Oxidation Behavior of Selected Bond Coats Based on the γ′ + γ Structure and Their Performance in Thermal Barrier Coatings Deposited on a Nickel-Based Superalloy

Three bond coats based on the γ′-Ni₃Al + γ-Ni microstructure were developed by diffusing pairs of Pt layers and metallic layers with selected compositions into a Ni-based superalloy. Thermal exposure tests at 1,150 °C with 24-h cycling period to room temperature were used to evaluate the thermal stability and oxidation behavior of the bond coats as well as their performance in thermal barrier coating systems utilizing zirconia-7 wt% yttria as the top coat. It is shown that a bond coat developed by a Pt layer and a layer of Ni-6 wt% Re-0.5 wt% Y alloy outperforms the conventional γ′ + γ Pt bond coats by more than two folds. Most evidence points out that the proper concentrations of Re and Y in the presence of balanced concentrations of other elements, particularly Al, Ti, Cr and Co can significantly enhance the thermal stability and oxidation resistance of γ′ + γ Pt bond coats.