Thermal oxidation of Ti6Al4V alloy: Microstructural and electrochemical characterization

Thermal oxidation (TO) of Ti6Al4V alloy was performed at 500, 650 and 800 °C for 8, 16, 24 and 48 h in air. The morphological features, structural characteristics, microhardness and corrosion resistance in Ringerʹs solution of TO Ti6Al4V alloy were evaluated and compared with those of the untreated one. The surface morphological features reveal that the oxide film formed on Ti6Al4V alloy is adherent to the substrate at 500 and 650 °C irrespective of the oxidation time whereas it spalls off when the alloy is oxidized at 800 °C for more than 8 h. X-ray diffraction (XRD) measurement reveals the presence of Ti(O) and α-Ti phases on alloy oxidized at 500 and 650 °C, with Ti(O) as the dominant phase at 650 °C whereas the alloy oxidized at 800 °C exhibits only the rutile phase. Almost a threefold increase in hardness is observed for the alloy oxidized at 650 °C for 48 h when compared to that of the untreated one. Thermally oxidized Ti6Al4V alloy offers excellent corrosion resistance in Ringerʹs solution when compared to that of the untreated alloy.