Effect of austenitising temperature on the microstructural evolution of a novel corrosion resistant bearing steel alloy

The investigation of carbide dissolution as a function of austenitising temperature is a decisive factor for optimizing the heat treatment processes of steels. Therefore, in this study, the kinetics of carbide dissolution at different austenitising temperatures at 880 °C, 1030 °C and 1200 °C for a iron-based alloy were examined. CALPHAD-based computational software JMatPro® was used to determine the targeted austenitising temperatures of the alloy. The alloy was produced by means of Plasma-Transferred-Arc welding and were investigated by microstructural analysis. The results showed that the morphology of the eutectic network depends on the austenitising temperature and  holding time. High temperatures resulted in grain growth, irrespective of the holding time applied. With increasing temperature and longer holding times, there was a general dissolution of the elements into the iron matrix. However, excessively long holding times caused an Ostwald ripening effect, which negatively impacted the homogeneity of the microstructure. The results of the study showed that an austenitising temperature of 1030 °C, combined with a holding time of 30 minutes, represented the optimal conditions for both heat treatment and subsequent forming.