Fabrication and characterisation of high-performance joints made of ZrB2-SiC ultra-high temperature ceramics

Joining is crucial for ultra-high temperature ceramics (UHTCs) to be used in demanding environments due to the difficulty in manufacturing large and complex ceramic components. In this study, ZrB2-SiC composite UHTCs parts were joined via Ni foil as filler, and the mechanical properties and oxidation behaviour of the fabricated ZrB2-SiC/Ni/ZrB2-SiC (ZS/Ni/ZS) joint were investigated. Firstly, dense ZrB2-SiC composites were prepared from nano-sized powders by spark plasma sintering (SPS). The ZrB2-SiC parts were then joined using SPS. Furthermore, the elastic modulus, hardness, shear strength and high temperature oxidation behaviour of the ZS/Ni/ZS joint were examined to evaluate its properties and performance. The experimental results showed that the ZrB2-SiC parts were effectively joined via Ni foil using SPS and the resultant microstructures were free from any marked defects or residual metallic layers in the joint. Although the elastic modulus and hardness in the joining zone were lower than those in the base ZrB2-SiC ceramics, the shear strength of the joint reached ∼161 MPa, demonstrating satisfactory mechanical properties. Oxidation tests revealed that the ZS/Ni/ZS joint possesses good oxidation resistance for a wide range of elevated temperatures (800–1600 oC), paving the way for its employment in extreme environments.