Innovative plasma spray coating of HA-Ti-MgO composite on Ti₆Al₄V alloy for enhanced performance

In this study, an innovative hydroxyapatite-titanium-magnesium oxide composite coating was successfully fabricated on Ti₆Al₄V alloy using plasma spraying to enhance its mechanical and corrosion performance for biomedical applications. Granulation of nano-sized HA powder (~100 ± 20 nm) produced spherical agglomerates in the range of 5-20 µm, ensuring suitable flowability for uniform coating deposition. SEM analyses confirmed dense and crack-minimized layers for both pure HA (~105 µm thick) and composite (~98 µm thick) coatings. XRD revealed the formation of additional CaTiO₃ and MgO phases in the composite, strengthening interfacial bonding. The composite coating exhibited a significant improvement in adhesion strength, reaching 29.2 ± 3.4 MPa, compared to 6.9 ± 0.6 MPa for pure HA. Vickers hardness also increased from 431.3 ± 5.8 HV (HA) to 537.9 ± 1.9 HV (composite coating), outperforming the uncoated Ti₆Al₄V substrate (360.8 ± 1.7 HV). Electrochemical tests showed that the composite coating achieved a lower corrosion current density (9.72 × 10^-8 A/cm²) and higher polarization resistance (41.2 kΩ·cm²) than the HA-only coating (1.19 × 10^-6 A/cm², 28.9 kΩ·cm²), indicating enhanced corrosion resistance.