JPS6213305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polycrystalline diamond body consisting of a dense mass of diamond crystals bonded by a silicon-containing bonding medium.

The method of the present invention utilizes pressures substantially lower than those required in the diamond stability zone to create a polycrystalline diamond body in which diamond crystals are bonded with a bonding medium containing silicon atoms. The polycrystalline diamond bodies of the present invention can be made in many shapes and a wide range of sizes. It is useful as an abrasive, cutting tool, nozzle or other wear-resistant member.

In general, the method of the present invention for producing polycrystalline diamond bodies includes a step of thermal compaction and pressure transfer under sufficient pressure to produce a powder that is at least substantially stable in shape. compacting a mold of a predetermined size in a powder medium at ambient temperature, said pressure transmitting powder medium transmitting the applied pressure substantially without reduction, and substantially not sintering during said hot compaction; placing a mass of silicon and a mass of diamond crystals in contact with the silicon mass in the cavity formed by removing the mold, and displacing the cavity and its contents with an additional amount of the pressure-transmitting powder medium. thereby enveloping the contents with said pressure transmitting powder and applying sufficient amount of said powder medium to said cavity and its contents to substantially stabilize the dimensions of said cavity and its contents. A substantially balanced pressure is applied to uniformly produce a shaped, substantially balanced system of powder-encased cavities, and the density of the compacted mass of diamond crystals formed, i.e., the body density (hereinafter referred to as (simply referred to as density) is greater than 65% by volume of the volume of the diamond crystal to be compressed, and the silicon is used in an amount sufficient to fill the interstices of the compressed mass of diamond crystal, and the silicon is used in an amount sufficient to fill the interstices of the compressed mass of diamond crystal, and providing an atmosphere in which the diamond crystals and silicon are at least substantially inert during the thermal compression, thermally compressing the formed substantially balanced system to produce fluid silicon;
The silicon is injected into the pores of the compressed mass of the diamond crystal, and the thermal compression is performed at a temperature from the temperature at which the silicon becomes a fluid to about 1600°C to form fluid silicon into the pores of the compressed mass of the diamond crystal. the thermal compression converts up to 5% by volume of the diamond crystals to non-diamond elemental carbon and causes the non-diamond carbon or the surface of the diamond crystals to react with silicon; silicon carbide is formed and maintained at a pressure sufficient to maintain at least substantially the dimensions of the thermocompressed system on the formed hot-compressed substantially isostatic system during its cooling; A formed polycrystalline diamond body consisting of diamond crystals bound by an atom-containing medium is recovered, wherein the diamond crystals are at least 65% by volume of the polycrystalline diamond body.
consists of making it exist in an amount of

Those skilled in the art will have a better understanding of the invention from the following detailed description taken in conjunction with the accompanying drawings.

In carrying out the method of the present invention, the mass of diamond crystals in contact with the mass of silicon is cold-heated at ambient or room temperature to substantially uniformize and substantially stabilize their dimensions. A compression step followed by a hot compression step causes silicon to penetrate into the compacted mass of diamond crystals.

Diamond crystal bodies and silicon bodies can take many forms. For example, each mass can be in the form of layers, one layer stacked on top of another. Alternatively, the silicon can be in the form of a tube or a cylinder with a core extending into the cylinder, and the diamond crystals can be filled within the core of the silicon cylinder. In yet another embodiment, the silicon can be in the form of a bar, which can be centered in the cavity, and the surrounding space between the silicon bar and the inner wall of the cavity can be filled with diamond crystals. can.

The diamond crystals used in the method of the invention can be natural diamonds or synthetic or man-made diamonds. Their maximum size is approximately 1μ~
They range in size from about 100 microns, with the particular size used depending on the particular desired diamond crystal packing or density and the respective use of the polycrystalline diamond body being formed. . However, crystals smaller than 5μ must be mixed with crystals larger than 10μ, and in order to allow satisfactory penetration by silicon, crystals smaller than 5μ should preferably not constitute more than 50% by volume of the diamond mixture. Diamond crystals no larger than about 60 microns are preferred for most polishing applications. Preferably, in order to maximize the filling factor of the diamond mixtures, they should be sized to contain a range of crystal sizes, namely small, medium and large sized crystals. Preferably the size-sorted crystals are about 1
μ to about 60 μ, and preferably within this size range a large fraction ranges from about 60 to about 80% by volume of the total mass of crystals, and from about 5 to about 10
% by volume of medium size, with the remainder made up of small size crystals or particles.

Grain sizing of diamond crystals can be easily accomplished by jet milling large diamond crystals. The diamond crystal is preferably chemically cleaned to remove oxides or other impurities from its surface before use in the method of the invention. This is the temperature of a diamond crystal in hydrogen at approximately 900℃.
This can be achieved by heating for about 1 hour.

In the present invention, silicon is used to inject or penetrate into the interstices or pores between diamond crystals. The silicon may be in solid or powder form, for example, and is used in an amount sufficient to fill the interstices or pores of the diamond crystal mass having a crystal density of 65% or more by volume of the volume occupied by the crystals. do. Generally silicon is about 25% by volume ~
It can be used in amounts ranging from about 80% by volume, but preferably for best results it is in the range from about 30 to about 60% by volume of the diamond crystal with a crystal density greater than 65% by volume. be.

The hot compaction step of the present invention is carried out in an atmosphere that does not have a significant deleterious effect on the properties of the diamond crystals or silicon intrusion. In special cases, the thermal compression step may be carried out in a substantial vacuum or in an inert gas such as argon or helium, or may be carried out in nitrogen or hydrogen. The thermal compression step of the present invention is conducted sufficiently fast so that no significant reaction between the fluid silicon and nitrogen or hydrogen occurs. The thermal compression step of the present invention cannot be carried out in air, since diamond
Rapidly turns into graphite in air over 800℃,
This is because the liquid silicon is oxidized to form solid silica before the implantation of the diamond mass with the fluid silicon occurs.

The thermal compaction of the present invention allows the silicon to become fluid under a pressure that is only sufficient to destroy the interfacial refractory layer in the diamond mass that prevents intrusion by the fluid silicon into the pores at the hot compaction temperature. From temperature about 1600
The weight is usually about 35.2Kg/
Requires a minimum pressure of cm ² (approximately 500 psi). In particular, the pressure of thermal compression is approximately 35.2Kg/cm ² to approximately 1406.1Kg/cm ² (approximately
500psi to about 2000psi), but typically it is about 70.3Kg/ ^cm2 to about 703.5Kg/ ^cm2
(ranging from about 1000psi to about 10000psi). about
Hot compression pressures greater than about ^10,000 psi do not provide significant benefits. Similarly, temperatures above 1600°C do not offer significant benefits and may overgraphitize the diamond.

The temperature at which silicon becomes fluid means here the temperature at which silicon becomes easily fluid. Especially when silicon is at its melting point (which ranges from about 1412°C to about
1430 °C), it has a high viscosity, but as you increase its temperature, it becomes less viscous, and at a temperature about 10 °C above its melting point it becomes a fluid. . The temperature at which silicon is fluid is the temperature at which it injects or penetrates through the capillary-sized passages of the interstices or pores of the compact mass of the present invention of diamond crystals having a crystal density greater than 65% by volume. When the temperature is further increased, the fluidity of the fluid silicon increases and its penetration speed into the diamond crystal mass becomes faster.
At the highest hot compression temperature of about 1600° C., liquid silicon has the highest fluidity and the highest rate of penetration into the crystal mass.

In the apparatus of FIG. 1, a cavity of predetermined size is formed by a mold 9 into a pressure transmitting powder medium
It is press-fitted into 9a. In this regard, sufficient pressure (generally from about 703.5 Kg/cm ² to about 3515.4 Kg/cm 2
cm ² (approximately 10,000psi to approximately 50,000psi)] to the piston 23
a, so that when the pressure is removed, ie when the piston 23a is pulled, the mold 9 can be removed, leaving a recessed cavity 11 therein. The mold 9 is of a material with a smooth surface finish, such as stainless steel or sintered carbide, which can withstand the applied pressure and leave a recessed cavity 11 after removal from the compressed powder.

In Fig. 1, mold 9 is removed and cavity 11 is removed.
When the silicon disk 1 is left in the cavity 11,
A diamond crystal mass 13 is placed in contact with 1 and silicon. To ensure that the diamond crystal mass has the desired thickness in the polycrystalline diamond body from which it is formed, the cavity is provided with the following steps to dimensionally stabilize the system as shown in FIG. It should be sized so as not to leave any free space within it to allow substantial movement or displacement of the diamond particles during cold compaction. Additional pressure transmitting powder is then placed over the cavity and its contents to form the powder-encased cell 1 as shown in FIG.
0, ie cavity and contents.

As shown in FIG. 2, the cell 10 is then subjected to a cold compression step, which takes place at room or ambient temperature, as necessary to create a dimensionally stabilized, substantially balanced system. Apply sufficient pressure. In particular, in the cylindrical core of the pressing mold 20 in FIG. 2, the cells 10 are surrounded by a mass 19 of pressure transmitting powder medium.

The pressure transmitting powder medium of the present invention remains substantially unsintered under the pressure and temperature conditions of the process of the present invention and is of very fine particles, preferably less than 400 mesh, that is substantially inert to fluid silicon. consisting of a pressure transmitting powder medium. Representative such powders include hexagonal boron nitride and silicon nitride.
This pressure transmitting particle or powder medium serves to provide a substantially or substantially equilibrium pressure in the cell 10.
The cell 10 and its contents are thereby dimensionally substantially homogeneously stabilized, i.e., densified to create a shaped, substantially balanced system of powder-encased cells, the crystals then forming. The density of the compacted layer is greater than 65% by volume of the compacted crystal volume. The pressure forming mold 20 (ring 22 and pistons 23, 23a) can be made from tool steel;
If desired, the ring 22 may be provided with a sintered carbide sleeve 22a as shown to enable the application of pressures as high as ^200,000 psi for the cold compression stage shown in FIG. .
Pressures greater than 14061.4 Kg/cm ² (200000 psi) do not offer significant benefits. Due to the cold compression stage, the second
Within the boundaries of piston 23, sleeve 22a and piston 23a as shown in the figure, the piston is actuated in a conventional manner until the applied pressure is stabilized as is done in conventional powder filling methods. The pressure transmitting powder medium is preferably
1406.1~Approx. 7030.7Kg/ ^cm2 (Approx. 20000~Approx.
100000psi), usually about 3515.4Kg/cm ² (about
Apply pressure up to 50,000psi).

In particular, the particular cold compaction used will be determined experimentally; pressures greater than those which create a dimensionally stabilized substantially equilibrium system will result in greater densification or size of the cell 10 and its contents. Does not cause stabilization.

The nature of the pressure transmitting powder media of the present invention, such as hexagonal boron nitride and silicon nitride, provides an approximate hydrostatic pressure response in response to uniaxially applied pressure to exert a substantially equilibrium pressure over the entire cell 10. It's like giving birth to something. The applied pressure is transmitted to the cell 10 substantially without reduction. The cold pressing process maximizes the presence of capillary sized pores in the diamond mass, thereby reducing pore size. And it is useful for producing the required density of diamond crystals in more than 65% by volume of the diamond mass. This reduction in pore volume also reduces the ultimate content of non-diamond material in the diamond mass, providing more parallel crystal-to-crystal areas for effective bonding.

After completing this cold compaction step, the density of the compacted diamond crystal in cell 10 is 65% of the crystal volume.
It should be at least % by volume. The diamond density of often compacted diamond crystals ranges from about 66% by volume of compacted diamond crystals to about 85% by volume, but less. The greater the density of the crystals, the less non-diamond material is present between the crystals, forming a proportionately harder abrasive body.

The substantially isostatic system 21 of powder-encased cells formed from the cold compaction stage is then subjected to a hot compaction stage.
This exposes it to hot compression temperatures and pressures at the same time.

Especially when the cold compression stage is completed, the piston 2
3, 23a and the formed unified, substantially balanced molding system 21 is removed from the liner 2.
2a and placed in a hole of the same diameter in a graphite mold 30, here the transferred system 21 is contained within the wall of the hole 31 between the graphite pistons 32, 32a. The graphite 30 is provided with a thermocouple 33 to provide an indication of the temperature imparted to the dimensionally stabilized substantially balanced system 21. The mold 30 with the substantially balanced system 21 thus contained is placed in a conventional thermal compression furnace (not shown). The furnace chamber is evacuated or substantially evacuated and the system 21 containing the cell 10 is removed.
is degassed to provide system 21 and cell 10 with a substantial vacuum in which the thermal compression step can be performed. However, if desired, nitrogen or hydrogen or an inert gas such as argon may be supplied to the furnace chamber at this point;
It is also possible to provide a suitable thermocompression atmosphere to the system 21, including not only the chamber but also the interior of the cell 10. The pistons 32, 32a apply a uniaxial pressure, that is, a thermal compression pressure, to the system 21, while raising its temperature to a temperature at which the silicon plate 12 flows.

During the hot compaction stage, the hot compaction temperature should be rapidly achieved and maintained under hot compaction pressure, usually for at least 1 minute, to ensure satisfactory penetration into the diamond crystal mass. be. Generally, heat compression times of about 1 minute to about 5 minutes are satisfactory. Since the conversion of diamond to the non-diamond elemental carbon phase is largely time and temperature dependent, the higher the temperature and the longer the time at such temperature, the faster the conversion to non-diamond elemental carbon. Due to the large conversion, the thermal compression stage is limited to 5% by volume of diamond.
must occur before it is converted to non-diamond elemental carbon, which can be determined experimentally. Conversion of more than 5% by volume of diamond to non-diamond elemental carbon produces an elemental non-diamond carbon phase that results in a final product that has a significant detrimental effect on its mechanical properties.

In the hot compression stage, the application of hot compression pressure to the fluid silicon removes the interfacial refractory layer or slag (mostly oxides and carbides) that is normally present or formed between the fluid silicon and the diamond surface. The fracture exposes a capillary pore system to the silicon, after which injection occurs by capillary action. Tests have shown that no injection of silicon into the diamond mass occurs unless sufficient pressure is applied to system 21 to maintain overall thermal compaction as the silicon becomes fluid and breaks the slag.

Also in the method of the invention, when the silicon is liquefied, the slag or oxides present or formed therein become suspended and the fluid silicon percolates into the compacted diamond mass. When will remain behind. As a result, the diamond compacts of the present invention do not contain a glass phase that prevents the formation of strong bonds between the diamond and the silicon-containing bonding medium.

During thermal compression, fluid silicon penetrates and flows into the diamond mass, so that it envelops the surface of the densified diamond crystals and reacts with the diamond surface or the non-diamond elemental carbon phase that forms. Silicon carbide forms on the surface of the diamond crystal, forming a strongly bonded diamond body.

During this thermal compression stage, when the silicon is changed into a fluid state, this fluid is transferred to the mass 13 and the cavity 11.
It is especially important to maintain a substantially balanced condition so that the diamond crystal mass 13 is forced to move through the mass 13 of diamond crystals, although it cannot pass through the diamond crystal mass 13 and cannot escape to any appreciable extent. The portion of the pressure transmitting powder that is proximate to the contents of the cavity, i.e. preferably about 2.54 cm from the interior wall of the cavity or cell.
The section of pressure transfer powder extending up to (about 1 inch) should not contain communicating pores larger than about 5 microns to prevent excessive leakage of fluid silicon during hot compaction.

Cooling of the thermocompression system 21 such that when the thermocompression stage is completed, the thermocompressed cells 10 retained within the system 21 during cooling experience a substantial isostatic pressure sufficient to maintain their dimensional stability. At least sufficient pressure should be maintained during the process. Preferably, the thermocompression system 21 is allowed to cool to room temperature and recover the formed diamond bodies of the present invention. Excess silicon leached onto the outer surface of the polycrystalline diamond body can be removed by conventional methods such as polishing.

The polycrystalline diamond body of the present invention consists of a mass of diamond crystals adhesively bonded to each other by a silicon-containing bonding medium consisting essentially of silicon carbide and elemental silicon, said diamond crystals being about 1 μm to In the size range of about 1000μ, the density of said diamond crystals ranges from about 65% by volume to about 80% by volume of said polycrystalline diamond body, but less, often in the range of 75% by volume, and above. The silicon atom-containing bonding medium is present in an amount ranging up to 35% by volume of the diamond body, the bonding medium being at least substantially uniformly distributed throughout the polycrystalline diamond body, and the bonding medium being at least substantially uniformly distributed throughout the polycrystalline diamond body, The surface or portion of the binding medium in contact with the surface is at least a substantial amount of silicon carbide, i.e. at least about 85% by volume of the portion or surface of the binding medium in direct contact with the surface of the diamond crystal, preferably 100% by volume is silicon carbide. The diamond bodies of the present invention are pore-free or substantially pore-free.

The amount of silicon carbide and silicon in the bonding medium of the diamond bodies of the present invention depends on the degree of reaction between the surface of the diamond crystal and the interstitial silicon and between the non-diamond elemental carbon phase and the interstitial silicon. It can be changed. Assuming all other factors remain the same, the respective amounts of silicon carbide present in the binding medium are highly dependent on the respective hot compression temperature used and the time held at such temperature. especially time and/or
Alternatively, increasing the temperature increases the silicon carbide content. For example, the production of diamond bodies of the present invention of bonded diamond crystals with desired amounts of individual silicon carbide to obtain certain desired properties can be determined experimentally. In particular, the binding medium can range in composition from detectable amounts of silicon carbide to detectable amounts of elemental silicon, where detectable amounts of silicon carbide and elemental silicon refer to the present invention. Refers to the amount that can be detected by selective area diffraction analysis using a transmission electron microscope in a thin section of a diamond body. Generally, however, the binding medium of the present invention comprises silicon carbide in an amount of about 20% to about 30% by volume of the polycrystalline diamond body of the present invention, and elemental silicon carbide in an amount of about 33% to about 5% by volume. Consists essentially of silicon. Additionally, the diamond content of the diamond bodies of the present invention is generally about
It ranges from 65% by volume to about 80% by volume, but less.

Transmission electron microscopy selected area diffraction analysis of a thin section of the polycrystalline diamond body of the present invention also shows that the portion of the bonding medium that is in contact with the surface of the bonded diamond is at least a substantial amount of silicon carbide.

The diamond bodies of the bonded diamond crystals of the present invention are pore-free, or at least substantially pore-free, i.e., such pores, if any, are small, less than 0.5 microns, and are pore-free, or at least substantially pore-free.
They may contain pores in amounts of less than % by volume and are sufficiently uniformly distributed within the diamond body that they therefore have no significant detrimental effect on its mechanical properties. The pore content of the diamond bodies of the present invention can be determined by standard metallographic techniques, such as optically inspecting a polished cross section of the diamond body.

The diamond bodies of the present invention also do not contain non-diamond elemental carbon phases in amounts detectable by X-ray diffraction analysis.

When the method of the invention is carried out with silicon and diamond crystal masses in the form of layers stacked on top of each other, the product formed can have at least one flat surface and is shaped like a disk, rod or bar. It can take many forms, such as:

carrying out the method of the invention with silicon in the form of a tube or cylinder having a core or hole extending therein;
When the diamond is filled into the core, silicon penetrates throughout the core of the compacted diamond crystal during hot compression, resulting in the diamond of the invention in the form of a circular rod.

When the method of the invention is carried out with a silicon rod in the center of the cavity and the space between the diamond-filled silicon and the cavity wall, the silicon penetrates into the surrounding diamond crystal mass and forms a tube or hollow cylinder. produces the diamond body of the present invention.

One particular advantage of the present invention is that the polycrystalline diamond bodies of the present invention can be made in a wide range of sizes and shapes. For example, diamond bodies of the present invention can be made as long or wide as 1 inch or more. A polycrystalline diamond body having the diamond density of the present invention and having a length of 2.54 cm (1 in.) or more is limited by the limitations of the equipment required to sustain extreme pressure-temperature conditions for the required time (i.e., the equipment is not at its capacity). They are so complex, large and strong that they cannot be produced practically, or at all, by techniques that take advantage of the extremely high pressures and temperatures of the diamond stability zone. In contrast, the polycrystalline diamond bodies of the present invention can be made as small or thin as desired, but always no larger than a monolayer of diamond crystals.

A portion of the diamond body of the invention may be made of a metal such as molybdenum, or a sintered carbide, or a sintered or hot-pressed metal, forming a tool stud that can be held by a tool shank adapted to be mounted in a machine tool. It can be brazed, soldered or otherwise joined to a suitable support material such as silicon nitride or sintered or hot-pressed silicon carbide, so that the exposed surface of the diamond body can be used directly for machining. . Alternatively, the diamond body of the present invention can be mechanically gripped in a race tool for direct machining through the exposed surface of the diamond body.

The present invention will be explained below with reference to Examples.

EXAMPLE The apparatus used in the present invention was substantially the same as that shown in FIGS. 1-3.

Hexagonal boron nitride powder ranging in size from about 2 microns to about 20 microns was filled into the die and cylinder when the mold was pressed into the powder as shown by 19a and 9 in FIG.

The cylinder is made of sintered metal carbide and has a diameter of 8.9
mm (0.35in) and thickness 6.4mm (0.25in). The axis of the cylinder was approximately parallel to the central axis of the die.

In this example, unlike FIG. 1, after inserting the cylinder into the powder, additional hexagonal boron nitride powder was placed into the die to completely encapsulate the cylinder, and the powder encapsulated cylinder formed
It was pressed at room temperature under a pressure of 3515.4 Kg/cm ² (50000 psi). Piston 23a was then withdrawn and piston 23 was used to partially extrude the formed compacted powder encased cylinder from the die. The exposed portion of the compacted powder was removed, leaving a partially exposed cylinder. Then take out the cylinder and
A cavity with a recess was left.

A 140 mg silicon disc with the same diameter as the inside diameter of the cavity was placed at the bottom of the cavity. On the silicon board, about 40% by weight is smaller than 10μ, about 1μ to about 60
Approximately 250 mg of diamond powder sized in the μ range was filled.

A disk of hot-pressed hexagonal boron nitride powder with the same diameter as the inside diameter of the cavity was placed in the cavity on top of the diamond powder to ensure that the surface of the polycrystalline diamond body formed was flat.

The entire mass was then forced into the center of the die by means of the piston 23a and then withdrawn. An additional amount of hexagonal boron nitride powder was added into the die to cover the hot pressed disk of hexagonal boron nitride, creating a hexagonal boron nitride encased cavity and contents as shown at 19 in FIG. . Next, the formed charge was heated to 5624.6Kg/cm ² (80000psi) as shown in Figure 2.
The powder-encased cavity and contents are compressed at room temperature in a steel die under the pressure of A dimensionally stabilized shaped substantially balanced system of objects was created. From previous experiments, it has been found that in the compacted assembly formed, i.e. the powder-encased cavity formed and the compacted substantially balanced system of contents, the density of the diamond crystals is 75% by volume of the compacted diamond mass. It turned out to be larger. The amount of silicon present is approximately 40% in the compressed diamond mass.
It was % by volume.

The compacted assembly 21, formed with powder-wrapped cavities and contents, was then hot-pressed, i.e., pressed into a graphite mold of the same diameter as the steel die, as shown in FIG. 3, and placed in an induction heater. I placed it inside. The inside of the cavity was evacuated and the heater was evacuated before being filled with dry nitrogen to 10 Torr and a nitrogen atmosphere was introduced into it. Approx. by graphite die
A pressure of 351.5 Kg/cm ² (approximately 5000 psi) was applied to and held above the compressed assembly 21 and then heated to 1500° C. for 7 minutes by an induction heater. Using this heating, the entire system expands to 703.1Kg/cm ²
(approximately 10,000 psi) pressure was reached.

At 1500°C, the piston 23a and pressure are approximately 351.5
Kg/cm ² (approximately 5000 psi), indicating that the silicon has melted, become a fluid, and penetrated into the diamond mass. Pressure is increased again to 703.5Kg/cm ²
(10000psi) and held at 1500°C for 1 minute to ensure complete penetration of silicon into the diamond mass. The power supply was then cut off, but additional pressure was applied. This provides stable pressure at high temperatures. However, at low temperature, the pressure was reduced to give adequate geometrical stability. Polycrystalline diamond bodies formed at room temperature were recovered.

After removing the surface scale of the hexagonal boron nitride powder, the integral polycrystalline diamond body formed is 8.89 mm (350 mils) in diameter and 1.27 mm (50 mils) thick.
It had the shape of a disk.

It has been found that the polycrystalline diamond disk has a substantially smooth surface and is well penetrated by the binding medium. Optical examination of the disc under a 100x microscope showed that it contained no pores.

Using a hammer and wedge, the board was essentially broken in half. Examination of the fracture cross-section of the disc showed that the fracture was transgranular rather than intergranular, ie, it fractured within the diamond grain rather than along the grain periphery. This indicates that the binding medium is highly adhesive and as strong as the diamond particles or crystals themselves. Furthermore, the fracture surface did not contain any pores, and the binding medium was uniformly distributed throughout the diamond body.

The cross-sectional fracture surface of the disk was polished on a cast iron scaife. Inspection of the polished surface shows no streaks of pores formed by the diamond flakes being pulled apart, indicating strong bonding therein and its usefulness as an abrasive. A polished cross section is shown in FIG.

The diamond density was determined to be approximately 72% by volume of the disk. Diamond density was determined using standard point counting techniques using micrographs of polished cross sections at approximately 690x magnification; the surface analyzed was large enough to represent the microstructure of the entire diamond body.

X-ray diffraction analysis of the crushed body showed it to be composed of diamond, silicon carbide and elemental silicon,
This indicated that silicon carbide and elemental silicon were present in an amount of at least 2% by volume of the diamond body. However, X-ray diffraction analysis of the crushed body did not detect any elemental non-diamond carbon.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an apparatus for forming cavities in a pressure-transmitting powder medium, and FIG. 2 is a cross-sectional view of an apparatus for forming cavities in a pressure-transmitting powder medium, and FIG. 1 is a cross-sectional view of an apparatus for applying at least a substantial isostatic pressure to a cell or cavity and its contents by;
Figure 3 is a cross-sectional view of a graphite type for simultaneously applying pressure and heat to a substantially balanced system showing the cells enclosed therein; Figure 4 shows a diamond content of 72 volumes of a diamond body; % is a 690x photograph of a polished cross section of a diamond body made by the method of the present invention, where the light grayish-white phase is the binding medium, the gray phase is diamond crystals, and the dark spots are foreign substances. 9 is a mold, 19a is a pressure transmitting powder medium, 23 and 23a are pistons, 11 is a cavity, 12 is a plate, 10 is a powder-covered cell or cavity, 20 is a mold, 19 is a mass, 22 is a ring, and 22a is a sleeve , 21 is a balanced system, 22a is a liner, 30 is a mold, 31 is a hole, 32, 32a is a graphite piston, and 33 is a thermocouple.

Claims (1)

Claims: 1. A pressure-transmitting powder medium comprising: (a) a pressure-transferring powder medium which transmits an applied pressure substantially without reduction and which remains substantially unsintered during said thermal compression; (b) placing a mass of silicon and a mass of diamond crystals in contact with said mass in a cavity formed excluding said mold; (c) said cavity and its contents; (d) covering the object with an additional amount of said pressure-transmitting powder medium, thereby enveloping the contents with pressure-transmitting powder medium; (d) discharging said cavity and its contents through said powder medium; substantially stabilizing the dimensions of its contents and applying a substantially balanced pressure sufficient to uniformly create a shaped, substantially balanced system of the powder-encased cavity and contents; the density is greater than 65% by volume of the compacted mass of diamond crystals formed, and the silicon is used in an amount sufficient to fill the interstices of the compacted mass of diamond crystals; (f) subjecting the substantially balanced system containing the contents to an atmosphere that does not have a significantly deleterious effect on the diamond crystals and the silicon during the thermal compression; (f) thermally compressing the substantially balanced system formed; to form fluid silicon that penetrates into the interstices of the compacted mass of diamond crystal, and the thermal compression is performed under sufficient pressure to cause fluid silicon to penetrate into the interstices of the compacted mass of diamond crystal. , carried out at a temperature range from the temperature at which the silicon becomes a fluid to about 1600° C., the thermal compression converts less than 5% by volume of the diamond crystals to non-diamond elemental carbon, and the non-diamond carbon or the diamond crystals are reacting the surface with silicon to form silicon carbide; (g) depositing on the formed thermocompacted substantially isostatic system sufficient to at least substantially maintain the dimensions of said thermocompacted system during cooling thereof; (h) a formation in which diamond crystals are bound by a silicon-containing medium consisting of silicon carbide and silicon, and the diamond crystals are present in an amount of at least 65% by volume of said polycrystalline diamond body; A method for producing a polycrystalline diamond body, characterized in that the polycrystalline diamond body contains a polycrystalline diamond body. 2. The method of claim 1, wherein the diamond crystals have a size grade ranging from about 1 micron to about 60 microns. 3. The method of claim 1 or 2, wherein the amount of silicon ranges from about 25% to about 60% by volume of said compacted mass of diamond crystals. 4 The density of the compacted diamond crystal above is about 85% by volume of the volume of the compacted crystal, but it is 85% by volume.
A method as claimed in claim 1, 2 or 3 with the scope of: 5. Any one of claims 1 to 4, wherein the silicon mass is in the form of a layer, and the diamond crystal mass is in the form of a layer stacked on the silicon layer. The method described in. 6. Claim 6, wherein said silicon mass is in the form of a bar substantially centered within said cavity, and said diamond crystal mass is filled in an enclosed space between said silicon and said cavity. The method according to any one of Items 1 to 4. 7. Any one of claims 1 to 4, wherein the silicon mass is in the form of a cylinder having a core extending through the cylinder, and the diamond crystal mass is filled in the core of the silicon cylinder. The method described in one of the above.