Wire-arc directed energy deposition of steel onto tungsten substrate: fabricability and mechanical performance of synergistic structures

This study investigates the fabricability, microstructures, and mechanical properties of multi-material structures composed of W7Ni3Fe tungsten alloy and SS316L stainless steel using a wire-arc directed energy deposition process. Direct deposition of SS316L onto W7Ni3Fe substrate resulted in cracks at the edges of the structure, caused by residual stresses and the formation of brittle Fe-W intermetallic phases at the interface. However, introducing a nickel alloy (IN625) as an interlayer significantly alleviated these stresses and suppressed intermetallic phase formation. The W7Ni3Fe alloy primarily consisted of α-W and γ-(Ni-Fe-W) phases, while the deposited IN625 interlayer contained γ-austenite and Laves phases, and the SS316L formed γ-Fe and δ-Fe phases. Chromium diffusion from the IN625 into the γ-(Ni-Fe-W) phase of the W7Ni3Fe alloy promoted a strong metallurgical bond at the W7Ni3Fe/IN625 interface. Uniaxial tensile tests demonstrated a tensile strength of 521 ± 4 MPa and an elongation of 22 ± 2%.