A comparison between novel Gd2Zr2O7and Gd2Zr2O7/YSZ thermal barrier coatings fabricated by plasma spray-physical vapor deposition

Spherical Gd(2)Zr(2)O(7)hollow powders with a mean size of 8.8 mu m were fabricated as feedstock for thermal barrier coatings (TBCs) by spray-drying. The single-ceramic-layer (SCL) Gd2Zr2O7TBCs 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 Gd2Zr2O7TBCs and DCL Gd2Zr2O7/YSZ TBCs is 36.5 MPa and 15.4 MPa, respectively. The delamination of SCL Gd2Zr2O7TBCs and DCL Gd2Zr2O7/YSZ TBCs in the tensile test takes place at the middle and bottom of Gd(2)Zr(2)O(7)layer, respectively, due to relatively lower fracture toughness of Gd(2)Zr(2)O(7)layer. After 40 cycles of water-quenching test, DCL Gd2Zr2O7/YSZ TBC surface keeps relatively intact, while SCL Gd2Zr2O7TBC surface shows 20% visible destroyed regions, which demonstrates that DCL Gd2Zr2O7/YSZ TBCs have a better thermal shock resistance than SCL Gd2Zr2O7TBCs. 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 Gd(2)Zr(2)O(7)layer due to its relatively lower fracture toughness.

Automated summary

In this study, spherical Gd(2)Zr(2)O(7) hollow powders were fabricated as feedstock for TBCs by spray-drying, leading to the successful fabrication of SCL and DCL Gd2Zr2O7TBCs with quasi-columnar structure by PS-PVD. Tensile and water-quenching tests demonstrated higher adhesion strength and better thermal shock resistance of DCL Gd2Zr2O7/YSZ TBCs compared to SCL Gd2Zr2O7TBCs, due to their different crack propagation mechanisms.