JPS5916942A - Composite diamond-sintered body useful as tool and its manufacture - Google Patents

Abstract

PURPOSE:To obtain the composite diamond-sintered body useful as a tool having both of excellent wear resistance and toughness, by sintering coarse diamond particles using binders such as superfine diamond particles and WC, each particle being specified in size. CONSTITUTION:The composite diamond-sintered body useful as a tool manufactured by connecting a hard sintered body comprising 50-80vol% coarse diamond particles of 10-100mu in zine and the balance binders such as 60-90vol% superfine diamond particles of 1mum or less in size and WC of 1mum or less directly or through an intermediate layer to a cermet substrate prepd. by binding specified carbide crystals to a ferrous-group metal. Said hard sintered body is composed of up to 70vol% boron nitride of type-high pressure phase and the balance one or more of Group-IVa and Va metal carbides, nitrides and carbonitrides (e.g. TiN), etc. The composite diamond-sintered body has both of excellent wear resistance derived from a coarse diamond-sintered body and high toughness derived from a superfine diamond-sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION Currently, a sintered body with a diamond content of 70% by volume or more and diamond particles bonded to each other is sold, and is used for cutting non-ferrous metals, plastics, ceramics, dressers, drill picks, etc. When these diamond sintered bodies are conveniently used as dies for cutting non-ferrous metals or drawing relatively soft wires such as copper wires, their performance is very excellent. However, there is currently no diamond sintered body that has satisfactory performance when used in drill bits, etc. The present invention relates to a diamond sintered body that can be used also in drill bits. First, in order to investigate the reason why commercially available diamond sintered bodies do not show satisfactory performance when used as drill bits, we investigated the following results:
Five types of diamond sintered bodies with a grain size of 0.00 μm were used to cut andesite. As a result, the diamond sintered bodies with a grain size of 1 μm or less had a large amount of wear, although the cutting edge did not break. On the other hand, the cutting edges of both the sintered bodies with diamond particle sizes of 50 to 60 .mu.m and the sintered bodies of 80 to 100 .mu.m were damaged at an early stage.The reason for this can be assumed to be as follows. As shown in FIG. 1, the strength of the diamond sintered body decreases as the grain size increases. Fine-grained diamond sintered bodies have high transverse rupture strength and excellent toughness, so the cutting edge is resistant to breakage. However, since each particle is held by a small diamond skeleton, the bonding strength of individual particles is It is considered that the wear resistance is poor because the individual particles are likely to fall off during cutting. On the other hand, coarse-grained diamond sintered bodies are held by a large skeleton, and the bonding force between individual diamond particles is strong, so they have excellent wear resistance, but because the skeleton is large, once a crack occurs, it will propagate. It is thought that the cutting edge would be damaged immediately. A diamond sintered body that can be used for these purposes must have excellent wear resistance and high toughness.

The present inventors have continued to conduct intensive research in order to develop a diamond sintered body with excellent wear resistance and toughness, and as a result,
Diamond particles with a particle size of 1d to 100 μm are combined with ultrafine diamond particles of 1 μm or less, WC of 1 μm or less, or (Mo, W)0 having the same crystal structure as this, and iron group metals, or a trace amount of boron or boride. It was found that the sintered body using the binder contained therein has both the good wear resistance of the coarse-grained diamond sintered body and the high toughness of the ultra-fine-grained diamond sintered body.

In order to find the optimal composition of the above-mentioned materials, the present inventors
Coarse diamond particle size and content, 1μ included in the binder? Diamond sintered bodies with different contents of diamond particles of ζ or less were prototyped and evaluated by cutting andesite.The results are shown in Figures 2 and 5. In the figure, 1 indicates normal wear and 2 indicates a region of cutting edge damage.0 If the coarse diamond grain size is 10 μm or less, the wear resistance decreases.

If the coarse diamond particle size exceeds 100 μm, f, cracks will occur within the diamond particles during sintering, and the cutting edge will be damaged through these cracks, resulting in a significant amount of wear.

The content of coarse diamond particles is 50-85% by volume
is good. If the content of coarse diamond particles is less than 50%, the amount of binder containing fine diamond particles increases, resulting in a decrease in wear resistance. On the other hand, if the content of coarse diamond exceeds 85%, the toughness decreases because the coarse diamonds bond together.

The particle size of the fine diamond particles in the binder is 1 μm.
The following is good. The particle size of the fine diamond particles is preferably 1 μm or less, preferably 0.5 μm or less. When the particle size of fine diamond particles exceeds 1 μm, toughness decreases. The content of fine diamond particles in the binder is 60-90% by volume.
% is preferred. The content of fine diamond particles is 60%
If it is less than that, the wear resistance of the binder phase will be reduced, the binder phase will wear out early, and coarse diamond particles will fall off. On the other hand, if the content of fine diamond particles exceeds 90, the binder becomes brittle, or the content of WC or (Mo, W)C, which has the same crystal structure as this, decreases, so that diamond particles of 1 μm or less become It grows and its toughness decreases.

In particular, the sintered body of the present invention has a weight of 0.005 to 0.01 by weight of the sintered body.
When containing 5% boron or boride, the performance is further improved. Usually, diamond particles are sintered under ultra-high pressure and high temperature by the phenomenon of diamond dissolution and precipitation using a catalyst such as an iron group metal. When boron or boron compounds are added, borides of iron group metals are formed and the melting point is lowered, and the melt deposition rate is increased, which causes the bonds between diamond particles (
It can be inferred that the diamond skeleton part) has grown and the holding power of the diamond particles has improved. If the content of boron or boride is less than 0.005%, the formation of the diamond skeleton portion will be slow. On the other hand, if the content of boron or boride exceeds 0.15%, a large amount of 1illll element will invade the diamond skeleton, reducing the strength of the diamond skeleton.

Next, a blank in which the diamond sintered body of the present invention was directly bonded to a WC-CO plate was brazed to the pit body to create a core pit, and an excavation test was performed. As a result, although the diamond sintered body did not break when the excavation conditions were severe, a problem occurred in that the diamond sintered body peeled off from the WO-Oo base material. Particularly in brazing, as the temperature rose, the frequency of peeling increased. In order to investigate the cause of this, we observed the structure near the joint and found that there was a CO-enriched layer at the interface between the diamond sintered body and the cemented carbide. Furthermore, free carbon was present in the cemented carbide near the interface. The temperature for brazing is generally 750-800℃,
A large amount of CO exists at the interface, and due to the CO
The diamond becomes graphitized and its strength decreases (~,
It is thought that it will peel off. Furthermore, the presence of free carbon in the cemented carbide reduces the strength of the cemented carbide, which is also considered to be a cause of peeling.

In order to obtain a bond with high strength, the present inventors conducted various studies and found that high-pressure phase boron nitride is less than 70% by volume, and the remainder is made of carbides, nitrides, and carbonitrides of groups 4a and 5a of the periodic table. I discovered that it is sufficient to use the remaining intermediate layer.

According to experiments conducted by the present inventors, the diamond sintered body and the cemented carbide base material were firmly bonded via this intermediate bonding layer under the ultra-high pressure and high temperature conditions used to produce the diamond sintered body. These composite sintered bodies having an intermediate bonding layer consisting of high-pressure phase type boron nitride, carbide, and nitride are leaked from the cemented carbide base material, etc. at the interface between the diamond sintered body layer and the intermediate bonding layer. Diamond solvent metals are not present in large quantities;
There is a large area where the diamond particles and the intermediate bonding layer are in direct liquid contact. Therefore, there is no decrease in strength due to reheating.

In addition, since there is almost no free carbon in the cemented carbide near the interface, the bonding strength is high, such as 0 or more, and according to the present invention, the diamond sintered layer can be firmly attached to the cemented carbide base material. , is very useful, but the reason for such a strong bond is presumed to be as follows.

First, regarding the adhesion between the intermediate bonding layer and the cemented carbide base material, it is important to note that
5 Group A carbides and nitrides form a mutual solid solution with we, which is the main component of the cemented carbide base material, and furthermore, the high-pressure phase boron nitride in the intermediate layer reacts with the We-Co of the cemented carbide base material. It is thought that the two will adhere strongly because all of the polide is generated during the process.Next, for adhesion between the intermediate bonding layer and the diamond sintered body, diamond powder, iron group metals and carbides, which are usually used as a bonding phase for diamond, are used. Nitride has excellent affinity with carbides and nitrides of groups 4a and 5a of the periodic table in the intermediate bonding layer, and furthermore, the intermediate bonding layer and the diamond sintered body layer are in contact with each other in a powder state before sintering. Therefore, it is thought that after sintering, there is a layer in which the intermediate bonding layer and the diamond sintered body layer are mixed, resulting in strong bonding.

In addition, carbides and nitrides of groups 4a+5a of the periodic table have 0,
By adding 1% by weight or more of A7 or Si'j5, the sinterability of the intermediate bonding layer itself is improved, and the affinity between these carbides and nitrides and diamond particles is also improved. In particular, if TiN, which is a nitride in Group 4a of the periodic table, contains At '50.1 or more by weight, the effect will be poor. The intermediate bonding layer according to the present invention contains high-pressure phase boron nitride. Because of this, it has high thermal conductivity, high high-temperature strength, and a coefficient of thermal expansion comparable to that of diamond sintered bodies. When the content of high-pressure phase type boron nitride becomes 70 volume coefficient or more, the amount of remaining carbides and nitrides of groups 4a and 5a of the periodic table becomes less than 50 volume coefficient, and these carbides and nitrides and cemented carbide base material The amount of mutual solid solution formed with WC, which is the main component of
-The bonding strength between the intermediate bonding layer and the cemented carbide base material tends to decrease because the override produced by the reaction of co is brittle.
Therefore, the content of high-pressure phase type boron nitride in the intermediate bonding layer is 7
It is desirable that the volume ratio is less than 0.

The base material to be bonded using this intermediate bonding layer is WC-C.
o Cemented carbide or Mo k as main component (Mo, W
) A cermet in which C-type carbide crystals are bonded with iron group metals is good. WC-CO and (Mo, W) O-iron group metal base materials have high rigidity and excellent thermal conductivity, and also have good toughness because they contain metal binders, so they are suitable for use as diamond sintered bodies for drill bits. Examples of carbides and nitrides in the intermediate bonding layer of the present invention include carbides such as TiC, Zr○, HfO, NbC, and TaC, as well as TiN, ZrN, HfN, and Nb.
A nitride of N, TaN, a mixture thereof, or a carbonitride such as 'ri(c,N)IZr(0,N) is used. In particular, when TiNi is used, the performance as an intermediate bonding layer is the best.

The diamond raw material powder used for the sintered body of the present invention is 10
These are diamond particles with a diameter of 1 μm or more, and micron powder with a diameter of 1 μm or less, preferably 0.5 μm or less. Synthetic diamonds or natural diamonds may be used. This diamond powder and WC powder or iron group metal powders of (Mo, W)0 and F6, Co, Ni, or powders containing boron or boride are processed by means such as a ball mill. Mix evenly. This iron group metal may be infiltrated during sintering without being mixed in advance. Also, as in the previous application of the present inventors (Japanese Patent Application No. 52-51581), WC or (Mo, W) in which pots and balls are mixed during ball milling is used.
0 carbide and a sintered body of iron group metal,
There is also a method of grinding diamond powder in a ball mill and simultaneously mixing fine powder of sintered body of WC or (MO, W) C and iron group metal from a pot and ball.0 As a method for manufacturing a sintered body of these mixed powders, The required amount of high-pressure phase type II nitride and carbide or nitride powder is placed between the cemented carbide matrix and the diamond-containing hard layered acid powder in powder form or as an embossed body. A powder layer that forms the entire intermediate bonding layer is created by applying a powder made into a slurry by adding an appropriate solvent to the cemented carbide base material, which is then hot pressed under ultra-high pressure and high temperature. Contains carbide at the same time as sintering of the hard layer.

It is also possible to adopt a method in which an intermediate bonding layer made of nitride is sintered and bonded to the base material at the same time.

The carbides and nitrides of metals from Groups 4a+5a of the periodic table in the intermediate bonding layer used in the present invention are high-strength compounds.
0 Kb to 90 Kb), the powder particles of these compounds are deformed when they are pressurized at a pressure close to the ideal shear strength of these compounds9.

It is crushed, easily filled into a dense state, and then heated to become a dense sintered body.

In addition, it is also possible to impregnate a molten diamond-forming catalyst metal or other binding metal into the diamond powder layer under ultra-high pressure and high temperature. The above-mentioned CO, which is the bonding metal that is directly bonded to the currently commercially available cemented carbide base material, penetrates into the diamond powder layer and becomes the bonding metal of the diamond sintered body. In the case of the present invention, the bonding metal can be selected regardless of the bonding metal of the base cemented carbide.

This will be explained in detail below using examples.

Example 1 Synthetic diamond powder with particle size of 05μ, WC and Co
Powder f was pulverized and mixed using a pot and ball made of WC-Co cemented carbide. The composition of the obtained mixed powder was 80% by volume of fine diamond with an average particle size of 05 μm, 12% by volume of WO, and 8% by volume of Co. This mixed powder and particle size 20
~50 μm diamond powder was mixed 75:25 by volume. 0.15% by weight of B powder was added to this powder.

Next, V/C-6% com11. Outer diameter of 10. Cubic boron nitride (C!
TiN J containing N ) and the balance Atf20 weight ratio:
The powder was mixed into an organic solvent containing ethylcellulose to form a slurry, which was then applied. This cemented carbide f
A container made of Mo was filled with a hard layer of powder containing diamond so as to be in contact with an intermediate layer containing all cubic crystal nitride elements, and first a pressure of 55 K was applied using an ultra-hard pressure device.
b was added, followed by heating to 1500°C and holding for 20 minutes.

After cooling, the sintered body was taken out and observed.
Diamond particles of 0 μm were bonded through a bonding material containing ultrafine diamond particles. At the bonding interface, the diamond sintered body was firmly bonded to the cemented carbide via an intermediate layer containing cubic boron nitride.

Using this composite sintered body, we made a core bit (z) consisting of 4 teeth with an outer diameter of 46, and a compressive strength of 1800 kg/c1
n 2 andesite was drilled at a speed of 250 revolutions/min. Note that the bit load was 800 ni. For comparison, we prototyped a commercially available bit sintered body (a diamond sintered body and the above-mentioned diamond sintered body, but directly bonded to the cemented carbide without using an intermediate layer), and conducted similar tests.
The diamond sintered body of the present invention could be used without any breakage even after 20 m of excavation, whereas the core pit using a commercially available diamond sintered body for bits could be used without diamonds after 5 m of excavation. The life span was reached due to damage and peeling of the sintered body.

Further, in the core pit of the sintered body whose hard layer had the same composition as the sintered body of the present invention but did not have the intermediate bonding layer, the diamond sintered body was separated from the cemented carbide after 15 m of excavation.

Example 2 A binder powder shown in Table 1 was prepared. As a fine diamond, 0.5 μm is a good friend to use. This binding material and particle size 1
Completed powder by mixing diamond particles of 0 μm or larger in the proportions shown in Table 2? Created.

Table 2 This intermediate layer powder was mixed into an organic solvent containing ethyl cellulose to form a slurry, and the slurry was applied to a cemented carbide having a composition of WC-8% CO. This cemented carbide (5M.

The container was filled with the diamond-containing powder shown in Table 2 so as to be in contact with the intermediate layer powder.

This was sintered under ultra-high pressure in the same manner as in Example 1 to create a diamond sintered body, and a core piratra consisting of five teeth was fabricated.Table 4 shows the composition of the prototype diamond sintered body and the intermediate layer. Unconfined compressive strength of 2000 K using this bit 2
9/Qn2 andesite' (z excavated 10 m at a speed of 50 m/min. Test WC-6 CO cemented carbide (Mo, W
A diamond sintered body was prototyped in the same manner as in Example 1 except that the CO ratio was changed to IO-10 ratio + 11° and 10 ratio CO.
Create a core pit consisting of two teeth. Using this bit, I made 1 piece of andesite with a compressive strength of 1700K17cm2.
Although the diamond sintered body was excavated for 20 m at a speed of 0.00 m/min, no chipping or peeling occurred in the diamond sintered body.

[Brief explanation of drawings]

Figure 1 shows the strength (transverse rupture strength) of a diamond sintered body.
This shows the relationship between diamond grain size and diamond particle size. Second
The figure shows the particle size of coarse diamond particles and rock cutting performance in the sintered body of the present invention. FIG. 5 is a graph showing the content of coarse diamond and rock cutting performance in the sintered body of the present invention. Agents 1) Akira Agent Ryo Hagiwara - Figure 2: Particle size of coarse-grained diamond (, um) Figure 3: Content of coarse-grained tire upper back (volume %) Procedural amendment, book (method) % formula % 1. Indication of the case Patent Application No. 124512 of 1982 2. Name of the invention Machine diamond sintered body for tools and its manufacturing method 3. Person making the amendment Relationship to the case Patent applicant 11 Location 5-chome, Kitahama, Higashi-ku, Osaka No. 15, No. 4, Agent (I-Toramon-cho, Minato-ku, Tokyo), No. 24-11, No. 2, Subject of amendment (1) Contents of page A written in ballpoint pen of the specification (1) No. 22 of the specification Correct pages 23, 25, and 27 as shown in the attached sheet. (No changes were made to the content) and conducted a similar test. As a result, the diamond sintered body of the present invention could be used even after 20m excavation without any breakage, whereas the core pit using the commercially available diamond sintered body for bits could be used after 5m excavation. However, the life of the diamond sintered body came to an end due to chipping and peeling. Further, in the core pit of the sintered body whose hard layer had the same composition as the sintered body of the present invention but did not have the intermediate bonding layer, the diamond sintered body was separated from the cemented carbide after 15 m of excavation. Example 2 A binder powder shown in Table 1 was prepared. As the fine diamond, one with a diameter of 15 μm was used. This binder and diamond particles having a particle size of 10 μm or more were mixed in the ratio shown in Table 2 to prepare a finished powder. Table 2 Table 4 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1 Case description Showa 5740ζ1 Patent Application No. 124512 2° issued “JJ
2') Name: Composite diamond sintered body for tools and its manufacturing method 3, Relationship to the case of the person who committed the arrest '1'T:'1' Applicant fiIsui Representative, 5-15 Kitahama, Higashi-ku, Osaka
Business Tetsubu 4, Agent 11 Address: 16-2, Toranomon, Minato-ku, Tokyo (1 idiot) Contents of the amendment (1) Column a “Detailed Description of the Invention” of the specification to be amended (1) ) On page 23, line 20 of the specification, the phrase ``1, but the core pit is also'' is corrected to ``the core pit is also the same.'' (2) In the first line of page 23 of the specification, "particle size 10 μm or more" is corrected to "particle size 5 μm or more." (3) In the upper left column of Table 2 on page 23 of the specification, "10 μm or more" is corrected to "5 μm or more." (4) Correct that it is in the lower right corner of Table 4 on page 27 of the specification.

Claims (1)

[Claims] Mayu has the same crystal structure as this (
The hard sintered body made of a binder composed of Mo, W) 0 and iron group metal is made of high-pressure phase boron nitride with a capacity of 2ya or less, and the remainder is carbides, nitrides, and carbonitrides of groups 4a and 5a of the periodic table. A WC-Co alloy base material or a solid solution or mixture of two or more of these, or a WC-Co alloy base material or M. A composite diamond sintered body for tools, characterized in that it is bonded to a cermet base material in which (Mo, W)C-type carbide crystals containing gold as a main component are bonded with an iron group metal. (The hard sintered body accounts for 50 to 80% by volume of coarse diamond particles with a particle size of 10 μm or more and 100 μm or less,
A capacity of 60 ultra-fine diamond grains with a remainder of 1 μm or less
~90% and 1μm or less WC or (Mo, W)O and iron group metals having the same crystal structure as this and 000% by weight
The composite diamond sintered body for tools according to claim 1, characterized in that it contains 5 to 15% of boron or/and Misaki monoride. (3) WC used as a part of the binder in the hard sintered body according to claim (1) or (2), or (MO, W)C having the same crystal structure as WC and an iron group metal. A composite diamond sintered body for tools, characterized in that the carbide content is higher than that corresponding to its eutectic composition. (4) The composite diamond sintered body for tools according to claims 1 to 5, which is a nitride 75fTiN of Group 4a of the periodic table, which is a component of the intermediate layer. (5) WC! - Co alloy base material or Mo f main component (+vo, high pressure phase type nitrided jJl
ll element and the remainder are carbides, nitrides, carbonitrides of groups 4a and 5a of the periodic table, or solid solutions or mixtures of two or more of these, or these contain At' = or sl or both of them in an amount of 01% or more by weight Place the powder in powder form or in the form of an embossed body, or apply it on the base material in advance, and add 50 to 85 volumes of 10 to 100 μm diamond powder and the remainder ultrafine diamond powder of 1 μm or less. 'z 60-90 capacity factor, 1 μm or less WC or a mixed powder of (Mo, W)O having the same crystal structure as this, and iron group metal powder is filled, and the whole is heated using an ultra-high pressure and high temperature equipment to form diamonds. A method for producing a composite diamond sintered body for a tool, which comprises hot pressing under stable high temperature and high pressure to sinter the hard layer and intermediate layer powder containing diamond v, and simultaneously bonding them to a base material. (6) WO-00 alloy base material or Mo (MO, WJ) In contact with a cermet base material in which C-type carbide crystals are bonded with iron group metal, high-pressure phase boron nitride and the remainder are in periodic order. Powder containing carbides, nitrides, carbonitrides of groups 4a and 5a, or solid solutions or mixtures of two or more of these, or At or Sl or both by weight of 0.1 or more or by applying it on the base material in advance,
On top of this, add 50~10~100μm diamond powder.
Ultra-fine diamond powder with 85 volume fraction and the balance of 1 μm or less is filled with 60 to 90 volume fraction and WC with 1 μm or less or a mixed powder of (Mo, W) O having the same crystal structure as this, and on top of this, iron group After placing an alloy plate of one metal or two or more metals, we use an ultra-high pressure and high temperature equipment using a solid pressure medium to heat the diamond under stable high temperature and pressure. A composite diamond sintered body for tools, characterized in that a hard layer containing diamond and an intermediate layer powder are sintered and bonded to a base material at the same time by infiltrating a liquid phase of an alloy of at least one species into a mixed powder. Manufacturing method 0 (7) WC-Co alloy base material or MoF as main component (Mo, WJC type carbide crystal bonded with iron group metal in contact with cermet base material, high pressure phase type boron nitride and the remainder) Carbides, nitrides, carbonitrides of groups 4a and 5a of the periodic table,
Or a solid solution or mixture of two or more of these, or At-! For this purpose, a powder containing Si or both of them by weight of 0.1 or more is placed in powder form or in the form of an embossed body, or it is coated on the base material in advance, and then diamond powder of 10 to 100 μm is applied on top of this. ? 50 to 85 volume fraction and the balance is a mixture of ultrafine diamond powder of 1 μm or less and 60 to 90 volume fraction and 1 μm or less we - or (Mo, W) O boron or boride having the same crystal structure as this by weight. The method is characterized in that a mixed powder of 0.0 [15 to 0.15% of the powder and an iron group metal is prepared, and the hard layer containing diamond and the intermediate layer powder are sintered and simultaneously bonded to the base material. Manufacturing method of composite diamond sintered body for tools 0 (8) We-C! o Alloy base material or Mo f In contact with a cermet base material in which (Mo, W) O-type carbide crystals as main components are bonded with iron group metal, high-pressure phase boron nitride and the remainder are from groups 4a and 5a of the periodic table. carbides, nitrides, carbonitrides, solid solutions or mixtures of two or more of these, or a powder containing At or Si or both of these in an amount of 0.1% or more by weight, in powder form or in a molded form. Alternatively, it may be coated on the base material in advance, and 50 to 85 μm of diamond powder with a diameter of 10 to 100 μm is applied thereon.
Ultra-fine diamond powder with a capacity factor and the remainder of 1 μm or less is 60 to 90 WC with a capacity factor of 1 μm or less! t* has the same crystal structure as this (Mo, W) O, boron,! A mixed powder containing 0006 to 016% of the mixed powder by weight is filled with 0006 to 016% of the mixed powder, and an alloy plate of one or more iron group metals is placed on top of the mixed powder, and then a solid pressure medium is used. A hard layer containing diamond is formed by infiltrating the entire liquid phase mixed powder of one or more alloys of iron group metals under stable high temperature and high pressure conditions using an ultra-high pressure and high temperature apparatus 7. A method for manufacturing a composite Gouy-V Monde sintered body for tools, characterized by sintering the intermediate layer powder and simultaneously bonding it to the base material. (9) Claims No. (5), (6), (7)
), WC used as a part of the binder forming powder of the hard layer in the manufacturing method described in (8) or having the same crystal structure as this (MO, W) The ratio of C and iron group metal Insulator's eutectic composition Composite for tools characterized by using a mixed powder with a larger amount of carbide than the equivalent powder, and sintering with suppressing the grain growth of ultrafine diamond at a temperature higher than the eutectic formation temperature of carbide and iron group metal. A method for producing a diamond sintered body. 00 Claims (5) and (6), wherein the nitride of Group 4a of the periodic table, which is a component of the intermediate layer, is TiN. (7), (SL) Composite diamond for tools described in item (9)