Molecular dynamics study on the initial oxidation behavior of FeCr alloys in supercritical H2O and supercritical CO2 with O2

The initial oxidation behavior of Fe10Cr and Fe20Cr alloys in supercritical H2O and supercritical CO2 with O2 at 650 degrees C is investigated by molecular dynamics. O2 has the higher average adsorption energy of -2.54 eV than that of H2O and CO2, indicating that the adsorption state of O2 molecule on FeCr alloys is the most stable. The reactions between O2 and FeCr alloys are the occurs firstly, followed by H2O and CO2. The reaction rates of both FeCr alloys with O2 in supercritical CO2 are higher than that in supercritical H2O. Due to the addition of Cr to FeCr alloys, the outward diffusion coefficients of Cr from FeCr alloys both increase 1.59 x 10-23 cm2/s in supercritical CO2 and H2O with O2.