Preservation of Natural Phase Balance in Multi-pass and Wire Arc Additive Manufacturing-Made Duplex Stainless Steel Structures

This work investigates the effects of Ar-based shielding gases on the microstructure and phase balance of duplex stainless steel (DSS) depositions. The results are then used for fabrication of DSS walls using wire arc additive manufacturing (WAAM), and the microstructural characteristics and mechanical performance of the products are assessed. WAAM currently poses as one of the most interesting methods of manufacturing by enabling joining of materials to fabricate structures layer by layer. However, the extreme conditions imposed by the process, such as high heat inputs and re-melt and solidification of the deposited layers, could compromise the performance of the products. A detailed microstructural analysis is conducted on single layer and double layer depositions of DSS to assess the effects of different shielding gases on the ferrite/austenite phase balance in the specimens. The results show that the depositions shielded with a small fraction of carbon dioxide (CO2) present better microstructural features in comparison to depositions shielded with the other selected gases. A mixture of 98%Ar + 2%CO2 was employed for fabrication of a 60-layer DSS WAAM-made wall and some mechanical characteristics were studied. The mechanical examinations demonstrate that the properties of the parts fabricated using WAAM are comparable with their wrought counterparts.