镍基高温合金高温失塑裂纹的晶界滑移机制和多尺度预测模型

Inconel690 has excellent high-temperature strength, corrosion resistance and has a wide application on welded construction design of nuclear key equipment. However, a solid-state intergraunlar cracking, called ductility-dip cracking (DDC) was found in filler metals of Inconel690 (FM-52 series) during the welding process. It was extremely hard to detect DDC like microcracks by common nondestructive testing. As the key equipments served in a severe condition combined with high pressure & temperature and corrosive atmosphere, the existence of DDC would greatly affect the safety and life expansion of nuclear power plant. .A lot of efforts had been made to improve the composition of FM-52 series alloys and develop the evaluation of DDC susceptibility. However, the welding conditions, like welding parameters, welded construction, intensity of restraint and welded microstructure, have a much complex influence on thermal deformation applied on weldment, which made it even harder to guide welding procedure improvement by existing evaluation tests. Currently, it was still not found effective means to avoid defects of DDC on welded construction of the thick-wall pipe line for nuclear plant..In order to resolve the evaluation problems on FM-52 series weldment, a 3D multiple dimensioned model of weld pool was developed based on grain boundary sliding mechanism. By combined hydromechanical calculation and finite element method, the dynamical propagation of intergranular microcrack was simulated to reveal the DDC forming mechanism during welding process. The evaluation and prediction of DDC susceptibility by means of the proposed model would provide a significant help to improve the accuracy of welded construction design and improve the saftey of nuclear power plant.

镍基合金Inconel690具有优异的高温强度、耐腐蚀性，被广泛用于核电关键部件的焊接结构。但焊接中发现，其对应的熔敷金属FM-52系列具有明显的高温失塑裂纹（DDC）倾向。该裂纹通常尺寸微小，难以用无损检测方法识别，在核电运行的严苛环境中服役时会造成极大的安全隐患。尽管国内外已有大量研究致力于FM-52系合金成分优化和DDC敏感性评估，但焊接工艺、焊接结构、拘束度、微观组织的不均匀性等对焊接热变形过程的影响规律复杂，尚未形成明确的作用机理指导焊接设计，在厚壁管道焊接结构中仍无法有效避免该缺陷的出现。针对该问题，本文提出采用流体计算和有限元数值方法耦合，并结合晶界滑移失效机制研究，建立焊缝的3D多尺度模型模拟微观尺度的晶间裂纹动态形核和扩展过程，揭示焊缝中的晶间微裂纹的形成机理。通过该方法对焊缝中DDC裂纹进行评估和预测，对提高核电关键部件焊接设计的准确性和提高核电运行安全有重要意义。

镍基合金Inconel690具有优异的高温强度、耐腐蚀性，被广泛用于核电关键部件的焊接结.构。但焊接中发现，其对应的熔敷金属FM-52系列具有明显的高温失塑裂纹（DDC）倾向。该裂纹通常尺寸微小，难以用无损检测方法识别，在核电运行的严苛环境中服役时会造成极大的安全隐患。尽管国内外已有大量研究致力于FM-52系合金成分优化和DDC敏感性评估，但焊接工艺、焊接结构、拘束度、微观组织的不均匀性等对焊接热变形过程的影响规律复杂，尚未形成明确的作用机理指导焊接设计，在厚壁管道焊接结构中仍无法有效避免该缺陷的出现。针对该问题，本文提出采用流体计算和有限元数值方法耦合，并结合晶界滑移失效机制研究，建立焊缝的多尺度模型模拟微观尺度的晶间裂纹动态形核和扩展过程，揭示焊缝中的晶间微裂纹的形成机理。通过该方法对焊缝中DDC裂纹进行评估和预测，对提高核电关键部件焊接设计的准确性和提高核电运行安全有重要意义。