Preparation And Properties Of Fluor-hydroxyapatite Coating On Pure Titanium By Sol-Gel

Preparation of a bioactive coating on the surface of metal implants can combine the excellent bioactivity and biocompatibility of bioceramic with the high strength and superior toughness of metal alloy. However, the drawbacks such as poor bonding condition and low crystallinity will lead to de-bonding of the bioactive coating, and subsequent implant failure. In this paper, through laser gas nitriding technique, TiN dendrite layer was made on pure titanium. Then FHA bioactive coatings were fabricated on pure titanium and laser gas nitriding titanium by using sol-gel method, respectively. OM, SEM, EDS and XRD were employed to study microstructure, composition and morphologies of the fluor-hydroxyapatite coating, and bond strength between coating and substrate were also investigated. The main conclusions are as follows:A TiN dendrite layer could be successfully prepared on pure titanium by using laser gas nitriding technique, which improved the corrosion resistance and wear resistantance of pure titanium remarkably.The microstructures of the FHA coating showed a typical sol-gel characteristics, and were mainly composed of FHA and minor tricalcium phosphate phases after crystallization at 600°C, 700°C and 800°C. However, a higher crystallization temperature would cause partial oxidation of the substrate and led to emergence of TiO2 in coating. With the increasing of crystallization temperature, the thickness of coating increased.The incorporation of F into the HA coating was favorable for obtaining high crystalline the apatite phase. Energy dispersive spectroscopy tests showed that the actual Ca/P value in coating was close to that in sols. With increase of F content within coating, the thermal expansion coefficient became small and near to that of substrate, and cracking trend decreased as well. The thickness of the coating layer increased with increase of the temperature.The TiN dendritic structure fabricated on pure titanium using laser gas nitriding technique in advance could help anchor the FHA coating and improved the interfacial adherence significantly compared with the the polished surface, the bonding strength between the coating and the laser gas nitrided substrate was about 2 times higher than that on the polished substrate, and bonding strength between coating and substrate was increase with increase of fluorine content. In vitro experiental results showed that FHA coating possessed good stability and bioactivity.