Preclusion of Carbide Segregation and Enhancing Mechanical Strength of Inconel 690 through PCGTAW Process

Superalloys based on nickel find common usage in high temperature corrosive conditions, where conventional stainless steels cannot be used due to stress corrosion cracking. Inconel 690 made of around 30 wt.% chromium has proven to have resistance to oxidation and intergranular attack. But microsegregation of alloying elements is common in welding resulting in the formation of chromium carbides deteriorating mechanical properties. The impact of filler metals, ERNiCrFe-7 (I52) and ERNiCr-3 (I82), on microsegregation, microstructural development, and mechanical properties of Inconel 690 weldments made via pulsed current gas tungsten arc welding (PCGTAW). The pulse current minimized the use of heat input with 0.922 for I52 fillers and 0.865 for I82 fillers and enhanced the microstructure of fusion zones. SEM/EDS also showed that the amount of chromium carbide segregation in the I52 weldments was considerably less than in the I82 weldments. As a result, I52 weldments had better tensile strength of 681.53 MPa and better impact toughness of 63 J. Fractographic studies revealed the presence of finer and uniformly distributed dimples in I52 weldments, signifying better energy absorption. These results indicate that the synergistic interaction between the optimized filler chemistry (I52) and PCGTAW has potential in restricting microsegregation, driving metallurgical stability, and building better mechanical reliability of Inconel 690 weldments used in critical high-temperature applications.