Fraunhofer-Institut für Lasertechnik ILT
Laser Powder Bed Fusion (LPBF) enables the production of complex component geometries with increased functionality, such as components with integrated cooling channels or topology-optimised lightweight structures. In addition to the realisation of the geometry, the material structure is also created during the build-up process. This results in a further degree of freedom for component design, namely the local, application-oriented adjustment of the material structure and thus the mechanical properties within a component, which further expands the potential for function-optimised component design. The microstructure of an LPBF component is formed by melting a powder material track by track using a focused laser beam, which is guided continuously (continuous wave - cw) over the powder layer to be exposed. This generally results in directional, epitaxial grain growth, as the heat dissipation is mainly directed against the build-up direction into the underlying component volume. Studies at Fraunhofer ILT have shown that processing using a pulsed-modulated laser beam (pulsed wave - pw) can produce a fine-grained, isotropic microstructure and significantly suppress epitaxy in the material structure. Complementary use of cw and pw exposure allows the integration of complex spatial microstructures distributions with locally different properties within additively manufactured components. The implemented microstructure distrbution is not affected by phase transformations during post-process heat treatments such as Hot Isostatic Pressing. Hence, the approach demonstrated allows tailoring of local mechanical properties, e.g. according to locally inhomogenous load cases within additively manufactured components as well as the integration of microstructural watermarks for forgery-proof components.
Abstract
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Poster
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