JPH04310567A - Carbon fiber reinforced carbon composite material having low coefficient of friction - Google Patents

Abstract

PURPOSE:To provide a carbon fiber reinforced carbon composite material having a low coefficient of friction. CONSTITUTION:This carbon fiber reinforced carbon composite material consists of a base composed of carbon fiber reinforced carbon and 1-20wt.% metal boride powder and/or fiber having >=1,800 deg.C melting point, hardly being reacted with carbon of the base, embedded in the base. TiB2, ZrB2, CrB or CrB2 may be used as the metal boride. When content of the carbon fiber is <=40wt.%, apparent density of the composite material is >=1.65g/cm<2> and an average thermal expansion coefficient alpha1 of the carbon fiber reinforced carbon of the base at 20-1,000 deg.C and average thermal expansion coefficient alpha2 of the metal boride at 20-1,000 deg.C have a correlation shown by the formula -2<=alpha1-alpha2<=+3.5, the carbon fiber reinforced carbon composite material has more excellent wear resistance than the base itself not containing the metal boride.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has a low coefficient of friction, excellent heat resistance and oxidation resistance, and is applicable to bushes, thrust washers, piston rings, pump vanes, rotors, sleeves, etc.
The present invention relates to a carbon fiber-reinforced carbon composite material suitable for use in bearings, high-temperature bearings, and the like. The carbon composite material of the present invention has a low coefficient of friction under dry sliding and has excellent seizure resistance, and can be used in mechanical structures to contribute to reducing friction loss. Therefore, the carbon composite material of the present invention can be used as a sliding member,
In particular, it can be used as a sliding member used at high temperatures or without lubrication.

0002

2. Description of the Related Art Conventionally, sliding parts of mechanical structures have low seizure resistance and are therefore usually used under oil lubrication. Sintered materials impregnated with oil and copper-based sintered alloys are known as sliding members used under dry conditions. On the other hand, materials used at high temperatures or without lubrication are required to have low friction characteristics, heat resistance, and wear resistance. Carbon materials are known as such materials. The carbon material used is one obtained by baking and solidifying carbon powder and pitch powder, or one obtained by graphitizing by sintering at high temperature.

[0003] In recent years, carbon fiber-reinforced carbon materials have been provided as materials with improved strength of carbon materials used for such purposes. This carbon fiber-reinforced carbon material is made of, for example, carbon fibers that are carbonized or graphitized and subjected to surface treatment such as oxidation treatment as a reinforcing material, and combined with tar, pitch, or thermosetting resin as a binder. It is manufactured by impregnating a liquid carbon material, firing it in an inert atmosphere, and graphitizing it if necessary.
6351).

Furthermore, for the purpose of increasing the friction coefficient of carbon fiber reinforced carbon materials, a carbon fiber reinforced carbon composite material has been reported in which carbon fiber reinforced carbon materials are blended with metal or carbide ceramic powder (Japanese Unexamined Patent Application Publication No. 63 -13926, Japanese Unexamined Patent Publication No. 63-60173).

[0005]

[Problems to be Solved by the Invention] Conventional carbon fiber-reinforced carbon materials have a characteristic of having a low coefficient of friction μ in a relatively low temperature range such as room temperature or under a low load. However, under high temperatures or high loads, the coefficient of friction is relatively high. The present invention has been made in view of this problem, and an object of the present invention is to provide a carbon fiber-reinforced carbon composite material having a low coefficient of friction. A further object of the present invention is to provide a carbon fiber-reinforced carbon composite material that has a low coefficient of friction, high strength, and excellent wear resistance.

[0006]

[Means for Solving the Problems] The carbon fiber-reinforced carbon composite material of the present invention has a base material made of carbon fiber-reinforced carbon, and has a melting point of 1800°C or higher and a carbon fiber of the base material. 1 to 2 metal boride powders and/or fibers that are difficult to react
It is characterized by being buried at 0% by weight. The present inventor created various carbon fiber-reinforced carbon composite materials by blending various ceramics with carbon fiber-reinforced carbon materials, and the density, strength, friction coefficient under dry and wet conditions, and amount of wear of the resulting composite materials. have been investigated in detail. It has been found that when metal boride is used as the ceramic, it has a lower coefficient of friction than the carbon fiber-reinforced carbon material of the base material, unlike when other ceramics are mixed.

[0007] Therefore, the inventors of the present invention filed patent applications for some of their findings in Japanese Patent Application No. 1-341883 and Japanese Patent Application No. 2-163388. These patented inventions are mainly characterized by a base material made of carbon fiber-reinforced carbon material, and are made by integrally sintering carbon powder with self-sintering properties and uncarbonized carbon fibers before complete carbonization. It is a solid sintered body with particularly excellent wear resistance. A carbon fiber-reinforced carbon composite material made of this sintered body as a base material and mixed with various ceramics has excellent wear resistance and, by selecting the ceramic, can obtain a desired coefficient of friction.

The present inventor has further expanded the range of carbon fiber-reinforced carbon materials that can be used as base materials, and as a result of research on combining a wide range of ceramics, has found a material with a low coefficient of friction and mechanical strength that can be used as a structural material. The present invention was completed by discovering a new carbon fiber-reinforced carbon composite material having the following characteristics. The carbon fiber-reinforced carbon composite material of the present invention comprises a base material made of carbon fiber-reinforced carbon, and metal boride powder and/or fibers 1 to 20 that have a melting point of 1800°C or higher and are difficult to react with the carbon of the base material. % by weight.

[0009] The base material is composed of carbon fibers and matrix carbon. As the carbon fiber, carbon fiber spun using PAN (polyacrylonitrile), coal, or petroleum pitch as a raw material and carbonized can be used. A preferred carbon fiber is a pitch-based optically isotropic carbon fiber. This optically isotropic carbon fiber has no anisotropy in thermal expansion coefficient depending on the fiber direction, and has an average thermal expansion coefficient of 2 to 4 x 10-6/°C in the range of 20 to 1000°C. Further, PAN-based and pitch-based carbon fibers having high strength, high rigidity, and optical anisotropy are known. This carbon fiber has a negative thermal expansion coefficient in the fiber direction from room temperature to about 400°C, and a thermal expansion coefficient of 0 to 2 x 10-6 from 400 to 1000°C.
/°C, and the coefficient of thermal expansion in the longitudinal direction of the fiber is different from that in the direction perpendicular thereto. This fiber can also be fully utilized depending on the purpose.

[0010] The fiber length of these carbon fibers is not limited to short fibers or long fibers. However, in the case of short fibers, 0.01~
A 50mm one can be used. In particular, 0.0
A diameter of 3 to 10 mm is preferred from the viewpoint of ease of mixing and aspect ratio. If the length is too long, the fibers will become entangled with each other and the dispersibility will decrease, resulting in poor uniformity of product properties.
．． If it is shorter than 0.1 mm, the strength of the product will drop rapidly, which is not preferable. Further, the fiber diameter is preferably about 5 to 25 μm. Furthermore, these fibers can also be used as nonwoven fabrics or coated fabrics.

[0011] It is preferable that the carbon fiber is further surface-treated with a material containing a caking component such as tar, pitch, or organic polymer to improve its compatibility with the binder. This surface treatment can be carried out by adding about 100 to 1000 parts by weight of a material containing a viscous component to 100 parts by weight of carbon fibers, stirring the mixture, washing with an organic solvent, and drying. The carbon fibers are subjected to a dispersion treatment if necessary. That is, since the dried fibers may be lumped or aggregated, in such a case, dispersion is carried out by any means such as a conventional powder mill, an atomizer, or a pulverizer.

[0012] Matrix carbon can be carbonized by thermal decomposition of resin such as phenol resin, carbonized by heating coal or petroleum pitch, crushed coke, or self-sintering materials such as mesocarbon microbeads. Powder with a carbon dioxide, carbon obtained by a vapor phase method using CVD, etc. can be used. The metal boride needs to have a high melting point of 1800° C. or higher and be difficult to react with carbon during composite material production. Such metal borides include TiB2,
ZrB2, CrB, CrB2, etc. can be mentioned. As will be explained later, the metal boride preferably has a low coefficient of thermal expansion (α2) in addition to the above-mentioned conditions of high melting point and being difficult to react with carbon. From the viewpoint of low thermal expansion, TiB2 (α2; 7.6 to 8.3×
10-6/℃), ZrB2 (α2; 5.3-6.2
×10-6/°C) is recommended.

When a metal boride powder is used, it is preferable to have a particle size of 0.1 to 10 μm in consideration of compatibility with the base material, dispersibility, and strength and wear resistance as a composite material. More preferably, the particle size is 0.3 to 5 μm. If the particle size is smaller than 0.1 μm, uniform mixing is difficult;
If the particle size is larger than 10 μm, abnormal wear may occur. When using metal boride fibers, the diameter should be 0.7 to 40 μm and the length should be 0.01 to 40 μm, taking into account compatibility with the base material, dispersibility, strength and abrasion resistance as a composite material.
A diameter of 8 mm is preferable, and a diameter of 1 to 15 mm is more preferable.
It is preferable to have a length of 0.05 to 3 mm. Note that the fibers include whiskers and ceramic fibers.

The carbon fiber reinforced carbon composite material of the present invention includes:
Other borides, such as boron carbide and boron nitride, can be blended with the metal boride. The blending ratio is preferably such that the total boride content, including metal borides, is within 20%. Based on numerous test results, the present inventor has found that the closer the thermal expansion coefficient of the base material constituting the carbon fiber reinforced carbon composite material and the thermal expansion coefficient of the metal boride, the greater the mechanical strength of the carbon fiber reinforced carbon composite material. It is known that this improves the physical properties. 20 to 100 expected to use the carbon fiber reinforced carbon composite material of the present invention
In the temperature range of 0° C., the average coefficient of thermal expansion of the carbon fiber-reinforced carbon material constituting the base material is relatively low, and conversely, the average coefficient of thermal expansion of the metal boride is high.

[0015] Therefore, it is preferable that the base material has a coefficient of thermal expansion as high as possible within a range where a decrease in strength is acceptable. Note that the thermal expansion coefficient of the carbon fiber-reinforced carbon material constituting the base material can be arbitrarily adjusted to some extent by selecting the matrix carbon raw material and the type of carbon fiber to be used, or by changing the manufacturing method. It is preferable to select a metal boride with a small coefficient of thermal expansion. When it is necessary to select a ceramic with a high coefficient of thermal expansion depending on the application, methods such as reducing the amount of ceramic to be blended or using it in combination with other borides with a low coefficient of thermal expansion can be adopted.

The average coefficient of thermal expansion α1 at 20 to 1000°C of the base material of the carbon fiber reinforced carbon composite material of the present invention and the average coefficient of thermal expansion α2 at 20 to 1000°C of the metal boride have the following relationship. preferable. −2×10−6/℃≦α1 −α2 ≦3.5×10−
6/°C (α1 - α2) is smaller than -2, that is, when the average coefficient of thermal expansion α1 of the base material is 2×10-6/°C smaller than the average coefficient of thermal expansion α2 of the metal boride, the base material and the metal boride A non-negligible gap is created at the interface with the compound, resulting in lower wear resistance. The same thing can be said that (α1 - α2) is larger than +3.5, that is, the average coefficient of thermal expansion α1 of the base material is 3.5×10−6/
If the temperature is too high, non-negligible distortion will occur at the boundary between the base material and the metal boride, resulting in lower wear resistance. In addition, (α1
The reason why α2) differs between the positive and negative sides is that the relationship between the base material and the metal boride in the carbon fiber reinforced carbon composite material is determined by the firing temperature, and when the temperature decreases from the firing temperature to room temperature, the We believe that this is because the relationship between the boundary between the base material and the metal boride changes due to thermal contraction caused by the change. If (α1 − α2 ) is negative, that is, the coefficient of thermal expansion of the metal boride is large, the metal boride will shrink significantly when the temperature drops to room temperature, and a gap will be created at the boundary between the base material and the metal boride. Conversely, if (α1 - α2) is positive, that is, the coefficient of thermal expansion of the metal boride is small, the base material will shrink significantly when the temperature drops to room temperature, and the base material will strongly shrink the metal boride using the same principle as shrink fitting. No confinement gap occurs. Note that if (α1 − α2 ) is too large, the base material will not be able to absorb the strain caused by the difference in thermal expansion, and the base material will be destroyed, resulting in a significant decrease in wear resistance.

For reference, several types of carbon fiber-reinforced carbon composite materials were prepared in which the difference in thermal expansion coefficient (α1 - α2) was varied by keeping the base material constant and changing the type of ceramics such as metal boride to be mixed. Difference in thermal expansion coefficient (α1 − α2)
Figure 1 shows a diagram showing the relationship between and specific wear amount.
Here, the difference in thermal expansion coefficient (α1 − α2) is shown as an absolute value. From FIG. 1, it can be seen that the closer (α1 − α2) is to zero (0), the lower the specific wear amount is.

[0018] The carbon fiber reinforced carbon composite material of the present invention
The proportion of the metal boride powder and/or fiber is preferably 1 to 20% when 0% by weight (hereinafter, % indicates weight% unless otherwise specified). If it is less than 1%, it is not sufficient to reduce the coefficient of friction, and if it exceeds 20%, the material strength is significantly reduced. Further, the content of carbon fiber is preferably 40% or less. If it exceeds 40%, the material strength will drop significantly.

The carbon fiber-reinforced carbon composite material of the present invention preferably has an apparent density of 1.65 g/cm 3 or more. The higher the apparent density, the better the mechanical properties such as material strength and wear resistance. The shape of the carbon fiber-reinforced carbon composite material of the present invention is not particularly limited, and may be any predetermined shape such as a bush, washer, rotor, or sleeve.

The carbon fiber-reinforced carbon composite material of the present invention can be produced by a known method. When using self-sintering carbon powder as the matrix carbon, it can be manufactured by a simple process of dry mixing, dry molding, and firing, as shown in FIG. 2, for example. In order to make the carbon powder, metal boride powder, and fiber isotropic in strength and wear resistance, it is preferable to uniformly mix the above-mentioned raw materials.

[0021] Molding can be carried out by a conventional method, and the molding may be carried out into a predetermined shape under pressure of about 1 to 10 ton/cm2. Alternatively, the molding may be performed by a CIP method, a HIP method, a hot press method, or the like. The molding is
This can be carried out at room temperature or under heating up to about 500° C. in an inert atmosphere. In the firing, carbon fibers and self-sintering carbon powder are carbonized and solidified by heating to about 700 to 1500°C. Note that, if necessary, this carbonized composite may be heated to a temperature higher than the sintering temperature in a graphitization furnace to graphitize it.

[0022] When a liquid material or a raw material that can be liquefied by heating is used as the matrix carbon, the metal boride is mixed with the matrix carbon raw material. The carbon fibers may be mixed with the matrix carbon raw material as in the conventional method, or the matrix carbon raw material may be attached to a preformed body made of carbon fibers. To obtain a composite, the obtained molded body is heated to promote carbonization of the matrix carbon raw material, and the whole is integrated. The carbonization conditions are not particularly limited, but usually the temperature is raised from room temperature to about 1500°C at a rate of about 0.1 to 300°C/hour in a non-oxidizing atmosphere, and
This may be carried out by holding it for about 10 hours. Note that during sintering, if the composite is sintered at a higher temperature, a portion of the composite will be carbonized and then graphitized.

[0023] Furthermore, the conditions for graphitization are not particularly limited;
0.1 to 500℃ from the temperature during sintering in a non-oxidizing atmosphere
The temperature may be raised to a temperature of about 1500 to 3000° C. at a rate of about 100° C./hour and maintained for about 0.5 to 10 hours. When graphitization is performed, graphite crystals grow sufficiently and are oriented in an orderly manner, thereby further improving the density, strength, wear resistance, etc. of the product.

[0024]

[Examples] Examples of the present invention will be described below. (Example 1) As the carbon fiber, a coal pitch-based infusible carbon fiber having a length of 20 mm was used. Coal tar-based mesocarbon microbeads (manufactured by Osaka Gas) with an average particle size of 7 μm were used as the matrix carbon raw material. Furthermore, as a metal boride, TiB2 (α2;
8.1×10 −6 /° C.) powder was used. Then, carbon fibers, mesocarbon microbeads, and TiB2 powder were blended in a weight ratio of 30:65:5. This mixture was mixed in a Raikai machine, and then 1 to
Molding was performed at a molding pressure of n/cm2. Thereafter, the molded body was heated for 1 hour at a heating rate of 150°C/hour in a non-oxidizing atmosphere at normal pressure.
The temperature was raised to 000°C, held at the same temperature for 1 hour, and further heated to 2000°C at a rate of 500°C/hour in a non-oxidizing atmosphere for sintering. As a result, a carbon fiber-reinforced carbon composite material of the present invention was obtained.

[0025] Ti of the obtained carbon fiber reinforced carbon composite material
The proportion and apparent density of B2 are 5% and 1.7, respectively.
It was 5g/cm3. Moreover, the average thermal expansion coefficient α of this carbon fiber reinforced carbon composite material at 20 to 1000°C is 7.
It was 5x10-6/°C. Note that TiB2 in this example
A carbon fiber-reinforced carbon material containing no TiB2 powder was produced using the same method as in this example, except that it did not contain any powder, and was used as the base material constituting the carbon fiber-reinforced carbon composite material of this example. did. And 20 to 10 of this base material
The average coefficient of thermal expansion α1 at 00°C was determined. 20~ of base material
The average coefficient of thermal expansion α1 at 1000℃ is 7.3×10-6
/℃. The average coefficient of thermal expansion α1 of this base material and Ti
From the average thermal expansion coefficient α2 of B2 (α1 − α2 )
When calculating, (α1 - α2) of the carbon fiber-reinforced carbon composite material of this example containing TiB2 is -0.8×10
-6/℃. (Example 2) Coal pitch-based infusible carbon fibers, mesocarbon microbeads, and T used in Example 1
iB2 was blended in proportions of 25%, 70% and 5%, respectively, and mixed in a Raikai machine, and the resulting mixture was
kg/cm 2 by cold isostatic pressing (CIP method), and sintered by heating to 1000° C. in a nitrogen gas atmosphere. In order to further increase the density, the obtained sintered body was immersed in a phenol resin liquid to impregnate it with phenol resin, and was heated to 1000° C. in nitrogen gas to carbonize and sinter it. After repeating this operation 10 times, it was heated to 2200° C. in argon gas to graphitize it to obtain a carbon fiber-reinforced carbon composite material of the present invention.

The TiB2 proportion and apparent density of Example 2 were 5% and 1.85 g/cm3, respectively. Also, the average coefficient of thermal expansion from 20 to 1000℃ is 7.7×1
It was 0-6/°C. A carbon fiber-reinforced carbon material containing no TiB2 powder was produced using the same method as in this example except that it did not contain any TiB2 powder, and the carbon fiber-reinforced carbon composite material of this example was It was used as the base material that constitutes the material. And 20~1000℃ of this base material
The average coefficient of thermal expansion α1 was determined. 20-100 of base material
The average coefficient of thermal expansion α1 at 0°C was 7.5×10 −6 /°C. The average coefficient of thermal expansion α1 and TiB2 of this base material
Calculating (α1 - α2) from the average coefficient of thermal expansion α2, (α1 - α2) of the carbon fiber-reinforced carbon composite material of this example containing TiB2 is -0.6×10-6/
℃. (Example 3) In place of TiB2 used in Example 1, CrB2 (α2; 10.
A carbon fiber-reinforced carbon composite material was produced in the same manner as in Example 1 except that a carbon fiber-reinforced carbon composite material was used. The CrB2 proportion and apparent density of this Example 3 were 5% and 1.76 g/cm3, respectively. Also,
The average coefficient of thermal expansion from 20 to 1000℃ is 8.3 x 10-6
/℃.

[0027] The only difference was that the TiB2 powder of this example was not included at all, but otherwise, the method was exactly the same as that of this example,
A carbon fiber-reinforced carbon material containing no CrB2 powder was produced and used as a base material constituting the carbon fiber-reinforced carbon composite material of this example. Then, the average coefficient of thermal expansion α1 of this base material at 20 to 1000°C was determined. The average coefficient of thermal expansion α1 of the base material from 20 to 1000°C was 7.3×10 −6 /°C. Calculating (α1 - α2) from the average coefficient of thermal expansion α1 of this base material and the average coefficient of thermal expansion α2 of CrB2, C
(α1 − α2 ) of the carbon fiber-reinforced carbon composite material of this example containing rB2 is −3.2×10 −6 /°C. (Comparative Example 1) The metal boride used in Example 1 was not used, and 30% of the same carbon fiber and 70% of the same matrix carbon raw material were used as in Example 1, and the rest was exactly the same as Example 1. A carbon fiber-reinforced carbon material without metal borides was made using the same method. The apparent density of Comparative Example 1 was 1.74 g/cm3. Also, 20-1
The average coefficient of thermal expansion at 000°C was 7.3 x 10-6/°C. Note that the carbon fiber-reinforced carbon material obtained in Comparative Example 1 corresponds to the base material of Example 1 and Example 3. (Evaluation 1) Regarding the amounts of carbon fiber-reinforced carbon composite materials and carbon fiber-reinforced carbon materials of Examples 1 to 3 and Comparative Example 1, the coefficient of friction without lubrication was measured. This measurement was performed using a mechanical testing laboratory type friction and wear tester at a rotation speed of 160 rpm (
At a sliding speed of 2 cm/sec), the load was increased by 10 kgf every 2 minutes from 50 kgf, and the friction coefficient μ was measured up to 500 kgf. The mating material is high carbon chromium bearing steel (JIS SUJ2, hereinafter SUJ2).
It is called. )It was used. The results are shown in FIG.

As is clear from FIG. 3, in all of the carbon fiber reinforced carbon composite materials blended with metal boride of Examples 1 to 3 of the present invention, as the load increases, the friction coefficient decreases to 0.1.
Or even lower, and is rapidly declining. This trend is
This is in contrast to Comparative Example 1, where the friction coefficient increases as the load increases. The reason why the coefficient of friction of the carbon fiber-reinforced carbon composite materials of Examples 1 to 3 decreases as the load increases is considered to be due to the effect of the metal boride compound. The relatively high coefficient of friction of the carbon fiber-reinforced carbon composite material of Example 3 is due to the difference in average coefficient of thermal expansion (α1) between CrB2 and the base material.
-α2) is large at -3.2×10-6/℃, and C
This is thought to be because the rB2 powder falls off from the base material.

In Comparative Example 1, in which no metal boride was blended, there was a tendency for the friction coefficient to increase rapidly from about 0.15 as the load increased. (Evaluation 2) The wear amount of the carbon fiber-reinforced carbon composite materials and carbon fiber-reinforced carbon materials of Examples 1 to 3 and Comparative Example 1 was measured under wet conditions (oil lubrication). This measurement is based on LFW
Using a friction and wear tester, the load was 15 kgf and the rotation speed was 160.
The test is conducted at rpm for 15 minutes and the depth of the resulting wear scar is measured. A SUJ2 ring was used as the mating material, and the test piece was 10.0 mm x
A 15.7 mm flat plate was used, and 5W-30 base oil was used as the lubricating oil. The results are shown in Table 1. For reference, the difference between the base material and the metal boride in each example is 20 to 100.
The difference in average coefficient of thermal expansion at 0°C (α1 − α2) is also shown.

[0030]

[Table 1] −−−−−−−−−−−−−−−−−−−−−
−−−−−−−−− Test material Depth of wear scar Difference in average coefficient of thermal expansion (α1 −α
2)------------------
−−−−−−−−−−−− Example 1
25μm -0.8×10-6/
℃−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−− Example 2 1
8μm -0.6×10-6/℃-
−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−− Example 3 60μ
m -3.2×10-6/℃---
−−−−−−−−−−−−−−−−−−−−−−−−−
------- Comparative example 1 32 μm
------
−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−− The reason why the wear marks of the carbon fiber reinforced carbon composite materials of the present invention in Examples 1 and 2 are shallow is that the compounded metal This is thought to be because the difference in average coefficient of thermal expansion (α1 - α2) between the boride and the base material is small, and the apparent density of the composite material is high, close to the true density. On the other hand, the reason why the wear marks of the carbon fiber reinforced carbon composite material of the present invention in Example 3 are deep is that the difference in thermal expansion coefficient between the compounded metal boride and the base material is -3.2 x 10-6/℃. This seems to be because the metal boride falls off from the base material because it is large.

[0031]

[Effect] The carbon fiber-reinforced carbon composite material containing the metal boride of the present invention has a lower coefficient of friction than the carbon fiber-reinforced carbon material containing no metal boride. In addition, the difference (α1 − α2) between the thermal expansion coefficient α1 of the base material serving as the matrix and the thermal expansion coefficient α2 of the metal boride is −2×10−6/℃≦α
Those in the range of 1-α2≦3.5×10-6/°C also have a small amount of wear. Therefore, the carbon fiber-reinforced carbon composite material of the present invention is suitable for parts where lubricating oil cannot be used, particularly bushes that are exposed to high temperatures, and mechanical seal materials. Therefore, by using the carbon fiber reinforced carbon composite material of the present invention in the sliding parts of aircraft and automobile engines,
This results in an excellent engine with low sliding resistance and high durability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the difference in average coefficient of thermal expansion between a base material and ceramics constituting a carbon fiber-reinforced carbon composite material and specific wear amount.

FIG. 2 is a block diagram showing one method for manufacturing the carbon fiber-reinforced carbon composite material of the present invention.

FIG. 3 is a diagram showing the friction coefficient under dry friction of carbon fiber-reinforced carbon composite materials obtained in Examples and Comparative Examples.

Claims (4)

[Claims] [Claim 1] The base material is composed of carbon fiber reinforced carbon,
The base material contains 1 to 100% of metal boride powder and/or fibers that have a melting point of 1800° C. or higher and are difficult to react with the carbon of the base material.
A carbon fiber-reinforced carbon composite material with a low coefficient of friction characterized by 20% by weight of embedded material. 2. The carbon fiber reinforced carbon composite material according to claim 1, wherein the carbon fiber content is 40% by weight or less. 3. The carbon fiber reinforced carbon composite material according to claim 1, which has an apparent density of 1.65 g/cm 3 or more. 4. Between the average thermal expansion coefficient α1 of the base material at 20 to 1000°C and the average thermal expansion coefficient α2 of the metal boride at 20 to 1000°C, -2×10-6/°C≦α1 −α2≦. 3.5×10−
The carbon fiber reinforced carbon composite material according to claim 1, which has a relationship of 6/°C.