A Study of Different Deposition Strategies in Direct Energy Deposition (DED) Processes

Abstract

The stepover of adjacent deposition lines (or beads), when stacking layers to build a 3D-solid shape, is found to be of great importance to minimize voidage and so, improving density of parts produced by the Directed Energy Deposition (DED) process. During such process, in which the stacking of layers occurs, the complex thermal activity of metal deposition affects the part geometry, microstructure, physical and mechanical properties. The correlation between deposition path, bead stepover, and the direct effect on the part density, microstructure and geometry distortions are yet to be found in the literature. Therefore, the aim of this study is to evaluate the effect of deposition paths and bead stepover on the final part geometry form, microhardness and density. In order to do so, four deposition paths (linear, zigzag, chessboard and contour) and beads stepover of 0.44 mm and 0.55 mm were performed on the production of Stainless Steel 316L cubes by a 5-axis laser based DED BeAM Machine Magic800 with laser spot size of 0.80 mm. The paths shown considerable influence on the variation of both final part geometry and density. Contour (spiral-like) was the path, which produced workpieces with finer form and finishing, with density and microhardness closer to the conventional AISI 316L material. The bead stepover was also found to influence the surface finishing, as larger critical valleys between adjacent beads were noticed when using the higher stepover value.