Titanium and Stainless Steel Bimetallic Structures via Wire Arc-Directed Energy Deposition

Bimetallic structures unlock the ability to combine the superior properties of dissimilar alloys within a single component, yet their fabrication remains constrained by the inevitable formation of brittle intermetallic phases at metallurgically incompatible interfaces. This study employed a hybrid wire arc-directed energy deposition (WA-DED) system to manufacture CPTi–SS316L bimetallic structures. ER CuSi-A was introduced as an intermediate bond layer (IBL) between the two alloys, preventing direct Ti-Fe reactions and the associated formation of brittle intermetallic phases at the interface. A customized WA-DED system featuring localized high-purity argon shielding enabled defect-free deposition of the CPTi in an open environment. Two distinct metallurgical interfaces were identified: ROI 1 at the CPTi/ER CuSi-A junction (200 ± 22 μm), and ROI 2 at the ER CuSi-A/SS316L junction (18 ± 9 μm). Stress-relief heat treatment at 480 °C reduced residual stress in the CPTi zone by 77%. The bimetallic specimens achieved compressive yield strengths of 219 ± 6 MPa and 211 ± 8 MPa in the as-printed and heat-treated conditions, respectively, exceeding those of the wrought CPTi Grade 1 and SS316L counterparts by up to 29%. Tensile testing revealed brittle fracture at ROI 1 with an ultimate tensile strength of 182.5 ± 3 MPa. The fabrication of a functional auger screw prototype with a CPTi overlayer on an SS316L core further demonstrated the mechanical reliability and validated industrial applicability of the proposed approach.