Wire Additive Manufacturing (WAM) is based on the direct deposition of a locally melted metallic wire using an energy source such as electric arc (WAAM, Wire Arc Additive Manufacturing) or laser (WLAM, Wire Laser Additive Manufacturing), being particularly suitable for large-scale components manufacturing. However, the thermal load imposed throughout the process parameters influences both the geometry and the microstructure of the produced components. This work studies the quality of 316L stainless steel components produced by WAM, from the macro- to the microscopic scale, based on experimental characterizations and numerical simulations through a finite element model.

At the macroscopic scale, a calibration of the primary process parameters affecting the geometry of the beads (the deposition velocity, v, the wire feed rate, v_w, and the power of the energy source, P) was performed. Parameters were selected according to geometrical criteria taken from the literature. In addition, the number of inclusions and precipitates of intermetallic phases, the solidification microstructure, and the chemical segregation was studied at the microscopic scale. Notably, the grains size, morphology, and texture were investigated, first on single beads, then on thin walls and tiles realized by WAAM and WLAM. The directional thermal gradient leads to a formation of grains of about 100 µm, elongated in the building direction, resulting in grain texture and might lead to anisotropic mechanical properties in the final component. Microhardness measurements were used as first probe of the microstructure effect on mechanical properties. In addition, austenitic-ferritic microstructure and fully austenitic structure were observed in single beads obtained by WAAM and WLAM, respectively. Finally, the numerical computations using the finite element model allow better thermal behavior analysis. The thermal gradient, G, and the solidification rate, V, were estimated by extracting the fusion isotherm from these simulations. These values could be related to the solidification behavior and the experimentally estimated cooling rate.