Effects of traditional heat treatment and a novel deep cryogenic treatment on microstructure and mechanical properties of low-carbon high-alloy martensitic bearing steel

The effects of traditional heat treatment (quenching and then tempering) and deep cryogenic treatment on the microstructure and mechanical properties of a low-carbon high-alloy martensitic bearing steel were studied by Rockwell hardness test, X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. The results show that the deep cryogenic treatment promotes the transformation of the retained austenite to martensite during cooling, which leads to the hardness of the sample after deep cryogenic treatment higher than that at the quenched state. Also, the carbon content in the martensite matrix after different treatments was calculated and the results indicated that deep cryogenic treatment can promote the segregation of carbon atoms in martensite to dislocations. The segregated carbon atoms act as and grow into nuclei for the formation of fine carbide particles during subsequent tempering. And this resulted in the fact that the hardness of the tempered experimental steel after deep cryogenic treatment is higher than that without deep cryogenic treatment.

Automated summary

The traditional heat treatment and deep cryogenic treatment have different effects on the microstructure and mechanical properties of low-carbon high-alloy martensitic bearing steel. Deep cryogenic treatment can promote the transformation of austenite to martensite, increase the hardness of the sample, and facilitate the segregation of carbon atoms in martensite. This segregation of carbon atoms acts as nuclei for the formation of fine carbide particles during subsequent tempering, leading to an increase in hardness.