The research project DaNiSh aims to develop a new type of nickel-based superalloy for applications in harsh environments. By adapting alloying elements, an alloy will be created, which exhibits sufficient thermo-mechanical strength for the application in the hot gas section of gas turbines. Furthermore, the alloy will be processable by Laser Powder Bed Fusion (LPBF) without formation of hot cracks.
Nickel-based superalloys with a high amount of γ' precipitations are suitable for applications in turbo machinery construction due to their high thermo-mechanical strength. Existing alloys have been designed for casting and are usually not suitable for welding or LPBF, because cracks often occur during the process or during the subsequent heat treatment. The use of LPBF for the production of highly loaded components in the hot gas section of gas turbines is therefore currently excluded. Overcoming this limitation is crucial, since LPBF offers several advantages over conventional technologies: Novel designs are possible, no tools or moulds are required, and the straightforward path from the digital model to the physical part increases the flexibility and efficiency, particularly in small series production.
The main objective of the research project DaNiSh is to develop a nickel-based superalloy with a high amount of γ' precipitations that can reliably be processed by LPBF. The challenge is to achieve material properties that allow the use in turbomachinery. For this purpose, the microstructure has to be adapted in such a way that creep resistance and creep rupture strength are comparable to those of conventional cast alloys. Furthermore, a suitable strategy must be found to process the new alloy and avoid hot cracks during LPBF or the subsequent heat treatment.
The development of a novel high γ'-content nickel-based superalloy is based on a simulation-supported material development. Starting from a casting composition, specific chemical adjustments are made in order to achieve weldability while ensuring the required microstructure. Process parameters are developed for the "cold", i.e. without high temperature pre-heating, and "hot", i.e. with high temperature pre-heating, LPBF process. The presumed crack initiation and growth mechanisms are examined in detail by coupling material and process simulations with cross-scale material analyses. In addition, possibilities for avoiding or at least reducing crack formation during additive processing of the advanced nickel-based superalloy are being determined.
The research project "Development of advanced Ni-based Superalloys with improved properties for harsh environments" is funded by the Federal Ministry of Education and Research (BMBF) (funding code 03XP0215H) and supervised by the Project Management Jülich. We thank the BMBF and the Project Management Jülich for their excellent support.