Effect of surface texture on transfer layer formation and tribological behaviour of copper–graphite composite

Metal matrix composites (MMC) containing graphite particulates usually have reduced friction under dry sliding, which is closely dependent on the formation of continuous transfer layer on the sliding surface of counterpart. The transfer process, understandably, may be affected by the actual variance of texture on counterpart surface. Thus the transfer behaviour of Cu–graphite composite onto steel discs with different textures was investigated, where the evolution of the transfer layers on the counterparts with different textures under both low and high loads was highlighted. It was found that the textures had different ratcheting effects on the contact surface of Cu–graphite composite, which led to diverse extent of extruded surface layer and size of extruded sliver. Moreover, fractured sliver acted as the precursor of the transfer layer and played a key role in determining the continuity of the transfer layer, which in turn led to different friction and wear behaviour of the composite sliding against steel counterparts with different textures.