Corrosion behaviors of Ni-based GH3625 alloy in molten solar salt

Abstract

The high-temperature corrosion behavior of GH3625 alloy was investigated in molten solar salt (NaNO3/KNO3 (60/40 mass %)) under an argon atmosphere. The dynamic corrosion rate increased with rising temperature, from 4.3 to 21.6 μm/y. Through the sophisticated sample preparation on the oxidation layer using FIB technology, and the fine characterization using TEM analysis, the corrosion type shows no influence on the oxide types. Meanwhile, the oxidation layers were discovered to be constituted by the Cr2O3 particles in the matrix, a depleted region of Cr, a Cr2O3 layer, a layer consisting of NiO and Cr2O3 particles, and a dense NiO layer from the matrix to the outer layer. The Cr2O3 was found to form before NiO. The NiO was confirmed to protect the alloy during the corrosion process. A narrow depletion zone of Cr was discovered. The silicon was indicated to be harmful to the corrosion resistance. This work provides insight into the corrosion mechanism of GH3625 in molten solar salt.

Keywords

• CSP station
• Superalloys
• Molten salt
• Hot corrosion
• Oxidation