超临界水氧化环境下800H合金的应力腐蚀开裂机理研究

Revealing the stress corrosion cracking (SCC) mechanism of nuclear structural materials exposed to supercritical water (SCW) is of great importance for guiding the choice of candidate materials and development of new materials for supercritical water cooled reactor(SCWR). However, the SCC behavior of materials in SCW is complicated and the mechanism is unclear due to fact that the SCC behavior in SCW is influenced not only by creep of the materials and also the corrosion of the materials. So in the present research, we choose high corrosion resistance alloy 800H as researching materials, and firstly investigate its creep behavior in high temperature Ar, then analyze the SCC behavior of alloy 800H exposed to SCW with different temperature and oxygen content. Based on this, the coupling influence of creep and corrosion on the SCC behavior of materials is revealed. Furthermore, based on the analysis of the crack growth path, the crack tip chemistry and crack tip plastic deformation for creep and SCC respectively, the SCC mechanism of alloy 800H in SCW is revealed.

揭示核结构材料在超临界水中的应力腐蚀开裂机理，对于指导超临界水冷堆结构材料的甄选及新材料的制备具有重要的意义。针对高温蠕变及腐蚀对结构材料在超临界水氧化环境下的应力腐蚀开裂行为影响规律复杂，材料的应力腐蚀开裂机理不明的问题，本课题拟选取具有优良耐腐蚀性能的800H合金作为研究对象，首先研究其在高温氩气中的蠕变行为，然后进一步研究其在不同温度及溶解氧含量超临界水中的应力腐蚀开裂行为，厘清蠕变及不同状态超临界水的腐蚀对材料裂纹扩展的耦合作用规律；最终结合蠕变及应力腐蚀裂纹扩展路径﹑裂纹尖端氧化规律以及塑性变形机理的研究，揭示800H合金在超临界水中的应力腐蚀开裂机理。

由于超临界水极强的腐蚀能力和较高的温度，材料在该环境下服役会面临严重的应力腐蚀开裂的问题。因此，揭示核材料在超临界水中的应力腐蚀裂纹扩展的机理，对于指导超临界水冷堆材料的甄选及新材料的制备具有重要的意义。.针对高温蠕变及腐蚀对材料在超临界水氧化环境下的应力腐蚀裂纹扩展行为影响规律复杂，材料的应力腐蚀开裂机理不明的问题，本课题采用800H合金作为研究对象，首先测量材料高温氩气中的蠕变裂纹扩展速率，然后进一步测量其在不同温度及溶解氧含量超临界水中的应力腐蚀裂纹扩展速率，通过相互的对比，厘清了超临界水的腐蚀和高温蠕变对材料的应力腐蚀裂纹扩展速率的贡献，从而获得其耦合作用规律；同时，采用SEM、TEM以及TKD等高分表表征技术，对裂纹扩展路径﹑裂纹尖端氧化规律以及塑性变形机理进行了表征，最终成功揭示800H合金在超临界水中的应力腐蚀裂纹扩展的机理，建立起了材料裂纹扩展失效过程的物理模型。