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-pr essure chemical vapor deposition (LP-CVD), and their cyclic oxidation behav ior is investigated. The results show that the coating degradation primaril y results from Al-depleting to heal the oxide scale on the outer surface du ring the cyclic oxidation, unlike that primarily from inward Al diffusion t o the substrate during the isothermal process. The effect of Ti on the oxid ation resistance is very different for various intermetallic alloys, and th e addition of Ti will increase the degradation for the present coating duri ng high-temperature oxidation. These experimental results are helpful to cl arify the understanding of the Ti-modification effect on aluminide coatings for Co-based superalloys. (C) 2001 Elsevier Science B.V. All rights reserv ed.