INVESTIGATIONS ON THE EFFECTS OF PROCESS PARAMETERS ON THE HIGH-TEMPERATURE AND WEAR BEHAVIOR OF PVD COATINGS

Metal nitride coatings are of particular interest for the improvement of the service behavior of forming tools for the thermoplastic molding of optical components from anorganic glasses at high temperatures. In the present study AlN and TiN coatings were deposited on steel, glass and silicon substrates in reactive sputtering processes by variation of the process parameters total pressure, partial pressures of nitrogen and argon, substrate temperature and distance between target and substrate. In particular the effect of the process parameters on the film stresses as well as the mechanical behavior of films with various tensile and residual stresses have been analyzed. A transition f rom tensile to compressive stresses by variation of the total pressure and of the distance between target and substrate was obtained for AlN coatings prepared by a reactive d.c. tetrode process. In coatings with compressive residual stresses an increased resistance to microcrack initiation and improved wear behavior could be achieved.