Performance of High-Layer-Thickness Ti6Al4V Fabricated by Electron Beam Powder Bed Fusion under Different Accelerating Voltage Values.

Hongxin Li,Yang Li,Feng Lin,Xiaoyu Liang

doi:10.3390/ma15051878

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https://doi.org/10.3390/ma15051878

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The electron beam powder bed fusion (EB-PBF) process is typically carried out using a layer thickness between 50 and 100 μm with the accelerating voltage of 60 kV for the electron beam. This configuration ensures forming accuracy but limits building efficiency. The augmentation of the accelerating voltage enlarges the molten pool due to the rise in penetrability, suggesting that a higher layer thickness can be used. Therefore, the effects of layer thickness and accelerating voltage were investigated simultaneously in this study to explore the feasibility of efficiency improvement. Ti6Al4V was fabricated by EB-PBF using layer thicknesses of 200 and 300 μm. Two accelerating voltage values of 60 and 90 kV were used to study their effects under expanded layer thickness. The results reveal that dense parts with the ultimate tensile strength higher than 950 MPa and elongation higher than 9.5% could be fabricated even if the layer thickness reached 300 μm, resulting in a building rate of up to 30 mm3/s. The expansion of the layer thickness could decrease the minimum bulk energy density needed to fabricate dense parts and increase the α platelet thickness, which improved the energy efficiency. However, expanding layer thickness had a significant negative effect on surface roughness, but it could be improved by applying augmented accelerating voltage.

Highlights

Electron beam powder bed fusion (EB-PBF) is a kind of additive manufacturing technology which uses electron beams to selectively melt the powder layer by layer based on three-dimensional (3D) digital models and form 3D parts [1,2]
The typical layer thickness for the EB-PBF process varies between 50 and 100 μm [10,11]. This is larger than the typical layer thickness between 20 and 50 μm used in laser powder bed fusion (L-PBF) which uses a laser as the heat source to melt the metal powder
Rännar et al [21] manufactured 316 L stainless steel with a layer thickness of 100–200 μm using the A2 ARCAM machine, where the density of the sample with 200 μm layer thickness was 3.2% lower than that of the sample with 100 μm layer thickness. These results indicate that lack of fusion is the primary defect for EB-PBF parts manufactured with high layer thickness

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Electron beam powder bed fusion (EB-PBF) is a kind of additive manufacturing technology which uses electron beams to selectively melt the powder layer by layer based on three-dimensional (3D) digital models and form 3D parts [1,2]. As a powder bed fusion process, layer thickness plays a key role in EB-PBF. The typical layer thickness for the EB-PBF process varies between 50 and 100 μm [10,11] This is larger than the typical layer thickness between 20 and 50 μm used in laser powder bed fusion (L-PBF) which uses a laser as the heat source to melt the metal powder. A smaller layer thickness results in higher dimensional accuracy and surface roughness, but a lower building rate, which increases the building cost and limits its ability to form large-scale parts [12]

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