Sputter-deposited zirconium doped nickel-aluminide coatings for high-temperature oxidation-resistant applications

Zr-Ni3Al coatings were deposited over the Inconel-718 substrate using DC cosputtering. The deposition was carried out in a custom-designed chamber at a substrate temperature of 400 °C. The evolution of phases, microstructure, surface topography, and elemental composition were characterized using x-ray diffraction, field emission scanning electron microscopy (FESEM), atomic force microscopy, and energy dispersive spectroscopy (EDS), respectively, whereas the adhesion strength and the mechanical properties of the coatings were characterized using nanoindentation. The oxidation properties of the coatings were studied at 900, 1000, and 1100 °C in open air to determine the kinetics of oxidations. The results reveal that with the increase in Zr concentration in the host Ni3Al matrix, the adhesive strength and mechanical properties of the films increase. The highest hardness and Young’s modulus of ∼9.2 and ∼150.3 GPa, respectively, are observed for 30 W Zr-Ni3Al coatings. Additionally, 1.51 at. % of Zr in Ni3Al coatings has shown the best oxidation resistance properties at all temperatures. However, an increase in the rate of oxidation has been observed with an increase in exposure temperature. The formation of different oxide layers after oxidation has been elucidated using FESEM and EDS after looking into the surface morphologies of the oxidized coatings.