Effect of neighboring-microstructure on the rolling contact fatigue around non-metallic inclusion

Abstract

It is well known that the flaking of a raceway causes the bearing failure, and the flaking mechanism depends on the lubrication condition. In the case of ideal lubrication condition with sufficient oil film thickness, the flaking originates from a non-metallic inclusion at the subsurface. It occurs through the formation of butterfly structure due to stress concentration around the inclusion. Therefore, the countermeasure of this type of flaking is to make cleaner steel by the reduction of inclusions. However, further reduction of inclusion imposes an extra challenge for the current steel making process. Therefore, in this paper, the effect of neighbouring microstructure on the butterfly structure is evaluated to propose a new life improvement method for rolling contact fatigue. It was suggested that it’s important to eliminate strain localization near inclusion for improving bearing life.

Crack path and regularities for ball‐bearing fracture in the very‐high‐cycle fatigue regime

“…On slices prepared perpendicular to the raceway surface, it was demonstrated experimentally 32 that cracks initiated from inclusion may grow at different angles of inclination to the rolling contact surface. The process of fatigue spalling was not considered by stages, and because of this, it does not allow to analyze the total process of material spalling from the moment of crack origination up to the separation of the material fragment.…”

“…Nevertheless, both appearance and absence of "butterfly" along with increase and decrease in microhardness of surface layer in bearing steels AISI 52100, AISI M50, and M50NiL were noted with regard to microstructural changes in material. 25,[28][29][30][31] On slices prepared perpendicular to the raceway surface, it was demonstrated experimentally 32 that cracks initiated from inclusion may grow at different angles of inclination to the rolling contact surface. The process of fatigue spalling was not considered by stages, and because of this, it does not allow to analyze the total process of material spalling from the moment of crack origination up to the separation of the material fragment.…”