JP2008201611A - Titanium carbide-impregnated carbon fiber-reinforced carbon composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a C/C composite manufactured by a low temperature treatment and having improved oxidation resistance. <P>SOLUTION: A part or the whole of a base material comprising the carbon fiber-reinforced carbon composite (C/C) has a titanium carbide impregnated layer. In the manufacture of the composite, the composite is obtained by applying a coating liquid comprising metal titanium and a carbon source on the base material comprising the carbon fiber-reinforced carbon composite (C/C) and next, applying high frequency induction heating on the base material coated with the coating liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a titanium carbide-impregnated carbon fiber reinforced carbon composite material and a method for producing the composite material using high frequency induction heating.

  C / C composite is a high-performance material with excellent lightness, mechanical strength, and heat resistance in an inert atmosphere. Therefore, it is expected to be used in various fields such as automobile / aircraft structural materials and industrial robots. However, C / C composites have a problem of low oxidation resistance in a high-temperature atmosphere.

  As a method for imparting high-temperature oxidation resistance to a carbon material, a method of converting the surface of a carbon fiber reinforced carbon composite (hereinafter referred to as C / C) into a ceramic with a carbide or the like (or further coating with glass or the like thereon) Method) is well known and is also used as a method for producing heat and oxidation resistant materials for US space shuttles. However, in order to obtain C / C having sufficient oxidation resistance performance by this method, the surface layer SiC is increased in thickness, and then impregnated / fixed with a large amount of glass or the like in the surface layer SiC. It was necessary to prevent the diffusion of gas components and the like that cause damage to the base material C / C. For this reason, since the strength of C / C as a base material is greatly reduced, it is necessary to increase the thickness of C / C, and the light weight characteristic of C / C is sacrificed.

  Therefore, it is desired to provide a carbon fiber reinforced carbon composite material having a high oxidation resistance performance against oxidation load, particularly high-speed high-temperature external load such as high-speed airflow, and the carbon fiber-reinforced carbon composite material (C / C). A carbon fiber reinforced carbon composite material having a coating layer (CVD layer) having a dense oxidation resistance by vapor phase chemical vapor deposition on the surface thereof, and further having an overcoat layer made of an amorphous material on the surface thereof. A carbon fiber reinforced carbon composite material characterized in that is a CVD layer having irregularities on the surface has been proposed (Patent Document 1).

In addition, for the purpose of providing a rolling device that can be suitably used as a bearing that supports a rotating shaft of a machine that rotates at a high speed, such as a jet engine or a gas turbine, is lightweight, high-strength, and excellent in high-speed rotation. It has been proposed to form a cage for holding rolling elements from a carbon fiber reinforced carbon composite material having a density of 3.5 g / cm ³ or less and impregnated with molten metal after firing (Patent Document 2).

  In Patent Document 2, when the carbon fiber reinforced carbon composite material is impregnated with a molten metal by pressurization or the like, the carbon fiber reinforced carbon composite material is preheated at a temperature higher by 100 ° C. to 250 ° C. than the melting point of the molten metal, Thereafter, when the carbon fiber reinforced carbon composite material is impregnated with a molten metal at a temperature 50 ° C. to 250 ° C. higher than the melting point of the molten metal, the molten metal is preferably impregnated in the carbon fiber reinforced carbon composite material. It is described.

  Furthermore, for the purpose of providing a material suitable for a super heat resistant composite material for aerospace use or the like, a metal vapor and a carbon fiber reinforced carbon composite material are reacted on the surface of the composite material, and a metal carbide is formed on the composite material surface. A method for producing a surface-coated carbon fiber reinforced carbon composite material that forms a layer has been proposed (Patent Document 3). According to this method, the interface between the carbon fiber reinforced carbon composite material and the metal carbide layer is free from peeling, and a metal carbide layer without cracks can be formed on the surface of the carbon fiber reinforced carbon composite material. Has been.

In the method described in Patent Document 3, a metal carbide layer is formed by a reaction between metal vapor and a C / C composite material. The surface of the coating layer is completely metal carbide, while the inside of the coating layer is a metal A composite of carbide and carbon is formed. The ratio of the metal carbide and carbon in the composite is such that carbon gradually increases from the surface to the inside of the C / C composite to form a so-called functionally graded structure.
JP-A-8-239285 JP 2002-327754 A Japanese Patent Laid-Open No. 5-124147

  The film forming process by the CVD method described in Patent Document 1 takes a long time, so that the material becomes expensive, so that it is only used in limited applications such as the aerospace field.

  Moreover, the carbon fiber reinforced carbon composite material impregnated with the metal described in Patent Document 2 is preheated at a temperature higher by 100 ° C. to 250 ° C. than the melting point of the molten metal, and then the molten metal Although it is manufactured by pressure impregnating a molten metal into a carbon fiber reinforced carbon composite material at a temperature 50 ° C. to 250 ° C. higher than the melting point, it requires a treatment at a very high temperature.

  The metal carbide surface-coated carbon fiber reinforced carbon composite described in Patent Document 3 has excellent oxidation resistance. However, for the production thereof, it is necessary to react the carbon, which is the raw material of the carbide, with the carbon fiber reinforced carbon composite material as a vapor. In the case of titanium carbide, the melting point of titanium is 1675 ° C., and in Example 2 of Patent Document 3, a temperature of 1850 ° C. is required for producing the titanium carbide surface-coated carbon fiber reinforced carbon composite material.

  Accordingly, an object of the present invention is to provide a C / C composite having improved oxidation resistance that can be produced by a lower temperature treatment.

  The present inventors have found that by using a high frequency induction heating method, a carbon / metal composite material having a titanium carbide surface-impregnated layer can be produced even at a heating temperature lower than the melting point of titanium metal. The present invention was completed by finding that the composite material has excellent oxidation resistance.

The present invention for solving the above problems is as follows.
[1] A composite material having a titanium carbide impregnated layer on part or all of the surface of a base material made of a carbon fiber reinforced carbon composite material (C / C).
[2] The composite material according to [1], wherein the titanium carbide impregnated layer has a thickness in the range of 1 μm to 10 mm.
[3] The composite material according to [1] or [2], wherein the titanium carbide impregnated layer has a non-gradient structure.
[4] The composite material according to any one of [1] to [3], wherein the titanium carbide impregnated layer contains titanium oxide.
[5] A coating liquid containing titanium metal and a carbon source is applied to a base material made of a carbon fiber reinforced carbon composite material (C / C), and then high frequency induction heating is applied to the base material to which the coating liquid is applied, [1] A method for producing a composite material, wherein the composite material according to any one of [4] is obtained.
[6] The production method according to [5], wherein the titanium metal contained in the coating liquid is a titanium metal powder.
[7] The production method according to [5] or [6], wherein the metal titanium powder has an average particle diameter in the range of 100 μm to 2 mm.
[8] The production method according to any one of [5] to [7], wherein the carbon source is a hydrocarbon compound.
[9] The production method according to [8], wherein the hydrocarbon compound is polyvinyl alcohol.
[10] The production method according to any one of [5] to [9], wherein the high-frequency induction heating temperature is 1550 to 1650 ° C.

  According to the present invention, it is possible to provide a carbon / metal composite material having a titanium carbide surface impregnated layer having excellent oxidation resistance. Furthermore, according to the present invention, the carbon-metal composite material can be produced in a short time at a heating temperature lower than the melting point of titanium metal by using a high frequency induction heating method.

[Carbon / metal composite materials]
The present invention relates to a carbon / metal composite material, which is a composite material having a titanium carbide impregnated layer on part or all of the surface of a substrate made of a carbon fiber reinforced carbon composite material (C / C).

  A carbon fiber reinforced carbon composite material (hereinafter abbreviated as C / C) used as a base material is a composite material having carbon fibers as reinforcing fibers and carbon as a matrix. Examples of carbon fibers include pitch, polyacrylonitrile, rayon, and the like, with pitch being most preferred. Two or more of these can also be used in combination. Matrix carbon has various properties depending on its production method. There are roughly two types of organic substances due to thermal decomposition. One is based on thermal decomposition of thermosetting resins, and specific examples include those based on thermal decomposition of phenol resins, furan resins, and the like. The other is due to thermal decomposition of a thermoplastic resin, and specific examples include those due to thermal decomposition of petroleum pitch, coal pitch, and the like. In addition, vapor deposition is also effective, and specific examples include vapor deposition of methane, propane, butane, carbon tetrachloride, benzene, and the like. As described above, the matrix of the fiber reinforced composite material constituting the present invention can include many types, but all of them are effective, and the above-mentioned matrix can be combined alone or in combination of two or more types. Even the fiber-reinforced composite material used in this manner does not hinder the effects of the present invention.

  The carbon / metal composite material of the present invention has a titanium carbide impregnated layer on a part or all of the surface of the substrate. The thickness of the titanium carbide impregnated layer is preferably in the range of 1 μm to 10 mm from the viewpoint of having excellent oxidation resistance. The thickness of the titanium carbide impregnated layer is preferably in the range of 10 μm to 1 mm, more preferably in the range of 100 μm to 500 μm.

  The titanium carbide impregnated layer is a layer in which the surface of C / C is impregnated with TiC, and has a substantially non-graded structure. The carbon / metal composite material of the present invention is formed by high frequency induction heating of a coating film containing titanium metal and a carbon source provided on the surface of C / C, as will be described later. The titanium carbide-impregnated layer is formed mainly by the reaction between titanium metal and a carbon source, and this TiC is impregnated into the C / C pores. Although some of the titanium metal may react with C / C carbon, the one that reacts with the carbon source to become TiC is substantially superior, so that the titanium carbide impregnated layer is substantially It has a non-inclined structure.

  That the titanium carbide impregnated layer has a non-tilted structure means that the titanium carbide impregnated layer is formed without substantially destroying the structure originally possessed by C / C. , A material having both the advantages of excellent C / C characteristics and improved oxidation resistance due to the titanium carbide impregnated layer is provided. It can be confirmed that the titanium carbide impregnated layer has a non-tilted structure by observing the cross section of the titanium carbide impregnated layer with EPMA.

  The titanium carbide impregnated layer of the carbon / metal composite material of the present invention may contain titanium oxide for manufacturing reasons. Whether the titanium carbide-impregnated layer of the carbon / metal composite material of the present invention consists of titanium carbide alone or contains a trace amount or a small amount of titanium oxide can be confirmed by XPS measurement. However, it is appropriate that the content of titanium oxide is within a range that does not impair the characteristics of titanium carbide.

[Production method of composite material]
The present invention includes the method for producing the carbon-metal composite material of the present invention. In this production method, a coating liquid containing titanium metal is applied to a base material made of a carbon fiber reinforced carbon composite material (C / C), and then the base material to which the coating liquid is applied is heated by high-frequency induction, This is a method for obtaining a composite material.

  The carbon fiber reinforced carbon composite material (C / C) used as the substrate is as described above. A coating liquid containing metallic titanium is applied to a portion of the base material where the metallic titanium impregnated layer is to be formed. When applying a coating liquid to the whole surface of a base material, you may immerse a base material in a coating liquid. The coating amount of the coating liquid can be appropriately determined in consideration of the amount (concentration) of metallic titanium contained in the coating liquid and the thickness of the metallic titanium impregnated layer to be formed.

  Specifically, the coating liquid containing metallic titanium contains metallic titanium powder and a carbon source. The metal titanium powder is preferably a fine powder having an average particle diameter in the range of 100 μm to 2 mm from the viewpoint of easy impregnation into the gap of C / C by induction heating. The average particle diameter of the titanium metal powder is preferably in the range of 200 to 800 μm, more preferably in the range of 400 to 600 μm.

  The carbon source contained in the coating liquid containing titanium metal is used for the purpose of forming a titanium carbide impregnated layer. When C / C is impregnated with metallic titanium at high temperature, carbon and titanium react at the interface between C / C and metallic titanium to produce TiC. However, by including a carbon source in the coating liquid containing metallic titanium, Part of the titanium metal reacts with the carbon source to form TiC.

  The carbon source can be, for example, a hydrocarbon compound, but can also be, for example, activated carbon. However, when using a granular material such as activated carbon, it is appropriate that the average particle diameter is in the same range as that of the metal titanium particles in consideration of the ease of diffusion into the C / C pores. As the hydrocarbon compound, those which are liquid or fluid at normal temperature are preferable from the viewpoint of coating liquid. As the hydrocarbon compound, for example, polyvinyl alcohol or the like can be used. The solvent of the coating solution can be used without any particular limitation as long as it can uniformly disperse or dissolve the above-described metal titanium powder and carbon source. A hydrocarbon compound can also be used as the solvent, and in that case, can the solvent be used as a carbon source? The type of carbon source and the amount of carbon source used can be appropriately determined in consideration of the fact that metallic titanium can preferentially react with the carbon source to form an impregnated layer of TiC.

  The base material coated with the coating solution is heated by high frequency induction. The melting point of metallic titanium (Ti) is 1668 ° C. In the method of the present invention, the titanium carbide impregnated layer can be formed by setting the high frequency induction heating temperature to be lower than the melting point of titanium metal (Ti), for example, 1550 to 1650 ° C. This is presumably because Ti applied to the surface was directly heated by induction heating and reached a temperature higher than the melting point. Of course, it can also be set to a temperature higher than the melting point of titanium metal (Ti).

  In the high frequency induction heating, a base material coated with a coating liquid is made into a reaction container, for example, a carbon case (consisting of a main body and a lid, and the inside of the case can be substantially sealed. However, it has a mechanism for leaking internal pressure. Is preferable in terms of safety.) And can be performed by high-frequency induction from the outside. The heating temperature can be determined, for example, by measuring the outer wall of the reaction container with an infrared radiation thermometer.

  The time of high frequency induction heating can be made into 1 minute-1 hour, for example. However, the heating time can be appropriately determined in consideration of the composition of the coating liquid, the coating amount, the type of C / C, and the like.

  In the production method of the present invention, application of the coating liquid and high-frequency induction heating can be repeated twice or more. The thickness of the titanium carbide impregnated layer can be increased by repeatedly applying the coating liquid and high frequency induction heating twice or more.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[experimental method]
High-frequency induction heating apparatus Fig. 1 shows a schematic view of the chamber portion of the apparatus used in the experiment. When a high-frequency alternating current is passed through the coil with the carbon case inside the coil, an induction current is generated in the case by electromagnetic induction, and the case is directly heated by Joule heat between the current and the case, and the temperature rises efficiently. Can be warmed.

1 mmol / cm ^{2 of} Si, Ti, Mo, W powder, which is known to easily form impregnated carbides of metal samples, is applied to the surface of C / C composite (hereinafter referred to as “base material”), and an induction heating device is used. The impregnation treatment was performed. The powder was attached by making a slurry obtained by adding a 5 wt% -PVA solution and n-butanol to the powder, and applying and drying the slurry. The treatment was performed in an Ar substitution atmosphere with an initial pressure of 0.5 atm. The treatment time was 10 min, and the pressure at the treatment temperature was adjusted using a leak valve so that it did not exceed 1 atm.

  We also tried to improve oxidation resistance by using binary metal impregnated samples of Si and Ti. The addition amount of the second component was 10 wt%, and after mixing for one day and night, the substrate was impregnated by the same attachment method and treatment method as the single component system.

Impregnation of metal oxide sample
W and Mo were impregnated with an oxide having a much lower melting point than metals. Further, similarly to MoO ₃ and WO ₃ , an impregnation treatment of V oxide V ₂ O ₅ , which is a metal that easily forms carbides and whose melting point is lowered by using an oxide, was also performed. The amount of deposition, the deposition method and the impregnation treatment time are the same as in the case of metal. The treatment temperature was 900 ° C. for MoO ₃ and V ₂ O ₅ , and 1500 ° C. for WO ₃ .

Evaluation of oxidation resistance The oxidation resistance of the untreated substrate and the sample prepared by the impregnation treatment was evaluated by high-temperature heat oxidation in the atmosphere using a muffle furnace. The temperature was set to 500 ° C. and 600 ° C., and oxidation was performed for 50 hours while measuring the weight every 5 hours. The oxidation resistance was evaluated from the transition of the residual weight ratio.

Examination of treatment conditions Based on the results of forced oxidation experiments on various impregnated samples, the impregnation treatment was carried out by changing the conditions for Ti with the most improved oxidation resistance. The effect of the processing conditions on the sample was verified by changing the processing temperature, processing time, amount of attachment, and number of processing.

Characteristics of C / C composite
When the weight transition with respect to temperature was verified by TG-DTA, it was confirmed that the weight reduction started in the range of 500 to 600 ° C. As a result of the thermal oxidation in the atmosphere, as shown in Fig. 2, the weight loss was small at 550 ° C, but at 600 ° C, the weight decreased rapidly. Based on this result, the target temperature for oxidation resistance was set to 600 ° C in this experiment.

Metal impregnated sample
Although impregnation of Si at 1500 ° C treatment and Ti at 1600 ° C treatment was confirmed, Mo and W did not melt under the treatment conditions in this experiment.
As a result of observing the surface with SEM for the sample impregnated with Si and Ti, the surface of the sample using Si was mostly attached with particles, whereas in the sample using Ti, Fig. 3 Thus, it was found that a smooth surface of a sintered body was obtained. When the cross section was observed, metal was observed in the gap between the carbon fibers in the vicinity of the surface layer in both samples, and the impregnation of the metal from the surface pores was confirmed. In particular, in the sample impregnated with Ti, it was clarified that Ti filled the voids near the surface layer as shown in FIG.

  When XRD analysis was performed on samples impregnated with Si and Ti, only the base material and carbide peaks were detected in both samples (FIG. 5). Since the metal peak could not be confirmed, the molten metal is highly reactive, and it is considered that almost the entire amount reacted with carbon or carbon fiber contained in the binder. This is the result along with the standard free energy of formation of SiC and TiC taking negative values.

Figure 6 shows the change in weight of the base material and the impregnated sample in an oxidizing atmosphere at 600 ° C. It is clear that the oxidation resistance of both samples is improved compared to the substrate. In addition, oxidation resistance was improved by using Si as a binary system with Al and Ti. However, oxidation resistance of Ti decreased due to the binary system with Si and Al.
As a result of comparing the single component and binary components together, it was found that the improvement in oxidation resistance was most improved in the sample impregnated with Ti. This is due to the formation of the oxidation-resistant substance TiC at the contact interface between the carbon fiber and the Ti melt, and the interruption of the oxygen supply path to the inside of the sample by filling the voids near the surface.

As a result of the impregnation treatment of the metal oxide impregnated sample oxide, good impregnation was obtained with V ₂ O ₅ and MoO ₃ treated at 900 ° C. This is presumably because the melting point of each oxide was reached before the oxide was reduced. As a result of XRD analysis, it was confirmed that the impregnated oxide formed a carbide in either sample.
However, as shown in FIG. 7, the oxidation resistance of the sample was significantly lower than that of the untreated C / C composite and could not withstand the thermal oxidation at 500 ° C. This is presumably because the carbide obtained by the impregnation treatment has low oxidation resistance, easily returns to oxide in the test atmosphere, and the oxide generated on the carbon fiber surface acts as an oxidation catalyst.
Even in the sample using WO ₃ , carbide was obtained by treatment at 1500 ° C. using an induction heating apparatus. The oxidation resistance at 500 ° C. was improved because the surface was modified with an oxidation-resistant substance and the oxidation catalytic action of the oxide generated even when the surface was oxidized was small.
However, the change in weight in the oxidation test at 600 ° C. for 50 hours was the same as that of untreated, and oxidation resistance exceeding Ti and Si could not be obtained.

  From the above, it was found that it is most effective to improve the oxidation resistance of the C / C composite by impregnating Ti to form a TiC impregnated layer. Therefore, samples with different impregnation conditions were prepared and the effects were examined.

Consideration of Ti impregnation and differences due to processing conditions In this study, impregnation was possible at a processing temperature (1600 ° C) lower than the melting point of Ti (1668 ° C). This is presumably because Ti applied on the surface was directly heated by induction heating and reached a temperature higher than the melting point.
From the EPMA results shown in FIG. 8, there was no gradual change in the distribution of Ti impregnated. This is thought to be because the Ti melt impregnated from the pores on the surface and passed through the gap was dammed up by the carbon fiber bundle layer.
As a result of analyzing the bonding state of the surface by XPS, it was confirmed that the surface was mainly composed of TiC as shown in FIG.

As a result of attempting to change the set processing temperature, it was confirmed that Ti was satisfactorily melted and impregnated even at 1550 ° C. However, the impregnation depth was shallower than 1600 ° C., and the impregnation property decreased.
When the amount of impregnation (Ti impregnation amount) was changed, the depth of impregnation increased in proportion to the increase in the amount of Ti impregnation. On the other hand, when the treatment time of the sample with the same amount of impregnation was changed, no change was seen in the impregnation depth.
From these results, it was clarified that the impregnation property of Ti was increased by high-temperature treatment, and the impregnation depth was influenced by the amount of Ti addition regardless of time.
Furthermore, it has been found that the oxidation resistance is improved by increasing the number of treatments. This is considered to be because the TiC layer is constructed on the surface modified to TiC by the first treatment, and the thickness of the coating layer having oxidation resistance is increased.

  The sample surface was modified to TiC by impregnating Ti into a C / C composite and succeeded in improving the oxidation resistance at 600 ° C. It has been found that this treatment can be performed at a treatment temperature not higher than the melting point of Ti by using a high frequency induction heating device. In addition, we realized "shortening of processing time" by reducing the series of processing time of "temperature increase from room temperature to processing temperature" and "impregnation" to 30 minutes or less.

  The composite material of the present invention is expected to be used in various fields such as automobile / aircraft structural materials and industrial robots. In particular, since the composite material of the present invention has excellent oxidation resistance, its use is expected to expand.

The schematic of the chamber part of the apparatus used for the experiment of the Example is shown. The result of verifying the weight transition of the C / C composite with respect to the temperature in the air atmosphere by TG-DTA is shown. The SEM surface observation result of the sample impregnated with Si or Ti is shown. The SEM cross-sectional observation result of the sample which impregnated Si or Ti is shown. The XRD analysis result of the sample which impregnated Si or Ti is shown. The change in the weight of the substrate and the Si or Ti impregnated sample in an oxidizing atmosphere at 600 ° C is shown. The weight transition of the base material and the oxide impregnated sample in an oxidizing atmosphere at 500 ° C. is shown. The result of EPMA of Ti impregnated sample is shown. The result of analyzing the bonding state of the surface of the Ti impregnated sample by XPS is shown.

Claims (10)

A composite material having a titanium carbide-impregnated layer on part or all of the surface of a substrate made of a carbon fiber reinforced carbon composite material (C / C). The composite material according to claim 1, wherein the titanium carbide impregnated layer has a thickness in the range of 1 μm to 10 mm. The composite material according to claim 1, wherein the titanium carbide impregnated layer has a non-tilted structure. The composite material according to claim 1, wherein the titanium carbide impregnated layer contains titanium oxide. A coating liquid containing titanium metal and a carbon source is applied to a base material made of a carbon fiber reinforced carbon composite material (C / C), and then high frequency induction heating is applied to the base material to which the coating liquid has been applied. 5. A method for producing a composite material, wherein the composite material according to any one of 4 is obtained. The production method according to claim 5, wherein the metal titanium contained in the coating liquid is a titanium metal powder. The manufacturing method according to claim 5 or 6, wherein the metal titanium powder has an average particle diameter in a range of 100 µm to 2 mm. The production method according to claim 5, wherein the carbon source is a hydrocarbon compound. The production method according to claim 8, wherein the hydrocarbon compound is polyvinyl alcohol. The manufacturing method according to any one of claims 5 to 9, wherein the high-frequency induction heating temperature is 1550 to 1650 ° C.