Influence of Chitosan Concentration and Post-deposition Heat Treatment on Hydroxyapatite-Chitosan Coatings Produced by Electrophoretic Deposition on Ti-6Al-4V for Biomedical Applications

Hydroxyapatite-chitosan (HAP-CS) composite coatings were deposited on Ti-6Al-4V substrates (fabricated by laser powder bed fusion (LPBF)) using electrophoretic deposition (EPD). HAP-CS coatings were fabricated with 0-40% chitosan (0, 10, 20, 30, 40%). Post-deposition heat treatment at 550 °C in nitrogen enhanced structural stability and interfacial bonding. The coatings were characterized for phase composition using x-ray diffraction (XRD). Surface morphology and elemental analysis were assessed by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX). Fourier transform infrared spectroscopy (FTIR) was used for functional group identification, and progressive as well as multi-pass scratch tests were performed to evaluate tribological performance. Chitosan addition and heat treatment yielded smoother, more uniform coatings (SEM) while retaining the HAP phase (XRD). Tribological performance improved: Wear volume decreased from 7.13 × 10⁶ μm³ (0% CS) to 3.73 × 10⁶ μm³ (30% CS), identifying 30% CS as optimal; the scratch critical load increased by ~ 20% after heat treatment.