Properties of Additively Manufactured Deposits of Alloy 718 Using CMT Process Depending on Wire Batch and Shielding Gas

Wire + arc additive manufacturing (WAAM®) is a versatile, low-cost, energy-efficient technology used in metal additive manufacturing (AM). This process uses arc welding to melt a wire and form a three-dimensional (3D) object using a layer-by-layer deposit. In the present study, the effect of heat input and shielding gas during CMT-WAAM welding on cooling time, mechanical properties at room temperature, and macro- and microstructure was investigated based on different part geometries (wall, block) using two S Ni 7718 wire batches. The heat input and consequently the cooling rate were varied by changing the wire feed and the travel speed. As expected, increasing the heat input leads to higher cooling times. Due to the 2D-heat conduction, the thin walls cool significantly slower than the multi-pass block welds. Nevertheless, the influence on mechanical properties is only marginal. Both the AM batch of S Ni 7718 with the lower Nb/C and the multi-pass block welds with the higher thermomechanical reactions exhibit a high susceptibility to unacceptable seam defects, such as hot cracks or lacks of fusion. But even the standard batch causes hot cracks. An influence of the shielding gas on microstructure, mechanical properties, and occurrence of the seam defects cannot be detected