Additive manufacturing by laser powder bed fusion (3D printing)
Additive manufacturing enables the production of metallic components with complex geometries starting from powder or wire. At the MATERIALS Institute, we are involved in the further development of these processes for new materials and applications.
In the early days, these processes were often only used to produce models and prototypes under the name "rapid prototyping", but today this technology is also used for industrial production of components as "3D printing".
Laser powder bed fusion (L-PBF, laser powder bed fusion), which is also known by its popular name “3D printing”, is one of two additive manufacturing technologies for the fabrication of metallic components with high quality. This technology allows the production of components having structures below 100 μm und roughness below 50 μm, besides offering nearly complete freedom of design.
This offers the possibility to produce multifunctional metallic components which were either impossible or only feasible with unprofitable expenses using classic (subtractive) production methods.
All this results are feasible because the final component is produced by laser melting out of the powder bed – layer per layer. Limitation of precision is only given by the grain size of the used powder and the spot size of the laser beam.
Two main applications of this technology currently lie in medical engineering and aerospace industries: In medical engineering, it is possible for the first time to produce implants and dentures tailored to the individual patient. In aerospace industries, in turn, there is now the feasibility to produce functional components with drastically reduced weight. This is enabled on one hand by nowadays simulation tools, giving the possibility to spare volume in spots that will not be stressed, and on the other hand by substituting full volumes with lattice special structures, which show similar macroscopic physical properties.
The aim of the work carried out at MATERIALS for and with industrial partners is to research and solve innovative scientific and technological issues in order to be able to use metal 3D printing even more efficiently in the future and to realise new products.
Hybrid AM processes
The L-DED process is characterised by high build-up rates and the possibility of combining different materials, but very fine and complex geometric structures cannot be realised. In contrast, such structures can be produced with the L-PBF process with higher accuracy and better surface quality, but composite components made of different materials can only be produced with a great deal of effort and at significantly lower build-up rates. Hybrid AM processes combine the advantages of both processes and enable new applications.
Hybrid materials - material composites and composite materials
Functional components often consist of different materials, which are joined together in conventional production using positive or non-positive joining methods or by welding, soldering or bonding. With the help of the aforementioned hybrid AM processes, material composites (hybrid materials) are produced. In addition to material composites, composites are also very important in technology. Examples are fibre- or particle-reinforced metal alloys (MMC metal matrix composite).
Process, component and material simulation
Additive manufacturing processes are relatively new technologies in which a great many process parameters have to be taken into account. Simulation methods are an interesting tool for process development, but also for quality-assured production of new components. While very good simulation programs are already available for the prediction of residual stresses and component distortion and also for the temperatures occurring in the component during printing, the simulation of the microstructures and component properties that occur is still in its infancy.