Development of gas tungsten arc welding using current pulsing technique to preclude chromium carbide precipitation in aerospace-grade alloy 80A
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.
KeywordsNi-based superalloy welding pulse current microsegregation chromium carbide
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The authors thank Mr. Natarajan R, Delta Wearteach Engineers Pvt. Ltd. for his welding support and thank to Dr. Narendra Kumar, Vellore Institute of Technology, for helping the microstructural analysis. We also thank to Department of Science and Technology, Government of India, for supporting the SEM and INSTRON universal testing machine facility established at Vellore Institute of Technology utilized for this research work.
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