Ring-shaped laser used to eliminate multiple defects in metal PBF-LB Additive Manufacturing
November 28, 2024
Researchers at the University of Wisconsin-Madison, Wisconsin, USA, have found a way to simultaneously mitigate three types of defects in parts produced using Laser Beam Powder Bed Fusion (PBF-LB) Additive Manufacturing. The findings were detailed in a recent paper published in the International Journal of Machine Tools and Manufacture.
Led by Lianyi Chen, an associate professor of mechanical engineering at UW-Madison, the team discovered the mechanisms and identified the processing conditions that can lead to this significant reduction in defects.
“Previous research has normally focused on reducing one type of defect, but that would require the usage of other techniques to mitigate the remaining types of defects,” Chen stated. “Based on the mechanisms we discovered, we developed an approach that can mitigate all the defects—pores, rough surfaces and large spatters—at once. In addition, our approach allows us to produce a part much faster without any quality compromises.”
Multiple industries, including aerospace, medical and energy, are increasingly interested in using Additive Manufacturing to produce metal parts with complex shapes that are difficult or impossible to create using conventional methods.
But the big challenge is that metal parts created with Additive Manufacturing can have defects, explained the researchers. These can include pores, voids, rough surfaces and large spatters, which can compromise the finished part’s reliability and durability. These quality problems could prevent additively manufactured parts from being used for critical applications, it was highlighted.
In this research, the UW-Madison team used an innovative ring-shaped laser beam, provided by nLight, instead of the usual Gaussian-shaped beam. The ring-shaped laser beam played a key role in this breakthrough, as did critical in-situ experiments, said Jiandong Yuan, the lead author of the paper and a PhD student in Chen’s group.
To see how the material behaved within the part as it was being additively manufactured, researchers went to the Advanced Photon Source, an ultra-bright, high-energy synchrotron X-ray user facility at Argonne National Laboratory. Combining high-speed synchrotron X-ray imaging, theoretical analysis and numerical simulation, the researchers revealed the defect mitigation mechanisms, which involve phenomena that reduce instabilities in the Laser Beam Powder Bed Fusion process.
The researchers also demonstrated that they could use the ring-shaped beam to drill deeper into the material without causing instabilities in the process. This enabled them to build thick layers, increasing manufacturing productivity. “Because we understood the underlying mechanisms, we could more quickly identify the right processing conditions to produce high-quality parts using the ring-shaped beam,” stated Chen.
Lianyi Chen is the Kuo K & Cindy F Wang Associate Professor of mechanical engineering. Collaborators from UW-Madison included Qilin Guo, Luis Escano, Ali Nabba, Minglei Qu, Junye Huang, Qingyuan Li, Allen Jonathan Román, and Professor Tim Osswald. Samuel Clark and Kamel Fezzaa from Argonne National Laboratory also collaborated on this project.
The work was supported by the National Science Foundation and the Wisconsin Alumni Research Foundation.
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