Microstructural Changes and Crack Initiation with White Etching Area Formation under Rolling/Sliding Contact in Bearing Steel

Abstract

Microstructural changes during the formation of White Etching Area (WEA) were investigated using a rolling/sliding contact fatigue test machine. In particular, interfaces between WEA and retained austenite or spherodized carbide in a high carbon chromium bearing steel have been observed. Fatigue tests were carried out by means of a disk on roller-type equipment. It was found that acicular structures are formed at an initial stage of the WEA formation process. Plastic deformations of spherodized carbides were caused by shear stress in the initial stage of this process as well. Additionally, micro voids were found near the interfaces. Furthermore, amorphous-like structures were found in the WEA. It was suggested that WEA formation is caused by the local plastic deformation of the material. The shear stress was caused by slipping between the roller and the disk. As a result, it was suggested that martensite forms an amorphous-like phase and then changes into a WEA. Cracks developed in the amorphous-like structure/the granular area interface in the WEA and in the Matrix/WEA interface.