Abstract: To address the issues of high pollution and high energy consumption in the current isothermal quenching process in bath furnaces, three alternative processes (vacuum quenching, step quenching and atmospheric furnace composite isothermal quenching) for 18Cr2Ni4WA steel were investigated. The microstructure, hardness and mechanical properties of the carburized layer and core of the tested steel were comparatively analyzed after carburizing and undergoing three kinds of quenching, deep cooling and tempering. The results indicate that the carburized layer microstructure of the 18Cr2Ni4WA steel treated with three quenching schemes is mainly tempered martensite, but the core microstructure is different. Under vacuum quenching and step quenching processes, the core structure is tempered martensite, while under composite isothermal quenching process, the core structure is tempered martensite. Consequently, under vacuum quenching and step quenching, the hardness and tensile strength are higher, while under composite isothermal quenching process, the plasticity and toughness are better. The performance indicators of the 18Cr2Ni4WA steel treated by three alternative processes can all meet the application requirements, but not using high-pollution and high-energy consumption alkali tank equipment, which can achieve the goal of green heat treatment after carburizing.

Key words: 18Cr2Ni4WA steel, microstructure, composite isothermal quenching, vacuum quenching, step quenching, mechanical properties