Fabrication and characterization of austenite-ferrite stainless steel bimetals by twin wire arc additive manufacturing

In this work, gas metal arc welding (GMAW) based twin wire arc additive manufacturing (TWAAM) system has been employed to deposit to wire materials simultaneously to fabricate austenite-ferrite stainless steel (AFSS) bimetal of austenite stainless steel (SS304L) and ferrite stainless steel (SS430L). A combination of high voltage and wire feed with low torch speed and gas flow resulted in optimal deposition as determined through response surface analysis based on experimental data of single-track bimetal bead on plate depositions. Mechanical and microstructural characterization of the AFSS bimetal was carried out using tensile test, hardness tests, fractography, SEM with EDS, and phase analysis. Tensile properties of the AFSS bimetal were seen to improved with the yield strength of 343 MPa, ultimate strength of 613 MPa and elongation of 67%, and a hardness value of 225 HV. The interface of the AFSS bimetal was found defects free and microstructures contained both austenite and ferrite phases with higher amounts of Ni-content. The fracture morphology of the fabricated AFSS bimetal was seen to contain dimple sizes lying between that of individual steels and resulted in higher elongation than that of the pure ferrite steel. This study demonstrated defects free fabrication of bimetallic structures with unique microstructural features and enhanced mechanical properties. © 2024 Informa UK Limited, trading as Taylor & Francis Group.