Contact-reactive brazing of Ti3SiC2 ceramic to TC4 alloy using a Ni interlayer: Interfacial microstructure and joining properties

Abstract Ti3SiC2 ceramic and TC4 alloy were successfully joined by a contact-reactive brazing technique using a Ni interlayer. The results showed that liquid phase formed by the eutectic reaction between Ni interlayer and TC4 alloy, which further reacted with Ti3SiC2 ceramic, and Ti2Ni, Ti3AlC, TiC, Ti5Si3Cx and τ3 formed in the brazing layer. The width of the brazing layer increased and the amount of Ti2Ni phase decreased with increased brazing temperature and holding time. When the temperature reached 1040 °C, micro-voids appeared nearby the TC4 substrate in the joint, leading to a low joint strength. The microstructure of the brazing layer and the brazing fillet shape changed with increasing Ni foil thickness. Cracks were observed in the Ti3SiC2 substrate near the fillet when 60-μm and 120-μm Ni interlayers were used. The formation mechanism of the joints during the bonding process is discussed on the basis of the phase diagram and the microstructural evolution. The maximum shear strength of the Ti3SiC2/TC4 brazed joints was 126 MPa, which was 69% of that of the Ti3SiC2 substrate. The corresponding fracture occurred in the brazing layer and the Ti3SiC2 substrate.