C/C composites with an oxidation protection SiC coating have been evaluated by using high frequency air plasma flow at temperatures between 1554 and 1945K, and at pressures between 1.0 and 5.0 kPa. The oxidation behavior of the coatings after heating tests was investigated. The thickness reduction of the coating was 5.5×10−2 \\micron s−1 at 1945 K and 2.5 kPa. The coating recession was larger at higher temperatures and lower pressures. X-ray photoelectron spectroscopy of the coating surface indicated that SiO2 film was formed on the coating surface below 1856 K, and that high SiC recession rates were observed above 1884 K . At 2.5 kPa under subsonic plasma flow conditions, the active oxidation occurred above 1884 K and gradually changed from the passive oxidation with increasing temperature.
