toughness to hardness(KdH). From Fig. 11, maximum abrasion resistance is obtained by optimizing the ratio KdH while maintaining the indentation hardness or groove size slightly below that at which the transition to fragmentation occurs(Ref 11) angularity of the abrasive particles, shifts the nt, by increasing either the applied load or the size, hardness,or Increasing the severity of the wear environme transition from fragmentation to cutting/plowing to higher values of fracture toughness(Fig. 11). This results in a decrease in the maximum wear resistance Microstructure Microstructural effects on abrasive wear depend on the overall magnitude or scale of the wear environment. For high-impact loads, large abrasive particle size, and so on, the size of the microstructural features is generally much smaller than that of the abrasive wear damage. In this case, the role of microstructure on wear resistance is limited to its effect on bulk mechanical properties. Abrasive wear rates, particularly for materials that exhibit homogeneous microstructures, may correlate with bulk hardness(Ref 11). Figure 12 shows the effect of microstructure and hardness on the high-stress abrasion resistance of steels Over a limited hardness range(200 to 300 HV, or 2.0 to 3.0 GPa), relative abrasion resistance decreases in the order(Ref 11) austenite> bainite pearlite >martensite 3.0 Bainitic steels alloys Quenched and 201 Cold work Pearlitic steels 1002003004005006007008009001000 Hardness, HV Fig. 12 Effect of microstructure and hardness on the abrasion resistance of steels: high-stress abrasion, alumina abrasive. Source: Ref 7 This effect can be attributed to the influence of microstructure on plastic deformation behavior. However, bainitic and martensitic microstructures offer greater abrasion resistance at higher hardness levels(400 HV,or 4.0 GPa) At lower loads, and with smaller abrasive particle sizes, microstructural features are more effective as discrete components, and the mechanical properties of individual phases assume increased importance. This occur when the size of the microstructural features is approximately equal to, or larger than, that of the abrasive Under these conditions, materials with duplex microstructures, for example, alloy white irons and some ceramics, are more sensitive to microstructural effects. In such materials, size, spacing, and volume fraction of the harder phase, as well as the mechanical properties of both hard and soft(matrix) phases, can significantl affect wear behavior. Thus the abrasion resistance of the material either increases decreases or remains the same by increasing the volume fraction of the harder phase. The net effect depends on the various contributions of the plowing, cutting, fragmentation, and pull-out mechanisms to the total wear rate. Figure 13 shows schematically this behavior for alloy white irons and alloy carbide materials. The transition from increasing to decreasing abrasion resistance with increasing carbide volume fraction is associated with the relative contributions of fragmentation of the carbides and plowing/cutting of the matrix to the total wear. Carbide hardness, and size relative to that of the wear damage, also influences these trends (ref 11, 26) Thefileisdownloadedfromwww.bzfxw.com
toughness to hardness (Kc/H). From Fig. 11, maximum abrasion resistance is obtained by optimizing the ratio Kc/H while maintaining the indentation hardness or groove size slightly below that at which the transition to fragmentation occurs (Ref 11). Increasing the severity of the wear environment, by increasing either the applied load or the size, hardness, or angularity of the abrasive particles, shifts the transition from fragmentation to cutting/plowing to higher values of fracture toughness (Fig. 11). This results in a decrease in the maximum wear resistance. Microstructure. Microstructural effects on abrasive wear depend on the overall magnitude or scale of the wear environment. For high-impact loads, large abrasive particle size, and so on, the size of the microstructural features is generally much smaller than that of the abrasive wear damage. In this case, the role of microstructure on wear resistance is limited to its effect on bulk mechanical properties. Abrasive wear rates, particularly for materials that exhibit homogeneous microstructures, may correlate with bulk hardness (Ref 11). Figure 12 shows the effect of microstructure and hardness on the high-stress abrasion resistance of steels. Over a limited hardness range (200 to 300 HV, or 2.0 to 3.0 GPa), relative abrasion resistance decreases in the order (Ref 11): austenite > bainite > pearlite > martensite. Fig. 12 Effect of microstructure and hardness on the abrasion resistance of steels: high-stress abrasion, alumina abrasive. Source: Ref 7 This effect can be attributed to the influence of microstructure on plastic deformation behavior. However, bainitic and martensitic microstructures offer greater abrasion resistance at higher hardness levels (>400 HV, or 4.0 GPa). At lower loads, and with smaller abrasive particle sizes, microstructural features are more effective as discrete components, and the mechanical properties of individual phases assume increased importance. This occurs when the size of the microstructural features is approximately equal to, or larger than, that of the abrasive. Under these conditions, materials with duplex microstructures, for example, alloy white irons and some ceramics, are more sensitive to microstructural effects. In such materials, size, spacing, and volume fraction of the harder phase, as well as the mechanical properties of both hard and soft (matrix) phases, can significantly affect wear behavior. Thus, the abrasion resistance of the material either increases, decreases, or remains the same by increasing the volume fraction of the harder phase. The net effect depends on the various contributions of the plowing, cutting, fragmentation, and pull-out mechanisms to the total wear rate. Figure 13 shows schematically this behavior for alloy white irons and alloy carbide materials. The transition from increasing to decreasing abrasion resistance with increasing carbide volume fraction is associated with the relative contributions of fragmentation of the carbides and plowing/cutting of the matrix to the total wear. Carbide hardness, and size relative to that of the wear damage, also influences these trends (Ref 11, 26). The file is downloaded from www.bzfxw.com
Fragmentation gcgc0g0g hardness Carbide volume fraction. Fig. 13 Influence of microstructure on abrasive wear behavior of alloy white irons and chromium carbide materials. Source: Ref 5 Other Properties. Wear processes that involve plastic deformation (i.e, cutting and plowing) also generate significant increases in temperature at the wearing surface. These increases occur as a result of frictional energy dissipation at the interface between the wearing surfaces. Under these circumstances, the wear behavior is influenced by characteristics such as the friction coefficient and thermal conductivity of the two wear bodies. In materials that exhibit low values of thermal conductivity, one of two additional effects may arise, depending on other material properties. Localized thermal expansion in ceramics may result in additional material loss by spalling; conversely, localized temperature increases in polymers may give rise to melting. Materials that exhibit low friction coefficients under dry sliding conditions(e.g, some polymers and finely ground ceramics) suffer less degradation through frictional temperature rise effects References cited in this section Winer,Ed, American Society of Mechanical Engineers, 1980, P 17-3 book. M.B. Peterson and WO 5. H. Czichos, Systems Approach to Wear Problems, Wear Control Har 6. J.D. Gates and G.J. Gore, Wear of Metals: Philosophies and Practicalities, Mater. Forum, Vol 19, 1995 p53-89 7.K.-H. Zum Gahr, Microstructure and Wear of materials, Elsevier Science Publishers, 1987 9. T.E. Norman, Wear in Ore Processing Machinery, Wear Control Handbook, M.B. Peterson and wo Winer, Ed, American Society of Mechanical Engineers, 1980, p 1009-1051 10. P.J. Mutton, Abrasion Resistant Materials for the Australian Minerals Industry, Vol 1, Australian Minerals Industries Research Association Limited. 1988 11. M.A. Moore, Abrasive Wear, Fundamentals of Friction and Wear of Materials, D A. Rigney, Ed American Society for Metals, 1981, p 73-118 12. M.J. Murray, P.J. Mutton, and J D. Watson, Abrasive Wear Mechanisms in Steels, Wear of materials, W.A. Glaeser, K.C. Ludema, and S.K. Rhee, Ed, American Society of Mechanical Engineers, 1979, p 257-265
Fig. 13 Influence of microstructure on abrasive wear behavior of alloy white irons and chromium carbide materials. Source: Ref 5 Other Properties. Wear processes that involve plastic deformation (i.e., cutting and plowing) also generate significant increases in temperature at the wearing surface. These increases occur as a result of frictional energy dissipation at the interface between the wearing surfaces. Under these circumstances, the wear behavior is influenced by characteristics such as the friction coefficient and thermal conductivity of the two wear bodies. In materials that exhibit low values of thermal conductivity, one of two additional effects may arise, depending on other material properties. Localized thermal expansion in ceramics may result in additional material loss by spalling; conversely, localized temperature increases in polymers may give rise to melting. Materials that exhibit low friction coefficients under dry sliding conditions (e.g., some polymers and finely ground ceramics) suffer less degradation through frictional temperature rise effects. References cited in this section 5. H. Czichos, Systems Approach to Wear Problems, Wear Control Handbook, M.B. Peterson and W.O. Winer, Ed., American Society of Mechanical Engineers, 1980, p 17–34 6. J.D. Gates and G.J. Gore, Wear of Metals: Philosophies and Practicalities, Mater. Forum, Vol 19, 1995, p 53–89 7. K.-H. Zum Gahr, Microstructure and Wear of Materials, Elsevier Science Publishers, 1987 9. T.E. Norman, Wear in Ore Processing Machinery, Wear Control Handbook, M.B. Peterson and W.O. Winer, Ed., American Society of Mechanical Engineers, 1980, p 1009–1051 10. P.J. Mutton, Abrasion Resistant Materials for the Australian Minerals Industry, Vol 1, Australian Minerals Industries Research Association Limited, 1988 11. M.A. Moore, Abrasive Wear, Fundamentals of Friction and Wear of Materials, D.A. Rigney, Ed., American Society for Metals, 1981, p 73–118 12. M.J. Murray, P.J. Mutton, and J.D. Watson, Abrasive Wear Mechanisms in Steels, Wear of Materials, W.A. Glaeser, K.C. Ludema, and S.K. Rhee, Ed., American Society of Mechanical Engineers, 1979, p 257–265
13. D.R. Danks and P. Clayton, Comparison of the Wear Process for Eutectoid Rail Steels: Field and Laboratory Tests, Wear, Vol 120, 1987, p 233-250 14. R C D. Richardson. The Maximum Hardness of Strained Surfaces and the abrasive Wear of Metals and Alloys, Wear, Vol 10, 1967, p 353-382 15.R.C. D Richardson, The Wear of Metals by Hard Abrasives, Wear, Vol 10, 1967, p 291-309 16. M. M. Khruschov, Resistance of Metals to Wear by abrasion as Related to Hardness, J. Mech. Eng 1957,p655-659 17. M. M. Khruschov and M.A. Babichev, Issledovaniya iznashivaniya metallo, Izdat. Akad. Nauk SSSR, 1960, p 889-893: Research on Wear of Metals, N.E.L translation 18. M.A. Moore, The Relationship Between the Abrasive Wear Resistance, Hardness and Microstructure of Ferritic Materials, Wear, Vol 28, 1974, p 59-68 19.R.C. D Richardson, The Wear of Metals by Relatively Soft Abrasives, Wear, Vol 11, 1968, p 245-275 20. J F. Archard, Contact and Rubbing of Flat Surfaces, J. Appl. Phys., Vol 24, 1953, p 981-988 21. A. Misra and I. Finnie, On the Size Effect in Abrasive and Erosive Wear, Wear, Vol 65, 1981, p 359 373 22. I.M. Hutchings, Tribology: Friction and Wear of Engineering Materials, CRC Press, 1992 23. T.H. Kosel, Solid Particle Erosion, Friction, Lubrication, and Wear Technology, Vol 18, ASM Handbook, P.J. Blau, Ed, ASM International, 1992, p 199-213 24. A.R. Lansdown and A L. Price. Materials to Resist Wear A Guide to Their selection and Use Pergamon Press. 1986 25K -H. Zum Gahr. Relation Between Abrasive Wear Rate and the fracture Toughness of metallic Materials, Z. Metallkd, Vol 69, 1978, p 643-650 26. K.-H. Zum Gahr and D V. Doane, Optimizing Fracture Toughness and Abrasion Resistance in White Cast Irons, Metall. Trans. A, Vol 11, 1980, p 613-620 Abrasive wear Failures Jeffrey A. Hawk and Rick D. Wilson, Albany Research Center; Daniel R. Danks, Danks Tribological Services: Matthew T. Kiser, Wear Failure analysis Table 3 presents the procedural sequence used in general failure analysis studies. Failure analysis studies can be broken down into the following major categories through the collection of documentary evidence: service conditions; materials, handling, storage, and identification; interviews; field investigation; laboratory analysis and dimensional analysis(Ref 2 ). The same general procedure is used in analyzing wear failures Table 3 General fracture failure analysis procedural sequence Thefileisdownloadedfromwww.bzfxw.com
13. D.R. Danks and P. Clayton, Comparison of the Wear Process for Eutectoid Rail Steels: Field and Laboratory Tests, Wear, Vol 120, 1987, p 233–250 14. R.C.D. Richardson, The Maximum Hardness of Strained Surfaces and the Abrasive Wear of Metals and Alloys, Wear, Vol 10, 1967, p 353–382 15. R.C.D. Richardson, The Wear of Metals by Hard Abrasives, Wear, Vol 10, 1967, p 291–309 16. M.M. Khruschov, Resistance of Metals to Wear by Abrasion as Related to Hardness, J. Mech. Eng., 1957, p 655–659 17. M.M. Khruschov and M.A. Babichev, Issledovaniya iznashivaniya metallov, Izdat. Akad. Nauk SSSR, 1960, p 889–893: Research on Wear of Metals, N.E.L. translation 18. M.A. Moore, The Relationship Between the Abrasive Wear Resistance, Hardness and Microstructure of Ferritic Materials, Wear, Vol 28, 1974, p 59–68 19. R.C.D. Richardson, The Wear of Metals by Relatively Soft Abrasives, Wear, Vol 11, 1968, p 245–275 20. J.F. Archard, Contact and Rubbing of Flat Surfaces, J. Appl. Phys., Vol 24, 1953, p 981–988 21. A. Misra and I. Finnie, On the Size Effect in Abrasive and Erosive Wear, Wear, Vol 65, 1981, p 359– 373 22. I.M. Hutchings, Tribology: Friction and Wear of Engineering Materials, CRC Press, 1992 23. T.H. Kosel, Solid Particle Erosion, Friction, Lubrication, and Wear Technology, Vol 18, ASM Handbook, P.J. Blau, Ed., ASM International, 1992, p 199–213 24. A.R. Lansdown and A.L. Price, Materials to Resist Wear, A Guide to Their Selection and Use, Pergamon Press, 1986 25. K.-H. Zum Gahr, Relation Between Abrasive Wear Rate and the Fracture Toughness of Metallic Materials, Z. Metallkd., Vol 69, 1978, p 643–650 26. K.-H. Zum Gahr and D.V. Doane, Optimizing Fracture Toughness and Abrasion Resistance in White Cast Irons, Metall. Trans. A, Vol 11, 1980, p 613–620 Abrasive Wear Failures Jeffrey A. Hawk and Rick D. Wilson, Albany Research Center; Daniel R. Danks, Danks Tribological Services; Matthew T. Kiser, Caterpillar Inc. Wear Failure Analysis Table 3 presents the procedural sequence used in general failure analysis studies. Failure analysis studies can be broken down into the following major categories through the collection of documentary evidence: service conditions; materials, handling, storage, and identification; interviews; field investigation; laboratory analysis; and dimensional analysis (Ref 2). The same general procedure is used in analyzing wear failures. Table 3 General fracture failure analysis procedural sequence The file is downloaded from www.bzfxw.com
Step 1: Determine prior history Review documentary evide Test certificates Mechanical/wear test data Pertinent specifications Correspondence Interviews Depositions and interrogatories Review service parameters Design or intended operating parameters Actual service conditions Temperature data( magnitude and range) Environmental conditions Service loads/stresses Step 2: Clean failed parts or specimens Step 3: Perform nondestructive tests Macroscopic examination of wear/fracture surface Presence of color or texture Temper color Oxidation Corrosion product Contaminants Presence of distinguishing surface features Shear lips Beach marks Chevron markings Gross plasticity Large voids or exogenous inclusions Secondary cracks
Step 1: Determine prior history Review documentary evidence Test certificates Mechanical/wear test data Pertinent specifications Correspondence Interviews Depositions and interrogatories Review service parameters Design or intended operating parameters Actual service conditions Temperature data (magnitude and range) Environmental conditions Service loads/stresses Step 2: Clean failed parts or specimens Step 3: Perform nondestructive tests Macroscopic examination of wear/fracture surface Presence of color or texture Temper colors Oxidation Corrosion products Contaminants Presence of distinguishing surface features Shear lips Beach marks Chevron markings Gross plasticity Large voids or exogenous inclusions Secondary cracks
Direction of propagation Fracture origin Detection of surface and subsurface defects UX e penetrant Ultrasonics Hardness measurements Macroscopic Microscopic Chemical and microstructural analysis Macrochemistry(wet chemical analysis) Spectrographic analysis X-ray diffraction Electron beam microprobe analysis Step 4: Perform destructive tests Metallographic (light microscopy, scanning electron microscopy, transmission electron microscopy) Mac MicroscopIc Structure Grain size Cleanliness Mechanical tests Tensile Impact Fracture toughness Corrosion tests Wet chemical analysis Step 5: Perform stress analysis Step 6: Store and preserve parts or specimens Source: Ref 1 Thefileisdownloadedfromwww.bzfxw.com
Direction of propagation Fracture origin Detection of surface and subsurface defects Magnaflux Dye penetrant Ultrasonics Hardness measurements Macroscopic Microscopic Chemical and microstructural analysis Macrochemistry (“wet” chemical analysis) Spectrographic analysis X-ray diffraction Electron beam microprobe analysis Step 4: Perform destructive tests Metallographic (light microscopy, scanning electron microscopy, transmission electron microscopy) Macroscopic Microscopic Structure Grain size Cleanliness Mechanical tests Tensile Impact Fracture toughness Corrosion tests Wet chemical analysis Step 5: Perform stress analysis Step 6: Store and preserve parts or specimens Source: Ref 1 The file is downloaded from www.bzfxw.com