Bulk Phase Proportion Governs the Wear Performance of PEO Coatings Grown on Biomedical Ti-6Al-4V Alloy

This study investigated the combined influence of the α/β phase proportion and Plasma Electrolytic Oxidation (PEO) on the wear behavior of Ti-6Al-4V alloy. Samples with distinct α/β phase ratios induced by previous heat treatments (600, 800, and 1000 °C) were subjected to dry sliding wear tests before and after PEO treatment. The untreated samples exhibited major abrasive and minor adhesive wear mechanisms, characterized by broad scratches and minor adhered debris. In contrast, PEO-treated samples exhibited predominant adhesive wear, indicating a significant tuning in the wear mechanism. The coefficient of friction (COF) was unaffected by phase proportions in untreated samples but was influenced by PEO treatment. Volume loss and wear rate were sensitive to phase composition, with the untreated samples heat-treated above 800 °C exhibiting the highest values, likely due to the retention of the metastable α′ phase. Conversely, PEO-treated samples demonstrated markedly reduced wear, confirming the protective role of the oxide layer. Energy-dispersive spectroscopy (EDS) revealed the counterbody’s particle adhesion in untreated tracks, whereas PEO-treated tracks retained the coating, evidencing superior wear resistance. These findings highlight that tailoring the α/β ratio through heat treatment combined with PEO treatment enhances wear performance, offering promising implications for clinical translation in biomedical implants.