HAF/YSZ Gradient Composite Coatings Fabricated By Magnetron Sputtering On Ti6Al4V Substrate And The Characterization Of Its Properties

Bioactive gradient coatings containing HAF and YSZ were designed and prepared by RF magnetron sputtering on the Ti6Al4V substrates. In this paper, XRD, FTIR, SEM, AFM, EDS and XPS analysis of HAF/YSZ gradient coatings were made. The phase constitution, structure of the surface and interface, influence of fluorine on the coatings were studyed. Bioactivity of as obtained coatings was revealed by in vitro experiment. The conclusions are obtained from the above works as follows:Fluoridated-Hydroxyapatite (HAF) powder was prepared by wet chemical precipitation method. TEM results showed that the morphology of the HAF precipitation is needle-like and clavate with the average size of 37.2nm in diameter. Moreover, with the increasing contents of fluorine, HAF particle will become more perfect. The synthesis of HAF target and HAF/YSZ targets were studied by hot pressing. Results indicated that the relative densities of all targets could satisfy the request of the RF magnetron sputtering to the target material, meanwile, fluorine could improve the solvent stability of the targets.RF magnetron sprayed HAF/YSZ gradient coating was consisted of amorphous phase and dehydroxylated HAF structure. The n(Ca)/n(P) ratio in sputtered coatings changes from 1.69 at the surface of the coatings to 1.75 at the substrate, which were all close to the stoichiometric n(Ca)/n(P) ratio (1.67) of HA. HAF/YSZ gradient coating showed a porous structure and a rough surface, which provides the growth conditions for tissue, even to improve the osteal combination ability.The appropriate post-annealing treatment was carried out under suitable atmospheric condition so that the dehydroxylated HAF structure was highly crystallized. Furthermore, fluorine converted the HAF/YSZ gradient coating into calcium deficient coating with needle like crystals and made the coatings have good bioactivity.The bonding strength of HAF/YSZ/Ti6Al4V gradient coating composites prepared by RF magnetron sputter technique is 55.8MPa. For sputtered coating, surface roughness of Ti6Al4V substrates was not the key factor which decided the bonding strength. Since there existed chemical reaction between coating and substrate, the bonding strength was controlled by the chemical bond.The HAF/YSZ bioactive gradient coating composites indicated good bioactivity with in vitro experiment. It had the better chemical stability and mechanics stabilities than the HA coating composites.