Oxidation behavior of γ-TiAl coated with zirconia thermal barriers

The applicability of the thermal barrier coating concept, which is an established concept for Ni-base alloys, was investigated for the first time for γ-TiAl. As potential bond coats, the following surface treatments were applied: Al-diffusion coating, Al-diffusion coating combined with short term pre-oxidation in air, short term pre-oxidation in oxygen of a rough surface finish γ-TiAl sample without aluminide coating. For the purpose of lowering the temperature of the γ-TiAl substrate surface, and thus, to prolong the life time, a zirconia thermal barrier coating (TBC) was applied on top of the above-mentioned modified TiAl surfaces. Oxidation resistance of the modified γ-TiAl alloys/TBC systems was evaluated by isothermal oxidation tests at 900 °C for 100 h in air. Whatever the pre-treatment conditions, the TBC was adherent to the oxide scale after 100 h oxidation, which was not the case for untreated γ-TiAl.