JPH0790465A - Composite body of refractory and metal and its manufacture - Google Patents

Abstract

PURPOSE:To infiltrate a molten intermetallic compound into skeletal space of a refractory and to make a composite body dense by mixing metallic powder composed of Al and Ni with the refractory particles, pelletizing, charging the pelletized material into a metallic mold and executing combustion reaction. CONSTITUTION:The metallic powder composed of Al and Ni and the refractory particles of one or more kinds of carbine, boride and nitride of metals selected from Ti, Zr, Ta, Nb, Si, Cr, W and Mo which can produce the alloy or the intermetallic compound with Al and Ni, are mixed, compacted and pelletized. The pellets 3 are charged into the combustion-sintering metallic mold device 1 and mixed powder 4 of Ti and C is charged around the pellet 3 and molding sane 5 is filled into the remaining space. A graphite ribon 6 is set at the upper ends of the pellets 3 and electric current is conducted to the graphite ribon 6 and ignition is executed to the pellets 3. When the pellets 3 become high temp., rapid pressurization is executed. The metallic material is fluidized by the reactional heat and the skeletal structural body of refractory compound is formed, and also, the structural space is filled by the flowing metallic material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite of a refractory material and a metal and a method for producing the same, and more particularly to a production method by a combustion method.

[0002]

2. Description of the Related Art A composite of refractory and metal is useful as a structural material and the like as a new material having the characteristics of both materials. A so-called combustion synthesis (SHS) method is known as one of the methods for producing such a composite. This is because, in the reaction between certain substances, when a part of the starting material is ignited to start the reaction, the temperature of the unreacted part increases due to the transfer of strong reaction heat generated thereafter, and the reaction propagates accordingly. It utilizes the phenomenon that continues. This technique is particularly advantageous in that a compound having a melting point of about 2000 ° C. or higher can be easily prepared, and therefore Ti, Zr, T
It is used for the synthesis of various functional materials such as carbides, nitrides, borides, silicides, oxides and intermetallic compounds of group IV or V metals such as a and Si.

In this combustion synthesis method, large heat generated in a short time in a state close to adiabaticity is used to synthesize and sinter the high melting point material at the same time or under pressure over time. . As a pressurizing method, a method by static pressure or impact pressing using a press machine, an isotropic pressurizing method using a HIP device, a molding sand put in a mold,
A pseudo HIP method has been proposed in which a pressure applied by a press machine is applied to the periphery of a molded product.

The start of the combustion synthesis reaction is carried out by contacting a heat source such as an electric heater with one end of a molded body obtained by press molding the unmixed powder into a predetermined shape to ignite it, or contacting one end of the molded body to generate heat. Place the mixed powder that causes the reaction as an ignition agent,
There are known a method of igniting a molded body with a large heat source generated by igniting this and a method of igniting by heating with a heat source (for example, an electric heater) arranged around the molded body. Further, when the amount of heat generated by the combustion reaction is small, it is also widely used that the heat source arranged around the molded body as described above is used as an auxiliary heat source to facilitate ignition by the main heat source.

When the product of the combustion synthesis reaction is melted or softened by the reaction heat, a dense sintered body can be obtained by the above-mentioned combustion synthesis sintering method. However, for example, when a titanium carbide sintered body is prepared from a mixture of titanium powder and carbon powder, the product becomes porous and it is difficult to obtain a dense substance. The reason for this is considered to be that, in addition to the high melting point of the carbide, TiC is generated by the solid-phase reaction between Ti and C even at a relatively low temperature, and this has a relatively strong network structure. In this case, although it was possible to densify to some extent by pressurization, it was impossible to obtain a sintered body having substantially no pores. The same applies to the synthesis of other refractory materials.

[Purpose of the present invention]

Therefore, one of the objects of the present invention is to densify a refractory material such as the above-mentioned titanium carbide in which it is difficult to produce a dense sintered material by a combustion synthesis method, especially a skeleton of the refractory material. The gap between them is filled with a melt of Ti—Al alloy (intermetallic compound) by infiltration to obtain a structural material densified with a metal phase. Another object is to obtain a new material useful as an abrasive or a functional material by dispersing superabrasive grains in the metal phase.

In producing the sintered body of the present invention, first, a mixed powder of a material for forming a refractory material, for example, titanium metal and carbon, and an additive element for forming an alloy (relatively low melting point), for example, aluminum. Alternatively, a mixed powder of titanium and carbon or titanium and aluminum is prepared. If necessary, superabrasive grains such as diamond and cubic boron nitride can be mixed in this.

Pellets of a predetermined shape are prepared from the above-mentioned mixed powder by die molding, placed in a sintering die having an inner size slightly larger than the pellets, and a molding sand is filled in a gap between the die and the pellets. Then, one end of the pellet is contacted with a heater for ignition.

Superabrasive grains such as diamond or cubic boron nitride can be contained in the entire metal phase or in the surface layer portion depending on the purpose and application. This can be done during the mixing of the raw material powders or by placing the pellets in a molding die during the molding of the final product so that the superabrasives are dispersed on the working surface. This method is
It can also be used to make other wear resistant materials.

When the surface layer of the pellet contains a super-abrasive grain layer, a diamond-containing layer can be formed by disposing a refractory metal foil or plate or a graphite plate between the pellet and the molding sand. Prevents contamination with impurities resulting from foundry sand. In addition, a large amount of heat is transferred to the superabrasive grains by taking measures such as directly or indirectly contacting the superabrasive grain layer with metal or ceramics having a large thermal conductivity and heat capacity to release a part of the generated heat. It is preferable to prevent the diamond and cubic boron nitride from transforming to the low pressure phase.

The sintering die filled with the material is placed in a pressurizing device, and in a state where no pressure is applied or a state where light pressure is applied, the heater for ignition is energized to burn the pellets. Start. After a certain time (several seconds) from the start of combustion, the sintering die is pressurized to compress and mold the molten or semi-molten pellets.

In the molding / sintering process of the final product, it is also effective to dispose an auxiliary heat source around the pellets in order to compensate the heat generation when the amount of heat generated by the reaction is small or to moderate the cooling rate. . Furthermore, it is also possible to utilize combustion reactions for this purpose. For example, when placing molded pellets in a sintering mold, a mixed powder that undergoes an SHS reaction is placed adjacent to the pellets in the surroundings or mixed with foundry sand and ignited at about the same time as the pellets, By supplementing the ongoing reaction system with heat or by adding heat during cooling to gradually cool the product, cracking of the sintered pellet due to rapid cooling is prevented. The combustion product of this auxiliary heat source can be used as a pressurizing medium together with foundry sand.

In the composite material of the present invention, the densification proceeds by filling the skeleton gap with the metal phase. Therefore, the pressure operation for densification can be omitted by considering so as to obtain a sufficient liquid phase in the blending of the raw materials. For example, when a Ti—Al—C system is used as the composite material, the melting point of the Ti—Al alloy is 1460 ° C. Therefore, the heat generated by the combustion synthesis reaction of this system is the melting point of TiC (3070 ° C.). However, it is usually sufficient for forming a liquid phase of a TiAl alloy.
Therefore, in this case, densification by the interposition of liquid phase and infiltration is achieved.

The degree of densification of the obtained composite material changes depending on the ratio of the metal phase component contained in the material. As an example, in the case of manufacturing a TiC / TiAl composite material, the variation of the bulk density with respect to the ratio of the TiAl component is shown in FIG. 1 together with the theoretical density (broken line). The load applied to the pellet was 100 MPa. As shown here,
In the range of the TiAl content of about 30 to 80 mol%, a product close to the theoretical density is obtained.

When manufacturing the diamond-containing tool according to the present invention, it is effective to use titanium carbide as the refractory and TiAl alloy as the metal phase. In this case, the diamond particles are chemically bonded to the matrix via TiC formed on the surface of the particles, so that a strong holding force is achieved. Therefore, it is possible to increase the effective utilization period until particles come off, and it is also possible to increase the amount of protrusion of particles from the matrix, and it is possible to secure sufficient space for chip removal and coolant passage. The tool performance is improved.

In the production of diamond grinding tools, a strong bond with a chemical bond occurs between the abrasive particles and the matrix, so that the diamond particles are even in the form of surface contact where the embedding rate in the matrix is close to zero. Since sufficient holding is performed, it is possible to obtain an effective tool in which the entire working surface is practically made of only diamond.

In a conventional diamond grinding tool manufacturing process, when diamond is brought into contact with titanium and heated, the reaction between carbon atoms of the diamond and titanium causes the diamond to be eroded to form a large number of vacancies. The problem of reduced strength often occurs.
However, since the high temperature reaction is completed in a short time in the above-mentioned method of the present invention, such erosion of diamond particles is very small, and this problem of particle strength reduction is substantially solved.

Metallic nickel is also a harmful substance that graphitizes diamond that is in contact at high temperature, but in the present invention, nickel-containing particles are closely arranged with diamond as a matrix or tool supporting material and subjected to high temperature treatment. However, substantially no graphitization is observed. This is because the TiC film covering the surface of the diamond is C and Ni.
It is thought that this is because it functions as a barrier against the diffusion of. Next, examples of the present invention will be described.

[Example 1]

A Ti powder having a particle size of 22 μm, a graphite powder having a particle size of 7 μm, and an Al powder having a particle size of 300-mesh were weighed in a weight ratio of Ti: C: Al = 73: 11: 16, and sufficiently mixed to start. I used it as a material. This corresponds to a 50/50 vol% composition in terms of TiC / TiAl. This mixed powder is put into a mold and press-molded, and the diameter is 16 mm and the height is 4 mm.
Pellets were prepared. For sintering, the sintering die device 1 shown in FIG.
Was used. The female mold part 2 of this device has an inner diameter of 30 mm and a height of 60.
The mixed powder 4 having a thickness of 1 mm and a weight ratio of Ti: C = 80: 20 was arranged around the pellet 3, and the remaining space was filled with molding sand 5. Further, a graphite ribbon 6 was arranged in contact with the upper end of the pellet for ignition.

The assembled sintered mold was attached to a uniaxially pressurized hydraulic press device, and the graphite ribbon was energized without pressing the pressing piston to ignite the pellets. 5 seconds after ignition, when the temperature of the whole pellet became high, rapid pressurization was performed with a hydraulic press,
A load of about 100 MPa was continuously applied to the pellet for 30 seconds. The maximum temperature of the pellet instantaneously reached 1700 ° C. according to the thermocouple instructions. The product exhibits a metallic luster, and the hardness on the polished surface is Vickers hardness of 8 to 12 GP.
It was a. The presence of pores was not observed on this surface by optical microscope observation.

FIG. 3 shows the measured temperature and load of the pellets with respect to the elapsed time after ignition in this example.

Example 2

Pellets were made using the same starting materials as in Example 1. However, when pelletizing, an average particle size of 10
Synthetic diamond abrasive grains of 0 μm were added to the above mixed powder in an amount of 15 vol% and sufficiently mixed, and then filled in a molding die to form pellets. The same sintering die apparatus and sintering method as in Example 1 were used. Optical microscope observation performed on the polished surface of the obtained sintered pellets, diamond particles are distributed almost uniformly in the matrix,
No graphitization was observed on the surface of the diamond particles.
In the matrix part, bond tails are observed for each diamond, and the matrix of this product
It has been revealed that the diamond can be sufficiently retained. The pellets were attached to a holder and subjected to end face grinding of ceramics.

Example 3

Pellets were made using the same starting materials as in Example 1. However, during pellet molding, 300 mg of synthetic diamond F having a particle size of 100 μm was previously filled in the lower part of the molding die. The sintering die device and the sintering method are almost the same as in Example 1, but a metal tantalum cup (plate thickness 50 μm) having an inner diameter of 16 mm and an edge height of 2 mm is provided in the lower part of the pellet (that is, the synthetic diamond side). Was covered with it to form a diamond protective layer, and a disc made of sintered alumina having a diameter of 16 mm and a height of 10 mm was placed in contact with the bottom of the cup to prepare a cooling body. The obtained sintered pellet had a diamond-containing layer having a thickness of about 1 mm on one side. No graphitization was observed on the diamond surface by observation with an optical microscope, and in this case as well, it was presumed that the diamond retention strength by the matrix was sufficient. The obtained pellet was processed into a predetermined size and used as a cutting tool, but in another shape, it was used as a detection end and a stand of a thickness measuring device.

[Brief description of drawings]

FIG. 1 shows the variation of the bulk density of the produced pellet with respect to the ratio of the contained TiA component in the production of the TiC / TiAl composite material according to the present invention.

FIG. 2 is a schematic cross-sectional view of a sintering die device used in Examples.

FIG. 3 Example 1 plotted against elapsed time after ignition
Temperature and applied load of pellets in.

[Explanation of symbols]

 1 Sintered Mold Device 2 Female Mold Part 3 Pellets 4 Ti-C Mixed Powder 5 Foundry Sand 6 Graphite Ribbon

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Mitsuyuki Oyanagi Mitsuyuki Oyanagi 1-9-14 Ogaya, Otsu City, Shiga Prefecture Maison Eiko 903 Seta 903 (72) Inventor Akira Hosomi 1-41-14-505 Higashidori, Oyama Station, Tochigi Prefecture

Claims (12)

[Claims] 1. One or more refractory particles of a carbide, boride, nitride or silicide of a metal selected from titanium, zirconium, tantalum, niobium, silicon, chromium, tungsten and molybdenum are three-dimensionally bonded. A refractory / metal composite containing one or a plurality of skeletal structures formed by the above, and a metal phase composed of an alloy or an intermetallic compound existing in the skeletal structures or filling the gaps between the skeletal structures. 2. The refractory / metal composite according to claim 1, wherein the metal phase contains a binary alloy or an intermetallic compound selected from Ti—Al, Ti—Ni and Ni—Al. 3. The refractory / metal composite according to claim 1, wherein the refractory is a carbide, boride or nitride of titanium and the metal phase is a Ti—Al system. 4. The refractory / metal composite according to claim 1, wherein 10% by volume or more of superabrasive grains are dispersed and contained as a whole in the structures or in the gaps between the structures. 5. The refractory material according to claim 1, wherein 60% or more of the exposed surface area of the material is covered with dispersed superabrasive grains.
Metal composite. 6. A powder of a first metal made of Al and / or Ni and a second metal material capable of forming an alloy or an intermetallic compound with this metal and capable of producing a refractory compound by a combustion synthesis method. The first step of mixing the mixed powder of and non-metal and molding and pelletizing the whole, and after putting this pellet in the mold, and further filling the heat resistant pressure medium between the pellet and the mold , The pellets are ignited to initiate a combustion reaction, and the heat of reaction causes at least partial melting and fluidization of both metal materials to form a skeletal structure of a refractory compound, while generating a fluidized metal material. A method for manufacturing a refractory / metal composite having a second step of filling the structure voids by means of. 7. The method for producing a refractory / metal composite according to claim 6, wherein the second step is performed under pressure. 8. The method for producing a refractory / metal composite according to claim 6, wherein the mixed powder contains diamond or high-pressure phase boron nitride. 9. When the molding is performed in the first step, superabrasive grains are spread in the mold and then the mixed powder is filled.
The method for producing a refractory / metal composite according to claim 6. 10. The method for producing a refractory / metal composite according to claim 6, wherein after the superabrasive grains are uniformly distributed in the mold, pellets are put into the mold to perform the second step. 11. In the second step, a mixed powder that causes a combustion reaction is placed around the pellet in contact with the pellet or mixed with molding sand to allow the combustion reaction to proceed.
The method for producing a refractory / metal composite according to claim 6, wherein the pellets are supplementarily heated from the environment during the combustion reaction and / or the cooling. 12. The refractory material according to claim 6, wherein the first metal is Al, the second metal is Ti, the nonmetal is carbon, and the TiAl / TiC molar ratio is 30 to 80%.・
Manufacturing method of metal composite.