Coated cutting tool comprising a kappa-alumina layer

Abstract

The invention relates to a coated cutting tool comprising a substrate and a coating wherein the coating comprises i) a first Ti(C,N) layer; ii) a layer of ƙ-Al2O3; iii) a second Ti(C,N) layer, wherein said second Ti(C,N) layer as measured with Electron Backscatter Diffraction (EBSD) on a 25x25 μm area exhibits an orientation on the rake face wherein ≥ 60%, preferably ≥ 65%, of the grains have a <111> direction within 15 degrees from the surface normal of said second Ti(C,N) layer; wherein the thickness of the first Ti(C,N) layer ranges from 1 to 10 µm wherein the thickness of the ƙ-Al2O3 layer ranges from 0.3 to 4 µm wherein the thickness of the second Ti(C,N) layer ranges from 2 to 12 µm; and wherein the layers of i), ii), and iii) are arranged in the mentioned order counted from the substrate.

Description

[0001] Coated cutting toolThe present invention relates to a coated cutting tool, especially for use in machiningoperations such as milling of stainless steel.Background of the invention Adhesive machining operations such as milling of stainless steels are generally associated with adhesive and chemical wear of coated inserts.Inserts with an outermost Al2O3 coating layer have shown short lifetime due to adhesive andchemical wear of the oxide layer, especially for stainless steel milling operations. When theoxide layer is worn-out, an inner layer on which the Al2O3 layer is deposited will usually sufferfrom abrasive and adhesive wear.An object of the present invention is thus to provide a coated cutting tool having improvedwear resistance for milling operations of stainless steel. A further object of the invention is toprovide a coated cutting tool with a relatively thin coating while still obtaining satisfyingperformance. The invention The present invention relates to a coated cutting tool comprising a substrate and a coating wherein the coating comprises i) a first Ti(C,N) layer ii) a layer of ƙ-Al2O3 iii) a second Ti(C,N) layer, wherein said second Ti(C,N) layer as measured with Electron Backscatter Diffraction (EBSD) on a 25x25 μm area exhibits an orientation on the rake facewherein ≥ 60%, preferably ≥65%, of the grains have a <111> direction within 15 degreesfrom the surface normal of said second Ti(C,N) layer; wherein the thickness of the first Ti(C,N) layer ranges from 1 to 10 µmwherein the thickness of the ƙ-Al2O3 layer ranges from 0.3 to 4 µm wherein the thickness of the second Ti(C,N) layer ranges from 2 to 12 µm; and wherein the layers of i), ii), and iii) are arranged in the mentioned order counted from the substrate. According to one embodiment, the first Ti(C,N) layer has a texture coefficient TC (hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula (1) wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection; I0(hkl) is the corresponding reference intensities: I0(111) = 7871, I0(200) = 10000, I0(220) = 5369, I0(3 11) = 2550, I0(331) = 1128, I0(420) = 2366, I0(422) = 2479, and I0(511) = 1427; n is the number of reflections used in Harris formula (1), wherein the (hkl) reflections used are (111), (200), (220), (311), (331), (420), (422), and (511), wherein TC(422) ≥ 3 on therake face. According to one embodiment, the ƙ-Al2O3layer has a texture coefficient TC(hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula (1) wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection; I0(hkl) is the corresponding reference intensities: I0(111) = 105, I0(013) = 5026, I0(122) = 10000, I0(11 3) = 1116, I0(200) = 795, I0(201) = 1342, I0(004) = 291 , I0(040) = 387, I0(015) = 429 and I0(204) = 1312; n is the number of reflections used in Harris formula (1), and wherein the (hkl) reflections used are (111), (013), (122), (113), (200), (201), (004), (040), (015) and (204), wherein TC(004) ≥ 4 on the rake face, preferably ≥ 5, and more preferably ≥ 6. According to one embodiment, ≥ 70% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, ≥ 75% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, ≥ 80% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, ≥ 85% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, ≥ 90% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, ≥ 95% of the grains have a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer. According to one embodiment, the second Ti(C,N) layer has a compressive stress ranging from 1 to 3 GPa, preferably from 1.5 to 2.5 GPa as measured on the rake face. According to one embodiment, the total thickness of the coating ranges from 5 to 20 µm, preferably 7 to 13 µm.According to one embodiment, the thickness of the first Ti(C,N) layer ranges from 1 to 8 µmor from 1 to 6 µm or from 1 to 5 µm or from 1.5 to 4 µm or from 1.5 to 3 µm.According to one embodiment, the thickness of the ƙ-Al2O3 layer ranges from 0.5 to 4 µm or0.7 to 4 µm or 0.8 to 4 µm or 1 to 4 µm or from 1.5 to 4 µm or from 1.5 to 3 µm.According to one embodiment, the thickness of the second Ti(C,N) layer ranges from 2 to 10µm or from 2 to 7 µm or from 3 to 5 µm.According to one embodiment, the thickness of the first Ti(C,N) layer ranges from 1 to 5 µm,the thickness of the ƙ-Al2O3 layer ranges from 1 to 4 µm, and the thickness of the secondTi(C,N) layer ranges from 2 to 7 µm.According to one embodiment, the thickness of the first Ti(C,N) layer ranges from 1.5 to 4µm, the thickness of the ƙ-Al2O3 layer ranges from 1 to 4 µm, and the thickness of the secondTi(C,N) layer ranges from 2 to 7 µm.According to one embodiment, the thickness of the first Ti(C,N) layer ranges from 1.5 to 3µm, the thickness of the ƙ-Al2O3 layer ranges from 1.5 to 3 µm, and the thickness of thesecond Ti(C,N) layer ranges from 3 to 5 µm. According to one embodiment, the coating does not comprise any additional Ti(C,N) layer and / or additional ƙ-Al2O3 layer as specified herein. According to one embodiment, the coating does not comprise any nano-multilayer ofalternating layers such as alternating first and second nanolayers of Ti(C,N) and / or ƙ-Al2O3.According to one embodiment, the coating does not comprise a top layer above thesecond Ti(C,N) layer with a layer thickness > 200 nm.According to one embodiment, the coating does not comprise an additional layer with a layerthickness > 200 nm in direct contact with the ƙ-Al2O3 layer.According to one embodiment, the coating does not comprise any α-Al2O3 layer.According to one embodiment, the substrate is selected from cemented carbide, cermet, ceramics and / or cubic boron nitride, preferably cemented carbide. According to one embodiment, the substrate of the coated cutting tool consists of cementedcarbide comprising 4-14 wt% Co, for example 8-12 wt% Co, and optionally 0.1-10 wt% cubiccarbides, nitrides or carbonitrides of metals from groups IVb, Vb and VIb of the periodictable, preferably Ti, Nb, Ta or combinations thereof; and balance WC.According to one embodiment, the cutting tool is an insert, preferably a milling insert.By the term “shot peening” is herein meant that the surface of a cutting tool is bombardedwith a media comprising particles, so called beads, that are non-abrasive and typically ofrounded shape. The media can be beads of a hard material such as an oxide, e.g. ZrO2;ceramics, steel or cemented carbide.The shot peening is preferably performed in a dry process whereby beads (media) may beintroduced by various methods into the path of high pressure air.According to one embodiment, the shot peening is performed with peening media beadshaving a diameter of 70-150 µm, a peening pressure of 3 - 6 bar at a distance of 15 to 25 cmduring 0.5 to 3 seconds per tool. The impact or energy from the beads during the shotpeening should not be too high since this would increase the risk of damaging the surface and the cutting edge of the cutting tool. Neither should the impact or energy from the beads be too low since the desired technical effect would not be obtained. If the beads are too large the risk of damaging the cutting edge is increased. If the beads are too small the energy andimpact transferred from the media to the coated tool are less pronounced.By the term “wet blasting” is meant a process using abrasive grains wherein material typically is removed from the treated surface by abrasive wear. Wet blasting is well known in the fieldof cutting tools and is for example known to introduce residual stresses in the coatingsthereof.According to one embodiment, wet blasting is performed subsequent to shot peening with ablasting media comprising Al2O3particles of a diameter of 20-80 µm. According to one embodiment, the wet blasting is performed at a distance of 15 to 25 cm forabout 1 to 3 seconds per tool with a blasting pressure of 1.2 - 2.0 bar.According to one embodiment, the shot peening and the wet blasting are performed in a shot direction that is perpendicular or substantially perpendicular to the surface of the cutting tool.A perpendicular direction is advantageous in the sense that a maximal depth in the impactedsubstrate is obtained.Description of embodiments in the drawingsFigure 1a illustrates a coating structure according to the invention, wherein a first Ti(C,N)layer 1 is deposited on a substrate (not shown), a ƙ-Al2O3 layer 2 is deposited on the firstTi(C,N) layer 1, and a second Ti(C,N) layer 3 is deposited on the ƙ-Al2O3 layer 2.Figure 1b illustrates a coating structure according to a reference, wherein a first Ti(C,N) layer4 is deposited on a substrate (not shown) and a ƙ-Al2O3 layer 5 is deposited on the firstTi(C,N) layer 4.Figure 2 shows a fractured cross-section of the thicknesses of the coating layers 1, 2, and 3as further shown in figure 1a.Figure 3 shows a fractured cross-section of the thicknesses of the coating layers 4 and 5 ofthe reference.Figure 4a shows standard Pole figures of an FCC (face-centred cubic) symmetry of thesecond Ti(C,N) layer in example 2a based on EBSD measurements as further describedherein.Figure 4b shows a pole plot of a {111} pole with indicated integrated intensity areas A1 andA2 obtained from the pole figure in figure 4a.Measurement methods In the below, the measurement methods used in the working examples herein are defined. X-ray diffraction measurement Texture coefficient values, TC(hkl), were measured using XRD with CuKα radiation on the rakeface of the coated cutting tools using a Bruker D8 Advance diffractometer running a Cu tubeat 40 kV and 40 mA, equipped with a LynxEye XE-T detector, operating in θ-2θ mode. Thediffractometer was equipped with fixed beam optics: on the primary side, a 2.3° Soller slit anda 0.6 mm divergence slit and on the secondary side an anti-scatter slit of 8 mm, followed by a2.5° Soller slit and a 0.5 mm Ni filter. Diffraction patterns were recorded for the range 18° to143° in steps of 0.05° in 2θ for a total measurement time of about 5 min. The coated cuttingtools were mounted in insert holders to ensure that the measured sample surface was parallelto the reference surface of the insert holder at the appropriate height.The data analysis was made using whole-pattern fitting with the Le Bail method using theBruker TOPAS 5 program. The output, i.e. the integrated peak areas for the profile fitted curvefrom this programme was (after corrections further described below) used to calculate thetexture coefficients of the layers by comparing the ratio of the measured intensity data and thereference intensities of the TiCN of the first layer and the ƙ-Al2O3 layers using Harris formula: The measured intensities were thin film corrected due to differences in relative intensities ofthe peaks scattered by the layers at different 2θ angles which were different compared to thebulk samples due to the differences in path length through the layer(s). Therefore, thin film correction was applied to the extracted integrated peak area intensities for the profile fittedcurve taking into account the linear absorption coefficient of layer(s) when calculating the TCvalues. Since possible further outer layers above, for example above the ƙ -Al2O3 layer, willinfluence the X-ray intensities entering the ƙ-Al2O3 layer and exiting the whole coating,corrections need to be made for these layers as well thus taking into account the linearabsorption coefficient for the respective compound in the layer(s). The same applies for the X-ray diffraction measurements of the first TiCN layer located below, for example the ƙ -Al2O3layer. Alternatively, a further layer, such as a TiN or the second Ti(C,N) layer, above the ƙ -Al2O3 layer, can be removed by means of e.g. chemical etching that does not substantiallyinfluence the XRD measurement results.In order to investigate the texture of the ƙ -Al2O3 layer, X-ray diffraction was conducted usingCuKα radiation and texture coefficients TC (hkl) for different growth directions of the grains ofthe k-Al2O3 layer which were calculated according to Harris formula (1), wherein I(hkl) equalsthe measured integrated area intensity of the (hkl) reflection with corresponding reference intensity I0(hkl). In this case the (hkl) reflections and their corresponding reference intensities used were: I0(111) = 105, I0(013) = 5026, I0(122) = 10000, I0(113) = 1116, I0(200) = 795, I0(201) = 1342, I0(004) = 291 , I0(040) = 387, I0(015) = 429 and I0(204) = 1312. The measured integrated peak area is thin film corrected and corrected for any further layers on top of the ƙ-Al2O3layer before said ratio is calculated. The texture coefficients TC (hkl) for different growth directions of the columnar grains of thefirst Ti(C,N) layer were calculated according to Harris formula (1), wherein I(hkl) equals themeasured integrated area intensity of the (hkl) reflection with corresponding reference intensity I0(hkl). In this case the (hkl) reflections and their corresponding reference intensities used were: I0(111) = 7871, I0(200) = 10000, I0(220) = 5369, I0(311) = 2550, I0(331) = 1128, I0(420) = 2366, I0(422) = 2479, and I0(511) = 1427. The reflexes (511) and (333) are completely overlapped and the intensity of the (511) peak was therefore calculated from the sum of theintensities for (511) and (333) which was the peak measured. This correction was performedas follows: I(511) was set to the sum of the integrated peak areas for (511) and (333)followed by subtraction of a calculated value of the (333) reflex, Ic(333), using the relation ofthe reference intensities of the intensities of the (111) and (333) reflexes: Ic(333) = I(111)* I0(333) / I0(111). The value used for I0(333) = 476. The measured integrated peak area is thin film corrected and corrected for any further layers above, for example the ƙ-Al2O3 layerbefore the ratio is calculated.Peak overlap is a phenomenon that can occur in X-ray diffraction analysis of coatingscomprising for example several crystalline layers and / or layers that are deposited on asubstrate comprising crystalline phases which have to be considered and compensated for bythe skilled person conducting the analysis. The peak overlap of the peaks of the ƙ -Al2O3 layerand the peaks of the first Ti(C,N) layer may influence measurements needs to be considered.Also for example WC in the substrate can have diffraction peaks close to the relevant peaksof the present coating which have to be considered.Residual stress measurements for the second Ti(C,N) layerThe residual stress for the second Ti(C,N) layer was evaluated on the rake face of aCNMG12 insert by the sin2y method using the elastic constants 450 GPa and 0.22 forYoung’s modulus and Poisson’s ratio, respectively, and the Ti(C,N) (200) lattice spacings as determined by x-ray diffraction (XRD). The (200) peak position was determined at 2 φ angles(0 and 180°) and 7 y angles (corresponding to sin2 y values of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and0.8). The measurements were made on a Bruker D8 Discover instrument using point focus CuKα radiation. On the primary side, the instrument was equipped with a polycapillary opticand a 2 mm pin hole. On the secondary side, an equatorial Soller slit (0.4^) was usedtogether with a Bruker LynxEye-XET detector operated in 0D mode. The peak fitting was done using the software Bruker Topas5 and Pseudo-Voigt peak functions after which the lattice spacings, d, were calculated and the stress evaluated. Residual stress measurements ƙ -Al2O3 layer (reference)The residual stress of the k-Al2O3layer was evaluated on the rake face of an CNMG12 insertby the sin2^ method using the elastic constants 391 GPa and 0.24 for Young’s modulus andPoisson’s ratio, respectively, and the k-Al2O3(122) lattice spacings as determined by x-ray diffraction (XRD). The (122) peak position was determined at 2 φ angles (0 and 180°) and 6^ angles (corresponding to sin2 ^ values of 0.225, 0.315, 0.405, 0.495, 0.585, and 0.675).The instrumental angles were selected so that the penetration depth, τ, was kept constant at 2 µm throughout the measurements, following the method outlined by A. Kumar, U. Welzel, E.J. Mittemeijer, J. Appl. Cryst. (2006) 39, 633-646. A linear absorption coefficient of 12300 m-1was used when calculating the penetration depth in Al2O3. The measurements were made on a Bruker D8 Discover instrument using point focus CuKα radiation. On the primary side, the instrument was equipped with a polycapillary optic and a 2 mm pin hole. On the secondary side an equatorial Soller slit (0.4^) was used together with a Bruker LynxEye-XET detector operated in 0D mode. The peak-fitting was done using the software Bruker Topas5 and Pseudo-Voigt peak functions after which the lattice spacings, d, were calculated and the stress evaluated. EBSD analysisThe growth orientation of the second Ti(C,N) layer of the invention was evaluated on the rakeface by Electron Backscatter Diffraction (EBSD) analysis on the top surface of the secondTi(C,N) layer. The top surface was subjected to gentle mechanical polishing withsubsequently finer mesh prior to analysis in order to make the top surface flat enough for the EBSD measurements. The growth orientation of the grains was analyzed using EBSD in a Zeiss Ultra SEM, equipped with an Oxford-symmetry EBSD detector at 20 kV accelerating voltage. Regions ofat least 25x25 μm were analyzed with a step size of 0.2 μm. The Sensitivity mode was used.The growth orientation of the top TiCN grains of the second Ti(C,N) layer was analyzed usingthe Aztec Crystal software package (v 6.0). One auto-clean-up using the Aztec Crystal software (v 6.0) was applied for a gentle noise reduction. The sample was analyzed so that the surface of the specimen was parallel to the substrate surface. Software settings usedwas a grain detection angle (threshold) of 10° and an area of at least 40 pixels.The Ti(C,N) reference pattern, J.Electrochem. Soc. [JESOAN], (1950), vol 97, pp 299-304,was used for the Ti(C,N) measurements of the second Ti(C,N) layer.89 reflectors were usedfor the measurements. Pole figures and Pole plots were produced using the Aztec Crystalsoftware (v 6.0) and the (111) Pole plot chart data was exported to a calculation programme.The intensity of the (111) oriented grains was determined by calculating the (111) orientedgrain contribution to the total intensity in the (111) Pole plot. The fraction of the (111) orientedgrains is defined as the sum of the integrated areas A1 and A2 as shown in figure 4b. A1 isthe integrated area from 0 – 15 degrees in the (111) pole plot and A2 is the integrated areafrom 45 – 75 degrees in the (111) pole plot. Due to the cubic symmetry of the unit cell of thesecond TiCN layer of the invention, additional {111} planes appear at 60 degrees from thesurface normal of the observed (111) plane appearing from 0-15 degrees which needs to beaccounted for to obtain the intensity fraction of the (111) oriented grains. The total intensity isthe integrated area from 0 – 90 degrees in the (111) pole plot. The fraction of the (111)grains is calculated as (intensity A1 + intensity A2) / total intensity.Surface roughness measurement from SEM images A surface roughness value for and interface between a substrate and a coating on the rake face can be evaluated from SEM images taken from polished or fractured cross-sections. The method used was performed as follows: A fractured cross-section was collected on a coated insert using a Zeiss Ultra scanning electron microscope equipped with InLens and SE2 detectors operating at 2 kV at working distances between 3 and 4 mm at 10000 magnification, creating images of about 35 μm by 27 μm of the interface of the cross-section between the substrate and the coating. After identification of the interface the image was digitalized using the Digitizer tool in Origin 2018b (b9.5.5.409) by OriginLab and an Ravalue was calculated as follows: The image was imported using the Origin tool Digitizer. Axes were defined in accordance with the scale in the image. Individual points on the interface between the substrate and the coating were collected at about 0.5 μm average interval, shorter intervals for curved and longer intervals for straighter features, thus creating a surface roughness profile. A linear least-squares line was fitted to the obtained profile. The obtained linear least-squares line wassubtracted from the individual data points on the profile, ensuring that possible image rotationwould not affect the evaluation. An Ravalue was calculated using the formula where n = number of points used on the profile and yi is the distance in μm between the point i and the least-squares line. Thickness measurement The coating layer thicknesses were obtained by fractured cross-sections exemplified inFigure 2 (Invention) and figure 3 (Reference) collected on the coated samples. This wasperformed using a Zeiss Ultra scanning electron microscope equipped with InLens and SE2detectors. This microscope was operating at 2 kV at working distances between 3 and 4 mmat a 10000 magnification creating images of about 35 μm by 27 μm. ExamplesThe coatings of the reference and the invention below were deposited in a radial SuCoTecmodel SCT600 tandem CVD equipment capable of housing 10000 half-inch size cuttinginserts. The samples tested and analysed were selected from the middle of the chamber at aposition along half the radius of the plate between the centre and the periphery of the plate.A first type of cemented carbide substrates, X, of ISO-type XOMX120408TR, consisting of 10.0 wt-% Co, 1.4 wt-% Ta, 0.15 wt-% Nb and balance WC was manufactured.The substrates X (same for reference and invention) were polished on the rake face using awet brushing process. The equipment used was a model Sinjet IBX12 with a set-up consisting of two operations:i) coarse polishing and edge preparation using a brush with a flat SiC 240K grain size bristleii) fine polishing by means of a Diamond 1000K bristle. The polishing was performed until asurface roughness of 0.05 µm <Ra< 0.2 µm was obtained on the rake face as defined above.After the polishing a cleaning operation with ultrasonic bath and alkaline solution was used in order to remove any residues from the polishing process. Example 1 - ReferenceThe substrates of the reference were first coated with a thin TiN layer having a thickness ofapproximately 0.4 µm, then with a TiCN layer having a thickness of approximately 2 µm bymeans of well-known MTCVD technique using TiCl4, CH3CN, N2, and H2 as process gases at 860 °C. The volume ratio of TiCl4 / CH3CN of the MTCVD deposition of the TiCN layer was 3.7. The process conditions for the TiN and TiCN depositions are shown in Table 1. Table 1 - MTCVD of TiN and TiCNMT CVD of TiN Pressure H2N2TiCl4CH3CN and TiCN (860 [mbar] [vol%] [vol%] [vol%] [vol%] °C): TiN 120 70.0 28.0 2.0 -TiCN 70 64.4 32.2 2.6 0.7On top of the MTCVD TiCN layer, a 2 µm thick bonding layer was deposited at 1020 °C by aprocess consisting of five separate reaction steps: First a HTCVD TiN-1 step using TiCl4, N2, and H2 at 200 mbar, then a second step (HTCVD TiC-1) using TiCl4, CH4, and H2at 80 mbar, then a third step (HTCVD TiN-2) using TiCl4, HCl,N2 and H2 at 500 mbar; a fourth step (HT TiCN-1) using TiCl4, CH4, HCl, N2 and H2 at 60 mbarand finally a fifth step (HT TiCNO-1) using TiCl4, HCl, CO, N2and H2at 60 mbar wereperformed as further set out in table 2. Prior to the start of the subsequent ƙ-Al2O3 nucleation,the bonding layer was exposed for 33 minutes in an atmosphere of H2at 45-55 mbar. Table 2 - Bonding layer depositionBonding Pressure H2 N2 HCl CO TiCl4 CH4 layer [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] (1020 °C): HTCVD200 70.2 28.1 - - 1.7 -TiN-1 HTCVD80 89.6 - - - 3.5 6.9TiC-1 HTCVD500 47.6 47.6 3.6 - 1.2 -TiN-2 HT-TiCN-60 66.6 15.6 10.0 - 3.4 4.41 HT-60 78.9 - 11.8 5.3 4.0 -TiCNO-1 A ƙ-Al2O3layer was deposited on top of the bonding layer. The ƙ-Al2O3steps were performedat 1020 °C and 55 mbar as further set out in table 3. The first step (Al2O3-1) resulted in athickness of about 0.05 µm ƙ-Al2O3, the second step (Al2O3-2) resulted in a total ƙ-Al2O3layer thickness of about 4 µm.

[0002] Table 3 - ƙ-Al2O3 deposition stepsƙ-Al2O3 Pressure H2 HCl CO2 H2S AlCl3 deposition steps [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] AlCl3-1 55 95.9 2.2 - - 1.9Al2O3-1 55 92.7 2.1 3.4 - 1.8Al2O3-2 55 92.2 2.1 3.4 0.5 1.8Example 2a - InventionThe substrates were coated with an innermost thin TiN layer having a thickness ofapproximately 0.4 µm, then with an approximately 2 µm thick TiCN layer by employing well-known MTCVD technique using TiCl4, CH3CN, N2, and H2 as process gases at 860 °C. The volume ratio of TiCl4 / CH3CN of the MTCVD deposition of the TiCN-1 and TiCN-2 layers were8 and 5 respectively. The process conditions of the TiN and TiCN depositions are shown inTable 4. Table 4 - MTCVD of TiN and TiCNMT CVD of TiN Pressure H2 N2 TiCl4 CH3CN and TiCN (860 [mbar] [vol%] [vol%] [vol%] [vol%] °C): TiN 550 73.5 24.5 2.0 -TiCN-1 50 96.4 0 3.2 0.4TiCN-2 50 85.4 12.2 2.0 0.4On top of the MTCVD TiCN layer, an about 0.3 µm thick bonding layer was deposited at 980°C by a process consisting of four separate reaction steps. First a HCl-etching step using HCland N2 at 60 mbar, then a second step (HTCVD TiCO) using TiCl4, CO, and H2 at 60 mbar,then a third etching step using TiCl4 and H2 at 60 mbar, and then a fourth purging step usingN2 at 60 mbar. Further process conditions of the bonding layer deposition are shown in Table5.Table 5 - Bonding layer depositionBonding Pressure H2 N2 HCl CO TiCl4 layer (980 [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] °C): HCl-etch 60 0 93.0 7.0 - -HTCVD60 91.7 - - 5.0 3.3TiCO TiCl4-etch 60 96.1 - - - 3.9Purge N2 60 100.0 - - - -A ƙ-Al2O3 layer was deposited on top of the bonding layer. The three first steps were depositedat 980 °C and 60 mbar and the fourth step at 980 °C and 150 mbar. The Al2O3-1 stepcontributed most to the total ƙ-Al2O3 layer thickness of about 2.0 µm and the Al2O3-2 stepresulted in about 0.7 µm. The process conditions of the depositions are shown in Table 6.Table 6 - ƙ- deposition steps ƙ-Al2O3Pressure H2HCl CO2H2S AlCl3deposition steps [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] AlCl3-1 60 98.4 - - - 1.6AlCl3-2 60 96.8 1.6 - - 1.6Al2O3-1 60 92.81 1.75 3.55 0.44 1.46Al2O3-2 150 90.0 1.9 6.3 0.08 1.7On top of the ƙ-Al2O3 layer, an about 4 µm thick HTCVD TiCN layer was deposited at 960-980°C by a process consisting of four separate reaction steps while the temperature was ramped down from 980 to 960 °C in the last step. The process conditions of the top layer deposition are shown in Table 7.Table 7 - Top HTCVD-TiCN depositionTop TiCN Pressure H2 N2 CO TiCl4 CH3CN AlCl3 layer (930 [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] -980°C): AlTiCO 60 92.85 - 4.64 1.62 - 0.88TiCO 80 92.99 - 4.98 2.03 - -TiN 80 72.71 25.97 - 1.32 - -TiCN 80 86.0 12.09 - 0.99 0.92 -All coated substrates (samples) of examples 1 and 2a (reference and invention) weresubsequently subjected to shot-peening and wet-blasting as further described below:Shot-peening The shot peening was performed with peening media beads having a diameter of 70-150µm, a peening pressure of 3 - 6 bar at a distance of 10 cm during 1 second per sample.Wet-blastingThe invention samples were subjected to a strong wet blasting programme: A blastingmedia comprising Al2O3 particles of a diameter of 20-80 µm was used at a distance ofabout 20 cm for 1 s duration per sample with a blasting pressure of 1.6 - 2.0 bar. Thesecond Ti(C,N) layer stresses presented in table 8 were determined as further describedherein.The reference samples were subjected to a gentle wet blasting programme with a blastingmedia comprising Al2O3particles of a diameter of 20-80 µm. The wet blasting wasperformed at a distance of about 20 cm for 1 s duration per sample and with a blastingpressure of 1.2 - 1.6 bar. The Al2O3 layer stresses presented in table 9 were evaluated asfurther described herein.Table 8 - the stress in the second Ti(C,N) layer before and after post treatmentSample Stress (GPa) Error (+ / -)Invention (Post treated) -2.15 0.2Invention (As deposited) 0.35 0.07As evident from table 8, the compressive stresses on the rake face were imparted by thestress-inducing treatment. Table 9 – Stress in ƙ- layer of ref. B before / after post treatment Sample Stress (GPa) Error (+ / -)Ref: ƙ-Al2O3 layer post treated -0.23 0.13Ref: ƙ-Al2O3 layer as deposited 0.83 0.05Texture measurements (Invention)To be able to evaluate the texture coefficients of the first Ti(C,N) layer and the ƙ-Al2O3 -layerof Invention, the second Ti(C,N) layer needed to be etched away or mechanically polishedwithout affecting the other layers. A sample of invention A thus had the second Ti(C,N) layerremoved and the texture coefficients for the first Ti(C,N) layer and the ƙ-Al2O3 -layer weredetermined as further described herein. The resulting TC for the first Ti(C,N) layer ispresented in table 10 below. The resulting TC for the ƙ-Al2O3 -layer is found in table 11.Table 10 - Texture coefficients of the first Ti(C,N) layer of the InventionSample InventionTC(111) 0.03TC(200) 0.01TC(220) 0.31TC(311) 1.67TC(331) 1.12TC(420) 0.26TC(422) 4.43TC(511) 0.16Table 11 - Texture coefficients of the ƙ-Al2O3-layer of the InventionSample InventionTC(111) 0.0TC(013) 0.34TC(122) 0.03TC(113) 0.1TC(200) 0.13TC(201) 0.13TC(004) 6.36TC(040) 0.0TC(015) 2.88TC(204) 0.03EBSD measurements of the second Ti(C,N) layerThe second Ti(C,N) layer of a sample of the invention was treated and measured with EBSDanalysis as described herein. Figure 4a shows standard Pole figures of an FCC (face-centred cubic) symmetry of the second Ti(C,N) layer of the EBSD measurement of which theright-most pole figure regards (111) oriented grains. Figure 4b shows the Pole plot of the{111} pole with intensity areas A1 and A2 indicated. The intensity of the fraction of the (111)oriented grains was calculated to be 75 % following the EBSD analysis described herein(meaning that 75% of the grains had a <111> direction within 15 degrees from the surfacenormal of the second Ti(C,N) layer. Almost all counts are within 7° from the {111} pole whereas none are in the center of the {100} and {110} poles. The invention sample thus shows high {111} growth orientation of the grains in the second Ti(C,N) layer. Cutting test 1The coated cutting tools of the ISO type XOMX120408TR, substrate X, as coated, shot peenedand wet blasted, as shown in table 12, were tested in a linear side radial milling operation in M3 stainless steel (SS2353) using the below cutting data; Table 12 - Variants for cutting testsVariant Substrate Coating Shot Peened Wet blastedReference X According to Yes Yes, blastingexample 1 pressure 1.2 –1.6 barInvention X According to Yes Yes, blastingexample 2a pressure 1.6 –2.0 barMilling cutter:R220.69-0063-12-6ANCutting speed vc: 120 m / minCutting feed, fz: 0.1 mm / toothDepth of cut, ap: 3 mmRadial depth of cut, ae: 18 mmRPM: 606Life time criterion: Flank wear > 0.3 µmThe machining was performed using a coolant emulsion of 6% at a pressure of 40 bar. Fourcutting edges of each cutting tool were evaluated. All edges in all variants were run in identicalmanner and stopped when the flank wear reached 0.3 µm which was observed by means of alight optical microscope with respect to visible wear of the coating on the clearance (flank) sidein the nose section of the samples below the area of contact with the workpiece material. Table 13 - Resistance to flank wear in M millingVariant Mean machining time before life time criteria met (minutes) Reference 29Invention 58It was clearly shown the invention sample comprising the second Ti(C,N) layer deposited onthe ƙ-Al2O3 layer outperformed the reference with respect to mean machining time beforethe lifetime criteria was met.

[0003] Example 2bThe coatings of references 1 and 2 and the invention below were deposited in a radialBernex model 530L tandem CVD equipment capable of housing 10000 half-inch size cuttinginserts. The samples tested and analysed were selected from the middle of the chamber at a position along half the radius of the plate between the centre and the periphery of the plate. A first type of cemented carbide substrates, X, of ISO-type XOMX080408TR-ME08-K6, consisting of 10.0 wt% Co, 1.4 wt% Ta, 0.15 wt% Nb and balance WC was manufactured. Example 2b - ReferencesThe substrates of the references 1 and 2 were first coated with a thin TiN layer having athickness of approximately 0.4 µm, then with an approximately 3 µm thick TiCN layer byemploying well-known MTCVD technique using TiCl4, CH3CN, N2, and H2 as process gases at 885 °C. The volume ratio of TiCl4 / CH3CN of the MTCVD deposition of the TiCN-1 and TiCN-2layers were 6 and 3.7 respectively. The process conditions of the TiN and the TiCN depositionsare shown in Table 14. Table 14 - MTCVD of TiN and TiCNMT CVD of TiN Pressure H2N2TiCl4CH3CN and TiCN (885 [mbar] [vol%] [vol%] [vol%] [vol%] °C): TiN 400 48.8 48.8 2.4 -TiCN-1 55 58.9 37.6 3.0 0.5TiCN-2 55 88.6 8.1 2.6 0.7On top of the MTCVD TiCN layer, an about 1 µm thick bonding layer was deposited at 1000°C by a process consisting of four separate reaction steps:First, a HTCVD TiCN-1 step using TiCl4, N2, and H2 at 400 mbar, then a second step (HTTiCNO-1) using TiCl4, HCl, CO, N2and H2at 70 mbar, then a third step (HT TiCNO-2) using TiCl4, HCl, CO, N2and H2at 60 mbar; and a fourth step (HT TiN-1) using TiCl4, CH4, HCl, N2and H2at 60 mbar were performed as further set out in table 15.Table 15 - Bonding layer depositionBonding Pressure H2 N2 HCl CO TiCl4 CH4 CH3CN layer [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] (1000 °C): HTCVD400 67.9 25.5 1.7 - 1.6 3.4 -TiCN-1 HT-70 83.8 11.9 1.2 1.2 1.5 - 0.4TiCNO-1 HT-70 61.2 30.6 - 4.6 3.0 - 0.7TiCNO-1 HT-TiN-1 70 64.6 32.3 - - 3.2 - -Exclusively for reference 2, an additional oxidation step with initial ^-Al2O3 step and ^-Al2O3growth were added after the bonding layer. These three steps were deposited at 1000 °C and60 mbar. The Al2O3-2 step contributed most to the total ^-Al2O3layer thickness of about 0.9 µm. The process conditions of the depositions are shown in Table 16. Table 16 - ^-Al2O3 deposition steps^-Al2O3Pressure H2N2HCl CO2CO H2S AlCl3deposition [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] steps oxidation 60 57.1 26.0 - 3.9 13.0 - -Al2O3-1 60 92.3 - 1.8 4.7 - - 1.2Al2O3-2 60 90.6 - 2.9 4.7 - 0.6 1.2For reference 1, six repetitions of ƙ-Al2O3 and HT-TIN layers was deposited on top of thebonding layer.For reference 2, six repetitions of ƙ-Al2O3 and HT-TIN layers were deposited on top of the ^-Al2O3 layer as described in table 16.The three steps were deposited at 1000 °C and 55 mbar. The HT-TIN layer contributed to 0.2µm of thickness for each repetition. The Al2O3-2 step contributed most to the total ƙ-Al2O3 layerthickness with about 0.9 µm per repetition. The total thickness for all six repetitions was about6.6 µm. The process conditions of the depositions are shown in Table 17. Finally, for bothreferences 1 and 2, an HT-TIN-1 layer of about 0.2 µm of thickness was deposited on top ofthe last ƙ-Al2O3 layer.Table 17 - ƙ- deposition steps ƙ-Al2O3 Pressure H2 N2 TiCl4 HCl CO2 H2S AlCl3 deposition [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] steps HT-TiN-1 55 55.4 43.1 1.4 - - - -Al2O3-1 55 91.5 - - 1.7 4.6 - 2.3Al2O3-2 55 87.6 - - 5.6 4.4 0.33 2.2Example 2b - InventionThe substrates were coated with an innermost thin TiN layer having a thickness ofapproximately 0.4 µm, then with an approximately 4 µm thick TiCN layer by employing well-known MTCVD technique using TiCl4, CH3CN, N2, and H2 as process gases at 860 °C. The volume ratio of TiCl4 / CH3CN of the MTCVD deposition of the TiCN-1 and TiCN-2 layers were 8 and 5 respectively. The process conditions of the TiN and TiCN depositions are shown in Table 18.Table 18 - MTCVD of TiN and TiCNMT CVD of TiN and Pressure H2 N2 TiCl4 CH3CN TiCN (860 °C): [mbar] [vol%] [vol%] [vol%] [vol%] TiN 550 73.5 24.5 2.0 -TiCN-1 50 96.4 0 3.2 0.4TiCN-2 50 85.4 12.2 2.0 0.4On top of the MTCVD TiCN layer, an about 0.3 µm thick bonding layer was deposited at 980 °C by a process consisting of four separate reaction steps. First a HCl-etching step using HCl and N2 at 60 mbar, then a second step (HTCVD TiCO) using TiCl4, CO, and H2 at 60 mbar, then a third etching step using TiCl4 and H2 at 60 mbar, and then a fourth purging step using N2 at 60 mbar. Further process conditions of the bonding layer deposition are shown in Table 19. Table 19 - Bonding layer depositionBonding Pressure H2 N2 HCl CO TiCl4 layer (980 [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] °C): HCl-etch 60 0 93.0 7.0 - -HTCVD60 91.7 - - 5.0 3.3TiCO TiCl4-etch 60 96.1 - - - 3.9Purge N2 60 100.0 - - - -A ƙ-Al2O3layer was deposited on top of the bonding layer. The three first steps were deposited at 980 °C and 60 mbar and the fourth step at 980 °C and 150 mbar. The Al2O3-1 step contributed most to the total ƙ-Al2O3layer thickness of about 2.0 µm and the Al2O3-2 stepresulted in about 0.1 µm. The process conditions of the depositions are shown in Table 20.Table 20 - ƙ-Al2O3 deposition stepsƙ-Al2O3 Pressure H2 HCl CO2 H2S AlCl3 deposition steps [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] AlCl3-1 60 98.4 - - - 1.6AlCl3-2 60 96.8 1.6 - - 1.6Al2O3-1 60 92.81 1.75 3.55 0.44 1.46Al2O3-2 150 90.0 1.9 6.3 0.08 1.7On top of the ƙ-Al2O3 layer, an about 6 µm thick HTCVD TiCN layer was deposited at 960-980°C by a process consisting of four separate reaction steps while the temperature was ramped down from 980 to 960 °C in the last step. The process conditions of the top layer deposition are shown in Table 21. Table 21 - Top HTCVD-TiCN depositionTop TiCN Pressure H2N2CO TiCl4CH3CN AlCl3layer (930 [mbar] [vol%] [vol%] [vol%] [vol%] [vol%] [vol%] -980°C): AlTiCO 60 92.85 - 4.64 1.62 - 0.88TiCO 80 92.99 - 4.98 2.03 - -TiN 80 72.71 25.97 - 1.32 - -TiCN 80 86.0 12.09 - 0.99 0.92 -All coated substrates (reference samples and invention samples) were subsequentlysubjected to shot-peening and wet-blasting as further described below: Shot-peening The shot peening was performed with peening media beads having a diameter of 70-150µm, a peening pressure of 3 - 6 bar at a distance of 10 cm during 1 second per sample. Wet-blastingAll samples (reference and invention samples) were subjected to a strong wet blastingprogramme: A blasting media comprising Al2O3particles of a diameter of 20-80 µm wasused at a distance of about 20 cm for 1 s duration per sample with a blasting pressure of1.6 - 2.0 bar.Table 22 - Invention; the stress in the second Ti(C,N) layer before and after post treatmentSample Stress (GPa) Error (+ / -)Invention (Post treated) -1.35 0.22Invention (As deposited) 0.55 0.19As evident from table 22, the compressive stresses on the rake face were imparted by thestress-inducing treatment. Measurement of the stress in the ƙ-Al2O3 layer of references 1 and2 before / after post treatment is not possible due to their multi-layered nature of the coatingstructure. Texture measurements (Invention) To be able to evaluate the texture coefficients of the first Ti(C,N) layer and the ƙ-Al2O3 -layerof the invention, the second Ti(C,N) layer needed to be etched away or mechanicallypolished without affecting the other layers. A sample of the invention thus had the secondTi(C,N) layer removed and the texture coefficients of the first Ti(C,N) layer and the ƙ-Al2O3 -layer were determined as further described herein. The resulting TC for the first Ti(C,N) layeris presented in table 23 below. The resulting TC for the ƙ-Al2O3 -layer is found in table 24.

[0004] Table 23 - Texture coefficients of the first Ti(C,N) layer of the InventionSample Reference 1 Reference 2 InventionTC(111) 1.58 1.52 0.17TC(200) 0.67 0.67 0.01TC(220) 0.78 0.55 0.15TC(311) 1.87 1.29 1.06TC(331) 0.42 1.04 0.87TC(420) 0.30 0.59 0.13TC(422) 2.14 2.22 5.38TC(511) 0.23 0.12 0.23Table 24 - Texture coefficients of the ƙ-Al2O3-layer of the InventionSample Reference 1 Reference 2 InventionTC(111) 0.00 0.00 0.0TC(013) 1.69 1.05 0.09TC(122) 0.14 0.1 0.07TC(113) 0.05 0.00 0.00TC(200) 0.14 1.64 0.00TC(201) 0.01 0.02 0.22TC(004) 4.91 6.36 4.54TC(040) 0.03 0.06 0.98TC(015) 2.80 047 4.10TC(204) 0.21 0.23 0.00 EBSD measurements of the second Ti(C,N) layerThe second Ti(C,N) layer of a sample of the invention was treated and measured with EBSDanalysis as described herein. Using the same method as in example 2a above, the fraction ofthe (111) oriented grains was determined to be 65%. Most counts are within 15° from the{111} pole whereas none are in the center of the {100} and {110} poles. The inventionsample thus shows clear {111} growth orientation of the grains in the second Ti(C,N) layer.Cutting test 2 The coated cutting tools of the ISO type XOMX080408TR-ME08-K6, substrate X, as coated, shot peened and wet blasted, as shown in table 25, were tested in a linear side radial milling operation in M3 stainless steel (SS2353) using the below cutting data. Table 25 - Variants for cutting testsVariant Substrate Coating Shot Peened Wet blastedReference 1 X According to Yes Yes, blastingreference 1pressure 1.6 –2.0 barReference 2 X According to Yes Yes, blastingreference 2pressure 1.6 –2.0 barInvention X According to the Yes Yes, blastingInvention pressure 1.6 –2.0 barMilling cutter:R220.69-0063-12-6ANCutting speed vc: 120 m / minCutting feed, fz: 0.1 mm / toothDepth of cut, ap: 3 mmRadial depth of cut, ae: 18 mmRPM: 606Life time criterion: Flank wear > 0.3 µmThe machining was performed using a coolant emulsion of 6% at a pressure of 6 bar. Threecutting edges of each cutting tool were evaluated. All edges in all variants were run in identical manner and stopped when the flank wear reached 0.3 µm which was observed by means of a light optical microscope with respect to visible wear of the coating on the clearance (flank) side in the nose section of the samples below the area of contact with the workpiece material. Table 26 - Resistance to flank wear in M millingVariant Mean machining time before life time criteria met (minutes) Reference 1 18Reference 2 18Invention 27It was clearly shown the invention sample comprising the second Ti(C,N) layer deposited onthe ƙ-Al2O3 outperformed the reference samples with six repetitions of ƙ-Al2O3 and TiNlayers, with respect to mean machining time before the lifetime criteria was met.

Claims

Claims1. Coated cutting tool comprising a substrate and a coating wherein the coatingcomprises i) a first Ti(C,N) layer ii) a layer of ƙ-Al2O3iii) a second Ti(C,N) layer, wherein said second Ti(C,N) layer as measured withElectron Backscatter Diffraction (EBSD) on a 25x25 μm area exhibits an orientationon the rake face wherein ≥ 60%, preferably ≥65%, of the grains have a <111>direction within 15 degrees from the surface normal of said second Ti(C,N) layer;wherein the thickness of the first Ti(C,N) layer ranges from 1 to 10 µmwherein the thickness of the ƙ-Al2O3 layer ranges from 0.3 to 4 µm wherein the thickness of the second Ti(C,N) layer ranges from 2 to 12 µm; and wherein the layers of i), ii), and iii) are arranged in the mentioned order counted fromthe substrate.

2. Coated cutting tool according to claim 1, wherein the first Ti(C,N) layer has a texturecoefficient TC (hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula (1)wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection; I0(hkl) is the corresponding reference intensities: I0(111) = 7871, I0(200) = 10000, I0(220) = 5369, I0(311) = 2550, I0(331) = 1128, I0(420) = 2366, I0(422) = 2479, and I0(51 1) = 1427; n is the number of reflections used in Harris formula (1), wherein the (hkl)reflections used are (111) , (200), (220), (311), (331), (420), (422), and (511), wherein TC(422) ≥ 3 on the rake face.

3. Coated cutting tool according to claim 1 or 2, wherein the ƙ-Al2O3 layer has a texturecoefficient TC(hkl) as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula (1)wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection; I0(hkl) is the corresponding reference intensities: I0(111) = 105, I0(013) = 5026, I0(122) = 10000, I0(113) = 1116, I0(200) = 795, I0(201) = 1342, I0(004) = 291 , I0(040) = 387, I0(015) = 429 and I0(204) = 1312; n is the number of reflections used in Harris formula (1), and wherein the (hkl) reflections used are (111), (013), (122), (113), (200), (201), (004), (040), (015) and (204), wherein TC(004) ≥ 4 on the rake face, more preferably ≥ 5, more preferably ≥ 6.

4. Coated cutting tool according to any one of claims 1 to 3, wherein ≥ 70% of the grainshave a <111> direction within 15 degrees from the surface normal of the secondTi(C,N) layer.

5. Coated cutting tool according to any one of claims 1 to 4, wherein ≥ 75% of the grainshas a <111> direction within 15 degrees from the surface normal of the second Ti(C,N) layer.

6. Coated cutting tool according to any one of claims 1 to 5, wherein ≥ 80% of the grainshave a <111> direction within 15 degrees from the surface normal of the secondTi(C,N) layer.

7. Coated cutting tool according to any one of claims 1 to 6, wherein ≥ 85% of the grainshave a <111> direction within 15 degrees from the surface normal of the secondTi(C,N) layer.

8. Coated cutting tool according to any one of claims 1 to 7, wherein ≥90% of the grainshave a <111> direction within 15 degrees from the surface normal of the secondTi(C,N) layer.

9. Coated cutting tool according to any one of claims 1 to 8, wherein ≥95% of the grainshave a <111> direction within 15 degrees from the surface normal of the secondTi(C,N) layer.

10. Coated cutting tool according to any one of claims 1 to 9, wherein the second Ti(C,N)layer has a compressive stress ranging from 1 to 3 GPa as measured on the rakeface.

11. Coated cutting tool according to any one of claims 1 to 10, wherein the secondTi(C,N) layer has a compressive stress ranging from 1.5 to 2.5 GPa as measured onthe rake face.

12. Coated cutting tool according to any one of claims 1 to 11, wherein the total thicknessof the coating ranges from 5 to 20 µm, preferably 7 to 13 µm.

13. Coated cutting tool according to any one of claims 1 to 12, wherein the substrate iscemented carbide.

14. Coated cutting tool according to any one of claims 1 to 13, wherein the thickness ofthe first Ti(C,N) layer ranges from 1.5 to 4 µm, the thickness of the ƙ-Al2O3 layerranges from 1 to 4 µm, and the thickness of the second Ti(C,N) layer ranges from 2 to 7 µm.

15. Coated cutting tool according to any one of claims 1 to 14, wherein the thickness ofthe first Ti(C,N) layer ranges from 1.5 to 3 µm, the thickness of the ƙ-Al2O3 layerranges from 1.5 to 3 µm, and the thickness of the second Ti(C,N) layer ranges from 3 to 5 µm.

Images