HIGH-TEMPERATURE OXIDATION OF (TI,PD)N AND (CR,PD)N COATINGS STUDIED WITH AES AND XPS SPUTTER DEPTH PROFILING

(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 degrees C. At all temperatures the oxidation rate of (Ti,Pd)N is increased as compared with pure TiN. The oxide layers consist of TiO2 on top and a Ti-oxynitride layer below. The TiO2 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 Cr2O3 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.