Effect of Pulsed Current Gas Tungsten Arc Process on the Dissimilar Weldments between Nickel-based Superalloy/Austenitic Stainless Steel

Abstract

The present work aims at investigating the microstructural and mechanical properties of dissimilar welds between Superalloy C-276 and Grade 321 austenitic stainless steel sheets, fabricated by pulsed current gas tungsten arc welding. The microstructural examination was carried out using an optical microscope and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy. The weld metal microstructures divulged finer equiaxed grains. SEM images revealed migrated grain boundaries adjacent to weld line on both Superalloy C-276 and Grade 321. In addition, the presence of Mo-rich phases was also observed in the weld metal and at the weld interface of Superalloy C-276, which needs further investigation. Mechanical tests were carried out with respect to microhardness, tensile and impact properties. Furthermore, the presence of finer dendritic structure and controlled distribution of elements obtained with PCGTAW contributed for higher corrosion resistance of WM compared to BMs. The results of the present study would help in obtaining high quality dissimilar joints. Moreover, Grade 321 being a low-priced material as compared to Superalloy C-276 would be an economical substitution and would facilitate in saving huge material costs.

A Fractographical Study on Dissimilar Weld Joints of SAF 2205 and Hastelloy C-276

“…Among the superalloys, Hastelloy C-276, a nickel-based superalloy, is commonly used in chemical, petrochemical, aviation and nuclear power plant applications due to their high corrosion resistance and high strength properties at elevated temperatures. The alloying elements like chromium, molybdenum and iron provide high yield strength and high corrosion resistance [3][4][5]. On the other hand, instead of austenitic and ferritic stainless steels, duplex (DSS) and super duplex ones (DSS) have become more attractive in many applications.…”