Directed Energy Deposition roughness mitigation through laser remelting
Zoé Jardon, Julien Ertveldt, Raphaël Lecluyse, Michaël Hinderdael, Lincy Pyl
Abstract
One of the remaining challenges faced by Directed Energy Deposition is the poor surface finish induced by unmolten particles and the inherent superposition of layers during the process. The DED roughness levels are known to be significantly higher than for conventional parts and can become critical for the fatigue life and corrosion of the component. This is why the production of a DED part always requires a post-processing surface finishing step, which is known to be costly and to have a significant impact on the production time. This paper therefore presents an evaluation of single-track roughness induced by the DED process through transversal cross-sections, top-view micrographs, in situ process monitored images, laser triangulation, and contact-type measurements. The main DED process parameters defining the roughness are identified as being the particle diameter, laser beam diameter, and laser power. Finally, laser remelting during the production of cubic samples is proposed as a solution to further mitigate the roughness. Roughness levels on the top surface are reduced up to 86% with sufficiently high laser power settings. Laser remelting is therefore recommended to minimize the roughness, in combination with an optimal process parameter selection.