DIAMOND-COATED MACHINING TOOL AND METHOD FOR PRODUCTION THEREOF

Abstract

A machining tool comprising at least one diamond-coated functional region having a substrate surface composed of a hard metal or a ceramic material arranged beneath the diamond layer. The substrate surface contains hard material particles on the basis of carbide and/or nitride and/or oxide, which are embedded in a cobalt-containing binding matrix. The diamond layer is directly arranged on the substrate surface without cobalt having been removed by chemical or physical methods in substantial amounts out of the binding matrix of the substrate surface. Such a tool is produced by pre-treating a hard metal substrate surface with a positively charged ion beam, followed by conventional CVD-diamond coating directly onto the ion beam-pre-treated cobalt-containing substrate surface. The ion-underlying atoms thereby largely remain in the substrate. The tools according to the invention have good diamond layer bonding to the substrate and a high wear resistance.

Claims

1. A machining tool having at least one diamond-coated functional region with a substrate surface made of a hard metal or a ceramic material lying under the diamond layer, wherein the substrate surface contains hard material particles on a carbide and/or nitride and/or oxide basis which are embedded into a cobalt-containing binding matrix, and wherein the diamond coating is arranged directly on the substrate surface, without cobalt having been removed in substantial quantities from the binding matrix of the substrate surface by chemical or physical methods.

2. The tool according to claim 1, wherein the tool is configured as a rotating or stationary tool.

3. The tool according to claim 1, wherein the tool is monolithic.

4. The tool according to claim 1, wherein at least one cutting body is provided on a carrier body and/or at least one guide rail is provided, wherein the cutting body or the guide rails is diamond-coated at least in a partial region.

5. The tool according to claim 1, wherein the hard material particles are chosen from the group consisting of carbides, carbon nitrides and nitrides of the metals in subgroup IV, V and VI of the periodic table of the elements and boron nitride, as well as oxidic hard materials including aluminum oxide and chromium oxide, titanium carbide, titanium nitride, titanium carbon nitride, vanadium carbide, niobum carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide and also mixtures and mixed phases thereof.

6. The tool according to claim 1, wherein the binding matrix comprises, apart from cobalt, aluminum, chromium, molybdenum and/or nickel.

7. The tool according to claim 1, wherein the ceramic material is a sintered material made of hard material particles selected from the group consisting of carbides, carbon nitrides and nitrides of the metals in subgroup IV, V and VI of the periodic table of the elements and boron nitride, as well as oxidic hard materials including aluminum oxide and chromium oxide, titanium carbide, titanium nitride, titanium carbon nitride, vanadium carbide, niobum carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide and also mixtures and mixed phases thereof, in a binding matrix that further comprises, apart from cobalt, aluminum, chromium, molybdenum and/or nickel.

8. The tool according to claim 7, wherein the ceramic material is a sintered carbide or carbon nitride hard metal.

9. The tool according to claim 1, wherein the diamond coating is polycrystalline and is applied by means of chemical vapor deposition (CVD).

10. The tool according to claim 1, wherein the diamond coating has a thickness of between 3 and 15 m.

11. A method of producing a diamond coating on a functional region of a machining tool, wherein the diamond coating is applied to a substrate surface made of a hard metal or a ceramic material, wherein the substrate surface contains hard material particles on a carbide and/or nitride and/or oxide basis which are embedded into a cobalt-containing binding matrix, and wherein the substrate surface is pretreated using a positively charged ion beam of at least one ion species, wherein the atoms underlying the ion species substantially remain in the substrate and the diamond coating is applied by means of chemical vapor deposition (CVD) directly onto the ion beam-pretreated cobalt-containing substrate surface.

12. The method according to claim 11, wherein the ion species comprises at least one of lithium, boron, carbon, silicon, nitrogen, phosphorous and oxygen.

13. The method according to claim 12, wherein an ion beam with a kinetic energy of 3.210.sup.15 J to 3.210.sup.14 J [20 KeV to 200 KeV] is used.

14. The method according to claim 11, wherein the pretreatment of the substrate surface is carried out by means of ion beams in the vacuum between 20 C. and 450 C.

15. The method according to claim 11, wherein the carbon source for the CVD diamond coating is methane, wherein hydrogen is mixed into the methane in the molar surplus.

16. The tool according to claim 15, wherein following the ion beam pretreatment of the substrate surface, diamond nano-crystals are applied by means of ultrasound to the substrate surface for seeding for the following CVD diamond coating.

17. A machining tool having at least one diamond-coated functional region, wherein the diamond coating of the functional region following the method according to claim 11 can be obtained.

18. The tool according to claim 17, wherein the tool is configured as a rotating or stationary tool.

19. The tool according to claim 17, wherein the tool is monolithic.

20. The tool according to claim 18, wherein at least one cutting body is provided on a carrier body and/or at least one guide rail is provided, wherein the cutting body or the guide rails is diamond-coated at least in a partial region.

21. The tool according to claim 17, wherein the diamond coating is applied to a substrate surface made of a hard metal or a ceramic material, wherein the substrate surface contains hard material particles on a carbide and/or nitride and/or oxide basis which are embedded into a cobalt-containing binding matrix.

22. The tool according to claim 17, wherein the hard material particles are chosen from the group consisting of carbides, carbon nitrides and nitrides of the metals in subgroup IV, V and VI of the periodic table of the elements and boron nitride, as well as aluminum oxide and, chromium oxide, titanium carbide, titanium nitride, titanium carbon nitride, vanadium carbide, niobum carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide and also mixtures and mixed phases thereof.

23. The tool according to claim 17, wherein the binding matrix further comprises, apart from cobalt, aluminum, chromium, molybdenum and/or nickel.

24. The tool according to claim 17, wherein the ceramic material is a sintered material made of hard material particles selected from the group consisting of carbides, carbon nitrides and nitrides of the metals in subgroup IV, V and VI of the periodic table of the elements and boron nitride, as well as aluminum oxide, chromium oxide, titanium carbide, titanium nitride, titanium carbon nitride, vanadium carbide, niobum carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide and also mixtures and mixed phases thereof, in a binding matrix that further comprises, apart from cobalt, aluminum, chromium, molybdenum and/or nickel.

25. The tool according to claim 24, wherein the ceramic material is a sintered carbide or carbon nitride hard metal.

26. The tool according to claim 17, wherein the diamond coating is polycrystalline and can be applied by means of chemical vapor deposition (CVD), wherein the diamond layer has a thickness of between 3 and 15 m.

Description

[0048] In particular, the present invention relates to a machining tool having at least one diamond-coated functional region with a substrate surface made of a hard metal or a ceramic material lying under the diamond layer, wherein the substrate surface contains hard material particles on a carbide and/or nitride and/or oxide basis which are embedded into a cobalt-containing binding matrix, wherein the diamond coating is arranged directly on the substrate surface, without cobalt having been removed in substantial quantities from the binding matrix of the substrate surface by means of chemical or physical methods.

[0049] The present invention further relates to a method of producing a diamond coating on a functional region of a machining tool, wherein the diamond coating is applied to a substrate surface made of a hard metal or a ceramic material, wherein the substrate surface contains hard material particles on a carbide and/or nitride and/or oxide basis which are embedded into a cobalt-containing binding matrix, wherein the substrate surface is pretreated using a positively charged ion beam of at least one ion species, wherein the atoms underlying the ion species substantially remain in the substrate and the diamond coating is applied by means of chemical vapour deposition (CVD) directly onto the ion beam-pretreated cobalt-containing substrate surface.

[0050] The pretreatment of the substrate surface of a functional region of a tool which contains hard material particles, e.g. WC grains, which are embedded in a cobalt-containing binding matrix, by means of ion beams, e.g. N.sup.+, N.sup.++ and/or C.sup.+ means that substantially no cobalt is removed from the binding matrix, but the radiated ions are incorporated into the structure of the binding matrix.

[0051] Without being bound to it, cobalt could, for example, be converted by the radiated light ions into cobalt nitrides or cobalt carbon nitrides or also cobalt carbides which do not exhibit the catalytic action for conversion of the cubic diamond phase into the hexagonal graphite phase, so that the cubic diamond crystals have sufficient time to grow on the substrate surface, without an in-situ reconversion into graphite taking place.

[0052] Diamond-coated functional regions of this kind which can be produced using the method according to the invention have, surprisingly, proved substantially more stable in the long term in the case of machining tools than diamond layers which have been applied to cobalt-depleted substrate surfaces by means of CVD. In the practical test, improved layer adhesion of the diamond coating compared with the standard process of the prior art could be achieved.

[0053] This is even more surprising, since the teaching according to the invention practically suggests the opposite of the measures propagated in the prior art, namely instead of the conservative teaching of depleting the binding matrix of cobalt, it is essential for the present invention to retain practically the entire Co content in the binding matrix and to change the structure by means of an ion beam in such a manner that the Co atoms no longer affect the diamond deposition during a CVD process.

[0054] Although in the prior art in U.S. Pat. No. 5,082,359 ion beams were already used in the form of a focused ion beam of Ga.sup.+ for substrate treatment prior to CVD diamond deposition, only heavy Ga.sup.+ cations were used in that case whichfollowing collision with the Co atoms of the binding matrixforce the Co atoms out of the metal lattice of the binding matrix, so that the binding matrix is heavily cobalt-depleted. Hence the use of heavy Ga.sup.+ ion beams can be introduced seamlessly into the cobalt depletion teaching and only represents an alternative to the prior-art chemical etching method described above and therefore a massive removal of Co atoms from the binding matrix.

[0055] Unlike the use of ion beams with heavy ion species in the prior art, the cobalt remains during radiation of the substrate surface according to the invention with the substantially lighter ion species N.sup.+, N.sup.++ and/or C.sup.+ substantially in the binding matrix and consequently leads to substantially better adhering diamond coatings than in the prior art. Moreover, the embedding of the hard material particles, such as WC in the binding matrix, for example, and therefore the integrity of the hard material particle cobalt phase is practically unaffected, as a result of which it retains its advantageous properties for machining tools and does not become brittle, for example.

[0056] A preferred embodiment of the present invention is a machining tool with at least one diamond-coated functional region, in which the diamond coating of the functional region can be obtained according to the method in the invention.

[0057] The machining tools according to the invention can be used for all purposes in which the use of an at least partially diamond-coated tool is technical feasible, in order to machine either particularly abrasive materialse.g. CFK materialsor to achieve long tool lives in the production of machine components, or both. In particular, the tools may be configured as a rotating or stationary tool, in particular as a drilling, milling, countersinking, turning, tapping, contouring or reaming tool.

[0058] The tools may be tools of monolithic or modular design.

[0059] An advantageous tool is one in which at least one cutting body, in particular a cutting plate, preferably an interchangeable or reversible plate, is provided on a carrier body and/or at least one guide rail, in particular a supporting strip, is provided, wherein the cutting body or the guide rails is diamond-coated at least in a partial region.

[0060] The tools in the present invention contain hard material particles which are chosen from the group comprising: carbides, carbon nitrides and nitrides of the metals in subgroup IV, V and VI of the periodic table of the elements and boron nitride, in particular cubic boron nitride; as well as oxidic hard materials, in particular aluminium oxide and chromium oxide; and also in particular titanium carbide, titanium nitride, titanium carbonitride, vanadium carbide, niobum carbide, tantal carbide, chromium carbide, molybdenum carbide, tungsten carbide and also mixtures and mixed phases thereof.

[0061] The binding matrix for the hard material particles may additionally contain, apart from cobalt, aluminium, molybdenum and/or nickel.

[0062] A preferred tool with functional regions or monoliths made of ceramic material is one in which the ceramic material is a sintered material made of the aforementioned hard material particles in a binding matrix which, apart from cobalt, additionally contains aluminium, chromium, molybdenum and/or nickel.

[0063] As a ceramic material, an advantageous tool is a sintered carbide or carbon nitride hard metal.

[0064] Typically, the diamond coating of the machining tools is polycrystalline and is applied by means of chemical vapour deposition (CVD).

[0065] CVD diamond deposition methods of this kind have probably been known to the person skilled in the art since 1982 (cf. MATSUMOTO, S, SATO, Y, KAMO M, & SETAKA, N (1982): Jpn J Appl Phys; 21 (4), L183-185: Vapor deposition of diamond particles from methane). In relation to the diamond coating of hard metal substrates by means of CVD methods, reference is made, for example, to the aforementioned review article by HAUBNER et al.

[0066] Typical layer thicknesses for the diamond coating on the tool surfaces lie in the range of 3 to 15 m, in particular of 6 to 12 m.

[0067] The ion beam used for the method according to the invention is produced by means of a standard ion beam generator, wherein the following ion species can be used: lithium, boron, carbon, silicon, nitrogen, phosphorous and/or oxygen, wherein nitrogen, in particular N.sup.+ and N.sup.++ and/or carbon, in particular C.sup.+, are preferred.

[0068] Experiments have revealed that an ion beam with a kinetic energy of 3.210.sup.15 J to 3.210.sup.14 J [20 KeV to 200 KeV] is optimal for the deactivation of the catalytic effect of the cobalt in the binding matrix (in particular, inhibition of the conversion from diamond to graphite).

[0069] If the pretreatment of the substrate surface is carried out by means of ion beams in the vacuum between 20 C. and 450 C., in particular between 300 C. and 450 C., outstanding diamond adhesions to the substrate surface can be achieved.

[0070] Methane is used as the carbon source for the CVD diamond coating, wherein hydrogen is mixed into the methane in the molar surplus.

[0071] A particularly advantageous growth behaviour and adhesion of the diamond layer and also crystal size of the individual diamond crystals during the CVD deposition from methane/H.sub.2 can be achieved if, following the ion beam pretreatment of the substrate surface, diamond nano-crystals are applied by means of ultrasound to the substrate surface for seeding for the following CVD diamond coating.

[0072] In this way, particularly stable diamond layers are produced and the hard metal or cermet tools coated in this manner exhibit long tool lives during the series production of components machined with them.

[0073] Further advantages and features result based on the description of a specific exemplary embodiment.

EXAMPLE

[0074] Hard metal tools made of 10M % Co hard metal with an average WC grain size of 0.6 m (Ghring trade name DK460UF) were radiated for 3.5 hrs according to the invention using an ion current of nitrogen ions, wherein the ion current was produced with a voltage of 30 kV with 3 mA plasma current at a nitrogen pressure of 110.sup.5 mbar. A standard ion generator was used to produce the ion beam (Hardion iron generator from Quertech, Caen).

[0075] In this case, there is a temperature of approx. 400 C. on the tool. Following this, the tool was coated with diamond in a standard hot wire CVD unit (CemeCon CC800/5). An adhesive diamond layer 12 m thick grew in a coating time of 60 hrs.

[0076] The coating adhesion was tested using the conventional radiation wear test according to a CemeCon standard. This radiation wear test involves the layer being blasted using a corundum jet with an average grain size of approx. 13 m until the diamond layer being tested either blistered or is penetrated. If, after a blasting time of 2 minutes, no damage has occurred to the layer, the sample is classed as fatigue-tested without rupture. Good layer adhesion is assumed if the blasting time to failure is >30 secs. Of the tools treated according to the invention, 80% were fatigue-tested without rupture and no single result had a blasting time of under 110 secs, while the average life of conventionally prepared specimen tools was around 95 secs.