A comparison between novel Gd2Zr2O7 and Gd2Zr2O7/YSZ thermal barrier coatings fabricated by plasma spray-physical vapor deposition

Abstract

Spherical Gd2Zr2O7 hollow powders with a mean size of 8.8 μm were fabricated as feedstock for thermal barrier coatings (TBCs) by spray-drying. The single-ceramic-layer (SCL) Gd2Zr2O7 TBCs and double-ceramic-layer (DCL) Gd2Zr2O7/YSZ TBCs with quasi-columnar structure were successfully fabricated by plasma spray-physical vapor deposition (PS-PVD). Tensile and water-quenching tests were applied to evaluate TBCs performances. The results show that adhesion strength of SCL Gd2Zr2O7 TBCs and DCL Gd2Zr2O7/YSZ TBCs is 36.5 MPa and 15.4 MPa, respectively. The delamination of SCL Gd2Zr2O7 TBCs and DCL Gd2Zr2O7/YSZ TBCs in the tensile test takes place at the middle and bottom of Gd2Zr2O7 layer, respectively, due to relatively lower fracture toughness of Gd2Zr2O7 layer. After 40 cycles of water-quenching test, DCL Gd2Zr2O7/YSZ TBC surface keeps relatively intact, while SCL Gd2Zr2O7 TBC surface shows 20% visible destroyed regions, which demonstrates that DCL Gd2Zr2O7/YSZ TBCs have a better thermal shock resistance than SCL Gd2Zr2O7 TBCs. The cracks in the SCL system propagate near thermally grown oxide (TGO) due to thermal mismatch and TGO growing stress, while cracks in the DCL system propagate in the Gd2Zr2O7 layer due to its relatively lower fracture toughness.