Avanços no desenvolvimento de ligasproduzidas "in-situ" pelo processo soldagem MIG/MAG duplo arame

Abstract

This study aimed to develop specific alloys by combining the nickel-based alloys Hastelloy C-276 and Inconel 625, applying welding techniques to minimize macrosegregation. Three compositions were produced: 50%H/50%I, 70%H/30%I, and 30%H/70%I. The electrode with the highest deposition rate operated in pulsed mode, while the one with lower contribution operated in short-circuit mode. Pulse parameters were evaluated for all alloys, while in short-circuit mode, the variables Ks, Kd, and Ur were analyzed. The total wire feed speed was kept constant. An exploratory analysis was also conducted regarding electrode arrangement (leading/following) and weaving parameters (speed, frequency, and amplitude), assessing alloy mixing and bead geometry. In the overlay welds, the influence of electrode distance on macrosegregation formation was also investigated. The samples were subjected to chemical, microstructural, and mechanical characterization, including Vickers microhardness, Charpy impact, and tensile tests. The results indicated that it is possible to produce alloys with controlled chemical compositions by properly adjusting the welding parameters according to the intended application. The pulsed and short-circuit modes were optimized to achieve weld beads with good surface finish and without defects. Electrode arrangement did not significantly affect homogenization, but metal transfer mode influenced the bead appearance: when both wires operated in pulsed mode without weaving, distinct color regions were observed (50%H/50%I), while in the mixed mode (pulsed/short-circuit), the weld presented a homogeneous appearance. Increasing weaving frequency, but especially amplitude, improved alloy mixing. Electrode distance showed no significant effect on segregation. Chemical analyses confirmed that the obtained compositions were close to the theoretical ones, and with adequate welding parameters it was possible to avoid macrosegregations. The resulting microstructure exhibited a Ni-FCC matrix, predominantly with columnar and cellular dendritic growth. Regarding mechanical properties, microhardness varied statistically among the alloys, with average values around 260 HV for the alloy with higher Inconel 625 content. Impact toughness showed no significant differences, with average absorbed energy values of about 150 J. In tensile tests, all alloys demonstrated mechanical performance close to commercial Inconel 686, confirming that twin-wire MIG/MAG welding is a viable route for in situ alloy production, eliminating the need for casting or less conventional techniques.