Microstructures and mechanical behavior of the bimetallic additively-manufactured structure (BAMS) of austenitic stainless steel and Inconel 625

Abstract

Bimetallic additively manufactured structures (BAMSs) can replace traditionally-fabricated functionally-graded-components through fusion welding processes and can eliminate locally-deteriorated mechanical properties arising from post-processing. The present work fabricates a BAMS by sequentially depositing the austenitic stainless-steel and Inconel625 using a gas-metal-arc-welding (GMAW)-based wire + arc additive manufacturing (WAAM) system. Elemental mapping shows a smooth compositional transition at the interface without any segregation. Both materials being the face-center-cubic (FCC) austenite, the electron backscattered diffraction (EBSD) analysis of the interface shows the smooth and cross-interface-crystallographic growth of long-elongated grains in the <001> direction. The hardness values were within the range of 220–240 HV for both materials without a large deviation at the interface. Due to the controlled thermal history, mechanical testing yielded a consistent result with the ultimate tensile strength and elongation of 600 MPa and 40 %, respectively, with the failure location on the stainless-steel side. This study demonstrates that WAAM has the potential to fabricate BAMS with controlled properties.