JPH0631162B2 - Adhesive for bonding silicon nitride ceramic sinter and bonding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive and a bonding method for bonding silicon nitride-based ceramic sintered bodies to each other.

[Conventional technology]

Since silicon nitride (Si ₃ N ₄ ) based sintered products are hard and have high toughness among various ceramics, they are high-temperature materials that require strength, toughness, wear resistance, etc., such as valves and bearings. It is useful as a material for heat-resistant parts such as, and its application has been tried variously as a new material replacing the conventional heat-resistant alloy.

However, since these structural members have complicated shapes and strict dimensional accuracy is required, it is not easy to manufacture them as an integral sintered product. For this reason, as a method of manufacturing these structural members, the members are divided into a plurality of parts to produce a plurality of sintered products having a simple shape, and these are joined with an adhesive to obtain a desired shape and size. A method of assembling into a structural member having
Also, some useful proposals have been made regarding adhesives and bonding methods therefor (see, for example, JP-A-55-94975).
No. 58-91086, No. 59-190277).

[Problems to be solved]

However, most of the adhesives used for joining the ceramic sintered bodies without pressure have a heat-resistant glass composition. When silicon nitride ceramic sintered products are bonded together using a glass adhesive, the bonding strength at the joint and the hardness of the adhesive layer are extremely low, less than half that of the sintered body, and the adhesive layer is made of glass. Therefore, the toughness is also poor.

The present invention intends to provide an improved adhesive and a bonding method for bonding silicon nitride-based ceramic sintered products to each other in order to cope with the above situation.

[Means and Actions for Solving Problems]

The ceramic adhesive of the present invention comprises MgO: 5-23%, Al
₂ O _3: 20 to 50% and SiO _2: the _MgO-Al 2 O 3 -SiO ₂ powder 100 parts by weight consisting of 40% to 60%, average particle diameter: 1.5 [mu] m or less the _Si 3 _{N 4} powder: 26 It is constituted as a mixed powder composition containing ~ 65 parts by weight.

Further, the present invention interposes the above adhesive on the joint surface between the silicon nitride ceramic sintered products, and the temperature: 15
By heat treatment at 00 to 1700 ° C, Mg-Al-
Provided is a bonding method, which comprises forming a bonding layer in which Si ₃ N ₄ particles are uniformly dispersed in a matrix of Si—O—N oxynitride glass or glass ceramic.

All% showing the composition ratio of the adhesive of the present invention are% by weight.

When the adhesive of the present invention is interposed between the bonding surfaces of a set of silicon nitride-based sintered products to be bonded (hereinafter, also referred to as “bonded object”) and heat-treated, MgO—Al ₂ O is produced. _3- S
The io ₂ glass melt is well compatible with the glass phase of the adherend, and the glass melt reacts with fine particles mixed and dispersed therein, that is, Si ₃ N ₄ particles having a large specific surface area ( Ni ₃ -containing glass (this is higher in hardness and toughness than general glass) is formed by the solid solution of Si ₃ N ₄ in the glass melt, and the remaining Si
_{The 3} N ₄ particles are uniformly dispersed in the nitrogen-containing glass (matrix). In this way, the two effects of forming a matrix of nitrogen-containing glass having high hardness and toughness and mixing hard fine Si ₃ N ₄ particles as a dispersed phase in the matrix are combined to form an adhesive layer. Hardness, toughness and strength are improved.

In the present invention, the compounding ratio of _MgO-Al 2 O 3 -SiO ₂ -based mixed powder, MgO: 5 to 23%, preferably from 10 to 23
%, Al ₂ O ₃ : 20 to 50%, and SiO ₂ : 40 to 60%. The composition of this three-component system is shown in FIG.
Located in. The composition of these three components is limited in this way, because the melting point in this region (A) is the lowest, the mixed powder is easily melted, and the wettability with Si ₃ N ₄ particles mixed therein is good. Further, the melt and the glass phase of the adherend are well compatible with each other, and if any direction is deviated from this region (A), the melting is likely to be incomplete, and Si ₃ N ₄ particles or the adherend is adhered. This is because, in addition to insufficient wetting and familiarity with, the thermal expansion coefficient mismatch between the adherend and the adhesive layer to be formed causes cracks, resulting in problems such as reduced strength.

In addition, MgO-Al ₂ O ₃ -SiO ₂ system three-component mixed powder
The reason why the compounding amount of Si ₃ N ₄ particles to 100 parts by weight is limited to 26 to 65 parts by weight is that if the compounding amount is less than 26 parts by weight, the amount of Si ₃ N ₄ particles dispersed in the matrix glass is small. In addition, the effect of dispersion, in particular, the increase in hardness is insufficient, and the effect of hardening and toughening the glass matrix due to the solid solution of Si ₃ N ₄ particles is also poor, while when the compounding amount exceeds 65 parts by weight, This is because the wettability of the adhesive is deteriorated, and rather the adhesive strength and toughness are deteriorated.

When the Si ₃ N ₄ particles are coarse, the reaction with the glass melt is small and the toughness of the glass matrix is insufficient, so the particle size is preferably 1.5 μm or less.
From both aspects of increasing the toughness of the glass matrix by the reaction with this glass melt and increasing the hardness by dispersing the residual particles,
The Si ₃ N ₄ particle size is particularly preferably in the range of 0.8 to 1.5 μm.

The adhesive of the present invention is prepared by mixing powders of MgO, Al ₂ O ₃ , SiO ₂ and Si ₃ N _{4 in} a predetermined mixing ratio and kneading the mixed powder with a ball mill or the like. When kneading the mixed powder, it is possible to prepare a paste-like adhesive by adding water, alcohol, and other solvents to the mixed powder and performing wet kneading.

The heat treatment temperature in the case of bonding using the adhesive of the present invention is 1500 to 1700 ° C. The lower limit of 1500 ° C is that if it is lower than that, the viscosity of the glass melt is high and the fluidity is insufficient, so that minute pores are generated in the formed adhesive layer, resulting in adhesive strength, toughness, etc. Is impaired, while 17
The reason why the upper limit is 00 ° C. is that, at a temperature higher than that, the viscosity of the glass melt becomes low, and the glass melt flows out from the adhesive interface, so that an adhesive layer having an appropriate layer thickness cannot be formed.

The layer thickness of the formed adhesive layer is suitably 20 to 100 μm. This layer thickness is adjusted by the amount of adhesive applied to the adhesive interface between the adherends.

〔Example〕

Example 1 [I] Preparation of Adhesives MgO, Al ₂ O ₃ , SiO ₂ and Si ₃ N ₄ powders were weighed, and the mixed powders were kneaded with an alcohol in a ball mill to give a mixing ratio shown in Table 1. Adhesives having Nos. 10 to 29 were prepared. In addition, both adhesives,
The average particle size of the powder is 1 μm, and MgO—Al ₂ O
The compounding ratio of Si ₃ N ₄ powder to 100 parts by weight of _3- SiO ₂ powder was constant at 26 parts by weight.

_MgO-Al 2 O 3 -SiO of each test試接adhesive No.10~29
FIG. 1 shows the _two compositions on the ternary graph. The number attached to each point in the figure is the number of the adhesive, and the area (A) defined by the solid line is the MgO defined by the present invention.
-Al ₂ O ₃ shows the composition range of the ternary -SiO _2.

Of the tested adhesives No.10-29, No.13-16, No.18-22,
And No. 25 is an example of the present invention, other adhesives,
The composition ratio of _{MgO-Al 2} O 3 -SiO ₂ is a comparative example which is off the specified the scope of the present invention.

[II] Adhesion treatment of adherends Prepare two silicon nitride sintered bodies (20 × 20 × 20, mm),
Apply the adhesive on one side and overlap the coated side,
Bonding was performed by heating and baking at 1600 ° C. for 15 minutes in a nitrogen atmosphere (1 atm). The thickness of the adhesive layer is
20 to 100 μm.

Note that the adherend to be tested was prepared by blending silicon nitride powder with spinel (MgOAl ₂ O ₄ ) as a sintering aid (the blending amount was 10% by weight) and firing by atmospheric pressure sintering method. The obtained sintered body has a bending strength of 60 to 70 kgf / mm ² and a hardness of H.
It is v1800kgf ÷ mm ² .

From the adherends bonded as described above, test pieces (3 × 4
(× 40, mm) was cut out and subjected to a three-point bending test to measure the adhesive strength of the joint, and the results shown in the right column of Table 1 were obtained. In the table, “*” in the “bending strength (kg / mm ² )” column indicates that the adhesive strength is low and the bonded surface was broken during the production of the test piece for strength measurement.

As shown in Table _{1, MgO-Al 2 O 3 -SiO} 2
Comparative example (No. 10 to 1) whose composition ratio deviates from the definition of the present invention
2, No.17, No.23 to 24, No.26 to 29) are appropriate amount of Si ₃ N ₄
It can be seen that, although they contain particles, all of them are inferior in adhesive strength such as breaking from the joint surface during preparation of the test piece for bending test, whereas the inventive examples have excellent adhesive strength.

Example 2 [I] Preparation of Adhesive MgO, Al ₂ O ₃ , SiO ₂ and Si ₃ N ₄ powders were weighed, and the mixed powders were kneaded with alcohol in a ball mill to mix ratios shown in Table 2. An adhesive was prepared.

Test numbers (No.) 30 to 33 are examples of the present invention, and Nos. 40 to 43 are comparative examples. Among Comparative Examples Nanba40～43 example No.40 is free of Si ₃ N ₄ particles, although No.41 comprises Si ₃ N ₄ particles, the example the amount is insufficient, the No.42 An example in which Si ₃ N ₄ particles were excessively blended, and No. 43 was an example in which an appropriate amount of Si ₃ N ₄ particles was contained, but the particle size was coarse.

[II] Adhesion treatment of adherends Using the above adhesives, the silicon nitride sintered bodies were joined together under the same conditions as in Example 1, and the adhesive strength and toughness of the joints were measured and the presence or absence of cracks. Was investigated and the results shown in the right column of Table 2 were obtained.

(a) Measurement of adhesive strength: Measured by a three-point bending test using a test piece (3 × 4 × 40, mm) cut out from the bonded portion of the adherend as in Example 1.

(b) Hardness: Measured by driving a micro Vickers indenter into the center of the adhesive layer.

(c) Toughness: A micro Vickers indenter was driven into the adhesive layer (load: 300 g), and qualitatively evaluated by the presence or absence of cracks generated from the ridge of the indentation. In Table 2, “◯” in the “toughness” column means no crack, and “x” means crack generation.

As shown in Table 2, the invention examples Nos. 30 to 33 all have high adhesive strength and hardness, and also have excellent toughness.
On the other hand, Comparative Examples No. 40 (without Si ₃ N ₄ particles) and No. 41 (insufficient amount of Si ₃ N ₄ particles) have low hardness and poor toughness. Further, in No. 42 (Si ₃ N ₄ particle excess amount), the hardness is high, but the bending strength is extremely low and the toughness is poor. Further, No. 43 (containing an appropriate amount of Si ₃ N ₄ particles but having a coarse particle size) has low toughness and insufficient hardness and strength, neither of which falls below the examples of the present invention.

The bending strength of the example of the present invention is a measured value at room temperature, but it has been confirmed that the strength hardly changes up to around 900 ° C.

[Advantages of the Invention] The joint portion formed by adhering silicon nitride-based sintered products to each other by the method of the present invention has high adhesive strength, is hard, and has excellent toughness. Therefore, it is useful for joining and manufacturing silicon nitride-based sintered products to assemble and manufacture valves, bearings, and other structural members for heat-resistant applications, and to expand and diversify engineering applications of silicon nitride-based ceramics. It contributes.

[Brief description of drawings]

FIG. 1 is a diagram showing the matrix composition of the adhesive according to a ternary graph of MgO—Al ₂ O ₃ —SiO ₂ .

Claims (2)

[Claims] 1. A _{MgO: 5~23%, Al 2 O} 3: 20~50
%, And SiO _2: MgO-Al ₂ consisting of 40% to 60%
An average particle size of 1.5 μm in 100 parts by weight of O ₃ —SiO ₂ powder
An adhesive for joining a silicon nitride ceramic sintered body, which comprises 26 to 65 parts by weight of the following Si ₃ N ₄ powder. Wherein _{MgO: 5~23%, Al 2 O} 3: 20~50
%, And SiO _2: MgO-Al ₂ consisting of 40% to 60%
An average particle size of 1.5 μm in 100 parts by weight of O ₃ —SiO ₂ powder
By interposing an adhesive formed by mixing 26 to 65 parts by weight of the following Si ₃ N ₄ powder on the joint surface of the silicon nitride ceramic sintered body and heat-treating at 1500 to 1700 ° C., Mg-
A method for adhering a silicon nitride ceramic sintered body, which comprises forming an adhesive layer in which Si ₃ N ₄ particles are dispersed in an Al-Si-NO glass or glass-ceramic matrix.