PLASTIC-FLOW PROCESS OF SURFACE-LAYERS IN FLOW WEAR UNDER BOUNDARY LUBRICATED CONDITIONS

The process of filmy wear debris generation in boundary lubrication was observed successively using scanning electron microscopy. On a rough surface, the contact occurred alternatively between higher asperities and filmy wear debris was generated as a result of the accumulation of plastic flow of surface layers of deformed asperities. The following two types of plastic flow were observed: forward plastic flow and side plastic flow. On a smooth surface, filmy wear debris was generated as a result of side plastic flow accompanying ploughing. Thus, the wear type, which was controlled by the plastic flow of asperities and the generated filmy wear debris, was called 'flow wear'. The particle sizes of filmy wear debris, which were estimated in flow wear, were less than 15 mu m and dependent on the surface roughness.