Effect of time on the formation of hydroxyapatite in PEO process with hydrothermal treatment of the Ti-6Al-4V alloy

A titania layer containing calcium and phosphate with rough and porous structure was prepared by plasma electrolytic oxidation (PEO) and hydrothermal treatment (HT) at different time treatment. The most corresponding to the stoichiometry of hydroxiapatite ratio of Ca: P in the oxide layer can be achieved by the optimization of the electrolyte composition and the main parameters of PEO. While at the stage of PEO hydroxiaptite precursors are formed with only residual quantity of the hydroxyapatite, the subsequent hydrothermal treatment results in the formation of a much more pronounced hydroxyapatite phase.