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The particle shape influences the part properties in laser powder bed fusion, and powder flowability and powder layer density (PLD) are considered the link between the powder and part properties. Therefore, this study investigates the relationship between these properties and their influence on final part density for six 1.4404 (316L) powders and eight AlSi10Mg powders. The results show a correlation of the powder properties with a Pearson correlation coefficient (PCC) of −0.89 for the PLD and the Hausner ratio, a PCC of −0.67 for the Hausner ratio and circularity, and a PCC of 0.72 for circularity and PLD. Furthermore, the results show that beyond a threshold, improvement of circularity, PLD, or Hausner ratio have no positive influence on the final part density. While the water-atomized, least-spherical powder yielded parts with high porosity, no improvement of part density was achieved by feedstock with higher circularities than gas-atomized powder.

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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.