Surface and in vitro corrosion properties of spark plasma sintered Ti–Zr–Nb–Ta–Ag high entropy alloy for dental implant applications

In this study, the surface and in vitro corrosion behaviors of Ti–Zr–Nb–Ta–Ag high-entropy alloys (HEA) processed through mechanical alloying and spark plasma sintering (SPS) were investigated to assess their potential for dental bioimplant applications. The results showed that the SPS HEA yielded a dual-phase body-centered cubic structure and an ultrafine Zr-based phase. The HEA exhibits nearly double the hardness (8.2 GPa) and significantly higher resistance to plastic deformation (H³/E² =0.0312 GPa) compared to Ti6Al4V, which showed a hardness of 4.11 GPa, and H³/E² value of 0.00349 GPa. X-ray photoelectron spectroscopy revealed the formation of biocompatible surface oxides including TiO₂, ZrO₂, Nb₂O₅, Ta₂O₅ and Ag. The potential of HEA for dental implant applications was evaluated by examining its corrosion behavior in artificial saliva (AS) at different pH values. Compared with Ti6Al4V, the HEA exhibited significantly enhanced corrosion resistance at all pH values. The HEA exhibited the highest charge transfer resistance (1.0805 × 10⁷ Ω⋅cm²) and the lowest double-layer constant phase element value (0.085 µΩ⁻¹⋅cm⁻²⋅sⁿ), indicating more stable and protective passive film formation. The improved surface characteristics and in vitro corrosion resistance of SPSed HEA demonstrate its potential in dental bioimplants.