JPH0230668A - Sintered material of diamond consisting of ultrafine particle and production thereof - Google Patents

Abstract

PURPOSE:To improve toughness by sealing specific polycrystalline diamond powder of raw material for sintering in a metallic capsule, generating high pressure and high temperature under a specific condition and sintering. CONSTITUTION:Polycrystalline diamond powder 2 of raw material for sintering having 10-100nm diameter of primary particles, 100nm-1mum minimum diameter of secondary particles and 100nm-10mum maximum particle of secondary particles is packed into a metallic capsule 1, a cover 3 is screwed into the capsule, the capsule is evacuated through a hole 4 and the hole 4 is sealed. Then the capsule 1 is packed into a momentum trap consisting of a combination of a storage part 5 of test specimen, a ring 6 and a disc 7, embedded in clay 9, a plane wave generator 17 is placed through a steel plate 14 and an explosive compound 15 on the trap. Then the explosive compound 15 is exploded through a detonator 18, the shot metallic plate or bullet is collided at more than 1.8kg/second velocity when calculated as a collision condition between stainless steels SUS 304, high pressure and high temperature are generated, the diamond is sintered, the polycrystalline diamond powder is directly bonded to give sintered material of diamond having >=90% density free from orientation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a high-hardness diamond sintered product obtained by sintering powdered diamond, including inclusions, by ultra-high pressure and high temperature generated by impact. body and its manufacturing method.

[Prior Art] Conventionally, two main types of manufacturing methods have been known for producing sintered bodies containing diamond. One is diamond powder with Co and Nt.
It is a diamond sintered body that is created by adding metals such as metals, generating static ultra-high pressure by pressing, and simultaneously generating high temperature with a heater and sintering it with metal intervening. When using a sintered body as a cutting tool, it is known that there is a limit to its performance because the metal is weaker than diamond. Another method is to enclose diamond powder without any additives in a metal capsule, and either directly transmit the ultra-high pressure generated by the explosion of explosives from the outside, or to receive the ultra-high pressure generated by the explosion of explosives. By colliding metal plates flying at high speed,
A method of compression molding diamond powder and sintering it without inclusions was known. For example, eight kashi and sawao
ka is Journal of Material 5c
ience (Materials Science Journal: Japanese translation of the magazine name) Volume 22 32
76 Shin (1987), single-crystal diamond powder with two particle size ranges of 2-4 μm and 10-20 μm was
They reported that they applied a GPa impact and obtained relative densities of 88.5% and 91.0% of the true density of diamond. In addition, Kitihichi, Kuninaka, Aomai, and Fujiwara wrote 5-7 μm, 0.5-1
It is said that a sintered body was obtained by applying impact pressure to samples with three particle size distributions of μm, O-0, and 5μm, but the hardness value and other properties of the sintered body have not been reported. It is reported that there are many variations in hardness, and in many cases it is not possible to measure indentations, and that gelaphalite formation of diamond was particularly noticeable in diamonds with a particle size range of 0.065 μm.

[Problems to be Solved by the Invention] In the case of the above-mentioned "prior art" method, if diamond particles of 500 nm or less are present, they will graphitize due to the high temperature that is generated at the same time as applying ultra-high pressure, and diamond sintering will occur. The high hardness peculiar to the body cannot be obtained, and the
Sintering must be carried out using only diamond particles of this size, and it was considered appropriate to use particles of several micrometers or more.

When particles of 500 nm or more are used as a sintering raw material, the above problems due to graphitization are less likely to occur, but generally three problems occur.

First, when large diamond particles are used as a raw material, the voids between the particles naturally become large. Therefore, in order to firmly bond the particles, it is necessary to give the diamond particles a large amount of deformation to fill the large voids. In principle, bonding can be achieved by overcoming the high hardness of diamond particles and therefore their high deformation resistance, by applying high pressure to bring the particles into close contact with each other, and by utilizing the high temperature that is generated at the same time, but as is well known, Diamond is a brittle material, and when subjected to impact treatment, it is inevitable that cracks will develop through the diamond particles. On the other hand, even if cracks occur, it can be expected that they will be rejoined by high pressure and high temperature, but it is unlikely that all the cracks will be rejoined.
It remains as a crack and has the effect of lowering the strength of the sintered body.

The second problem is caused by applying high pressure to solve the first problem. That is,
By applying high pressure, the aggregate of diamond particles is strongly compressed and the temperature increases adiabatically. However, the higher the pressure is applied, the higher the temperature becomes, reaching an undesirable high temperature, resulting in the formation of graphite. There is a great possibility that increasing the particle size in order to avoid oxidation may have the opposite effect and promote graphitization, making it impossible to maintain the required hardness of the sintered body.

The third problem occurs when a sintered body is produced by solving the above problem. It is a well-known fact that diamond has interfold planes in the (111) plane. That is, (1
11) By applying stress parallel to the plane, diamond easily cracks along that plane. Therefore, when a single crystal diamond, whether natural or synthetic, is used as it is in a tool, care must be taken so that the main stress is not applied in the direction parallel to the (111) plane. However, no matter how careful you are, when used as a tool, it is natural that stress will be applied in each direction, and the destruction of a single-crystal diamond tool due to creases is considered to be a so-called fate. To avoid this, a large number of particles are randomly arranged and sintered to create a strong, integrated sintered body that is used in tools, but when looking at the fine structure of sintered diamond, The individual particles are single crystals and each still exhibits interfold nature. Therefore, when used as a tool for cutting, wire drawing, excavation, etc., concentrated and impactive stress is applied locally, and the strength of individual particles becomes a problem, resulting in the formation of crystal lattices where interfolds appear. When stress is applied to a particle at an angle close to the (111) plane, the particle is easily damaged and broken, and in some cases, cracks propagate to adjacent diamond particles one after another, accelerating the wear and tear of the sintered body. In short, even if the sintered body is sintered in a random direction, microscopically it is a collection of single crystals.
The problem is that these shortcomings remain and have not been resolved.

[Means to solve the problem]

The inventors conducted many theoretical and experimental studies to solve the problem mentioned above, and arrived at the present invention.

First, consider each of the three problems mentioned in the previous section individually and consider countermeasures.

(1) The voids become larger due to the use of larger particles,
As a result, it is necessary to apply a strong impact, which can cause cracks to occur. Basically, we can reduce the diameter of the diamond particles used as raw materials and use diamond particles that are less likely to cause cracks. It is manageable.

(2) According to the previous item, by not using large particles, there is no need to apply a strong impact, and sintering can be performed by applying a weaker impact. Graphitization, which is harmful to maintenance, no longer occurs. Of course, if too fine particles are used, harmful graphitization will occur due to the selective high temperature of the entire particle during sintering, making it impossible to obtain the necessary hardness, but as described in the previous section, By using particles graphitization can be kept to a minimum. Moreover, various experiments have shown that in order to minimize the cracks that penetrate through the diamond particles, it is of course no different from a sintered body made by conventional technology, so the measures described in the next section are necessary.

(3) Based on the above 2, it cannot be said that it is possible to minimize harmful graphitization and create a sintered body that can be used as a tool material even with conventional technology if impact strength is carefully examined. That's what I found out. However, they cannot solve the problem caused by the fact that individual diamond particles retain their single-crystal properties even after becoming a sintered body.

The conclusion is that this problem is unavoidable as long as single crystal diamond particles are used. Therefore, the inventors believe that diamonds synthesized by the ultra-high pressure associated with the explosion of explosives, or the impact ultra-high pressure generated when a metal plate or bullet fired by a gunpowder gun, two-stage light gas gun, or electric method collide. By focusing on the fact that diamond (hereinafter referred to as impact synthetic diamond) is polycrystalline and using it as a sintering raw material, we solved the problems that occur when single-crystal diamond particles are sintered, and in effect sintered diamond particles. Because there is no crystal orientation within the body, there is no interfolding characteristic of single-crystal diamonds, whether natural or synthetic, and the wear resistance is far superior to that of conventional sintered diamonds. It has been discovered that a diamond sintered body having good properties and impact resistance can be obtained. The fact that impact-synthesized diamond is polycrystalline means that many single-crystal particles (referred to as secondary particles) whose individual dimensions are extremely fine come together to form a single particle (referred to as secondary particles). It means that there is. The size of the primary particles is from 10nm to 1100n,
It is known that the size of secondary particles ranges from several tens of micrometers to several 1.00 μm. When secondary particles formed by aggregation of primary particles with a size of 1100n or less are sintered with virtually no inclusions, the sintered body is made up of single crystals of 1100n or less arranged randomly and integrated. becomes 110
In the case of extremely fine single crystals of 0n or less, interfoldability is not a problem at all. Therefore, when a sintered body is made from impact-synthesized diamond as a raw material, an ideal diamond with no directionality and of uniform quality can be obtained. Furthermore, a diamond sintered body produced by impact sintering using conventional single crystal diamond has a particle size of 500 nm in raw diamond powder.
In contrast, a diamond sintered body produced by impact sintering using the impact-synthesized diamond according to the present invention as a sintering raw material has a particle size that is smaller than that of the impact-synthesized diamond. Even if it is less than 500 nm, 1
It has been found that a sintered body with sufficiently excellent performance can be obtained if the thickness is 100 n or more. At that time, if 1% or more of diamond particles less than 1100n are included, they will preferentially graphitize during impact loading or due to the high temperature that remains even when the pressure drops to near normal pressure, resulting in the formation of a diamond sintered body. It was found to reduce hardness. Incidentally, the particle size or particle diameter as used in the present invention refers to the average size of the largest and smallest portions of the particles.

In addition, the polycrystalline diamond sintered body made of ultrafine particles according to the present invention contains a very small amount of graphite that is converted from diamond by high temperature, but this is due to the protruding part on the surface of the amorphous impact-synthesized diamond. It is thought that this was caused by local exposure to high temperatures in the diamond unstable region. Originally, graphite was considered to be soft enough to be used as a solid lubricant, and its presence in diamond sintered bodies, which require high hardness and high strength, was undesirable.

However, in the case of the diamond sintered compact according to the present invention, which has a very fine structure, it has better performance than the conventional commercially available diamond sintered compact produced by static ultra-high pressure, as long as the amount described later is present. This is considered to be a characteristic of the diamond sintered body according to the present invention, rather than being a problem.

〔Effect of the invention〕

The sintered body according to the present invention is sintered by impact using impact-synthesized diamond as a sintering raw material, and the entire sintered body is composed of extremely fine polycrystalline diamond, so it has extremely high toughness. In the body, cutting tools,
Traditional diamond tool materials, natural and synthetic single crystal diamond, are used as dies, drilling tools, and wear-resistant materials.
This is a completely new and excellent sintered body made from single-crystal diamond, which virtually does not have the interfold nature of crystalline diamond.

〔Example〕

Next, the present invention will be explained by examples.

Use a sample container as shown in the cross-sectional view in Figure 1, with an outer diameter of 25+n.
Explosion impact inside the capsule part 1, which is made of 5US304 stainless steel and has a cylindrical shape with a height of 30 m and a sample chamber of 121 mm in diameter and 27 mm in depth. Synthesized by
Filled with sintered raw material diamond 2 in the range of m, the same < 5 made of US304 steel, height 22 mm, diameter 12n + n
+, the lid 3 having a male thread over a length of 10 mm at one end of the side surface was tightened using the screw groove. A vacuum hole 4 with a diameter of 1 mm was pre-drilled in the lid 3, and after enclosing diamond, it was held at 400 degrees for 4 hours in a 10-' torr vacuum furnace to remove the adsorbed oxygen. . After completing the oxygen removal work, the vacuum hole was sealed with silver solder in a vacuum to maintain the internal vacuum.

The amount of encapsulated diamond was 1.18 g, and the bulk specific gravity was 2.08 g/cm', which corresponds to about 59.4% of the true specific gravity of diamond.

In the same way, a total of four capsules were prepared, and a circular plate with a diameter of 80 mm and a thickness of 301 cm, called a momentum trap made of 5S41 steel, as shown in the cross-sectional view of FIG.
A sample storage part 5 has four holes perpendicular to a plane with a diameter of 25 mm arranged at equal intervals on a concentric circle of +u+, and an outer diameter of 1201II.
11. A combination of a ring 6 with an inner diameter of 80 mm and a thickness of 30 mm and a disc 7 with a diameter of 1201 wl11 and a thickness of 30 mm, and a capsule is packed into a hole with a diameter of 25 mm with M3 of the capsule positioned at the bottom. , total depth 120
The specimen was embedded in clay 9 filled in a lidless polypropylene container 8 with a diameter of 200 mm, with the sample storage section 5 facing upward. Next, a wooden board 12 is passed over a steel tank 11 filled with water 10 in an explosion silencer, and a structure 13 made of the sample is placed in the center of the tank.
Furthermore, 14 5S41 steel plates with a thickness of 3.2 mm and a square of 150 mm
Specific gravity 1.64g/cm' in the center of the explosion velocity 9.00
0 m/sec explosive 15 with a thickness of 30 m and a diameter of 120 m
Place a disc shape of 30 mm in height, 30 mm in width, and 15 mm in thickness at the four corners of the steel plate 14 so that the bottom surface of the steel plate 14 and the top surface of the structure 13 are parallel and the distance is 30 mm.
16 mm pieces of wood were arranged and placed. Further, a plane wave generator 17 was placed on the top of the explosive, and a No. 6 electric detonator 18 was attached to it and energized to detonate the explosive 15 with a detonation wave front parallel to the plane of the rope plate 14. Due to the explosion, the steel plate 14 on the lower surface of the explosive 15 was blown downward at high speed and collided with the upper surface of configuration I3 in parallel at a speed of 2.8 km/sec. At that time, we calculated the pressure generated on the collision surface between the steel plate 14 and the SO3304 stainless steel on the surface of the structure 13. 1.8GPa (
(approximately 730,000 atm).

The component 3 that the steel plate collided with is the water 1 filled in tank II.
0 and was recovered from the bottom of tank 11.

Of structure 13, the sample storage section 5 and ring 6 were broken into pieces, but the capsule 1 was recovered with the lid 3 still attached and in almost its original shape, although some deformation was observed.

The opposite end of the lid 3 of the recovered capsule 1 was cut with a cutting tool using a lathe until the surface of the filled diamond was exposed, and the diamond was found to be a sintered body that was firmly bonded throughout.

The surface of the obtained diamond sintered body was polished with a diamond paste having a particle size range of 5 to 10 μm to make it smooth enough to perform a micro Vickers hardness test, and then the micro Vickers hardness was measured under a load of 1 kgf. Average of 4.680 kgf/m on the shock wave incident side
m” (n = 12), average 5.990 on the opposite side
kgf/mm” (n = 12) was obtained.

When the density of the crystal obtained by the Archimedes method was measured, it was found to be 3.22 g/cmff, which is 91.7% of the true density of diamond, which is 3.51 g/cm3.

When the surface of the diamond sintered body was examined by an X-ray diffraction test, the presence of a small amount of graphite was observed over a wide range of diffraction angles on both the upper and lower surfaces of the disk.

A sintered body with a diameter of 12 mm and a thickness of about 3.5 cm was cut crosswise with a laser to make a fan-shaped chip with a tip of about 5.8 m and an apex angle of 90'', and a length of 12.7 mm square. 150am
A diamond sintered body was wrapped and attached to the long end of the steel handle with silver wax, and it was used as a cutting tool for cutting tests.

For the target test, a similar cutting tool was created using a commercially available diamond sintered body containing Go by static ultra-high pressure sintering.

On the other hand, W(J]92 wt,% and CoFA8 wt,%
The mixture was mixed and shaped, and then fired at 900°C for 1 hour to obtain a calcined body. A cylinder with a diameter of 100 mm and a length of about 250 m was cut using a cutting tool equipped with a diamond sintered body according to the present invention. The cutting conditions were a peripheral speed of 55 to 30 m/min, depth of cut of 0.3 to 0, 5 order, and feed of 0.2 cylinders/rev.

As a result, the sharpness decreased slightly after a total of 1 hour and 48 minutes of cutting, so the test was terminated. When the cutting edge of the sintered body was examined using a stereomicroscope with a magnification of 20 times, it was found that the tip was o, due to wear.
IA circle was retreating.

Next, a similar cutting test was carried out using a commercially available static ultra-high pressure sintered C.
The test was carried out using a cutting tool equipped with a diamond sintered body containing o. As a result, the cutting edge broke 13 minutes after the start of cutting, making it impossible to carry out subsequent cutting tests.

The experiment of Example 1 was repeated. However, the filled diamond was synthesized using a molten catalyst under static ultra-high pressure.The individual diamond particles were single crystal. In addition, the particle size of diamond is such that more than 99% of all particles are 2
The particle size was within the range of 50nm to 50On111, and 1.18g could be filled into a capsule of the same size as in Example 1. In this case, the bulk specific gravity is 2.08 g/cm',
This corresponds to approximately 59.4% of the true specific gravity of diamond.

The recovered capsule was cut in the same manner as in Example 1, and the diamond portion was exposed. At first glance, the diamond appeared to be strongly sintered.

When the micro Vickers hardness was measured in the same manner as in Example 1, the average hardness was 3.710 kg on the shock wave incident side.
f/1m” (n = 12), average 4 on the opposite side,
A value of 920 kgf/mm'' (n = 12) was obtained.

In addition, when the surface of the diamond sintered body was examined by an X-ray diffraction test, peaks indicating the diffraction of the (002) plane of graphite were observed over a wide diffraction angle on both the upper and lower surfaces of the disk, suggesting the presence of a small amount of graphite. However, the value obtained by dividing the height of the diffraction peak by the height of the (111) peak of diamond was 0.03 in Example 1, whereas it was 0.
．． 18, indicating a higher degree of graphitization. This is also considered to be the reason why the micropinkers hardness was lower than that of Example 1.

Next, a diamond sintered cutting test tool was manufactured in the same manner as in Example 1, and a similar cutting test was conducted. As a result, the tip of the cutting tool broke 8 minutes after the start of cutting, and was inferior to a commercially available diamond sintered body produced by static ultra-high pressure sintering.

The experiment of Example 1 was repeated once again. However, various combinations were made and tested regarding the particle size and type of diamond used and the speed at which the steel plate collided with the surface of the capsule containing the sample diamond. The conditions and results are shown in Table 1. The filling rate in the table refers to the true specific gravity of diamond of 3.
Assuming 515 g/cm3, the value divided by the bulk specific gravity when filled with diamond particles is expressed as a percentage. Moreover, the generated pressure is a pressure value generated at the collision surface between the steel plate and the stainless steel capsule.

table

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a capsule that stores a sample, and FIG. 2 is a sectional view of a momentum trap and a recovery container for shock-treating and recovering the sample. 1... Capsule 2... Sintering raw material 3...
Capsule lid 4... Hole for vacuuming... Sample storage section 6... Ring 7... Disc
8... Polypropylene container 9... Clay
10...Water 11...Preparation tank 1
2... Wooden board 13... Composition consisting of samples etc. 14... Steel plate 15... Explosives 16...
・Wood piece 17...Plane wave generator 18・
・Electric detonator diagram 2

Claims (5)

[Claims] 1. Polycrystalline diamond powder with a primary particle diameter of 100 nm to 10 nm, a secondary particle diameter of the smallest particle of 100 nm to 1 μm, and a maximum diameter of 500 nm to 10 μm is produced directly without the intervention of other substances except for inevitable impurities. A diamond sintered body that is bonded together and is substantially integrated and has no orientation. 2. In the diamond sintered body defined in claim 1,
A diamond sintered body characterized in that its density is 90% or more. 3. The diamond sintered body according to claim 1 or 2, characterized in that the diamond contains a trace amount of graphite. 4. In the method for producing a diamond sintered body according to any one of claims 1 to 3, the primary particle diameter of all the diamond powders is 100 nm to 10 nm, the diameter of the smallest secondary particle is 100 nm to 1 μm, and the diameter of the largest secondary particle is 100 nm to 1 μm. Polycrystalline sintering raw material diamond powder with a diameter of 50 nm to 10 μm is sealed in a metal capsule, and a metal plate or bullet fired by an explosive explosion, a powder gun, a two-stage light gas gun, or an electric method is made of SUS304. A method for producing a directly sintered diamond sintered body, which comprises colliding at a speed of 1.8 km/sec or higher to generate high pressure and high temperature to sinter the stainless steel. 5. 5. The method of manufacturing a diamond sintered body as defined in claim 4, wherein the diamond powder as the sintering raw material is diamond synthesized by impact ultra-high pressure.