Anti-oxidation properties of TiAlN film prepared by plasma-assisted chemical vapor deposition and roles of Al

The high temperature oxidation behaviors of Ti-Al-N films prepared by plasma-assisted chemical vapor deposition (PACVD) technique were studied at temperatures ranging from 500 degrees C to 800 degrees C in air. Ti0.88Al0.12N film, which showed excellent microhardness in the previous work, was investigated on its anti-oxidation properties compared with pure TiN film and on the roles of Al in anti-oxidation properties. TiAlN film showed superior anti-oxidation properties of up to 700 degrees C, whereas TiN film was fast oxidized into rutile-structure TiO2 crystallites from 500 degrees C. It was found that an aluminum oxide layer was formed on the surface of TiAlN film due to outward diffusion of Al ions at the initial stage of oxidation. The aluminum oxide layer played a role as the barrier against oxygen diffusion, protected the remaining nitride layer from further oxidation, and, thus, resulted in the high anti-oxidation characteristics of TiAlN film. (C) 1997 Elsevier Science S.A.