Influence of different production parameters on the functional behaviour of tools and parts after coating

Abstract

The efficiency of using wear-resistant coatings for tools and components depends considerably on the adhesion between the coating and the substrate. Therefore we investigated how different production parameters of the substrate influence the functional behaviour of tools and machine parts after coating. Before coating by physical and chemical vapour deposition processes (PVD, PACVD and CVD), the surfaces of tools and parts were differently machined to obtain different roughnesses, topographies and residual stresses in the substrate. The surfaces were carefully examined before and after coating by measuring their surface roughnesses and residual stresses. The surfaces were investigated by modern surface analysis (SEM, AES, ESCA) in order to detect coating defects and to obtain information about the chemical composition of the coated surface or the coating itself. Finally, the functional behaviour was checked by cutting, forming and model wear tests under laboratory and field conditions. Applied tests with vane pumps were also carried out. The examination of the results of all the tribological tests shows that the functional behaviour of coated model wear specimens, tools and parts depends strongly on the surface conditions of the substrate before coating. According to the type of stressing, different surface pre-treatments are recommended. The tribological behaviour is influenced by the interaction of many different parameters, such as the surface roughness and topography and the residual stress in the coating and substrate. With optimized surface pre-treatment of the substrate, the life of coated tools or parts can be increased considerably.