Fraunhofer-Center HTL develops ceramic coatings for use at high temperatures. Based on the customer request a concept for the development is drawn up and agreed on with the customer, involving material and thermodynamics databases first. Questions about the requirements of the coating, coating technology, substrate material, operating conditions, etc. are clarified at this time.
The focus of Fraunhofer-Center HTL is the formulation of liquid paints which can be applied using simple and commercially viable application methods such as dipping, spraying or brushing. As a basis for the coatings, sol-gel precursors, ceramic and metallic slurries or preceramic polymers are used. A high level of material selection and diverse options for adaptation are opened up by this. Thus, for example paints for coatings of Al2O3, Al2O3-SiO2, SiO2, rare earth (Di) silicates, yttrium aluminum garnet, TiO2, SiC, BN or SiBNC are offered as standard. The paints are matched to the respective application technique with regard to their processing properties. Therefore extensive characterization capabilities and development tools are available. The Fraunhofer-Center HTL develops coatings on behalf of customers and samples with existing coating systems.
The coatings are adjusted depending on the favored application technique by the customer with respect to their processing properties. Layer thicknesses of about 50 nm to more than 100 µm are possible, depending on the application method and the formulation of the coating. Metallic and ceramic components are primarily coated. After the application of the coating, the layers normally need to be fired. For that ovens with different atmospheres (air, inert, vacuum, reducing) and sizes are available at the Fraunhofer-Center HTL. Alternative firing processes such as laser sintering are also possible (see Baber, J.; Raether, F.: Production of oxide ceramic coatings on glass by laser sintering). For the development of the firing process it is important not to damage the substrate material. This is done in close coordination with the customer.
The ceramic coatings are used as corrosion and wear protection, for surface sealing (see Nöth, A.; Vogt, J.: High-temperature stable gas-tight sealings for plasma-sprayed ceramic components), as heating layers or as non-adhesive coatings for metal melts. To characterize the layers, extensive testing capabilities are available, also according to DIN EN standards. Often further tests are required for the application, in addition to the standardized tests. Therefore the test methods that are of relevance for the layer development or the use of the layer are realized in coordination with the customer. On behalf of customers, Fraunhofer-Center HTL coats components or test pieces and tests them under application-oriented conditions, if necessary.