Mid Sweden University

Metal additive manufacturing technologies, such as electron beam powder bed fusion (PBF-EB), rely on layer heating to overcome the so-called “smoke” phenomenon. When scaled up for industrial manufacturing, PBF-EB becomes less productive due to the lengthy preheating process. Currently, only the electron beam (EB) is used for preheating in PBF-EB, resulting in increased manufacturing times, energy consumption, and in some cases limiting the applicability of the technology. In this study, a new preheating approach is suggested that incorporates a near-infrared radiation (NIR) emitter inside an PBF-EB system. The NIR unit eliminates the need for EB heating, reducing build time and powder charging. Successful builds using 316 L and Ti6Al4V precursor powders validate the feasibility of the proposed approach. The produced samples exhibit similar properties to those obtained by the standard PBF-EB process. The introduction of NIR technology also reduced build cost and increased the service intervals of the electron gun. 

The use of an electron beam (EB) as a heating source in EB-based powder bed fusion (PBF-EB) has several limitations, such as reduced powder recyclability, short machine service intervals, difficulties with heating large areas and the limited processability of charge-sensitive powders. Near-infrared (NIR) heating was recently introduced as a feasible replacement and/or complement to EB heating in PBF-EB. This work further investigates the feasibility of using NIR to eliminate the need for a build platform as well as to enable easier repairing of parts in PBF-EB. NIR-assisted Ti-6Al-4V builds were successfully carried out by starting from a loose powder bed without using a build platform. The results do not only confirm that it is possible to eliminate the build platform by the aid of NIR, but also that it can be beneficial for the process cleanliness and improve the surface quality of built parts. Furthermore, a 430 stainless-steel (SS) component could be repaired by positioning it in a loose 316L SS powder bed using a fully NIR-heated PBF-EB process.

Most Powder Bed Fusion (PBF) methods for the Additive Manufacturing (AM) of metals are based on the melting of powder of one specific metallic material; either of pure-elemental or pre-alloyed composition. Although the potential to build components from different materials in AM has recently gained a lot of attention, it is still not feasible in the current metal PBF systems. In the specific case of Electron beam- based PBF (PBF-EB), it is possible to precisely control the beam parameters in each site of the build area, which opens great possibilities for adaptive processes that allows melting powders of different nature in the same build. In this investigation, different steel-based and Ti6Al4V alloy powders are used to create metal-metal assemblies. By steering the fetching of two powders loaded in different hoppers it was possible to build different metal-metal assemblies. The microstructure and mechanical properties of the final materials were evaluated. 

Electron beam powder bed fusion (PBF-EB) is a known metal additive manufacturing (AM) technology. Processing non-conducting powders such as ceramics has so far been considered as not feasible because of the inherent problems with Coulomb repulsion due to insufficient electrical conductivity. In this study, a method for functionalizing ceramic powder is proposed where particles are electroless coated by a ~ 1 µm Ni layer to decrease the surface resistivity. The feasibility of the suggested approach is tested on Al2O3 powder, and the results show that the coated ceramic powder has a decreased surface resistivity, which enables processing by PBF-EB. Heating and melting parameters were investigated and samples were manufactured at ~ 1600 °C. Sintered and melted powders were analyzed by microscopy and micromechanically tested by nanoindentation. Calculations, visual observation and SEM–EDX suggest that the Ni coating is evaporated during the process, which suggests that the process could be feasible for the manufacturing of pure ceramic parts.