Plasma sprayed wollastonite/TiO2 composite coatings on titanium alloys.

Wollastonite/TiO2 composite coatings were prepared using plasma spraying technology onto Ti-6Al-4V substrate. The composite coatings exhibit obvious lamellar structure with alternating wollastonite coating and TiO2 coating. No obvious cracks exist on the interface between coatings and substrate. In the case of composite coatings, the primarily crystalline phases of the coatings are wollastonite and rutile, indicating wollastonite and TiO2 did not react during plasma spraying process. Some of rutile in the powders transforms into anatase due to plasma spraying. The mean bond strength of the composite coatings is higher than 30 MPa. The Vickers microhardness of coatings increase with the increase in the content of TiO2. Wollastonite/TiO2 composite coatings were soaked in simulated body fluid to examine their bioactivity. Carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the wollastonite and W7T3 coatings soaked in simulated body fluid, while was not formed on the surface of the TiO2 and W3T7 coatings after immersion. In addition, a rich-silica layer appeared at the interface of CHA and wollastonite and W7T3 coatings. In order to investigate the cytocompatibility of the coatings, osteoblast was seeded onto the surface of the coatings. The scanning electron microscopy observation showed that the addition of wollastonite promote the proliferation of osteoblast. It is enough to prove that the wollastonite and wollastonite/TiO2 composite coatings possess excellent cytocompatibility.