Sliding wear of nanocrystalline Nb-Ag at elevated temperatures: Evolution of subsurface microstructure and its correlation with wear performance

Abstract An in-depth understanding of the formation of subsurface microstructure and its correlation with wear performance is a prerequisite towards controlling friction and wear at high temperatures, but such information for nanostructured binary immiscible alloys is rather limited. Here, we systematically investigated the sliding wear of nanocrystalline Nb90Ag10 two-phase alloy against Inconel alloy 600 disks at temperatures from 25 to 500 °C. Detailed characterizations on the subsurface layers show that their microstructures have a strong correlation with the corresponding wear performance. At 25 and 200 °C, no oxidation layer formed. The metallic sliding contacts result in higher coefficients of friction (CoF) and wear rates, and the formation of nanolayered structure near the sliding surface. At 350 °C, the tribo-oxidation reaction occurred only within the counterface material and a mechanical mixing layer was formed below the sliding surface of the pin. The third-body wear yielded pronounced reduction in CoF but the highest wear rate. At 500 °C, the tribo-oxidation occurred within both the pin and the counterface material. A protective glaze layer formed on the top of the pin and thus leads to the lowest wear rate.