RESEARCH PROGRESS

RESEARCH PROGRESS

The Institute of Energy has made Progress in Research on Corrosion of Molybdenum Alloy by Liquid Lithium.

2022/3/17 15:33:46 Hits:1 Source:

Recently, Meng Xiancai, an associate researcher at the Neutron Technology Application Research Center of the Institute of Energy of Hefei Comprehensive National Science Center, has made important progress in the research of corrosion behavior and mechanism of liquid alkali metal lithium on the molybdenum alloy. The related research result "Corrosion characteristics of Mo and TZM alloy for plasma facing components in molten lithium at 623 K" was published in Corrosion Science, a top international academic journal in the field of corrosion.[X.C. Meng, L. Li, C.L. Li et al., Corros. Sci. 200, 110202 (2022)]

The research on the corrosion characteristics of cladding module materials and liquid lithium in fusion devices can provide a scientific basis for the selection of materials in the working environment of the liquid lithium cladding of fusion reactors and the corrosion protection during service, which is of great significance. The immersion method was adopted for this research. The corrosion characteristics of pure molybdenum (Mo) and molybdenum-based alloy (TZM) in 623 K liquid lithium were compared by characterization of mass loss, surface morphology and composition, and corrosion depth, and the related corrosion mechanism was revealed. The results show that corrosion does not become a critical issue for the short-term application of Mo and TZM materials to 623 K liquid lithium. However, for TZM materials, the adoption of necessary corrosion protection measures must be considered during long-term service in the lithium environment. The research also shows that the reduction reaction occurs after the liquid lithium contacts the material surface, causing the oxide layer (MoO3) to dissolve first. Carbon (C), titanium (Ti) and zirconium (Zr) atoms on the surface of the material are preferentially and selectively dissolved into lithium, which results in pitting corrosion of Mo and pitting corrosion and grain boundary corrosion of TZM. In liquid lithium, carbon and lithium form unstable Li2C2, which is quickly captured by Mo, Zr and Ti to form stable carbides (Mo2C, ZrC and TiC) and deposited (the introduction of N impurities will form corrosion products such as ZrN and TiN), thus accelerating the corrosion of TZM. Therefore, strictly controlling the content of N in C and Li in the material can effectively alleviate the corrosion of TZM material. While ensuring performance, replacing Ti and Zr with elements with solubility lower than Mo in lithium can avoid grain boundary corrosion caused by selective dissolution.

This research has received full support from researcher Hu Jiansheng of the Institute of Plasma Physics and the research group of Professor Deng Huiqiu of Hunan University. It has also benefited from the joint efforts of the partners from PPPL, UIUC and JHU in the United States. It has also received grants from major cultivation projects of the Institute of Energy, national key research and development projects, national natural science foundation and other projects.

Link to the paper: https://doi.org/10.1016/j.corsci.2022.110202

图片20.png

Fig. 1: Corrosion process of TZM in liquid lithium