Hot corrosion and internal spallation of laser-cladded inconel 625 superalloy coatings in molten sulfate salts

Hot corrosions of laser-cladded inconel 625 in molten salt Na2SO4-MgSO4 mixture have been studied at 900 °C to address its anticorrosion behaviors. Elemental and microstructural characterizations provide direct evidence for the formation MgO/Cr2O3 external layers outward-diffusion Cr atoms. The Cr-depletion promotes precipitation δ-Ni3(Nb/Mo), nucleation accumulation dislocations, pores, internal spallation corroded alloy. They also diffusion sulfur into near-surface region, leading sulfide scales (i.e., Nb4−xCrxS6, CrS, MnCr2S4). Grain boundaries play important roles atomic diffusions formations.