Preliminary results of HiPerComp  project demonstrate an increasing defect tolerance of the bearing steel 100Cr6 with higher amount of retained austenite. Beside the higher ductility and cyclic hardening potential of the austenitic phase, the transformation of retained austenite to α’-martensite leads to a higher defect tolerance. For this purpose, two standardized 100Cr6 alloys were modified with an increased silicon (1.5Si-100Cr6 ) and an increased aluminum (1.5Al-100Cr6) content (IEHK Aachen), which were subsequently bainitized (IWT Bremen).

In high cycle fatigue tests (HCF) at ambient temperature, the alloy 1.5Si-100Cr6 yield a higher fatigue strength than the  1.5Al-100Cr6. In addition, a temperature of 100 °C results in a reduced fatigue strength of the 1.5Si-100Cr6, which cannot be observed for the alloy 1.5Al-100Cr6. This indicates that in the fatigue tests at ambient temperature an austenite-α'-martensite transformations occurred, since the stability of the austenitic phase increases with increasing temperature. These phase transformations increased the defect tolerance, which was confirmed using the √area approach established by Murakami. Consequently, a higher austenite stability can be assumed for the 1.5Al-100Cr6, which will be investigated by high-resolution microstructure analyses and in additional very high cycle fatigue tests (VHCF).