Dry sliding tribological behaviors of nanocrystalline Cu–Zn surface layer after annealing in air

Powder compacting process was employed to fabricate nanocrystalline Cu–Zn alloy layer on the surface of coarse-grained copper matrix. The tribological behaviors of nanocrystalline surface layer after annealing in air were investigated. Sliding wear tests were performed on a pin-on-disk test machine under dry conditions. The morphologies and element chemical states of the worn surfaces were examined with scanning electron microscopy (SEM) and X-ray photoelectron spectrometer (XPS), respectively. It was found that 300 °C annealed nanocrystalline surface layer presented optimum mechanical and tribological properties. The 300 °C annealed nanocrystalline surface layer showed remarkably high load-bearing capacity. A tribo-surface film almost covering entire worn surface was observed at applied load range from 60 to 160 N. This tribo-surface film was found to comprise elements from both the sliding counterparts. XPS analysis revealed the enrichment of nanocrystalline ZnO in the tribo-surface film, which can contribute to reduce friction coefficient and form a more steady and long life tribo-surface film.