Heat treatment of bearing steels: an industrial investigation

Bearings are critical components used in rotating machinery to enable motion with minimal friction for which the material and, in turn, the heat treatment selection are crucial. The heat treatment typically involves austenitization followed by cooling to achieve the desired microstructure and hardness. In this study, the effects of process parameters during different salt quenching heat treatment routes on two bearing steels (EN 100Cr6 and EN 100CrMo7) were investigated, focusing on the industrial austempering of high-thickness rings, to achieve a bainitic structure with high toughness. Hardness evolution and microstructural changes were analyzed to test the efficacy of the isothermal heat treatment for different steels and on varying the geometry of the components. The results provide a basis for selecting an effective industrial austempering process for different steel and part geometries.