Effect of Subzero Treatments on Microstructure and Hardness of AISI D2 Steel

Abstract

Cryogenic treatment is a secondary process to traditional heat treatment used for improving the hardness and wear resistance of tool steels. Though the potential use of subzero treatment on AISI D2 tool steel under laboratory conditions has been well established by the researchers, it is essential to do the analysis to ensure its sustainable use for industrial application. Therefore, impact of subzero treatment on AISI D2 steel blanking punch was evaluated in terms of variation in microstructure and hardness. The cryogenically treated D2 tool steel punches were used and subjected to manufacture the control levers using blanking operations. The improved wear resistance of cryogenically treated punch resulted in increase in production and punch life more than 200%. After studying the punch life, it was correlated to increase in production and wear pattern. The AISI D2 steel samples were prepared and subjected to laboratory tests comprising of metallographic observations and hardness. It has been observed that the improvement in mechanical properties can not be predicted just by conducting the laboratory tests. Field test are essential to confirm the increase in tool life. The mechanism responsible for augmented wear resistance by subzero treatment was the conversion of retained austenite to martensite and precipitation of new secondary carbides.