JPH044268B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to Si ₃ N ₄ with a brazable surface layer.
The present invention relates to a ceramic composite composition containing as a main component and a method for producing the same. (Prior Art) When ceramics and metal are soldered together, brazing is generally performed after the surface of the ceramic is metallized in order to increase the wettability between the ceramic and metal solder. A conventional method for metallizing oxide ceramics such as Al ₂ O ₃ ceramics is to use a humidified H ₂
Telefunken method (high melting point metal method)
It has been known. When the base ceramic is Al ₂ O ₃ , some of Mo, W and most of Mn are oxidized and react with Al ₂ O ₃ and the glass component contained in the Al ₂ O ₃ ceramics to form a liquid phase. The adhesive strength is improved by filling the voids in the metallized layer. However, when the base material is ceramics mainly composed of Si ₃ N ₄ , the above liquid phase is not formed, so the adhesive strength between the base material Si ₃ N ₄ ceramics and the metallized layer is very low, making it difficult to use as a structural material. It is not suitable for use. Another method of metallizing oxide ceramics has been reported in which the oxide ceramics and Cu plate are bonded together and heated in the air to oxidize the Cu and react with the oxide ceramics. In the case of ceramics whose main component is _3N4 , it was found that when heated in _the air at around 1000°C, the base material _Si3N4 ceramics oxidizes, resulting in _a significant drop in performance. Another method is to use a metal solder with a eutectic composition of active metals such as Ti and Zr and Ni, Cu, and Ag, which form low-melting-point alloys, and heat it in a vacuum to join ceramics and metals. Although it is known,
It requires a high vacuum of around 10 ^-5 Torr, so it cannot be called an industrial method. (Problems to be Solved by the Invention) As described above, it has been impossible to produce Si ₃ N ₄ ceramics that can be brazed using conventional metallization methods. The present inventors solved this problem and conducted research to enable brazing of Si ₃ N ₄ ceramics.
We have completed a Si ₃ N ₄ ceramic composite composition and a method for producing the same. (Means for Solving the Problems) That is, the ceramic composite composition of the present invention containing Si ₃ N ₄ as a main component contains one or more of Mo, Nb, Ta, Ti, and W, and B, C, A compound consisting of one or more of N and Si, Si ₃ N ₄ , an element of group a of the periodic table, one or more of Si, Al, and Mg, and one or two of N and O. It is characterized by having on its surface a thin composition consisting of a compound consisting of: Further, the method for producing a ceramic composite composition of the present invention includes adding one _or more of Mo, Nb, Ta, _Ti , and W, B, C, The method is characterized in that a layer made of a mixed composition of a powder made of a compound group containing one or more kinds of N and a ceramic powder mainly composed of Si ₃ N ₄ is provided and then sintered. (Function) The biggest difference between the present invention and the conventional metallization method is that the metallization process is not performed on the sintered body of Si ₃ N ₄ ceramics, but on the formed body before sintering.
A layer is formed of a mixed powder of powders of carbides, borides, and nitrides of Mo, Nb, Ta, Ti, and W and powders mainly composed of Si ₃ N ₄ , and then a Si ₃ N ₄ ceramic base material is formed. The surface layer is simultaneously sintered to form a brazable surface. At this time, the powder mainly composed of Si ₃ N ₄ mixed with the metal powder contains Al ₂ O ₃ ,
MgO One or two oxides of group a elements of the periodic table
Contains more than one species. Therefore, at the interface between the Si ₃ N ₄ ceramic base material and the surface layer after sintering, the crystal grains of the base ceramic and the crystal grains of the surface layer have a complex structure, and mechanical bonding other than bonding by atomic diffusion is required. Also, the adhesive strength at the interface is improved. Furthermore, the surface layer becomes a complex structure of carbides, borides _, and nitrides _{of Mo, Nb, Ta, Ti, and W, and ceramics whose main components are Si 3 N 4} . Because the ceramic base material Si ₃ N ₄ ceramics, which is the main component, is bonded, the adhesive strength between the base ceramic material and the surface layer has been greatly improved. Here, the composition ratio of Mo, Nb, Ta, Ti, W carbides, borides, nitrides and Si ₃ N ₄ in the surface layer is as follows in order to maintain high brazing strength when brazing with metal. It is. In order to increase the adhesive strength between the base material Si ₃ N ₄ ceramics and the surface layer, it is possible to increase the proportion of ceramic powder whose main component is Si ₃ N ₄ in the surface layer.
On the other hand, if Si ₃ N ₄ exceeds 60% by volume, the adhesive strength between the metal solder and the surface layer decreases rapidly, so the proportion of Si ₃ N ₄ in the surface layer must be kept below 60% by volume. This roughly corresponds to the fact that the molar ratio of one or more of Mo, Nb, Ta, Ti, and W to Si is 1 or more when converting all the compounds contained in the surface layer into atoms. There is. Because there is a difference in the coefficient of thermal expansion between the surface layer and the base material Si ₃ N ₄ ceramics, thermal stress may occur during cooling after sintering and destroy the base material ceramics, so it is better to keep the thickness of the surface layer as thin as possible. is good. If the difference in thermal expansion coefficient between the surface layer and the base material Si ₃ N ₄ ceramics is within 4 × 10 ^-4 , the thickness of the surface layer after sintering is 1
If it is kept within mm, the base material will melt during cooling after sintering.
There was no thermal stress that would destroy Si ₃ N ₄ and it could be used without any problems. In contrast, the surface layer and base material Si ₃ N ₄
Even if the difference in coefficient of thermal expansion with ceramics is within 4 × 10 ^-6 , if the thickness of the surface layer exceeds 1 mm, the inner surface of the base material Si ₃ N ₄ ceramic will be removed during cooling after sintering. There were cases in which cracks occurred in the base material Si ₃ N ₄ ceramics due to thermal stress generated near the interface with the layer. Furthermore, even if the difference in thermal expansion coefficient between the surface layer and the base material Si ₃ N ₄ ceramics is 4×10 ^-6 or more, it is possible to prevent cracks in the base material Si ₃ N ₄ by further reducing the thickness of the surface layer. was able to prevent this from occurring. Furthermore, by using carbides, borides, and nitrides of Mo, Nb, Ta, Ti, and W in the surface layer, the oxidation resistance and corrosion resistance of the metallized surface are improved compared to the case where the above-mentioned metals are used alone. This oxidation resistance is extremely important when using Si ₃ N ₄ ceramics as a high-temperature structural material. Mo, Nb, Ta, Ti, W
All of these are metals that are easily oxidized, and by using carbides, borides, and nitrides of the above metals instead of single metals, the oxidation resistance could be dramatically improved. (Examples) The present invention will be described below with reference to detailed examples. Example 1 A powder consisting of 95% by volume of Si ₃ N ₄ powder with an average particle size of 0.1 μm and 5% by volume of MgO powder with an average particle size of 0.05 μm was wet mixed in ethyl alcohol for 3 days using a ball mill. This mixed powder is molded using a mold press, and WC and the above Si ₃ N ₄ −
After scattering a 5 volume % MgO mixed powder in the ratio shown in Table 1, it was further lightly compressed to bring the surface layer and the base material Si ₃ N ₄ ceramic into close contact. This composite was sintered at 1700° C. in 1 atmosphere of N ₂ without pressure. The thickness of the surface layer after sintering was 0.3 mm. As a result of analyzing the surface layer by X-ray diffraction, WC, WSi ₂ ,
Peaks of W ₅ SiB ₂ and β-type Si ₃ N ₄ were observed. Silver solder was sandwiched between this surface layer and the steel, and 650°C was placed in an _H2 air stream.
Brazing was carried out at ℃. Table 1 shows the results of shear tests on these Si ₃ N ₄ ceramic and steel joints. Among samples containing 60% by volume or less of Si ₃ N ₄ in the surface layer, the bonding strength between Si ₃ N ₄ ceramics and steel was high, with some samples having shear strength exceeding 10 Kg/mm ² . At this time, the part that breaks depends on the content of Si ₃ N ₄ in the surface layer.
In a shear test, a sample containing Si ₃ N ₄ peeled off at the interface between the Si ₃ N ₄ ceramic base material and the surface layer, and the Si ₃ N ₄ content was 30 to 60%.
Samples containing % by volume fractured in the surface layer or in the silver solder. In samples where the amount of Si ₃ N ₄ in the surface layer exceeds 60% by volume, the adhesive strength between the silver solder and the surface layer decreases, so when a shear test is performed, the bond breaks at the interface between the silver solder and the surface layer, resulting in low strength. .

_{[Table] Example 2 60% by volume of Mo 2 C ,}
A molded body of a mixture of powders of NbC, TaC, TiC, and WC, 40% by volume of base material Si ₃ N ₄ ceramics, and powders of the same composition is stacked together under a pressure of 200 Kg/cm ² in 1 atm of N ₂
Hot pressed at 1700℃. The thickness of the surface layer after hot pressing was adjusted to approximately 0.4 mm. After applying Ni plating on this surface layer and performing Ni diffusion treatment at 900℃ in _H2 gas flow,
The steel was silver-brazed at 650 °C in a stream of _H2 . these
Table 2 shows the results of the shear test of the Si ₃ N ₄ ceramic and steel joint. After hot pressing, X-ray diffraction of the surface layer shows that the second
As shown in the table, in addition to carbides, the formation of silicides, borosilicides, etc. was observed. The formation of silicide is thought to be caused by the reaction of the metal with Si ₃ N ₄ in the surface layer and the base material Si ₃ N ₄ . Furthermore, Si ₃ N ₄
and metal, and BN interposed as a mold release agent between the carbon mold and the ceramic molded body during hot pressing.
It is thought that borosilicide was produced by the reaction of these three substances. Each sample of Examples G to K was held at 400° C. in the atmosphere for 1 hour, but no significant oxidation was observed. On the other hand, for comparison, when the metals Mo, Nb, Ta, Ti, and W were oxidized under the same conditions, the formation of an oxide film was observed, confirming that the oxidation resistance was improved by using carbide. Example 3 A mixture of 50% by volume of WC and 50% by volume of powder having the same composition as the base material Si ₃ N ₄ ceramics was placed on the top surface of a molded body of Si ₃ N ₄ prepared in the same manner as in Example 1. Stack the molded bodies, 200Kg/cm ² in N ₂ 1atm
It was hot pressed at 1700℃ under pressure of At this time, the thickness of the surface layer molded product was varied so that the thickness of the surface layer after hot pressing was adjusted to various thicknesses of 0.1 to 2 mm. As a result of analyzing the surface layer by X-ray diffraction, WC, WSi ₂ ,
Peaks of W ₅ SiB ₂ and β-type Si ₃ N ₄ were observed. Ni plating was performed on this surface layer, Ni was diffused in H ₂ at 900°C, and then silver brazing was applied to the steel at 650°C in H ₂ . Table 3 shows the results of the shear test of the Si ₃ N ₄ , ceramic and steel joint.

【table】

[Table] When a surface layer with a thickness of 2 mm was formed after hot pressing, the thermal stress generated during the cooling process of the hot pressing exceeded the breaking strength of the base material Si ₃ N ₄ ceramics and cracks occurred inside the base material ceramics. . On the other hand, when the surface layer thickness was 1 mm or less, no cracks were generated inside the base ceramic even though hot pressing was performed under exactly the same sintering conditions.
At this time, the thickness of the base material Si ₃ N ₄ ceramics after hot pressing was set to be 5 mm for all samples. The shear strength after silver brazing was as shown in Table 3. Example 4 90% by volume of Si ₃ N ₄ powder with an average particle size of 0.1 μm and 5% by volume of Al ₂ O ₃ powder with an average particle size of 0.05 μm, average particle size of 0.5 μm
A powder consisting of 5% by volume of Y ₂ O ₃ powder was wet mixed in ethyl alcohol for 3 days using a ball mill. This mixed powder is molded using a mold press,
After scattering a powder mixture of Mo ₂ C and the above-mentioned Si ₃ N ₄ -5 volume % Al ₂ O ₃ -5 volume % Y ₂ O ₃ mixed powder in the ratio shown in Table 4 on the upper surface of this compact, further The surface layer and base material Si ₃ N ₄ ceramics were brought into close contact by light compression. This composite was sintered at 1800° C. in 1 atmosphere of N ₂ without pressure. The thickness of the surface layer after sintering was 0.5 mm. Results of analyzing the surface layer by X-ray diffraction
Peaks of Mo ₂ C, MO ₃ Si ₂ , MoSi ₂ and β-type Si ₃ N ₄ were observed. Silver solder is sandwiched between this surface layer and the steel.
Brazing was carried out at 650° C. in a stream of H ₂ . these
Table 4 shows the results of the shear test of the Si ₃ N ₄ ceramic and steel joint. Among samples containing 60% by volume or less of Si ₃ N ₄ in the surface layer, the bonding strength between Si ₃ N ₄ ceramics and steel was high, with some samples having shear strength exceeding 10 Kg/mm ² .

[Table] At this time, the part that breaks depends on the content of Si ₃ N ₄ in the surface layer.
In a shear test, a sample containing Si ₃ N ₄ peeled off at the interface between the Si ₃ N ₄ ceramic base material and the surface layer, and the Si ₃ N ₄ content was 30 to 60%.
Samples containing % by volume fractured in the surface layer or in the silver solder. In samples where Si ₃ N ₄ in the surface layer exceeds 60% by volume, the adhesive strength between the silver solder and the surface layer decreases, and when a shear test is performed, the bond breaks at the interface between the silver solder and the surface layer, resulting in low strength. Example 5 Average particle size: 0.1 μm Si ₃ N ₄ powder 85% by volume and average particle size
10% _Al2O3 powder with _0.1μm , _CeO2 with average particle size 0.5μm
A powder consisting of 5% by volume of powder was wet mixed in ethyl alcohol for 3 days using a ball mill. This mixed powder is molded using a mold press, and a molded body of a mixture of powders having the same composition as 50 volume % TiN and 50 volume % base material Si ₃ N ₄ ceramics is placed on the top of this molded body under N ₂ 1 atm. It was hot pressed at 1700°C under a medium pressure of 200 kg/cm ² . By changing the thickness of the surface layer molded product at this time, the thickness of the surface layer after hot pressing can be 0.1 to 2 mm.
It was adjusted to have various thicknesses. As a result of X-ray diffraction analysis of the surface layer, peaks of TiN and β-type Si ₃ N ₄ were observed. Ni plating is applied to this surface layer _.
After diffusion treatment of Ni at 900°C in H2, the steel was silver-brazed at 650°C in _H2 . Table 5 shows the results of the shear test of the Si ₃ N ₄ ceramic and steel joint.

[Table] When a surface layer with a thickness of 2 mm was formed after hot pressing, the thermal stress generated during the cooling process of the hot pressing exceeded the breaking strength of the base material Si ₃ N ₄ ceramics and cracks occurred inside the base material ceramics. . On the other hand, when the surface layer thickness was 1 mm or less, no cracks were generated inside the base ceramic even though hot pressing was performed under exactly the same sintering conditions.
At this time, the thickness of the base material Si ₃ N ₄ ceramics after hot pressing was set to be 5 mm for all samples. The shear strength after silver brazing was as shown in Table 5. (Effects of the Invention) As explained above, according to the present invention, a ceramic composition containing Si ₃ N ₄ as a main component and having high brazing adhesive strength can be obtained. Moreover, such a composition can be obtained by a simple method.

Claims (1)

[Claims] 1. On the surface of ceramics whose main component is Si ₃ N ₄ ,
A compound consisting of one or more of Mo, Nb, Ta, Ti, and W and one or more of B, C, N, and Si, Si ₃ N ₄ , elements of group a of the periodic table, and Si ,
A ceramic composite characterized by having a thin composition layer made of a compound consisting of one or more of Al and Mg and one or more of N and O. 2. One or more of Mo, Nb, Ta, Ti, and W and one or more of B, C, N, and Si in a thin composition layer on the ceramic surface containing Si ₃ N ₄ as the main component. A compound consisting of a group a element of the periodic table and
Claim 1, wherein the volume ratio of the mixture of Si ₃ N ₄ and one or more of Si, Al, and Mg and one or more of N and O is 2/3 or more. Ceramics composite. 3. The ceramic composite according to claim 1, wherein the thin composition layer on the ceramic surface containing Si ₃ N ₄ as a main component has a thickness of 1 mm or less. 4 Compound group containing one or more of Mo, Nb, Ta, Ti, and W and one or more of B, C, and N on the molded ceramics mainly composed of Si ₃ N ₄ 1. A method for producing a ceramic composite comprising: providing a layer made of a mixed composition of a powder consisting of Si 3 N 4 and a ceramic powder containing Si ₃ N ₄ as a main component, and then sintering it. 5 Mo, Nb, as described in claim 4,
A powder consisting of a compound group containing one or more of Ta, Ti, and W and one or more of B, C, and N.
5. The method for producing a ceramic composite according to claim 4, wherein the volume ratio of the mixed composition of ceramic powder containing Si ₃ N ₄ as a main component is 2/3 or more. 6. A method for producing a ceramic composite according to claim 4, wherein the sintering according to claim 4 is performed while pressurizing. 7. A method for producing a ceramic composite according to claim 4, wherein the sintering according to claim 4 is performed in a non-oxidizing atmosphere. 8 Mo, Nb, as described in claim 4,
Ceramics whose main component is Si ₃ N ₄ mixed with powder consisting of a compound group containing one or more of Ta, Ti, and W and one or more of B, C, and N are _4. A method for producing a ceramic composite according to claim ₄ , which has the same composition as a ceramic whose main component is 3N4.