MECHANICAL AND METALLURGICAL INVESTIGATION ON GAS METAL ARC WELDING OF SUPER AUSTENITIC STAINLESS ST

The main purpose of this paper is to present the investigations of the microstructure and mechanical properties of super austenitic stainless steel butt joints made by gas metal arc welding with different shielding gas mixtures. Welding was performed under two sets of optimized parameters employing three different shielding gases, namely 100% argon, 80% argon+20% CO2 and 100% CO2. The microstructure and the mechanical properties of the welds were examined. The fully austenitic base microstructure got transformed into primary dendritic and secondary interdendritic phases in the weld zone. Higher amount of secondary interdendritic phase was observed in the welds made under 100% argon gas whereas a rich amount of long columnar dendritic structures were observed in the welds made under 100% CO2 gas. Welds made under 80% argon+20%CO2 gas under the second set of parameter was found to exhibit comparatively better mechanical properties due to proper amount of the dendritic and interdendritic grain structures in the weld region