Nano-TiO(2) reinforced CoCr matrix wear resistant composites and high-temperature tribological behaviors under unlubricated condition

The CoCrMo matrix composites with nano-TiO(2) particle (2 wt.%, 4 wt.% and 6 wt.%) were fabricated by using a powder metallurgy technique (P/M), and the nano-TiO(2) content was optimized in matrix. The microstructures, mechanical and high-temperature tribological properties of the synthesized composites were systematically studied. Friction and wear behaviors were studied by using a disk-on-ball tribo-tester sliding against Si(3)N(4) ceramic ball from room temperature (23 (o)C) to 1000 (o)C in air. TiO(2) obviously strengthened the hardness and high-temperature wear resistance of composites. It was attributed to the high load-carrying capacity of matrix, in-situ formed high-temperature solid lubricants and stable oxides film on the wear tracks. 4 wt.% TiO(2) was the critical threshold at which there was a transition of tribological properties over a broad temperature range. The composite containing 4 wt.% nano-TiO(2) exhibited the most reasonable high-temperature friction coefficient and wear rate at all testing temperatures. At different testing temperatures, the composites showed different wear mechanisms.