The Effect of Hydroxyapatite Fraction in Titanium—Hydroxyapatite Composite Coatings on Ti‐6Al‐4V Alloy With TIG Cladding

ABSTRACT In this study, Hydroxyapatite (HA) modified HA‐Ti composite coatings were applied to the surface of the Ti‐6Al‐4V (Ti64) alloy, which is crucial for biomedical applications, using the TIG cladding method. HA fraction caused a notable decrease in adhesion strength and ductility; however, the 5% HA composition maintained mechanical integrity while providing biological advantages. Surface contact angle measurements showed that HA addition made the surfaces more hydrophilic, with the lowest contact angle (~58°) observed in the 10%HA coating, which suggests improved interaction with biological fluids, cell adhesion, and protein adsorption. Electrochemical test results indicated that the 10% HA coatings exhibited the highest corrosion resistance and the most stable oxide film behavior. In immersion tests conducted in simulated body fluid (SBF), significant Ca‐P deposition was observed on the 10% HA surfaces, supporting their high bioactivity potential. Overall, the results demonstrate that HA‐reinforced Ti composite coatings produced through TIG welding are highly promising candidates for surface modification of biomedical implants, offering both structural and biological functionality.