A Numerical Study on the Influence of Cohesive Non-Spherical Powders on the Powder Bed Quality in Additive Manufacturing

  • Jaggannagari, Sujith Reddy (Indian Institute of Technology Madras)
  • Annabattula, Ratna Kumar (Indian Institute of Technology Madras)
  • Gan, Yixiang (The University of Sydney)

Please login to view abstract download link

Powder bed fusion (PBF) is a metal additive manufacturing (AM) technique that uses metallic powders to produce components with high dimensional accuracy. Powder spreading and fusion are two processes involved in PBF. A dense powder layer is spread for selective fusion, and this process is repeated layer by layer to obtain the desired product. The powder bed quality depends on the spreadability of the powder, and the powder bed's homogeneity defines the quality of the finished parts. Powders used in PBF are in the order of microns and are composed of spherical and non-spherical shapes[1]. At the microscale, powder particles experience cohesive forces like van der Waals and electrostatic forces[1,2]. Several studies have been reported on cohesive spherical particles with a range of particle sizes. However, limited studies were performed on the effect of non-spherical particles with cohesive forces on the bed quality. In the present work, Discrete Element Method (DEM) simulations were carried out to analyze the spreading process of powders composed of cohesive particles with particle shapes and sizes similar to experimental findings. Further, simulations were carried out to study the powder spreading dynamics on the sintered layer. The influence of shape, mass fraction, and roundness of non-spherical particles on the powder dynamics and the bed quality is studied. The powder bed is characterized by its packing fraction, surface roughness, and segregation index. The results showed that the increase in the aspect ratio or mass fraction of non-spherical particles increases the porosity of the spread layer for a given layer thickness. This work helps analyze particle shape's effect on the bed quality and contributes to a better understanding of the powder spreading process. It provides insights to improve the powder bed's quality that enhances the finished part of PBF.