Corrosion behavior and deuterium permeability of aluminide coating in high-temperature carbon dioxide atmosphere

Abstract

In the thermionic space nuclear power, the hydrogen released by the moderator ZrH2 penetrates into the core and affects the power generation performance. Therefore, it is necessary to prepare hydrogen permeation barrier materials such as aluminide coatings on the surface of structural components. In this study, the aluminide coating was prepared by a composite low-temperature aluminizing process. Since the working environment was a mixture of helium (He) and carbon dioxide (CO2), the corrosion behavior of aluminide coatings in this atmosphere at 600 °C for 1000 h was studied. The results showed that an oxide layer of about 1–2.3 μm was formed on the surface, which was mainly composed of alumina, mixed with a small amount of chromia. There was a carbon-containing layer in the outer part of the oxide layer. The aluminide coating surface morphology was significantly improved, and CO2 gas had a repairing effect on the coating surface. In addition, the effect of CO2 gas on the hydrogen permeation resistance of aluminide coatings was comparatively investigated in pure D2 and D2 + CO2 atmospheres. The permeation reduction factors (PRF) under pure D2 and D2 + CO2 were 7.76 and 77.4, respectively, indicating that CO2 gas improved the PRF of the aluminide coatings by an order of magnitude.