SURFACE AND INTERFACE CHARACTERIZATION OF HEAT-TREATED (TI,AL)N COATINGS ON HIGH-SPEED STEEL SUBSTRATES

(Ti,Al)N hard coatings have been shown to be more oxidation resistant than TiN coatings. Furthermore, they seem to be a promising alternative coating for high speed steel cutting tools. In order to obtain information on the oxidation behavior and the adhesive properties, the surface and interface composition of heat-treated samples were determined by Auger electron spectroscopy (AES) as a function of temperature (500-800 degree C), time (15 min-16 h) and surrounding atmosphere (air, vacuum). The AES results were obtained by sputter depth profiling and crater edge profiling. The oxidation always produces an aluminum oxide layer at the outermost surface followed by a mixed oxynitride and an aluminum-depleted zone in the (Ti,Al)N coatings. The coating-substrate interface shows no distinct change caused by the heat treatments.