A novel approach for fabrication high-N austenitic stainless steel with high strength by powder metallurgy and nitriding

In this study, a powder metallurgical high N austenitic stainless steel (HNASS) was fabricated by powder nitriding at temperatures of 700 to 900 oC followed by spark plasma sintering, which is a new novel method to fabricated HNASS. We did detailed microstructural and mechanical characterizations of this newly produced high N alloys, and analysis the strengthening mechanisms. We found that these superior mechanical properties are mainly attributed to solid solution strengthening and grain boundary strengthening, through quantitative calculations of the respective contributions of each strengthen mechanisms. There is a limited contribution from the precipitation strengthening although with a high amount due to the coarse nitrides. This work shows important significance and it may provide an alternative route to design and produce high-strength austenitic stainless steels with high N content.