Microstructure of ZrC-SiC composite ceramic joint vacuum brazed with Ti-Ni filler metal

ZrC-20% (volume fraction) SiC(ZS) composite ceramic was brazed with a Ti-Ni high melting point filler metal. The effect of change in filler metal composition on the interface microstructure and mechanical property was investigated. At last, the interfacial reaction rate was controlled via the change of the filler metal composition. The effect of Ni content in filler metal on the interface microstructure and mechanical property was investigated. The results showed that the interfacial reaction was violent when ZS was brazed with Ti-83% (mole fraction) Ni filler metal, and a transition layer of 50 μm was formed. In this transition layer, some reactions occurred in Ni-SiC system and the reacted products were Ni₂Si and C. When the content of Ni in Ti-Ni filler metal decreased to 61%, Ni reacted firstly with SiC. Also, Ti reacted with the reaction product C, and a large amount of TiC formed in the transition layer as well as the interface. The formed TiC hindered the transport of Ni atoms to the ZS composite ceramic, thus causing the reduction of the interfacial reaction. In this condition, the thickness of the transition layer decreased to 10-15 μm. Furthermore, only TiC formed on the interface when brazed with Ti-50%Ni filler metal. The thickness of TiC layer was 5 μm. The shear strength of the joint brazed with Ti-61%Ni filler metal reached 127 MPa, which was the maximum value for its relative uniform microstructure on the interface.