<p>Decreasing the high content of residual silicon in the sintered bodies is the main method to improve the performance of reaction-bonded silicon carbide (RBSC) ceramics fabricated by additive manufacturing. In this work, high-performance SiC ceramics were fabricated by fused deposition modeling (FDM) combined with liquid silicon infiltration (LSI) and the content of residual silicon was decreased through adjustment of nozzle geometry and graphite content. The results showed that the rectangular nozzle minimized interlayer and inter-filament gaps, allowing the subsequently formed SiC to better fill these voids and thereby reduce localized residual silicon. Graphite content influenced the extent of the Si–C reaction and the resulting microstructure. The flexural strength initially increased with graphite content, reaching a maximum at 25 wt.%, and subsequently decreased at higher graphite loadings. The optimized specimen containing 25 wt.% graphite exhibited a flexural strength of 336 MPa, a density of 3.02 g·cm⁻³, and a thermal conductivity of 134 W·m⁻¹·K⁻¹, together with a low coefficient of thermal expansion (CTE) of 3.84 × 10⁻⁶ K⁻¹ at 800 °C. These results demonstrate that the FDM–LSI technique is a promising route for the fabrication of high-performance SiC ceramics.</p>