JPH1135374A - Sintered compact for drilling bit and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the diamond sintered compact which is used for a drilling bit and has high strength and also is excellent in fracture resistance, heat resistance, acid resistance and wear resistance, under industrially-producible conditions and at a low cost by using an oxide or double oxide of an iron group metal(s) as a sintering aid for the sintered compact. SOLUTION: This sintered compact comprises 1 to 20 vol.% of a material consisting of a compound that contains an iron group metal(s) and oxygen, and the remainder of a diamond powder having a 20 to 200 μm average particle size. As the compound contg. an iron group metal(s) and oxygen, an oxide of an iron group metal or a double oxide or solid solution of iron group metals, such as FeO, CoO or CoFe2 O4 , is used. This production of the diamond sintered compact for a drilling bit comprises: mixing a powdery oxide or double oxide of an iron group metal(s) with a diamond powder having a 20 to 200μm average particle size or a powdery mixture of this diamond powder and non-diamond carbon to obtain a mixed powder; and maintaining the resulting mixed powder under pressure and temp. conditions within the thermodynamically stable region of diamond to sinter the mixed powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a sintered body for a drill bit, and more particularly to a diamond sintered body used as a cutting edge material of a drill bit for oil drilling or the like. The present invention also relates to a method for manufacturing such a sintered body for a drill bit.

[0002]

2. Description of the Related Art Conventional diamond sintered bodies for drill bits include Co, Ni, and sintering aids or binders.
Those using an iron group metal for Fe or the like and those using ceramics such as SiC are known and used industrially.

Also, a diamond sintered body using a carbonate as a sintering aid has been known (Japanese Patent Laid-Open Publication No.
No. 74766, JP-A-4-114966)
However, it is not currently used as a drill bit.

[0004] In addition, there is a natural diamond sintered body (carbonado), but it is not widely used as a drill bit because of a large variation in the material and an extremely small output.

[0005]

A diamond sintered body using an iron group metal such as Co as a sintering aid has a low heat resistance because the iron group metal such as Co acts as a catalyst for promoting the graphitization of diamond. Inferior. That is, it is graphitized at about 700 ° C. in an inert gas atmosphere. Further, since a metal such as Co exists as a continuous layer at the grain boundaries of diamond grains, the strength of the sintered body is not very high. Furthermore, thermal degradation is likely to occur due to the difference in thermal expansion between the metal and diamond. For this reason, when such a diamond sintered body is used as a drill bit, there is a problem that the cutting edge is easily damaged or worn.

It is also known that the above-mentioned metal at the grain boundary is removed by an acid treatment in order to increase heat resistance. As a result, the heat-resistant temperature is improved to about 1200 ° C., but the strength is further greatly reduced (about 30%) because the sintered body becomes porous.

[0007] A diamond sintered body using SiC as a binder is excellent in heat resistance, but has low strength because there is no bonding between diamond grains.

On the other hand, a diamond sintered body using a carbonate as a sintering aid has better heat resistance than a sintered body using a Co binder, but decomposition of the carbonate starts at about 1000 ° C. The strength of the unit is reduced. Also, the carbonate is soluble in the acid, which causes a problem in the use of the drill bit. In this case, 7.7 GP is required to manufacture the diamond sintered body.
a. Since extremely severe pressure and temperature conditions of 2000 ° C. or more are required, the cost is considerably increased, and industrial production is difficult.

The present invention has been made to solve the above problems, and has high strength, excellent fracture resistance and heat resistance.
An object of the present invention is to provide a drilled diamond sintered body having acid resistance and wear resistance.

Another object of the present invention is to provide a method for producing such a diamond sintered compact for excavation at a low cost under conditions capable of industrial production.

[0011]

The sintered body for a drill bit according to the present invention contains 1 to 20% by volume of a substance composed of a compound containing an iron group metal and oxygen, and the remainder has an average particle diameter of 20 μm.
It is made of diamond having a size of 200 μm or more.

In the sintered compact for a drill bit according to the present invention, the compound containing an iron group metal and oxygen is an oxide, a double oxide or a solid solution of an iron group metal.

According to a third aspect of the present invention, there is provided a method for manufacturing a sintered body for a drill bit, wherein an oxide or a double oxide of an iron group metal is used as a sintering aid.
m or less, or an average particle diameter of 20 μm
It is characterized in that a mixed powder of diamond and non-diamond carbon having a diameter of 200 μm or less is mixed, and the mixed powder is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a sintered body for a drill bit, wherein an oxide or a double oxide of an iron group metal is used as a sintering aid. The following compact of diamond powder or a compact of mixed powder of diamond and non-diamond carbon having an average particle diameter of 20 μm or more and 200 μm or less is laminated, and this is held under the pressure and temperature conditions of the thermodynamically stable region of diamond. And sintering.

According to a fifth aspect of the present invention, there is provided a method for manufacturing a sintered body for a drill bit, wherein an oxide or a double oxide of an iron group metal is formed on the surface of diamond powder having an average particle diameter of 20 μm or more and 200 μm or less. It is characterized by holding and sintering under the pressure and temperature conditions of the thermodynamic stability region.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has not been known that oxides or double oxides of iron group metals are effective sintering aids for sintered diamond. By using the oxides and double oxides as sintering aids, the present inventors have obtained a diamond sintered body having an unprecedented high strength, and excellent fracture resistance, heat resistance, and corrosion resistance. The present invention was newly found to be obtained under lower pressure and temperature conditions than in the case where a conventional nonmetallic catalyst was used as a sintering aid, and to be effective as a drill bit, leading to the present invention.

That is, the feature of the present invention is that an oxide of iron group metal (FeO, F
Using e ₂ O _3, CoO, etc.) or a composite oxide (such as CoFe ₂ O _4), lies in using the following diamond 200μm average particle size 20μm or more in the raw material.

These iron group metal oxides and double oxides are:
It exhibits a strong catalytic action on diamond, and when these are used as sintering aids, a matrix is formed in which diamond particles are very strongly bonded.

Further, the catalytic action of these oxides and double oxides occurs at a temperature lower by about 600 ° C. than that of the carbonate catalyst. Therefore, when these complex oxides and mixtures are used as sintering aids, the above-mentioned strong sintered body can be obtained under mild conditions such as 6 GPa and 1500 ° C.

[0020] That is, a diamond sintered body having an unprecedented high strength and excellent fracture resistance can be obtained under conditions that facilitate industrial production.

The diamond sintered body thus obtained is
It is characterized by containing a substance consisting of a compound containing an iron group metal and oxygen.
Examples include iron group metal oxides such as eO, Fe ₂ O ₃ , CoO, and Co ₃ O ₄ , and multiple oxides such as CoFe ₂ O ₄ .
Such a substance is stable even at a high temperature of about 1000 ° C. Therefore, the diamond sintered body of the present invention has high strength and excellent fracture resistance, and also exhibits excellent heat resistance, and is very effective as a drill bit application.

In the diamond sintered body of the present invention, the content of a substance comprising a compound containing an iron group metal and oxygen is preferably 1 to 20% by volume. This is because the bondability, that is, the sinterability is reduced, and when the content exceeds 20% by volume, the strength and the fracture resistance are reduced due to the influence of the excess compound.

As a raw material, the average particle size is 20 to 200 μm.
Synthetic diamond powder, natural diamond powder, polycrystalline diamond powder and the like. Average particle size is 20μm
If it is smaller, the impact resistance and fracture toughness of the sintered body will be low, and if it exceeds 200 μm, the wear resistance will be reduced, and neither can be used as a drill bit. In some cases, in order to reduce voids in the diamond particles, 2
A small amount of fine diamond particles of 0 μm or less may be added, but the average particle diameter of the whole needs to be 20 μm or more.

Further, the formability,
In order to improve sinterability, an appropriate amount of non-diamond such as graphite, glassy carbon, and pyrolytic graphite may be added.

The method for producing a diamond sintered body of the present invention comprises the steps of: preparing a diamond powder including a diamond powder and a non-diamond powder;
A method in which diamond is held under thermodynamically stable pressure and temperature conditions, a compact of diamond powder containing diamond powder and non-diamond graphite, and a compact of oxides and complex oxides of iron group metals There is a method in which the raw material is kept under the above pressure and temperature conditions.

Further, when an oxide or double oxide of an iron group metal is previously formed on the surface of the raw material diamond powder and this is sintered under the above pressure and temperature conditions, a more homogeneous sintered body is obtained. Can be

[0027]

Example 1 FeO having a particle size of 1 μm was used as a sintering aid. Particle size 20
４０40 μm (average particle size: 30 μm) of natural diamond powder and FeO powder are sufficiently mixed at a ratio of 90% by volume and 10% by volume, respectively, and the mixture is placed in a Mo capsule. 6.5G
Pa, maintained at a pressure of 1650 ° C. and temperature conditions for 15 minutes,
Sintered. For the obtained diamond sintered body, X
When the composition was identified by line diffraction, about 10% by volume of iron oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated using a Knoop indenter,
The hardness was as high as Kg / mm ² . Further, when the fracture toughness was relatively compared with a conventional commercially available Co binder sintered body by the indentation method, it was found that the conventional sintered body had a fracture toughness of about 1.5%.
Double relative toughness. Further, after the obtained sintered body was subjected to heat treatment in vacuum at 1000 ° C., the hardness and toughness were measured. When a cutting tool was prepared from the obtained sintered body and the wear resistance was evaluated by cutting the granite, the wear resistance of the sintered body was 10 times that of the conventional sintered body for a drilling bit of a Co binder. That was all.

Example 2 A diamond sintered body was produced in the same manner as in Example 1 except that Fe ₂ O ₃ was used as a sintering aid. The obtained sintered body contained iron oxide, and the hardness, toughness, heat resistance, and abrasion resistance were the same as those in Example 1.

Example 3 As a sintering aid, CoO and Fe ₂ O ₃ were mixed at a molar ratio of 1: 1.
A diamond sintered body was produced in the same manner as in Example 1 except that the mixture obtained in (1) was used as a sintered body assistant. The obtained sintered body contained a double oxide of cobalt and iron, and the hardness, toughness, heat resistance, and wear resistance were the same as in Example 1.

Example 4 A diamond sintered body was produced in the same manner as in Example 1, except that CoO was used as a sintering aid. The obtained sintered body contained an oxide of cobalt, and the hardness, toughness, heat resistance, and abrasion resistance were the same as in Example 1.

Example 5 FeO having a particle size of 1 μm was used as a sintering aid. Particle size 4
Synthetic diamond powder of 0 to 80 μm and FeO powder molded into a thickness of 2 mm and 1 mm, respectively, are alternately laminated, placed in Mo capsules, and heated to 6.5 GPa, 1600 using a belt type ultra-high pressure and high temperature generator. It was kept at a pressure and temperature of 15 ° C. for 15 minutes and sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 2% by volume of iron oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated using a Knoop indenter, it was as high as about 7100 kg / mm ² . Further, when the fracture toughness was compared with a conventional commercially available Co binder sintered body by an indentation method, the relative toughness was about 1.5 times that of the conventional sintered body. Further, after heating the obtained sintered body to 1000 ° C. in a vacuum,
The hardness and toughness were measured, but hardly changed from those before the treatment.

Example 6 A diamond sintered body was produced in the same manner as in Example 5, except that CoFe ₂ O ₄ was used as a sintering aid. The obtained sintered body contained a double oxide of cobalt and iron, and the hardness, toughness, heat resistance, and wear resistance were the same as in Example 5.

Example 7 The surface of a diamond powder having a particle size of 20 to 40 μm was coated with about 1
0% by volume of FeO was coated in a Mo capsule, and the resultant was coated with a belt-type ultra-high pressure and high temperature generator.
The sample was held at GPa, a pressure of 1550 ° C. and a temperature condition for 15 minutes, and sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 10% by volume of iron oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated using a Knoop indenter, it was found to be about 7
The hardness was as high as 500 kg / mm ² . Further, when the fracture toughness was compared with a conventional commercially available Co binder sintered body by an indentation method, the relative toughness was about 1.5 times that of the conventional sintered body. Further, after the obtained sintered body was subjected to heat treatment in vacuum at 1000 ° C., the hardness and toughness were measured. Also,
When a cutting tool is manufactured from the obtained sintered body and the wear resistance is evaluated by cutting the granite, the wear resistance of the sintered body is at least 10 times that of the conventional sintered body for the drill bit of the Co binder. Met.

Comparative Example 1 FeO was used as a sintering aid. Particle size 20-40 μm
Production of a diamond sintered body was attempted in the same manner as in Example 1 except that a small amount of the powder of the above-mentioned mixture (about 0.1% by volume) was added to the synthetic diamond powder of Example 1 and the mixture was used as a raw material. Was. However, many unsintered portions remained in the obtained sintered body.

Comparative Example 2 FeO was used as a sintering aid. Particle size 40-80 μm
Production of a diamond sintered body was attempted in the same manner as in Example 1, except that 60% by volume of the synthetic diamond powder and 30% by volume of the powder of the above mixture were added and used as a raw material. However, in the obtained sintered body, the bonding between the particles was not sufficient, and the hardness was as low as about 3300 Kg / mm ² .

Comparative Example 3 FeO was used as a sintering aid. 95 volume% of synthetic diamond powder having an average particle size of 3 μm and powder 5 of the above mixture
An attempt was made to produce a diamond sintered body in the same manner as in Example 1, except that the raw material was a mixture obtained by adding volume% and sufficiently mixing. However, the obtained sintered body has a fracture toughness value of conventional C
o No significant improvement was observed, comparable to that of the binder.

Comparative Example 4 Y ₃ Fe ₅ O ₁₂ was used as a sintering aid. Average particle size 2
Production of a diamond sintered body was attempted in the same manner as in Example 1, except that 95% by volume of 70 μm synthetic diamond powder and 5% by volume of the powder of the above mixture were added and used as a raw material. However, when a cutting tool was prepared from the obtained sintered body and the wear resistance was evaluated by cutting granite, the wear resistance of this sintered body was comparable to that of a conventional sintered body for a drill bit made of a Co binder. It was about several times, and no significant improvement was seen.

[0038]

As described above, the diamond sintered body of the present invention has unprecedented high strength, heat resistance, chipping resistance, and wear resistance. This has the effect that it can be used effectively.

Claims (5)

[Claims] 1. A composition comprising 1 to 20% by volume of a substance comprising a compound containing an iron group metal and oxygen, and the balance having an average particle size of 20 μm.
A sintered body for a drill bit made of diamond having a diameter of 200 μm or less. 2. The compound containing an iron group metal and oxygen is an oxide, a double oxide or a solid solution of an iron group metal,
The sintered body for a drill bit according to claim 1. 3. An oxide or double oxide of an iron group metal is used as a sintering aid, and the powder is mixed with an average particle size of 20 μm or more.
Diamond powder of 00 μm or less or average particle size 2
A sintered body for a drill bit, comprising mixing a mixed powder of diamond and non-diamond carbon having a diameter of 0 μm or more and 200 μm or less, holding the mixture under the pressure and temperature conditions in the thermodynamically stable region of diamond, and sintering. Manufacturing method. 4. An oxide or a double oxide of an iron group metal is used as a sintering aid.
A molded body of diamond powder having a diameter of not less than m and not more than 200 μm or a molded article of a mixed powder of diamond and non-diamond carbon having an average particle diameter of not less than 20 μm and not more than 200 μm is laminated, and this is subjected to pressure and temperature conditions in the thermodynamically stable region of diamond. A method for producing a sintered body for a drill bit, wherein the method comprises holding and sintering. 5. An oxide or double oxide of an iron group metal is formed on the surface of diamond powder having an average particle diameter of not less than 20 μm and not more than 200 μm, and this is maintained under pressure and temperature conditions in a thermodynamically stable region of diamond. A method for producing a sintered body for a drill bit, comprising sintering.