The effects of active element additions on the oxidation performance of a platinum aluminide coating at 1100 degrees C

The beneficial effects of active element additions to both overlay coatings and beta-NiAl intermetallics are well documented in the literature. The ad dition of such elements has been noted to increase the adherence of a prote ctive oxide scale, decrease the oxide growth rate and improve the mechanica l properties of the oxide. The present study aimed to assess the effects of the ion implantation of either Hf or Y to a platinum aluminide on a MarM00 2 substrate, to determine whether the additions would act to improve the co ating's performance under hot oxidation conditions. The samples were isothe rmally exposed to laboratory air for 100, 250 and 500 h at 1100 degrees C. Their performance was assessed by comparing the oxide growth rate, adherenc e and composition to that formed by an untreated coating. The additions wer e found to have had no observable effects on the performance of the coating , promoting oxides that had a similar adhesion, growth rate and composition as were formed on untreated systems. However, the study did reveal the det rimental effects of excessive hafnium peg formation and their role in the d egradation of the coatings. (C) 1998 Elsevier Science S.A. All rights reser ved.