Micromechanism of wear at polymer-metal sliding interface

Abstract

Sliding experiments between polymer and steel surfaces were conducted to investigate the mechanism of wear. The nature of fracture as well as the changes in the surface as a result of sliding were studied by scanning and transmission electron microscopy and differential thermal analysis. Electron microscopy revealed that, in the case of PTFE, high density polyethylene and polyoxymethylene at very low velocity, where heating at the interface can be neglected, thin films are sheared and are laid across the sliding surface. The shearing of films was anticipated to be due to interlamellar shear. At high velocities it was probable that the same mechanism of interlamellar shear for wear was also present for PTFE. Thermal softening or melting was not detected in PTFE by differential thermal analysis even at high velocities, whereas for the other two polymers it was shown by scanning electron microscopy and differential thermal analysis that thermal softening or even melting was the important mechanism of wear at high velocities.