Effect of CO2 gas pressure on composition, growth rate, and structure of duplex oxide formed on 9Cr steel at 550 °C

Abstract

The oxidation behaviour of F91 in 0.1, 5, and 10 MPa CO2 was studied at 550 °C for 500 h. Previous results on the effect of CO2 pressure were summarised and compared with the results in this study. The oxidation kinetics decreased from 0.1 to 5 MPa and thereafter showed a lower dependence on the pressure (5–10 MPa). The carbon concentration at the oxide–alloy interface increased with time, but with different rates depending on the CO2 pressure. The amorphous carbon layers, and M23C6 carbides were identified in the inner oxide layer in the case of 5 MPa CO2.