Single Crystal Crack Cladding of Cmsx-4

High-pressure turbine blades made of single crystal CMSX-4 belong to the most cost-intensive parts of aero engines. They are essential for the functionality and have to withstand high temperatures as well as high levels of wear and tear. To increase the economic life time, repairing cracks in modern single crystal (SX) blades is of high priority. Currently only polycrystalline structures of the nickel base alloy CMSX-4 can be established using laser cladding. The success of SX crack repair strongly depends on the realization of a large directed thermal gradient and the need of a precise process control. To meet these requirements, a closed loop of process simulation and subsequent experimental trials has been utilized. This should establish a theoretical base in order to support and reduce development efforts of future SX cladding processes. Initial scope of the investigations was the computational prediction of the temperature field and its verification. Using these results, the required directed thermal gradient could be defined. Subsequently, the necessary process setup including a stationary inductive heating source and a cooling process to realize the thermal gradient was developed. Starting with single SX-cladding on flat substrates (30x30x2 mm³), the process results were transferred towards crack repair on flat samples. The achieved results were validated using metallographic and EBSD (Electron Backscatter Diffraction) analysis. Next, the process will be tested for SX-repair of real CMSX-4 blades as well to verify the industrial applicability. Currently it could be proven, that single crystal cladding using flat CMSX-4 samples is possible by using inductive heating and a cooling mount.