Tribological behaviour at elevated temperatures of thin physical vapour deposited coatings

TiCN, WTiN, TiCON and silver-TiN hard coatings were deposited on high speed steel substrates by d.c. magnetron sputtering. The roles of the temperature and normal load were investigated for non-coated high speed steel discs against tungsten carbide pins using a pin-on-disc tribometer in order to establish the friction parameters. The friction coefficient and wear resistance of samples coated with thin films were measured at 500 degrees C in air. The pins were made of uncoated tungsten carbide. The tribological results for the different coatings were compared. It is shown that the friction coefficient is not decreased by the coatings and has a very high value (between 0.9 and 1.1). However, the wear resistance increases especially for the silver-TiN coating.