Influence of ceria and yttria on the protective properties of SiO2-Al2O3 coatings deposited by sol-gel method on FeCrAl alloy

Three-layer Y2O3, CeO2, SiO2-Al2O3 and SiO2-Al2O3-Y2O3-CeO2 coatings were deposited by sol-gel method on the FeCrAl alloy foil substrate. The protective properties of the coatings during high-temperature cyclic oxidation and the changes in the topography of the surface, the structure, and chemical composition of the FeCrAl alloy surface layer were examined. It has been shown that small additions of cerium and yttrium affect the morphology of the growing Al2O3 scale. After 10 oxidation cycles in air (T = 900 A degrees C, t = 120 h, one cycle = 12 h), the smallest change in the mass of the samples was observed for Y2O3 and SiO2-Al2O3-Y2O3-CeO2 coatings with an appropriate yttrium and cerium content. The protection effectiveness of the coatings to that of uncoated substrate after 10 oxidation cycles ranges from 28 to 66 %. The oxidation scale thickness (h) and the designated value of the parabolic rate constant (k (p)) depended on the yttrium and cerium content in the coating.