State of the art overview material degradation in high-temperature supercritical CO2 environments

The supercritical CO2 (S-CO2) Brayton cycle has drawn much attention in the field of thermal cycles due to its merits of high efficiency, simple layout and compact turbomachinery. Several Fe-based, Ni-based and other heat-resistant alloys are the preferred constructional materials for crucial components, but their corrosion-related degradations still hinder the broad applications of this technology. S-CO2 could induce coupled oxidation and carburization, causing undesired alloy consumption, microstructure change and rapid failure. Besides, other physical and chemical factors from both materials and S-CO2 environment sides would further complicate the corrosion process and make the material selection difficult. To reveal the degradation mechanisms and provide a guideline for selecting suitable materials, this comprehensive review elucidates corrosion-related behavior of alloys in S-CO2 environments. The effects of temperature, pressure, impurity, alloying elements & structure, sample thickness, welding, coating and surface treatments on corrosion are systematically scrutinized. In addition, stress-assisted corrosion, including tensile behavior, creep, stress corrosion cracking, fatigue and thermal cycling are also thoroughly discussed. Based on these analyses, a summarization covering related corrosion mechanisms and predicting models has been made, with an attempt at proposing the material selection strategy and providing suitable candidate materials. The future research perspectives are outlined in the end.