The primary coolant of the High-temperature Gas-cooled Reactor (HTGR) is expected to contain impurities such as CO, CH4, H2, H2O，which can make corrosion to structural metallic materials at elevated temperatures. Mainly, it includes oxidation, decarburization, and carburization. The chrome-rich protective scale on the alloy surface is an important factor to prevent the alloys from being severely corroded. The simulative corrosion test was conducted on the four alternative materials of the steam generator in HTGR: Inconel 617, Incoloy 800H, Hastelloy X, and T-22 respectively. At 950 , the alloys were exposed to the helium and argon with specific impurities for 200 hours respectively. The corrosion results were analyzed by weighing, scanning electron microscope (SEM), electron probe microanalyzer (EPMA), and the carbon-sulfur analyzer. In the helium and argon with impurities, alloys exhibited similar corrosion behaviors. Inconel 617, Incoloy 800H, and Hastelloy X had formed the chrome-rich scale on the surface. Due to the low content of the oxidizable elements, the continuous scale of T-22 alloy was not observed. Hastelloy X alloy has formed a continuous dense oxide layer, which may be related to the manganese element. Although the Inconel 617 and Incoloy 800H formed the thick oxidation layer, pores in the surface were observed which may affect their corrosion resistance. In addition, the chromium element in Inconel 617 appeared the expected depletion phenomenon near the corrosion layer, which is consistent with the results of theoretical analysis.

Oxidation Behaviors of the High Temperature Alloys in the Impure Helium and Argon

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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