A study of local microstructure decay in GCr15 due to Rolling Contact

This study investigated the microstructural alteration of GCr15 bearing steel under Rolling Contact condition. It was found that Decay Region, a feature microstructure, formed in the subsurface of materials with the dominant effect of cyclic contact stress. The Decay Region is composed of discretely distributed micro-regions where phase transition occurred, presenting a hollow crescent shape. The microstructure after phase transformation was highly susceptible to corrosion by Nital solution. The formation of Decay Region was related to the orthogonal shear stress and there was an upper threshold. Excessively high stress suppressed the appearance of Decay Region. During Rolling Contact, the hardness of materials evolved simultaneously. The evolution of hardness and microstructure exhibited a parallel development, as the dominant stresses were different.