Since the fatigue life of high strength steels, e.g., roller bearing steel 100Cr6, depends on microstructural defects, an improvement of their defect tolerance can enhance the performance of components. To improve the defect tolerance, the retained austenite content can be increased. Thus, in this work the high cycle and very high cycle fatigue behavior of two modified laboratory variants of 100Cr6, which have an increased content (1.5 wt%) of Al and Si, respectively, were analyzed since these alloying elements lead to higher fractions of austenite. Moreover, an industrially available variant with 0.6 wt% Si was analyzed as a reference. All steels were investigated in the bainitic condition and had austenite contents of about 20 vol-%. However, the distribution and chemical composition of the austenite differed. The presented results demonstrate that the effect of retained austenite on defect tolerance is caused by i) the increased ductility and ii) the local deformation-induced phase transformation. To strengthen the effects of the austenitic phase, a finer distribution as well as a lower austenite stability are useful. Consequently, to evaluate the effect of retained austenite on the fatigue behavior the content, the distribution and the chemical composition of the austenitic phase must be considered.

中文翻译：

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高残余奥氏体含量的改性贝氏体 100Cr6 的 VHCF 行为和缺陷容限


由于高强度钢（例如滚动轴承钢 100Cr6）的疲劳寿命取决于微观结构缺陷，因此提高其缺陷容限可以提高部件的性能。为了提高缺陷容限，可以增加残余奥氏体含量。因此，在这项工作中，分析了两种改进的 100Cr6 实验室变体的高循环和极高循环疲劳行为，这两种变体分别增加了 Al 和 Si 的含量 (1.5 wt%)，因为这些合金元素会导致更高的 100Cr6 含量。奥氏体。此外，还分析了工业上可用的含 0.6 wt% Si 的变体作为参考。所有钢均在贝氏体条件下进行研究，其奥氏体含量约为 20 vol-%。然而，奥氏体的分布和化学成分不同。所提出的结果表明，残余奥氏体对缺陷容限的影响是由 i) 延展性增加和 ii) 局部变形引起的相变引起的。为了增强奥氏体相的作用，更精细的分布以及更低的奥氏体稳定性是有用的。因此，为了评估残余奥氏体对疲劳行为的影响，必须考虑奥氏体相的含量、分布和化学成分。