| Microstructural changes and variation in microhardness as a function of depth under the raceway during rolling contact fatigue of high-carbon chromium bearing steel (STB 2 or AISI 52100) have been studied to clarify rolling contact fatigue in the bearing steel. It was observed that dispersed spherical carbides in tempered martensitic matrix consisting of twinned martensite were produced by partial austenitizing, oil quenching and tempering of spheroidized annealed specimens. Platelike carbides were formed during rolling contact fatigue, at an angle of almost 90 deg to the rolling direction, along the depth of between 300 and 600 ㎛ below the raceway. The initial matrix subjected to cyclic rolling contact stress, transformed to ferrite and decayed martensite, resulted in local softening between 300 and 600 ㎛ below the raceway. In the present research, these structural changes and softening caused by rolling contact fatigue revealed that the region of maximum shear stress was the narrow zone between 300 and 600 ㎛ below the raceway. |
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