Oxidation Protection Coatings
For the protection of such components, graphite-based and CFC materials are the first choice, however there are also other ceramics resistant to high temperatures that are used, such as SiC. In an oxidative environment, the use of carbon-based materials and compounds as well as of non-oxidised ceramics is very limited, when unprotected. That's why, the components are coated with layer systems, mostly be applying the CVD process. This Chemical Vapour Deposition (CVD) allows to apply thin layers onto a substrate through thermal decomposition of gasses. The layer thickness is between some hundred nanometres and some hundred micrometres. Since the pile-up of these layers is carried out very slowly, it is possible to generate very dense and highly-structured layers, which account for the excellent properties.
The coating components suited for such processes comprise above all silicon carbide, boron carbide and pyrocarbon as well as their combinations. For extremely high temperatures, combined layers composed of these materials and oxidised ceramics are used.