  An experimental study is presented to characterize the ripple formations in
the directed energy deposition (DED) process and study the influence of the
ripples on the heterogenous microstructure in the scan direction of a
DED-printed 316L components. While considerable studies on ripple formations
exist in the welding literature, these formations in DED process have not
received much attention. Also, little prior efforts exist on the microstructure
along the scan direction (or the scan surface) as compared with the build
direction. Experiments consisted of printing 10 mm x 10 mm x 10 mm cubical
components on a Optomec LENS 500 Hybrid Machine Tool under different laser
power, scan speed and dwell time combinations, chosen according to a Latin
hypercube design. The surface of the scan face of the prints were finished to
an Ra < 30 nm, and etched with Aqua regia for 90 sec. An optical microscope was
employed to observe the microstructure at 4 difference scales. The studies
suggest a significant influence of ripple formations as well as the scan width
on the solidification front, the dendritic patterns as well as the heterogenous
microstructure.
