Abstract：For the reuse of crucibles used to smelt nuclear metals and the recovery of spent fuel, a series of double-layer gradient composite Yttria-coatings were prepared on the surface of Niobium 521 alloy by slurry sintering process. Trace amounts of Si and Mo were added as reinforcing agents in the coating, the surface of the coating was pure Y2O3. With the help of finite element simulation, X-ray diffractometer, scanning electron microscopy, energy spectrometer and other means, the microstructure and thermal shock resistance of the coating were studied. The results show that the Nb/Y2O3 coating has a typical layered structure, which is composed of irregular powder particles stacked on top of each other, and the matrix area, diffusion area, transition layer and Y2O3 layer have distinct structures. The finite element simulation calculation and experimental results both prove that the double-layer gradient coating can change the stress distribution and effectively reduce the stress generated inside the material during thermal shock. Among them, the maximum principal stress of the 70%Y2O3+22% Nb+6%Si+2%Mo (7022) coating is 163.2 MPa, which decreases by 47.93% compared to the single-layer Y2O3 coating (313.4 MPa). After 60 thermal cycles, the microstructure of the 7022-Y2O3 coating is dense without obvious defects, and the morphology is the least damaged.
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2023, Vol. 28 
