ASM Specialty Handbook: Tool Materials Copyright © 1995 ASM International® Joseph R. Davis, Editor All rights reserved www.asminternational.org
General Guidelines for Selecting Cutting Tool Materials
SELECTING Tiffi PROPER CUTIING Because of the wide range of conditions and • TYpe, capability, and condition of the machine TOOL MATERIAL for a specific machining ap requirements, no single cutting tool material tool to be used plication can provide substantial advantages, in meets the needs of all machining applications. • Rigidity of the tool and workpiece cluding increased productivity, improved quality, Each tool material has its own combination of • Production requirements influencing the and reduced costs (Ref 1). Increased productivity properties that makes it best for a specific opera~ speeds and feeds selected can be obtained by increasing cutting speeds tion. The fol1owing factors affect the selection of • Operating conditions, such as cutting forces and/or feed rates. Increasing the speeds and feeds, a cutting tool material for a specific application and temperatures however, is limited by the capability of the cUt (Ref 1): • Tool cost per part machined, including initial ting tool material and machine tool. Speeds and tool cost, grinding cost, tool life, frequency of feeds must be kept low enough to provide an • Hardness and condition of the workpiece rna~ regrinding or replacement, and labor cost. The terial acceptable tool life. Otherwise, tool changing and most economical tool is not necessarily the one • Operations to be performed (optimum tool se~ grinding costs can outweigh the advantages of providing the longest life or having the lowest lection may reduce the number of operations faster machining rates by increasing the cost per initial cost. part produced. Machine tool downtime for re required) placement of dull or broken tools is a major • Amount of stock to be removed • Accuracy and finish requirements deterrent to increasing productivity. Desirable Properties
In evaluating a cutting tool material in a ma chining operation, the applicability is dependent Toughness on having the correct combination of physical Transverse rupture Abrasion resistance prbperties. Because maximizing one property strength, MPa (ksi) Hardness, HRA typically means lowering some other property f-----, (e.g., extremely wear-resistant materials gener High-speed 3447-4826 ally have poor toughness, as shown in Fig. 1), the stee I l ~6.5 (500-700) (60-70 HRC) workpiece properties and cutting operations f---, strongly influence the selection of a cutting tool Cast 2068-2413 81-84 alloy l material. Similarly, developing an understanding (300-350) Taii:65 HRC) of the tool properties and their relationship to Micro grain cutting performance is the key to understanding 2758-3723 91.5-92.0 carbide l l the potential application range. (400-540) Properties of primary concern in cutting tool C-1 and C~2 1655-2241 90.0-92.0 design are fracture resistance (toughness), plastic carbide l l (240-325) or thermal deformation resistance, and wear re C-3and C4 sistance. Also of concern is the resistance of the '1207-1793 92.0-93.0 carbide l l material to cracking, notching, cratering, and, in (175-260) the case of coated inserts, spalling (poor coating and C-6 adherence). C-5 1379-2068 90.0-92.5 carbide l I Machine tests have been developed to measure (200-300) the resistance of cutting tools to these failure C-7 and C-8 689.5-1724 92.0-95.0 mechanisms. This is accomplished by matching carbide I (100-250) the workpiece and tool materials, adjusting ma e:---. chining parameters over the likely application Ceramic ~-758.4 93.5-94.0 I range, and then carefully evaluating the failure (80-110) modes and their relationship to basic physical properties of materials. Common failure mecha Polycrystalline 6500·8000 HK diamond ~379 nisms are shown in Fig. 2. The cutting tool prop (100-200) erties of most concern in evaluating these failures are described below. Additional information on Fig. 1 Comparison of toughness and wear resistance for various cutting tool materials. Source: Metcut Research Associates, Inc. cutting tool failures can be found in the articles 4 I Materials for Machining and Grinding
"Cemented Carbides" and "Wear and Failure Modes for Cutting Tools" in this Volume. Predominant failure mechanisms Toughness is commonly defined by cutting tool users as the resistance of the cutting edge to Heavy roughing Roughing Semifinishing Finishing breakage or fracture under unfavorable condi Fracture Chipping Wear land Deformation tions, which typically include one or more of the Chipping Deformation Deformation Crater following: Deformation Cracking Crater Wear land Crater • High feed rates • Moderate-to-severe interruptions Increasing feed \ Increasing speed • Inconsistent or difficult workpiece material ~------t------~ • Lack of rigidity Fig. 2 Predominant failure mechanisms of coated carbides when machining steels Flank Wear Resistance. The resistance of the cutting tool to flank wear is a primary concern in the applicability of the material to a cutting opera The resistance of whisker-reinforced ceramics to Other alloying elements include tungsten, chro tion. The tool must have adequate resistance to this crack formation is one reason they have been mium, vanadium, and cobalt. These steels reach both abrasive and chemical wear, so the chemical successful in cutting this type of material. ·exceptionally high hardness after heat treatment inertness of the material as well as its hardness Chipping is a less severe and more common and can maintain that hardness at relatively high must be considered. Figure 3(a) shows a typical form of breakage. If the strength of the cutting temperatures. wear land generated during a turning or facing tool material is exceeded in localized areas due to Type T steels also have high carbon contents, operation. The balancing of abrasive and chemi chatter, variations in the workpiece, or buildup on with tungsten as the primary alloying element. cal wear resistance, along with toughness, gives the cutting edge, small fragments of the cutting Chromium and vanadium are present as alloying each tool material family its own application edge break away during the cutting operation elements in all type T steels; most also contain range. Generally, as the cutting speed increases, (Fig. 3!). Edge preparation plays an important cobalt. The tungsten types tend to be less tough, chemical wear resistance becomes more impor role in minimizing chipping. more resistant to heat, and slightly higher in abra tant. Therefore, inert materials such as oxides and Ultimately, the intent in targeting application sion resistance than type M high-speed steels. nitrides perform better at higher cutting speeds. ranges is to avoid fracture of the insert (Fig. 3g). Compositions and properties of both types can be Deformation. A secondary effect of high cut When this occurs, the insert (and often the work found in the articles "Wrought High-Speed Tool ting speeds is plastic deformation due to in piece) is rendered unusable. Steels" and "Powder Metallurgy High-Speed creased cutting temperatures . .Under these condi Tool Steels" in this Volume. tions, the binder phase of a cemented carbide When compared with competing cutting tool cutting tool material may soften and deform, materials, high-speed steels are characterized by causing a bulging effect (Fig. 3b). Such an effect Cutting Tool Materials moderate wear resistance and high transverse can cause breakage, a higher flank wear rate, or rupture strengths (Fig. 1), giving them wide ap spalling of the coatings. This effect is accentuated The classes of tool materials currently in use plicability on machining operations. Their pri under high chip loads and is a typical failure for machining operations are high-speed tool mary limitation is speed/metal removal rate, as mode for rough cutting, in which the toughness steels, cobalt-base alloys, cemented carbides, cer they typically suffer plastic deformation at rela requirements prevent the use of ceramic or other mets, ceramics, polycrystalline cubic boron ni tively low cutting speeds (30 to 60 rn!min, or 100 binderless cutting materials. tride, and polycrystalline diamond. The different to 200 sfm). As a result, their primary applica Crater Resistance. A secondary result of abra materials vary greatly in wear resistance and tions are in form cutters, reamers, taps, drills, and sive and chemical wear is the formation of a toughness. Figure 4 shows schematically their small-diameter end mills. High-speed steels are crater on the rake surface of the insert. In this relative application ranges in terms of machining also used in the milling of high-temperature ma case, the chips formed during the operation rub speeds and feed rates. Higher machining speeds terials and on older machines with less rigidity and weld on the rake face, causing a dish-shaped require tool materials with greater wear resis and limited speed capability. depression to form (Fig. 3c). As a result of this tance, whereas higher feed rates require tools Cobalt-based cutting tools have been avail formation, cutting forces can increase and, cou with increased toughness. High-speed tool steels able since about 1920 (Ref 1). These materials are pled with the weakening of the insert, can result are the toughest materials; however, their rela generally cast cobalt-chromium-tungsten alloys in catastrophic failure due to chipping or break tively low wear resistance limits their application with carbon and other alloy additions. They are age. Crater formation can be inhibited, however, to lower-speed machining operations. At the not heat treatable, and the maximum hardness (55 with the proper chip-breaker geometry. other end of the spectrum, ultrahard materials to 65 HRC) occurs near the cast surface. As a Cracking occurs under heavy mechanical load such as CBN and PCD are highly wear resistant result, cast alloy tools must be used as-cast with and/or as a result of rapid and repeated tempera and can be employed at high speeds. However, as little grinding as possible. ture changes during the cutting operation. Cracks there is a tradeoff between wear resistance and Cast alloy materials are not widely used. How typically initiate at high-stress areas and extend toughness that can limit the application of these ever, they find limited use as a compromise, be parallel or perpendicular to the cutting edge (Fig. ultrahard tools to slower feed rates. Figure 5 pro cause th~y perform well at higher surface speeds 3d). Commonly seen in milling operations, these vides specific cutting tool recommendations for than conventional high-speed steels and are more cracks eventually lead to catastrophic failure due machining a variety of ferrous and nonferrous resistant to chipping than standard carbide to chipping or breakage. materials. Manufacturers of cutting tool materials grades. More detailed infonnation on both cast Notching occurs most commonly in the ma should also be consulted for information on se and powder metallurgy forms of these alloys can chining of high-temperature materials such as lection criteria of the various grades they pro be found in the article "Cobalt-Base Alloys" in nickel-base superalloys. It arises in a localized duce. this Volume. area at the depth of cut and is a result of the high High-Speed Tool Steels. There are two classi Cemented carbides belong to a class of hard, stresses in that area. Under these conditions, mi fications of high-speed steels: molybdenum high wear-resistant, refractory materials in which the nor chipping, coupled with an accelerated wear speed steels (type M) and tungsten high-speed hard carbides of Group IVB-VIB metals are rate, results in a failure of the type shown in Fig. steels (type T). bound together or cemented by a ductile metal 3(e). As this notch grows, the likelihood of crack l'ype M steels have high carbon contents, with binder, usually cobalt or nickel. The first ce formation and subsequent breakage is increased. molybdenum as the major alloying element. mented carbide was produced in the 1920s and Selecting Cutting Tool Materials I 5
(a) H (b) (c) 100 J.l.m 1 mm 1 mm
(d) H (e) 100 p,m 1 mm
(f) (g) 1 mm 1 mm fig. 3 Failure mechanisms of cutting tools. (a) Typical flank wear on a carbide insert. (b) Typical edge deformation on a carbide insert. (c) Typical crater wear on a carbide insert. (d) Typical perpendicular cracks on a carbide insert. (e) Typical notching at depth of cut on a whisker-reinforced ceramic insert. (f) Typical chipping on a carbide insert. (g) Typical fracture on a carbide insert
consisted of tungsten carbide (WC) with a cobalt WC-TiC-(Ta,Nb)C, and other solid-solution cu and compressive strengths that enable them to cut binder (Ref2). A remarkable feature of cemented bic carbides. The commercially significant alloys a wide variety of materials at favorably high carbides is that they can be tailored to provide for machining contain 5 to 12 wt% Co and up to material removal rates. Uncoated carbides are different combinations of abrasion resistance and 15 wt% cubic carbides. Carbide grain sizes from typically found in the machining of cast irons, toughness by controlling the amount of cobalt 0.5 to 5 Jlm are commonly used. Compositions steels, stainless steels, and nonferrous and high and the we grain size. and properties of these materials are described in temperature materials at speeds up to 150m/min Over the years, the basic WC-Co material has the article "Cemented Carbides" in this Volume. (500 sfm). been modified to produce a variety of cemented Cemented carbides dominate the metal re Coatings such as titanium nitride (TiN), tita carbides containing WC-TiC, WC-TiC-TaC, moval market. They possess high wear resistance nium carbide (TiC), and aluminum oxide (A[z03) 6/ Materials for Machining and Grinding
white Ah03 ceramics, and they also possess ex ce11ent hot hardness and thermal-shock resis ~ tance. These characteristics pennit them to be used at high speeds and feed rates and in inter ~ rupted cutting of nickel-base superalloys and cast I irons (Ref 10, 11). However, the chemical stabil ity of SbN4/Sialon tool materials is lower than "C Q) Ceramics that of alumina ceramics, which prohibits their Q) c. application in most steel machining. ., Cermets The high hardness and thermal-deformation Cl resistance of ceramic cutting tool materials allow r::: metal removal at speeds as high as 1220 rn!min ~ Carbides (4000 sfm). Additional information on the prop (,) erties and applications of Ah03- and Si3N4-based Cl High- cutting tool materials can be found in the article c: "iii Speed "Ceramics" in this Volume. Tool Ultrahard Tool Materials. Cubic boron ni- · "'~ Steels tride (CBN) and polycrystalline diamond (PCD) (,) c: are extremely wear-resistant materials commonly referred to as ultrahard or superhard tool materi increasing feed rate als. Synthesis, properties, and applications of CBN and PCD are described in the article ..Ultra hard Tool Materials" in this Volume. The use of Fig. 4 Relative machining application ranges of various cutting tool materials CBN and PCD as abrasive grains for grinding applications is described in the article .. Abrasives were added to enable still-higher metal removal The metal removal operations may include turn for Grinding Applications" in this Volume. rates to be achieved (Fig. 6). These coatings en ing, boring, milling, threading, and grooving; Cubic boron nitride, which has a hardness of hance the wear and crater resistance of cemented speeds up to 365 rn!min (1200 sfm) are common. 4500 HK, is the material of choice for machining carbides with a modest loss in strength. As a Ceramic tools are inherently more stable than steels with hardnesses exceeding 50 HRC. Other result, a major portion of the market in cast iron, carbide tools at high temperatures (high cutting applications include machining of cast irons steel, and stainless steel machining is served by speeds) but are less fracture resistant, so recent (typically 180 to 240 HB) and superalloys (>35 these materials, with machining speeds up to 275 work has focused on improving their fraclure HRC). Polycrystalline diamond, on the other m/min (900 sfm). More detailed information on toughness. There are basically two classes of ce hand, cannot be used for steel machining because coating methods used to extend the life and pro ramic cutting tools: A)z03-based ceramics and of its solubility and the catalytic effect of iron, ductivity of cemented carbide inserts can be silicon nitride (Si]N4)-based ceramics. The white which causes graphitization of the diamond. The found in the article "Coated Carbide, Cermet, and Ab03-based ceramics may contain low levels of primary application of PCD tools is in the very Ceramic Tool Materials" in this Volume. zirconia (Zr02) as a sintcring aid and are used for high-speed machining of aluminum-silicon al Cermets. A cermet is a composite of a ceramic machining cast iron. Higher Zr02levels are used loys, composites, and other nonmetallic work material with a metallic binder. Although WC-Co in tools to machine steels. The Zr02 improves pieces. Speeds as high as 2000 m!min (6500 sfm) tools also fit this definition, in the North Ameri fracture toughness by a transformation toughen can be achieved during machining of aluminum can machining industry the term cennets is ap ing or crack deflection mechanism (Ref 6, 7), but silicon alloys with PCD tooling. plied more specifically to TiC-based tools that it decreases the thermal conductivity and hard contain mainly nickel as a binder. The first cut ness of the tool. ting tool in this family, a TiC-Ni alloy, was com Additions of up to 30 val% TiC to Ah03 make mercialized as early as the 1930s but could not the inserts black and improve the thermal con Application/Grade Selection compete with the inherently stronger WC-Co ductivity, hardness, and toughness of the tools Knowledge of the machinability charac based tools. Additions of molybdenum to TiC-Ni without seriously degrading their chemical stabil teristics of the workpiece material and the prop alloys in 1960 brought cermets closer in perform ity. The Ah03-TiC ceramics are employed on a erties of the cutting tool material is the starting ance to WC-Co-based tools for finish machining wide range of workpiece materials, including cast point for selecting a grade-geometry combination of steels. iron, steel, and nickel-base superalloys. for any machining operation. The task of the Titanium carbonitride cermets based on Silicon carbide (SiC) whisker~reinforced Ti(C,N)-Ni-Mo were introduced in 1970, fol A]z03 (A]z03-SiCw) ceramics, developed in the tooling engineer is to select, from the vast num lowed by (Ti,Mo)(C,N)-based compositions that early 1980s (Ref 8), are tougher than white ce bers of possibilities, the grade that will give the provided a balance of wear resistance and tough ramics due to crack deflection by the dispersed best performance, predictability, reliability, and ness due to their finer microstructures (Ref 4). SiC whiskers in the microstructure (Ref 9). The cost. To accomplish this, it is necess&ry to evalu Continued development in this area has resulted whiskers also increase hardness and improve ate the operation characteristics, insert and chip in complex cermets having a variety of additives, thermal-shock resistance by increasing thermal groove selection criteria, and machining econom such as Mo2C, TaC, ZrC, HfC, we, vc, Cr3c2, conductivity and reducing the thermal expansion ics (Ref 12). and aluminum (Ref 5). Various mixes of these coefficient. The major application of these tool Operation Characteristics additives impart different combinations of wear materials is high-speed, high-feed machining of resistance, thermal-shock resistance, and tough nickel-base superalloys. These ceramics can be The operation category involves determin ness, and they allow tools to be tailored for a wide used on cast irons but are rarely used on steels ing whether heavy roughing, roughing, semifin range of machining applications. The newer cer because of the poor chemical stability of SiC. ishing, or finishing is needed. For example, the mets are used in semifinishing and finishing of Tools based on Si3N4 and solid solutions of high-speed finishing of steel requires high wear carbon and alloy steels, stainless steels, ductile aluminum and oxygen in Si]N4 (Sialons) were and deformation resistance. Coated grades, cer irons, free-machining aluminum and other non introduced in the early 1980s. Their whisker-like mets, and ceramics are candidates fm: this type of ferrous alloys, and some high-temperature alloys. grain structure makes them tougher than the operation. Selecting Cutting Tool Materials I 7
Alz03-based ceramics may be more economi Speed attainable when cutting free-machining cal. and/or nonferrous materials Surface finish, part geometry, and part tol Typical speed range erance should also be considered. For example, =,,,,,,,,d Occasional usage - coated carbide inserts generally produce a better Speed, sfm Generally surface finish than uncoated carbides. 100 successful Machine capabilities and limitations are the Aluminum, final operation characteristics that must be deter Rough, high-silicon aiolminwnl mined. For example, older machines with poor PCO semifinish, alloys, nonferrous, finish rigidity and low horsepower cannot make effec nonmetallic tive use of advanced ceramic materials, and high speed tool steels are generally recommended. Rough, Silicon nitride Gray, ductile, semifinish, {SiAION) malleable irons Insert and Chip Groove Selection finish A variety of insert shapes, sizes, nose radii, and chip grooves are available for any machining Rough, High-temperature semifinish, hard steels, operation. Proper selection is essential to opti finish cast irons mize the operation for productivity and cost. The shape of an insert determines its relative strength and cost (Fig. 7). In general, the stronger Rough, Irons, steels, insert has more available cutting edges and there semifinish, powdered metals finish fore can be more economical on a cost-per-index basis. However, the part geometry may limit the Irons and steels, use of the desired insert shape. The general rule is Rough, above 40 HAC, to select the strongest insert capable of producing semifinish, pearlitic gray finish irons below 30 HAC the required part configuration. Size and Nose Radii. The size of an insert is Rough, Irons, steels, detennined by the inscribed circle. The depth of semifinish, high-temperature cut should not exceed one-half the inscribed cir finish alloys, stainless steels cle size, and the insert thickness should be at least four times the operating feed rate. Finally, the largest possible nose radius should be selected. Rough, Irons, steels, semifinish, stainless steels Larger radii produce better surface finishes, han finish dle heavier feed rates, and strengthen the insert. Chip groove selection is almost as crucial as selecting the proper grade. The performance of Semifinish, Irons, steels, finish stainless steels the cutting tool is determined not only by the grade properties and coating type but also by a chip groove style that will allow lower cutting Rough, Irons, steels, forces, better chip handling and control, extended semifinish, nickel-base, tool life, and lower machining costs. Modem finish stainlesi? steels numerically controlled machining operations put a high demand on reliable chip flow. Long chips Rough, Irons, steels, titanium, cause ihterruptions of the machining cycle, a loss iii high-temperature of productivity, and damage to the cutting tool finish alloys, stainless steels and workpiece. Long chips also represent a per sonal hazard to the operator. Heavy Irons, steels, Commercially available inserts with chip rough, stainless steels semifinish grooves are designed to produce acceptable chips throughout the widest possible range of feed rates and depths of cut while maintaining high edge Rough, Irons, steels, semifinish, high-temperature strength. General recommendations are listed be finish alloys, stainless steels low for proper chip groove selection on carbide tools: 0 30 60 120 180 245 305 610 915 1220 1525 1830 2135 2440 Speed, m/min • For general-purpose applications, select a chip groove that has its nominal feed range as Fig. 5 Approximate speed ranges and applications of various cutting and tool materials. Source: GTE Valenite Corp. near as possible to the intended operating feed rate. This will ensure acceptable chips, predict able and reliable tool life, and a lower cost per Workpiece material type (hard, soft and Production volume (large or small scale, index. gummy, or difficult to machine) must also be periodic or long-range production) is a third • For heavy feeds/high material-removal rates, determined. For example, the machining of soft important consideration. For example, the ma select single-sided inserts. The improved rigid and gummy low-carbon steel at moderate speeds chining of difficult-to-cut Inconel 718 in large ity and resultant higher effective edge strength requires a TiN -coated insert or a cermet to resist scale production using whisker-reinforced ce permit higher speeds and feeds while generat buildup at the cutting edge and to provide a good ramics will increase productivity and lower ing lower forces than double-sided inserts. In surface finish. cost. In small-scale production, conventional most cases, this will improve productivity. 8 I Materials for Machining and Grinding
1000 Table 1 Different types of ceramic edge preparation with recommended application BOO Al~:rcoated Operation Rake angle Chamfer 600 0 General purpose Negative 0.20 mm X 20° (0.008 in. X 20°) Finishing Negative or positive 0.075 mmx25° (0.003 in.x25°) ~ 400 General purpose and milling Negative 0.15mmx 30°(0.006 in x30°) Heavy roughing Negative 0.38mmx25°(0.Q15 in. x25°) • Special Negative or positive Special '"•0. • ~ Width IL Width IJ::__t ~ 200 u ~~ngle ~"Angle I }' R•dou' I ,A 100 1 2 I Tool life, min to 0.25 mm flank wear Special applications, fine finishing General-purpose grades, higher forces, negative rake angles (a)
1000
600 though the general rule for hones is that less is and the material being machined. Generally, cut 400 better, the toughness of the cutting tool material ting tool manufacturers supply the optimum cut and the integrity of the insert cutting edge should ting speed range for all grades in their grade .0 200 be considered. A larger hone or chamfer gives handbooks. .€ E additional protection against catastrophic failure -o 100 by fracture, which results in the loss of all cutting • edges . •0. 60 Testing of Cutting Tool Materials Increasing strength Optimum cutting speed I Minimum/ cost Cutting speed Increasing cost Fig. 8 Chart for determining minimum cost, maximum production, and optimum cutting speed. Source: Fig. 7 Relationship among insert shape, strength, and cost Ref13 Selecting Cutting Tool Materials f 9 rate is varied to determine the overall toughness • Mat",ial: AISI4150 steel, 220 HB, facing 175 REFERENCES of the cutting tool. Typical conditions for this test to 50 mm (7 to 2 in.) diameter in Carbide testing are: • Speed: 275 m/min (900 sfm) 1. Cutting Tool Materials, Machining, Vol 1, Tool • Feed: 0.40 mm/rev (0.015 in./rev) and Manufacturing Engineers Handbook, 4th • Material: AISI 4150 steel (resulfurized), 265 • Depth of cut: 1.6 mm (0.0625 in.) ed., T.J. Drozda and C. Wick, Ed., Society of HB, 75 by 40 mm (3.0 by 1.5 in.) cross section Manufacturing Engineers, 1983, p 3-1 to 3-48 • Speed: 230m/min (750 sfm) Nodular Iron Impact Test. A specialized test 2. K. Schroeter, U.S. Patent 1,549,615,1925 • Depth of cut: 3.2mm (0.125 in.) used to determine relative coating adherence is 3. D.E. Graham, Aluminum Oxide Coatings for conducted using a gu,mmy nodular (ductile) iron. Cemented Carbide Cutting Tools, Ceramic Cut The centerline of the cutter is aligned with the entry This is a flycut test that uses a !50 mm (6.0 in.) ting Tools, B.D. Whituey, Ed., Noyes Publica of bar, and the insert is run one pass per comer at diameter cutter loaded with a single insert. The tions,1994,p22!-240 successively higher feed rates until chipping or insert is exposed to a single pass at a specified 4. E. Rudy, S. Worcester, and W. Elkington, High breakage occurs. speed, feed, and depth of cut. Adhered iron is then Temp. High Pressures, Vol 6 (No.4), 1974, p The turning test is generally used to deter removed in an acid bath, and the insert is in 447-454 mine wear resistance and high-speed deformation spected to determine the amount of coating that 5. H. Dei, Science of Hard Materials, Proceedings resistance. In this test, speed, feed, and depth of has spalled away from the substrate. 'This is ex of the Second International Conference on the cut are constant, and tool life is measured as the pressed as a percentage of the total chip contact Science of Hard Materials (Rhodes), 23-28 time required to form a 0.38 mm (0.015 in.) wear area. Typical conditions for this test are: Sept 1984,Ser.No. 75,AdamHilgerLtd.,l986, land ora0.!3 mm (0.005 in.) crater depth. A wide p 489-523 variety of conditions are used, depending on the • Material: 80-55-06 ductile iron, 235 HB, 50 6. N. Claussen, Materials Science and Engineer material being tested, but typical conditions mm (2 in.) diameter cross section ing, Vol 71, 1985, p 23-38 might be: • Speed: 275 m/min (900 sfm) 7. F.F. Lange, J. Mater. Sci., Vall? (No. 1), 1982, • Feed: 0.23 mm/tooth (0.0092 in./tooth) p 225-234 • Material: AISI!045 steel, 180 HB • Depth of cut: 3.2 mm (0.125 in.) 8. G.C. Wei and P.F. Becher, Am. Ceram. Soc. • Speed: 210m/min (700 sfm) Bull., Vol64(No. 2),1985,p298-304 • Feed: 0.50 mm/rev (0.020 in./rev) 9. K.T.FaberandA.G.Evans,ActaMetal/., Vol31 • Depth of cut: 2.55 mm (0.100 in.) (No.4), 1983, p 565-576 10. B. North and R.D. Baker, Int'l Jour. Refract. During the test, inserts are checked and wear lands ACKNOWLEDGMENTS Hard Met, Vol3 (No. 1), 1984, p46-51 are measured at regular intervals. The tool 1ife is 11. C.W. Beeghly and A.F. Shuster, in Advances in expressed as the number of minutes required to The information in this article is largely taken Tool Materials for Use in High Speed Machin achieve a 0.38 mm (0.015 in.) wear land or a 0.13 from: ing, Society of Carbide and Tool Engineers, mm (0.005 in.) crater depth. ASM International, Feb 1987, p 91-99 A facing test is used to provide a rapid means • C. Zimmerman, S.P. Boppana, and K. Katbi, 12. H. Pastor, Present Status and Development of of evaluating the wear and crater resistance of Machinability Test Methods, Machining, Vol Tool Materials: Part 1--Cutting Tools, Refract. cutting tools (particularly coated materials). In 16, ASM Handbook (formerly 9th ed., Metals Hard Met., Dec 1987, p 196-209 this test, speed, feed, and depth of cut are held Handbook), ASM International, 1989, p 639- 13. C. Donaldson, G.H. Lecain, and V.C. Goold, constant while the insert is run through multiple 647 Tool Design, 3rd ed., McGraw-Hill, 1973, p facing passes. The total number of passes re • AT. Santhanam and D.T. Quinto, Surface 270-271 quired to achieve a0.38 mm (0.015 in.) wear land Engineering of Carbide, Cermet, and Ce 14. H. Yaguchi, Appendix: Machinability Testing of or a 0.13 mm (0.005 in.) crater depth is consid ramic Cutting Tools, Surface Engineering, Carbcn and Alloy Steels,Machining, Voll6,ASM ered-the tool life. Typical conditions for testing a Vol 5, ASM Handbook, ASM International, Handbook (formerly 9th ed., Metals Handbook), coated carbide material are: 1994, p 900-908 ASM International, 1988, p 677-680