Effect of an annealing process on the tribological properties of sputtered hard coatings

This paper describes the influence of vacuum heat treatments up to 700 degrees C on the mechanical and tribological properties of sputtered PVD-coatings. We have deposited titanium, hafnium and chromium based nitride and boride layers on different substrate materials such as steel SAE 52100, ASP 23 high speed steel and titanium alloy Ti6Al4V. It is shown, that hardness, adhesion as well as the brittleness of the coating varied strongly depending on the residual stresses of the film. The highest wear resistance could be achieved with hexagonal chromium nitride films. The annealing process could lead to a significant change of the wear properties, depending strongly on the layer composition. Titanium and chromium nitride coatings were hardly influenced by the heat treatment, whereas titanium and hafnium borides and ternary boron nitrides showed a remarkable increase of wear, when deposited with a thin titanium intermediate layer. (C) 1997 Elsevier Science S.A.