Direct observations of fretting wear of steel

An investigation was performed to study the factors affecting the transition between fretting and reciprocating sliding wear using a new technique in which a transparent (sapphire) disc is rubbed against a steel sphere under both lubricated (hexadecane) and dry conditions. The technique allows direct observation of the wear occurring in the contact as well as the appearance, size and transport of the wear debris. The wear behaviour was qualitatively similar to that occurring between steel-on-steel surfaces. Increasing the stroke length led to much more rapid removal of debris from the contact, together with accompanying changes in size and composition. In general, the results lend support to the contention that the transition to reciprocating sliding behaviour is controlled by the instantaneous quantity of debris remaining within the contact.