EFFECT OF PROCESS PARAMETERS ON THE RESIDUAL-STRESSES AND THE WEAR BEHAVIOR OF ALUMINUM NITRIDE PHYSICAL VAPOR-DEPOSITION COATINGS

Aluminum nitride films are of particular interest for the improvement of the wear and corrosion resistance of precisely machined elements in mechanical engineering and optics. In this study, AlN coatings were deposited on substrates of glass, metal and silicon in a reactive d.c. tetrode process by variation of the following process parameters: total pressure, partial pressures of nitrogen and argon, and the target to substrate distance. Residual film stresses were evaluated using the interference optical method and related to the process parameters. The tribological behavior was investigated in wear service simulation experiments. Film microhardness and adhesion were investigated in depth-sensing indentation and scratch experiments. The experimental results show that by variation of the total pressure between 0.05 and 0.3 Pa and of the target to substrate distance between 10 and 30 cm, defined tensile and compressive residual film stresses could be achieved. According to the investigations on the scratching and wear behavior, the state of the residual stress influences both the critical load by more than a factor of 2 and the service loading time until critical damage occurs by at least an order of magnitude. Interdependencies between kinetic deposition parameters, mechanical properties of the coatings and the tribological behavior of the coated substrates in service simulation tests are discussed.