CH647487A5 - METHOD FOR PRODUCING A ONE-PIECE COMPOSITE MATERIAL FROM A POLYCRISTALLINE DIAMOND BODY AND A SILICON CARBIDE OR SILICON NITRIDE SUBSTRATE. - Google Patents

Description

The invention relates to a method for producing a one-piece composite material from a polycrystalline diamond body and a silicon carbide or silicon nitride substrate using a hot pressing process, and to a composite material produced by this method.

A technical obstacle to a high-density diamond compact that has a high diamond volume and has been manufactured under the diamond-stable pressure range has been the development of a suitable binder that penetrates into the capillaries of a densely packed, fine-particle diamond powder. The binder must form a thermally stable, firm bond with the diamond and should not graphitize the diamond or react excessively with the diamond.

According to the invention, a silicon-rich alloy containing a eutectic is used which penetrates well into the capillaries of a molding compound made of diamond crystals and wets the diamond crystals, so that a diamond body with an excellent bond is formed. The impregnating alloy also creates a tight bond in situ with a silicon carbide or silicon nitride substrate. The method according to the invention also uses pressures which are substantially below the pressures required by the diamond-stable area in order to produce a composite material from a polycrystalline diamond body and a silicon carbide or silicon nitride substrate in a number of configurations and in a wide range of sizes. The composite material can be used as an abrasive, cutting tool, nozzle or other wear-resistant component.

The inventive method for producing a one-piece composite material from a polycrystalline diamond body and a silicon carbide or silicon nitride substrate using a hot pressing process is characterized by the combination of process cuts specified in claim 1. Advantageous embodiments of the method result from the dependent claims.

In one embodiment of the method according to the invention, no container or bowl serving as a shield is used. In this embodiment, the solid mass of the silicon-rich alloy containing the eutectic or the solid components for forming such an alloy, as well as the diamond mass and the silicon carbide or silicon nitride substrate, are introduced directly into a preformed cavity which has previously been molded into a pressure-transmitting powder medium with a predetermined size. The cavity can be molded into the powder in a variety of ways. For example, the pressure-transmitting powder medium can be placed in a die, a rigid molding tool of the desired size can be inserted into the powder, and the resulting system can be pressed at ambient temperature under a pressure that is sufficient to bring the powder into a stable shape, that is to say the pressed one To give the powder sufficient strength so that after removal of the molding tool, a cavity remains in the powder, which serves as a container for holding the silicon carbide or silicon nitride substrate, the diamond compound and the silicon-rich alloy. If the silicon carbide or silicon nitride substrate, the diamond mass and the silicon-rich alloy have been introduced into the cavity on the condition that the diamond compound is between the substrate and the alloy, the cavity is covered with further pressure-transmitting powder and the entire system is cold at ambient temperature pressed to stabilize the cavity and its contents in terms of dimensions and to provide an essentially isostatic system for the powder enclosed cavity with contents.

The invention is explained in more detail below with reference to drawings. The drawings show:

1 shows a section of a state diagram of a silicon-zirconium alloy with the equilibrium diagram for a 'silicon-rich zirconium alloy containing a eutectic, which is suitable for the invention,

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2 shows a cross section through a cell consisting of container and contents, which is used for flushing in the silicon-rich alloy according to the invention,

3 shows a schematic representation of a device for exerting a slight pressure on the cell shown in FIG. 2, the cell being set in vibration to increase the packing density of the diamond crystals,

4 shows a cross section through a device for exerting an at least substantially isostatic pressure on the cell with the aid of a pressure-transmitting powder medium in order to stabilize the dimensions of the cell and to create an essentially isostatic system,

Figure 5 shows a cross section through a graphite mold for simultaneous application of heat and pressure, i.e. for hot pressing the essentially isostatic system with the enclosed cell,

6 is a side view of a composite material made from a polycrystalline diamond body and a silicon carbide or silicon nitride substrate, and

7 shows a microphotograph (690 times magnification) of a polished cross-sectional area of a composite material produced according to the invention.

According to the invention, a layer structure is formed in which the diamond crystal mass lies between a silicon carbide or silicon nitride substrate and a solid mass composed of a silicon-rich alloy containing eutectic and is in contact with the substrate and the alloy. When carrying out the method according to the invention, the layer structure is subjected to a cold pressing process at ambient or room temperature in order to stabilize the dimensions of the layer structure essentially uniformly. The layer structure is then subjected to a hot pressing process in which the silicon alloy forms a liquid, silicon-rich alloy, which is washed into the mass of the compressed diamond crystals and brought into contact with the silicon carbide substrate.

In another embodiment, the diamond crystal mass may be in contact with at least one of the components used to form the silicon-rich alloy containing the eutectic in situ. This means that the diamond crystal mass can also be in contact with silicon or alloy metal. The silicon carbide or silicon nitride substrate, the diamond crystal mass and the components for forming the silicon-rich alloy are first cold-pressed at ambient or room temperature to substantially stabilize their dimensions, and then hot-pressed, whereby a liquid, eutectic-containing, silicon-rich alloy is formed and in the mass of the compressed diamond crystals is washed in and brought into contact with the silicon carbide or silicon nitride substrate. The components for forming the silicon alloy are arranged so that the formation of the silicon alloy begins before hot pressing, i.e. before the hot pressing temperature is reached.

The mass of the diamond crystals, the mass of the solid phase, silicon-rich starting alloy or the solid components for forming the silicon-rich alloy and the silicon carbide or silicon nitride substrate can take a number of forms. For example, each mass can be in the form of a layer, with the layer of diamond crystals lying between the other layers. The silicon-rich starting alloy can also have the shape of a tube or a cylinder with a continuous core. The alloy tube is cast so that it fits snugly against the inside wall of the container. The substrate may be in the form of a rod placed in the center of the core of the silicon alloy tube, with diamond crystals packed in the annular space between the silicon alloy tube and the substrate rod.

In the method according to the invention, both natural and synthetic, i.e. artificial diamond crystals can be used. In the direction of their greatest expansion, the diamond crystals have a size in the range of about 1 to about 1000 micrometers, the grain size or the grain sizes largely depend on the desired packing density of the diamond crystals and also on the intended use of the resulting diamond body. If, for example, the diamond body is to be used for 15 grinding purposes, diamond crystals which are not larger than about 60 micrometers are preferred. In order to achieve an optimal packing of the diamond crystals in the method according to the invention, the crystals should be graded in size and comprise a range of grain sizes in which small, medium and large crystals are contained. The graded crystals range from about 1 to about 60 microns, preferably within this size range from about 60 to about 80 percent by volume of the total crystal mass to the upper portion 25 of the particle size range, from about 5 to about 10 percent by volume the middle portion of the particle size range and the rest belong to the lower part of the particle size range.

The size determination of the diamond crystals is made easier by grinding the larger diamond crystals in a jet mill. The diamond crystals are preferably chemically cleaned in order to remove any oxides or other impurities from the surface before the diamond crystals are used in the method according to the invention. This can be done by heating the diamond crystals in hydrogen at about 900 ° C for about an hour.

The solid phase, eutectic-containing, silicon-4ocium-rich starting alloy used in the process according to the invention, that is to say an alloy which also comprises an intermetallic compound, consists of silicon and a metal, that is to say an alloy metal which is a silicide with the silicon forms. The eutectic-containing, silicon-rich alloy preferably consists of silicon and a metal from the group consisting of cobalt (Co), chromium (Cr), iron (Fe), hafnium (Hf), manganese (Mn), molybdenum (Mo ), Niobium (Nb), nickel (Ni), paladium (Pd), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), tantalum (Ta), thorium (Th), titanium (Ti), uranium so (U), vanadium (V), tungsten (W), yttrium (Y), zirconium (Zr), and mixtures thereof.

The silicon-rich starting alloy containing a eutectic is solid at room temperature and contains more than 50 atomic percent, but less than 100 atomic percent and 55 percent silicon. The starting alloy usually contains a maximum of about 99.5 atomic percent silicon, with the silicon content largely dependent on the specific effect that the alloy metal has on the resulting silicon-rich alloy. The solid phase si-60 licium-rich alloy contains a eutectic, i.e. a certain eutectic structure, and can be of under-eutectic, over-eutectic or of eutectic composition. 1 it can be seen, for example, that the eutectic 2 is an alloy with a special composition that solidifies under equilibrium conditions when cooling at constant temperature to a solid with at least two phases and melts completely when heated at the same constant temperature . These

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constant temperature is referred to as the eutectic temperature, which is also represented by reference number 2. The eutectic 2 is the composition in which two falling liquidus curves 3 and 4 meet at the electrical point 2. The eutectic 2 therefore has a lower melting point than the neighboring hypoeutectic or hypereutectic compositions. Under equilibrium conditions, the liquidus curve or liquidus line in a state diagram represents the temperatures at which the silicon alloy stops melting when heated and begins to solidify on cooling. The solid phase, eutectic-containing, silicon-rich alloy used in the method according to the invention is an alloy of a series of alloys on a eutectic horizontal 1, i.e. a horizontal passing through the eutectic point 2 and starting from any alloy, the composition of which is to the left of eutectic point 2 in an equilibrium diagram and contains some eutectic structure, that is to say is hypoeutectic, and extends to any alloy whose composition lies to the right of eutectic point 2 in the equilibrium diagram and contains something eutectic structure, that is to say hypereutectic.

The solid, silicon-rich starting alloy can

However, it does not need to have the same composition as the silicon-rich impregnation alloy. When all of the solid, silicon-rich starting alloy becomes liquid at the hot pressing temperature, it has the same composition as the silicon-rich impregnating alloy. However, if only a portion of the silicon-rich parent alloy, i.e. the hypoeutectic or hypereutectic alloy becomes liquid at the hot pressing temperature, the starting alloy does not have the same composition as the liquid, silicon-rich impregnating alloy. In this case, the silicon-rich impregnation alloy is richer in silicon than the hypereutectic starting alloy, but poorer in silicon than the hypereutectic, silicon-rich starting alloy.

1 shows that the composition of the silicon-rich impregnating alloy containing a eutectic used according to the invention and its melting temperature lies on the liquidus curves 3 and 4 and includes the eutectic point 2. Area 5 delimited by 1, 2 and 4 comprises a solid phase Si and a liquid phase, i.e. a liquid impregnation alloy, the amount of the solid phase increasing and the amount of the liquid phase correspondingly decreasing as the distance from the eutectic point 2 increases to the right along the horizontal 1, i.e. when the amount of silicon in the alloy rises above the eutectic amount. Region 6, delimited by 1, 2 and 3 similarly comprises a solid phase ZrSi2 and a liquid phase, i.e. a liquid impregnation alloy, the amount of the solid phase increasing and the amount of the liquid phase correspondingly decreasing as the distance from the eutectic point 2 to the left increases along the horizontal 1, i.e. when the amount of suicium in the alloy drops below the eutectic amount.

In the method according to the invention, the desired composition of the silicon-rich impregnating alloy containing a eutectic and its melting temperature lie in one point on the liquidus curves of the phase diagram containing the eutectic point for the silicon-rich alloy used in the method according to the invention. The hot pressing temperature is the temperature at which the desired composition of the silicon-rich impregnating alloy is liquid, i.e. is in a sufficiently fluid state to be able to penetrate the compressed diamond mass. If as fe6

The first raw material used is a silicon-rich alloy which has the same composition as the desired impregnating alloy, the hot pressing temperature is the temperature at which the alloy is liquid. The 5 hot pressing temperature is in a range from about 10 ° C to preferably a maximum of about 100 ° C above the melting point of the alloy. Depending on the alloy currently used, however, hot press temperatures which are above this preferred maximum can also be used, however hot press temperatures above 1600 ° C. are not suitable, since in this case there is a tendency to excessive. There is graphitization of the diamonds.

However, if the starting alloy does not have the same composition as the desired impregnation alloy, but is heated to the melting point of the desired impregnation alloy, an impregnation alloy is formed as a liquid phase. The hot pressing temperature is then a temperature at which the penetrating alloy phase is formed in liquid form, which is the case at about 10 ° C. above the melting point of the penetrating alloy phase.

As can be seen from FIG. 1, the melting point of a certain impregnating alloy with a hypereutectic composition lies on the liquidus line 4. If, for example, the desired hypereutectic impregnating alloy contains 95 atom-25 percent Si, the melting point on the liquidus line 4 is approximately 1400 ° C. as this is shown by line 7. If the starting silicon-rich alloy had the same composition as the desired penetrating impregnating alloy represented by line 7, the entire starting alloy would melt at the melting temperature of 1400 ° C and the liquefaction or hot pressing temperature would range from about 1410 ° C to preferably about 1510 ° C or possibly down to below 1600 ° C. However, if the silicon-rich parent alloy ir-35 is a hypereutectic alloy that lies on the horizontal 1 to the right of line 7 in the equilibrium diagram of Figure 1, the hot pressing temperature is the temperature at which the desired penetrating impregnating alloy of 95 atomic percent Si and 5 atomic percent is Zr is brought into 40 liquid form, which would be the case at about 1410 ° C.

At the hot-pressing temperature, the desired penetrating impregnating alloy in liquid form should also be produced from the starting alloy in an amount sufficient to fill the cavities of the compressed diamond mass, the crystal density of which is above 70 percent by volume, and the impregnating liquid with the contact surface of the Bring silicon carbide substrate in contact so that the pores or voids at the interface between the polycrystalline body and the substrate in contact with the polycrystalline body are filled and the resulting composite material has a non-porous or at least substantially non-porous interface. The liquid impregnating alloy should practically be produced at the hot pressing temperature in an amount of at least about 1 percent by volume of the silicon-rich starting alloy.

The hot pressing process is carried out at a temperature at which the silicon-rich impregnating alloy is liquid, under 60 a pressure which only needs to be sufficient to tear open intermediate layers present at the hot pressing temperature in the diamond mass between opposing diamond surfaces, which prevent the penetration of the liquid alloy into the interstices of the Reduce diamond mass 65. This usually requires a minimum pressure of around 35 kp / cm2. The hot press pressure can range in particular from about 35 to about 1410 kp / cm 2. However, the hot press pressure is usually in the range of about 70

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up to about 700 kp / cm2. Hot pressing pressures above 1410 kp / cm2 bring no noticeable advantages in the method according to the invention.

A temperature at which the penetrating impregnating alloy is liquid means a temperature at which the impregnating alloy is able to flow easily. When the impregnating alloy is at its melting point, which is represented by the liquidus line or, in the case of a eutectic alloy, by the eutectic point, the penetrating impregnating alloy is a viscous, viscous mass. However, if the temperature rises above the melting point, the soaking liquid becomes less viscous. At a temperature which is about 10 ° C above the melting point, the liquid impregnating alloy becomes easily flowable, i.e. liquid. The temperature at which the silicon-rich impregnating alloy is liquid is the temperature at which the impregnating alloy penetrates into the capillary-like channels, spaces or cavities of the compressed diamond crystal mass, the crystal density of which is above 70 percent by volume. If the temperature increases further, the fluidity of the liquid, silicon-rich impregnating alloy increases, which leads to a faster penetration of the alloy into the diamond crystal mass. At a temperature of about 100 ° C above the melting point, the impregnating alloy usually has its highest fluidity, so that temperatures above this maximum temperature usually do not need to be used.

The silicon-rich alloy with eutectic composition melts at a temperature below about 1430 ° C. For the group of silicon-rich alloys preferred here, the eutectic melting point ranges from 870 ° C. for a eutectic SiPd alloy with approximately 56 atomic percent Si to 1410 ° C. for a eutectic SiMo alloy with approximately 97 atom percent Si. 1 shows that the eutectic SiZr alloy 2 contains 90.4 atomic percent Si and has a eutectic melting temperature of 1360 ° C. The predominant phase of the solid, silicon-rich, eutectic alloy is almost pure silicon.

The penetrating, eutectic-containing, silicon-rich impregnating alloy has a melting point below about 1500 ° C, usually from about 850 ° C to about 1450 ° C. The temperature at which the impregnating alloy becomes liquid

is at least about 10 ° C above the melting point.

The solid, silicon-rich starting alloy or the solid components for forming the silicon-rich alloy can be in solid or in powder form. The amount of the solid, silicon-rich starting alloy used in each case can vary depending on the achievable amount of the liquid, silicon-rich impregnating alloy and on the capacity of the device. In general, the amount of the silicon-rich impregnating alloy is in the range of about 25 percent by volume to about 80 percent by volume, but for optimal results it is preferably in the range of about 30 to about 60 percent by volume of the compressed diamond crystal mass whose crystal density is above 70 percent by volume.

The hot pressing process is carried out in an atmosphere which has no appreciable deleterious effect on the diamond crystals or the silicon-rich impregnating alloy or the silicon carbide substrate. The hot pressing process can be carried out under vacuum or in an inert gas such as argon or helium or else in nitrogen or hydrogen. The hot pressing process is carried out sufficiently quickly that there is no noticeable reaction between the silicon-rich impregnating alloy and the nitrogen or hydrogen. The hot pressing process cannot be carried out in air since the diamond easily graphitizes in air at a temperature above 800 ° C and would oxidize the liquid, silicon-rich impregnating alloy and form solid silicon dioxide before a significant amount of liquid alloy had penetrated the diamond mass.

The silicon carbide substrate is a polycrystalline body with a density of about 85 to about 100 percent of the theoretical density of silicon carbide. The density of silicon carbide given here is the partial density based on the theoretical density for silicon carbide of 3.21 g / cm3. A polycrystalline body made of silicon carbide with a density below about 85% is not suitable since it would not have the required mechanical strength for most applications, for example for a tool insert. The higher the density of the silicon carbide body, the higher its mechanical strength.

The silicon nitride substrate is a polycrystalline body with a density in the range from about 80% to about 100% of the theoretical density of silicon nitride. The silicon nitride density given here is a fraction of the density based on the theoretical density for silicon nitride of 3.18 g / cm3. A polycrystalline body made of silicon nitride with a density below 80% is not suitable since such a polycrystalline body would not have the required mechanical strength for most purposes, for example for use as a tool insert. The higher the density of the silicon nitride body, the higher its mechanical strength.

The polycrystalline silicon carbide or silicon nitride substrate is a hot pressed or sintered body, the silicon nitride, i.e. Contains silicon nitride in an amount of at least 90 percent by weight and usually at least 95 percent by weight and generally in the range of 96 percent by weight to 99 percent by weight or more based on the weight of the substrate body. All components or components of the polycrystalline body containing silicon nitride, which are used in addition to the silicon nitride, should not have any appreciable disadvantageous influence on the mechanical properties of the resulting composite material. In particular, these constituents and components should not have any noticeable adverse influence on the properties of the silicon nitride and all the other materials used in the method according to the invention for producing the composite material or on the properties of the composite material itself.

The silicon carbide body used according to the invention can be produced by sintering processes which are described in US Pat. No. 4,004,934 and in US Pat. Nos. 681,706 of April 29, 1976 and 707 117 of July 21, 1976.

The sintered silicon carbide body can be produced by forming a submicron particle mixture of B silicon carbide, boron additive and a carbon-containing additive in the form of free carbon or a carbon-containing organic material that decomposes under heat and generates free carbon, and in that a so-called green body is formed from this mixture. In another method, a submicron particle mixture of A silicon carbide, in which the average particle size is twice as large as that of the mixture of B silicon carbide, becomes the particle mixture of B silicon carbide in an amount of 0.05 up to 5 percent by weight based on the B-silicon carbide. The green body is sintered to the required density at a temperature in the range from approximately 1900 ° C. to 2300 ° C.

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The boron additive may be in the form of an elemental boron carbide or boron compound that decomposes at a temperature below the sintering temperature and provides boron or boron carbide and gaseous decomposition products and is used in an amount based on 0.3 to 3 percent by weight of elemental boron is equivalent to the amount of silicon carbide. During the sintering process, the boron additive changes into a solid solution with the silicon carbide. If the amount of the additive exceeds the equivalent value by about one percent by weight of elemental boron, a boron carbide phase also fails.

The carbonaceous additive is used in an amount equivalent to about 0.1 to about 1.0 weight percent free carbon based on the amount of silicon carbide. The additive can be free carbon or a solid or liquid carbon-containing organic material that decomposes completely at temperatures of 50 ° C to 1000 ° C into a submicron free carbon and gaseous decomposition products. Examples of carbon-containing additives are polymers of aromatic hydrocarbons, such as polyphenylene or polymethylphenylene, which are soluble in aromatic hydrocarbons.

The sintered body consists of silicon carbide, about 0.3 to about 3 percent by weight of boron and up to about one percent by weight of free carbon, the percentages by weight being based on the amount by weight of the silicon carbide. The boron is in a solid solution with the silicon carbide or as a boron phase in a solid solution with the silicon carbide. If the free carbon is detectable, it is in the form of submicron particles that are distributed over the entire sintered body.

The hot-pressed silicon carbide bodies can preferably be made by methods described in U.S. Patent No. 3,853,566 and in U.S. Patent No. 4,509,486. 695 246 from June 11, 1976.

A dispersion of a submicron silicon carbide powder and an amount of boron or boron carbide, which corresponds to an amount of boron of 0.5 to 3.0 percent by weight, is in a single hot pressing process at a temperature of 1900 ° C to 2000 ° C under a pressure of 350 up to 700 kp / cm2 hot pressed to produce a silicon carbide body containing boron. In another hot pressing operation, 0.5 to 3.0 percent by weight of elemental carbon or carbon-containing additives are added to the dispersion, which decompose into elemental carbon under heat.

The polycrystalline silicon nitride body can be made by the sintering processes described in U.S. Patent Applications 756,085 and 756,086 dated January 3, 1977.

The U.S. note 756 085 refers to a sintered silicon nitride body made by forming a homogeneous dispersion from a submicron silicon nitride and a beryllium additive selected from the group consisting of beryllium, beryllium carbide, beryllium fluoride, beryllium nitride, beryllium silicon nitride, and mixtures thereof. The beryllium additive is present in an amount in which the beryllium component is equivalent to an amount of about 0.1 to about 2 percent by weight of elemental beryllium based on the amount of silicon nitride. A green body is formed from the dispersion, which is sintered at a temperature of about 1900 ° C to about 2200 ° C in a sintering atmosphere formed by nitrogen under a pressure above atmospheric pressure, which prevents a noticeable thermal decomposition of the silicon nitride at the sintering temperature and a sintered body with a density of at least about 80% of the theoretical density of silicon

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trid creates. The minimum pressure of nitrogen is in a range from about 20 atm at a sintering temperature of 1900 ° C to about 130 atm at a sintering temperature of 2200 ° C.

5 The method according to US patent application 756 086 corresponds to the method according to US patent application 756 085 with the exception that a magnesium additive is added to the dispersion of silicon nitride and beryllium additive. The green body is sintered at a temperature of about 1800 ° C. to about 2200 ° C. in a sintering atmosphere formed by nitrogen at a pressure above atmospheric pressure, that of at least about 10 atm at a sintering temperature of 1800 ° C. up to at least about 130 atm at a sintering temperature of 15 2200 ° C is sufficient. The magnesium additive is selected from the group consisting of magnesium, magnesium carbide, magnesium nitride, magnesium cyanide, magnesium fluoride, magnesium silicide, magnesium silicon nitride, and mixtures thereof. The magnesium additive is used in an amount at which the magnesium component corresponds to an amount of about 0.5 to about 4 percent by weight of elemental magnesium based on the amount of silicon nitride.

The polycrystalline body described in U.S. Patent Application 756,085 has a density in the range of about 25 80 to about 100% of the theoretical density of silicon nitride. The polycrystalline body is composed of silicon nitride and beryllium, the amount of which ranges from less than about 0.1 to about less than about 2.0 percent by weight of the silicon nitride. The polycrystalline body described in US patent application 30 756 086 corresponds to the polycrystalline body according to US patent application 756 085 with the exception that it also contains magnesium in an amount ranging from less than about 0.5 to less than about 4 percent by weight of the silicon nitride. 35 The hot-pressed, polycrystalline silicon nitride bodies can be produced by the methods described in US patent applications 756 083 and 756 084 dated 3.1.1977.

U.S. Patent Application 756,083 relates to a 40 hot pressed silicon nitride body made by forming a submicron homogeneous powder dispersion of silicon nitride and magnesium silicide, the magnesium silicide being present in an amount ranging from about 0.5 to about 3 percent by weight based on the amount of silicon nitride is sufficient. The powder dispersion is hot pressed in a nitrogen atmosphere at a temperature of about 1600 ° C to 1850 ° C under a minimum pressure of about 140 kp / cm2. The resulting polycrystalline silicon nitride body has a density of from about 80% to about 100 percent of the theoretical density of silicon nitride. The polycrystalline body consists of silicon nitride and magnesium, the amount of which ranges from about 0.3 to about 1.9 percent by weight, based on silicon nitride.

The US patent application 756 084 relates to a 55 hot-pressed, polycrystalline silicon nitride body which is produced by forming a submicron powder dispersion from silicon nitride and a beryllium additive, which is selected from the group consisting of beryllium, beryllium nitride, beryllium fluoride, beryllium silicon mixture and nitride of these is selected, the beryllium component being present in an amount which corresponds to an amount of about 0.1 to about 2 percent by weight of elemental beryllium based on the amount of silicon nitride. The dispersion is hot pressed in a nitrogen atmosphere at a temperature of about 1600 ° C to about 1850 ° C under a minimum pressure of about 140 kp / cm2. The resulting polycrystalline silicon nitride body has a density of about 80% to about 100% of the theoretical density of

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Silicon nitride. The polycrystalline body consists of silicon nitride and beryllium, the amount of which ranges from about 0.1 to about 2.0 percent by weight, based on silicon nitride.

The thickness of the silicon nitride substrate can vary depending on the ultimate use of the resulting composite. However, the substrate should be at least sufficiently thick so that a suitable carrier for a polycrystalline diamond body attached to it is achieved. A carrier suitable for most applications for receiving a polycrystalline diamond body attached to it is achieved if the silicon nitride substrate is preferably at least twice as thick as the polycrystalline diamond body attached to the carrier.

In the arrangement shown in Fig. 2, the cell 10 consists of a bowl 11, which has a vertical circular-cylindrical wall with a bottom. Arranged within the bowl 11 is a disk 12 made of a silicon-rich alloy containing a eutectic, a diamond crystal mass 13 in contact with the silicon-rich alloy 12 and a thick plug 14. The thick plug 14 is a cylinder made of polycrystalline silicon nitride substrate which fits exactly into the cup 11 and serves as a closure.

The cup 11 is made of a material which is essentially inert during hot pressing, i.e. H. has no noticeable adverse influence on the properties of the diamond body. Such a material can be a non-metal, such as, for example, compressed hexagonal boron nitride. However, the material is preferably a metal and in particular a metal from the group comprising tungsten, yttrium, vanadium, tantalum and molybdenum.

There should be no free space within the cup sealed with the stopper, which allows the contents to mix or move freely, so that the contents, at least substantially in the original position, are subjected to the essentially isostatic pressure during the cold pressing process.

The purpose of the graded diamond crystals is to achieve a maximum packing density of the diamond crystals. As an alternative or additional measure, the arrangement shown in FIG. 3 can also be expedient in order to increase the packing density of the diamond crystals. In the arrangement according to FIG. 3, the cell 10 is placed on an oscillating table 16 and held there during the oscillating movement under a slight pressure of approximately 3.5 × 10 s, so that the diamond crystals can be rearranged accordingly to fill in the cavities, thereby reducing the proportion of the cavities is reduced and the density of the diamond mass is increased to over 70 percent by volume based on the volume of the diamond mass. The required densification can be determined by tests which are carried out with diamonds of the same grain size in a form having fixed dimensions.

The cell 10 is then cold pressed as shown in FIG. 4 at room or ambient temperature, only a pressure having to be used which is sufficient to achieve a dimensionally stable, essentially isostatic system. The cell 10 is placed within the cylindrical core of a die 20. The cell 10 is enclosed by a mass 19 made of a pressure-transmitting powder medium. The powder medium consists of very fine particles with a particle size of 160 mesh / cm, again particles with a particle size of about 2 to about 20 micrometers being preferred. The pressure-transmitting powder medium remains essentially unsintered under the pressure and temperature conditions used here. The pressure-transmitting powder medium is, for example, hexagonal boron nitride and silicon nitride. The pressure-transmitting powder medium ensures that an approximately or essentially isostatic pressure is exerted on the cell 10, whereby the cell 10 and its contents are stabilized in terms of their dimensions substantially uniformly, i.e. are compacted, and an essentially isostatic system of corresponding shape is formed, which contains the cell enclosed by the powder, the density of the compressed diamond crystal layer being over 70 percent by volume of the volume of the compressed diamond crystals. The die 20 with a ring 22 and a die 23 and 23a can be made of tool steel. The ring 22 can optionally be provided on the inside with a sintered carbide bushing 22a, as shown in FIG. 4, in order to enable the use of pressures of up to 14,000 kp / cm 2. Pressures over 14,000 kp / cm2 bring no noticeable advantage. Within the space delimited by the punch 23, the bushing 22a and the punch 23a, a pressure in the range of about 1400 to 7000 kp / cm 2 and usually up to 3500 kp / cm 2 is preferably exerted on the pressure-transmitting powder medium when the press punches operate in a conventional manner until the applied pressure has stabilized, as is known in conventional powder compaction.

The pressure used in cold pressing can be determined empirically. An increase in the pressure above the pressure value, which provides a dimensionally stable, essentially isostatic system, does not result in any additional compression or dimensional stabilization of the cell 10 and its contents.

The pressure-transmitting powder medium, such as hexagonal boron nitride or silicon nitride, approximately leads to a hydrostatic pressure effect when the pressure is exerted on the powder medium in an axial direction. Due to the hydrostatic pressure effect, an essentially isostatic pressure is exerted over the entire area of the cell 10. The applied pressure is believed to be transmitted to the cell 10 substantially unabated. The cold pressing process reduces the size of the cavities so that capillary-like cavities are optimally formed in the diamond compound. The cold-pressing process also brings the diamond crystal mass to the required packing density of over 70 percent by volume. This reduction in the void volume also results in a reduction in the content of non-diamond-shaped material ultimately present in the diamond body and results in more closely opposing crystal surfaces which can be effectively connected to one another.

After the end of the cold pressing process, the density of the compressed diamond crystals in cell 10 should be over 70 percent by volume of the volume of the crystals. The density of the compressed layer of the diamond crystal mass is in the range from 71 to about 95 percent by volume and often in the range from about 75 to about 90 percent by volume of the volume of the diamond crystals. The higher the density of the crystals, the lower the proportion of non-diamond-shaped material between the crystals, so that a correspondingly harder diamond body is also produced.

The essentially isostatic system 21 of the powder-coated container, which is created by the cold pressing process, is then hot pressed, the system being subjected to the hot pressing temperature and the hot pressing pressure simultaneously.

After the cold pressing process, one of the two press punches 23 or 23a is withdrawn. Essentially, this is now in the form of a solidified molded body

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Isostatic system 21 is removed from sleeve 22a and placed in graphite mold 30, shown in FIG. 5, which has a hole of the same diameter as sleeve 22a. The transferred system 21 is then enclosed by the wall of the hole 31 and the two graphite stamps 32 and 32a. The graphite mold 30 is provided with a thermocouple 33 which indicates the temperature which is applied to the dimensionally stabilized, essentially isostatic system 21. The graphite mold 30 with the essentially isostatic system 21 is then placed in a conventional hot press furnace, not shown. The furnace chamber is at least substantially evacuated, which also causes evacuation of the system 21 with the cell 10, so that the system 21 and the cell 10 are essentially under a vacuum, in which the hot pressing process can be carried out. Optionally, nitrogen or hydrogen or an inert gas such as argon can also be introduced into the furnace chamber in order to expose the system in the furnace chamber with the contents of the cell 10 to an atmosphere suitable for hot pressing. While the punches 32 and 32a exert a pressure acting in the axial direction, i.e. the hot pressing pressure on the system 21, the temperature is raised to a temperature at which the silicon-rich alloy disc 12 becomes a liquid, silicon-rich alloy which forms in the Diamond mass penetrates.

When hot pressing, the hot pressing temperature should be reached quickly. The hot pressing temperature is then usually maintained under the hot pressing pressure for at least one minute in order to ensure sufficient pressure impregnation of the diamond crystal mass. A hot pressing time of about 1 to about 5 minutes is usually sufficient. Since the conversion of diamond into non-diamond-shaped elemental carbon largely depends on time and temperature, and the higher the temperature and the longer the time at this temperature, the greater the likelihood of conversion into non-diamond-shaped elemental carbon the hot pressing process must be carried out before 5 percent by volume of the diamond has been converted into non-diamond-shaped elemental carbon. The extent of the conversion can be determined empirically. If 5 or more percent by volume of diamond is converted to non-diamond-shaped elemental carbon, a phase of non-diamond-shaped elemental carbon may remain in the end product. This phase of non-diamond-shaped, elemental carbon would have a considerable, disadvantageous influence on the mechanical properties of the end product.

The hot press pressure acting on the liquid, silicon-rich impregnating alloy causes the difficult-to-melt layer or slag, mostly oxide as well as carbide, to break up, which is usually formed between the liquid, silicon-rich alloy and the diamond surfaces, thereby opening the capillary-like cavity system and making it accessible to the silicon-rich alloy is made, which then penetrates into the cavities due to the capillary action. Experiments have shown that the alloy does not penetrate into the diamond mass if, during the hot pressing process and in the case of an alloy in the liquid state, a pressure is exerted and maintained on the system 21 which is not sufficient to break up the slag.

When the liquid, silicon-rich alloy penetrates into the diamond mass during hot pressing and passes through it and comes into contact with the substrate, the liquid alloy envelops the surfaces of the compressed diamond crystals, the liquid alloy with the diamond surfaces or possibly with the resulting non-diamond-shaped elemental carbon reacts to form carbide, which is at least predominantly and usually essentially silicon-5 carbide. During the hot pressing process, the impregnating alloy also fills the interface between the contact surfaces of the polycrystalline diamond body and the substrate, resulting in a firmly bonded connection in situ. The resulting product is a one-piece, well-bonded composite material. The impregnating alloy can also penetrate or diffuse into the substrate.

It is particularly important that substantially isostatic conditions are maintained on the 15 during the hot pressing process, so that when the silicon-rich alloy becomes liquid, the liquid alloy cannot penetrate between the diamond mass 13 and the bowl 11 and escape to a significant extent, but rather into the Diamond crystal mass 13 is forced into it. After the hot pressing process has ended, at least sufficient pressure should be maintained during the cooling of the hot-pressed system 21, so that the hot-pressed cell 10 is exposed to an essentially isostatic pressure which is sufficient to maintain the shape stability of the system 21. The hot pressed system 21 is preferably allowed to cool to room temperature. The hot-pressed cell 10 is then removed from the system, whereupon a composite material 36 is obtained in which the polycrystalline diamond body 13a is connected in situ 30 directly to the substrate 14a. Any metal adhering to the container or excess, squeezed out silicon alloy on the outer surfaces of the composite material can be removed in a conventional manner, for example by grinding.

If the components are used in the form of coexisting layers in the method according to the invention, the resulting composite material can have a number of shapes, such as the shape of a disk, a square or rectangle, a rod or a bar, and a flat surface from bonded diamonds.

If the silicon-rich alloy is in the form of a tube or cylinder with a core or hole therethrough and the substrate is in the form of a rod centrally located in the core of the tube, and the annulus between the silicon alloy tube and the substrate rod is packed with diamond crystals, this has it resulting composite material in the form of a circular rod.

The composite material thus produced using the method according to the invention has a polycrystalline diamond body which is connected as if from a single piece by means of a connection formed in situ to a polycrystalline substrate made of a silicon carbide or silicon nitride body.

55 The glued-on polycrystalline diamond body of the composite material according to the invention has diamond crystals which are firmly connected to one another by a binder containing silicon atoms. The diamond crystals have a size of approximately 1 to approximately 1000 micrometers. The 60 density of the diamond crystals ranges from at least about 70 to about less than 90 volume percent and often up to about 89 volume percent of the volume of the polycrystalline diamond body. The diamond body contains up to about 30 percent by volume of a binder containing silicon atoms, which is at least substantially uniformly distributed in the polycrystalline diamond body. The part of the binder that is in contact with the surfaces of the diamond crystals consists at least predominantly of silicon

11

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carbide, i.e. More than 50 percent by volume of the part of the binder that is in direct contact with the surfaces of the diamond crystals is silicon carbide. The portion of the binder in contact with the surfaces of the diamond crystals preferably consists at least essentially of silicon carbide, i.e. at least about 85 and preferably 100 percent by volume of the portion of the binder that is in direct contact with the surfaces of the diamond crystals is silicon carbide. The diamond body of the composite material according to the invention is pore-free or at least essentially pore-free.

The polycrystalline silicon nitride substrate of the composite material according to the invention has a density in the range of approximately 80 to 100% of the theoretical density of the silicon nitride and contains at least 90 percent by weight of silicon nitride based on the substrate body and is free of constituents which have a visibly disadvantageous influence on the mechanical properties of the composite material .

The polycrystalline silicon carbide substrate of the composite material according to the invention has a density in the range from about 85 to about 100% of the theoretical density of the silicon carbide and contains at least 90% by weight of silicon carbide based on the substrate body and is free from constituents which have a noticeably adverse effect on the mechanical properties of the composite material to have.

At the interface between the polycrystalline diamond body and the silicon carbide or silicon nitride substrate, the binder extends from the polycrystalline diamond body to the substrate, at least essentially the pores present at the interface being filled, so that the interface is pore-free or at least essentially pore-free, that is to say that the interface may contain voids or pores in an amount of less than 1 volume percent of the total volume of the interface, provided that the pores or voids are small and less than 0.5 microns and are sufficiently evenly distributed in the interface so that the pores have no noticeably adverse effect on the bond in the interface. The proportion of pores in the interface is determined by conventional metallographic measures, for example by optically examining a cross section of the composite material. The distribution and the thickness of the binder at the interface essentially corresponds to the distribution and thickness of the binder in the polycrystalline diamond body of the composite material. Assuming a polished cross-section of the composite material, the average thickness of the binder at the interface would be substantially the same as the average thickness of the binder between the contacting diamond crystals of the polycrystalline diamond body of the composite material. Assuming a polished cross-section of the composite material, the maximum thickness of the binder at the interface would also be substantially the same as the thickness of the binder between the largest contacting diamond crystals of the polycrystalline diamond body of the composite. The maximum thickness of the binder at the interface is therefore about 50 percent of the largest dimension of the diamond crystals in the polycrystalline diamond body if the diamond crystals are measured along their longest dimension. The silicon carbide substrate may also contain binders which are in the form of the impregnating alloy which penetrated and diffused into the substrate during the hot pressing process.

The binder containing silicon atoms always contains silicon carbide. In one embodiment, the binder consists of silicon carbide and metal silicide. In another embodiment, the binder consists of silicon carbide, metal silicide and elemental silicon. In a further embodiment, the binder consists of 5 silicon carbide, metal silicide and metal carbide. In a further embodiment, the binder consists of silicon carbide, metal silicide, metal carbide and elemental silicon. In yet another embodiment, the binder consists of silicon carbide, metal carbide and demental silicon. The metal components of the metal silicide and metal carbide in the binder according to the invention are the alloy metal or metals which are present in the impregnation alloy.

The metal component of the metal silicide in binder 15 is preferably selected from the group consisting of cobalt, chromium, iron, hafnium, manganese, rhenium, rhodium, ruthenium, tantalum, thorium, titanium, uranium, vanadium, tungsten, yttrium, zirconium and alloys of these metals includes.

2o The metal component of the metal carbide present in the binder is a strong carbide former, which results in a stable carbide, and preferably a metal from the group consisting of chromium, hafnium, titanium, zirconium, tantalum, vanadium, tungsten, molybdenum and alloy -25 of these metals.

The proportion of elemental silicon and silicon carbide which may be present in the binder of the adhered polycrystalline diamond body can be dependent on the extent of the reaction between the surfaces of the diamond crystals and the silicon-rich impregnating alloy and on the extent of the reaction between the non-diamond-shaped elemental carbon and of the silicon-rich impregnation alloy fluctuate. If one assumes that all other factors are the same, the amount of silicon carbide present in the binder in the bonded polycrystalline diamond body largely depends on the hot pressing temperature and the residence time at this temperature. As the residence time and / or temperature is increased, the amount of silicon carbide increases as the amount 40 of elemental silicon decreases or decreases to an undetectable level. It is therefore possible, for example, to empirically determine the process conditions which must be observed in order to achieve a polycrystalline diamond body with a silicon carbide content 45 which leads to the desired properties.

The binder in the adhered polycrystalline diamond body always contains an at least detectable amount of silicon carbide and at least a detectable amount of silicide and / or carbide of the alloy metal present in the impregnating alloy. Depending on the alloy used, the metal silicide is usually in the form of a disilicide. The binder can also contain at least a detectable amount of elemental silicon. A detectable amount of silicon carbide, metal silicide, 55 metal carbide or elemental silicon means the amount that can be detected with an electron microscope when a thin part of the diamond body is irradiated due to the electron beam diffraction that occurs. However, the binder in diamond body 60 generally contains silicon carbide in an amount of about 1 to about 25 percent by volume based on the volume of the polycrystalline diamond body and generally metal silicide in an at least detectable amount and often a minimal amount of about 0.1 percent by volume of the polycrystalline diamond body. The amount of metal silicide present largely depends on the composition of the silicon-rich impregnating alloy. The metal silicides are hard and often have lower, linear ones

647 487

coefficients of thermal expansion than the metals or, in some cases, diamond, such as rhenium, which property is desirable for a phase in a diamond body. The amount of silicon carbide and elemental silicon present largely depends on the composition of the silicon-rich impregnating alloy and on the extent of the reaction between the silicon-rich alloy and a diamond-shaped or non-diamond-shaped carbon. The amount of metal carbide present largely depends on the composition of the silicon-rich impregnation alloy.

Electron beam diffraction when irradiating a thin section of the composite material with the aid of an electron microscope shows that the part of the binder which is in contact with the surfaces of the diamond crystals consists at least predominantly of silicon carbide.

The polycrystalline diamond body is non-porous or at least substantially non-porous, i.e. it may contain voids or pores of less than 1 percent by volume based on the volume of the body, provided the voids or pores are small, i.e. are less than 0.5 micrometers and are sufficiently evenly distributed in the body so that they have no visibly adverse effect on the mechanical properties of the diamond body. The void or pore content of the polycrystalline diamond body is determined by conventional metallographic measures, for example by optically examining a polished cross section of the body.

The diamond body according to the invention is also free of a non-diamond-shaped carbon phase insofar as it does not contain a non-diamond-shaped, elementary carbon phase in an amount that can be detected by an X-ray diffraction analysis.

A particular advantage of the invention is that the polycrystalline diamond body of the composite material can be produced in a variety of sizes and shapes. The diamond body can have a width or length of up to 25 mm or more, for example. Polycrystalline diamond bodies that are longer than 25 mm and have a diamond density according to the invention can practically not be produced using processes in which ultra-high pressures and temperatures of the diamond-stable region are used in the state diagram of carbon, since they are used to achieve and maintain such high pressure and temperature conditions necessary equipment require an extremely complex structure and therefore have only a limited capacity. On the other hand, the glued polycrystalline diamond body can be as small or thin as desired. However, the diamond body will always have a thickness that is greater than a single diamond crystal layer.

The composite material is ideal as an abrasive, cutting tool, nozzle or as any other wear-resistant component.

The invention will now be explained in more detail with reference to examples, in which the following procedure was used, unless stated otherwise:

Silicon carbide substrate

A hexagonal boron nitride powder with a fine particle size of about 2 to about 20 micrometers was used as the pressure-transmitting medium.

The polycrystalline silicon carbide substrate was in the form of a disk approximately 3.05 mm thick.

A device was used which essentially corresponded to the device shown in FIGS. 4 and 5.

The filling material used in the device according to FIG. 4 was cold pressed at room temperature up to a pressure of 5600 kp / cm 2.

The available amount of impregnation alloy was sufficient to completely soak the compressed diamond mass and to wet the contact surface of the substrate and to fill the pores of the interface.

The impregnation alloy was a silicon-rich alloy containing a eutectic.

The density of the polycrystalline silicon carbide body used as substrate is a fraction of the theoretical density of the silicon carbide of 3.21 g / cm3.

All of the sintered and hot-pressed polycrystalline silicon carbide bodies used as the substrate had essentially the same composition. The silicon carbide bodies contained silicon carbide, about 1 to 2 percent by weight boron based on the silicon carbide and less than about 1 percent by weight of elemental, submicron carbon based on silicon carbide. The carbon was in the form of small particles, the size of which was in the submicron range. The diamond powder used had a particle size of 1 to about 60 microns with at least 40 percent by weight of the diamond powder having a particle size below 10 microns.

A diamond density, given in percent by volume of the diamond body, was determined using the standardized point-counting technique, using a micrograph of a polished surface at a magnification of 690 and the analyzed surface area being of a size which was sufficient to represent the microstructure of the entire body.

The information about diamond density, which is in the range of over 70 percent by volume but less than 90 percent by volume based on the volume of the polycrystalline diamond body, is based on experience and results with similar experiments and in particular on experiments in which the polycrystalline diamond body was produced alone. The information about the appearance of the whole, glued polycrystalline body and also the volume of the formed, cleaned polycrystalline diamond body of the composite material in comparison to the volume of the diamond powder originally used are based on the assumption that less than 5 percent by volume of the diamond powder in non-diamond-shaped, elementary Carbon have been converted.

Examples 1 to 5

In Examples 1 to 5 compiled in Table I, a molybdenum bowl was used, which was lined with a zirconium sleeve. A disc made of a cast alloy with the specified composition and thickness and with a diameter substantially corresponding to the zirconium sleeve was placed inside the zirconium sleeve on the bottom of the cup. The diamond powder was packed over the disc with the specified amount. Finally, the specified polycrystalline silicon carbide disk was placed on top of the diamond powder, so that the cup was closed at the top with a stopper 14, as shown in FIG. 2.

The stoppered cup was then packaged in a hexagonal boron nitride powder as shown in FIG. The entire feed was cold pressed at room temperature in a steel mold to a pressure of about 5600 kp / cm 2, an essentially isostatic pressure being exerted on the contents of the bowl. The pressing pressure was maintained until the pressure increased to form a dimensionally stable shaped body, i.e. of an essentially isostatic system of the

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sealed container, had stabilized. From previous attempts it was known that the density of the diamond crystals in the compressed arrangement, i.e. in the essentially isostatic system, which is in the form of a shaped body, of the powder-enclosed bowl sealed with a stopper, was more than 75% by volume of the compressed diamond mass.

The compressed arrangement 21 of the bowl enclosed by powder and sealed with a stopper was then hot pressed. The arrangement 21 was inserted into a graphite mold which had the same diameter as the steel die, as shown in FIG. 5. The graphite mold was placed in an induction furnace. The interior of the cup sealed by the stopper was first evacuated and then filled with a nitrogen atmosphere by evacuating the induction furnace to a pressure of approximately 10 torr and then filling it with nitrogen. A pressure of about 350 kp / cm 2 was then exerted and maintained on the assembly 21 in the graphite mold. The graphite mold with the arrangement 21 was then heated to the specified maximum hot pressing temperature by the induction furnace in about 5 to 7 minutes. When the arrangement was heated, the pressure rose to the specified maximum hot pressing pressure due to the thermal expansion of the system.

At the specified temperature at which penetration begins or progresses, the pressure drops to about 350 kp / cm2. This drop in pressure indicates that the alloy had become liquid and had begun to penetrate the compressed diamond mass. The pressure was then increased again to the specified maximum hot pressing pressure and held at this maximum hot pressing pressure at the specified maximum hot pressing temperature for one minute in order to ensure that the alloy penetrated completely into the small capillaries of the compressed diamond mass. The heater was then turned off, but no additional pressure was applied. This provided a high pressure at a high temperature, but a reduced pressure at a low temperature, so that sufficient geometric stability was achieved and the hot-pressed arrangement retained its dimensions until it had cooled to a temperature which was sufficient for handling.

The composite material was ultimately obtained by the fact that the enveloping metal, i.e. the molybdenum bowl and the zirconium bushing as well as the excess alloy on the outer surfaces of the composite material were removed by grinding and sandblasting.

The resulting one-piece, cleaned composite bodies were in the form of a substantially uniform disc which was approximately 5 mm thick in Examples 1 to 3 and approximately 4 mm thick in Example 4.

Examples 6 and 7

In Examples 6 and 7 compiled in Table I, no metallic container, no liner sleeve or substrate was used. However, the device used essentially corresponded to the device shown in FIGS. 4 and 5. In Examples 6 and 7, the hexagonal boron nitride powder was packed in the die shown in Fig. 4 and a cylinder used as a mold was pressed into the powder. The cylinder was made of sintered metal carbide and was about 9 mm in diameter and about 6.3 mm in thickness. The axis of the cylinder was approximately aligned with the central axis of the die.

After the cylinder was inserted into the powder, further hexagonal boron nitride powder was added to the

Matrix was given until the cylinder was completely covered. The powder-enclosed cylinder was pressed at room temperature under a pressure of 3500 kp / cm2. The punch 23a was then withdrawn and the punch 23 was used to partially eject the cylinder surrounded by the pressed powder from the die.

The free part of the pressed powder was removed, exposing part of the cylinder. The cylinder was then pulled out, leaving a cavity that had been pressed into the powder by the cylinder. In Examples 6 and 7, a disc made of a cast alloy with the specified composition and thickness and with a diameter corresponding to the inside diameter of the cavity was placed on the bottom of the cavity. A layer of diamond powder with the specified particle size, quantity and thickness was packed on top of the alloy disc.

A disk of hot-pressed hexagonal boron nitride powder serving as a plug and having a diameter approximately equal to the inside diameter of the cavity was placed on top of the diamond powder within the cavity to ensure that the surface of the resulting polycrystalline diamond body became flat.

The entire mass was then pressed by the punch 23a into the center of the die. The stamp 23a was then withdrawn. Subsequently, further hexagonal boron nitride powder was added to the die until the hot-pressed hexagonal boron nitride disk was covered, so that the cavity or the cavity with contents was enclosed by the hexagonal boron nitride, as shown in FIG. 4. The feed was then cold pressed at room temperature in the steel die under a pressure of 5600 kp / cm2, as shown in Figure 4, with the contents cavity being subjected to a substantially isostatic pressure. The pressing pressure was maintained until it formed a dimensionally stable molded body, i.e. of an essentially isostatic system of the powder-enclosed cavity with content. From previous experiments it was known that the compressed diamond mass in the essentially isostatic system of the powder-enclosed cavity with content, which is in the form of a shaped body, has a diamond density of over 75 percent by volume.

The compressed arrangement of the powder-enclosed cavity essentially corresponded to arrangement 21, with the exception that no metal container was used. The resulting pressed arrangement was then hot pressed and for this purpose pressed into a graphite mold shown in FIG. 5 with the same diameter as the steel die. The graphite mold was then placed in an induction furnace. The interior of the cavity was first evacuated and then filled with a nitrogen atmosphere by first evacuating the induction furnace to a pressure of approximately 10 torr and then filling it with dry nitrogen. A pressure of about 350 kp / cm2 was applied and maintained on the assembly in the graphite mold. The pressurized assembly was then inductively heated to the specified maximum hot pressing temperature in about 5 to 7 minutes. When the arrangement was heated, the pressure rose to the specified maximum hot pressing pressure due to the thermal expansion of the entire system.

At the specified temperature at which the impregnation started, the pressure dropped to about 350 kp / cm 2. This drop in pressure indicates that the specified alloy had melted, become liquid and penetrated the diamond mass. The pressure was then on the

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specified maximum hot pressing pressure and kept at this pressure value for one minute at the specified maximum hot pressing temperature in order to ensure complete penetration of the alloy into the smaller capillaries of the compressed diamond mass. The heater was then turned off but no additional pressure was applied. This ensured a high pressure at high temperature and a reduced pressure at low temperature, which achieved sufficient geometric stability. The polycrystalline diamond body was removed at room temperature. The sealing plug does not adhere to the diamond body. After removing hexagonal boron nitride powder adhering to the surface of the diamond body in the form of scales

14

and of excess alloy by grinding and sandblasting, the one-piece polycrystalline diamond body was in the form of a disk of the specified thickness.

In Table I, the hot pressing temperature at which the impregnation begins is the temperature at which the alloy is liquid and begins to penetrate into the compressed diamond mass. The specified maximum hot pressing temperature and the specified maximum hot pressing pressure were simultaneously maintained for one minute in order to ensure that the smaller capillaries of the compressed diamond crystal mass were completely filled.

The X-ray analysis given in Table I for Examples 6 and 7 was carried out with the comminuted, polycrystalline diamond body.

Table I

example

Potions Alloy

Diamond powder

Metal container

Substrate or max. Hot

Hot stamping

Quantity approx.

Quantity approx.

so far

Stopper pressure ratur in

° C

in (mg)

Thickness in mg

Powder-

available

in kp / cm2

Start max.

in mm

thickness

the

Tem

inmm

Tear pera

kung tur

1

Atom%

226

1

300

1.65

Mo bowl with hot pressed

770

1325

1375

'95 Si

Zr lining

SiC substrate

5 re

dung

(~ 98% density)

2nd

85 Si

259

1

300

1.65

as in sintered SiC

770

1275

1375

15 cr

game 1)

Substrate (~ 95%

Density)

3rd

90 Si

323

1

300

1.65

as in case as in example 2)

880

1375

1525

10 pt

game 1)

4th

86 Si

230

1

140

0.76

as in case as in example 2)

770

1275

1375

14 Ti

game 1)

5

79 Si

318

1

280

1.57

as in case as in example 2)

880

950

1400

21 Rh

game 1)

6

95 Si

260

1

250

1.4

none

Plug out

910

1390

1495

5 RE

hot pressed,

hexagonal

Boron nitride powder

7

86 Si

1A Ti

210

1

250

1.4

none as in example 6

910

1345

1540

Table I (continued)

Example Melting point of the drinking alloy in the literature in ° C

Polycrystalline diamond body approximate properties

Thickness in mm

X-ray analysis of the polycrystalline diamond body

(1250)

predicted (Si, Re binary)

1335

(Si, Cr binary) 1350

(Si, Pt binary)

1.78 1.78 1.78

The diamond body of the composite material appeared to be well soaked and well bonded as in Example 1)

as in example 1)

(cleaned surface of the diamond body of the composite material) diamond and SiC

(cleaned surface of the diamond body of the composite material) diamond, Si and SiC

(cleaned surface of the diamond body of the composite material) diamond, PtSi and SiC

15

Table 1 (continued)

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Example Melting point of the drinking alloy in the literature in ° C

Polycrystalline diamond body approximate properties thickness in mm

X-ray analysis of the polycrystalline diamond body

1330 0.89

(Si, Ti binary)

(1250) 1.52

predicted

1330

1.52

as in example 1)

as in example 1)

Pore-free, hard and extremely resistant to abrasion, as evidenced by the absence of abrasion after exposure to silicon carbide particles.

Diamond, SiC and TiSi2

(crushed, polycrystalline diamond body)

Diamond, SiC, ReSi2 and traces of

The invention will now be explained in more detail with reference to Table I. The interface between the polycrystalline diamond body and the silicon carbide substrate could not be determined in any single composite pane according to Examples 1 to 5. Each composite body had a continuous structure over its thickness and the diamond part differed from the substrate by the grain size. The outer surface of each polycrystalline diamond body was well saturated with the binder. The binder was distributed uniformly. The individual diamond bodies were well connected.

The polycrystalline diamond bodies of the composite materials according to Examples 1 to 4 had a diamond density which was above 70% by volume but below 90% by volume of the volume of the polycrystalline body.

The diamond surface of the composite body according to Example 5 was polished on a cast iron block. Examination of the polished surface revealed no holes due to broken diamond particles. This indicates that the bond is very tight. The density of the diamond crystals was about 73 percent by volume based on the volume of the polycrystalline diamond body.

The polycrystalline diamond bodies according to Examples 6 and 7 were well saturated and firmly bonded. Each disk-shaped polycrystalline diamond body was broken in essentially two halves using a hammer and a wedge, and the fracture surfaces were visually examined under a microscope at 100 times magnification. Examination of the fracture surfaces showed that the fracture surfaces were free of pores, the binder was uniformly distributed in the body and the fracture surfaces were transgranular and not intergranular. This shows that the fracture ran across the crystals and not along the crystal faces. This indicates that the binding caused by the binder is extremely good and as strong as the diamond crystals themselves.

The diamond density of the disk according to Example 6 was above 70, but below 90 percent by volume of the body.

A fractured surface of the disk according to Example 7 was polished on a cast iron block. Examination of the polished surface revealed no holes due to broken diamond particles, suggesting a very strong bond. The density of the diamond crystals was about 80 percent by volume of the polycrystalline diamond body.

Example 8

25 The composite material produced according to Example 1 was used as a cutting tool. The free surface of the poly-crystalline diamond body of the composite material was ground smooth with a diamond grinding wheel and provided with a sharp cutting edge. The substrate of the composite material was then clamped in a tool holder.

Part of the cutting edge was examined on a lathe, with which a Jackfork sandstone was turned at a feed rate of 0.13 mm per revolution and a depth of cut 35 of 0.5 mm.

At a cutting speed of about 30 m per minute measured on the surface, the wear was 1.26 x 10 "6 cm3 per minute. Another part of the cutting edge was examined at a cutting speed of 84 m per minute measured on the surface The wear was 8.6 x 10 ~ ô cm3 per minute. Another part of the cutting edge was examined at a cutting speed measured on the surface of 88.4 m per minute. The wear in this case was 24 cm3 x 45 10 " 6 per minute.

The composite body was removed from the tool holder. An examination of the interface between the diamond body and the substrate showed that these processing attempts had no effect on the interface.

Example 9

The procedure was the same as in Example 8, with the exception that the composite body according to Example 2 was used.

Part of a cutting edge had a wear rate of 3.32 x 10 "6 cm3 per minute at a cutting speed measured on the surface of 33.5 m per minute. Another part of the cutting edge had a cutting speed measured on the surface of 97, 5 m per minute a wear of 24.3 x 10 "6 cm3 per minute.

An examination of the composite body after the mechanical processing showed that these processing attempts had no effect on the interface between the polycrystalline diamond body and the silicon carbide substrate.

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16

Example 10

The procedure was as in Example 8 with the exception that the composite material according to Example 3 was used.

Part of a cutting edge had a wear rate of 3.8 x 10 "6 cm3 per minute at a cutting speed of 33.5 m per minute measured on the surface. Another part of the cutting edge had a cutting speed of 97.5 measured on the surface m per minute wear of 30.3 x 10-6 cm3 per minute.

An examination of the composite material after machining showed that these processing attempts had no effect on the interface between the polycrystalline diamond body and the silicon carbide substrate.

Example 11

The procedure was as in Example 8, with the exception that the composite material according to Example 4 was used.

After 4 minutes of successful cutting with a cutting speed of 30 m per minute measured on the surface, small pieces broke out of the cutting edge. In another part of the cutting edge, after 6 minutes of successful cutting, small pieces broke out of the cutting edge at a cutting speed of 85 m per minute measured on the surface. It is believed that the cutting edge was broken due to hot press temperatures that were not high enough to wash the liquid, silicon-rich alloy into the small capillaries of the polycrystalline diamond mass during the hot press process. A comparison with Example 7 of Table I shows that the higher hot pressing temperatures result in a well-soaked and firmly bonded polycrystalline diamond body.

Example 12

The composite was made essentially as in Example 2, except that 260 mg of the silicon chromium alloy was used and the alloy disc was 1.3 mm thick.

250 mg of the diamond powder were also used, 60% by weight having a grain size of 53 to 62 micrometers, 30% by weight having a grain size of 8 to 22 micrometers and 10% by weight having a grain size of 1 to about 5 micrometers. The diamond powder was packed to a thickness of about 1.4 mm. A zirconium bowl with a zirconium lining was also used.

The maximum hot pressing pressure was about 910 kp / cm2 and the hot pressing temperature ranged from about 1250 ° C at the beginning of the penetration of the liquid, silicon-rich alloy into the pressed diamond crystal mass up to a maximum hot pressing temperature of about 1500 ° C. The composite material was obtained in the same manner as in Example 2. The composite material was in the form of a substantially uniform disc about 1.5 mm thick.

The silicon carbide substrate was ground away from the composite material and the polycrystalline diamond body was subjected to a thermal stability test. The substrate was heated in air to a temperature of 900 ° C, which was the limit temperature of the furnace. During the heating process, the linear thermal expansion coefficient was determined for the temperatures from 100 ° C to 900 ° C. The furnace was switched off at 900 ° C.

The experimental data and the examination of the sample, i.e. of the polycrystalline diamond body after the experiment showed that there was no sudden change in length in the sample during the entire heating process. There was no evidence of permanent damage to the sample caused by the heating process.

Example 13

The procedure was essentially as in Example 2, except that a silicon wafer in a zirconium bowl with a zirconium liner was used to form a silicon-rich zirconium alloy in situ.

6 composite materials were produced. A diamond powder was used to produce 3 composite materials, in which 60% by weight had a grain size of 53 to 62 micrometers, 30% by weight had a grain size of 8 to 22 micrometers and 10% by weight had a grain size of 1 to about 5 micrometers. The other three composite materials were made using a diamond powder that had a grain size of 1 to 60 microns with at least 40% by weight of a grain size less than 10 microns.

The maximum hot press pressure was about 910 kp / cm2 and the hot press temperature ranged from about 1340 ° C to a maximum hot press temperature of about 1500 ° C. The temperature at the lower end of the specified temperature range of approximately 1340 ° C. is the temperature at which the impregnation process begins and it becomes clear that the silicon-rich zirconium alloy was formed in situ and has become liquid.

Each composite was obtained in essentially the same manner as in Example 2. Each composite material was in the form of a disk.

The surface on the face and cylinder surfaces of the polycrystalline diamond body of all 6 composite materials was ground. The difficulty in grinding these composite materials with a diamond grinding wheel showed that the abrasion resistance of these diamond bodies was comparable to that of the commercially available polycrystalline diamond products.

The 3 composite materials made from the diamond powder with a grain size of 1 to 60 microns had insufficiently mixed aggregates of diamond powder with a grain size of less than 2 microns. An examination of the ground edges of the polycrystalline body showed that these aggregates were incompletely impregnated with the alloy. However, the rest of the cut diamond area was well bound.

An optical examination of the composite materials showed no detectable defects or different intermediate layers between the silicon carbide substrate and the diamond layer. Four composite materials were broken to look at the internal structure. No visible intermediate layers or defects at the interface between the silicon carbide substrate and the polycrystalline diamond layer were found during the optical examination of the fracture surfaces.

The continuity of the structure at the interface between the substrate and the diamond layer was excellent and only the different grain sizes of the diamonds and the silicon carbide allowed the interface between the substrate and the diamond layer to be determined.

Two of the composite materials were tested as cutting tools on a lathe, with which a rod-shaped, sanded smoothing grindstone with a strong grinding effect was turned. The cutting depth was 0.76 mm, the feed rate was 0.13 mm per revolution and the cutting speed measured on the surface was 183 m per minute.

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After a cutting time of 16 minutes and 22 seconds, the front cutting edge of the two tools showed a uniform abrasion of approximately 0.13 mm. This shows that the cutting edge had excellent abrasion resistance.

Example 14

The composite material produced according to Example 1 was broken apart essentially in half with a hammer and a wedge. The fracture surfaces were examined under a microscope with a 100-fold magnification. Examination of the fracture surfaces revealed that both the polycrystalline diamond body and the interface of the composite material were pore-free, the binder was evenly distributed in the diamond body and the fracture was transgranular and not intergranular, i.e. that the fracture ran across the crystals and not along the crystal faces. This indicates that the binding caused by the binder is very good and as firm as the diamond crystals themselves. There were also no visible interlayers or defects at the interface between the silicon carbide substrate and the attached polycrystalline diamond layer. The fracture surface of the composite material had a continuous structure and only the different grain size between the diamond and the firmly adhering substrate revealed the boundary between the substrate and the attached polycrystalline diamond body.

The fracture surface of the composite was polished. Optical inspection of the polished fracture surface shown in Fig. 7 revealed no holes due to broken diamond particles. This shows that there is a very strong bond. 7 shows the polycrystalline diamond body in its upper part and the substrate in its lower part. The area in between can be identified by the different crystal structure between the diamond body and the substrate. The density of the diamond crystals was approximately 71 volume percent of the polycrystalline diamond body in the sample shown in FIG. 7.

Silicon nitride substrate

A fine-grained powder made of hexagonal boron nitride with a grain size of about 2 to about 20 micrometers was used as the pressure-transmitting medium.

The polycrystalline silicon nitride substrate was in the form of a disk which was approximately 3.18 mm thick in Examples 16 and 17 and approximately 2.5 mm thick in Examples 19 and 20. The polycrystalline silicon nitride substrate was a commercially available hot pressed material which had a density of over 99%, i.e. had almost a density of 100%. The material contained, based on the weight of the hot-pressed silicon nitride body, Zi% MgO, approximately 'A% Fe, approximately Vzoo% metallic impurities such as Ca, Al, and Cr, 2% free Si, 1% SiC and silicon nitride as the balance.

The device used essentially corresponded to the device shown in FIGS. 4 and 5.

The feed was cold pressed as shown in FIG. 4 at room temperature up to about 5600 kp / cm 2. The density of the diamond crystals in the compressed assembly was over 75 volume percent of the compressed diamond mass.

The amount of the impregnating alloy was sufficient to completely soak the compressed diamond mass and to wet the contact surface of the substrate and to fill the pores of the interface.

The impregnating alloy was a silicon-rich alloy containing a eutectic.

The density of the polycrystalline silicon nitride body used as substrate is the fractional density of the theoretical density of the silicon nitride of 3.18 g / cm 3.

The composite material or the polycrystalline diamond body was broken apart using a hammer and a wedge.

The optical examination of the break points was carried out under a microscope at a magnification of approximately 100 times.

The fracture surface of the polycrystalline body was polished on a cast iron block.

A diamond density, given in percent by volume of the body, was determined using the standardized point-counting technique, using a micrograph of the polished cross-sectional area at 690 times magnification and the analyzed surface area being of a size which sufficiently represented the microstructure of the entire body.

The information about the diamond density, which is in the range of over 70 but less than 90 percent by volume based on the volume of the polycrystalline body, is based on experience and similar tests, in particular on tests in which the polycrystalline diamond body was produced on its own. The appearance of the polycrystalline body as a whole and also the volume of the cleaned, cleaned polycrystalline diamond body of the composite material compared to the volume of the diamond powder originally used are based on the assumption that less than 5 percent by volume of the diamond powder has been converted into non-diamond-shaped, elemental carbon.

In Examples 15 and 16, the silicon-rich impregnation alloy was an in situ silicon and zirconium alloy.

Example 15

In this example, a polycrystalline diamond body was made without a substrate.

A cast silicon wafer weighing 330 mg was placed within a zirconium can in a molybdenum bowl. About 500 mg of fine diamond powder, the grain size of which was in the range from about 1 to about 60 micrometers and of which at least 40% by weight had a grain size of less than 10 micrometers, was packed on top of the silicon wafer. A molybdenum bowl, which had a slightly larger diameter than the original bowl filled with silicon and diamonds, was placed over the opening of the original bowl coated with silicon and diamonds.

The container formed in this way was then packed according to FIG. 4 in a powder made of hexagonal boron nitride. The entire feed was cold pressed at room temperature in a steel die to a pressure of about 5600 kp / cm2, with an essentially isostatic, i.e. an essentially uniform pressure was exerted from all directions. The pressing pressure was maintained until the pressing pressure with formation of a dimensionally stable molded body, i. H. stabilized an essentially isostatic system of the powder-enclosed container. It was known from previous experiments that the compressed diamond mass in the system in the form of a shaped body has a diamond density of more than 75 percent by volume based on the volume of the compressed diamond mass. The silicon was present in an amount of approximately 80 percent by volume of the compressed diamond mass.

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The resulting, compressed arrangement 21 of the container enclosed by the powder was then hot pressed. For this purpose, the arrangement 21 was inserted into a graphite mold in the manner shown in FIG. 5, which had the same diameter as the steel die. The graphite mold was placed in an induction furnace. The interior of the container was first evacuated and then filled with a nitrogen atmosphere by first evacuating the induction furnace to about 10 torr and then filling it with nitrogen. A pressure of approximately 350 kp / cm2 was then applied to and maintained on the graphite mold assembly 21. The pressurized assembly 21 was then inductively heated to a temperature of 1500 ° C in 7 minutes. When the assembly was heated, the pressure rose to about 700 kp / cm 2 due to the thermal expansion of the system. After reaching a temperature of about 1350 ° C, the pressure dropped to about 350 kp / cm2. This drop in pressure indicates that silicon-rich zirconium alloy had formed, had become liquid, and had begun to penetrate the compressed diamond mass. The pressure was increased to the maximum hot press pressure of 700 kp / cm2. When the temperature of 1500 ° C was reached, the assembly was held at this maximum hot pressing temperature of 1500 ° C for one minute under the pressure of 700 kp / cm 2 to ensure complete soaking of the smaller capillaries of the compressed diamond mass. The heater was then turned off but no additional pressure was applied. In this way, a high pressure at a high temperature was ensured, but a reduced pressure at a low temperature and thus adequate geometric stability. In this way, the hot-pressed arrangement maintained its dimensions until it had cooled to a temperature sufficient for handling.

The resulting polycrystalline diamond body was obtained by the fact that the cladding metal, i.e. the molybdenum bowl and the zirconium sleeve as well as excess silicon on the outer surfaces of the body were removed by grinding and sandblasting.

The resulting one-piece polycrystalline diamond body had the shape of a disk with a thickness of about 3 mm. The diamond body seemed to be well soaked and had a tight bond.

X-ray diffraction analysis of the cleaned surface through which the alloy penetrated shows that the body consisted of diamond, silicon carbide and elemental silicon and silicon carbide and elemental silicon were present in an amount of at least 2 percent by volume of the body. However, no non-diamond-shaped elemental carbon was found in the X-ray diffraction analysis.

An examination of the fracture points of the disk showed that the fracture surface was transgranular and not intergranular, that is to say that the fracture surface ran across the crystals and not along the crystal surfaces. This indicates that the binding caused by the binder is very good and as firm as the diamond crystals themselves.

When examining the fracture surfaces, it was found that the fracture surfaces were free of pores and the binder was evenly distributed over the body.

When examining the polished fracture surface, it was found that the polished surface had no holes due to broken diamond particles, which indicates that there is a strong bond and the diamond body is suitable as an abrasive.

The density of the diamond crystals was approximately 81 volume percent of the polycrystalline diamond body.

A micrograph of the polished surface at 690x magnification showed a white phase. An x-ray spectral analysis of this phase revealed that the phase consisted of zirconium and silicon, which indicates that this phase was zirconium silicide.

Example 16

In this example, the composite material was made using a hot pressed polycrystalline silicon nitride as the substrate.

A cast silicon wafer weighing 15,142 mg was placed within a zirconium sleeve in a zirconium cup. 270 mg of diamond powder with a layer thickness of approximately 1.5 mm were applied to the silicon wafer. The diamond powder contained 85% by weight of diamond particles with a grain size of 53 to 62 micro-20 meters and 15% by weight of diamond particles with a grain size of about 5 micrometers. Instead of the metal cover used in Example 1, a stopper 14 shown in FIG. 2 made of hot-pressed, polycrystalline silicon nitride was used.

The sealed bowl was then packed in a powder made of hexagonal boron nitride as shown in FIG. 4. The entire feed was cold pressed at room temperature in the manner described in Example 1, with the sealed well and its contents being subjected to a substantially isostatic pressure. The pressing pressure was maintained until the pressure developed to form a dimensionally stable molded body, i.e. stabilized an essentially isostatic system of the powder-enclosed bowl. The density of the diamond crystals was over 75 35 percent by volume of the compressed diamond mass. The resulting compressed assembly 21 of the powder-covered sealed cup was then hot pressed in the same manner as in Example 15 except for the information contained in Table II. 40 The resulting composite material was obtained by removing the coating metal and excess silicon on the outer surfaces of the composite material by grinding and sandblasting.

Examples 15 and 16 are shown in Table II. In Examples 17, 19 and 20 listed in Table II, too, a cast alloy in the form of a disk with the specified composition and thickness and with a diameter corresponding to the diameter of the specified lining was arranged within the sleeve-like lining on the bottom of the specified bowl. The diamond powder was packed on top of the disc in the amount indicated. Finally, the specified polycrystalline silicon nitride substrate was applied on top of the diamond powder. The silicon nitride substrate formed a stopper which closes the cup and is provided with the reference symbol 14 in FIG. 2. The sealed cup was then cold and hot pressed in the manner described in Example 2 with the exception of the information contained in Table II. The resulting composite was obtained in essentially the same manner as in Example 16.

The resulting, cleaned, one-piece composite material of Examples 16, 17, 19 and 20 was in the form of a substantially uniform disc, which was about 4.7 mm thick in Examples 16 and 17 and a thickness in Examples 19 and 20 of about 3.8 mm.

In Example 18, a polycrystalline diamond body was used without the use of a metallic container

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Lining or a substrate made. However, the devices used essentially corresponded to the devices shown in FIGS. 4 and 5. The hexagonal boron nitride powder was packed into the die of FIG. 4. A cylinder serving as a shape was pressed into the powder. The cylinder was made of sintered metal carbide and was about 8.9 mm in diameter and about 6.3 mm in thickness. The axis of the cylinder was essentially aligned with the central axis of the die.

After inserting the barrel into the powder, additional powdered hexagonal boron nitride was added to the die to completely cover the barrel. The cylinder enclosed by the powder was pressed at room temperature under a pressure of 350 kp / cm2. The plunger 23a was then pulled out and the plunger 23 was used to partially push the cylinder enclosed by powder out of the die.

The exposed part of the pressed powder was removed to partially expose the cylinder. The cylinder was then pulled out, leaving a cavity pressed in by the cylinder. In Example 4, a disc made of a cast alloy with the specified composition and thickness and with a diameter substantially corresponding to the inside diameter of the cavity was placed on the bottom of the cavity. A layer of diamond powder with the specified grain size, quantity and thickness was packed on top of the alloy disc. A disk of hot-pressed, powdered, hexagonal boron nitride with a diameter corresponding to the inside diameter of the recess was placed in the recess on top of the diamond powder. The hot pressed disc served as a stopper to ensure that the surface of the resulting polycrystalline diamond body was flat.

The entire mass was then pressed into the center of the die with the aid of the stamp 23a, whereupon the stamp 23a was withdrawn. An additional amount of powdered, hexagonal boron nitride was placed in the die to cover the hot-pressed hexagonal boron nitride disc and to completely enclose the recess and its contents with hexagonal boron nitride in the manner shown in FIG. 4. The resulting feed was then cold pressed at room temperature in the steel die under a pressure of 5600 kp / cm2 in the manner shown in Fig. 4, the cavity and its contents being subjected to a substantially isostatic pressure. The pressing pressure was maintained until the pressing pressure with formation of a dimensionally stable shaped body, i.e. an essentially isostatic system that had stabilized the powder-covered recess and its contents. It was known from previous experiments that the diamond crystals in the essentially isostatic system, which is in the form of a shaped body, were coated with powder

Recess with content has a density of over 75 percent by volume of the compressed diamond mass.

The resulting, pressed arrangement of the recess encased by powder and its contents essentially corresponds to the pressed arrangement 21, with the exception that no metal container was used. The resulting pressed arrangement was then hot pressed, i.e. given in the graphite shape shown in Fig. 5, which had the same diameter as the steel die. The graphite form io was then placed in an induction furnace. The interior of the recess was first evacuated and then filled with a nitrogen atmosphere by first evacuating the furnace to about 10 torr and then refilling it with dry nitrogen. A pressure of about 350 kp / cm2 was then applied to and maintained on the assembly in the graphite mold. The pressurized assembly was then heated to the specified maximum hot pressing temperature in about 5 to 7 minutes. When the assembly 20 was heated, the pressure rose to the specified maximum hot pressing pressure due to the thermal expansion of the entire system.

At the specified temperature at which the impregnation started, the pressure dropped to about 350 kp / cm 2. This drop in pressure indicates that the specified alloy has melted and become liquid and has begun. had to penetrate the diamond mass. The pressure was then increased again to the specified maximum hot pressing pressure and held for one minute at the specified maximum hot pressing temperature in order to ensure complete penetration of the alloy into the smaller capillaries of the compressed diamond mass. The heater was then turned off but no further pressure was applied. This ensured a high pressure at high temperature, but a reduced pressure at a low temperature and thus adequate geometric stability. The resulting polycrystalline diamond body was removed at room temperature. The sealing plug did not adhere to the diamond body. After removal of scale-like hexagonal boron nitride powder adhering to the surface of the polycrystalline diamond body and excess alloy by grinding and sandblasting, the one-piece polycrystalline diamond body had the shape of a disk with the indicated thickness.

45 The hot pressing temperature specified in Table II, at which the impregnation process begins, is the temperature at which the alloy is liquid and begins to penetrate into the compressed diamond mass. The specified maximum hot pressing temperature and the specified maximum hot pressing pressure were maintained at the same time for one minute in order to ensure that the smaller capillaries of the compressed diamond crystal mass were completely filled.

Table II

Example drinking potions

Atom% quantity approx.

in mg thickness in mm

Diamond powder

Grain size in Mi amount approx. crometer in mg powder thickness

Open metal container (so- substrate or stop available)

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cast silicon

330

1 to 60, of which 40% by weight is less than 10

500

Mo bowl with Zr lining no, Mo bowl as lid

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Table II (continued)

Example triangle alloy diamond powder metal container {so- substrate or stop-

Aiom% quantity approx. Grain size in Mi amount approx. widely available) in mg thickness crometer in mg powder in mm thickc in mm

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85 Si 15 Cr

86 Si 14 Ti

86 Si 14 Ti

95 Si 5 Re

260 210

133

121

0.76

1 1

0.76

82% by weight with 53 to 62.15% by weight with ~ 5

like example 1) like example 1)

270 1.5 Zr bowl with

Zr lining

290 1.6 Mo bowl with Zr lining

250 1.4 none like example 1) 227

70% by weight with 1 to 60, of which 17% by weight with 1 to 10, and 30% by weight with 1 to 5

Mo bowl with Mo lining

200 mo bowl with

Mo liner hot pressed silicon nitride hot pressed silicon nitride hot pressed hexagonal boron nitride powder hot pressed silicon nitride hot pressed silicon nitride

Table II (continued)

Example Maximum hot-hot pressing temperature Melting point of the press pressure impregnation Maximum impregnation alloy in kp / cm2 C temperature in literature

° C ° C

Pollycrystalline diamond body approx. Thick X-ray analysis in mm lysis of the diamond body

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910 910

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4300

1260 1345

1322 1340

1500

1525

1450 1540

1525 1540

1360

(Si-9.6 wt% Zr eutectic)

1360

(Si-9.6 wt% Zr eutectic)

1335

(SiCr binary) 1330

1330 1250

(predicted)

2.9 1.5

1.4

1.5

1.3 1.1

(cleaned surface) diamond, SiC and Si

(broken body) Diamond SiC and TiSi2

Examples 16, 17, 19 and 20 show the production of the composite material according to the invention. After an optical examination, it was found that each composite material of these examples had a continuous structure, but the interface between the diamond body and the substrate could be determined due to the different grain size and due to color differences between the diamond body and the substrate. The silicon nitride substrate was darker than the gray diamond body. The outer surface of each polycrystalline diamond body was well saturated, with the binder evenly distributed. The diamonds were well connected.

60 The polycrystalline diamond body of the composite materials according to Examples 17 and 18 had a diamond density which was over 70 percent by volume but less than 90 percent by volume of the volume of the polycrystalline body.

The diamond surface of the composite material according to Example 65 16 was polished. Upon visual inspection of the polished surface, it was found that the polished surface had no holes due to broken diamond particles, indicating that a firm bond

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is present. The density of the diamond crystals was about 71 percent by volume of the polycrystalline diamond body according to Example 16.

The polycrystalline diamond body in Example 18 was a well-soaked, hard-bonded, hard disc. The diamond body was essentially broken apart in half. During the optical examination of the fracture surfaces, it was found that the fracture surfaces were pore-free, the binder was evenly distributed in the diamond body and the fracture was trans-granular and not inter-granular, which means that the fracture ran across the crystals and not along the crystal boundaries. This indicates that the binding caused by the binder is very good and as firm as the diamond crystals themselves.

A fractured surface of the disk of Example 18 was polished. When the polished surface was examined, it was found that the polished surface had no holes due to broken diamond particles, which confirmed the strong bond. The density of the diamond crystals in the diamond body of Example 18 was about 80 volume percent of the polycrystalline diamond body.

Example 21

The composite material according to Example 17 was used as a cutting tool. The free surface of the polycrystalline diamond body of the composite material was ground with a diamond grinding wheel in order to smooth the free surface of the diamond body and to provide it with a sharp cutting edge. The substrate of the composite material was then clamped in a tool holder.

Part of the cutting edge was examined on a lathe, with which a Jackfork sandstone was turned with a feed of 0.13 mm per revolution and a depth of cut of 0.5 mm.

At a cutting speed of 28.5 m per minute measured on the surface, the abrasion was 3.6 × 10 6 cm 3 per minute. Another part of the cutting edge was examined at a cutting speed of 79.3 m per minute measured on the surface. The abrasion in this case was 8.2 x 10 "6 cm3 per minute.

The composite was removed from the tool holder and the interface between the diamond body and the substrate was examined. It turned out that the processing carried out had no influence on the composite material.

Example 22

The procedure was the same as in Example 21, except that the composite material prepared according to Example 19 was used.

Part of the cutting edge was examined at a surface speed of 30.5 m per minute. After a cutting time of 2 minutes, the cutting edge produced a very small scar, which indicated excellent wear resistance. However, the Jackfork sandstone had a deep furrow. Since the composite material was brittle, a small piece of the cutting edge broke out.

Examination of the composite material after the cutting process showed that the cutting tests had no effect on the interface between the polycrystalline diamond body and the silicon nitride substrate.

Example 23

The composite material produced according to Example 20 was essentially broken apart in two halves. The fracture surfaces were examined optically. When examining the fracture surfaces, it was found that both the polycrystalline diamond body and the interface of the composite material were pore-free, the binder was evenly distributed in the diamond body, and the fracture was transgranular and not intergranular, i.e. that the break was across the crystals and not along the crystal boundaries. This indicates that the bond caused by the binder is very good and as strong as the diamond crystals themselves. There were also no visible intermediate layers or defects at the interface between the silicon nitride substrate and the polycrystalline diamond layer. The fracture surface of the composite material had a continuous structure. Only the different grain size between the diamonds and the firmly adhering substrate as well as the darker color of the Hessen substrate recognize the boundary between the substrate and the polycrystalline diamond body.

The fracture surfaces of the composite material have been polished. When the polished fracture surface shown in Fig. 7 was visually examined, it was found that the polished surface had no holes due to broken diamond particles. This is an indication that there is a firm bond. 7 shows the polycrystalline diamond body in its upper part and the substrate in its lower part. The interface between them can be identified by the different crystal structure and the different color between the diamond body and the substrate. The density of the diamond crystals was about 75 volume percent of the polycrystalline diamond body shown in FIG. 7.

Example 24

The composite materials made according to Examples 16, 17 and 19 were essentially broken apart in half. The fracture surfaces were examined optically. When examining the fracture surfaces, it was found that both the polycrystalline diamond body and the interface of each composite material were pore-free, the binder was evenly distributed in the diamond body, and the fracture was transgranular and not intergranular, i.e. that the break was across the crystals and not along the crystal boundaries. This indicates that the binding caused by the binder is very good and as strong as the diamond crystals themselves. There were also no visible intermediate layers or defects at the interface between the silicon nitride substrate and the adherent, polycrystalline diamond layer. The fracture surface of each composite material had a continuous structure. Only the different grain size between the diamonds and the firmly adhering substrate, as well as the darker color of the Hessen substrate, recognize the boundary between the substrate and the polycrystalline diamond body.

The fracture surface of the composite material according to Example 19 was polished. When examining the polished fracture surface, it was found that the polished surface had no holes due to broken diamond particles, which indicates that there is a strong bond. A micrograph of the polished surface at a 690x magnification showed an intermediate layer of the binder at the interface. When evaluating an electronic micrograph of the polished surface with a 1000-fold magnification, an intermediate layer of binder was found at the interface, which had a maximum thickness of about 3 micrometers.

An X-ray spectral analysis of the binder in the intermediate layer and in the polycrystalline diamond body showed that the components were the same in both cases.

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Claims (20)

647 487 PATENT CLAIMS 1. A method for producing a one-piece composite material from a polycrystalline diamond body and a silicon carbide or silicon nitride substrate using a hot pressing process, characterized in that a) a solid mass from a silicon-rich alloy containing a eutectic or solid components to form a eutectic is contained in a cavity of a body silicon-rich alloy, a diamond crystal mass and a silicon carbide or silicon nitride substrate are introduced, the diamond crystal mass being arranged between the substrate and the solid mass or the solid components and with the substrate and the solid mass of the silicon-rich alloy or with at least one solid component to form the eutectic containing silicon-rich alloy is in contact and the eutectic-containing, silicon-rich alloy consists of silicon and a metal, which with Siliciu m forms a silicide; b) the body and its contents are arranged in a pressure-transmitting powder medium which transmits the acting pressure essentially unabated and remains essentially unsintered during the hot pressing process; c) a substantially isostatic pressure is exerted on the body and its contents via the powder medium in order to stabilize the dimensions of the body and the contents substantially uniformly and thereby to create a dimensionally stable, essentially isostatic system of the body encased in powder, whereby the volume of the compressed mass of diamond crystals is over 70 percent by volume of the volume of the compressed diamond crystals; d) the resulting isostatic system is subjected to a hot pressing process in order to form a liquid, eutectic-containing, silicon-rich alloy and to flood this liquid, silicon-rich alloy into the interstices of the compressed mass of the diamond crystals and to bring them into contact with the contact surface of the substrate , which forms an interface with the compressed crystal mass, the hot-pressing process being carried out at a hot-pressing temperature of below 1600 ° C. under a hot-pressing pressure sufficient to wash the liquid, silicon-rich alloy into the interstices of the compressed diamond crystal mass, which is a eutectic containing silicon-rich solid alloy or the solid components for forming the eutectic-containing silicon-rich alloy can be used in an amount which is at the hot pressing temperature for forming a eutectic-containing silicon-rich alloy It suffices to fill the gaps of the compressed mass of the diamond crystals and to wet the contact surface of the substrate, thereby filling the pores at the interface, so that the interface is at least substantially non-porous, the hot pressing process being carried out in an atmosphere which no noticeable harmful influence on the diamond crystals, the liquid silicon-rich impregnating alloy or the substrate, and wherein during the hot pressing process less than 5 percent by volume of the diamond crystals are converted into non-diamond-shaped elemental carbon and the non-diamond-shaped carbon or the surfaces of the diamond crystals with the liquid, silicon-rich React alloy with carbide formation; e) the resulting hot-pressed, substantially isostatic system is maintained during cooling under a pressure which is at least substantially sufficient to maintain the dimensions of the hot-pressed system; and f) removing the resulting composite material, s in which the polycrystalline diamond body is bonded with a binder containing silicon atoms and the diamond crystals are present in an amount of at least 70 volume percent of the volume of the polycrystalline diamond body. io 2. The method according to claim 1, characterized in that the binder contains silicon carbide and a metal silicide, the metal component of the metal silicide being selected from the group consisting of cobalt, chromium, iron, hafnium, manganese, molybdenum, niobium, nickel , Palladium, 15 platinum, rhenium, rhodium, rhutenium, tantalum, thorium, titanium, uranium, vanadium, tungsten, yttrium, zirconium and alloys of these metals, or that the binder contains silicon carbide and a metal carbide, wherein the metal component of the metal carbide consists of the Group selected is selected, which includes chromium, hafnium, titanium, zirconium, tantalum, vanadium, tungsten, molybdenum and alloys of these metals, and that the binder optionally also contains elemental silicon. 3rd 647 487 wetting the pores at the interface so that the interface is at least substantially pore-free, the hot pressing process being carried out in an atmosphere which has no appreciable deleterious effect on the diamond crystals, the liquid silicon-rich alloy or the substrate, and wherein less than 5 percent by volume of the diamond crystals are converted to non-diamond-shaped elemental carbon during the hot pressing process and the non-diamond-shaped carbon or the surfaces of the diamond crystals react with the liquid, silicon-rich alloy to form carbide; e) the resulting hot-pressed, substantially isostatic system is maintained during cooling under a pressure which is at least substantially sufficient to maintain the dimensions of the hot-pressed system; and f) removing the resulting composite material from which the polycrystalline diamond body is bonded to the silicon carbide or silicon nitride substrate and in which the diamond crystals are present in an amount of at least 70 percent by volume of the volume of the polycrystalline diamond body. 3. The method according to claim 1, characterized in that a) in a cavity of a container serving as a body and shield, a solid mass made of a binder-forming, eutectic-containing silicon-rich alloy or solid components for forming a eutectic-containing silicon-rich Alloy, a diamond crystal mass and a silicon carbide or silicon nitride substrate are introduced, the diamond crystal mass being arranged between the substrate and the alloy or the solid components and being in contact with the substrate and the alloy or the solid components or with at least one component thereof and wherein the eutectic-containing, silicon-rich alloy consists of silicon and a metal that forms a silicide with silicon, 40 b) the container and its contents are arranged in a pressure-transmitting powder medium which transmits the acting pressure essentially unabated and remains essentially unsintered during the hot pressing process, 45 c) an essentially isostatic pressure is exerted on the container and its contents via the powder medium, the dimensions of the container and the contents being stabilized essentially uniformly and thereby creating a dimensionally stable, essentially isostatic system of the container thus coated with powder , wherein the content of the polycrystalline diamond body of diamond crystals is over 70 percent by volume of the volume of the compressed diamond crystals, d) the resulting isostatic system is subjected to a hot pressing process in order to form a liquid, eutectic-containing, silicon-rich alloy and to flood this liquid, silicon-rich alloy into the spaces between the compressed mass of the diamond crystals and with the contact surface of the sub-6o strat to bring into contact, which forms an interface with the compressed crystal mass, the hot pressing temperature of below 1600 ° C is carried out under a hot pressing pressure, the amount used of a 'eutectic containing, silicon-rich alloy or 65 solid components to form the eutectic containing , silicon-rich alloy is sufficient to fill the gaps of the compressed mass of the diamond crystals and the contact surface of the substrate 4th distributed, the part of the binder in contact with the surfaces of the diamond crystals is at least largely silicon carbide, the diamond body is essentially non-porous, the density of the substrate from 85 to 100 percent of the theoretical density of the silicon carbide or from 80 to 100 percent of the theoretical Density of silicon nitride, the substrate contains silicon carbide or silicon nitride in an amount of at least 90 percent by weight of the substrate and is free of constituents which have a noticeably detrimental effect on the mechanical properties of the composite material, the polycrystalline diamond body interfaces with the Has silicon carbide or silicon nitride substrate and the binder extends from the polycrystalline diamond body to the contact surface with the substrate and at least substantially fills the pores at the interface, so that the interface is at least substantially pore-free, manufactured according to the Verfa hear according to claims 2 and 3 or 2 and 8. 4. The method according to claim 3, characterized in that the diamond crystals are used with graded grain sizes in the range of 1 to 60 microns. 5. The method according to any one of claims 3 or 4, characterized in that the liquid, silicon-rich alloy is used in an amount which makes up 25 to 80 percent by volume of the volume of the compressed diamond crystal mass. 6. The method according to any one of claims 3 to 5, characterized in that the content of the compressed diamond crystal mass is 71 to less than 95 percent by volume of diamond crystals of the volume of the compressed crystals. 7. The method according to any one of claims 3 to 6, characterized in that the solid mass of the silicon-rich alloy is used in the form of grains. 8. The method according to claim 1, characterized in that a) as a cavity, a recess is pressed into a pressure-transmitting powder medium acting as a body, which transmits the acting pressure essentially unabated and remains essentially unsintered during the hot pressing process; b) a solid mass composed of a binder-forming, a eutectic-containing, silicon-rich alloy or solid components for forming a eutectic-containing silicon-rich alloy, a diamond crystal mass and a polycrystalline silicon carbide or silicon nitride substrate are introduced, the diamond crystal mass being between the substrate and the Alloy or the solid components is arranged and is in contact with the substrate and the alloy or the solid components or at least with a component for forming the eutectic-containing, silicon-rich alloy, and wherein the eutectic-containing, silicon-rich alloy of silicon and a metal which forms a silicide with the silicon; c) the recess and its contents are covered with an additional amount of the pressure-transmitting powder medium and the recess is thereby coated with the pressure-transmitting powder medium; d) an essentially isostatic pressure is exerted on the recess and its contents via the powder medium, the dimensions of the recess and its contents being stabilized essentially uniformly and thereby creating a dimensionally stable, essentially isostatic system of the recess encased in powder, whereby the content of diamond crystals in the polycrystalline diamond body is more than 70 percent by volume of the volume of the compressed diamond crystals; e) the essentially isostatic system is subjected to a hot pressing process in order to form a liquid, eutectic-containing, silicon-rich alloy and to flood this liquid, silicon-rich alloy into the interstices of the compressed diamond crystal mass and to bring it into contact with the contact surface of the substrate the compressed crystal mass forms an interface, the hot pressing process being carried out at a hot pressing temperature of below 1600 ° C. under a hot pressing pressure, the amount used of a silicon-rich alloy containing a eutectic or of solid components being sufficient to form the silicon-rich alloy containing a eutectic in order to fill the spaces between the compressed mass of the diamond crystals and to wet the contact surface of the substrate while filling the pores at the interface, so that the interface is at least substantially non-porous i The hot pressing process is carried out in an atmosphere which has no noticeable, harmful influence on the diamond crystals or the liquid, silicon-rich alloy or the substrate, and during the hot pressing process less than 5% by volume of the diamond crystals are converted into non-diamond-shaped, elemental carbon, and that non-diamond carbon or the surface of the diamond crystals react with the liquid, silicon-rich alloy to form carbide; f) the hot-pressed, essentially isostatic system is kept during the cooling under a pressure which is at least essentially sufficient to maintain the dimensions of the hot-pressed system; and g) removing the resulting composite material from which the polycrystalline diamond body is bonded to the silicon carbide or silicon nitride substrate and the diamond crystals are present in an amount of at least 70 percent by volume of the volume of the polycrystalline diamond body. 9. The method according to claim 8, characterized in that the solid mass of the silicon-rich alloy is used in granular form. 10th 10. One-piece composite material, produced by the method according to claim 1. 11. Composite material according to claim 10, of a polycrystalline diamond body and a silicon carbide or silicon nitride substrate, in which the polycrystalline diamond body is connected to the polycrystalline substrate made of silicon carbide or silicon nitride, the polycrystalline diamond body consists of a mass of diamond crystals, which contain one another by a silicon atom Binders are firmly connected, which binder always comprises silicon carbide and a carbide and / or silicide of a metal component, which forms a silicide with silicon, the present diamond crystals have a size of 1 to 1000 micrometers, the diamond crystal content of the body from 70 percent by volume to below 90 Volume percent of the volume of the diamond crystal body, the proportion of the binder containing silicon atoms is up to 30 volume percent of the body, the binder at least substantially uniform in the body 12. Composite material according to claim 11, characterized in that the binder also contains elemental silicon. 13. Composite material according to claim 11, characterized in that the proportion of diamond crystals is from 70 volume percent to 89 volume percent of the polycrystalline diamond body. 14. Composite material according to claim 11, characterized in that the diamond crystals are graded in size and the grain size is from 1 to 60 micrometers. 15. Composite material according to claim 11, characterized in that the binder contains silicon carbide and metal silicide. 15 20th 25th 30th 35 40 45 50 55 60 65 647 487 16. Composite material according to claim 15, characterized in that the binder additionally contains elemental silicon. 17. Composite material according to claim 15, characterized in that the metal component of the metal silicide is selected from the group consisting of cobalt, chromium, iron, hafnium, manganese, molybdenum, niobium, nickel, palladium, platinum, rhenium, rhodium, rhutenium , Tantalum, thorium, titanium, uranium, vanadium, tungsten, yttrium, zirconium and alloys of these metals. 18. Composite material according to claim 11, characterized in that the binder contains silicon carbide and metal carbide. 19. Composite material according to claim 18, characterized in that the metal component of the metal carbide is selected from the group comprising chromium, hafnium, titanium, zirconium, tantalum, vanadium, tungsten, molybdenum and alloys of these metals. 20. Composite material according to claim 18, characterized in that the binder additionally contains elemental silicon.