Metallic Powder Flowability: A Comparison Between Testing Methods and The Effect of Particle Size Distribution

The flowability of a powder is a characteristic dependent on both the particle ensemble's physical properties as well as the testing equipment and conditions. In powder bed additive manufacturing processes (SLM, EBM), flowability can be used to predict the quality of the deposited powder layer. However, how representative flowability is for the powder bed layer quality is not always clear.In this work, we compared several steel powders, as well as different testing methods. Each powder had an individual combination of composition or particle size distribution. Furthermore, the flowability testing equipment and methods were selected according to standards (Tap density, Hall flow) or referring to the published literature (angle of repose, FT4 Powder Rheometer). After measuring the flowability of different samples for each testing method, we created a database to evaluate a first correlation between the different testing methods. Finally, with a Powder Rheometer, we investigated for one sample some flow properties as function of different particle size distributions.