核电汽轮机转子堆焊焊接接头的电偶腐蚀行为及有限元仿真

Galvanic corrosion behavior and finite element simulation of overlaying welded nuclear steam turbine rotor

采用宏观电化学试验和浸泡试验研究25Cr2Ni2MoV汽轮机转子堆焊焊接接头在80℃,3.5%Cl−环境下的电偶腐蚀行为.电化学试验结果表明,焊缝为腐蚀薄弱区,腐蚀电位从高到低依次为热影响区、母材、焊缝.浸泡试验结果表明,随着母材面积的增大,焊缝平均腐蚀厚度逐渐加深.进一步利用宏观电化学测试所获的电化学参量建立焊接接头电偶腐蚀有限元模型对比浸泡试验结果.结果表明,有限元仿真结果能有效模拟堆焊焊接接头的电偶腐蚀行为,为实际生产提供电偶腐蚀速率预测.创新点:(1)堆焊焊接接头的化学成分及微观结构差异导致了材料的电化学性能差异.(2)随着阴阳面积比的增大,阴极和阳极的腐蚀深度均加深,但阳极的增大程度远大于阴极.(3)利用宏观电化学测试所获的电化学参量建立焊接接头电偶腐蚀有限元模型,能有效预测堆焊焊接接头的电偶腐蚀行为.

The galvanic corrosion behavior of 25Cr2Ni2MoV overlaying welded nuclear steam turbine rotor was investigated by macro-electrochemical tests and immersion tests in chloride solution at 80℃.The results of electrochemical experiments show that the weld metal is the weak corrosion zone,and the corrosion potential from low to high is the heat-affected zone,the base metal,and the weld metal.The results of the immersion tests show that as the area of the BM increases,the average corrosion thickness of the WM gradually increases Furthermore,the galvanic corrosion finite element model of welded joint was established by using the electrochemical parameters obtained from macro electrochemical test.The results show that the finite element simulation results can effectively simulate the galvanic corrosion behavior of overlaying welding joint and provide galvanic corrosion rate prediction for actual production.Highlights:(1)The difference of chemical composition and microstructure of overlaying welded joint leads to the difference of electrochemical performance of materials.(2)With the increasing of the area ratio of cathode to anode,the corrosion depth of both cathode and anode are increased,but the increasing of anode is more deeper than that of cathode.(3)The galvanic corrosion finite element model based on the electrochemical parameters which obtain from macro electrochemical tests can effectively predict the galvanic corrosion behavior of overlaying welded joint.