This paper reports results from a larger study that has focused on the development of novel Pt+Hf-modified γ-Ni+γ′-Ni 3 Al-based compositions for high temperature bond coatings with improved reliability and durability. The effects of Pt, Hf and Cr contents on resistance to both isothermal and cyclic oxidations at 1150°C in air were analyzed. It was found that Pt contents of up to 20at.% significantly enhanced the selective oxidation of aluminum so as to suppress the formation of less-protective NiO and NiAl 2 O 4 . The Pt also served to decrease the reactivity of Hf in the γ′ phase, to the extent that unwanted HfO 2 formation could be suppressed. Balanced Pt+Hf-modified γ+γ′ compositions exhibited remarkably slow oxidation kinetics. Moreover, γ+γ′ coatings were shown to offer clear potential advantages over β-NiAl-based coatings, with the former exhibiting excellent surface stability (i.e., no rumpling) and compatibility with the superalloy substrate (i.e., no SRZ formation).
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