Study on the formation mechanism of the glaze film formed on Ni/Ag composites

The results of the study on the sliding wear behavior of a Ni/Ag-15 at% material showed that the well-compacted glaze film mainly consisting of NiO, Ni and Ag was formed on the contact surface at 600 °C, which played an important part in decreasing friction coefficients. Microscopic observations showed the film possessed a multi-layered structure with silver-rich, outer layer and moderately-oxidized, non-silver-containing inner layer. The formation of the multi-layered structure is believed to have developed as a result of the joint factors involving repeated oxidization, fracturing, mixing and consolidation, followed by heat-induced silver diffusion from the dense wear debris layer to the outmost surface under the flash temperature. The effect of the second diffusion and coalescence of silver on the tribological performance of the Ni/Ag material was briefly discussed.