Coating method for a tool component of a cutting tool

Abstract

The present invention relates to a method for producing a coated tool component of a cutting tool. The tool component is coated with a coating comprising at least one aluminum oxide (Al2O3) containing an Al2O3 layer having an alpha-Al2O3 phase fraction and a gamma-Al2O3 phase fraction. The at least one Al2O3 layer is produced using a reactive magnetron sputtering process.

Description

Technical Field

[0001] The present invention relates to a method for producing a coated tool part of a cutting tool. In particular, the method according to the invention is intended to produce a tool coating comprising at least one layer containing aluminum oxide (Al2O3). This aluminum oxide layer will hereinafter be referred to as the Al2O3 layer. Such an Al2O3 layer can consist entirely of Al2O3 or can also contain, in addition to Al2O3, other components, such as a mixture of other metals or metal oxides and / or a certain proportion of impurities.

Background Art

[0002] Today, the production of innovative coatings is a core competence in the manufacture of industrial tools for metal machining. Due to the constantly increasing requirements regarding the possible uses, cutting speeds, and service lives of such machine tools, generally referred to as cutting tools, the demands on the aforementioned tool coatings are also increasing.

[0003] Al2O3 coatings, i.e., coatings comprising at least one layer containing Al2O3, are very suitable for the aforementioned uses due to their material properties. Thus, according to the prior art, such Al2O3 coatings have already been used in various ways for coating cutting tools.

[0004] Al2O3 has several phases. Alpha-aluminum oxide (α-Al2O3) refers to the thermodynamically stable Al2O3 phase of rhombohedral crystals. The thermodynamically stable α-Al2O3 phase is the high-temperature phase of aluminum oxide. This phase is described by the space group R-3c and is called corundum. In addition to the α-Al2O3 phase, there are a number of metastable Al2O3 phases such as the kappa-aluminum oxide phase (κ-Al2O3) or the gamma-aluminum oxide phase (γ-Al2O3). The drawback of these metastable Al2O3 phases is that they transform into the thermodynamically stable α-Al2O3 phase at higher temperatures. The metastable Al2O3 phases transform into the α-Al2O3 phase directly or in the form of different transformation sequences.

[0005] The transformation temperature depends on purity, particle size, and, for example, the thermodynamic pretreatment of the material. These transformation processes limit the maximum operating temperature of the metastable Al2O3 phases in machining applications.

[0006] In the literature and industrial applications, both metastable Al2O3 phases and the thermodynamically stable α-Al2O3 phase are used according to the prior art.

[0007] The α-Al2O3 phase is typically deposited using chemical vapor deposition (CVD) according to the prior art. Such CVD coatings usually have a high proportion of α-Al2O3 in the Al2O3 layer. The Al2O3 coatings produced using CVD provide effective wear protection in classical turning applications. The drawback of these CVD-Al2O3 coatings is the high residual tensile stress. CVD coatings are also typically deposited at temperatures between 1000 °C and 1100 °C. These high coating temperatures lead to tool embrittlement.

[0008] Alternatively, the plasma-assisted CVD process is used to produce the α-Al2O3 phase at a low deposition temperature. This CVD process also requires a high temperature, for example 800 °C, and incorporates adverse chlorine residues from the carrier gas into the coating. CVD coatings using α-Al2O3 typically have a very high layer thickness of 20 μm. Another drawback is the large amount of rounding required at the cutting edge of the tool due to the relatively high coating thickness with a complex residual stress state.

[0009] Alternatively, Al2O3 coatings produced by physical vapor deposition (PVD) are currently used in metal cutting (see, for example, European Patent No. 1762637 B1). These Al2O3 coatings are used in metal cutting in combination with other coatings containing nitrides and / or carbides in the form of multilayer coatings. These coatings have sufficient toughness, but at the same time have disadvantages at very high cutting speeds, insufficient temperature and oxidation resistance. Therefore, there are limitations to these materials.

[0010] In the PVD sputtering process, the starting material is converted into the gas phase by sputtering. Particles, mainly atoms and ions, released from the so-called target are accelerated by the energy input to the substrate to be coated and deposited on the surface of the substrate as a coating. The material to be deposited, i.e., the target material, usually exists as a solid in the PVD process and is located in a vacuum coating chamber, also known as a reaction chamber. In this reaction chamber, the substrate to be coated is spatially separated from the target. Depending on the type of PVD process, not only one target but also two or more targets are used.

[0011] The target is connected to a power supply unit. Energy is typically applied to the target using a plasma and an electric field. The reaction chamber is filled with an inert process gas, which is ionized (plasma formation) by the energy input of the electric field. The charged process gas ions are accelerated in the direction of the target by the electric field, and this "impact", i.e., the transfer of physical impulse, knocks out the atoms and ions of the target material from its surface. The atomized target material then moves in the direction of the substrate, providing a coating on its surface.

[0012] In a reactive PVD process, a reactive gas is also used in the reaction chamber. In the case of an )Al2O3 coating, typically oxygen (O2) and / or nitrogen oxides (NO x ) are contained. The nitrogen oxides can be, for example, nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), and / or dinitrogen tetroxide (N2O4).

[0013] The following subgroups of PVD processes are typically used in machining techniques to produce tool coatings, namely the arc process, also known as arc PVD, and the sputtering process. The sputtering process includes a direct current (DC) sputtering process or a high-power impulse magnetron sputtering process (HiPIMS). In the field of tool coatings, the preferred sputtering process is magnetron sputtering. In the latter magnetron sputtering process, in addition to the electric field between the cathode and the anode, a magnetic field is generated behind the target by one or more electromagnets or permanent magnets.

[0014] The deposition of an Al2O3 coating using a DC sputtering process is not possible due to the electrical insulation of Al2O3. The arc process is also not suitable for the deposition of industrial Al2O3 coatings on cutting tools due to the formation of a large amount of macro droplets.

[0015] Al2O3 coatings deposited using a dual magnetron sputtering process are known from the prior art (see WO 2019 / 092009 A1 pamphlet). In the dual magnetron sputtering (DMS) technique, two targets are connected to each other via a power network. During the deposition process, the two targets act alternately as anode and cathode, enabling the deposition of an electrically insulating coating such as Al2O3.

[0016] However, in the method known from WO 2019 / 092009 A1 pamphlet, the Al2O3 coating is deposited in the γ-Al2O3 phase. The drawbacks of these γ-Al2O3 coatings are, in addition to a relatively low elastic modulus, typically limited temperature stability above 900 °C. As already mentioned, the metastable cubic γ-Al2O3 phase transforms under such conditions into the thermodynamically stable rhombohedral α-Al2O3 phase (e.g., corundum known from PDF number 42-1468 of the ICDD database). This phase transformation is typically associated with a significant loss of coating hardness and is thus detrimental to the cutting performance of the tool. γ-Al2O3 coatings exhibit hardness values in the range of about 3000 HV - 3500 HV and reduced elastic modulus values in the range of 350 GPa - 370 GPa (see WO 2019 / 092009 A1 pamphlet).

[0017] WO 2020 / 094718 A1 pamphlet also discloses a method for producing Al2O3 coatings deposited using a HiPIMS process. The Al2O3 coatings deposited by this process have both an α-Al2O3 phase fraction and a γ-Al2O3 phase fraction. SUMMARY OF THE INVENTION

[0018] In view of this, an object of the present invention is to provide a method for producing a coated tool component of a cutting tool, which can produce an Al2O3 coating having advantageous properties as compared with the Al2O3 coating produced using the aforementioned process / method from the prior art. The disadvantageous high-temperature stability of the PVD-γ-Al2O3 coating having a relatively low elastic modulus value should be avoided, similar to the embrittlement of the tool during coating by the CVD-α-Al2O3 coating, which exhibits the described disadvantageous tensile residual stress.

[0019] This object is achieved by: providing a tool component as a substrate comprising a substrate material selected from the group consisting of cemented carbide, cermet, cubic boron nitride (CBN), polycrystalline diamond (PCD), or high-speed steel; coating the tool component with a coating comprising at least one aluminum oxide (Al2O3) containing an Al2O3 layer having an alpha-Al2O3 phase fraction and a gamma-Al2O3 phase fraction; wherein at least one Al2O3 layer is produced by a reactive magnetron sputtering process, and in the reactive magnetron sputtering process, at least one aluminum target is used; a mixed gas having a noble gas as a first component and oxygen (O2) and / or nitrogen oxide (NO x ) as a second component as a reactive gas is used; the total gas pressure is set to <1 Pa; a process temperature of 400 °C to 650 °C is set; the maximum target power density ≦ 100 W / cm 2 and the maximum target current is set to ≦ 200 A; and generating a magnetic field using at least one solenoid coil operating with a coil current of ≧ 7 A, as solved by the method according to claim 1.

[0020] Furthermore, the above object is solved by a coated tool part of a cutting tool, the tool part comprising a substrate material selected from the group consisting of cemented carbide, cermet, cubic boron nitride (CBN), polycrystalline diamond (PCD), or high-speed steel, and a coating comprising at least one aluminum oxide-containing Al2O3 layer having an α-Al2O3 phase fraction and a γ-Al2O3 phase fraction, wherein at least the Al2O3 layer is produced by the above-described method according to the invention.

[0021] Using the method according to the invention, the inventor has succeeded in producing an Al2O3 coating having very positive machining properties with a relatively high α-Al2O3 phase fraction and a variable γ-Al2O3 phase fraction. The inventor has achieved this, in particular, by a suitable selection of the process parameters used, such as the total gas pressure, the process temperature, the maximum target power density, the maximum target current, and the coil current for generating the magnetic field.

[0022] It is also advantageous that a technically established and controllable reactive magnetron sputtering process is used for this purpose. Thus, the method according to the invention can be carried out in a conventional industrial plant for production in large batches. In addition, in contrast to the arc process, the formation of macro droplets of metal particles can be completely or at least almost completely avoided.

[0023] Furthermore, the method according to the invention is IT capable of being used to produce an Al2O3 coating having a relatively high hardness value of H IT ≧20 GPa and a relatively high value of the instrumented elastic modulus E

[0024] ≧350 GPa. Thereby, the above problem is completely solved.

[0025] Compared with the method disclosed in WO 2019 / 092009 A1, the method according to the invention is carried out at a lower total gas pressure of less than 1 Pa. In addition, the coil current used to generate the magnetic field is selected to be significantly higher with a value ≥ 7 A.

[0026] Compared with the method disclosed in WO 2020 / 094718 A1, a major difference in the method according to the invention is that the reactive magnetron sputtering process is not designed as a HiPIMS process. This is particularly evident from the parameters selected according to the invention, namely a maximum target power density of ≤ 100 W / cm 2 and a maximum target current of ≤ 200 A. Thus, technically speaking, the reactive magnetron sputtering process according to the invention is a completely different process.

[0027] According to an improvement, the reactive magnetron sputtering process used in the method according to the invention is a pulsed magnetron sputtering process.

[0028] In other words, the electric field required for the magnetron sputtering process is preferably generated using the time series of individual voltage pulses. The voltage pulses can be, for example, sinusoidal, triangular, or rectangular. According to a preferred improvement, the voltage pulses are configured as rectangular voltage pulses. According to a further improvement, the voltage pulses are bipolar voltage pulses. Bipolar rectangular voltage pulses have been found to be particularly advantageous compared to bipolar sinusoidal voltage curves in the method according to the invention.

[0029] According to an improvement, the voltage pulses have a pulse frequency in the range of 10 kHz to 150 kHz. Particularly preferably, the voltage pulses have a pulse frequency in the range of 40 kHz to 80 kHz. The pulse frequency preferably remains constant during the process.

[0030] According to a preferred improvement, the operating point is set for each target as part of process control via the supplied oxygen gas flow rate. Separate oxygen inlets are provided for each target. Depending on the amount of oxygen supplied through the oxygen inlets, the operating point can be set using automatic process control. The operating point refers to the time-averaged voltage at the target.

[0031] According to a further improvement, the reactive magnetron sputtering process used in the method according to the invention is a dual magnetron sputtering process having two targets connected to each other via a bipolar power supply, and the two targets act alternately as anodes and cathodes.

[0032] It is sufficient if one of the two targets is an aluminum target (for example, the other target can have additional / other metals or metal mixtures), but if the reactive magnetron sputtering process used according to the invention is a dual magnetron sputtering process using two pure aluminum targets, it is advantageous for the production of the Al2O3 coating according to the invention.

[0033] The total gas pressure extending into the reaction chamber, which is composed of the partial pressures of the components of the gas mixture (on the one hand a noble gas and on the other hand oxygen and / or nitrogen oxides or nitrogen), is set to <700 mPa according to a preferred improvement of the method according to the invention.

[0034] According to a further improvement, the coil current for generating the magnetic field is selected to be ≤10 A. Thus, the coil current is preferably in the range of 7 A to 10 A.

[0035] It should be noted here that the phrases "from X to Y" and "between X and Y" refer to a range of values including both the stated lower limit (X) and the stated upper limit (Y). This applies not only to the coil current mentioned last but also to all other parameters mentioned in this specification.

[0036] Regarding the system for generating the magnetic field required for the magnetron sputtering process, the following should be specifically mentioned. In the method according to the present invention, the magnetic field is preferably generated by a permanent magnet and at least one magnetic coil arranged behind at least one target. The distance between the permanent magnet and the target is preferably adjustable. For example, the permanent magnet can be automatically moved via a drive system. In order to generate the Al2O3 layer according to the present invention, it has been found that the permanent magnets are preferably permanently arranged at their foremost positions closest to the target. Furthermore, the magnet system can have magnetic plates with different thicknesses and SNS or NSN orientations. Furthermore, the magnet system has a single coil or a plurality of electric coils, preferably at least four coils. Each of these coils is connected to its own DC power supply unit. The coil currents described above can be specified and set for each of the power supply units. Preferably, the polarity of the output voltage of each power supply unit can be set separately. This polarity results in a coil current with an SNS or NSN orientation. It is particularly preferred that two of the four coils mentioned operate in the method according to the present invention. It is preferable to turn off the power supply units of the remaining two coils. The coil currents described above refer to the coils that are turned on in any case.

[0037] Thus, ultimately, there is a superposition of the magnetic fields generated by the coils and the permanent magnets. The deposition of the coating according to the present invention is affected by the combination of the magnetic field of the permanent magnet and the magnetic field of the coil. The number of turns of the coil can be, for example, 800 per coil.

[0038] According to a further improvement, for the reactive magnetron sputtering process, a time-averaged target power density of 3 W / cm 2 ~30 W / cm 2 , preferably 4 W / cm 2 ~20 W / cm 2 is set.

[0039] The time-averaged power density at the target (herein referred to as the target power density) is calculated by averaging the power over time at at least one target and averaging the size of the area of at least one target. In the case of a dual magnetron sputtering process (DMS) where the output power of the DMS power supply is, for example, 20 kW and the size of two targets is, for example, 83 cm × 17 cm, the time-averaged power density is 20 kW ÷ 2 ÷ 83 cm ÷ 17 cm = 7.09 W / cm 2 is calculated as.

[0040] The maximum power density at the target is calculated using the time-averaged power at at least one target, the curve factor D, and the size of the area of at least one target. The curve factor D is the ratio between the pulse duration and the repetition interval. The repetition interval is the time interval from the start of a pulse at the target to the start of the next pulse at the same target. At an exemplary frequency of 40 kHz, the repetition interval is 1 / (40 kHz) = 25 μs. For an exemplary pulse duration of 12.5 μs, the curve factor at a frequency of 40 kHz is correspondingly 12.5 μs / 25 μs = 0.5. Thus, in the case of a dual magnetron sputtering process, the maximum power density per target can be calculated as follows. For example, the average output power of a DMS power supply with 20 kW, i.e., 10 kW per target, a curve factor of 0.5, and a target size of 83 cm × 17 cm: 10 kW ÷ 83 cm ÷ 17 cm ÷ 0.5 = 14.17 W / cm 2

[0041] In the method according to the invention, it has also been found advantageous for the bias voltage applied to the substrate to be in the range from 125 V to 300 V. It is understood that the bias voltage is a negative voltage. Particularly preferably, the bias voltage applied to the substrate is a pulsed bias voltage having a bias pulse frequency of 5 kHz to 80 kHz, preferably 10 kHz to 40 kHz, particularly preferably 20 kHz to 30 kHz. The bias voltage is preferably a bipolar bias voltage.

[0042] Furthermore, it has been found that a bias current in the range of 10 A to 60 A is advantageous. If the bias voltage is set too low, this increases the proportion of amorphous Al2O3 in the Al2O3 layer, ultimately reducing the hardness and elastic modulus of the coating. On the other hand, if the bias voltage is set too high, the deposition rate decreases. If the bias current is set too high, the process may also become unstable.

[0043] According to a further improvement, the noble gas used in the gas mixture within the reaction chamber contains argon (Ar) and / or krypton (Kr) and / or neon (Ne). Argon is particularly preferred. However, mixtures of the aforementioned noble gases can also be used.

[0044] According to a further improvement, at least one Al2O3 layer is deposited directly on the substrate material, and the substrate material is cemented carbide. It has been found that it is advantageous to deposit the Al2O3 layer directly on the cemented carbide.

[0045] According to an alternative improvement, a plurality of layers are deposited on the substrate material, and at least one of the layers is a metal oxide layer on which at least one Al2O3 layer is directly deposited, and the metal oxide layer contains oxides of one or more of the metals Ti, Si, V, Zr, Mg, Fe, B, Gd, La, and Cr.

[0046] It has been found that a metal oxide layer containing TiO2 or consisting of TiO2 is particularly advantageous. When the Al2O3 layer is directly deposited on such a TiO2 layer, this also promotes the formation of the α - Al2O3 phase component in the Al2O3 layer.

[0047] In particular, an Al2O3 layer having a layer thickness of ≧ 10 nm can be produced using the method according to the present invention.

[0048] It is understood that the above features and the features described below can be used not only in the combinations shown in any case without departing from the scope of the present invention, but also in other combinations or by themselves.

[0049] Examples of embodiments of the present invention are shown in the accompanying drawings and will be described in more detail in the following description.

Brief Description of the Drawings

[0050]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0051] FIG. 1 is a schematic diagram of a coated tool part. The coated tool part is entirely designated by reference numeral 10.

[0052] The coated tool part can be, for example, an indexable insert. In the present embodiment, the coated tool part 10 includes a cemented carbide substrate 12 coated with a coating 14 on a part of its surface. Of course, the entire surface of the tool part 10 can also be coated.

[0053] In this case, the coated surface may be, for example, the rake face 16 of an indexable cutting insert having one or more cutting edges 18.

[0054] FIG. 2 schematically shows the layer structure of the coating 14 on the substrate 12.

[0055] According to this embodiment, the coating 14 was performed with a Hauzer HTC1000 coating system. For the deposition of the coating 14, a cemented carbide substrate 12 with a Co content of 9.0 m% was used. Furthermore, the substrate 12 has a mixed carbide content of about 1 m% and a WC content of about 90 m%.

[0056] According to this embodiment, the cemented carbide substrate 12 used has dimensions of 15 mm × 15 mm × 5 mm. Preferably, the cemented carbide substrate 12 has holes (not shown) for holding it during deposition. One side surface of the substrate 12 is polished.

[0057] It is understood that a number of such substrates 12 were coated simultaneously in the coating system. For this purpose, the substrates 12 were accommodated on a rotating substrate table. More precisely, the substrates 12 were mounted on the substrate table and arranged in a tower that rotates with the substrate table. A 3f rotation was performed during the coating process.

[0058] The 2f rotation describes an implementation method of rotating the substrate using both the substrate table and the tower thereon. Thereby, a 2f rotation occurs around two parallel but non-concentric axes. The 3f rotation describes an implementation method of rotating the substrate using both the substrate table and the tower thereon, as well as the square on which the substrate is mounted. Thereby, a 3f rotation occurs around three parallel but non-concentric axes. The tool part 10 was aligned on a rotary polishing surface aligned parallel to the rotation axis so that the coating thickness was measured.

[0059] In the first embodiment shown in FIG. 2, a coating 14 having four individual layers was produced. According to the first embodiment, the coating 14 comprises an AlTiN layer 20 deposited directly on the cemented carbide substrate 12. A TiC layer 22 was deposited on this AlTiN layer 20. By oxidation, a TiO2 / TiO x layer 24 was produced. An Al2O3 layer 26 having both an α-Al2O3 phase fraction and a γ-Al2O3 phase fraction was deposited on the TiO2 / TiO x layer 24.

[0060] The AlTiN layer 20 was applied using HiPIMS sputtering. An AlTi55 / 45 target consisting of 55 atomic % Al and 45 atomic % Ti was used for this purpose. A target power of 15 kW was set. The pulse-on time was 150 μs, the current was controlled at 200 A, the starting voltage was 1400 V, and the coil current was 4 A. The argon gas flow rate was set at 450 sccm. The total gas pressure in the reaction chamber was controlled at 420 mPa. Nitrogen (N2) was used as the reactive gas for pressure control. The bias voltage was DC80 V. The rotation of the substrate table was set at 3 rpm. The deposition time was 4 hours and 30 seconds. The deposition temperature was 550 °C. The layer thickness of the thus-produced AlTiN layer 20 was about 1.2 μm.

[0061] Subsequently, the TiC layer 22 was also applied using HiPIMS sputtering. For this, a Ti target was used. The target power was set at 15 kW. The pulse-on time was 60 μs, the current was controlled at 500 A, the starting voltage was 1800 V, and the coil current was set at 4 A. The bias voltage was set at DC60 V. An argon gas flow rate of 500 sccm was used. As the reactive gas, acetylene (C2H2) with a flow rate of 32.5 sccm was used. The coating time was 3 hours. The substrate temperature was set at 550 °C. The rotation of the substrate table was set at 3 rpm. The TiC layer 22 has a layer thickness of about 0.4 μm.

[0062] Subsequently, using an oxidation process, the upper part of the TiC layer 22 was converted into a TiO2 / TiO x layer 24. The oxidation of the TiC layer 22 into the TiO2 / TiO x layer 24 was carried out at a substrate temperature of 600 °C, an oxygen gas flow rate of 994 sccm, and a duration of 45 minutes. In this way, a TiO2 / TiO x layer 24 with a layer thickness of approximately 0.1 μm was produced.

[0063] After the oxidation process, the Al2O3 layer 26 was applied to the existing layer composite using a dual magnetron sputtering process. For this purpose, two aluminum targets were used. The two targets used were located on both sides of the reaction chamber. The pulse shape of the power supply used was in bipolar mode and was rectangular. The power of the pulsed power supply was set to a constant 20 kW during deposition. The frequency of the power supply was 40 kHz. The duty cycle of the rectangular pulse was 50% (i.e., 50% positive voltage pulse and 50% negative voltage pulse). A mixed gas of argon and oxygen was used inside the reaction chamber. The argon gas flow rate was set to a constant 500 sccm. The oxygen gas flow rate was adjusted at 430 V via the set operating point of the process control. The oxygen gas flow rate was approximately 105 sccm. The total gas pressure was approximately 457 mPa. During deposition, a pulsed bias voltage (substrate bias voltage) of negative polarity with a frequency of 30 kHz and an off-time of 10 μs was applied to the substrate 12. The level of the negative bias voltage was 175 V. The rotation of the substrate table was 2 rpm. The substrate temperature during deposition was 570 °C. The coil current was set to 10 A. The deposition time was 2 hours and 10 minutes. The α-γ-Al2O3 layer 26 deposited in this way has a layer thickness of approximately 1.2 μm.

[0064] The deposition of the α-γ-Al2O3 layer onto the TiO2 / TiO x layer 24 has been found to be particularly advantageous as it increases the formation of the α-Al2O3 phase component. Further tests by the applicant have shown that the TiO2 / TiO x layer 24 should have a minimum layer thickness of 5 nm and the Al2O3 layer 26 should have a layer thickness of at least 10 nm.

[0065] The layer structure of the coating 14 according to the second embodiment shown in FIG. 3 is mainly the same as the layer structure according to the first embodiment shown in FIG. 2. Therefore, the layers 20, 22, and 24 were also produced by the same manufacturing process using the same process parameters. Therefore, for simplicity, these are not repeated again.

[0066] For the first embodiment, during the deposition of the Al2O3 layer 26, the voltage was varied in the form of a time gradient from 175 V to 125 V. The bias current of about 21 A was slightly lower than that of the first embodiment (about 26 A). The time variation of the bias voltage resulted in the Al₂O₃ layer 26 having a higher α-γ-Al₂O₃ phase fraction towards the upper end of the layer 26. The layer thickness of the α-γ-Al₂O₃ layer 26 was 1.4 μm in the second embodiment.

[0067] In the third embodiment shown in FIG. 4, the Al₂O₃ layer 26 was also deposited using a dual-reactive magnetron sputtering process. However, the Al₂O₃ layer 26 was deposited directly on the cemented carbide substrate 12 here (therefore, the layers 20, 22, and 24 do not exist here). The deposition of the α-γ-Al₂O₃ layer 26 was carried out at a substrate temperature of about 550 °C in an argon-oxygen gas mixture. The output of the two aluminum targets was set to 20 kW. The total gas pressure during deposition was 454 mPa. A negative bias voltage of 200 V was applied to the substrate during the deposition process. The rotation of the substrate table was 2 rpm. The layer thickness of the α-γ-Al₂O₃ layer 26 was 0.8 μm in the third embodiment.

[0068] FIG. 5 shows a fourth embodiment of the coating 14. According to this fourth embodiment, the coating 14 has the following coating sequence starting from the substrate 12: an AlTiN layer 20 having a layer thickness of about 2000 nm, a thin Al₂O₃ layer 26' having a layer thickness of about 15 nm, a TiO₂ / TiO having a layer thickness of about 60 nm xlayer 24, an α-γ-Al2O3 layer 26 having a layer thickness of about 500 nm, and a four-layer composite including an AlTiN layer each having a layer thickness of about 150 nm, an Al2O3 layer 26' disposed thereon having a layer thickness of 15 nm, a TiO2 / TiO layer having a layer thickness of 60 nm, and an α-γ-Al2O3 layer 26 having a layer thickness of about 150 nm. In the fourth embodiment, the uppermost layer of the coating 14 is an AlTiN layer 20 having a layer thickness of about 150 nm. x It has a four-layer composite including a layer, and an α-γ-Al2O3 layer 26. In the fourth embodiment, the uppermost layer of the coating 14 is an AlTiN layer 20 having a layer thickness of about 150 nm.

[0069] The α-γ-Al2O3 layer 26 contained in the coating 14 according to the fourth embodiment was produced in the same manner as described above. The following table summarizes again the process parameters during the production of the α-γ-Al2O3 layer 26 in all four embodiments.

[0070]

Table 1

[0071] As can be seen from the above table, the total gas pressure in the four embodiments was selected in the range of 454 mPa to 465 mPa. However, further tests by the applicant have shown that the total gas pressure can be selected somewhat higher without losing the positive characteristics of the Al2O3 layer. However, the total gas pressure should always be selected <1 Pa.

[0072] According to the four embodiments shown here, the process temperature was selected to be 550 °C or 570 °C. However, tests by the applicant have shown that other process temperatures in the range of 400 °C to 650 °C are also possible.

[0073] The coil current was selected to be 10 A in all cases. Tests by the applicant have shown that the coil current should generally be selected ≧7 A to achieve the desired characteristics of the Al2O3 layer.

[0074] The following changes to the above-described embodiments are conceivable in principle. The TiO2 / TiO by the oxidation processx Instead of generating layer 24, a TiO2 layer can also be generated by direct deposition. Furthermore, TiO2 / TiO x Regarding the oxidized TiC layer on layer 24, it should be noted that these may also have C as an additional component, and as a result, can be made into a Ti-C-O layer.

[0075] It is also conceivable to use a WC-Co layer instead of the TiO2 layer 24 as a sublayer of the α-γ-Al2O3 layer 26.

[0076] The following table summarizes the analysis results of the coating characteristics of the four coatings 14 shown in FIGS. 2 to 5. For comparison, this table shows the coating characteristics of a reference coating consisting of an AlTiN coating having a thickness of about 1.2 μm directly deposited on the cemented carbide substrate 12.

[0077]

Table 2

[0078] The coating thickness was determined in all cases by grinding a spherical cap with a 20 mm diameter steel ball. A steel ball was used to grind the spherical cap. Then, the ring visible within the spherical cap was measured using an optical microscope. The measurement was performed on the polished free surface of the carbide substrate 12.

[0079] Instrumented coating hardness H IT and instrumented elastic modulus E IT were determined by nanoindentation using the Oliver-Pharr method. An NHT1 device from manufacturer CSM Instruments equipped with a diamond Berkovich indenter was used for the measurement. During the measurement, the maximum load was 10 mN, the load time was 30 s, the creep time was 10 s, and the unloading time was 30 s. The load curve and the unloading curve were recorded. The hardness value and the reduced modulus of elasticity (red.modulus of elasticity) E IT) The value was determined from these load curves and unloading curves using the Oliver-Pharr method. The measurement was performed on the coating surface. The reduced elastic modulus was determined using a lateral strain coefficient of 0.25.

[0080] Figures 6 and 7 show the results of the phase analysis of coating 14 using X-ray microstructural diffraction. The phase analysis was performed using grazing incidence X-ray diffraction (GIXRD) at an incident angle of 1°. A diffractometer from Malvern Panalytical (Empyrean) using Cu K α radiation at 40 kV and 40 mA was used. The measurement was performed with a line focus in a parallel beam through a mirror. A 2 mm mask, a 1 / 8° slit diaphragm for reducing divergence, and a set point of 0.04 rad were used. For the measurement, a 0D proportional detector equipped with a 0.27° plate collimator was used. For the measurement shown in Figure 6, for example, a 2-theta measurement range of 20 to 65° with a step width of 0.07° and a count width of 60 seconds was selected. The incident angle was kept constant at 1°. The obtained diffractogram was used for phase analysis. For better comparability, the background of the XRD diagram was corrected, the diffraction pattern was normalized to the maximum intensity, and a y offset was added as necessary.

[0081] In addition to the reflections of the cemented carbide substrate 12 (hexagonal WC, space group P-6m2, space group number 187, PDF number 51-939 in the ICDD database, vertical dashed line), there are several reflections of both α-Al2O3 (rhombohedral Al2O3, space group R-3c, space group number 167, PDF number 42-1468 in the ICDD database, vertical dotted line), and γ-Al2O3 (cubic Al2O3 - space group Fd-3m, space group number 227, ICDD database PDF number 10-425, vertical line). For clarity, the TiO2 and AlTiN phases were not marked in the diffraction pattern. The coating according to the present invention exhibits a (024) reflection of α-Al2O3 at about 52.559° of 2-theta. This demonstrates the presence of the α-Al2O3 phase in the coating 14 according to the present invention. Furthermore, the γ-Al2O3 phase is also present.

Claims

Claim 1 A method for producing a coated tool component of a cutting tool, comprising: providing the tool component as a substrate comprising a substrate material selected from the group consisting of cemented carbide, cermet, cubic boron nitride (CBN), polycrystalline diamond (PCD), or high speed steel; Alpha - Al 2 O 3 Phase fraction and gamma - Al 2 O 3 Al having a phase fraction 2 O 3 Coating the tool part with at least one aluminum oxide (Al 2 O 3 ) - containing coating, and said at least one Al 2 O 3 layer is generated by a reactive magnetron sputtering process, and in said reactive magnetron sputtering process, using at least one aluminum target; It has a noble gas as the first component and oxygen (O 2 ), and / or nitrogen oxides (NO x ) as the second component as the reactive gas, and a mixed gas having these is used. setting the total gas pressure < 1 Pa; setting a process temperature of 400°C to 650°C; Maximum target power density ≤ 100 W / cm 2 and set to a maximum target current ≤ 200 A, generating a magnetic field using at least one solenoid coil operated with a coil current of ≧ 7 A. Claim 2 The method according to claim 1, wherein the reactive magnetron sputtering process is a pulsed magnetron sputtering process, preferably a pulsed magnetron sputtering process using rectangular voltage pulses. Claim 3 The method according to claim 2, wherein the voltage pulse is a bipolar voltage pulse. Claim 4 The method according to claim 2 or 3, wherein the voltage pulse has a pulse frequency of 10 kHz to 150 kHz, preferably 40 kHz to 80 kHz. Claim 5 The method according to any one of claims 1 to 4, wherein the reactive magnetron sputtering process is a dual magnetron sputtering process, preferably a dual magnetron sputtering process using two aluminum targets. Claim 6 The method according to any one of claims 1 to 5, wherein the total gas pressure is set < 700 mPa. Claim 7 The method according to any one of claims 1 to 6, wherein the coil current is ≦ 10 A. Claim 8 In the reactive magnetron sputtering process, 3 W / cm 2 to 30 W / cm 2 , preferably 4 W / cm 2 to 20 W / cm 2 The method according to any one of claims 1 to 7, wherein a time-averaged target power density is set. Claim 9 In the reactive magnetron sputtering process, a bias voltage of 125 V to 300 V is applied to the substrate, according to any one of claims 1 to 8. Claim 10 The method according to claim 9, wherein the bias voltage is a pulsed bias voltage having a bias pulse frequency of 5 kHz to 80 kHz, preferably 10 kHz to 40 kHz, more preferably 20 kHz to 30 kHz. Claim 11 The method according to claim 9 or 10, wherein the bias current is 10 A to 60 A. Claim 12 The method according to any one of claims 1 to 11, wherein the noble gas comprises argon (Ar) and / or krypton (Kr) and / or neon (Ne). Claim 13 said at least one Al 2 O 3 The method according to any one of claims 1 to 12, wherein the layer is deposited directly on the substrate material, and the substrate material is cemented carbide. Claim 14 A plurality of layers are deposited on the substrate material, and at least one of the layers is the at least one Al 2 O 3 layer is a metal oxide layer on which the layer is directly deposited, and the metal oxide layer contains an oxide of one or more of the metals Ti, Si, V, Zr, Mg, Fe, B, Gd, La, and Cr. The method according to any one of claims 1 to 13. Claim 15 The metal oxide layer contains TiO 2 The method according to claim 14, wherein the metal oxide layer contains TiO Claim 16 A coated tool component of a cutting tool, wherein the tool component comprises a substrate material selected from the group consisting of cemented carbide, cermet, cubic boron nitride (CBN), polycrystalline diamond (PCD), or high-speed steel, and an aluminum oxide (Al 2 O 3 phase fraction and a gamma-Al 2 O 3 phase fraction, and an Al 2 O 3 layer containing at least one aluminum oxide (Al 2 O 3 ), and the at least one Al 2 O 3 layer is produced by the method according to any one of claims 1 to 15, the coated tool component. Claim 17 said at least one Al 2 O 3 layer has an instrumentation layer hardness H IT ≧ 20 GPa, the coated tool component according to claim 16. Claim 18 said at least one Al 2 O 3 layer has an instrumented elastic modulus E IT ≧ 350 GPa, preferably ≧ 380 GPa, the coated tool component according to claim 16 or 17. Claim 19 said at least one Al 2 O 3 layer has a layer thickness of ≧ 10 nm, the coated tool part according to any one of claims 16 to 18.

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