Effects of B4C addition on the microstructure and properties of porous alumina ceramics fabricated by direct selective laser sintering

Direct selective laser sintering (dSLS) is a promising method for the fabrication of complex-shaped ceramic parts. In this paper, boron carbide (B4C) was used as an inorganic additive to improve the laser sintering behavior of alumina. The effects of B4C addition on the microstructure and mechanical properties of porous alumina ceramics were investigated. Mixture of alumina powders and different amount of B4C were directly sintered using different SLS parameters. Results indicated that the process window of alumina could be expanded by the addition of B4C. Furthermore, the amount of B4C played an important role in surface morphologies of alumina ceramics. It could be explained by the increase of mass transfer due to the addition of B4C, which enhanced the densification process. The compressive strength of sintered samples increased with the increase of B4C, which reached its maximum value when the content of B4C was 7 wt% and the density of the samples after post treatment could reach 1.4 g/cm3. In addition, a size expansion phenomenon was observed. The size expansion could reach 5% after SLS, which could be attributed to the pin effects and oxidation behavior of B4C particles.