Compatibility of ferritic steels with sintered Li2O pellets in a flowing-helium environment

The compatibility of ferritic HT-9 alloy and Fe-9Cr-1Mo steel with Li2O pellets has been investigated at 823 K (5500C) in flowing helium containing 93 or 1 ppM H2O and 1 ppM H2. The results indicate that the alloy specimens gain weight whereas the Li2O pellets lose weight after exposure. There is a net loss in weight of the total reaction couple. Both steels develop an iron-rich outer scale and chromium-rich subscale. The reaction rates in helium containing 93 ppM H2O are greater than in helium containing 1 ppM H2O. The depth of internal penetration for specimens exposed in helium with 1 ppM H2O reaches a constant value after approx. 3.6 Ms. The specimens exposed in helium containing 93 ppM H2O show a gradual increase in penetration up to 7.2 Ms. For both moisture contents, the total scale thickness follows a power law and the reaction rates decrease with time. The weight losses for Li2O pellets follow a linear law and yield values of 12.2 and 3.8%/year in helium with 93 and 1 ppM H2O, respectively