Boosting NiTi implant performance with crystalline Ta2O5: Role of deposition rate and post-heat treatment

This study decisively investigates how deposition rate and post-heat treatment impact the performance of tantalum pentoxide coatings on nickel-titanium shape memory alloys using magnetron sputtering. Coatings are deposited at different deposition rates and then vacuum-annealed to induce crystallization and improve the alloy's superelastic response. A systematic analysis is performed to evaluate microstructure, surface morphology, wettability, adhesion strength, corrosion resistance, radiopacity, and cellular behavior. The findings revealed that a deposition rate of 1.2 Å s−1 followed by heat treatment yields dense, crack-free orthorhombic Ta2O5 coatings with excellent uniformity and adhesion (critical load ≅ 53.9 N). The optimized coating demonstrated increased hydrophilicity (contact angle 62.7°), improved corrosion protection (≅ 95.9 %), and complete prevention of Ni ion release. Additionally, the surface facilitated calcium phosphate nucleation (Ca/P ≅ 1.64) and supported endothelial cell growth up to 186 % compared to the blank untreated cells, confirming strong biocompatibility. Radiographic analysis showed a notable enhancement in X-ray visibility, which is due to higher coating density. Overall, tuning the deposition rate and annealing conditions significantly boosts the durability, biocompatibility, and radiopacity of nickel–titanium implants, positioning crystalline Ta2O5 as a versatile surface coating for advanced biomedical uses.