Different 3D printing processes for tungsten metal with complementary advantages and unlimited potential
Tungsten is the material of choice for high temperature applications due to its good thermomechanical properties such as high melting point, high density, high thermal conductivity and moderate thermal expansion. In addition, its high density and very low sputtering erosion rate make it suitable for radiation or other extreme environments, and can be used to manufacture waveguides, collimators, nuclear reactor plasma surface components, etc., covering multiple fields such as aerospace, aviation, military, medical, and nuclear industries.
The wide range of advantages of tungsten metal is also the reason why it is difficult to process. Pure tungsten has a melting point of 3410 degrees Celsius, and although tungsten alloys have a reduced melting point, they are all refractory metals and are difficult to manufacture by conventional methods. The 3D printing industry has a long history of interest in tungsten materials.
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Applications of tungsten
In recent years, 3D printing technology has provided a means of manufacturing tungsten metal, and different 3D printing processes based on both direct melting and sintering-based pathways using SLM, BJ, FDM extrusion, and DLP have explored the manufacturing feasibility of this material. Cemented carbide manufacturing companies are banking on this new technology to open up new avenues for tungsten manufacturing, and mainstream 3D printing equipment manufacturers have actively explored tungsten forming processes and have reported breakthroughs.
Melting-based, direct laser 3D printing
Selective laser melting (SLM/L-PBF) is one of the most successful additive manufacturing technologies for manufacturing high-precision and high-quality functional parts. For many years, well-known domestic metal 3D printing manufacturers have stated that they have conquered laser 3D printing of tungsten and successfully implemented applications, the examples given are invariably tungsten grids for medical use, and there are few ongoing reports.
The biggest problem with laser-based technology is the presence of temperature gradients that can lead to residual stresses and cracking. Researchers at Lawrence Livermore National Laboratory point out that in 3D printing studies on tungsten, all of which have reported densities greater than 98%, microcrack formation is difficult to avoid. 3D Printing Technology Reference spoke to researchers at a number of institutions working on the material and found that tungsten grids are relatively easy to print, although not as strong, to meet the medical requirement for radiation shielding, while tungsten blocks are highly susceptible to cracking during the printing process.
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A tungsten grating printed with laser 3D printing
While laser printing of tungsten can be improved by alloying and process optimization, both methods have had limited success. For high specific gravity tungsten alloys, properties vary greatly due to the diverse composition, with melting points varying up to 2400°C and different saturation vapor pressures for each element. Researchers from Tianjin University and Central South University also pointed out that it is difficult to ensure the controllability of each component in tungsten alloys using SLM, and it is equally difficult to manufacture full-density tungsten alloys with excellent mechanical properties.
While laser fabrication of tungsten grids is undoubtedly the most successful application of direct laser melting, the application of tungsten is not just for grids.
Sintering-based, indirect 3D printing
Indirect 3D printing based on sintering offers an alternative means of forming tungsten materials. The main processes include extrusion, light curing, and binder injection. All of these processes involve forming the part blank first and then sintering the tungsten metal to densify it using a traditional powder metallurgy process.
