Fabrication Of A Bioactive Coating On Surface Of The Microarc Oxidated Ttitanium Alloy

In order to improve the bioactive of Ti6Al4V alloy and to accelerate bone growth and healing, a porous TiO2 coating containing calcium and phosphate prepared on Ti6Al4V alloy substrate using micro-arc oxidation (MAO) technique. Effect of applied voltage and Ca/P ratio, heat treatment and alkali/heat treatment on the microstructure, crystal structure and in vitro bioactivity of micro-arc oxidated coatings were studied. The main conclusions are as follows:(1) An oxide coating containing calcium and phosphate ions could be prepared on Ti6Al4V alloy substrate using MAO technique. The MAO coatings showed rough and porous structure with spherical pores of several microns in diameter, and some pores connected each other. The pore size and the thickness of the coating increased with increase of the applied voltage. The coating was mainly composed of rutile and anatase (TiO2), which was not affcetd by anode voltage significantly. The wear resistance and corrosion resistance of Ti6Al4V alloy has been markedly improved by micro-arc oxidation treatment.(2) The pore size and the amount of rutile phase within coating increased with increase of Ca/P value. CaTiO3, hydroxyapatite with low crystalinity and amorphous phase appeared within coating at Ca/P=20:1. The amorphous phase promoted the formation of apatite nucleation and resulted in enhancing the apatite forming ability significantly.(3) The diffraction intensity of rutile increased, crystal orientation became obvious, and the bioactivity was improved after heat treatment of the micro-arc oxidation coatings (Ca/P=1:1, 400/100V) at 400°C for 1 hour. The reason could be ascribed to the structure matching of rutile (101) and apatite (0004), which reduced nucleaation energy and was conducive to hydroxyapatite growth.(4) After alkali treatment followed by heat treatment, the surface morphology of the micro-arc oxidation coating (Ca/P=1:1, 400/100V) showed a porous network structure and a great amount of CaTiO3 phase appeared within coating. Hydrolysis of CaTiO3 was conductive to apatie nucleation and led to a significant improvement of the apatite-forming ability of the MAO coating on Ti6Al4V alloy.