Investigation of double pulsed gas metal arc welding (DP-GMAW) technique to preclude carbide precipitates in aerospace grade hastelloy X

Hastelloy X develops hot fissuring during fusion welding, which could be precluded using single-pulsed gas metal arc welding (SP-GMAW) and double-pulsed gas metal arc welding (DP-GMAW). The outcome of this research is to provide a better insight into microstructural characteristics, and mechanical properties of Hastelloy X welded by GMAW, SP-GMAW, and DP-GMAW techniques. GMAW depicts the cellular dendrites, whereas DP-GMAW and SP-GMAW displayed fine equiaxed dendrites. Mo-rich segregation is identified in the interdendritic region of GMAW owing to high solidification time. Mo-rich segregation is reduced for SP-GMAW, whereas it is completely precluded for DP-GMAW due to the existence of refined grain. The development of M3C (Fe2MoC) and M6C (Fe2Mo4C) carbide precipitates is identified in GMAW and SP-GMAW. But, DP-GMAW displays the absence of Mo-rich carbides and the development of Mo1Ni4 intermetallic precipitates. DP-GMAW provides better joint efficiency (96.32%), UTS, and ductility, which is followed by SP-GMAW and GMAW. DP-GMAW shows higher mean microhardness (7.31% and 3.52%) and impact toughness (49.01% and 26.67%) on comparison with GMAW and SP-GMAW, respectively. Inverse pole figure (IPF) maps of SP-GMAW weldment confirmed that the broad and straight dendrites formed tend to grow along < 100 > direction during the entire solidification process. DP-GMAW also displays the major intensity shift from < 100 > to < 111 > direction. Evidence for the formation of equiaxed grains of random orientation along with dendrites is confirmed by IPF maps from DP-GMAW weldments. The presence of these equiaxed grains in the DP-GMAW weldment might have contributed to the enhancement of tensile properties.