Electron Beam Method for Creating Combinatorial Libraries: Application to Next Generation Thermal Barrier Coatings Systems

摘要

The next generation of thermal barriers coating (TBC) systems used on turbine engines must be able to endure higher operating temperatures. The thermally protective top coat layers of these TBC systems must therefore exhibit lower thermal conductivity and improved thermochemical stability. The underlying bond coat layers should have substantially improved oxidation resistance and increased high temperature strength. These properties strongly depend upon coating composition. However, as these layers become increasingly complex the relationship between composition and properties becomes difficult to predict and thus, the development of advanced materials systems is slowed. To accelerate the design and manufacture of advanced coatings we have developed a combinatorial synthesis approach. A library of compositions is created and their properties are measured using parallel measurement techniques to allow rapid investigation of a wide range of compositions. Compositionally graded libraries are directly deposited using multi-source electron beam evaporation in conjunction with an inert, transonic gas jet. The properties of the gas jet control the degree of intermixing between co-evaporated melt pools and thus, the compositional gradient of the library. Direct Simulation Monte Carlo simulations along with binary collision theory has been used to investigate the origin of the lateral compositional variation. Deposition conditions which lead to sharp, lateral composition gradients across a substrate have been identified.