Preparation of Li4SiO4 Ceramics Tritium Breeder and Its Interface Corrosion Behavior with 14Cr-ODS Steel

Abstract:

The chemical compatibility between Li₄SiO₄ pebbles and ODS steel is important for the safe operation of the fusion reactor. In the present paper, the transformation of microstructure and component for contact interface between ODS steel and pebbles after 300 h heat preservation in an argon atmosphere at 500, 600, and 700 °C was investigated. The results show that serious element interdiffusion and reaction can be observed at the interface between Li₄SiO₄ pebbles and ODS steel at temperatures of 600~700 °C. For the surface of Li₄SiO₄ pebbles, a thin reaction layer appears due to the diffusion of Fe and Cr from ODS steel, which also causes the increase of density and decrease of crush load from 51 N (500 °C) to 32 N (700 °C). XRD patterns show that the new phase of LiCrO₂ and LiFeO₂ appears on the surface of ODS steel, which suggests that the Li and O atoms in Li₄SiO₄ pebbles can diffuse into ODS, and react with Fe and Cr elements to form corrosion layers at high temperature. The corrosion layers can be divided into two oxide sub-layers at 700 °C. The outermost layer is a mixture of LiFeO₂ and LiCrO₂, and the next layer is mainly LiFeO₂. For the surface of ODS steel, the oxygen diffusion coefficient is 2.2×10^-14 cm²/s at 700 °C for 300 h. It suggests that the ODS steel as a blanket structure material steel needs a resisted corrosion coating in the design of a blanket in the future.