Laser Powder Bed Fusion: New approach to reducing defects in 3D-printed metal parts

Researchers at the University of Wisconsin-Madison have developed an innovative approach to simultaneously minimize three common defect types in metal parts produced with Laser Powder Bed Fusion (LPBF). This additive manufacturing process is particularly in demand for the production of components with complex geometries, but defects such as pores, rough surfaces and spatter pose a challenge. These defects impair the reliability of the components and limit their use in critical applications.

Under the leadership of Professor Lianyi Chen, the team investigated the mechanisms behind these defects and identified the process conditions that enable a significant reduction. The use of a ring-shaped laser beam provided by nLight, as opposed to the usual Gaussian beam, played a central role. This laser shape reduced instabilities in the melt pool and allowed thicker layers to be printed without compromising quality. The results of this research were published in the International Journal of Machine Tools and Manufacture on November 16, 2024.

“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,” says Lianyi Chen, Kuo K. & Cindy F. Wang Associate Professor of mechanical engineering. “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.”

To better understand the processes, the researchers carried out high-resolution “in-situ” experiments. Using synchrotron X-ray images taken at the Advanced Photon Source at Argonne National Laboratory, they were able to analyze the dynamics of the melt pool. This combination of experiments, theoretical analyses and numerical simulations showed how instabilities in the process can be reduced.

The results have the potential to increase the acceptance of LPBF in industry. In addition to improved component quality, the researchers were also able to increase production speed by optimizing the process for thicker layers.

“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,” says Chen.

This research was funded by the National Science Foundation and the Wisconsin Alumni Research Foundation. The project emphasizes the importance of interdisciplinary collaboration, which involved Chen, researchers from Argonne National Laboratory and several doctoral students.