EP3596248A1

EP3596248A1 - Use of a diamond layer doped with foreign atoms to detect the degree of wear of an undoped diamond function layer of a tool

Info

Publication number: EP3596248A1
Application number: EP18710853.5A
Authority: EP
Inventors: Immo Garrn
Original assignee: Guehring KG
Current assignee: Guehring KG
Priority date: 2017-03-13
Filing date: 2018-03-12
Publication date: 2020-01-22
Also published as: US20200094364A1; DE102017204109A1; US10974360B2; WO2018166941A1; DE102017204109B4

Abstract

The present invention relates to the use of a first diamond layer which is made of polycrystalline diamonds and doped with foreign atoms, and which is arranged on a metal surface of a machining tool, to detect the degree of wear of an undoped polycrystalline second diamond layer, which is arranged on the doped diamond layer and forms a functional region of the machining tool, wherein at least one physical parameter is detected continuously or periodically during operation of the tool, and wherein a change in the parameter indicates the degree of wear of the undoped second diamond layer. As a result, the doped diamond layer forms a kind of "intelligent stop layer" for the tool because as a result of the change in the transition from the undoped to the doped layer, the conductivity of the system changes, for example, and this change can be used to form a stop signal for the machine drive before the tool and the machined workpiece are damaged.

Description

description

Use of a doped with foreign atoms diamond layer for detecting the degree of wear of an undoped diamond functional layer of a

tool

The present invention relates to the use of a doped with foreign atoms first diamond layer of polycrystalline diamond, which is arranged on a metal surface of a cutting tool, for detecting the degree of wear of an undoped polycrystalline second diamond layer, which is disposed on the doped diamond layer according to claim 1 and a method for continuous detection of the degree of wear of an undoped

A diamond layer forming a functional area of a cutting tool according to claim 14.

Tools for machining with a tool head, a tool shank and with a clamping section for receiving in one

Tool holder are known in a variety of forms from the prior art.

Such tools have in their cutting area on functional areas, which are adapted to the specific requirements of the materials to be processed.

The tools mentioned are, in particular, those which are designed as drilling, milling, countersinking, turning, threading, contouring or reaming tools which can have cutting bodies or guide strips as a functional area, the cutting bodies being used, for example, as alternating or indexable inserts may be formed and the guide rails may be formed, for example, as a support strips.

Typically, such tool heads on functional areas, which the tool has a high wear resistance in the machining of highly abrasive Materials such as Si-alloyed aluminum, for example AISi9Cu4Mg [AISi9], AISi17Cu4Mg [AISi17] or AlMgl SiCu + 20% SiC [AI-MMC] and glass and

carbon fiber reinforced plastics.

In DE 20 2005 021 817 U1 of the present applicant

Tool heads are described, which consist of a hard material with at least one functional layer comprising a superhard material such as cubic boron nitride (CBN) or polycrystalline diamond (PCD).

With such tools, long tool life and long tool life can be achieved at high cutting speeds in terms of mechanical or thermal requirements for drilling, milling or rubbing.

Methods for depositing a polycrystalline diamond layer on non-diamond substrates have also been known for a long time. For example, US 5,082,359 describes the deposition of a polycrystalline diamond layer by means of chemical vapor deposition (CVD) on metallic

Substrates.

In US 5,082,359, typical materials used in the semiconductor industry, such as germanium, silicon, gallium arsenide and polished monocrystalline silicon wafers, are cited as CVD substrates, and other useful substrates are titanium, molybdenum, nickel, copper, tungsten, tantalum, steel , Ceramics,

Silicon carbide, silicon nitride, silicon aluminum oxynitride, boron nitride, aluminum oxide, zinc sulfide, zinc selenide, tungsten carbide, graphite, quartz glass, glass and sapphire.

In addition, the CVD according to US 5,082,359 is performed by reacting methane and hydrogen in vacuo on a hot tungsten wire to deposit the carbon generated in the high vacuum on the substrate surface.

Furthermore, it is known for tools to provide functional surfaces with a diamond layer, also using a CVD process for diamond coating. Such a diamond coating process is described, for example, in WO 98/35071 A1. In particular, the deposition of a polycrystalline diamond layer on a cemented carbide substrate of tungsten carbide embedded in a cobalt matrix is described in WO 2004/031437 A1.

Typically, a hard metal includes sintered materials of hard material particles and bonding material, such as tungsten carbide grains, wherein the tungsten carbide grains form the hard materials and the cobalt-containing binder matrix acts as a binder to the WC grains and gives the layer the toughness required for the tool.

Diamond-coated carbide or cermet tools are effective

naturally positive for the wear protection of the tool as well as on its

Service life in continuous use.

However, the problem is always the good adhesion of the diamond coating on such a cemented carbide substrate, which is why it is known in the art

requires different pretreatment methods, all of which aim to produce cobalt from the binder matrix for the hard material particles, e.g. WC, because investigations have shown that cobalt, the diamond deposition by different influences, in particular by a kind of catalytic

Graphite transformation tendency, can disturb.

Furthermore, DE 10 2006 026 253 A1 states that the cobalt binder of the substrate is removed from the surface because it is harmful during the long process time and high temperatures in the CVD diamond coating

Interactions between the carbon that is to form the diamond layer and the cobalt comes, whereby cobalt prevents the diamond formation and instead leads to graphitic phases.

This effect of the cobalt-containing binder layer on the CVD diamond coating is also described in recent literature, for example in the review article by HAUBNER, R. and KALSS, W. (2010): Int. Journal of Refractory Metals & Hard Materials 28, 475-483: "Diamond deposition on hard metal substrates - Comparison of Substrate pre-treatments and industrial applications".

According to HAUBNER et al. For example, carbon can diffuse from the CVD diamond coating into the cobalt-containing binder matrix, forming cobalt droplets during diamond deposition from the gas phase, which deleteriously disrupt the substrate texture and cause some brittleness. In addition, according to HAUBNER et al. recognized that cobalt is a catalyst for diamond growth and its more or less spontaneous conversion into graphite.

Therefore, it is understandable that, for empirical reasons, it has been attempted in the art to remove cobalt from the binder matrix to reduce the influence of cobalt on diamond deposition.

However, it is common to all prior art processes that although removal of cobalt from the binder matrix leads to relatively good adhesion of the CVD diamond coating, the cobalt-depleted binding matrix for the hard material particles, in particular WC, is sensitively disturbed and, as a result, the

Embedding of the WC grains as hard material particles is no longer possible. As a result, the integrity and mechanical strength of the substrate surface can no longer be guaranteed, especially in the case of heavy loads as a tool. Therefore, microstructural disturbances occur in the substrate / diamond interphase, so that

Finally, the diamond layer can detach with parts of the substrate structure, so that such coated tools are unusable.

Here, the teaching of DE 10 2014 210 371 A1 of the applicant of the present invention, which relates to a cutting tool, having at least one diamond-coated functional area with a lying below the diamond layer substrate surface of a hard metal or a ceramic material, wherein the substrate surface hard material particles on carbide and / or nitride base and / or oxide base, which are embedded in a cobalt-containing binding matrix, wherein the

Diamond layer without cobalt in substantial amount from the binding matrix of Substrate surface to have removed by means of chemical or physical processes, is disposed directly on the substrate surface. Such a tool can according to the teaching of DE 10 2014 210 371 A1 by pretreatment of a

Carbide substrate surface can be prepared with a positively charged ion beam and a subsequent conventional CVD diamond coating directly on the ion beam pretreated cobalt-containing substrate surface. In this case, the atoms underlying the ions remain essentially in the substrate. The tools obtained in the prior art have a good diamond layer adhesion to the substrate and high wear resistance.

Having said that, polycrystalline diamond coated and in particular diamond CVD coated tools have become established in many industries by machining highly abrasive materials such as the above-mentioned Si-alloyed aluminum alloys as well as carbon fiber reinforced and glass fiber reinforced polymers and the like [ see. Fiona Sammler, Dissertation TU Berlin: Reports from the production technology center Berlin, "Increase the potential of use of CVD diamond coated

Tools ", Fraunhofer-Verlag, Stuttgart, 2015].

According to the above-mentioned thesis, the deposition of a CVD diamond layer on a tool surface as a substrate typically occurs at a coating pressure of 1 kPa to 100 hPa and coating temperatures between 800 ° C and 1100 ° C in a high carbonaceous atmosphere

Hydrogen concentration. The gas phase is activated by means of plasma or thermally. The starting materials for the coating are gaseous, for example in the form of methane (CH ₄ ) and / or acetylene (C2H2) and / or carbon dioxide (CO2) in admixture with hydrogen (H2). According to Sammler 2015, two parallel chemical processes are required to produce diamond by means of low-pressure synthesis. A hydrocarbon (or also CO2) is split by pyrolysis and the atomically present hydrogen under the reaction conditions reacts selectively with all carbon compounds except for the diamond modification of the carbon and thus suppresses graphitization. According to Sammler 2015, it is possible to differentiate between CVD thick film and CVD thin film depending on the desired application. For efficient production of CVD thick films, CVD processes with high deposition rates are primarily used to deposit layer thicknesses of up to 2 mm. These are separated from their substrate after deposition, brought into arbitrary shapes by laser cutting and soldered or glued as cutting inserts on tools.

While PCD and CVD thick film tools are more applicable to geometrically simple shapes such as e.g. Cutting inserts are limited, the deposition of thin diamond layers directly on a substrate body by means of CVD offers the possibility to coat geometrically complex tools directly. It can also be tools such. Drills, threading tools and end mills as well as cutting and micro tools as well as tools with large diameters can be coated. The layer thickness is in CVD thin films in the range of 1 μιτι to 500 μιτι, often between 1 μιτι and 40 μιτι.

According to Collector 2015, the most common diamond coating processes are the hot filament (CVD or HF-CVD) process

Microwave plasma [microwave plasma CVD, MWP-CVD] and the plasma jet process. The methods differ by the amount of activated species and thus by coating speed and coating quality,

coatable surface and geometry as well as scalability. In particular, the HF-CVD method offers, for example, in comparison to the plasma process, the greatest flexibility at lower coating temperatures and is therefore often used industrially for the direct diamond coating of tool surfaces. The wires - as already mentioned may be W-wires - can be adapted to the different geometries of the tools to be coated, as for the layer structure a certain distance from the hot wires must be maintained, which typically in the range of approx 5 mm to 30 mm. The substrates are thereby uniformly heated to temperatures of 500 ° C to 1 100 ° C. So it is possible to also undercuts and backs too

coat. The coating rates are typically between 0.1 μιτι / h and 3 μιτι / h in HF-CVD method (see Sammler 2015). However, since very hard materials - such as the diamond cutting materials addressed by the present invention - with corresponding industrial

Stress also subject to a more or less severe wear occurs at high operating speeds and long service life of the diamond-coated tools more often the problem that the diamond cutting wear after a period of time such that the diamond-coated tool seizes into the workpiece just worked, which destroys the tool by breakage and usually also destroys the machined workpiece and in the worst case also damages the machine driving the tool.

It therefore exists in the field of diamond-coated metal-cutting

Tools a need to timely recognize the problems described above and in particular the wear of a diamond layer in a functional area of a tool during tool operation and

To take countermeasures that prevent damage to the tool, the machined workpiece and the device driving the tool.

After a diamond coating has long proven in the prior art to increase the wear resistance especially in the machining of highly abrasive materials and the technologies are available for diamond coating in carbide tools, it is therefore the object of the present invention, cutting tools and a method for their Making it possible to provide the degree of wear of the

To continuously detect diamond coating of the functional area of a tool during operation in order to stop the tool early in order to avoid destruction of the same and / or of the workpiece being processed.

The solution of this object is achieved by a use with the features of claim 1.

In procedural terms, the above object is achieved by a method having the features of claim 14. In particular, the present invention relates to a use of a doped with foreign atoms first diamond layer of polycrystalline diamond, which is arranged on a metal surface of a cutting tool, for detecting the degree of wear of an undoped polycrystalline second

Diamond layer disposed on the doped diamond layer and forming a functional area of the cutting tool, wherein at least one physical parameter is detected continuously or periodically during operation of the tool, and wherein a change in the parameter indicates the degree of wear of the undoped second diamond layer.

The present invention further relates to a process for continuous

Detecting the degree of wear of an undoped diamond layer, which constitutes a functional area of a cutting tool, and which is disposed on a doped with foreign atoms diamond layer, during operation of the tool; wherein the doped diamond layer is directly on the substrate surface of the

is arranged cutting tool; at least one measurement parameter resulting from both diamond layers, the tool and a workpiece machined with the tool, is detected continuously or periodically during operation of the tool; setting a predefined threshold for the measurement parameter; and wherein a change of the measurement parameter is above or below the predefined ones

Threshold indicates the degree of wear of the undoped diamond layer.

The invention is based on the fact that doped with foreign atoms

Diamond layers - with more or less the same hardness - have different physical properties than undoped diamond layers. For example, the electrical conductivity of doped diamonds depends on the type of doping, ie with which Foreign atoms has been doped and / or whether an n- or p-type doping is present significantly higher at a given temperature than that of undoped diamonds. These act practically as an insulator and have no significant electrical conductivity.

In the simplest case one measures the electrical resistance or the electrical conductivity of an overall system comprising a metallic workpiece and the tool with the layer sequence:

Metallic substrate layer - doped diamond layer - undoped diamond layer continuously or periodically during operation, so when using an unused diamond-coated tool no significant electrical

Conductivity be measured, or the ohmic resistance is the values of a

Isolator and go towards infinity, since the undoped diamond layer of the functional range of the tool with the metallic workpiece, although mechanically in contact, but due to the insulating property of the undoped

Diamond layer does not form an electrical contact with the metallic workpiece.

If, however, during operation, the undoped diamond layer, which forms the functional area of the tool, wears or partially breaks off, gradually more and more doped diamond material with the metallic

Workpiece come into contact, which is due to the conductive or at least

Semiconducting property of the doped diamond material of the doped layer to a change in the electrical conductivity of the system and to a change in the

Ohm resistance of the system leads. This change may be detected and evaluated using a suitable control device well known to those skilled in the art. As soon as a predetermined threshold, which is to be determined by calibration in a customary manner, is exceeded or fallen below, the control device sends a stop command to the drive of the tool so that it comes to a standstill. This measure makes it possible for the tool to be replaced before the tool, workpiece and / or the tool-carrying machine are damaged. If necessary, of course, in a first step, first the cutting speed of the cutting tool can be throttled, for example, to complete the work process before the machine is then finally stopped and the tool must be replaced.

The invention thus makes itself next to the example described

Differences in the electrical properties between doped and undoped diamond layer also exploits the fact that both diamond layers have comparable hardnesses, so that when the typically thicker undoped diamond layer with the doped diamond layer is worn, the tool can still be worked to some extent, because the inventively

coated tools after erosion of the actual functional layer of undoped diamond "runflat" have, similar to those of modern tires, when the tire is damaged and still can be driven a certain distance.

In summary, it can be stated that the doping of diamond makes the non-electrically conductive diamond into a semiconductor which is orders of magnitude better electrically conductive.

A particular advantage is obtained if at least the undoped diamond layer was produced by a CVD method. Depending on the condition of the coating after wear and tear of the undoped diamond layer of the functional area of the tool, the tool, typically after cleaning, e.g. by

Sandblasting and / or plasma cleaning in a CVD chamber are re-coated with diamond so that no new (basic) tool needs to be made, which pays off particularly for complex and expensive tools.

For the purposes of the present invention, the term "doping" is understood to mean the deliberate introduction of impurities in the form of impurities into a diamond crystal lattice. The amount of impurities (dopant) introduced by means of doping is relatively small in comparison with the diamond material form so-called impurities in the crystal lattice and can thus specifically change the properties of the starting material.

The doping of diamonds with foreign atoms - that is, non-carbon atoms - is generally well known to those skilled in the art. An overview of the theoretical foundations and practical possibilities of diamond doping by means of ion beams and CVD methods can be found in the dissertation by Thomas Vogel, Ruhr University Bochum (2005), Faculty of Physics and Astronomy, with the topic "Doping of Diamond by MeV- ion implantation ", to which reference is hereby incorporated by reference.

In addition, DE 691 17 140 T2 describes polycrystalline diamond cutting tools and a method for their production in which also doped with impurities diamond coatings are used. These are tools which polycrystalline diamonds in the form of a

Have cutting tip, which typically on a surface of the

Tool body to be soldered.

According to DE 691 17 140 T2, the diamond flakes are produced by a CVD coating, wherein the material gas used is a carbon-containing gas,

Hydrogen gas and optionally a dopant gas are introduced into a vacuum chamber, the material gas is excited in a state in which form plasma or radicals, the material gas is passed onto a heated substrate, thereby depositing diamond on the substrate, being initially carried out without doping and then gradually increasing the dopant concentration.

Following the CVD process, the substrate is etched away leaving a polycrystalline diamond plate. The (former) substrate side of the diamond plate, which is undoped or lightly doped, is then arranged on the tool body so that it comes to rest on the cutting side of the tool, with which the doped diamond layer is located as a fixing directly on the tool body. Typically, the fusing side of the CVD diamond coated diamond plate is metallized and this through Soldering on the tool body fixed as an insert. According to DE 691 17 140 T2, the thickness of the resulting diamond plate is up to 1000 μιτι.

In summary, DE 691 17 140 T2 thus describes diamond tools which have a diamond insert which has a gradient of

Dopant concentration in their diamond layer, wherein the gradient may have a dopant concentration of 0% dopant on the chip side to a maximum value on the tool side surface.

In contrast to the purpose of the present invention, namely the detection of when an undoped diamond layer is worn down so far that the tool can be replaced without damaging the tool, workpiece and drive device, the doping according to DE 691 17 140 T2 should have the following further advantages :

The diamond at or near the rake face is synthesized as a

Diamond of better quality with little or no dopant concentration. The diamond at or near the fixing surface of the cutting tip is

compounded as a diamond of poorer quality with higher

Dopant concentration. Because of this higher dopant concentration, the diamond has less rigidity and sufficient elasticity in the vicinity of the fixing surface, which is important because sufficient elasticity and low rigidity can eliminate high stresses applied to the rake face by an object to be cut. According to DE 691 17 140 T2 plays the doped

Diamond layer on the fixing surface of the diamond plate a role as

Stress removal layer or as shock absorber layer.

As a carbon source for the local CVD method, document DE 691 17 140 T2 et al. Methane, ethane, acetylene, ethanol, methanol and acetone in the presence of hydrogen gas.

Suitable dopants according to DE 691 17 140 T2 are for example Si, B, Al, W, Mb, Co, Fe, Nb, Ta and their carbides, oxides and nitrides, halogens, P and N, which are used as gaseous dopant compounds , A doping with boron can be carried out, for example, according to DE 691 17 140 T2 in a simple manner by supplying B2H6 to the material gas from methane and hydrogen.

The diamond coating method according to DE 691 17 140 T2 is performed as a hot wire CVD method at a pressure of 10 KPa to 17 KPa and a substrate temperature of 250 ° C to 950 ° C and a wire of W, Ta or Re. The

Dopant concentrations in the finished end product are up to 9%.

With regard to the implementation of a diamond coating CVD process with and without dopants, reference is hereby made in full to the teaching of DE 691 17 140 T2.

Of course, the thermodynamic conditions disclosed in the prior art of the CVD process used for the purposes of the present invention may be adjusted and / or optimized as needed.

The measurement technique for detecting the required physical parameters can in the simplest case of metallic materials, a resistance measurement or a

Measurement of the electrical conductivity, in which a measuring chain can consist on the one hand of the tool used, comprising the doped and undoped diamond layer and on the other hand, the electrically conductive workpiece. As long as the undoped diamond layer is intact, the electrical conductivity will go to zero or the electrical resistance will be high. However, as soon as the undoped diamond layer is worn due to wear and tribological stresses, a significantly higher conductivity or a significantly lower resistance will be measured.

After calibration of the system to a suitable threshold, the overshoot or undershooting of this threshold, for example, for the electrical conductivity and / or the electrical resistance can be monitored and with a known separate electronic control or control circuit or a corresponding in the drive device of the tool integrated software controlled control, for example, the drive device of the tool are stopped or the movement of the tool are initially slowed down.

In addition to the exemplified measurement of the electrical resistance and the electrical conductivity, any physical measuring parameter can be used which allows a significant distinction between doped and undoped diamonds. This can be especially in the case of non-electrically conductive

Tools made of ceramic materials and / or non-electrically conductive materials, such as carbon fiber reinforced plastics, from which the workpiece to be machined, be a measurement of capacity, which also changes when the undoped diamond layer has worn so far that essentially only the doped diamond layer is in contact with the workpiece.

Also, other physical quantities and physical effects, which differ for doped and undoped diamonds, such as the Hall effect, can be exploited to determine the continuous or periodic detection of the

To allow wear of the undoped diamond layer. If necessary, suitable commercially available Hall probes can be used for this purpose.

The measurement parameters in question can be queried analog or digital in the context of the present invention. The interrogation can be continuous or periodic, with a periodic interrogation in a short interval, e.g. every 100 ms, in practice corresponds to a continuous detection. Depending on requirements, however, the polling interval can also be adapted to the conditions and, for example, be periodically measured every 5 seconds for the respectively relevant parameters.

For the purposes of the present invention, both n-type doped and p-type doped diamond layers are preferably used as doped diamond layers. Preferred impurities for doping are those which are selected from the group consisting of: aluminum, boron, silicon, tungsten, iron, molybdenum, cobalt, niobium, tantalum, rhenium, nitrogen and phosphorus, and also mixtures thereof.

By choosing the type of doping (p-type, hole line and n-type,

Electron conduction) and choice of impurity and dopant concentration, the sensitivity of the measuring system and the physical, in particular electrical properties of the semiconductor formed can be controlled as needed.

It is preferable to use boron for p-type doping, because an easy to

controlling CVD method for B-doping in the prior art is available.

If the use of n-type doped diamond is intended, nitrogen or phosphorus are used in the present invention because they are readily available in the form of gaseous dopants, e.g. as Phb and / or N2 into a CVD vacuum chamber initiate. In a preferred embodiment, the physical parameter is the electrical resistance and / or the electrical

Conductivity and / or the capacitive resistance and / or the Hall voltage or the Hall current of a Hall sensor detected. For the measurement of these parameters, a number of devices are available in the prior art.

In the context of the present invention, the physical parameter between the tool and a machined workpiece is detected, wherein

preferably the electrical conductivity and / or the electrical resistance and / or the capacitance between the machined workpiece and the tool is measured.

It is further preferred that the doped first diamond layer on a

cobalt-containing hard metal surface is applied. This ensures that the diamond layer forms well, adheres firmly to the surface and the

Tool surface has sufficient toughness and elasticity. If necessary, however, the surface can also be pre-treated before the diamond coating in order to further improve the adhesion of the diamond layer. This can

for example, with ion beams or by chemical treatment. By pretreatment of the substrate surface of a functional area of a tool, which contains, for example, hard particles, eg WC grains, which are embedded in a cobalt-containing binder matrix, substantially no cobalt is removed from the substrate by means of ion beams, eg NT, N ⁺⁺ and / or C ⁺ Binding matrix removed, but the irradiated ions are incorporated into the structure of the binding matrix.

Without being bound by it, for example, cobalt could be converted by the irradiated light ions to cobalt nitrides or cobalt carbonitrides or else to cobalt carbides, which have the known catalytic activity for the

Reconversion of the cubic diamond phase in the hexagonal graphitic phase does not show, so that the cubic diamond crystals have sufficient time to grow on the substrate surface without an in situ re-conversion takes place in graphite.

In the context of the present invention, it is fundamentally preferred that the doped and the undoped diamond layer are applied to the metal surface by means of chemical vapor deposition (CVD) from a methane / hydrogen atmosphere, hydrogen preferably being added to the methane in molar excess. Such as HF-CVD method trained

Coating process is relatively easy, fast and inexpensive

feasible. Furthermore, the doping of the first diamond layer can be produced by supplying a doping gas, in particular B2H6, during the CVD method in a CVD chamber. Thereby, the undoped second diamond layer can be easily generated by interrupting the supply of the doping gas in the CVD chamber, so that no further steps for producing the doped and the undoped diamond layer are required.

If required, however, it is of course also possible in the context of the present invention for example to produce a first (still undoped) polycrystalline diamond layer by means of CVD and to irradiate the resulting layer with an ion beam from the desired impurity atom for doping the first diamond layer. Typically, an annealing step is carried out following the ion beam treatment or a so-called "annealing step" to "heal" occurring during irradiation lattice damage. Thereafter, the undoped second diamond layer can then be deposited on the now doped first diamond layer.

In the present invention, the first doped and the second undoped diamond layer is applied to the metal surface by means of chemical vapor deposition (CVD) from a methane / hydrogen atmosphere in a CVD chamber, wherein preferably hydrogen is added to the methane in a molar excess. Furthermore, the inventive method in a

Coating temperature of 800 ° C to 1 100 ° C and a coating pressure of 1 kPa to 100 hPa performed.

If required, the substrate surface can be germinated before the first doped diamond layer is applied, for example by dusting with diamond powder.

The CVD method according to the invention is preferably carried out as an HF-CVD method in which a W-wire is used as a heating wire.

It has been found in practice that satisfactory results can be achieved with respect to the requirements of the tribological loadability of the diamond layers and the sufficient differences in the electrical properties of the doped and the undoped diamond layer with the method described above and the p-type doping means Boron is designed to be particularly simple, because only a boron-containing gas, preferably B2H6, is supplied as doping gas for doping the first diamond layer and for switching to the generation of the undoped diamond layer, the supply of the doping gas can be easily interrupted.

The tools produced according to the invention may be

act monolithic or modular tools. As mentioned above, the tools of the present invention may contain hard particles. These are preferably selected from the group consisting of: the carbides, carbonitrides and nitrides of the metals of IV., V. and VI. Subgroup of the Periodic Table of the Elements and boron nitride, in particular cubic boron nitride; as well as oxidic hard materials, in particular aluminum oxide and chromium oxide; and in particular titanium carbide, titanium nitride, titanium carbonitride;

Vanadium carbide, niobium carbide, tantalum carbide; Chromium carbide, molybdenum carbide

tungsten carbide; and mixtures and mixed phases thereof.

Further advantages and features of the present will become apparent from the description of specific embodiments.

example 1

Production of tools with doped and undoped diamond layers

Carbide twist drills made of a 10M% Co carbide with a mean WC grain size of 0.6 μιτι (Guhring trade name DK460UF) were after cleaning and degreasing the surface with acetone or other organic solvent and after particle blasting with quartz particles, the tools to be coated an acidic Subjected to etching step to remove Co from the surface. For this purpose, a mixture of HCI / HNO3 was used according to WO 2004/031437 A1. After rinsing and drying, the tools pretreated in this way were introduced into the vacuum chamber of a commercially available hot-wire CVD system (CemeCon CC800 / 5). The tungsten wires (99.99% purity) of the CVD system are arranged at a distance of about 4 mm parallel to each other. The drills were surrounded by the filaments all around, parallel to their longitudinal axis. The temperature of the filaments was set at about 2100 ° C. The temperature was measured by means of an optical thermometer. The removal of the filaments to the tool to be coated was 5 mm.

First, a doped diamond layer on the surface of the tools by supplying H2 / _CH4 as a material gas and B2H6 was prepared as doping gas. In this case, following preliminary tests, the following mass flows were used: H ₂ 600 sccm

CH ₄ 5 sccm

"Sccm" stands for standard cubic centimeters per minute, independent of pressure and temperature

Gas quantity per unit time described, so a mass flow specified.

The standard cubic centimeter is a gas volume of V = 1 cm ³ under standard conditions (T = 0 ° C and p = 1013.25 hPa), the so-called physical

Standard conditions according to DIN 1343.

The indicated mass flows were applied for 80 hours. Thereafter, the supply of the dopant diborane was frozen and maintain the mass flow rates of H2 and CH ₄ for an additional 180 h. The temperature of the tools to be coated was 970 ° C, the pressure in the CVD chamber was about 13 kPa.

A layer thickness measurement (SEM with Focused Ion Beam [FIB], Helios NanoLab 600 from FEI) of the doped diamond layer gave values of 70 to 90 μm. The total layer thickness was in the present example case about 220 μιτι, resulting in a layer thickness of about 130 μιτι results for the undoped diamond layer.

The concentration of boron was determined by the curcumin method. The boron-containing diamond material is removed with oxygen by heating to 700 ° C. from the metal surface according to DE 101 17 867 A1. This burns the

Diamond carbon to CO2 and boron is oxidized to boron trioxide and borates, which are treated in the acid with curcumin, which forms a red complex of rosocyanine with borates, which analyzed photometrically at 540 nm and with

Standard borate solutions is compared. In the doped diamond layer, the boron content according to this method was between 7 and 10 atom%, based on C + B in the doped diamond layer. In the context of the present invention, the electrical

Properties of the doped and undoped diamond layers measured.

After measuring the absolute sheet resistance of the boron-doped layer (four-point method according to Vogel 2005), the resistivity of the obtained boron-doped diamond layers (p-type doping) was determined by multiplication with the layer thickness and is at room temperature and a doping level of 10 atom%, based on C + B in the doped diamond layer 1, 58 Ωcm, whereas the resistivity of a pure undoped diamond layer (made on the tool as described above but without doping gas supply) is 5.6 × 10 ¹³ Ωcm. Thus, it is shown that the conductivity of diamond by doping in

Generally - in the example with boron - can be changed by many orders of magnitude, which can be used metrologically for the purposes of the present invention for detecting the degree of wear of an undoped polycrystalline diamond layer.

Example 2

Measuring principles and drilling tests

The drilling tools obtained according to Example 1 were tested in highly abrasive test pieces made of AISi9 and AlSil 7. These materials are electrically conductive.

Cuboid blocks with a base area of 5 × 5 cm and a height of 10 cm were produced as workpiece specimens from these materials. The specimens were clamped in the workpiece holder of an industrial drilling device from GÜHRING KG, Albstadt. In the tool holder of the

Drilling device was clamped a 10 mm drill, which was acted upon according to Example 1 with a doped and a span undoped diamond layer. The total layer thickness was about 220 μιτι. The drilling device was programmed to drill one 9 cm deep hole per specimen and then to the next Workpiece was transferred. For the purposes of the present tests, no coolants or lubricants were used.

The drilling trials were designed as follows:

Process: Full drilling, drilling depth 900 mm

Cutting speed: 100 m / min

It was a measuring device for conductivity measurement of the entire system drill holder - drilling tool - doped diamond layer - undoped

Diamond layer - Probewerkstück created. The measurement was carried out in the usual way of conductivity measurement of non-ferrous metals without contact (eddy current method according to DIN EN 2004-1) with a commercially available device (SIGMASCOPE® SMP350 HELMUT FISCHER GmbH, Sindelfingen) and corresponding probes with a frequency of 15 kHz, in which the Measurement data were read into a computer via a USB interface, compared with a threshold value and when the threshold was exceeded by the software, a switch for switching off the drive means of the drill to be tested was pressed. The measuring probes of the conductivity meter were placed on the workpiece and at the

Tool holder arranged so that the conductivity of the above

Total system was recorded. At the beginning, a conductivity of the

Total system of practically 0 MS / m.

In preliminary tests, when testing drills which were only provided with a B-doped diamond layer but did not have an undoped diamond layer, a conductivity of approximately 12 to 17 MS / m was determined for this system. From this, a threshold value of 15 MS / m was formed. If this threshold at the

According to the test system according to the invention should be exceeded, this means that the undoped diamond layer, which is the actual functional area of the

Tool, worn out and the drill is already running in "emergency mode" on the doped diamond layer, but still fulfills its function Once the test in the value of 15 MS / m is exceeded, the computer gives a signal to shut down the drill, which prevents is that the drill the workpiece or the Drive machine can be damaged and the drill can be replaced in time.

In practical experiments, it has been found that the drills used in accordance with the invention fulfill all the expectations of wear resistance, service lives and service life of a conventional diamond tool.

It has also been found that although the change in conductivity is gradual, it does occur within a few minutes of the given one

Cutting speed reaches its maximum. Thus, it can be seen that not only the absolute value can serve as a measurement parameter, but also, for example, the speed of change or the slope of the change of a measurement parameter can be used to accomplish the inventive detection of the degree of wear of an undoped diamond layer.

Thus, the doped diamond layer serves as a sort of "intelligent stop layer" for diamond-coated tools.

Example 3

ion beam treatment

Hard metal twist drills made of a 10M% Co carbide with a mean WC grain size of 0.6 μιτι (Guhring trade name DK460UF) were coated as described in Example 1, but no chemical pretreatment of

Substrate surface, but this was for 3.5 h with a stream of ions

Nitrogen ions irradiated, the ionic current having a voltage of 30 kV at 3 mA plasma flow at a nitrogen pressure of 1 x 10 ^{~ 5} mbar was generated. To the

Generation of the ion beam, a commercial ion generator was used (ion generator "Hardion" from the company Quertech, Caen). This raises a temperature at the tool of about 400 ° C. Following this, the tool was provided with a doped and an undoped diamond layer in a commercially available hot-wire CVD system (CemeCon CC800 / 5) as in Example 1, and the conductivity measurement was carried out as described in Example 2.

As expected, lower absolute conductivity values of the overall system were found, as the doped layer was deposited on a more insulating substrate layer.

However, the conductivity data could also be used with these diamond-coated dies, which are improved in terms of their service life, in order to detect the degree of wear of the undoped diamond layer and shut down the drilling apparatus in good time or to reduce the cutting speed.

Claims

claims

Use of a doped with impurities first diamond layer

polycrystalline diamond, which on a metal surface of a

is arranged to detect the degree of wear of an undoped polycrystalline second diamond layer, which is arranged on the doped diamond layer and which has a functional range of

forming a chip-removing tool, wherein at least one physical

Parameter is detected continuously or periodically during operation of the tool, and wherein a change of the parameter indicates the degree of wear of the undoped second diamond layer.

Use according to claim 1, characterized in that as doped

Diamond layer is used an n-type doped or a p-type doped diamond layer.

Use according to claim 1 or 2, characterized in that the

Foreign atoms for doping are selected from the group consisting of:

Aluminum, boron, silicon, tungsten, iron, molybdenum, cobalt, niobium, tantalum, rhenium, nitrogen and phosphorus, and mixtures thereof.

Use according to one of claims 1 to 3, characterized in that boron is used for p-type doping.

Use according to one of claims 1 to 3, characterized in that nitrogen or phosphorus is used for n-type doping.

Use according to one of claims 1 to 5, characterized in that as the physical parameter of the electrical resistance and / or the electrical conductivity and / or the capacitive resistance and / or the Hall voltage or the Hall current of a Hall sensor is detected.

7. Use according to one of claims 1 to 6, characterized in that the physical parameter between the tool and a machined

Workpiece is detected.

8. Use according to claim 7, characterized in that the electrical

Conductivity and / or the electrical resistance and / or the capacitance between machined workpiece and the tool is measured.

9. Use according to one of claims 1 to 8, characterized in that the doped first diamond layer on a cobalt-containing hard metal surface

is applied.

10. Use according to one of claims 1 to 9, characterized in that the doped and the undoped diamond layer are applied by chemical vapor deposition (CVD) from a methane / hydrogen atmosphere on the metal surface, preferably hydrogen is added to the methane in a molar excess ,

1 1. Use according to one of claims 1 to 10, characterized in that the doping of the first diamond layer is produced by supplying a doping gas, in particular B2H6, during the CVD process in a CVD chamber.

12. Use according to one of claims 1 to 11, characterized in that the undoped second diamond layer by interrupting the supply of the

Doping gas is generated in the CVD chamber.

13. Use according to one of claims 1 to 10, characterized in that a first polycrystalline diamond layer is produced by means of CVD and the obtained layer is irradiated with an ion beam from the desired impurity atom for doping the first diamond layer; afterwards

Annealing step takes place; and then depositing the undoped second diamond layer on the doped first diamond layer.

14. A method for continuously detecting the degree of wear of an undoped diamond layer, which forms a functional area of a cutting tool, and which is arranged on a doped with foreign atoms diamond layer, during operation of the tool; wherein a) the doped diamond layer directly on the substrate surface of

is arranged cutting tool; b) at least one measuring parameter, which consists of two diamond layers, the

Tool and a workpiece machined with the tool, during the operation of the tool is detected continuously or periodically; c) setting a predefined threshold for the measurement parameter; and wherein d) a change of the measurement parameter above or below the predefined ones

Threshold indicates the degree of wear of the undoped diamond layer.

15. The method according to claim 14, characterized in that as a measurement parameter, the electrical conductivity and / or the electrical resistance and / or the capacitance between the machined workpiece and the doped and undoped

Diamond coated tool is used.

16. The method according to claim 14 or 15, characterized in that the

Impurities for doping are selected from the group consisting of: aluminum, boron, silicon, tungsten, iron, molybdenum, cobalt, niobium, tantalum, rhenium, Nitrogen and phosphorus, as well as mixtures thereof.

17. The method according to any one of claims 14 to 16, characterized in that the p-type doping boron is used and for n-type doping nitrogen or phosphorus is used.

18. The method according to any one of claims 14 to 17, characterized in that the doped diamond layer is applied to a cobalt-containing hard metal surface.

19. The method according to any one of claims 14 to 18, characterized in that the first doped and the second undoped diamond layer by means of chemical

Deposited vapor deposition (CVD) from a methane / hydrogen atmosphere in a CVD chamber on the metal surface, preferably hydrogen is added to the methane in a molar excess, a

Coating temperature of 800 ° C to 1100 ° C and a coating pressure of 1 kPa to 100 hPa is set.

20. The method according to claim 19, characterized in that the CVD method is a hot wire method is used, in which a W-wire is used as the heating wire.

21. A method according to any one of claims 14 to 20, characterized in that the doping of the first diamond layer by supplying a doping gas, in particular B2H6, is generated during the CVD process in the CVD chamber.

22. The method according to any one of claims 14 to 21, characterized in that the undoped second diamond layer by interrupting the supply of the

Doping gas is generated in the CVD chamber.

23. System comprising: a) a cutting tool with the layer sequence: i) metallic substrate layer,

ii) impurity doped diamond layer of polycrystalline diamond,

iii) undoped polycrystalline diamond layer, wherein a distinction between the doped diamond layer i) and the undoped diamond layer ii) is given with respect to a physical measurement parameter, and

wherein the undoped polycrystalline diamond layer forms a functional area of the cutting tool,

and b) a workpiece.

24. The system of claim 23, wherein the physical measurement parameter is electrical resistance or electrical conductivity.

25. The system according to any one of claims 23 or 24, wherein the workpiece is an electrically conductive workpiece.