Effect of impurity ratios on the high-temperature corrosion of Inconel 617 and Incoloy 800H in impure helium

Helium is utilized to be the coolant of the high-temperature gas-cooled reactor (HTGR), which contains trace impurities in the primary circuit. The impurities may cause various corrosion behaviors of superalloys at elevated temperatures. In this study, the oxidation and carburization of Inconel 617 and Incoloy 800H at 950 degrees C in impure helium were investigated. According to thermodynamics and kinetics, the different ratios PH2/PH2O and PCH4/ PH2O were set in this research, which leads to different oxidation and carburization behaviors of alloys at 950 degrees C. When PH2O is at a constant concentration, high PH2 would reduce the oxidation capacity of the atmosphere, and high PCH4 will cause severe carburization. Due to the presence of the silicon oxide interlayer, the oxide layer of Incoloy 800H has poor adhesion and it is easier to be destroyed at high temperatures. It may be the reason that Incoloy 800H has weaker resistance to carburization.

Automated summary

In this study, the oxidation and carburization behaviors of Inconel 617 and Incoloy 800H in impure helium at 950 degrees C were investigated. Different ratios of PH2/PH2O and PCH4/ PH2O were set, which resulted in different oxidation and carburization behaviors of the alloys. The presence of a silicon oxide interlayer in Incoloy 800H led to poor adhesion of the oxide layer, making it more susceptible to destruction at high temperatures and weaker resistance to carburization.