Microstructure and properties of additively-manufactured WC-Co microlattices and WC-Cu composites
Liquid ink-printing followed by sintering is used to fabricate WC-Co microlattices and cutting tools. The microstructure of WC-xCo (x=0.5-20 wt.%) is studied for a range of carbide-to-binder ratios and for various sintering temperatures. For 0.5≤Co≤5 wt.%, struts in microlattices exhibit residual porosity due to incomplete densification, even at the highest sintering temperature of 1650 °C. With 10 wt.% Co, fully dense lattice struts are achieved after sintering at 1450 °C for 1 h. For 1450-1650 °C sintering temperatures, the hardness of WC-xCo struts initially increases (due to increasing densification with increased Co) and then gradually decreases (due to an increase of softer Co phase, at near-full density). Finite-element modeling (FEM) shows that the uniaxial elastic deformation of WC-10Co lattices is mostly supported by stretching-dominated vertical columns formed by stacking filaments in a 0/90˚ cross-ply geometry. WC-10Co lattices are infiltrated with Cu at 1300 °C to obtain dense WC-Cu composites, with an internal architecture consisting of a WC-rich lattice and Cu-rich channels, with a high thermal conductivity of 140±7 W/(m·K). Under compression, WC-Cu infiltrated composites are supported by the ductile Cu phase after compressive failure of the internal WC-rich lattice, unlike the WC-Co open lattices which show brittle failure. A cutting tool with an internal WC-Cu lattice architecture is fabricated by 3D WC-Co ink-extrusion printing, sintering, and Cu infiltration. Laser heating experiments and FEM confirm that the 3D-printed/infiltrated/architectured WC-Cu composite cutting tool maintains lower temperatures than a uniform WC-Co tool, for equal heat input at the corner of the tool.