JP2000034174A - Manufacturing method of ceramic composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a ceramic composite material with high mechanical strength, applicable to products of complicated design such as engine parts. SOLUTION: This method for producing a ceramic composite material comprises incorporating ceramic particles 2 such as of Al2O3 to be served as matrix with 0.5-10 vol.% of non-oxide-based ceramic disperse particles (e.g. of Si3N4, SiC, TiN, TiC, TiB2) 1<=1 μm in the maximum size and <=0.5 μm in average size each having a surface oxide layer followed by normal-pressure sintering into a primary sintered compact of low open porosity with a relative density of >=90% but < 95% and densifying the primary sintered compact to a relative density of >=99% by sintering under pressurized atmosphere to effect dispersion of part of the disperse particles 1 in the matrix particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic composite material having excellent mechanical properties, and more particularly to a method suitable for producing a ceramic composite material having a complicated shape.

[0002]

2. Description of the Related Art Conventionally, ceramics have been widely used for substrates and packages of integrated circuits, chips for cutting tools, wear-resistant materials, and the like. However, ceramics have been difficult to apply to structural materials such as engine parts because of their higher cost, lower reliability, and more complicated manufacturing process than metal materials.

[0003] In order to solve such problems of ceramics, a composite in which different second phases are dispersed is used.
Attempts have been made to improve its mechanical properties and improve its reliability. For example, Japanese Patent No. 2507479 discloses that AlC particles and SiC particles are used as matrix Al ₂ O ₃ particles.
A composite sintered body having excellent strength and toughness in which C whiskers are dispersed is disclosed.

Further, JP-A-59-3766, JP-A-61-21964, and JP-A-61-174165.
Japanese Patent Application Laid-Open Publication No. H10-15064 discloses that Al ₂ O ₃ particles serving as a matrix have Si
It is described that the strength and toughness of an Al ₂ O ₃ sintered body are improved by dispersing C particles.

[0005]

Since the above-mentioned composite materials are generally difficult to densify, they can be produced by hot press sintering under mechanical pressure or hot press sintering. Subsequently, the method is limited to a method of sintering under an atmospheric pressure. Therefore, it is limited to the manufacture of a product having a simple shape such as a flat plate, and it is difficult to apply the method to a product having a complicated shape.

In the case of a two-stage sintering in which a ceramic composite material containing micron-sized particles is subjected to atmospheric pressure sintering followed by atmospheric pressure sintering, a dense sintered body is obtained by secondary sintering. Requires that the relative density of the primary sintered body be 95% or more. However, in normal pressure sintering of primary sintering, 9
In order to achieve a relative density of 5% or more, it is necessary to increase the sintering temperature, so that the grain growth is promoted, the grain size increases, and the bending strength of the final composite material decreases. there were.

The present invention has been made in view of such a conventional situation,
An object of the present invention is to provide a method for producing a ceramic composite material having a high strength, which can be applied to a product having a complicated shape and can be practically used as a structural material for an engine part or the like.

[0008]

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for producing a ceramic composite material, wherein a ceramic particle serving as a matrix has a surface oxide layer having a maximum particle size of 1 μm or less and an average particle size. 0.5μ diameter
m and less than 90% and less than 95% relative density by atmospheric pressure sintering, and then densified to a relative density of 99% or more by atmospheric pressure sintering. It is characterized in that a ceramic composite material in which a part of dispersed particles is dispersed in matrix particles is obtained.

In the present invention, the amount of the dispersed particles made of non-oxide ceramics is 0.5 to 10% by volume.
Is preferably within the range. The dispersed particles preferably have an oxygen content of 0.15% by weight or more due to the surface oxide layer. Preferred examples of such dispersed particles include at least one selected from Si ₃ N ₄ , SiC, TiN, TiC, and TiB ₂ .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, dispersed ceramic particles (hereinafter, referred to as fine particles) composed of fine non-oxide ceramics having a maximum particle size of 1 μm or less and an average particle size of 0.5 μm or less are used as matrix particles. (Also simply referred to as dispersed particles). By the addition and mixing of such fine dispersed particles, closed porosity in normal pressure sintering is promoted, and it is possible to easily obtain a primary sintered body in which the open pores are drastically reduced, and furthermore, there are few open pores. The primary sintered body can be densified by atmospheric pressure sintering of secondary sintering.

The primary sintering process in the method of the present invention is shown in FIG.
This will be described with reference to FIG. That is, in the method of the present invention, the liquid phase 3 is formed by the reaction between the surface oxide layer of the dispersed particles 1 and the surface of the ceramic particles 2 serving as a matrix without adding a sintering aid. Since the fine dispersed particles 1 exist between the ceramic particles 2, the closed phase of the liquid phase 3 existing near the pores, at the triple point and at the grain boundary is promoted.
Therefore, although the closed pores 4 are formed, the proportion of the open pores formed is small, and when normal pressure sintering is performed to a relative density of 90% or more and less than 95%, the primary sintering is performed with an open porosity of 10% by volume or less. The body is obtained.

On the other hand, when the dispersed particles are not added, mutual reaction (mass transfer) occurs at a point where the ceramic particles 2 serving as a matrix come into contact with each other by normal pressure sintering, as shown in FIG. Although the liquid phase 3 may be formed, the liquid phase 3 cannot sufficiently fill the gaps between the ceramic particles 2, so that a primary sintered body having many open pores 5 is obtained.

In such a case, in order to crush the open pores 5 and make them denser, a method of further raising the temperature in normal pressure sintering or extending the sintering time, or hot pressing in subsequent secondary sintering is used. It is necessary to employ any of the methods of mechanically pressing in a mold such as the method, and a dense sintered body cannot be obtained even if the atmosphere is pressed and sintered in the secondary sintering. As in the case of ordinary sintering, open pores can be reduced by adding a sintering aid to increase the amount of liquid phase, but in this case, abnormal grain growth is likely to occur.

As described above, according to the method of the present invention, even if the sintering aid is not added or the addition amount of the sintering aid is small, the atmospheric pressure sintering of the primary sintering allows the subsequent atmospheric pressure sintering. The ratio of open pores, which is a factor that hinders densification in sintering, can be reduced, and there is no abnormal grain growth of ceramic particles or matrix particles (ceramic particles after sintering), and the relative density is 90% or more. A primary sintered body of less than 95% can be obtained. Since the primary sintered body has a small open porosity of 10% by volume or less, even if the relative density is less than 95%, the relative density is increased to 99% or more by performing atmospheric pressure sintering in the secondary sintering. Can be In the secondary sintering, densification can be performed by atmospheric pressure sintering, and there is no need to apply mechanical pressure in a mold. Therefore, the present invention can be applied to products having complicated shapes.

When the relative density of the primary sintered body is less than 90%,
Since the open porosity increases, densification by secondary sintering in atmospheric pressure sintering becomes difficult. Atmospheric pressure sintering is possible even if the relative density is 95% or more. However, in order to reach a density of 95% or more, the temperature of normal pressure sintering must be increased. Due to the abnormal grain growth of the grains, the bending strength of the obtained sintered body decreases. The atmosphere pressure during the secondary sintering is preferably 10 MPa or more, but is a pressure range that is economically practical.
Desirably, sintering is performed at a pressure of 00 MPa or less.

Further, according to the method of the present invention, in the primary sintering step of normal pressure sintering and the secondary sintering step of atmospheric pressure sintering,
The ceramic particles or matrix particles take some of the dispersed particles into the grains and grow slightly. As a result, the secondary sintered body (ceramic composite material) after sintering is completed
Some dispersed particles are present within the grains of the matrix particles and serve to strengthen the matrix particles. Thus, by dispersing the dispersed particles having a maximum particle size of 1 μm or less and an average particle size of 0.5 μm or less, the dispersed particles contribute to the reduction of the sinterability and the open porosity as described above. Can be dispersed in the matrix particles with almost no grain growth, strengthening the matrix itself, and achieving an improvement in bending strength.

In the present invention, the added or dispersed amount of the dispersed particles is preferably in the range of 0.5 to 10% by volume, and 1 to 10% by volume.
% By volume is more preferred. The amount of addition or dispersion is 0.5
If the content is less than the volume%, the particle size of the ceramic composite material becomes non-uniform, so that the bending strength at room temperature tends to decrease,
Since the pinning effect is reduced, the bending strength at high temperatures is also reduced. Conversely, if the amount of addition or dispersion exceeds 10% by volume, sinterability is reduced and densification is inhibited, so that high bending strength cannot be obtained.

According to the method of the present invention, Al ₂ O ₃ , MgO, Si ₃
It is applicable to typical ceramic particles such as N ₄ , SiC, AlN, etc. Ceramic composites with improved mechanical properties such as strength by selecting appropriate dispersed particles composed of non-oxide ceramics Material can be provided. Further, as preferred dispersed particles,
Si ₃ N ₄ , SiC, Ti that does not grow in the matrix
N, TiC, TiB _{2 and the} like.

A surface oxide layer usually exists on the surface of these dispersed particles, and the surface oxide layer reacts with the ceramic particles serving as a matrix as described above to form a liquid phase, thereby promoting closed pores. . Therefore, the oxygen content of the surface oxide layer of the dispersed particles is desirably 0.15% by weight or more. When the oxygen content is lower than this, the effect of reducing the open pores is reduced, so that the primary sintering to a relative density of 90% or more and less than 95% requires a high temperature or a long time. This is because the characteristics deteriorate.

Although the method of the present invention basically does not require a sintering aid, the effect becomes more remarkable when a sintering aid is added. It is the same as above. These sintering aids promote liquefaction at the sintering temperature, in which case the sintering agents gather around the dispersed particles at the grain boundaries by capillary action. As a result, the closed pores of the open pores are further promoted and the ratio of the open pores is further reduced, so that the secondary sintering by the atmospheric pressure sintering is possible even with a low-density primary sintered body.

As such a sintering aid, in the case of Al ₂ O ₃ in which ceramic particles are usually used, it is effective to add 0.5% by weight or less of MgO or the like. When the ceramic particles are Si ₃ N ₄ (including sialon), Al ₂ O ₃ , Y ₂ O ₃ , MgO, etc. are about 10% by volume,
When the ceramic particles are SiC, Y ₂ O ₃ , Yb ₂ O ₃
About 5% by volume or the like, 0.5 volume of SiO ₂ or the like in the case of _{Y 2 O 3, Yb 2 O} 3 or the like for about 2 vol%, and the ceramic particles are MgO particles in the case of ceramic particles AlN particles It is effective to add about%. Although it is possible to add more sintering aids, it is not preferable because grain growth is likely to occur and the high-temperature strength of the sintered body is reduced.

[0022]

EXAMPLES Example 1 Si ₃ N ₄ particles, SiC particles and AlN serving as a matrix
Predetermined amounts of the dispersed particles shown in Table 1 below were mixed with the particles and the MgO particles. As a sintering aid, Si ₃ N ₄ particles contain 5% by weight of Y ₂ O ₃ -2% by weight Al ₂ O ₃ and SiC
2% by weight of Y ₂ O ₃ for the particles and 2% by weight for the AlN particles
Of Y ₂ O ₃ was added. The average particle size of each of the ceramic particles and the sintering aid is Si ₃ N ₄ particles, AlN particles, MgO
Particles, Al ₂ O ₃ particles of 0.1 μm each, and SiC
Particles and Y ₂ O ₃ particles were each 0.3 μm. still,
The average particle size was calculated from the linear density.

Thereafter, the mixed powder of each sample was molded and subjected to primary sintering and secondary sintering under the conditions shown in Table 2 below to produce ceramic composite materials. The primary sintering was normal pressure sintering for 4 hours in a normal pressure nitrogen atmosphere, and the secondary sintering was atmospheric pressure sintering (hereinafter also referred to as HIP) for 1 hour in a 100 MPa nitrogen atmosphere. . However, the primary sintering was not performed for Sample 9, and the secondary sintering was performed by hot pressing (HP) in which mechanical pressure was applied.

With respect to the obtained ceramic composite material of each sample, a bending test piece in accordance with JIS R 1601 was cut out, and the three-point bending strength was measured at room temperature. The results are shown in Table 2 below, together with the relative density and open porosity of the primary sintered body, the relative density of the secondary sintered body (ceramic composite material) and the average particle size of the matrix particles.

[0025]

TABLE 1 Matrix partial dispersion particle child sample particle child species such maximum particle diameter ([mu] m) average particle size ([mu] m) amount _{(wt%) 1 Si 3 N} 4 SiC 1.0 0.5 5 2 * Si 3 N 4 SiC 3.0 1.0 5 3 * Si ₃ N ₄ SiC 0.8 0.3 0.1 4 Si ₃ N ₄ SiC 0.8 0.3 0.5 5 Si ₃ N ₄ SiC 0.8 0.3 16 Si ₃ N ₄ SiC 0.8 0.3 10 7 * Si ₃ N ₄ SiC 0.8 0.3 15 8 * Si ₃ N ₄ SiC 0.8 0.3 1 9 * Si ₃ N ₄ SiC 0.8 0.3 5 10 MgO SiC 0.8 0.3 5 11 SiC TiB ₂ 0.9 0.5 5 12 AlN SiC 0.8 0.35 Note: Samples marked with * in the table are compared It is an example.

[0026]

Table 2 primary sintered open porosity secondary sintering matrix flexural strength sample temperature (℃) Density (%) (vol%) Temperature (℃) Density (%) particle diameter ([mu] m) (MPa) 1 1750 92 9 1650 99.5 1.7 1200 2 * 1750 88 15 1650 96 1.7 560 3 * 1700 95 5 1650 99.9 2.2 600 4 1700 94 8 1650 99.5 2.0 900 5 1750 92 7 1650 99.8 1.9 1020 6 1850 90 9 1700 99.1 1.1 1100 7 * 1850 85 25 1850 89 0.8 640 8 * 1800 96 4 1650 99.9 2.8 620 9 * No primary sintering-1750 / HP 99.5 1.7 1200 10 1750 92 8 1650 99.2 2.5 650 11 1900 91 9 1850 99 3.0 500 12 1750 92 10 1650 99.5 3.5 450 (Note) Samples marked with * in the table are comparative examples.

From the above results, in each sample, when the maximum particle size of the dispersed particles is 1 μm or less and the average particle size is 0.5 μm or less, if the relative density in the primary sintering is 90% or more, HI
It is understood that densification with a relative density of 99% or less can be achieved by secondary sintering with P. Each sample after secondary sintering is HP
It can be seen that the sample has a bending strength equivalent to that of Sample 9 and that a high bending strength can be obtained particularly when the added amount of the dispersed particles is 1 to 10% by volume. In the primary sintering, the relative density was 95
%, Sample 3 and sample 8 exhibit abnormal grain growth, so that it is understood that high bending strength cannot be obtained even when densification by HIP in secondary sintering.

Example 2 As in the case of the sample 5 of the above-mentioned Example 1, but the HI of the secondary sintering was used.
By changing the atmosphere pressure and sintering temperature in P as shown in Table 3 below, a ceramic composite material was manufactured. The relative density, the average particle size of the matrix particles, and the three-point bending strength at room temperature of the obtained ceramic composite material of each sample were measured in the same manner as in Example 1. The results are shown in Table 3 below.

[0029]

[Table 3] Secondary sintered matrix Flexural strength Sample pressure (MPa) Temperature (° C) Density (%) Particle size (μm) (MPa) 13 5 1700 99.1 2.3 850 14 10 1700 99.4 2.3 920 15 50 1650 99.5 1.9 1000 5 100 1650 99.8 1.9 1020 16 200 1650 99.9 1.9 1050 (Note) Sample 5 in the table is the same as Sample 5 in Example 1.

Example 3 Al ₂ O ₃ —SiC which is a representative ceramic composite material
A composite material was produced as follows. That is, the average particle size is 0.
1 μm α-Al ₂ O ₃ particles, SiC dispersed particles having a maximum particle diameter of 0.8 μm, an average particle diameter of 0.3 μm and an oxygen content of 0.2% by weight, and an average particle diameter of 0.1 μm as a sintering aid. MgO was added at the ratio shown in Table 4 below, and mixed and molded. next,
After primary sintering of each compact under a normal pressure nitrogen atmosphere at a sintering temperature of 1600 ° C. to 1800 ° C., 1600 ° C. and a nitrogen pressure of 1
Secondary sintering was performed using a HIP of 00 MPa.

Each of the obtained ceramic composite materials was subjected to a three-point bending test in the same manner as in Example 1.
The three-point bending strength was measured at 00 ° C., and the results are shown in Table 4. It can be seen that high strength is exhibited when the added amount of the SiC dispersed particles is in the range of 1 to 10% by volume. In this case, the relative densities of the ceramic composite materials of Samples 18 to 22 were all 99% or more. However, in Sample 23, the amount of MgO as a sintering aid exceeded 0.5% by volume, so that the strength at high temperatures was reduced.

[0032]

[Table 4] Addition amount of SiC Addition amount of MgO Primary sintering bending strength (MPa) Sample (vol%) (vol%) Temperature (° C) Room temperature 1200 ° C 17 * 0 0 1600 600 400 18 1 0 1600 900 780 19 5 0 1800 1100 900 20 5 0.1 1800 1150 850 21 10 0.1 1800 1120 850 22 10 0.5 1800 1200 850 23 * 10 0.6 1800 1200 650 Note: Samples marked with * in the table are comparative examples.

A representative sample 1 of the above samples
7, Sample 19, Sample 20, and Sample 21
FIG. 3 is a graph showing the relationship between the relative density of the primary sintered body before P and the relative density of the secondary sintered body (ceramic composite material) after HIP. From FIG. 3, it can be seen that, in the sample 17 containing no dispersed particles, the density before the HIP cannot be increased to 99% or more by the secondary sintering unless the pre-HIP density exceeds 95%. In the sample, it can be seen that even if the pre-HIP density is less than 95%, the density is increased to 99% or more by the secondary sintering.

Example 4 In the same manner as in Sample 19 of Example 3 above, but as shown in Table 5 below, 5% by weight of SiC-dispersed particles having different oxygen contents were added and mixed. After primary sintering under pressure atmosphere, 1600 ° C and nitrogen pressure 100MP
The secondary sintering was performed by the HIP of a.

For each of the obtained ceramic composite materials, a three-point bending strength was measured at room temperature by a bending test according to JIS R 1601, and the results are shown in Table 5. From this result, the oxygen content of the dispersed particles was 0.15% by weight.
In the following Samples 24 and 25, it is necessary to perform sintering at a high temperature during the primary sintering, so that the growth of matrix particles occurred, and the three-point bending strength after the secondary sintering was reduced.

[0036]

[Table 5] Oxygen content Primary sintering Secondary sintering Flexural strength sample (wt%) Temperature (° C) Density (%) Density (%) (MPa) 24 0.1 1800 93 99 700 25 0.1 1850 94 99 750 26 0.15 1800 91 99 1080 19 0.2 1800 92 99 1100 27 0.3 1750 92 99 1250 (Note) Sample 19 in the table is the same as Sample 19 of Example 3.

[0037]

According to the present invention, a ceramic composite material having a high strength can be manufactured by a simple method using normal pressure sintering and atmospheric pressure sintering, so that it can be applied to products having complicated shapes such as engine parts. Applicable.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a primary sintering process including dispersed particles according to a method of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining a primary sintering process when no dispersed particles are included.

FIG. 3 shows pre-HIP density and HI for each sample of Example 3.
It is a graph which shows the relationship of density after P.

[Explanation of symbols]

 1 dispersed particles 2 ceramic particles 3 liquid phase 4 closed pores 5 open pores

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA07 AA36 AA45 AA47 AA49 AA51 AA52 AA54 BA20 GA11 GA23 GA24 GA28

Claims (6)

[Claims] 1. A non-oxide ceramic dispersed particle having a surface oxide layer and having a maximum particle size of 1 μm or less and an average particle size of 0.5 μm or less is added to and mixed with ceramic particles serving as a matrix. Relative density 90% or more 9
After reducing to less than 5%, the relative density was 99
%, Thereby obtaining a ceramic composite material in which a part of the dispersed particles is dispersed in matrix particles. 2. The method for producing a ceramic composite material according to claim 1, wherein the amount of the dispersed particles is in the range of 0.5 to 10% by volume. 3. The method for producing a ceramic composite material according to claim 1, wherein the amount of oxygen in the surface oxide layer of the dispersed particles is 0.15% by weight or more. 4. The method according to claim 1, wherein the ceramic particles are Al ₂ O ₃ , Mg
_{O, Si 3 N 4, SiC} , and wherein the at least one selected from AlN, method of producing a ceramic composite material according to claim 1. 5. The method according to claim 1, wherein the dispersed particles are Si ₃ N ₄ , SiC, Ti
N, TiC, and wherein the at least one selected from TiB _2, method of producing a ceramic composite material according to claims 1-4. 6. The ceramic according to claim 1, wherein said ceramic particles are Al ₂ O ₃ , and 0.5% by weight or less of MgO is added as a sintering aid. Manufacturing method of composite material.