침질탄화처리한 고탄소 크롬 베어링강의 회전접촉 피로거동에 미치는 잔류오스테나이트의 영향 = Effect of Retained Austenite on Rolling Contact Fatigue on Nitrocarburzed High-Carbon Chromium Bearing Steel

다국어 초록 (Multilingual Abstract)

Effect of retained austenite on rolling contact fatigue of nitrocarburized high-carbon chromium bearing steel has been investigated to develop surface-hardened bearing steel with imprved resistance to rolling contact fatigue. Fatigue tests were conducted in elesto-hydrodynamic lubricating conditions at a shaft speed of 5,000rpm, under max. hertzian stress of 492㎏/㎟. Volume fraction of retained austenite in austenitic nitrocarburized STB2 steel was controlled by tempering at various temperature, 200∼250℃. It was observed using TEM that decomposition of retained austenite during tempering at 250℃ was the highest in quantity, resulted in formation of lower bainite. Rolling contact fatigue life of the specimens with lower bainite, formed by decomposition of retained austenite, was improved in comparison with there of specimens with more amount of retained austenite.