Development of gas tungsten arc welding using current pulsing technique to preclude chromium carbide precipitation in aerospace-grade alloy 80A

Abstract

Weldments were produced using gas tungsten arc welding (GTAW) and pulsed current gas tungsten arc welding (PCGTAW) techniques with ERNiCr-3 filler wire. Macro examination revealed that the resultant weldments were free from defects. A refined microstructure was observed in the weldment fabricated through PCGTAW. Scanning electron microscopy (SEM) analysis revealed secondary phases in the grain boundaries. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that microsegregation of Cr carbide precipitates was completely eradicated through PCGTAW. The microsegregation of Nb precipitates was observed in the GTA and PCGTA weldments. X-ray diffraction (XRD) analysis revealed the existence of M₂₃C₆ Cr-rich carbide and Ni₈Nb phases in the GTA weldments. By contrast, in the PCGTA weldments, the Ni₈Nb phase was observed. The Cr₂Ti phase was observed in both the GTA and the PCGTA weldments. Tensile tests showed that the strength and ductility of the PCGTA weldments were slightly higher than those of the GTA weldments.

Keywords

Ni-based superalloy / welding / pulse current / microsegregation / chromium carbide

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