Finite element modelling of the corrosion of stainless steels/CuCrZr for STEP

STEP计划的路线图非常紧凑，如果该计划要在2040年交付，那么在2032年开始建造之前，需要在未来几年内减少材料的选择。有必要选择携带冷却剂的材料来去除反应堆的热量，可能是不锈钢，就像在许多裂变工厂中使用的那样，也被提议用于ITER，使用含硼的冷却剂水。为了实现聚变的宏伟目标，需要最先进的腐蚀建模能力来支持实验。该项目将使用嵌入有限元模型的相场方法，由帝国理工学院的Martinez-Paneda和Wenman团队联合开发，以模拟腐蚀发展（包括微观结构，电解质离子浓度，坑形核和生长以及向应力腐蚀裂纹的转变）。该工作将使用COMSOL和ABAQUS有限元代码中的一种或两种。目前的模型建立在特恩布尔等人（2008）的工作基础上。这表明，不锈钢的凹坑生长可以用凹坑边塑性应变的发展来解释，塑性应变导致氧化物断裂，增加了下伏金属的腐蚀速度。这些模型最近通过添加电解质离子浓度得到了进一步的增强，因此可以用于模拟一系列冷却剂的化学性质，然后可以通过晶体塑性方法添加微观结构进一步推进，允许在腐蚀过程中考虑由于晶体取向引起的局部应力/应变的影响。虽然这些模型最初在不锈钢上进行了测试，但可以进一步开发/适应其他冷却剂/材料组合，如CuCrZr或马氏体/铁素体钢。

The STEP programme roadmap is very tight, with a need to down select materials in the next few years, before build can begin in 2032, if the programme is to deliver by 2040. There is a need to select the materials that will carry coolant to remove reactor heat, which might be stainless steels, as used in many fission plants, and also proposed for ITER, using boronated coolant water.To achieve the ambitious goals for fusion state-of-the art corrosion modelling capabilities will be needed to support experiments. This project will use phase field approaches embedded in finite element models, being developed at Imperial College, jointly by the Martinez-Paneda and Wenman groups to model corrosion development (including microstructure, electrolyte ion concentrations, pit nucleation and growth and transition to stress corrosion cracks). The work will use either or both the COMSOL and ABAQUS finite element codes. The current models build on the work of Turnbull et al. (2008). that showed that pit growth in stainless steels can be explained by the development of plastic strains at the pit sides that lead to oxide fracture and increase the corrosion rate of the underlying metal. These models have very recently been enhanced further to by addition of electrolyte ion concentrations and thus can be used to model a range of coolant chemistries and then can be further advanced by addition of microstructure via crystal plasticity approaches allowing the effects of localised stress/strains, due to crystal orientation, to be considered in the corrosion process. The models, whilst initially tested on stainless steels can be developed further/adapted to other coolant/materials combinations such as CuCrZr or martensitic/ferritic steels as proposed for STEP.