904L超级奥氏体不锈钢在模拟核电一回路环境中的腐蚀行为研究

Corrosion Behavior of 904L Super-austenitic Stainless Steel in Simulated Primary Water in Nuclear Power Plants

采用动电位极化曲线、电化学阻抗谱(EIS)以及U形弯浸泡实验,研究了原始、敏化和固溶等3种微观组织状态下904L超级奥氏体不锈钢在模拟核电一回路环境中的电化学和应力腐蚀开裂(SCC)行为及机理。结果表明:904L不锈钢在模拟核电一回路中的腐蚀过程基本由电化学活化控制。温度对原始、敏化和固溶等组织状态下的904L不锈钢的耐腐蚀性能有很大影响,随温度升高,电化学反应极化电阻降低,钝化区变窄,腐蚀电位下降,3种组织状态的904L不锈钢耐蚀性均急剧降低。3种组织状态的904L不锈钢在模拟核电一回路环境中均存在一定SCC敏感性。表面腐蚀产物膜内层为均匀较薄的黑色腐蚀产物,外层为尺寸较大的颗粒状白色腐蚀产物。敏化组织的904L不锈钢SCC敏感性最高,固溶处理能降低其SCC敏感性。

In this work,the electrochemical properties and stress corrosion cracking(SCC)behavior of 904L super-austenitic stainless steel with various kinds of microstructure in simulated primary water were studied through potentiodynamic polarization curve measurement,electrochemical impedance spectroscopy(EIS)and U-bend immersion tests.The results show that the corrosion process of 904L stainless steel in simulated primary water is completely controlled by electrochemical reaction.Temperature has a strong influence on the corrosion resistance of 904L stainless steel.With the increase of temperature,the polarization resistance decreases;the passive range narrows down;corrosion potential shiftsnegatively,and corrosion resistance declines sharply.U-bend immersion test results prove that 904Lstainless steel with the three kinds of microstructure has certain SCC susceptibility in simulated primarywater.The corrosion products exert a two-layered structure,where the inner layer is uniform and thinblack corrosion product,and the outer layer is granular and coarse white corrosion products.Among thethree kinds of microstructure,the sensitized 904L stainless steel presents the highest SCC susceptibility,while solid solution treatment can decrease SCC susceptibility.