Oxidation behaviour of Super 304H stainless steel in supercritical water

Oxidation of Super 304H steel in supercritical water at 600 degrees C and 25 MPa was investigated, for the oxidation time of up to 1000 h. The oxidation kinetics approximately followed a parabolic law. The composition and microstructure of the oxide were investigated using the SEM equipped with EDS, EBSD and XRD. The phase compositions of the oxide evolve with increasing time. Cr2O3 was present at the initial stage and not detected while Fe2O3 appeared at longer time. EBSD indicated that continuous Cr2O3 formed at the interface of oxide and matrix for HR3C at 600 degrees C for 40 h but only scattered Cr2O3 can be observed for 200 h. After the formation of a thin Fe-Cr-Ni oxide film on the Super 304 H steel surface, the Fe-rich outer nodular oxide begins to grow and forms a continuous layer after 1000 h. The growth process of Super304H steel in supercritical water was discussed.