CRC871: Near net shape turbine blade repair using a joining- and coating hybrid process (Subproject B1)

Components of aircraft engines and stationary gas turbines like turbine- and compressor blades (airfoils and vanes) are subjected to extreme conditions. To increase the life time of such components, maintenance, repair and overhaul (MRO) play a paramount role. The subproject B1 of the CRC871 develops and investigates a near net shape joining and coating hybrid process which allows to shorten the state of the art process chain of turbine blade repair significantly. Since the turbine blades taken into consideration in this subproject are components of high pressure turbines, the focus of this work lies on nickel based alloys. The shortening of this process chain is achieved by applying the nickel based filler-metal together with the hot gas corrosion protective coating (e.g. NiCoCrAlY alloys) and the thermal barrier coating (TBC) with aluminium as a bond coat onto the substrate using the thermal spray technology. The following material combination results: substrate/nickel based filler-metal/NiCoCrAlY/Al/TBC. Subsequently this coating systems is subjected to a heat treatment which represents a common brazing- and aluminising process. The working hypothesis of this research project is that a thermal coating and joining process can be transferred to a hybrid technology and to achieve qualitative as well as economic advantages at the same time.