JP2012056778A - Fiber-reinforced ceramic composite material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced ceramic composite material with copper uniformly dispersed and included therein, which can be suitably applied to a brake disk, and a production method efficiently obtaining the same.SOLUTION: The fiber-reinforced ceramic composite material in which copper is uniformly dispersed and included is obtained by impregnating a fiber-reinforced porous ceramic base material, which includes a ceramic matrix composed of silicon carbide and carbon and at least one reinforcing fiber of carbon fiber and silicon carbide fiber having porosity of 5% or more and 50% or less, with a Cu-Si alloy having a Cu/Si weight ratio of 1-3 and one or more metals of Cr, Sn and Sb in an amount of 0.5-3.0 wt.%, relative to the Cu-Si alloy, at 1,350-1,800°C under a decompressed atmosphere.

Description

  The present invention relates to a composite material of fiber-reinforced silicon carbide ceramics comprising a ceramic matrix and reinforcing fibers, and more particularly to a fiber-reinforced ceramic composite material that can be suitably applied to a brake disk and a method for manufacturing the same.

Disc brakes are a type of braking device, and are mainly used in railway vehicles, automobiles, bicycles, and the like. Friction force is generated by sandwiching a brake disk that rotates with the wheels with brake pads from both sides, and the kinetic energy is converted into thermal energy for braking.
Steel materials such as stainless steel and chrome steel are usually used for brake disks of railway vehicles and automobiles.

However, in recent years, in order to improve driving performance and fuel efficiency, reduction of vehicle body weight and unsprung weight has been demanded, and the brake disc is also being considered to be changed to a material that is lighter than steel. As one of such materials, silicon carbide ceramics are attracting attention because of their light weight and high strength.
However, the conventional silicon carbide ceramics is a brittle material, has no toughness, and does not have sufficient characteristics to be applied to an impact brake disk.

Therefore, in order to make silicon carbide ceramics a material having high fracture energy, it has been studied to use a carbon fiber or a composite material with silicon carbide fiber, which is easily available as long fibers.
As a method for obtaining a higher strength silicon carbide ceramic composite material, a method of impregnating silicon carbide with molten silicon is known.

  By the way, as the required braking performance becomes higher, the material of the brake pad has been changed from organic to copper. For this reason, in order to prevent seizure with a copper brake pad, a conventional steel brake disc is also made to contain copper, and similarly, a ceramic brake disc contains copper. It is demanded.

However, since copper has a melting point of 1084 ° C., which is lower than the manufacturing temperature of ceramics, it is difficult to melt and uniformly contain copper even if it is included in a ceramic material.
In response to this, for example, Patent Document 1 discloses a silicon carbide composite material in which silicon carbide is impregnated with a penetrating material made of silicon and a metal such as aluminum or copper.

  In addition, it is considered that wettability of molten metal to ceramics is an important factor in the composite of ceramics with metal. For example, Non-Patent Document 1 discloses an alloy of copper and titanium (Cu-Ti alloy). It is described that the wettability with respect to silicon carbide can be improved.

Special table 2003-505329 gazette

Journal of the Japan Institute of Metals, Vol. 54, No. 12 (1990), p.1401-1407

  However, in the above Patent Document 1, the silicon infiltrant is merely alloyed for the purpose of lowering the melting point of the silicon infiltrant and reducing the solidification expansion of the silicon component. Only the alloying with aluminum with a melting point of 660 ° C. which is lower than the melting point of copper 1084 ° C. is described.

  Non-Patent Document 1 describes the wettability of the molten metal in the composite by joining the silicon carbide ceramics produced by the hot press method and the metal. However, it cannot always be said that the silicon carbide ceramics are uniformly contained. Moreover, the wettability with respect to the fiber reinforced silicon carbide ceramics by carbon fiber or silicon carbide fiber is not clarified. Furthermore, titanium is a very expensive material and is disadvantageous in terms of cost.

As described above, conventionally, studies have been made for uniformly impregnating copper into silicon carbide ceramics, and copper is also uniformly contained in fiber-reinforced silicon carbide ceramics with increased strength. Attempts were made to try.
However, in the conventional impregnation method, sufficient investigation has not been made on a method for efficiently impregnating a silicon carbide ceramic containing reinforcing fibers with a necessary and sufficient amount of copper.

  The present invention has been made to solve the above technical problem, and relates to a fiber-reinforced silicon carbide ceramic, in which copper is uniformly dispersed and contained, and can be suitably applied to a brake disc. An object of the present invention is to provide a reinforced ceramic composite material and a production method capable of efficiently obtaining the same.

The fiber reinforced ceramic composite material according to the present invention includes Cu ₃ , a fiber reinforced ceramic composed of a ceramic matrix composed of silicon carbide, carbon and silicon, and one or more reinforcing fibers of carbon fibers or silicon carbide fibers. Si and one or more metals of Cr, Sn, or Sb of 0.5 wt% or more and 3.0 wt% or less with respect to Cu ₃ Si are included.
By adding the metal components as described above and containing copper as an alloy with silicon, a fiber-reinforced ceramic composite material containing copper uniformly dispersed can be obtained.

The method for producing a fiber reinforced ceramic composite material according to the present invention comprises a ceramic matrix composed of silicon carbide and carbon, and a porosity of 5% to 50% comprising any one or more reinforcing fibers of carbon fiber or silicon carbide fiber. % Of the fiber-reinforced porous ceramic substrate with a Cu / Si weight ratio of 1 to 3 and a Cu-Si alloy of 0.1 to 3.0% by weight with respect to the Cu-Si alloy. It is characterized by impregnating at least 1350 ° C. to 1800 ° C. in a reduced pressure atmosphere with one or more metals of Cr, Sn or Sb.
According to such a manufacturing method, the wettability of the Cu-Si alloy with respect to silicon carbide and carbon in the base material can be improved, and copper is uniformly and efficiently dispersed in the obtained fiber-reinforced ceramic composite material. Can be contained.

ADVANTAGE OF THE INVENTION According to this invention, the fiber reinforced silicon carbide ceramics in which copper is disperse | distributed uniformly can be obtained efficiently.
Therefore, the fiber-reinforced ceramic composite material according to the present invention can be suitably used as a lightweight and high-strength brake disc material. It is also possible to prevent seizure with the copper brake pad.

Hereinafter, the present invention will be described in more detail.
The fiber-reinforced ceramic composite material according to the present invention is a silicon carbide-based fiber-reinforced ceramic composed of a ceramic matrix and reinforcing fibers, and includes Cu ₃ Si and one or more metals of Cr, Sn, or Sb. Is.
By adding these metal components and containing copper as an alloy with silicon, it is possible to obtain a composite material in which copper is uniformly dispersed and contained in fiber-reinforced silicon carbide ceramics as Cu ₃ Si.

In the composite material, the ceramic matrix is composed of silicon carbide, carbon, and silicon. These are the main raw materials for silicon carbide ceramics. Each raw material may be a commonly used material, and its form and manufacturing method are not particularly limited.
Among these, it is preferable that silicon carbide is the main component from the viewpoint of high strength.

Moreover, the said reinforcement fiber is a fiber mix | blended in order to reinforce silicon carbide ceramics, and consists of any 1 or more types of a carbon fiber or a silicon carbide fiber. Depending on the use of the composite material, only one of carbon fiber or silicon carbide fiber may be used, or both may be used in combination.
Since carbon fiber and silicon carbide fiber have good wettability with molten silicon, it is preferable to obtain a dense composite ceramic material when the composite material utilizing capillary action is produced by silicon impregnation.

  The shape and size of the reinforcing fiber is not particularly limited, but a so-called short fiber having a diameter of 0.5 to 20 μm and an average length of 0.5 to 20 mm, and a fiber bundle formed by collecting the short fibers. Is preferred. Furthermore, in addition to the short fibers, so-called long fibers longer than the short fibers may be included.

The content of the reinforcing fiber in the composite material is preferably 15% by volume or more and 40% by volume or less.
When the content is less than 15% by volume, the ceramic reinforcing effect by the reinforcing fibers cannot be sufficiently obtained.
On the other hand, when the content exceeds 40% by volume, there are too many reinforcing fibers, which may prevent uniform dispersion of a predetermined amount of Cu ₃ Si in the composite material.

Further, the content of Cu ₃ Si in the composite material is preferably 0.5 wt% or more and 40 wt% or less, although it depends on the porosity of the ceramic matrix.
When the content is less than 0.5% by weight, the amount of copper added is too small to show the effect of the addition, and when the composite material is used for a brake disc, seizure with a copper brake pad is caused. The prevention effect is not sufficiently obtained.
On the other hand, when the content exceeds 40% by weight, Cu ₃ Si has a lower strength than silicon carbide, so that the mechanical strength of the entire composite material is lowered and it is difficult to use it for a disc brake.

Moreover, Cr, Sn, or Sb, which is a metal component added together with the Cu ₃ Si, may be only one type or two or more types, and the total content is 0.1 weight with respect to the Cu ₃ Si. % To 3.0% by weight.
By adding the metal component as described above, the wettability of the Cu-Si alloy with respect to the silicon carbide fiber-reinforced ceramic is improved, and copper can be more uniformly dispersed in the composite material.

The fiber reinforced ceramic composite material as described above has a porosity of 5% to 50% comprising a ceramic matrix composed of silicon carbide, carbon and silicon, and one or more reinforcing fibers of carbon fiber or silicon carbide fiber. A Cu-Si alloy having a Cu / Si weight ratio of 1 or more and 3 or less, and Cr of 0.1 wt% or more and 3.0 wt% or less based on the Cu-Si alloy. , Sn, or Sb is impregnated at 1350 ° C. or higher and 1800 ° C. or lower in a reduced pressure atmosphere.
Thus, when impregnating the fiber-reinforced porous ceramic base material with the Cu-Si alloy, by adding Cr, Sn or Sb, the fiber-reinforced ceramic composite material in which copper is uniformly dispersed and contained Is obtained.

That is, by adding Cr, Sn or Sb to the impregnating material, the wettability of the Cu-Si alloy with respect to silicon carbide and carbon in the base material is improved as described above. It is possible to increase the Cu / Si weight ratio. Therefore, copper can be evenly distributed and uniformly and efficiently dispersed in the obtained composite material.
The mechanism by which the wettability is improved by the addition of these metal components has not been clarified at this time, but the improvement of wettability promotes the impregnation of Cu-Si alloy by capillary action. Conceivable.

When copper and silicon are heated above the melting point of silicon, they are melted together to form a uniform alloy liquid (Cu—Si alloy). When the substrate is impregnated with the liquid Cu—Si alloy, silicon and carbon in the substrate react to generate silicon carbide at the interface. When cooled below the melting point of silicon, the Cu—Si alloy generates two phases of silicon and Cu ₃ Si and solidifies. At this time, copper hardly dissolves in the silicon phase.
Therefore, in the composite material obtained by impregnating the Cu—Si alloy as described above, copper is contained in the form of a compound, Cu ₃ Si.

In the above manufacturing method, the Cu—Si alloy as the impregnating material has a Cu / Si weight ratio of 1 or more and 3 or less.
When the weight ratio is less than 1, depending on the porosity of the substrate, when it is close to 5%, the Cu ₃ Si content in the obtained composite material cannot be 0.5% by weight or more.
On the other hand, if the weight ratio exceeds 3, the wettability of the Cu-Si alloy with respect to silicon carbide and carbon in the base material decreases, so that impregnation by capillary action does not proceed sufficiently, and copper is not contained in the base material. It becomes difficult to spread evenly.

Cr, Sn, or Sb, which is a metal component added to the impregnating material, may be used alone, or alternatively, two or more of these may be mixed and used in an arbitrary ratio. The total addition amount is 0.1 wt% or more and 3.0 wt% or less with respect to the Cu—Si alloy.
When the addition amount is less than 0.1% by weight, the effect of increasing the upper limit of the Cu / Si weight ratio of the Cu—Si alloy that can be impregnated cannot be sufficiently obtained.
On the other hand, when the addition amount exceeds 3.0% by weight, a compound phase containing these metal elements is likely to precipitate. Since these precipitated compounds are brittle and low in strength as compared with silicon carbide, the strength characteristics of the entire composite material obtained are deteriorated.

The fiber-reinforced porous ceramic used as a base material impregnated with the Cu-Si alloy is composed of a ceramic matrix and reinforcing fibers.
This reinforcing fiber is at least one of carbon fiber and silicon carbide fiber, and is the same as described above. The ceramic matrix is also composed of silicon carbide and carbon.
Since silicon is more brittle than silicon carbide, it is preferably not contained in the base material from the viewpoint of obtaining a high-strength composite material. The silicon component in the composite material produced by the above method is derived from the impregnated material.

The porosity of the fiber-reinforced porous ceramic base material is 5% or more and 50% or less.
When the porosity is less than 5%, the amount of the alloy to be impregnated decreases, so that it is difficult to make the content of Cu ₃ Si in the obtained composite material 0.5% by weight or more.
On the other hand, when the porosity exceeds 50%, the amount of impregnation of the silicon component, which is more brittle than silicon carbide, increases, so in the resulting composite material, the silicon physical properties become dominant and the strength required for the brake disc And impact resistance is not obtained.

The temperature at which the base material is impregnated with the Cu—Si alloy is 1350 ° C. or higher and 1800 ° C. or lower.
When the temperature is less than 1350 ° C., it is difficult to obtain a uniform alloy liquid of copper and silicon. The higher the temperature, the lower the viscosity of the alloy and the easier it is to impregnate. However, at temperatures exceeding 1800 ° C., no further improvement in impregnation is observed and the production cost increases.

  Further, the impregnation is preferably performed in a reduced pressure atmosphere from the viewpoint of allowing the Cu—Si alloy to spread evenly in the pores of the base material.

EXAMPLES Hereinafter, although preferable embodiment of this invention is described based on an Example, this invention is not limited by the following Example.
First, each sample of the fiber reinforced ceramic composite material was produced as follows.
Silicon carbide powder OY-15 (manufactured by Yakushima Electric Works), carbon fiber trading card (registered trademark) (manufactured by Toray Industries, Inc.), phenol resin Sumilite resin (registered trademark) (manufactured by Sumitomo Bakelite Co., Ltd.), 15% by weight Were pressed into a disk shape having a diameter of 50 mm and a thickness of 40 mm, and then fired at 2000 ° C. for 2 hours in an argon atmosphere to prepare a fiber-reinforced porous ceramic substrate having a porosity of 20%.
To this porous reinforcing fiber ceramic substrate, a Cu—Si alloy having a predetermined Cu / Si weight ratio and one or more metals of Cr, Sn, or Sb are placed in a reduced pressure atmosphere at 1450 ° C. for 2 hours. Each sample of fiber reinforced ceramic composite material was produced by holding and impregnating.
In addition, the said carbon fiber was mix | blended so that content in the sample of the obtained composite material might be 20 volume%. Further, the Cu—Si alloy was adjusted and blended so that the content of the obtained composite material in the sample was within the range of 30 to 35% by weight.
In each sample, the Cu / Si weight ratio of the Cu-Si alloy, the metal species added thereto, and the amount added to the Cu-Si alloy are as shown in Examples 1 to 21 and Comparative Examples 1 to 11 in Table 1 below. is there.

Each sample produced above was subjected to various evaluations as follows.
The density and porosity were measured and calculated by the Archimedes method.
Further, the copper content of each sample was measured by ICP-MS. In Table 1, the content converted to Cu ₃ Si is shown.
Furthermore, the impregnation state of the Cu-Si alloy was determined by observing the cleaved surface with an optical microscope at a total of three locations, the central portion and the outer peripheral portion of each sample, and whether or not the base material had penetrated into the pores. confirmed. In the evaluation of the impregnation state in Table 1, ○: When the impregnation of the Cu—Si alloy was confirmed in any of the three observation places, ×: Two or less observation places where the impregnation of the Cu—Si alloy was confirmed Shows the case.
The bending strength was measured in accordance with Japanese Industrial Standard JIS R 1663 “Bending Strength Test Method for Long Fiber Reinforced Ceramic Composite Material” by processing each sample into a predetermined shape.
These evaluation results are summarized in Table 1.

  As shown in Table 1, the Cu / Si weight ratio of the impregnated Cu-Si alloy is 1 or more and 3 or less, and Cr, Sn or Sb is added to the Cu-Si alloy in an amount of 0.5% by weight. All of the fiber reinforced ceramic composite materials (Examples) obtained by adding 3.0% by weight or less were excellent in the impregnation state of the Cu—Si alloy. Further, in the examples, since a bending strength of 100 MPa or more was obtained, it was recognized that strength characteristics represented by bending strength were also excellent.

  The fiber-reinforced ceramic composite material according to the present invention can be suitably applied particularly as a brake disk for railway vehicles, automobiles, etc., but takes advantage of its light weight, high strength, and excellent wear resistance. For example, it can be applied to a sliding member such as a mechanical seal member of a high-speed rotating device.

Claims (2)

To a fiber reinforced ceramic comprising a ceramic matrix composed of silicon carbide, carbon and silicon, and one or more reinforcing fibers of carbon fiber or silicon carbide fiber, Cu ₃ Si and 0 to Cu ₃ Si A fiber reinforced ceramic composite material comprising 5% by weight or more and 3.0% by weight or less of one or more metals of Cr, Sn, or Sb.   A method for producing a fiber-reinforced ceramic composite material according to claim 1, wherein the porosity comprises a ceramic matrix composed of silicon carbide and carbon, and one or more reinforcing fibers of carbon fiber or silicon carbide fiber. 5% or more and 50% or less of fiber reinforced porous ceramic base material, Cu / Si weight ratio of 1 or more and 3 or less of Cu-Si alloy, and 0.5% by weight or more and 3.0% of the Cu-Si alloy A method for producing a fiber-reinforced ceramic composite material comprising impregnating at least 1 wt.% Or less of Cr, Sn, or Sb with one or more metals in a reduced pressure atmosphere at 1350 ° C. or higher and 1800 ° C. or lower.