JP6286865B2 - Wear resistant parts - Google Patents

Description

  The present invention relates to a wear-resistant member. In particular, the present invention relates to a carbon fiber reinforced composite material having excellent wear resistance.

  Carbon fiber reinforced composite materials include carbon fiber reinforced plastic materials (CFRP), carbon fiber reinforced carbon materials (C / C composites), etc., and C / C composites as wear members are brake disks, brake pads, etc. for aircraft and automobiles. In practical use. C / C composites are lightweight and excellent in chemical stability, but because the matrix is also made of carbon, it is excellent in lubricity but low in hardness. There was a problem in the oxidation resistance and the like.

  Examples of materials with improved wear resistance include carbon fiber reinforced silicon carbide materials such as carbon fiber reinforced composite materials with ceramics in the matrix. Since the hardness of the matrix is high, a material with better wear resistance is obtained. be able to. Since the carbon fiber reinforced silicon carbide material uses high-hardness silicon carbide as a matrix among ceramics, it is possible to obtain a material with excellent wear resistance. However, the carbon fiber reinforced silicon carbide material has a problem that the material becomes very expensive because an expensive manufacturing method such as impregnation of SiC into a carbon fiber molded body by a method such as CVI is used.

  In recent years, carbon fiber reinforced silicon carbide materials can be manufactured at low cost by using reactive sintering to impregnate molten silicon into carbon fiber reinforced carbon materials and generating silicon carbide by the reaction of carbon and silicon in the matrix. Is disclosed in Patent Document 1 and the like.

  As a method of obtaining a carbon fiber reinforced silicon carbide material by this method, there is a method of producing a carbon fiber reinforced silicon carbide material using carbon fiber and a phenol resin which is a thermosetting resin as raw materials. In this case, since a method of press molding while heating a mixture of carbon fiber and resin is common, a CFRP molded body in which carbon fibers are oriented perpendicular to the press axis is obtained. The carbon fiber reinforced silicon carbide material obtained by carbonizing the molded body obtained by this method and impregnating with silicon retains the orientation of the carbon fiber during molding, so the carbon fiber is oriented two-dimensionally parallel to the press surface. Material is obtained. When such a material is used as a wear-resistant member, the press surface is generally used as a friction surface, but the carbon fiber is oriented in the fiber length direction, and the carbon fiber portion is prone to wear. there were.

  On the other hand, as an attempt to improve the characteristics of the material by utilizing the orientation of the carbon fiber, Patent Document 2 obtains a material having high bending strength and bending elastic modulus in one direction by using the material in which the carbon fiber is oriented in one direction. Technology is disclosed. However, in order to obtain such a material in which the fibers are oriented in one direction, it is necessary to prepare a sheet in which carbon fibers are aligned in one direction and to laminate the sheets, which is time-consuming and expensive to manufacture. There was a problem.

Japanese Patent No. 4226100 JP 2011-168414 A

Conventionally, the carbon fiber reinforced silicon carbide composite material has a problem that the carbon fiber portion is easily worn.
An object of the present invention is to provide a carbon fiber reinforced composite material having excellent wear resistance.

The gist of the present invention is as follows.
(1) At least a pitch-based carbon fiber having a fiber length of 3 to 20 mm and a synthetic resin are mixed, the mixture is hot press-molded, and then the molded body carbonized by heat treatment is impregnated and heated with molten silicon. In the method for producing a wear-resistant member comprising a carbon fiber reinforced silicon carbide composite material produced by
The carbon fiber content in the carbon fiber reinforced silicon carbide composite material is 30 to 70% by volume,
A method for manufacturing a wear-resistant member, wherein a surface that forms an angle of 0 to 45 ° with a normal direction of a hot press-formed surface is a friction surface.
(2) The method for producing a wear-resistant member according to (1), wherein at least two or more carbon fiber reinforced silicon carbide composite materials are joined together by a hot press-molded surface to form a laminate.

  The carbon fiber reinforced silicon carbide composite material of the present invention has high wear resistance and high impact resistance, and is useful as a wear resistant member.

It is a figure explaining the friction surface with respect to a hot press molding surface.

  In the carbon fiber reinforced silicon carbide composite material obtained by hot press-molding a mixture containing carbon fibers and a synthetic resin, and then two-dimensionally orienting the molded body carbonized by heat treatment with a molten silicon, It was newly found that the wear resistance can be remarkably improved by controlling the angle between the orientation surface and the friction surface.

  When a carbon fiber reinforced silicon carbide composite material produced by impregnating and heating a molded body carbonized by heat treatment after hot press molding a mixture containing carbon fiber and synthetic resin is used as a wear resistant member, The press-molded surface is a surface in which fibers are two-dimensionally oriented in the length direction and has strength, so that a structure used as a friction surface is generally used. The carbon fiber used for the wear resistant member is preferably a carbon fiber obtained by graphitizing the pitch-based carbon fiber by heat treatment, since the carbon fiber having a higher degree of crystallinity has better wear resistance. However, in the graphitized carbon fiber, since the longitudinal direction of the fiber is the C-axis direction of the graphite crystal, the crystal plane in the longitudinal direction of the fiber is bonded with a weak van der Waals force, and the crystal layer is peeled off. The structure is easy to do. For this reason, a hot press-molded surface in which carbon fibers are two-dimensionally oriented in the length direction is inferior in wear resistance.

  On the other hand, since the in-plane bond in the C-axis direction of the carbon fiber is a strong covalent bond, the cross section of the fiber is difficult to cause such peeling and is a surface resistant to abrasion. For this reason, in the carbon fiber reinforced silicon carbide composite material, the surface where the cross section of the carbon fiber is exposed is less likely to be worn than the surface where the length direction of the carbon fiber is exposed. That is, in the carbon fiber reinforced material in which the carbon fibers are two-dimensionally oriented by hot press molding, the normal direction of the press-molded surface is excellent in wear resistance compared to the surface (press-molded surface) in which the fibers are oriented. By utilizing this, it becomes possible to make a member of a carbon fiber reinforced silicon carbide composite material excellent in wear resistance.

  However, as described above, in the carbon fiber reinforced silicon carbide composite material, it is easier to obtain a surface having a larger area when the fiber is oriented in the length direction, but the vertical surface of the fiber orientation is larger. Thus, it is difficult to produce a member. As means for solving this problem, by using the following method, a member made of a carbon fiber-reinforced silicon carbide composite material having excellent wear resistance can be realized.

  As a method for producing a carbon fiber reinforced silicon carbide composite material, carbon fiber is mixed with a carbon-containing raw material as a carbon source, molded, carbonized by heat treatment, and then impregnated and heated with molten silicon. A method of producing silicon carbide by reacting carbonized carbon with silicon is used.

  As a carbon-containing raw material used as a carbon source, a thermosetting resin such as a phenol resin, a thermoplastic resin such as an epoxy resin, pitch, or the like can be used. In particular, when a phenol resin which is a thermosetting resin is used, a molded body can be easily obtained by hot press molding in which a resin and carbon fiber are mixed and pressed while heating. At this time, the phenol resin is once melted and then cured, but once the resin is melted, the carbon fibers in the resin can freely move, so that the carbon fibers are oriented two-dimensionally in a direction perpendicular to the press axis. It is possible to obtain a molded body. In addition, since the phenol resin has a high residual carbon ratio in which the carbon content remains by 50% or more by heat treatment, the carbon fiber can be coated with a sufficient amount of carbon. It is highly effective to suppress carbon fibers from reacting with silicon to produce silicon carbide when silicon impregnated and heated, and the carbon fibers themselves are worn out. desirable.

  It is desirable to use short fibers in the form of fiber bundles for the carbon fibers. Since the carbon fiber itself is as thin as several μm to several tens of μm, it is possible to obtain the effect of improving the wear resistance due to orientation by using bundled fibers rather than the state in which individual fibers are dispersed. It is also effective for improving the toughness of the material and obtaining a strengthening effect that makes it difficult to break.

  Moreover, there exists an advantage which a fiber tends to orientate in a press process by using a short fiber. The number of fiber bundles used is desirably 1000 to 10,000. When the number of fiber bundles is less than 1000, the fibers are easily broken, so that a sufficient reinforcing effect by the carbon fibers cannot be obtained. In the case of a fiber bundle exceeding 10,000, the size of the fiber bundle becomes too large, and the fibers inside the fiber bundle that are not bonded to the matrix easily fall off during wear, so that a material with high wear resistance can be obtained. Can not.

  It is desirable to use carbon fibers having a fiber length of 3 to 20 mm. With fibers shorter than 3 mm, the fibers are difficult to orient during press molding, and it is difficult to obtain a fiber-oriented material necessary for exhibiting high wear resistance. When fibers having a fiber bundle of 20 mm or more are used, it is difficult to obtain a highly oriented material because the fibers are deformed at the portion where the fiber bundles are overlapped during press molding. For this reason, it is desirable to use carbon fibers having a fiber length of 3 to 20 mm.

  Further, as the carbon fiber to be used, PAN-based and pitch-based carbon fibers can be used. In particular, pitch-based carbon fibers are preferable because pitch-based carbon fibers have high rigidity and excellent wear resistance. In order to further improve the wear resistance, it is more desirable to use carbon fibers in which the pitch-based carbon fibers are heat-treated at a temperature of 2000 ° or more to increase the graphitization rate.

  The carbon fiber content is desirably 30 to 70% by volume of the obtained material. When the amount is less than 30% by volume, the effect of reinforcement by fibers cannot be obtained, and a material having excellent wear resistance cannot be obtained. If the volume is more than 70% by volume, the amount of fibers with respect to the matrix is increased, which makes it difficult to mold, which is not desirable.

  The molded body in which the carbon fibers are oriented can be heat-treated to obtain a carbon fiber-carbon composite material while maintaining the orientation of the fibers. By performing a heat treatment called carbonization treatment, the carbon-containing raw material is decomposed and converted to carbon. When the carbon-containing raw material is not completely decomposed, when impregnating silicon, the decomposition component volatilizes, which prevents the penetration of molten silicon and makes it impossible to obtain a healthy material. It is desirable to completely decompose and carbonize the raw material. The carbonization treatment is desirably performed at 600 to 2000 ° C. A temperature lower than 600 ° C. is undesirable because the carbon-containing raw material may not be completely decomposed. Further, when the treatment is performed at a temperature higher than 2000 ° C., carbon is graphitized, and the reaction of generating silicon carbide by reacting with silicon is difficult to proceed. Therefore, it is desirable to perform heat treatment at a temperature of 2000 ° C. or less. In addition, when the carbonization treatment is performed in an oxidizing atmosphere, the carbon-containing raw material and the carbon fiber are oxidized and worn out due to combustion. Therefore, the carbonizing treatment is preferably performed in an inert gas atmosphere such as argon or in a vacuum.

  Furthermore, by impregnating and heating the carbon fiber-carbon composite material with molten silicon at a temperature equal to or higher than the melting point of silicon, the carbon and silicon react to produce silicon carbide, and the carbon fiber reinforced silicon carbide composite in which the carbon fibers are oriented. Material can be obtained. The impregnation / heat treatment is performed at a temperature equal to or higher than the melting point of silicon, but is desirably performed in an inert gas atmosphere such as argon or in vacuum so as not to cause oxidation of carbon. In particular, in order to infiltrate silicon into the details of the molded body, it is most desirable to perform the treatment in a vacuum.

  When the material thus obtained is used as a wear-resistant member, the surface that forms an angle of 0 to 45 ° with the normal direction of the hot press-formed surface that is the two-dimensionally oriented surface of the carbon fiber is the friction surface. By processing the member, it can be used as a member having excellent wear resistance. When processed so that the surface having an angle greater than 45 ° with respect to the normal direction of the hot press-molded surface becomes a friction surface, the carbon fiber is likely to be peeled off on the crystal plane in the C-axis direction, which has a weak bond, A material with excellent wear resistance cannot be obtained. On the other hand, the C-axis direction of the carbon fiber is in contact with the friction surface at a high angle by processing the surface at an angle of 0 to 45 ° with respect to the normal direction of the hot press-formed surface to be a friction surface Therefore, separation at the crystal plane of carbon in the C-axis direction is difficult to occur, and a material with high wear resistance can be obtained. In addition, since the carbon fibers are randomly oriented with a two-dimensional orientation surface, the friction surface is processed at an angle of 0 ° with respect to the normal direction of the hot press-molded surface, so that the wear resistance is maximized. An excellent wear-resistant member can be obtained.

  In the method of forming by hot press forming, it is easy to obtain a press surface having a large area, but the surface forming an angle of 0 ° with the normal direction of the hot press forming surface, that is, the thickness of the press formed body It is difficult to obtain a large area in the direction. Similarly, it is difficult to produce a large-area member from a single material with a surface that forms an angle of 0 to 45 ° with the normal direction of the hot press-molded surface. Is possible.

As a method of combining and processing materials by bonding or the like, a laminate in which carbon fiber reinforced composite materials are bonded on a hot press-molded surface can be created. Silicon or metal brazing material can be used as a bonding agent as a bonding method in the case of combination processing by bonding. As the metal brazing material, silver brazing such as Ag-Cu and Ag-Cu-Ti can be used.
For materials to be combined by bonding, a method is adopted in which a plurality of materials are bonded so that the surface that forms an angle of 0 to 45 ° with the normal direction of the hot press-formed surface becomes a friction surface. be able to. Further, it is possible to arrange a carbon fiber reinforced carbon material material before silicon impregnation in a desired structure and join it simultaneously with silicon impregnation.

FIG. 1 is a diagram illustrating a friction surface against a hot press-formed surface. (A) shows the laminated body 1 of the molding surface 2 which carried out the hot press molding of the carbon fiber reinforced composite material. The fiber bundle 5 of carbon fibers is oriented parallel to the molding surface 2. The surface 3 at 0 ° with respect to the normal direction of the hot press-molded surface can be a friction surface. (B) is a case where the surface 4 of 45 degrees with respect to the normal line direction of a hot press molding surface is made into a friction surface.
It is possible to obtain a wear member in which a surface forming an angle of 0 to 45 ° with respect to the normal direction of the press shaft is a friction surface.

Examples of the present invention and comparative examples are shown below.
(Example 1) -Refer to Table 1. A powdery phenol resin having a residual carbon ratio of 59%, 6000 fiber bundles, and a pitch-based carbon fiber (elastic modulus of 620 GPa) having a fiber length of 6 mm are mixed in the composition shown in Table 1, and 50 × 50 A molded body obtained by hot press molding at 160 ° C. × 20 mm was produced. The obtained molded body was heat-treated in argon at 1000 ° C. to carbonize the phenol resin, and then impregnated and heated in vacuum at 1600 ° C. to prepare a carbon fiber reinforced silicon carbide composite material. The density of the obtained material was measured by Archimedes method.

  Moreover, a 10 × 10 × 10 mm size high temperature wear test specimen was cut out from the obtained sample and processed. In the test piece, the surface that forms an angle of 0 ° with the normal direction of the press surface of hot press molding in which the fiber bundles are oriented in the two-dimensional plane direction (cutting angle 0 °) is the friction surface of the wear test. The cut and processed samples were cut into a cut angle of 0 °, and the cut and cut normal surfaces and 30 °, 45 ° and 60 ° angles with respect to the normal direction of the press surface were normal surfaces and the press surface. A sample (cutout angle 90 °) cut out so that the surface perpendicular to the direction was a friction surface was produced. In the high temperature wear test, an S45C (φ100 × 15 mm) disk heated to 800 ° C. was rotated at 1000 rpm, and the 10 × 10 mm surface of the cut sample was pressed for 10 min with a pressing force of 490 N, and the friction coefficient, wear The amount was measured.

As a result, the present invention showed excellent friction characteristics with a friction coefficient of 0.2 or less, and excellent wear resistance with a specific wear amount of 2.4 × 10 ⁻⁵ mm ³ / Nm or less. . On the other hand, what was cut out at an angle outside the range of the present invention, which is a comparative example, has a high friction coefficient of 0.24 or more and a specific wear amount of 3.9 × 10 ⁻⁵ mm ³ / Nm or more, resulting in a wear amount of more than 3.9 × 10 ⁻⁵ mm ³ / Nm. There were many results.

(Example 2)-See Table 2 A carbon fiber reinforced silicon carbide composite material having different carbon fiber content and different carbon fiber length was used in the same manner as in Example 1 using 6000 short-fiber carbon fibers. It was made with.
The density of the obtained material was measured by Archimedes method. In the test piece, the surface that forms an angle of 0 ° with the normal direction of the press surface of hot press molding in which the fiber bundles are oriented in the two-dimensional plane direction (cutting angle 0 °) is the friction surface of the wear test. Were cut and processed, and a high-temperature wear test was performed under the same conditions as in Example 1 to measure the friction coefficient and the wear amount.
As a result, those using carbon fibers having a fiber length of ^{3 to 20} mm exhibited excellent wear characteristics with a friction coefficient of 0.21 or less and a specific wear amount of 2.8 × 10 ⁻⁵ mm ³ / Nm or less. In addition, when the amount of carbon fiber added is changed with 6 mm carbon fiber, the specific wear amount is 2.9 × 10 ⁻⁵ mm ³ / Nm or less with a carbon fiber addition amount of 30 to 70% by volume and excellent wear characteristics. Indicated.

  It can be used as a carbon fiber reinforced composite material having excellent wear resistance.

  DESCRIPTION OF SYMBOLS 1 ... Laminated body, 2 ... Molding surface which carried out hot press molding, 3 ... 0 degree surface with respect to normal direction of hot press molding surface, 4 ... 45 degrees with respect to normal direction of hot press molding surface Surface 5, a fiber bundle of carbon fibers.

Claims (2)

At least, pitch-based carbon fibers having a fiber length of 3 to 20 mm and a synthetic resin are mixed, the mixture is hot press-molded, and then the molded body carbonized by heat treatment is impregnated with molten silicon and heated. In the method for producing a wear-resistant member comprising a carbon fiber reinforced silicon carbide composite material,
The carbon fiber content in the carbon fiber reinforced silicon carbide composite material is 30 to 70% by volume,
A method for manufacturing a wear-resistant member, wherein a surface that forms an angle of 0 to 45 ° with a normal direction of a hot press-formed surface is a friction surface.   The method for producing a wear-resistant member according to claim 1, wherein at least two or more carbon fiber reinforced silicon carbide composite materials are joined together by a hot press-molded surface to form a laminate.

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