Metal transfer behavior during CMT-based Wire Arc Additive Manufacturing of Ti-6Al-4V alloy

Abstract

CMT-Wire Arc Additive Manufacturing (CMT-WAAM) has the advantages of low heat input and high production efficiency. However, the surface geometric accuracy of the CMT- fabricated sample is inferior, especially for the deposition of titanium alloy. The focus of this study was to analyze the metal transfer behavior during CMT-WAAM of titanium alloys by a high-speed camera. The metal transfer and molten pool behaviors during the single-layer and multi-layer deposition in both CMT and CMT + P modes were compared to optimize the characteristic process parameters. The results showed that the hybrid metal transfer mode, including the short-circuit transition and the globular transition, occurred in the CMT + P mode. The effect of Ip1 on the droplet diameter was more significant than that of tp1. Under these two modes, the size and spread ability of the molten pool increased with the increase of Iboost, tp1 and Ip1. While in the CMT + P mode, Ip1 did not yield a significant influence compared with tp1. Simultaneously, noticeable oxide skin was observed on the surface of the flowing molten pool when Iboost reached 350 A in the CMT mode. Compared with the CMT mode, new spatter types were generated by arc force and droplet free-fall motion in the CMT + P mode. Ultimately, the maximum effective rate of 70.4 % was obtained in the CMT + P mode when the parameters were selected as Ip1 = 400 A and tp1 = 4 ms.