OXIDATION OF TERNARY TIZRN HARD COATINGS STUDIED BY XPS

Electrochemical and thermal oxidation of TiZrN hard coatings deposited by the plasma beam sputtering technique are investigated using x-ray photoelectron spectroscopy (XPS), Ternary TiZrN coatings are found to be more susceptible towards oxidation compared to binary TiN and ZrN c oatings. Electrochemical oxidation results in the formation of a mixed Ti(N,O) + Zr(N,O) oxynitride layer in the lower potential range (up t o 1.1 V), whereas at higher potentials a mixed TiO2 + ZrO2 oxide layer is formed. This layer still incorporates a certain amount of nitrogen released during transformation of nitride to oxide. A similar is obse rved in the case of thermal oxidation at 350-600 degrees C, where the main product is a mixed TiO2 + ZrO2 layer. Nitrogen, which should norm ally be evolved during oxidation, remains incorporated in the growing oxide layer. No tendency towards alternate layer formation, i.e. ZrO2/ TiO2, was observed under the experimental conditions investigated. (C) 1998 John Wiley & Sons, Ltd.