Parameter development for regeneration of high-pressure turbine components of two nickel-based superalloys by laser metal deposition (DED-LB/M)

High-pressure turbine components in civil aircraft engines are economically highly relevant capital goods due to their single-crystalline material conditions and complex manufacturing. Their service life is directly determined by the degree of damage caused during use. To improve sustainability, there is a particular interest in optimizing the regeneration of damaged areas to ensure optimum use of these investments. Currently used methods such as arc or brazing processes result in a limited service-life extension with a corresponding degradation of component properties compared to the initial state.
Novel repair strategies based on additive manufacturing (AM) techniques demonstrate considerable potential in this regard, due to their high degree of geometrical freedom and well-controllable process. Previous research has demonstrated the potential of the powder-based Laser Metal Deposition process (LMD; DED-LB/M) as a promising approach for epitaxial growth of similar materials through a series of successive deposition and remelting steps. It has been demonstrated that a turbine blade tip of up to 2.3 mm and a maximum single-crystalline proportion in the microstructure of 95 % can be regenerated. In addition, the approach for the regeneration of artificial crack-like structures was applied to successfully fill and close 300 μm depth.
This study addresses the development of process parameters for two different nickel-based superalloys in use of similar powder compositions. The objective is to maintain and subsequently increase directionally solidified, single-crystalline microstructure in the regenerated areas. In addition, the increase of processing speed while maintaining the desired level of single crystallinity is a further objective. Therefore, the process development is performed on directionally solidified, single-crystalline substrates with a similar chemical composition to the high-pressure turbine components. After process development, verification is conducted in the form of multi-layered cubes. For both analyzed alloys, a maximum single crystallinity of 96.15 % can be achieved.