JPS61163180A - High size precision and anti-abrasivity silicon carbide composite body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a carbon carbide composite having excellent dimensional accuracy and wear resistance, and a method for producing the same. A silicon carbide-based composite with excellent dimensional accuracy and wear resistance, in which metallic silicon is filled in the open pores of a porous silicon carbide sintered body whose shape is sintered without substantially causing firing shrinkage, and the same. Regarding the manufacturing method.

[Conventional technology]

Silicon carbide has extremely excellent chemical and physical properties, and is used in catalyst carriers, pump parts, and various jigs used in high-temperature oxidizing atmospheres, strongly corrosive atmospheres such as acids and alkalis, etc. This material is suitable for applications such as.

Conventionally, methods for manufacturing silicon carbide sintered bodies include pressure sintering,
Methods such as pressureless sintering, reaction sintering, and recrystallization sintering are known.

[Problem that the invention seeks to solve]

By the way, among these methods, according to the pressure sintering method and the pressureless sintering method, it is possible to obtain a sintered body with high density and high strength.
Both are sintering methods that involve large firing shrinkage during firing.
Since the dimensions of the sintered body are greatly affected by the firing shrinkage and the density of the formed body, it is extremely difficult to produce a sintered body with specific dimensional accuracy without special machining.

In addition, both the reaction sintering method and the recrystallization sintering method are sintering methods that do not cause much shrinkage during firing, but the sintered body by the former reaction sintering method is produced by combining metallic silicon and carbon powder with S.
Since the iC reaction occurs, the surface roughness of the sintered body increases.The latter recrystallization sintering method hardens coarse and fine silicon carbide particles with an organic binder and binds them together. 20
It is a method of bonding coarse particles by firing in a recrystallization temperature range of 00 to 2400 ° C to recrystallize fine silicon carbide particles and exert a bonding action.
Not only does it require an extremely high sintering temperature of 2,400°C, but the surface roughness is large due to the use of coarse grains as a starting material. It is difficult to manufacture without applying

As mentioned above, with conventionally known sintering methods, there was no known method for inexpensively and easily producing structural silicon carbide sintered bodies that require high dimensional accuracy without special machining. .

[Means for solving problems]

By the way, the present inventors have developed a sintering method different from the conventionally known sintering methods as described above, that is, sintering a green body formed into a desired shape without substantially causing firing shrinkage, and achieving dimensional accuracy. The aim is to provide a method for manufacturing structural silicon carbide sintered bodies that require strength at low cost without special machining, starting from fine silicon carbide powder that easily shrinks during firing. As a raw material, as a result of various research efforts to develop a sintering method that can suppress firing shrinkage caused by sintering, we have been able to control the impurity components contained in silicon carbide powder and sinter it within a specific atmosphere and temperature range. We discovered a new method of producing a high-strength silicon carbide sintered body with high surface precision without causing substantial firing shrinkage by sintering the material. -245599, “average particle size is 5
7kQ/, characterized in that after molding silicon carbide powder of micrometer or less into a green body, the green body is sintered in a non-oxidizing atmosphere within a temperature range of 1700 to 2100°C without substantially shrinking. - A method for manufacturing a silicon carbide sintered body having an average bending strength of at least -

However, the silicon carbide sintered body is a porous body,
In particular, it is difficult to apply it to applications that require wear resistance or airtightness.

Therefore, the present inventors aimed to solve the above-mentioned problems, and as a result of further research on the silicon carbide sintered body, it was found that the open pores of the silicon carbide sintered body were filled with metallic silicon. As a result, the present invention was completed based on the new finding that it is possible to produce a silicon carbide composite with improved wear resistance and airtightness without impairing dimensional accuracy and surface accuracy.

The present invention provides dimensional accuracy in which metallic silicon is filled into the open pores of a porous silicon carbide sintered body that is sintered without substantially shrinking to form open pores in a three-dimensional network structure. and a silicon carbide composite with excellent wear resistance and a method for producing the same.

The present invention will be explained in detail below.

The porous silicon carbide sintered body needs to be a silicon carbide sintered body sintered without substantially shrinking. The reason for this is that silicon carbide sintered bodies that are shrunk during sintering are preferable in terms of strength and wear resistance, but the dimensions of sintered bodies manufactured by a sintering method that involves shrinkage depend on the density of the formed body and the sintered body. Since it is greatly affected by the amount of shrinkage during sintering, it is necessary to uniformly cause shrinkage during sintering in order to produce a sintered body with excellent dimensional accuracy. By the way, in order to cause the above-mentioned contraction uniformly, it is important to obtain a formed body having a uniform density.
This is because it is extremely difficult to obtain a green body having such a uniform density, and it is difficult to produce a sintered body with extremely excellent dimensional accuracy by causing firing shrinkage.

The sintering shrinkage rate of the silicon carbide sintered body sintered without substantially shrinking is advantageously 2% or less, and more preferably 1% or less.

The silicon carbide composite of the present invention needs to be a porous silicon carbide sintered body whose open pores are filled with metallic silicon. The reason is that metallic silicon has good compatibility with silicon carbide sintered bodies, and by filling the open pores of porous silicon carbide sintered bodies with metallic silicon, the porous silicon carbide sintered bodies can be removed from the porous silicon carbide sintered bodies. This is because the detachment of crystal grains can be prevented, and wear resistance can be significantly improved.

The porous silicon carbide sintered body has an average crystal grain size of 10
It is preferable that the open porosity is 18 to 56% by volume. The reason why it is preferable that the average grain size of the crystals is 10 μm or less is because if the average grain size of the crystals is larger than 10 μm, the surface roughness of the sintered body becomes large and the dimensional accuracy deteriorates. The reason why the open porosity is preferably 18 to 56% by volume is that the open porosity is 18% to 56% by volume.
This is because if it is lower than 8% by volume, it is difficult to fill with metallic silicon, whereas if it is higher than 56% by volume, the strength of the porous silicon carbide sintered body is low and particles are likely to separate.

The porous silicon carbide sintered body must have excellent dimensional accuracy, and is composed of silicon carbide crystals with an average aspect ratio of 5 or less and has a three-dimensional network structure. It is preferable that it be made of the following.

In the silicon carbide composite of the present invention, it is preferable that at least 650 parts by volume of metallic silicon is filled with respect to 100 parts by volume of the open pores of the porous silicon carbide sintered body. The reason is that if the filling amount of metallic silicon is less than 50 parts by volume, the effect of preventing the detachment of crystal grains from the silicon carbide sintered body will not be sufficient, and it will be difficult to improve the wear resistance. It is.

Next, a method of manufacturing a silicon carbide composite material having excellent dimensional accuracy and wear resistance according to the present invention will be described.

According to the present invention, after forming silicon carbide powder with an average particle size of 5 μm or less into a green body, the green body is
A porous silicon carbide sintered body having open pores with a three-dimensional network structure is produced by sintering within a temperature range of 100° C. without substantially shrinking, and then the open pores are filled with metallic silicon. By this method, a silicon carbide composite with excellent dimensional accuracy and wear resistance can be manufactured.

The reason for using a silicon carbide powder bed with an average particle size of 5 μm or less is that silicon carbide with a particle size larger than 5 μm is preferable for suppressing firing shrinkage, but it reduces the number of bonding points between grains in the sintered body. Therefore, it is not only difficult to obtain a high-strength silicon carbide sintered body, but also the surface roughness is deteriorated.

By the way, the crystalline system of silicon carbide includes α type, β type and amorphous type, and any of them or a mixture thereof can be used. Among them, β type is 5 types.
It can be advantageously used because it is easy to obtain IIXn or less in fine powder form and can produce a sintered body with relatively high strength, and in particular, it contains β-type silicon carbide in an amount of 50% by weight or more. It is advantageous to use silicon carbide powder.

Advantageously, the silicon carbide powder has a total content of boron, aluminum and iron of 0.3 M% or less in terms of elements. The reason is that the total content of boron, aluminum and iron is 0.3 in terms of elements.
If it exceeds % by weight, it tends to shrink during sintering due to interaction with free carbon contained in the silicon carbide powder,
This is because it becomes difficult to manufacture a sintered body without causing substantial shrinkage.

In addition, when the content of boron, aluminum, and iron in the silicon carbide powder is within the above range, the starting material should contain free carbon of 5 weight 1% or less (carbonaceous substances may not be added). The free carbon has the effect of suppressing the coarsening of crystal grains, and by making it present in the starting raw material, the crystal grain size of the sintered body can be made uniform and a sintered body with relatively high strength can be obtained. The reason why the free carbon content is set to 5% by weight or less is that if it is more than 5% by weight, excess carbon will exist between the silicon carbide powder particles, which will prevent the bonding between particles. This is because the strength of the sintered body deteriorates due to significant interference.

The carbonaceous material may be any material that allows carbon to be present at the start of sintering, such as phenol resin, lignin sulfonate, polyvinyl alcohol, cornstarch, saccharide, coal tar pitch, a/L/kyate. or pyrolytic carbons such as carbon black, acetylene black, etc. can be advantageously used.

When the total content of boron, aluminum and iron exceeds 0.3% by weight in terms of elements, the silicon carbide powder has a content of carbonaceous substances and free carbon in terms of fixed carbon content. Advantageously, it is less than 0.6% by weight. The reason is that when the total content of boron, aluminum and iron exceeds 0.3% by weight in terms of elements, the content of carbon purchasing substances and free carbon is O-6 in terms of fixed carbon content. If the amount is larger than 1% by weight, as explained above, the interaction between boron, aluminum, or iron and carbon tends to cause sintering shrinkage during sintering, and it is difficult to obtain a sintered body without causing substantial shrinkage. This is because it becomes difficult.

In addition, if the content of boron, aluminum, and iron is too high, the physical properties of the sintered body will deteriorate, so it is preferable that the content be as low as possible, and the total content should be 2% by weight or less in terms of elements. That is advantageous.

The resulting shaped body is fired within a temperature range of 1400-2100°C. The reason for this is that if the temperature is lower than 1400"C, it is difficult to reach the neck that connects the grains, and a sintered body with high strength cannot be obtained.
On the other hand, at temperatures higher than 2100°C, some of the necks that have grown once are smaller than a certain size (become slanted, or in severe cases disappear, resulting in a lower strength, and some particles This is because the roughness of the surface deteriorates as the surface becomes coarser.

The resulting shaped body is fired in a non-oxidizing atmosphere without substantial shrinkage. The reason for this is that shrinkage during sintering is preferable for improving the strength of the sintered body, but generally speaking, the amount of shrinkage during sintering has a large effect on the density of the formed body, so it is necessary to generate uniform shrinkage. Therefore, it is important to obtain a formed body with uniform density. However, it is extremely difficult to obtain a formed body having such uniform density, and it is therefore difficult to produce a sintered body with extremely high dimensional accuracy by causing firing shrinkage.

In addition, in order to obtain a sintered body with high dimensional accuracy as mentioned above, there should be no substantial shrinkage (the firing shrinkage rate during sintering is 2%).
It is preferably at most 1%, and more preferably at most 1%.

Further, it is advantageous that the formed body is fired in an atmosphere in which the partial pressure of at least one of CO and N is maintained at 100 Pa or more within a temperature range of 1400 to 210:00 C for at least 10 minutes. It is. The reason is that within the temperature range at least 10
By setting the gas partial pressure of at least one of CO or N2 in the atmosphere to 100 Pa or more, neck growth can be promoted and sintering shrinkage during sintering of silicon carbide can be effectively suppressed. It is.

According to the present invention, it is advantageous to charge the green body into a heat-resistant container in which the firing atmosphere can be controlled and to fire it. The reason why it is advantageous to charge the material into a heat-resistant container and fire it while controlling the firing atmosphere is as follows.
This is because bonding between adjacent silicon carbide crystals and growth of necks can be promoted. The reason why bonding between adjacent silicon carbide crystals and neck growth can be promoted by charging the formed body into a heat-resistant container and firing while controlling the firing atmosphere as described above is as follows.
This is thought to be because movement of silicon carbide between silicon carbide particles by evaporation-recondensation and/or surface diffusion can be promoted.

As the heat-resistant container, it is possible to advantageously use materials such as graphite and silicon carbide, and materials having functions equivalent to these materials.

Furthermore, it is advantageous to control the volatilization rate of silicon carbide during firing to 5% by weight or less by charging the formed body into a heat-resistant container in which the firing atmosphere can be controlled and firing it. be.

Advantageously, the product form has a density of 45 to 80% by volume. The reason for this is that if the density of the formed body is lower than 45% by volume, there will be fewer points of contact between the silicon carbide particles, which will inevitably result in fewer bonding points, making it difficult to obtain a high-strength sintered body. .

On the other hand, this is because it is difficult to produce a formed body with a content higher than 80% by volume.

First, during the heating process up to 1400'C, CO in the atmosphere was heated at 1300°C or higher for at least 30 minutes.
By maintaining the total gas partial pressure of N2 and N2 at 100 Pa or less, it is possible to uniformly generate necks between silicon carbide particles and to firmly bond them.

According to the present invention, it is necessary to fill the open pores of the porous silicon carbide sintered body with metallic silicon.

The reason for this is that metallic silicon has good compatibility with silicon carbide sintered bodies, and by filling the open pores of porous silicon carbide sintered bodies with metallic silicon, the porous silicon carbide sintered bodies can be removed. This is because it is possible to prevent cracking of crystal grains and to significantly improve wear resistance.

The method for filling the open pores of the porous silicon carbide sintered body with the metallic silicon is to impregnate the metallic silicon by heating and melting it, or to disperse pulverized metallic silicon in a dispersion medium and dispersing the metallic silicon. An applicable method is to impregnate a porous silicon carbide sintered body with a liquid, dry it, and then heat it to a temperature higher than the melting temperature of metal silicon.

According to the present invention, it is advantageous to fill at least 50 parts by volume of the metal filler per 100 parts by volume of open pores of the porous silicon carbide sintered body. The reason is that if the filling amount of metallic silicon is less than 50 parts, the effect of preventing the detachment of crystal grains from the silicon carbide sintered body is insufficient, and it is difficult to improve the wear resistance. It is from.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Silicon carbide powder used as starting material was 94.6% by weight
is β-type crystal, the remainder is substantially 2H-type crystal, and 0.
29 wt% free carbon, 0.17 wt% oxygen, 0.0
It mainly contained 3% by weight of iron, 0.03% by weight of aluminum, and had an average particle size of 0.28 um, and no boron was detected.

5 parts by weight of polyvinyl alcohol and 300 parts by weight of water were blended with 100 parts by weight of the silicon carbide powder, mixed in a ball mill for 5 hours, and then dried.

An appropriate amount of this dry mixture was collected, granulated, and then molded using a metal mold at a pressure of aQOO kg/d. The dimensions of this generated form are 2501111X250ffx30s
At o+, the density was 2.0f shoulder (62% by volume).

The formed body was charged into a graphite crucible, and heated mainly with argon gas at 1 atm using a Tammann type kiln.

Fired in an atmosphere. The heating process is 450°C/hour for 2
The temperature was raised to 000°C and maintained at the maximum temperature of 2000°C for 10 minutes. The partial pressure of 0017 during sintering is 130 Pa or less at room temperature to 1700℃, and 300± at temperatures below 1700℃.
The argon gas flow rate was appropriately adjusted and controlled so that the pressure was within the range of 59 Pa.

The density of the obtained sintered body was 2.05 f/d, and the open porosity was 3.
When observed using a scanning electron microscope, the crystal structure was found to have a three-dimensional structure in which silicon carbide plate crystals with an average aspect ratio of 2.5 were intricately intertwined in multiple directions. The linear shrinkage rate was within the range of 0.25±0.02% in any direction, and the dimensional accuracy of the sintered body was within ±o, osam. Further, the average bending strength of this sintered body was as high as 18.5#/-.

Next, 100% of metallic silicon powder with an average particle size of 20 μm and a purity of 99.9% was applied to the surface of the porous sintered body. A layer of slurry containing 60 parts of acrylic acid ester and benzene solution of 5% acrylic acid ester and 60 parts of 5% acrylic acid ester benzene solution was spread on the surface, and 170 parts of metal silicon was coated on the surface.
0f coating. This porous sintered body coated with metallic silicon was heated at 45σC/in an argon gas stream.
Heating at a heating rate of 1 hour, with a maximum temperature of 1450°C, approximately 1 hour.
The metallic silicon applied to the surface of the sintered body was allowed to penetrate into the sintered body by holding the sintered body for a period of time to obtain a silicon carbide composite.

The porosity of the obtained silicon carbide composite was 1.6%,
Dimensional change is 0.0 compared to before filling with metal silicon
05 ff was only larger. The average bending strength of the tube was 35.3 kljf/-, which was significantly increased by filling with metallic silicon.

Example 2 Same as Example 1, but with 92.8 as silicon carbide powder.
% by weight of β-type crystals and the remainder substantially of 2H-type crystals, 0.21% by weight of free carbon, 0.17% by weight of oxygen,
O, aS wt% iron, 0.1 wt% aluminum, 0
．． Mainly contains 2% by weight of boron, 0.27 Irr
Silicon carbide powder having an average particle size of n is used, and the fixed carbon content is 51.6 parts per 100 parts by weight of the silicon carbide powder.
A dry mixture of 0.4 parts by weight of novolac type phenolic resin and 300 parts by weight of benzene was mixed in a ball mill for 5 hours and then dried.
The formed body of x50 tar was molded and sintered to obtain a porous sintered body.

The density of the obtained sintered body was 2.05 f/d, the open porosity was 36%, and the linear shrinkage rate for the formed body was 0.52±.
Although it is slightly larger at 0.03%, the dimensional accuracy is ±0.08
fi was relatively good. Note that the average bending strength of this sintered body was a significantly high value of 32.5 kQ/-.

Next, the porous sintered body is placed in a graphite crucible,
Massive metallic silicon having a purity of 99.9% was placed around the porous sintered body and heated at 1450°C for 1 hour to obtain a silicon carbide composite.

The porosity of the obtained silicon carbide composite was 2.2%,
Almost no dimensional change was observed. Further, the dimensional accuracy of this composite was high within ±0.05 fi, and the average bending strength was 42.6 to 9 f/-, which was high strength.

〔Effect of the invention〕

As mentioned above, the silicon carbide composite of the present invention has extremely excellent dimensional accuracy and wear resistance, and can be used in semiconductor diffusion and oxidation treatments, diode bonding, glass sealing, and package lead frame brazing. heat-resistant jig materials for the electronic industry, wear-resistant materials such as mechanical seals and bearings,
It is possible to provide a silicon carbide composite at a low cost that is suitable for use as a corrosion-resistant material such as pump parts for highly corrosive solutions such as acids and alkalis, and is extremely useful industrially.

Claims (1)

[Claims] 1. Metallic silicon is filled into the open pores of a porous silicon carbide sintered body that is sintered without substantially shrinking to form open pores with a three-dimensional network structure. A silicon carbide composite with excellent dimensional accuracy and wear resistance. 2. The silicon carbide composite according to claim 1, wherein the porous silicon carbide sintered body has a shrinkage rate of 2% or less during sintering. 3. The silicon carbide composite according to claim 1 or 2, wherein the porous silicon carbide sintered body has an average grain size of 10 μm or less and an open porosity of 18 to 56% by volume. 4. The porous silicon carbide sintered body has a three-dimensional network structure mainly composed of silicon carbide crystals having an average aspect ratio of 5 or less. Siliceous complex. 5. The silicon carbide according to any one of claims 1 to 4, wherein the metallic silicon is filled in at least 50 parts by volume with respect to 100 parts by volume of open pores of the porous silicon carbide sintered body. quality complex. 6. After molding silicon carbide powder with an average particle size of 5 μm or less into a green body, the green body is sintered within a temperature range of 1400 to 2100°C without substantially shrinking to open a three-dimensional network structure. A method for producing a silicon carbide composite having excellent dimensional accuracy and wear resistance, comprising producing a porous silicon carbide sintered body having pores, and then filling the open pores with metallic silicon. 7. The manufacturing method according to claim 6, wherein the porous silicon carbide sintered body has a shrinkage rate of 2% or less during sintering.