Towards understanding the time-dependent microstructural evolution mechanism of GCr15 bearing in rolling contact fatigue

Abstract

We conducted an in-depth investigation into the subsurface-initiated rolling contact fatigue failure of GCr15 bearing elements subjected to high-cycle loading, emphasizing the comprehensive understanding on the time-dependent microstructural evolutions mechanism with respect to the rolling element ball and inner/out raceway. To this end, a specialized experimental strategy was implemented, maintaining consistent bearing geometry through systematic replacement of rolling elements while preserving structural integrity. This methodology enabled comprehensive observation and analysis of time-dependent microstructural transformations throughout the failure process, facilitating precise temporal tracking of microstructural evolution during progressive degradation. Microstructural features, including grain size, dislocation density, and phase transformations, were quantified using electron backscatter diffraction. These metrics were then correlated with the distribution of dark etching regions (DERs) and the stress fields generated under varying alternating stress conditions. The analysis revealed that grain refinement was the dominant mechanism governing the subsurface microstructural changes, with the near-surface region exhibiting approximately a 50% reduction in grain size during operation. Furthermore, the study suggests that stress conditions in different bearing elements may significantly influence their microstructural responses, potentially leading to notable DER formation. These findings provide insights into rolling contact failure mechanisms and highlight importance of relationship between stress conditions and microstructural changes.