| In this study, nickel layer and copper layer were prepared on the surface of SiC tube, respectively, by using the electroless plating method, and the effects of the absence of coating and two kinds of plating on the microstructure and mechanical properties of SiC-Kovar alloy heterojunction connected by AgCuTi solder were investigated. The results show that the thickness of the interface reaction layer is about 2.03 μm with the main components being Fe2Si+TiC+Ti5Si3+Ni2Si, when AgCuTi solder is directly connected to SiC and Kovar alloys. When nickel-plated SiC and Kovar alloy are connected, nickel reacts with SiC to produce excessive Ni2Si, and the thickness of the reaction layer is 2.82 μm. When copper-plated SiC and Kovar alloy are connected, the thickness of the interface reaction layer is reduced to 1.68 μm, because the copper layer limits the diffusion of active element Ti into SiC matrix. The shear strength of the three joints is 25.4 MPa, 33.3 MPa and 37.7 MPa, respectively. Although the plated nickel can prevent the direct contact between Ti and SiC in the solder, this effect is limited by the increase of intermetallic compounds, resulting in a decrease in the strength of the joint. On the contrary, copper can suppress the formation of intermetallic compounds in the interface reaction layer and improve the performance of the joint. |
