Influence of Powder Feed Density on Mechanical Properties and Microstructure in L-DED Additive Manufactured STS316L

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Laser Directed Energy Deposition (L-DED) is a notable additive manufacturing method in which metal powder is sprayed through a nozzle and then consolidated layer by layer using a laser. Unlike other additive manufacturing processes, DED has fewer constraints on the size of the fabricated parts, making it advantageous for the production of large-scale components. However, the use of DED in additive manufacturing requires careful optimization of various process parameters, including laser power, powder feed rate, nozzle scanning speed, and deposition path, as these parameters significantly influence the geometry and properties of the fabricated parts. Recent studies have extensively investigated the microstructure and properties of parts fabricated via DED at different energy densities, but research on variables related to powder feed is still lacking. In this study, using Powder Line-Density (PLD) as a parameter, changes in bead geometry, microstructure and mechanical property followed by variation in powder feed density while conducting DED additive manufacturing with STS316L were observed. Controlled by powder feed rate and scanning speed, the Powder Line-Density was utilized for 1-line deposition with STS316L alloy powder, enabling the observation of bead geometry and melt-pool shape during the deposition process. Additionally, square-shaped specimens were manufactured via DED with controlled Powder LineDensity to observe the resulting microstructure and mechanical properties. It was observed that, even for the same energy density, specimens exhibited distinct grain morphologies, microstructure, and mechanical properties depending on the Powder Line-Density, with a particularly significant change in anisotropy. This highlights the importance of powder feed density as a key variable alongside energy density to optimize DED additive manufacturing processes. The findings of this study are expected to contribute to the control of anisotropy and strength of fabricated components in metal additive manufacturing processes by the regulation of powder feed density.