Effect of Cryogenic Treatment on Microstructure, Mechanical Properties and Distortion of Carburized Gear Steels

Abstract

The effects of cryogenic treatment and low temperature tempering on the microstructure, mechanical properties and distortion of the 20Cr2Ni4A and 17Cr2Ni2MoVNb carburized gear steels were investigated. The results showed that the case hardness of the experimental steels was increased after the cryogenic treatment, due to the decrease of the retained austenite content and the precipitation of the tiny carbides. The wear resistance of the two steels after cryogenic treatment was improved, although the wear mechanisms were different for 17Cr2Ni2MoVNb and 20Cr2Ni4A steels. The distortion of the Navy C-ring specimens underwent shrinkage before expansion during the cryogenic process, and the distortion of 17Cr2Ni2MoVNb steel was smaller than that of 20Cr2Ni4A steel.