Wear Behavior and Friction Mechanism of Titanium–Cerium Alloys: Influence of CeO2 Precipitate

This work investigated the effect of cerium (Ce) addition on the wear behavior of commercially pure titanium (CP-Ti) by varying the Ce content to 0.8, 1.4, and 2.0 wt.%. Alloys were fabricated using plasma arc melting, and wear resistance was evaluated under loads of 1 N and 5 N dry sliding condition. Microstructural characterization confirmed the formation of CeO2 precipitates, whose size and distribution varied with the Ce content. The Ti-0.8Ce alloy exhibited the highest hardness (203 HV), showing a 35% increase compared to CP-Ti, and the lowest wear rate reduced by approximately 47% and 22% under 1 N and 5 N loads, respectively. In contrast, Ti-1.4Ce and Ti-2.0Ce formed coarse CeO2 precipitates, which acted as third-body abrasives. Although these alloys showed lower average friction coefficients than CP-Ti (up to 22% reduction), the enhanced abrasive interaction promoted material removal and increased wear rates. Notably, Ti-2.0Ce exhibited the most severe degradation in wear resistance, with wear rates increases of 21% and 27% under 1 N and 5 N loads, respectively. These findings demonstrate that while CeO2 precipitates reduce friction by suppressing direct metal–metal contact, their abrasive nature adversely affects wear resistance when the particle size and volume fraction are excessive. Therefore, 0.8 wt.% Ce was identified as the optimal composition for improving the wear resistance, achieving the best combination of high hardness, low wear rate without excessive third-body abrasion.