JPH0427193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method of joining silicon carbide ceramics and metal by brazing, and can be used for manufacturing silicon carbide ceramic products.

(Conventional technology) Silicon carbide ceramics are considered the most promising as engineering ceramics or high-performance ceramics, and in the field of energy conservation, they are used in ceramic engines and heat exchangers, and in the field of new energy development, they are used in the first generation of nuclear fusion reactors. It is being considered to use silicon carbide ceramics for walls.

However, silicon carbide ceramics has the disadvantage that it is difficult to mold and process parts with complex shapes, and it is very expensive compared to metals.

For this reason, parts having a desired shape are obtained by bonding parts obtained by molding and processing metals that are easy to process to silicon carbide ceramics.

Conventionally, as a method for joining silicon carbide ceramics and metal, a metallization method is known in which the surfaces of silicon carbide ceramics to be joined are once metalized and then the silicon carbide ceramics and metal are brazed. Further, a method of brazing silicon carbide ceramics and metal by interposing an active metal between them is described in JP-A-59-137373 and JP-A-61-215272.

(Problems to be Solved by the Invention) When joining silicon carbide ceramics and metal by brazing, the metallization method requires metallization treatment, which increases process time and cost, and reduces workability. The advantages of the brazing method as being good were lost. Furthermore, the method using an active metal has the problem that the surface of the active metal is oxidized when it comes into contact with the atmosphere, resulting in poor reactivity, and sufficient bonding strength cannot be obtained.

(Object of the Invention) An object of the present invention is to solve the problems of the prior art described above and to provide a method for joining silicon carbide ceramics and metal with good workability and excellent joining strength.

(Technical Means for Solving the Problems) The present invention provides that when silicon carbide ceramics and metal are joined by brazing, an active metal or a hydride of the active metal is added to the surface of the silicon carbide ceramic to be joined. The present invention relates to a method for joining silicon carbide ceramics and metal, which is characterized by applying a paste made of powder and an organic silicon compound in advance.

In the present invention, as the active metal or the hydride of the active metal, a metal such as titanium or zirconium or a hydride of the metal is used.

As the organosilicon compound, one that undergoes thermal decomposition at 400 to 800° C. and generates active hydrogen, hydrocarbon, or silicon hydride compound is used, and in particular, one whose residual rate after thermal decomposition is 10% by weight or more is preferable. For example, JP-A-51-126300, JP-A-52-112700
Polycarbosilane and polytitanocarbosilane described in JP-A-54-61299, JP-A-56-92923, JP-A-56-74126, and JP-A-57-16029. , polyzirconocarbosilane, or polydimethylsilane, which is a raw material thereof, can be effectively used.

The ratio of the active metal or the hydride of the active metal to the organosilicon compound is determined by the active hydrogen, hydrocarbon, or silicon hydride compound generated by thermal decomposition of the organosilicon compound. It is sufficient if the oxide layer can be completely removed, and the volume ratio of the active metal or the hydride of the active metal to the organosilicon compound is preferably in the range of 0.5 to 20:1.

The paste used in the present invention is usually prepared by dissolving an organosilicon compound in an organic solvent and then adding and mixing a powder of an active metal or a hydride of the active metal. As an organic solvent,
Any material that dissolves the organic silicon compound may be used, and for example, toluene, xylene, etc. are used.

The obtained paste is applied to the surface of silicon carbide ceramics to be joined. The amount of paste applied depends on the thickness.
The range of 20 to 70 μm is preferable, and the bonding strength will be insufficient even if it is larger or smaller than this range.

Next, a brazing material is interposed between the silicon carbide ceramics coated with the paste and the metal, and these are heat-treated to join the silicon carbide ceramics and the metal.

As the metal to be joined, any ferrous alloy or non-ferrous metal having a melting point higher than that of the brazing material can be used.

Silver solder is generally used as the brazing material.
The shape of the brazing material is not particularly limited, but foil or powder is usually used. The amount of brazing filler metal to be used may be as long as the thickness is about the same as or greater than the thickness of the paste, but if it is 200 μm or more, it will cause problems in terms of strength.

The atmosphere for the heat treatment may be in a vacuum or in an inert gas atmosphere, for example, in order to prevent oxidation of the metal to be joined and to convert the organic silicon compound contained in the paste into an inorganic substance such as silicon carbide. It is necessary to carry out in nitrogen gas or argon gas.

The temperature of the heat treatment must be higher than the melting point of the brazing filler metal, especially 20 to
A temperature 300°C higher is preferred.

(Function) The active metal or the hydride of the active metal is covered with an oxide film in the atmosphere and is very stable. For this reason, in the conventional method, the reactivity of the active metal was poor and sufficient bonding strength could not be obtained. but,
In the present invention, when the active metal or the organosilicon compound mixed with the active metal hydride is thermally decomposed, active hydrogen, hydrocarbon, or silicon hydride compound is released, and its reducing action causes the active metal or Since the oxide film covering the surface of the active metal hydride is completely removed, it becomes a very active metal. The activated metal then diffuses into the brazing material and reacts with the silicon carbide ceramics to form a strong bond.

Further, the organic silicon compound is also decomposed and converted into an inorganic substance of silicon carbide as a result of the heat treatment, forming a strong bond with the silicon carbide of the base material.

It is thought that the above-described effects greatly improve the bonding strength between silicon carbide ceramics and metal compared to the conventional case of using active metal alone.

(Example) The present invention will be explained below with reference to Examples.

Example 1 Titanium powder of 325 mesh or less and polytitanocarbosilane as an organosilicon compound in a volume ratio of 3:
After dissolving polytitanocarbosilane in xylene, titanium powder was added to form a paste.

Next, the paste was applied to the surface of silicon carbide ceramics with a surface size of 7 x 6 mm and a length of 18 mm.
After coating to a thickness of 50 μm, silver solder (BAg-8) is applied to a thickness of 50 μm between the surface to be joined of the silicon carbide ceramic and the surface of stainless steel (SUS304) of the same type as the silicon carbide ceramic. to intervene,
These were held at a temperature of 900°C for 15 minutes in a nitrogen gas atmosphere, and then slowly cooled to form silicon carbide ceramics.
A stainless steel joint was obtained.

The joint strength of the obtained silicon carbide ceramic-stainless steel joint was measured at a span of 30 mm and a loading rate of 0.5.
As determined by a three-point bending test under the conditions of mm/min,
A strength of 30.6Kg/mm ² was obtained.

Example 2 A silicon carbide ceramic-stainless steel bonded body was obtained in the same manner as in Example 1, except that zirconium powder was used instead of titanium powder and the heat treatment was performed at 830° C. in an argon gas atmosphere.

The bonding strength of the silicon carbide ceramic-stainless steel bonded body obtained was 25.8 Kg/mm ² .

Example 3 A silicon carbide ceramic-stainless steel bonded body was obtained in the same manner as in Example 1, except that TiH ₂ powder was used instead of titanium powder and the heat treatment was performed at 800° C. in a nitrogen gas atmosphere.

The bonding strength of the silicon carbide ceramic-stainless steel bonded body obtained was 23.6 Kg/mm ² .

(Effects) According to the present invention, when joining silicon carbide ceramics and metal by brazing, an active metal or a hydride of the active metal mixed with an organosilicon compound can be used to join the silicon carbide ceramics to the metal. It is possible to obtain a bonded body of silicon carbide ceramics and metal with significantly improved bonding strength compared to the case of using only the active metal.

Further, unlike the metallization method, the present invention does not require metallization treatment, so it has good workability and is economically advantageous.

Furthermore, the resulting joined body also has good heat resistance, and although it depends on the heat resistance temperature of the metal to be joined, it usually has heat resistance up to a temperature about 300°C lower than the melting point of the brazing filler metal. For example, when silver solder is used as the brazing material, the heat resistant temperature of the joined body is approximately 500°C.

Claims (1)

[Scope of Claims] 1. When joining silicon carbide ceramics and metal by brazing, a paste consisting of an active metal or a hydride powder of the active metal and an organic silicon compound is applied to the surface of the silicon carbide ceramics to be joined. A method for joining silicon carbide ceramics and metal, characterized by pre-coating. 2. The method according to claim 1, wherein the active metal is titanium or zirconium.