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.

中文翻译：

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了解 GCr15 轴承在滚动接触疲劳中随时间变化的微观结构演变机制

我们对 GCr15 轴承元件在高周载荷下引发的滚动接触疲劳失效进行了深入研究，强调了对滚动体球和内/外滚道随时间变化的微观结构演变机制的全面理解。为此，实施了一项专门的实验策略，通过系统地更换滚动体来保持一致的轴承几何形状，同时保持结构完整性。这种方法能够对整个失效过程中随时间变化的微观结构转变进行全面观察和分析，有助于在进行性退化过程中对微观结构演变进行精确的时间跟踪。微观结构特征，包括晶粒尺寸、位错密度和相变，使用电子背散射衍射进行量化。然后将这些指标与暗蚀刻区域 （DER） 的分布和在不同交变应力条件下产生的应力场相关联。分析表明，晶粒细化是控制地下微观结构变化的主要机制，在作过程中，近表面区域的晶粒尺寸减少了约 50%。此外，该研究表明，不同轴承元件中的应力条件可能会显着影响其微观结构响应，从而可能导致显着的 DER 形成。这些发现为滚动接触失效机制提供了见解，并强调了应力条件与微观结构变化之间关系的重要性。