Improvement in stress rupture properties of inconel 718 gas tungsten arc welds using current pulsing

Weld fusion zones in Inconel 718 are known to exhibit poor mechanical properties in relation to the base metal as a result of extensive interdendritic Nb segregation and consequent formation of Nb-rich, brittle, intermetallic Laves phase ((Ni, Fe, Cr)2 (Nb, Mo, Ti)) during weld metal solidification, which depletes the matrix of useful alloying elements and aids in easy crack initiation and propagation. Post-weld solution treatments cannot be entirely relied upon in dealing with the Laves problem as dissolution of Laves phase to any significant extent is not possible without simultaneously causing undesirable grain coarsening in the base metal. Therefore, there is a need to control Nb segregation and Laves formation during welding itself. In an effort to control Nb segregation and Laves formation in gas tungsten arc (GTA) welds, current pulsing technique was used. Autogenous, bead-on-plate, full-penetration GTA welds were produced using constant current (CC) and pulsed current (PC) in Inconel 718 cold-rolled sheets (2 mm thick) in 980 DGC solution treated condition