The effect of thermal treatments on the tribological properties of PVD hard coatings

Thermal stability in air is an important requirement for many industrial ap plications of PVD hard coatings. The objective of this study is to evaluate the thermal stability of a number of PVD coatings with respect to their me chanical, physical and chemical properties. The coatings studied were TiN, TiCN, Ti diamond-like carbon and Graphit-iC (TM) carbon, which were deposit ed on steel substrates by magnetron sputtering. The performance of these co atings was evaluated both before and after heat treatment (up to 500 degree s C) in air. The initiation of thermal decomposition of the coating was mar ked by a decrease in the coating wear life, as observed using pin-on-disk m easurements. Other tribological properties assessed were friction: adhesion and hardness. Optical microscopy and glancing angle X-ray diffraction were also used to monitor the influence of the thermal treatment on the coating s. (C) 1999 Elsevier Science S.A. All rights reserved.