Effect of quenching and tempering on microstructure and corrosion resistance of aerospace-bearing steel

CSS-42L steel is not only highly competitive for aerospace bearing applications but also for core components such as gears and shafts used in high-temperature or corrosive environments. This puts higher requirements on its microstructure, mechanical properties, and corrosion resistance. In this paper, CSS-42L steel was subjected to quenching, cryogenic and tempering treatments to study the effects of different heat treatments on the microstructure, hardness, and corrosion resistance of CSS-42L steel. It was found that the microstructure of the specimen after quenching contained martensite, a large amount of residual austenite, and trace amounts of fine carbides, and its hardness and corrosion resistance were improved. The residual austenite in the tempered sample underwent almost complete decomposition and transformed into fine martensite, and numerous finely dispersed and uniformly distributed carbides were precipitated, its hardness was further increased to 578.6 Hv concerning the quenched specimen, but concurrently exhibited a decrease in corrosion resistance. CSS-42L steel can be hardened by quenching, cryogenic and tempering to obtain martensite, but fine martensite reduces corrosion resistance. Since the amount of martensite or residual austenite affects the mechanical properties and corrosion resistance of CSS-42L bearing steel, the ratio of martensite and residual austenite needs to be adjusted to obtain optimum mechanical properties and corrosion resistance.