Temperature effect on oxidation protection life of multi-layer coating for C/C composites

A multi-layer coating for carbon-carbon composites with a Si-W outer layer, a SiC barrier layer and a SiC transition layer is prepared by the combination of siliconization, CVD and liquid reaction method. The effect of temperature on the oxidation protection life from 1600°C to 1700°C is investigated. The thickness of the oxide film on the coating surface is measured through SEM and EMPA. A concept of critical oxide film thickness and a critical oxidation protection time is put forward, and, based on it, the relation of the critical time with temperature is analyzed. The results show that the relation of the critical oxidation protection time with temperature found by the experiments is fully identical with that calculated based on the critical thickness. The physical significance and the effect factors of the critical oxide film thickness are discussed.