Effect of Cr2O3 nanoparticle dispersions on oxidation kinetics and phase transformation of thermally grown alumina on a nickel aluminide coating.

Highlights • Ni 2 Al 3 coatings without and with Cr 2 O 3 dispersion were developed. • The Cr 2 O 3 dispersion promoted θ-to-α alumina transformation during oxidation. • Faster alumina transformation caused a lower oxidation rate of the Ni 2 Al 3 coating. • Faster θ-to-α transformation helped to form an adherent alumina scale. Abstract Cr 2 O 3 -free and-dispersed Ni 2 Al 3 coatings were prepared by correspondingly aluminizing as-electrodeposited Ni films without and with dispersion of Cr 2 O 3 nanoparticles. The Cr 2 O 3 -dispersed aluminide coating has a lower oxidation rate than the Cr 2 O 3 -free one in air at 900 °C. The reason lies in that the Cr 2 O 3 dispersion promoted the θ-to-α alumina transformation on the aluminide coating during oxidation, on a basis of investigations of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photo stimulated luminescence spectroscopy (PSLS). The result also indicates that the faster θ-to-α phase transformation can significantly prevent the cavities formation at the alumina/coating interface. [ABSTRACT FROM AUTHOR]