压水堆一回路冷却剂中加锌对不锈钢焊接接头腐蚀行为的影响

Influence of Zinc Injection in Primary Coolant of Pressurized Water Reactor Power Plant on Corrosion Behavior of Stainless Steel Welding Joint

为研究AP1000一回路冷却剂中加锌对安全端同材焊接区域的影响,采用金相显微镜、扫描电镜(SEM)、能谱仪以及X射线光电子能谱仪(XPS)等测试方法,分析了316LN/316L不锈钢焊接接头在模拟压水堆一回路冷却剂加锌环境下的氧化特性。结果表明:焊接接头母材区、热影响区和焊缝区的金相组织之间存在明显的熔合线,母材区与热影响区均为奥氏体,且热影响区晶粒稍显粗大,焊缝区则有少量铁素体析出;未加锌环境中母材区氧化膜呈黑色,焊缝区氧化膜呈暗红色,氧化膜表面与焊缝区无明显差异;加锌10μg/L母材区与焊缝区氧化膜均呈现黑色,比未加锌时焊接接头氧化物的颗粒更小,未加锌焊缝区的氧化膜比母材区更薄;加锌溶液中各区域氧化膜厚度趋于一致,比未加锌的减小近45%。

The oxidation behavior and corrosion behavior of the welding joint of 316LN/316 L stainless steel in simulated pressurized water reactor(PWR) primary coolant with Zn injection were investigated by metallographic microscopy,scanning electron microscopy,energy dispersive spectrometry and X-ray photoelectron spectroscopy.It was found that there was a fusion line between the microstructures of the base metal,heat affected zone and welded zone of the welding joint.The base metal and heat affected zone consisted of austenite.The grains of the heat affected zone were bigger than those in the base metal,and a small amount of ferrite precipitated in the welded zone.In the absence of Zn injection in the primary coolant,black oxide film was formed in the base metal and red oxide film was formed in the welded zone,while there were few differences in the surface morphology of the oxide film and welded zone.When 10 μg/L Zn was added in the primary coolant,black oxide films were formed in the base metal and welded zone as well,and the size of the gains of the oxides at welding joint was smaller than that in the absence of Zn injection.In the meantime,the oxide films obtained in the presence of Zn injection at different zones exhibited similar thickness,and the thickness of the oxide films was reduced by about 45%as compared with that of the same films obtained in the absence of Zn injection.