核电装备焊接接头的应力腐蚀开裂与电偶腐蚀的耦合效应与机理研究

Focus on the reliable requirements of nuclear power welding component, the coupling behavior and mechanism between stress corrosion cracking and galvanic corrosion in weld joint of nuclear power equipment will be studied. The main contents include: 1) Based on immersion and localized electrochemical tests of weld joint, a time dependent galvanic corrosion model will be built according to electrochemical-mass transport of Nernst-Planck equation and electroneutral Laplace equation. 2) Based on constant loading interrupt tests, the mechanical property difference in different part of weld joint will be studied, furthermore, a time dependent galvanic corrosion model which couples the equivalent plastic train distribution within the pits near fusion line will be built to investigate the role of applied loading on the galvanic corrosion of weld joint. 3) The effect of loading mode on stress corrosion cracking position of weld joint will be studied, the contribution of the galvanic corrosion and key mechanical parameters to fracture position will be clarified, finally clarify the galvanic corrosion assisted stress corrosion cracking mechanism of weld components. The purpose of present study is to establish a reasonable method for stress corrosion cracking sensitivity assessment of weld joint of nuclear power equipment, finally enhance the reliability of key components of nuclear power plant and the core competitive power of major equipment manufacture.

面向核电装备焊接构件的可靠性需求，针对核电装备焊接接头的应力腐蚀开裂与电偶腐蚀的耦合效应与机理展开研究。主要内容包括：1）基于焊接接头浸泡实验和微区电化学实验，以溶液中离子传质过程的Nernst-Planck方程和溶液电中性的Laplace方程为基础建立描述时间相关的电偶腐蚀界面效应理论模型。2）基于恒载荷应力腐蚀中断实验，考虑焊接接头不同区域的力学性能差异，建立纳入熔合线附近点蚀坑处等效塑性应变分布规律的电偶腐蚀界面模型，合理描述外载作用下焊接接头的电偶腐蚀效应。3）研究不同加载模式对焊接接头应力腐蚀断裂位置的影响，阐明关键力学参量与电偶腐蚀效应的作用对断裂位置的贡献程度,从焊接接头的电偶腐蚀效应出发探明长寿命焊接构件的应力腐蚀开裂机理。本研究旨在建立适用于评定焊接构件应力腐蚀敏感性的合理方法，为提升我国核电关键部件的可靠性、增强我国重大装备制造业的核心竞争力提供科学支持。

本项目面向核电装备焊接构件的可靠性需求，针对核电装备焊接接头的应力腐蚀开裂与电偶腐蚀的耦合效应与机理展开研究。首先，基于焊接接头浸泡实验和电化学实验，研究了氯离子浓度、温度、溶解氧和PH值等环境因素，面积比对电偶腐蚀效应的影响规律及作用机理。以溶液中离子传质过程的Nernst-Planck方程和溶液电中性的Laplace方程为基础建立描述时间相关的电偶腐蚀界面效应理论模型，所建的模型与实验结果获得了较好的一致。其次，进行基于恒载荷应力腐蚀中断实验，分析核电汽轮机焊接接头不同区域的点蚀形成及扩展机理。考虑焊接接头不同区域的力学性能差异，研究电偶腐蚀效应对裂纹萌生位置及扩展的作用机制，合理描述外载作用下焊接接头的电偶腐蚀效应。最后，研究不同加载模式对焊接接头应力腐蚀断裂位置的影响，阐明关键力学参量与电偶腐蚀效应的作用对断裂位置的贡献程度,从焊接接头的电偶腐蚀效应出发探明长寿命焊接构件的应力腐蚀开裂机理。针对不同加载模式所获的应力腐蚀敏感部位不一致的问题，进一步建立了焊接接头应力腐蚀敏感性评定方法。本项目的实施为提升我国核电关键部件的可靠性、增强我国重大装备制造业的核心竞争力提供一定的科学支持。