Argon atmospheric plasma sprayed hydroxyapatite/Ti composite coating for biomedical applications

20 wt.% hydroxyapatite/Ti composite coatings were fabricated via an in-house developed argon atmospheric plasma spraying (AAPS) system on Ti substrates. The phase and morphologies of the coatings were identified by X-ray diffraction and scanning electron microscopy. The electrochemical corrosion behavior of the coatings was evaluated in a simulated biomedical environment by using potentiodynamic polarization and electrochemical impedance spectroscope techniques. The bioactivity of the composite coatings was studied by immersing the coatings in simulated body fluid (SBF) for up to 8 months. The mechanical properties such as microhardness, friction and bonding strength were also investigated. Results demonstrate that dense composite coatings with a typical morphology of HAP homogenously distributed in Ti matrix are obtained and the decomposition of HAP during plasma spraying process is avoided. The bonding strength is significantly higher than that of HAP or Ti reinforced HAP coatings and the frictional property is comparable to Ti substrate. A relatively higher corrosion current of HAP/Ti composite than that of pure Ti coating in simulated body fluid indicates a good bioactivity for composite coating, which is also testified by the formation of apatite layer in vitro test. After eight months immersion, a thick, tortoise-shell like apatite layer covered the entire top surface of composite coating. The study indicates the potential of AAPS deposited HAP/Ti composites as load bearing implant materials. (C) 2012 Elsevier B.V. All rights reserved.