Stress-assisted corrosion behaviour of Hastelloy N in FLiNaK molten salt environment

Abstract The use of molten-salt–based energy production and storage systems requires high-temperature corrosion- and creep-resistant structural materials. This study investigated the microstructure evolution and corrosion characteristics of Hastelloy N under working stress in a molten salt environment. Selective diffusion of Cr at the grain boundaries (GBs) of the Hastelloy N degraded the properties of the GBs, making them preferred locations for corrosion crack invasion. Stress further promoted Cr diffusion and accelerated GB carbide precipitation, thereby forming a corrosion couple between the carbide and matrix that facilitated the expansion of intergranular corrosion cracks into the grains. These findings are useful for providing advances in the design of novel structural alloys with extraordinary property-microstructure stability combinations for resistant to complex molten salt environments.