Microstructural characterization and corrosion analysis of HA/TiO2 and HA/ZrO2 composite coating on Ti- alloy by laser cladding

Titanium alloy implants release metallic ions into the bloodstream and high corrosion rate in physiological environment due to change in pH level. Here in, bio-ceramic HA coating and HA based binary composite coating (HA/TiO₂ and HA/ZrO₂) have been developed on Ti-6Al-4 V alloy for improvement in corrosion resistance and reduction in the metal ion release. In this study, HA, HA/TiO₂, and HA/ZrO₂ coating have been developed by using a 400 W, 1070 nm fiber laser cladding process. Microstructural characterization was performed using 3D-optical profilometer, FESEM, EDS, and XRD, while electrochemical properties were analyzed in simulated body fluid. The Ca/P ratio indicated HA decomposition into calcium phosphate during the laser process. Phase analysis identified α-Ti, Ca₂P₂O₇, TiO₂, and CaTiO₃ in HA/TiO₂ cladding, and α-Ti, Ca₃(PO₄)₂, Ca₂P₂O₇, TiO₂, CaTiO₃, and CaZrO₃ in HA/ZrO₂ cladding. The analysis revealed that HA-based composite cladding produced a more corrosion resistant surface as compared to HA cladding and Ti-6Al-4 V alloy. However, HA/TiO₂ composite cladding significantly reduced corrosion current density, corrosion rate and increasing polarization resistance.

From the obtained results it is concluded that HA/ TiO₂ and HA/ ZrO₂ composite coating developed by laser cladding process, give cracks free structure and significantly decreased corrosion rate as compared to HA coating. This composite coating would be beneficial for improving orthopedic implant performance, and long-term durability.