JP2560930B2 - Surface treatment method for ceramics substrate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating the surface of a ceramic substrate, and more particularly to coating the surface of the ceramic substrate with a composite material of ceramic and metal (hereinafter sometimes referred to as "cermet"). The present invention relates to a surface treatment method for a ceramic base material, which enables a layer to be easily formed with high adhesion strength.

[0002]

2. Description of the Related Art In many cases, a so-called metallizing treatment for forming a metal coating layer on the surface of a ceramic substrate is carried out as a pretreatment for joining ceramics or ceramics and metal. According to this metallizing process, it is possible to use a joining method such as brazing at a relatively low temperature. Therefore, by selecting a metallization treatment method suitable for the materials to be joined, it is possible to obtain a highly reliable joined body at low cost.

Conventionally, there have been many methods such as thermal spraying, plating, spraying, PVD (physical vapor deposition method), CVD (chemical vapor deposition method), etc.
All of these are carried out on the ceramic sintered body.

For example, Japanese Patent Application Laid-Open No. 1-1119589 discloses that
A method of subjecting a ceramics sintered body to a metallizing treatment by ion plating is disclosed.

[0005]

In the above conventional method,
When the coating layer is formed of the metallized ceramic and the metal having good wettability, a certain degree of adhesion strength can be obtained. However, the metal used for forming the coating layer does not always have good wettability with the ceramic to be metallized, and often has poor wettability. In this case, sufficient adhesion strength of the metal coating layer cannot be obtained,
As a result, there is a problem that the bonding strength of the bonded body is poor.
Further, in the case of the thermal spraying method, a large thermal shock may be applied to the ceramics sintered body which is the object to be sprayed, and the ceramics sintered body may be damaged, as disclosed in JP-A-1-119587. Although a method of improving the adhesion of the coating layer by implanting a metal element into the ceramics has been proposed, the method using such high energy has a drawback that the processing cost is high.

The present invention solves the above-mentioned conventional problems, and a coating layer made of cermet, which is effective for brazing and the like, can be easily and inexpensively formed on the surface of a ceramic substrate with high adhesive strength. An object of the present invention is to provide a surface treatment method for a ceramics base material.

[0007]

The method for surface treatment of a ceramic base material according to claim 1 is a method of forming a coating layer of a composite material of ceramics and a metal on the surface of a ceramic base material. It is characterized in that a powder of a composite material of ceramics and a metal oxide (hereinafter referred to as "composite powder") is adhered to the surface and then baked, and the formed coating layer is subjected to a reduction treatment.

According to a second aspect of the present invention, there is provided a surface treatment method for a ceramic base material according to the first aspect, wherein the ceramic material of the composite material is mainly composed of the ceramic material forming the green body. The ceramic powder and the metal oxide powder are mixed, calcined, and then pulverized.

The present invention will be described in detail below. In the method of the present invention, an unfired ceramic green body is obtained, for example, by molding a molding material obtained by mixing ceramic powder constituting a base material in a suitable organic solvent together with a binder, a plasticizer and the like into a desired shape. By doing so, it can be easily manufactured.

The composite powder to be adhered to the surface of the unfired ceramic green body thus obtained is, for example, mixed with the ceramic and the metal oxide forming the green body and calcined to pulverize the calcined product. Therefore, it can be easily prepared. The ceramics forming the composite powder is preferably made of the ceramics forming the ceramic green body. On the other hand, examples of the metal oxide include those having a high solid solubility in the ceramic green body with the ceramic and easily becoming a metal by reduction, such as NiO and CoO. NiO is particularly preferable in terms of cost because it is inexpensive.

There is no particular limitation on the method for adhering such a composite powder to the surface of the ceramic green body,
The composite powder sized to a suitable particle size is dispersed in an organic solvent such as ethanol or toluene, preferably an organic solvent of the same or similar nature as the organic solvent used in the production of the ceramic green body, and a suitable binder is added if necessary. A method is preferred in which a coating solution is added to prepare a coating solution, and the coating solution is applied to the surface of the ceramic green body by spraying, printing, brush coating, or the like.

In this case, the concentration of the composite powder in the coating solution is 10
It is preferably about 50 to 50% by weight, and when a binder is used, the binder may be P.I. V. B can be used, and the amount thereof is preferably 1 to 5% by weight based on the coating liquid.

In the present invention, there is no particular limitation on the ratio of the ceramic and the metal oxide constituting the composite powder, 0.1 to 99.9% by weight of the ceramic and 99.9 to 0.1 of the metal oxide. Various compositions may be employed in the range of wt%.

In the method of the present invention, the coating liquid is applied to the surface of the ceramic green body and dried to adhere the composite powder, and then the composite green body is fired at the sintering temperature of the base material. And sintering the coating layer.
After that, the coating layer is reduced by a method such as firing in a reducing atmosphere. As a result, the metal oxide in the coating layer is reduced to a metal, and a cermet coating layer of ceramics and metal is formed.

In the method of the present invention, a coating solution is prepared from each of a plurality of kinds of composite powders having different ceramic contents, and the coating solution of the composite powder having a large ceramic content is prepared.
The coating solution of composite powder with a small ceramic content is sequentially coated on the ceramic green body, and then dried.
By firing and reducing, it is also possible to form a coating layer in which the ceramic content decreases in the layer thickness direction from the base layer side (ceramic sintered body side) to the surface layer side. In this case, since the base layer side has a large ceramic content, the adhesiveness with the ceramic sintered body as the base material is good, and
Since the surface layer side has a low ceramic content and a high metal content, a coating layer effective for joining treatment such as soldering or brazing is formed. It is also possible to form a coating layer having a metal layer as the surface layer by further applying a coating solution containing only a metal oxide on the surface, followed by drying, firing and reduction.

[0016]

In the surface treatment method for the ceramic substrate of the present invention, since the composite powder of the ceramic and the metal oxide is adhered to the green body of the ceramic and fired,
The formed coating layer is firmly sintered and integrated with the ceramic sintered body of the base material. Moreover, since the metal component can be present in the coating layer as a composite powder with ceramics in a uniformly dispersed state, a cermet coating layer in which the metal is contained in the ceramics in a uniformly dispersed state can be obtained. However, a strong interfacial adhesion strength can be obtained, and there is almost no risk of peeling of the coating layer.

In particular, even higher adhesion can be obtained by adopting the ceramics forming the ceramic green body as the composite powder ceramics.

When the composite powder is applied to the surface of the ceramic green body as a coating liquid, the solvent of the coating liquid slightly dissolves the surface of the ceramic green body, and the base material and the coating film are mixed at the interface. , Even higher adhesion can be obtained.

According to the method of the present invention, a cermet coating layer having various compositions ranging from a low metal content to a high metal content can be formed on the surface of a ceramic substrate with high adhesion, and from the substrate side. It is also possible to form a coating layer on the surface side of which the metal content increases in the thickness direction and to make the outermost surface a metal layer. The metal layer having the outermost surface in this manner is extremely effective for joining such as brazing.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 Production of Ceramic Green Body 8 mol% yttria-stabilized zirconia (hereinafter referred to as "YSZ")
Called. ) The powder was put into a mixed solvent of ethanol and toluene, and a binder and a plasticizer corresponding to the powder amount were added to this solvent. This was stirred for a long time in an automatic mortar. The high viscosity slurry obtained was dried and then molded to obtain a green body.

Preparation of spray material The composition after firing and reduction should be as follows.
Weigh NiO powder and YSZ powder (however,
O powder only), and these were mixed using a planetary ball mill. After thorough mixing, molding with a uniaxial press,
Calcination was performed in the air at 200 ° C. for 5 hours. This was crushed to obtain a composite powder. This composite powder was put into an ethanol-toluene mixed solvent similar to that used in the production of the green body (concentration: ◯% by weight), and P.O.
V. 3.5 wt% of B was added to prepare a spray material. Formation of 40 vol% Ni-YSZ 70 vol% Ni-YSZ Ni cermet coating layer The spray materials shown in Table 1 were sequentially sprayed onto the surface of the ceramic green body. The spray process was carried out by the spray device shown in FIG. In the figure, 1 is a spray chamber having an opening 1A in the upper portion, 2 is a mounting table, 3 is a ceramic green body, 4 is a two-fluid nozzle, 5 is a regulator, 6 is a pump, 7 is an air cylinder, 8 is a spray material, 9 Is a spray material supply pipe, 10 is an air supply pipe, 11
Is a valve. The two-fluid nozzle 4 is inserted from the upper opening 1A of the spray chamber 1 and is located above the ceramic green body 3 on the mounting table 2. The spray material 8 is supplied to the two-fluid nozzle 4 via the supply pipe 9 by the pump 6, and the air supplied from the air cylinder 7 via the supply pipe 10 by the regulator 5 is also supplied from the tip of the two-fluid nozzle 4 to the ceramic green body. It is jetted toward the surface of No. 3.

[0023]

[Table 1]

Then, after allowing to stand overnight to naturally dry the solvent, it was placed in an electric furnace and slowly heated to 1200 ° C. to degrease and calcine the binder, plasticizer solvent and the like. After the calcination, sintering was performed in the atmosphere at 1500 ° C. for 5 hours while applying a load to correct the warpage of the sample. Then, a reduction treatment is performed in a hydrogen-nitrogen mixed gas at 1000 ° C. for 1 hour to convert NiO in the formed coating layer to Ni.
To give a cermet coating layer.

As a result, no. 1 is 4 with a thickness of 70 μm
The 0% by volume Ni-YSZ cermet coating layer is No. In No. 2, a 70 volume% Ni-YSZ cermet coating layer having a thickness of 40 μm was formed in No. In No. 3, 40 volume% Ni- with a thickness of 70 μm
YSZ cermet layer and 70 volume% Ni with 40 μm thickness
The two-layer coating layer with the YSZ cermet layer is No. In No. 4, a 40 volume% Ni-YSZ cermet layer having a thickness of 70 μm,
A three-layer coating layer of a 70 volume% Ni-YSZ cermet layer having a thickness of 40 μm and a Ni layer having a thickness of 20 μm was obtained.
No. It was confirmed that all of the coating layers obtained in Nos. 1 to 4 had a high adhesive force and did not peel off even by heat treatment up to 1500 ° C.

[0026]

As described in detail above, according to the surface treatment method for a ceramic base material of the present invention, a cermet coating layer useful for brazing with a metal or the like is formed on the surface of the ceramic base material with high adhesion. It is possible to easily, efficiently and inexpensively form.

[Brief description of drawings]

FIG. 1 is a perspective view showing a spray device used in Examples.

[Explanation of symbols]

 1 Spray chamber 3 Ceramic green body 4 Two-fluid nozzle 8 Spray material

Claims (2)

(57) [Claims] 1. A method of forming a coating layer of a composite material of ceramics and a metal on the surface of a ceramic substrate, comprising depositing a powder of the composite material of a ceramic and a metal oxide on the surface of an unfired ceramic green body. A method for treating the surface of a ceramic base material, which comprises subjecting the formed coating layer to a reduction treatment after firing. 2. The ceramic of the composite material is mainly composed of the ceramic constituting the green body, and the powder of the composite material is a mixture of ceramic powder and metal oxide powder. The method for surface treatment of a ceramic substrate according to claim 1, wherein the surface treatment is performed by calcination and crushing.