Abstract
The oxidation kinetics of Ti-6Al-4V samples nitrided in forming gas (N2+5%H2) between 520 and 805 °C is investigated using infrared emissivity measurements. Several kinetic exponents have been observed depending on temperature and time. The activation energy corresponding to the main parabolic rutile growth stage is 223 ± 10 kJ/mol. This value is significantly higher than that corresponding to TiN oxidation, which suggests that it is not the rate-limiting step. The protective role of the nitridation is attributed to the internal Ti2N layer. The microstructural characterization reveals a reduction in the oxygen-diffusion depth compared to non-nitrided Ti-6Al-4V, and a multi-layered Al2O3-TiO2 oxide.
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