Characteristic, cell response and apatite-induction ability of microarc oxidized TiO₂-based coating containing P on Ti6Al4V before and after chemical-treatment and dehydration

The structure, cell response and induction capability for apatite formation of the microarc oxidized (MAO) coating before and after chemical-treatment and subsequent dehydration at 400 °C were investigated. The surfaces of the chemically treated MAO (C-MAO) coatings before and after dehydration showed ribbon-like amorphous phase mainly containing Na, Ti and O elements with network morphology. Subsequent dehydration has no pronounced effect on the surface roughness, wetting ability, surface constituents and chemical state of Ti, Na and O of the C-MAO coating. The outer layers of the C-MAO coating before and after dehydration showed Na, Ti and O elements with uniform distributions along the surface depth. Chemical-treatment improves the apatite-forming ability of the MAO coating; however, subsequent dehydration greatly lowers that of the C-MAO coating, since it changed the ability of C-MAO coating to release Na⁺ ions, which is unfavorable for the formation of Ti-OH groups. The apatite formed on the two coatings contained HPO₄^2- and CO₃^2- ions. In addition, the dehydration of the C-MAO coating seemed to be unsuitable for the cell proliferation on its surface.