Strong and densified 3D metal-ceramic composite with strengthened layer structure by material extrusion additive manufacturing

Material extrusion (MEX) of high-filled polymers with metal or ceramic powders has showed great potential in fabricating 3D structure combined via the powder metallurgy route. However, defects between deposited layers adversely affect the final performance of 3D components. Here, we introduced a high-flow filling approach based on effective viscosity control and optimized printing strategies for preparing high-density NiFe2O4-based cermet. We investigated the influence of powder loading and filling paths on both green and sintered samples regarding density, microstructure and mechanical properties. Polyformaldehyde (POM)-based feedstocks were developed with powder loading of 62vol% and 56vol%. 3D cermet with high powder loading demonstrated good shape retention but contained periodic pores due to low-flow filling between adjacent filament. Cermets with high relative density were achieved using 56vol% POM-based feedstock because of satisfactory fluidity and high-filling effect during deposition. Filling paths determined the distribution and size of the pores, with cermet based on the (45°, 135°) trace exhibiting the most uniform and dense structure. Cermets using 62vol% feedstock showed significant differences in flexural strength depending on the filling path, much lower than those achieved with the high-flow filling approach. Finally, 3D NiFe2O4-based cermets utilizing 56vol% feedstock demonstrated an optimal average flexural strength of 173.5MPa, close to 178.4MPa of conventional injection molded samples. Hence, high-qualified metal-ceramic composites can be fabricated using MEX via the high-flow filling approach, with potential applications in complex-shaped anode, cutting tools and wear-resistant parts.