Air oxidation behaviour of a Ti-6Al-7Nb alloy

Air oxidation behavior of a Ti6Al7Nb alloy was examined over the temperature range of 873 -1173 K for different time intervals ranging in between 12 and 72 h. The rate of oxidation evaluated according to the weight gain measurements, fitted parabolic kinetics by yielding oxidation activation energy of 226 kJ/mol. Rutile and anatase modifications of TiO₂ formed on the surface as the result of air oxidation. Oxidation temperatures higher than 923 K encouraged rutile formation rather than anatase. As temperature of oxidation was increased, the thickness of the oxide layer increased. Thicker oxide layer provided higher surface hardness and better protection against a corrosive media (5 M HCl solution) was provided.