Surface Characterization of Plasma Immersion Nitrogen Ion Implanted Austenitic Stainless Steel

Abstract

Plasma immersion ion implantation (PIII) of nitrogen has been performed on three austenitic stainless steels namely, Type 304L SS, MnSS-1 (16%Cr-6%Mn-4Ni) and MnSS-2 (16%Cr-9%Mn) with at three different temperatures namely, 250, 380 and 500°C for 3 h. The GXRD studies shows that mixed iron nitride phases were formed along with expanded austenitic, when sample implanted at 250°C and 380°C. These nitrides are with different stoichiometry along the thickness and their formation is less favorable in nickel free Mn alloy at lower implantation temperature and timing (250°C for 3 h). On higher implantation condition (500°C, 6 h), Ni promotes the ′ formation and Mn suppress the ′ formation. Microhardness measurements revealed a significant increase in hardness after PIII treatment for all the alloys under investigation, but it is more effective in Ni free Mn containing SS.