Analysis of surface roughness in metal directed energy deposition

To improve technology readiness and realize the cost reduction of additive manufacturing as-built components for nuclear applications where quality, performance, and lifetimes are highly critical, further research into process parameter optimization is necessary. This study looks at the effects of directed energy deposition (DED) process parameters and correlations on the resulting surface roughness of single-track clads. Material feed mechanism types significantly affect surface roughness and a comparative parametric analysis of single-track clads fabricated with blown powder and wire-fed DED methods, laser-engineered net shaping (LENS), and wire-arc additive manufacturing (WAAM), respectively, was performed. Arithmetic mean surface roughness was characterized via non-destructive testing with laser-optical microscopy and analyzed against process parameter correlations of linear mass density and volumetric energy density. Results showed values of surface roughness ranges of 8.94-38.77 mu m and 3.21-42.91 mu m, for LENS fabricated 316L SS and IN718, respectively, and 1.00-8.33 mu m for WAAM fabricated 316L SS. LENS clad showed both high volumetric energy density and low linear mass density resulted in the lowest roughness for blown powder DED clads. In WAAM, low current and high energy density were observed to increase surface roughness and discontinuous wire transfer. Based on literature, inference of physical mechanisms of material inclusion and melt pool interactions are discussed regarding resulting surface roughness and clad properties.