Surface treatment of a Ti6Al7Nb alloy by plasma electrolytic oxidation in a TCP suspension

In this work, we describe surface modifications to a Ti6Al7Nb alloy resulting from plasma electrolytic oxidation (PEO) in two different solutions: one containing 0.1 mol/dm3 Ca(H2PO2)2 and 100 g/dm3 TCP (tricalcium phosphate) and another containing 0.1 mol/dm3 Ca(H2PO2)2, 25 g/dm3 TCP and 1 g/dm3 NH4F. As a result of the PEO process, a porous oxide layer containing incorporated calcium and phosphorous compounds was formed on the Ti6Al7Nb alloy surface. The morphology and chemical composition of the Ti6Al7Nb alloy samples were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (TL-XRD). The contact angle and roughness of the oxide layer were measured. The anodized samples exhibited a higher surface roughness than the non-modified Ti6Al7Nb alloy. Bioactivity investigations using an SBF solution confirmed the formation of apatite on the anodized surfaces. Additionally, the modified surface of the titanium alloy exhibited a higher corrosion resistance than as-ground examples due to the formation of a thin oxide layer on the surface.