Effects of deep cryogenic treatment on microstructural evolution and alloy phases precipitation of a new low carbon martensitic stainless bearing steel during aging

It is evident from controversial statements in the literature that the effects of deep cryogenic treatment on the microstructural evolution of low carbon martensitic steels are not fully understood yet. An investigation has been started to clarify this situation by analyzing the microstructural evolution and alloy precipitation after aging. The results show that the hardness is enhanced after deep cryogenic treatment and this is mainly contributed to the transformation of retained austenite to martensite at low temperature. By comparing with the samples subjected to quenching and deep cryogenic treatment, the hardness behaviors produced different variation tendency and characteristics during aging. According to obtained results and comparing with the characterization of carbides during aging, it showed that deep cryogenic treatment is an advantage for the formation and precipitation of alloy carbides during aging. The results indicated that deep cryogenic treatment increases the diffusion driving force of atoms (especially the carbon atoms) which promotes the formation of fine carbides in the process of aging.