Application of brazing in metal and ceramic welding

Ceramic has incomparable insulation, heat resistance, corrosion resistance, wear resistance and other excellent properties, its application is increasingly expanding. However, the plasticity of ceramic materials is poor, and it is difficult to make complex structural parts, and cold processing is difficult. Therefore, in many occasions, ceramic materials need to be combined with other types of materials to be used in the form of connectors, so as to better play the superior performance of ceramic as structural materials and electrical insulators.

There are many connection methods between ceramic and metal, such as brazing, diffusion welding, fusion welding and oxide glass solder connection method, among which brazing method is one of the main methods to obtain high strength ceramic/metal joint.

The principle of brazing is to use the solder between the ceramic and the metal base metal to melt at high temperature, where the active components react with the ceramic raw material, forming a stable reaction gradient layer that binds the two materials together. Ceramic/metal brazing is generally divided into indirect brazing and direct brazing.

Indirect brazing is first metallized on ceramic surface and then brazed with solder to metal parts. Mo-mn is the most commonly used method for premetallization of ceramics, in addition to physical vapor deposition (PVD), chemical vapor deposition (CVD), thermal spraying and ion implantation.

Direct brazing method, also known as active metal brazing method, is to add active elements in the solder, such as transition metals Ti, Zr, Hf, Nb, Ta, etc., through chemical reaction to decompose the ceramic surface, forming a reaction layer, so as to connect with the metal together. The limitation of direct brazing lies in the low high temperature strength of joint and the spread of solder in large area brazing.

The direct brazing process is simple, but the high temperature strength of the joint is low. Indirect brazing process is relatively complex, and the joint has high strength and good density after forming. It has been widely used in mechanical manufacturing, Marine engineering, aerospace, electronic technology and other fields.

Suntech has been engaged in brazing ceramics and metal parts for many years and has rich project experience. At present, the product leakage rate after brazing is less than 10¹¹Pa•m³/s, reaching the world advanced level.