Abstract
Nickelvac 23 is prone to hot fissuring due to elemental segregation in arc welding. The goal of the present research is to assess the possibility of mitigating the elemental segregation using arc welding processes with nickel-based filler wire. In this work, Nickelvac 23 weldments are made by gas tungsten arc welding techniques (Continuous and pulsed current modes) with ERNiCrMo-10 filler wire. The result of the macro evaluation depicts that defect-free welding with the proper fluid flow was accomplished in both weldments. The microscopical examination reveals the cellular and columnar structures in the weldment with CCGTAW and equiaxed structure in weldment with PCGTAW. Weldment with CCGTAW is detected with Mo segregation which forms the Mo23C6 phases in the interdendritic region. Segregation of Si is noticed in all the weldments. Suppression of elemental segregation is noticed with PCGTAW while using ERNiCrMo-10 filler wire. XRD analysis shows the formation of interstitial compounds like MC, M12C, M23C6 at the weldments. Tensile strength, hardness and toughness values are slightly improved in the PCGTAW as compared to CCGTAW due to the formation of interstitial compounds. Electron Backscatter Diffraction (EBSD) analysis confirmed the HAZ failure is due to the coarse grain structure. EBSD results also showed 36 % lesser grain sizes for the PCGTAW than the respective CCGTAW.
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