Abstract
Close-Coupled Gas Atomization (CCGA) is often used to produce spherical metal powders with a wider Particle Size Distribution (PSD) (10 – 500 µm) compared to that required by the main Additive Manufacturing processes (10 – 105 µm). This work presents an accuracy evaluation of a mathematical model based on the Lubanska equation to predict the d50 for CCGA. Atomization experiments of 316L steel were conducted to evaluate the tip diameter and atomization gas pressure effects on PSD and, the d50 experimental results were used as the reference to the mathematical model evaluation. The mathematical model accuracy could be improved by: (i) considering the backpressure phenomenon for the metal flow rate calculation, since it was an important inaccuracy source; (ii) reviewing the tip diameter effect, which had a lower impact on d50 than that predicted by the Lubanska equation. The atomization gas pressure was the most influential parameter on d50 and d90 and the increase of the gas pressure led to a significant reduction in PSD and, consequently, increased yield.
Highlights
Close-Coupled Gas Atomization (CCGA) is often used to produce fine and spherical metal powders, highly needed for Additive Manufacturing (AM) of metallic alloys
For the parameters influence evaluated from the experimental d50, the atomization gas pressure was the most influential parameter (28%), while the tip diameter had a low influence (2.4%) on the d50. These results are in agreement with what is established in the literature for close-coupled atomization[8,38,44] and are similar to the results presented by Pariona et al.[45] who used the fractional factorial method to determine the effects of the main parameters and identified that the gas pressure has the most significant effect on the d50, followed by the opening area of the gas nozzle and tip diameter
The applicability and accuracy of a mathematical model based on the Lubanska equation was analyzed to predict the median particle size (d50)
Summary
Close-Coupled Gas Atomization (CCGA) is often used to produce fine and spherical metal powders, highly needed for Additive Manufacturing (AM) of metallic alloys. In CCGA with discrete jets, the metallic alloy is melted in a reservoir that contains a tube that guides the metal flow to the atomization chamber, which consists of a melt feed nozzle and a gas die around the melt tip feed. Short distances between the gas exit and melt stream favor energy transfer and, the smaller droplets formation. In this type of nozzle, the volume of gas consumed is small
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