Vat photopolymerization additive manufacturing of reaction bonded boron carbide composites

Boron carbide (B₄C) ceramic exhibit excellent mechanical properties. However, they are known for its difficulty in machining and sintering. Although vat photopolymerization (VPP) additive manufacturing can enable the high-precision fabrication of complex ceramic structures, the high light absorption value of B₄C deteriorates the curing ability of the photosensitive slurry, resulting in a low success rate for VPP process. Moreover, the high content of photosensitive resin complicates the densification process of the fabricated components. In this study, by optimizing the particle size of the B₄C powder and the solid loading of the slurry, a slurry with the desired viscosity, curing ability, and sedimentation stability was developed, meeting the requirements for VPP process. Through the optimization of VPP process parameters, the deviation rate between the green body size and the design size was significantly reduced. By analyzing the thermogravimetric curve of the green body in an argon atmosphere, an optimized heating program for debinding was established, yielding debinding samples with minimal defects. Furthermore, a sucrose infiltration-pyrolysis process was applied to introduce free carbon into the samples, enhancing the phase composition and mechanical properties of the samples after liquid silicon infiltration. The flexural strength and Vickers hardness of the reaction bonded B₄C (RBBC) composites increased as the residual silicon content decreased, while the fracture toughness showed a slight decrease. Finally, the 2C-Si sample exhibited the optimal mechanical properties. This study presents a promising method for manufacturing RBBC composites with complex structures using VPP additive manufacturing.