Study on droplet transition behavior, bead geometric characteristics and formability of wire + arc additively manufactured Inconel 718 alloy by using CMT MIX+ Synchropulse process

In this paper, the droplet transfer behavior, geometric characteristics of weld bead and formability of CMT MIX + Synchropulse (CSP) wire + arc additively manufactured Inconel 718 alloy under high wire feeding speed are studied. The results show that a CSP cycle is composed of a CSP high-frequency pulse stage (CSP–HFP) and CSP-CMT stage, and the periods ratio is about 1.7:1. The high frequency and large average welding current of CSP-HFP increase the arc force, which further increases the droplet impact force on the molten pool. The molten pool is significantly deformed, resulting in the penetration depth of the CSP weld bead (1.8 mm) apparently higher than that of CMT (0.5 mm). The surface of the CMT-WAAM sample is more rough and irregular. The large penetration depth provides sufficient support for the molten pool, which promotes the overall stability of the molten pool. The increase of the droplet impact and arc forces enhance the convections in the molten pool, which finally suppresses the overflow phenomenon.