Wear experiments in the scanning electron microscope

Wear experiments using a ball-on-flat configuration were performed in a scanning electron microscope. The sequence of events occurring during the initial or wear-in phase was followed for three different materials: these were mild steel, brass and aluminum. Differences in behavior among the materials were striking. Adhesion and prow formation were observed in the aluminum experiment. A change from sharp microstriations to increasing macrodeformation was characteristic of the behavior of the mild steel. In addition, readily identifiable microstriations persisted for many cycles of sliding contact on the steel surface, while on the brass surface these features changed with each cycle. Microscopic extrusions and lip formation were observed to progress from asperities to incipient wear debris. The tendency for debris to transfer to the harder surface and to influence striation formation in the opposing surface was observed.