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Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion

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Abstract

In the laser powder bed fusion additive manufacturing process, the presence of porosity may result in cracks and significantly affects the part performance. A comprehensive understanding of the melt pool process dynamics and porosity evolution can help to improve build quality. In this study, a novel multi-physics computational fluid dynamics (CFD) model has been applied to investigate the fluid dynamics in melt pools and resultant pore defects. To accurately capture the melting and solidification process, major process physics, such as the surface tension, evaporation as well as laser multi-reflection, have been considered in the model. A discrete element method is utilized to model the generation of powder spreading upon build plate by additional numerical simulations. Multiple single track experiments have been performed to obtain the melt pool shape and cross-sectional dimension information. The predicted melt pool dimensions were found to have a reasonable agreement with experimental measurements, e.g., the errors are in the range of 1.3 to 10.6% for melt pool width, while they are between 1.4 and 15.9% for melt depth. Pores are captured by both CFD simulation and x-ray computed tomography measurement for the case with a laser power of 350 W and laser speed of 100 mm/s. The formation of keyholes maybe related to the melt pool front wall angle, and it is found that the front wall angle increases with the increase in laser line energy density. In addition, a larger laser power or smaller scanning speed can help to generate keyhole-induced pores; they also contribute to produce larger sized pores.

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Acknowledgments

The authors would like to thank Michael Kuntzer for the preparation of L-PBF experiments.

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Authors and Affiliations

  1. Robert Bosch LLC, Research and Technology Center, Cambridge, MA, 02139, USA

    Bo Cheng & Charles Tuffile

  2. Robert Bosch GmbH, Renningen, 71272, Germany

    Lukas Loeber, Hannes Willeck & Udo Hartel

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  1. Bo Cheng
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  2. Lukas Loeber
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  3. Hannes Willeck
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  4. Udo Hartel
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  5. Charles Tuffile
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Correspondence to Bo Cheng.

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Cheng, B., Loeber, L., Willeck, H. et al. Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion. J. of Materi Eng and Perform 28, 6565–6578 (2019). https://doi.org/10.1007/s11665-019-04435-y

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  • DOI: https://doi.org/10.1007/s11665-019-04435-y

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