JPH01133986A - Method for bonding silicon carbide-based ceramic - Google Patents

Abstract

PURPOSE:To bond compacts with high strength by adding boron and carbon to silicon carbide-based powder as a sintering aid, compacting the mixture, filling a slip consisting of a sintering aid, silicon carbide powder, a deflocculant, and a liq. medium between the bonding surfaces of the compacts, and sintering the slip. CONSTITUTION:The compacts or calcined bodies 1 and 2 are produced by using the silicon carbide powder added with boron and carbon as the sintering aid. The slip 3 consisting of a sintering aid contg. boron and carbon, silicon carbide powder, a deflocculant (e.g., dimethylamine and polycarboxylic acid), and a liq. medium (e.g., water) is filled between the bonding surfaces of the compacts 1 and 2 and sintered, and the compacts 1 and 2 are bonded. A part of the particles ot SiC, carbon, boron, etc., in the slip are diffused and infiltrated into the spaces between the particles in the compacts 1 and 2 by the action of the deflocculant 3. Since sintering is carried out under such conditions, the compacts 1 and 2 are integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for joining silicon carbide (SiC) ceramics.

<Prior Art> Silicon carbide ceramics have excellent heat resistance and high hardness, and are therefore expected to be used as high-temperature structural materials for engine parts, turbine parts, and the like. Ceramic parts are manufactured by obtaining molded bodies from SiC particles and firing them (see Japanese Patent Laid-Open No. 61-163167). During manufacturing, each part must be molded and then joined to form a part with its original shape. In this case, it goes without saying that bonding strength is of great importance.

Conventionally, the following method has been known as a general method for joining ceramics of the same type.

■ A method of applying slip (slurry containing ceramic raw material particles) to two undried molded bodies immediately after demolding by slip casting molding, aligning the coated surfaces, drying and sintering to form an integrated ceramic part, ■ Above ■ This is essentially different from the method of bonding through a bonding material such as a metal layer or glass phase (Japanese Patent Laid-Open No. 61-2198
(See No. 2).

<Problems to be Solved by the Invention> However, both of these methods have the following problems.

Method (2) can achieve good bonding, but it can only be applied to molded bodies immediately after demolding, so there is a problem in that it is not possible to obtain a high-strength ceramic bonded product with a well-shaped shape by machining. Ta. It should be noted that even if compression molded bodies (dried bodies) or temporary sintered bodies that are easily shaped by machining are attempted to be joined according to the method (2) above, only those with extremely weak bonding strength will be obtained.

On the other hand, method (1) has the problem that the bonding operation is complicated and the resulting bonding strength is clearly inferior to method (2).

The present invention was developed in view of the above circumstances, and involves joining compression-molded bodies or provisionally sintered bodies that have been shaped by machining at the plane determined at the time of design to create a final shaped part that maintains a predetermined strength. An object of the present invention is to provide a method for joining silicon carbide ceramics for manufacturing.

<Means for Solving the Problems> The method for joining silicon carbide ceramics of the present invention which can achieve the above object is to form a compression molded body or calcined a silicon carbide powder to which boron and carbon are added as sintering aids. The present invention is characterized in that a compact is produced, and a slip consisting of the above-mentioned sintering aid, silicon carbide powder, deflocculant, and liquid medium is filled between the joint surfaces thereof, and then sintered.

Here, the term "silicon carbide powder" refers to a powder whose main component is SiC, and although a small amount of other inorganic substances may be mixed in, it is preferable that it consists only of SiC. Further, the above-mentioned "temporary sintered body" preferably means one that is temporarily sintered at a temperature of about 1600°C or lower.

The sintering aids added to the silicon carbide powder for producing a molded body are mostly boron and carbon in an amount of 1.1 to 5% by weight in the form of powder, and the above-mentioned slip It is preferable that the sintering aid and the silicon carbide powder in the molded article have the same mixing ratio as in the molded body.

The above slip uses diethylamine and polycarboxylate as the deflocculant when water is used as the medium, and organic phosphate salt and polyoxyethylene as the deflocculant when benzene is used as the medium. Preference is given to using alkylamines and polycarboxylic acid salts.

In order to fill the slip between the joint surfaces, it is preferable to apply the slip to one or both of the joint surfaces and then bring the two joint surfaces together (bring them into contact). By doing so, it is preferable that the thickness of the slip layer interposed between the two wave-bonded materials is 0.2 to 1. This is because if the slip is too thick, it is likely to crack during handling after drying, and if it is too thin, the slip will tend to be applied unevenly, making it impossible to achieve a desired bonding strength.

By applying the slip and sintering the bonded objects in a non-oxidizing atmosphere at a temperature of 1950 to 2200° C., an integrated silicon carbide ceramic bonded article can be obtained.

<Function> The action of the peptizing agent contained in the slip filled between the joint surfaces causes the SiC in the slip to break down.

A portion of each particle of carbon and boron diffuses between the particles of the object to be joined and is sintered in that state, so that the object to be joined is integrated.

<Examples> The present invention will be described in more detail below using Examples along with Test Examples.

Example a) Preparation of samples to be joined First, two types of samples A and B were prepared from the following raw materials (
A molded body) was produced.

human) β type 5iC (average particle size CJ, SiLm)
9B, 5wt% amorphous boron (average particle size α6μrn)
0.5wt% carbon black (average particle size 0.5wt%)
02 μm) towt% B) α-type 5iC (average particle size 0.4 μFF!) 98, Owt% amorphous boron (average particle size 0.6 μm) towt% carbon black (average particle size 0.02 μm) tOwt
%Each sample was prepared by processing the above raw materials in a plastic ball mill.
Mix for 48 hours using ethyl alcohol as a medium,
The powder obtained by drying was first molded at a pressure of 200 Kz/d, and the fire-molded product was sealed in a rubber bag and immersed in water at 5000 Kg/d.
A plate-like sample having a width of 30 cm, a length of 150 cm, and a thickness of 6 cm was prepared by isostatic compression molding at CDL pressure. The bulk density of the molded body is A: 53% of the theoretical density, B: 5% of the theoretical density.
It was 8%.

In addition, the above samples A and B (molded bodies) were each placed in argon for 1
Samples A and B (temporary sintered bodies) which were pre-sintered at 500°C were also produced.

b) Preparation of slips Three types of slips (1), (2) and (2) having the following compositions were prepared by a conventional method. These slips are the above sample A,
A deflocculant and water are added to each raw material mixture of B.

Slip I Medium: Benzene 30 parts by weight Medium: Water 60 parts by weight Slip ■ Medium: Water 30 parts by weight The viscosity of the above slips I, ■, and ■ is 390 cp, respectively.
, 480cp and 366CI).

C) Wet the joint in advance with the medium of the slip to be used, immediately apply the slip, put the two plate-shaped samples together by sandwiching the applied slip, and as shown in Figure 1, use the graphite jig 4. Place it upright. The thickness of the slip layer 6 between the plate-shaped samples 1 and 2 is approximately 1 inch. 1st
The sintered joint is placed in a heating furnace as shown in the figure and sintered in argon gas at a temperature of 2,050°C to 2,100°C for 1 hour, resulting in a sintered joint that is so integrated that the joints cannot be discerned. was gotten.

Test Example The bond strength of various bonded products obtained by combining various samples and slips obtained in the above examples and sinter bonding was tested. The test was conducted using a test piece 5 cut out with the joint 6 in the center as shown in FIG. The size of the test piece is 3ws (length) x 4w (width) x 50mm (height)
■A 4-point bending strength test was conducted on snow with an upper span of 10 and a lower span of 30 in accordance with the JIS R1601 test method.

The results are shown in the table below.

This test confirmed that the bending strength does not depend on the type of slip and is almost the same as the bending strength of the welded samples of the same size.

<Effects of the Invention> As is clear from the above explanation, according to the method for joining silicon carbide ceramics of the present invention, the strength of the joint part can be improved from a molded body or a temporarily sintered body that has been shaped into a shape by machining. It is now possible to provide ceramic bonded products whose strength is comparable to that of non-bonded parts. Therefore, it is now possible to manufacture silicon carbide ceramic parts such as gas turbine parts, which are large and have complex structures that are difficult to mold in one piece, by molding each part and joining them together to form the final shape. Ta.

Furthermore, since it can be manufactured separately into small parts, it has become possible to obtain ceramic products in which the reliability of each part is much higher than that of large, integrally molded products.

Furthermore, in place of complicated bonding methods that use other bonding materials such as metals, it is now possible to apply the method of the present invention, which is easier and more powerful, allowing silicon carbide-based ceramic bonded products to be provided at low cost. Now you can.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing objects to be joined arranged in a jig according to an embodiment of the method of joining carbonized porcelain ceramics of the present invention, and FIG. 2 is a perspective view of ceramics joined according to an embodiment. It is a perspective view showing a test piece cut out from. In the figure: 1, 2 --- Sample (molded body) 3 --- Slip layer Patent applicant Toyota Motor Corporation

Claims (3)

[Claims] (1) A compression molded body or a temporary sintered body is manufactured using silicon carbide powder to which boron and carbon are added as sintering aids, and the sintering aid, silicon carbide powder, A method for joining silicon carbide ceramics, characterized in that the slip is filled with a deflocculant and a medium and then sintered. (2) The method according to claim 1, wherein the medium is water and the peptizers are diethylamine and polycarboxylic acid. (3) The method according to claim 1, wherein the medium is benzene and the peptizer is an organic phosphate ester salt, a polyoxyalkylamine, and a polycarboxylic acid salt.