Fabrication of SiC composites by selective laser sintering and reactive melt infiltration

Silicon carbide (SiC) ceramics face numerous challenges in fabrication due to their strong covalent bonding structure. Conventional additive manufacturing methods typically require the addition of binders, such as resins, to the original powder. These binders melt and resolidify to bond primary SiC particles, forming silicon carbide (SiC) preforms. However, the binder content is critical to the preform shaping process. During the debinding stage, where the binder is removed, the preform undergoes dimensional shrinkage, which significantly compromises the dimensional accuracy of the final product. This study proposes a binder-free fabrication method that combines selective laser sintering (SLS) with reactive melt infiltration (RMI) to produce SiC composites. The effects of varying laser power on the properties of SLS-prepared SiC preforms and the final RMI-SiC composites were systematically investigated. Microstructural analysis revealed that bonding between SiC particles is achieved through SiC sublimation and a silicon melting-solidification process. Results indicate that as laser power increases, both the bulk density and mechanical properties of the SiC preforms and RMI-SiC composites first increase and then decrease. Under optimal conditions, the RMI-SiC composites achieved a bulk density of 2.74 +/- 0.06 g/cm3 and a flexural strength of 212.63 +/- 10.41 MPa. Furthermore, at 1000 degrees C, the coefficient of thermal expansion (CTE) was 5.16 x 10-6/K. This study offers a novel approach to the fabrication of high-precision, complex SiC ceramics through SLS technology.