CMT welding sources are garnering attention as alternative heat sources for wire arc additive manufacturing because of their low-heat input. A comprehensive experimental and numerical study on the multi-layer deposition of STS316L was performed to investigate effect of heat accumulation during the deposition. The numerical model which is appropriate for WAMM was developed considering the characteristics of the CMT heat source for the first time. Using a high-speed camera, the transient behavior of the CMT arc was investigated, and applied to the heat source of the numerical model. The model was then used to analyze 10-layered deposits of STS316L, fabricated using CMT-based WAAM. During deposition, the temperature is measured using a pyrometer to analyze the microstructure, after which the cooling rate of each layer is estimated. The measured and simulated SDAS were compared. Based on the comparison, a guideline for the equation regarding the SDAS size and cooling rate was suggested.

Wire and arc additive manufacturing (WAAM) is among the most promising additive manufacturing techniques for metals because it yields high productivity at low raw material costs. However, additional post-processing is required to remove redundant surface material from components manufactured by the WAAM process, and thus the productivity decreases. To increase productivity, multi-variable process parameters need to be optimized, including thermo-mechanical effects caused by high deposition rates. When the process is modeled, deposit shape and productivity are challenging to quantify due to uncertainty in multiple variables of the complicated WAAM process. Therefore, we modeled the WAAM process parameters, including uncertainties, using a Gaussian process regression (GPR) method, thus allowing us to develop a WAAM optimization model to improve both productivity and the quality of the deposit shape. The accuracy of the optimized output was verified through a close agreement with experimental values. The optimized deposited material had a wide effective area ratio, small height differences, and near 90° deposition angle, highlighting the usefulness of the GPR model approach to deposit nearly ideal material shapes.

This study aimed to suggest a solidification map based on the solidification parameters G and R of each layer in the multilayer deposition for the investigation of heat accumulation on the deposit. Through the solidification map, the appropriate solidification conditions of the microstructure were determined. In order to investigate the solidification parameters, the temperature profile of the deposit was experimentally acquired during deposition. A simulation model reflecting the characteristics of the deposition process was developed and verified. The solidification parameters from the simulation model and the microstructure from experiments were correlated. Based on the analysis, a solidification map of 316L SS processed with CMT-WAAM process was derived, which is suggested as a guide for controlling and predicting the morphology of the microstructure in the deposit.