JPH0437650A - Fracture resisting diamond and processing of diamond-combined article - Google Patents

Abstract

PURPOSE: To provide a diamond article which is free from distortion and excellent in breakage-resistance by heating the charging material containing fine diamond particles at high temperature, compacting and forming the material, keeping the material at high temperature before cooling, and eliminating the dislocation generated during the compaction.

CONSTITUTION: The charging material containing fine diamond particles is heated at high temperature, and compacted to form a dense article. The formed article is kept at high temperature, the dislocation in the article generated during the compaction is re-arranged, and substantially eliminated. Then, the article is cooled to the room temperature to obtain a breakage-resistant diamond and a diamond composite article. The obtained diamond article is excellent in wear resistance and crack resistance, and suitably used for cutting and drilling applications.

COPYRIGHT: (C)1992,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a method for preparing fully dense consolidated diamond or diamond composite articles, such as for use in the cutting and drilling fields.

The invention involves heat treating the article to improve abrasion and fracture resistance.

(Prior Art) The usual synthesis of diamond grids or powders involves high temperature,
It involves the conversion of non-Dayamont carbon to diamond in the presence of a metal acting as a solvent-catalyst under conditions of high pressure. A variety of carbonaceous materials can be used as carbon sources, such as charcoal, coal, coke and graphite, but typically graphite,
In particular, spectrally pure graphite is almost exclusively used for the commercial production of diamond grids or powders.

It is also possible to use carbon-containing organic compounds as carbon sources, such as anthracene, fluorene, pyrene, sucrose, camphor, and the like.

When graphite is used as a carbon source according to the preferred practice, it may be a powder, a compressed and machined disk of powder, or a capsule in which the graphite is placed with a solvent-catalyst. Typically, a graphite-loaded material in one of the forms described above is converted to diamond in the presence of one or more metals or metal-containing compounds that serve as solvent-catalysts. Graphite can be converted directly to diamond in the absence of a catalyst, but at a pressure of about 130 kbar and 3000-400 kbar.
Temperatures in the range of 0°C are required. With the addition of conventional solvent-catalysts, lower pressures and temperatures of 12
It can be used in the range 00-1600°C and 50-80 kbar. The solvent catalyst dissolves the graphite until a saturated solution of carbon to graphite is obtained. The catalytic effect is the promotion of structural rearrangement from graphite to diamond. Important solvent-catalysts are Group I transition metals, including platinum, chromium, tantalum, manganese and alloys containing at least one of these metals. Iron, nickel, cobalt and manganese are the preferred pure metal solvent-catalysts, and iron-manganese, nickel-chromium, nickel-manganese, iron-
Nickel, nickel-cobalt and various other nickel-containing alloys are generally preferred alloys for this purpose.

The solvent-catalyst may be in powder form (which may be loose or compacted) or in the form of discs.

Other additives, such as boron, are sometimes used as additives to the charge material to be compacted to alter one or more of the properties of the resulting diamond compacted article. The solvent-catalyst to carbon volume ratio is typically between 0.1 and 10;
The preferred ratio is 0.5-2. Consolidation is typically obtained through the use of a held press or cubic press. The ingredients are filled into cylindrical cells. Heating is typically provided by passing electrical current directly through the charge material in the cell.

Conversion of graphite to diamond is 1200-25 respectively.
It is carried out in the diamond stability region at temperatures and pressures in the range 000C and 50 to 120 kbar.

The reaction time is usually within the range of 0.5 to 20 minutes.

- For boat fishing, the consolidation sequence includes pressurization, heating to the desired maximum O reaction temperature, reaction time to allow conversion, cooling and release of pressure.

After cooling of the consolidated charge or mass, the diamond crystals are separated from the metal matrix by acid dissolution. For this purpose, nitric acid may be used at a temperature of 100-300°C, which dissolves all components except diamond. The diamonds can then be separated from the liquid by centrifugation or filtration. After this dissolution step, if the diamonds are agglomerated, they can be separated by optical crushing. The separated diamonds can then be sorted according to size and shape. The size of the resulting diamond grid or powder can vary within the range of 1 micron to about 1 mm.

The diamond particles thus produced can be compressed into substantially fully dense compacted articles, such as drill blanks for use in the manufacture of drill bits. For this purpose, the charge material may be compressed to produce a monolithic structure, or onto a disk or substrate of, for example, tungsten carbide and cobalt. The resulting disc or substrate with the diamond layer thereon can be assembled into various forms depending on the cutting or drilling equipment on which it is assembled. In any case, consolidation is
Diamond powder is sintered at high temperatures and pressures in the diamond stability region in the presence of catalytic or non-catalytic sintering aids to form a strong, internally bonded, polycrystalline, substantially densely consolidated diamond powder. obtained by obtaining a lump or article. The equipment used for compression may be the same as the equipment used for synthesis of diamond particles. Cell assemblies typically used in these applications are described in U.S. Pat.
, No. 407,455 and No. 4,604,106.

According to prior art compaction or consolidation practices, including the US patents listed below, the preferred charging material is diamond powder, although graphite powder may be mixed therewith. In this context, diamond powder generally constitutes at least 70% by volume of the total material, preferably 90-99%. The final compacted article has diamond particles of 10-20 microns, but depending on temperature, may have a coarse grain structure of about 100 microns.

Before loading the diamond powder into the cell, the diamond powder is dried for 8 hours, typically in the presence of hydrogen gas.
It may be cleaned by heating at a temperature within the range of 00-1000°C. Boron may be used as a sintering aid for the diamond powder and is typically introduced by doping the diamond powder before introducing the diamond charge into the cell for compaction. In addition, a pretreatment process involving surface graphitization of the diamond powder is carried out.
A uniform coating of graphite can then be provided on top of which the continuous melting of the graphite facilitates the penetration of the catalyst into the diamond layer within the cell to produce diamond during hot compression. . The catalyst carbide charge material may consist of cobalt, nickel or iron catalyst powder mixed with tungsten carbide, titanium carbide or tantalum carbide powder.

The table below features patents representative of common practices relating to consolidated diamond or diamond composite articles. 13/71 Diamond compact abrasive by sintering a mixture of diamond powder (50+% by volume) and catalytic metal powder (one or more of Fe, Ni, Co and Ti) in the diamond stability region, optionally with sintering aid U.S. Pat. No. 3,745,623 by sintering clean diamond powder mixed with up to 3% by weight of B, Si, or Be powder as an agent in the diamond stability region. , 380 U.S. Patent No. 4.288.248 Method for manufacturing bonded diamond compressed body 7/17/73 70+ adhered to bonded carbide base material
9/23/80 Relating to Powdered Diamond Compacted Blanks with Volume % Internally Bonded Diamond- Layers and Process for Their Production Heat-resistant, Leached Powdered Diamond Compacts Produced by Removal of the Metal Catalyst Phase from Internally Bonded Diamond Method of manufacturing leached powder diamond material by acid leaching and compression of U.S. Pat. No. 4,224,380 9/8/81 U.S. Pat. No. 4,518,659 5/21/85 Cylinder 6/3/86 No. 4.592.433 - Improved method for manufacturing a powder diamond compact by cleaning the diamond-loaded material using a catalyst (copper) prior to a Co catalyst Grooved bonded carbide substrate Powdered diamond compaction blank with diamond strips in it.As described in U.S. Pat. It may include layers and additional zirconium disc separators. The filling order is zirconium or tantalum metal sheath or capsule (
This involves stacking several single charges of this configuration into cells (which are placed into cells after the capsules are filled).

The steps involved in consolidation are similar to those for the synthesis of diamond powder. That is, the method involves applying pressure from 0.001 kbar to 50 kbar or more and from 20°C to 1
Sintering involves heating to a sintering temperature of 500°C or higher.
It can be carried out for 10 minutes at a pressure of 50 kbar and a temperature of 1500°C. After that, cooling is 5 Q + Lohar Karo 0
．． With the release of pressure below 001-t-Lohar,
Sintering is generally carried out in the temperature range 1200-1600°C and in the pressure range 40-70 kbar. If a press is used, sintering times are generally in the range of 10 to 15 minutes; with the use of a cubic press, sintering times of less than 3 minutes are possible.

After consolidation, the stack of sintered consolidation blanks is manually separated and the zirconium capsules are removed. A ramping operation and a grinding operation are used to remove particles of material that adhere to the edges and flat surfaces of the blank. Then,
The blanks are milled to the shape (which is typically; exactly cylindrical) and the dimensions required by the particular cutting or drilling arrangement in which they are used. The sizes commonly used for this purpose are approximately 1-5.5 cm in diameter and 3 cm in thickness.
．． 5-8 mm, which is 0.5 mm on the blank assembly.
Contains a diamond layer with a thickness of 7-1 mm. The resulting product is a bilayered disk, specifically a substrate of composition such as tungsten carbide and cobalt, with a fully dense layer of bonded diamond particles.

Additionally, post-consolidation acid leaching treatments with nitric and hydrochloric acids have been used to process refractory powdered diamond materials and compacts, from which most of the CO interpenetration network is removed. Ta.

This prior art is described in U.S. Pat. No. 4,224,380 and U.S. Pat. No. 4,288,248.

For special applications, such as the manufacture of drill bits used in oil well drilling applications, the disc is attached to the cutter using a brazing process.

Specifically, the blank is brazed to a tungsten carbide/cobalt post. A plurality of these bottom-sous disk assemblies are then attached to drill bits of various configurations, each with a diamond portion acting as a cutting surface. Also, multiple cutters of leached powdered diamond material may be brazed to the surface of the matrix-body drill bit, including a portion of the natural diamond layer or All can be replaced. Drill bits of these types of configurations are known in the art.

During the use of the above-mentioned consolidated diamond articles in cutting and drilling applications, it is advantageous that these articles are characterized by high wear and crack resistance.

In this regard, the applicant has determined that during hot compaction operations to obtain a fully dense consolidated diamond article, dislocations in the diamond crystal structure occur. Dislocations in crystalline materials, such as diamond, are linear regions of lattice defects. These defects enable the crystal to undergo plastic deformation at sufficiently high temperatures and are also generated by the deformation process. Since these defects consist of regions of lattice strain, they generate highly localized stress fields. As such, they provide sites for crack initiation and propagation when diamond articles are under the high applied stresses characteristic of their use in cutting and drilling applications. Similarly, these dislocations in the diamond crystal structure can cause failure of the article or failure of the article in the region of stress differentials caused by these dislocations that occur during hot compression of diamond grains to form consolidated articles from diamond grains. This can adversely affect the wear resistance of a consolidated diamond article during use of the diamond article in cutting or drilling applications by imparting areas of chipping and cracking (which in severe cases can lead to catastrophic failure). The performance of the article is adversely affected both in terms of wear resistance (which can lead to wear and tear) and wear resistance.

OBJECTS OF THE INVENTION Therefore, the main object of the present invention is to reduce the occurrence of dislocations in the crystal structure which adversely affect crack resistance and promote wear. An object of the present invention is to provide a method for processing a diamond composite article.

A more particular object of the present invention is to provide a method of consolidating diamond grains in which a heat treatment step is used to rearrange and remove dislocations in the crystal structure to obtain substantially strain-free diamond grains therein. It is.

Another object of the present invention is to provide a heating step during compaction of diamond powder to produce a substantially strain-free or restored state in the microstructure of the compacted article and, in addition, to improve the integrity of its crystal structure. It's about giving control.

Yet another object of the present invention is to provide an improved leaching process for extracting substantially all the cobalt from a strain-free compacted body, thereby further improving its thermal stability.

Additional objects and features of the invention will be set forth in part in the following description, will be obvious in part from the description, or may be learned by practice of the invention. The objects and advantages of the present invention are:
It may be realized and achieved by the methods particularly pointed out in the claims.

SUMMARY OF THE INVENTION In accordance with the method of the present invention, consolidation of fine diamond particles is obtained to produce substantially fully dense articles. The method includes heating a charge material containing fine diamond particles to a high compaction temperature and compressing the charge material while at this high temperature to form a desired substantially fully dense article. include. Then, according to the invention,
The article is held at an elevated temperature and time sufficient to rearrange and eliminate substantially all dislocations in the article that occur during said compression. This results in a substantially strain-free condition in the article.

Finally, the article is cooled to room temperature.

Further, in accordance with the present invention, maintaining the article at an elevated temperature includes maintaining the article at an elevated temperature after compression and before cooling from the elevated compression temperature to room temperature. The elevated temperature at which the article is maintained may be lower than the compression temperature, but still sufficient to rearrange and eliminate the dislocations. Also, according to the present invention,
Holding the article at an elevated temperature includes cooling the article from the elevated compression temperature and then reheating the article to a sufficiently elevated temperature for a sufficient period of time to rearrange and substantially eliminate dislocations in the article that occur during compression. and obtaining a substantially strain-free condition in the article. The reheating may be to a high enough temperature to obtain diamond crystal growth, or it may be below the diamond crystal growth temperature.

Further, in accordance with the present invention, the article is heated to an elevated temperature prior to cooling the article to room temperature and then at a controlled cooling rate sufficient to rearrange and substantially eliminate dislocations in the article that occur during compression. It is possible to cool down from this high temperature to obtain a substantially strain-free state.

This heating step may be at a temperature sufficient to obtain diamond crystal growth, or may be at a temperature that does not result in substantial diamond crystal growth. In another implementation of the invention, after compaction, acid leaching may be performed on the article to remove metals used during its synthesis from the article. The leaching agent is nitric acid, a combination of nitric acid and hydrochloric acid,
Or it may be hydrogen peroxide. The metal used during the synthesis of the article may be iron, cobalt, or nickel.

In accordance with the practice of the present invention, maintaining the diamond compact at an elevated temperature for the purpose of relocating and removing a substantial portion of the dislocations in the diamond compact to obtain a substantially strain-free condition comprises:
The temperature may be in the range of 1200 to 2000°C for 13 to 125 minutes.

Typically, the fine diamond particles used to produce consolidated articles in accordance with the practice of the present invention range from 1 to 20
It is within the particle size range of 0μ.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Detailed description of presently preferred embodiments of the invention will now be described;
Examples thereof are described below.

In the experimental work leading to the present invention, the inventors tested conventional diamond particle consolidation articles that undergo the wear and tear inherent in typical cutting and drilling applications. The wear and fracture properties of the particles tested indicate that the wear results from scraping at dislocations, and that these dislocations also provide sites for crack propagation under applied stresses that can result in cataclysmic failure of the article. It was shown that By heat treating the article according to the IM Dai invention, the inventors:
These dislocations were rearranged and removed to provide a substantially strain-free condition in the article. In this way, both wear and crack resistance are improved.

The following constitute exemplary embodiments of the invention.

Example 1 - 1 A diamond particle charge prepared in accordance with the conventional practice described above is placed in a zirconium tube with salt and zirconium spacers over a tungsten carbide-cobalt substrate, which is then bonded to a zirconium disc at each end. I made a sole. This capsule structure was developed in U.S. Pat.
745,623 and 4,604.106.

The capsules are heated to a temperature of 1550° C. while pressure is applied by use of a heald press constructed and operated according to the disclosure of US Pat. No. 3,407,455. Each sample was exposed to a temperature of 1550°C and a pressure of 60 kbar for 10
Hold for a minute to obtain a substantially fully dense article. after that,
The article is kept at a temperature of 1550° C. for 60 minutes before cooling to room temperature. This heating step results in the rearrangement and removal of a substantial portion of the dislocations in the article that occur during hot compression, resulting in a substantially strain-free condition therein.

Example 2 The practice of Example 1 is repeated, except that after consolidation the article is heated to a higher temperature (the temperature being 1700° C.) and controlled cooling from this temperature to room temperature over a period of about 15 minutes, whereby: Obtaining the rearrangement and removal of dislocations in the article that occur during compression, resulting in a substantially strain-free condition.

Daisenkan-1 The cycle of Example 1 was repeated except that after compression, the article was cooled from the compression temperature to 1300°C and then reheated to an elevated temperature of 1700°C for 45 minutes. The number of dislocations is substantially reduced to obtain a substantially strain-free condition.

Example 4 Improved acid leaching of the compacts produced according to the above examples was carried out using the following practice, which resulted in a leached diamond composite free of cobalt impurities, thereby reducing the leaching process. Provides even better heat resistance for compressed bodies.

First, a diamond compressed layer was cut into a tungsten carbide-cobalt base material by electrical discharge machining. The resulting diamond composite disks were then leached with an acid reagent in a glass beaker under the action of heat and ultrasonic stirring as described below. EDS analysis of the leached composite in SEM showed that all of the cobalt within the particles was removed. Two operations were shown to be effective, each at a temperature lower than the boiling point (93°C).
(over 200°F) for approximately 72 hours.

In the first operation, 50% by volume - 50% by volume of HCl
A combination of 8202 and H2O (hydrochloric acid and water) was prepared, and the combination 8202 (peroxide water S) was added thereto at 95% to 5% by volume. This mixture reacted violently with the diamond compact. When the reaction subsided, more H2O2 was added and further treatment was continued until no violent reaction occurred anymore. At that point, the above steps were repeated until the reagents were consumed and the leaching was complete.

In the 20th operation, HCl and HNO3 (hydrochloric acid and nitric acid)
0 combinations were prepared at 75% to 25% by volume, respectively, and heated to boiling point in contact with the diamond composite material. A violent reaction occurred with the formation of a strong ``) brown color in the solution and the development of dark brown smoke. When the reaction began to subside, the used reagents were discarded and fresh reagents were added according to the order listed. ) produced the reagent.

The present invention ○As can be seen from the above-mentioned special embodiments, fine-
Typical processing sequence for consolidating two diamond grains
: By introducing a heat treatment step, it is possible to readjust and substantially reduce the number of dislocations in the article produced during compression, and to obtain a strain-free condition in the article. In this way, these dislocations do not act as sites for crack nucleation. Thus, in typical cutting and drilling applications, crack propagation, which can result in catastrophic failure of the article under conditions of applied stress that occurs during use of the article, is avoided.

Therefore, the implementation of the present invention for processing dense compacted articles of diamond and diamond composite materials provides an improvement over the conventional practice for compacting such articles, providing improved crack resistance and It can be seen that both improved wear resistance is obtained. Furthermore, it has been found that practice of the present invention for leaching improved compacts provides the additional benefits of improved thermal stability as well as superior fracture resistance.

procedure Supplementary Positive Book (method) ・、1X

Claims (14)

[Claims] (1) A method of compacting fine diamond particles to produce a substantially fully dense article, the method comprising: heating a charge material containing fine diamond particles to a high compaction temperature; to form said substantially fully dense article while at a high compaction temperature of A method of making an article as described above, characterized in that the article is maintained at an elevated temperature for a period sufficient to remove the article to obtain a substantially strain-free condition in the article, and then the article is cooled to room temperature. 2. The method of claim 1, wherein maintaining the article at an elevated temperature comprises maintaining the article at an elevated temperature after compression and before cooling from the elevated compression temperature to room temperature. 3. The method of claim 1, wherein maintaining the article at an elevated temperature comprises maintaining the article at an elevated temperature below the compression temperature prior to cooling from the compression temperature to room temperature. (4) maintaining said article at an elevated temperature after compression cools said article from said high compression temperature and then rearranges said article to rearrange dislocations in said article that occur during said compression; 2. The method of claim 1, further comprising reheating to said elevated temperature for a time sufficient to substantially eliminate distortion in the article. 5. The method of claim 4, wherein said reheating is to a high enough temperature to obtain diamond crystal growth. (6) The method according to claim 4, wherein said reheating is reheating to a high temperature lower than a diamond crystal growth temperature. (7) After said compression and before cooling said article to room temperature, said article is heated to a higher temperature, and then said article is heated to a higher temperature to rearrange and eliminate dislocations in said article that occur during said compression. 2. The method of claim 1, wherein the article is cooled from said higher temperature at a controlled cooling rate sufficient to provide a substantially strain-free condition in the article. 8. The method of claim 7, wherein said heating to a higher temperature results in the growth of diamond crystals. 9. The method of claim 7, wherein said heating to a higher temperature does not result in substantial diamond crystal growth. 10. Acid leaching is performed on the article after compaction to remove metals used during the synthesis of the article from the article. , or 6, or 7, or 8, or the method according to 9. (11) The leaching is performed using nitric acid, a combination of nitric acid and hydrochloric acid,
11. The method of claim 10, wherein the method is carried out using a leaching agent selected from hydrogen peroxide and hydrogen peroxide. 12. The method of claim 11, wherein said metal is selected from the group consisting of iron, cobalt, and nickel. 13. The method of claim 1, wherein said article is held at an elevated temperature in the range of 1200-2000°C for 13-125 minutes. (14) The fine diamond particles mentioned above are 1 to 200μ
2. The method of claim 1, wherein the particle size range is within the range of .