Abstract
Selective electron beam melting (SEBM) is an additive manufacturing method where complex parts are built from metal powders in layers of about 50 μm. SEBM works under vacuum conditions which results in a perfect protection of the metal alloy. The electron beam is used for heating (about 900 ∘C building temperature) and selective melting. The high beam velocities allow innovative scanning strategies in order to adapt the local solidification conditions which determine the epitaxial solidification process of IN718. We show how scanning strategies can be used either to produce a columnar grain structure with a high texture in building direction or a complete texture-free fine grained structure. Numerical simulations of the selective melting process are applied to reveal the fundamental mechanisms responsible for the completely different grain structures. In addition the influence of the different grain structures on the mechanical properties of IN718 is briefly discussed.
Highlights
Nowadays, industry and science are increasingly interested in additive manufacturing (AM) of metal powders and join their efforts to bring AM processes into commercial production [1]
In case of selective laser melting (SLM), a wide spread AM technique, a laser is used as a heating source and is moved by mechanical lenses resulting in a limitation of the maximum deflection speed
Influence of beam deflection speed and line offset on grain aspect ratio
Summary
Industry and science are increasingly interested in additive manufacturing (AM) of metal powders and join their efforts to bring AM processes into commercial production [1]. Concerning powder based AM processes, there are still challenges to overcome like low build-up rates and a high anisotropy in mechanical proporties [2,3,4]. The build-up rate depends strongly on the deflection speed of the used heating source. In case of selective laser melting (SLM), a wide spread AM technique, a laser is used as a heating source and is moved by mechanical lenses resulting in a limitation of the maximum deflection speed. In selective electron beam melting (SEBM), an alternative AM technique, there are virtually no limitations with respect to the deflection speed, as the used electron beam is deflected by electromagnetic lenses, leading to deflection speeds > 6000 m/s [5]. High deflection speeds can be used to alter the local solidification conditions in such a way that either columnar or equiaxed grain structures can be produced. In the current paper we discuss the influence of scanning strategies on the solidification conditions on base of experimental and numerical results
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