Oxidation of nano-multilayered CrN/AlMgSiN thin films between 600 and 900 °C in air

Abstract

Thin CrN/AlMgSiN films with a composition of 30.6Cr–11.1Al–7.3Mg–1.2Si–49.8N (at.%) were deposited on steel substrates in a cathodic arc plasma deposition system. They consisted of alternating crystalline Cr–N and AlMgSiN nanolayers. During oxidation at 800°C for 200h in air, a thin oxide layer was formed by outward diffusion of Cr, Mg, Al, Fe, and nitrogen, and inward diffusion of oxygen. Silicon was relatively immobile at 800°C. The oxidation at 900°C for 10h in air resulted in the formation of a thin Cr2O3 layer containing dissolved ions of Al, Mg, Si, and Fe. Silicon became mobile at 900°C. The oxidation at 900°C for 50h in air resulted in the formation of a thin SiO2-rich layer underneath the thin Cr2O3 layer. The film displayed good oxidation resistance. The main factor that decreased the oxidation resistance of the film was the outward diffusion and subsequent oxidation of Fe at the sample surface, particularly along the coated sample edge.