High-temperature Mechanical Properties Of Diffusion Bonding Joints Between SiC Ceramics With Ti/Ni Interlayers

The SiC ceramics was joined by diffusion bonding method with Ti/Ni interlayers. The influence of the types and composition of metal interlayers(Nano Ti/Ni powder or Ti/Ni foils), the parameters of diffusion bonding, and the high-temperature oxidation on the microstructure and mechanical properties of the ceramics joints were investigated.The results showed that the ceramics joints processed by diffusion bonding with Ti/Ni interlayers were compact. The phases in joints were composed of Ti C, Ti3 SiC2, Ti Ni, Ni3 Si, Ni2 Si, etc. The formation mechanism of the ceramics joints was discussed by thermodynamic calculations combining with XRD and EDS.The types of metal interlayers had a great influence on the joints thickness. The thickness of joints with nano metals powders were 150μm and changeless with the change of the composition, while the thickness of joints with metal foils were thinner, 10~50μm, and influenced by the composition. The mechanical properties of the joints with nano metals powders had a great change in room temperature and high temperature conditions. The shear strengths at room temperature and 1000℃ were close, while it improved greatly at 1200℃. The mechanical properties of the joints with metals foils improved at high temperature, which got the maximum value at 1000℃ and dropped a little at 1200℃. The joints with metals foils interlayers of Ti:Ni=1:1(at.) had the better comprehensive properties, 52 MPa at room temperature, 128 MPa at 1000℃, 120 MPa at 1200℃.For joints with better comprehensive properties, the parameters of the diffusion bonding were researched. It was found that the mechanical properties at each temperature improved with the joining temperature increasing. The shear strengths were 69 MPa at room temperature, 130 MPa at high temperature. The hardness was over 28 GPa and elastic modulus were about 400 GPa. The joints’ oxidations at high temperature were studied and found that the shear strengths improved to 120 MPa after the oxidation for 5h at 1200℃, which is close to the shear strengths at high temperature. The shear strengths improved continuously with higher temperature or longer time, which improved to 190 MPa after the oxidation at 1200℃ for 20 hours.