Formation of hard surface layer on austenitic stainless steels via simultaneous chromising and nitriding by pack cementation process

This study aims to increase surface hardness of austenitic stainless steels via simultaneous chromising and nitriding by the pack cementation process. The pack powder mixtures used for the process consisted of Cr2N as a source of both N and Cr for the simultaneous process, NH4Cl as activator and Al2O3 as inert filler; in some cases, Cr powder was added as an additional source for depositing Cr. The AISI204 austenitic stainless steel is studied as a substrate. It is demonstrated that a top Cr2N layer with a Cr enriched layer underneath can be formed on the steel surface at 1100 °C. Hardness values of more than 1800 HV are obtained at the outermost surface of the treated specimen. It has been shown that the hardness profile at the cross-section of the surface depends on the pack chemistry.

► It is feasible to simultaneously chromise and nitride the surface of austenitic stainless steels by pack cementation process. ► Cr2N powders can be used as a source of both N and Cr for the simultaneous process. ► A top Cr2N layer with a Cr enriched alloy layer underneath is formed on the steel surface. ► Hardness values higher than 1800 HV can be achieved in the outermost surface. ► Hardness profile at cross-section of treated surface depends on the chemistry of pack powders.