The Role of Plastic Deformation in Wear of Thin Films

Abstract

The correlation between mechanical stresses and tribological behavior for thin films was studied. A noble metal layer was applied on different substrates. Depending on the thickness of the film and the mechanical properties of the substrate, the wear of the film in a pin-on-plate configuration changed. Using finite element calculations it was shown that the geometry of the system, the mechanical properties of the substrate and the contact load determined the mechanical deformations of the top layer. The calculated von Mises stress averaged over the contact area and the depth of the thin film correlated well with the wear measured. If this average von Mises stress was above the yield stress of the thin film, the wear increased enormously, indicating the importance of plastic deformation in the film. A relatively simple low cycle fatigue model using the Coffin-Manson relation gave a good description of the wear behavior as a function of the average von Mises stress.