Effect of austempering temperatures on microstructure and mechanical properties of 52CrMoV4 spring steel

52CrMoV4 alloy spring steel has excellent mechanical properties and is widely used in the production of automobile suspension systems, spring sheets, torsion bars, and other parts. This paper improves the traditional oil quenching process. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Electron Backscattered Diffraction (EBSD), tensile testing, and other methods were used to experimentally study the effect of heat treatment process on the microstructure and mechanical properties of 52CrMoV4 alloy spring steel. The results showed that specimens treated with traditional oil quenching process have higher strength but poor impact toughness. The introduction of bainite into the microstructure was achieved via austempering at 300 °C followed by low-temperature tempering, leading to a 32.1 % enhancement in impact toughness while maintaining the strength level. Furthermore, we demonstrated that tempering can effectively improve the distribution of carbides in the microstructure and reduce its dislocation density. By reducing the formation of nucleation sites on cleavage planes of impact specimens, this process significantly enhances the impact toughness. By optimizing the bainite austempering process of 52CrMoV4 spring steel, it can achieve excellent comprehensive mechanical properties, especially impact toughness. Thus, it can reduce the risk of damage under the impact and ensure the safety of equipment and personnel.