Effect of Nb-free consumables on the microstructure and structural integrity of pressure vessel grades of dissimilar austenitic stainless steel welded joints

Abstract

The research article demonstrates the role of fillers in the evolution of the microstructure and mechanical integrity of dissimilar joints of stabilized austenitic stainless steels. Pulsed direct current (PDC) gas tungsten arc welding (GTAW) technique was adopted to obtain the joints of dissimilar grades of stabilized austenitic stainless steels such as AISI 321 and AISI 347. The joints of these dissimilar grades of stainless steels were achieved using a ferritic-austenitic stainless-steel filler ER2553 and Ni-rich austenitic fillers ERNiCrMo-4, ERNiCrMo-10. Delta ferrite was observed in heat-affected areas (HAZ) on both sides of stainless steels, regardless of joints. Precipitation of Mo–Nb, Mo–W rich phases was noticed in the fusion zones (FZ) while adopting Ni-based austenitic fillers. During the tensile load, the fractures occurred on the base metal side of the AISI 321 for the Ni-based fillers and on the FZ while using the ER2553 fillers. The joint efficiencies achieved by these dissimilar joints were 103.2%, 128.11% and 116.16% for ER2553, ERNiCrMo-4 and ERNiCrMo-10 fillers respectively. The joints established with the ERNiCrMo-4 filler improved the notch's impact resistance in ambient temperature and below zero conditions compared to other weld seams.

Keywords

• Gas tungsten arc welding
• Stabilized stainless steels
• Micro-segregation
• Microstructure
• Tensile properties
• Impact toughness