Three-dimensional printing of tungsten structures by directed energy deposition

Although three-dimensional (3D) printing of tungsten parts by Powder Bed Fusion (PBF) has been demonstrated by multiple research groups, a directed energy deposition (DED) process for fabricating pure tungsten structures has never been reported. This work reports successful fabrication of pure tungsten structures by DED, revealing the required process conditions. The effect of laser power, scan speed, powder feed rate and carrier gas velocity on the stability and properties of the structures is first analyzed, based on which the proper process condition for effective 3D printing of tungsten parts is proposed. Fabrication of a rectangular tube of 110 mm in height is demonstrated using an in-house DED printing system. Analyses of the fabricated samples show that the density and the hardness can be as high as 18.9 g/cm³ (98.4% of the theoretical value) and 3.9 GPa, respectively. The results indicate that the optimal condition for 3D printing of tungsten is 400 ~ 530 J/mm² in terms of specific energy and that high-speed or high-mass injection of powder can induce waviness on the surface. This work suggests that DED can be a promising alternative to produce pure tungsten parts in various applications.