Study of corrosion behavior of Inconel 625 cladding metal in KCl-MgCl2 molten salt under isothermal and thermal cycling conditions

Inconel 625 flux-cored wire is widely used in the repair of solar energy storage pipelines because of its excellent corrosion resistance. In the application environment of molten salt pipeline containing high-temperature chloride, the surface of the repaired pipeline is easy to deposit salt film, which leads to high-temperature hot corrosion. In this paper, in order to study the hot corrosion mechanism of Inconel 625 cladding metal. Inconel 625 cladding metal was prepared by MAG welding. The corrosion behavior of Inconel 625 cladding metal under isothermal (800 & DEG;C) and thermal cycle (600-800 & DEG;C) conditions in KCl-MgCl2 (60-40 mol %) molten salt environment was investigated. The results showed that the corrosion rate of Inconel 625 cladding metal was 12.39 & mu;m/year under 72-h isothermal conditions, and the corrosion products mainly included MgO and NiCr2O4. Under the condition of 3 thermal cycles, the corrosion rate of the sample was 11.21 & mu;m/year, and the corrosion products mainly included MgO, NiCr2O4 and Cr2O3. This was because the Cr2O3 protective shell dissolved and fell off under isothermal conditions. Besides, the hot corrosion path penetrated along the random HAGBs. The larger number of HAGBs increased the diffusion path of Cr element, which led to increased corrosion under isothermal conditions. Under the condition of thermal cycle, there was an intermittent cooling effect, and the corrosion time was less at the highest temperature, which improved the stability of the Cr2O3 protective shell. At the same time, it reduced the number of HAGBs and reduced the penetration path of hot corrosion. The diffusion coefficient of Cr element was reduced by 55.6%, which reduced the corrosion rate.