Study on the Mechanical Performance of Dissimilar Butt Joints between Low Ni Medium-Mn and Ni-Cr Austenitic Stainless Steels Processed by Gas Tungsten Arc Welding

In the present work, dissimilar butt joints between a low-Ni, medium-Mn austenitic stainless steel, M-Mn SS, and a Ni-Cr austenitic stainless steel, Ni-Cr SS, were processed by utilizing the gas tungsten arc welding (GTAW) technique at different heat inputs. A filler metal of ER308 was employed in the welding process. The filler yields 480 MPa, which is equivalent to the yield strength of M-Mn SS. The microstructural analysis and mechanical performance (i.e., tensile strength and hardness properties) of the concerned joints were studied by using an optical microscope and uniaxial tensile tests, respectively. The results revealed that a duplex structure from austenite matrix and delta ferrite is promoted in the fusion zone (FZ) of the dissimilar joints processed with low and high energy inputs (0.486 kJ/mm and 0.558 kJ/mm). The FZ of the specimens welded at high heat input exhibited the lowest hardness value (151.2 HV) in comparison to heat affected zone (HAZ) (166.3 HV). Moreover, the joints exhibited a low tensile strength of 610 MPa. The achieved strength is significantly lower than the strengths of the base metals (BMs) M-Mn SS and Ni-Cr SS. This is mainly attributed to the inhomogeneous dendritic structure of the FZ with Cr-carbides precipitation.

Automated summary

In this study, dissimilar butt joints between a low-Ni, medium-Mn austenitic stainless steel and a Ni-Cr austenitic stainless steel were processed by gas tungsten arc welding technique with ER308 filler metal. Microstructural analysis revealed a duplex structure in the fusion zone of joints processed under low and high heat inputs. Joints with high heat input showed lower hardness values and tensile strength, attributed to inhomogeneous dendritic structure and Cr-carbide precipitation in the fusion zone.