Investigating Influence of Mo Elements on Friction and Wear Performance of Nickel Alloy Matrix Composites in Air from 25 to 800 °C

Rapid developments in aerospace and nuclear industries pushed forward the search for high-performance self-lubricating materials with low friction and wear characteristics under severe environment. In this paper, we investigated the influence of the Mo element on the tribological performance of nickel alloy matrix composites from room temperature to 800 °C under atmospheric conditions. The results demonstrated that composites exhibited excellent lubricating (with low friction coefficients of 0.19–0.37) and wear resistance properties (with low wear rates of 2.5–28.1 × 10−5 mm3/Nm), especially at a content of elemental Mo of 8 wt. % and 12 wt. %. The presence of soft metal Ag on the sliding surface as solid lubricant resulted in low friction and wear rate in a temperature range from 25 to 400 °C, while at elevated temperatures (600 and 800 °C), the effective lubricant contributed to the formation of a glazed layer rich in NiCr2O4, BaF2/CaF2, and Ag2MoO4. SEM, EDS, and the Raman spectrum indicated that abrasive and fatigue wear were the main wear mechanisms for the studied composites during sliding against the Si3N4 ceramic ball. The obtained results provide an insightful suggestion for future designing and fabricating solid lubricant composites with low friction and wear properties.