Cyclic oxidation behavior of aluminide coatings on the Co-base superalloy DZ40M

Aluminide coatings are prepared on a new Co-base superalloy DZ40M by low-pressure chemical vapor deposition (LP-CVD), and their cyclic oxidation behavior is investigated. The results show that the coating degradation primarily results from Al-depleting to heal the oxide scale on the outer surface during the cyclic oxidation, unlike that primarily from inward Al diffusion to the substrate during the isothermal process. The effect of Ti on the oxidation resistance is very different for various intermetallic alloys, and the addition of Ti will increase the degradation for the present coating during high-temperature oxidation. These experimental results are helpful to clarify the understanding of the Ti-modification effect on aluminide coatings for Co-based superalloys.