DE2805460C2 - - Google Patents

Description

The invention relates to a cutting insert made of abrasive particles like diamond and cubic boron nitride for assembly cutting tool.

It has been found that according to the teaching of US-PS 37 45 623 and US-PS 36 09 818 manufactured Diamond body is only of limited use because of it damaged at temperatures above about 700 ° C. Similarly, it has been found that an after the teaching of US-PS 37 67 371 and US-PS 37 43 489 body made of cubic boron nitride even limited is operational because it is also at temperatures thermally degraded above about 700 ° C. The The use of such bodies is therefore not possible there. where (1) for attaching the body to a pad Brazing is required, its melting point close or is above the temperature at which the body is thermally is broken down, or where (2) embedding the body into a high melting point, wear resistant Matrix is required, for example in the case of a drill bit used for drilling rock Case is, the surface of which is usually with cutting inserts is populated.

In the introduction to US Pat. No. 3,141,746, it is assumed that the earlier manufactured tool parts because the premature wear of the metal matrix and with it associated diamond crystal loss not the necessary Had wear resistance. For this reason, is there have been proposed to keep tool parts with a minimum of  to manufacture a metal matrix. It is corresponding largely a direct diamond Diamond bond has been achieved.

The US-PS 32 03 775 proposes that the metallic bonded diamond tools because of the metallic Binder greasing caused by interruption to avoid the continuity of the metallic bond. This is done by using pores a pore-forming material, such as Sodium pyrophosphate. This document deals with however not by providing one in the High temperature / high pressure technology can be used Cutting insert.

DE-PS 21 17 056 describes cutting inserts for Cutting tools for machining with a base and a bonded diamond crystals contained diamond part of a diamond concentration of at least 50% by volume, the high-strength Diamond part a diamond concentration of 90 to 99 vol .-% and the base is made of carbide sinter powder or preformed cemented carbide with 87 to 97% carbide and 3 to 13% cobalt, by volume considerably larger rigid sintered carbide base is and both components to a monolithic Composite bodies are united. This cutting insert has a high strength, so that also particularly tough and hard materials are processed can. However, this material is not suitable for Applications in high temperature technology.

The object of the invention is a temperature-resistant one Creating cutting insert.

This task is solved by a cutting insert for cutting tools, which are 70 to 95 vol .-% self-bonded particles of diamond or cubic Boron nitride and a metallic phase contains a sintering aid for the particle mass, the cutting insert being a network of one another has associated empty pores in the cutting insert dispersed and distributed by the particles and the metallic phase are defined, the pore fraction 5 up to 30 vol .-% of the cutting insert and the proportion of metallic phase 0.05 to 3 vol .-% of the cutting insert is.

The essentially from self-bonded abrasive particles existing and a network of each other related dispersed distributed pores containing insert is made by a mass of abrasive particles into a self-bound Body using a sintering aid immediately at high pressures and temperatures be connected to each other. The one under the influence the high pressures and temperatures formed bodies contains self-bound, d. H. immediately with each other connected particles and is with the sintering aid material, for example cobalt, cobalt alloys or an alloy of aluminum with nickel, manganese, Iron, vanadium or chrome as an alloy metal enforced. The sintering aid material is then removed for example by immersing the body in an acid such as nitric acid, hydrochloric acid, aqua regia and / or hydrofluoric acids. It turned out  that one can remove by essentially of the entire sintering aid material an abrasive particle body receives a much improved Resistance to thermal decomposition has high temperatures.

A further embodiment designed as a laminate, which are similar to those above first embodiment explained can consist essentially of a layer self-bonded abrasive particles and one to them Layer-bound base made of preferably cemented carbide.

The invention will now be explained in more detail with reference to the drawing, which is a micrograph of an area of a ground surface of a manufactured according to the invention Diamond body shows.

The grinding surface shown in the drawing relates Although referring to a diamond body, it can as well as explaining the alternative embodiments the invention are used in which the abrasive particles made of cubic boron nitride (CBN) exist.

The body shown in the drawing contains diamond particles 11 , which make up between 70 and 95 vol .-% of the body. Particles here mean a single crystallite or a fraction of a crystallite. At the interfaces 13 , the self-bonding of adjacent particles 11 can be seen, ie diamond-diamond bonding between adjacent particles 11 . The diamond crystals 11 lying in the cut surface shown in the drawing are also bound in the third dimension to adjacent diamond crystals (not visible). The body is penetrated essentially uniformly by a metallic phase made of sintering auxiliary metal (not shown in the drawing). The metallic phase is believed to be encapsulated in sealed areas formed by adjacent diamond particles. The metallic phase comprises between approximately 0.05 and 3% by volume of the body. A network of interconnected empty pores 15 is dispersed over the entire body and is defined by the diamond particles 11 and the metallic phase (not shown). The pores 15 make up between 5 and 30% by volume of the body.

According to one embodiment, the cutting insert is made only from self-bound particles. According to one another embodiment, it is bound to a base (not shown), which preferably consists of Tungsten carbide cobalt cemented carbide.

The diamond particles 11 expediently have a particle size in the range from 1-1000 micrometers. For particles made from cubic boron nitride, a particle size in the range between 1-300 micrometers is expedient.

A preferred method of manufacturing a tool part according to the invention includes the following Process steps:

• a) In a reaction vessel or a loading chamber is a Mass of diamond particles or CBN particles and a mass of given a material that sinters together from the diamond particles or CBN particles existing mass or favored,
• b) the reaction vessel and its contents simultaneously become temperatures exposed in the range of 1200-2000 ° C and pressures over 40 kb,
• c) the heat supply to the reaction vessel is switched off,
• d) the pressure on the reaction vessel is removed,
• e) from the reaction vessel through the process steps a) -d) removes the abrasive body formed, which consists of self-bound, d. H. directly bound particles and a metallic one Phase exists that of the penetrated into the abrasive body Sintering aid material is formed, and
• f) the penetrated metallic phase is in essentially completely removed so that the remaining in the body metallic phase only about 0.05 to about 3% by volume of the body.

The expression "simultaneously" used in process step b) means that the action of high pressures and high temperatures takes place at the same time, but this does not require that the exposure to high pressure and high temperature starts or ends at the same time, although it may be possible can.

The term "sintering aid material" used here denotes a Material that acts as a catalyst for diamond and / or sintering favored by CBN. It is not known how (catalytically  or in another way) the sintering aids the self-binding of Promote or promote CBN (CBN-CBN binding).

Preferred embodiments of the above-mentioned method steps a) to e) for the production of a diamond body Diamond particles are in U.S. Patent No. 37 45 623 and U.S. Patent No. 36 09 818 explained in more detail.

Diamond bodies are according to these patents under the Exposure to high pressures and high temperatures, where the hot, compressed diamond particles with be infiltrated with a catalyst material that is axial or radial penetrates and penetrates the mass of diamond particles. While this penetration and infiltration process is catalyzed Sintering of the diamond particles takes place, which leads to an extensive diamond Diamond bond leads. Used as catalyst material one of those already in US-PS 29 47 609 and US-PS 29 47 610 described materials, namely (1) a catalyst metal in elemental form from the metals of group VIII of the periodic system, including chrome, manganese and tantalum Group, (2) a mixture of one or more alloyable Catalyst metals and one or more alloyable non-catalyst metals, (3) an alloy of at least two catalyst metals or (4) an alloy of one or more Catalyst metals and one or more non-catalyst metals. Cobalt in is preferably used as the catalyst elementary form or in the form of an alloy. The catalyst material forms a metallic phase in the under the action abrasive bodies formed by high pressures and high temperatures, as has already been mentioned in process step e).  

Preferred embodiments of process steps a) to e) for Production of a tool part from CBN particles are in the US Patent 37 67 371 explained. According to Example 1 of US Pat. No. 3,767,371 become CBN bodies under high pressures and high temperatures generated by an infiltration process in which CBN particles with a molten sintering aid material (cobalt metal) that are washed axially through the CBN particles becomes. During this infiltration or flooding process there is a sintering of the CBN particles, which leads to an expanded CBN-CBN binding leads. Other suitable as sintering aids for CBN Materials are alloys made of aluminum and an alloy component from the nickel, cobalt, manganese, iron, vanadium and chromium-containing group, as in U.S. Patent No. 37 43 489 in column 3, lines 6-20. Cobalt and cobalt alloys are preferred. The sintering aid material forms the at Explanation of process step e) addressed metallic Phase.

In one embodiment of the invention, in which the method steps a) to e) according to US-PS 37 45 623, US-PS 37 67 371 and US Pat. No. 3,743,489 are carried out, a composite body is obtained, by using an abrasive particle layer (made of diamond or CBN) binds in situ on a sintered carbide base. The source of the auxiliary sintering material is preferably used the one intended to form the cemented carbide base Material (either in the form of a powder mixture or a preformed Body). For more details on the document is referred to US-PS 37 45 623, in particular Column 5, line 58 to column 6, line 8 and column 8, line 57 to column 9, line 9.  

In another embodiment of the invention, one is obtained Body of essentially self-bonded abrasive particles. At In this embodiment, the process steps a) to e) in performed in the same manner as explained above, except that that to form the cemented carbide base for the abrasive particle layer provided material in the form of a powder mixture or a preformed body is preferably omitted. In this case, the sintering aid material is added separately, for example in the manner described in US-PS 36 09 818. Of course, a body can be removed after removing the metallic Phase (process step f) by brazing on a base Cemented carbide or other material to be attached a body or insert for equipping a tool create.

According to the invention, the metallic phase is removed from the body Acid treatment, extraction with liquid zinc, electrolytic removal or similar procedures removed so that a body essentially 100% abrasive particles in self-bound form remains. The remaining body contains essentially none or hardly any metallic phase. With the previously known Bodies with a metallic phase can have insufficient temperature resistance can be explained theoretically by the fact that the metallic Phase the conversion of the direct bonds between catalyzes the abrasive particles and / or the direct bond between the particles due to the thermal expansion of the metallic phase breaks. It turned out that the body according to of the invention, which is essentially free of metallic phase is able to withstand temperatures up to 1200-1300 ° C without a noticeable thermal damage occurs.  

The invention will now be explained in more detail using exemplary embodiments.

Example 1

Disc-shaped diamond bodies were produced by (1) a 1.4 mm thick layer of fine diamond particles with a particle size of less than 8 micrometers and a disc with a thickness of 3.2 mm and a diameter of 8.8 mm made of cemented carbide (13 wt .-% Co, 87 wt .-% WC) were arranged within a zirconium container with a thickness of 0.05 mm, (2) several of these containers were stacked on top of one another in a reaction vessel of the type shown in FIG. 1 of US Pat. No. 3,745,623 (3) the reaction vessel feed was subjected to a pressure of about 65 kb and a temperature of about 1400 ° C for 15 minutes, (4) the temperature was slowly reduced first and then the pressure was reduced, and ( 5 ) the samples were taken from the Reaction vessel were ground, resulting in bodies that had a 0.5 mm thick diamond layer that was bonded to a 2.7 mm thick cemented carbide layer. The sintered hard metal layer was then removed from each body by surface grinding.

As indicated in Table I, half of the samples became one Subjected to leaching treatment in hot concentrated acids, around the metallic phase and other soluble non-diamond substances to remove. To remove the infiltrated material two different treatment methods were used. From a first group comprising samples A-1 to A-4 samples A-3 and A-4 only with a hot mixture of acids concentrated nitric acid and concentrated hydrofluoric acid in a ratio of 1: 1  treated. In a second, samples B-1 to B-4 group, samples B-3 and B-4 were hot Aqua regia (concentrated hydrochloric acid and concentrated sulfuric acid treated in a ratio of 3: 1). It turned out that leaching considerably when using aqua regia was done faster. Samples A-3 and A-4 were 8 to 12 days long leached, while samples B-3 and B-4 between 3 and Were drained for 6 days. In both cases changed the dimensions of the samples during acid treatment and no elimination of diamond was found. Since diamond is not dissolved by acids, they are with the Acid treatment occurring weight loss on removal attributed to the metallic phase.

Before leaching, the proportion of those present in the samples metallic phase with approximately 8.1 vol.% or 19.8 wt.% calculated (based on density measurements of the samples before leaching and the raw materials used in the manufacture). After leaching, about 0.5% by volume remains or 0.2 wt% metallic phase. The distance from to 90% by weight of the metallic phase (sample B-4) also indicates this indicates that the metallic phase is mainly in a coherent Pore network is located. When checking a fracture surface a leached sample with a scanning electron microscope showed that the pore network spanned the entire diamond layer runs. The pores are distributed over the entire diamond layer and most pores are less than one in diameter Micrometer. This suggests that the acid covers the entire diamond layer permeated and a substantially uniform Removal of the metallic phase from the diamond layer causes Has.  

As indicated in Table I, the bending strength (fracture deflection) and the elastic modulus of the diamond layers were measured. The strength test was carried out with a three-point load device performed on the two steel rollers a pad were arranged while a third steel roller in the middle above the two steel rollers parallel to the axis was provided. The samples were centered over the lower rolls and burdened to break. The elongation of the samples was measured parallel to the tensile stress using strain gauges, connected to a strain gauge. The Samples A-1 to A-4 were prepared for the strength test, by coating their surfaces with a diamond disc (diamond particles with a particle size of 177-250 microns) were. Samples B-1 through B-4 were prepared for the Strength test on a lapping machine using Processed diamond lapping powder with a particle size of 15 micrometers, in order to achieve a better surface quality than this with samples A-1 to A-4 was possible by grinding. It is believed, that the better polished surfaces of those with diamond powder lapped samples give higher strength values because the Surface has a higher quality, d. H. fewer mistakes like cracks or the like, where it is under load for Stress concentration comes. It can be assumed that the leached samples (A-3, A-4, B-3, B-4) measured lower Bending strength values attributable to such surface defects are.  

Table I

In contrast to the bending strength values, when measuring the Elastic modulus E (Table I) has no influence on the porosity, since the Modulus of elasticity is a measure of the internal strength and rigidity of the Material and does not depend on the formation of microcracks. To Removed the infiltrated metallic phase from the samples the modulus of elasticity is only about 12%. That difference is due to the porosity of the leached samples, since the following applies to the modulus of elasticity E:

in the
E = modulus of elasticity
M = moment
C = distance to the outer fiber
I = moment of inertia of the surface

and M · C do not change while I has decreased because the effective area has decreased in proportion to the porosity. If therefore it is assumed that the pores have the shape of spheres and distributed randomly applies

in which x = the proportion the porosity, so that the modulus of elasticity must be greater than the measured value of E. For the leached samples B-3 and B-4 became an elastic modulus of 79 × 10³ kg / mm² on average measured so that taking into account the porosity correction the modulus of elasticity amounts to 85 × 10³ kg / mm², which is only 5% lower than that measured on samples B-1 and B-2 Average value of 90 × 10³ kg / mm².

The removal of the infiltrated metallic phase therefore has one very little influence on the modulus of elasticity, from which it follows that the strength of the diamond layer almost exclusively on the diamond Diamond bond is due.

The modulus of elasticity of 90 × 10³ kg / mm² is only 10% lower than the average value of 100 × 10³ kg / mm², which results from the elastic constants of a diamond single crystal.

Example 2

A diamond body was made according to that in Example 1 for the Samples A-1 through A-4 are prepared in the manner described, only instead of diamond particles with a particle size below 8 microns a mixture of diamond particles of equal proportions of Diamond particles with a particle size of 149 to 177 microns and diamond particles with a particle size of 105 to 125 microns were used.  

The composition of the body before leaching is calculated 89.1% by weight of diamond (96.5% by volume) and 11.9% by weight metallic phase (4.5 volume percent). After leaching had the body has a 11.5% lower total weight, so that only 0.15 wt .-% of the metallic phase (0.06 volume percent) in Body remain.

Example 3

Four diamond bodies were produced in accordance with Example 1. The cemented carbide was ground from every body. At the infiltrated metallic phase became two bodies by leaching in hot acid mixtures of 1 HF: 1 HNO₃ and 3 HCl: 1 HNO₃ away. All bodies were epoxy resin onto a round tungsten carbide cemented carbide disc with a diameter of 0.89 cm glued. The composite body thus formed was on attached to a tool holder of a lathe and for wear resistance checked when turning. A quartz sand was used as the workpiece used as a filler-containing rubber stick. The following were Test conditions applied: surface speed 107-168 m / min (the maximum range within one of the same heat treatment exposed group was 24 m / min), cutting depth 0.76 mm, cross feed 0.13 mm / per revolution, and test time 60 minutes. To In the test, the samples were placed in a heating tube under a dry Argon gas stream heat treated. The treatment temperatures ranged from 700-1300 ° C with intervals of 100 ° C. The heat treatment time was 10 minutes at each treatment temperature. After each heat treatment, the samples were scanned with a Electron microscope examined for damage and then with exception of the wear test samples treated at 1000, 1100 and 1300 ° C subject. After both the top and the  lower edges were used as cutting edges the edges reground.

The results of the wear test are shown in Table II. The samples showed a fair level during the wear test consistent behavior. It turned out that the 700 ° C for the first time heat-treated samples compared to the still non heat-treated samples have a lower wear resistance exhibit. Samples 3 and 4 that were not leached showed no changes in terms of wear resistance until between 800 and 900 ° C failed due to thermal damage. It turned out that the wear resistance was independent as long from the heat treatment until the diamond phase is the encapsulated can no longer enclose metallic phase and cracking occurs. This behavior also indicates existence from two different phases, namely the bound Diamond phase, which takes care of the chip removal during the test, and the metallic phase, which is a leftover from the sintering process is. Leached Samples 1 and 2 withstood Very good heat treatment, even at 1200 ° C. At 1200 ° C the tendency to slight damage to the sample, suggesting it indicates that thermal re-conversion begins on the surface.  

Table II

The test results listed in Table II are by the time per wear unit, being one wear unit Corresponds to 0.25 mm. The tool wear was measured the width of the wear mark determined on the with the Cutting insert engaged in workpiece was created. The determined Data is only in terms of relative behavior the leached and unleached samples matter.

The leached samples gave on average a higher test value than the unleached samples. This can be attributed to this be that during the wear test the not leached Samples can be thermally damaged. Both during the wear tests as well as during the heat treatments same damage effect occur. So if that engages with tool tip at a high temperature is heated, the cobalt phase expands more than the diamond phase, whereby at the tool tip within the foremost particle layers  Cracks appear. The damaged tool tip will weakened as a result and is therefore no longer as efficient. The Leached samples are, however, up to a higher operating temperature thermally stable and therefore become when engaging with the workpiece not thermally damaged.

Examinations with a scanning electron microscope showed that unleached samples compared to leached samples showed different behavior. With samples that were not leached out, the metallic phase emerge from the surface between 700 and 800 ° C, as could be determined with a magnification of 2000 times. After the temperature was raised to 900 ° C the rounded edge running radially to the center of the sample Cracks found. The leached samples remained up to approximately 1300 ° C relatively unchanged. The diamond layers were still clean after heat treatment at 1200 ° C, but were after heat treatment at 1300 ° C with 20x magnification Photos out of focus and blurry and with 1000 times Enlarged photos showed an etched surface with many exposed crystals. This may be due to the thermal decomposition of the surface, but can also minor oxygen residues in the provided in the heat treatment furnace Argon atmosphere can be attributed.

Example 4

Two diamond bodies (samples IV-1 and IV-2) were made according to example 1 was produced, but the cemented carbide layer was not ground. Sample IV-1 was treated with epoxy resin (Epon 826 with methyl anhydride at the nodes and benzyldimethylamine hardener)  and the epoxy resin hardened. The surface of the diamond layer was then exposed by grinding the epoxy resin. The sample IV-1 was then set out in a boiling mixture for 37.15 hours 3 HCl: 1 HNO₃ kept. After removal from the acid mixture the embedding resin is removed from the cemented carbide layer. In the visual inspection showed signs of a minor reaction between the acid mixture and the unexposed surfaces. However, the surface of the carbide layer did not appear to be noticeably different from that Acid to have been attacked. The surface of the diamond layer was then used with a scanning electron microscope (up to 2000 times Magnification). The surface of the diamond layer had a look similar to the surface of the diamond layer of the leached Samples according to Example 1. Sample IV-1 then became one X-ray spectroscopic analysis to compare the intensities of the Components of the metallic phase with those of an unleached one Subjected to trial. The one with a scanning electron microscope performed as well as the radiographic examinations, that the acid penetrates the diamond layer and the removal a significant proportion of the metallic phase.

Samples IV-1 and IV-2 were then made in the same manner as in Example 3 explains tested for wear resistance. For the drained Sample IV-1 resulted in a calculated according to Example 3 Wear value of 120-150, while for the not leached Sample IV-2 a wear value of 100-120 was found. These test results, from which the superiority of the leached Sample can be seen, agree with those set forth in Example 3 Results agree and therefore prove that by removing the metallic phase in the area of the cutting edge Performance of the diamond body is achieved.

Claims (16)

1. Cutting insert for cutting tools, which consists of 70 to 95 vol .-% of self-bonded particles of diamond or cubic boron nitride and contains a metallic phase from a sintering aid for the particle mass, characterized in that the cutting insert is a network of interconnected empty pores has, which are dispersed in the cutting insert and are determined by the particles and the metallic phase, the pore fraction is 5 to 30 vol .-% of the cutting insert and the proportion of the metallic phase is 0.05 to 3 vol .-% of the cutting insert. 2. Cutting insert according to claim 1 with particles Diamond, characterized in that the metallic Phase from a catalyst metal in elementary form from which the metals of VIII. Group of the Periodic Table, Chromium, Manganese and tantalum group, or from a mixture of one or more alloyable catalyst metals and one or more alloyable Non-catalyst metals, or from a Alloy of at least two catalyst metals or an alloy of one or more Catalyst metals and one or more non-catalyst metals consists. 3. Cutting insert according to claim 1 or 2, characterized characterized in that the diamond particles have a Particle size in the range of approximately 1 to 1000 Have micrometers.   4. Cutting insert according to claim 1 with particles cubic boron nitride, characterized in that the cutting insert is essentially uniform penetrating metallic phase made of cobalt, a cobalt alloy or an alloy Aluminum with nickel, manganese, iron, vanadium or chromium as an alloying agent. 5. Cutting insert according to claim 1 and 4, characterized characterized in that the particle size in the range between Have 1 to 300 microns. 6. Cutting insert according to claims 1 to 5, characterized characterized that the flexural strength of the cutting insert at least 35 kg / mm² is. 7. Cutting insert according to claims 1 to 6, characterized characterized in that the elastic modulus of the Cutting insert at least 50,000 kg / mm² is. 8. Cutting insert according to claims 1 to 7, characterized characterized that the self-bound Particles on a sintered carbide base are bound. 9. A method of manufacturing a cutting insert according to claims 1 to 8, in which

• a) a mass of diamond particles or particles consisting of cubic boron nitride and a mass of sintering aids for the respective particle mass is placed in a reaction vessel,
• b) the reaction vessel and its contents are simultaneously exposed to temperatures in the range from 1200-2000 ° C. and pressures of over 40 kb,
• c) the heat supply to the reaction vessel is turned off, and
• d) the body formed by process steps a) -c) is removed from the reaction vessel and consists of the directly bonded particles and the sintering aid located between the particles,

characterized in that brought into the body Sintering aids essentially complete is removed so that the remaining in the body Share of this sintering aid only about 0.05 to about 3 percent by volume of the Body. 10. The method according to claim 9 with particles of diamond, characterized in that as a sintering aid a catalyst metal in elemental form from which the metals of the VIII. group of the periodic Systems, including chrome, manganese and tantalum Group, or a mixture of one or several alloyable catalyst metals and one of the several alloyable non-catalyst metals, or an alloy of at least two catalyst metals or an alloy of one or more Catalyst metals and one or more non-catalyst metals is used. 11. The method according to claim 9 with particles of cubic Boron nitride, characterized in that as sintering aid cobalt, or a cobalt alloy or an alloy of aluminum with  one made of nickel, manganese, iron, vanadium or Chromium existing alloy metal used will. 12. The method according to claims 9 to 11, characterized characterized that the metal from the body removed by immersing the body in an acid becomes. 13. The method according to claim 12, characterized in that that as acid aqua regia, nitric acid, hydrochloric acid and / or hydrofluoric acid used becomes. 14. The method according to claims 9 to 11, characterized characterized that the metal from the body removed by extraction with liquid zinc becomes. 15. The method according to claims 9 to 11, characterized characterized in that the metal from the body by means of Electrolysis is released.