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3D print tungsten
3D printing technique keeps brittle tungsten crack-free – Physics World
Tungsten component produced by 3D printing using electron beam melting. Photo: Markus Breig, KITTungsten has many excellent properties. It resists corrosion, and its melting point of 3422 °C is the highest of all metals, making it an ideal material for components that operate at extreme temperatures. There is a problem, though: it is highly brittle at room temperature, which means it is hard to process using conventional techniques.
Researchers at the Karlsruhe Institute of Technology (KIT) in Germany have now addressed this problem by adapting an additive manufacturing technique called electron beam melting (EBM) for use in tungsten processing. The resulting crack-free metal could be used in high-temperature components such as rocket nozzles, heating elements for furnaces, or parts for fusion reactors and medical imaging systems.
Additive manufacture
The KIT researchers, led by Steffen Antusch from the Institute for Applied Materials – Materials Science and Engineering (IAM-WK), have studied several ways of using additive manufacturing (also known as 3D printing) to make tungsten components that require little to no post-production processing. In their latest work, they used EBM to reduce strain in tungsten during processing and thus produce a soft material with no cracks that is easier to handle.
The EBM technique uses electrons accelerated in a vacuum to melt metal powder. By moving the electron beam, it is possible to produce a 3D component from the metal in an additive way – that is, layer-by-layer. The technique was originally developed for titanium alloys and materials requiring high processing temperatures.
Pre-heating reduces deformation and inherent stress
To create 3D-printed parts from tungsten instead, Antusch and colleagues used the electron beam in the EBM machine to pre-heat the tungsten metal powder before melting it. The researchers explain that this pre-heating procedure reduces deformation and inherent stress in the metal, making it possible to process materials that break easily at room temperature but can be deformed when hot.
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Compared to other techniques, such as laser printing, the new approach is much better at producing crack-free tungsten, Antusch tells Physics World.
And unlike powder injection moulding — another widely-employed advanced manufacturing technology for fabricating complex, high volume net-shape components – Antusch notes that with the new method “you don’t need expensive tools and are free to design the printed parts”.
The IAM-WK researchers are involved in work for the Helmholtz Association and the European Fusion Programme (EUROfusion), with the long-term goal of developing materials and processes for high-temperature applications in fusion energy and medical engineering (such as making parts for CT scanners). They now plan to characterize and test the mechanical properties of their printed tungsten materials for use in such applications.
3D Printing with Tungsten and Tungsten Carbide
What is tungsten and tungsten carbide used for?
As mentioned in the introduction paragraph, tungsten has a high melting temperature. It has the highest melting temperature of all metals at 3,422 °C . This in combination with hardness makes it an interesting material for applications that need hardness and heat resistance.
Tungsten composites are used in industries ranging from aerospace, automotive, nuclear, defense, medical to leisure.
Examples of applications are: rocket engine nozzles, weapon heads (to penetrate hard surfaces), turbine blades for aircraft (heat resistant), and smaller tools such as saw blades, drill bits, bearings, pistons and welding equipment.
The medical industry uses pure tungsten for MRI scanning, collimators, and radiation shielding.
3D printing with tungsten
The hardness of tungsten carbide and other such composites also has its drawback. Its hardness makes it a difficult material to create models using traditional manufacturing techniques like CNC and tooling. Additive manufacturing by its nature could prove to be a solution to this problem.
Additive Manufacturing also offers the ability to manufacture complex parts without the need for tooling. Tungsten composite models can be produced more cost-effectively and faster using AM.
Parts made by AM can be highly detailed and thin.
Details as small as 100 μm with a positional accuracy down to 25 μm can be achieved.
There are currently two AM technologies available for pure tungsten and tungsten composites:
Selective Laser Melting
Selective Laser Melting (SLM) or Direct Metal Laser Sintering (DMLS) is an additive manufacturing method whereby a laser melts and fuses together metal powder to form 3-dimensional objects.
Initially, the high melting point posed some technical hurdles to apply the material to 3D printing, but these have been overcome.
Pure tungsten powder is bound using nickel-copper or nickel-iron
Binder jetting
Leading 3D metal print machine manufacturer ExOne is working with a material manufacturer to develop a copper-tungsten composite, that can be used in ExOne’s binder jetting machines.
The composite will have high heat resistance, high electrical and thermal conductivity, and low thermal expansion. Binder Jetting has the advantage over SLM that it is more economical.
There are currently different powders available, at different stages of qualification.
Also available for binder jetting is a bronze-tungsten alloy.
Properties of tungsten:
- High melting point, melting at 3422 °C, higher than that of platinum.
- High density (19,25g/cm3), comparable to gold
- It has the highest tensile strength at temperatures over 1650°C
- Excellent corrosion resistance
- Excellent X-ray and Gamma-ray absorption/shielding
- Resistance to most acids
- Biocompatible / non-toxic
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Scientists of the National Research Technological University “MISIS” proposed a technique that allows you to carry out 3D-spray tungsten parts of complex shape using selective laser melting technology.
The developed method makes it possible to grow structures with walls one hundred micrometers thick, that is, at the level of the thickness of a human hair.
The technique can be used in the production of parts for experiments on particle accelerators, the press service of the university reports. Tungsten is the most refractory metal with a melting point of 3422°C and is critical to the successful operation of many modern industries, from metalworking and aerospace to engine building and medicine. Tungsten effectively absorbs radiation and is not susceptible to corrosion, but exhibits extreme brittleness at room temperature, which makes it difficult to machine.
One of the most promising ways to create complex shaped parts from tungsten is 3D printing. NUST MISIS scientists managed to obtain a complex-shaped part with a wall thickness of 100 µm from tungsten powder using the method of selective laser melting of metal-powder compositions (SLM).
“Despite the refractoriness of tungsten, we were able to select the technological parameters of 3D printing for the production of thin-walled parts using selective laser melting technology.
Studying the conditions for the formation of a molten pool for tungsten under the influence of laser radiation made it possible to increase the resolution of 3D printing with tungsten to a physically possible limit,” said Ivan Pelevin, a researcher at the Laboratory of Catalysis and Processing of Hydrocarbons at NUST MISIS, Candidate of Physical and Mechanical Sciences.
In the future, the technology can be used to create a new generation of high-energy particle detector - a calorimeter - for experiments at the Large Hadron Collider at CERN and at Russian particle accelerators. A radiation absorber made of thin-walled tungsten is able to effectively absorb high-energy particles and form the so-called electromagnetic shower, which is formed when high-energy particles interact with the absorber material. A calorimeter with such an absorber will make it possible to increase the particle flux density in experiments and, in the future, to gain new knowledge about the properties of hadrons with heavy quarks.
In addition, 3D-printed screens made of tungsten can be used as an anti-scattering matrix for proton beam therapy, an innovative method of treating oncological diseases using an extracted beam of charged particles on medical accelerators. The density of the tumor differs from the density of healthy tissue, which makes it possible to target non-invasive impact on the tumor tissue with high-energy charged particles. However, there is a problem with the scattering of these particles: when irradiated, it is difficult to focus them on the desired area. The screen printed from tungsten will allow focusing particle streams on tumors, thus increasing the effectiveness of therapy and avoiding negative effects on neighboring healthy tissues.
In the future, the proposed method of thin-walled 3D printing can be applied to other refractory materials.
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| 3DNews Technologies and IT market. News at the forefront of science Russian scientists have learned a thin 3D pe... The most interesting in the reviews 06/09/2022 [12:21], Gennady Detinich It is reported that NUST MISIS scientists for the first time in the world have proposed a technology for creating thin-walled 3D parts of complex shape from tungsten using selective laser melting. The difficulty is that tungsten is a metal of exceptional refractoriness and is very brittle at room temperature. Image source: NUST MISIS “Despite the refractoriness of tungsten, we managed to select the technological parameters of 3D printing for the production of thin-walled parts from it using selective laser melting technology. The study of the conditions for the formation of a molten pool for tungsten under the influence of laser radiation made it possible to increase the resolution of printing tungsten to a physically possible limit, " - said a representative of the development group, a researcher at the Laboratory of Catalysis and Processing of Hydrocarbons, National University of Science and Technology MISiS, Ph.D. .n. Ivan Pelevin. The melting point of tungsten is 3422 °C. At the same time, it effectively absorbs radiation and is little susceptible to corrosion. The developed method makes it possible to print structures with a wall thickness of 100 µm. Three-dimensional thin-walled 3D tungsten models can be used to create a new generation of high-energy particle detector - calorimeter. Calorimeters are an essential tool for accelerators, including the Large Hadron Collider. Radiation absorbers are made from thin-walled tungsten, which are capable of absorbing high-energy particles. In the process of absorption, a so-called electromagnetic shower is formed, which gives an idea of the characteristics of the initial particles - this will allow us to gain new knowledge about the properties of hadrons with heavy quarks. In medicine, thin-walled tungsten focusing screens help to concentrate radiation on tumor tissue and protect healthy tissue. A new technology for 3D printing from tungsten powder using lasers promises to be implemented soon, but scientists themselves do not give any predictions. |
It’s just that you can’t make products of complex shape with thin walls from tungsten, but they are needed for breakthrough scientific experiments and in medicine. 
This can be used to make parts for experiments at Russian particle accelerators and to create focusing elements for radiation therapy of tumors. 
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