Corrosion behavior of dual-phase Fe36Ni36Al17Cr10Mo1 multi-principal component alloy in LiCl–KCl–CsCl molten salt at 700 °C

Abstract

Molten chloride salts with good heat capacity, thermal conductivity, high thermal stability and broader temperature range play a vital role in improving the thermal conversion efficiency of the concentrated solar power plant. However, the dissolution of active elements caused by the Cl⁻ and impurities severely affects the service time of structural materials and hinders the application of the power plant. Multi-principal components alloy with excellent mechanical properties, good oxidation and corrosion resistance are expected to be applied in molten chloride salts at high temperature. To investigate the corrosion behavior of the dual-phase Fe₃₆Ni₃₆Al₁₇Cr₁₀Mo₁ alloy at different time (48, 96, 144, 192 and 240 h), immersion test was conducted at 700 ℃ in a ternary LiCl–KCl–CsCl molten salt. By analyzing the optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) results and the standard Gibbs free energy, three corrosion stages (oxidation–dissolution–corrosion) over time were drawn. Active elements such as Al and Cr oxidized first and then experienced dissolution in the acidic environment. After the oxides were depleted, the bare metal started to corrode, and many defects formed on the surface of the alloy, causing severe corrosion. However, for the low corrosion ability of LiCl–KCl–CsCl molten salts, the alloy exhibited excellent performance with corrosion rate of 274.9 μm/y and corrosion depth of 5.52 μm after 240 h, and there was no obvious preferential corrosion of the B2 phase. This work studied the corrosion process of the Fe₃₆Ni₃₆Al₁₇Cr₁₀Mo₁ alloy in LiCl–KCl–CsCl molten salt., which may provide certain guiding implications for industrial applications.