Achieving high mechanical properties of ultrafine-grained WC-Co cemented carbide via material extrusion additive manufacturing

Abstract

The urgent demand for additive manufacturing (AM) cemented carbide parts with complex geometric structures has emerged. However, the powder bed fusion AM WC-Co cemented carbide exhibits poor mechanical properties due to cracks, pores, and abnormal WC grain growth caused by low formability, particularly ultrafine-grained cemented carbide. We employed material extrusion (MEX) AM to prepare an ultrafine-grained WC-0.5Cr₃C₂-0.2CeO₂-9Co cemented carbide. MEX AM eliminated defects, inhibited the abnormal WC grain growth, and increased the residual α-Co content at room temperature by improving the W and C solubility in α-Co to increase the stacking fault energy. The cemented carbide achieved a relative density of 99.52%, as well as α-Co content, an average grain size of WC, the adjacency of the WC phase, and the mean free path of the Co phase were measured at 16.5 vol.%, 384.6 nm, 0.58, and 208 nm, respectively. The synergistic effects of densification reinforcement, fine grain strengthening, and residual α-Co phase toughening, simultaneously improved the mechanical properties of the cemented carbide, achieving a Vickers hardness of 2123 ± 11 HV₃₀, a transverse rupture strength of 3639 ± 28 MPa, and a fracture toughness of 13.13 ± 0.03 MPa m^1/2, respectively, which demonstrated significantly superior mechanical properties compared with cemented carbide prepared via AM or traditional powder metallurgy. These findings effectively address the challenge of simultaneously enhancing the hardness and fracture toughness of ultrafine-grained cemented carbide and provide important guidance for the development of cemented carbide with excellent mechanical properties via AM.