Additive Manufacturing & Local Modification
Additive or generative manufacturing by thermomechanical processing of materials in coating, joining and forming processes, tailored to the respective field of application, is the focus of the research work of the AM group. By modifying the microstructure, the properties of the base material are tailored to the requirements for the subsequent use of the layers, layer composites or additive manufactured components. Higher strengths, reinforcements and higher local damage tolerances can be specifically tailored. The AM Group conducts research and development on equipment developed in-house. The AM Group's process expertise includes friction surfacing (FS) and its variants, hybrid friction diffusion bonding (HFDB) developed at Hereon (former Hereon) and patented in a variant together with LINDE AG, friction stud welding and friction extrusion (FE).
The AM Group develops processes and procedures in basic and application-oriented research in the areas of friction surfacing and its variants, e.g. friction surfacing layer deposition (FSLD), towards friction surfacing additive manufacturing (FSAM), as well as HFDB and friction stud welding. The AM Group is involved in the development of friction extrusion development across research groups.
The AM Group's scientific work primarily aims at process understanding through clarifying underlying bonding mechanisms. This knowledge is used in process development for different industrial sectors including the aircraft industry (FS, FSLD, FSAM, HFDB, FE) for e.g. increasing the damage tolerance of metallic aircraft structures by local thermomechanical optimisation, the energy sector (HFDB) for e.g. cryogenic and high temperature heat exchangers, and the shipbuilding sector (FSLD, HFDB) for e.g. dissimilar multi-material joints.
FS is a solid-state joining process used to metallically bond layers or deposits to a substrate. The FS process uses frictional heat in combination with severe plastic deformation (SPD) to produce a fine-grained non-equilibrium microstructure. The process variants FSLD as well as FSAM are used for generative manufacturing of structural components.
FE is investigated with the aim of producing controlled fine- and ultra-fine microstructures through the process' inherent frictional heat and massive plastic deformation work of the processed material. Materials produced by FE can be used for structural applications that require the highest strength at high possible strain rates and low mass, e.g. fasteners in the aerospace industry.
HFDB is a friction induced joining process developed in its standard form to bond thin sheets together or thin sheets to substrates. By adapting the HFDB tool alignment as well as the process control, dissimilar metallic butt joints as well as overlap joints have been successfully produced.
A variant of the HFDB process has been developed in close cooperation with LINDE AG for tube in tube sheet welds e.g. for large cryogenic heat exchangers.
The scalability of the above-mentioned joining processes as well as the basic idea of a future further development in a scalable joining process development system at the AM Group should unite ideas regarding "one-button processing/manufacturing". This should enable higher levels of automation/integration in later industrial manufacturing processes. The data collected from the experiments should enable automated data processing for e.g. solid-state process simulations, as well as improved traceability and reproducibility in scientific work through suitable interfaces to electronic lab notebooks (ELN).