JPH08295564A - Diamond sintered compact and its production - Google Patents

Abstract

PURPOSE: To produce a diamond sintered compact having heat, chipping and wear resistances under conditions capable of industrial production. CONSTITUTION: This diamond sintered compact consists of 0.1-30vol.% material made of a compd. contg. an alkali metal or an alkaline earth metal and phosphorus and the balance diamond. Phosphate hydrate, hydrogenphosphate or hydrogenphosphate hydrate of the alkali metal or alkaline earth metal is used as a sintering aid, powder of the sintering aid is mixed with diamond powder, non-diamond carbon powder or a mixture of them and the resultant mixture is sintered by holding under conditions of pressure and temp. in a region in which diamond is thermodynamically stable.

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 conventional diamond sinters, those using an iron group metal such as Co, Ni and Fe as a sintering aid or a binder, and one using a ceramic such as SiC are known. And is industrially used for non-ferrous metal cutting tools and drill bits. Further, there is known one using a carbonate as a sintering aid (JP-A-4-7).
4766, JP-A-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 is inferior in heat resistance because the iron group metal such as Co acts as a catalyst for promoting graphitization of diamond. . That is, in an inert gas atmosphere,
Graphitizes at about 700 ° C. In addition, since a metal such as Co exists as a continuous phase in the grain boundary of the diamond grain, the strength of the sintered body is not so high and the sintered body is easily broken. There is also a problem that thermal deterioration easily occurs due to the difference in thermal expansion between the metal and diamond. It is also known that the metal of the grain boundary is removed by acid treatment in order to improve heat resistance. Thereby, the heat resistant temperature is improved to about 1200 ° C., but the sintered body becomes porous, so that the strength is further significantly reduced (about 30%). The diamond sintered body using SiC as a binder has excellent heat resistance, but the diamond grains do not bond to each other and thus have low strength. On the other hand, a diamond sintered body using a carbonate as a sintering aid is excellent in heat resistance and has relatively high strength, but its production is 7.7 GP.
a, 2000 ° C. or higher, which requires very severe pressure and temperature conditions, makes industrial production difficult and has not been put to practical use.
In addition, carbonate has a lower catalytic ability than conventional iron group metals, and the dissolution and precipitation action of diamond is insufficient, so that the bonds between diamonds are not sufficient and the fracture resistance is poor. The present invention intends to solve the above problems and provide a diamond sintered body which has heat resistance, chipping resistance, and abrasion resistance and which can be manufactured under the conditions in which industrial production is possible, and a method for producing the same. It was done.

[0004]

As a means for solving the above-mentioned problems, the present invention provides a substance comprising a compound containing an alkali metal or alkaline earth metal and phosphorus.
Provided is a sintered body containing 1 to 30% by volume and the rest being diamond. Further, as a method for producing this diamond sintered body, a hydrous phosphate of an alkali metal or an alkaline earth metal is used as a sintering aid, and this powder, a diamond powder or a non-diamond carbon powder, or a diamond and a non-diamond carbon. Provided is a method of mixing with a mixed powder, holding the mixed powder under the pressure and temperature conditions of the thermodynamically stable region of diamond, and sintering. In this case, the sintering aid is
It is blended so as to be 0.1 to 30% by volume in the mixture. As another method for producing this diamond sintered body, a molded body of hydrous phosphate powder of alkali metal or alkaline earth metal used as a sintering aid, and a molded body of diamond powder or a non-diamond carbon powder Alternatively, there is provided a method in which a diamond and a non-diamond carbon mixed powder compact are laminated, and this is sintered under the pressure and temperature conditions of the thermodynamically stable region of diamond. Further, for the production of this diamond sintered body, as another sintering aid, alkali metal or alkaline earth metal hydrogen phosphate,
Alternatively, a method using a hydrate of an alkali metal or alkaline earth metal hydrogen phosphate is provided.

[0005]

It is known that a phosphate of an alkali metal or an alkaline earth metal serves as a catalyst for synthesizing diamond (JP-A-3-242235). However, even if a diamond sintered body is manufactured using these as a sintering aid, a good sintered body cannot be obtained. It is considered that the alkali metal or alkaline earth metal phosphate does not have sufficient catalytic ability for diamond, and abnormal grain growth is likely to occur so that a homogeneous structure cannot be obtained.

The feature of the present invention is that the sintering of the diamond sintered body is performed.
As an auxiliary agent, an alkali metal or alkaline earth metal
Hydration of hydrous phosphates, hydrogen phosphates or hydrogen phosphates
It is in the point of using things. Alkali metal or alkaline earth
Of hydrous phosphates, hydrogen phosphates and hydrogen phosphates of group metals
As a hydrate, for example, Na₃PO_Four・ NH₂O, Ca
₂P₂O₇・ 2H₂O, Mg₃(PO_Four)₂・ 8H
₂O, Na₃HPO_Four, K ₂HPO_Four, K₃HPO_Four,
CaHPO_Four, Ca (H₂PO_Four)₂, Na₃HPO_Four
・ NH₂O, Mg₂HPO_Four・ 3H₂O, Mg₂(H₂
PO_Four)₂・ 2H₂O, CaHPO_Four・ 2H₂O etc.
Can be mentioned. Such a sintering aid is 0.1 to 10 μm.
Those having a particle size range of are preferable. These alkali metals also
Water-containing phosphates and hydrogen phosphates of alkaline earth metals
And hydrogen phosphate hydrate are strong against diamond
It shows a catalytic action. Therefore, the diamond particles are extremely polar.
A tightly bound matrix is formed. Also,
Abnormal grain growth is unlikely to occur, and it is necessary to obtain a sintered body with a uniform structure.
You can As a result, it has unprecedented high strength and fracture resistance.
An excellent diamond sintered body can be obtained.

The characteristics of the diamond sintered body thus obtained are
Features include alkali metals and alkaline earth metals and phosphorus
It is characterized in that it includes a substance composed of a compound. Alkaline gold
Consisting of compounds containing genus or alkaline earth metal and phosphorus
As the substance, for example, Na ₃PO_Four, K₃PO_Four, M
g₂P_FourO₁₂, Mg₂P₂O₇, Ca₃(PO_Four)₂What
There is a throat. These materials are stable at high temperatures, for example
K₃PO_FourAnd Mg₂P ₂O₇Is 1300 ℃, Ca₃(P
O_Four)₂Is stable up to 1600 ° C. For this reason,
Akira diamond sintered body has excellent heat resistance
Is shown. In addition, of alkali metal or alkaline earth metal
Hydrous phosphates, hydrogen phosphates and hydrates of hydrogen phosphates
Since the catalytic action works at a relatively low temperature, the diamond of the present invention
The sintered body is disclosed in, for example, Japanese Patent Laid-Open No. 4-74766.
When a carbonate such as Mg or Ca is used as a sintering aid
It is possible to manufacture under pressure and temperature conditions of low pressure and low temperature.
That is, for example, about 6 GPa and 1500 ° C. is sufficient.
A strong sintered body can be obtained.

In the diamond sintered body of the present invention, the content of the alkali metal or alkaline earth metal and phosphorus-containing compound is preferably 0.1 to 30% by volume, because the reason is less than 0.1% by volume. The bondability between diamond particles, that is, the sinterability decreases, and if it exceeds 30% by volume, strength and wear resistance decrease due to the influence of an excessive alkali metal or alkaline earth metal and a compound containing phosphorus. As the raw material, 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 the particle size is made into fine particles or coarse particles depending on the use, or fine particles,
A coarse-grained mixture is used. Further, instead of these diamonds, non-diamond such as graphite, glassy carbon, and pyrolytic graphite can be used as a raw material. It is also possible to use a mixture of diamond and these non-diamond graphites.

The method for producing a diamond sintered body of the present invention is a method in which diamond powder or non-diamond powder is mixed with hydrous phosphate of alkali metal or alkaline earth metal or hydrate of hydrogen phosphate. As a raw material, a method for holding diamond under thermodynamically stable pressure and temperature conditions, a compact of diamond powder or non-diamond graphite, a hydrous phosphate of alkali metal or alkaline earth metal, hydrogen phosphate Alternatively, there is a method of holding a molded body of a hydrate of hydrogen phosphate as a raw material under the above-mentioned pressure and temperature conditions. In the method of mixing the raw material and the sintering aid, mechanically dry or wet mixing the raw material and the sintering aid is subjected to high pressure and high temperature sintering. Even if the raw material powder is fine, 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-grain raw material is used, it is difficult to mix the sintering aid uniformly. On the other hand, in the method of stacking and placing the raw material and the sintering aid, plate-shaped compacts of the raw material and the sintering aid are produced, and these are stacked and brought into contact with each other, and subjected to high pressure and high temperature treatment. At this time, the raw material layer is diffused and impregnated with the sintering aid, 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.

[0010]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Using MgHPO ₄ · 3H ₂ O (Example 1) sintering aid. A synthetic diamond powder having an average particle diameter of 3.5 μm and MgHPO ₄ .3H ₂ O powder were sufficiently mixed at a ratio of 95% by volume and 5% by volume, respectively, and the mixture was mixed with
The mixture was placed in a capsule and held at a pressure / temperature condition of 6.5 GPa and 1650 ° C. for 15 minutes using a belt-type ultra-high pressure / high temperature generator to be sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 5% by volume of Mg ₂ P ₂ O ₇ was detected in addition to diamond. When the hardness of this sintered body was evaluated by a Knoop indenter, it was about 8000 kg / mm ² , which was a high hardness. In addition, the fracture toughness was measured by the conventional indentation method
As a result of relative comparison with the binder sintered body, the relative toughness was about 1.4 times that of the conventional sintered body. The hardness and toughness of the obtained sintered body were measured at 1000 ° C. in vacuum, and the hardness and toughness were measured.

Example 2 A diamond sintered body was produced in the same manner as in Example 1 except that 5% by volume of CaHPO ₄ was used as a sintering aid. CaP was added to the obtained sintered body.
O ₄ is included, and the hardness, toughness, and heat resistance of Example 1
Was similar to.

Example 3 A diamond sintered body was produced in the same manner as in Example 1 except that 5% by volume of Na ₃ PO ₄ .2H ₂ O was used as a sintering aid. The obtained sintered body contained Na ₃ PO ₄ and had the same hardness, toughness, and heat resistance as in Example 1.

Example 4 A diamond sintered body was produced in the same manner as in Example 1 except that 5% by volume of K ₂ HPO ₄ was used as a sintering aid. K ₄ P was added to the obtained sintered body.
₂ O ₇ was contained, and the hardness, toughness, and heat resistance were the same as in Example 1.

Example 5 As a sintering aid, Mg (H₂
PO_Four)₂・ 2H₂O was used. When the average particle size is 15 μm
Body made of synthetic diamond powder and graphite powder with an average particle size of 10 μm
It was mixed at a mixing ratio of 3: 2 and was pressed and molded to a thickness of 2 mm.
Noto, Mg (H₂PO_Four)₂・ 2H₂O powder 1 thickness
mm embossed and laminated alternately
Put in a bag and use a belt type ultra high pressure high temperature generator,
Hold for 15 minutes under pressure and temperature conditions of 6.5GPa and 1650 ℃
Hold and sinter. About the obtained diamond sintered body
The composition was identified by X-ray diffraction.
Other than Mg, about 3% by volume of Mg₂P _FourO₁₂Was detected. This
When the hardness of the sintered body was evaluated by Knoop indenter, it was about 8
500 kg / mm²And had high hardness. Also, fracture toughness
The conventional commercial Co-vine by the indentation method.
Compared to the sintered body,
The relative toughness was 1.3 times. In addition, the obtained sintered body
Measure hardness and toughness after heat treatment at 1000 ℃ in vacuum
However, there was almost no change from before treatment.

Example 6 CaHPO ₄ as a sintering aid
Was used. Thickness of high-purity isotropic graphite with an average particle size of 3 μm 2
mm plate sintered body and CaHPO ₄ powder with a thickness of 1 mm
5. The mold-pressed products are alternately laminated and placed in a Mo capsule, and a girdle-type ultra-high pressure and high temperature generator is used.
The pressure and temperature conditions of 5 GPa and 1750 ° C. were maintained 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 CaPO ₄ was detected in addition to diamond. The hardness of this sintered body was evaluated by a Knoop indenter to be about 850.
The hardness was as high as 0 kg / mm ² . 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 3 times. The hardness and toughness of the obtained sintered body were measured at 1000 ° C. in vacuum, and the hardness and toughness were measured.

Comparative Example 1 An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1 except that NaPO ₃ powder was used as a sintering aid. However, a diamond sintered body having sufficient sinterability was not obtained.

(Comparative Example 2) An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1 except that NaPO ₃ powder was used as a sintering aid and the sintering temperature was 7.5 GPa and 2000 ° C. It was A diamond sintered body was obtained, but the hardness was 7
It was slightly lower than 500, and the toughness was comparable to that of the conventional Co binder sintered body.

(Comparative Example 3) MgHPO ₄ as a sintering aid
· Using 3H ₂ O. Similar to Example 1, except that a small amount of MgHPO ₄ .3H ₂ O powder (about 0.05% by volume) was added to a synthetic diamond powder having an average particle size of 3.5 μm, and the mixture was used as a raw material. An attempt was made to manufacture a diamond sintered body. However, many unsintered parts remained in the obtained sintered body.

(Comparative Example 4) MgHPO ₄ as a sintering aid
· Using 3H ₂ O. 60% by volume of synthetic diamond powder having an average particle diameter of 3.5 μm and 40% by volume of MgHPO ₄ .3H ₂ O powder were added and sufficiently mixed, and the mixture was used as a raw material, and diamond-baked as in Example 1. Attempted to produce a body. However, in the obtained sintered body, the particles were not sufficiently bonded to each other, and the hardness was low at about 4000 kg / mm ² .

[0020]

As described above, since the diamond sintered body of the present invention has unprecedented heat resistance and chipping resistance, it is possible to cut nonferrous metals and ceramics, materials for grinding tools, and oil drilling. It can be effectively used as a cutting edge material for drill bits for various purposes. Moreover, since it can be sintered at a relatively low pressure and a low temperature, it has a great economic effect.

Claims (5)

[Claims] 1. A diamond sintered body characterized by containing 0.1 to 30% by volume of a substance consisting of a compound containing an alkali metal or an alkaline earth metal and phosphorus and the balance being diamond. 2. A hydrous phosphate of an alkali metal or an alkaline earth metal 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,
The method for producing a diamond sintered body according to claim 1, characterized in that the diamond sintered body is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered. 3. A hydrous phosphate of an alkali metal or an alkaline earth metal is used as a sintering aid, and a compact of this powder, a compact of diamond powder or a compact of non-diamond carbon powder or diamond and non-diamond. 2. The production of a diamond sintered body according to claim 1, wherein a compact of a mixed powder of carbon is laminated, and this is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered. Method. 4. The method for producing a diamond sintered body according to claim 2, wherein the sintering aid is hydrogen phosphate of an alkali metal or an alkaline earth metal. 5. The method for producing a diamond sintered body according to claim 2, wherein the sintering aid is a hydrate of a hydrogen phosphate of an alkali metal or an alkaline earth metal.