Effects of the powder, laser parameters and surface conditions on the molten pool formation in the selective laser melting of IN718
Résumé
A series of single-track selective laser melting (SLM) experiments was carried out on IN718 plates with and without a powder layer and with different laser processing parameters (power and scan velocity) and surface conditions (original surface and sand blasted surface). The impacts of the powder, laser parameters, and surface conditions on the molten pool (MP) formation in SLM were systematically investigated through characterizations of the geometry of the resolidified MP, including width, depth, and area. Clear-cut correlations between the dimensions of the MP and the parameters were deduced from the measured data, such as between width/depth of the MP and the power of the laser beam, or between the area of the MP and the laser energy density. We also show that without a powder layer, an increased roughness of the surface consistently increases the MP cross-section area, whereas it has no impact for the cases with powder layer. Finally, the occurrence of defects, such as insufficient melting, unstable MP, and porosities/keyhole effect, is investigated and linked to the SLM parameters. We propose a processing map that defines the range of laser velocity and power for a defect-free solidification of the MP and the occurrence of the different types of defects.
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