镍基合金耐氟盐腐蚀防护涂层的性能研究

Properties of Protective Coating on Nickel Alloy Substrate against Corrosion Attack in Fluoride Salt

作为第四代反应堆堆型之一的钍基熔盐堆(TMSR,thorium molten salt reactor)具有固有安全性和防止核扩散等特点,由于使用熔盐做冷却剂和慢化剂,熔盐堆结构材料要具备高温下与氟盐良好的相容性,因此对材料性能也有更加苛刻的要求。目前作为TMSR结构材料的镍基合金对抗氟盐腐蚀的效果不明显,因此本研究采用了表面涂层技术在镍基合金表面获得一层防护层,以提高材料的耐氟盐腐蚀能力。通过电化学方法在镍基合金基体上沉积得到一层纯镍防护层,采用扫描电子显微镜(SEM)和背散射电子衍射(EBSD)等分析测试手段,研究了镀液体系、电沉积时间等对涂层性能的影响。研究发现,在氨基磺酸镍镀液体系中得到的涂层性能优于瓦特液体系,涂层厚度随沉积时间延长不断增大。同时对涂层的耐腐蚀性能进行了研究,研究结果表明涂层在700℃氟盐中400 h后未发生明显的腐蚀,因此利用表面涂层技术能够提高TMSR结构材料的耐氟盐腐蚀性能。

Thorium molten salt reactor（ TMSR） is one of the Generation 1V reactors. It has good non-proliferation and inherent safety. Therefore, the requirements of structure materials are more rigorous for TMSR, as the coolant and the moderator are fluoride salt, the structure materials should have good compatibility with fluoride salt at high temperature. As the compatibility between nickel alloy and fluoride was unsatisfactory, a protective coating was obtained on nickel alloy substrate to enhance the anti-con＇osion ability. The electro- chemistry method was applied to obtain pure nickel layer on nickel alloy substrate in this research, and the influence of electrolyte and duration on performance of coating was analyzed by scanning electronic microscopy （SEM） and electron backscatter diffraction （EBSD）. Coating obtained from Ni sulfamate baths was better than that from Watts Ni baths. The thickness of coating increased with the duration of plating. The corrosion resistance of coating was analyzed, the nickel coating was not significantly corroded in fluoride salt at 700 ℃ for 400 h, and therefore the compatibility of TMSR structure materials with fluoride salt could be enhanced using coating technique.