Preparation Of Micro-arc Oxidation Coatings On The Surface Of Ti-25Nb-2Zr Alloy

Porous TiO2 coatings were prepared on Ti-25Nb-2Zr alloy by micro-arc oxidation(MAO) technique in this paper. Then its bioactivity were evaluated by immersion the MAO samples in a simulated body fluid(SBF) for the biomimetic deposition of the apatite layer onto the surface of TiO2 coating . The apatite coatings as well as the surface oxide layer on Ti-25Nb-2Zr alloy were characterized using scanning electron microscopy(SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction(XRD).The Results showed the samples treated by MAO produced a porous layer on the surface of Ti-25Nb-2Zr alloy. The surface morphology of MAO samples and the thickness of the coatings are closely relative to the electrical parameter used during MAO. The average pore diameter increase with the increasing the applied voltage, oxidation time, the temperature of the electrolyte as well as pulsed duty ratio. With the pulsed frequency increasing, the average pore diameter decrease. The thickness of the coatings increase with increasing the applied voltage and oxidation time. XRD analysis indicates that the mainly phase of the MAO coating are TiO2. With the applied voltage increasing, some anatase TiO2 traslated to rutile TiO2. The porous surface of the MAO coating could promote the formation of apatite, but the ability to induce the formation and growth of apatite is different on the different MAO surface, which indicates that formation and growth of apatite is relative to composition of the surface on the Ti-25Nb-2Zr alloy. The quantity of the apatite increase with the immersion time.