Influence of Processing Parameters and Heat Treatments on Microstructure and Mechanical Properties of WAAM-Deposited SS308L

Wire Arc Additive Manufacturing (WAAM) is a promising technology for producing large-scale components with high deposition rates compared to other additive manufacturing technique. However, several defects such as deposited bead quality and porosity formation, besides mechanical anisotropy remain challenging for WAAM technologies. This study aims to mitigate these defects by studying the effect of processing and post-processing parameters for 308 L stainless steel structures fabricated by MIG-based WAAM process. Initially, the effects of two key processing parameters including stand-off distance and torch travel speed were studied on single tracks quality. Best possible parameters leading to the most deposited consistency, least porosity, and defects were further used to fabricate multi-layer vertical structures. Additionally, post-WAAM solution annealing treatments at 1000 °C, 1050 °C, and 1100 °C were applied to study microstructural evolution and mechanical performance. The main results indicate that a 7 mm stand-off distance and 400 mm/min travel speed produced the most stable bead geometry with minimal porosity of 0.012%. Moreover, solution annealing treatments at 1100 °C showed the most significant reduction in delta ferrite content from 31.7% to 2.9% and lead to microstrural homogeneity compared to as-built condition. Additionally, the applied post-WAAM treatment would slightly decrease the tensile strength, significantly reducing the fracture elongation anisotropy from 10.5% to 4.6%, while maintaining the hardness profile along the deposition direction.