Statistical analysis on rolling contact fatigue in railroad axle bearing steel

摘要

High-strength steels are widely used in high-performance bearings utilized in most mechanical systems. However, there has been little statistical analysis regarding the fatigue failure behaviour of the material, where surface peeling resulted from contact fatigue during rolling is a significant life-limiting mechanism. In this study, we examine the statistical behaviour of surface-crack nucleation, propagation, and peeling in a high-speed train axle bearing made of GCr15 steel by using a laboratory rolling-contact equipment. We reveal that cyclic rolling-contact leads to the formation of a hardness gradient in the outer ring of the bearing. The gradient layer is of several millimetres. The peeling rate could be as high as 28 mu m per million cycles when the contact pressure is close to that applied in real service. Peeling-induced cracking is dominantly transgranular. The incipient angle is about 23.2 degrees, and its depth could be hundreds of micrometres. The findings reported here could be employed to assess the lifetime of bearings made of GCr15 steel and possible other engineering metals.