Understanding the materials performance of additive manufactured stainless steel components in high temperature water

奥氏体不锈钢和镍基合金因其良好的耐腐蚀性而被广泛应用于压水堆一次回路内件。然而，众所周知，当材料暴露在高温水环境中的水冷却剂中时，材料的加工工艺对这些材料的应力腐蚀开裂(SCC)敏感性有很大影响。过去，零件是通过锻造和焊接等传统制造方法制造的；然而，由于加工成本降低、制造更灵活、交货期更短，人们希望通过添加制造来生产接近净形状的零件。然而，目前对这种工艺生产的材料的冶金质量对材料性能的影响了解不足。因此，至关重要的是，必须从根本上了解通过激光粉床熔化等现代近净形状制造技术进行制造和制造之间的关系，以便能够判断改变当前制造做法所造成的潜在退化。这反过来需要以科学为基础了解影响/控制环境退化的各种潜在机制及其与最终影响的联系。应力腐蚀是材料降解最隐蔽的形式之一，其在制成品中的引发行为是主要的技术挑战。虽然不锈钢和镍基合金在轻水反应堆环境中的应力腐蚀开裂性能已经得到了广泛的研究，但使用近净成形技术生产的组件的应力腐蚀开裂数据还不可用。

Austenitic stainless steels and Ni base alloys are extensively used in the primary circuit internals of pressurized water reactors (PWR) due to their high corrosion resistance properties. However, it is also well known that materials processing can have a strong impact on the susceptibility to stress corrosion cracking (SCC) of these materials when exposed in high temperature aqueous environment water coolant under active loading. Historically, components have been manufactured via conventional manufacturing routes, such as forging and welding; however, there is the desire to produce near net shape components via additive manufacturing thanks to the reduce machining costs, more agile manufacturing, and shorter lead times. However, there is currently insufficient knowledge on the impact of the metallurgical quality of the material produced by such processes on the materials performance. It is critical, therefore, to have a fundamental understanding of the relationship between manufacturing via modern near-to-net-shape manufacturing technologies, such as laser powder bed fusion, so that potential degradation caused by changes to current manufacturing practices can be judged. This, in turn, requires a scientifically-based understanding of the various underlying mechanisms influencing/controlling the environmental degradation and their linking to the end effects.SCC is one of the most insidious forms of materials degradation and its initiation behaviour in as manufactured components are major technical challenges. Although the SCC performance of stainless steels, Ni-base alloys in light water reactors environments has been studied extensively, the SCC data are not available for components produced using near-net-shape technologies.