Carbon Depositions Within The Oxide Scale And Its Effect On The Oxidation Behavior Of Low Alloy Steel In Low (0.1 Mpa), Sub-(5 Mpa) And Supercritical (10 Mpa) Co2 At 550 Degrees C

The oxidation behavior of CrMoV steel in 0.1, 5, and 10 MPa CO2 was studied at 550 degrees C for 500 h. Reaction rates decreased from 0.1-5 MPa, and breakaway occurred sooner with increasing pressure. Amorphous carbon was identified within the inner layer in all CO2 pressure values, while graphite was mainly detected under 5 and 10 MPa. Carbon deposition may link to the formation of Fe- and (Fe, Ni)-rich M3C carbides at the oxide/steel interface, which catalyzed the Boudouard reaction. A high external CO2 pressure and the oxidation of Cr-rich carbides within the steel may favor carbon depositions.