Joining C/C Composite To Molybdenum

C/C composite and molybdenum have more and more cross application in aerospace, defense industry, the nuclear industry and other areas for their excellent performance, such as high temperature strength, high heat conductivity, low coefficient of thermal expansion and so on. Therefore, there is a necessary requirment for joining the two kinds of material. The paper preliminary investigatied the joining technology analyzed the interfacestructure, mechanical properties of the joints and discussed the reaction mechanism. The main conclusions are as follows:C/C composite cannot achieve direct diffuision welding with molybdenum due to excessive residual stress in cooling stage by their thermal expansion coefficient dismatch. By adding W-Co-Cr-Ti inter-layer, C/C composite can be brazing jointed to molybdenum under argon protective atmosphere in1900℃for15minutes. When the weld is broad (0.5mm), pore defects apperes in the joints which decrease the mechanical properties. When the weld is appropriated (0.05mm), the joint is jointed closely, the joint strenth attains30MPa, the fracture occurred in the interface near C/C composite. The joints can be improved by means of designing conical interface which increases the connection area, enhances the pinning effect and reduces the residual stress. The joint strength with conical interface increases to45MPa and the fracture completely occurred in C/C composite matrix.In soldering process, the active element Ti, Cr enrich in the interface near C/C composite, molybdenum diffuses into the matrix of C/C composite, which leads to TiC, Cr7C3, Mo2C generated in the interface near C/C composite. The element Ti in solder layer diffuses to molybdenum interface to form a certain thickness of reaction diffusion layer which mainly consist of Ti-Mo, Ti-W solid solution.