Microstructural evolution and its influence on thermal insulation performance and oxidation behavior of multiscale-reinforced YSZ thermal barrier coatings

Multiscale silicon carbide (SiC) reinforcement is expected to enhance the mechanical properties of thermal barrier coatings (TBCs), while maintaining excellent thermal insulation and oxidation resistance. In this study, yttria partially stabilized zirconia (YSZ) coatings reinforced with different ratios of silicon carbide nanowires (SiC_nw) and particles were fabricated, and their thermal insulation performance and oxidation behavior when serving as an intermediate layer (TC1) were systematically investigated. Results show that as the SiC_nw content increases, the porosity increases, accompanied by a transition in pore structure from regular spherical features to more irregular and interconnected morphologies, while the fracture toughness shows a continuous increase. In addition, partial oxidation of multiscale SiC during spraying leads to the formation of a small amount of SiO₂. For multilayer TBCs containing the TC1 layer, thermal insulation performance improves with increasing SiC_nw content, whereas the TGO thickness varies non-monotonically with SiC_nw content, with oxidation resistance reaching an optimum at 1.0 wt% SiC_nw. The enhancement in thermal insulation performance is associated with the interfacial thermal resistance of the multilayer architecture, the formation of low thermal conductivity SiO₂, and increased porosity. The improved oxidation resistance is related to the higher fracture toughness of the TC1 coating, as well as the reduced oxygen transport due to SiO₂ formed during high-temperature oxidation of SiC. However, with continued oxidation, the gradual consumption of SiC may reduce crack resistance, and its long-term stability needs to be further evaluated.