Electrophoretic deposition of hydroxyapatite coating on Ti6Al4V alloy: impact of chitosan on adhesion properties and microstructure

The Ti6Al4V alloy is a common choice for biomedical implants due to its biocompatibility and corrosion resistance, though improvements are continually sought for long-term safety and performance. To address this, a hydroxyapatite (HAP), a bioceramic material structurally similar to bone, was utilized as coating agent. To enhance its properties, HAP was blended with chitosan (CS) to create a hydroxyapatite-chitosan (HAP/CS) nanocomposite coating. The Ti6Al4V alloy substrates were uniquely fabricated using laser powder bed fusion (LPBF) to mimic natural bone structure, and the HAP/CS coatings were deposited by electrophoretic deposition (EPD). The phase composition and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. A scratch test was performed to evaluate the adhesion strength and durability. The integration of chitosan significantly improved the interfacial bond and cohesion of the coating. Specifically, the 30% CS/HAP coating exhibited the optimal adhesion performance, achieving a total delamination critical load (LC3) of 6.87 ± 0.34 N, a 28.4% increase compared to the pure HAP coating (5.35 ± 0.27 N). This study indicates that HAP/CS coatings can ameliorate Ti6Al4V performance and enhance the biocompatibility of implants for biomedical usage.