KR20010023707A - Method of manufacturing a diamond-silicon carbide-silicon composite and a composite produced by this method - Google Patents

Abstract

The present invention relates to a method for preparing a diamond-silicon carbide-silicon composite from diamond particles, the method comprising the steps of forming a working specimen, heating the working specimen and adjusting the heating temperature and the heating time to produce a predetermined amount of graphite. And thereby producing an intermediate body by graphitization of diamond particles and infiltrating silicon into the intermediate body. The present invention also relates to diamond-silicon carbide-silicon composites prepared by this method.

Description

METHOD OF MANUFACTURING A DIAMOND-SILICON CARBIDE-SILICON COMPOSITE AND A COMPOSITE PRODUCED BY THIS METHOD}

Extremely hard (ultra-hard,> 40 kPa) materials are generally needed for many applications. Such applications can be used as tools in cutting, turning, milling, drilling, sawing or grinding operations. The hard materials may also be used for wear, friction and erosion when used in bearings, seals, nozzles or similar cases. The material can be used for or in contact with grinding wheels such as cast iron, steel, nonferrous metals, wood, paper, polymers, concrete, stone, marble, soil, carburized carbide and aluminum oxide, silicon carbide, diamond or boron nitride tools. have. As the hardest material known, monocrystalline or polycrystalline diamond is suitable for this purpose. Other common materials used for hardness purposes are, for example, boron nitride tools (CBN), boron nitride and other ceramics and carburized carbides, but only materials containing diamond or CBN will reach the superhard group of engineering materials. Can be.

By sintering diamond particles in the presence of the material, a polycrystalline body in which diamond particles are bonded to a matrix composed of metal and ceramic phases is known. Due to diamond instability and graphitization tendency, conditions of diamond stability are achieved by heat treatment at 1300-1600 ° C. in a high pressure chamber with a pressure of 30,000-60,000 atm (HP / HT).

A defect of this process is that a body of relatively small size is produced. In addition, manufacturing techniques are rather complex and require special equipment.

Some patents disclose techniques for producing materials containing diamond, silicon carbide and silicon without using high pressure / high temperature. There are a number of modified processes associated mainly with using other carbonaceous materials (hereinafter referred to as all kinds of non-diamond carbon materials such as carbon black, carbon fiber, coke, graphite, pyrolytic carbon, etc.). Importantly, the following steps are followed.

A. Carbon-coated diamond particles or uncoated diamond particles and carbonaceous materials are used as precursor materials.

Typically carbon coated diamonds are used. The example of US Pat. No. 4,220,455 begins with the addition of a thin layer of carbon (500-1000 Angstroms) on diamond by pyrolysis reaction. Pyrolysis is carried out in vacuo for several minutes by feeding natural gas or methane to the furnace at 1200 ° C with diamond particles. Sometimes diamonds without a pyrolytic carbon layer are used, as in US Pat. No. 4,381,271, EP 0 043 541, EP 0 056 596, and Japanese Patent 6-199571 A. Both carbon-coated and non-coated diamond are mixed with the carbonaceous material as a major source of carbon, such as carbon black, short carbon fiber or fabric or binder, before the unbaked body is formed.

B. In the mold, sometimes an appropriate pressure is used to form an unbaked body of diamond particle / carbon material mixture. The unbaked body formed additionally contains a solvent of an organic material and a temporary or permanent binder to facilitate formation and increase the strength of the unbaked body.

C. Work-pieces are prepared by heat treating the unbaked body. Some binders are evaporated without leaving any residue, for example paraffin. Some binders cure with residual carbonaceous residues in work-pieces, for example phenol-formaldehyde and other resins such as epoxy resins.

D. Infiltration of porous work-samples with dissolved silicon forms silicon carbide upon reaction between carbon and silicon. The silicon carbide produced fills the void with a certain amount of residual silicon. Heat treatment is done in this way to minimize the graphitization of the diamond, which is considered harmful. The example of US Pat. No. 4,220,455 discloses silicon infiltration in vacuum when the body is in the mold at a temperature between 1400-1550 ° C. for 15 minutes, during which time the reaction between silicon and carbon is complete. U.S. Patent No. 4,242,106 uses a vacuum of 0.01-2.0 Torr during silicon infiltration. The time required, which depends largely on the size of the body, is determined experimentally and takes about 15-20 minutes above 1400 ° C or 10 minutes at 1500 ° C. U.S. Patent No. 4,381,271 uses carbon fibers that promote infiltration of flowable silicon by capillary action. Most patents perform infiltration into a mold. Some prior patents carry out infiltration outside the mold, as in EP 0 043 541.

There is a method of mixing carbon-coated or uncoated diamond with a carbonaceous material, and there are disadvantages, for example, difficulty in preparing a uniform mixture of the materials, namely very small pore size and a special device for producing a uniform mixture. There is a difficulty of silicon infiltration due to the necessity.

The addition of carbon by pyrolysis in Russian Patent No. 2064399 is carried out only after work-pieces have been formed and manufactured. Mixtures of diamond particles and carbide particle sizes or preformed work-pieces of diamond particles, for example as fillers such as silicon and titanium carbide, are prepared with water or ethyl alcohol as temporary binders. The binder is evaporated and the working specimen is placed in the reactor where pyrolytic carbon is deposited on all particle sizes of the body by pyrolysis reaction from methane at gas phase, ie, 950 ° C. for 10 hours. Thereafter, silicon infiltration is performed.

The drawback of the process is that it uses a large amount of hydrocarbon gas and the run time is too long. If carbide particle size is used as filler, homogenization problems such as those mentioned above appear.

When heat treated in air, diamond begins to graphitize and oxidize at a temperature of about 700 ° C. Pressure, temperature, residence time, diamond particle type, size and quality, impurities in the diamond, and the atmosphere have an impact on slowing down the diamond process. In order to prevent the deterioration, heating is carried out in a vacuum or inert gas. High quality diamonds at high vacuum and hydrogen gas are stable for a long time at about 1700 ° C and 2000 ° C, respectively. The method of intentionally using graphitization as described above has not been described. Instead graphitization is considered harmful and useless.

Russian Patent No. 2036779 finally performs the preforming of the diamond powder with water or ethyl alcohol. The work is placed in a furnace and infiltrated with liquid silicon at 1420-1700 ° C. in argon or vacuum. In this process the surface of the diamond grain size is graphitized to a minimum, so that a larger portion of the diamond still remains unchanged. The small amount of graphite is in contact with the impregnated silicon, which produces a thin surface layer of silicon carbide, so that diamond no longer forms graphite during the process used. The drawback of this process is that it is difficult to control and there is no way to control the amount of manufactured SiC, residual silicon or voids left in the composite.

The previous patent thus teaches a well-controlled step of adding carbonaceous materials and intentional graphitization steps for the production of materials with the desired amount of diamond, silicon carbide and silicon, which do not include electroporation and graphite. none.

There are several ways to improve the diamond composite material produced by the techniques described above. One of them is to arrange the diamond particles in the material according to the graded structure of concentration and size. Some properties and also the field of application of the composite are thus influenced by the diamond arrangement.

A method for producing a diamond sized material is disclosed in EP 0 196 777. The material is prepared by sintering a stable zone in diamond at high and high temperatures. Particle size and / or packing density change between layers between the front and back surfaces to be wear resistant at this portion. The hardness or wear resistance of other parts of the material is determined by variations in the particle size of the diamond or by the addition of other low hard materials to the diamond particles. Diamond sizes range from less than 10 μm at the front and 75-500 μm at the back.

The drawback of the method is that because of the use of high pressure-high temperatures, the product of the material is more expensive, requires special equipment and is limited in size.

There are also a number of patents using different amounts of diamond in different parts of the composite body. The following patents, US Pat. No. 4,242,106; No. 4,247,304; No. 4,453,951; European Patent No. 0 043 541; 0 056 596 and some other patents disclose the preparation of composites having a diamond composite layer in contact with, for example, a supported silicon carbide or silicon carbide-silicon substrate. U. S. Patent 4,698, 070 discloses the preparation of composites having a central portion bound by a matrix of diamond and silicon carbide and silicon containing one portion. Additional particle layers with other concentrations in addition to the first may also be provided. The layers are placed in different arrangements on the top, for example in corners, centers and the like.

A drawback of such layered materials, which generally have different diamond sizes or concentrations, is that there may be differences in physical / mechanical properties within the diamond containing and supporting the layer. For example, differences in coefficients of thermal expansion and E-rate can cause undesired stresses at the interface, thereby weakening the composite when stress is applied. Diamonds have relatively low tensile strength and low toughness, and distinct differences in diamond content in other parts bound by the inner layer affect the fracture resistance of the composite. There is no method described for a body with diamond particles of different size distribution of material volume, which has uniformly varying properties in any prior art.

In both Russian Patent No. 2036779 and Russian Patent No. 2064399, the material produced has diamond particles of a single size, which significantly reduces their frictional properties.

The composite prepared according to US Pat. No. 4,220,455 consists of a mixture of diamond particles of different sizes. The mixture is used for the whole complex, ie the complex does not have a layered structure. The specific size or sizes used are chosen depending on the filler and the desired body. Particles up to about 60 μm are preferred for most wear applications. Preferably, the size should be graded to cover a range of sizes, ie small, medium and large particles, to minimize filler particles. Preferably the graded particles are about 1 μm to about 60 μm. Some patents also control mixing density by mixing diamonds of different sizes; U.S. Patent 4,231,195; US Patent No. 4,353,953.

An object of the present invention is a method of producing a diamond-silicon carbide-silicon composite having excellent properties and an ultrahard material produced thereby. The method also needs to be easy to carry out, fast and costly, and offers the possibility of adjusting some properties and the cost of the final material.

Summary of the Invention

It is an object of the present invention to produce a working specimen, to heat the working specimen and to control the heating temperature and the heating time so that a specific amount of graphite is produced by graphitization of the diamond particles, thereby producing an intermediate body, A method of making a diamond-silicon carbide-silicon composite from diamond particles, comprising the step of infiltrating silicon into an intermediate body.

In a preferred embodiment, the amount of graphite produced by graphitization is 1-50% by weight, preferably 6-30% by weight of diamond and the heating temperature during graphitization is less than 1700 ° C. The heating temperature and heating time required for graphitization are determined experimentally for the heater used. Working specimens are produced with porosities of 25-60% by volume.

In a variant, a certain amount of carbon is deposited on the work piece by exposing it to gaseous hydrocarbons or gaseous hydrocarbons at a temperature above the decomposition temperature for the hydrocarbons or hydrocarbons, and the work piece is subjected to a decomposition temperature for the hydrocarbons or hydrocarbons. At least some graphitization of the diamond crystals is carried out before exposure to gaseous hydrocarbons or gaseous hydrocarbons at temperature. The intermediate body is processed to the desired shape and size of the final body before the infiltration step of the liquid silicone.

In another variant, the intermediate body is heated in the presence of vapor phase silicone and then processed to the desired shape and size of the final body prior to the infiltration phase of the liquid silicone.

Working specimens are produced as non-uniform distributions of diamond particles of various sizes and qualities. The diamond particles in the working specimen can be distributed to continuously reduce in size from the surface of the working specimen to its center. Working specimens may be formed from a uniform mixture of diamond crystals of various sizes by finally adding the binder in a variant.

In another variant, two or more working specimens are separated and obtained before the heat treatment and infiltration steps.

The production of working specimens is carried out in a mold, and the heat treatment and infiltration of silicon are performed after the working specimens leave the mold.

The invention also relates to a body in which diamond particles are bonded to a matrix of silicon carbide, which body comprises at least 20% by volume diamond particles, at least 5% by volume silicon carbide, preferably more than 15% by volume silicon carbide, and silicon. Young's modulus is over 450㎬.

In one embodiment, the body comprises at least 29 volume percent diamond particles, at least 14 volume percent silicon carbide, and silicon, with a Young's modulus greater than 540 GPa.

In a preferred embodiment, the body comprises at least 46% by volume diamond particles having a size of about 30 μm or less and a Young's modulus is greater than 560 GPa.

In another preferred embodiment, the body comprises at least 54 volume% diamond particles, at least 60 volume% diamond particles having a size of at least 50 μm, with a Young's modulus greater than 650 GPa.

In all embodiments, the body maintains its shape and its Young's modulus is up to at least 1500 ° C.

In a variant, diamond particles having a size of about 10 μm or less are used and included in the matrix, the Vickers microhardness of the matrix measured in the region between the diamond particles being greater than 30 μs for a load of 20 N, Knoop microhardness is greater than 36 kPa for a load of 20 N.

In another variant, the diamond particles have a size fraction of particles of less than 50 μm and a size fraction of particles having a size of 50 μm or less, with mass ratios and average particle sizes falling in the range of 0.25 to 2.5 being greater than 10 μm, preferably Is greater than 20 μm.

In another variant, the diamond has a size fraction of particles that are large diamond particles and a size fraction that is small diamond particles, the mass ratio and average particle size falling in the range of 0.25 to 2.5 is greater than 10 μm, preferably greater than 20 μm.

In another embodiment, the diamond particles have a size fraction and a small diamond grain size fraction of large diamond particles are particles, the friction velocity is a 26㎛ ³ / m, preferably 10㎛ ³ / m or less.

In another embodiment, the diamond particles have a size fraction of particles that are large diamond particles and a size fraction that is small diamond particles, with an erosion ratio of less than 0.34 mg / g, preferably 0.25 mg / g.

In another embodiment, the diamond particles have a size less than go 20㎛, friction speed was 26㎛ ³ / m, preferably 10㎛ ³ / m or less.

In another embodiment, the diamond particles have a size of less than 20 μm and the erosion rate is 0.34 mg / g, preferably less than 0.25 mg / g.

In a variant of the embodiment, the body is a cavity.

In another embodiment, the surface of the body is coated with a diamond film.

In another embodiment, the body comprises large diamond particles larger than 20 μm, 0-50 volume% small diamond particles having a size less than 20 μm, 20-99 volume% silicon carbide and 1-30 volume% silicon. Matrices, wherein the matrix hardness is greater than 20-63 mm 3.

In a first variant, the matrix hardness is 20-30 kPa.

In a second variant, the matrix hardness is 50-63 mm 3.

In a third variant, the matrix hardness is 30-50 kPa.

The present invention relates to a method for producing a diamond-silicon carbide-silicon composite and thereby to a diamond-silicon carbide-silicon composite produced.

The invention will be described with reference to the accompanying drawings.

1 shows the preferred steps of the method according to the invention in a flow chart.

2 shows graphitization time versus graphitization degree at a specific temperature.

3a is in the final body _The amount of carbon inserted into the body at different initial porosity ε ₀ that satisfies _Si ≥ ₀ (α and ) Represents a relationship between

3b.c shows the relationship between the final body composition and the diamond graphitization degree, where the initial working specimen porosity is ε ₀ = 0.3 and ε ₀ = 0.5, respectively.

4A-C show the results of the respective X-ray diffraction analysis on the working specimen, intermediate body and final body.

5 shows the change in working specimen porosity during graphitization at different initial working specimen porosities.

6A1 and 6A2 show scanning electron micrographs of the worn surfaces of two different samples.

It is an object of the present invention to produce diamond-silicon carbide cyrylcone-composites with good properties in a fast, efficient, cost-effective and uncomplicated manner. The present invention includes several principles:

The process is intentionally used without avoiding diamond graphitization.

Different types of gradients or parameters are used to control both the final properties of the product and the manufacturing cost.

Implementing nearly pure shape technology with reinforcing intermediate bodies that allow complex final body shapes and avoid expensive and difficult machining of infiltrated bodies.

-The production of large body and mass products as authors.

In the process according to the invention, diamonds of any size may be used. Submicron sized diamonds are diamond particles of less than 1 μm, and small diamond particles are less than 20 μm, more preferably less than 10 μm. Large diamonds> 20 μm are used in some applications. For high mechanical strength, especially in engineering components, the size of the diamond particles used is preferably less than 20 μm. Very large diamonds larger than 60 μm are often used for friction with small diamonds.

Uses and methods available for diamond graphitization with the use of pyrolytic carbon

The material according to the invention is achieved for the production of diamond-silicon carbide-silicon composites, possibly by means of pyrolytic deposition of carbon and for use in graphitizing diamonds. This is sufficient for the present invention to use diamond graphitization, ie, to efficiently transform a portion of the diamond into graphite in a planned and controlled manner.

1 preferably describes the method steps in the flowchart. Other steps of the method according to the invention are described below.

The production of the unbaked body is carried out from a mixture of diamond particles of various sizes without the use of small amounts of temporary or permanent binders (up to 5% by weight) or binders. This is done using techniques established by pressing, for example using slip and slurry casting. When the mold is used for production, the unbaked body is removed from the mold.

Preparation of working specimens is carried out by evaporation or curing and decomposition of the present solution formulation and / or binder in an unbaked body. If the unbaked body is made without a binder, it is considered a working specimen. In order to provide uniform and controllable graphitization throughout the entire working specimen volume, it is not desirable to have impurities from the binder present therein. This can catalyze or inhibit the graphitization process. It is evident that the reason for having more than 95% by weight of diamond in the working specimen is that it is possible to precisely control the amount of carbon that may be present and that fillers and other additives in the body are possible.

Heat treatment of working specimens to obtain intermediate body. Working specimens having diamonds of 95-100% by weight of the total mass were heat treated to obtain an intermediate body using a controlled graphitization of diamonds, or a combination of controlled graphitization of diamonds and deposition of pyrolytic carbon, which is called pyrolysis carbon. Call. When formulated, graphitization is preferably used prior to pyrolytic carbon deposition.

Graphitization to obtain intermediate body.

During graphitization the working specimen (or intermediate body with deposited pyrocarbon) is heat-treated in a vacuum or controlled atmosphere, preferably an inert gas, at 1000-1900 ° C., preferably 1200-1700 ° C. Graphitization is ignored at temperatures below 1000 ° C. At temperatures above 1900 ° C, the graphitization rate is very high, making it difficult to precisely control using low quality diamonds. The vacuum pressure is preferably less than 1 mm Hg. Nitrogen, argon, hydrogen or helium is used as the inert gas, which is provided in the absence of oxygen in the system. The inert gas pressure is not critical and is chosen to the extent applicable to the process such as 760 mm Hg.

Pyrolysis deposition of carbon into graphitized intermediate bodies

During pyrolysis deposition of carbon into the graphitized intermediate body (or working specimen), the body may be a flowing gas or gases, for example natural gas at T = 750-950 ° C., or acetylene, methane at T = 510-1200 ° C. For gases containing ethane, propane, pentane, hexane, benzene and derivatives thereof, they are exposed to a gas of hydrocarbons or hydrocarbons at temperatures above the decomposition temperature.

Pre-infiltration of the intermediate body is performed to enable processing of the intermediate body and to increase the strength alternatively to pyrocarbon deposition. Partial pre-infiltration is achieved by chemical deposition (CVD) using organic silanes such as methylchlorosilane systems or by heating the intermediate body in the presence of vapor phase silicon. The strength of the body can be controlled by the amount of silicon reacted with graphite.

Infiltration of the silicone into the intermediate or pre-infiltrated body is carried out by known methods. The infiltration preferably dissolves the solid silicone or supplies the liquid silicone onto the outer surface of the intermediate or pre-infiltrated body, or immerses the intermediate or pre-infiltrated body in the liquid silicone using differential vacuum infiltration techniques to Performed externally. It is also possible to carry out the high temperature reaction after application to the silicon, in part or fully, by chemical methods or by infiltration of porous silicon, for example using techniques similar to sol-gel, chemical deposition and the like.

Properties for Carbon Production

Non-diamond carbon in the body is achieved in the following different ways:

1. Graphite diamond particles in working specimens by heat treatment to convert the surface layer of diamond to graphite.

2. If a reinforcing body for processing purposes is desired, it is useful to deposit pyrolytic carbon in the body. The pyrolytic carbon portion of the total carbon required is determined by the strength required for the processing action.

3. Further graphitization is performed during the heat treatment for silicon infiltration.

4. Final residual pyrocarbon from binder.

Therefore, the crystal added to the total amount of non-diamond carbon is performed by the following.

a) Establish the need for pyrolysis carbon.

b) establishment of degree of graphitization during heat treatment for silicon infiltration.

c) establishing a quantity of specific residual pyrolysis carbon from the binder.

d) Initial graphitization pays for the additional carbon required.

It should be noted that when pyrolysis carbon is not needed, process steps 1 and 3 are combined.

One feature according to the invention is the simultaneous adjustment of the time-temperature curve, ie the type, size, type and quality of temperature, residence time and heating rate and impurities in the diamond particles, and process and material parameters such as atmosphere and pressure. It is the ability to control and change the degree of diamond graphitization. Conditioning conditions include the following.

1. The relative volume of silicon or, alternatively, residual voids, silicon carbide and diamond in the final body, depends on the degree of graphitization in which the precise control should be performed.

2. For submicron and small diamond particles, it is important that the graphitization does not proceed until the particles disappear. Graphitization is less than 50% by weight and preferably between 6-30% by weight.

3. When mixing small diamond particles with large particles, the size of the plot particles should be chosen very carefully so that the small particles do not disappear if they are not desired and the large particles are sufficiently graphitized. Graphitization should be between 50% and 6-30% by weight.

4. The main method of controlling graphitization is to select the correct shape of the temperature-time curve at about 1200 to about 1700 ° C. in an inert gas under vacuum, or at atmospheric pressure, as a function of diamond particle size and quality.

5. For other preferred graphitization degrees suitable for materials intended for other technical applications, different shapes for the curve should be selected.

6. By choosing the correct heat treatment, it is possible to obtain a final body with a very low porosity, no graphite and a well balanced composition between diamond, silicon carbide and silicon. If the graphitization degree is low, the final composite will contain large amounts of silicon or porosity. The higher the graphitization degree, the higher the content of silicon carbide in the final body.

Increasing temperature and residence time generally increases the amount of graphite produced. The rate of graphitization forward movement from the surface of the diamond to the diamond particles is determined by the crystal orientation and the amount and impurity of impurities in the material. When all other conditions are the same, the graphitization forward travel speed is the same for large and small diamond particles. However, differences in particle size determine different relative graphitization degrees for large and small particles. The graphitization degree is significantly high for small particles and proportional to the surface area of the diamond. Therefore, it is important to select the optimum conditions of heat treatment to control the production of materials by the proposed method, which is especially important when using small diamond particles.

Since the graphitization rate is very temperature dependent for small particles, it is important to accelerate the heating rate in a temperature area above 1200 ° C. Thereby the graphitization is reduced (compared to heating low at the same temperature) and the degree of graphitization does not exceed the desired limit (≦ 50% by weight). This allows for continuous liquid silicon infiltration of the intermediate body. Silicone infiltration does not occur in the body unless there is a sufficient size of voids in the body. The graphitization process is sensitive to control and substantiation. The equipment and materials used must be adjusted. Some of these parameters must be experimentally matched to the equipment and materials used.

2 shows graphitization degree, α vs. graphitization time τ at a specific temperature. As shown, the graphitization degree increases faster for smaller diamond particles (5/3, 10/7 and 14/10 μm) compared to larger particles 28/20 and 63/50. The larger the particles, the slower the rate of relative graphitization increases.

One of the advantages of this graphitization process is the enhancement of the diamond surface. In general, diamond cost is related to quality and size. It is known that the surface layer of most diamond particles has a number of defects. Defects and impurities on the surface reduce mechanical and chemical stability. It is preferred that the diamond be of high quality without defects and impurities on the surface and without being expensive. This is accomplished by intentionally converting the surface layer of diamond into graphite by heat treatment. Graphitization starts on the surface and gradually propagates deeper into the particles. The diamond surface is also improved not only by diamond graphitization but also by bulk properties. The diffusion process starts with diamond when heated. The diffusion process causes metals and other impurities to migrate to the surface of the diamond and adhere to silicon carbide or silicon. As graphitization converts the defect layer on the diamond surface, the total particle properties are improved and as a result the overall composite layer material is improved. In order to achieve this improvement, the graphite layer surrounded by diamond particles should be at least 50 nm, preferably more than 200 nm. The graphitization should be at least 1% by weight and preferably at least 6% by weight.

Another very important achievement of diamond graphitization is the extremely strong bonding of the resulting SiC, each coated with individual diamond particles. Diamond is bonded to the matrix and will not fall out of the required application.

During the total manufacturing process leading to a dense or nearly dense body free of graphite, certain rules must be observed:

The porosity of the material consists of pores of different sizes, larger pores and smaller pores. Preformed working specimens are determined by diamond particle size and size distribution, by other materials present or added, prior to heat treatment and silicon infiltration, and by volume compression and specific pore size of specific voids by final compaction of the unbaked body. Has

The diamond content decreases by the amount corresponding to the amount of graphite produced during the graphitization of the diamond. For base silicon filling voids that produce a dense or nearly dense body, added pyrolysis carbon or possible to achieve a final body with an optimal amount of silicon carbide (made in the reaction between non-diamond carbon and silicon) The total amount of non-diamond carbon in the body, including the residual binder, must be controlled.

The effect of the initial porosity and the degree of graphitization on the properties of the final body was studied by the present inventors. At working specimen porosity greater than 60% by weight, the strength of the working specimen is insufficient to materialize subsequent steps of the process. When the porosity of the working specimen is less than 25% by volume, it is difficult to infiltrate the silicon into the intermediate body, and the final body has an important residual porosity. If the graphitization degree is greater than 50% by weight or the amount of pyrolytic carbon and residual carbon deposited from the binder is greater than 25% by weight (the carbon layer is too thick), the same problem arises because the small pores are limited so as not to be large enough. In this case, during silicon infiltration, a dense layer of silicon carbide is formed in the surface area of the intermediate body, preventing liquid silicon from penetrating into the intermediate body.

For the initial porosity ε ₀ of a given working specimen, the maximum amount of carbon produced by graphitization, deposition of pyrolysis carbon and any possible residual pyrolysis carbon from the binder is illustrated in FIG. The reaction takes place in between to produce silicon carbide. For any acceptable combination, the residual carbon (from graphite (α) The relative amounts of) are indicated from the figure above. The process is limited by the total amount of carbon associated with the porosity. At certain initial porosities, the final composite contains large amounts of silicon if the amount of carbon is too small. If the amount of carbon is too large, a certain amount of residual carbon remains in the final composite, which is undesirable since the carbon acts like a defect in the material. Also shown in the two graphs FIGS. 3A and 3B is the relationship between graphitization and composition of the final composite for a specific initial porosity. As can be seen in the variant of the diamond component, silicon carbide and silicon are linear. As the graphitization degree increases, the carbon content increases, while the diamond and silicon content decreases.

The figure was made using the following equation under conditions where the total body volume did not change and there were no voids in the body produced:

The volume content of diamond in the final material

Where α is the graphitization degree, i.e. the amount of graphite, and ε ₀ is the initial porosity of the working specimen.

The volume content of silicon carbide in the final material is determined by the amount of carbon that reacts with the silicon:

Wherein ρ _D and ρ _SiC are the densities of diamond and silicon carbide, and M _SiC and M _C are the molecular weights of silicon carbide and carbon.

The volume content of silicone in the final body

To manufacture nonporous materials, _It is necessary to satisfy the condition of _Si ≧ 0. The condition is α and corresponding to the region shown in FIG. 3A. Satisfied by the value. So among the final ingredients The amount of pyrolytic carbon and binder residues that can be inserted to meet the conditions of _Si ≧ 0 depends greatly on the degree of graphitization.

The solutions of equations 1, 2 and 3 at = 0 suggest a correlation between the diamond composite composition and the initial porosity of the working specimen according to FIGS. 3b-c.

Figure 4 shows the results of the X-ray diffraction analysis of the sample prepared according to the above process. It is apparent from FIG. 4A that the initial working specimen formed of the diamond powder contains a diamond phase (denoted by <D>). The working specimen was subsequently subjected to heat treatment to obtain an intermediate body, whereby a graphite phase (indicated by &lt; G &gt;) was formed therein as shown in Fig. 4B. The intermediate body is then silicon infiltrated so that the silicon reacts with the graphite and produces silicon carbide. 4C shows that graphite is not in the final product and that diamond, silicon carbide (denoted by <SiC>) and silicon (denoted by <Si>) are present.

Use of different kinds of parameter variations

Parameter variations can be applied to the material during various process steps to adjust the final properties of the product and manufacturing costs. The variation may be a continuous change, ie a gradient, of the parameter. Other combinations of gradients and / or parameter variations can be applied to the entire body or to a portion of the body.

The parameters applied are:

Diamond particle size

Diamond quality

Diamond bonding

Porosity and pore size

Amount of silicon carbide and silicon

Some of the above parameters are dependent on each other. The following example shows the adjustment of the final properties by the use of the gradient and its combination.

Variation in Diamond Particle Size:

Combination of diamonds of different sizes:

The material according to the invention may comprise one as well as several diamond particle sizes. The use of diamonds of different sizes in the material gives special characteristics. Large diamond particles supply materials with good frictional properties (here referred to frictional, wear, cutting and other mechanical material removal properties). However, the relatively lower wear resistance of the SiC / Si matrix results in a weaker bonding force, thereby slowing the life of the composite tool under particularly severe operating conditions, resulting in a large diamond loss from the matrix. By incorporating large diamond particles together with small diamond particles in a uniform mixture, the life of the tool is increased due to the increased wear resistance of the new matrix formed. Small diamond particles strengthen the composite. When distributed over the entire SiC-Si matrix, small diamond particles increase the Young's modulus, thermal conductivity, hardness, and wear resistance. For example, when about 40% by volume of diamond with a size of about 10 μm is included in the SiC-Si matrix, the Young's modulus increases from 400 to 650 GPa and the thermal conductivity is 80 compared with the SiC-Si matrix without diamond. To 250 W / mK. Thus, the use of small diamonds with large diamond particles not only improves the material properties but is also much more economical than using only large particles.

Diamond-sized gradient

In general, a drawback in producing materials with different diamond sizes or concentrations among other parts (compressed together prior to silicon infiltration) is that the physical and mechanical properties in the layers may be different. This difference can lead to unwanted stresses at the interface and thereby weaken the composite.

By the method of the present invention, it is possible to produce a size gradient material having a previously specified distribution of diamond particles that continuously changes in size in a body volume that changes properties uniformly and overcomes or strongly reduces the above-mentioned drawbacks.

The practical way of producing a composite with a gradient arrangement is to create a body with three different parts in the mold, for example. In the first part a mixture of particles of size A, B and C is used. The second part consists of particles of size A, C and D. The third part consists of A, D and E in order of particle size. Diamond particles of size A are the smallest. When the entire body becomes small diamond (size A), there is material between the larger diamond particles, which increases the strength of the matrix. After being placed in the mold, each individual part is vibrated and then finally pressed together. The parts are then joined by graphitization, pyrolytic bonding during silicon infiltration. Through the body volume, a smooth transition in the particle size occurs between the parts, causing a size gradient of the material and a small diamond of size A strengthens the matrix.

Fluctuations in diamond quality

High quality diamonds are generally much more expensive than low quality diamonds. The term quality is noted as being something that changes with the following parameters, mechanical and optical properties, whether or not crystallization is good, such as inclusions, and breaks the shape if synthetic or natural (mostly on the surface) .

The material according to the invention can be produced using low quality diamonds of low quality among the above parts of the composite, with poor performance in application. Good quality diamonds are used to improve properties and performance in critical areas. By this method, the total cost of diamond can be lowered. In addition, graphitization improves diamond surface of low surface quality.

Bonding Fluctuations in Large Diamonds

When the material in contact with the composite according to the process of the present invention is not affected, it can be used for a variety of applications such as applying tools for grinding, turning and milling to the application.

The method allows for tailoring the material to other applications by optimizing the performance of the composite for the additive field. Due to its excellent hardness, diamond is used for the main part of the working effect, so the adjustment is made with diamond parameters; Ie by modifying the type, particle size and concentration.

There are several types of diamond particles, such as onion type and each layer with cutting edges, such as a well crystallized blunt single crystal type with sharp cutting edges in a type each composed of a different diamond layer on top. The latter type is sometimes soft. The two types have very different properties and most of the diamond types are completely different between them.

In other materials, it is known that the diamond type selected greatly affects the properties of the polishing wheel, for example when used in the polishing wheel. It is necessary to match the diamond's bonding force to the diamond type used in order to adjust the properties in an appropriate manner.

In known abrasive wheel materials, it is difficult to fine tune the bond required for optimal performance. Mainly three types of combinations for use in grinding wheels; That is, resin bonds, metal bonds and glassy bonds are used.

The method according to the invention makes it possible to tune the bonding of large diamonds (> 20 μm) and the bonding matrix properties (here consisting of small diamond, silicon carbide and silicon) well. Suitable hardness of the matrix is small diamond <20 μm, preferably 10 μm (0-50% by volume); It can be selected by varying the concentration of silicon carbide (20-99% by volume) and silicon (1-30% by volume), thereby the wear resistance of the matrix and the accompanying bonding of larger diamond particles.

By varying the composition of the matrix, the matrix hardness can be selected within the range of about 20-63 mm 3, the diamond hardness is about 100 mm 3, the silicon carbide is about 25 mm 3 and the silicon is less than 10 mm 3. By such adjustment the performance of the improved materials of the present invention is optimized for various applications.

Matrix hardness of 20-30 kPa is preferred for diamond types requiring relatively weak bonding; 50-63 mm diamond type, which requires strong bonding; And hardness of 30-50 GPa for diamond types or mixtures in which intermediate bond strength is desired.

Variation of Porosity and Pore Size in Working Specimens: Porosity and Pore Size

By the method of the present invention, it is possible to produce intermediate bodies having different amounts of porosity and various pore sizes in the body. By this method working specimens having a pore size with a total porosity in the range of 25 to 60% and a size of diamond particles can be produced.

The pore structure determines the extent to which silicon can infiltrate, so that all non-diamond carbon in the intermediate body reacts with the silicon. Too small pore size and too small porosity, inadequate pore channel distribution, inadequate infiltration, or too high viscosity of the silicon throughout the body will interfere with the infiltration, since the silicon carbide produced will prevent molten silicon from further infiltrating the material. to be. Particularly narrow voids are dangerous and they easily become bumpy, clogging and preventing further infiltration.

This impediment to infiltration was one of the limitations of the manufacture of thick and large infiltrating bodies useful for purposes such as load transfer devices such as engineering details, structural components, bearings, and the like.

By diamond particle distribution whose size is continuously reduced from the surface of the unbaked body toward the center, a body having a pore size distribution is produced. The pores, which increase in size from the center of the body towards the surface, facilitate the penetration of silicon into the body by minimizing the risk of infiltration near the surface area. By building up these porosities, a larger body than before can be manufactured. It is also advantageous in this method that the controlled amount of carbon is densely placed on the diamond particles and not between the diamonds, creating a suitable pore structure.

In practice, the pore size gradient is easily achieved by the diamond size gradient and the variation in diamond loading and diamond loading in the unbaked body.

Variation in Silicon Carbide and / or Silicon Amount and Gradient Structure

Silicon carbide and silicon matrix are tightly bonded to the diamond particles, which provide the excellent properties of the material according to the invention. Silicon carbide content is also important for the properties of materials that affect the hardness and bonding of diamonds. The amount of silicone also affects this property, with the increased silicone content lowering the hardness and wear resistance. Other properties affected by the composition are, for example, thermal conductivity which increases with diamond content, electrical conductivity which increases with silicon content and the like.

Therefore, a composition well balanced between diamond, silicon carbide and silicon is desirable. This balance in the composition depends on the particular application desired for the composite. As the composition varies, the properties can be adjusted and thereby the composition can be adjusted for a particular application. A way to change the content of silicon and silicon carbide in the final body is to change the amount of non-diamond carbon in relation to the effective porosity. This is accomplished by modifying the conditions of heat treatment in which the formed graphite and added pyrocarbons are provided in different amounts, other amounts of non-diamond carbon left from binder residues, diamond size / pore size variations, and the like.

Sufficient filling bodies are preferred when used as engineering materials. However, porous end bodies are preferred in certain applications, such as abrasive wheels. If possible, the residual porosity must be controlled, which is very difficult as it impregnates the intermediate body with liquid silicone. One reason is that it is difficult to accurately add the amount of silicon needed for all processes, especially to small objects. This is insufficient to control the uniformity of the infiltrated body. Too little silicon results in excess carbon in the material. Another reason is that it is out of control when possible excess silicon is deposited.

Residues in the final body are easily controlled by the method by pre-wetting silicon, ie exposing the intermediate body to silicon vapor or Si-deposition by CVD techniques. The amount of silicone added to the intermediate body in the process can be controlled by the combination of process time, pressure and temperature, and amount of vaporized silicone.

The addition of vapor phase silicon is therefore another way of influencing silicon carbide and silicon content in the final material, independent of other parameter variations.

Preform and nearly pure shape technology combined with strengthening intermediate body

By this method it is possible to produce bodies of various predetermined sizes and shapes. The body produced has a large and complex shape and is described in the section above.

Using prior known methods, the creation of an unbaked body of carbon-coated or non-coated diamond mixed with a carbonaceous material is carried out in the mold as evaporation / decomposition and temporary silicon infiltration of the temporary mold or binder. Relatively large amounts of binder are needed when using this product, especially large diamond interest. The production efficiency is reduced when each unbaked body mold is required when placed in the furnace. The consumption of the mold is high, which reduces the life of the mold due to high wear in the heat treatment process. There is also a problem of detachment of the composite from the mold. Graphite molds are commonly used and cause problems that some silicon reacts with and thereby leaves the mold during the liquid silicon infiltration step.

Performing the techniques of the method as some known method does not limit the mold having the ability of a mold of complex shape or the ability of the body to infiltrate from or leave the mold. The production of the unbaked body according to the invention is made by known methods such as pressing, tape and slip casting, injection molding in a mold. However, it is not necessary to use the mold during the production step, heat treatment step or infiltration step. Preferably the heat treatment and infiltration steps are performed without a mold.

During graphitization diamond converts to low density graphite and therefore requires greater volume. However, the process according to the invention is characterized by maintaining a constant shape and size throughout all process steps, from creating unbaked body / working specimens through subsequent steps to the final body (excluding internal processing of the intermediate body). . The conclusion is that graphitization of diamond particles affects the voids, ie the porosity changes the intermediate body. The method thus makes the size and shape constant throughout the process. The near pure shape technology provides waste-free production and enables the production of final bodies of pre-determined size and shape, so that the final body does not require processing except for the final finishing operation.

5 illustrates a linear change in intermediate body porosity during graphitization versus graphitization at different initial working specimen porosities.

If it is not desirable to further process or carry out the shape of the intermediate body, i.e., unless a particularly required shape is required, it is preferred to use carbon derived from the graphitization process.

The nearly pure shape technology of the method is most applicable. However, it is advantageous to process preferred intermediate bodies in addition to near pure shape techniques, for example, if the final body requires very complex production, pre-wetting onto the body of pyrolytic carbon deposition or silicone. This deposition provides an intermediate body that has a film left in the body and has good strength without using any binder, which is not the case when it is an intermediate body that only contains diamond particles with graphitized surfaces.

This allows the intermediate body to be processed in a relatively advanced method, such as milling, turning and drilling, without breaking the intermediate body. This results in a much more complicated shape compared to what is obtained by producing an unbaked body / work specimen. In addition, there is a significant cost savings since it is much more difficult to process the final product due to its high hardness.

Further processing and analysis of the desired properties must be done to select the most optimal relationship between the amount of carbon derived from graphitization and pyrolysis carbon. It takes only 3 minutes to convert pyrolytic carbon onto the unbaked body at about 1550 ° C. to convert about 15% by weight of diamond to graphite, while only 20/28 diamond in pyrocarbon is contained in an amount of 5% by weight of the total mass. The heat treatment should be performed at about 850 ° C. for about 5-6 hours to deposit on a hairy body having Still, using pyrolytic carbon is much more economical than processing the final manufactured body because it is time consuming to process and it is difficult to make the material produced have very high hardness and extreme wear resistance.

By using diamond graphitization or by diamond graphitization with pyrolytic carbon deposition or prewetting of silicon, a body of large size and very complex production can be produced. Hollow bodies and bodies with holes and cavities can be prepared by combining working specimen components prior to heat treatment and silicon infiltration. For example, hollow spheres can be made by combining two hollow hemispheres, and hollow cubes can be made by combining six faces. The technique offers the possibility of saving expensive diamond materials and weight in the final body, producing hollow components suitable for other engineering purposes, while at the same time boring the final material and reducing further costs. It is also possible to produce a body having a cavity that matches the shape and size of the axis of the acyclic cross-sectional area. By finally bonding the shaft to the composite, the shaft is fitted to the final composite body. Thick and large bodies can also be made using a pore size gradient that facilitates infiltration of silicon, as described above.

In the production of composite bodies, it is also possible to use pyrolytic carbon deposition using molds, such as separable molds, which are pressed in the shape processing manufacture which was previously not allowed or could not be used without breaking the mold.

Obviously, a large body can be made by stacking intermediate layers sandwiched with a silicone layer. This can lead to heterogeneous mixtures, heterogeneous infiltration, shrinkage and shape stability problems of the body. Therefore, this method is preferable.

It is also possible, for example, by adding a large amount of binder at the start to add a carbonaceous material at the start and co-internal graphitization, but the method according to the invention is more preferred. A test was conducted to mix a carbonaceous material such as carbon black and carbon fiber and a binder such as paraffin and epoxy resin together with diamond. The test results showed cracks and gaps after the infiltration of working specimens and samples, and also showed a change in shape.

Advantages of Materials and Processes According to the Invention

One of the great advantages of the present invention is to achieve the desired diamond graphitization in the working specimen in order to provide the optimum conditions for producing a polycrystalline body of predetermined desired shape and size with the desired strength, physical and mechanical properties. To change. Suggested methods using graphitization, and, if necessary, pyrolytic carbon deposition or silicon, as compared to mixing carbon-coated or uncoated diamond with carbonaceous materials for the production of diamond-silicon carbide-silicon composites The use of pre-infiltration is several advantages.

1) During graphitization of diamond, graphite is produced directly on the surface of all diamond particles, and pyrolysis carbon is deposited directly on the graphitized diamond as much as possible. Thus, during subsequent silicone infiltration of the final body, very little voids remain between the particles. When using a known technique of mixing a carbonaceous material with diamond particles, smaller particles of carbon black or carbon fiber are placed between the diamonds. The smaller particles agglomerate in the narrowed pores, thereby making the pore size even smaller, which negatively affects silicon-infiltration.

2) The distribution of carbon is important as a characteristic of the final material. The carbon layer converts the diamond into graphite and the pyrolytic carbon is deposited on the body to make a dense contact with the diamond surface. This close contact ensures that silicon carbide is produced directly on the surface of the diamond particles and thus creates a high adhesion diamond-matrix interface, ie, the diamond binds tightly to the silicon carbide-silicon matrix. This property is improved due to the high tack of small and large diamonds. Diamonds do not break easily from the matrix when used in other applications. The material is extremely wear resistant. When used in operations requiring very strong bonding, large diamond particles are used throughout the process, and in conventional (metal or organic bonding) friction materials, only about 50% by volume of diamond is used before leaving the matrix.

3) Heat treatment of the final binder and graphitization can be accomplished using the same apparatus as far as silicon infiltration is concerned (when no pyrolytic carbon deposition is used). The process steps are thus embodied step by step in the same furnace, resulting in reduced overall time for producing the final material.

4) Graphitization of diamond begins by gradually propagating deeper onto the surface of the diamond particles. Graphitization converts the defective layer on the diamond surface, thereby improving particle properties, as a result of improving all composite materials, for example related to thermal stability. This leads to the use of relatively low cost diamonds.

5) In the present invention, graphitization of diamond with or without deposited pyrocarbon can avoid various problems of physically mixing the carbonaceous material as a carbon source. These problems include inhomogeneities due to differences in different sizes, shapes and densities of mixed materials, uneven distribution of carbon, incomplete reaction with silicon and blocking of voids.

6) The graphitization starts from the surface of the diamond and provides fast and adequate carbon production over the entire body volume extending linearly. Only relatively small amounts of diamond are converted. Thus, when producing very thick and large bodies, graphitization is advantageous because of the ability to produce carbon into the deeper parts of the body without the risk of blocking the voids for subsequent infiltration.

7) The initial unbaked body in this method contains only a solid material, diamond. This is advantageous when using modern production methods such as slip casting or slurry casting. The production method provides for the production of molded articles with complex shapes. When using a mixture in which the particles have large differences in density and size, and when using fibers, this production method can be further complicated.

8) The process can provide a variety of different complex shapes due to the almost pure shape technology and the ability to process the intermediate body in an advanced manner. Pyrolytic carbon deposition or preliminary infiltration of silicon provides sufficient wet strength to process complex shapes. The shape and size of the final body is not limited to the molding technique. This is not limited to the production technology by the use of molds and the cost is saved since it is possible to avoid using expensive molds during the heat treatment and silicon infiltration steps. In addition, there is no problem of leaving the body from the mold.

9) The process according to the invention is that the majority of bodies are produced in batch and the main method of carbon production and graphitization of diamond is faster than pyrolytic carbon and does not use gas. Due to the processability of the strong intermediate body, tedious and expensive processing of the final body can be avoided. If no further processing is required, the process is a very simple "one step process", ie the graphitization of diamond is carried out while the temperature is rising before silicon infiltration. In some cases it is not necessary to use a mold for production. Due to the pure shape, dressing and processing of the final body is unnecessary or almost unnecessary and the cost is further reduced. Diamonds of relatively low prices are available.

The material according to the invention has several advantages:

The utility of the process is unique. The process parameters can be varied to provide a material made to have the desired properties. The method can be made from structural and engineering purposes, load bearing materials as well as materials with good wear resistance and improved performance of friction, polishing and other mechanical removal operations.

One feature of the present invention is characterized by the ability of the proposed material to combine other superior properties simultaneously and the ability to match the properties that are best for various desired applications.

1. High Young's modulus and sufficient strength in formulations with low viscosity

2. The high hardness and high bond strength of diamond result in excellent friction and erosion resistance.

3. High thermal conductivity, low thermal expansion coefficient, depending on diamond content.

Maintain mechanical properties after exposure to temperatures of 4.1500-1600 ° C.

5. Ceramic composite with high thermal shock resistance.

6. Electrical conductivity.

When mixing small diamond particles and large diamond particles together, there are two factors; The high abrasion resistance between the diamond particles and the matrix and the small diamond distributed therein affect the material properties. Insufficient bonds in the matrix or low low abrasion resistance of the matrix causes large diamonds to escape from the material. Small diamond particles reinforce the matrix giving high wear resistance and increased stiffness, strength and thermal conductivity. All of the above are the frictional properties of the material (wear, cutting and other mechanical material removal properties): the increased thermal conductivity reduces the temperature in the working zone of the diamond particles. The increased rigidity of the final body extends the life of the tool when used for very accurate machining.

Examples of Method Specificity and Material Properties

The following other diamond types were tested for sample preparation:

ACM 5/3 synthetic diamond particles (size 3-5 μm), ACM 10/7 synthetic diamond particles (size 7-10 μm), ACM 14/10 synthetic diamond particles (size 10-14 μm), ACM 28/20 synthesis Diamond particles (size 20-28 μm), ACM 63/50 synthetic diamond particles (size 50-63 μm), and A-800 / 630 natural diamond particles (size 630-800 μm), all of Ukraine, Kiev, ultrahard materials Commercially available.

Example 1 Properties Adjustment

To illustrate the ability of the present invention to produce materials with other important properties, the inventors are selected from a) E-rate and b) electrical resistivity variations. The process of the present invention obtains these results by controllably selecting the following process steps:

1. In an amount of 2% by weight dry resin of the diamond powder mass,-25% alcohol solution of phenol formaldehyde resin-creates a mixture of binder and diamond micro-powder of ACM 28/20. The mixture was stirred vigorously and filtered through a sieve as a 200 μm mesh.

2. A rectangular cross section having a size of 6 x 5 mm and a length of 50 mm is produced by pressing at room temperature using a metal mold having a force of 45 kN.

3. While maintaining at room temperature in air for 10 hours, remove the unbaked body from the mold, then dry at 70 ° C. for 1 hour and cure at 150 ° C. for 1 hour. The prepared working specimen contained 98% by weight diamond (56% by volume) and had a porosity of 41% by volume.

4. The heat treatment of the sample is carried out at 1550 ° C. under vacuum (pressure 0.1 mm Hg). Sample No. 1 is heated for 3 minutes, Sample No. 2 is heated for 10 minutes, Sample No. 3 is heated for 20 minutes, and Sample No. 4 is heated for 30 minutes.

5. Infiltrate the molten silicon on the surface of the intermediate body at 1550 ° C.

The result is a polycrystalline bar having a rectangular cross-sectional area of 6 x 5 mm and a length of 50 mm, i.e. the size and appearance do not change within the measurement accuracy (± 0.001 mm). The body contains diamond particles bound by silicon carbide and a matrix of silicon.

In addition, Samples 5-7 are produced as diamond powder (5 × 6 × 50) mm using a temporary binder. Sample 5 is prepared from diamond powder ACM 10/7, sample 6 is prepared from a mixture of diamond powder ACM 63/50 and ACM 14/10 and sample 7 is prepared from a mixture of ACM 63/50 and ACM 10/7.

The working specimens are heat treated at 1550 ° C. in vacuo and then infiltrated with liquid silicon.

Table of properties as a prepared sample:

The experiment demonstrates that a material having the desired properties can be obtained by adjusting the process parameters and the material composition.

In particular, the reduction of the silicon content in the material results in an increase in electrical resistance. The electrical resistivity of the material is equivalent to that of the semiconductor material. The material has sufficient electrical conductivity and, for example, electro-erosion processing can be used to further process the material. Electrical resistance was measured by four probe methods.

As shown, the E-rate can vary widely. E-rates can be increased by varying the small diamond ACM 10/7 in sample 6 and even the smaller diamond ACM 10/7 in sample 7.

Example 2 Infiltration by Soaking in Dissolved Silicone

Diamond powder ACM 14/10 and an amount of 10% by weight resulted in a mixture of ethyl alcohol added. The mixture is stirred vigorously and passed through a 200 μm mesh size sieve.

A rectangular cross-sectional area of 6 x 5 mm and a length of 50 mm is produced by pressing at room temperature using a metal mold having a force of 45 kN.

The unbaked body is removed from the mold and kept at room temperature for 3 hours. The working specimen contains 100% by weight diamond and has a porosity of 42% by volume.

The heat treatment of the working specimens is carried out in an argon medium for 4 minutes at 1550 ° C. under a pressure of 800 mm Hg. The heat treatment reduces the diamond concentration in the intermediate body by 22% by weight. It should be noted that the temperature and time of the heat treatment are chosen so that the silicon melts completely except for the first time after the heat treatment of the working specimen is completely finished. Infiltration of the intermediate body is carried out by dipping the intermediate body up to the dissolving silicone at 1550 ° C.

The resulting polycrystalline body produces a polycrystalline bar that is substantially nonporous (<1% by volume) with a rectangular cross section of 6x5 mm and a length of 50 mm, i.e. size and appearance do not change within the measurement accuracy (± 0.001 mm). .

The final body contains diamond carbide bound by a matrix of silicon carbide and silicon (45 vol% diamond, 48 vol% SiC, 7 vol% Si) with a density of 3.28 g / cm ³ . The three-point flexural strength was 400 MPa and measured on samples prepared without any processing or polishing.

Example 3 Measurement of Thermal Stability, E-Rate and Specific Stiffness

Sample 1 is made from diamond powder ACM 10/7, Sample 2 is made from diamond powder ACM 14/10, Sample 3 is made from diamond powder ACM 28/20 and Sample 4 is made from ACM 63/50 and ACM 10/7 Prepared from a mixture of The temporary binder is used to produce bars 5 × 6 × 50 mm in size from the diamond powder. The working specimens are heat treated at 1550 ° C. in vacuo and then infiltrated with liquid silicon.

Measure the density, Young's modulus and thermal stability and use H = E / (ρ * g) (E = Young's modulus, ρ = density and g = 9.8 m / sec ² , gravitational factor (see table)) , The specific stiffness was calculated.

The thermal stability was investigated by sequentially heating the samples under vacuum at a temperature of 1200 ° C., 1300 ° C., 1400 ° C., 1500 ° C., 1600 ° C. for 45 minutes. Young's modulus and samples were tested at room temperature after each heat treatment of the shape. The stabilization temperature for maintaining the Young's modulus is defined herein as the maximum temperature when the Young's modulus does not change by more than 4% from the initial value after heat treatment.

Characteristic table of the prepared sample sample Final content characteristic number Initial Diamond Powder Material composition [vol-%] Density [kg / m ³ ] Young's Rule Stiffness H (10 ⁶ m) Thermal Stability [℃] Young's modulus Keep shape One 10/7 Diamond 46SiC 47Si 7 3290 630 19.1 1500 ℃ 1500 ℃ 2 14/10 Diamond 46SiC 42Si 12 3250 580 17.8 1500 ℃ 1500 ℃ 3 28/20 Diamond 49 SiC 31 Si 20 3180 560 17.6 1500 ℃ 1700 ℃ 4 60 wt% 63/5040 wt% 10/7 Diamond 62SiC 31Si 7 3340 718 21.5 1600 ℃ 1600 ℃ Data for SiC Ceramics, Circle 1) 3100-3200 400-420 13 - -

The results show that the material produced has an unusual thermal stability (keeping its properties up to 1500 ° C.), ie 300-400 ° C. higher than other diamond polycrystalline materials, see 2). The material thus produced can be used at high temperature conditions. The table also shows that the material has a much higher stiffness than the properties of known materials.

1) G.G. Gnesin. "Anoxic Ceramic Materials", Kiev, Technology, 1987, p139-142.

2) A.A. Shulzhemko, "Diamond-Based Polycrystalline Materials", Kiev, 1989.

Example 4 Measurement of Bending Strength

Sample 1 is made from diamond powder ACM 14/10 and sample 2 is made from ACM 28/20. Sample 3 is prepared from a mixture of diamond powders ACM 63/50 and ACM 10/7. Sample 4 is prepared from a mixture of diamond powders ACM 63/50 and ACM 28/20. Sample 5 is prepared from ACM 28/20. Samples 1-5 were prepared according to Example 3, but Sample 1-4 and Sample 5 were prepared as ring plates: (Ø = 20 mm, h = 2 mm) as three-point flexural strength measurement bars.

Properties Table as Prepared Sample sample Initial diamond powder Material composition [vol%] Density [kg / m ³ ] σ _{biaxial curvature} [MPa] One 14/10 Diamond 46SiC 42Si 12 3250 260 2 28/20 Diamond 49 SiC 32 Si 19 3190 115 3 90 wt% 63/5010 wt% 10/7 Diamond 58SiC 14Si 28 3140 125 4 80 wt% 63/5020 wt% 28/20 Diamond 57 SiC 14 Si 29 3120 136 - - - - σ _3-p [MPa] 5 28/20 Diamond 44SiC 48Si 8 3270 310

The manufactured plate of the material has sufficient flexural strength for the application, for example as a construction material. Flexural strength is measured on samples made without any processing or gloss.

Example 5 Measurement of Thermal Conductivity

All samples were prepared according to Example 3. Samples 1-3 are made cylindrical ( = 15 mm, h = 10 mm). Samples 4-8 are made cylindrical. = 20 mm, h = 2 mm). See the table for the diamonds used. The thermal conductivity of the sample was determined by measuring the temperature difference on the sample while the stagnant heat flow was traveling. Two radial openings 1 mm in diameter and 8 mm in width, parallel to the bottom of the cylinder, were prepared in Samples 1-3 using electron-erosion. The length between the openings is 6 mm.

Sample 9 was prepared from a mixture of diamond powders ACM 63/50 and ACM 14/10. The coefficient of thermal expansion was measured using a quartz dilatometer in the temperature range of 20-100 ° C. The linear dimensional change of the sample versus the increase in temperature was measured. Thus, the thermal expansion coefficient was measured according to the sample length.

Property table

sample Initial diamond powder Composition [vol%] Thermal Conductivity [W / mK] D SiC Si One 5/3 29 70 One 180 2 28/20 49 20 31 200 3 14/10 46 42 12 260 4 60 wt% 63/5 040 wt% 5/3 54 40 6 370 5 10/7 45 48 7 267 6 28/20 47 32 21 259 7 Al - - - 225 8 Cu - - - 400 Data on Silicon Carbide Ceramics, Circle 1) - - - 80-85 - - - - - Thermal expansion coefficient [× 10 ⁶ / K] 9 60 wt% 63/5 040 wt% 14/10 65 21 14 2.2

The table shows that samples made according to the invention have much better thermal conductivity than silicon carbide ceramics and aluminum. Sample 4, which has a higher concentration than diamond, has higher thermal conductivity than copper.

The coefficient of thermal expansion of diamond composites is very low.

1) G.G. Gnesin. "Anoxic Ceramic Materials", Kiev, Technology, 1987, p139-142.

Example 6 Measurement of Biaxial Strength of Unbaked Body, Work Specimen and Intermediate Body

After graphitization and pyrolysis carbon, the strength of the intermediate body is increased, allowing the intermediate body to be processed before Si-infiltration. In this test the biaxial strength of the unbaked body, working specimen and intermediate body was measured. The intermediate body consisted of deposited pyrocarbon and graphitized body.

An unbaked body was prepared by pressing diamond powder. Working specimens were prepared by heating the unbaked body under vacuum at 1000 ° C. for 20 minutes. The intermediate body was graphitized at 1550 ° C. for 3-30 minutes and the pyrolytic carbon was deposited at 850 ° C. up to 5% by weight or prepared in another order.

Samples can be divided into nine groups according to treatment. Two types of samples (different diamond particle size) were prepared for each group. Five samples of each treatment and particle combination were tested and the results are presented as averages.

As shown in the table, the strength of the working specimen was much higher than the initial unbaked body (about 2 times). Deposition of pyrolytic carbon is an effective way to increase sample strength and can be used before and after graphitization.

Overall, the results show that by processing before Si-infiltration, an intermediate body of good mechanical strength is obtained.

Example 7 Thermal Shock Resistance

The primary test was thermal shock resistance. The sample was heated to 1000 ° C. in air and placed directly in water (quenched) at room temperature. The sample shape remained the same and no debris was observed.

In the second, similar test, the strength after thermal shock was measured. Samples of size 5 × 6 × 50 mm were prepared from ACM 14/10 diamond particles. The sample was heated to 500 ° C. and placed in water at room temperature. Irradiation with an optical microscope was then performed but no uniformity or defects appeared on the surface. Similar results were obtained after heating to 800 ° C. following the same procedure. After this, the sample was heated to 1100 ° C. and quenched. At this time, small micro cracks appeared on the surface of the sample under the optical microscope. The three-point flexural strength was measured at about 38 MPa, which is much lower than the original strength.

Examples of technological tests

The following different diamond types were used for sample preparation and tested:

EMBS 30/40 mesh natural diamond grain, SDB 1025 30/40 mesh, synthetic diamond crystal, SDB 1125 30/40 mesh synthetic diamond crystal and DEBDUST 30/40 mesh natural diamond (all 30/40 mesh available from De Beers) are 420 Same as diamond particles in the size range of -600 mu m.

Diamond micropowders ACM 10/7 (size range 7-10 μm), ACM 14/10 (size range 10-14 μm), ACM 28/20 (size range 20-), all available from Superhard Materials Institute, Kiev, Ukraine 28 μm), ACM 40 (particle size less than 40 μm), ACM 63/50 (size range 50-63 μm) and A-800 / 630 natural diamond particles (size range 630-800 μm).

Example 8 Dressing Tool Test; Comparison of wear resistance

In conjunction with the above examples, we will show that the properties can be adjusted by selecting diamond type, diamond quality, particle size and particle size distribution.

In the above embodiment the dressing conditions are:

V _wheel = 35 m / s, S _longitudinal = 0.8 m / min, S _transverse = 0.02 mm / 1 revolution.

The samples were tested for dressings of other Russian friction wheels (600 mm in diameter and 63 mm in width) of the following type: 600 × 63 × 305 14A40II CM1 6K7II (electric corundum wheel, soft to medium); 600 × 63 × 305 14A40II CT3 7K5 (electric corundum wheel, medium to hard); 600 × 63 × 305 14A25II CM2 6K5 (electric corundum wheel, soft to medium); 600 × 63 × 305 14A40II CT3 37K5 (electric corundum wheel, medium to hard) and 600 × 63 × 305 63C40II CM1 6K7 (microplastic silicon carbide wheel, soft to medium).

Dressing Tool Test 1.

Samples 1-11 were tested for a reference material, which is a composite material << Slavutich>, available from Superhard Materials Institute, Kiev, Ukraine (with diamonds of type A-800 / 630 in the matrix of carburized carbides).

Sample manufacturing

See the table below for the diamond type used in the relationship between sample preparation and different sizes. All samples are prepared from a mixture of very large (> 420 μm) fine diamonds.

A binder ((polyvinylacetate) PVAC20% water emulsion) is added to the diamond mixture for samples 1-2 (the amount of dry PVAC is 1% by weight diamond mass). A binder (25% alcohol solution of phenol formaldehyde resin) is added to the diamond mixture for samples 3-7, 10 and 11 in an amount of 8% diamond mass (ie 2% by weight of dry resin). Ethyl alcohol is added to the diamond mixture for Samples 8 and 9 in an amount of 10% by weight.

All mixtures are thoroughly stirred, the mixture of Samples 1-2 is sieved through a 1.5 mm mesh sieve, and the compound of Samples 3-11 is sieved through a 1 mm mesh sieve. The production of all samples is carried out by pressing using a metal mold with a force of 15 kN at room temperature. The pressed body is removed from the mold. The sample is cylindrical with a diameter of 10 mm and a height of 10 mm. Sample 1-2 is dried at 70 ° C. for 1 hour. Samples 3-7, 10 and 11 are left in air at room temperature for 10 hours and then dried at 70 ° C. for 1 hour and cured at 150 ° C. for 1 hour. Samples 8 and 9 are kept in air at room temperature for 3 hours to evaporate the temporary binder, ethyl alcohol. Sample 1-2 was heated at 1550 ° C. for 4 minutes under vacuum (pressure of 0.1 mm Hg). Pyrolytic carbon was added to Sample 3-4 at 870 ° C. up to 5% by weight. Graphitization of Samples 3-11 is carried out under vacuum (pressure of 0.1 mmHg) at 1550 ° C. for 3 minutes. The reduction of diamond in the prepared intermediate body is 8-14% by weight.

All samples were infiltrated with liquid silicon at 1550 ° C. when the silicon placed on the intermediate body surface began to melt.

The final bodies 1-2, 3-7 and 11 comprise very large particles of natural diamond bonded by dummy diamond particles, silicon carbide and a matrix produced by silicon. The final body 8-10 is identical except that large diamond particles are synthetic.

Final body composition sample Bigger Diamond [vol%] Micro Diamond [vol%] SiC [vol%] Si [vol%] Calculated hardness of the matrix Number 1 25 34 35 6 57 Number 2 25 36.6 30.6 7.8 60 Number 3 37.5 30.1 14.1 18.3 57 Number 4 37.5 27.8 26.6 8.1 57 Number 5 25 33.5 34.7 6.8 57 Number 6 37.5 23.9 27.7 10.9 51 Number 7 50 16.2 21.0 12.8 45 Number 8 37.5 23.9 27.7 10.9 51 Number 9 37.5 23.9 27.7 10.9 51 Number 10 25 33.5 34.7 6.8 57 No11 25 32.6 34.2 8.2 57

The theoretical hardness of the matrix was obtained by assuming that the diamond hardness was 100 GPa, the silicon carbide hardness was 25 GPa, and the silicon hardness was 10 GPa.

Samples 1-4 were tested for dressings of 600 × 63 × 305 14A40II CM1 6K7II friction wheels:

Relative consumption of large diamond particles [mg large particles / kg friction wheel]

sample Initial diamond (+ pyrocarbon content) Relative medium consumption of test sample [mg / kg] Relative medium consumption of larger diamonds [mg / kg] Sample 1 A-800 / 630 + ACM 10/7 - 0.66 Sample 2 A-800 / 630 + ACM 14/10 - 0.63 Sample 3 EMBS 30/40 Mesh + ACM 14/10 (+ 5% pyC) 1.91 0.78 Sample 4 EMBS 30/40 Mesh + ACM 28/20 (+ 5% pyC) 1.59 0.59 Slavutic A-800 / 630 - 2.16

Accordingly, the wear resistance of the body produced by the given embodiment is about three times greater than the wear resistance of the &lt; Slavutich &gt; material.

Sample 5-9 was tested for dressing of a friction wheel of type 600 × 63 × 305 14A25II CM2 6K5:

Relative consumption of large diamond particles [mg large particles / kg friction wheel]

sample [mg / kg of friction] Sample 5 0.52 Sample 6 0.54 Sample 7 0.72 Sample 8 0.60 Sample 9 0.45 Slavutic 1.5

The wear resistance of the sample is about 2-3 times greater than the wear resistance of the Slavutich material.

From the table, it can be seen how the silicon content affects the wear resistance of the body by selecting samples having small diamonds of the same size and type and small diamonds of the same size and type, ie the same conditions.

By comparing Samples 5, 6 and 7, the trend between silicon content and theoretical hardness can be seen and the abrasion resistance of the matrix (small diamond, silicon carbide and silicon). See table. The theoretical hardness value corresponds to the measured total hardness 57-61 mm 3 (see Example 12).

sample Bigger diamond Smile diamond Si content of the matrix [vol%] Si content of the composition [vol%] Calculated hardness of the matrix Wear resistance Number 5 EMBS 30/40 Mesh ACM 10/7 9 6.8 57 0.52 Number 6 EMBS 30/40 Mesh ACM 10/7 17 10.9 51 0.54 Number 7 EMBS 30/40 Mesh ACM 10/7 26 12.8 45 0.72

Sample 5 with the best wear resistance also has the highest theoretical matrix hardness and the lowest silicon content. By comparing samples 8 and 9 with the same small diamond type (ACM 10/7) and the same theoretical matrix hardness (57㎬) but with different larger diamonds, SDB 1025 and SDB 1125, respectively, the better the quality of the sample 9 diamond It can be seen that the wear resistance is improved.

Samples 10-11 were tested for dressing of friction wheels of i) 600 × 63 × 305 14A40II CT3 37K5 type and ii) 600 × 63 × 305 63C40II CM1 6K7 type:

Relative Consumption of Larger Diamond Particles [mg Larger Particles / kg Friction Wheel]

Wheel mode i [mg / kg of friction] Wheel mode ii [mg / kg kg] Sample number 10: 1.57 2.31 Sample number 11: 1.07 2.16 Slavutić: 4.13 13.2

The wear resistance of the body 10-11 is about 2.5-3.5 times greater than the Slavutich material in the dressing of wheels of medium hardness. Dressing of unbaked silicon carbide wheel is more than 6 times.

Dressing tool test 2

Sample 1 was prepared according to dressing tool test 1 using EMBS 30/40 mesh and ACM 14/10 type diamond. As a reference, a material dressing tool, sample 2-3, of WINTER (Ernst Winter & Sohn Diamantwerkzeuge GmbH & Co., Norderstedt, Germany) was tested.

Sample 2-WINTER PRO 88 D601 H770 (Diamond in Carburized Carbide Matrix)

Sample 3-WINTER PRO 88 D711 H770 (Diamond in Carburized Carbide Matrix)

Samples 1-3 were tested for dressings of friction wheels of type 600 × 63 × 305 14A40II CT3 7K5. The duration of the test was 20 minutes. 3% Na ₂ CO ₃ emulsion was used as coolant.

sample Relative consumption of large diamonds [mg large particles / kg friction wheel]: Sample 1 0.9 Reference Sample 2 6.4-6.6 Reference Sample 3 4.0-12.0

The wear resistance of the samples prepared according to the invention is 4-10 times greater than the wear resistance of the reference material.

Example 9 Microstructure Analysis:

Specifications of dressing tools used for microstructure analysis:

sample Content / Name Dimensions (mm) matrix One A-800 / 630 25 vol% ACM 14/10 75 vol% φ = 8h = 7.5 SiC + Si 2 PRO88 D601 H770 φ = 8h = 7.9 Cement WC

The abrasive surfaces of the two samples were observed with a scanning electron microscope (SEM), JSM-840. Both samples were dense and contained large diamonds of 400-800 μm particle size. The surface of Sample 2 was very rough and some diamond particles were pushed out of the matrix. There is some scratches on the surface, which may be from the extruded diamonds. The surface of Sample 1 is flatter than the surface of Sample 2. No diamond particles were pushed out of the matrix, indicating that the diamond was strongly bound to the matrix.

Example 10 Friction Test, Erosion Test and Hot Steel Slip Test

The following test shows a strong bond between the diamond particles and the matrix.

Two diamond composites were evaluated in a friction test, erosion test and slip test on hot steel. Sample 1 was made of 60% diamond powder ACM 63/50 and 40% ACM 10/7. Sample 2 was made of diamond particles ACM 14/10.

The following reference material was used. All standard diamonds are commercially available and the data given above is Data Sheet information.

Reference Example 1: Commercially available alumina, grade AZ96, 2.8% by weight zircon from Sandvik Coromant AB. Hardness 1820 HV and fragment roughness 5.4 MN / m ^3/2 .

Reference Example 2: Goodfellow commercially available reaction bonded (Si impregnated) silicon carbide, designation SiSiC, containing about 10% free silicon. Hardness 2500-3000 kgf / mm ² . No fragment roughness.

Reference Example 3: Commercially available pure silicon carbide from Matenco AB, name SiC. Hardness 2000 HV and fragment roughness 3.8 MN / m ^3/2 .

Reference Example 4: Carbide carburized from Sandvik AB, grade H6M, with 1.3 μm particles of WC in 6 wt% cobalt. Hardness 1720 HV and fragment roughness 10.1 MN / m ^3/2 .

Reference example 5: Polycrystalline diamond (PDC) on the cutting piece of T-MAX U from Sandvik Coromant AB.

Friction with diamond slurry

Crater polishing techniques were used. Spherical craters are made on a sample surface by rotating a stainless steel wheel with a rounded rim without rotating the sample. The combined motion of the wheel and the sample moves the polished spherical craters onto the sample surface.

A steel wheel with a diameter of 20 mm and a load of 20 g was used. 4 μm single crystal diamond mixed with a commercial standard solution (Kemet type 0) was rubbed to a concentration of 25 g / l.

The volume of the crater was measured with an optical profilometer and the volume removed per sliding distance was calculated.

Due to the large difference in the wear resistance of the material, different total slip distances were chosen from the material. Diamond composite, samples 1-2 were tested for 30,000 revolutions (corresponding to 1861 m of sliding); Polycrystalline diamond (PDC) was tested at 8,000 revolutions (500 mm); Ceramics were tested at 800 revolutions (50 m) and carburized carbides were tested at 600 revolutions (38 m). By varying the total number of revolutions, the final wear trace diameter was maintained at 1-2 mm. Five or more craters were prepared on each sample.

Measurement result table material Average crater diameter μm Revolutions Friction Speed μm ³ / m Sample 1: ACM 63/50 + ACM 10/7 1.04 ± 0.10 30,000 0.85 ± 0.14 Sample 2: ACM 14/10 1.11 ± 0.14 30,000 2.49 ± 0.20 PCD 0.48 ± 0.02 8000 26.9 ± 0.15 SiSiC 1.64 ± 0.03 800 274.2 ± 12.7 SiC 1.38 ± 0.03 800 279.8 ± 5.6 AZ96 1.82 ± 0.04 800 530.8 ± 10.4 H6M 1.80 ± 0.02 600 693.9 ± 18.7

Both diamond composites exceeded most reference materials with at least two orders of magnitude (about 100 times greater) and even ten times wear resistance of PCD. Compared with diamond composites, samples containing only one particle size 10/14 wear about three times more than samples with two particle sizes 50 / 63-7 / 10.

Scanning electron microscopy showing the friction surfaces of Samples 1 and 2 showed that most of the diamond was still retained in the matrix. Traces due to friction did not have common characteristics on the surface. The matrix appeared to be removed around the large diamond leaving the diamond protruding from the surface. In particular, the larger diamonds in the 50 / 63-7 / 10 materials exhibited flat, polished surfaces. The diamond phase can be seen without signs of fractionation, pruning or crushing. See Appendix, Scanning electron microscope for A) for sample 1 and A2) for sample 2.

The rubbed surface of the PCD material shows better removal of the intergranular phase, for example a metal binder, causing the diamond particles to be pushed out. All other reference material wear marks also have friction grooves with other types of damage. Also shown are local scale fractions, such as particle size boundaries.

The main wear mechanism of diamond composites is believed to be that the matrix is removed by the entire diamond as the support disappears from the matrix; Large diamond phases are more difficult to remove from the surface than small diamond phases. This illustrates that Sample 1 corresponding to Sample 2 has better performance.

Dry particle erosion resistance

The test was carried out in a centrifuge device. A certain amount of erosive batch is added to the vessel and fed at a continuous rate to the center of the rotating disk. The erosion is rapidly filtered through the channel into the disc by centrifugal force, striking the protruding edge of the sample with a fixed force associated with the flow of the erosion.

The test was carried out with a silicon carbide erodent of 80 mesh (200 μm) with a hardness of about 2500 HV. The impact angles were 45 ° and 90 ° and the impact velocity of the eroded particles was 93 m / s. Samples were masked out of an unprotected 8.5 × 8.5 mm area.

The weight loss of each sample per mass of impact pendant was eroded prior to testing and at four specific intervals before erosion and the samples were weighed and measured. Fillings of eroded samples, respectively, for 1000 g were hit at 10.8970 g and 7.1265 g for impact angles of 90 ° and 45 °, respectively. Erosion rate was calculated from the slope of the curve describing the mass loss of the sample per impact mass of the etchant.

Result table material Impact angle Average material loss mg Corrosion rate mg / g Sample 1: ACM 50/63 + ACM 10/7 90 ° 45 ° 0.90.5 0.080.07 Sample 2: ACM 10/14 90 ° 45 ° 2.21.2 0.210.17 SiSiC 90 ° 45 ° 16.37.8 1.501.10 SiC 90 ° 45 ° 6.52.2 0.630.34 AZ96 90 ° 45 ° 14.76.3 1.350.88 H6M 90 ° 45 ° 13.56.3 1.240.88

Diamond composite, Sample 1 and Sample 2 performed better than the reference material. For most reference materials, the diamond composite was about 1 order of magnitude (about 10 times). However, Sample 2 (ACM 14/10) was only several times better (especially at 45 ° erosion) than the best materials (SiC and H6M).

Moderate impact erosion is consistently faster than wear at 45 ° erosion, consistent with the experience from soft materials, see circle 3). However, the difference in erosion rate between the two impact angles is relatively low for diamond composites, especially for sample 1.

3). Jacobson and S. Hogmark, "Tribologi", Karlebo forlag, 1996.

Scanning electron microscopy of the eroded surface of the diamond composite shows that both the diamond and the matrix are clear. Compared to the rubbed surface, signs of chipping or debris can be seen in particularly large diamond particles. The diamond appears to adhere well to the matrix. There is no evidence that all diamonds in the composite are removed or all diamond phases are ground. Instead, continuous wear of the particles and the matrix together seems to be the main wear mechanism.

The eroded surface of silicon carbide exhibited a large amount of debris over the entire eroded surface. Small scale debris appears to be the main wear mechanism. While carburized carbide appeared to be worn out by a softer mechanism without many debris traces on the surface, alumina AZ96 showed traces of both debris and ductile indentations.

Related properties test on dry slip for hot steel

Only diamond composites were evaluated in this test. A 5 mm wide composite rod was pressed by hand with a load of about 50-100 N against a rim (AISI 316) in which a stainless steel heated to a temperature between 600 ° C. and 950 ° C. with an acetylene-oxygen flame. The steel was 600 mm in diameter, about 40 mm in width, and rotated at about 10 rpm.

The wheel rim was scaled and polished before testing. The composite rod was pressurized for glowing the steel wheel for 1 minute or less. The process was repeated several times to produce a scratch.

The test did not result in any significant removal of material from the composite. At temperatures above about 900 ° C., steel often tends to stain on the composite. At this temperature the steel is also easily cut from the wheel using the composite specimen as the cutting edge. After the thermal steel slide, the scanning electron microscope showed no change on the surface.

In addition to the above test for a rotating steel wheel heated to about 900 ° C., the composite was alternatively pressed for about 2-3 minutes and then polished against 220 mesh SiC friction paper. The procedure was repeated for 10 minutes at different locations on the rod. The further test prevented the material from being removed distinctly.

Example 11: Swirl test; Turning of Al-Si 390

Four diamond-SiC-Si composites, Samples 1-4, were subjected to a swivel test with an aluminum-silicon alloy as the working material and evaluated by unlubricated continuous cutting. The material is characterized by wear and scanning electron micrographs of the piece after a particular turn sequence.

Sample 1 is made from diamond particles ACM 5/3, sample 2 is made from ACM 10/7, sample 3 is made from ACM 40 and sample 4 is made from ACM 63/50. The sample tested was a 3 × 12 × 4 mm body with all corners at right angles. The composite has a relatively sharp edge and varies in radius between about 0.01 and 0.1 mm.

Two commercially available cutting tool inserts, commercially available from Sandvik Coromant AB, were used as reference materials: commercially available polycrystalline diamond (PCD) under the trade names CCMW 09 T3 04F, CD10 and T-MAX U series, and CCMW 09 T3 04 carburized carbide ( CC) cutting inserter. The inserter has a declination angle of 80 °, a clearance angle of 5 ° and a piece radius of 0.4.

Cutting tests were performed on the lathe. As the working material, a length 270 mm cylinder having a radius of 200 mm of an aluminum silicon alloy under the trade name Al-Si 390 was used. The Al-Si 390 working specimen was projected onto the chuck with one end free left. The cylindrical surface was initially cleared from the scale by removing a millimeter of force from its diameter. Machining was performed at the cylindrical end by feeding the inserter in the direction of the axis of rotation. Given a maximum sliding speed of about 10 m / s, the cutting depth was 0.25 mm, the feed speed was 0.5 mm per revolution and the rotation speed was 1000 rpm. The composite body was tilted at an angle of 4 ° to simulate the clearance angle of a commercial inserter.

After cutting 10 pieces, the projected area of the piece removed was used as the value of piece wear. Pieces were evaluated by scanning electron microscopy (SEM). One or two ten cutting sequences were performed for each material. Abrasion was measured by SEM microscopy using phase analysis for area measurement.

Since the composite had a much sharper nose (smaller nose radius) than commercially available inserters of PDC and CC, it was further tested with 5/3 and 40 on a blunted nose from the first 10 working sequences to produce a nose radius of about 0.2 mm. Obtained.

result :

All composites, Samples 1-4, can be used for turning Al-Si 390 alloy. Cutting piece debris occurred once for 10/7 composites, but the entire test was performed on the other sharp edge of the body without debris.

All composites performed much better than conventional carburized carbides (about 4 factors of the measured removal area), but PCD diamonds were better than any composites, as shown in the table below.

Result of turning examination material 1 area of removal area [mm ² ] Removal area second operation [mm ² ] Sample 1-5/3 0.05 0.04 Sample 2-10/7 0.06 - Sample 3-40 0.04 0.04 Sample 4-63/50 0.05 - CC 0.14 0.17 PCD 0.01 0.008

Scanning electron microscopy of the cutting piece after cutting showed that the wear of the piece was the result of continuous wear and turning of the cutting piece.

It can be concluded that dry, continuous cutting by turning can be performed as the composite evaluated on Al-Si 390. The composite is rough enough to withstand this kind of stress, and while the geometry of the composite is not optimized during operation, it does not violate the PCD diamond cutting insert and is much better than conventional carburized carbides.

The difference in sharpness of the cutting edge between Samples 1-4 and the material insert is inadequate because it makes the two unjust ones to be compared. As expected, complexes with optimal geometries (for PCD inserts) perform much better.

Example 12 Hardness Measurement

The composite of Vicker hardness and Knoop hardness was measured.

Samples were prepared according to Example 3. Sample 1 was prepared from ACM 5/3 diamond powder and Sample 2 was prepared from ACM 10/7.

Before the test, a 12 x 12 x 5 mm sample was polished and polished by a standard method for hardness measurement. A flat sample was obtained but not sufficiently gloss because the material was extremely hard.

Vicker hardness of the selected zone was measured using a microhardness tester MXT-α1. Standard for calculating Vicker hardness: Hv = 0.47P / α ² (Equation 1) (wherein P is a load and α is half the length of the oblique indentation).

Knoop hardness of the random zone was measured using INSTRON 8561 and directly by H _k = P / S (Equation 2), where P is the load and S is the projected area.

Table of Vicker Hardness of Diamond / SiC / Si Cutting Tools material Load (N) 2a (μm) Hv (㎬) Indent Place Sample 15 / 3㎛ 5 17 32.5 Between diamond particles 20 30.8 39.6 Between diamond particles 20 32.3 36.0 Between diamond particles 20 29 44.7 Between diamond particles 20 23.9 65.8 Diamond particles 20 28.3 47.0 Diamond particles 20 26 55.6 Diamond particles Sample 210/7 μm 20 34.5 31.6 Between diamond particles 20 33 34.5 Between diamond particles 20 33.5 33.5 Between diamond particles 20 28.5 46.3 Between diamond particles 20 25.5 57.8 Diamond particles 20 27 51.6 Diamond particles 20 25.8 56.5 Diamond particles 20 27 51.6 Diamond particles

Table of Knob Hardness of Diamond / SiC / Si Cutting Tools sample Load (N) Long diagonal (μm) Short diagonal (μm) H _k (㎬) Sample 15 / 3㎛ 20 82.9 8.5 56.8 20 84.1 8.5 56.0 30 125 13 36.9 30 114.9 12.1 43.2 Sample 210/7 μm 20 84.2 7.9 60.1 20 86.4 8.1 57.2

According to the design of Knoop indentation, the ratio of long diagonal to short diagonal is 7: 1. The ratio of long diagonal to short diagonal is almost 10: 1 at indentation, indicating that the cutting tool has a high modulus of elasticity.

From the table it can be concluded that the Vicker hardness of the microstructure depends on the measurement zone. The Vicker hardness in the zone between the diamonds is 30-40㎬ and 50–60㎬ in the diamond particle zone, ie the micro-zone is very hard.

As shown in the table, there is a slight difference between the Knoop hardness of Sample 1 and Sample 2, 37-57 and 57-60 kPa, respectively. Smaller diamonds graphate faster because the relative diamond content decreases much more in Sample 1 than in Sample 2. This is important for choosing the correct size of diamond.

Overall material hardness, reflecting Knoop hardness measurements, shows that the composites belong to the group of ultrahard materials (> 40 kPa). All measurements were well repeated.

Table of commonly reported ranges of Knoop hardness for some materials material Knoop hardness [㎬] Diamond particles 80-120 Multi Hard Diamond, PCD 65-80 Hexagonal Boron Nitride, CBN 35-45 Boron carbide 25-35 Aluminum oxide 15-22 Silicon carbide 21-30 Tungsten carbide 17-22 *) It depends on the crystallographic direction.

Example 13: Irradiation of D-SiC-Si Composite and Metal Soldering Method

Experiments of soldering surface diamond composites of steel and carburized carbides have been performed with the main goal to assess the possibility of connecting the composites to metals by soldering. Soldering is performed using a Cu-Ti base alloy.

Experiments show that diamond composites are wetted with alloys of selected metals and that they are soldered to steel and carburized carbide. Some difficulties are found when soldering a diamond composite to steel. The adhesion of the sample to the metal is very high and the cracks found are likely to be related to the thermal stress generated due to the large difference in the coefficient of thermal expansion.

sample D-SiC Hardened carbide steel Thermal expansion coefficient 2 4-6 17

Example 14 Coating of D-SiC-Si Composite with Diamond Film

D / SiC / Si samples prepared according to the present invention are successfully diamond coatings.

Deposition Conditions:

Standard high temperature filament CVD reactor, tantalum filament, substrate maintained at 2300 ° C, -900 ° C, 1% H2 / CH4 ratio, total gas flow rate 200 sccm, pressure 20 Torr, typically crystal size 1-2 micrometers Provided deposition rate ˜0.5 μm / h.

Surface pretreatment: Manual friction 1 to 3 [mu] m (this is unnecessary for most of the above substrates because its surface is already rough enough).

result:

The study of the cross section by microscopic technique shows no detachment or cracking and the mechanical scratch test shows that the coating adhered very well.

The original surface of the composite has a bimodal grain size distribution of large and small diamonds in the SiC / Si matrix (large area slightly above the matrix due to mechanical pretreatment). It has been found that the finely ground diamond coating grows between large diamonds that aggregate and form a precise continuous film. Thus, the diamond coating partially flattens the surface and the matrix is completely coated, but the large particles still protrude up to about 5 μm out of the current diamond coated surface.

Composite materials prepared according to the invention are advantageous when a combination of different storm properties is required.

The properties mentioned make the valuable material valuable for such applications as for the manufacture of fine tools, including equipment for operating mechanical engineering size compatible supports for rapid heat cycles, equipment, etc. (products for sprayers, mud pumps). Serve

It is very necessary to dispose materials relating to toughness in impacting operations, for example milling and turning of asymmetric objects, and operations in which the composite tool is exposed to vibration. The hardness and wear resistance of the material in the drilling operation is important. The high E module provides mechanical stability for applications requiring size accuracy.

The high thermal conductivity of the composite tool is important in applications where a large amount of frictional heat is generated at the contact surface.

Size change materials are useful in applications where the material in contact with the composite is intended to be unchanged, ie when used as bearings or similar products. The area near the contact area should have a diamond size that provides the best wear resistance possible and the rest of the composite should provide optimum mechanical properties, strength and toughness.

Another application of interest is sawing and turning of wood and stone, etc., which combines high toughness with sufficient toughness.

Yet another application is dressing pencils and bars replacing single crystal diamond dressing tools, diamond needles, and tools intended for mock dressing of grinding discs of complex profiles.

Also drill; Saw components for machining concrete, granite and marble; It is possible to manufacture other building materials and machining tools.

The composite material prepared according to the invention is also suitable for use as a substrate for diamond film growth (see Example 17). Techniques for crystalline diamond coatings using active low pressure gases are known. This offers the potential for the use of component surfaces with diamond coatings in a range of applications. However, in order to take full advantage of this coating, it must be well bonded to the substrate material and preferably very finely ground without cracks or flaws. Most engineering materials suitable as substrates will not fulfill the requirement to act as nucleating agents for dense fine grained films, and the "coefficient of thermal expansion mismatch" is not low enough to avoid stress and cracking at the interface or diamond coating. Diamond-silicon carbide-silicon composites have a "low coefficient of thermal expansion mismatch" and fulfill the requirement to act as a good nucleating agent for diamond film growth that bonds extremely well between the composite and the diamond film. It is possible to grow diamond films on composite materials for many abrasive application parts. The film thickness should be greater than 3 μm, preferably greater than 10 μm for most wear applications. The coated composite will be particularly useful in cutting tools and bearings in which the polished surface can be obtained with standard techniques such as rotating hot iron or steel wheels. Exceptionally good performance is a combination of a diamond coating and a strong wear resistant composite. Partial wear damage through the diamond coating will not result in any significant change in the good properties of the component.

Method specification

The properties of the claimed material are measured by the following method.

Density is measured by hydraulic weighing method. The method is described in the measurement of its mass in air and in water. The apparent density (ratio of porous body mass (m ₁ ) to the volume of space it occupies, including the volume of all voids in the material) is determined by the formula:

ρ = m ₁ × ρ _H20 / (m ₂ -m ₃ )

[Wherein,

m ₂ : mass of the sample filled with water,

m ₃ : mass when weighing in water to balance the sample filled with water, g ρ _{H 20} -density of water, kg / m ³ ].

Thermal conductivity has radiation apertures at different heights for placing thermocouples Measure with a calorimeter using a sample of = 15 mm and height = 10 mm. Thermal conductivity is calculated as the ratio of the thermal resistance to the thermocouple. Sample thermal resistance measures the temperature drop of a sample in steady state heat flow through the sample. It is calculated by considering the corresponding constant of the equipment. The official measurement error is ± 10%.

3-point bend as a receptive form (without polishing) at room temperature.

Load ratio-300 N / sec.

The intensity (σ _3p ) is calculated by the formula:

σ = 3Pl / 2bh ²

[Meal,

P-breaking load (N),

l-length between supports (40 mm),

b-the width of the sample (6 mm),

h-thickness of the sample (5 mm)].

The bicyclic flexure test is a ring-on-ring test in which the load fixture consists mainly of two concentric rings. The stress field in this test is the biaxial axis of the centerline and tangential directions in radiation. The biaxial strength (σ biaxial) of four samples is calculated as follows:

σ-biaxial = 3P / 4πt ² [2 (1 + υ) ln (r _s / r _l ) + (1-υ) (r _s ² -r _l ² ) / R ₂ ]

[Meal,

P = breaking load (N), t = sample thickness (mm)

υ = Poisson's ratio, r _s = radius of the support ring (7 mm)

R = radius of the sample, r _l = radius of the load ring (3.13 mm)].

The Young's modulus is evaluated in the axial direction of the sample having a length of 50 mm and a cross section of 5 x 6 mm by excitation and recording of the resonance frequency of the longitudinal vibration of the sample at room temperature. Elongation modulus is calculated by the formula:

_{E = (ρ / k 4)} × (2l × f 4/4) 2

[Meal,

E-dynamic elongation, Pa, l-sample length (0.05 m)

k ₄ -correction factor, 0.98 ρ- density of material, kg / m ³

f ₄ -resonant frequency, Hz (corresponds to a third order ober-tone (typically 500-600 kHz)).

The electrical conductivity of the sample is evaluated by using a sample of size 5 × 6 × 50 mm depending on the sample length by the 4-probe method. In this case the voltage drop between the two inner probes is evaluated while the outer probe conducts current through the sample.

Claims (33)

A method of making a diamond-silicon carbide-silicon composite from diamond particles, Shaping the working specimen, Heat treating the working specimen to control the heat treatment temperature and time to form a predetermined amount of graphite by graphitization of diamond particles, thereby forming an intermediate body, and Infiltrating silicone into the intermediate body. The method according to claim 1, wherein the amount of graphite produced by the graphitization is 1 to 50% by weight, preferably 6 to 30% by weight of the diamond. The method of claim 1 or 2, wherein the heat treatment temperature during the graphitization is 1700 ° C or less. 4. The method of claim 3, wherein the heat treatment temperature and heat treatment time required for the graphitization are determined experimentally depending on the heat treatment equipment used. The method of claim 1, wherein the working specimen is formed at a porosity of 25 to 60% by volume. 6. The method of any one of claims 1 to 5, wherein a predetermined amount of carbon is deposited on the work specimen by exposing the work specimen to gaseous hydrocarbons at a temperature above the decomposition temperature of the hydrocarbon. 7. The method of claim 6, wherein graphitization of at least a portion of the diamond crystals is performed prior to exposing the working specimen to gaseous hydrocarbons at a temperature above the decomposition temperature of the hydrocarbons. 8. Method according to claim 6 or 7, characterized in that the intermediate body is machined to the desired formation and size of the final body prior to the infiltration of liquid silicone. 2. The method of claim 1, wherein the intermediate body is heat treated in the presence of vapor phase silicon prior to the infiltration of the liquid silicon and then machined to the desired shape and size. 10. The method of any one of claims 1 to 9, wherein the working specimen is formed such that diamond particles of various sizes and qualities are unevenly distributed. 10. The method of any one of claims 1 to 9, wherein the working specimen is molded into a homogeneous mixture of diamond particles of various sizes to which a binder is added. 10. The method of any one of the preceding claims, wherein the diamond particles in the workpiece specimen are distributed in a continuous decrease towards the center thereof from the surface of the workpiece specimen. 13. A method according to any one of claims 1 to 12, wherein at least two working specimens are each prepared and then collected prior to said heat treatment and infiltration steps. The method according to any one of claims 1 to 7, wherein the forming of the working specimen is carried out in a mold, heat treatment and silicon infiltration is carried out after extracting the working specimen from the mold. How to. A body wherein diamond particles are bonded to a matrix of silicon carbide, the body containing at least 20% by volume diamond particles, at least 5% by volume silicon carbide, preferably at least 15% by volume silicon carbide, and silicon with a Young's modulus of 450 Body characterized by exceeding. 16. The body of claim 15, wherein the body contains at least 29% by volume of diamond particles, at least 14% by volume of silicon carbide, and silicon, and the Young's modulus is greater than 540 GPa. 16. The body of claim 15, wherein the body contains at least 46% by volume of diamond particles having a size of about 30 μm or less and a Young's modulus of greater than 560 GPa. 16. The body according to claim 15, wherein the body contains at least 54% by volume of diamond particles, at least 60% of diamond particles having a size of 50 µm or more, and a Young's modulus of more than 650 GPa. 19. The body according to any one of claims 15 to 18, wherein the body maintains its shape and Young's modulus after exposure to a temperature of at least 1500 ° C. 16. The body of claim 15, wherein diamonds having a size of about 10 micrometers or less are incorporated into the matrix and wherein the beaker microhardness of the matrix is greater than or equal to 30 kPa at 20 N load as measured in the region between the diamond particles. 21. The body of claim 20, wherein diamond particles having a size of about 10 micrometers or less are incorporated into the matrix and the Knoop macrohardness of the matrix is 36 kPa or more at a 20 N load. The method of claim 15, wherein the diamond particles have a size fraction having a particle size of 50㎛ or more, and a size fraction having a particle size of 50㎛ or less, the weight ratio thereof is 0.25: 2.5, the average particle diameter is 10㎛ or more, preferably Body which is 20 micrometers or more. 16. The method according to claim 15, wherein the diamond particles have a size fraction of large diamond particles having a particle size of 50 µm or more and a size fraction of small diamond particles having a particle size of 50 µm or less, and have a weight ratio of 0.25: 2.5, and an average particle diameter. Silver is 10 micrometers or more, Preferably it is 20 micrometers or more. The method of claim 23, wherein the diamond particles have a size fraction and a size fraction of small diamond particles of large diamond particles, the wear rate is 26㎛ ³ / m, preferably up to 10㎛ ³ / m (Example 10) of Body characterized in that. 24. The method according to claim 23, wherein the diamond particles have a size fraction of large diamond particles and a size fraction of small diamond particles, and the erosion rate is 0.34 mg / g or less, preferably 0.25 mg / g or less (Example 10). Body made with. The method of claim 15, wherein the diamond particles have a size less than 20㎛, wear rate 26㎛ ³ / m or less, preferably 10㎛ ³ / m or less (Example 10), characterized in that body. 16. The body according to claim 15, wherein the diamond particles have a size of 20 µm or less, and a wear rate is 0.34 mg / g or less, preferably 0.25 mg / g or less (Example 10). 16. The body of claim 15, wherein the body is hollow. The body of claim 15, wherein the surface of the body is covered with a diamond film. The body of claim 15, wherein the body is made of large diamond particles having a size of 20 μm or more, and the matrix comprises 0-50% by volume of small diamond particles having a size of 20 μm or less, 20-99 volume% of silicon carbide, and 1-1 silicon. 30 vol% and the hardness of the matrix is 20 to 63 kPa. The body according to claim 30, wherein the matrix hardness is 20 to 30 kPa. The body according to claim 30, wherein the matrix hardness is 50 to 63 kPa. The body according to claim 30, wherein the matrix hardness is 30 to 50 kPa.