亚共析铀铌合金激光焊接微观结构及电化学行为

Microstructure and Corrosion Behavior of the Laser

摘要:

采用光学显微镜、扫描电镜、X射线衍射仪和电化学综合测试仪对亚共析珠光体铀铌合金激光焊接接头的微观结构和电化学行为开展了研究，结果显示：亚共析珠光体铀铌合金焊缝晶粒尺寸约50 μm，焊缝相结构为单相正交结构α`马氏体；在50 μg/g Cl-的NaCl 溶液中，焊缝金属腐蚀电位比基材低约400 mV，构成了电偶腐蚀对，在电偶腐蚀和自腐蚀共同作用下，焊接接头的腐蚀电流比焊缝金属和基材分别高约3至10倍，接头整体抗腐蚀性能低于基材，腐蚀形式表现为均匀腐蚀

Abstract:

The microstructures and corrosion behavior of the hypoeutectoid U-Nb alloy laser welded joint were investigated by OM, SEM, XRD and electrochemical analysis. The results indicate that the grain size of the weld zone of the hypoeutectoid pearlite U-Nb alloy is about 50 μm and the weld zone is only composed of α′ martensite with orthogonal crystal structure. After immersion in 3.5%NaCl solution, the corrosion potential of weld metal is ~400 mV lower than the substrate’s, and the corrosion couple forms between weld metal and the rest of the welded. The results of surface morphology and linear polarization show that the corrosion process of the welded joint includes galvanic corrosion and self-corrosion while galvanic corrosion behavior is the dominated. The corrosion current of welded joint is about 3 times higher than that of the substrate and 10 times higher than that of the weld metal. The overall anti-corrosion property of welded joint is depressed. The corrosion is uniform