Structure and Strength of SiC/Ti Bonding Interface

Abstract

The solid state bonding of pressureless-sintered SiC to SiC using 20 μm Ti foil was conducted at bonding temperatures ranging form 1373 to 1673 K for 0.3 to 72 ks in vacuum. For a constant bonding time of 3.6 ks, the granular TiC next to Ti and a mixture of Ti₅Si₃C_x+TiC phases next to SiC were formed. Increasing the bonding temperature in 100 K intervals from 1473 K to 1773 K, the Ti₅Si₃C_x single phase, Ti₃SiC₂ phase and TiSi₂ phase sequentially appeared. Fracture shear testing was used to measure bonding strength. The bonding strength was found to increase up to a maximum of 153 MPa at 1473 K. At higher temperatures it decreases to 54 MPa at 1573 K. At still higher temperatures bonding strengh again increases. The highest strengh of 250 MPa was measured at 1773 K. This variation of bonding strength with bonding temperature will be correlated with the microstructure observed at the interfase of the joints. The SiC/Ti joint with a duplex phase of Ti₃SiC₂+TiSi_z shows the stable strength up to testing temperature 973 K.