Temperature-Dependent Performance of Thermally Oxidized Zr2.5Nb Alloy for Orthopedic Implants: Mechanical Properties, Wear Resistance, and Biocompatibility

This study investigates the critical influence of oxidation temperature on the intrinsic characteristics and surface properties of thermally oxidized Zr2.5Nb alloy. The resulting oxide layers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface hardness, and nanoindentation. The tribological behavior of the untreated and thermally oxidized Zr2.5Nb alloy was evaluated via reciprocating ball-on-disc wear tests under a load of 29.4 N. MC3T3-E1 cells were employed to assess the biocompatibility. The results show that oxide layers primarily composed of m-ZrO2 formed on the alloy surface, with thickness increasing from 2.43 µm to 13.59 µm as the oxidation temperature rose from 500 °C to 700 °C. However, this thickness increase was accompanied by elevated defect density. Compared to the untreated alloy, thermally oxidized samples exhibited significantly enhanced hardness and wear resistance. Notably, oxidation at 600 °C produced a dense 5.31 µm oxide layer with optimal structural integrity, achieving an 85% reduction in wear rate and a superior MC3T3-E1 cell relative activity of 123.07 ± 6.02%. These findings provide foundational data for developing zirconium-based implants with improved stability.