Challenges for single-crystal (SX) crack cladding

Abstract

The formation of cracks in single-crystal (SX) turbine blades is a common problem for aero-engines. If cracks are located under the tip-area, the blade-repair is not possible. A new method to repair these cracks is to clad with single-crystal-technology. To reduce the loss of material and working time, notches are used to remove the affected crack zone. The used notch geometries must be weldable and also permit the material solidification in the same oriented plane as the original microstructure. For that, a thermal gradient has to be introduced in order to guide the grain growth. The process characteristics of laser cladding, such as small local heat input and controlled material supply, make it an efficient process to fill the notch. However, there are challenges to achieve a SX structure without cracks and pores. The unstable energy distribution may result in a polycrystalline structure. Current achievements and further challenges are presented in this paper.