Contribution of hardness and work hardening to the wear resistance of Pt-based metallic surfaces revealed by nanoscale reciprocating sliding

Abstract

The contribution of hardness and work hardening to the wear resistance of Pt-based metallic surfaces under reciprocating sliding contact have been investigated by atomic force microscopy. The atomically flat surfaces of the Pt-BMG and Pt (111) enable the sliding friction to be a single-asperity contact. It was found that at low loads where the sliding contact was primarily elastic, the Pt(111) produced a larger adhesion than the Pt-BMG, which was ascribed to the larger mixing enthalpy between counterbodies. When the sliding contact entered into wear regime at high loads, the Pt-BMG that displayed a high hardness nearly-six times of Pt (111) was expected to have a higher wear resistance according to the Archard’s law, yet the Pt(111) actually performed better. We further explore that the work hardening mechanism associated with dislocated-mediated deformation contributes to the high wear resistance of Pt(111), as corroborated by a significant friction force decrease within scratched region on Pt(111) surface. However, such a hardening mechanism is not expected to operate in Pt-BMG due to the lack of mobile structural defects like dislocations, as confirmed by the little change in friction force between scratched and unscratched regions.