Role of Mo and W in molten salt corrosion resistance and elemental redistribution of Ni model alloys

The corrosion behavior of Ni model alloys containing Cr, Mo and W was investigated in NaCl–MgCl 2 molten salt at 700 ℃. Weight-loss measurements showed that Cr addition accelerated corrosion, whereas Mo and W additions significantly reduced mass loss compare to pure Ni. EPMA analysis revealed distinct behaviors: Mo formed an enriched layer coincident with the Cr-depleted region, while W remained uniformly distributed in the matrix. DFT calculations confirmed that Mo promotes surface segregation through higher mobility than its base metal Ni, whereas W, with low mobility, remains immobile within the lattice. Both Mo and W were also found to suppress Cr diffusion by inhibiting vacancy-Cr exchange in their vicinity. These findings clarify the complementary role of Mo and W in corrosion resistance and provide mechanistic insights into elemental redistribution in Ni-based alloys under molten salt conditions. • Molten salt corrosion resistance of Ni-based model alloys was studied by experiments and DFT. • Mo suppresses Cr depletion by forming a segregation layer via rapid vacancy diffusion. • W hinders Cr diffusion through immobilization within the lattice • Alloying effects are clarified through vacancy-mediated diffusion mechanisms. • Findings provide mechanistic insights into how Mo and W affect elemental redistribution and corrosion.