Arc weldability of Incoloy 825 to AISI 321 stainless steel welds

Composition effect of Inconel 625, Incoloy 65 and ER347 fillers on microstructural evolution and solidification crack (SC) sensitivity of gas tungsten arc welded Incoloy 825 to AISI 321 SS was investigated. The structure of welds had been mostly austenitic, and solute segregation caused formation of eutectic-nature secondary phases in inter-dendritic/cellular spaces of three weld alloys. The dilution effect led to a transition from FA to AF mode of solidification in ER347 weld and decreased its ferrite content. Inconel 625 and ER347 welds had the highest and lowest resistance to SC during Longitudinal Varestraint Test, respectively. Fine dendritic structure of Inconel 625 weld resulted in easier strain accommodation and better weldability properties of this alloy. Severe cracking and high sensitivity of ER347 weld to SC were characterized because of low ferrite content and easier wettability of solidification grain boundaries due to formation of low-melting Nb and Ti-rich phases. Inconel 625 filler could play an effective role in establishing an appropriate bridge in terms of thermal expansion coefficient between dissimilar parent metals.