Plastic deformation of quenched and tempered 52100 bearing steel in compression
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this paper the results of compression tests run on samples of 52100 ball b e a r i n g s t e e l given a wide variety of heat treatments are reported. The flow stress and work hardening behavior of hard s t e e l s such as this are of interest for two reasons: 1) these properties should be useful guides for the selection of heat treatments for 52100 steel. Indentation h a r d ness is the only m e a s u r e of monotonic (as opposed t o cyclic) flow properties generally employed in specifying or describing the flow characteristics resulting from a given heat treatment; and 2) knowledge of the work hardening characteristics of these steels in compression may aid in understanding microstructural mechanisms of fatigue d a m a g e produced by r o l l i n g contact. 52100 steel, heat treated for b e a r i n g applications, consists of a martensite matrix, p r i m a r y carbides (undissolved during austenitization) and, typically, five t o fifteen percent retained austenite. The austenite is known t o transform t o martensite u n d e r the stresses imposed by r o l l i n g contact,1 and in fully rev e r s e d cyclic straining as well.2 The monotonic tensile and compressive behavior of steels containing retained austenite is quite different. Tensile s t r e s s e s promote austenite transformation while compressive s t r e s s e s tend to suppress i t .3 Austenite will transform in simple compression, however, because s h e a r s t r e s s e s always aid the transformation. The added s t r a i n produced by austenite transformation is in the same sense as an applied tensile strain, but o p p o s i t e t o an a p plied compressive strain. As a result, the effect of austenite transformation on work hardening is different in tension and compression. Transformation of retained austenite in the plastic zone at a c r a c k tip i n c r e a s e s the resistance to c r a c k propagation.4 Retained austenite has also been found t o improve fatigue life1 and to produce "cyclic h a r d ening", i . e . , the cyclic stress-strain c u r v e lies well C. A. STICKELS is on the Research Staff of Ford Motor Company, Dearborn, MI48121. Manuscript submitted March 23, 1976. METALLURGICAL TRANSACTIONS A
above the tensile stress-strain c u r v e if sufficient retained austenite is present.2'5 This is primarily a consequence of austenite transformation in monotonic tension at stresses below the martensite yield point; the cyclic stress-strain c u r v e is much c l o s e r to, but lies slightly below, the monotonic stress-strain c u r v e in compression. 2'5 While some qualitative idea of prob a b l e cyclic behavior can be obtained by examining monotonic flow s t r e s s and work hardening data, quantitative predictions of cyclic behavior from monotonic tests, even for completely martensitic steels, is not possible. For s t e e l s containing retained austenite, prediction is even less certain. In a previous paperG it was shown that reducing the primary carbide size of 52100 s t e e l austenitized at temperatures typical of commercial practice
