Behavior of powder particles on melt pool surfaces
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Additive Manufacturing is in progress to change the production and manufacturing environments and possibilities; however, the complex processes taking place are not completely understood yet. A better understanding of the incorporation mechanism of the particles into the melt pool during blown powder processes could lead to methods to increase the powder and energy efficiency. Therefore, the incorporation mechanism was investigated in experiments and simulation. High-speed images made it possible to observe the behavior of single particles on the melt pool. A model based on the temperature-dependent surface tension/energy difference between the particle and the melt pool calculated the time until particle incorporation. It was shown that the surface tension characteristics during particle heating can even lift the particle from the melt pool. The calculated wetting behavior in combination with high kinetic energies should lead to an immediate immersion of the particle into the melt pool. Since observations do not show this behavior, it is concluded that the surface tension plays a role in the incorporation mechanism, but other effects like the occurrence of oxide layers or additional particle heating by the laser beam seem to lead to different mechanisms and heat conductions to support an earlier incorporation.
KeywordsLaser additive manufacturing Powder particle Surface tension Direct metal deposition
The authors acknowledge subcontracting from Fraunhofer ISW Dresden, Germany in the Agent3D project funded by the Bundeministerium fuer Bildung und Forschung (BMBF), Germany and the funding by VINNOVA—Sweden’s innovation agency (project ÖVERLAG, no 2017-03240).
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