Improvement of Mechanical Properties of Composites with Surface Modified B₄C for Precision Machining

In order to solve the problem of difficult sintering and high brittleness of B₄C-based ceramics, B₄C@ZrB₂-TiB₂ composite powder was synthesized by molten salt method, and B₄C-(Zr, Ti)B₂ composite ceramics were successfully prepared by spark plasma sintering. The effects of different raw material ratios on the composition, microstructure, and mechanical properties of the prepared composite ceramics were characterized by XRD, XPS, SEM, and TEM. The results show that ZrB₂ and TiB₂ were grown on the surface of B₄C by template mechanism to form a dense nanocrystalline coating, and the original surface of B₄C was exposed gradually with the decrease of the ratio of metal powder. When the composite powders were sintered at 1700 °C, ZrB₂ and TiB₂ formed a solid solution, which can refine grains and improve strength. When the raw material ratio is n(B₄C): n(Zr): n(Ti) = 12:1:1, the composite ceramics have excellent comprehensive properties, the Vickers hardness reaches 41.2 GPa.