Résumé
The research hypothesis is that the addition of Pt within the superalloy would enhance the stability of the γ’-Ni3(Al,Ti,Ta) phases present in the microstructure while modifying Al activity and/or its diffusion coefficient contained in the superalloy thus allowing the formation of a protective Al2O3 layer on the surface. The results will show that the low content of Al and Pt seems to be insufficient to completely protect the superalloy against the damage caused by oxidation at the highest temperatures. The oxide layers formed are mainly composed of Cr and Ti until 1000°C. Above this temperature, a highTa content is observed as well as the formation of a continuous thin layer of Al2O3 that undergoes spallation likely derived from the 7 ppm of S contained in the alloy. The low content Pt does not arrest the outward flow activity of Ta which forms an oxide of crystallography incompatible with the crystallographic structure of Cr2O3 or Al2O3 oxides. Pt incorporates into the γ’-Ni3(Al,Ti,Ta) phase by substituting for Ta. In order to better understand the growth mechanisms of the oxide layers, particular attention will be given to the oxidation of model γ and γ’ alloys composing the TROPEA superalloy.