Effects of diffusion bonding temperature and holding time on the microstructure and strength of diffusion bonded B4C-HfB2-SiC composite ceramic joint

Diffusion bonding of B 4 C-HfB 2 -SiC composite ceramic with Ti and NiCoCr medium-entropy alloy as the composite interlayer material was studied in this work. The effects of diffusion bonding temperature and holding time on the interfacial microstructure and mechanical properties of the joints were investigated. The results indicated that diffusion bonding with Ti and NiCoCr medium-entropy alloy as the composite interlayer material could fabricate ceramic joints with good metallurgical bonding without cracks and discontinuities. With a holding time of 10 min, the flexural strength of the joint increased with the diffusion bonding temperature. The joint flexural strength reached the maximum value of 309 MPa when the diffusion bonding temperature was 1200°C. The joint strength increased firstly and then decreased with the holding time increased from 10 min to 70 min for the joints diffusion bonded at 1100°C. The interfacial reaction phases between B 4 C-HfB 2 -SiC composite ceramic and the interlayer materials were characterized in detail by various analysis methods.