Intermediate layer selection for ceramic metal connection

    In the diffusion connection of ceramics and metals, an important process measure is to use various metal intermediate layers to control the interface reaction (inhibit or change the interface reaction products) and slow down the residual caused by the different thermal expansion coefficients of ceramic and metal Stress, thereby improving the mechanical properties of the joint.

    From the point of view of controlling the interface reaction, an active metal intermediate layer can be selected, or an adhesive metal intermediate layer can be used. The active metal intermediate layer includes V, Ti, Nb, Zr, Hf, Ni-Cr, Cu-Ti, etc., which can interact with the ceramic to form a reaction product, and the resulting reaction product makes the ceramic and the connected metal firmly connected Together. Adhesive metal intermediate layers include Fe, Ni, Fe-Ni, etc., which do not react with certain ceramics, but can mutually diffuse with ceramic components to form a diffusion layer. The study found that the combination of adhesive metals and active metals can achieve better results. From the perspective of easy connection and control interface response, the choice of the intermediate layer mainly pays attention to the following points.

    (1) It is easy to be plastically deformed, and its melting point is lower than that of the base material;

    (2) The difference between the physical and chemical properties and the base material is smaller than the difference between the connected materials;

    (3) No adverse metallurgical reaction with the base metal, such as no brittle phase or undesirable eutectic phase;

    (4) Does not cause electrochemical corrosion of the joint.

    Sometimes the intermediate layer is added to relieve the residual stress of the joint. At this time, the choice of the intermediate layer can be divided into three types, namely, a single metal intermediate layer, a multi-layer metal intermediate layer and a graded metal intermediate layer.

    The main methods of adding the middle layer are:

    (1) Adding thin metal foils can be processed into amorphous foils for brittle materials that are difficult to make foils;

    (2) Add a powder intermediate layer, which can be mixed with acetone to form a paste, or it can be pressed into a sheet at low temperature;

    (3) Surface coating, such as evaporation, PVD, electroplating, ion plating, electroless plating, sputtering, ion implantation, etc.

(Huiputech)