Oxidation of Nano-Multilayered AlTiSiN Thin Films Between 600 and 1000 °C in Air

Multilayered AlTiSiN films with a composition of 32.0Al-12.4Ti-4.9Si-50.7N (at.%) were deposited on a steel substrate in a nitrogen atmosphere by cathodic arc plasma deposition. The films consisted of crystalline ∼8 nm-thick AlSiN nanolayers that originated from the Al-Si target and ∼3 nm-thick TiN nanolayers that originated from the Ti target. Their oxidation characteristics were studied between 600 and 1000 °C for up to 20 h in air. They displayed good oxidation resistance due to the formation of a thin, dense Al₂O₃ surface scale below which an (Al₂O₃, TiO₂, SiO₂)-intermixed inner scale existed. They oxidized slower than TiN films because protective Al₂O₃-rich scales formed on the surface. However, they oxidized faster than CrN films because impure Al₂O₃ scale formed on the AlTiSiN film. Their oxidation progressed primarily by the outward diffusion of nitrogen and substrate elements, combined with the inward transport of oxygen that gradually reacted with Al, Ti, and Si in the film.