High temperature oxidation behaviors of bulk SiC with low partial pressures of air and water vapor in argon

[Display omitted] •CVD SiC oxidation behaviors in an Ar/H2O/air atmosphere up to 1400 °C are studied.•A parabolic and passivating oxidation behavior is found.•SiO2 formation and crystallization, pores, and cracks are observed on SiC surface.•The crack formation depends on oxide layer thickness.•A water vapor-dominant oxidation model is proposed with high accuracy. Oxidation behaviors of bulk SiC at 1000–1400 °C in Ar-20 vol% H2O-10 vol% air were investigated. The thickness of the passivation oxide layer showed a parabolic increase with time. Dense and uniform layers formed below 1200 °C, whereas pores and cracks were observed at higher temperatures. An analytical model was proposed to estimate the oxide layer growth and SiC mass loss rate. The SiC layer should be effective in retaining the fission products after oxidation by excessive water and air. This work is the first detailed study of SiC layer oxidation during loss of coolant accidents (LOCA) for HTGRs.