Microscopic investigation on the origin of wear by surface fatigue in dry sliding

Simple statistics and morphological analysis in conjunction with the general theory of surface fatigue were used to determine the origin(s) of the mechanisms of wear by surface fatigue (SFW) and their progress with time. New mechanisms of crack initiation and propagation that account for the wear particle formation are envisaged. Surface fatigue is mostly controlled by surface cracks that originate from various site types, depending on the nature of the tested material and testing conditions. It is also shown that cracks propagate at depths between 10 and 60 μm, at deeper levels than previously reported. Several competing mechanisms generate cracks at the contact surface layer. Delamination, as a wear process that is based on wear particles generated from subsurface cracks, plays only a minor role in the overall wear that is generated by surface fatigue phenomena.