High-temperature oxidation of (Ti,Pd)N and (Cr,Pd)N coatings studied with AES and XPS sputter depth profiling

Abstract

(Ti,Pd)N and (Cr,Pd)N coatings with Pd content of 10 at% were deposited on polished high-speed steel substrates by reactive magnetron sputtering using a multiple target technique. The coatings were annealed in air at temperatures between 350 and 700°C. At all temperatures the oxidation rate of (Ti,Pd)N is increased as compared with pure TiN. The oxide layers consist of TiO 2 on top and a Ti-oxynitride layer below. The TiO 2 layers grow according to a parabolic diffusion law with an activation energy of 135 kJmol −1 (TiN 184 kJmol −1). For (Cr,Pd)N the Cr 2O 3 layers grow according to a parabolic diffusion law with an activation energy of 113 kJmol −1 (CrN 123 kJmol −1). The increase of the oxidation rate with respect to CrN is much smaller than in the case of (Ti,Pd)N. The results can be explained by a different mobility of Pd in (Ti,Pd)N and (Cr,Pd)N according to the ratios of the atomic radii of the respective metallic components.