Effects of Platinum on the Hot Corrosion Behavior of Hf-Modified γ′-Ni3Al + γ-Ni-Based Alloys

The establishment of a protective α-Al2O3 scale is critical for providing high temperature protection from oxidation and hot corrosion, thereby improving lifetimes of advanced gas turbine engine components. Recent work by our group has shown that a wide range of Pt + Hf-modified γ′-Ni3Al + γ-Ni alloy compositions form a very adherent and slow-growing Al2O3 scale and exhibit excellent oxidation resistance. The main thrust of the present study was to understand the effects of Pt addition on the Type I (900 °C) and Type II (705 °C) hot corrosion (HC) behavior of model Hf-modified γ′ + γ alloy compositions. The salt used to bring about hot corrosion was Na2SO4. It was found that the Type I HC resistance of γ′ + γ alloys improved with up to about 10 at.% Pt addition, but then decreased significantly with increasing Pt content up to 30 at.% (the maximum level studied); however, under Type II HC conditions the resistance of γ′ + γ alloys progressively improved with increasing Pt content up to 30 at.%. The effect of pre-oxidation on hot corrosion resistance was also examined, and the results indicated that pre-oxidation generally improved Type II HC resistance for the test duration studied.