ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3; a promising TBC material with high resistance to hot corrosion

Abstract

Hot corrosion in Na2SO4-V2O5 environments has been regarded as a major challenge in the destruction of thermal barrier coatings (TBCs). The present study introduces a new TBC (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) with enhanced resistance to hot corrosion compared to the yttria-stabilized zirconia (YSZ). ZGYbY and YSZ were applied on CoNiCrAlY, as a bond coat to nickel-based superalloy (IN738LC) using the atmospheric plasma spray (APS) technique. Hot corrosion behavior of TBCs was investigated in a cyclic approach (4 hours for each cycle) using Na2SO4-55 wt.% V2O5 salts at 950°C. The findings showed the higher hot corrosion resistance of ZGYbY TBC compared to YSZ coating system. Regarding the lower basicity of Yb2O3 and Gd2O3 (compared to Y2O3), the driving force for the reaction of Yb2O3/Gd2O3 + Na2SO4-55 wt.% V2O5 will be lower than that of Y2O3 + Na2SO4-55 wt.% V2O5. Moreover, the stabilizers in the zirconia coating could be dissolved by sodium sulfate and vanadium oxide at high temperatures giving rise to the dis-integrity of the TBCs.