Fraunhofer-Center HTL holds the whole powder metallurgical production chain to develop metal components. From powder optimization to raw material processing, via forming and heat treatment to finishing, ferrous and non-ferrous metals can be produced as well as metal-ceramic-composites. The focus lies on additive manufacturing processes. These are realized with the help of a powder bed printer with the binder jetting method (see Powder Bed Process). This way, green bodies can be produced with complex geometries. Densification is achieved through sintering processes or the infiltration of molten metals into the porous preforms.
The development of materials begins with the selection of suitable components. For this, extensive material and thermodynamics databases are available at Fraunhofer-Center HTL (see Material Design). The material properties of multiphase metals and metal-ceramic-composites can be precisely predicted using specially developed in-house software. This helps to optimize the structure of the materials. The component design is performed using finite element methods (see Component Design).
Especially for 3D printing flowable powders are needed. Therefore the material development often begins with the selection and optimization of preconditioned starting powders. For this purpose, particle shape, size distribution, density and flowability of powders and their interaction with the binder have to be investigated. For forming, in addition to the 3D printing, also conventional methods such as uniaxial or isostatic pressing are available at Fraunhofer-Center HTL. The quality of green bodies is examined with special in-house methods. Variations in porosity, among others, can be precisely measured on different size scales.
The heat treatment of green bodies is generally carried out in graphite heated furnaces. Thereby inert or reducing atmospheres, as well as vacuum and overpressure can be realized. The optimization of the parameters of the heat treatment is carried out directly with specific ThermoOptical Measuring (TOM) methods. For instance, dimensional changes can be detected during heat treatment in a special measuring furnace, TOM_metal, which can be operated with up to 30 bar or a pure hydrogen atmosphere (see Thermal Processes). During heat treatment, a low-melting metal can be infiltrated into the porous preform of a higher-melting metal (e.g. bronze in steel) or a ceramic (e.g. cobalt in tungsten carbide). This melt infiltration process is also investigated and optimized by in-situ measurement methods.
A computer-controlled 5-axis machining center is available for the finishing of the components. The material and component properties are evaluated with non-destructive methods, material testing and structural analysis (see Material Testing). The microstructures of etched samples are analyzed by optical and scanning electron microscopy. Their pore and particle size distribution, morphology, phase proportions and bonding are determined this way, too. We also characterize the elastic and plastic behavior and failure mechanisms at different loading cases.