Effect of addition of Pt, Pd and Ir to β-NiAl-bond coat on oxidation resistance and growth of interdiffusion zone

Abstract

The addition of Pt to the β-NiAl bond coat enhances the service life of the turbine blade in jet engine application. However, it increases the growth of the unwanted precipitate containing an interdiffusion zone between the bond coat and superalloy. The role of Pd and Ir addition is examined in this study by comparing the growth of the interdiffusion zone without compromising the thermal cycle resistance of the oxide layer. The oxide layers on all the bond coats grow with duplex morphology. Ni and Ir-containing precipitates are found inside α-Al2O3 oxide layer on Ir-containing bond coats. The microstructural evolution of the interdiffusion zone is explained with the help of the diffusion path. The addition of Ir is found to decrease the growth of the interdiffusion zone significantly compared to the Pt containing bond coat without compromising the thermal cycle resistance of the oxide layer, which could be considered as an important addition in next-generation turbine blades.