Wire arc additive manufacturing (WAAM) is highly sought after for producing complex-shaped products with high deposition rates and relatively low cost compared to other additive manufacturing processes. However, the cumulative heat input during processing leads to low-dimensional accuracy, high distortion, and high residual stress, which requires heat control and thermal monitoring. The current work offers a study on the applicability of experimental and numerical thermal monitoring in detecting thermal effects generated during the WAAM processing of a corrosion-resistant SS308L austenitic alloy commonly used in nuclear, aerospace, and marine industries. Temperatures were measured during processing for vertical and horizontal structures by a mono-wavelength pyrometer and coupled with thermo-mechanical simulations. The simulation models were successfully validated through the distortion measured in the substrates of the processed structures, confirming the acquired thermal cycles. Results showed that mono-wavelength pyrometry was only effective for vertical structures away from the deposition area, with emissivity varying from 0.6 to 0.41 for temperatures between 600 and 1700 °C, respectively. For horizontal structures, temperature measurements relied solely on simulations, which predicted heat accumulation and cooling rates. These predictions were validated through secondary dendritic arm spacing and hardness measurements, confirming the impact of intermittent deposition in reducing heat build-up and leading to relatively finer microstructures and less variant hardness profile compared to continuous deposition. Graphical abstract

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. Graphical Abstract