Study Of Diffusion Bonding Process And Mechanism Of SiC Ceramic To Ti Under Electric Field

SiC ceramic has many excellent properties, but brittleness and poor machinabilitylimit its uses, bonding SiC ceramic to metal can give full play to their excellentperformance and can make up their respective shortcomings. Diffusion bonding is morecommonly used in the methods of connection between ceramic and metal, its joint hasgood stability, high quality and corrosion resistance, but has low bonding efficiency.Therefore, in order to improve the efficiency of diffusion bonding, in this paper, thediffusion bonding under the electric field between SiC and Ti was carried out on thebasis of conventional diffusion bonding. The interfacial microstructure of joint underdifferent process conditions and the influence to the joint quality by different processparameter were investigated by using SEM, EDS, XRD, TEM, shear performancetesting and other means.The process parameters of diffusion bonding SiC to Ti such as temperature, time,pressure etc have great influence on the diffusion bonding joints quality, and influenceeach other. Studies suggest that, the joint quality is better in the process parameters of1000℃/2h/7.5MPa and its shear strength reached66.4MPa. On this basis, applyingvoltage to bond SiC to Ti was studied through the orthogonal experiment, the primaryand secondary order of the parameters which influence the joint quality is: temperature﹥voltage﹥time.950℃/1.5h/7.5MPa/400V is the best parameter and its shear strength is69.6MPa. On the premise of not reducing the shear strength, applying voltage duringthe bonding process can lower bonding temperature, shortened bonding time andimprove the efficiency of the bonding.Joint microstructure shows that: In the process of SiC/Ti interface diffusionreaction, new phase Ti₅Si₃C_xand TiC generate at the interface, and the interfacestructure from SiC to Ti is SiC/TiC/（Ti₅Si₃C_x+TiC）/Ti. When metal connects the anode,ceramic connects the cathode, the electric field promotes the interface react anddiffusion layer thicken, but reversed connection can inhibit the diffusion of the interface.With the increase of voltage, the promotion and inhibition of electric field have themore obvious trend. When the temperature is low and reaction layer is thinner, SiC andTi diffusion bonding joint was fractured in the TiC layer and the interface between SiCand TiC. But the joint was fractured in the TiC layer and the interface between TiC and（Ti₅Si₃C_x+TiC） when the reaction layer was thicker.Electric field contributes to every stage of diffusion bonding. In the stage ofinterface contact, voltage makes the interface contact tightly because of the greatlyimage interaction, and the image interaction will increase obviously with the increase of voltage and decrease of interface distance; in diffusion reaction stage, the ion diffusionflux will increase by applying voltage, that means applying voltage can promote the iondiffuse in SiC/Ti interface, and the greater the voltage is, the promoting is moreobvious.