Oxidation resistance of a Zr-doped NiAl coating thermochemically deposited on a nickel-based superalloy

The influence of the reactive element Zr on the oxidation behavior of the AM1/NiAl system has been investigated by means of cyclic oxidation combined with SEM microstructural characterizations and ToF-SIMS depth-profiling, and by isothermal oxidations followed by thermogravimetric analyses. Although Zr significantly improves the scale adhesion (spallation is delayed and interfacial cavities are avoided), it has no major effect on the alpha-alumina growth in the stationary regime of oxidation. Zr modifies the coating oxidation behavior (parabolic constant rate and cavities) only during the first hours of oxidation but with beneficial long-term consequences. Zr is homogeneously distributed within the oxide scale after cyclic oxidation.