Experimental and numerical thermal monitoring of SS308L structures processed by wire arc additive manufacturing

Abstract 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