Material extrusion additive manufacturing of WC-9Co cemented carbide

Abstract

Additive manufacturing (AM) cemented carbide is primarily challenged by critical issues of difficult-to-eliminate pores, cracks, deleterious phases, and non-uniform microstructure, which result in poor mechanical properties. This study utilizes material extrusion (MEX) AM technology to prepare a WC-9Co cemented carbide. The results show that green body printing and solvent debinding process significantly affect its stacked voids, interlayer bonding defects, and debound cracks. These green body defects are eliminated through liquid phase flow and WC particles flow-rearrangement during sintering, resulting in Co-rich regions or Co pools, abnormal growth of WC grains, and residual pores. A green body free of visible defects is prepared using a feedstock with a powder loading of 54 vol.%, a printing temperature of 150 ℃, a microfilament overlap ratio of 30%, and a printing-layer thickness of 0.1mm. Followed by a two-step solvent debinding and continuous thermal debinding-vacuum-pressure sintering, a nearly fully dense WC-9Co cemented carbide is fabricated, with a uniform microstructure of two phases and free of pores, cracks, and Co pools. Its Vickers hardness, transverse rupture strength, and fracture toughness reach 1525±3 HV30, 3492±45MPa, and 20.4±0.5MPa·m1/2, respectively, which are significantly better than those of similar reports and could be comparable to similar cemented carbides prepared by powder metallurgy. This study could provide a new technological path for developing high-performance cemented carbide complex-structured components.