Friction and Wear in Nanoscratching of Single Crystals: Effect of Adhesion and Plasticity.

Friction and wear are two main tribological behaviors that are quite different for contact surfaces of distinct properties. Conventional studies generally focus on a specific material (e.g., copper or iron) such that the tribological result is not applicable to the other contact systems. In this paper, using a group of virtual materials characterized by coarse-grained potentials, we studied the effect of interfacial adhesion and material plasticity on friction and wear by scratching a rigid tip over an atomic smooth surface. Due to the combined effects of adhesion and plasticity on the nanoscratch process, the following findings are revealed: (1) For shallow contact where interfacial adhesion dominates friction, both friction coefficient and wear rate increase as the adhesion increases to a critical value. For deep contact where plasticity prevails, the variation of friction coefficient and wear rate is limited as the adhesion varies. (2) For weak and strong interfacial adhesions, the friction coefficient exhibits different dependence on the scratch depth, whereas the wear rate becomes higher as the scratch depth increases. (3) As the material hardness increases, both the friction coefficient and wear rate decrease in shallow and deep contacts.