High-temperature oxidation behaviour of a TiAl-based alloy subjected to aluminium hot-dipping

In this research the oxidation resistance at high temperature of a TiAl-based alloy has been improved by hot-dipping the alloy in molten aluminium and by performing an interdiffusion process. After selecting the best process parameters, a compact TiAl3 coating characterized by an almost constant thickness was formed on the surface. Isothermal oxidation tests, carried out at 900, 950 and 1000 °C, showed that the coated alloy is able to form a continuous and thin alumina layer that is very protective. Microstructural investigations highlighted that, above 900 °C, long residence times at high temperature determine the diffusion through the TiAl3 layer of Cr that favours migration toward the outer surface of Al and thus the formation of a self-healing alumina layer.