A team from Lawrence Livermore National Laboratory, Stanford University, and the University of Pennsylvania has introduced a new wet chemical etching process to modify the surface of traditional metal powders used in 3D printing. By creating nanoscale grooves and textures, the researchers reportedly increased the absorption rate of these powders by up to 70%, allowing for more effective energy transfer during the laser-fused 3D printing process. . Credit: Brendan Thompson/LLNL
In a significant advance in metal additive manufacturing, researchers at Lawrence Livermore National Laboratory (LLNL) and their academic partners have developed a technique that increases the light absorption of metal powders used in 3D printing.
The researchers say this approach to creating nanoscale surface features on metal powders promises to improve the efficiency and quality of printed metal parts, especially in difficult materials such as copper and tungsten.
Additive manufacturing (AM), commonly known as 3D printing, has transformed the way products are designed and manufactured, enabling the creation of complex shapes and customized components that are difficult to achieve using traditional manufacturing methods.
However, one of the persistent challenges in laser powder bed fusion (LPBF) metal 3D printing is the high reflectivity of certain metals, which results in inefficient energy absorption during the printing process and some It may also damage the printing press. According to the researchers, this inefficiency often results in poor print quality and increased energy consumption.
Addressing this issue head-on in research published on the September cover of Science Advances, a team led by scientists from LLNL, Stanford University, and the University of Pennsylvania describes a new wet chemical etching process that modifies the surfaces of conventional metals. has been introduced. powder. The researchers reported that by creating nanoscale grooves and textures, they increased the absorption rate of these powders by up to 70%, allowing for more effective energy transfer during the laser melting process.
“Currently, high-quality pure copper metal AM is generally considered infeasible with standard commercial laser-based machines,” said co-lead author and LLNL materials scientist Philippe Desponds. . “Our method combines the effects of traditional surface treatments (which increase absorption), but without compromising copper’s purity or material properties (copper’s high thermal and electrical conductivity).
“More fundamentally, we have shown that the laser-powder interaction extends beyond the melt pool, which has been shown in simulations, particularly high-fidelity simulations performed at LLNL. However, they have not been shown in much detail experimentally. We have demonstrated that those interactions exist and are possible to be beneficial to the process. ”
Researchers say the wet-etching technique is relatively simple but highly effective. The researchers dipped metal powders, such as copper and tungsten, into a specially formulated solution that selectively removed the material from the surface.
This process forms complex nanoscale shapes that enhance the powder’s ability to absorb laser light. To characterize the surface features of the etched powder, the researchers employed advanced imaging techniques such as synchrotron X-ray nanotomography. This provided a detailed 3D representation of the powder particles, allowing the team to analyze and accurately model the electromagnetic effects of the nanoscale modifications.
The research team conducted extensive experiments to demonstrate the mechanism of increased absorption and attribute it to the modified powder. Process optimization studies and ultimately high-volume, complex sample printing were performed using a custom-built LPBF system installed in LLNL’s Advanced Manufacturing Laboratory and MIRILIS Laser Material Interaction Laboratory.
Researchers said improving the absorbency of metal powders is a promising step toward reducing energy consumption in manufacturing, especially as demand for more sustainable and efficient manufacturing processes continues to grow. .
One of the research team’s key findings is that lower energy inputs (less than 100 J/mm3 for copper, which is closer to the range for dense titanium and stainless steel alloys, and about 700 J/mm3) It was possible to print structures using high purity copper and tungsten. In the case of tungsten, it is J/mm3, which is about 1/3 less energy than normally used.
“In a broader sense, we are enabling copper printing without the risk of damaging the AM system itself,” DePond explained. “The window for process parameters will also be wider, allowing consideration of a more diverse range of scanning conditions that are often required when printing complex geometries.Finally, a small number of machine manufacturers will be able to create entirely new machines. It turns out that when processing copper and other highly reflective materials, traditional machines cost nearly twice as much, making the barrier to entry for printing these materials very high. It’s getting expensive.”
The potential applications of the discoveries could have an immediate impact on production. Researchers say being able to print with less energy not only reduces operational costs, but also minimizes the environmental impact of the manufacturing process, opening copper 3D printing to a whole new class of producers. states.
Dan Flowers, Energy Security Program Leader, said: “This method allows commercial machines with much lower laser power to print copper, democratizing the process and providing access to a wider community. ”, he said, adding that he hopes this initiative will enable the industry to use it more effectively. Copper in cutting-edge manufacturing.
“From heat exchange to catalysis, more efficient printing of copper will support the development of many clean energy and decarbonization technologies,” Flowers said. “The LLNL community and our low-carbon energy mission will benefit from this capability.”
Enhanced absorption and improved powder kinetics may also enable the production of high-quality printed parts with higher relative densities. Researchers have shown in experiments that they achieved up to 92% relative density with half the energy input compared to other printed copper parts, and more than 99% relative density with higher energy, making them stronger and more durable. It showed the possibility of manufacturing certain metal parts.
The researchers are next looking to investigate the effects of nanotexturing on elemental mixes in powders, such as materials that typically require significantly different energies to melt.
Further information: Ottman A. Tertuliano et al. Highly absorbent nanotextured powders for additive manufacturing, Science Advances (2024). DOI: 10.1126/sciadv.adp0003
Provided by Lawrence Livermore National Laboratory
Source: New Etching Technique Enhances Absorptivity of Metal 3D Printing Powders (October 9, 2024) From https://phys.org/news/2024-10-etching-technique-absorptivity-powders-metal.html Retrieved October 9, 2024
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