Mechanical and chemical indicators for SCC in Alloy 800 steam generator tubing

600合金蒸汽发生器（SG）管材的应力腐蚀开裂（SCC）是CANDU和PWR核反应堆的主要问题。替代合金800（A800）管材也不能免于SCC;最近在欧洲报告了开裂。为了提高对800合金在使用条件下裂纹发生的预测，必须彻底了解这种材料的机械和化学行为的相互作用。化学环境的影响是众所周知的;在微观尺度上对机械应力的影响还不太清楚，因此它们的组合效应还没有得到很好的表征。目前一个由行业赞助的研究项目已将重点放在600 SG合金管材应力腐蚀开裂方面，项目团队已开发出用于确定表现出晶间开裂的样品的微应变、晶界沉淀和微观结构的方法。更重要的是，在理解这些参数如何促进裂纹扩展过程方面也取得了一些进展。因此，下一步是应用这些方法中的一些来研究合金800 SG管材的SCC行为，CANDU反应堆的当前材料选择和先进CANDU反应堆（ACR）的指定材料。

Stress corrosion cracking (SCC) of Alloy 600 steam generator (SG) tubing is a major issue both CANDU and PWR nuclear reactors. Replacement Alloy 800 (A800) tubing is also not immune to SCC; cracking has recently been reported in Europe. To improve the prediction of the onset of cracking in Alloy 800 under service conditions, the interplay of mechanical and chemical behaviour of this material be thoroughly understood. The effects of chemical environments are well known; the effects on mechanical stress on a microscopic scale are less well understood and their combined effects therefore have not been well characterized. A current industry-sponsored research project has focused on this aspect for the stress corrosion cracking of Alloy 600 SG tubing materials and the project team has developed methodologies for determining the microstrain, grain boundary precipitation and microstructure of the samples exhibiting intergranular cracking. More importantly, some progress has also been made in understanding how these parameters contribute to the crack growth process. Thus, the next step is apply some of these methodologies to study the SCC behaviour of Alloy 800 SG tubing material, the current material choice for CANDU reactors and the specified material for Advanced CANDU reactors (ACRs).