JP5859850B2 - Composite material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a composite material composed of a boron carbide reinforcing material and a metal silicon matrix, and a method for producing the same.

In recent years, a composite material of a boron carbide reinforcement and a metal silicon matrix (hereinafter referred to as a B ₄ C / Si composite material) has been used as an impact resistant member or the like. The B ₄ C / Si composite is produced by impregnating boron carbide preform with metallic silicon. However, since the B ₄ C / Si composite material can be cracked by impregnation, a method for preventing this has been proposed. For example, in the methods described in Patent Documents 1 and 2, it is noted that the reaction between silicon and boron carbide during impregnation contributes to cracking, and boron carbide-containing material is mixed and dissolved in advance in molten metal silicon. The preform is impregnated with a molten material to prevent cracking.

  On the other hand, a technique is known in which a metal is pressed and penetrated into a porous body of silicon carbide ceramics. For example, in the method described in Patent Document 3, a silicon carbide ceramic porous body is sintered and aluminum is pressurized and infiltrated. In the method described in Patent Document 4, a silicon carbide powder is mixed with silicon powder and carbon powder to form a preform. Then, silicon and carbon are converted into silicon carbide by heating at 1400 ° C. or higher, and metal silicon is pressed and infiltrated into the preform thus prepared. In the method described in Patent Document 5, metal silicon is impregnated into a preform that has been pre-sintered at normal pressure and high temperature using fine powder of silicon carbide.

Special table 2007-513854 gazette JP 2011-132093 A JP 2000-336438 A JP 2010-083715 A JP 2007-230822 A

As described in Patent Document 1, conventionally, a method for preventing cracks that may occur during the production of the B 4 _{C /} Si composite materials have been proposed, in B 4 _{C /} Si composites, metal silicon Cracks caused by impregnation of metal and cracks due to metal vanes cannot be sufficiently prevented.

  Typically, boron carbide preforms contain a binder and are degreased before silicon impregnation. By this degreasing, the strength of the preform is reduced to, for example, a little less than 10 MPa before degreasing, and cracking may occur after degreasing or during impregnation with metal silicon. Patent Documents 2 to 4 describe a technique for forming a preform with respect to a SiC / Si composite material or the like. However, in a SiC / Si composite material, the degreasing strength of a silicon carbide preform is a boron carbide preform. The composite material using SiC as a reinforcing material is less likely to cause cracking during impregnation. In order to increase the filling rate, it is necessary to reduce the pores between the particles of the preform, but high filling with a boron carbide preform that requires the addition of a binder to maintain strength has not been achieved at present.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a composite material having a high Young's modulus and a high hardness without cracks, and a method for producing the same.

  (1) In order to achieve the above object, the composite material of the present invention is a composite material composed of a boron carbide reinforcing material and a metal silicon matrix, and the boron carbide reinforcing material has a network structure, The filling rate is 80% or more.

  Thus, in the composite material of the present invention, since the boron carbide reinforcement has a network structure and the filling rate is 80% or more, a composite material having a high Young's modulus and high hardness without cracking can be obtained. Such a composite material can be applied as a high-performance impact resistant material.

  (2) A method for producing a composite material according to the present invention is a method for producing a composite material comprising a boron carbide reinforcing material and a metal silicon matrix, wherein the boron carbide particles are heated while being pressurized, and a network is formed. And a step of producing a porous boron carbide preform having a structure and a filling rate of 80% or more, and a step of impregnating the boron carbide preform with a molten material containing metallic silicon. Yes.

  As described above, in the method for producing a composite material of the present invention, a porous boron carbide preform having a network structure with a filling rate of 80% or more is produced, so that the strength of the preform can be increased. Moreover, since a network structure is formed by particles without using a binder, the strength is not reduced by degreasing. Therefore, a high shape retention force can be maintained during impregnation of the molten material, and cracks and cracks due to metal vanes can be prevented.

  (3) The method for producing a composite material of the present invention is characterized in that the boron carbide particles are heated by a discharge plasma sintering method. Thereby, a porous preform having a network structure with a filling rate of 80% or more can be produced. As a result, the Young's modulus and hardness of the composite material can be increased, and the composite material can be applied to a high-performance impact-resistant material.

  According to the present invention, the Young's modulus and hardness of the composite material can be increased. Such a composite material can also be applied to a high-performance impact-resistant material.

  Hereinafter, embodiments of the present invention will be described.

(Composition of composite material)
The B ₄ C / Si composite material (composite material) according to the present invention is formed of a boron carbide reinforcement and a metal silicon matrix. B ₄ C / Si is obtained by impregnating metallic silicon into a boron carbide (B ₄ C, boron carbide) preform. The penetrating material used may be a metal silicon simple substance or an alloy. The B ₄ C / Si composite material is substantially composed of a boron carbide reinforcing material and a metal silicon matrix, and may contain some impurities.

  The boron carbide reinforcement has a network structure and a filling rate of 80% or more. The network structure is a network structure formed by necking between particles. Thereby, the Young's modulus and hardness of the composite material can be increased. Such a composite material can also be applied to a high-performance impact-resistant material.

(Preform production)
The manufacturing method of the composite material comprised as mentioned above is demonstrated. First, a preform made of a porous ceramic body of boron carbide is prepared. In that case, the boron carbide granules are heated while being pressed to produce a porous boron carbide preform having a network structure. For example, a preform can be produced by heating with a heater while pressing boron carbide particles with a carbon jig.

  When the preform is produced, the particles are directly heated while being pressed, so that the particles are bonded to each other without using a binder, and necking can be formed. And the intensity | strength of a preform becomes high and the intensity | strength fall by degreasing is also lost. As a result, the preform can maintain a high shape retaining force even during the impregnation of metal silicon, which will be described later, and the possibility of occurrence of cracks and cracks due to metal vanes can be reduced.

  The smaller the particle size of each particle in the boron carbide granules and the narrower the particle size distribution, the lower the sintering conditions and the lower the pressure.

  When producing the preform, it is preferable to heat the boron carbide particles by a discharge plasma sintering method. Other methods such as reaction sintering and atmospheric sintering can be used to make the preform, but additives such as binders are not essential, and a porous body is produced at a relatively low pressure of about several tens of MPa. Since it is possible, the discharge plasma sintering method is excellent.

  The filling rate of the preform can be controlled by restricting the volume and feeding the raw material granules after fixing the thickness of the preform with a spacer or the like during pressure heating. Although it is possible to control by heating and pressing conditions without using a spacer or the like, the variation between lots becomes large.

In this manner, a porous preform having a network structure with a filling rate of 80% or more can be produced. Even when the discharge plasma sintering method is performed, a binder such as C, Al ₂ O ₃ , or Si may be added to the boron carbide granules as necessary. A decrease can occur.

Next, the preform is placed in the container. The container is a container having a bottomed opening, and is used for holding a molten metal, which will be described later, and infiltrating the installed preform. When the preform is installed, it may be installed on a setter of B ₄ C / Si composite material.

(Dope)
On the other hand, a molten material containing metallic silicon is prepared. In that case, a boron carbide containing material can be prepared by mixing with molten metal silicon and dissolving (doping) in advance. As the boron carbide-containing material, an end material of a B ₄ C / Si composite material can be used. The boron carbide-containing material may be in the form of a lump or powder.

  The boron carbide-containing material dissolves and reacts with metallic silicon by doping, and the material constituting the preform can be dissolved into the metal before impregnation. And the reaction at the time of impregnation to a preform can be reduced, and a crack can be prevented.

(Impregnation into preform)
The preform thus obtained is impregnated into the preform at 1450 ° C. or higher and 1500 ° C. or lower. At that time, the molten material is put into the container while maintaining the container at 1450 ° C. or higher and 1500 ° C. or lower. As the impregnation method, for example, pressureless permeation is used. In the impregnation step, the preform may be floated from the bottom of the container.

  When impregnating metal silicon, boron carbide and metal silicon are inherently good in wettability, and a small amount (about 0.5 percent) of carbon, which is the driving force for impregnation, is mixed from the carbon jig used for sintering the preform. Therefore, it is possible to sufficiently impregnate the metal silicon without particularly performing the operation of adding carbon. The small amount of carbon produces a small amount (around 1 percent) of silicon carbide after impregnation with metallic silicon.

(Cooling, taking out)
After the impregnation step, the inside of the container is naturally cooled and cooled to room temperature. The composite material thus cooled is separated from the container and taken out. As a result, a composite material having a boron carbide filling rate of 80% or more can be manufactured. And the Young's modulus and hardness of a composite material can be made high. The obtained composite material is processed as designed and can be used, for example, as an impact resistant material.

Example 1
A disk-shaped boron carbide preform having a diameter of 100 mm and a thickness of 6.0 mm was produced by a discharge plasma sintering method. The preform was produced by adding 110 g of boron carbide powder (particle size: 2 μm) as a raw material, applying a pressure of 30 MPa at 1900 ° C., and holding for 10 minutes. As a result, a preform having a filling rate of 93% and a thickness of 6.0 mm was obtained. In this way, 10 preforms were prepared and placed in an immersion container and impregnated with metallic silicon to obtain a B ₄ C / Si composite material.

(Example 2)
The raw material charge was changed to 105 g, and the other conditions were the same to prepare a boron carbide preform. As a result, a preform having a filling rate of 89% and a thickness of 6.0 mm was obtained. In this way, 10 preforms were prepared and placed in an immersion container and impregnated with metallic silicon to obtain a B ₄ C / Si composite material.

(Example 3)
The raw material charge was changed to 98 g, and the other conditions were the same to prepare a boron carbide preform. As a result, a preform having a filling rate of 83% and a thickness of 6.0 mm was obtained. In this way, 10 preforms were prepared and placed in an immersion container and impregnated with metallic silicon to obtain a B ₄ C / Si composite material.

(Comparative Example 1)
A slurry in which 12.8% and 60% water as a binder is mixed with boron carbide powder and poured into a mold is baked at 150 ° C., and is made of a disc-shaped boron carbide having a diameter of 100 mm and a thickness of 6.0 mm. Created a preform. In this way, 10 preforms were prepared and placed in an immersion container and impregnated with metallic silicon to obtain a B ₄ C / Si composite material.

(Experimental result)
Table 1 is a table showing characteristics of ceramic sintered bodies, comparative examples and examples of preforms and products. In Table 1, the properties of the sintered ceramics of boron carbide and silicon carbide are also listed for reference. In Comparative Example 1, a crack was generated during degreasing in a part of the preform, and the crack remained as a metal vane in the composite material after impregnation with metal silicon. On the other hand, no metal vane was generated in any of Examples 1 to 3.

  As described above, in Examples 1 to 3, the boron carbide filling rate was higher than that in Comparative Example 1, and as a result, a composite material having a high Young's modulus and a high hardness could be obtained. Moreover, about the hardness of Examples 1-3, it was higher than the silicon carbide ceramic sintered compact, and the value close | similar to the boron carbide ceramic sintered compact was able to be obtained. Further, the bending strengths of Examples 1 to 3 were remarkably improved as compared with those of Comparative Example 1, and were close to ceramic levels.

Claims (3)

A composite material comprising a boron carbide reinforcement and a metallic silicon matrix,
The boron carbide reinforcing material has a network structure, and the filling rate of the boron carbide is 80% or more. A method for producing a composite material comprising a boron carbide reinforcement and a metallic silicon matrix,
The granules of the boron carbide to heat while pressing a step of the boron carbide has a network structure, the filling rate of the boron carbide to produce a preform of boron carbide 80% or more of the porous body,
Impregnating the prepared preform with a molten material containing metallic silicon, and a method for producing a composite material.   3. The method of manufacturing a composite material according to claim 2, wherein the heating of the boron carbide particles is performed by a discharge plasma sintering method.