Effects of shell printing and directional infiltration in binder jetting and reaction sintering of silicon carbide

Binder jetting (BJT) is a promising additive manufacturing (AM) method for fabricating complex silicon carbide (SiC) ceramics. Producing high-quality SiC products for advanced engineering applications requires a fine, homogeneous, and pore-free microstructure, This has been pursued by combining of BJT with reaction sintering through liquid silicon infiltration (LSI). This study examines key processing parameters in BJT and the reaction sintering of SiC composites. Green SiC parts were fabricated using BJT and subsequently densified via LSI. Additionally, some samples underwent phenolic resin impregnation and pyrolysis (I&P) to induce carbonization before LSI. Key variables—such as printing layer thickness (LT, 35 and 70 μm), printing strategy (normal printing versus shell printing), and initiation surfaces for LSI (top or bottom of the samples)—were optimized to minimize printing and layering imperfections, reduce porosity, and achieve a more uniform phase distribution in the final siliconized samples. The results demonstrated a significant influence of printing variables on green density and porosity, with higher LT and shell printing leading to a reduction in green density. Final porosity was notably lower when LSI was initiated from the bottom surface (LSI/B) compared to the top surface. Moreover, shell printing and higher LT resulted in reduced porosities during LSI/B. I&Ped samples fabricated using normal printing exhibited the highest SiC content, achieving a maximum density of 2.82 g/cm³ at an LT of 35 μm. Furthermore, siliconizing I&Ped shell-printed samples produced a more uniform microstructure in the core compared to those created through normal printing.