Wear Mechanism and Wear Debris Characterization of ULWPE in Multidirectional Motion

Ultralow-wear polyethylene (ULWPE) was proposed to replace conventional UHMWPE as an artificial joint material. Different molecular weights of ULWPE, ULWPE-200, ULWPE-300, and ULWPE-700 were examined against CrCoMo compared to conventional UHMWPE in multidirectional motion. The wear mechanism was elucidated from the perspective of macroscopic wear behavior and microscopic wear debris characterization. It was found that the morphologies of the ULWPE worn surface were similar to that of UHMWPE, with scratches, burnishing, and protuberances. ULWPE-700 possessed the lowest wear loss at all loading conditions, and the wear loss was 40.3% lower than that of UHMWPE at 3 MPa. Furthermore, wear debris was consistent in morphology and size range but showed differences in quantity, size distribution, and shape distribution. Combined with the wear surface morphology and wear debris analysis, it showed that plastic deformation was the main cause of wear debris formation and the wear mechanisms were adhesive wear and abrasive wear. Moreover, the FBA of ULWPE-700 was 64% lower than that of UHMWPE at 3 MPa, suggesting that ULWPE-700 wear debris had the lowest potential osteolysis. This study provides deeper insight into the bio-tribological behavior and the potential biological activity of ULWPE as an artificial joint material.