Biocompatibility study of multi-layered hydroxyapatite coatings synthesized on Ti-6Al-4V alloys by RF magnetron sputtering for prosthetic-orthopaedic implant applications

Triple-layered RF magnetron sputtered HAp/Al₂O₃/TiO₂ coatings synthesized onto Ti-6Al-4V alloys were studied to improve the surface biocompatibility and corrosion resistance features. It was seen that the HAp layers played a substantial role in the biocompatibility, while the intermediate Al₂O₃/TiO₂ layers were used to enhance the corrosion behavior of the substrate. XRD results showed an enhanced crystallinity along with the (2 1 1) HAp phase after the simulated body fluid (SBF) immersion experiment. Local electronic and chemical bonding states of atomic phosphorus and calcium phosphate groups in the coatings, before and after immersion process, were confirmed via XPS studies. The electrochemical impedance spectroscopy (EIS) evaluated the corrosion, which indicated a reduction in capacitance values and a significant improvement of the corrosion resistance of such coatings; with improved bio-medical properties of Ti alloys.