JPH1135380A - Method for bonding ceramic and metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding method giving high bonding strength of a ceramic and a metallic material, having a wide application range regardless of the kind of metal and ensuring easy bonding operation. SOLUTION: A metal and a ceramic having 5-20% porosity in at least the surface layer of the bonding face are placed opposite to each other as a pair of bodies 1, 2 to be bonded and a layer 3 of a bonding metal having a lower m.p. than the metal to be bonded is held between the bodies 1, 2. They are heated in vacuum and held at the melting temp. of the bonding metal for a prescribed time to allow the bonding metal to penetrate into the pores 4 in the ceramics and the bodies 1, 2 to be bonded are bonded by the anchoring effect of the penetrated metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining ceramics and metal, and more particularly, to a method for joining ceramics and metal with high strength without using an adhesive or brazing material.

[0002]

2. Description of the Related Art The use of ceramics has been expanding by utilizing the characteristics of being excellent in high hardness, wear resistance, corrosion resistance, heat resistance and the like. Along with this, the importance of technology for joining ceramics and metal has increased.

Conventionally, as a simple method of joining ceramics and metal, there is a joining method using an organic adhesive or an inorganic adhesive.

As an organic adhesive used for joining ceramics, there is an adhesive having a high adhesive strength such as an epoxy adhesive or a polyurethane adhesive. Organic adhesives are inexpensive and easy to bond, but do not have heat resistance. When the temperature of the joint becomes 200 ° C. or more, the adhesive strength becomes 0.01 kgf / cm ² or less, and heat resistance is required. Not suitable for bonding members.

[0005] On the other hand, some inorganic adhesives, such as refractory cement, can be heated to about 650 ° C, but have the disadvantages of low adhesive strength and poor airtightness.

In addition to the bonding method using an adhesive, other conventional bonding methods used for bonding ceramics and metal include an active metal method and a frit method.

[0007] The active metal method is a joining method using a brazing material containing an active metal such as Ti or Zr. In this active metal method, brazing is performed in a vacuum or an inert gas by interposing a brazing material mixed with Ti, Zr, and TiH ₂ between the ceramic and the metal so that the brazing material is wetted. This active metal method is a joining method whose joining operation is relatively simple.

[0008] The frit method is a method of melting glass powder put between bonding surfaces to bond ceramics and metal. This frit method is a bonding method that has a wide range of application to oxide ceramics and non-oxide ceramics.

[0009]

However, due to advances in ceramic manufacturing and processing techniques, the area in which ceramics can be used in place of metals as mechanical materials used under harsh conditions has been expanding. The demands cannot be met with the adhesive strength and heat resistance obtained with adhesives and inorganic adhesives.

When a ceramic and a metal are joined by the conventional active metal method, there is a problem that an active metal such as Ti or Zr is expensive and that a delicate difference in joining conditions greatly affects the joining quality.

The conventional frit method has a drawback that the metal to be bonded to ceramics cannot be applied to bonding of a low melting point metal such as a Cu alloy because the glass powder is melted by heating to a high temperature.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, obtain a high bonding strength between ceramics and a metal material, and have a wide application range regardless of the type of metal. It is another object of the present invention to provide a method of joining ceramics and metal, which can easily perform a joining operation.

[0013]

In order to achieve the above object, a joining method according to the present invention is a method of joining one of a ceramic body and another metal body. A bonding metal layer made of a metal material having a melting point lower than that of the metal to be bonded is sandwiched between bonding surfaces of a pair of a ceramic and a metal having a porosity of at least 5 to 20% in a surface layer of the bonding surface; The bonding object pair holding the layer is heated in a vacuum, the temperature at which the bonding metal is melted is maintained for a predetermined time, and the bonding metal penetrates into pores in the ceramic.

The bonding method according to the present invention utilizes pores present in ceramics, infiltrates the metal of the bonding metal layer into the pores, and uses the anchor effect of the permeated metal to effect bonding between the ceramic body and the metal. Joins the body.
When joined by this joining method, the heat resistance of the joint is obtained, and if the metal to be joined has a low melting point, a joining metal having a lower melting point can be used according to the metal to be joined, and the type of metal is also limited. Without having a wide range of application. Further, as compared with the active metal method using an active metal for bonding, aluminum, copper and their alloys can be used for the bonding metal layer, so that the cost is low.

The porosity of the ceramic is 5 to 20%, and the thickness of the bonding metal layer is 2 to 5 times the average pore diameter of the ceramic. preferable.

The bonding metal layer may be made of Au, A
g, Al, Cu, or a foil of a highly malleable metal material such as an alloy thereof may be sandwiched between the joining surfaces of the joined objects, and the joining metal layer may be formed of a metal. A metal film deposited or welded on the joining surface of the joined body may be used.

Further, in the bonding method according to the present invention, even if the porosity of the ceramic is out of the above range, the ceramic fine powder is plasma-sprayed on the bonding surface of the ceramic body to be bonded, and the ceramic is coated. A pretreatment for adjusting the pore diameter and the porosity of the surface layer of the joint surface of the joined body may be performed in advance. According to this, the range of ceramics to which the joining method of the present invention can be applied can be expanded.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for joining ceramics and metal according to the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes an object to be joined made of a metal material, and 2 denotes an object to be joined made of ceramics. The applicable range of the metal material of the one joined body 1 is as follows.
Any steel or non-ferrous metal material may be used, including steel, copper and its alloys, tungsten, molybdenum and its alloys, titanium and its alloys, and the like.

Regarding the applicable range of the ceramics of the other body 2, any type of ceramics including oxide ceramics such as alumina ceramics and zirconia ceramics and nitride ceramics such as silicon nitride ceramics can be used. It may be.

Although the type of ceramics is not limited, the porosity is preferably 5 to 20% in order to obtain sufficient bonding strength. Regarding the porosity, it is possible to form the ceramic so as to be within the range from the beginning, and even if the original porosity is out of the range of 5 to 20%, the ceramic is sprayed at the time of joining. By spraying ceramic fine powder, the porosity of the surface layer of the joint surface 2a may be adjusted to a range of 5 to 20%. Further, as described later, the size of the pores, that is, the average pore diameter is also related to the bonding strength. This average pore diameter may also be adjusted for the surface layer of the joint surface 2a by a thermal spraying method.

A bonding metal layer 3 made of a very thin metal foil or a metal film formed by vapor deposition or thermal spraying between the bonding surfaces 1a and 2a of the metal bonding target 1 and the ceramic bonding target 2 , And put in a vacuum furnace and heat it in this state. To obtain high bonding strength,
The thickness t of the bonding metal layer 3 is related to the size of the pores 4 of the ceramic, which will be described later.

As the metal foil used as the joining metal layer 3, a foil of a highly malleable metal material such as Al and its alloy, Cu and its alloy, Ag and its alloy, Au and its alloy is used. Then, the metal foil is pressed after being sandwiched between the joining surfaces 1a and 2a of the joined objects 1 and 2.

In the heating in the vacuum furnace, heating is performed to a temperature at which the metal of the bonding metal layer 3 melts (near the melting point), and this temperature is maintained for a predetermined time. The heating temperature changes according to the type of metal of the bonding metal layer 3. The metal of the bonding metal layer 3 is
It is a metal having a lower melting point than the metal of the body 1 to be joined. Therefore, when the material of the body 1 to be bonded is a metal having a low melting point, the bonding metal layer 3 may be formed of aluminum having a low melting point.

Thereafter, the objects 1 and 2 are cooled in a vacuum furnace, and the joining of the metal object 1 and the ceramic object 2 is completed.

Next, FIG. 2 is a view schematically showing the joined state of the objects 1 and 2 to be joined. The metal of the bonding metal layer 3 penetrates into the pores 4 from the bonding surface 2 a of the ceramic body 2 while being heated in the vacuum furnace, and enters the pores 4.
The metal is welded to the article 1 to be joined. As a result, the objects 1 and 2 are joined via the joining metal layer 3.

[0026]

EXAMPLES Next, specific examples of the method of joining a metal and a ceramic according to the present invention will be described. In particular, the relationship between the porosity of the ceramic and the joining strength, the size of the pores of the ceramic and the thickness of the joining metal layer will be described. Will be described. First Example The object 1 was steel (JIS S20C), the object 2 was alumina ceramics, and the joining metal layer 3 was aluminum foil. This aluminum foil is bonded to the objects 1 and 2
And pressurized between the joining surfaces 1a and 2a, and placed in a vacuum furnace and maintained at 670 ° C. for about 10 minutes. In this example,
As shown in Table 1, 20 kinds of samples having different porosity, the size of the pores 4, and the thickness of the aluminum foil were respectively bonded, and the bonding strength was tested with a universal testing machine.

[0027]

[Table 1] As can be seen from Table 1, the porosity of the ceramic is 1
% And 3%, samples 1 and 2 have significantly inferior bonding strength as compared with the other samples. If the porosity is too low, there is no room for the metal in the bonding metal layer 3 to penetrate into the body 2 to be bonded, so that the bonding strength is considered to decrease. On the other hand, samples 19, 2 having porosity of 25% and 30%
It can be seen that the bonding strength is also low at 0. This is thought to be because although the amount of metal that permeates the ceramic increases, the strength of the ceramic itself decreases due to the permeating metal.

Therefore, the porosity of the ceramic for obtaining a sufficient bonding strength is 5 to 20%.

This porosity range is a necessary condition,
Even in this range, there are samples such as sample 10 having low bonding strength. Therefore, next, the relationship between the bonding strength, the size of the pores, and the thickness of the bonding metal layer will be described.

[0030]

[Table 2] Table 2 shows that among the samples of Table 1, the porosity was 10%, 15%.
%, The joining strength is arranged in ascending order. Table 2 shows that there is a correlation between the pore diameter d and the thickness t of the bonding metal layer in order for the metal of the bonding metal layer to function suitably as a brazing material. It can be seen that the joint strength tends to decrease when the thickness t of the joining metal layer is too large with respect to the pore diameter d, common to the 10% and 15% samples. Also, it is useless if the thickness t of the joining metal layer is too thin. In order to obtain sufficient joining strength as a mechanical part,
The thickness t of the joining metal layer may be about 2 to 5 times the average pore diameter d.

SECOND EXAMPLE The bonding object 1 is made of a Ti alloy (Ti-4Al-6V) and the bonding object 2 is made of silicon nitride ceramics.
A gold foil having a thickness of 0 μm was used. This gold foil is bonded to the object 1
2 was pressed between the joining surfaces 1a and 2a, and was placed in a vacuum furnace and maintained at 1060 ° C. for about 15 minutes.

In the case of the second embodiment, the porosity of the silicon nitride ceramic is 5%, and the average pore diameter d is 5 μm. The thickness of the used gold foil is four times the average pore diameter d. The joining strength was as high as 6 kgf / mm ² .

THIRD EXAMPLE The article 1 to be joined is made of steel (JIS SCM440) and the article 2 is made of zirconia ceramics.
An aluminum foil having a thickness of 0 μm was used.

In the third embodiment, the zirconia ceramic of the article 2 to be bonded has a porosity of 1% or less. Then, a fine powder of zirconia ceramics is sprayed onto the joining surface 2a of the porosity zirconia ceramic to a thickness of 100 μm by plasma spraying, the porosity of the surface layer portion of the zirconia ceramic is 10%, and the average porosity d.
Was adjusted to 10 μm.

The joining surfaces 1a of the objects 1 and 2
The aluminum foil was sandwiched between 2a and pressurized, placed in a vacuum furnace and maintained at 670 ° C. for about 10 minutes. In the case of the third embodiment, the bonding surface 2 of zirconia ceramics is
Although the porosity of the surface layer of a was increased, the joint strength was measured after cooling, and a good result of 4.5 kgf / mm ² was obtained.

Fourth Embodiment A bonded article 1 was bonded as a steel material (JIS S20C), and a bonded article 2 was bonded as a zirconia ceramic having a porosity of 10%. As the joining metal layer 3, a 5 μm-thick aluminum film was formed on the joining surface 1 a of the article 1 by vapor deposition. With the joining surfaces 1a and 2a of the joined bodies 1 and 2 facing each other through the aluminum film, the joined bodies 1 and 2 were placed in a vacuum furnace and held at 650 ° C. for about 10 minutes.

In the case of the fourth embodiment, after cooling, when the bonding strength was measured to give the result that 3.0 kgf / mm ^2.

[0038]

As is clear from the above description, according to the present invention, high bonding strength between ceramics and a metal material is achieved.
It can be joined with heat resistance, has a wide range of application irrespective of the kind of metal, and can be easily and inexpensively joined.

[Brief description of the drawings]

FIG. 1 is an explanatory view of one embodiment of a method for bonding a ceramic and a metal according to the present invention.

FIG. 2 is a diagram schematically showing a bonding state between a ceramic and a metal.

[Explanation of symbols]

 Reference Signs List 1 bonded object (ceramic) 1a bonded surface 2 bonded object (metal) 2a bonding surface 3 bonding metal layer 4 pore d pore diameter t bonding metal layer thickness

Claims (5)

[Claims] 1. An object to be joined comprising ceramics,
A method for joining another metal object to be joined, wherein the melting point is lower than that of the metal to be joined between at least the joining surfaces of the ceramic and metal object pairs having a porosity of 5 to 20% in the surface layer of the joining surface. The joining metal layer sandwiching the joining metal layer is heated in a vacuum, and the temperature at which the joining metal is melted is held for a predetermined time, and the joining metal is inserted into the pores of the ceramic. A method of joining ceramics and metal, characterized by infiltrating a ceramic. 2. The bonding metal layer according to claim 1, wherein the thickness of the bonding metal layer is 2 to 5 times the average pore diameter of the ceramic.
3. The method for joining ceramics and metal according to 1. 3. The method according to claim 1, wherein the joining metal layer is made of a foil of a highly malleable metal material. 4. The method according to claim 1, wherein the joining metal layer is formed of a metal film deposited or deposited on a joining surface of a metal member to be joined. 5. A pre-treatment for plasma-spraying a ceramic fine powder on a bonding surface of the ceramic body to be bonded and adjusting a pore diameter and a porosity of a surface layer of a bonding surface of the ceramic body to be bonded. The method for joining ceramics and metal according to any one of claims 1, 2, 3, and 4.