MICRO-LAMINATED (ZrO2–Y2O3)/(Al2O3–Y2O3) COATINGS ON Fe–25Cr ALLOY AND THEIR HIGH TEMPERATURE OXIDATION RESISTANCE

The micro-laminated (ZrO2–Y2O3)/(Al2O3–Y2O3) composite coatings were prepared on the surface of Fe–25Cr alloy by an electrochemical process and a sintering process alternately. FE-SEM analyses show that the cross section of the micro-laminated coatings has alternate six-layer films of ZrO2–Y2O3 and Al2O3–Y2O3, with the thickness of each layer in the range of nanometer or submicron. The surface of the micro-laminated coatings is composed of nanoparticles. SEM, XRD, and mass gain measurements were adopted to study the oxidation resistance of coatings on the Fe–25Cr alloy. It has been found that all the coatings are effective in protecting the substrate from oxidation, and micro-laminated coatings exhibit more excellent protectiveness performance, and the oxidation resistance is increased with increasing the layers of the micro-laminated coatings. These beneficial effects can be contributed to the mechanism, by which such a micro-laminated coating synthesizes all the beneficial effects and overcomes all the disadvantages of both the ZrO2–Y2O3 coating and the Al2O3–Y2O3 coating during the oxidation of the alloy.