Effects of exposure temperature and time on corrosion behavior of a ferritic-martensitic steel P92 in aerated supercritical water

Oxidation behavior of a ferritic-martensitic steel P92 exposed to aerated supercritical water at 400-550 °C and 25 MPa was investigated by gravimetry, X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The weight gain approximately followed near-power oxidation kinetics. The oxidation rate was strongly dependent on temperature and followed Arrhenius behavior. The oxide film consisted of porous outer layer with hematite and magnetite and dense inner layer with Fe-Cr spinel. Exposure temperature and time showed significant influences on oxide surface morphologies, thickness and constituents. Higher temperature accelerated the formation of pores in oxide film. Related oxidation mechanism was also discussed.