Post-processing of additively manufactured IN625 thin-walled structures using laser remelting in directed energy deposition

Blown-powder directed energy deposition (DED) is especially useful for depositing on an existing part for the purpose of repair or adding features. Thin substrate deposition, wherein the width of the substrate is smaller than the laser diameter, is an important configuration for building and repairing complex components in various geometries. The present study seeks to understand the efficacy of in-line post-processing methods based on laser remelting (LR) for reducing internal (e.g., porosity) and external (e.g., surface roughness) for such thin-walled repair configurations. In this work, different levels of LR energy density and substrate width were evaluated using the LR process. Post processing outcomes in terms of deposit geometry as well as spatial distribution of porosity, pore density, pore volume fraction, pore diameter, and surface roughness were evaluated using X-ray microcomputed tomography and optical profilometry. The results showed that LR reduced pore density up to 88 % and reduced areal surface roughness to 4.159 mu m. At some threshold, increasing LR energy density increased surface waviness and modified deposition geometry, this indicative of limits to the post processing method. Strategies for using LR to reduce total porosity, near-surface porosity, and improving surface roughness are briefly discussed.