Method for coating of superabrasive with metal

FIELD: method for coating of superabrasive, in particular, diamond particles, with metal for manufacture of cutting tools, such as grinding or milling tools, or plated diamond articles.

SUBSTANCE: method involves using coating forming metal powder including compound; providing thermal reduction of metal from compound by placing superabrasive particles and powder adapted for forming of coating together into inert atmosphere; heating superabrasive particles and said powder to temperature of from at least 500⁰C to temperature below superabrasive destruction temperature during time interval sufficient for effective deposition of metal layer onto at least one portion of surface of each superabrasive particle and providing chemical bonding between said particles and said powder; cooling said particles and said powder to temperature below temperature of reaction between superabrasive particles and powder; separating mixture for obtaining of product fraction in the form of superabrasive particles coated with metal and substantially free from coating forming powder and by-product fraction in the form of coating forming powder substantially free from superabrasive particles coated with metal. Described are superabrasive particles coated with metal by means of said method, method for manufacture of abrasive tool with the use of superabrasive particles coated with metal, abrasive tool comprising said particles, and plated product comprising constructional diamond part and equipped with metal layer chemically bonded with at least one portion of surface of said constructive part.

EFFECT: provision for obtaining of material having superthin coatings of chemically active metal uniformly covering superabrasive over the entire surface of substrate.

27 cl, 2 tbl, 8 ex

The present invention relates to the creation of a method of coating superabrasive particles of metal, and more particularly it relates to the creation of a method of producing diamond abrasive particles, coated with a thin layer of metal, chemically associated with the underlying abrasive, and these coated particles are particularly useful for the manufacture of tools from superabrasive with metal bundle, designed for grinding and cutting, or metallic diamond jewelry.

Diamond superabrasive have the highest hardness that enables them to be used for processing other very hard materials. For example, superabrasive tools are often used for forming edits or other abrasive sharpening tools. Therefore, tools for grinding and cutting using abrasive portion containing superabrasive are of great importance in industry.

In its simplest form superabrasive tools mainly include particles superabrasive materials, high-quality structural metal core tool metal bond that holds superabrasive in a composite structure or a single layer of superabrasive associated with the core. These particles may be particles of irregular shape, which is then referred to as grit, grains or granules, or it may be products accurately predetermined shape such as a diamond film and shaped polycrystalline composites. Shaped diamond inserts are also used for machining hard and abrasive materials, such as composites with metal matrix and cast aluminum alloys. The so-called tools with a single layer of the particles have a layer of abrasive material associated with the core, and the thickness of the specified layer is equal to the nominal thickness of the sole abrasive particles.

There are many ways of making superabrasive tools with metal keyring. Many of them, such as soldering, provide for the introduction of granules on the core in contact with the composition bundles, heat collected (mounted) ingredients until then, until the transformation of the liquid composition of the ligament, and then cooling for hardening composition ligaments. Ideally, the composition of the metal bond solidly connected to the metal core and concatenates the granule core. The main disadvantage of this process is that many preferred compositions of metallic bundles do not form a strong coupling with superabrasive. Weak coupling leads to low strength of the ligaments, which in turn leads to premature loss of abrasive particles is an instrument in the process. This creates special problems for instruments with a single layer of particles, in which it is desirable to have a possibly smaller weight ligaments around the granules to open maximum cutting surface. If you increase the thickness of the ligament to improve adhesion, abrasive granules will be more deeply immersed in the bunch and tools will have a smaller area of the cutting surface facing to the workpiece. Moreover, the use of a thick bundle gets worn away and is too small the number of low-strength ligament to hold the granules, which as a result can easily fall out of the tool.

A well-known method of improving the adhesion of superabrasive with metal bond involves the use of compositions of the ligaments, which are reactive towards superabrasive, so that during manufacture of the tool composition ligament attaches itself to the surface of the abrasive particles. However, many compositions of powder metal bond for superabrasives are not reactive and do not form chemical bonds with superabrasives. The absence of a chemical bond with superabrasives leads to premature loss of superabrasive.

More advanced technology enhance grip provides for the inclusion of the ingredient of chemically active meta is La in the precursor composition ligaments. This ingredient can engage in a direct reaction with superabrasives with the formation of strong chemical connection between metal and pellets. The so-called song chords with "active metal" contain no chemically active and reactive components. Not normally reactive components form a large part of the composition of the ligament. Not chemically active ingredients fused with the formation of strong and durable ligament, which attaches itself to the core. Chemically active component firmly connected by chemical interaction with superabrasives and coupled with non-reactive alloy. For example, in U.S. patent No. 4968326 described a method of manufacturing diamond tools for cutting and grinding, which provides for mixing of forming a carbide material with solder and a temporary binder, applying the mixture to the substrate of the tool, causing the diamond particles coated with a mixture tool and heating the joint thus materials for the initial formation of the carbide coating on the diamond. After that make the brazing of diamond with carbide coating on the tool.

Despite the undoubted progress in comparison with previously known technology, the use of copulas with an active metal adds to the problem of ensuring the presence of an ingredient from chemically the active metal from the surface of the granules superabrasive, where it is desirable to create a chemical bond. In accordance with the primary aspect of this technology is the ingredient of a chemically active metal are mixed in powder form with other components of the composition of the metal ligaments. The mixture is then applied in paste form or in dry form. Only that part of the ingredient of a chemically active metal, which is close to superabrasive directly bonded with the abrasive. Ingredient of the reactive metal in other places compositions ligament is unnecessary or, at worst, harmful and detrimental properties of copulas in General. Therefore, it is important to have the ingredient of a chemically active metal in the form of a possible fine powder and uniformly to enter ingredient of a chemically active metal in the mixture, to obtain close contact between superabrasives and ingredient during the formation of ligaments.

One of the known approaches to solving this problem is coated granules superabrasive ingredient of a chemically active metal previously mixing with other components of the ligament. Due to this ingredient of the chemically active metal will be optimally introduced at the right time for the formation of bundles. For example, in U.S. patent No. 5855314 described method of coating in which particles of the ingredient of a chemically active metal is mehanicheskij coupled with the surface of the grains superabrasive. This is achieved by mixing the powder ingredient of the reactive metal with a liquid binder to obtain a paste-like adhesive, after which the resulting paste is mixed with abrasive grains to soak grains and produce drying the mixture for adhesion of the active component with grains. It is important to use particles of the ingredient of a chemically active metal may smaller size to ensure uniform coating of the grains. Even in the case when ingredient of a chemically active metal is in the form of fine powder, it is present at the surface in macromolecular number and therefore usually has in excess compared to the amount needed for cementing links to superabrasives. For the reason that ingredient of a chemically active metal and superabrasive often represent particles of irregular shape, it is difficult to ensure that the floor was full (solid) or uniform over the surface of superabrasive.

There are other ways of applying very thin layers of metal on a substrate, among which you can specify the condensation of the steam (gas) phase (PVD) and chemical deposition from the vapor (gas) phase (VD). The PVD method involves the use of electrical or thermal energy for sputtering the metal target and condensate the obtained hot metal atoms on the cooler substrate. This method does not allow to form a chemical bond between the deposited metal and the substrate. The CVD method includes the introduction of the metallic compound in gaseous form in a heated CVD chamber which contains the substrate on which to apply the coating. Heat leads to dissociation of the metal compounds in gaseous form (e.g., tungsten hexafluoride) with the formation of metal atoms, which cover the substrate, while deleted normally gaseous by-product dissociation.

In some cases, instead of a simple mechanical coating substrates by metal CVD allows to obtain a chemical bond to the metal substrate. This is a very attractive feature, as it allows the clutch is pre-associated with coated metal superabrasive material core tool using a simple flux and solder or use process in the induction furnace in air. If the metal coating is not chemically bound in advance with superabrasives, the method of manufacturing a tool becomes much more complicated and expensive, such as soldering in a controlled atmosphere of inert gas or in vacuum.

CVD allows you to form a bond of metal to the substrate only in some systems, metal/superabrasive is only under the influence of extreme heat. In addition, gaseous by-product can be harmful to the substrate. This is seen in U.S. patent No.5224969, which describes the method of applying tungsten on chromium plated diamond particles using CVD. This patent explains that when CVD using tungsten hexafluoride is released fluorine gas, which enters into harmful reaction with chromium. Therefore, in the specified patent proposed a complex method of applying a three-layer coating in which CVD is used for the deposition of the third layer. Moreover, the gaseous reactants and by-products that use and get with CVD are highly toxic to humans.

It would be highly desirable to obtain superabrasive material having ultrafine coating of chemically active or even not chemically active metal, without any difficulties or complications associated with the above methods. In addition, it is desirable to simplify the process of coating a chemically active metal and apply it directly on the surface of superabrasive, without the need for the introduction of barrier metal layers. There is also the need to create a quick method of obtaining chemically bound metal coating on superabrasive material. This could allow, for example, to obtain a coated metal superabrasive for manufacturing is the service having a long life and efficient abrasive tools or inserts for cutting tools, which could be connected with the holders of the instrument using conventional methods such as soldering with arc or induction heating in a furnace in air. Such tools will be characterised by the presence of a metal bond between superabrasives and core having exceptionally high strength, low weight ligaments and a very high degree of opening (outcrop) of abrasive particles toward the workpiece. It would be desirable to obtain chemically active metallic coating on superabrasive particles, which uniformly cover superabrasive over the entire surface of the substrate.

Thus, in accordance with the present invention proposed a method of coating superabrasive metal, which comprises heating operation in an inert atmosphere of superabrasive and forming a powder coating containing metal, this metal is thermally reclaimed by superabrasives, extract powder and superabrasive in a period of time sufficient for the efficient recovery of metal, which is formed metallized superabrasive having a metal layer, chemically bonded at least to the surface of superabrasive, and the separation of forming a powder coating on metallized superabrasive.

In the proposed new method of use which form a precursor coating in the solid state, moreover, this method does not require heating to extreme temperatures, supplying gaseous metal compounds in CVD reactor and carrying out processing in the reactor, as well as the introduction of such large quantities of energy per unit mass of the product, as is required in conventional PVD or CVD methods. The proposed method allows uniform coating of metal on top of all of superabrasive. Mainly the thickness of the coating can be controlled in the molecular range, so that there is just so much metal coating, as necessary, to ensure adhesion of the cords with superabrasives. Superabrasive product with a metallic coating obtained by using the proposed method is ideal for making all types of related and covered by superabrasive tools for grinding, cutting and machining, in particular for the manufacture of tools with a single layer of superabrasive and metal bond, as well as tools for grinding, cutting and editing with superabrasives in a metal matrix.

Used herein, the term "particle" means any General discrete object of solids and does not limit its exact size or shape. Applied to superabrasive the term "particle" means a particle superabrasive material of irregular shape sludge is a predefined form. Particle superabrasive incorrect alternative can sometimes be referred to as a grain, grit or granules. Typical examples of the structures of the predetermined shape is a sphere, a cube or other polyhedron, and the layer ("sheet") or film. Under "layer" or "film" is usually understood as a flat geometric object that has three orthogonal characterizing size, two of which are significantly more third. Used here, the term "powder" means a discrete solid particles forming the coating material, regardless of their size and shape. With reference to forming the coating material, the term "powder" can mean only one discrete solid particle powder, and many such particles. Unless specifically stated otherwise, the size and shape of the particles superabrasive can be the same as in the powder forming a coating of metal compounds, or may be different.

In accordance with the primary aspect of the present invention is primarily associated with the formation (formation) coating of elemental metal particles superabrasive. The metal, which is applied in the form of a coating on the particle superabrasive, is supplied as a component of a chemical compound in powder form. The coating produced using the fundamental reduction reaction of inorganic x is MIA, which flows at elevated temperature in an inert atmosphere. Superabrasive serves as a reductant that reacts with the elemental metal of the metallic compound, which then forms a chemically linked coating on the surface of the particles superabrasive.

In the specified process mainly uses a chemical reaction between the plated metal and superabrasives to create a strong chemical bond at the border between metal and superabrasives. Under the application of high temperature proposed new method allows to obtain a structure that contains superabrasive substrate and the metal layer, and connected with a substrate by means of chemical bonding, which forms an intermediate layer between superabrasive substrate and outer metal layers. This creates a strong adhesion between the metal and superabrasives, which is usually stronger in mechanical coatings.

Characteristic of the new method is that the source forming a metal coating is a powder metal connection, which may be thermal-chemically recovered in elemental metal using a reducing agent. Moreover, superabrasive mainly is the only reducing agent present, allowing thermochemical vosstanovlenie is. Thus, the recovery operation can be carried out in the environment, mainly free from other reductants. The expression "mostly free" means that other reducing agents are absent in such quantities that significantly affect the coating superabrasive, but it should not be interpreted as the complete absence of all other reductants. From the above it is clear that a small part of the surface of the particles superabrasive spent in the recovery operation, a metallic compound. Moreover, to obtain a coated metal superabrasive grains, suitable for reception of a strong metal bond in an abrasive tool, sufficient very thin layer of metal on superabrasive, and therefore only a small number of superabrasive will be absorbed when used as a reductant.

Synthetic, natural and CVD diamond, and polycrystalline diamond (PCD) and a mixture of these diamonds are suitable for use in the proposed new method. Superabrasive with conventional grain sizes, which are used in abrasive tools, work well in a new way. Such particles superabrasive usually have an irregular shape and preferably have a characteristic size in the range of approximately 0.1 μm - 5 mm is Much narrower ranges for the n particle size, if necessary, can be used in any of the abrasive tool. The particle size of a typical commercially available superabrasive usually lie in the range from approximately 0.0018 inch (0.045 mm) to 0.046 inch (1.17 mm).

Some superabrasive, which is sometimes called the "microabrasive", have a particle size in the range of approximately from 0.1 μm to 60 μm. The grain size of the abrasive is usually determined by sieving through a sieve with the exact size of the cells. Thus, the term "characteristic size" refers to the nominal cell size of the sieve through which the particles pass or not pass.

The proposed new method is also well suited for coating metal superabrasive objects the size of more than 5 mm, These objects can be irregular in shape, granular, large crystals, or it may be products of predefined forms, such as thin sheets or more structurally complex shaped objects, such as cones, rods, rods, disks, etc. Thin superabrasive sheets include rectangular diamond leaves, mainly with the length and width of approximately 5-250 mm and a thickness of approximately 0.2-2 mm, and mainly approximately 0.5-1 mm, Such sheets can be produced by using CVD and often referred to as "diamond film". The proposed new method can be easily applied to cover large parts superabrasive through N. the bearing superabrasive on the layer forming the powder coating of the metal compound or the introduction of superabrasive in this layer.

Normally the coating applied on the entire surface, including on both sides forming a sheet of abrasive particles. If necessary, large particles can be masked to provide the specified pattern surface, and the mask does not allow to cover the metal some parts of the surface. For example, the mask overlay allows selective coating only one side, only faces, and all except the faces and plots of each of the parties forming the sheet superabrasive particles.

Superabrasive particle can be masked by applying a layer of barrier material on the surface before heat treatment operations. During the coating or after coating the mask may be removed, after which get superabrasive particle, which has a coating of metal on the area of its surface, which was not covered by a mask, and has a coating on its surface area, which was closed by the mask. Among suitable barrier materials, you can specify refractory oxides, nitrides, carbides, i.e. compounds that are more stable than those containing metal compound. As an example of barrier materials, you can specify the aluminum oxide, yttrium oxide, zirconium carbide and titanium carbide.

Metal connection must be chemical is a compound selected pre-forming a metal coating, which can be thermal-chemically restored superabrasives to obtain the metal in elemental form.

Mostly metal chosen primarily so that to solve the problem in the specific case of the coating. For example, in the manufacture of abrasive tools with a metal bond, among other things, is especially desirable to obtain forming the coating metal, which is compatible with the composition of the metal ligaments and chemically active when interacting with superabrasives. The composition of the metal bond abrasive tools are already well known. Representative metal components in a typical compositions of metal cords are tin, copper, silver, Nickel, zinc, aluminum, iron, cobalt, and mixtures thereof. Tungsten is particularly preferred to form a coating metal. Mostly metal compound is an oxide of a pre-selected forming the coating metal, the oxide of tungsten is preferred.

The number of available source materials should be sufficient to obtain the desired thickness of metal coating on superabrasive. Thus, the total amount of metal must be greater than the stoichiometric quantity necessary to obtain the desired thickness m is a metallic coating. Superabrasive particles, which are used in a single layer of abrasive tools with metal bond should be sufficiently covered, when the metal layer has a thickness equal to at least two molecules. Usually in practice, such small sizes are not measured, however, to determine the present invention indicate that the average thickness of the metal coating should probably be at least about 100 nm. Generally speaking, the total weight of the forming powder coating will depend on the surface area of superabrasive, which cause the floor. Smaller abrasive particles may require more forming powder coating per unit weight than larger abrasive particles because smaller abrasive particles have a large specific surface area.

In accordance with a preferred embodiment of the present invention, the diamond can be coated with tungsten by heating of the diamond and forming the powder coating of the oxide of tungsten together in an inert atmosphere. Tungsten has the appearance of brittle yellow powder, and diamond has the form of granules or shaped particles. Provided that forms a coating powder and superabrasive particles are in General the oxygen-free atmosphere, and preferably in close proximity to each other is, is formed (generated) chemically related coverage, despite the fact that superabrasive and forming a coating powder are not in mutual physical contact.

Not wishing to be bound to any particular theory, it is still possible to believe that the formed bound tungsten carbide coating of tungsten on the diamond in accordance with the following chemical reactions [I] and [II]:

The unexpected phenomenon of the formation of the coating without touching each other solid raw materials can happen because part of the tungsten evaporates and chemically dissociates with the formation of tungsten coatings with acceptable speed. Tungsten is subjected to carburizing for the formation of tungsten carbide at the surface of the diamond. The reduction also produces gaseous carbon monoxide, which, if the purge is produced in the atmosphere, which will be described hereinafter in more detail.

Other metal oxides can be used instead of tungsten oxide or in combination with him during carbothermic reduction when receiving superabrasive coating in accordance with the present invention. Suitable metal oxides and the initial reaction temperature for each metal oxide is listed in the table below.

When heated in the presence of these powders is formed a coating on the surface of the diamond particles in accordance with the following reaction:

MeO+C(diamond)=Mo+CO (gas),

where Me is a metal, MeO - metal oxide and Mo - carbide metal.

The temperature of the process will depend on the initial reaction temperature for the selected metal oxide. As shown in the following table, the reaction temperature necessary for evaporation and chemical dissociation of these metal oxides may be in the range approximately from 600 to 1100°C. the Preferred metal oxides are the oxides of tungsten (W), vanadium (V), tantalum (TA) and molybdenum (Mo), and combinations thereof. In contrast to these metal oxides titanium oxide (Tio₂) will form a metallic coating TiC is and superabrasive particle however, superabrasive may undergo undesirable thermal degradation at a temperature of disintegration of Tio₂approximately 1300°C. In the case of TA₂About₅temperature decay 1100°With, natural diamond particles can be used as a substrate, and they are not exposed to any thermal damage, however, the synthetic diamond particles undergo thermal decomposition. Thus, a metal oxide, which has a maximum temperature of evaporation or decomposition 1100°C, is preferred for use as a reagent in the carbothermic reduction process for coating superabrasive particles. When using tungsten, the temperature is about 1050°is preferred for both synthetic and natural diamond. Observed that the coating formed at such high temperatures, reduces the fragility of the diamond compared to the diamond to the heating and coating.

With continued thermal process, the metal layer increases on the first diamond in the form of a carbide of the metal, and then in the form of metal. The speed of coating metal exposed surfaces of the diamond depends on the crystallographic orientation of the surface of the diamond. The process mainly allows you to create a floor with a relative who sory uniform thickness on the surface of superabrasive. Usually the longer the time of coating, the thickness of the formed metal layer. Applying a metal stop when reaching the desired thickness of coating by removing forming the powder coating from the surface of superabrasive or by removing forming the powder coating from the total inert atmosphere. Other ways to stop the development of coating are lowering the temperature of the mixture of particles and/or passing an inert gas over reacts particles at high speed to effectively clean the atmosphere from reactive tungsten.

Inert atmosphere creates the environment for transportation of chemical species in the form of steam, which are involved in the recovery processes and deposition. It is therefore important for forming the coating powder and superabrasive, which cause the floor, was in the same inert atmosphere. The inert atmosphere can be static, however, some movement in it can result in movement (mobilize) variations in the direction of the solid materials and to increase the speed of coating. It is therefore desirable to pass an inert atmosphere through a layer of solid source material, and the thread in the process can be stopped. Note that excessive velocity can dilute and carry the reagent is in the form of steam before their admission to the surface of superabrasive. The concentration of the by-product of reduction reaction, such as carbon monoxide, in a static atmosphere and even when it recirculation may increase. This may slow down the process of coating metal. Therefore, it is desirable to remove from the atmosphere by-products during the process. This can be done by issuing part of the atmosphere and the introduction of fresh inert gas to fill the released volume. Mainly, you should make a full replacement of the amount of inert gas is approximately 5-20 times per hour.

The term "inert" atmosphere realize that the composition of the inert atmosphere mainly contains no oxygen or other substances that can participate in the reaction and recovery. Lack of oxygen can be achieved by displacing the inert gas or vacuum over superabrasive and forming the powder coating. You should create this vacuum in the vacuum, which enables the effective removal of mainly all the oxygen from the atmosphere. Mainly when you get a vacuum atmosphere with an absolute pressure of less than approximately 3 PA.

Inert atmosphere mainly create by replacing oxygen-containing atmosphere oxygen-free gas in an ambient atmosphere or in an atmosphere with high blood pressure. You can use the transmission of ha is and through solid reagents with speeds which effectively mobilize to make mobile) agents in the form of steam, thereby increasing the efficiency of the coating superabrasive. Representative gases that are suitable for use in accordance with the present invention are argon, helium, krypton, neon, nitrogen, xenon, and mixtures thereof. Argon and nitrogen are preferred.

As mentioned here previously, forming a coating powder and superabrasive particle does not necessarily have to be in mutual physical contact for the implementation of the proposed new method, and the particles and the powder can be separated from each other. For example, forming a coating powder may be placed in a crucible and superabrasive particles can be placed in a sieve, suspended above the crucible in the same inert atmosphere. Mainly the coating is conducted by the parties, subjecting to heat treatment of the party forming the powder coating and superabrasive in the crucibles. However, a continuous process is not beyond the scope of the present invention. For example, forming a coating powder and superabrasive particles can be laid in a continuous layer on the adjacent parallel, but separate belts of conveyors, with constant movement, and the tape can move through the furnace with an inert atmosphere. This process separated the particles makes it easy to separate the particles are covered with superabrasive product from the particles forming the coating source material upon completion of the process. This is desirable in the case, when forming the coating particles and superabrasive particles have approximately the same size. It also allows you to collect particles of different product sizes, which could be damaged during such mechanical operations as sifting.

The proposed new method can be carried out using a mixture forming the coating powder and superabrasive particles. With the release of batches of the mixture is placed in a single crucible, and then subjected to heat treatment as the material batch.

Mainly a mixture is prepared by dry mixing of forming a powder coating with superabrasive material. The mixture can be prepared by batch or continuously. Can be used with conventional equipment for mixing, such as tape-screw mixers, drum tilters and V-cone mixer. Mixer with low capacity are preferred, because they allow you to avoid crushing superabrasive particles. In accordance with another preferred embodiment of the present invention forms a coating powder has a size different from the sizes of the particles superabrasive, and the size of the particles forming the powder coating is usually less than the size superabrasive particles. Due to this superabrasive hour the Itza can be easily separated from the forming powder coating simply by passing the mixture through a sieve of appropriate sizes. In the method of separation of product particles from a mixture of predominantly not use elutriate (otmuchivanie), because using this method is abrasion particles in contact with each other and with the shock plate apparatus for otmuchivanie that can change the particle size and/or damage covered by metal superabrasive product. Superabrasive particles can be separated from the powder by introducing the mixture into a liquid, such as water, this powder with lower density floats, and superabrasive higher density falls to the bottom.

In accordance with another preferred aspect of the present invention forms a coating powder and superabrasive must have a large surface area exposed to an inert atmosphere. This can be done by placing the solid materials in the form of small stationary layers. Mainly the depth of the layer is approximately should not exceed more than 20 times the average particle size in the layer. For granular particles or particles of irregular shape determination of average particle size produced by the nominal size (mesh) cell sit very large and very small sizes, which respectively allow the passage of all particles and not pass a single particle. When forming the coating powder is mixed with superabrasive frequent the judgments, the preferred depth of the layer is approximately should not exceed more than 20 times the average particle size of superabrasive. If superabrasive has the form of a sheet, the amount used to determine the depth of the layer, will be the thickness of the sheet. Thus, predominantly should be stacked forming a coating powder in a layer of depth at most 20 mm to cover the diamond film thickness of about 1 mm.

Tanks containing forming the coating powder and superabrasive particles during heat treatment, should be made of a material that can withstand high temperatures and has no adverse effect on the coating process. Preferably, use ceramic crucibles, and can be used any refractory ceramics, in addition to graphite ceramics, such as ceramic clay with graphite.

The primary parameters that should be monitored in the proposed new method are temperature and time. After forming the coating powder and superabrasive put together in an inert atmosphere, increase the temperature to start the reaction recovery. Usually the threshold temperature for the start of the reaction depends on the properties of superabrasive and metal compounds. This temperature is generally at m is re 500° C.

Normally the process takes place faster at higher temperatures, however, should not exceed the temperature of destruction of superabrasive, which is the temperature at which superabrasive changes the shape and loses its superabrasive properties. The impact on the diamond temperature of approximately 1200°C, at atmospheric pressure or below it, in the atmosphere of inert gas, leads to a rapid transformation of diamond to graphite. For optimum reaction kinetics and minimal thermal damage to the preferred temperature range is a range from approximately 700 to 1100°C.

The time required to complete the process of applying a metallic coating, depends on such factors as the size and type of particles superabrasive, the flow rate of the inert gas, the heating rate and reaction temperature. To achieve the desirable results of heat treatment time at temperatures over approximately 500°in accordance with the present invention should be at least about 30 minutes, mostly at least about 1 hour, and even better 2-4 hours. Can be used more specified time at a high temperature. Typically when the preferred conditions of temperature, in an atmosphere of inert gas, the covering thickness of about 0.1 μm can be obtained within one every hour heat treatment of diamond abrasive particles with a size of about 300-800 μm. When using the descriptions of the present invention, the person skilled in the art can easily determine the appropriate combination of process conditions required to obtain satisfactory results without holding excessive additional experiments.

In a typical case, the implementation of the proposed new method select the desired superabrasive, metal coating, and forming a coating on the connection.

The surface of the coated particles should not have any metal contamination, therefore, can be used conventional methods of removing such contaminants. Particles superabrasive and forming the coating compound is placed in close proximity to each other in an inert atmosphere, but mainly in the atmosphere of inert gas. Mainly particles are mechanically mixed with each other for the formation of the mixture, then increase the temperature and maintain it at the level below the destruction temperature of superabrasive in a period of time sufficient to effectively produce coatings on superabrasive particles. During the coating process, the flow of inert gas may be passed through the layer of starting material and product at a rate that effectively increases the rate of deposition of the metallic coating. After the formation of sufficient due process stopping the pad from sliding is more and particles superabrasive cool. Chilled covered superabrasive separated from an excess of forming a powder coating. This process allows to obtain a product in which the outer metal layer is chemically linked to superabrasives.

The cooling rate covered superabrasive particles to the ambient temperature is not critical. Considering the fact that it is recommended not to damage the product due to thermal shock during cooling, can be cooled from the reaction temperature to ambient temperature over a time of at least 1 hour, but mainly approximately less than 30 minutes. The inert gas can be removed, i.e. oxygen-containing gas may be admitted, when the temperature of the layer of particles will decrease below approximately 150°C. then the excess forming a powder coating separated from the coated metal superabrasive particles. This powder can then be classified according to size and used again in a subsequent procedure, the coating in accordance with the present invention. Covered superabrasive can then be purified due to the impact on the external metal surface of the stream of hydrogen at a temperature of about 600-800°for the time is at least about 30 minutes. Finally, the product is analyzed, checked and Packed for hraneniya for transportation.

It was found that replacing the inert gas with hydrogen for a time of at least about 30 minutes at the lower temperature of the layer of particles during the operation of the cooling eliminates subsequent separate cleaning operation to remove oxidation. Mainly product is exposed to the flow of hydrogen when the temperature is maintained in the range of about 700-800°C. This effect of hydrogen during cooling not only allows you to clean the metal surface is covered with particles, but also recovers a portion of the excess forming a powder coating in elementary metal or a lower oxide that allows you to facilitate their separation from the product. Incomplete cleaning can cause remains too many metal compounds. If conducted on the location (in situ) the cleaning process is incomplete, the coated metal product looks discolored. For example, the oxidized tungsten covered with the diamond can have a brown color. In this case, can be used in subsequent normal operation cleaning with hydrogen, that is, the product isolated from forming powder coating, can be re-heated in hydrogen.

Covered with metal superabrasive particles obtained in accordance with the proposed Novem way, can be introduced into the abrasive portion AB is asinah tools with metal keyring with metal core, using various well-known technologies. For example, particles may be combined with the powder components of the composition metal bond, sealed by application of a pressure ("cold pressing") for the formation of shaped abrasive parts, and then sintered. Particles may also be subjected to hot pressing", which provides for the simultaneous application of heat and pressure for the formation of the abrasive part. Particles can also be used in the so-called infiltration process (impregnation) in the manufacture of the tool, which covered superabrasive particles fill in the mold cavity together with the powder matrix component metal bond, previously voids infiltraion molten metal or alloy with a low melting point. Furthermore, the covered superabrasive that are suitable for connection with abrasive tools (for example, in the form of a single layer of abrasive grains on the surface of the body or core metal tool), can be connected by means of electrodeposition and brazing, and possibly soldering with soft solder.

Using covered superabrasive significantly increases the adhesion of the diamond metal bond and increases the service life of the abrasive tool in VI is e cutting discs, blades diamond blades and drill bits, tools with a single layer of abrasive and metal bond, grinding wheels, tools for machining, grinding tools, as well as other coated abrasive tools and abrasive belts. Moreover, the covered superabrasive has high resistance to oxidation, which enables to produce some components of an abrasive tool in the presence of oxygen, without the need for an inert atmosphere.

Special advantages due to the use of coated superabrasive in accordance with the present invention can be obtained by hard soldering abrasive elements to the core or body of the instrument. In the past, some instruments were designed due to brazing the abrasive or cutting element to the metal core or substrate of the instrument (e.g., liner, cylinder or core of a circle or disk) in non oxidizing atmosphere in order to avoid thermal damage of superabrasives. However, the use of non-oxidizing atmosphere increases the cost and increases the complexity of the production process. In the presence of the metallic coating on the surface of superabrasive operations brazing can be carried out in atmospheric conditions, and can be used higher t is mperature soldering. Higher soldering temperature allow to get a more solid connection between the tool body and an abrasive or cutting element, which further increases the service life of the tool.

EXAMPLES

Hereinafter the invention will be described with reference to illustrative examples of some representative of its variants, in which all dimensions, proportions and percentages are given by weight, unless specifically indicated otherwise. All units that are initially received in SI units, converted to SI units. When measuring particle sizes used ratio "x/y mesh", in which x and y represent the number of a series of sieves USA, and x corresponds to the small size (mesh) cell sieve through which all particles and corresponds to the largest size (mesh) cell sieve, through which there is no particle. So, for example, diamond powder 40/50 mesh passes through the cell 420 μm and delayed cell 297 microns.

Example 1

Fifty grams of the powder of synthetic diamonds 40/50 mesh brand Debirs SDA 100+ were placed in a ceramic crucible together with 75 g of particles of tungsten oxide (WO₃) -400 mesh (particles pass through the hole sieve 37 microns). The diamond particles and tungsten oxide were mixed manually using a spatula to obtain volatile homogeneous mixture. The crucible was placed in re artnow furnace Lindberg, which as usual was purged with nitrogen with a flow rate of 142 litres per hour (5 cubic feet per hour, "CFH"). The oven temperature was increased to 1050°With a speed of about 10°in a minute. When the temperature reaches 250°started flowing argon instead of nitrogen and at the same time with the same speed. The mixture of diamond particles and tungsten oxide was kept in an argon atmosphere at a temperature of 1050°C for 30 minutes. Then the heating jacket with the retort was removed, it was cooled in the furnace to 750°for a time of about 10 minutes. At this temperature began to pass the hydrogen through the retort instead of argon and at the same time with the same speed. At this point the heating jacket was again put on the retort and supported the oven temperature 750°in which withstood the material in an argon atmosphere for 30 minutes. After that, the heating jacket with the retort was again removed, and it was cooled in the furnace to room temperature over a time of about 20 minutes. The flow of hydrogen into the retort was stopped when the temperature dropped to 100°C. the Diamonds were removed by passing the mixture through a sieve of 100 mesh. Visual inspection showed that the diamonds have a matte gray surface color. The diamonds that were previously coated with tungsten, which is confirmed by the results of the diffraction analysis, have the same krasivyi is. Therefore concluded that the diamonds in this example were satisfactorily covered with metal tungsten. In addition, the results of the diffraction analysis showed the presence of tungsten carbide in a metal layer, and the Auger analysis confirmed the presence of carbon and tungsten in the coating.

Example 2

The procedure of example 1 was repeated, except that 7.68 g of powder of synthetic diamonds 30/40 mesh brand Debirs SDB 1125 were mixed with 11.52 g of tungsten oxide. After the separation of diamonds from tungsten oxide visual inspection showed that the surface is covered with diamonds has a mottled brown-gray color. This surface is characteristic of a diamond with tungsten coating, in which tungsten is oxidized.

Diamonds with oxidized tungsten coating were placed in a clean crucible, which was then introduced into the furnace. Oven, as before, was purged with nitrogen and raised the temperature to 750°C. When the temperature reaches 250°With the nitrogen was replaced by hydrogen, which was passed with the same speed. Covered with diamonds kept in an atmosphere of hydrogen for 30 minutes at 750°C. After the heating jacket with the retort was removed, it was cooled in the furnace to room temperature when the flow of hydrogen was stopped. Visual inspection showed that the diamonds have a matte gray surface color, and what that suggests, that tungsten coating on the diamond is satisfactory. Covered with diamonds weigh 7.92 g, which talks about increasing the weight in the coating on 0.24,

Example 3

The procedure of example 1 was repeated, except that 1.03 g of natural diamonds were covered using 1.54 g of tungsten oxide. Working conditions were similar, except that the furnace was heated to 1000°C and maintained for 4 hours to obtain coverage. The flow of hydrogen was also stopped by cooling the furnace to room temperature. After separation from the particles of the tungsten oxide coated diamonds have a matte gray surface and the total weight 1.0414, Therefore, the diamonds have a coating of metallic tungsten weight 0.3737, the Analysis of the Auger depth profile of the diamonds that were previously covered using the same method, showed that the thickness of the tungsten coating is about 0.4 μm.

Example 4

The procedure of example 2 was repeated, except that 40.0117 g natural diamond 30/40 mesh were coated using 60.0176 g of tungsten oxide. After the second heat treatment, hydrogen diamonds have a matte gray surface, which suggests that the tungsten coating on the diamond is satisfactory.

Example 5

Were used two square sample of diamond film once the apostrophes 25.4 × 25.4 mm and a thickness of about 0.5 mm (manufactured by Norton Company, Worcester, Massachusetts)that have initial weight, respectively 0.9428 and 0.895, Each film has a rough textured matte one side and a smooth shiny opposite side. The shiny side of each film was painted with paint type Nicrobraz® Green Stop-Off® Type II paint (manufactured by Wall Colmonoy Corp., Madison Heights, Michigan). This paint is a latex with a suspension of ceramic powder. After drying the paint hides the shiny side of the film. Each film was placed in a ceramic crucible with reversed painted down the side, on a layer of particles of tungsten oxide 400 mesh with a weight of 1.5 times the initial weight of the diamond film. Then on the rough side of the film samples was coated with tungsten in accordance with the method of example 2.

After the second heat treatment with hydrogen in the diamond films have a matte gray surface on the rough side, which suggests that the tungsten coating is satisfactory. Then on the shiny side of the film was removed the masking material. Small tungsten coating can be seen near the edges of these parties, however, in the Central zone of the coating no. After coating the film samples weigh respectively 0.9852 and 0.9061 g, which indicates the increase in weight respectively 0.0154 and 0.0111,

Example 6

The layer of particles of tungsten oxide was introduced into the crucible and steel screen was installed over this layer, then the screen filled natural diamonds so that they were not in contact with the particles of the oxide of tungsten. The contents of the crucible was heated up to 1000°With argon, was maintained at this temperature for 4 hours and was processed as in example 5. The analysis of the obtained product showed that the diamond surface is partially covered with spots of shiny gray metal. Despite the fact that the metal does not completely cover the diamonds, the coating has a sufficient surface area to produce brazing to create a strong metallic bond between the partially covered in diamonds and the metal substrate of the grinding tool.

Example 7

Just 5.1569 g diamond 40/50 mesh brand Debirs SDB 1125 and 7,7354 g of the powder of the oxide of tungsten -400 mesh were introduced into a ceramic crucible. The diamond particles and tungsten oxide were mixed manually using a spatula to obtain volatile homogeneous mixture. The crucible was placed in a vacuum oven (Oxy-Gon Industries, Inc., Epsom, New Hampshire), and the temperature controller was set to increase the temperature of the furnace to 1050°C. the Furnace was evacuated using a mechanical vacuum pump to an absolute pressure of about 3 PA (0.03 mbar). Mix diamonds with hydroxy what Ohm tungsten kept at a temperature of 1050° C for 60 min in vacuum, after which the temperature controller furnace was installed to reduce the temperature of the furnace to room temperature (38°). The furnace was equipped with internal valves, which allow the cooling air injected by means of an automatic fan that allows you to lower the temperature at a rate of about 1°in a minute. Obtained after this treatment, the mixture was passed through a sieve of 100 mesh for separating diamonds from tungsten oxide.

The diamonds have a purple color characteristic of strongly oxidized tungsten coating. The diamonds were placed in a clean crucible, which was placed in a retort furnace Lindberg. The furnace was purged with gaseous hydrogen with a flow rate of 142 litres per hour and the temperature was raised to 750°C. After that, the diamonds kept at a temperature of 750°C in an atmosphere of hydrogen for 30 minutes. Then the temperature controller furnace turned off and removed the heating jacket from the retort. When the furnace temperature was dropped to 100°With, the flow of hydrogen gas ceased. Received the diamonds have a matte gray surface, indicating the presence of a satisfactory, not oxidized tungsten coating. Found that the weight of the coated metal diamond is 5.7206 g, which corresponds to an increase in weight on 0.5637,

Example 8

Was the conduct is but a study to determine the effects of reaction temperature on the fragility of the diamond crystal and establish whether the use of the method of coating in accordance with the present invention for receiving abrasive grains with a dense coating required for the production of the tool.

Diamond abrasive grain (manufacturer American Boarts Crushing, natural blocky diamond, size 25/30 mesh) was mixed with powder WO₃that was purchased at the company Cerac Inc., Milwaukee, WI (5 g diamonds and 7.5 g WO₃), after which the produced heat at temperatures and for time as described next. Except for the variables listed in the table below, the reaction was carried out as described in example 4.

After the separation of the covered grain from the remaining oxide powder of tungsten fragility of diamond grains was measured using a modification of the standard FEPA (European Federation of abrasive products) to measure the relative strength of diamond grains drank, first edition, may 30, 1994

Modification of standard FEPA consisted of: (1) the use of steel ball bearing brand 25 52100 as a test bulb; (2) in carrying out the weighing of the diamond sample with accuracy 0.4000±0.0005 g; (3) replacement of some sizes of sieves (in particular, the upper size of the sieves 915 was replaced with the 920, and the size of 645 650 μm; bottom size test sieves 600 was replaced by 605, 505 to 509 and 425 to 429 and the size of the sieve of destruction 600 was replaced by 605, 505 to 509 and 425 to 429); (4) were used vibrating sieve instead of a CR is the perfect shaker for sieves and (5) results were obtained in the form of cycles required to achieve half-life of the diamond grain (standard FEPA use the time necessary for the destruction of half of the diamond). Data on fragility and characteristics of visual observation of the diamond coating in the following table:

These data indicate that the unexpected increase in toughness of the diamond abrasive grains (i.e. reducing its brittleness), for grains, coated with tungsten at a temperature of 1050°With (sample 6), compared with grains, coated with tungsten at a temperature of 800 or 850°With (samples 2-4). Improvement was also observed in comparison with grains that do not have coverage (samples 1 and 5). When the process conditions chosen for this experiment, the floor was solid in the case of carrying out the reaction at a higher temperature and intermittent in the case of carrying out the reaction at a lower temperature. These results suggest that continuous coating helps to increase toughness. Since the coefficient of thermal expansion of tungsten approximately 49% higher than the coefficient of thermal expansion of the diamond, the increase in toughness is covered with diamonds may occur due to shrinkage of the solid tungsten coating during cooling, in which there is compression of the diamond.

Despite what the were chosen specific forms of the invention for explaining the principles of its implementation, it should be borne in mind that it specialists in this field can be amended and supplemented, which provide equivalent or better results and/or operational parameters that does not go however beyond the scope of the following claims.

1. Method of coating superabrasive metal, comprising heating superabrasive and forming a powder coating containing a metal, wherein the metal is thermally reactivated by superabrasives in an inert atmosphere, then hold the shutter powder and superabrasive in a period of time sufficient for the efficient recovery of the metal, thereby forming a metallized superabrasive having a metal layer, chemically bonded to at least one surface superabrasive, and the separation of forming a powder coating on metallized superabrasive.

2. The method according to claim 1, wherein forming the coating powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, and combinations thereof.

3. Method of coating superabrasive particles of metal, including the use of powder, which forms the floor of compounds containing metal, wherein the metal is thermally recover from a connection by placing superabrasive particles and abrazos the th floor powder together in an inert atmosphere, postheating superabrasive particles and forming the powder coating from at least 500°With up to temperatures below the destruction temperature of superabrasive in a period of time sufficient for the effective deposition of the metal layer at least on one surface of each superabrasive particles and formation of chemical bonds between them, cooling superabrasive particles and forming a powder coating to a temperature below the temperature of interaction superabrasive particles and powder and separating the mixture to obtain a fraction of the product in the form of a coated metal superabrasive particles mainly containing forming a powder coating, and fraction a by-product in the form of forming a powder coating, the main not containing coated metal superabrasive particles.

4. The method according to claim 3, characterized in that place many superabrasive particles with sizes in the range from 0.1 μm to 5 mm together with forming the coating powder, which is used in a larger amount compared to the amount defined stoichiometric ratio, to effectively create a metallic coating superabrasive particles with a predetermined thickness, forming at least 100 nm.

5. The method according to claim 4, characterized in that the size superabrasive particles find the camping in the range of 300-600 μm, weight forming a powder coating 1.5 times the weight superabrasive particles.

6. The method according to claim 3, characterized in that the metal layer associated with the surface superabrasive particles is a continuous layer.

7. The method according to claim 3, characterized in that the heating superabrasive particles and forming the powder coating is carried out in a mixture thereof, present in the form of a fluidized bed having a thickness in excess of not more than 20 times the average size superabrasive particles.

8. The method according to claim 3, characterized in that an inert atmosphere using a vacuum with an absolute pressure of less than 3 PA.

9. Method of coating metal according to claim 3, wherein the inert atmosphere contains gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon, and mixtures thereof.

10. The method according to claim 3, characterized in that superabrasive particle represents a diamond film having a characteristic size of more than 5 mm

11. The method according to claim 10, characterized in that superabrasive particle represents a diamond film obtained by chemical deposition from the vapor phase.

12. The method according to claim 10, characterized in that additionally provide for masking at least one portion of the surface superabrasive particle barrier material before heating superabrasives chastity forming the powder coating.

13. The method according to claim 10, characterized in that at least one superabrasive particle is a flat diamond film having a thickness of less than 1 mm.

14. The method according to claim 3, characterized in that it further includes the operations of replacement of the inert gaseous atmosphere of hydrogen and maintenance superabrasive particles in the atmosphere of hydrogen gas at a temperature that prevents oxidation component 700-800°With, for at least 30 min prior to separation of the fractions of the product and fraction a by-product.

15. The method according to claim 3, characterized in that superabrasive particles, and forming a coating powder is subjected to heating at a temperature of its interaction with superabrasive particles in the absence of other reducing agents, except superabrasive particles.

16. The method according to claim 3, wherein forming the coating powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, and combinations thereof.

17. Covered with metal superabrasive particles obtained by the method involving the use of powder, which forms the floor of compounds containing metal, wherein the metal of thermally vosstanovlen of compounds containing the metal, by placing superabrasive particles, and forming a coating powder together in an inert atmosphere, at the roar superabrasive particles and forming the powder coating from at least 500° With up to temperatures below the destruction temperature superabrasive particles, in a period of time sufficient for the effective deposition of the metal layer at least on one surface of each superabrasive particles and formation of chemical bonds between them, cooling superabrasive particles and forming a powder coating to a temperature below the temperature of each interaction superabrasive particles and powder and separating the mixture to obtain a fraction of the product in the form of a coated metal superabrasive particles mainly containing forming a powder coating, and fraction a by-product in the form of forming a powder coating mainly containing coated metal superabrasive particles.

18. Covered with metal superabrasive particles through 17, characterized in that the heating of superabrasive and forming a powder coating is carried out in the range of from at least 700 to 1075°C.

19. Covered with metal superabrasive particles 17, wherein forming the coating powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, and combinations thereof.

20. A method of manufacturing an abrasive tool, comprising a metal core, the use of coated metal superabrasive particles obtained by using the project superabrasive particles and powder, forming a coating of compounds containing metal, wherein the metal is thermally recover from a connection by placing superabrasive particles, and forming a coating powder together in an inert atmosphere, heated superabrasive particles, and forming a coating powder from at least 500°With up to temperatures below the destruction temperature superabrasive particles for a time sufficient for the effective deposition of the metal layer at least on one surface of each superabrasive particles and formation of chemical bonds between them, and then cooled superabrasive particles, and forming a coating powder to a temperature below the temperature of interaction superabrasive particles and powder and divide the mixture to obtain a fraction of the product in the form of a coated metal superabrasive particles mainly containing forming a powder coating, and fraction a by-product in the form of forming a powder coating mainly containing coated metal superabrasive particles, followed by brazing covered with metal superabrasive particles to the metal core.

21. The method according to claim 20, wherein forming the coating powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, as well as their com is inali.

22. Abrasive tool comprising a metal core, characterized in that the specified tool is made by concatenating covered with metal superabrasive particles in the composite is in the form of a powder containing the metal matrix and the subsequent attachment of the composite to the core, and covered with metal superabrasive particles obtained by the method involving the use of superabrasive particles and powder, forming the floor of compounds containing the metal which is thermally recovered from the connection by placing superabrasive particles, and forming a coating powder together in an inert atmosphere, heating superabrasive particles and forming the powder coating from at least 500°With up to temperatures below the destruction temperature superabrasive particles for a time sufficient for the effective deposition of the metal layer at least on one surface of each superabrasive particles and formation of chemical bonds between them, cooling superabrasive particles and forming a powder coating to a temperature below the temperature of interaction superabrasive particles and powder and separating the mixture to obtain a fraction of the product in the form of a coated metal superabrasive particles mainly containing forming a powder coating, and the fraction of side products is the same as forming a powder coating, mainly not containing coated metal superabrasive particles.

23. Abrasive tool according to item 22, wherein forming the coating powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, and combinations thereof.

24. Abrasive tool according to item 22, wherein the coated metal superabrasive particles are diamond film at least partially covered with metal, which you solder to the metal core at a temperature of 850-1100°C.

25. Abrasive tool according to item 22, wherein the heating superabrasive particles and forming a powder coating is carried out in the temperature range from 700 to 1075°C.

26. Metallic product containing diamond constructive part, covered with metal, characterized in that it is covered by a process comprising heating a constructive diamond part and forming a powder coating containing a metal oxide, restraint of powder and diamond constructive part in a period of time sufficient for efficient recovery of oxide, thereby forming a metallic product having a metal layer, chemically bonded to at least one portion of the surface diamond constructive part, and separation of the powder from metallized products.

27. Metallizer the bath product on p, characterized in that the powder forms a coating selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum, and combinations thereof.