Corrosion of Ultra-High Temperature Ceramics in Molten Chloride Salt

Abstract Molten chloride salts have been proposed as heat transfer fluids for high temperature systems such as nuclear reactors, concentrated solar power, and thermal energy storage, because of their high temperature stability and heat transfer properties. However, these chloride salts present new challenges due to their corrosivity. For this reason, ultrahigh temperature ceramics (UHTCs) are viewed as a potential salt-facing material. Tungsten carbide, molybdenum carbide, titanium carbide, silicon carbide, titanium diboride, and Haynes 230 were exposed to purified and impure KCl-MgCl₂ at 800°C. Samples were then characterized with SEM and EDS. With the eventual goal of using additively manufactured UHTCs in a heat exchanger between molten chloride salt and supercritical CO₂, additional ceramic blends intended to improve CO2 oxidation resistance and sinterability were also tested and compared to pure ceramics. This work showed that samples tested in purified chloride salt had massively slower corrosion rates than samples exposed in simple heat-dried salts. Additionally, samples with and without additives performed similarly in impure salt, but the samples with additives had worse corrosion rates in purified salt.

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