Additive manufacturing of metallic components by selective electron beam melting — a review

Abstract

Selective electron beam melting (SEBM) belongs to the additive manufacturing technologies which are believed to revolutionise future industrial production. Starting from computer-aided designed data, components are built layer by layer within a powder bed by selectively melting the powder with a high power electron beam. In contrast to selective laser melting (SLM), which can be used for metals, polymers and ceramics, the application field of the electron beam is restricted to metallic components since electric conductivity is required. On the other hand, the electron beam works under vacuum conditions, can be moved at extremely high velocities and a high beam power is available. These features make SEBM especially interesting for the processing of high-performance alloys. The present review describes SEBM with special focus on the relationship between process characteristics, material consolidation and the resulting materials and component properties.

Additively Manufactured Inconel 718 : Microstructures and Mechanical Properties

“…Until now Arcam AB is still the only pattern holder for EBM processes and hardware, and powder supplies for EBM processes are also available from Arcam AB's own manufacturing company. Research activities on self-built electron beam melting machines based on the similar principles can also be found in literatures, but gave inferior performances to the Arcam AB's hardware [45]. In this chapter, the EBM process is reviewed but not just limited to that conducted with Arcam AB's hardware, to provide readers a broad view of the nature and applications of this process.…”

“…The powder properties, i.e. size, shape, morphology, composition, porosity and flowability, significantly affect the process stability and resulted material properties [45]. While finer size of the powder might give better geometry accuracy and surface roughness, it is also easier for finer powders to trigger the unfavourable smoke phenomenon than coarser powder.…”

“…The roughness is largely affected by the process parameters: it increases with increasing the beam current and decreasing scan speed and focus offset [73]. Körner Electron beam melting et al [45] suggested that the coarser powder, thicker powder layer and larger beam size lead to higher EBM surface roughness than that of SLM. Though post surface machining is able to improve the surface condition for simple-geometry builds, it offers no solutions for complex-geometry components.…”

“…When the entire process is finished, the build will be embedded within a slightly sintered powder bed. The sintered powders can be easily removed by sand blasting, and with appropriate sieving these powders can be nearly completley recycled [45].…”

“…This is to slightly sinter the powders for better electric conductivity and process stability, and to maintain the relatively high building temperature within the whole building chamber [45]. Sintering is a solid state process that atoms at the particle interfaces diffuse to the contiguous particles and form a "neck", binding them together at the temperature between half melting point and full melting point [56].…”