Comparisons of dry sliding tribological behaviors between coarse-grained and nanocrystalline copper

Dry sliding tribological behaviors of nanocrystalline (NC) and coarse grained (CG) Cu were studied by using a ball-on-plate tribometer with a counterface ball of cemented tungsten carbide. The results showed that prior to oxidation and delamination, the steady-state friction coefficients (FCs) of NC and CG Cu are comparable (∼0.35). As oxidation with delamination of wear surface occur, the FC for either CG or NC Cu increases gradually, approaching a steady-state FC (∼0.63). The wear resistance of the NC Cu was enhanced by at least one order of magnitude under the measured loads ranging from 5 N to 25 N in comparison with the CG counterpart, which is mainly attributed to the higher hardness of the NC layer.