Abstract
A dense ceramic oxide coating, about 50 µm thick, was prepared on a Ti–6Al–4V alloy by alternating current microarc oxidation in an aluminate solution. Its microstructure and phase composition were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The oxide coating contains two layers: an outer layer and a dense internal layer. The coating is mainly composed of TiO2 rutile and TiAl2O5 spinel phases. In the outer layer coating, the TiAl2O5 fraction is much higher than the rutile fraction. However, in the internal layer, rutile becomes the main phase while the TiAl2O5 fraction decreases significantly. During microarc oxidation, local melt–solidification processes take place in the coating, however, the microstructure of the Ti–6Al–4V substrate near the coating/metal interface is not changed. Aluminium from the solution is enriched in the outer layer coating, although it has also diffused into the interior of the coating.
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