Abstract
A high-density TiB2-TiC-SiC composite ceramic was prepared through hot pressing. The average flexural strength, fracture toughness, and hardness of the sintered composite ceramic were 486 MPa, 6.21 MPa·m1/2, and 20.6 GPa, respectively. Then, the active brazing of the composite ceramic and Nb using Ti and Ni foils was investigated. The results revealed that the TiNi-Nb eutectic structure was formed in the brazing seam by dissolving Nb. The interfacial reactions between the three components of the TiB2-TiC-SiC ceramic and the liquid TiNiNb filler were essential for obtaining a robust joint. During the brazing process, the TiB2 component reacted with active Ti in the liquid filler to form TiB, and then the TiB reacted with Nb to form NbB and Nb3B2 at the ceramic interface. Meanwhile, a thin (Ti, Nb)C reaction layer was generated near the TiC and SiC components. By increasing the brazing temperature from 1160 °C to 1220 °C, the width of the reaction zone neighboring the TiB2-TiC-SiC ceramic increased from 13 μm to 29 μm, resulting in a change in the shear strength of the brazed joints. When the joint was brazed at 1180 °C for 10 min, the shear strength of the joint reached a maximum value of 179 MPa. The crack was observed on the ceramic substrate close to the reaction zone.
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