To promote the spent fuel recycling, mitigate its hazards, MoSi2/Y2O3 composite coating was fabricated on pure Ta surface by slurry sintering in this study, MoSi2-Ta coating as the interlayer and Y2O3 as the top layer. The microstructural evolution of the coatings before and after thermal shock testing was characterized using techniques such as X-ray diffractometer, scanning electron microscope, and energy spectrometer, and the thermal shock resistance was investigated in combination with finite element simulations. The results demonstrate that the MoSi2/Y2O3 coating consists of irregular, incompletely melted particles stacked together; new phases including Mo5Si3, MoO3, SiO2, TaSi2, and Y2SiO5 are generated during sintering and thermal shock processes. Significant diffusion characteristics of Si element are observed in the coating system, accompanied by oxygen content increase during thermal shock. After thermal shock, interfacial delamination failure occurres at the substrate-coating interface, with spalling of MoSi2/Y2O3 bilayer coating that serve as crack initiation sources for longitudinal propagation cracks. The formation mechanisms of defects such as delamination and spalling in the coating system including thermal stress accumulation induced by thermal expansion coefficient mismatch; growth stress accumulation caused by new phase formation; strength reduction due to oxide film rupture from volatile phase evaporation.
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