Abstract In order to advance material development for future nuclear systems, an insight into the cracking conditions of T91 ferritic-martensitic steel in heavy liquid metals (HLM) is provided. The paper critically reviews previous experimental data and summarizes them with new results. The new testing of T91 steel was performed in contact with slow flow and static HLM to study crack initiation, especially in liquid PbBi eutectic at 300°–350°C and Pb at 400°C with about 1 × 10−6 wt.% of oxygen. Pre-stressed coupons were exposed to the liquid metals for up to 2000 h. Constant extension rate tests (CERTs) were performed in the liquid metals to accelerate cracking development. Under static conditions, the testing resulted in oxidation without any crack observation. Under the CERT ones, the T91 steel showed a tendency to crack initiation in PbBi, while in Pb, cracks were not initiated even when the oxide layer was broken. Moreover, the environmentally assisted crack initiated at the maximum load and continued to grow under further loading without unstable failure. Both previous and new data have confirmed that high stress and plastic strain are pre-conditions for the environmentally assisted cracking of T91 in static HLM. It indicates that in the systems utilizing continuous oxygen control of HLM, the LME/EAC of the T91 could develop only in the beyond design load conditions. Further testing is necessary to address the HLM flow speed effect.

中文翻译：

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T91铁素体-马氏体钢在重金属液态环境辅助开裂

摘要 为了推进未来核系统的材料开发，深入了解 T91 铁素体-马氏体钢在重金属液态金属 (HLM) 中的开裂条件。该论文批判性地回顾了以前的实验数据，并用新的结果对其进行了总结。T91 钢的新测试是在与慢流和静态 HLM 接触的情况下进行的，以研究裂纹萌生，特别是在 300°–350°C 的液态 PbBi 共晶和 400°C 的 Pb 中，其中约 1 × 10−6 wt.%氧。预应力试样暴露在液态金属中长达 2000 小时。在液态金属中进行恒定延伸率测试 (CERT) 以加速裂纹发展。在静态条件下，测试导致氧化，没有任何裂纹观察。在 CERT 下，T91 钢在 PbBi 中表现出裂纹萌生的趋势，而在 Pb 中，即使氧化层破裂，也不会产生裂纹。此外，环境辅助裂纹在最大载荷下开始并在进一步载荷下继续增长而不会出现不稳定失效。先前和新的数据都证实，高应力和塑性应变是静态 HLM 中 T91 环境辅助开裂的先决条件。这表明在采用 HLM 连续氧气控制的系统中，T91 的 LME/EAC 只能在超出设计负载的条件下发展。需要进一步测试以解决 HLM 流速效应。先前和新的数据都证实，高应力和塑性应变是静态 HLM 中 T91 环境辅助开裂的先决条件。这表明在利用 HLM 连续氧气控制的系统中，T91 的 LME/EAC 只能在超出设计负载的条件下发展。需要进一步测试以解决 HLM 流速效应。先前和新的数据都证实，高应力和塑性应变是静态 HLM 中 T91 环境辅助开裂的先决条件。这表明在利用 HLM 连续氧气控制的系统中，T91 的 LME/EAC 只能在超出设计负载的条件下发展。需要进一步测试以解决 HLM 流速效应。