold molding (room temperature) is often used with epoxy to mount samples by simply mixing the epoxy and pouring it over a sample that is positioned face- down in a cold-mounting ring. When the epoxy cures the specimen can be prepared. Caution must be exercised when cold mounting due to relatively poor adhesion between the specimen edges and the epoxy plug; gaps often form which can degrade the quality of the specimen. Lab Procedure Mounting Procedure (Hot-Mounting Equipment Currently Unavailable @ LSU!) Supplies for Cold-Mounting: - KoldMound Kit (Vernon-Benshoff Co.): Mix 2 parts powder with 1 part liquid - Plastic Mounting Ring with Removable Bottom - 8 Ounce Paper Cup with Stirrer - Weight Scale - Liquid Soap 1. Apply liquid soap to the inner walls and base of the mounting ring. 2. Place the specimen in the center/bottom of the plastic mounting ring base with the examination surface face- down. 3. Attach the mounting ring cylinder to the base by simple pressing firmly in place. 2 ME 3701, Materials of Engineering, LSU 4. Mix the appropriate amount of KoldMount (2/1 Powder/Liquid - 15 grams of Powder/7.5 grams of Liquid per Sample) in a paper cup. 5. Simply pour the epoxy mixture into the mounting ring; sample should be approximately 0.75" thick. 6. After one hour, remove the sample from the mounting ring and proceed with course grinding. Coarse Grinding In view of the perfection required in an ideally prepared metallographic sample, it is essential that each preparation stage be carefully performed. The specimen must: 1. Be free from scratches, stains and others imperfections which tend to mark the surface. 2. Retain non-metallic inclusions. 3. Reveal no evidence of chipping due to brittle intermetallic compounds and phases. 4. Be free from all traces of disturbed metal. The purpose of the coarse grinding stage is to generate the initial flat surface necessary for the subsequent grinding and polishing steps. As a result of sectioning and grinding, the material may get cold worked to a considerable depth with a resultant transition zone of deformed material between the surface and the undistorted metal. Course grinding can be accomplished either wet or dry using 80 to 180 grit electrically powered disks or belts, but care must be taken to avoid significant heating of the sample. The final objective is to obtain a flat surface free from all previous tool marks and cold working due to specimen cutting. An important factor throughout the Coarse Grinding and Fine Grinding Stages is that the scratches be uniform in size and parallel to each other in any one grinding stage. Proper grinding involves rotation of the sample by 90o between stages while the grinding angle must be held constant during the grinding at any one stage. The sample MUST be washed thoroughly before proceeding from one grinding stage to the next ! ! ! Failure to follow this basic rule will result in transferring abrasive particles between stages and will cause time- consuming, frustrating problems in removing unwanted scratches. Lab Procedure-Coarse Grinding: *Note: Safety Glasses must be worn when operating the Course Grinding Equipment ! ! ! 1. Label the specimen with your name so that it can be easily identified. 2. Turn the Motor On, then the water, adjust the flow to obtain a good film of water. Too much water will cause a spray when it contacts the sample. 3. Beginning with the 120 grit belt and using both hands to hold the specimen, carefully place the sample face onto the exposed area of the belt being careful not to contact the rotating surface with a sharp edge of the specimen or your hand.
Load more

Recommended publications
  • Metallography – a Powerful Instrument for Material Characterisation, Material Development and Failure Analysis
    771 Microsc. Microanal. 21 (Suppl 3), 2015 doi:10.1017/S1431927615004651 Paper No. 0386 © Microscopy Society of America 2015 Metallography – A Powerful Instrument for Material Characterisation, Material Development and Failure Analysis Michael Panzenböck1, Francisca Mendez-Martin1, Boryana Rashkova1, Patric Schütz1 1. Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Austria A. Widmanstätten (1754-1849) was one of the first scientists who developed techniques for studying the microstructure of meteorites by grinding and etching them with nitric acid. Also H.C. Sorby (1826- 1908) used such methods for microstructural investigations of minerals and rocks to identify their origin, as well as to examine steels and meteorites. Other famous and nowadays well known researchers such as R. Hadfield (1858—1940), A. Martens (1850-1914), E.C. Bains (1891-1971), K.H. Ledebur (1837- 1906), and H. Brearley (1871-1948) further developed these basic methods to get more information about the microstructure, especially in case of steels. Many microstructural parts or phases of the Fe- Fe3C phase diagram are called in honour of these scientists, e.g., “Widmanstätten ferrite”, “Sorbite”, “Bainite”, “Martensite”, or in case of cast iron “Ledeburite”. Without doubt, a material’s microstructure is decisive, because it is the arrangement, size and distribution of different phases which is responsible for the mechanical properties such as strength, ductility and toughness. In order to develop high-performance materials for existing and new applications it is necessary to establish a basic understanding of the material behaviour or its response under service loads. In addition to the standard methods such as light microscopy (LM), scanning electron microscopy (SEM), focused ion beam (FIB), also high-resolution methods (transmission electron microscopy (TEM), atom probe tomography (APT)) have been developed over the last three decades.
    [Show full text]
  • Ceramics Overview: Classification by Microstructure and Processing Methods
    Clinical Ceramics overview: classification by microstructure and processing methods Edward A. McLaren 1 and Russell Giordano 2 Abstract The plethora of ceramic systems available today for all types of indirect restorations can be confusing and overwhelming for the clinician. Having a better understanding of them is important. In this article, the authors use classification systems based on microstructural components of ceramics and the processing techniques to help illustrate the various properties. Introduction component atoms, and may exhibit ionic or covalent Many different types of ceramic systems have been bonding. Although ceramics can be very strong, they are also introduced in recent years for all types of indirect extremely brittle and will catastrophically fail after minor restorations, from very conservative nonpreparation veneers, flexure. Thus, these materials are strong in compression but to multi-unit posterior fixed partial dentures and everything weak in tension. in between. Understanding all the different nuances of Contrast that with metals: metals are non-brittle (display materials and material processing systems is overwhelming elastic behaviour) and ductile (display plastic behaviour). This and can be confusing. This article will cover what types of is because of the nature of the interatomic bonding, which is ceramics are available based on a classification of the called metallic bonds; a cloud of shared electrons that can microstructural components of the ceramic. A second, easily move when energy is applied defines these bonds. This simpler classification system based on how the ceramics are is what makes most metals excellent conductors. Ceramics can processed will give the main guidelines for their use. be very translucent to very opaque.
    [Show full text]
  • Texture and Microstructure
    Texture and Microstructure • Microstructure contains far more than qualitative descriptions (images) of cross-sections of materials. • Most properties are anisotropic •it is important to quantitatively characterize the microstructure including orientation information (texture). In latin, textor means weaver In materials science, texture way in which a material is woven. Polycrystalline material is constituted from a large number of small crystallites (limited volume of material in which periodicity of crystal lattice is present). Each of these crystallites has a specific orientation of the crystal lattice. A randomly texture sheet A strongly textured sheet The cube texture (001) ND (Sheet Normal Direction) [100] RD (Sheet Rolling Direction) Crystallographic texture is the orientation distribution of crystallites in a polycrystalline material Texture :Metallurgists and Materials Scientists Fabric :Geologists and Mineralogists Preferred Orientation :Everybody Why textures? Texture influences the following properties: •Elastic modulus •Yield strength •Tensile ductility and strength •Formability •Fatigue strength •Fracture toughness •Stress corrosion cracking •Electrical and Magnetic properties Major fields of application A. Conventional • Aluminium industry • Steel industry • LC steels • Electrical steels • Titanium alloys • Zirconium base nuclear grade alloys B. Modern • High Tc superconductors • Thin films for semiconducting and magnetic devices • Bulk magnetic materials • Structural Ceramics • Polymers Beverage Cans Aluminium beverage
    [Show full text]
  • Met-Manual-2B.Pdf
    1 2 METALLOGRAPHIC HANDBOOK Donald C. Zipperian, Ph.D. Chief Technical Officier PACE Technologies Tucson, Arizona USA Copyright 2011 by PACE Technologies, USA No part of this manual may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner. First printing, 2011 3 Great care is taken in the compilation and production of this book, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by PACE Technologies, PACE Technologies cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of PACE Technologies control, PACE Technologies assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products or information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OR BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY.
    [Show full text]
  • Metallographic Preparation 2009
    Inc. DRP Ventures Division METALLOGRAPHIC PREPARATION 2009 y Copyright DRP Ventures Inc. 2007 2008 Division DRP Ventures Inc. # We would like to welcome the opportunity to introduce our latest catalogue. It provides an increasing range of quality products in abrasive cutting, mounting, grinding and polishing. ANAMET Sales and Technical Services are supported by competent and motivated personnel who continue to make every effort to earn and maintain your trust. They are committed to serving their customers by providing sample preparation supplies and offering assistance in improving their metallographic procedures. Over the years, ANAMET has been meeting the requirements of many industries such as aerospace, automotive, ceramics, composites disk drives, electro-optical materials, electronics, geological services, metal converters, metal powders, foundries, mineralogy, optics, plastics, primary and secondary metals, printed circuits, pulp industry, semiconductor substrates, tolls, mold and die finishing, educational institutions and nanotechnology. We thank you for being at the heart of our commitment and look forward to a continued relationship. Our dedication for excellence begins with our commitment in providing you with only the very best. Sincerely, Diane R. Pilley , B.Sc. ANAMET Division DRP Ventures Inc. 655 Jean-Paul Vincent, Suite 9, Longueuil, Qc, Canada J4G 1R3 • Tel: 450.646.1290 • Fax: 450.646.4309 • E-mail: [email protected] • Website: www.anamet.com Î ORDERING INFORMATION ON THE NEXT PAGE Í SECTIONING Abrasive Cut-Off Wheels. 1 Small Abrasive Cut-Off Wheels. 8 Diamond Cut-Off Wheels. 9 Wafering Diamond Wheels. 10 Cubic Boron Nitride. 11 Sectioning Accessories. 12 MOUNTING Compression Mounting. 13 Ambient Mounting. 16 Castable Mounting Accessories.
    [Show full text]
  • Metallographic Sample Preparation Techniques
    Materials Characterization 1ecliniques-Principle s and Applications Eds : G. Sridliar; S. Ghosh Chowdhurv & N. G. Goswanri NML. Janislredpur-83100711999) pp. 163-176 Metallographic Sample Preparation Techniques SAMAR DAS National Metallurgical Laboratory, Jamshedpur-831007 E-mail : [email protected] ABS'T'RACT Microstructure plays an important role in controlling the properties in metals and allcrvs. Hence i nicrostructu•al study called metallographv has been extensively used for materials selection, failure investigation and materials development. The microstructure of metals are com- monly observed under optical and/or electron microscopes, though other types of microscopes have been developed for specific uses. For any microscopic observation, the preparation of proper sample, which reveals the true microstructure is of prima ti, importance. Numerous and diverse techniques have been developed not only to suit the ma- terial but also for the type of microscope to be used. The techniques also vary with the details to be observed. It is difficult to prepare a comprehensive survey of the techniques developed and practised to- day. An attempt has been made here, to briefly discuss the most corn- monly used specimen preparation techniques for optical, scanning electron and transmission electron microscopy together with their merits and demerits. Any specimen preparation method involves several steps. Proper care in each step is essential to avoid difficulty in the subse- quent steps and to reveal the true microstructure. The choice of a technique depends mainly on the materials, the detail required to be observed and the type of microscope to be used. INTRODUCTION The study of microstructural details of metals and alloys is termed as metal- lography.z The microstructure of steel was first observed by H.C.
    [Show full text]
  • Metallographic Etching
    Metallographic Etching 2nd Edition By Günter Petzow In collaboration with Veronika Carle Translated by Uta Harnisch Techniques for Metallography Ceramography Plastography Contents Preface to the German Edition . VIII Preface . IX Introduction . 1 1 Metallography . 7 1.1 Preparation of Metallographic Specimens . 7 1.2 Specimen Sectioning . 8 1.3 Mounting. 11 1.3.1 Clamping . 12 1.3.2 Embedding . 13 1.3.3 Special Mounting Techniques . 15 1.4 Identification (Marking). 18 1.5 Grinding and Polishing . 18 1.5.1 Mechanical Grinding and Polishing . 19 1.5.2 Microtome Cutting and Ultramilling . 29 1.5.3 Electrolytic Grinding and Polishing . 30 1.5.4 Chemical Polishing . 34 1.5.5 Combined Polishing Methods . 34 1.5.6 Evaluation of Polishing Methods . 36 1.6 Cleaning . 37 1.7 Metallographic Etching . 38 1.7.1 Optical Etching . 39 1.7.2 Electrochemical (Chemical) Etching . 40 1.7.3 Physical Etching . 44 1.7.4 Etching Reproducibility . 45 1.7.5 Etching Terminology . 47 1.7.6 Definitions of Etching Terms . 47 1.8 Field Metallography/Nondestructive Metallography. 50 1.9 Preparation and Etching Recipes for Metallic Materials . 51 1.9.1 Silver . 53 1.9.2 Aluminum . 57 1.9.3 Gold . 64 v 1.9.4 Beryllium. 67 1.9.5 Bismuth and Antimony . 70 1.9.6 Cadmium, Indium, and Thallium . 72 1.9.7 Cobalt . 75 1.9.8 Refractory Metals (Chromium, Molybdenum, Niobium, Rhenium, Tantalum, Vanadium, and Tungsten) . 80 1.9.9 Copper. 88 1.9.10 Iron, Steel, and Cast Iron . 94 1.9.11 Semiconductors (Germanium, Silicon, Selenium, Tellurium, AIIIBVI, and AIIBVI Compounds).
    [Show full text]
  • Introduction to Material Science and Engineering Presentation.(Pdf)
    Introduction to Material Science and Engineering Introduction What is material science? Definition 1: A branch of science that focuses on materials; interdisciplinary field composed of physics and chemistry. Definition 2: Relationship of material properties to its composition and structure. What is a material scientist? A person who uses his/her combined knowledge of physics, chemistry and metallurgy to exploit property-structure combinations for practical use. What are materials? What do we mean when we say “materials”? 1. Metals 2. Ceramics 3. Polymers 4. Composites - aluminum - clay - polyvinyl chloride (PVC) - wood - copper - silica glass - Teflon - carbon fiber resins - steel (iron alloy) - alumina - various plastics - concrete - nickel - quartz - glue (adhesives) - titanium - Kevlar semiconductors (computer chips, etc.) = ceramics, composites nanomaterials = ceramics, metals, polymers, composites Length Scales of Material Science • Atomic – < 10-10 m • Nano – 10-9 m • Micro – 10-6 m • Macro – > 10-3 m Atomic Structure – 10-10 m • Pertains to atom electron structure and atomic arrangement • Atom length scale – Includes electron structure – atomic bonding • ionic • covalent • metallic • London dispersion forces (Van der Waals) – Atomic ordering – long range (metals), short range (glass) • 7 lattices – cubic, hexagonal among most prevalent for engineering metals and ceramics • Different packed structures include: Gives total of 14 different crystalline arrangements (Bravais Lattices). – Primitive, body-centered, face-centered Nano Structure – 10-9 m • Length scale that pertains to clusters of atoms that make up small particles or material features • Show interesting properties because increase surface area to volume ratio – More atoms on surface compared to bulk atoms – Optical, magnetic, mechanical and electrical properties change Microstructure – 10-6 • Larger features composed of either nanostructured materials or periodic arrangements of atoms known as crystals • Features are visible with high magnification in light microscope.
    [Show full text]
  • Correlation Between Crystal Structure, Surface/Interface Microstructure, and Electrical Properties of Nanocrystalline Niobium Thin Films
    nanomaterials Article Correlation between Crystal Structure, Surface/Interface Microstructure, and Electrical Properties of Nanocrystalline Niobium Thin Films L. R. Nivedita 1, Avery Haubert 2, Anil K. Battu 1,3 and C. V. Ramana 1,3,* 1 Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA; [email protected] (L.R.N.); [email protected] (A.K.B.) 2 Department of Physics, University of California, Santa Barbara, Broida Hall, Santa Barbara, CA 93106, USA; [email protected] 3 Department of Mechanical Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA * Correspondence: [email protected]; Tel.: +1-915-747-8690 Received: 10 May 2020; Accepted: 26 June 2020; Published: 30 June 2020 Abstract: Niobium (Nb) thin films, which are potentially useful for integration into electronics and optoelectronics, were made by radio-frequency magnetron sputtering by varying the substrate temperature. The deposition temperature (Ts) effect was systematically studied using a wide range, 25–700 ◦C, using Si(100) substrates for Nb deposition. The direct correlation between deposition temperature (Ts) and electrical properties, surface/interface microstructure, crystal structure, and morphology of Nb films is reported. The Nb films deposited at higher temperature exhibit a higher degree of crystallinity and electrical conductivity. The Nb films’ crystallite size varied from 5 to 9 ( 1) nm and tensile strain occurs in Nb films as Ts increases. The surface/interface morphology of ± the deposited Nb films indicate the grain growth and dense, vertical columnar structure at elevated Ts. The surface roughness derived from measurements taken using atomic force microscopy reveal that all the Nb films are characteristically smooth with an average roughness <2 nm.
    [Show full text]
  • Metallographic Procedures and Analysis – a Review
    ISSN 2303-4521 PERIODICALS OF ENGINEERING AND NATURAL SCIENCES Vol. 3 No. 2 (2015) Available online at: http://pen.ius.edu.ba Metallographic Procedures and Analysis – A review Enes Akca Erwin Trgo Department of Mechanical Engineering, Faculty of Engineering and Natural Department of Mechanical Engineering, Faculty of Engineering and Natural Sciences, International University of Sarajevo, Hrasnicka cesta 15, 71210 Sarajevo, Sciences, International University of Sarajevo, Hrasnicka cesta 15, 71210 Sarajevo, Bosnia and Herzegovina Bosnia and Herzegovina [email protected] Abstract The purpose of this research is to give readers general insight in what metallography generally is, what are the metallographic preparation processes, and how to analyse the prepared specimens. Keywords: metallography; metallographic specimens; metallographic structure 1. Introduction depends generally on the type of material, and so you can clearly differentiate abrasive cutting (metals), thin Metallography is the study of the microstructure of sectioning with a microtome (plastics), and diamond various metals. To be more precise, it is a scientific wafer cutting (ceramics). discipline of observing chemical and atomic structure of those materials, and as such is crucial for These processes are mostly used in order to minimize determining product reliability. the damage which could alter the microstructure of the material, and the analysis itself. Not only metals, but polymeric and ceramic materials can also be prepared using metallographic techniques, 2.2. Mounting hence the terms plastography, ceramography, materialography, etc. This process protects the material’s surface, fills voids in damaged (porous) materials, and improves handling Steps for preparing metallographic specimen include a of irregularly shaped samples. There are plenty of ways variety of operations, and some of them are: to conduct this operation, and all of them depend on the documentation, sectioning and cutting, mounting, type of material that is being handled.
    [Show full text]
  • Rotary Friction Welding of Inconel 718 to Inconel 600
    metals Article Rotary Friction Welding of Inconel 718 to Inconel 600 Ateekh Ur Rehman * , Yusuf Usmani, Ali M. Al-Samhan and Saqib Anwar Department of Industrial Engineering, College of Engineering, King Saud University, Riyadh 11451, Saudi Arabia; [email protected] (Y.U.); [email protected] (A.M.A.-S.); [email protected] (S.A.) * Correspondence: [email protected]; Tel.: +966-1-1469-7177 Abstract: Nickel-based superalloys exhibit excellent high temperature strength, high temperature corrosion and oxidation resistance and creep resistance. They are widely used in high temperature applications in aerospace, power and petrochemical industries. The need for economical and efficient usage of materials often necessitates the joining of dissimilar metals. In this study, dissimilar welding between two different nickel-based superalloys, Inconel 718 and Inconel 600, was attempted using rotary friction welding. Sound metallurgical joints were produced without any unwanted Laves or delta phases at the weld region, which invariably appear in fusion welds. The weld thermal cycle was found to result in significant grain coarsening in the heat effected zone (HAZ) on either side of the dissimilar weld interface due to the prevailing thermal cycles during the welding. However, fine equiaxed grains were observed at the weld interface due to dynamic recrystallization caused by severe plastic deformation at high temperatures. In room temperature tensile tests, the joints were found to fail in the HAZ of Inconel 718 exhibiting good ultimate tensile strength (759 MPa) without a significant loss of tensile ductility (21%). A scanning electron microscopic examination of the fracture surfaces revealed fine dimpled rupture features, suggesting a fracture in a ductile mode.
    [Show full text]
  • Metallography of Titanium and Its Alloys
    MICROSTRUCTURE OF TITANIUM AND ITS ALLOYS George F. Vander Voort Director, Research & Technology, Buehler Ltd., Lake Bluff, Illinois, 60044, USA ABSTRACT A three-step preparation procedure was developed for titanium and its alloys. Attack polishing is utilized in the third step for optimal results, particularly for imaging alpha-Ti with polarized light. Two-phase α-β alloy specimens and all alloys are easier to prepare than single-phase α specimens. Kroll’s reagent appears to be adequate for most alloys. A modification of Weck’s reagent was used for color metallography. INTRODUCTION Titanium and its alloys have become quite important commercially over the past fifty years due to their low density, good strength-to-weight ratio, excellent corrosion resistance and good mechanical properties. On the negative side, the alloys are expensive to produce. Titanium, like iron, is allotropic and this produces many heat treatment similarities with steels. Moreover, the influences of alloying elements are assessed in like manner regarding their ability to stabilize the low temperature phase, alpha, or the high temperature phase, beta. Like steels, Ti and its alloys are generally characterized by their stable room temperature phases - alpha alloys, alpha-beta alloys and beta alloys, but with two additional categories: near alpha and near beta. Titanium and its alloys are more difficult to prepare for metallographic examination than steels. As for all refractory metals, titanium and its alloys have much lower grinding and polishing rates than steels. Deformation twinning can be induced in alpha alloys by overly aggressive sectioning and grinding procedures. It is safest to mount relatively pure Ti specimens, especially those from service in a hydrogen-containing environment, in castable (“cold”) resins rather than using hot compression mounting due to the potential for altering the hydride content and morphology.
    [Show full text]