Effect of nitrogen and tempering temperature on microstructure evolution and mechanical properties of 0Cr15Ni6Mo2 martensitic stainless steel

Abstract

The effects of nitrogen and tempering temperature on microstructure evolution and mechanical properties of 0Cr15Ni6Mo2 martensitic stainless steel are studied by means of the OM, SEM, XRD and TEM. The results show that the addition of 0.12% N can effectively inhibit the formation of δ ferrite and significantly increase the volume fraction of retained austenite. N can inhibit the precipitation of carbides, but it promotes the precipitation of Cr2N in the grain boundary of original austenite, martensitic lath boundary and grain interior in the 0Cr15Ni6Mo2 with N. The addition of 0.12% N not only increases the tensile strength by at least 9.6% but also increases the elongation and Charpy impact toughness by at least 12.3% and 47.5%, respectively. And N increases the yield ratio and improves the work hardening ability of the test steel. It is considered that the increase of retained austenite, the inhibition of the formation of δ ferrite and the segregation and precipitation of Cr2N at grain boundaries play an important role. Comprehensive mechanical properties are more likely to obtain when tempered in 700–750°C.