高温超临界CO2中铁素体-马氏体钢氧化与碳化耦合腐蚀机理

高温高压超临界CO2环境发生严重碳化剥落腐蚀是制约超临界CO2新型动力循环技术发展的关键瓶颈问题之一。为了抑制碳化剥落腐蚀，申请人提出在高温超临界CO2中添加适量O2，利用氧气加速氧化层中孔洞“自愈合”，提高铬氧化物生成比例，促进致密氧化层生成来阻碍CO2向内扩散，进而抑制金属基体发生碳化剥落腐蚀。这种促进氧化来抑制碳化腐蚀的方法，是降低超临界CO2环境碳化剥落腐蚀的有益探索。本项目拟开展不同O2含量高温超临界CO2环境铁素体-马氏体钢碳化腐蚀试验研究，定量检测孔洞和碳化物的分布规律，揭示孔洞诱导碳化物生成机制。使用环境透射电镜原位观察Fe-Cr合金碳化腐蚀过程，探究O/C比对铬氧化物和铬碳化物的生成演化竞争机制，揭示高温超临界CO2环境金属氧化和碳化耦合腐蚀机理。为超临界CO2新型动力装备碳化腐蚀速率预测和腐蚀防护提供科学基础和技术方法，推动超临界CO2新型循环在能源动力领域中的应用。

It is a key bottleneck to develop supercritical CO2 Brayton cycle power generation technology that the severe carburization and exfoliation in high-temperature and high-pressure supercritical CO2. In order to prohibit the carburization corrosion, an innovative method of adding O2 into supercritical CO2 is proposed by the applicant. The self-healing of pores in oxides can be induced by oxygen and the ratio of Cr-oxide and Cr-carbide can be also changed by oxygen. So, appropriate oxygen is added into supercritical CO2 in which a relative thick and compact oxide scale will be formed. The compact oxide scale hinders the inward diffusion of CO2 resulting in the inhibition of carburization of metals. This method of inhibiting carburization through enhancing oxidation is a meaningful exploration. Therefore, experimental investigation on carburization in supercritical CO2 containing different O2 concentration will be carried out. The distribution of pores and carbides will be quantitatively characterized and the mechanism of void-induced carbide formation will be revealed. The process of carburization of Fe-Cr alloy will be in-situ observed by employing environmental transmission electron microscope (ETEM). The competitive mechanism of O/C ratio on the formation of Cr-oxide and Cr-carbide will be deeply discussed. Then, the mechanism of oxidation and carburization of ferritic-martensitic steels in high-temperature supercritical CO2 will be revealed. This study will be the fundamental knowledge and technology support for prediction and protection of carburization and also push forward the application of the new supercritical CO2 cycle in energy power field.