Interdisciplinary study on degradation of material strength due to high-temperature hydrogen for safety of advanced high-temperature hydrogen technologies

了解和控制氢对材料的影响是实现碳中和和可持续未来的必要步骤。结构材料如铁基和镍基合金将在氢气的产生、储存、运输和最终使用中发挥核心作用。这些材料在室温下的氢致降解（氢脆）对能源基础设施的可靠性构成了严重威胁，已经得到了广泛的研究。由此得出的理解是，室温脆性是由氢增强的局部塑性或氢诱导的脱粘驱动的。另一方面，人们对氢在高温下如何影响结构合金的机械行为知之甚少，例如，在固体氧化物电解电池（SOEC）和固体氧化物燃料电池（SOFC）用于氢气和发电的工作温度（50 ~ 500℃）下。最近在宏观构件水平上的研究表明，600°C氢加速了蠕变变形，但潜在的机制尚不清楚。该研究的重点是探索和理解材料在高温（>500℃）下原子水平氢与空位、位错和晶界等微观结构缺陷相互作用的宏观响应。这些研究对于开发用于soec和sofc设计的不锈钢的蠕变行为的机械理解非常重要。该项目的最终目标是在对氢对位错塑性影响的缺陷级理解的基础上，开发304和310不锈钢蠕变响应的宏观本构规律，可用于SOEC和SOFC部件的失效分析和设计。为了实现这一目标，我们将使用一种尺度桥接方法，包括：(i)气体环境下的高温宏观蠕变试验，以获得蠕变应变率如何依赖于氢气和微观结构的定量信息；（ii）有和没有现场氢气加载的原位TEM力学试验，直接观察氢气如何影响蠕变中涉及的缺陷。（iii）基于物理的动力学建模，将缺陷动力学与蠕变应变率联系起来，并预测变形和微观结构在氢降解中的作用；（iv）从这种机制理解中，确定必须抑制的过程以减少损伤。

Understanding and controlling the effect of hydrogen on materials is a necessary step toward achieving a carbon-neutral and sustainable future. Structural materials such as Fe- and Ni-based alloys will play a central role in hydrogen generation, storage, transport, and end-use. Hydrogen-induced degradation of these materials at room temperature (hydrogen embrittlement), which poses a serious reliability threat to energy infrastructure, has been extensively studied. The resultant understanding is that room temperature embrittlement is driven either by hydrogen enhanced localized plasticity or hydrogen induced decohesion. On the other hand, very little is known about how hydrogen affects the mechanical behavior of structural alloys at elevated temperatures, for example, at the operating temperatures (>500°C) of Solid Oxide Electrolysis Cells (SOEC) and Solid Oxide Fuel Cells (SOFC) for hydrogen and power generation. Recent studies at macroscopic component level reveal that 600°C hydrogen accelerates creep deformation, but the underlying mechanisms are not understood.The focus of the proposed research is to explore and understand the macroscopic response of materials at high temperatures (>500°C) in terms of atomic level hydrogen interactions with microstructural defects such as vacancies, dislocations, and grain boundaries. These studies are important to develop a mechanistic understanding of the creep behavior of stainless steels that are used in the design of SOECs and SOFCs. The ultimate goal of the project is to develop macroscopic constitutive laws for the creep response of 304 and 310 stainless steels on the basis of defect-level understanding of the effect of hydrogen on dislocation plasticity that can be used in the analysis and design of SOEC and SOFC components against failure.Toward this goal we will use a scale bridging approach consisting of (i) high temperature macro-scale creep testing under gas environment to obtain quantitative information about how creep strain rates depend on hydrogen and microstructure, (ii) in-situ TEM mechanical tests with and without in-situ hydrogen loading to directly observe how hydrogen effects the defects involved in creep, (iii) physical-based kinetics modeling to relate the defect kinetics with creep strain rates and to predict the role of deformation and microstructure on hydrogen degradation, and (iv) from this mechanistic understanding, identification of the processes which must be inhibited to reduce damage.