Study of the microstructure and metallurgical properties in tungsten inert gas welded Incoloy 925 superalloy

In this research, welding of Incoloy 925 nickel-iron based superalloy was examined in order to investigate the effect of chemical composition of used filler metals on the microstructure, mechanical properties and corrosion resistance of welded zones. For this purpose, shielding gas tungsten arc welding process and two nickel-base filler metals including ERNiCrMo-3 and ERNiCr-3 were used. Morphological observations showed that at the end of solidification, microstructure of weld metals were stabilized in the form of austenitic with dendritic morphology. In addition, in tensile test although tensile strength of weld metals were lower than Incoloy 925 base alloy but rupture in specimens occurred in heat-affected zone of base metal. In charpy impact test, ERNiCr-3 weld metal was broken by more attracting fracture energy compared to Incoloy 925 base metal and ERNiCrMo-3 weld metal. By performing potentiodynamic polarization test also determined that the corrosion potential difference between base metal and ERNiCrMo-3 weld metal can persuade occurrence of galvanic corrosion in the joint. Finally, with regard to the achieved results, ERNiCr-3 filler metal was diagnosed better selection for welding of Incoloy 925 superalloy.