Nanoscale self-organization reaction in Cu-Ag alloys subjected to dry sliding and its impact on wear resistance

Two-phase Cu90-Ag10 alloys are subjected to dry-sliding wear using pin-on-disk testing at room temperature with either a bronze or a martensitic stainless steel as counterface material. Thermal annealing prior to wear testing is used to vary the initial Ag-rich precipitate size in the Cu-rich matrix from ≈30 to 260 nm. The wear debris and the sub-surface microstructure are characterized by scanning and transmission electron microscopy. For large enough initial precipitate size, wear induces the spontaneous formation of alternating Cu and Ag nanolayers, and this chemical nanolayering correlates with a significant reduction in wear rate. This correlation is analyzed by considering the role of chemical nanolayering on third bodies and on the mechanical properties of the near-surface microstructure.