Weldability assessment, microstructural evolution, and mechanical performance of Hastelloy X weld metals using different filler metals via GTAW

This study evaluates the effect of filler metal composition on the microstructural evolution, mechanical performance, and solidification cracking susceptibility of Hastelloy X weld joints produced by gas tungsten arc welding (GTAW). Three commonly used Ni-based filler metals, ERNiCrMo-2, ERNiCrMo-3, and ERNiCr-3, were comparatively investigated. The results show that filler metal chemistry strongly governs elemental segregation, carbide formation, and weldability. ERNiCrMo-2 produced a more uniform dendritic microstructure with Mo-rich M 6 C carbides, while ERNiCrMo-3 and ERNiCr-3 exhibited pronounced Nb segregation and Nb-rich MC-type carbides. Among the weld metals, ERNiCrMo-2 demonstrated the best mechanical performance, with an average hardness of ∼207 HV, impact energy of 62 J, ultimate tensile strength of ∼743 MPa, and elongation of ∼34%. In contrast, ERNiCr-3 exhibited the lowest strength and toughness. Solidification cracking susceptibility, quantified by the Varestraint test, was lowest for ERNiCrMo-2 (maximum crack length and total crack length of 1.95 and 4.72 mm, respectively) and highest for ERNiCrMo-3 (5.89 and 8.65 mm), consistent with their solidification temperature ranges and segregation behavior. These findings demonstrate that ERNiCrMo-2 offers the most favorable combination of mechanical performance and resistance to solidification cracking, making it the most suitable filler metal for GTAW of Hastelloy X in critical high-temperature applications.