阅读说明：本技术 涂覆的切削工具 (Coated cutting tool ) 是由 法伊特·席尔 约翰尼斯·库梅尔 沃尔夫冈·恩格哈特 于 2020-05-05 设计创作，主要内容包括：本发明涉及一种涂覆的切削工具,所述涂覆的切削工具包含具有涂层的基材,所述涂层包含氮化铝层,所述氮化铝层包含氮化铝相(P),所述氮化铝相(P)显示如下电子衍射图案,其中在高达q＝8.16nm～(-1)的散射矢量下,存在在所述立方和六方氮化铝衍射图案中发现的任一反射以外的至少一个附加反射(R)。(The present invention relates to a coated cutting tool comprising a substrate having a coating comprising an aluminium nitride layer, said coated cutting tool comprisingThe aluminum nitride layer comprises an aluminum nitride phase (P) exhibiting an electron diffraction pattern in which up to q-8.16 nm ‑1 There is at least one additional reflection (R) other than any one of the reflections found in the cubic and hexagonal aluminum nitride diffraction patterns.)

1. A coated cutting tool comprising a substrate having a coating comprising an aluminum nitride layer comprising an aluminum nitride phase (P) that exhibits an electron diffraction pattern wherein up to q-8.16 nm^-1There is at least one additional reflection (R) other than any one of those found in the cubic and hexagonal aluminum nitride diffraction patterns.

2. The coated cutting tool of claim 1, wherein one additional reflection (R) originates fromLattice plane spacing therebetween.

3. The coated cutting tool of any of claims 1-2, wherein one additional reflection (R) originates fromLattice plane spacing therebetween.

4. A coated cutting tool according to any of claims 1 to 3, wherein one additional reflection (R) originates fromLattice plane spacing therebetween.

5. The coated cutting tool according to any one of claims 1 to 4, wherein in the aluminum nitride phase (P), there are lattice planes having the same lattice plane spacing (d), the lattice planes having the same lattice plane spacing (d) being at an angle of between 40 ° and 58 °, preferably between 46 ° and 55 °, most preferably between 48 ° and 52 ° to each other.

6. The coated cutting tool of claim 5, wherein one lattice interplanar spacing (d) corresponds to the innermost spot in the electron diffraction pattern.

7. The coated cutting tool of any of claims 1-6, wherein

Absence of lattice interplanar spacing of hexagonal aluminum nitride in the aluminum nitride phase (P)(110 orientation, pdf-Nr.00-025-1133), and/or

Absence of cubic aluminum nitride lattice interplanar spacing in the aluminum nitride phase (P)(200 orientation, pdf-Nr.00-046-.

8. The coated cutting tool of any of claims 1-7, wherein the aluminum nitride phase (P) comprisesLattice plane spacing therebetween.

9. The coated cutting tool of claim 8, wherein the aluminum nitride phase (P) hasThe preferred orientation of the lattice interplanar spacing therebetween is at an inclination of 50 deg. to 70 deg. relative to the surface normal.

10. The coated cutting tool of any of claims 1-9, wherein the aluminum nitride phase (P) is present in the aluminum nitride layer in the form of domains having an average size of less than or equal to

11. The coated cutting tool of any of claims 1-10, wherein the aluminum nitride layer has a Vickers hardness of ≥ 2700 HV.

12. The coated cutting tool of any of claims 1-11, wherein the aluminum nitride layer has a reduced young's modulus of 380GPa or greater.

13. The coated cutting tool of any of claims 1-12, wherein the aluminum nitride layer has a plastic deformation ratio of ≧ 42%.

14. The coated cutting tool of any of claims 1 to 13, wherein the aluminum nitride layer has a thickness of 0.5 to 10 μ ι η.

15. The coated cutting tool of any of claims 1-14, wherein the substrate is selected from cemented carbide, cermet, cBN, ceramic, PCD, and HSS.

16. A method of making a coated cutting tool according to any of claims 1-15, comprising:

providing a substrate; and

in HIPIMS mode>0.2kW/cm²Preferably, the>0.4kW/cm²Most preferably>0.7kW/cm²At peak power density of>0.2A/cm²Preferably, the>0.3A/cm²Most preferably>0.4A/cm²And the aluminum nitride layer is deposited at a maximum peak voltage of 1000V or more.

Background

There is a continuing desire to improve cutting tools for metal machining so that they have longer service lives, withstand higher cutting speeds and/or other increasingly demanding cutting operations.

Generally, a cutting tool for metal machining includes: a substrate of a hard material such as cemented carbide, cubic boron nitride or cermet; and a thin wear resistant coating deposited on the surface of the substrate.

Ideally, the coating should have a high hardness, but at the same time sufficient toughness to withstand the harsh cutting conditions for as long as possible.

Ideally, coatings for metal cutting tools should also have as low a thermal conductivity as possible, as this property is related to the heat resistance of the coating.

Aluminum nitride coatings deposited by Physical Vapor Deposition (PVD) are well known. However, the main field of application of aluminum nitride coatings is in the semiconductor industry, and only a few applications as wear resistant coatings in metal cutting are known. The crystal structure of aluminum nitride is a cubic structure (sphalerite structure or rock salt structure) and a hexagonal structure (wurtzite structure).

For example, reference crystallographic data for cubic aluminum nitride are provided in the journal of physics (Zeitschrifft fur Physik), volume 22 (1924), pages 201-214. Reference crystallographic data for hexagonal aluminum nitride is provided, for example, in Journal of Applied Physics, volume 73 (1993), pages 8198-. In addition, crystallographic data from powder diffraction analysis for cubic aluminum nitride was found in ICDD pdf-Nr.00-046-.

Cubic aluminum nitride comprises an angle of 90 ° between the lattice planes of the largest lattice plane spacing, and hexagonal aluminum nitride comprises an angle of 60 ° between the lattice planes of the largest lattice plane spacing.

In aluminum nitride deposited by PVD, the hexagonal phase is typically found. Hexagonal aluminum nitride is not very wear resistant and is susceptible to plastic deformation, which is why its use in metal cutting is limited. The main use of PVD deposited aluminum nitride, which has been used in the past as a coating for cutting tools, is as an uppermost layer provided on some other wear resistant layer to provide lubrication.

It is an object of the present invention to provide a coated cutting tool with improved tool life.

Disclosure of Invention

There is now provided a coated cutting tool comprising a substrate having a coating comprising an aluminium nitride layer comprising an aluminium nitride phase (P) which exhibits an electron diffraction pattern wherein up to q-8.16 nm^-1There is at least one additional reflection (R) other than any one of those found in the cubic and hexagonal aluminum nitride diffraction patterns.

Thus, the aluminum nitride layer comprises at least one aluminum nitride phase that is neither hexagonal nor cubic.

In one embodiment, the aluminum nitride phase (P) in the electron diffraction pattern appears to originate from At least one additional reflection (R) of the lattice plane spacing therebetween.

In one embodiment, the aluminum nitride phase (P) in the electron diffraction pattern appears to originate fromAt least one additional reflection (R) of the lattice plane spacing therebetween.

In one embodiment, the aluminum nitride phase (P) in the electron diffraction pattern appears to originate fromAt least one additional reflection (R) of the lattice plane spacing therebetween.

In one embodiment, the aluminum nitride phase (P) in the electron diffraction pattern appears to originate fromIn betweenAt least one additional reflection (R) of the lattice interplanar spacing and originating from At least one additional reflection (R) of the lattice plane spacing therebetween.

In one embodiment, the aluminum nitride phase (P) in the electron diffraction pattern appears to originate fromAt least one additional reflection (R) of the lattice interplanar spacing therebetween, originating fromAt least one additional reflection (R) of the lattice interplanar spacing therebetween and originating fromAt least one additional reflection (R) of the lattice plane spacing therebetween.

In electron diffraction analysis, there is a mismatch in the pattern derived from the aluminum nitride phase (P) and the reference cubic aluminum nitride diffraction pattern and hexagonal diffraction pattern in one embodiment. This mismatch means that the location of the diffraction spot is a lack of match compared to literature structural data for cubic or hexagonal crystal structures. This is illustrated by the following: for a particular lattice spacing, some of the diffraction spots from the reference pattern are completely missing, and the angle between the diffraction spots of the aluminum nitride phase (P) originating from the particular lattice spacing is different from that in the reference pattern.

In one embodiment, in the aluminum nitride phase (P), there are lattice planes having the same lattice plane spacing (d), and the lattice planes having the same lattice plane spacing (d) are at an angle of 40 ° to 58 °, preferably 46 ° to 55 °, and most preferably 48 ° to 52 ° with respect to each other.

In one embodiment, one lattice interplanar spacing (d) corresponds to the innermost spot in the electron diffraction pattern. Said corresponding to electron diffractionThe lattice interplanar spacing (d) of the innermost spots in the pattern is suitably atIn the meantime.

In one embodiment, the lattice interplanar spacing of the hexagonal aluminum nitride is absent from the aluminum nitride phase (P)(110 orientation, pdf-Nr.00-025-1133).

In one embodiment, the lattice interplanar spacing of cubic aluminum nitride is absent from the aluminum nitride phase (P)(200 orientation, pdf-Nr.00-046-.

In one embodiment, the lattice interplanar spacing of the hexagonal aluminum nitride is absent from the aluminum nitride phase (P)(110 orientation, pdf-Nr.00-025-1133) and the lattice interplanar spacing of cubic aluminum nitride(200 orientation, pdf-Nr.00-046-.

The aluminium nitride phase (P) suitably comprisesPreferablySuitably determined by XRD peaks at 2theta between 37 and 39 deg. of the aluminium nitride phase (P).

In one embodiment, the aluminum nitride phase (P) hasPreferablyThe preferred orientation of the lattice interplanar spacings therebetween is at an inclination from 50 deg. to 70 deg. relative to the surface normal, preferably at an inclination from 55 deg. to 65 deg. relative to the surface normal.

The aluminium nitride phase (P) is suitably present in the form of domains in the aluminium nitride layer.

The domains of the aluminium nitride phase (P) are suitably present throughout the aluminium nitride layer.

The average size of the domains of the aluminum nitride phase (P) is suitably less than or equal toPreferably less than or equal to

The average size of the domains of the aluminium nitride phase (P) is suitablyPreference is given to

The average distance between the domains of the aluminium nitride phase (P) is suitablyPreference is given to Most preferably

In the aluminum nitride layer, there are regions that release coherent diffraction signals. This can be seen in dark field TEM. These regions are suitably distributed throughout the aluminium nitride layer. The average size of the areas releasing coherent diffraction signals is suitably from 50 to 500nm, preferably from 75 to 300 nm.

In one embodiment the aluminium nitride layer comprises, in addition to the aluminium nitride phase (P), a phase of hexagonal and/or cubic structure, preferably hexagonal structure.

The amount of aluminium nitride phase (P) in the aluminium nitride layer relative to the total amount of aluminium nitride is suitably at least 50 volume%, preferably at least 75 volume%, more preferably at least 90 volume%.

In one embodiment, the amount of aluminum nitride phase (P) in the aluminum nitride layer relative to the total amount of aluminum nitride is substantially 100 vol%.

The aluminium nitride layer suitably has a Vickers hardness of ≥ 2700HV, preferably ≥ 2800 HV.

The aluminum nitride layer suitably has a Vickers hardness of 2700-3300 HV or 2800-3200 HV.

The aluminium nitride layer suitably has a reduced Young's modulus of 380GPa or more, preferably 400GPa or more.

The aluminum nitride layer suitably has a Young's modulus of 380-430 GPa or 400-425 GPa.

The aluminium nitride layer suitably has a plastic deformation ratio of 42% or more, preferably 44% or more. A high plastic deformation ratio means a more ductile layer, i.e. a layer with low brittleness, and this is beneficial in metal cutting operations, as it reduces the risk of damage to the coating of the cutting tool.

The thermal conductivity values of aluminum nitride vary widely in the literature and values up to 170W/mK are reported. The aluminum nitride layer of the present invention exhibits a relatively low value, which is beneficial in metal cutting operations.

The aluminum nitride layer suitably has a thermal conductivity of 5 to 50W/mK, preferably 15 to 40W/mK.

For wear resistant coatings on cutting tools, low thermal conductivity is advantageous to keep the thermal load on the tool substrate during cutting as low as possible.

In one embodiment, the aluminum nitride layer contains Ar in an amount of 0.05 to 10 atomic%, preferably 0.1 to 5 atomic%, most preferably 0.8 to 2 atomic%.

The thickness of the aluminum nitride layer is suitably 0.3 to 20 μm, preferably 0.5 to 10 μm, most preferably 1 to 5 μm.

In one embodiment, the coating comprises one or more additional metal nitride and/or oxide layers below or above the aluminum nitride layer. The metal nitride is suitably one or more nitrides of one or more metals belonging to groups 4 to 6 of the IUPAC periodic table of the elements and optionally Al and/or Si. Examples of such metal nitrides are TiN and (Ti, Al) N. An example of an oxide is alumina.

The substrate of the coated cutting tool may be of any kind commonly used in the field of cutting tools for metal machining. The substrate is suitably selected from: cemented carbide, cermet, cBN, ceramic, PCD and HSS.

In a preferred embodiment, the substrate is cemented carbide.

The coated cutting tool may be a coated cutting insert, such as a coated cutting insert for turning or a coated cutting insert for milling, or a coated cutting insert for drilling, or a coated cutting insert for threading or a coated cutting insert for parting and grooving. The coated cutting tool may also be a coated solid cutting tool, such as a solid drill, end mill, or tap.

The aluminum nitride layer is suitably deposited by high power pulsed magnetron sputtering (HIPIMS).

Accordingly, there is further provided herein a method of making a coated cutting tool as disclosed herein, the method comprising: providing a substrate; and in HIPIMS mode>0.2kW/cm²Preferably, the>0.4kW/cm²Most preferably>0.7kW/cm²At peak power density of>0.2A/cm²Preferably, the>0.3A/cm²Most preferably>0.4A/cm²And a maximum peak voltage of 1000V or more.

The maximum peak voltage is suitably 1000 to 3000V, preferably 1500 to 2500V.

The substrate temperature during magnetron sputtering is suitably 350 to 600 ℃ or 400 to 500 ℃.

The DC bias voltage used in the HIPIMS step is suitably 20 to 150V, preferably 30 to 100V.

The average power density in the HIPIMS step is suitably 20 to 100 W.cm^-2Preferably 30 to 75 W.cm^-2。

The pulse length used in the HIPIMS step is suitably from 2. mu.s to 200ms, preferably from 10. mu.s to 100ms, more preferably from 20. mu.s to 20ms, and most preferably from 40. mu.s to 1 ms.

Method

XRD-phase analysis:

the X-ray diffraction pattern for phase analysis was obtained by grazing incidence mode (GIXRD) on a diffractometer from Panalytical (Empyrean). CuK α radiation with line focus was used for analysis (high voltage 40kV, current 40 mA). The incident beam is defined by a 2mm mask and an 1/8 ° diverging slit and an X-ray mirror that produces a parallel X-ray beam. Lateral divergence is controlled by Soller slits (0.04 °). For the diffracted beam path, a 0.18 ° parallel plate collimator and proportional counter (0D detector) were used. The measurement was performed in a grazing incidence mode (Ω ═ 1 °). The 2theta range is about 28 deg. -45 deg. with a step size of 0.03 deg. and a counting time of 10 seconds. For XRD line profile analysis, reference measurements (using LaB6 powder) were made using the same parameters as above to correct for instrument spread.

The lattice plane spacing (d) is calculated from the reflected peak position using Bragg's law n λ 2dsin θ, i.e.:

reflection order (n) × wavelength (λ) × 2 × lattice spacing (d) × Sin θ,

where θ is the peak position by XRD (2Theta [ Theta ] θ)]) Given that λ is the wavelength of the X-rays from which it is derivedGiven (for Cu), and where n is 1.

From the Williamson-Hall equation using XRD profile data (peak width), the average domain size of the phase in the coating can be calculated.

XRD-texture analysis

For the analysis of the texture in the coating, a diffractometer (Chi-Scan) from Seifert/GE (PTS 3003) was used. The analysis was performed using CuK α radiation with a polycapillary lens (for producing a parallel beam) (high voltage 40kV, current 40 mA). The incident beam is defined by a 2mm pinhole. For the diffracted beam path, an energy dispersive detector (Meteor 0D) was used. The measurement is done by tilting the Chi axis from-89 to 89 deg. with a step size of 1 deg. and a counting time of 30 seconds.

TEM analysis

Transmission electron microscopy data (diffraction pattern and dark field image of selected areas) were obtained by transmission electron microscopy from FEI (FEI TITAN 80-300). For the analysis, a high voltage of 300kV was used.

When referring to electron diffraction experiments herein, these are TEM measurements performed under parallel illumination. The target area is selected using the select aperture.

For the preparation of TEM samples, FIB (focused ion beam) grids (lift out) were used. For the final polishing, the Ga ion beam was adjusted to a current of 200pA at 5 kV.

The cross-section of the coating was analyzed perpendicular to the coating surface.

FIB-SEM analysis

For the FIB cross-section, FIB-SEM Crossbeam 540 (manufacturer: Zeiss Corp.) was used. For the cross-section, the following parameters (after Pt deposition) apply: rough cutting is carried out for 30kV 30 nA; fine cutting 30kV 3 nA; polishing: 30kV 700 pA. SEM images were obtained by SE 2-and Inlens-detectors at a high voltage of 5kV and an electron beam current of 300 pA.

Vickers hardness:

vickers hardness was measured by nanoindentation (load-depth map) using picocode HM500 from Helmut Fischer, sinaderfen, germany. For the measurement and calculation, the Oliver and Pharr evaluation algorithms were applied, in which a diamond test body according to vickers was pressed into the layer and the force-path curve was recorded during the measurement. The maximum load used was 15mN (HV 0.0015), the time periods for load increase and load decrease were 20 seconds respectively and the holding time (creep time) was 10 seconds. Hardness was calculated from the curve.

Reduced Young's modulus

The reduced young's modulus (reduced elastic modulus) was determined using the nanoindentation (load-depth map) described for determination of vickers hardness.

Plastic deformation ratio:

the numbers are estimated from the load indentation curve obtained as described for determining vickers hardness. The area enclosed by the loading and unloading curves corresponds to the plastic deformation energy. The area under the loading curve gives the plastic and elastic deformation energy. The amount of plastic deformation energy can then be calculated.

Thermal conductivity:

a time-domain-thermal reflectance (TDTR) method having the following characteristics was used:

1. the sample is locally heated using a laser pulse (pump).

2. Thermal energy is transferred from the sample surface to the substrate according to thermal conductivity and heat capacity. The surface temperature decreases with time.

3. The reflected laser light depends in part on the surface temperature. The second laser pulse (probe pulse) is used to measure the temperature drop of the surface.

4. By using a mathematical model, the thermal conductivity can be calculated. Reference (d.g. caihill, scientific instruments review (rev.sci.instr.)75,5119 (2004)).

Thickness:

the thickness of the coating was determined by hemispherical grinding (calotte grinding). Whereby a steel ball with a diameter of 30mm was used to grind the dome-shaped depression and the diameter of the ring was further measured, whereby the layer thickness was calculated. The layer thickness of the Rake Face (RF) of the cutting tool was measured at a distance of 2000 μm from the nose and the flank face was measured in the middle of the Flank Face (FF).

Examples of the invention

Example 1 (invention):

an aluminum nitride film was deposited on the WC — Co based substrate of the mirror polished blade using HIPIMS mode in an HTC1000 Hauzer apparatus.

The composition of the substrate was 10 wt% Co and balance WC. The geometry of the cutting insert is S15.

Average power: 20kW

Pulse power: 1.14MW

Maximum peak voltage: 2000V

Pulse current: 600A

Pulse on time: 80 mus

Frequency: 800Hz

Temperature: 450 deg.C

Size of target: 18X 83cm

Material of the target: al (Al)

Total pressure: 5.68X 10^-3mbar

Argon flow: 500sccm

Bias potential: -80V (DC)

Target-substrate distance: about 20cm

Deposition time: 3 hours

Coating thickness: 1 μm, measured on a 2-fold surface of revolution (flank) parallel to the target surface

Example 2 (reference):

another aluminum nitride film was deposited on the WC — Co based substrate of the mirror polished insert using HIPIMS mode in an Oerlikon Balzers S3P Ingenia apparatus.

The composition of the substrate was 10 wt% Co and balance WC. The geometry of the cutting insert is S15.

Average power per source: 3.3kW

Pulse on time: 50ms

Pulse current: 45A

Frequency: 6Hz

Temperature: 450 deg.C

Size of target:

material of the target: al (Cr-containing blade)

Total pressure: 0.9Pa

Argon flow: 240sccm

Bias potential: -100V (Bipolar)

Target-substrate distance: about 12cm

Deposition time: 90 minutes

Coating thickness: 0.64 μm, measured on a 2-fold surface of revolution (flank) parallel to the target surface

Grazing incidence xrd (gixrd) analysis was performed on the samples from examples 1 and 2. The XRD pattern of the inventive coating is shown in fig. 1 and the XRD pattern of the comparative (hexagonal) reference coating is shown in fig. 2.

It can be seen that the inventive coating shows broad peaks between 35 deg. -40 deg. (2 theta), while the comparative (hexagonal) reference coating shows sharp peaks in the same interval.

In fig. 1 and 2, respectively, the XRD curves of the solid lines are raw diffraction curves with distinct signals originating from WC at about 31.5 ° and 36 ° 2 θ. However, a signal derived from aluminum nitride was observed as a shoulder peak at about 36 ° to 37 ° 2 θ in fig. 1 and 2. In fig. 2, there is also a sharp aluminum nitride peak at about 38 ° 2 θ. The dashed line in fig. 1 and 2 is the diffraction curve of aluminum nitride extracted from the original diffraction curve by peak profile fitting.

A detailed analysis of the position and width of the diffraction peaks observed at 2theta of about 37 to 38 ° gives the data seen in table 1 for the inventive coating and the reference hexagonal aluminum nitride coating:

table 1.

The profile (width) of the XRD peaks is affected by the average size of the domains giving a particular diffraction. The correlation length (considered here to be the same as the average domain size) can be calculated by using the Williamson-Hall equation. For the inventive coating it can be seen that the size of the domains that produce specific diffraction in the inventive coating is much smaller than such domains in the reference coating.

Since the X-ray has a wavelength ofThe possibility of more detailed structural analysis from XRD data is therefore limited. In addition, since the microcrystalline structure is very fine, XRD cannot be used to determine the angle between lattice planes.

However, information on the growth direction of the aluminum nitride layer can be obtained from XRD analysis. In FIG. 3, the equation according toThe chi scan of the diffraction signal at (a). For the coatings of the present invention, the lattice plane (at about) is comparable to the hexagonal reference coatingWhere) the tilt (as an average) relative to the surface normal is smaller. In addition, the peaks were fitted using a Gaussian (Gaussian) profile. The position of the maximum of the fitted gaussian profile corresponds to the tilt angle relative to the vertical plane and the variation of the profile corresponds to the full width at half maximum (FWHM) of the peak.

The samples were further subjected to electron diffraction analysis. FIGS. 4-6 show the same electron diffraction patterns obtained from coatings of the present invention. The black dots contained in fig. 4 correspond to a cubic pattern (from the literature) and the black dots in fig. 5 correspond to a hexagonal pattern (from the literature).

For the evaluation of the experimental data, use was made of up to q-8.16 nm^-1The scattering vector of (2). This vector is shown in the diffraction diagram as a dashed line in fig. 4 and 5. It can be seen from the electron diffraction images that there is no perfect match between the measured diffraction pattern of the coating and the theoretical diffraction patterns of cubic AlN and hexagonal AlN (black dots in fig. 4 and 5, respectively). For cubic and hexagonal crystals, each has many specific reflections originating from the lattice planes in their structure, but for the coatings of the present invention, some of these reflections are absent. It was therefore concluded that the crystal symmetry of the coating of the invention is neither cubic nor hexagonal.

As can be seen from the electron diffraction pattern, there are reflections originating from at least three d-spacings (see solid line rings in fig. 4 and 5) that do not match any of the d-spacings in the cubic or hexagonal structure.

In fig. 6, the angle between the innermost diffraction spots is marked and measured as 48 °.

Even if using distortionCell (variation of angle + -5 DEG; variation of cell parameters)) The diffraction patterns obtained for fitting the aluminum nitride phase (P) of the cubic or hexagonal aluminum nitride diffraction pattern cannot be indexed either. The conclusion is that the aluminum nitride phase (P) is not a distorted cubic or hexagonal structure, but rather a unique structure itself.

By using a Scanning Electron Microscope (SEM), crystallite sizes in the μm range can be detected. However, TEM DF images show the presence of substructures in the form of regions, each having dimensions from about 10nm to about several hundred nm (on average about 50-200 nm), which contribute coherently to the diffraction signal. Smaller domain structures with the same crystal orientation are also seen in this region and their size is in the range of 2-10 nm. The distance between these domain structures with the same crystal orientation seems to be in the same range, i.e. 2-10 nm. An example of a dark field TEM image of an aluminum nitride layer according to the present invention is seen in figure 7.

Hardness measurements (load 15mN) were performed on the flank of the coated tool to determine vickers hardness, reduced young's modulus (EIT) and plastic deformation ratio (n pl). Table 2 shows the results. To characterize the toughness (Young's modulus) of the coatings, Vickers indentation was carried out under a load of 500mN and cross sections were prepared.

Table 2.

From the SEM pictures it can be concluded that the crack propagation of the hexagonal aluminum nitride reference coating is characterized by straight cracks extending directly through the coating down to the substrate. The crack propagation of the coating according to the invention is characterized in that the crack does not reach the substrate and also deviates. See fig. 8 for the resulting cracked state of the hexagonal reference coating and fig. 9 for the resulting cracked state of the coating according to the invention.

Finally, for the coating according to the invention, a thermal conductivity in the range of 26 ± 3W/mK was determined.

Drawings

Figure 1 shows an X-ray 2theta diffraction pattern of an aluminum nitride layer according to the present invention.

Fig. 2 shows an X-ray 2 θ diffraction pattern of an aluminum nitride layer having a conventional hexagonal structure.

Figure 3 shows an X-ray chi scan of an aluminum nitride layer according to the invention and an aluminum nitride layer having a conventional hexagonal structure.

Fig. 4 shows an electron diffraction image of the aluminum nitride phase (P), in which the cubic aluminum nitride diffraction pattern is marked as black spots.

Fig. 5 shows an electron diffraction image of the aluminum nitride phase (P), in which the hexagonal aluminum nitride diffraction pattern is marked as black spots.

Fig. 6 shows an electron diffraction image of the aluminum nitride phase (P) in which angles are shown between the innermost diffraction spots. The hexagonal aluminum nitride diffraction pattern is marked as white spots.

Figure 7 shows a dark field TEM image of an aluminum nitride layer according to the present invention.

Fig. 8 shows crack propagation for a reference hexagonal aluminum nitride coating.

Fig. 9 shows the crack propagation of an aluminum nitride coating according to the invention.