Vat Photopolymerization Additive Manufacturing of WC-Co Hardmetals Enabled by In Situ Polymerization-Induced Microencapsulation

The additive manufacturing of hardmetals has attracted great attention recently but faces significant challenges in low printing resolution and low mechanical strength. Herein, the fabrication of hardmetal parts with complex structures and high surface quality by vat photopolymerization assisted with a sintering process has been achieved. This was enabled by in situ polymerization-induced microencapsulation of WC powder, which simultaneously enhances the photocuring ability and sedimentation stability of the WC-Co slurry. The WC powder is microencapsulated by a polystyrene (PS, WC@PS) coating with a thickness of ∼20 nm. The curing depth of the WC-Co slurry with WC@PS was dramatically increased from 32 to 336 μm compared to the slurry with original WC, exhibiting an average increment of 650%. The 3D-printed hardmetal parts exhibited a relative density of 99.5%, a Rockwell hardness of 86.9 HRA, and a surface roughness Ra of 2.26 μm, approaching the theoretical limits in classical powder metallurgy-derived WC-Co hardmetal parts. With high density and hardness, it is shown that a printed drilling bit can easily drill through metal sheets. This work paves a path for the vat photopolymerization 3D printing of miniature complex hardmetal components combined with high surface quality and high performance.