Printability of austenitic steel bimetallic structure by wire arc additive manufacturing: numerical modelling and experimental analysis

Bimetallic structures (BMS) are composed of two distinct metals joined together to leverage their unique thermophysical, mechanical, and corrosion/oxidation resistance properties. Wire arc additive manufacturing (WAAM) is adopted to fabricate BMS components to achieve the benefits of high deposition and efficiency at low cost. Stainless steel SS316L exhibits excellent weldability, biocompatibility and creep strength at elevated temperatures, making it a suitable candidate material for marine propellers and blades. The challenge in these austenitic steels occur due to hot cracking which is mitigated through adding a small amount of δ-ferrite. A new chemical composition containing stainless steel SS309 is known to be introduced to increase the δ-ferrite content in parent matrix. Since, both materials (SS316L and SS3309) possess distinct chemical compositions, predicting their interrelated characteristics through numerical modeling approach is required to understand the overall behaviour, which also significantly reduces cost and time. The present work performs the printability study of both materials using Finite Element Method (FEM) software Ansys workbench 2022 VR2 framework and validated through experimental results. It is seen through the thermal strain analysis that the maximum thermal strain as 3.44 × 10⁻³ is noticed at the second deposited layer of SS316L whereas minimum thermal strain as 1.48 × 10⁻³ is noticed at the end of the deposition (~ 20th layer). These locations are observed in SS316L regions. The microstructural analysis shows both materials has austenite dominating phase consist of δ-ferrite. The composition estimation through EDS quantification at the interface indicated the composition as a mid-value of SS316L and SS309 composition. The tensile results confirm the benefits of δ-ferrite presence as it improves the tensile strength for the BMS WAAM sample. Further, it eliminated the cracks which was observed on the fracture surface of SS316L.