目的 针对核电站乏燃料水池304L不锈钢覆板L型拐角位置损伤的在线修复需求,在模拟水下高压环境（20 m深,0.2 MPa）下,采用局部干法水下激光多层多道的填丝熔覆技术进行角焊修复试验研究。方法 通过金相分析、X射线衍射、能谱分析、显微硬度测试和电化学腐蚀测试等手段,系统研究了高压环境下激光填丝修复L型角焊缝的微观组织与耐腐蚀性能。结果 焊缝表面呈均匀鱼鳞状,无裂纹气孔等宏观缺陷,但水下高压环境使气体分子的运动变得更加剧烈,热输入损失加剧了熔池冷却,降低了熔池的流动性,导致表面平整度变差。L型角焊缝微观组织主要由奥氏体与残留铁素体组成。相较于母材,焊缝区域Cr、Ni元素含量升高,极化曲线与Nyquist图谱证实焊缝区耐腐蚀性优于母材。此外,焊缝平均硬度高于母材硬度,这归因于快速冷却的晶粒细化与Mo、Cr元素的强化作用。结论 该工艺能够有效保证304L不锈钢在高压水下环境的修复质量,且具有优异的耐腐蚀性与力学性能,为核电站水池拐角位置的水下原位修复提供了可靠的技术方案。
Abstract
To address the need for online repair of damages at the L-shaped corner of 304L stainless steel cladding in spent fuel pools of nuclear power plants, the work aims to investigate the repair of corner joints with local dry underwater laser wire filling multi-layer multi-pass cladding technology under simulated high-pressure underwater conditions (20 m depth, 0.2 MPa). The microstructure and corrosion resistance of the laser wire repaired L-shaped corner joints in a high-pressure environment were systematically examined through metallographic analysis, X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), microhardness testing, and electrochemical corrosion measurements. The weld surface exhibited a uniform fish-scale pattern without macroscopic defects such as cracks or pores. However, the intensified activity of gas molecules under high-pressure conditions accelerated heat loss and increased the cooling rate of the molten pool, reducing its fluidity and resulting in diminished surface flatness. The microstructure of the L-shaped corner joint consisted primarily of austenite and residual ferrite. Compared to the base metal, the weld zone showed increased Cr and Ni contents. Polarization curves and Nyquist plots confirmed that the corrosion resistance of the weld zone was superior to that of the base metal. Additionally, the average hardness of the weld was higher than that of the base metal, attributable to grain refinement from rapid cooling and the strengthening effect of Mo, Cr element. The findings demonstrate that this process effectively ensures the repair quality of 304L stainless steel in high-pressure underwater environments, offering excellent corrosion resistance and mechanical properties and providing a viable technical solution for in-situ underwater repair of corner areas in nuclear power plant pools.
关键词
乏燃料水池 /
激光焊接 /
拐角修复 /
局部干法 /
微观组织
Key words
spent fuel pool /
laser welding /
corner repair /
local dry method /
microstructure
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基金
北京市科技计划重点项目（3262002）; 国家自然科学基金联合基金重点支持项目（U22B20127）; 北京市属高校分类发展项目（11000023T000002199202）
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