Atomic insights into the coupled mechanism of oxidation and carburization of iron under supercritical CO2 environment with a new reactive force field

Abstract

Structural materials exposed to supercritical carbon dioxide (S-CO2) environment will face serious corrosion failure that presents significant challenges to the durability and safety of materials in critical industrial applications, such as nuclear reactors and energy storage systems. Based on density functional theory calculations, a new and highly accurate Fe/C/O reactive force field parameter set has been developed to reveal the corrosion mechanisms of iron (Fe) under S-CO2 environment via molecular dynamics simulation. The influence of temperature, oxygen atoms, and carbon atoms on the corrosion process is also discussed in this work. We demonstrate that high temperature significantly accelerates the corrosion rate without altering the corrosion mechanism. After exposure to the S-CO2 environment, a multilayered corrosion structure (including a porous outer oxide layer with a carbide layer, a dense inner oxide layer, and an innermost carburized layer) was observed on the surface. The dense inner oxide layer hinders the penetration of carbon atoms into deeper regions. However, the presence of carbon disrupts the oxide layer, hastening substrate degradation. Additionally, pre-oxidation treatment effectively suppresses Fe–C bond formation and substantially enhances substrate corrosion resistance. These findings offer crucial insights for guiding the design of corrosion-resistant materials and the development of effective surface treatments for high-temperature and high-pressure industrial applications.