Numerical investigation of the arc behaviour and air transport during pulsed tungsten inert gas arc-based additive manufacturing

In this study, we have developed a numerical model of the pulsed tungsten inert gas (TIG) arc, with a primary focus on the influence of the ambient atmosphere in wire arc additive manufacturing (WAAM), which is more approached to practical instances. The arc plasma behaviour and air transport during the pulsed TIG-based WAAM are investigated, and the effects of the nozzle diameter on the air transport are examined. It is indicated that the air is transported significantly into the zone near the sidewall of the AM buildup. Both the air concentration and the arc temperature vary periodically with the pulsed current, whereas the change in the air distributions noticeably falls behind that in the arc temperature fields. The variation in the air concentration is mainly caused by the backward flow of the arc plasma near the sidewall of the build, which varies periodically with the arc current and transports the air into the vicinity of the sidewall. Such an effect is an essential source of oxygen for the oxidation and contamination of the deposition layer during the WAAM process. Increasing the nozzle diameter can effectively lower air concentration near the build’s sidewall, suggesting an enhancement in both shielding effectiveness and part quality. Our simulated outcomes are in reasonable consistency with experimental measurements, encompassing both arc plasma flow as observed through shadowgraphy imaging and the element distribution gauged via EDS line scans of the oxide layer formed during the build’s deposition.