Microstructure and compressive properties of 3D-extrusion-printed, aluminized cobalt-based superalloy microlattices

Cobalt-based superalloy microlattices with γ/γ′ microstructure are manufactured by combining two additive methods: ink-extrusion 3D-printing and pack-cementation surface alloying. First, a microlattice green structure is 3D-printed at ambient temperature from inks comprised of Co3O4, NiO, and WO3 powders, an elastomeric binder and solvents. Organic removal followed by oxide reduction under Ar-5% H2, sintering and homogenization at 1250 °C lead to a metallic microlattice with dense struts with uniform γ (fcc)-Co–22Ni–8W (at.%) composition. Second, aluminum is deposited on the strut surfaces via pack-cementation at 1000 °C, diffused at 1300 °C through the strut volume to achieve a uniform composition (Co–20Ni–6W–10Al or Co–18Ni–5W–13Al, at.%), and precipitated during aging at 900 °C as γ′ precipitates within the γ matrix. The compressive strength, ductility and energy absorption of these γ/γ′ Co-based precipitation-strengthened microlattices is measured at ambient temperatures for two aging time (16 and 65 h) and found to be much superior to those of an unalloyed Co microlattice.