Failure Mechanism of Yb2O3-Gd2O3-Y2O3 Co-Dopzed Zirconia Double Ceramic Thermal Barrier Coating in Na2SO4+V2O5 Environment
A double ceramic(GYYZ/YSZ)thermal barrier(TBCs)coating with 9.5Y2O3-Y2O3-5.6Yb2O3-5.2Gd2O3 co-doped ZrO2(GYYZ)as outer layer and Y2O3 stabilized ZrO2(YSZ)as inner layer were prepared by atmospheric plasma spraying(APS)method,and compared to the traditional single-layer YSZ TBCs.Thermal cycling tests were conducted to investigate hot corrosion behavior and failure mechanism of the two coatings in the Na2SO4+V2O5 environment.The results show that compared with YSZ,GYYZ exhibitted stronger reactivity in corrosive environment due to its higher mass fraction of metal oxide stabilizers.The Gd2O3 and Y2O3 in GYYZ coating had strong Lewis basicity,which would preferentially participate in the reaction.The inactive Yb2O3 would be left behind to be the stabilizer of ZrO2,which was beneficial to maintain the phase stability of GYYZ/YSZ coating in the corrosive environment.Since GYYZ coating underwent less transformation from t'-ZrO2 phase to m-ZrO2 phase in the corrosion environment,the internal accumulated phase transition stress was smaller,so GYYZ/YSZ coating exhibited stronger resistance to crack propagation,and its thermal cycle corrosion life was significantly higher than that of YSZ coating.
thermal barrier coatingmultiple element rare earth dopinghot corrosionfailure mechanism
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