High-temperature oxidation of magnetron-sputtered Cr-N-coated steels

Single-, 15-, and 30-layered Cr-N coatings deposited on a steel substrate were oxidized in air at 700 and 800 °C. Oxidation occurred via the predominant outward diffusion of Cr, Fe, and nitrogen, and the inward diffusion of oxygen. Nitrogen escaping from the coating into the air made the multi-layered Cr-N coating act as a single-layered Cr-N coating during oxidation. The oxidation product was primarily Cr2O3, which contained a small amount of Fe and nitrogen. The unreacted coating beneath the Cr2O3 scale had some iron transported from the substrate.