Microstructure, mechanical properties and sensitization of ultra-low nickel Cr-Mn austenitic stainless steels

The present study deals with the effect of shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) processes with different welding speeds on microstructural and mechanical properties including intergranular corrosion susceptibility of ultra-low nickel chrome-manganese austenitic stainless steel (ASS). The microstructural analysis was performed by an optical microscope. The Fisher Ferritscope was used for determining ferrite content in the weldment. The microstructural analysis shows that the size of dendrites of delta ferrite and the width of heat affected zone (HAZ) decreases when welding speed increases. It was found more delta-ferrite in SMAW weld compared to GMAW weld. It was also found that when welding speed increases, tensile strength, impact strength and hardness values decrease for both welding processes. From the U-bending test, it was found that the welded joints are strong enough to withstand bend at 1800 without any cracks for both welding processes. It was also found that Cr-Mn ASS weld becomes susceptible to intergranular corrosion on welding. For both welding processes, the degree of sensitization value decreases with an increase in welding speed for both the welding processes as evaluated by the double loop electrochemical potentiodynamic reactivation (DLEPR) test. Also, the weld joint made using the GMAW process is more susceptible to intergranular corrosion than that made using the SMAW process.