A comparison between novel Gd_(2)Zr_(2)O_(7)and Gd_(2)Zr_(2)O_(7)/YSZ thermal barrier coatings fabricated by plasma spray-physical vapor deposition

摘要

Spherical Gd_(2)Zr_(2)O_(7)hollow powders with a mean size of 8.8μm were fabricated as feedstock for thermal barrier coatings(TBCs)by spray-drying.The single-ceramic-layer(SCL)Gd_(2)Zr_(2)O_(7)TBCs and double-ceramic-layer(DCL)Gd_(2)Zr_(2)O_(7)/YSZ TBCs with quasicolumnar 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 Gd_(2)Zr_(2)O_(7)TBCs and DCL Gd_(2)Zr_(2)O_(7)/YSZ TBCs is36.5 MPa and 15.4 MPa,respectively.The delamination of SCL Gd_(2)Zr_(2)O_(7)TBCs and DCL Gd_(2)Zr_(2)O_(7)/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 Gd_(2)Zr_(2)O_(7)/YSZ TBC surface keeps relatively intact,while SCL Gd_(2)Zr_(2)O_(7)TBC surface shows 20%visible destroyed regions,which demonstrates that DCL Gd_(2)Zr_(2)O_(7)/YSZ TBCs have a better thermal shock resistance than SCL Gd_(2)Zr_(2)O_(7)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 Gd_(2)Zr_(2)O_(7)layer due to its relatively lower fracture toughness.