3D-printed Tungsten Sheet-Gyroids via Reduction and Sintering of Extruded WO3-Nanopowder Inks

Abstract

Additive manufacturing of objects with complex geometries from refractory metals remains very challenging. Here, we demonstrate the fabrication of tungsten sheet-gyroids via 3D ink-extrusion of WO3 nano-powder followed by hydrogen reduction and activated sintering with NiO additions, as an alternative route to beam-based additive manufacturing of tungsten and other high melting metals and alloys. The microstructure and mechanical properties of the tungsten sheet-gyroids are measured for various wall architectures and processing conditions. The original gyroid architecture, separating two equally-sized volumes, is modified to achieve double-wall gyroids (with three separate volumes) with higher relative densities. The compressive properties of these single- and double-walled gyroids are compared to cross-ply lattice structures at 20 and 400 °C, below and above the ductile-to-brittle transition temperature of tungsten. Gyroids are similarly stiff but have lower peak stresses and absorption energy as compared to cross-plies, due to a more severe multiaxial stress state. Based on architecture changes (number, spacing and width of walls), the mechanical properties of the printed gyroids can be tailored to their application requirements. © 2020 Elsevier B.V.