关键词: 低碳高合金轴承钢, 渗碳, 滚动接触疲劳, 碳化物, 裂纹萌生

Abstract: Microstructure, hardness, and residual stress gradient and rolling contact fatigue behavior of a low-carbon high-alloy bearing steel after carburizing with different time were investigated. The results show that after treatment by different carburizing processes, the carburized layer microstructure is composed of high-carbon martensitic+carbide, and the carbide types are mainly M₂₃C₆, M₆C and M₇C₃. The core microstructure is tempered martensite+a small amount of retained austenite. There is not much difference between the surface and subsurface residual stress and microhardness of the bearing steel treated by two different processes. Compared with the short-term carburized bearing steel, the longer-time carburized bearing steel can obtain more carbides in the carburized layer, the size is finer, and the carbide tends to be oval. When the depth of carburized layer is increased from 980 μm to 1184 μm, the rated life of rolling contact fatigue L₁₀ is increased by about 192%, and the median life L₅₀ is increased by about 95%. The long-term carburized bearing steel has a relatively high rolling contact fatigue life, which is mainly due to the relatively small elliptical M₆C carbide and M₂₃C₆ carbide in the carburized layer, and the maximum shear stress and maximum shear strain generated near the carbide under the same cyclic load are small, and the crack is not easy to germinate.

Key words: low-carbon high-alloy bearing steel, carburizing, rolling contact fatigue, carbide, crack initiation