热影响区对316NG奥氏体不锈钢腐蚀疲劳裂纹扩展行为的影响研究

Primary pipe of pressurized water reactor is one of the key safe bounds, which is made of austenitic stainless steels. In pressurized water reactor, corrosion fatigue cracking of primary pipe can occur and the regular operation is threatened. 316NG austenitic stainless steel is the key material of primary pipe in the third generation nuclear power system in China. Primary pipe is connected by welding and hot-affected zone exists near the welding line in welded 316NG austenitic stainless steel pipe, which is caused by the hot of welding. The hot-affected zone is characterized as carbides and residue strain. In this program, corrosion fatigue cracking tests of hot-affected zone of 316NG austenitic stainless steel (made in China) will be conducted in simulated pressurized water reactor environments and the influence of hot-affected zone on corrosion fatigue cracking will be investigated. In addition, the effect of carbides and residue strain in hot-affected zone on corrosion fatigue cracking will also be comprehensively analyzed. The result of this study will be good for further understanding corrosion fatigue cracking process and related mechanism, and it can also afford some scientific proof for evaluating the corrosion fatigue cracking performance of 316NG austenitic stainless steel (made in China).

压水反应堆主管道通常由奥氏体不锈钢制造，是重要的安全边界之一。在压水堆反应堆环境下，主管道可能产生腐蚀疲劳开裂，影响反应堆的安全运行。316NG奥氏体不锈钢是我国第三代核电主管道的关键材料。316NG奥氏体不锈钢主管道采用焊接的方式相互连接，在焊接融合线附近形成热影响区。碳化物析出及残余应变是热影响区的主要特征。本项目将以国产316NG奥氏体不锈钢为研究对象，在模拟压水堆环境下开展腐蚀疲劳裂纹扩展试验，研究热影响区对国产316NG奥氏体不锈钢腐蚀疲劳裂纹扩展行为的影响；深入分析碳化物及残余应变在腐蚀疲劳裂纹扩展过程中的作用。本研究成果有助于深入认识腐蚀疲劳裂纹扩展过程及相关机理，为国产316NG奥氏体不锈钢腐蚀疲劳裂纹扩展性能评价提供科学依据。

压水反应堆主管道通常由奥氏体不锈钢制造，是重要的安全边界之一。在压水堆反应堆环境下，主管道可能产生腐蚀疲劳开裂，影响反应堆的安全运行。316NG奥氏体不锈钢是我国第三代核电主管道的关键材料。316NG奥氏体不锈钢主管道采用焊接的方式相互连接，在焊接融合线附近形成热影响区。碳（氮）化物析出及残余应变是热影响区的主要特征。本课题以国产316NG奥氏体不锈钢为研究对象，对热影响区的微观组织及残余应变进行了表征；并在模拟压水堆环境下开展腐蚀疲劳裂纹扩展试验，研究热影响区对国产316NG奥氏体不锈钢腐蚀疲劳裂纹扩展行为的影响，深入分析碳（氮）化物及残余应变在腐蚀疲劳裂纹扩展过程中的作用。研究发现，在主管道焊件根部存在较大的残余应变，显著加速腐蚀疲劳裂纹扩展速率；热影响区奥氏体晶粒内的碳（氮）化物同样有助于腐蚀疲劳裂纹扩展。本研究成果有助于深入认识腐蚀疲劳裂纹扩展过程及相关机理，为国产316NG奥氏体不锈钢腐蚀疲劳裂纹扩展性能评价提供科学依据。