This study investigated the effects of plasma electrolytic oxidation (PEO) treatment in a Ca- and P-rich electrolyte on the surface of the Ti-6Al-4V alloy with distinct α/β phase proportions previously induced by heat treatments. The results revealed that the α/β phase proportions were successfully altered by the heat treatment temperatures, forming α phase plates surrounded by β phase precipitates. PEO-treated samples exhibited a thick and microsized porous TiO₂ coating in the anatase and rutile crystalline forms. The oxide layer was depleted by Al and V atoms, while Ca and P were gradually enriched along the coatings. Chemical analysis also indicated the absorption of water and organic molecules into the outer layer. PEO-treated samples had microscale roughness and thickness, hydrophilic behavior, and surface energy mainly formed by the dispersive component. The bulk’s elastic modulus decreased with β phase precipitation, while the alloying elements directly influenced the Vickers microhardness. The corrosion tests indicated a stable and protective layer in the PEO-treated samples, showing better corrosion resistance than untreated ones. Overall, the findings indicated that the α and β phase proportion significantly impacts the mechanical properties, while the PEO treatment acts in the corrosion protection and surface aspects, suggesting that combining both approaches could be a powerful tool in biomedical applications.

This study evaluated the surface functionalization of a non-equiatomic TiZrNbTaMo high-entropy alloy (HEA) by micro-arc oxidation (MAO) in Cu-rich electrolytes to tailor its performance for biomedical implants. The Cu content was varied, and the resulting coatings were investigated for their morphology, phase constitution, chemical structure, wettability, and cytocompatibility. X-ray diffraction (XRD) measurements of the substrate indicated a body-centered cubic (BCC) matrix with minor HCP features, while the MAO-treated samples depicted amorphous halo with sparse reflections assignable to CaCO₃, CaO, and CaPO₄. Chemical spectroscopic analyses identified the presence of stable oxides (TiO₂, ZrO₂, Nb₂O₅, Ta₂O₅, MoO₃) and the successful incorporation of bioactive elements (Ca, P, Mg) together with traces of Cu, mainly as Cu₂O. MAO treatment increased surface roughness and rendered a hydrophilic behavior, which are features typically favorable to osseointegration process. In vitro cytotoxic assays with MC3T3-E1 cells (24 h) showed that Cu addition did not induce harmful effects, maintaining or improving cell viability and adhesion compared to the controls. Collectively, MAO in Cu-rich electrolyte yielded porous, bioactive, and Cu-incorporated oxide coatings on TiZrNbTaMo HEA, preserving cytocompatibility and supporting their potential for biomedical applications like orthopedic implants and bone-fixation devices.

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.