Effect of substrate alloy composition on the oxidation behaviour and degradation of aluminide coatings on two Ni base superalloys

The oxidation behaviour and microstructural evolution of aluminide coatings on the Ni base superalloys Rene 80 and alloy 625 were investigated during 1050 degrees C oxidation in air. Alumina based oxide scales formed on the coating surfaces of both alloys and only minor differences in scale growth and spallation kinetics were found. A coupled thermodynamic-kinetic model was employed to describe the effect of the base material on the depletion processes and microstructural changes in the aluminide coating thus providing a tool for coating life time prediction without very extensive test programs.