Protective multilayer coatings for carbon–carbon composites

Carbon fiber-reinforced composites (CFCs) are well-established lightweight materials combining high specific strength and damage tolerance, especially at elevated temperatures in the range above 1000 °C. For high-temperature applications, protective coatings have to provide oxidation and corrosion resistance for the CFC, with additional thermophysical and chemical compatibility requirements. Various technologies are introduced to produce coating architectures consisting of dense ceramic top layers and porous base coatings. The top layers should provide chemically inert surfaces, which are able to act as diffusion barriers. The porous base coatings serve as a structural link with compensation ability between the brittle top coating with a low strain-to-failure and the thermophysically anisotropic carbon–carbon substrate. Furthermore, they provide the chemical compatibility between the substrate and the functional ceramic top coating.