Spreadability of Metal Powders for Laser-Powder Bed Fusion via Simple Image Processing Steps.

Cekdar Vakifahmetoglu,Lisa Biasetto,Beyza Hasdemir

doi:10.3390/ma15010205

Cekdar Vakifahmetoglu, Lisa Biasetto + Show 1 more

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https://doi.org/10.3390/ma15010205

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Abstract

This paper investigates the spreadability of the spherical CoCrWMo powder for laser- powder bed fusion (PBF-LB) by using image processing algorithms coded in MATLAB. Besides, it also aims to examine the spreadability dependence with the other characteristics such as powder size distribution, apparent density, angle of repose. Powder blends in four different particle size distributions are prepared, characterized, and spreadability tests are performed with the PBF-LB. The results demonstrate that an increase in fine particle ratio by volume (below 10 µm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts also depends on other processing parameters such as spatter formation or powder size over layer height ratio.

Highlights

IntroductionThe results demonstrate that an increase in fine particle ratio by volume (below 10 μm) enhances the agglomeration and decreases the flowability, causing poor spreadability
Among 3D printing technologies powder bed fusion (PBF) wherein spread powder layers are consolidated by a heat source to obtain three-dimensional (3D) components, seems to be one of the most promising especially for multimetals 3D printing [1]
In PBF processes [3,4,5,6,7,8,9,10] that include selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM), homogeneous powder spreading is important since a well-controlled layer in terms of thickness and roughness may provide satisfying structural and functional properties

Summary

Introduction

The results demonstrate that an increase in fine particle ratio by volume (below 10 μm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts depends on other processing parameters such as spatter formation or powder size over layer height ratio. Homogeneity on the powder bed layer depends on powder properties such as shape, size, and roughness, that affect cohesion and apparent/tapped density, so as impurities (such as the presence of a passivating oxidation layer), moisture, etc.

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