Interfacial microstructure and mechanical properties of TC4/Ti3SiC2 contact-reactive brazed joints using a Cu interlayer

Abstract

Reliable contact-reactive brazed joints of TC4 alloy and Ti3SiC2 ceramic were obtained using a Cu interlayer. The interfacial microstructure of a TC4/Ti3SiC2 joint brazed at 920 °C for 10 min was TC4/Ti2Cu + α-Ti + β-Ti/Ti2Cu + AlCu2Ti + Ti5Si3/Ti5Si3 + Ti5Si4/Ti3SiC2. The interfacial microstructure and mechanical properties of TC4/Ti3SiC2 joints brazed at different temperatures were investigated. With increasing temperature, the shear strength of the brazed joints first increased and then decreased. The maximum shear strength was 132 ± 8 MPa, and the corresponding fracture occurred along the Ti–Si reaction layer and the Ti3SiC2 substrate adjacent to the Ti–Si reaction layer. The microhardness test also demonstrated that the Ti–Si reaction layer possessed the highest microhardness, 812 ± 22 HV. The Ti-Si reaction layer was the weakest part of the brazed joints. To eliminate the Ti-Si reaction layer and improve the mechanical properties of TC4/Ti3SiC2 brazed joints, a 40-μm Ni layer was plated on the surface of the Ti3SiC2 ceramic before brazing. The results showed that the Ti–Si reaction layer that formed adjacent to the Ti3SiC2 ceramic was thin and intermittent. Moreover, the interface between the Ti3SiC2 ceramic and the TC4 alloy became jagged. The shear strength of the TC4/nickel-plated Ti3SiC2 brazed joints improved to 148 ± 8 MPa; the corresponding fracture occurred mainly in the Ti3SiC2 ceramic and only a small portion of the fracture occurred in the brazing seam.