Joining of titanium diboride-based ultra high-temperature ceramics to refractory metal tantalum using diffusion bonding technology

Abstract The use of ultra-high temperature ceramics (UHTCs) requires effective methods to overcome the problems associated with manufacturing parts with complex shapes. In this study, a titanium diboride (TiB2)-based ultra-high-temperature ceramic, TiB2-20 vol.%TiC-20 vol.%SiC (TTS), was joined to refractory metal tantalum (Ta) using titanium (Ti) interlayer. The interface microstructure and mechanical properties of joints obtained at different bonding temperatures were investigated. The bonding mechanism of the joint was discussed based on TEM analysis and theoretical calculation. The results revealed that a (Ti, Ta)B + TiC + Ti5Si3 reaction layer formed adjacent to the TTS ceramic substrate while a β-(Ta, Ti)+β-(Ti, Ta)+α-Ti layer formed adjacent to the Ta substrate. The α-Ti was gradually replaced by β-(Ta, Ti) and β-(Ti, Ta), and the reaction layer of the ceramic side became thicker as the bonding temperature increased. The maximum joint shear strength of room temperature was 176 MPa when the joint was bonded at 1200 °C for 60 min under 20 MPa, and cracks propagated in the ceramic. The shear strength of the joint tested at 800 °C was 86 MPa, and fracture occurred at the β-(Ti, Ta).