Influence of nitriding on the oxidation behaviour of titanium alloys at 700 °C

The influence of nitridation treatments at 600 and 800 °C on the oxidation resistance of pure titanium, Ti-6Al-4V, and Ti-7Nb in air at 700 °C has been studied. Nitridation may increase the oxidation resistance, but the influence of the nitriding treatments depended on the composition of the material. For pure titanium and alloy Ti-6Al-4V, the nitride layer prevented oxygen dissolution into the alloy during the earliest stages of oxidation, thus reducing the contribution of this process to the total mass gain. For Ti-7Nb, a material that stabilises a nitride layer at the scale/alloy interface during air oxidation, small differences in mass gain between nitrided and nonnitrided samples were related to the different structures of the nitride layer.