This study aims to apply pack aluminization which contains ZrO2 powder to develop NixAly layers on the surface of pure Ni substrate to investigate the effect of ZrO2 content on phase development and oxidation behavior of the aluminized Ni. The surface of pure Ni substrate was aluminized at 1,000 °C for 6.25 hrs using a pack-cementation with three ZrO2 contents in the pack mixture. Aluminized specimens were subjected to cyclic oxidation with air-cooling in ambient air at 1,000 °C. A scanning electron microscope equipped with energy-dispersive X-ray spectroscopy and an X-ray diffractometer (XRD) were used for phase analyses. Layers of coatings consisted β-NiAl, γ’-Ni3Al and Al-alloyed γ-Ni. Thicknesses decreased with increasing ZrO2 contents. Incorporated Zr was in the forms of intermetallics. The absence of δ-Ni2Al3 indicated a reduction of diffusing Al activity. While the specimen with moderate ZrO2 content showed parabolic oxidation kinetics, the multiple linear kinetics along with the high-exponent power-law oxidation were observed in the oxidized specimens prepared at other conditions. The addition of ZrO2 in pack aluminization enables a modification of the thermodynamic Al activity. The stable α-Al2O3 formation was found to be promoted by the Zr addition rather than a higher Al concentration of aluminides.
