The effect of Pt content on γ–γ′ NiPtAl coatings

This study investigated the impact of Pt content on the coating composition and subsequent oxidation behavior of γ–γ′ NiPtAl diffusion coatings. Coatings were fabricated by vacuum annealing electroplated Pt on single-crystal and directionally-solidified superalloy substrates. Specimens with 7 and 12 µm thick layers of electroplated Pt were annealed at 1100 or 1175 °C. Coating compositions were characterized to evaluate the distribution of Pt and Al as a function of annealing temperature and Pt thickness. Selected coatings were evaluated in cyclic oxidation at 1100 and 1150 °C. Coatings with higher Pt contents showed improvements in spallation resistance, particularly at 1100 °C for a directionally-solidified superalloy substrate with higher Hf and S contents.