Numerical modeling of fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Inconel 718

Most of the researches published on the numerical modeling of laser welding are looking at similar welding, mainly due to the difficulty of simulating the mixing phenomenon that occurs in dissimilar welding. Furthermore, numerical modeling of dissimilar laser welding of titanium and nickel alloys has been rarely reported in the literature. In this study, a 3D finite volume numerical model is proposed to simulate fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Inconel 718. The laser source was simulated by volumetric heat distribution, which considers the effects of keyhole and heat transfer on the workpiece. The heat source parameters were calibrated through preliminary experiments, by comparing the simulated and experimental weld pool shapes and dimensions. The model was used to simulate both homogenous and dissimilar laser weldings of Ti-6Al-4V and Inconel 718, and a systematic comparison was carried out through a number of selected experiments. The effects of three distinct levels of laser power (1.25 kW, 1.5 kW, 2.5 kW) on temperature distribution and velocity field in the welds pool were analyzed. Results highlighted the effects of Marangoni forces in the weld pool formation. Furthermore, in order to analyze the mass transfer phenomenon in dissimilar welding, species transfer equations were considered, demonstrating the important role played by the mass mixture in the weld pool formation. Finally, a high level of agreement between simulations and experiments—in terms of weld pool shape and dimensions—was observed in all cases analyzed. This proves the ability of the proposed numerical model to properly simulate both the similar and dissimilar welding of Ti-6Al-4V and Inconel 718 alloys.