Gallium suboxide vapor attack of chromium, cobalt, molybdenum, tungsten, and their alloys at 1200 degrees C

Our prior work elucidated the failure mechanism of furnace materials (304 S S, 316 SS, and Hastelloy C-276) exposed to gallium suboxide (Ga2O) and/or g allium oxide (Ga2O3) during plutonium-gallium compound processing. Failure was hypothesized to result from concurrent alloy oxidation/Ga compound redu ction followed by Ga uptake. The aim of the current work is to screen candi date replacement materials. Alloys Haynes 25 (49 Co-20 Cr-15 W-10 Ni-3 Fe-2 Mn-0.4 Si, wt.%), 52Mo-48Re (wt.Yo), 62 W-38 Cu (wt.%), and commercially p ure Cr, Co, Mo, W, and alumina were examined. Preliminary assessments of co mmercially pure W and Mo-Re suggest that these materials may be suitable fo r furnace construction. Thermodynamic calculations indicating that material s containing Al, Cr, Mn, Si, and V would be susceptible to oxidation in the presence of Ga2O were validated by experimental results. The extent of att ack (oxidation, Ga uptake, and elemental redistribution) cannot be predicte d based on a simple rule of elemental mixtures-alloy composition plays a st rong role. In contrast to that reported previously, an alternate reaction m echanism for Ga uptake, which does not require concurrent alloy oxidation, controls Ga uptake for certain materials. Due to the lack of thermodynamic data, calculations cannot quantitatively predict Ga uptake. However, a corr elation between Ga solubility and uptake was noted.