JPH0699189B2 - High hardness fine crystal sintered body and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high hardness fine crystal sintered body useful as a wear-resistant component such as a cutting edge of a cutting tool, a dresser, a die, and a method for producing the same. is there.

[Prior Art] Since a diamond sintered body has a high hardness and abundant wear resistance, it has been conventionally used as a material for the cutting edge of a cutting tool or a wire drawing die. In comparison, there was a drawback that the finished surface of the processed product was rough and a dense surface that could be called a mirror surface could not be obtained. That is, in the commercially available diamond sintered body, the constituent diamond particles are about 2 to 20 μm, and the cutting edge using this sintered body has irregularities almost corresponding to the size of the crystal particles. It is believed that the main cause is that it is not a sharp cutting edge like a stone tool (see Japanese Examined Patent Publication No. 58-32224).

In order to avoid the above-mentioned inconvenience, it is easily conceivable that the diamond crystal particles forming the sintered body should be extremely fine with a particle size of 1 μm or less. However, it has been impossible to produce a desired sintered body by using the conventional general high temperature and high pressure method. That is, the inventors of the present invention have confirmed by experiments that fine diamond particles having a particle size of 1 μm or less are used as raw material diamond powder, Co plates are laminated and sintered by an ultrahigh pressure and high temperature generator at 60 kbar and 1450 ° C. However, fine diamond particles are about 500μ
However, the desired sintered compact could not be obtained because it only grew to large particles having a size of about m. On the other hand, when a raw material diamond powder having a particle size of 2 μm or more was used, no grain growth was observed and a sintered body could be obtained. This seems to be the reason why the finest diamond particles constituting the commercially available diamond sintered body have a particle size of about 2 μm.

A technique for suppressing grain growth during sintering using diamond powder having a grain size of 1 μm or less is described in, for example, Japanese Patent Publication No. 58-32.
It has already been developed as seen in Japanese Patent No. 224. In addition to diamond particles with a particle size of 1 μm or less, this technology has a particle size of 1 μm
Attempts to suppress grain growth of fine diamond particles by mixing carbides, nitrides, borides or mixtures thereof of metals of groups 4a, 5a, 6a of the periodic table of m or less as raw materials, and by using these as raw materials It is a thing.

However, the inventors of the present invention actually manufactured a sintered body according to the above technical contents and studied it, and although the grain growth suppressing effect of the diamond particles by the addition of the above compound was certainly confirmed, the hardness of the sintered body is usually It was revealed that the diamond sintered body showed a significant decrease as compared with the diamond sintered body. It is considered that this is because the hardness of the above compound is much smaller than that of diamond. Not only that, but since the above-mentioned technique uses a powdery raw material, there is a problem that gas is easily adsorbed on the surface of the raw material powder, and thus sintering is hindered and an unsintered portion remains.

[Problems to be Solved by the Invention] The present invention has been made in order to solve the problems of the conventional techniques, and its purpose is to provide a cutting edge of a cutting tool, a wire drawing die, or the like. It is another object of the present invention to provide a high-hardness fine crystal sintered body and a method for producing the same, which can give an excellent finished surface roughness when used.

[Means for Solving Problems] The high hardness fine crystal sintered body according to the present invention means a diamond having a grain size of 1 μm or less: 20 to 93% by volume, and a high pressure phase type boron nitride having a grain size of 1 μm or less: 75 to 5% by volume, metal catalyst for diamond synthesis (however, containing 5% by weight or more of iron group metal): 30% by volume
It is composed of less than the following, and has a gist in that the diamond forms a direct bond with the structure.

Further, the manufacturing method of the high hardness fine crystal sintered body according to the present invention,
Resin-derived amorphous carbon containing diamond powder with a particle size of 1 μm or less and high-pressure phase boron nitride powder with a particle size of 1 μm or less is contacted with a metal or alloy containing 5 wt% or more of an iron group metal, and at 1250 ° C. or more. The gist of the present invention lies in that pressure sintering is performed at a temperature and a pressure in a thermodynamically stable diamond region.

[Operation] The inventors of the present invention have conducted extensive studies to achieve the above object. As a result, high-pressure phase type boron nitride having hardness second to diamond is dispersed in diamond powder having a particle size of 1 μm or less under high temperature and high pressure. It was found that a high-hardness fine crystal sintered body can be realized by suppressing the grain growth of diamond at the time of sintering by sintering with, and the present invention was completed.

Further, as described above, in the prior art, powdery raw materials were sintered, so that inconveniences such as gas adsorption occurred.
In view of this point, the present inventors were able to eliminate the above-mentioned disadvantages by using a resin-derived amorphous carbon containing a diamond powder and a high-pressure phase boron nitride powder as a raw material. .

That is, since the resin-derived amorphous carbon can be produced from a liquid monomer as described in detail later, it is possible to appropriately disperse the high-pressure phase boron nitride powder and the diamond powder, and to cause the disadvantages such as gas adsorption described in the prior art. Instead, the desired high-hardness fine crystal sintered body was realized.

Resin-derived amorphous carbon is also called glassy carbon, and a typical example is furan resin-derived amorphous carbon, which is a furan obtained by dehydration condensation of furfuryl alcohol with an acid catalyst. The resin is carbonized. Therefore, when furan resin-derived amorphous carbon is used as the resin-derived amorphous carbon in the present invention, a predetermined amount of the raw material powder is obtained by mixing and dispersing the raw material powder in furfuryl alcohol and then performing the above treatment. A solid furan resin-derived amorphous carbon that is contained is obtained. The raw material powder-containing resin-derived amorphous carbon thus obtained is subjected to a degassing treatment under high temperature vacuum (this is a problem in the prior art), and then the metal catalysts are laminated or concentrically arranged and brought into contact with each other. -By sintering under high pressure, the above-mentioned resin-derived amorphous carbon itself is converted into diamond, and at the same time, a high-hardness sintered body in which the diamond is directly connected to the solid phase is obtained.

The resin-derived amorphous carbon in which the raw material powder is dispersed and contained is a dense solid substance, and once degassed, the gas component is less adsorbed, and moreover, the raw material powder is uniformly coated with carbon to form a compact.

In the above invention, the furan resin-derived amorphous carbon obtained by carbonizing the furan resin is shown as a representative example of the resin-derived amorphous carbon, but the resin-derived amorphous carbon used in the present invention is not limited to the furan resin-derived amorphous carbon. , Other phenol formaldehyde resin, acetone-furfural copolymer resin, furfuryl alcohol-phenol copolymer resin, urea resin, melamine resin, xylene resin, toluene resin, guanamine resin, etc. Can be processed into any type and is not limited to the type of resin.

The sintering temperature for obtaining the desired composite sintered body must be 1250 ° C or higher, and if it is lower than 1250 ° C, the sinterability is poor. As a matter of course, the pressure during sintering needs to be a pressure in the thermodynamic diamond stable region, and a pressure of about 40 kbar or more is required. Further, the metal catalyst used in the sintering step needs to be an iron group metal such as iron, cobalt, nickel, etc., and an alloy containing at least 5% by weight of any iron group metal has sufficient catalytic action. Is demonstrated. However, when the iron group metal is less than 5% by weight, the catalytic action is not exhibited and the sinterability is deteriorated.

The high-pressure phase type boron nitride in the present invention is meant to include two types of cubic type boron nitride and wurtzite type boron nitride, and therefore either one may be used alone in the present invention. However, it is also possible to mix and use both. However, the particle size of wurtzite boron nitride powder is 1 μm.
The following are general and can be used as they are. However, cubic boron nitride powders range from coarse ones to fine ones having a particle size of 1 μm or less. Therefore, when using cubic boron nitride in the present invention, It is necessary to select and use those having a particle size of 1 μm or less.

In the sintered body according to the present invention, the content of fine diamond needs to be 20 to 93% by volume. That is, when the content of diamond exceeds 93% by volume, the high-pressure phase boron nitride is relatively insufficient, and the grain growth of diamond occurs during sintering. Abrasion property decreases. The content of high-pressure phase type boron nitride is 75-
It must be 5% by volume. This is because when the content of high-pressure phase type boron nitride exceeds 75% by volume, the wear resistance is inferior and it is 5% by volume.
If it is less than the above, the effect of suppressing the grain growth of diamond during sintering is small.

On the other hand, as described above, the sintered body according to the present invention uses a metal or alloy containing 5% or more of iron group metal as a metal catalyst in the manufacturing stage thereof. It will be included. The content of this metal catalyst can be appropriately set by adjusting the mixing ratio of the raw material powder and furfuryl alcohol and the like, but the range must be less than 30% by volume. That is, this content is 30% by volume
When it becomes above, coarsening of the sintered body occurs. On the other hand, the lower limit of this content is not particularly limited, but 0.5
When the amount is less than the volume%, the catalytic action is lowered and the unsintered portion remains, so it is preferable to set the content to 0.5% by volume or more. The more preferable content of the metal catalyst is about 3 to 15% by volume.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are not of a nature limiting the present invention.
Any design changes made within the spirit of the later description are included in the technical scope of the present invention.

[Examples] Furfuryl alcohol was added to a mixed powder in which diamond powder having a particle size of 1 µm or less and cubic boron nitride powder (CBN) having a particle size of 1 µm or less were sufficiently mixed at various ratios, and further mixed to obtain a trace amount. After adding nitric acid, the mixture was heated to 70 ° C. for dehydration condensation to make furfuryl alcohol into a resin. 800 ° C
To obtain a dense solid furan resin-derived amorphous carbon containing the raw material powder.

The obtained furan resin amorphous carbon was processed into a disk shape having a diameter of 10 mm and a thickness of 1 mm, and degassed under the conditions of 1 × 10 ⁻⁵ Torr and 1450 ° C. These were sandwiched between 10% Co containing cemented carbide plates and iron group metal plates that have catalytic action, and sintered using an ultrahigh pressure and high temperature generator at 60 kbar and 1480 ° C. Got ~ 10.

With respect to each of the obtained sintered bodies, the composition ratio for each constituent, the sintered body structure, and the Vickers hardness were examined, and
The results shown in the table were obtained. Table 1 also shows the ratio of the amorphous carbon derived from the resin containing the raw material powder. At this time N
The particle diameters of the sintered bodies (Examples) of o.1 to 7 were almost the same as the particle diameters of the compounding raw materials, and a homogeneous fine crystal body having a particle diameter of 1 μm or less was obtained. The iron group metal content increased as the amount of furfuryl alcohol added to the raw material powder increased. The sintered bodies Nos. 8 and 10 are coarse-grained, so the Vickers hardness is not measured.

Fig. 1 is a drawing-substituting micrograph showing the crystal structure of the fracture surface of the No. 1 sintered body (after the removal of metal components by acid treatment). The diamond particles form a direct bond and a coalescence phase. You can see that It is considered that this is because the diamond particles exchanged from the resin-derived amorphous carbon contributed to the formation of the binder phase.

Next, the sintered bodies Nos. 1 to 7 according to the present invention were cut to form a cutting chip, and a cutting speed of 300 m / min was used for a round bar A1-12% Si alloy having a diameter of 80 mm as a work material. A cutting test was conducted under the conditions of feed 0.02 mm / revolution and depth of cut 0.05 mm. As a result, the roughness of the machined surface of the work material was almost the same as that obtained by cutting under the same conditions using a natural diamond monolithic tool, and a finished surface close to a mirror surface was obtained.

[Advantages of the Invention] As described above, according to the present invention, by adopting the above-described structure, a fine crystal sintered body suitable for a high hardness processing tool or the like that can obtain an excellent finished surface roughness can be provided. It was realized.

[Brief description of drawings]

FIG. 1 is a drawing-substituting micrograph showing the crystal structure of the fracture surface of the No. 1 sintered body.

Claims (2)

[Claims] 1. A diamond having a particle size of 1 μm or less: 20 to 93% by volume, a high-pressure phase type boron nitride having a particle size of 1 μm or less: 75 to 5% by volume, a metal catalyst for synthesizing diamond (however, an iron group metal is 5% by weight or more). Including): less than 30% by volume, a high hardness fine crystal sintered body, characterized in that the diamond directly forms a combined phase on the structure. 2. A metal or alloy containing 5 wt% or more of iron group metal is contacted with resin-derived amorphous carbon containing diamond powder with a particle size of 1 μm or less and high-pressure phase boron nitride powder with a particle size of 1 μm or less. And a pressure-sintering at a temperature of 1250 ° C. or higher and in a thermodynamically stable diamond region, for producing a high-hardness fine crystal sintered body.