Effect of ZrO₂ on the friction wear behavior of Ti–Zr–Mo alloys under high-temperature oxidation conditions

Hot-work molds often fail due to severe high-temperature wear. Mo–0.5Ti–0.08Zr–0.02C (TZM) alloys, known for their excellent thermal shock resistance and elevated-temperature strength, are widely used in the manufacturing of hot-working molds. To improve the high-temperature wear resistance of TZM alloys, this study investigated the effect of ZrO₂ (approximately 1.5 wt%) on their oxidative wear behavior at ~800 °C. The results revealed that increasing the ZrO₂ content refined the alloy grains and increased the hardness. Elevated wear temperatures promoted the formation of lubricious oxide layers on the alloy surface, significantly reducing friction. The friction coefficient of 1.5 wt% ZrO₂/TZM decreased from 0.55 at room temperature (RT) to 0.06 at 800 °C, accompanied by a progressive reduction in the wear rate. All the alloys exhibited optimal wear resistance at 600 °C, whereas a rapid increase in the wear rate occurred at 800 °C because of pronounced molybdenum volatilization induced by excessive thermal energy. At 600 °C, the wear rate of 1.5 wt% ZrO₂/TZM reached 0.73×10⁻⁵ mm³/(N·m), which was 3.5 times greater than that of pure TZM. The high-temperature wear mechanism of the TZM alloy involved a combination of oxidative, abrasive, and adhesive wear, with significant material volatilization observed at 800 °C. ZrO₂ effectively mitigated abrasive scratching, suppressed surface adhesion, reduced oxidation, and inhibited molybdenum volatilization, thereby significantly improving the wear performance. These findings provide new insights into grain refinement and oxide-mediated lubrication for the development of advanced wear-resistant alloys.