Effects of current path on structure and segregation during electroslag remelting process of Inconel 718 alloy with same power input

Current-conductive mold was recently developed to extend electroslag remelting (ESR) functions to overcome some solidification defects by changing the current path. The macrostructures, microstructures, macrosegregation, and microsegregation of the Inconel 718 ingots produced by the custom laboratory-scale ESR furnace under different current paths (the classical ESR and the single power, and two circuits ESR process with current-conductive mold (ESR–STCCM)) with the same power input were compared and investigated. The results indicate that when the ingot was produced during ESR and ESR–STCCM processes, at the same power input, the pool depth was 104 and 90 mm, respectively. A flatter and shallower molten pool was obtained during ESR–STCCM process. Moreover, compared with a classical ESR ingot, the cooling rate of the centerline of ESR–STCCM ingot was increased from 12.7 to 16.7 K min⁻¹. The increased cooling rates caused by decreased melting rate and thinner slag skin reduced the growth angle of columnar crystal to the vertical axis and the secondary dendrite arm spacing. Furthermore, the macrosegregation and microsegregation of segregation elements for ESR–STCCM process were dramatically reduced compared with ESR process. The average volume fraction of Laves phase was reduced from 7.39% to 6.14%, and the segregation of Nb in Laves phase was significantly reduced.