DE2845834C2 - - Google Patents

Description

The invention relates to a composite material with diamond crystals and a silicon-containing binder as well as a manufacturing method.

From US-PS 32 39 321 is a composite material on the Base of diamond crystals known by means of a Binder are connected to a homogeneous body. As binders u. a. Titanium-silicon alloys used, in which the silicon content by the factor 10 is less than the titanium content. In the preparation of of this homogeneous composite body are pressures and Temperatures used within or near the diamond stable region in the state diagram of Carbon. So they are complex high pressure devices required with which only bodies are proportionate small dimensions can be produced economically can.

A composite material is known from US Pat. No. 3,982,911, the one substrate body and thus with formation a laminated body made of cubic Has boron nitride crystals. The substrate body exists made of tungsten carbide, titanium carbide and / or tantalum carbide. Alloys of Aluminum with nickel, cobalt or iron or one Alloy of nickel and chrome used. The laminate  is made by hot pressing. Cubic boron nitride has a lower hardness than diamond, so that the known laminate is used there only to a limited extent can be where the greatest possible hardness is important.

The invention has for its object a composite material with diamond crystals and a silicon to contain containing binders characterized by high strength and without use elaborate high-pressure equipment in larger dimensions can be manufactured. Furthermore, a proportionate easy to perform manufacturing process be created.

The object on which the invention is based is achieved through a composite material with diamond crystals and a silicon-containing binder is characterized in that the composite material is a polycrystalline Substrate body and thus with formation a laminate, polycrystalline, in essential pore-free diamond body that the Silicon carbide substrate body with a density of 85 to 100% of the theoretical density of silicon carbide, containing at least 90 wt .-% silicon carbide, or Silicon nitride with a density of 80 to 100% of theoretical Density of silicon nitride containing at least 90% by weight Silicon nitride, the diamond body is made up of diamond crystals contains a size of 1 to 1000 micrometers, which make up 70 to less than 90% by volume of the diamond body and to each other by a uniformly distributed binder are bound up to 30 vol .-% of the diamond body constitutes and silicon carbide and a silicide and / or Contains carbide of a silicide-forming metal, the part of the surface in contact with the diamond surfaces Binder at least largely from silicon carbide  and that the interface between substrate and Diamond body through the binder essentially is filled without pores.

The composite material according to the invention stands out high strength, because the binder used an excellent bond between each Diamond crystals and between the diamond body and conditional on the substrate body.

The invention further relates to a production method, which is characterized in that

• a) in a container serving as a shield or in a recess in an applied pressure undiminished transmission and during a hot pressing process is not sintered powder medium, a Solid mass made of a silicon-rich alloy, that of silicon and one with silicon a silicide forming metal, as well as eutectic structure contains, or solid components to form these silicon-rich alloy and a diamond crystal mass and a polycrystalline silicon carbide or Silicon nitride substrate are introduced, the Diamond crystal mass between and in contact with the Substrate and the solid mass or at least one Solid component of the alloy is arranged
• b) the container and its contents in an acting pressure undiminished transmission and during a hot pressing process arranged non-sintering powder medium and in the case of recessing the contents with the powder medium is covered
• c) over the powder medium on container or recess and content exerted isostatic pressure and thereby the Diamond crystal mass to a diamond content of over  70 vol .-% compressed and a dimensionally stable powder medium enclosed isostatic system is formed,
• d) the isostatic system during a hot pressing process Is subjected to temperature below 1600 ° C at which a liquid silicon-rich impregnating alloy melted and under the applied pressure in the diamond crystal mass washed in and in contact with the substrate is brought as well as less than 5 vol .-% of the diamond crystal mass converted to carbon of another modification be, and the implementation of the hot pressing process takes place in an atmosphere that is not harmful Influence on the diamond crystal mass, the Impregnation alloy and the substrate has
• e) the hot pressed isostatic system for maintenance the dimensions are cooled under pressure, and
• f) the composite material formed is removed.

The method according to the invention can be done without great equipment costs are carried out, because proportionately easily manageable pressures are used.  

The invention is described below with reference to drawings explained in more detail. In the drawings shows

Fig. 1 a section of a state diagram of a silicon-zirconium alloy with the equilibrium diagram for eutectic containing silicon-rich zirconium alloy useful in the invention,

Fig. 2 shows a cross section through an existing container and contents cell that is used to Einschwemmen the silicon-rich alloy in accordance with the invention,

Fig. 3 is a schematic representation of an apparatus for applying a slight pressure to the one shown in Fig. 2 cell, wherein the cell is vibrated to increase the packing density of the diamond crystals,

Fig 4 to provide. A cross section through an apparatus for applying at least substantially isostatic pressure to the cell by means of a pressure-transmitting medium powder to the dimensions of the cell to stabilize and a substantially isostatic system,

Fig. 5 is a cross sectional view through a graphite mold for the simultaneous application of heat and pressure, ie for hot pressing of the substantially isostatic system with the enclosed cell,

Fig. 6 is a side view of a composite material according to the invention made of polycrystalline diamond body and Siliciumkarbid- or silicon nitride substrate, and

Fig. 7 is a photomicrograph (magnification 690fache) of a polished cross-sectional area of a composite material of the invention prepared in accordance with.

According to the invention, a layer structure is formed, in which the diamond crystal mass between a silicon carbide or silicon nitride substrate and a solid mass made of a silicon-rich alloy containing eutectic lies and in contact with the substrate and the alloy stands. When performing the invention The process of building up the layer is a cold pressing process at ambient or room temperature to the Dimensions of the layer structure are essentially uniform to stabilize. The layer structure is then one Subject to hot pressing process, in which the silicon alloy a liquid, silicon-rich alloy is created, which in the bulk of the compressed diamond crystals washed in and in contact with the silicon carbide substrate brought.

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

The mass of diamond crystals, the mass of those in solid Phase present, silicon-rich starting alloy or the solid components to form the silicon-rich alloy and the silicon carbide or silicon nitride substrate can have a number of shapes. For example, each Mass in the form of a layer, the layer the diamond crystals lie between the other layers. The silicon-rich starting alloy can also Shape of a tube or a cylinder with a continuous Have core. The alloy tube is cast in such a way that it sits snugly against the inside wall of the container. The substrate can have the shape of a rod, which in the middle of the Core of the tube made of silicon alloy arranged is, in the annular space between the tube made of silicon alloy and the substrate rod Diamond crystals are packed.  

In the method according to the invention, both natural as well as synthetic, d. H. artificial diamond crystals be used. The diamond crystals have in the direction of their greatest extent a size in the range from about 1 to about 1000 microns, the grain size or the grain sizes largely from the desired Packing density of the diamond crystals and also of the intended use depend on the resulting diamond body. If the Diamond bodies can be used, for example, for grinding purposes diamond crystals that are not larger should be preferred than about 60 microns. To achieve an optimal Packing of diamond crystals in the process according to the invention the crystals should be graded in size and include a range of grain sizes in which small, medium and large crystals are included. In the size graded crystals range from about 1 to about 60 microns, preferably within this size range about 60 to about 80 percent by volume of the total Crystal mass the upper part of the particle size range, about 5 to 10 volume percent of the middle part of the Particle size range and the rest the lower part of the Particle size range belong.

The size of the diamond crystals is determined by Grinding the larger diamond crystals in a jet mill facilitated. The diamond crystals are preferred dry cleaned to possibly oxides or other impurities to remove from the surface before the diamond crystals used in the method according to the invention will. This can be done in that the diamond crystals heated in hydrogen at about 900 ° C for about an hour will.

The used in the inventive method in  solid phase, containing a eutectic, silicon-rich Starting alloy, that is an alloy that also an intermetallic compound consists of silicon and a metal, i.e. an alloy metal, that forms a silicide with the silicon. It's a eutectic containing silicon-rich alloy is preferably made of silicon and a metal from the group that Cobalt (Co), Chromium (Cr), Iron (Fe), Hafnium (Hf), Manganese (Mn), Molybdenum (Mo), Niobium (Nb), Nickel (Ni), Paladium (Pd), Platinum (Pt), Rhenium (Re), Rohdium (Rh), Ruthenium (Ru), Tantalum (Ta), thorium (Th), titanium (Ti), uranium (U), vanadium (V), tungsten (W), yttrium (Y), zircon (Zr), and mixtures includes from this.

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 silicon. The starting alloy usually contains a maximum of about 99.5 atomic percent silicon, the silicon content largely depending on the specific effect that the alloy metal has on the resulting silicon-rich alloy. The solid phase silicon-rich alloy contains a eutectic and can be of hypoeutectic, hypereutectic or of eutectic composition. Referring to Fig. 1 it may be seen for example, that the eutectic 2 is an alloy having a specific composition which solidifies under equilibrium conditions when cooled at constant temperature to give a solid comprising at least two phases and melts completely on heating at the same constant temperature. This constant temperature is referred to as the eutectic temperature, which is also represented by reference number 2 . Eutectic 2 is the composition in which two falling liquidus curves 3 and 4 meet at eutectic 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 process 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 undereutectic, and extends to any alloy whose composition is to the right of eutectic point 2 in the equilibrium diagram and contains something eutectic structure, that is to say is overeutectic.

From Fig. 1 it is apparent that the composition of which is according to the invention used, a eutectic containing, silicon-rich Tränklegierung and their melting temperature to the liquidus curves 3 and 4 and comprises the eutectic point. 2 The area 5 delimited by 1, 2 and 4 comprises a solid phase (Si) and a liquid phase, ie 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 , ie when the amount of silicon in the alloy rises above the eutectic amount. The area 6 delimited by 1, 2 and 3 similarly comprises a solid phase ZrSi₂ and a liquid phase, ie a liquid impregnation alloy, the amount of the solid phase increasing and the amount of the liquid phase decreasing accordingly when the distance from the eutectic point 2 increases to the left along the horizontal 1 , ie when the amount of silicon in the alloy drops below the eutectic amount.

In the method according to the invention, the desired ones Composition of the eutectic containing silicon-rich impregnating alloy and its melting temperature in one point to the one containing the eutectic point Liquidus curves of the phase diagram for the in the invention Process used silicon-rich Alloy. The hot press temperature is the temperature in which the desired composition of the silicon-rich Impregnating alloy is liquid, d. H. in a sufficient flowable state exists to be compressed into the To be able to penetrate diamond mass. If as solid starting material a silicon-rich alloy ver  which has the same composition as that has the desired impregnation alloy, is the hot pressing temperature the temperature at which the alloy is liquid. The hot press temperature is in a range of about 10 ° C to preferably a maximum of about 100 ° C above the melting point the alloy. Depending on the alloy currently used however, hot pressing temperatures can also be used, which are above this preferred maximum. Hot press temperatures However, above 1600 ° C are not suitable because in this case a tendency to excessive graphitization the diamond is made.

However, if the starting alloy is not the same composition like the desired impregnation alloy, however heated to the melting point of the desired impregnating alloy an impregnation alloy is formed as a liquid phase. The Hot press temperature is then a temperature at which the penetrating alloy phase is formed in liquid form becomes what's penetrating at about 10 ° C above the melting point Alloy phase is the case.

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 . For example, if the desired hypereutectic impregnating alloy contains 95 atomic percent Si, the melting point on the liquidus line 4 is about 1400 ° C., as shown by line 7 . If the starting silicon rich alloy had the same composition as the desired penetrating impregnating alloy represented by line 7 , all of the 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, if necessary, reach below 1600 ° C.

However, if the source silicon-rich alloy is any hypereutectic alloy that lies on the horizontal 1 to the right of line 7 in the equilibrium diagram of Figure 1, the hot press temperature is the temperature at which the desired penetrating impregnating alloy of 95 atomic percent Si and 5 atomic percent Zr in liquid is Form, which would be the case at about 1410 ° C.

At the hot press temperature should also be from the base alloy the desired penetrating impregnation alloy be produced in liquid form in an amount sufficient around the cavities of the compressed diamond mass fill out, their crystal density over 70 percent by volume lies, and around the impregnating liquid with the contact surface of the silicon carbide substrate, so that the pores or voids at the interface between the polycrystalline body and the one with the polycrystalline Body in contact with the substrate and the resulting composite material is a non-porous or at least substantially pore-free interface. The liquid impregnating alloy should be at the hot press temperature practically in an amount of at least about 1 percent by volume of the silicon-rich starting alloy.

The hot pressing process is at a temperature at which is the silicon-rich impregnating liquid, below a pressure that only needs to suffice, to between at the hot pressing temperature in the diamond mass intermediate layers present on opposite diamond surfaces to tear open the penetration of the liquid Prevent alloy in the spaces between the diamond mass. This usually requires a minimum pressure of around 3.5 MPa. The hot press pressure can in particular be about 3.5 to about 141 MPa range. The hot press pressure is however usually in the range of about 7 to about 70 MPa.  Hot pressing pressures above 141 MPa bring in the process no noticeable advantages according to the invention.

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. From Fig. 1 it is apparent that the designated with the reference numeral 2 SiZr eutectic alloy containing 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 Impregnation 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 Solid components to form the silicon-rich alloy can be in solid or powder form. The amount of solid, Silicon-rich parent alloy can vary depending on the achievable amount of the liquid, silicon-rich impregnation alloy and fluctuate from the capacity of the device. In general, the amount of the silicon-rich impregnation alloy is in the range of about 25 volume percent to about 80 percent by volume, but to achieve optimal results preferably in the range of about 30 to about 60 volume percent the compressed diamond crystal mass, the Crystal density is over 70 percent by volume.

The hot pressing process is carried out in an atmosphere which have no noticeable harmful influence on the Diamond crystals or the silicon-rich impregnation alloy or has the silicon carbide substrate. The hot pressing process can be under vacuum or in an inert gas such as argon or Helium or carried out in nitrogen or hydrogen will. The hot pressing process is quick enough performed so that no noticeable reaction between the  silicon-rich impregnation alloy and the nitrogen or hydrogen takes place. The hot pressing process cannot Air run because the diamond is at a temperature slightly graphitized in air above 800 ° C and the liquid, Silicon-rich impregnating alloy oxidize and solid Silicon dioxide would form before a significant amount of liquid alloy would have penetrated into the diamond mass.

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

The silicon nitride substrate is a polycrystalline Bodies with a density ranging 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 such a polycrystalline body for most Applications, for example for use as Tool insert does not have the required mechanical strength would have. The higher the density of the silicon nitride body the higher is usually its mechanical Strength.  

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 bowl 11 and serves as a closure.

The cup 11 is made of a material which is essentially inert during hot pressing, ie has no noticeable adverse effect 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.

Inside the bowl closed with the stopper there should be no free space left to mix or allows free movement of the content so that the content at least essentially in the original location the essentially isostatic pressure during the cold pressing process is subjected.

The use of the diamond crystals graded in size has the purpose of achieving 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 P 1 of approximately 0.35 MPa, so that the diamond crystals can rearrange accordingly to fill in the cavities, as a result of which Part of the voids reduced and thus 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 using only a pressure sufficient to achieve a dimensionally stable, substantially 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 less than 98 microns, again particles with a particle size of about 2 to about 20 microns 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 approximately or essentially isostatic pressure is exerted on the cell 10 , as a result of which the cell 10 and its contents are substantially uniformly stabilized, ie compacted, in terms of their dimensions, and an essentially isostatic system of corresponding shape is produced, which contains the cell enclosed by the powder, the density of the compressed diamond crystal layer being over 70 volume percent of the volume of the compressed diamond crystals. The mold 20 with a ring 22 and a press ram 23 and 23 a can consist of tool steel. The ring 22 may optionally be provided with a sintered Kar bidbuchse 22 a inside, as shown in Fig. 4, to allow the application of pressures up to 1400 MPa. Pressures above 1400 MPa bring no noticeable advantage. Within the space delimited by the press ram 23 , the bushing 22 a and the press ram 23 a , a pressure in the range of approximately 140 to 700 MPa and usually up to 350 MPa is preferably exerted on the pressure-transmitting powder medium if the press rams operate in a conventional manner until the applied pressure has stabilized, as is known in conventional powder compaction.

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 the 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 void volume also results in a reduction in the level of non-diamond material ultimately present in the diamond body and results in more closely opposed crystal faces that can be effectively bonded together.

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

After the cold pressing process, one of the two rams 23 or 23 a is withdrawn. The essentially isostatic system 21 , which is now in the form of a solidified molded body, is removed from the bush 22 a and placed in the graphite mold 30 shown in FIG. 5, which has a hole with the same diameter as the bush 22 a . The transferred system 21 is then enclosed by the wall of the hole 31 and the two graphite stamps 32 and 32 a . 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 substantially 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 substantially 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 32 a exert a pressure acting in the axial direction, that is to say the hot-pressing pressure on the system 21 , the temperature is raised to a temperature at which the silicon-rich alloy disc 12 forms a liquid, silicon-rich alloy which is incorporated into the diamond mass penetrates.

When hot pressing, the hot press temperature should be quick can be achieved. The hot press temperature is then below the hot pressure usually for at least one minute maintained in order to adequately soak the Ensure diamond crystal mass. Usually one is Hot pressing time of about 1 to about 5 minutes is sufficient. Because the conversion of diamond to non-diamond, elemental carbon largely by time and temperature dependent and the likelihood of conversion in non-diamond-shaped, elemental carbon, the greater the higher the temperature and the longer the time is this temperature, the hot pressing process must be carried out be in before 5 volume percent of the diamond diamond-shaped elemental carbon are converted. The extent of the conversion can be determined empirically. When converting 5 or more volume percent diamond in non-diamond, elemental carbon can optionally a phase of non-diamond, elementa  Rem carbon remain in the end product. This phase out non-diamond, elemental carbon would have one considerable, adverse influence on the mechanical Properties of the end product.

The hot pressing 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 with an alloy in the liquid state, a pressure is exerted and maintained on the system 21 which is insufficient to break up the slag.

If the liquid, silicon-rich alloy during hot pressing penetrates into the diamond mass and penetrates it and comes into contact with the substrate, envelops the liquid Alloy the surfaces of the compressed diamond crystals, being the liquid alloy with the diamond surfaces or possibly with emerging, not diamond shaped elemental carbon under formation reacted by carbide, which is at least predominantly and usually is essentially silicon carbide. The impregnation alloy also fills during the hot pressing process the interface between the contact surfaces of the polycrystalline Diamond body and the substrate, whereby results in a tight bond in situ. The resulting Product is a one-piece, well bound product Composite material. The impregnating alloy can also be in the sub  penetrate or diffuse into strat.

It is particularly important that essentially isostatic conditions are maintained 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 degree, but rather is forced into the diamond crystal mass 13 becomes.

After the end of the hot pressing process, at least sufficient pressure is maintained during the cooling of the hot pressed system 21 so that the hot pressed cell 10 is subjected to a substantially isostatic pressure sufficient to maintain the dimensional 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 13 a is directly connected in situ to the substrate 14 a . Possibly. Metal adhering to the container or excess squeezed silicon alloy on the outer surfaces of the composite material can be removed in a conventional manner, for example by grinding.

If the components in the inventive method in the form of layers running together the resulting composite can be used a number of shapes, such as the shape of a Disc, square or rectangle, rod or of an ingot and have a flat surface made of bound Own diamonds.

If the silicon-rich alloy takes the form of a tube  or a cylinder with a core therethrough or Has hole and the substrate in the form of a center in the core of the tube arranged rod is present, and the annulus between the silicon alloy tube and the substrate rod packed with diamond crystals has the result Composite material in the form of a circular rod.

The manufactured with the inventive method Composite material has a polycrystalline diamond body on, as if made from one piece by means of an in situ Compound with a polycrystalline substrate connected to a silicon carbide or silicon nitride body is.

The diamond body of the invention Composite material has diamond crystals by a binder containing silicon atoms are firmly connected. The diamond crystals have about 1 to about 1000 microns in size. The concentration the diamond crystals range from at least about 70 to about below 90 percent by volume and often up to about 89 percent by volume of the volume of the polycrystalline diamond body. The diamond body contains up to about 30 percent by volume Binder containing silicon atoms, at least in the essentially uniform in the polycrystalline diamond body is distributed. The one with the surfaces of the diamond crystals there is at least part of the binder in contact predominantly made of silicon carbide, d. H. more than 50 percent by volume, preferably at least about 85 to 100 percent by volume of the in direct contact with the surfaces of the diamond crystals  Standing part of the binder is silicon carbide. The Diamond body of the composite material according to the invention non-porous or at least essentially non-porous.

At the interface between the polycrystalline diamond body and the silicon carbide or silicon nitride substrate the binder extends from the polycrystalline diamond body down to the substrate, the at the interface existing pores are filled so that the interface is pore-free or at least essentially is pore-free, that is, the interface voids or pores in an amount less than 1 volume percent of the total Provided the volume of the interface under the condition can that the pores or voids are small and are less than 0.5 micrometers and sufficiently uniform are distributed in the interface so that the pores do not noticeably adverse influence on liability in  the interface. The proportion of pores in the interface is achieved through conventional metallographic measures determined by, for example, a cross section of the composite material is examined optically. The distribution and the The thickness of the binder at the interface essentially corresponds the distribution and thickness of the binder in the polycrystalline diamond body of the composite material. If one from a polished cross section of the composite material would average the thickness of the binder at the interface essentially the average Thickness of the binder between those in contact standing diamond crystals of the polycrystalline diamond body of the composite material. The maximum thickness of the binder at the interface is about 50 percent of the largest Dimension of diamond crystals in polycrystalline Diamond body if you look at the diamond crystals along their longest dimension. The silicon carbide substrate can also contain binders in the form of the impregnation alloy is present, which during the hot pressing process in the substrate has penetrated and diffused into it.

The binder containing silicon atoms always contains Silicon carbide. It also contains Binder too  Metal silicide, metal carbide and / or elemental silicon. For the metal components of metal silicide and metal carbide it is in the binder the alloy metal or metals that are in the impregnation alloy are available.

The metal component of the metal silicide in the binder 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.

For the metal component of the one present in the binder Metal carbide is a strong carbide former, which gives a stable carbide, and preferably by one Metal from the group consisting of chrome, hafnium, titanium, zirconium, Tantalum, vanadium, tungsten, molybdenum and alloys of these Metals includes.  

The binder in the diamond body contains general silicon carbide in an amount of about 1 to about 25 volume percent based on the volume of the polycrystalline Diamond body and metal silicide in an at least detectable amount and often one minimal amount of about 0.1 volume percent of the polycrystalline Diamond body. The metal silicides are hard and have often lower, linear coefficients of thermal expansion than the metals or in some cases as a diamond, such as rhenium silicide, such property for a phase in a diamond body.  

The diamond body contains no non-diamond, elementary carbon phase in an amount by X-ray diffraction analysis is detectable.

A particular advantage of the invention is that the polycrystalline diamond body of the composite material in a variety of sizes and shapes can be made. The diamond body can be, for example, a width or length  of up to 25 mm or more. Polycrystalline Diamond bodies that are longer than 25 mm and a diamond density according to the invention can practically not are manufactured using processes in which ultra-high Pressures and temperatures of the diamond stable area in the State diagram of carbon are used because which are necessary to achieve and maintain such high pressure and temperature conditions necessary equipment require complex construction and therefore only have a limited capacity. On the other hand, the polycrystalline diamond body so small or be thin as desired. The diamond body, however always have a thickness that is greater than a single diamond crystal layer is.

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

The invention will now be described in more detail by means of examples explained in the following way, unless otherwise the following was specified:

Silicon carbide substrate

A powder made of hexagonal was used as the pressure-transmitting medium Boron nitride with a fine particle size of about 2 to about 20 microns are used.

The polycrystalline silicon carbide substrate had the Form a disc with a thickness of approximately 3.05 mm.

It was worked with a device that spoke essentially of the device shown in FIGS. 4 and 5 ent.

The filling material used in the device according to FIG. 4 was cold pressed at room temperature up to a pressure of 560 MPa.

The amount of impregnation alloy available was enough to fully compress the diamond mass to soak and the contact surface of the substrate to wet and fill the pores of the interface.

The density of the substrate polycrystalline silicon carbide body is in percent the theoretical density of silicon carbide of 3.21 g / cm³ specified.

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

One specified in volume percent of the diamond body Diamond density was determined using the standardized point counting technique determine, using a micrograph of a polished Area in 690x magnification was used and  the surface area analyzed had a size that was sufficient to re-examine the microstructure of the entire body present.

The information about diamond density, which is in the range of over 70 percent by volume, but less than 90 percent by volume lie on the volume of the polycrystalline diamond body, are based on experience and results with similar experiments and particularly in experiments in which the polycrystalline Diamond body was made alone. The details about the appearance of the whole polycrystalline Body and also the details of the volume of the formed, cleaned polycrystalline diamond body of the composite material compared to the volume of the originally used Diamond powder is based on the assumption that less as 5 volume percent of the diamond powder in non-diamond-shaped, elemental 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 560 MPa, applying essentially isostatic pressure to the contents of the well. The pressing pressure was maintained until the pressure had stabilized with the formation of a dimensionally stable molded body, ie an essentially isostatic system of the container enclosed with powder. From previous experiments it was known that the density of the diamond crystals in the compressed arrangement, that is to say in the essentially isostatic system 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 assembly 21 of the powder enclosed and stoppered cup 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 1330 Pa and then filling with nitrogen. A pressure of about 35 MPa was then applied and maintained on the located in the graphite mold assembly 21st The graphite mold with the assembly 21 was then heated to the specified maximum hot pressing temperature by the induction furnace in about 5 to 7 minutes. When the assembly was heated, the pressure rose due to the thermal expansion of the system to the maximum hot pressing pressure given in Table I.

At the specified temperature at which the penetration begins or progresses, the pressure drops to about 35 MPa. This drop in pressure indicates this indicates that the alloy had become liquid and started had to penetrate the compressed diamond mass. The pressure was then returned to the specified maximum Hot press pressure increased and for one minute at the specified maximum hot pressing temperature at this maximum Hot press pressure held to complete penetration the alloy into the small capillaries of the compressed Ensure diamond mass. The heater was on then turned off, but no additional pressure applied. This created a high pressure at a high temperature, but for a reduced pressure at low temperature, so that adequate geometric stability was achieved and the hot-pressed arrangement its dimensions maintained until it is sufficient for handling Temperature had cooled.

The composite material was ultimately obtained that the enveloping metal, i.e. H. the molybdenum bowl and the Zirconium bushing and the excess alloy on the External surfaces of the composite material by grinding and Sandblasting has been removed.

The resulting one-piece, cleaned composite body had the shape of a substantially uniform Disc, which in Examples 1 to 3 has a thickness of approximately 5 mm and in Example 4 a thickness of approximately 4 mm.  

In Table I, the hot press 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 to ensure that the smaller capillaries of the compressed diamond crystal mass were completely filled.

The invention will now be explained in more detail with reference to Table I. With no single composite pane according to Examples 1 to 5 the interface between the polycrystalline Diamond body and the silicon carbide substrate be determined. Every composite body had its own Thickness of a continuous structure and the diamond part differed by the grain size of the substrate. The outside surface of each polycrystalline diamond body was from Binder well soaked. The binder was uniform distributed. The individual diamond bodies were good with each other connected.

The polycrystalline diamond bodies of the composite materials according to Examples 1 to 4 had a diamond density that over 70 volume percent, but less than 90 volume percent of Volume of the polycrystalline body was.

The diamond area of the composite body according to Example 5 was polished on a cast iron block. An investigation the polished surface showed no broken diamond particles holes to be returned. This indicates indicates that there is a very strong bond. The The density of the diamond crystals was about 73 percent by volume based on the volume of the polycrystalline diamond body.  

Example 6

The composite material produced according to Example 1 was used as a cutting tool. The free area of the polycrystalline Diamond body of the composite material was with a diamond grinding wheel, ground smooth and with one 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 sandstone with a feed of 0.13 mm per revolution and a cutting depth of Was turned 0.5 mm.

With a cutting speed measured on the surface of about 30 m per minute, the wear was 1.26 × 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 × 10 ^-6 cm³ per minute. Another part of the cutting edge was examined at a cutting speed of 88.4 m per minute measured on the surface. The wear in this case was 24 cm³ × 10 ^-6 per minute.

The composite body was removed from the tool holder. An investigation of the interface between the diamond body and the substrate showed that these machining trials had no influence on the interface.

Example 7

It was used in the same manner as in Example 6 proceeded with the exception that the composite body according to Example 2 was used.

Part of the cutting edge had a wear rate of 3.32 × 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 wear rate of 24.3 × 10 ^-6 cm³ per minute at a cutting speed of 97.5 m per minute measured on the surface.

An examination of the composite body after the mechanical Machining showed that these machining attempts failed Influence on the interface between the polycrystalline Diamond body and the silicon carbide substrate.

Example 8

The procedure was as in Example 6, with the exception that  that the composite material according to Example 3 was used.

Part of a cutting edge had a wear rate of 3.8 × 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 wear rate of 30.3 × 10 ^-6 cm³ per minute at a cutting speed measured on the surface of 97.5 m per minute.

An examination of the composite material after the machining showed that these machining attempts does not affect the interface between the polycrystalline diamond body and the silicon carbide substrate had.

Example 9

The procedure was as in Example 6, with the exception that that the composite material according to Example 4 was used.

After 4 minutes of successful cutting with one cutting speed of 30 m measured on the surface small pieces broke out of the cutting edge every minute. Another part of the cutting edge broke after 6 minutes successful cutting with one on the surface measured cutting speed of 85 m per minute small Pieces from the cutting edge. It is believed that breaking out of the cutting edge at hot press temperatures that were not high enough to support the liquid, silicon-rich alloy in the small capillaries the polycrystalline diamond mass during the hot pressing process wash in.  

Example 10

In the manufacture of the composite material was essentially proceeded as in Example 2 with the exception that 260 mg of the silicon chrome alloy were used and the Alloy was 1.3 mm thick.

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

The maximum hot press pressure was about 91 MPa and the hot press temperature ranged from about 1250 ° C at the beginning penetration of the liquid, silicon-rich alloy into the pressed diamond crystal mass up to one maximum hot pressing temperature of about 1500 ° C. The composite material was in the same manner as in Example 2 won. The composite material was essentially in the form of a uniform disc with a thickness of about 1.5 mm.

The silicon carbide substrate was ground away from the composite material and the polycrystalline diamond body became one subjected to thermal stability testing. The substrate was heated in air to a temperature of 900 ° C, which was the limit temperature of the furnace. While heating was the linear coefficient of thermal expansion for the Temperatures from 100 ° C to 900 ° C determined. Was at 900 ° C the oven turned off.

The experimental data and the examination of the sample, i. H.  of the polycrystalline diamond body after the experiment showed that there is no sudden change in length in the sample during of the entire heating process. There was no sign of a permanent one, caused by the heating process Damage to the sample.

Example 11

It was essentially the same as in Example 2 with the exception proceeded that a silicon wafer in one Zirconium bowl with a zirconium lining was used to a silicon-rich zirconium alloy in situ form.

6 composite materials were produced. For the production a diamond powder was used from 3 composite materials, at which 60% by weight a grain size of 53 to 62 microns, 30% by weight, a grain size of 8 to 22 microns and 10% by weight of a grain size of 1 to about 5 microns had. The three other composite materials were made using a diamond powder that has a Grain size from 1 to 60 microns, with at least 40 wt.% had a grain size below 10 micrometers.

The maximum hot press pressure was about 91 MPa and the hot pressing temperature ranged from about 1340 ° C up to a maximum hot pressing temperature of about 1500 ° C. The at the lower end of the specified temperature range Temperature of about 1340 ° C is the temperature at which the watering process begins and it becomes clear that the silicon-rich zirconium alloy was formed in situ and has become fluid.

Each composite material was essentially in the obtained in the same way as in Example 2. Every association  material was in the form of a disc.

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

The 3 composite materials made from the diamond powder 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 incomplete were soaked with the alloy. The rest of the sanded However, the diamond area was well bound.

An optical examination of the composite materials left no detectable errors or contrasted, different intermediate layers between the silicon carbide substrate and recognize the diamond layer. Four composite materials were broken to look at the inner fabric. During the optical examination of the fracture surfaces no visible intermediate layers or defects on the Interface between the silicon carbide substrate and the polycrystalline Diamond layer found.

The continuity of the structure at the interface between The substrate and diamond layer was excellent and only that different grain size of diamonds and silicon carbide left the interface between the substrate and the Determine the diamond layer.  

Two of the composite materials were used as cutting tools tested on a lathe with which a rod-shaped, sand-smoothed with a strong grinding effect Grindstone was turned off. It was made with a depth of cut of 0.76 mm, a feed of 0.13 mm per revolution and a cutting speed measured on the surface worked at 183 m per minute. After a cutting time of The front cutting edge showed 16 minutes and 22 seconds of the two tools a uniform abrasion of about 0.13 mm. This shows that the cutting edge is excellent Had abrasion resistance.

Example 12

The composite material produced according to Example 1 was with a hammer and a wedge essentially in two Halves broken apart. The fracture areas were under a microscope with a 100x magnification optically examined. Examination of the fracture areas revealed that both the polycrystalline diamond body and the Interface of the composite material was pore-free, the binder evenly distributed in the diamond body and the break was transgranular and not intergranular, i.e. H. that the Break across the crystals and not along the crystal faces went. This indicates that through the Binder caused binding very well and as firm as is the diamond crystals themselves. They weren't visible either Interlayers or defects at the interface between the silicon carbide substrate and the attached polycrystalline Determine the diamond layer. The fracture surface of the composite material had a continuous structure and only the different ones Grain size between the diamond and the solid adhering substrate left the boundary between the substrate and recognize the attached polycrystalline diamond body.  

Silicon nitride substrate

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

The polycrystalline silicon nitride substrate was in the form a disc which in Examples 13 and 14 has a thickness of about 3.18 mm and a thickness in Examples 15 and 16 of about 2.5 mm. The polycrystalline silicon nitride substrate was a commercially available hot pressed material, that has a density of over 99%, d. H. almost a density of 100%. The material contained, based on the weight of the hot pressed silicon nitride body, ½% MgO, about ½% Fe, about ½₀₀% metallic impurities, such as Ca, Al and Cr, 2% free Si, 1% SiC and silicon nitride as the rest.

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 560 MPa. The density of the diamond crystals in the compressed assembly was over 75 percent by volume of the compressed diamond mass.

The amount of the impregnating alloy was sufficient, the one pressed together Soak the diamond mass completely and the To touch the substrate and the pores of the substrate To fill in the interface.

The density of the substrate polycrystalline silicon nitride body is in percent the theoretical density of silicon nitride from 3.18 g / cm³.

The composite material or the polycrystalline diamond body were made with the help of a hammer and a wedge broken each other.

The optical examination of the break points was under a microscope at about 100x magnification.

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

Example 13

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

A cast silicon wafer weighing 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 micrometers and 15% by weight of diamond particles with a grain size of about 5 micrometers. Instead of the metal lid used in Example 1, a plug 14 made of hot-pressed, polycrystalline silicon nitride, shown in FIG. 2, was used.

The sealed cup was then packaged in a powder 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, the sealed well and its contents being subjected to a substantially isostatic pressure. The pressing pressure was maintained until the pressure had stabilized with the formation of a dimensionally stable shaped body, ie an essentially isostatic system of the bowl enclosed with powder. The density of the diamond crystals was over 75 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.

The resulting composite material was obtained that the clad metal and excess silicon to the External surfaces of the composite material by grinding and sandblasting was removed.

Example 13 is summarized in Table II. In Examples 14-16 listed in Table II, too, a casting 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 on the bottom of the indicated cup within the sleeve-like lining. 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 plug closing the cup, which is identified in FIG. 2 by reference numeral 14 . The sealed well 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 material was obtained in substantially the same manner as in Example 15.

The resulting, cleaned, one-piece composite material Examples 14-16 were essentially in the form of uniform disc, which in Example 14 a thickness of about 4.7 mm and in Examples 15 and 16 had a thickness of about 3.8 mm.  

The hot pressing temperature given in Table II, at which the soaking process starts is the temperature in which the alloy is liquid and in the compressed diamond mass begins to penetrate. The specified, maximum hot pressing temperature and the specified, maximum hot pressures were simultaneously for one minute maintained to complete the smaller Capillaries of the compressed diamond crystal mass to guarantee.  

Table II

Examples 13-16 show the preparation of the composite material according to the invention. After an optical Investigation revealed that every composite material of these examples had a continuous structure, but the Interface between the diamond body and the substrate due to the different grain size and due to Color differences between the diamond body and the substrate could be determined. The silicon nitride substrate was darker than the gray diamond body. The outer surface of a every polycrystalline dimant body was well soaked, the binder was evenly distributed. The diamonds were well connected.

The polycrystalline diamond body of the composite material Example 14 had a diamond density that over 70 volume percent, but less than 90 volume percent of Volume of the polycrystalline body was.

The diamond area of the composite material according to Example 13 has been polished. When examining the polished It turned out that the polished surface was none holes due to broken diamond particles had, which indicated that there was a firm bond. The density of the diamond crystals was about 71 percent by volume of the polycrystalline diamond body.  

Example 17

The composite material according to Example 14 was used as a cutting tool used. The free area of the polycrystalline Diamond body of the composite material was made with a diamond grinding wheel honed to the free area of the diamond body smooth and with a sharp cutting edge Mistake. The substrate of the composite material was then in clamped in a tool holder.

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

With a cutting speed measured on the surface of about 28.5 m per minute, the abrasion was 3.6 × 10 ^-6 cm³ per minute. Another part of the cutting edge was examined at a cutting speed measured on the surface of 79.3 m per minute. The wear in this case was 8.2 × 10 ^-6 cm³ per minute.

The composite material was removed from the tool holder, whereupon the interface between the diamond body and the  Substrate was examined. It turned out that the Edits made have no influence on the composite material had.

Example 18

It was used in the same manner as in Example 17 proceeded with the exception that that prepared according to Example 15 Composite material was used.

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

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

Example 19

The composite material produced according to Example 16 was essentially broken apart in half. The fracture areas were examined optically. When examining the Fractures turned out to be both polycrystalline Diamond body as well as the interface of the composite material were pore-free, the binder evenly in the diamond body distributed and the fraction transgranular and not intergranular was, d. H. that the break across the crystals  and did not run along the crystal boundaries. This indicates indicates that the one caused by the binder Binding very good and just as firm as the diamond crystals itself is. There were no visible intermediate layers either or failure at the interface between the silicon nitride substrate and the polycrystalline diamond layer will. The fracture surface of the composite material had a continuous structure. Only the different ones Grain size between the diamond and the firmly adhering The substrate as well as the darker color of the substrate left the Border between the substrate and the polycrystalline diamond body detect.

The fracture surfaces of the composite material have been polished. Upon optical inspection of the polished fracture surface shown in Fig. 7, 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. Fig. 7 shows in its upper part the polycrystalline diamond body and in its lower part the substrate. 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 20

The composite materials produced according to Examples 13, 14 and 15 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 the composite material was pore-free,  the binder is evenly distributed in the diamond body and the fracture was transgranular and not intergranular, i.e. H. that the break across the crystals and not along the Crystal borders ran. This indicates that the binding caused by the binder is very good and likewise as solid as the diamond crystals themselves. It could too no visible intermediate layers or defects at the interface between the silicon nitride substrate and the adherent, polycrystalline diamond layer can be found. The Fracture area of each composite material was continuous Structure. Only the different grain size between the diamond and the firmly adhering substrate, as well the darker color of the substrate left the line between recognize the substrate and the polycrystalline diamond body.

The fracture surface of the composite material according to example 15 has been polished. When examining the polished fracture surface it turned out that the polished surface was not broken out Holes to be returned from diamond particles, which indicates that there is a tight bond. A 690x micrograph of the polished surface Magnification showed an intermediate layer of the binder at the interface. When evaluating an electronic Micrograph of the polished surface with a 1000x magnification an intermediate layer was formed at the interface Binder found a maximum thickness of about 3 microns.

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

Claims (10)

1. Composite material with diamond crystals and a binder containing silicon, characterized in that
that the composite material has a polycrystalline substrate body and a polycrystalline, substantially pore-free diamond body connected to form a laminated body,
that the substrate body made of silicon carbide has a density of 85 to 100% of the theoretical density of silicon carbide containing at least 90% by weight of silicon carbide, or of silicon nitride has a density of 80 to 100% of the theoretical density of silicon nitride containing at least 90% by weight Silicon nitride,
that the diamond body contains diamond crystals of a size of 1 to 1000 micrometers, which make up 70 to less than 90% by volume of the diamond body and are bonded to one another by a uniformly distributed binder which makes up to 30% by volume of the diamond body and silicon carbide and a Contains silicide and / or carbide of a silicide-forming metal, the part of the binder which is in contact with the diamond surfaces at least largely consisting of silicon carbide, and
that the interface between the substrate and the diamond body is filled essentially without pores by the binder. 2. Composite material according to claim 1, characterized in that the binder also contains elemental silicon.   3. Composite material according to claim 1 or 2, characterized in that the diamond crystals 70 to 89 vol .-% of the diamond body. 4. Composite material according to one of claims 1 to 3, characterized in that the diamond crystals of different size in the area from 1 to 60 microns. 5. Composite material according to one of claims 1 to 4, characterized in that the metal component of the metal silicide cobalt, chromium, Iron, hafnium, manganese, molybdenum, niobium, nickel, palladium, Platinum, rhenium, rhodium, ruthenium, tantalum, thorium, Titanium, uranium, vanadium, tungsten, yttrium and / or zirconium and the metal component of the metal carbide is chromium, Hafnium, titanium, zirconium, tantalum, vanadium, tungsten and / or is molybdenum. 6. A method for producing composite material according to claim 1, characterized in that

• a) a solid mass made of a silicon-rich alloy consisting of silicon and a metal forming silicon with silicon, is pressed into a container serving as a shield or into a recess which is uninterruptedly transmitted into a pressure medium which transmits an active pressure and does not sinter during a hot pressing process, and contains eutectic structure, or solid components for forming this silicon-rich alloy and a diamond crystal mass and a polycrystalline silicon carbide or silicon nitride substrate are introduced, the diamond crystal mass being arranged between and in contact with the substrate and the solid mass or at least one solid component of the alloy,
• b) the container and its contents are arranged in a powder medium which transmits the pressure unabated and does not sinter during a hot-pressing process and, in the case of a recess, the contents are covered with the powder medium,
• c) isostatic pressure is exerted on the container or recess and contents of the powder medium, thereby compacting the diamond crystal mass to a diamond content of more than 70% by volume and forming a stable isostatic system enclosed by the powder medium,
• d) the isostatic system is subjected to a hot pressing process at a temperature of below 1600 ° C., in which a liquid silicon-rich impregnating alloy is melted and, under the pressure acting on it, washed into the diamond crystal mass and brought into contact with the substrate, and less than 5% by volume the diamond crystal mass is converted into carbon of another modification, and the hot pressing process is carried out in an atmosphere which has no detrimental effect on the diamond crystal mass, the impregnating alloy and the substrate,
• e) the hot pressed isostatic system to maintain the dimensions cooled under pressure and
• f) the composite material formed is removed.

7. The method according to claim 6, characterized in that Diamond crystals of different sizes in the range of 1 to 60 microns can be used. 8. The method according to claim 6 or 7, characterized in that the impregnating alloy in a volume equal to the volume of the compressed diamond crystal mass related amount of 25 to 80% is applied.   9. The method according to any one of claims 6 to 8, characterized in that the diamond crystal mass is compressed to a volume, in which the diamond crystals make up 71 to less than 95% by volume. 10. The method according to any one of claims 6 to 9, characterized in that the solid mass of the silicon-rich alloy in the form of grains is used.