摘要
To improve the service reliability of components used during spent nuclear fuel electrorefining, La 2 Zr 2 O 7 (LZO) protective coatings were prepared on SS 316L by atmospheric plasma spraying (APS) followed by vacuum annealing. The effects of annealing temperature and holding time on the phase structure, apparent porosity, and surface wettability of the LZO coatings were systematically investigated. The optimized coating was then exposed to KCl-LiCl molten salt at 600 °C for up to 640 h to evaluate its corrosion behavior and degradation mechanism. Annealing at 1200 °C for 2 h reduced apparent porosity from 18.96% to 8.21% and suppressed spreading of the salt-containing test solution. Within the initial 80 h, the as-sprayed and annealed coatings gained 1.3 and 0.6 mg·cm -2 , respectively, with apparent mass-change rates of 0.015 and 0.0075 mg·cm -2 ·h -1 . Both coatings shifted from mass gain to mass loss during 80-160 h, and the apparent mass-change rate of LZO-C640 reached -0.0525 mg·cm -2 ·h -1 . During 160-320 h, the apparent rates became positive as connected defects enabled deeper salt penetration and local interaction with the NiCrAlY bond coating. Preferential degradation of Al- and Cr-rich regions exposed and redistributed Ni-bearing material. NiO and NiCr 2 O 4 were subsequently detected at 320 h as secondary products. LaOCl was also detected at 320 h, whereas LiAlO 2 appeared after extended exposure. Throughout the final stage of 320-640 h, LZO-C640 maintained a low positive rate of 0.0075 mg·cm -2 ·h -1 . In contrast, the cumulative mass-change of H/LZO-C640 increased from -0.6 to -0.3 mg·cm -2 as its apparent rate approached zero. After 640 h, the annealed coating retained its overall skeleton, whereas the as-sprayed coating underwent top-layer disintegration. These results indicate that vacuum annealing did not completely prevent degradation, but limited molten-salt ingress and improved the long-term corrosion resistance of LZO coating.
危险品化学品经营许可证（带存储）