Coatings of hydroxyapatite — nanosize alpha alumina composites on Ti-6Al-4V

Composites of hydroxyapatite (HA) and nanosize-alpha-(α)-Al2O3 with 5 wt.% CaF2 were coated on Ti-6Al-4V rods by cold pressing and sintered in air or argon atmosphere at 1100 °C to improve the bonding between the metal and the ceramic. 25 and 40 wt.% α-Al2O3-5 wt.% CaF2-HA composites gave the best results of strong bonding. 25 wt.% α-Al2O3-5 wt.% CaF2-HA and Ti-6Al-4V showed the same thermal expansion coefficients. The thermal expansion coefficient of the 40 wt.% α-Al2O3-5 wt.% CaF2-HA composite was slightly smaller than that of Ti-6Al-4V, which created a compressive stress on the coating, resulting in improved bonding between the metal and the ceramic.