JPH08310865A - Diamond sintered body and method for manufacturing the same - Google Patents

Abstract

PURPOSE: To obtain a high strength diamond sintered compact excellent in chipping resistance and capable of production under conditions which facilitate industrial production by incorporating a material made of a phosphorus-oxygen compd. into a diamond sintered compact. CONSTITUTION: This diamond sintered compact consists of 0.1-30vol.% material made of a phosphorus-oxygen compd. and the balance diamond. This sintered compact is produced, e.g. by mixing phosphorus oxide powder as a sintering aid with diamond powder, nondiamond carbon powder or a powdery diamond- nondiamond carbon mixture, compressing the resultant mixture at need and sintering it by holding under conditions of pressure and temp. in a region in which diamond is thermodynamically stable. Phosphorus oxide hydrate, phosphoric acid or phosphate hydrate may be used as other sintering aid for producing diamond.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond sintered body and a method for producing the same. INDUSTRIAL APPLICABILITY The diamond sintered body of the present invention can be effectively used as a material for cutting and grinding tools such as non-ferrous metals and ceramics and as a blade edge material for drill bits for oil drilling applications.

[0002]

2. Description of the Related Art As a conventional diamond sintered body, one using an iron group metal such as Co, Ni or Fe as a sintering aid or a binder, and one using a ceramic such as SiC is known. And is industrially used for non-ferrous metal cutting tools and drill bits. It is also possible to use a carbonate as a sintering aid.
Proposed by No. 4-114966. In addition, there is a natural diamond sintered body (carbonate), but it is rarely used industrially because of the large variation in the material and the minimal production.

[0003]

A diamond sintered body using an iron group metal such as Co as a sintering aid has strength of the sintered body because a metal such as Co exists as a continuous phase in the grain boundary of diamond grains. Is not very expensive and is easy to lose. It is also known that the metal of the grain boundary is removed by acid treatment for the purpose of improving heat resistance, but the strength becomes much lower (about 30%) because the sintered body becomes porous. The diamond sintered body using SiC as a binder has almost no bond between diamond grains, and therefore has low strength.

Further, a diamond sintered body using a carbonate as a sintering aid has been proposed, but the carbonate has a lower catalytic ability than the conventional iron group metal, and the dissolution and precipitation action of diamond is insufficient. Therefore, the bonds between diamonds are not sufficient, and it is hard to say that the strength and fracture resistance are still sufficient. Also,
Since its production requires severe pressure and temperature conditions of 7.7 GPa and 2000 ° C. or higher, it is difficult for industrial production. The present invention is intended to solve the above problems and provide a diamond sintered body which has high strength and excellent fracture resistance, and which can be manufactured under manufacturing conditions that facilitate industrial production, and a manufacturing method thereof. is there.

[0005]

As a means for solving the above-mentioned problems, the present invention provides a sintered body containing 0.1 to 30% by volume of a substance consisting of a compound of phosphorus and oxygen and the balance being diamond. . Further, as a method for producing this diamond sintered body, phosphorus oxide is used as a sintering aid, and this powder is mixed with a diamond powder or a non-diamond carbon powder or a mixed powder of diamond and non-diamond carbon. Provided is a method for holding or sintering a diamond under a pressure or temperature condition in the thermodynamically stable region of diamond by compression molding or compression molding.

As another method for producing the diamond sintered body, a phosphorus oxide powder compact used as a sintering aid, a diamond powder compact or a non-diamond carbon powder compact, or a diamond and a non-diamond carbon compact are used. Provided is a method for laminating mixed powder compacts, holding the mixture under the pressure and temperature conditions of the thermodynamically stable region of diamond, and sintering. Further, there is provided a method for producing the diamond sintered body, which uses a hydrate of phosphorus oxide, or phosphoric acid, or a hydrate of phosphoric acid as another sintering aid.

[0007]

The feature of the present invention resides in that phosphorus oxide or its hydrate or phosphoric acid or its hydrate is used as a sintering aid for the diamond sintered body. Heretofore, it has not been known that phosphorus oxide, phosphoric acid, or a hydrate thereof acts as a catalyst for diamond, and thus has never been used as a sintering aid for a diamond sintered body. This time, by the present inventors, these phosphorus oxide, phosphoric acid and hydrates thereof,
It has been found to exhibit a strong catalytic action on diamond. It was also found that by using these as sintering aids, a matrix in which diamond particles were extremely strongly bonded to each other was formed. As a result, it was found that a diamond sintered body having an unprecedentedly high strength and excellent fracture resistance was obtained, and the present invention was accomplished.

The phosphorus oxide used in the present invention is P_Four 
O, P₂ O, P₂ O₃ , PO, P_Four O ₇ , PO₂ , P_Four 
O₉ , P₂ O_Five , PO₃ And so on. Of phosphorus oxide
Hydrate P₂ O_Five ・ NH₂ As O, polyphosphoric acid (2> n
> 1), ultraphosphoric acid (1> n> 0), etc.
It As phosphoric acid, metaphosphoric acid (HPO₃ ), Ortoli
Acid (H₃ PO_Four ), Peroxophosphoric acid (H₃ PO
_Five ), Peroxodiphosphate (H_Four P₂ O₈ ), Etc.
As a hydrate of an acid, for example, H₃ PO_Four ・ 0.5H₂ O etc.
Can be raised.

Since these phosphorus oxides, phosphoric acids and hydrates thereof have a strong catalytic action on diamond, by using these as a sintering aid, the diamond particles are extremely strongly bonded to each other and have high strength. Thus, a diamond sintered body having excellent fracture resistance can be obtained. The diamond sintered body thus obtained is characterized by containing a substance composed of phosphorus and oxygen. Further, since phosphorus oxide, phosphoric acid or hydrates thereof act as a catalyst at a relatively low temperature, when these are used as sintering aids, for example, M as shown in JP-A-4-74766 is used.
Lower pressure than when using a carbonate such as g or Ca as a sintering aid,
It can be manufactured under low pressure and temperature conditions. That is, in this case, a sufficiently strong sintered body can be obtained even at about 6 GPa and 1500 ° C.

In the diamond sintered body of the present invention, the content of the substance consisting of the compound of phosphorus and oxygen is preferably 0.1 to 30% by volume. The reason for this is that if the content is less than 0.1% by volume, the bonding property between diamond particles, that is, the sintering. When the content exceeds 30% by volume, the strength and wear resistance are reduced due to the effect of excessive phosphorus and oxygen compounds.

As raw materials, synthetic diamond powder, natural diamond powder, polycrystalline diamond powder and the like can be used. The particle size of the powder is 0.01 to 200 μm, and fine particles or coarse particles having a uniform particle diameter or a mixture of fine particles and coarse particles is used depending on the application. Further, instead of these diamonds, non-diamond such as graphite, glassy carbon, and pyrolytic graphite can be used as a raw material. Also,
It is also possible to use a mixture of diamond and these non-diamond graphites.

As the method for producing a diamond sintered body of the present invention, a mixture of diamond powder or non-diamond powder with phosphorus oxide, phosphoric acid or a hydrate thereof, or a mixture obtained by compression molding the mixture, A method in which diamond is held under thermodynamically stable pressure and temperature conditions, and a laminate of diamond powder or non-diamond graphite compacts and phosphorous oxide, phosphoric acid or hydrates of these compacts As a method, there is a method of holding under the above pressure and temperature conditions.

In the method of mixing the raw material and the sintering auxiliary material, the raw material and the sintering auxiliary material are compression-molded from a powder obtained by mechanically dry- or wet-mixing, or filled in a capsule such as Mo or the like. The material is sintered at high pressure and high temperature. Even if the raw material powder is fine particles, the sintering aid can be uniformly dispersed, and a thick diamond sintered body can be manufactured. For example, it is suitable for manufacturing a cutting tool (fine-grained sintered body) that requires a good finished surface and a sintered body that requires a thick shape such as a die.
However, when a coarse-grained raw material is used, it is difficult to uniformly mix the sintering aid. On the other hand, in the method of stacking the raw material and the sintering aid, a plate-shaped molded body of the raw material and the sintering aid is manufactured, and these are stacked and brought into contact with each other, and subjected to high-pressure and high-temperature treatment. At this time, the sintering aid is diffused and impregnated into the raw material layer, and the diamond particles are sintered. With this method, even if a coarse-grained raw material is used, the sintering aid can be added uniformly, so that a diamond sintered body with higher strength and wear resistance can be stably obtained. Suitable for manufacturing sintered bodies such as bits.

[0014]

【Example】

Example 1 Phosphorus pentoxide (P ₂ O ₅ ) was used as a sintering aid. A synthetic diamond powder with an average particle size of 3.5 μm and phosphorous pentoxide powder were thoroughly mixed at a ratio of 95% by volume and 5% by volume, respectively, and the mixture was put into a Mo capsule, and a belt-type ultrahigh pressure and high temperature generator was installed. It was used for 15 minutes under the pressure temperature condition of 6.5 GPa and 1700 ° C. to be sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 5% by volume of phosphorus oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated by a Knoop indenter, it was as high as 8000 kg / mm ² . The fracture toughness of the conventional sintered Co binder was compared by conventional indentation method.
The relative toughness was 1.4 times.

Example 2 A diamond sintered body was produced in the same manner as in Example 1 except that 5% by volume of metaphosphoric acid (HPO ₃ ) was used as a sintering aid. The obtained sintered body contained phosphoric acid, and had the same hardness, toughness, and heat resistance as in Example 1.

Example 3 As a sintering aid, 5% by volume of orthophosphoric acid (H ₃ PO) was used.
_A diamond sintered body was produced in the same manner as in Example 1 except that ₄ ) was used. The obtained sintered body contained phosphoric acid, and had the same hardness, toughness, and heat resistance as in Example 1.

Example 4 As a sintering aid, 5% by volume of hydrous orthophosphoric acid (H ₃ P)
O ₄ · 0.5H ₂ O) and the sintering pressure temperature condition is 6.5G
A diamond sintered body was produced in the same manner as in Example 1 except that Pa and 1600 ° C. were used. The obtained sintered body contained phosphoric acid, and had the same hardness, toughness, and heat resistance as in Example 1.

Example 5 Example 1 was repeated except that 5% by volume of polyphosphoric acid was used as a sintering aid and the sintering pressure temperature conditions were 6.5 GPa and 1650 ° C.
A diamond sintered body was produced in the same manner as in. The obtained sintered body contained phosphoric acid, and had the same hardness, toughness, and heat resistance as in Example 1.

Example 6 P ₂ O ₅ was used as a sintering aid. A synthetic diamond powder with an average particle size of 15 μm and a graphite powder with an average particle size of 10 μm were mixed in a volume ratio of 3: 2 and pressed into a thickness of 2 mm, and P ₂ O ₅ powder was pressed into a thickness of 1 mm. These were alternately laminated and placed in a Mo capsule, which was then held for 15 minutes under a pressure temperature condition of 6.5 GPa and 1800 ° C. using a belt-type ultra-high pressure and high temperature generator to sinter. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 2% by volume of phosphoric acid was detected in addition to diamond. When the hardness of this sintered body was evaluated with a Knoop indenter, it was about 8300 kg / mm ² , which was a high hardness. Further, when the fracture toughness was compared with the conventional commercially available Co binder sintered body by the indentation method, it was about 1.
The relative toughness was 5 times.

Example 7 P ₂ O ₅ was used as a sintering aid. A plate-shaped sintered body of high-purity isotropic graphite having an average particle diameter of 3 μm and a thickness of 2 mm and a P ₂ O ₅ powder having a thickness of 1 mm which were embossed and molded were alternately laminated and put in a Mo capsule to form a girdle type. Using the ultra-high pressure and high temperature generator of No. 3, the product was held at a pressure and temperature of 6.5 GPa and 1800 ° C. for 15 minutes for sintering. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 3% by volume of phosphorus oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated with a Knoop indenter, it was approximately 8000 kg.
The hardness was as high as / mm ² . When the fracture toughness was compared with the conventional commercially available Co binder sintered body by the indentation method, the relative toughness was about 1.3 times that of the conventional sintered body.

Comparative Example 1 P ₂ O ₅ was used as a sintering aid. A small amount of P ₂ O ₅ powder (about 0.05
The production of a diamond sintered body was attempted in the same manner as in Example 1 except that a raw material was added to the mixture and mixed sufficiently. However, many unsintered parts remained in the obtained sintered body.

Comparative Example 2 P ₂ O ₅ was used as a sintering aid. 60% by volume of synthetic diamond powder having an average particle size of 3.5 μm and 40% by volume of P ₂ O ₅ powder were added and sufficiently mixed, and used as a raw material.
An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1.
However, in the obtained sintered body, the particles were not sufficiently bonded to each other, and the hardness was low at about 3500 kg / mm ² .

[0023]

As described above, since the diamond sintered body of the present invention has extremely high strength and has excellent fracture resistance, it is suitable for cutting and grinding tools such as non-ferrous metals and ceramics. It can be effectively used as a material and a cutting edge material for drill bits for oil drilling applications. Moreover, since it can be sintered at a relatively low pressure and a low temperature, it has a great economic effect.

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Claims (4)

[Claims] 1. A substance comprising a compound of phosphorus and oxygen is added to 0.1.
A diamond sintered body, characterized in that it contains up to 30% by volume and the balance is diamond. 2. A phosphorous oxide is used as a sintering aid, and this powder is mixed with a diamond powder or a non-diamond carbon powder or a mixed powder of diamond and non-diamond carbon,
2. The method for producing a diamond sintered body according to claim 1, further comprising the steps of: mixing, holding the mixture under conditions of pressure and temperature in a thermodynamically stable region of diamond, and sintering the mixture. 3. A molded body of this powder, a molded body of diamond powder or a molded body of non-diamond carbon powder, or a molded body of mixed powder of diamond and non-diamond carbon is laminated by using phosphorus oxide as a sintering aid. 2. The method for producing a diamond sintered body according to claim 1, wherein the diamond sintered body is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered. 4. The method for producing a diamond sintered body according to claim 2, wherein the sintering aid is any one of the following A, B, and C. A. Phosphorus oxide hydrate B. Phosphoric acid C.I. Phosphoric acid hydrate