Formation of hydroxyapatite on Ti–6Al–4V alloy by microarc oxidation and hydrothermal treatment

Microarc oxidation (MAO) was performed on Ti–6Al–4V in electrolytes containing calcium glycerphosphate (Ca-GP) and calcium acetate (CA) using a regulated direct current power supply. It was found that the MAO method was suitable for Ti–6Al–4V to form a ceramic coating in electrolytes of Ca-GP and CA, and the oxide films displayed a porous and rough structure on the surface of films. The film with a Ca/P ratio equivalent to hydroxyapatite was obtained when final voltage and current density were 350 V and 200 A/m2 in the electrolyte containing 0.06 M calcium glycerphosphate (Ca-GP) and 0.25 M calcium acetate (CA). After hydrothermal treatment, the hydroxyapatite was precipitated on the surface of the film obtained by MAO and the hydroxyapatite thickness was about 4 μm. The films were investigated by means of electron probe micro-analysis, atomic force microscopy, X-ray diffractometry and scanning electron microcopy before and after hydrothermal treatment.