Comparison of the cyclic oxidation behavior of β-NiAl, β-NiPtAl and γ-γ′ NiPtAl coatings on various superalloys

The cyclic oxidation behavior of simple aluminide and platinum aluminide coatings on various superalloy substrates was investigated at three temperatures. Coatings of β-NiAl, β-NiPtAl and Pt-modified γ-γ′ were tested and compared in dry oxygen at 1050, 1100 and 1150 °C. There was a clear influence of substrate sulfur content on the oxidation behavior of β-NiAl coatings at all temperatures. The impact of substrate impurities, especially S content, was significantly reduced for β-NiPtAl coatings at all temperatures. Simple Pt-modified γ-γ′ coatings showed excellent oxidation behavior up to 1100 °C on some alloys, but were more sensitive to substrate composition, especially Hf content, than were β-NiPtAl coatings.