THE WEAR BEHAVIOR OF HEAT-TREATED PVD COATINGS

Physical vapour deposition coatings are used in several applications. Owing to new applications such as extrusion and mould dies, new demands on such materials have to be considered, e.g. long-term stability and resistance against phase transformations, tribological and corrosive reactions and wear. This paper presents the wear behaviour and friction coefficient of Ti-Al-C-N coatings, a new system based on the well-known Ti(C,N) and (Ti,Al)N. The coating compositions are varied in their Ti/Al and C/N ratios. As substrate material cemented carbide has been used. The coatings were tested after deposition and annealing treatments at 600 and 1000 degrees C in a pin-on-disc tribometer at room temperature. The thermally induced changes in phases and particle sizes are investigated. Metallographic examinations such as microhardness and roughness were done as well. It is shown that Ti-Al-C-N coatings have a high wear resistance and a low friction coefficient. These properties are influenced by the coating composition and annealing treatment. The most wear-resistant coatings are deposited with a Ti/Al 50/50 at. % target. Independently of the target composition, the best results are obtained with a reactive gas (nitrogen and methane) ratio of 50/50. The lowest friction coefficient is found for Ti-C-N coatings. The annealing treatments effect a small increase in the wear resistance and roughness, while the friction coefficient and microhardness decrease.