Mechanical performance enhancement of wire-arc directed energy deposited tungsten/steel multi-material structures through heat treatments

Integrating materials with distinct properties (e.g., tungsten and steel) into a single structure offers significant performance benefits for demanding engineering applications. Among available manufacturing techniques, wire-arc directed energy deposition (DED) has gained attention for its capability to fabricate complex multi-material components with minimal waste. Nevertheless, the integration of tungsten and steel remains challenging due to their mismatched thermal and mechanical characteristics, which often result in high residual stresses and weak interfacial bonding. In this study, heat treatment was investigated to improve the structural integrity of wire-arc DED-fabricated tungsten/steel components. Instead of relying solely on experimental trial-and-error, simulations were employed to determine a suitable heat treatment condition—holding at 900 °C for 120 minutes followed by cooling at 5 °C/min. This treatment effectively relieved residual stress while simultaneously altering the microstructure: the tungsten alloy exhibited grain refinement, whereas the steel showed moderate grain coarsening. Mechanical testing demonstrated a 16% increase in tensile strength, from 521 ± 4 MPa in the as-printed condition to 602 ± 7 MPa after heat treatment. Notably, the fracture location shifted from interface in the as-printed state to within the steel region after heat treatment, confirming enhanced interfacial bonding.