Single-crystal repair of high-pressure single-crystal turbine blades for industrial conditions

Abstract

Single-Crystal (SX-) turbine blades are made of Ni-based superalloys for high-pressure stages of aircraft-turbines. During operation, turbine blades are subject of wear. Typical defects are cracks at the tip of blades. Conventional tip-repairs use welding materials with differing composition, which lead to local loss of SX-microstructure and impair the following service life. This work considers blades in flight condition with tips partially removed and conventionally repaired as the initial condition. The SX-repair follows a two-step strategy for the powder based DED-LB/M process. A powder welding material ‘PWA 1484’ is used, which is identical to investigated blades material. Laser powers of 120 – 160 W and powder feed rates of 1 – 4 g/min are subject of parameter investigations. The results show that conventionally repaired areas affect the build-up and a SX-microstructure negatively. In contrast, successful tip-repairs with SX-microstructures of up to 94.85 % and a maximum build-up of 2.3 mm are possible.