Evolution of hot corrosion resistance of YSZ, Gd2Zr2O7, and Gd2Zr2O7 + YSZ composite thermal barrier coatings in Na2SO4 + V2O5 at 1050 °C

This paper compares the hot corrosion performance of yttria stabilized zirconia (YSZ), Gd2Zr2O7, and YSZ + Gd2Zr2O7 composite coatings in the presence of molten mixture of Na2SO4 + V2O5 at 1050 °C. These YSZ and rare earth zirconate coatings were prepared by atmospheric plasma spray (APS). Chemical interaction is found to be the major corrosive mechanism for the deterioration of these coatings. Characterizations using X-ray diffraction (XRD) and scanning electron microscope (SEM) indicate that in the case of YSZ, the reaction between NaVO3 and Y2O3 produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. For the Gd2Zr2O7 + YSZ composite coating, by the formation of GdVO4, the amount of YVO4 formed on the YSZ + Gd2Zr2O7 composite coating is significantly reduced. Molten salt also reacts with Gd2Zr2O7 to form GdVO4. Under a temperature of 1050 °C, Gd2Zr2O7 based coatings are more stable, both thermally and chemically, than YSZ, and exhibit a better hot corrosion resistance.