Hot corrosion and thermal shock resistance of Dense-CYSZ/YSZ bilayer thermal barrier coatings systems applied onto Ni-base superalloy

Bilayer thermal barriers coatings of Dense Ceria-Yttria-Stabilized Zirconia (D-CYSZ)/Yttria-Stabilized Zirconia (YSZ) were deposited onto Inconel 625 using atmospheric plasma spray (APS). The thickness of the D-CYSZ layer varied (0, 50, 100, and 150 mu m), but the total thickness of the system was kept at 300 mu m. The thermo-me- chanical resistance of the multilayer system was evaluated through thermal shock tests, in which the bilayer systems evaluated exceeded 500 cycles with percentages of delamination of the coating below 20 % of the exposed area and showed higher thermomechanical resistance than a conventional YSZ system. Hot corrosion (HC) resistance of the bilayer system was evaluated using a salt mixture of 32 wt.% Na2SO4 and 68 wt.% V2O5 at 900 degrees C. The systems with a D-CYSZ layer showed higher resistance to HC, exhibiting fewer changes into the microstructure and presence of the monoclinic phase despite the presence of vertical cracks in the microstructure.