Influences of the characteristics of carbide particles on the rolling contact fatigue life of rare earth modified, highly clean bearing steel

Machine tool bearings made of rare earth modified, highly clean bearing steel subjected to rolling contact fatigue (RCF) under the same bench test conditions were studied. The morphology and initiation position of contact fatigue cracks of bearings were characterized macroscopically and microscopically. According to the characteristics of carbide particles in the metallographic structure of the crack source areas, the corresponding relationships between the difference of particle size and roundness of carbide and the change in RCF lives of bearings were proposed, as well as the corresponding different failure mechanisms. The results show that RCF life increases with the decrease in the percentages of large-sized and irregular carbides in the microstructure. When early RCF failure occurs, cracks originate mainly at the surface, and the size of carbides affects RCF; with the increase of service life, the cracks begin to originate at the subsurface, and at this time, the roundness of carbides exerts a significant influence.