Hydroxyapatite coatings prepared by micro-arc oxidation in Ca- and P-containing electrolyte

A novel method to directly prepare hydroxyapatite (HA) on Ti6Al4V by micro-arc oxidation (MAO) in Ca- and P-containing electrolyte was proposed in this paper. The results revealed that the MAO-formed coatings were composed of a bi-layer structure of HA/TiO2, containing α-TCP and CaCO3, and the applied voltage and the treated time were two important factors for HA formation. HA formed in the MAO coatings were probably the continuous decomposing products of Ca-deficient HA. The tensile strength of the coatings was about 44 and 24 MPa when the samples were treated for 15 min at 450 V and 480 V respectively. The fracture surfaces examined with EDX showed that failure occurred within the coatings.