AN INVESTIGATION ON HOT CORROSION RESISTANCE OF PLASMA SPRAYED COMPOSITE YSZ-GD2ZR2O7 AND GD2ZR2O7 THERMAL BARRIER COATINGS IN SIMULATED TURBINE ENVIRONMENT AT 1050°C

Thermal barrier coatings (TBCs) are frequently used on hot section components in gas turbines. Rare-earth zirconate ceramics used as thermal barrier coatings have attracted increasing interest in recent years due to their distinctly lower thermal conductivity than common TBC material; Yttria stabilized zirconia (YSZ). This paper investigates the hot corrosion resistance of composite YSZ+Gd2Zr2O7 and Gd2Zr2O7 coating, in Na2SO4+V2O5 at 1050 degrees C. 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 the reaction between NaVO3 and Y2O3 in YSZ produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. Then 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, thus the amount of monoclinic phase in the TBC coating is substantially reduced. Comparing to YSZ, under a high temperature of 1050 C, Gd2Zr2O7 is more stable, both thermally and chemically, So Gd2Zr2O7 exhibits a better hot corrosion resistance than YSZ+Gd2Zr2O7 composite coating.