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The connection method of ceramics and metals

Number of visits: Date:2018-12-26 08:46


In the brazed joint of ceramic and metal, the good wettability of the solder on the ceramic is a prerequisite for effective connection. According to the difference in wettability, brazing of ceramics and metals can be divided into two categories: one is to pre-metallize the ceramic surface, and then connect with solder, called indirect welding. Common metal surface treatment methods for ceramic materials include electroplating, sintered metal powder, active metal and vapor deposition.

The other is to directly use a brazing filler metal containing active metal elements, and the active elements react with the ceramic surface to increase the wettability of the ceramic and the metal, thereby achieving the purpose of welding, which is called direct (active) brazing. Currently used brazing active metals are mainly transitional elements, because their outermost electrons are not filled and have high activity. The active metal can be prepared by adding the active metal to a conventional Cu-based, Ag-based, Ni-based, and Au-based solder.

Further, Zr, Hf, V, Ti, Cr, W, etc. may also be used as the active metal linking element, but these elements have a relatively high melting point and are poor in chemical reactivity with the ceramic material, and are mainly used for the connection of non-metal oxide ceramics.

2.Solid phase diffusion connection

The advantage of the process is that the joint has stable quality, high joint strength, can weld joints with large cross-section, can weld multiple joints at a time, has high efficiency, can increase the intermediate layer, and does not need surface metallization for ceramic materials. However, the process is complicated and can meet the application requirements under high temperature and corrosion resistance conditions. High requirements for connection surface status and connection equipment.

3.Transition liquid phase diffusion connection

The method uses a heterogeneous multi-layer intermediate layer to form a local liquid phase alloy in the joint region by melting or A/B interface reaction of the joint layer B, forming a local liquid alloy in the joint region, and then interfacial reaction with the ceramic and the intermediate core. The long-term diffusion between the metals makes the liquid phase zone isothermal solidification and homogenization of the solid phase components.

4.Reaction forming connection

The reaction forming joining method has been developed from the SiC ceramic forming technology and is currently widely used in joining SiC ceramics. The advantage is that it overcomes the large thermal stress of ceramics and metals during active brazing and solid phase diffusion welding.

5.Self-propagating high temperature synthesis connection

Self-propagating high-temperature synthesis, also known as combustion synthesis technology, explosion synthesis technology, is to use the chemical reaction of the intermediate layer itself to promote the reaction, and finally rely on the product formed by the reaction to connect the ceramic and the metal together. The self-propagating high-temperature synthetic connection method has simple equipment and process, and can realize in-situ connection of ceramic and metal. Moreover, the intermediate layer may be added with reinforcing phases such as second phase particles and whiskers to enhance the strength of the connection.

6.Laser brazing

The high-energy beam laser welding method can be used for rapid heating and cooling, with nitrogen screen cooling and temperature field adjustment, to induce improved composite materials to enhance the camera matrix interface reaction, and a good strength joint can be obtained under suitable process conditions.

7.Binder connection

The same or different materials are firmly joined together by the adhesion of the adhesive on the solid surface. The method is simple in process, and can be used for aircraft emergency repair, joint connection of projectile missiles, repairing turbines, repairing compressor rotors, and the like. The ceramic and the metal are glued and connected, and the interface acts as a physical force and a chemical bond. The joint strength of the organic glue is less than 100 MPa, and the joint strength of the inorganic glue is less than 10 MPa.

8.Mechanical connection

The mechanical connection method of ceramics and metal mainly includes bolting and hot sleeve. The bolting joint is connected by bolts. The method is simple, the joint is detachable, but it needs to be drilled in ceramics, the processing is difficult, and the joint lacks airtightness. The heat jacket is a method of obtaining a gas-tight joint by utilizing a large difference in thermal expansion between the ceramic and the metal, but the joint generates a large residual stress, and the temperature of the workpiece to be connected is not excessively high in order to ensure effective airtightness.

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