Effects of alloying elements of nickel-based alloys on the hot-corrosion behavior in an electrolytic reduction process

Abstract

In this study, the isothermal and cyclic corrosion behaviors of custom-made nickel-based alloys (N105, N107, and N108) with various elemental compositions in a LiCl-Li2O molten salt were investigated at 650 °C in argon atmosphere. The isothermal and cyclic corrosion behaviors were studied by measuring the mass changes, surface morphologies, cross-sectional morphologies with elemental distribution, and the compositional changes of the subscale and substrate as well as the spalled oxide scale. Under the isothermal and cyclic corrosion test, the corrosion rate was in the order of N108 < N105 < N107, and N107 < N105 < N108, respectively, which depended on the morphology and structure of the crystals formed on the surface of the outer scale in contact with the molten salt, and was also related to the region of Al and Cr depletion. After the isothermal corrosion test, the hot corrosion products formed in N105 were Cr2O3, NiCr2O4, and Li2Ni8O10 and those in N107 were Cr2O3 and NiCr2O4, while Cr2O3, NiCr2O4, and LiTiO2 were identified as the hot corrosion products of N108. However, the hot corrosion products of N105, N107, and N108 were Cr2O3, NiCr2O4, and LiFeO2 after the cyclic corrosion test.