Atomistic Mechanisms of Stress-Dependent Molten Salt Corrosion in NiCr Alloys

Abstract

Ni-based structural alloys in molten salt environments often experience simultaneous mechanical loading and corrosive attack, yet the mechanisms governing stress-corrosion interactions remain unclear. Prior studies largely emphasize tensile stress, while the role of compressive stress has received limited attention. Here, reactive molecular dynamics simulations are used to investigate the coupled effects of applied strain and corrosion in Ni${}_{0.75}$Cr${}_{0.25}$ exposed to molten FLiNaK at 800${}^{\circ }$C. A $\Sigma 5(210)$ grain boundary model is subjected to tensile (+4%) to compressive (-4%) uniaxial strains, and corrosion behavior is evaluated through fluorine adsorption, charge redistribution, and grain boundary evolution. Tensile strain accelerates intergranular corrosion by reducing local atomic packing through elastic dilation and increasing excess free volume at the grain boundary, which enhances atomic mobility and salt infiltration. In contrast, compressive strain suppresses corrosion by promoting the formation of a ridge-like surface layer along the grain boundary, limiting salt access to the underlying alloy. These results provide atomistic insight into how stress states influence grain boundary corrosion in molten salts.

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References in corpus (5)

• One Dimensional Wormhole Corrosion in Metals
• A Reactive Force Field Approach to Modeling Corrosion of NiCr Alloys in Molten FLiNaK Salts
• First-Principles Investigation of Grain Boundary Effects on Fluorine-Induced Initial Corrosion of NiCr Alloys
• Surface Orientation-dependent Corrosion Behavior of NiCr Alloys in Molten FLiNaK Salt
• Percolating Corrosion Pathways of Chemically Ordered NiCr Alloys in Molten Salts