Achieving High Strength of Dissimilar TC4/304 Stainless Steel Joints by Laser Welding Using a Novel V/CuCrZr/CoCrNi Composite Layer

A novel V/CuCrZr/CoCrNi composite interlayer is successfully developed for dissimilar laser welding of 304 stainless steel (SS) to TC4 titanium alloy, where CoCrNi and V layers are first deposited on 304 SS and TC4 substrates, respectively, via laser metal deposition. By incorporating a 0.5 or 1.0 mm CuCrZr interlayer between these functional coatings and performing two‐pass laser welding at the V/CuCrZr and CuCrZr/CoCrNi interfaces, full‐penetration butt joints have been achieved without Fe–Ti brittle intermetallic compounds (IMCs). Microstructural characterization reveals that the fusion zone near TC4 (FZ‐1) primarily consists of (β‐Ti, V) solid solution, while the 304 SS‐side fusion zone (FZ‐2) contains (Cu) and (Co–Cr–Fe–Ni) solid solutions. The 304 SS/TC4 joints exhibit remarkable ultimate tensile strengths of 487.9 and 412.6 MPa for 0.5 and 1.0 mm CuCrZr thicknesses, respectively, attributable to both the elimination of softening zones in unmelted CuCrZr and the complete suppression of IMC formation. This study demonstrates an effective strategy for producing high‐strength dissimilar joints between SS and titanium alloys.