Microstructural optimization of Gd2O3-Yb2O3-Y2O3 co-stabilized ZrO2/YSZ coatings with enhanced thermal shock resistance

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Double-ceramic-layer (DCL) thermal barrier coatings composed of Gd2O3-Yb2O3-Y2O3 co-stabilized ZrO2 (GYYZO) top layer and yttria-stabilized zirconia (YSZ) bottom layer were fabricated using atmospheric plasma spraying (APS) technology. In this study, both experimental and numerical approaches were employed to evaluate the effects of porosity and thickness ratios on the thermal shock resistance of GYYZO/YSZ DCL thermal barrier coatings. Experimental results reveal that an increase in porosity leads to a reduction in deposition efficiency and bonding strength of thermal barrier coatings, but an improvement on their thermal insulation performance. Owing to the lower thermal conductivity and superior high-temperature stability of GYYZO, the thermal shock life initially prolongs with the thickness of GYYZO top layer increasing. Despite this, its relatively lower thermal expansion coefficient and fracture toughness render the coating more susceptible to delamination under extreme thermal shock conditions. Numerical simulations further indicated that elevated axial and shear stresses at the interface edge promote spallation of the coating. Therefore, the optimal performance was achieved with a coating featuring a porosity of 10–20% and a GYYZO/YSZ thickness ratio of 5:5, which provides the best compromise between thermal insulation and mechanical integrity.