DETERMINATION OF THE FATIGUE PROPERTIES OF MULTILAYER PVD COATINGS ONVARIOUS SUBSTRATES, BASED ON THE IMPACT TEST AND ITS FEM SIMULATION

The coating impact test, in combination with its finite elements metho d (FEM) simulation, is used to quantitatively characterize the fatigue behaviour of thin hard physical vapour deposited (PVD) coatings as we ll as of multilayer ones. Successive impacts of a cemented carbide bal l onto a plane coated specimen induce severe contact loads and strain superficially the layered compound. The fatigue failure mode of each s pecimen is classified by means of scanning electron microscope (SEM) o bservations, microspectral analyses and profilometry. FEM simulating m odels of the impact test are used to determine the critical stress com ponents, which introduce coating fatigue failure. The FEM computationa l results are correlated to the experimental ones and used to interpre t them quantitatively. Herewith, critical values for stress components , responsible for distinctive fatigue failure modes of the coating sub strate compounds are obtained and the fatigue limits of the examined m ultilayer coatings are inserted in general applicable Smith diagrams. Furthermore, the derived critical stresses are verified by investigati ng the same multilayer coatings on different substrates. (C) 1997 Else vier Science S.A.