Publication

Abstract : The hastelloy X is keen to solidification and liquation cracks during fusion welding methods. The microsegregation of Mo & Cr-rich elements at the final phase of solidification process causes the development of secondary precipitates such as M6C, M23C6 carbides, P & σ phases in the fusion zone and these phases act as an origin for initiation of hot cracking during conventional arc welding method. The present study adopts gas tungsten arc (GTA) welding and pulsed current arc welding technique to suppress the segregation of carbide phases using ERNiCrCoMo-1 filler wire. The metallographic results discovered the existence of Mo-rich secondary carbide precipitates in weld zone (WZ) of GTA weldment and no such of Mo-rich carbide precipitates identified in PCGTA weldment. The formation of Mo-rich M6C, Fe2MoC, and Cr2Ti phases were identified in GTA weldment and Ni3Ti, Ni3(Al, Ti) and γ- Co3Ti precipitate phases in PCGTA weldment by X-ray diffraction (XRD) inspection. The tensile strength and impact toughness of PCGTA weldment is better than GTA weldment by 4.18% and 20.18% respectively. The microhardness results also reveal an 8.05% increase in the mean hardness value of PCGTA weldment compared to GTA weldment. The improvement in strength of PCGTA welding is due to the refined microstructure with the absence of microsegregation of Mo & Cr-rich elements.