Corrosion and carburization behavior of chromia-forming heat resistant alloys in a high-temperature supercritical-carbon dioxide environment

Abstract

Corrosion and carburization behavior of chromia-forming heat resistant alloys in high-temperature supercritical-CO2 were investigated. For all alloys, a thin and continuous chromia (Cr2O3) layer was formed on the surface, while the existence of an amorphous carbon layer was identified at the chromia/matrix interface. Below the amorphous C layer, Cr-rich M23C6 carbides were extensively formed in Alloy 800HT but not in Alloy 600 or Alloy 690. The carburization resistance was dependent on whether the matrix is Fe-based or Ni-based. The existence of the carburized region with Cr-rich M23C6 carbides in Alloy 800HT contributed to additional loss of ductility.