Influence of electrolyte composition on microstructure, adhesion and bioactivity of micro-arc oxidation coatings produced on biomedical Ti6Al7Nb alloy

Micro-arc oxidation is a simple, single-step surface modification method used to produce coatings on titanium alloys for biomedical applications. The formation and properties of coatings can be widely controlled by adjusting process parameters such as applied voltage, frequency, processing time and electrolyte composition. In the present study, three different electrolytes were used to obtain well adherent, rough, porous, hydroxyapatite containing, oxide coating on Ti6A17Nb alloy. Coatings were investigated in terms of their microstructure, chemical composition, roughness, hardness, adhesion strength and biocompatibility. Among the coatings produced in different electrolytes, one of them exhibited both good mechanical properties and bioactivity, while containing crystalline hydroxyapatite on the surface, whereas the other two coatings were mostly amorphous. Thereby, we have proposed an efficient electrolyte containing calcium and phosphorous species in order to modify titanium based alloys to improve their biocompatibility and osseointegration. Such properties are achieved by formation of a rough outer layer with open pores, providing high surface area for cells to adhere, proliferate and migrate into the coating, promoting firm anchorage of the coated implant in the bone. (C) 2017 Elsevier B.V. All rights reserved.