Effect of Particle size of monomodal 316L powder on powder layer density in powder bed fusion
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FULL RESEARCH ARTICLE
Effect of Particle size of monomodal 316L powder on powder layer density in powder bed fusion Lukas Haferkamp1,2 · Adriaan Spierings1 · Marco Rusch2 · Dominik Jermann2 · Marvin A. Spurek1,2 · Konrad Wegener2 Received: 24 April 2020 / Accepted: 3 October 2020 © The Author(s) 2020
Abstract Powder layer density is an important measure for understanding the effect of powder on part quality in powder bed fusion. The density of thin layers, as they are deposited in powder bed fusion, differs from the density of powder in large containers. This study investigates this difference. Therefore, six monomodal powders with different particle size distributions, from coarse to fine, are spread in an 84.5 µm deep cavity to determine their powder layer densities for a single layer. A linear dependence of powder layer density on the D50 of powder is discovered for monomodal powders with good flowability. This dependence can be explained by the wall effect. Fine powders with low flowability show an increase in the standard deviation of the powder layer density. These findings suggest the existence of a particle size distribution that is sufficiently small to minimize the wall effect in a thin layer while still being sufficiently large to guarantee a good flowability of the powder. Keywords LPBF · Powder layer density · Powder · Additive manufacturing · Laser powder bed fusion · Powder layer
1 Introduction Powder significantly affects part quality in powder fusion bed (PBF) of metals [1, 2]. Meiners [3] demonstrated the effect of the particle size distribution (PSD) on part density, which was then confirmed in later studies [4, 5]. However, the effect of powder on final part properties is yet to be elucidated. A link between powder and part properties is the powder layer, most notably the powder layer density (PLD), as emphasized in several studies [2, 6–8]. The most frequently published method to measure powder bed density is to build cavities with a height of several powder layers during PBF and then measure the powder density in these cavities [6, 9–13]. However, Chen et al. [14], Wischeropp et al. [15], and Mahmoodkhani et al. [1] showed that the true PLD and the * Lukas Haferkamp [email protected] 1
Inspire, Innovation Center for Additive Manufacturing Switzerland (icams), Lerchenfeldstrasse 3, 9014 St. Gallen, Switzerland
Swiss Federal Institute of Technology, Institute of Machine Tools and Manufacturing (IWF), ETH Zürich, Leonhardstrasse 21, 8092 Zurich, Switzerland
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effective thickness of a single powder layer differ from the values obtained by measuring several layers at once. Wischeropp et al. [15] measured relative powder layer densities, as a fraction of the solid material density, to be between 0.44 and 0.56 in an experiment on a PBF machine for the powders and layer heights listed in Table 1. Chen et al. [14] investigated nine different powders, each at three different layer thicknesses, both experimentally and in a discrete element simulation. They obtained powder layer de
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