DK155659B - COMPOSITION BODIES FOR GRINDING OR FOR CUTTING TOOLS AND PROCEDURES FOR MANUFACTURING THE SAME - Google Patents

Description

in

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BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to composites for grinding or cutting tools, which body comprises cubic boron nitride (CBN) crystals.

US Patent No. 2,947,617 discloses a swivel steel whose cutting portion consists of a single cubic boron nitride crystal which is attached to the shaft of the swivel steel using a 1-oat flour 1-layer and a titanium hydride intermediate layer. Also known from this patent is an abrasive disc whose abrasive layers contain cubic boron nitride crystals embedded in a resin matrix. The abrasive layer is disposed on one of the resin base members. A single cubic boron nitride crystal suitable for turning on a swivel steel should be as large as possible. However, the production of large cubic boron nitride crystals is very difficult.

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US Patent No. 3,136,615 and German Patent Specification No. 1,169,833 disclose abrasive and cutting bodies containing crystals of diamond and / or cubic boron nitride embedded in a matrix of boron carbide. Such bodies are relatively brittle and therefore break easily under the influence of the stresses which occur during machining.

DE patent specification No. 661,132 discloses a method for providing a cutting tool with a cemented carbide layer, whereby the base part of the cutting tool 25 is coated with a cold pressed, sintered, finished sintered or melted cemented carbide layer which is connected to the base part during the application of pressure and heat.

GB Patent Specification No. 1,034,386 discloses a method for making a cemented carbide formers of several cemented carbide parts which are joined to a molded body, the individual cemented carbide parts being compressed with correspondingly adapted surfaces and heated to such an extent that the cemented carbide is present. binder metal melts.

35 from DE Publication No. 1,502,019, a carbide insert for cutting on a cutting tool is known, the insert comprising a thick base body of carbide on which is applied a thin wear layer of titanium carbide modified carbide. To produce such a cutting insert, a mold can be inserted into a mold 2

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powder for forming the base body, on which a powder suitable for forming the wear layer is sprinkled and where it is all pressed and sintered.

5 Very hard materials, especially nickel-based superalloys, are barely or very difficult to work with the known cutting inserts.

The object of the invention is to provide a tool insert 10 containing cubic boron nitride and of such strength that it is easy to process even particularly tough and hard materials.

This object is achieved with an composite body of the kind set forth in the preamble 15, which is characterized in that it comprises separate at a pressure of more than 40 kilobars of sintered masses, a first of which consists of cobalt, nickel or iron bonded tungsten, tantalum or titanium carbide, and another mass, which contains a polycrystalline mass of crystals of 20 cubic boron nitride, comprises more than 70% by volume of interconnected cubic boron nitride crystals.

The invention also relates to a process for preparing the above composite body. This method is characterized by (a) placing in a protective metal container a separate amount of sinterable carbide powder comprising a binder metal and a carbide carbide or a sintered carbide mass of cobalt, nickel-30 or iron-bonded tungsten, tantalum or titanium carbide and a separate amount of cubic boron nitride crystals or a polycrystalline mass of cubic boron nitride crystals which, in a subsequent pressure sintering step, form a separate mass comprising at least 70% by volume of cubic boron nitride, 35 (b) subjecting the container and its contents to simultaneous action of a temperature of 1300-1600 ° C and a pressure exceeding approx.

40 cb for at least 3 minutes; (c) the supply of heat to the container is stopped; (d) the pressure exerted on the container is abolished; and 3

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(e) the carbide composite squirrel is removed.

The invention will now be described in more detail in connection with the drawing, in which: 1 shows an apparatus suitable for use in the practice of the present invention; FIG. 2 is a sectional view of one embodiment of the filling composition for use in the apparatus of FIG. 1, 10 FIG. 3 is a three-dimensional view showing a composite CBN machine tool insert; FIG. 4 is a sectional view through the insert of FIG. 3 seen either along line X-X or along line Y-Y; FIG. 5 and 6 are both three-dimensional images of composite CBN-15 sintered carbide tool insert blanks manufactured in accordance with the present invention; 7 is a sectional view showing a combined liner / filling composition for use in preparing the structures shown in FIG. 3, 5 and 6, 20 FIG. 8 is a sectional view showing another embodiment of filling composition for use in the apparatus of FIG. 1, FIG. 9 is another three-dimensional image showing a composite CBN machine tool insert; FIG. 10 is another section through the insert of FIG. 9 is seen either along line X-X or along line Y-Y; and FIG. 11 is a sectional view showing a combined liner / filling composition for use in preparing the structures shown in FIG. 9, 5 and 6.

A preferred form of a high pressure, high temperature apparatus in which the composite tool insert of the present invention can be manufactured is disclosed in the description to U.S.A. No. 2,941,248 and are broadly shown in FIG. 1. Reaction vessel arrangements suitable for use in the practice of the method of the present invention are disclosed in U.S.A. Patent Specification No. 3609818.

The apparatus 10 comprises a pair of cemented tungsten carbide pistons 11 and 1Γ and an intermediate die portion 12 of the same material.

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The die portion 12 comprises an opening 13 in which a reaction vessel 14. is provided between the plunger 11 and the die 12 and between the plunger 1 mat and the die 12, packing members 15, 15 'are provided, each comprising a pair of heat insulating and electrically non-conducting 5 pyrophyllite parts. 16 and 17 and an intermediate metal gasket 18.

A preferred embodiment of the reaction vessel 14 comprises a hollow salt cylinder 19. The cylinder 19 may be of another material, such as talc, which a) does not convert during high pressure high temperature operation 10 to a stronger, stiffer state (such as in phase conversion and / or compression); and which b) is substantially free of volume discontinuities that occur with the use of high temperatures and pressures, such as e.g. occurs in association with pyrophyllite and porous alumina.

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Materials that meet the criteria set forth in the description to U.S.A. Patent No. 3,030,662 (column 1, line 59 to column 2, line 2) is suitable for the manufacture of cylinder 19.

20 An electrically resistive heating tube of graphite 20 is arranged concentrically within and adjacent to the cylinder 19. In the graphite heating tube 20, again, a cylindrical salt liner 21 is concentrically disposed. The ends of the liner 21 are provided with salt plugs 22, 22 ', respectively arranged above. and below. As will be discussed in more detail below, the liner may have a cylindrical hollow space 31 for accommodating a large filling composition containing sub-compositions, or the liner may consist of a series of molds arranged in a stack to produce several composite tool insert blanks. eg. as shown in FIG. 3, 5, 30 and 6.

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

Operating modes for simultaneous use of both high pressure and high 5

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temperatures in the present apparatus are well known to those skilled in the art.

FIG. Figure 2 shows an arrangement for producing a plurality of disc-5 or pill-shaped composite products (sintered carbide substrate having a layer of sintered CBN formed over it), using an alloy non-bonding compound. The filling composition, although not shown on the same scale, fits into the compartment 31 of FIG. First

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The filling composition consists of a cylindrical sleeve 32 of a shielding metal selected within the group consisting of zirconium, titanium, tantalum, tungsten and molybdenum. Inside the cylindrical shield metal sleeve 32 are arranged a series of 15 sub-assemblies which are separated by plugs 33 of the same material as the cylinder 19, e.g. hexagonal boron nitride or NaCl, which remains largely unchanged during the process and which facilitates later separation of the sub-compositions. Each subassembly is contained in a cylindrical portion 34 with a lid disc 34a 20 made of any of the materials suitable for the sleeve 32 but preferably made of zircon or titanium. In each subassembly, a mass 36 of finely divided (less than about 30 microns) CBN crystals is disposed between a mass 37 and a pair of metal discs, a disc 38 of aluminum and a disc 39 of a 25 alloy metal which is selected from nickel, cobalt, and iron. The relative positions of the washers 38 and 39 are not critical as long as the aluminum alloy is produced. The mass 37 may be of sintered carbide or it may be made of sintered carbide powder, the sintering thereof occurring during the consolidation of the CBN mass. The amount of aluminum used in relation to the amount of alloy metal is not critical and can range from equal parts by weight to approx. 1 part by weight of aluminum to 10 parts by weight of alloy metal.

In preparing tool insert blanks by means of this embodiment, the filling composition 30 is applied to the apparatus 10 which is pressurized and the system is then heated. The temperatures used range from 1300 to 1600 ° C for periods of more than 3 minutes, while at the same time subjecting the system to very high pressures, e.g. of the order of 55 kilobars to ensure thermodynamic 6

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stable conditions for the CBN content of the system. At 1300 ° C, the minimum pressure should be approx. 40 kilobars, and at 1600 ° C the minimum pressure should be approx. 50 kilobars. At the temperatures used, the sintering agent melts in mass 37 and releases cobalt, nickel or iron 5 (depending on the particular carbide composition) for movement from mass 37 to mass 36, forming alloys with the molten aluminum alloy formed from slices 38 and 39. and by reaction in the CBN mass. The metallic medium thus formed acts as an effective bonding agent for the CBN crystals near the interface of mass 36 and 37 to bond these crystals to each other and to the sintered carbide. The rest of the crystals in the mass of CBN are bonded by the metallic medium formed by alloying the slices 38, 39 and by reaction between this alloy and the CBN.

The amount of aluminum in the starting material can range from approx. 1 to approx.

40% by weight of CBN, while the amount of the alloy metal (nickel, cobalt and iron) can range from approx. 2 to approx. 100% by weight of CBN. The amount of these alloying metals remaining in the consolidated CBN as a matrix material will vary depending on the pressure and duration of the high pressure high temperature state. In all cases, the amount of aluminum and alloys of alloy metal in the compact CBN will be above approx. 1% by weight of the amount of CBN.

Of course, pre-formed aluminum alloys can be used instead of separate in situ alloy discs.

After completion of the high temperature high pressure treatment, the temperature is first reduced and then the pressure. When removing the tool insert masses, the protective shielding metal is strongly associated with their surfaces. Exposing of the desired surfaces to the composite tool insert is accomplished simply by grinding away the protective cover.

35 Using the embodiment described above and using an aluminum as the bonding medium, numerous composite bodies of CBS and sintered carbide have been successfully prepared using CBN crystals in a size range of from 1 to 10 ml. These composite bodies exhibit substantially improved 7

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abrasive properties compared to sintered carbide bodies.

In many of the examples listed below regarding this embodiment, a small excess of aluminum alloy is formed, 5 and this remains after the infiltration between the CBN crystals is completed. This slight excess may form alloy with the cylinder 34 or with portions of the sintered carbide mass 36.

After the temperature and pressure have been lowered, 10 composts are removed in the ten squirrels, and they can then be ground into shape for use as cutting tools.

When a polished surface of such a body is examined under a microscope, it is seen that many fine particles of CBN are close to up to 15 each other, the very small spaces between them being filled with another phase that is apparently metallic. Thus, scratches were observed on the polished surface as opposed to rows of holes from CBN fragment removal, as has been observed on polished surfaces on compact masses made using various other active metals as bonding medium.

The penetration and bonding of the CBN crystals by the bonding medium is excellent for composites and compact 25 CBN masses made in accordance with the present invention. Characteristic X-ray diffraction patterns occur for any given alloy system (aluminum as well as one of the alloying metals listed). These diffraction patterns have established the presence of CBN, A1N and additional non-identifiable phases.

30 Electron beam microsonde studies of composite bodies and compact CBN masses made with aluminum and nickel as the source of the bonding medium showed both Al and Ni in the interstices.

The finely divided CBN crystals are preferably prepared by jet grinding of larger CBN grains. Prior to introduction into the reaction vessel, the CBN feed is preferably heated (900 ° C, 1 hour) in ammonia to further purify the surfaces of the crystals.

Some composite bodies of CBN and sintered carbide made

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8 according to the invention have been formed into tools according to the invention (square, about 6.1 mm on each joint) and used to cut Inconel 718, a nickel-based super alloy. A typical Ni-Al bonded tool would have had a surface layer of bonded CBN with a thickness of from 0.76 mm to 0.25 mm firmly bonded to a sintered carbide support block (e.g. grade 883 Carboloy sintered carbide) about 3.05 mm thick. SI in that such tools were generally generally less than the wear associated with the use of quality 883 Carboloy tools under the same conditions.

A number of composite bodies made by this embodiment of the invention were subjected to abrasion tests, under which a rod of René 41 (a nickel-based super alloy) of 3.2 mm diameter rotating at a speed of 2000 rpm. per minute, was pressed against the CBN layer on the composite squirrel, which was tested with a force of 36.3 kg for 3 minutes. The depth of the wear groove on the compact mass was then determined. In each of the following examples, the arrangement used was substantially the same as that of an urw-20 composition as shown in Figure 2. The protective cylinder (or sleeve) used in each case had a diameter of 6.4 mm. . Unless otherwise stated in the Examples, all the CBN used was jet milled (1-10 microns as the largest dimension). The CBN used in Examples II and VI was heated in NH 3 prior to introduction. In each example, a pre-sintered carbide disc (grade 883 Carboloy sintered carbide) was used as a support block for the composite squirrel.

Example I 30

A Zr cylinder was filled with a pre-sintered carbide disk (1.3 mm thick), CBN grain (0.050 g), Al disk (0.010 g) and Co disk (0.034 g). At the same time, the composition was subjected to a pressure of 54 kb and a temperature of 1550 ° C for 61 minutes. The bond of CBN to the carbide and the bond between the CBN grains and the metal matrix were good. The consolidated CBN part provided a good polish. The wear test groove had a depth of 0.036 mm.

Example II

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A Mo sleeve (0.05 mm thick) with Mo end slices (0.05 mm thick) was filled with a pre-sintered carbide disk (1.3 mm thick), CBN grain (0.065 g), Al disk (0.010 g) and a layer of mixed Co (0.015 g) and Al (0.004 g) powders. This composition was simultaneously subjected to a pressure of 566 kb and a temperature of 1500 * 0 for 63 minutes. Good bonding between CBN and the sintered carbide and metal matrix was observed.

The CBN content of the metal matrix exhibited a tightly packed microstructure. The wear test groove had a depth of 0.025 mm.

Example III

A Zr cylinder was filled with a pre-sintered carbide plug (1.3 mm thick), CBN grain (0.060 g) and a mixture of coarse powders (Al 0.010 g and Mn 0.040 g). At the same time, the composition was subjected to a pressure of 55 kb and a temperature of 1550 ° C for 60 minutes. The connection between CBN and the carbide and the metal matrix was good. The CBN compact part of the composition provided good polishing. The wear test groove had a depth of 0.013 mm.

Example IV

An Mo cylinder was filled with a pre-sintered carbide plug (1.3 mm thick), CBN finger pad (0.060 g), an Al disk (0.005 g) and a mixture of V- (0.010 g) and Al- (0.010 g) powders. Observations in terms of composition and CBN compact part were as for the product of Example III. The wear test groove had a depth of 0.038 mm.

Example V

A Zr cylinder (0.05 mm thick) was filled with a sintered carbide disk (3.1 mm thick), a 90 Fe 10 Al disk (0.15 mm thick x 6.3 mm in diameter, 0.025 g) and CBN grain (100/120 masks), 0.093 g. The metal alloy disc was placed on the surface of the sintered carbide in contact with both the sintered carbide and the CBN mass. This composition was simultaneously subjected to a pressure of 55 kb and a temperature of 1500 ° C for 60 minutes.

The composite body thus prepared was examined and it was found that significant direct bonding had occurred between the CBN grains and between the CBN grains and the sintered carbide.

Example VI

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An Mo cylinder was filled with a sintered carbide disk (1.3 mm thick), CBN (0.080 g, l-20 / ί), an Al disk (0.015 g) and chips of Inconel 718 (0.035 g). Inconel 718 has the following weight composition: 52.5% Ni 0.6% Al 0.2% Mn 19% Cr 18% Fe 3% Mo 10 5.2% Cb 0.8% Ti

The composition was simultaneously subjected to a pressure of 54 kb and a temperature of 1500 ° C for 60 minutes. A good bond between the CBN mass and the carbide had developed. The CBN mass was very dense and 15 contained very little matrix metal. The matrix metal present was well bonded to the CBN grains. The wear test groove had a depth of 0.018 mm.

Example VII

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A Zr cylinder was filled with a pre-sintered disc (1.3 mm thick) and a mixture (0.065 g) of CBN grain and grade 55A Carboloy (13%

Co, 87% WC) carbide powder (0.032 g) and Al powder (0.003 g). The composition was simultaneously subjected to a pressure of 55 kb and a temperature of 1500 ° C for 30 minutes. Some sintering of the CBN grains occurred and good bonding was observed between the CBN grains and both the pre-sintered slab and the metal matrix. The wear test groove had a depth of 0.009 mm.

Example VIII

A Zr cylinder was filled with a pre-sintered carbide disk (1.3 mm thick), a layer of quality 190 Carboloy carbide powder (0.046 g, 25% Co, 75% WC), an Al disk (0, OlOg) and CBN. grain (0.060 g). The layer of 35 carbide powder was placed over the surface of the pre-sintered slice, and the Al slice was placed between the carbide powder yoke and the CBN grains. The composition was simultaneously subjected to a pressure of 57 kb and a temperature of 1550 ° C for 60 minutes. Good connection was obtained between the pre-sintered carbide and the sintered carbide

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π si tu. Good bonding between the CBN grains and the metal matrix was also observed. A few larger (20-30 microns) metal ranges were observed. The consolidated CBN part polished well. The wear test groove had a depth of 0.011 mm.

5 10 15 20 25 30 35

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Example IX

Two composite bodies were manufactured for use with lathe cutting tools. In each case, the arrangement shown for a sub-assembly of Figure 2 was used. A Zr cylinder 34 having a diameter of 8.9 mm and corresponding lid 34a was used. A sintered carbide disc (grade 883 Carboloycarbide) having a thickness of 2.9 mm was used as the mass 37, and 0.120 g of purified jet milled CBN (1-10 ml crown) was used as the mass 36. The Al disk 38 weighed 0.020 10 g, and the Ni disc 39 weighed 0.066 g. This composition was simultaneously subjected to a pressure of 55 kb and a temperature of 1500 ° C for 60 minutes.

The composite products were removed, formed to finished dimensions (3.2 mm thick and 6.1 mm square) and tested.

15 When compared to a quality 883 Carboloy tool, the two lathe cutting tools of Example IX were used to cut Inconel 718. Under conditions that produced approx. 0.30 mm wear on a quality 883 Carboloy tool, the CBN composite squirrels showed only (0.10 mm) wear on the compact surface rubbed against the workpiece. The 20 chip-deflecting (CBN) surface of the composite squirrel was also not greatly worn except for a hollow where the outer corner of the chip went against. The same type of wear also occurred on all other tested tools (including Carboloy tools). The prevalence of this particular type of wear on all tools was foreseeable, as all 25 tools had been manufactured with the same shape. The CBN composite squirrels performed better than the Carboloy tool when the cutting speed was increased.

The preferred direct bond is that formed in situ between very high strength CBN material and the substantially greater mass of underlying rigid carbide support material. This direct bond avoids any need for insertion of a bonding layer between the compact mass and the substrate, such as that which e.g. available by soldering or brazing. By bringing rigid, non-compliant support material into direct contact with a CBN-rich machining edge area, the occurrence of fractures in the CBN material is greatly diminished, and so much CBN is not needed to manufacture a tool.

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Reference is now made to the composite tool insert blanks shown in Figures 3, 5 and 6, where in the manufacture of these non-cylindrical forms, where a sintered carbide support and CBN finger tips are joined to a unit in the presence of particular combinations of 5 materials, a modified design of the salt liner 21 and plugs 22, 22 'is required. Thus, the structure fitting within the heating tube 20 may be formed by a series of cylindrical blocks in stacked cooperative arrangement to provide molds which may be filled with the reaction components. In Figure 7 10, for example, a salt block 21a is provided with a recess 72 which corresponds to the shape of the desired tool insert, opening space for the thickness of the protective metal shield 73. The recess 72 is lined with protective metal 73 (f. zirconium) and serves to hold a pre-formed sintered carbide body (or mass of sinterable carbide powder) 74, a mass of finely divided CBN crystals 76, and aluminum alloy discs (or powders) and the metal to be alloyed with this. A low salt block 21b is provided with recesses to accommodate a cover plate 77 which completes the protective metal enclosure and preferably a support sheet of sintered carbide SC to reduce puncture of the protective metal layer 77. A number of such cooperating pairs of salt blocks, such as 21a, 21b can be used with the above content.

In the tool insert assembly 40 of Figure 3, both surfaces 41 and 25 42 of the cemented carbide 43 and CBN composition of the spokes 44 are inclined (Figure 4) to facilitate the placement of the CBN cutting edges on the CBN composite spokes relative to the workpiece.

In designing the thin layers 51, 61 of consolidated CBN (about 90-97 30% by volume) in the tool insert assemblies 52, 62 shown in Figures 5 and 6, the layer of CBN finger pads is limited to a maximum thickness of approx. 1.5 mm and a minimum thickness of approx. 0.025 mm, although the possibility exists of making such layers in thicknesses up to approx. 2.0 mm. The intention to make these layers 51, 61 35 very thin is to a) produce the CBN layers 51, 61 as chipboard surfaces, b) to facilitate the sharpening of tool insert blanks 52, 62, and c) to economize with it used CBN. Ideally, the relationship between the properties of the CBN layer and the cemented carbide is such that the edge of the CBN layer will wear away slightly 14

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slower than the cemented carbide. When this is the case, a small portion of the CBN layer will continue to protrude from the cemented carbide body and provide a cutting edge, and the amount of CBN used will correspond to the tool life.

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As stated above, the aluminum alloy binder may be omitted by binding CBN sizes above 80 ml crown (largest dimension). However, when this occurs, the process is unsuitable for providing satisfactory bonding of CBN crystals measuring 30 10 microns (largest dimension) and below, presumably because of the high impurity content that remains concentrated on the large surface area of these small particles. Nevertheless, if desired, a method which does not make use of the above aluminum alloy bonding media can be used in applications where CBN sizes of 15 over 80 ml crown are appropriate.

Figure 8 shows an arrangement for producing a plurality of slab or pill shaped composite products (sintered carbide substrate over which a layer of sintered CBN is formed) without the presence of an aluminum alloy bonding medium. The filling composition 30 (A) fits, although not shown on the same scale in the space 31 of the apparatus shown in Figure 1.

The filling composition 30 (A) consists of a cylindrical sleeve 32 (A) 25 of shielding metal selected from zirconium, titanium, tantalum, tungsten, and molybdenum. Inside the cylindrical shield metal sleeve 32 (A) are arranged a plurality of sub-assemblies protected above and below by shield discs 33 (A) made of a metal selected from those listed for use by manufacture of the sleeve 32 (A), except as set forth below. Each sub-composition thus protected on all sides consists of a larger mass 34 (B) and a smaller mass 36 (A). Each mass 36 (A) is predominantly or wholly made up of CBN powder (greater than about 80 m in crown for the largest 35 dimension).

By using a pre-sintered carbide disk such as mass 34 (B) and pure CBN crystals larger than equivalent to a mesh size of 120 (US sieve standard), such as mass 36 (A) without additional additives, 15

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For example, a single abrasive body can be prepared as discussed below, wherein the CBN portion is substantially void-free and attached to the carbide disk by an excellent bond.

Example X

Virtually pure CBN grains with a size equal to a mass size of 100 were distributed as a mass over a surface of a hard sintered carbide disk made of grade 883 Carboloy® 10 carbide powder. The composition was placed in a thin zirconium shield to exclude and remove oxygen. This composition was again surrounded by NaCl portions (to fill volume 31) in a high pressure apparatus. After 1 hour under high pressure and high temperature supply (55-60 kb and 1500 eC), a composite abrasive body was obtained. It was found that the CBN portion was substantially free of voids and that an excellent bond existed between the sintered carbide and adjacent CBN.

The composition of the squirrels of Example X was examined and it was found that substantially complete removal of voids in the CBN mass (99% by volume CBN) had been achieved by various mechanisms.

a) Penetration of zirconium metal (from the sheath) to a shallow depth, e.g. 0.2 mm.

b) crushing of the CBN grains (which can then become a solid mass); c) withdrawing carbide material between the CBN grains during the high temperature treatment (when the carbide material is in the plastic state) and d) direct bonding between the CBN grains.

The 35 CBN grains had large contact surfaces, and it was found that they had been partially plastically deformed to adapt to each other.

To maintain the advantages of mechanically unstable construction of

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16, the disks 37 (A) are made of the same material as the cylinder 19, e.g. NaCl, hexagonal BN to fill the diminished volume of each sub-composition during treatment.

In the disclosed embodiments of the present invention, carbide powder which can be sintered as discussed below may be used in place of the sintered carbide as the mass 34 (B). In such a case, sintering of the carbide powder occurs in situ.

10

The direct bond formed between the very high strength CBN material and the substantially larger mass of underlying rigid carbide support material alleviates any need for insertion of a bonding layer between them such as e.g. that obtained by brazing 15 or brazing. By providing a rigid non-compliant support material in direct contact with the CBN-rich machining edge area, the occurrence of fractures in the CBN material is minimized using the tool insert for machining to a minimum. In connection with either the embodiment using aluminum alloy bonding media, or the embodiment where such is not used, compositions made in accordance with the present invention have been randomly interrupted during decompression of the reaction vessel to remove the product. This type of fracture occurs in a direction approximately 25 perpendicular to the vertical axis of the filling composition. In the case of composite bodies made with the sub-compositions of Figure 2 and Figure 8, the interface between CBN and the sintered carbide lies in the same direction. The high quality of bonding at this interface is seen by the fact that the breakage 30 usually occurs through the CBN layer. Rarely, rupture occurred only rarely at the interface, and in these cases the rupture surface was irregular, passing through the sintered carbide as well as along the interface. Thus, the interface is generally stronger than the CBN crystals themselves.

35

Microscopic (300X) examination of the polished edges of composite bodies formed for tool insert blanks has revealed the causes of this exceptionally strong interface bonding. By "good bonding" the CBN grains show at the interface (at 300X magnification) 17

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say either to be in direct contact with the sintered carbide, or to be connected by a thin reaction layer disposed between the CBN grains and the sintered carbide. Any reaction layer present is less than 10 microns thick, which shows that in all 5 circumstances, minimal bursting and attack of the sintered carbide structure occurs. The interface is free of voids and is irregular in scale (l-100 / ί) due to the CBN material being pressed into the sintered carbide and / or due to the movement of plastic deformed sintered carbide into the spaces between 10 adjacent CBN crystals. This type and quality of interlocked interface is clearly unattainable by soldering a pre-made compact CBN mass to a sintered carbide disk.

Preparation of Compact CBN Masses for Use as Wear Parts in Cutting and Grinding Tools are disclosed in the above-described U.S.A.

Patent Nos. 3,136,615 and 3,233,988. After preparation, the compact mass produced according to the prior art is attached to a carrier.

There is nothing in these patents that would guide one skilled in the art of making a tool insert in the form of a composite spindle, wherein a compact CBN mass, when formed, is simultaneously integrated with a sintered carbide support mass without the use of additives.

In addition to the type of composites disclosed above, in which a mass of CBN crystals is supported on and bonded to a pre-formed sintered carbide mass, two other types of composite bodies may be prepared. In both of the latter compositions, the sintered carbide is relatively uniformly distributed in a mass of abrasive grains. In the second type of composites, the abrasive grains are CBN grains, while the abrasive grains of the third type of composition are a mixture of CBN grains and diamond grains.

Example XI

35 A mixture of 94% by volume CBN grain and 6% by volume Carboloy grade 883 carbide powder (6% Co, 94% WC) was surrounded by a thin Zr shield (to exclude and remove oxygen). This composition was introduced into a high-pressure, high-temperature apparatus as described in Example X. The mixture was exposed to ca. 55 kb and 18

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1500 ° C for approx. 60 minutes. Microscopic examination of polished surfaces on the resulting composite spokes shows that the sintered carbide had moved into the smallest crevices between the CBN grains. Although direct bonding between the CBN grains was not extensive in this type of composites, the bonding between the CBN material and the metal (carbide) was excellent. A fractured surface of the composition showed very few places where a CBN grain had been pulled out of the system. Instead, the CBN grain was broken. No reaction layer was observed up to the CBN grains at 300X 10 magnification.

In the preparation of this type of composites, CBN crystal content of from about 10% is preferably used. 70% by volume to approx. 94% by volume. With this large CBN content, direct contact between the CBN crystals occurs at the high pressures used. As a result, crushing of grain occurs, and much of the original void is filled with broken CBN grains. Penetrating carbide powder apparently prevents direct bonding between the CBN grains, but the CBN / carbide bond provides a tough, strong abrasive body.

The sintering time can vary from approx. 10 to approx. 60 minutes. Pressures in the range of approx. 45 to 60 kb. The temperatures used can range from 1300 ° C to 1600 ° C. Combinations of 25 pressure and temperature must be selected in such a way as to ensure thermodynamic stability for the CBN.

This second type of composite body can again be attached to a sintered carbide support block by commonly known means, e.g. by means of soldering. As another option, this compositor / support block structure can be prepared in situ a) by applying the CBN grain / carbide powder mixture over the surface of a sintered carbide disk or b) using a combination of a sintering carbide powder and adjacent with this a 35 layer of CBN grain / carbide powder mixture. In these alternative arrangements, such as the arrangements discussed above, the reaction mass is preferably contained in a zirconium sheath.

In the practice of the present invention, 19

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the carbide powder, where used, preferably a tungsten carbide casting powder (mixture of carbide powder and cobalt powder) commercially available in particle sizes from 1 to 5 microns. Tungsten carbide may, if desired, be replaced in whole or in part by either titanium carbide or tantalum carbide or both. Since there has been some use of nickel and iron in the bonding of carbides, the material for providing the metal bond in the cemented carbide can be selected from cobalt, nickel, iron and mixtures thereof. However, cobalt is preferred as the metal bonding material. The composition of carbide mold powders suitable for use in the practice of the present invention may be comprised of mixtures containing approx. 75-97% carbide and approx. 3-25% metal bonding material. Examples of carbide powders used are Carboloy grade 883 carbide (6% Co, 94% WC) and Carboloy grade 905 (3% Co, 93% WC, 3.85% TaC, 0.15% TiC).

In preparing the third type of composite body (CBN grain, diamond grain and sintered carbide), the technique set forth above for use in preparing the second type of compact mass is applicable except for the abrasive grain content. Due to the diamond content, the discs 33 (A) must be either zirconium or titanium. Blanks of CBN and diamond ibekorn may be within wide limits, however, the cubic boron nitride must be at least 70% relative to the volume of CBN and carbide. Pressures, temperatures and sintering times are comparable to those used in the preparation of the second type of composite body except that, when present, the thermodynamic stability of diamond requires slightly higher pressure and / or lower temperatures than other type of composition.

30

Example XII

An assembly corresponding to a sub-assembly of FIG. 2 was made in a Zr container (6.4 mm diameter). The filling for this 35 consisted of a slab of quality 883 Carboloy sintered carbide (thickness 3.1 mm) and in contact with it a mixture of 0.046 g CBN grain (100-120 mesh), 0.046 g diamond grain (100-120 mesh) and 0.020 g grade 883 Carboloy powder. The unit was simultaneously subjected to a pressure of 55 kb and a temperature of 1500 ° C for 60 minutes. It 20

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manufactured composite bodies were polished to a cutting tool and tested by cutting René 41 superalloy on a lathe. The tool cut the super alloy, but the diamond part of the compact abrasive mass was worn away too quickly. Microscopic examination showed that good diamond / diamond bonding was obtained in the manufacture and that there was good bonding between the diamond and the CBN grains and the carbide support. Occasionally, CBN / CBN binding was observed, but no diamond / CBN binding.

10 As mentioned above, in connection with the composite tool insert blanks shown in FIG. 9, 5 and 6, and in making these non-cylindrical shapes, a modified design of the salt liner 21 and plugs 22, 22 'is required. Thus, a structure which fits within the heating tube 20 can be formed by a series of cylindrical blocks in stacked cooperating arrangement to provide molds which can be filled with the components, e.g. a mixture of carbide mold powder and CBN grain. By way of example, the salt block 21 (C) of FIG. 11 may be provided with a recess 72 (A) which corresponds to the shape of the desired tool insert but which provides space for the thickness of the protective metal sheath 73 (A). The recess 72 (A) is lined with protective metal 73 (A) (e.g. zirconium) as shown to contain the materials to be converted into a composite body. The lid salt block 21 (D) is provided with recesses to provide space for the lid plate 74 (A) which completes the protective metal enclosure and preferably a sintered carbide SC support block to minimize puncture of the protective metal layer 74 (A). A number of interacting pairs of salt blocks such as 21 (C), 21 (D) can be used to fill the volume 31.

30 in the tool insert assembly 40 (A) shown in FIG. 9, both surfaces 41 (A) and 42 (A) of the cemented composite body of carbide / abrasive grain 43 (A) are provided with an inclined surface (Fig. 10) to facilitate presentation of the CBN cutting edges thereon relative to the workpiece.

35

If desired, most of the tool body 40 (A) may consist of sintered carbide (either pre-formed or manufactured in situ), with only the area constituting and adjacent to point 44 (A) being of a cemented carbide composite body. grit.

21

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In this embodiment, where an aluminum alloy is not used as a bonding agent in forming the thin layers 51, 61 of consolidated CBN (about 99% by volume) in the tool insert assemblies 52, 62 shown in FIG. 5 and 6, the layer of CBN grain 5 is limited to a maximum thickness of approx. 1.0 mm and a minimum thickness of approx. 0.1 mm, although it is possible to make such layers with thicknesses of up to approx. 2.0 mm.

After completion of the high temperature high pressure treatment, 10 first decreases the temperature and then the pressure. After removing the tool insert masses, the protective metal sheath is firmly attached to their surfaces. Exposing the desired surfaces to the tool insert formed is accomplished by simply abrasive the protective shield.

15

It has also been found that the system is compatible with small amounts of additives such as tungsten and beryllium.

Example XIII

20

Two sub-compositions were inserted (top and bottom) into the cavity 31 of a high pressure high temperature apparatus. Each subassembly was surrounded by a Zr cylinder (6.4 mm diameter) and consisted of a plug of grade 883 Carboloy sintered carbide (1.3 mm thick) and a mass of 100/120 mesh CBN grain (0.065 g). The CBN grains of the lower sub-composition were covered only with a thin layer of Ta metal, which was sprayed over them. The sub-compositions were simultaneously subjected to a pressure of 55 kb and a temperature of 1510 ° C for 60 minutes. The sub-compositions were removed, polished and examined under microscope.

The upper sub-composition exhibited extensive direct bonding between the CBN grains, resulting in a strong abrasive body. There was also excellent adhesion between the CBN grains and the sintered 35 carbide.

The lower sub-composition (Ta-coated CBN) was found to have many areas where the CBN grains were sintered. Other CBN crystals were bound to the Ta matrix. That was clearly good

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22 the adhesion between the CBN / Ta system and the sintered carbide.

Example XIV

A unit similar to the sub-compositions of Example XIV was prepared. A Zr cylinder (wall thickness 0.05 mm and a diameter of 6.4 mm) was filled with a body (0.5g) cold pressed grade 883 Carboloy carbide powder and in contact with the surface thereof, a mixture of 400 mesh CBN grain (0.060 g), grade 883 10 Carboloy carbide powder (0.021 g) and Be powder (0.003 g). The unit was also subjected to a pressure of 56 kb and a temperature of 1520 ° C for 60 minutes. A composite disk was obtained consisting of a sintered carbide base (1.8 mm thick) covered on one side with a layer of consolidated CBN (thickness 0.71 mm) and a uniform diameter of 3.35 mm.

Strong bonding between the CBN grains and the sintered carbide as well as direct CBN / CBN binding was found.

It will be understood that the composite products produced by the practice of the present invention will usually be attached to a larger body, e.g. a tool shank or drill bit for advancing against the material to be cut.

25 30 35

Claims (15)

A composite body for grinding or cutting tools, said body comprising cubic boron nitride crystals bonded to a body of a metal material, characterized in that the composite spokes comprise separate at a pressure of more than 40 kilobars of sintered mass, a first of these masses consist of cobalt, nickel, or iron-bound tungsten, tantalum or titanium carbide, and another mass containing a polycrystalline mass 10 of cubic boron nitride crystals comprises more than 70% by volume of interconnected cubic boron nitride crystals. Composite body according to claim 1, and in particular in the form of a cutting body or a cutting tool for machining, characterized in that the mass of cubic boron nitride is shaped into a cutting edge and the carbide mass is shaped as a strength-forming substrate for the mass of cubic boron nitride. Composite body according to claim 1 or 2, characterized in that the mass of cubic boron nitride also comprises cobalt, nickel, or iron-bound tungsten, tantalum or titanium carbide and / or diamond portion K1. Composite body according to any one of the preceding claims, characterized in that the mass of cubic boron nitride is bonded to the carbide mass at a partition substantially free of pores and voids, where a cemented carbide or binder alloy fills the spaces with a size of 1-100 microns formed between the interfacial crystals of cubic boron nitride, such that the mass of cubic boron nitride is bonded and locked to the carbide mass. Composite body according to any one of the preceding claims, characterized in that the mass of cubic boron nitride 35 comprises a metal phase containing aluminum atoms and atoms of at least one alloying element consisting of one or more of the metals nickel, cobalt, manganese, iron, vanadium or chromium, the total amount of aluminum and alloying element exceeding 1% by weight of the amount of cubic boron nitride. DK 155659 B Composite body according to any one of the preceding claims, characterized in that the separate crystals of cubic boron nitride have a larger dimension of less than approx. 30 ml crown and preferably less than approx. 10 microns. 5 Composite body according to any one of the preceding claims, characterized in that the mass of cubic boron nitride crystals has a thickness of approx. 1.5 mm or less. Composite body according to any one of claims 1-5 or 7, characterized in that the concentration of cubic boron nitride crystals in the mass of cubic boron nitride exceeds approx. 90% by volume and preferably at least about 99% by volume. Composite body according to any one of the preceding claims, characterized in that the carbide mass is based on tungsten carbide and cobalt. A method of making a cementitious composite body according to any one of the preceding claims, characterized in that (a) a separate amount of sinterable cemented carbide powder comprising a binder metal and a cemented carbide is placed in a container. carbide or a sintered cemented carbide mass of cobalt, nickel or iron-bound tungsten, tantalum or titanium carbide and a separate amount of cubic boron nitride crystals or a polycrystalline mass of cubic boron nitride crystals, which in a subsequent pressure sintering step forms a separate mass comprising at least 70% by volume of cubic boron nitride; 30 (b) subjecting the container and its contents simultaneously to a temperature of 1300-1600 ° C and a pressure exceeding approx. (C) stopping the supply of heat to the container, (d) abolishing the pressure exerted on the container, and 35 (e) removing the cemented carbide composite. Process according to claim 10, characterized in that the mass of cubic boron nitride crystals comprises a metal phase containing aluminum atoms and atoms of at least one alloy of nickel, cobalt, manganese, iron, vanadium or chromium, wherein the total amount of aluminum and alloying element exceeds 1% by weight of the amount of cubic boron nitride. Process according to claim 10 or 11, characterized in that the crystals of cubic boron nitride are arranged as a layer on at least one side of the body of cemented carbide or sinterable powder of binder metal and cemented carbide, which layer has a thickness of 1.5 mm or less. 10 Process according to claim 11, characterized in that the material used as a source of an alloy of aluminum is present as a powder or in the form of plates, including an aluminum plate. 15 Process according to any one of claims 10-13, characterized in that the mass of cubic boron nitride also comprises diamond particles and / or a carbide carbide. Process according to any one of claims 10-14, characterized in that the cemented carbide mass is based on wool carbide and cobalt. 30 35