Characterization of new bioactive coatings of hydroxyapatite and TiO2 obtained by High-Velocity Oxy-Fuel

Hydroxyapatite (HAp: Ca-10(PO4)(6)OH2) is a biocompatible and bioactive ceramic material widely used as a coating on metal surfaces (dental implants, hip replacements ... ), but the low adhesion between HAp and the substrate, due to differences in thermal expansion coefficients of both (very important in thermal spraying because of the fast cooling of the coating, which can produce a lost of adherence), and the degradation of HAp, have been tried to be improved through the incorporation of TiO2 to get a good combination of mechanical properties. Therefore, the objective of this project is to produce coatings of HAp 80% TiO2 and 20% (by weight) on Ti6Al4V by High-Speed Thermal Spray (HVOF). The study of the microstructure has been carried out using scanning electron microscopy and characterization of the crystalline phases by X-ray diffraction and Raman spectrometry. The coatings adhesion has been measured by tensile tests according to ASTM C633-01 (2008), and their bioactivity also has been evaluated through its immersion in simulated body fluid (SBF), in order to measure their capacity to form an apatite layer on their surface.