Toughness and Thermal Shock of SiC Fiber and Yttria-stabilized-zirconia Composite Thick Thermal Barrier Coatings

Using ZrO2-8wt%Y2O3 (8YSZ) and agglomerated P7216 (8YSZ and Perlite powder ) powders as raw materials, SiC fiber/YSZ (SFY) composite thick thermal barrier coatings (TBCs, >4 mm in thick) were prepared by Atmospheric Plasma Spray (APS) on substrate. The microstructures of columnar coating were analyzed by scanning electron microscope (SEM). It showed that SFY coatings had a reinforced concrete frame structure, which protected the coatings from failure caused by thickened coatings. Based on the technique of computed tomography, the porosity of TBCs were investigated. And the thermal shock, fracture toughness and thermal conductivity (TC) of both SFY and YSZ coatings were examined and discussed for the SiC fiber toughening mechanism. Test results showed that the SFY coatings had higher fracture toughness and better thermal shock resistance than the YSZ TBCs. At 25°C, the TC of SFY coatings was 0.632 W/(m·K), about 50% reduction of typical APS YSZ TBCs. Data from this study showed that the SiC fiber effectively hindered crack growth and diffusion by crack deflection and crack termination of SFY coating, which was beneficial for growing of the reticular microcrack and improving thermal shock resistance and fracture toughness.