Effect of graphite content on the microstructure and mechanical properties of SLS-based RB-SiC ceramics

In this study, reactive bonded (RB)-SiC ceramics were fabricated using a combination of selective laser sintering (SLS) and reactive melt infiltration (RMI). The microstructure and mechanical properties of RB-SiC ceramics were optimized by adjusting the graphite content. The sintered bodies were found to consist of α-SiC, β-SiC, Si and C. The addition of graphite prolonged the reaction time between carbon and silicon, resulting in a greater infiltration of molten silicon and an increased formation of β-SiC. Furthermore, a correlation was observed between the proportion of graphite content and the bulk density and bending strength of RB-SiC ceramics. In the range of 0–10 wt%, the bulk density initially increased and then decreased as the graphite content increased. The maximum density was found to be 2.74 ± 0.15 g/cm3. The flexural strength reached the maximum value at 217.9 ± 16.9 MPa when the graphite content was 5 wt%. However, beyond this point, the flexural strength decreased rapidly. The present research demonstrates the promising potential of utilizing SLS additive manufacturing to fabricate SiC ceramics with exceptional mechanical properties.