The surface characteristics and corrosion behavior of plasma nitrided austenitic stainless steel containing Mo

The surface characteristics and corrosion behavior of plasma nitrided austenitic stainless steel containing Mo has been investigated using a wear tester, a micro-hardness tester and potentiostat equipment. It was found that plasma nitriding at 823 K, compared with at 653 K, resulted in a thick nitrided layer, and consequently good wear resistance and hardness, as the nitriding time increased. Whereas for the Mo addition, wear resistance and hardness decreased. Intergranular corrosion(IGC) resistance improved significantly in the case of plasma nitrided SS containing 4.05 mass%Mo at 653 K because the nitrogen and Mo act synergistically to form a protective surface layer which is responsible for the aggressive SCN- ion. Plasma nitriding at 823 K decreased IGC resistance as the Mo content increased owing to retardation of the nucleation and growth of chromium carbide (Cr23C6) or nitride(CrN) in grain boundary.