Surface, microstructural, and adhesion strength investigations of a bioactive hydroxyapatite-titanium oxide ceramic coating applied to Ti-6Al-4V alloys by plasma thermal spraying

Ti-6Al-4V alloy is employed in implants because of its good mechanical strength, excellent biocompatibility, and good resistance to corrosion in biological environments. Herein, a composite (HAp-TiO2, 50% by volume of both components) coating surface employing Ti-6Al-4V was characterized. Samples were analyzed post fabrication and post heat treatment to analyze the coating recrystallization, phases, crystallinity, porosity, and roughness. The coating showed rutile crystalline and amorphous Hap phases with crystallinity, porosity, and roughness of 55.6%, 13.6 ± 1.0%, and 4.2 ± 0.6 µm; whereas, after heat treatment, it showed a rutile hydroxyapatite phase and β-TCP with values 75.6%, 13.9 ± 1.9%, and 3.8 ± 0.2 µm, respectively. The composite exhibited 874 ± 26 HV100 hardness and 30 ± 2 MPa adhesion strength after heat treatment, which agree with previously reported data on other bioactive coatings. Therefore, this composite becomes much more crystalline after heating at 750 °C for 1 h.