SE454983B - HARD MATERIAL BODY OF CUBIC BORN NITRID - Google Patents

Description

454 983 2 - patent 7208677-0. Combinations of crystals of cubic boron nitride, carbide powder and diamond crystals were used with good results for the production of useful compacts. Composite bodies in which a layer of crystals of cubic boron nitride has been bonded to the surface of a cemented carbide sheet have been prepared, the layer of cubic boron nitride being found to be substantially free of voids.

The invention is further elucidated in the following with reference to the accompanying drawings.

Figure 1 shows an example of a device intended for high pressure and high temperature, which is suitable for carrying out the invention.

Figure 2 shows a section through a form of a charge unit intended for use in the device according to Figure 1 in the manufacture of composite cutting plates.

Figure 3 is a three-dimensional view showing a composite cutting insert of cubic boron nitride for machining.

Figure 4 is a section through the cutting plate according to Figure 3 along the line XX or the line YY.

Figure 5 and Figure 6 are three-dimensional views of composite cutting plates of cubic boron nitride / cemented carbide.

Figure 7 is a section showing a combination of liner and loading unit for making articles according to Figures 3, 5 and 6.

Figure 8 shows a section through another embodiment of a charging unit for use in the device according to Figure 1.

Figure 9 is another three-dimensional view showing a composite cutting plate containing cubic boron nitride. 454 983 3 Figure 10 is a further section along the line XX or the line YY through the cutting plate according to figure 9.

Figure 11 is a section showing a combination of liner and loading unit for making the articles of Figures 9, 5 and 6.

A preferred embodiment of a high pressure and high temperature device in which hard material bodies according to the invention can be produced is described in U.S. Pat. No. 2,941,248 (which is intended to form part of the present specification) and is shown sketched in FIG. 1.

Reaction vessel designs useful in the practice of the invention are described in U.S. Pat. No. 3,609,818, which is intended to be part of the present disclosure.

The device 10 comprises a pair of carbide plungers 11 and 11 'and an intermediate belt or die part 12 of the same kind of material. The matrix part 12 is provided with an opening 13, in which a reaction vessel 14 is arranged. Between the pressure piston 11 and the matrix 12 and between the pressure piston 11 'and the matrix 12 there is a packing insulation unit 15, 15', which in each case comprises a pair heat-insulating and electrically insulating pyrophyllite parts 16 and 17 and an intermediate metal gasket 18.

According to a preferred embodiment, the reaction vessel 14 contains a hollow salt cylinder 19. The cylinder 19 may be made of another material, for example talc, which a) is not converted under the influence of high pressure and high temperature in the process to a stronger, stiffer state (e.g. by phase transformations and / or compression) and b) is essentially free of volume discontinuities under the influence of high temperature and high pressure of, for example, the kind found in pyrophyllite and porous alumina. Materials that meet the requirements of U.S. Pat. No. 3,030,662 (column 1, line 59 - column 2, line 2, which is intended to be part of the present specification) are useful in the manufacture of cylinders. 19.

Concentrically in and next to the cylinder 19 is arranged an electric resistance heating tube 20 of graphite. In the graphite heating tube 20 there is in turn concentrically arranged the cylindrical salt liner 21. The ends of the liner 21 are provided with salt plugs 22, 22 ', arranged at the upper resp. lower end. As described below, the liner 21 may have a cylindrical hollow core for receiving a large loading unit containing subunits or the liner may consist of a series of mold units arranged in a stack for producing a plurality of hard material bodies, for example as shown in Figures 3, 5 and 6.

Electrically conductive metal end plates 23 and 23 'are used at each end of the cylinder 19 to provide electrical connection to the graphite heating tube 20. Adjacent each plate 23, 23' is an end cap assembly 24 and 24 ', each of which includes a pyrophyllite plug or plate 25. surrounded by an electrically conductive ring 26.

Working methods for the simultaneous effect of both high pressure and high temperature in this device are well known to those skilled in the art.

The foregoing description relates only to a type of high pressure and high temperature device. Various other types of devices can be used to provide the required pressure and temperature according to the invention.

Figure 2 shows an arrangement for producing a plurality of sheet or tablet-shaped composite bodies (cemented carbide substrate with a layer of sintered cubic boron nitride formed on the substrate) using aluminum alloy as a binder. The charge unit 30 (which is not shown on the same scale) fits into the space 31 of the device in figure 1.

The charging unit 30 consists of a cylindrical sleeve 32 of casing metal, which may be zirconium, titanium, tantalum, tungsten or molybdenum. In the cylindrical sleeve 32 of casing metal there are arranged a number of subunits, which are separated by plugs 33 of the same kind of material as the cylinder 19, for example hexagonal boron nitride or NaCl, which remains substantially unchanged during the execution of the process and facilitates the separation of the subunits after the process. . Each subassembly is enclosed in a cup-shaped portion 34 with end cap plates 34a made of any of the materials that can be used for the sleeve 32, preferably zirconium or titanium. In each subunit, a mass 36 of finely divided (less than about 30 μm) crystals of cubic boron nitride is arranged between a mass 37 and a pair of metal plates, a plate 38 of aluminum and a plate 39 of alloy metal, which may be nickel, cobalt, manganese, iron, vanadium and chromium.

The relative positions of the discs 38 and 39 are not critical, provided that aluminum formation occurs. The mass 37 may be cemented carbide (sintered carbide) or sinterable carbide powder, the sintering taking place during the consolidation of the cubic boron nitride. The amount of aluminum used in relation to the amount of alloy metal is not critical and can vary from about equal parts by weight to about 1 part of aluminum per 10 parts of alloy metal.

In the production of cutting plates with this embodiment, the charge unit 30 is arranged in the device 10, pressure is applied and the system is subsequently heated. The temperature used is in the range of about 1300-1600 ° C for a period exceeding about 3 minutes, the system being simultaneously subjected to very high pressure, for example of the order of 55 kilobars, to ensure that conditions are maintained in which the cubic boron nitride in the system is thermodynamically stable.

At 1300 ° C the minimum pressure should be about 40 kilobars and at 1300 ° C the minimum pressure should be about 50 kilobars. At the temperatures used, the sintering agent is melted in the mass 37, so that cobalt, nickel or iron (depending on the particular carbide composition) is made available for migration from the mass 37 into the mass 36, in which the metal is alloyed with the molten aluminum alloy. formed by disks 38 and 39 and by reaction in the cubic boron nitride. The metal material thus formed acts as an effective binder for the crystals of cubic boron nitride near the interface between the masses 37 and 36 for bonding these crystals to each other and to the cemented carbide. The rest of the crystals in the mass of cubic boron nitride are bonded together by the metal material formed by alloying the discs 38 and 39 and by reacting this alloy with the cubic boron nitride.

The amount of aluminum in the starting material may vary from about 1% to about 40% by weight of the amount of cubic boron nitride and the amount of alloying metal (nickel, cobalt, manganese, iron, vanadium and chromium) may vary from about 2% to about 100% by weight of the amount of cubic boron nitride. The amount of these alloying metals remaining in the consolidated cubic boron nitride as a matrix material varies depending on the pressure and the period of time during which high pressure and high temperature are caused to act. In many cases, the amount of aluminum plus alloy metal atoms in the compressed cubic boron nitride is more than about 1% by weight of the amount of cubic boron nitride.

Preformed aluminum alloys can of course be used instead of separate sheets for in situ alloying.

After completion of the process carried out at high temperature and high pressure, first the temperature is lowered and then the pressure. After recovering the masses useful as cutting plates, the protective casing metal is strongly bonded to their outer surfaces. Exposure of the desired surfaces of the composite cutting plates is most easily accomplished by grinding off the protective casing metal.

Using aluminum alloy as a binder, as described above, a variety of cubic boron nitride bodies have been successfully prepared using cubic boron nitride crystals having a size of 1-10 microns.

These compacts have significantly superior abrasion properties compared to cemented carbide bodies. Cubic compacts 454 985 7 _. boron nitride (which is not bonded to cemented carbide substrates) has also been made from cubic boron nitride crystals within this size range using subunits in which no mass 37 was used.

In many of the examples given below, which relate to this embodiment, a small excess of aluminum alloy is formed, which remains after the infiltration between the crystals of cubic boron nitride is completed. This small excess can be alloyed with the beaker 34.

After lowering the temperature and pressure, the bodies are removed and can then be ground to shape for use in cutting tools.

When examining a polished surface of such a body under a microscope, one can observe a plurality of fine cubic boron nitride particles which are tightly connected to each other with the small gaps between the crystals filled with a second phase which appears to be metallic. Thus, scratches were observed on the polished surface as opposed to strings of holes from fragments of cubic boron nitride picked out as had been observed on polished surfaces of compacts made using other active metals as binders.

Penetration between and bonding of the cubic boron nitride crystals through the binder is very good in cubic boron nitride compactors made according to the invention. Characteristic X-ray diffraction diagrams are obtained for each special alloy system (aluminum plus any of the specified alloy metals). These diffraction diagrams have shown the presence of cubic boron nitride, AlN and additional unidentifiable phases. Electron beam microprobe testing of composite and cubic boron nitride compacts made with aluminum and nickel as the source of the binder shows that both Al and Ni are present in the gaps.

The comminuted crystals of cubic boron nitride are preferably produced by jet milling of larger grains 8 of cubic boron nitride. Prior to the introduction of these into the reaction vessel, the fine crystals of cubic boron nitride (900 ° C, 1 hour) in ammonia are suitably heated for further cleaning of the surface of the crystals.

Some composite bodies of cubic boron nitride and cemented carbide prepared as described have been formed into tools (square surface, approx. 6.1 mm edge length) and used for cutting "Inconel 718", which is a nickel-based heat-resistant alloy. A typical Ni-Al bonded tool would have had a surface layer of bonded cubic boron nitride with a thickness ranging from 0.76 to 0.25 mm heavily bonded to a cemented carbide backing block (e.g. grade 883 Carboloy cemented carbide) having a thickness of about 3 .05 mm. The wear of such tools was generally significantly less than the wear obtained when using grade 883 Carboloy tools under the same conditions.

A number of composite bodies made according to this embodiment were subjected to abrasion testing, in which a bar with a thickness of 3.15 mm of "René 41" (a nickel-based heat-resistant alloy), which rotated at a speed of 200 rpm, was pressed against the layer of cubic boron nitride. on the tested composite body with a force of 36 kp for 3 minutes. The depth of the abrasion groove on the compact was then measured. In each of the examples given below, the arrangement used was essentially the same as for a subunit shown in Figure 2. The protective cup (or sleeve) used in each case had a diameter of 6.4 mm. Unless otherwise indicated in the examples, the entire amount of cubic boron nitride was jet ground (largest grain dimension 1-10 μm). The cubic boron nitride used in Examples 2 and 6 had been heat treated in NH 3 before loading. In each example, a sintered cemented carbide sheet (grade 883 Carboloy cemented carbide) was used as the backing block in the compact.

Example 1 A beaker of zirconium was filled with a pre-sintered cemented carbide disc (thickness 1.27 mm), grains of cubic boron nitride (0.050 g), Al-disc (0.010 g) and Co-disc (0.034 g) . The unit was simultaneously subjected to the influence of a pressure of S4 kb and a temperature of 1550 ° C for a period of 61 minutes. The bonding of the cubic boron nitride to the cemented carbide and the bonding of the grains of cubic boron nitride to the metal matrix were good. The consolidated part of cubic boron nitride could be polished well. Abrasion testing gave a groove depth of 0.034 mm.

Example 2 A Mo sleeve (thickness 0.051 mm) with Mo end plates (thickness 0.051 mm) was loaded with a sintered carbide plate (thickness 1.27 mm), grains of cubic boron nitride (0.065 g), Al plate (0.010 g ) and a layer of a mixture of powder of Co (0.015 g) and Al (0.004 g). The unit was simultaneously subjected to a pressure of 56 kb and a temperature of 1500 ° C for 63 minutes. Good bonding of the cubic boron nitride to the cemented carbide and to the metal matrix was obtained. The cubic boron nitride in the metal matrix showed a densely packed microstructure. Abrasion testing gave an abrasion groove depth of 0.025 mm.

Example 3 A beaker of Zr was charged with a sintered cemented carbide plug (thickness 1.27 mm), grains of cubic boron nitride (0.060 g) and a mixture of coarse powder of Al (0.010 g) and Mn (0.040 g).

The unit was simultaneously subjected to a pressure of 55 kb and a temperature of 150 ° C for 60 minutes. The binding of the cubic boron nitride to the cemented carbide and to the metal matrix was good. The compact part of cubic boron nitride in the composite body could be polished well. Abrasion testing gave an abrasion groove depth of 0.012? mm.

Example 4 A Mo beaker was charged with a sintered cemented carbide plug 454 983 (thickness 1.27 mm), fine-grained cubic boron nitride (0.060 g), an Al wafer (0.005 g) and a mixture of V powder (0.010 g) ) and Al (0.010 g). The observed properties of the composite body and the compact part of cubic boron nitride were similar to those of the product of Example 3 observed. The wear groove depth was 0.039 mm.

Example 5 A Zr beaker (thickness 0.051 mm) was loaded with a cemented carbide plate (thickness 3.08 mm), a plate of 90 Fe 10 Al (thickness 0.20 mm x diameter 6.25 mm, weight 0.025 mm) and grains of cubic boron nitride (grain size 0.149 / 0.125 mm, 0.093 g).

The metal alloy sheet was arranged at the surface of the cemented carbide in contact with both the cemented carbide and the cubic boron nitride.

This unit was simultaneously subjected to 55 kb pressure and a temperature of 1500 ° C for 60 minutes. The composite body prepared in this way was examined and it was found that considerable direct bonding between grains of cubic boron nitride and between grains of cubic boron nitride and cemented carbide had been obtained.

Example 6 A Mo beaker was loaded with a cemented carbide disk (thickness 1.27 mm), cubic boron nitride (0.080 g, 1-20 μm), an Al disk (0.065 g) and chips of Inconel 718 (0.035 g). ). Inconel 718 has the following composition in weight percent: 52.5% Ni 0.6% Al 0.2% Mn 19% Cr 18% Fe 3% MO 5.2% Nb 0.8% Ti The unit was simultaneously subjected to a pressure of 54 kb and a temperature of 1500 ° C for 60 minutes. Good bonding had been obtained between the cubic boron nitride and the cemented carbide.

The mass of cubic boron nitride was very dense and contained very little 11 '' amount of matrix metal. This metal matrix was very well bound to the grains of cubic boron nitride. Abrasion testing gave an abrasion groove depth of 0.018 mm.

Example 7 A Zr beaker was charged with a pre-sintered disk (thickness 1.27 mm) and a mixture (0.065 g) of cubic boron nitride grains plus grade 55A Carboloy (13% Co, 87% WC) carbide powder (0.032 g) and Al powder (0.003 g) The unit was simultaneously subjected to 55 kb pressure and a temperature of 1500 ° C for 30 minutes, a certain degree of sintering of the cubes of cubic boron nitride was obtained and good bonding was observed between the grains of cubic boron nitride and both the sintered board and the metal matrix.More abrasion test gave an abrasion groove depth of 0.0089 mm.

Example 8 A Zr beaker was loaded with a sintered carbide disc (thickness 0.27 mm), a layer of "grade 190 Carboloy" carbide powder (o, o4s g, zs% co, vs% wc), an A1 disc ( 0.10 g) and grains of cubic boron nitride (0.060 g) The layer of carbide powder was applied over the surface of the sintered plate and the Al plate was placed between the carbide powder layer and the cubic boron nitride, this unit was simultaneously subjected to a pressure of 57 kb and a temperature of lS50 ° C for a period of 60 minutes Good bonding was obtained between the sintered carbide and the in situ sintered carbide Good bonding was also observed between the cubic boron nitride and the metal matrix.

A few larger (20-30 pm) metal islands were observed. The portion of consolidated cubic boron nitride was well polished. Abrasion testing gave an abrasion groove depth of 0.0ll5 mm.

Example 9 Two composite bodies were prepared for forming into turning tools. In each case, the arrangement shown in 454 983 12 is used for a subunit of Figure 2. A Zr cup 34 having a diameter of 8.9 mm and a lid 34a are used. A cemented carbide plate (grade 883 Carboloy) with a thickness of 2.95 mm was used as pulp 37 and 0.120 g of purified jet ground cubic boron nitride (1-10 μm) was used as pulp 36. An Al disk 38 weighing 0.020 g and a disc 39 weighing 0.066 g was used.

This unit was simultaneously subjected to a pressure of 55 kb and a temperature of 1S00 ° C for 60 minutes. The composite bodies were recovered, formed into finished dimensions (thickness 3.15 mm x 6.1 mm square edge dimensions) and tested.

For comparison with a grade 883 Carboloy tool, the two lathe cutting tools of Example 9 were used to cut the "Inconel 718". Under conditions which gave about 0.3 mm abrasion to a grade 883 Carboloy tool, the cubic boron nitride composite body exhibited a wear of only 0.1 mm on the surface of the compression body which had abutment against the workpiece. The chip-breaking surface (of cubic boron nitride) of the composite body was not severely worn with the exception of a groove against which the outer corner of the chip abutted. The same type of abrasion occurred on all tested tools (including the Carboloy tools).

The presence of this particular type of abrasion on all tools was predictable, since all tools had been made with the same geometric shape. The composite bodies of cubic boron nitride gave better results than the tools of "Caiboloy", when the cutting speed was increased.

The preferred direct bond is the bond obtained in situ between the cubic boron nitride material, which has a very high strength, and the substantially larger mass of underlying cemented carbide substrate material. This direct bonding eliminates the need for any intermediate adhesive layer between the compact and the substrate, for example as would be obtained with brazing after soldering. By arranging a rigid, non-resilient support material in direct contact with the cutting part rich in cubic boron nitride, the tendency to crack formation in the material of cubic boron nitride and a smaller amount of cubic boron nitride is greatly reduced (p. 454 983 13 '' rid). required for the manufacture of a tool.

The composite cutting plates shown in Figures 3, 5 and 6 were made in a non-cylindrical shape, joining a cemented carbide substrate and fine-grained cubic boron nitride in the presence of a special material combination, a modified design of the salt liner 21 and the plugs 22, 22 'was required.

The structure fitted in the heating tube 20 can be embodied as a series of cylindrical blocks, which are stacked on top of each other and form molds which are filled with the reaction components. As an example, Figure 7 shows a salt block 21a formed with a recess 72 which represents the shape of the desired cutting plate with addition to the thickness of the protective metal casing 73. The recess 72 is lined with protective casing metal 73 (e.g. zirconium) such as is shown in the figure and contains a preformed cemented carbide body (or mass of sinterable carbide powder) 74, a mass of comminuted crystals of cubic boron nitride 76 and sheets (or powder) of aluminum and the metal to be alloyed with aluminum. Salt 2lb cover blocks are provided with recesses to receive a cover 77, which completes the protective metal casing, and preferably a base block of sintered carbide SC to reduce the puncture of the protective metal casing layer 77.

A number of such cooperating pairs of salt blocks, for example 2la, 2lb. can be used together with the described content. in the cutting plate structure 40 shown in Figure 3, the two surfaces 41 and 42 of the cemented carbide member 43 and the cubic boron nitride composite body 44 are formed with release (Figure 4) to facilitate the application of the cubic boron nitride cutting edge to the cubic composite body 44. boron nitride against the workpiece.

In making the thin layers 51, 61 of consolidated cubic boron nitride (about 90-97 volume percent) in the cutting plate structures 52, 62 shown in Figures 5 and 6, the layer of fine-grained cubic boron nitride is limited to a maximum thickness of about 1.5. mm and a minimum thickness of about 0.025 mm, although it is possible to produce such a layer with a thickness of up to 454 983 14 to about 2 mm. The purpose of making these layers 51, 61 very thin is a) to use the layers 51, 61 of cubic boron nitride as chip breaking surfaces, b) to make it easier to sharpen the cutting plates 52, 62 and c) to save on used cubic boron nitride.

Ideally, the ratio of the amounts of the layer of cubic boron nitride to the cemented carbide is such that the edge of the cubic boron nitride wears away slightly less rapidly than the cemented carbide part.

If these conditions are maintained, a small portion of the layer of cubic boron nitride will continuously protrude beyond the cemented carbide body and give a cutting edge and the amount of cubic boron nitride used will be proportional to the life of the tool.

A content of grains of cubic boron nitride of less than 70% by volume can of course be used. The sintering time can vary from about 10 to about 60 minutes. Pressures ranging from about 45 to 60 kb can be used. The temperature used can vary from 1300 to 1600 ° C. Combinations of pressure and temperature should be chosen, which ensures that the cubic boron nitride is thermodynamically stable.

This second type of composite body can in turn be bonded to a cemented carbide substrate block in a conventional manner, for example with solder material. Alternatively, the composite backing block structure can be prepared in situ a) by applying a mixture of grains of cubic boron nitride and carbide powder over the surface of a cemented carbide sheet or b) by using a combination of layers of sinterable carbide powder and associated therewith a layer of cubic boron nitride grains mixed with carbide powder. In these alternative arrangements, as in the arrangements described above, it is convenient to apply the reaction mass in a zirconium casing.

In carrying out the invention, the carbide powder, if used, preferably consists of tungsten carbide powder intended for molding (mixture of carbide powder and cobalt powder) which is commercially available with particle sizes from 1 to 5 μm. The tungsten carbide can, if desired, be completely or partially replaced with titanium carbide and / or tantalum carbide. Since some use of nickel and iron has taken place in the bonding of carbide materials, the material used to make the metal binder in the cemented carbide may be cobalt, nickel, iron or mixtures of these metals. However, cobalt is preferred as the metal binder. The composition of carbide forming powders suitable in the practice of the invention may comprise mixtures containing about 75-97% carbide and about 3-25% binder metal. Examples of carbide powders used are "Carboloy grade 883" (6% Co, 94% WC) and "Carboloy grade 905" (3% Co, 93% WC, 3.85% TaC, 0.15% TiC). .

For the production of the third type of composite body (grains of cubic boron nitride, diamond grain and sintered carbide), the foregoing description regarding the production of the second type of compacts is applicable with the exception of the content of abrasive grains. Due to the diamond content, the discs 33 (a) should be made of either zirconium or titanium. Mixtures of cubic boron nitride and diamond abrasive grains can have levels ranging from 1% by volume of cubic boron nitride and 99% by volume of diamond to 99% by volume of cubic boron nitride and 1% by volume of diamond. Pressure, temperature and sintering time are comparable to the values used in the production of the second type of composite body except that thermodynamic stability of diamond present which is present requires slightly higher pressure and / or lower temperature than for the production of the second type of composite body.

In other respects, reference is made to the particulars in the description with exemplary embodiments in patent 7208677-O, which are applicable in connection with the present invention.

Claims (12)

454 985 jk _ PATENTKRAV Hard material body, in particular for grinding or cutting tools, comprising crystals of cubic boron nitride, characterized in that the body comprises crystals of cubic boron nitride, which are bonded to each other with a metal phase containing aluminum atoms. Hard material body according to Claim 1, characterized in that it contains a metal phase containing aluminum atoms and atoms of at least one alloying element, which consist of one or more of the metals nickel, cobalt, manganese, iron, vanadium and chromium, the total amount of aluminum and alloying elements exceeding 1% by weight of the amount of cubic boron nitride. Hard material body according to claim 1 or 2, characterized in that the individual crystals of cubic boron nitride have a largest dimension of less than about 30 μm and preferably less than about 10 μm. n Hard material body according to one of the preceding claims, characterized in that the content of crystals of cubic boron nitride in the body is more than 70% by volume. Hard material body according to claim 4, characterized in that the content of crystals of cubic boron nitride in the body exceeds about 90% by volume and preferably amounts to at least about 99% by volume. Hard material body according to one of the preceding claims, in particular a cutting body or cutting plate for cutting machining, characterized in that a cutting edge is formed in the body. Hard material body according to one of the preceding claims, characterized in that the body has the shape 454 985 Fr 'of a layer with a thickness of about 1.5 mm or less. Process for producing a hard material body according to any one of the preceding claims, characterized in that a quantity of crystals of cubic boron nitride and a binder metal component comprising aluminum atoms are placed in a protective metal casing and the casing and the contents of this for the simultaneous effect fl of a temperature of l300-l600 ° C and a pressure exceeding about 40 kilobars for at least 3 minutes and utilizes the produced hard material body. 9. A method according to claim 8, characterized in that the binder metal component contains aluminum atoms and atoms of at least one alloying element, consisting of nickel, cobalt, manganese, iron, vanadium and chromium, wherein the total amount of aluminum and alloying elements over increases by 1% by weight of the amount of cubic boron nitride. 10. A method according to claim 8 or 9, characterized in that the crystals of cubic boron nitride are applied as a layer which after pressing has a thickness of 1.5 mm or less. 11. ll. A method according to any one of claims 8-10, characterized in that the material used as a source for an aluminum alloy is in powder form or in the form of sheets comprising a sheet of aluminum. 12. A method according to any one of claims 8-11, characterized in that the part of cubic boron nitride also contains diamond particles and / or cemented carbide.