The effect of enamel coating on the oxidation behavior of Ti3Al-based intermetallics at 750 °C in air

The synergistic effects of alloy element Nb and enamel coating on the oxidation behavior of Ti3Al-based alloys in open air at 750 °C were studied in the present paper. The results showed that 17Nb alloyed Ti3Al intermetallics showed better oxidation resistance due to the formation of a compact and adhesive TiO2 scale during oxidation. Enamel coating as a barrier could protect Ti3AlNb alloys from oxidation. The coating kept intact and adhesive during discontinuous oxidation due to its good compatibility and matched thermal expansion coefficient with the substrates of Ti-based alloys. Nevertheless, the enamel coating might be degraded due to the rapid formation of Nb enriched sublayer and depletion layer at the interface of enamel/Ti3Al-23Nb and enamel/Ti3Al-27Nb. In addition, there existed detectable internal oxidation beneath the interface of enamel/Ti3Al-xNb (x = 23 and 27 at.%) due to the inward diffusion of oxygen through the imperfect Nb enriched sublayer during discontinuous oxidation.