Effect of Heat Treatment on the Microstructure and Hardness of 17Cr-0.17N-0.43C-1.7 Mo Martensitic Stainless Steel

The microstructure and hardness of a nitrogen-containing martensitic stainless steel were investigated as a function of heat treatment using optical microscopy, electron microscopy, amount of retained austenite, and hardness measurement. The steel was subjected to three heat treatments: hardening, cryo treatment, and tempering. The hardness of the steel in different heat-treated conditions ranged within 446-620 HV. The constituents of microstructure in hardened condition were lath martensite, retained austenite, M23C6, M7C3, MC carbides, and M(C,N) carbonitrides. Upon tempering at 500 A degrees C, two new phases have precipitated: fine spherical Mo2C carbides and needle-shaped Cr2N particles.