Impact of thermo-oxidative aging on the dry tribological performance and wear mechanisms of UHMWPE/ZrO2 friction pairs

Ultra-high molecular weight polyethylene (UHMWPE) is esteemed for its superior wear resistance, making it a preferred material in various applications, including artificial joints, dental materials, and mechanical components. This study elucidates the effects of thermo-oxidative aging on the dry tribological performance and wear mechanisms of UHMWPE and zirconia (ZrO2) friction pairs using dynamic friction wear tests, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Results reveal that thermo-oxidative aging significantly compromises wear resistance and alters the degradation mechanisms of UHMWPE. The unaged UHMWPE exhibits exceptional wear resistance, indicated by minimal wear and pronounced polishing effects. Post-aging at 40 °C leads to the formation of fine scratches and rougher wear marks on UHMWPE surfaces, with the predominant wear mechanism transitioning from abrasive wear to fatigue wear as the number of cycles increases. Upon aging at 70 °C, more extensive spalling and pitting damages occur on UHMWPE, indicating more severe thermo-oxidative and wear damages that primarily exhibit fatigue wear and oxidative wear patterns. Notably, aging at 40 °C results in a friction coefficient increase to ∼0.165, whereas aging at 70 °C decreases the friction coefficient to around 0.118, indicating a complex relationship between aging temperature and tribological behavior. This research provides valuable insights into predicting and improving the durability of UHMWPE components used in orthopedic applications, thereby contributing to optimizing orthopedic implant materials for enhanced patient outcomes.