Solid‐State Diffusion Bonding of Carbon–Carbon Composites with Borides and Carbides

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Abstract
Solid‐state diffusion bonding of carbon–carbon (C─C) composites by using boride and carbide interlayers has been investigated. The interlayer materials used in this study were single‐phase borides (TiB 2 or ZrB 2 ), eutectic mixtures of borides and carbides (ZrB 2 + ZrC or TiB 2 + B 4 C), and mixtures of TiB 2 + SiC + B 4 C produced in situ by chemical reactions between B 4 C, Ti, and Si or between TiC, Si, and B. The double‐notch shear strengths of the joints produced by solid‐state reaction sintering of B 4 C + Ti + Si interlayers were much higher than those of joints produced with other interlayers. The maximum strength was achieved for C─C specimens bonded at 2000°C with a 2:1:1 mole ratio of Ti, Si, and B 4 C powders. The reaction products identified in the interlayers, after joining, were TiB 2 , SiC, and TiC. The joint shear strength increased with the test temperature, from 8.99 MPa at room temperature to an average value of 14.51 MPa at 2000°C.