Enhanced rolling contact fatigue property of a rare earth addition bearing steel with a gradient nanostructured surface layer

Rolling contact fatigue performance is among the most important issues for applications of bearing steels. In this work, a recently developed surface modification technique, surface mechanical rolling treatment, was applied on a rare-earth addition bearing steel. And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses. The results demon- strated that a 700 μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment. The grain size decreases while the microhardness increases gradually with decreasing depth, reaching ∼23 nm and ∼10.2 GPa, respectively, at the top surface. Consequently, the rolling contact fatigue property is significantly enhanced. The characteristic life of treated samples is ∼3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa. Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard mate- rial degradation and microcrack formation, but also prolong the steady-state elastic response stage under rolling contact fatigue.