Abstract: Ni-Mo-Y-CaF₂ high temperature self-lubricating composites with different CaF₂ addition amounts were prepared using spark plasma sintering (SPS) technology. The microstructure, mechanical properties, friction and wear properties of the composites were studied. The results showed that the microstructure of Ni-Mo-Y-CaF₂ composites is uniform and dense, and the density, hardness and yield strength of the composites decrease with the amount of CaF₂ added increasing. Temperature significantly affects the friction and wear properties of the composites. From room temperature to 800 ℃, the average friction coefficient of the composites decreases initially with increasing temperature, slightly increases between 400 ℃ and 600 ℃, and then decreases again. The average wear rate increases initially with increasing temperature,and then decreases reaching a maximum at 400 ℃. At room temperature,the average wear rate of Ni-Mo-Y-10CaF₂ composite has the lowest average wear rate, about 1/5 of that of Ni-Mo-Y alloy. At 800 ℃, the wear rates of the composites are lower than that of the Ni-Mo-Y alloy. A dense and smooth lubricating film forms on the wear surface, mainly composed of calcium molybdate, nickel molybdate, and the oxides of nickel and molybdenum.

Key words: Ni-Mo-Y-CaF₂ composites, microstructure, mechanical property, high temperature tribological properties