Abstract An excessive concentration of boron in the 9% Cr tempered martensitic steels alloyed with nitrogen has a detrimental effect on creep performance, as the relatively large boron nitride phases are formed and act as the preferred sites for cavity nucleation. In the current research, a systematic investigation has been performed documenting details of creep damage in the heat affected zone of a weld joint constructed by using a 9% Cr Grade 92 steel. A combination of correlative characterisation techniques has been applied to monitor and quantify the evolution of creep damage within the heat affected zone through the entire creep life. The utilisation of cryo-fractography, two-dimensional electron-based microscopic characterisation and three-dimensional tomography based on focused ion beam microscopy have confirmed the close association between creep cavities and boron nitride phases from the initial stage of creep. It is revealed that the thermal transients imposed during welding result in the decohesion at the interface of boron nitrides with the surrounding matrix. This decohesion is a result of significant thermo-mechanical mismatch between boron nitrides and the tempered martensitic matrix. The voids initiated at these locations grow and eventually link-up during creep exposure, leading to cracking and fracture.

中文翻译：

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9% Cr 回火马氏体钢焊缝热影响区氮化硼上的局部蠕变空化

摘要 含氮合金的 9% Cr 回火马氏体钢中硼的浓度过高会对蠕变性能产生不利影响，因为会形成相对较大的氮化硼相并作为空腔形核的首选位点。在当前的研究中，已进行了系统调查，记录了使用 9% Cr 92 级钢构建的焊接接头的热影响区蠕变损坏的详细信息。相关表征技术的组合已被应用于监测和量化整个蠕变寿命中热影响区内蠕变损伤的演变。冷冻断层法的应用，二维电子显微表征和基于聚焦离子束显微镜的三维断层扫描证实了蠕变初始阶段的蠕变腔和氮化硼相之间的密切联系。结果表明，焊接过程中施加的热瞬变导致氮化硼与周围基体界面处的脱聚。这种分离是氮化硼和回火马氏体基体之间显着的热机械失配的结果。在这些位置产生的空隙会在蠕变暴露期间增长并最终连接起来，导致开裂和断裂。结果表明，焊接过程中施加的热瞬变导致氮化硼与周围基体界面处的脱聚。这种分离是氮化硼和回火马氏体基体之间显着的热机械失配的结果。在这些位置产生的空隙会在蠕变暴露期间增长并最终连接起来，导致开裂和断裂。结果表明，焊接过程中施加的热瞬变导致氮化硼与周围基体界面处的脱聚。这种分离是氮化硼和回火马氏体基体之间显着的热机械失配的结果。在这些位置产生的空隙会在蠕变暴露期间增长并最终连接起来，导致开裂和断裂。