Abstract
A quantitatively representative Wire Arc Additive Manufacturing (WAAM) simulation requires a heat source definition constrained by the thermal field generated during deposition. In this study, ER70S-6 steel walls were produced by a Gas Metal Arc (GMAW)-based WAAM using the Cold Metal Transfer (CMT) Universal mode (hereafter referred to as CMT-WAAM), with two wire feed speeds and two travel speeds, while the interpass temperature was controlled at 120 °C.Thermal camera images were used to derive the process-specific surface-related Goldak parameters (C f , C r and b), while the effective depth parameter, a, was determined from transverse cross-sectional fusion-zone measurements. The calibrated model was evaluated against four experimentally produced walls using CMM-based displacement measurements, hardness mapping, simulated phase distribution and SEM microstructural observations. In addition to conventional linear heat input, deposited volume per unit length was introduced to distinguish thermal loading from material and geometrical loading.Unlike previous ER70S-6 WAAM studies that primarily established experimental or statistical relationships between process parameters, deposition behaviour, microstructure and mechanical properties, the present work integrates process-specific Goldak heat-source calibration with thermo-mechanical prediction and validation of distortion, hardness, phase evolution and SEM microstructure within a unified process–structure–property framework. The calibrated model reproduced the representative distortion tendency of the deposited walls, with the best agreement reaching 5.6% difference for wall displacement and 18.2% for substrate displacement after excluding start and stop regions affected by arc initiation and termination. The Goldak parameters obtained from thermal imaging varied systematically with the process conditions; higher heat-input cases exhibited larger calibrated heat source dimensions, indicating closer correspondence with the measured thermal footprint and heat accumulation behaviour. Hardness and phase results were consistent with the experimental observations, showing that lower heat input and lower deposited volume per unit length promoted higher bainite tendency and increased local hardness, whereas higher thermal and material loading favoured a softer ferrite-rich response. SEM analysis supported a ferritic-bainitic microstructure with local bainite enrichment. The results demonstrate that thermal-camera-based heat source calibration provides a practical basis for linking process parameters, thermal response, distortion, phase evolution and hardness in ER70S-6 WAAM within the investigated range.