Wire-arc directed energy deposition of Inconel 718: Effects of heat input and build interruptions on mechanical performance

Directed energy deposition via electric arc (DED-Arc) and wire-feed system can offer a low-cost, high deposition rate method to produce large-scale, near-net-shape structural components from Inconel 718 (IN718). In this work, DED-Arc with cold metal transfer (CMT) has been compared with pulsed-spray droplet transfer (GMAW-P) using different build strategies by correlating the local cyclic thermal histories and the position of deposition interruptions to the resulting tensile properties. The measured heat input (0.18 - 0.59 kJ/mm) and inter-pass temperature (80 - 650 degrees C) affected the thermal field and residence times in the 900 - 600 degrees C temperature range, where & gamma;'/& gamma;" phases are more likely to form, thereby impacting the yield strength along the build direction (370 - 460 MPa). Furthermore, CMT deposition with a lower travel speed (0.4 m/min vs. 1.0 m/min) prevented the onset of solidification defects, contributing to more consistent tensile ductility. Tensile properties of material surrounding build interruptions developed strain localisation and failed prematurely as compared to regions without, due to localised cracking and transient thermal fields generated once the deposition resumed.