Microstructure Of Calcification Coating On Micro-arc Oxidized Titanium Alloy And Corrosion Performance

Ti6Al4V alloy has good mechanical properties and widely applied in hard tissue implant. But it has a problem of biologically inert and has poor bone integration performence. Aiming at this problem, this paper using electrodeposition method to prepare calcium phosphate coating on the micro-arc oxidized Ti6Al4 V alloy.In this paper, we studied the relationship between the cathodic deposition parameters and the organizational structure of the calcium phosphate coating systematically. By adjusting the deposition process parameters, we could control the composition and morphology of the coating. Then we analyzed the nucleation and growth mechanism and the corrosion property of the coating.The result shows that the composition of the electropalting solution and the electric parameters during the deposition process have an significant influence on the organization and structure of the coating. Electroplating solution have an influence on the early process of electrodeposition, but their deposition mechanism are the same.Deposition process including HPO42- and H2PO4- ionization, water electrolysis, Ca2+and HPO42-, PO43- codeposite to form the calcium phosphate coating. The deposition time and temperature affect ionization and electrolysis, then influence the concentration of HPO42-, PO43- and OH-. In this way, obtain different organizations and morphology.At low temperature, HPO42-is difficult to turn into PO43-and the decomposition of water is also slowly. The composition of coating is DCPD. While at high temperature,the composition is HA. Under the long-term deposit, there will be Ca(OH)2 deposit in the coating due to water electrolysis. Electrodeposition parameters will affect the movement speed of electrons in the solution. Then influence the composition of coating.When the current density or the voltage is lower, will achieve DCPD coating. When the current density or the voltage is higher, will achieve HA coating. If the current density is too high, there will be Ca(OH)2 deposit on the sample.The morphology is related to the nucleation location. The morphology of DCPD and HA are large sheet, which are directly nucleate on the surface of the micro-arc oxidized coating. They form a porous structure. The DCPD and HA is needle-like with small size, which are nucleate on the coating deposited earlier. Corrosion property of the coating is related to the composition. The corrosion resistance of the DCPD mixed with HA is higher than that of single component DCPD or HA coating. The higher HA content the coating has, the poorer corrosion resistance the coating will be.