Influence of Si and Prior Heat Treatment on Long-Term Thermal Stability of 100Cr6-Type Bearing Steels
SourceThe evolution of retained austenite content during austempering or quenching and tempering is investigated for three high carbon steels. These materials were chosen for their increasing silicon content (100Cr6, 0.25 wt%; 100CrMnSi6-4, 0.6 wt%; and 100CrSiMn6-5-4, 1.2 wt%; with the latter being a proprietary alloy also referred to as Endurasco SC). The influence of tempering temperature on retained austenite content is first discussed for “conventional” tempering of steel blanks. Dilatometry is then used to investigate retained austenite evolution during tempering and, in particular, to compare it to that observed during austempering. The role of Si content is underlined and a new heat treatment schedule is proposed, which leads to the stabilization of austenite content for aging treatments of 1,000 h at 250°C.