CORROSION RESISTANT REFRACTORY HIGH-ENTROPY ALLOY COATINGS FOR HIGH-TEMPERATURE, MOLTEN-SALT REACTORS

Refractory High Entropy Alloys (RHEAs) are new generation unique equiatomic materials with extraordinary properties to counter corrosion and wear. High-temperature, molten-salt-cooled reactors have the potential to produce significant levels of carbon-free nuclear energy, but they can also experience corrosion issues. RHEAs in their bulk form have been extensively studied but their coating applications have not been explored at all. With that in mind, we developed novel, thermal spray and cold spray processes based on proven, bimetallic refractory high-entropy alloy (RHEA) coatings for enhanced corrosion protection. The thermal spray process has the capability to provide highly adherent and well bonded thick coatings that are resistant to peeling, spalling, scratching, and debonding. We selected RHEA combinations from nuclear reactor-compatible, high-temperature refractory elements, such as Cr, Nb, Ta, Ti, V, and W, and with a potential for corrosion-resistance in chloride- and fluoride-based molten salts. A set of corrosion tests were conducted under prototypical, chloride- and fluoride-based molten salts undergoing pool boiling at 700 C. These test results alongwith other coating properties will be presented in this paper.