Thermal simulation and bead geometry prediction in wire arc additive manufacturing of Inconel 617

Wire arc additive manufacturing (WAAM) has emerged as a promising technology for fabricating large-scale metal parts, offering high deposition rates, low material waste and compatibility with traditional welding systems. However, the geometric accuracy and structural integrity of WAAM materials remain highly sensitive to steep thermal gradients, particularly in dissimilar material systems, where asymmetric heat flow strongly influences melt pool behaviour. In this work, a three-dimensional, time-resolved thermal finite-element simulation involving WAAM single-layer deposition of Inconel 617 on a mild steel substrate was performed using COMSOL Multiphysics. The arc-based energy input is modelled using a Goldak double ellipsoid heat source, while temperature-dependent thermal properties and latent heat effects are included to realistically simulate melt pool behaviour. A dual-isothermal surface-based bead geometry extraction methodology is employed, using the melting range of Inconel 617 (1605–1653 K) to define bead width (BW) and bead height (BH) and the melting range of mild steel (1723–1793 K) to define penetration depth. This approach enables physically consistent identification of fully molten and thermally softened regions in a dissimilar material context, without reliance on empirical geometric assumptions. In 27 simulated cases, the BW ranged from 3.86 to 6.54 mm, BH from 2.23 to 3.86 mm and bead depth (BD) from 0.34 to 1.08 mm. The bead parameters exhibited a pronounced dependence on wire feed rate and torch travel speed, whereas the torch angle exhibited a comparatively secondary influence. Experimental measurements were used to calibrate and validate the numerical framework, demonstrating good agreement in bead geometry trends and approximate dimensions within the investigated parameter space. The model provides a calibrated thermal simulation tool suitable for parametric studies and process window analysis in WAAM of Inconel 617.