Compatibility studies of metallic materials with lithium-based oxides

The compatibility of Li2O, Li4SiO4 and Li2SiO3 with the cladding materials AISI 316, 1.4914, Hastelloy X and Inconel 625 was investigated at 800-10000C for annealing times up to 1000 h. A controlled oxygen reactivity was established by adding 1 mol% NiO per mole Li2O to the Li-based oxides. In addition, some compatibility tests were performed at 600-9000C on Be, which is of interest as a neutron multiplier material, with Li2SiO3 as well as AISI 316. Li2O accounted for the strongest cladding attack, followed by Li4SiO4 and Li2SiO3. In the absence of NiO, Li2SiO3 caused no chemical interactions at all. With respect to the cladding materials, there was no considerable difference in the reaction rates of AISI 316, Hastelloy X and Inconel 625. However, the steel 1.4914 was clearly more heavily attacked at and above 8000C. The compatibility of Be with Li2SiO3 or AISI 316 seems to be tolerable up to about 6500C. At higher temperatures a liquid Li silicide phase is formed which results in strong local attack and penetration into Li2SiO3. (orig.)