Construction and Significance of Chromium Nitride Pourbaix Diagrams based at 298 K (25 oC)

Abstract

Abstract Chromium nitrides such as CrN and Cr2N are often used for corrosion and wear resistant applications. Pourbaix diagrams can be used to help gauge the thermodynamic stability of elements and compounds. In this paper, Pourbaix diagrams are constructed for CrN and Cr2N using thermodynamical data for species at 298 K (25oC) and at a concentration of 10− 6 M for aqueous species. These diagrams are useful indicators for the stable regions in which these compounds can be used. The diagrams show that passive Cr2O3 films form on the surfaces where chromium nitride was present. It is argued that the very presence of Cr2O3 films will degrade chromium nitride and make it much less useful as a wear resistant layer. It is further argued that the presence of nitrogen in solid solution is better for the stability of passive films in stainless steels.