kohlenstoffkörper with oxidationsschutzschichten from sic and process for the manufacture of oxidationsschutzes

摘要

Carbon bodies are protected from oxidation by converting at least part of the surface into SiC, coating with three or more layers of SiC or Si3N4 followed by a layer of glassy SiO2 or mixture of SiO2 and Si. The carbon matrix pref. has a porosity of 2-15 vol.% and contains 30-70 vol.% reinforcement carbon fibre. The carbon matrix surface is converted partially with SiC by surface packing with I or liquid impregnating with Si or by treating with Si vapour at high temp. and correcting to SiC. The layers of SiC or Si3N4 are produced by chemically precipitating from the gas phase and pyrolysing alkylsilanes or alkylhalogensilanes. The final coating of SiO2 or SiO2/Si is tempered to produce the glassy state. ADVANTAGE - The protection layer is dense and adheres well to the substrate. It has good resistance to thermo shock stressing.