Coating type cutting tool

Abstract

The present invention relates to a coated cutting tool for metal machining comprising a rake face and a flank face and a cutting edge therebetween, the coated cutting tool further comprising a substrate and a coating thereon wherein on both the rake face and the flank face, the coating comprises a Ti1-xAlxN layer of 0.2 to 10 m thickness, 0.60 < = x < = 0.77, 0 < = x < = 0.70, 0 < = x < = 0.70, 0 < = x < = 0.70, 0 < = y < = 0.70, 0 < = y < = 0.70, 0 < = y < = 0.70, and 0 < = y < = 0.70. A ratio of an average grain size of grains in an upper 50% portion of the Ti1-xAlxN layer on the flank face to an average grain size of grains in an upper 50% portion of the Ti1-xAlxN layer on the rake face is 0.15 to 0.90.

Description

[0001] The present invention relates to a coated cutting tool for metal machining, wherein on both the rake face and the flank face, the coating comprises Ti 1-x Al x N layers, 0.60 ≤ x ≤ 0.77, and on the rake face the average grain size of the Ti 1-x Al x N layers is greater than the average grain size of the Ti 1-x Al x N layers on the flank face. Background Art

[0002] Cutting tools such as inserts are used in metal machining operations. A cutting tool typically has at least one rake face and at least one flank face. A cutting edge exists at the intersection of the rake face and the flank face. Metal machining operations include, for example, turning, milling, and drilling.

[0003] To provide a long tool life, a cutting tool should have high resistance to different types of wear. To improve the wear resistance of cutting tools, various types of wear-resistant coatings are known in the art.

[0004] (Ti,Al)N coatings made by physical vapor deposition (PVD) are commonly used in the field of cutting tools for metal machining.

[0005] The crystal structure of (Ti,Al)N in a PVD coating can be a cubic (NaCl (=B1)) structure or a hexagonal (wurtzite) structure. Generally, a lower Al content in (Ti,Al)N, such as ≤65 atomic % Al in Al + Ti, results in a single-phase cubic structure, and as the Al content continuously increases, such as ≥70%, it first results in a mixed structure of cubic and hexagonal structures and then finally results in a single-phase hexagonal structure. However, when a single-phase cubic structure or a mixed structure containing both cubic and hexagonal structures is brought about, the limit of the Al content level in the (Ti,Al)N coating varies to some extent depending on, for example, deposition conditions.

[0006] Compared with the hexagonal structure, the cubic structure of (Ti,Al)N is beneficial due to better mechanical properties such as hardness and elastic modulus. To provide high oxidation stability, (Ti,Al)N coatings containing a relatively high amount of Al, i.e., >60 atomic % or even >67 atomic % in the metal elements Ti and Al, are generally beneficial. Therefore, in the field of metal machining, it is desirable to provide a single-phase cubic high-Al content (Ti,Al)N coating for cutting tools.

[0007] Cutting tools, such as cutting tool inserts, are subject to different types of wear during use. One type is flank wear that occurs on the flank face of the cutting edge, mainly from an abrasive wear mechanism. The flank face bears the movement of the workpiece, and too much flank wear will result in poor surface texture of the workpiece, inaccuracy during the cutting process, and increased friction during the cutting process. Another type of wear is crater wear located on the rake face of the cutting tool. It results from a chemical reaction between the workpiece material and the cutting tool and is exacerbated by an increase in cutting speed. Excessive crater wear will weaken the cutting edge and may lead to fracture.

[0008] Different metal machining operations affect coated cutting tools in different ways. For example, turning is a continuous metal machining operation, while milling is more intermittent in nature. In milling, the thermal load and mechanical load will vary over time. The thermal load causes thermal stresses, which may cause so-called thermal cracks in the coating, referred to herein as "comb cracks", while the mechanical load may cause cutting edge fatigue, leading to chipping, i.e., small fragments of the cutting edge become loose from the rest of the substrate. Therefore, in milling, the common wear types of coated cutting tools are cracks and chipping. Thus, high resistance to comb cracks is important for tool life in milling operations.

[0009] There is a continuing need for wear-resistant coated cutting tools where the coating has high wear resistance, such as high flank wear resistance and / or high crater wear resistance, high resistance to comb cracks, etc.

[0010] Object of the Invention

[0011] One object of the present invention is to provide a coated cutting tool that exhibits high flank wear resistance or high crater wear resistance, preferably a combination of both, at least in turning operations. Most preferably, it also provides high resistance to comb cracks in milling operations. Summary of the Invention

[0012] There is now provided a coated cutting tool for metal machining that exhibits a surprisingly high level of flank wear resistance and / or crater wear resistance in metal cutting operations. Excellent resistance to comb cracks is also provided.

[0013] The present invention relates to a coated cutting tool for metal machining, the coated cutting tool comprising: a rake face and a flank face and a cutting edge therebetween, the coated cutting tool further comprising: a substrate and a coating thereon, wherein on both the rake face and the flank face, the coating comprises a Ti 1-x Al x N layer, 0.60 ≤ x ≤ 0.77, on the rake face Ti 1-xAl x The N layer contains grains with an average grain size of 40 to 200 nm measured parallel to the surface of the substrate and in the upper 50% portion of the Ti 1-x Al x Al N layer, and the Ti on the flank face 1-x Al x The N layer contains grains with an average grain size of 10 to 100 nm measured parallel to the surface of the substrate and in the upper 50% portion of the Ti 1-x Al x Al N layer, and the Ti on the flank face 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer to the average grain size of the Ti 1-x Al x in the upper 50% portion of the N layer on the rake face is 0.15 to 0.90.

[0014] On both the rake face and the flank face, for Ti 1-x Al x in the N layer, 0.63 ≤ x ≤ 0.75, preferably 0.66 ≤ x ≤ 0.75, most preferably 0.68 ≤ x ≤ 0.73.

[0015] In one embodiment, on both the rake face and the flank face, for Ti 1-x Al x in the N layer, 0.66 ≤ x ≤ 0.77, preferably 0.68 ≤ x ≤ 0.77, most preferably 0.68 ≤ x ≤ 0.75.

[0016] The Ti on the rake face 1-x Al x The N layer contains grains with an average grain size preferably of 50 to 150 nm measured parallel to the surface of the substrate and in the upper 50% portion of the Ti 1-x Al x Al N layer.

[0017] The Ti on the flank face 1-x Al x The N layer contains grains with an average grain size preferably of 20 to 80 nm measured parallel to the surface of the substrate and in the upper 50% portion of the Ti 1-x Al x Al N layer.

[0018] The Ti on the flank face 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer to the average grain size of the Ti 1-x Al xThe ratio of the average grain size in the upper 50% portion of the N layer is preferably from 0.20 to 0.75, and most preferably from 0.25 to 0.60.

[0019] In one embodiment, the Ti on the flank face 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer to the Ti on the rake face 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer is from 0.15 to 0.75, preferably from 0.20 to 0.60.

[0020] In one embodiment, the Ti on the rake face 1-x Al x In the N layer, the grains have a columnar microstructure throughout the Ti 1-x Al x The N layer has a columnar microstructure.

[0021] In one embodiment, the Ti on the flank face 1-x Al x The upper 50% portion of the N layer mainly comprises, or consists of, a nanocrystalline microstructure of grains. As used herein, "mainly" means that in the STEM image of the N layer as fabricated herein, more than 50 area % shows a nanocrystalline microstructure. 1-x Al x In one embodiment, the grains in the N layer on the rake face have a cubic structure.

[0022] In one embodiment, the Ti on the rake face 1-x Al x The grains in the N layer have a cubic structure.

[0023] As used herein, "having a cubic structure" means that in the XRD θ-2θ analysis of the Ti 1-x Al x N layer using the method as described herein, no hexagonal peaks are observed, but only cubic (NaCl (=B1)) peaks are observed.

[0024] In one embodiment, for the θ-2θ XRD analysis of the N layer on the rake face, the peak area intensity ratio of I(111) to I(200) is from 0.2 to 3.0, suitably from 0.35 to 2.5, preferably from 0.5 to 2.0, and most preferably from 0.8 to 1.5. 1-x Al x In one embodiment, the Ti on the flank face 1-x Al x

[0025] ​In the θ-2θ XRD analysis of the N layer, the peak area intensity ratio of I(111) to I(200) is ≤0.05, or ≤0.01.

[0026] In one embodiment, the coating comprises one or more additional layers below the Ti 1-x Al x N layer, and the additional layer(s) is / are layer(s) of (one or more) metal nitrides. The (one or more) metal nitrides are suitably (one or more) nitrides of one or more metal elements belonging to Groups 4 to 6 in the IUPAC Periodic Table of the Elements and optionally Al and / or Si. Preferably, they are (one or more) nitrides of one or more metal elements selected from Ti, V, Cr, and Zr and optionally Al and / or Si. Examples of such (one or more) metal nitrides are TiN, (Ti,Al)N, (Cr,Al)N, (Ti,Si)N, (Ti,Al,Si)N, and (Zr,Al)N. Below the Ti 1-x Al x N layer, the one or more additional layer(s) of (one or more) metal nitrides may be present as a single layer as a whole or as sub-layers in a multi-layer structure. The total thickness of these one or more layer(s) of (one or more) metal nitrides may be from about 0.1 to about 8 µm, or from about 0.2 to about 6 µm, or from about 0.5 to about 4 µm.

[0027] In one embodiment, the Ti 1-x Al x N layer is the outermost layer of the coating and preferably has a thickness of 0.2 to 1.5 µm.

[0028] In one embodiment, the Ti 1-x Al x N layer is directly on the substrate.

[0029] In one embodiment, the Ti 1-x Al x N layer on both the rake face and the flank face has a thickness of 0.5 to 8 μm, or 1 to 6 μm.

[0030] In one embodiment, the Ti 1-x Al x N layer on the rake face is thinner than the Ti 1-x Al x N layer on the flank face, and the ratio of the thickness of the Ti 1-x Al x N layer on the rake face to the thickness of the Ti 1-x Al x N layer on the flank face is suitably from 0.20 to 0.95, or from 0.35 to 0.90, or from 0.50 to 0.80.

[0031] In one embodiment, Ti 1-x Al x N layer is a PVD layer, preferably a cathodic arc evaporation deposition layer.

[0032] The substrate of the coated cutting tool can be made of cemented carbide, cermet, ceramic, cubic boron nitride or high-speed steel. In one embodiment, the substrate is made of cemented carbide containing 5 to 18 wt% of Co.

[0033] The coated cutting tool can be a cutting tool insert for metal machining. The cutting tool insert is preferably a milling, drilling or turning insert.

[0034] Ti according to the present invention 1-x Al x N layer can be made by physical vapor deposition (PVD) method, preferably cathodic arc evaporation method. A combination of a relatively high level of bias voltage (such as 300 V) and a relatively high level of N2 pressure (such as 10 Pa) is used. Other details of the suitable method are disclosed in the example section of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic view showing an embodiment of a cutting tool as a milling insert is shown.

[0036] Figure 2 A schematic view showing an embodiment of a cutting tool as a turning insert is shown.

[0037] Figure 3 A schematic cross-sectional view showing an embodiment of the coated cutting tool of the present invention, showing the substrate and the coating as Ti 1-x Al x N layer.

[0038] Figure 4 A schematic indication of the measurement positions of the microstructure on the rake face of the cutting insert is shown.

[0039] Figure 5 A schematic indication of the measurement positions of the microstructure on the flank face of the cutting insert is shown. DETAILED DESCRIPTION

[0040] Figure 1 A schematic view showing an embodiment of a cutting tool 1 having a rake face 2, a flank face 3 and a cutting edge 4 is shown. In this embodiment, the cutting tool 1 is a milling insert.

[0041] Figure 2 A schematic view showing an embodiment of a cutting tool 1 having a rake face 2, a flank face 3 and a cutting edge 4 is shown. In this embodiment, the cutting tool 1 is a turning insert.

[0042] Figure 3 A schematic cross-sectional view showing an embodiment of the coated cutting tool of the present invention, having a substrate 5 and a coating 6 composed of a Ti 1-x Al x N layer.

[0043] Figure 4 A schematic view of the rake face 2 of the cutting tool 1 is shown, where the positions for microstructure analysis are indicated.

[0044] Figure 5 A schematic view of the flank face 3 of the cutting tool 1 is shown, where the positions for microstructure analysis are indicated.

[0045] Method

[0046] Element Analysis:

[0047] To confirm the actual elemental contents of Ti 1-x Al x in the N layer, the average composition of some samples was analyzed by using energy-dispersive X-ray spectroscopy (EDX). The EDX measurements were carried out on the cross-section of the Ti 1-x Al x N layer. The measurements were performed using an energy-dispersive X-ray spectrometer (Oxford Instruments X-Max, 80 mm 2 silicon drift detector) on a Supra 40 (Carl Zeiss AG) scanning electron microscope at an accelerating voltage of 10 kV.

[0048] Microstructure Analysis:

[0049] The microstructure analysis of the TiAlN layer on the flank face and the rake face should be carried out in the regions on each face at a certain distance from the cutting edge but still close to the cutting edge, which is crucial during metal machining.

[0050] Therefore, the microstructure analysis on the flank face is carried out at a position at a distance of about 150 to 300 µm, preferably about 200 µm, from the surface of the rake face. In addition, it should be at a distance of at least 1 mm from any other flank face. Correspondingly, the microstructure analysis on the rake face is carried out at a position at a distance of about 150 to 300 µm, preferably about 200 µm, from the surface of one flank face. In addition, it should be at a distance of at least 1 mm from any other flank face. See Figure 4 for the schematic views of the analysis positions on the rake face and Figure 5 for the flank face analysis positions.

[0051] The TEM thin slice preparation is completed by cutting a part of the TiAlN coating in a direction perpendicular to the surface of the substrate at the positions defined above on the flank face and the rake face.

[0052] Quantification of the grain size is obtained by acquiring STEM images with a magnification of approximately 28,000 times using a transmission electron microscope (TEM). The pixel size of the images is 4096×4096.

[0053] The microscope used for taking STEM images is a Thermo Fisher Scientific Titan G2, operating at an accelerating voltage of 300 kV. The camera length is set to 91 mm, and images are acquired using three detectors: STEM BF (bright field), ADF (annular dark field), and HAADF (high-angle annular dark field).

[0054] Measure the grain size of the Ti 1-x Al x N layer grains along the total length such that at least 100 grains are measured. On the TEM image, within the upper 50% part of the Ti 1-x Al x N layer, the total length is plotted as lines with each line having a length of at least 1 µm at different distances from the surface of the cutting tool substrate.

[0055] The lines should be plotted parallel to the surface of the substrate.

[0056] For columnar grains, the growth direction is basically perpendicular to the surface of the substrate, so the columnar width of the grains needs to be considered. For nanograins, even though the nanograins are more equiaxed compared to columnar grains, the width of the grains also needs to be considered.

[0057] Suitable image processing software can be used to determine the number of grains along the plotted lines. The image processing software used in this article for grain size quantification is Gatan DigitalMicrograph. The contrast, brightness, and γ factor are adjusted for each image to obtain the best grain size contrast. For STEM images, since the grains become clear, ADF (annular dark field) images are used. Lines with a length of at least 1 µm are plotted parallel to the surface of the substrate, and the change in intensity along the line is determined when passing through the grains. The intensity change data is used to count the number of grains along the entire plotted line. The STEM image with the plotted lines is considered together with the intensity change data to assist in identifying individual grains. This process is repeated until at least a total of 100 grains are measured along the total length of the plotted line. Using the total length of the line and the total number of grains along the line, the average grain size is obtained by dividing the total length by the total number of grains.

[0058] X-ray Diffraction :

[0059] For the microstructure analysis, XRD analysis of the TiAlN layer on the flank face and the rake face should be carried out in the area at a certain distance from the cutting edge but still close to the cutting edge on each face, which is crucial during metal machining. Therefore, all XRD analyses were carried out at the positions on the flank face and the rake face as described in "Microstructure analysis" above.

[0060] X-ray diffraction (XRD) analysis of the rake face and the flank face of the coated inserts was performed using a Bruker D8 Discover diffractometer equipped with a two-dimensional detector (VANTEC-500) and an integrated parallel beam Montel mirror, with a Cu-K á , 50.0 kV, 1.0 mA X-ray source. The XRD measurements included the rake face and the flank face of the coated cutting tools at the same positions as considered in the above microstructure analysis. The coated cutting tool inserts were mounted on the sample holder, ensuring that the measured face of the sample was parallel to the reference surface of the sample holder and that the measured face was at the appropriate height. The diffraction intensity from the coated cutting tool was measured near the 2θ angle where relevant peaks appeared. Data analysis, including background subtraction and Cu-K α2 removal, was performed using PANalytical's X’Pert HighScore Plus software. A pseudo-Voigt fitting function was used for peak analysis. No film correction was applied to the obtained peak intensities. When determining the peak intensity and peak width, the software compensated for the overlap of the (200) peak with any diffraction peaks that did not belong to the PVD layer, such as possible peaks from substrate reflections of WC and / or Co (deconvolution of the combined peaks).

[0061] Examples

[0062] Example 1:

[0063] Different (Ti,Al)N coatings according to the present invention and outside the scope of the present invention were deposited on sintered carbide cutting tool insert blanks having geometries of SNMA120408 (flat insert for analysis), CNMG120804-MM (turning insert), and R390-11T308M-PM (milling insert).

[0064] The composition of the cemented carbide was 10 wt% Co, 0.4 wt% Cr, and the balance WC. The cemented carbide blanks were coated by cathodic arc evaporation in a PVD vacuum chamber including four arc flanges, each flange including a number of cathode evaporators.

[0065] Install targets of Ti-Al with the same composition in the evaporator in all flanges. The targets are circular and planar, with a diameter of 100 mm, and can be obtained on the open market. Suitable target technologies for arc evaporation can be obtained from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.), and Oerlikon Metco.

[0066] In different coating deposition runs, targets with compositions of Ti 0.33 Al 0.67 、Ti 0.29 Al 0.71 and Ti 0.25 Al 0.75 and Ti 0.20 Al 0.80 are used respectively.

[0067] The PVD chamber includes a circular rotatable base, and uncoated cutting tool blade blanks (each having a hole, such as the blade in the schematic Figure 1 and 2 ) are mounted on pins located at the circumference of the base. The diameter of the base is 0.82 m.

[0068] The distance between the circumference of the base and the target is about 27 cm.

[0069] The blades are mounted such that the flank face of the blade will be substantially facing the cathode evaporator during rotation in the PVD chamber during the deposition of the (Ti,Al)N layer. Thus, the rake face does not directly face the cathode evaporator.

[0070] In one method used, the chamber is pumped down to a high vacuum (less than 10 -2 Pa), and heated to about 450 °C by a heater located inside the chamber.

[0071] Then the blanks are etched in an Ar plasma for 60 minutes. Then the chamber pressure (reaction pressure) is set to 10 Pa of N2 gas, and a unipolar DC bias voltage of -300 V (relative to the chamber wall) is applied to the blank assembly. The cathode is operated in the arc discharge mode with a current of (each) 150 A.

[0072] During the coating deposition, the cutting tool blade blanks rotate three times in the PVD chamber.

[0073] For target compositions of Ti 0.33 Al 0.67 and Ti 0.25 Al 0.75, one deposition run was carried out at a low table speed of 1.2 rpm and one deposition run was carried out at a high table speed of 5 rpm. Assuming that the blade installed during deposition is located at the circumference of the base, the speed of the blade passing through the cathode evaporator can be calculated. A speed of 0.215 m / s corresponds to a rotational speed of 5 rpm and a table diameter of 0.82 m. A speed of 0.051 m / s corresponds to a rotational speed of 1.2 rpm.

[0074] For the target composition Ti 0.29 Al 0.71 and Ti 0.20 Al 0.80 , only one deposition run was carried out at a high table speed of 5 rpm.

[0075] A (Ti,Al)N layer with a thickness of approximately 3 μm was deposited on the workpiece. The thickness was determined in a cross-sectional slice by optical microscopy.

[0076] The reference samples included in the performance tests of the coated cutting tools were made by depositing a layer of (Ti,Al)N of approximately 3 µm using a target composition of Ti 0.40 Al 0.60 .

[0077] The (Ti,Al)N layer was deposited on sintered carbide cutting tool inserts with geometries SNMA 120408, CNMG120804-MM and R390-11T308M-PM. By using this reference TiAlN layer, any possible differences of any kind between the performance test runs were compensated for, and the results of different test runs could be compared. The composition of the carbide was 10 wt% Co, 0.4 wt% Cr and the rest WC. The carbide inserts were coated by cathodic arc evaporation in a PVD vacuum chamber including four arc flanges, each flange including a number of cathode evaporators.

[0078] Targets of Ti 0.40 Al 0.60 were installed in the evaporators in all flanges. The targets were circular and planar, with a diameter of 100 mm and were available on the open market. Suitable target technology packages for arc evaporation could be obtained from suppliers on the market such as IHIHauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Metco.

[0079] The PVD chamber included a circular base, and the uncoated cutting tool inserts were mounted on pins. The inserts were mounted such that the flank face of the insert would face directly towards the target during rotation.

[0080] The PVD chamber includes a circular rotatable base, and uncoated cutting tool blade blanks (each having a hole, such as the blade shown schematically Figure 1 and 2 in the figure) are mounted on pins located at the circumference of the base. The base diameter is 0.82 m.

[0081] The distance between the circumference of the base and the target is about 27 cm.

[0082] During the production of the reference samples, the chamber is pumped down to a high vacuum (less than 10 -2 Pa), and heated to about 450 °C by a heater located inside the chamber. Then the blanks are etched in an Ar plasma for 60 minutes. The chamber pressure (reaction pressure) is set to 4 Pa of N2 gas, and a DC bias voltage of -70 V (relative to the chamber wall) is applied to the blank assembly. The cathodes are operated at a current of (each) 150 A in the arc discharge mode. The base rotation speed is 2.4 rpm.

[0083] When depositing (Ti,Al)N, there may be a small difference between the Ti-Al composition in the target used and the Ti-Al composition in the deposited (Ti,Al)N layer.

[0084] To determine the actual elemental composition in the (Ti,Al)N layer, the average composition is analyzed by using energy dispersive X-ray spectroscopy (EDX). The EDX measurements are performed on the cross-section of the coating in the SEM.

[0085] As a result, the actual Al content in Ti+Al in the (Ti,Al)N layer deviates from the Al content in the target by -3 to -7 atomic % units.

[0086] The samples 1-7 produced are listed in Table 1.

[0087]

[0088] The average grain size of the (Ti,Al)N grains is determined by using STEM images obtained by TEM as defined herein.

[0089] Table 2 shows the average grain size on the rake face and flank face of the samples, as well as the ratio of the average grain size of the flank face to that of the rake face.

[0090]

[0091] As observed on the STEM images, the entire Ti 1-x Al x N layer on the rake face of samples 1 and 3 has a columnar microstructure.

[0092] As observed on the STEM image, the grains on the flank face of Sample 4 contain a nanocrystalline microstructure to the extent of approximately 95 area%.

[0093] XRD analysis was performed on the deposited (Ti,Al)N layers of the samples. X-ray diffraction (XRD) θ 2θ analysis was carried out on both the rake face and the flank face of the coated inserts. For the layers of Samples 1 to 5 and 7, there was no signal of any hexagonal peaks, but only the signal of cubic (NaCl (=B1)) peaks. Therefore, the conclusion of the XRD analysis is that the (Ti,Al)N layers present in Samples 1 to 5 and 7 have a cubic structure on both the rake face and the flank face. However, for Sample 6, the conclusion is that it contains a large amount of hexagonal phase on both its rake face and flank face.

[0094] Table 3 shows the peak area intensities I(111) and I(222) on the rake face of the samples.

[0095]

[0096] Table 4 shows the peak area intensities I(111) and I(222) on the flank face of the samples.

[0097]

[0098] Example 2:

[0099] In order to determine the performance of the fabricated samples, cutting tests were conducted.

[0100] Explanation of the Terms Used:

[0101] The following expressions / terms are commonly used in metal cutting, but are still explained in the table below:

[0102] V c (m / min): Cutting speed, in meters per minute

[0103] f z (mm / tooth): Feed rate, in millimeters per tooth (in milling)

[0104] f n (mm / rev) Feed rate, in millimeters per revolution (in turning)

[0105] z: (number) Number of teeth in the tool

[0106] a e (mm): Radial depth of cut, in millimeters

[0107] a p (mm): Axial depth of cut, in millimeters

[0108] Flank Wear Test:

[0109] Longitudinal turning

[0110] Workpiece material: Sverker 21 (tool steel), hardness ~210 HB, D = 180, L = 700 mm,

[0111] V c = 125 m / min

[0112] f n = 0.072 mm / rev

[0113] a p = 2 mm

[0114] No cutting fluid is used

[0115] The cut-off criterion for tool life (in minutes) is flank wear VB of 0.15 mm

[0116] Crater Wear Test:

[0117] Longitudinal turning

[0118] Workpiece material: Ovako 825B, ball bearing steel. Hot-rolled and annealed, hardness ~200 HB, D = 160, L = 700 mm,

[0119] V c = 160 m / min

[0120] f n = 0.3 mm / rev

[0121] a p = 2 mm

[0122] No cutting fluid is used

[0123] The cut-off criterion for tool life (in minutes) is crater area of 0.8 mm 2 .

[0124] Resistance to Comb Cracks:

[0125] Operation: Shoulder milling

[0126] Tool holder: C5-391.20-25 080

[0127] Workpiece material: Toolox 33 (tool steel), L = 600 mm, I = 200 mm, h = 100 mm,

[0128] Insert type: R390-11T308M-PM

[0129] Cutting speed V c = 250 m / min

[0130] Feed rate f z = 0.2 mm / rev

[0131] Cutting depth a p = 3 mm

[0132] Radial engagement a e = 12.5 mm

[0133] Use cutting fluid

[0134] The criterion for the end of tool life (in minutes) is that the maximum flank wear height VB > 0.3 mm.

[0135] Table 5 summarizes the cutting test results. To be able to compare the data of the samples tested in different test runs, sample 7 (reference) was used. Reference sample 7 was included in all tests, and its results were set to "100%". Then, by calculating the percentage of the reference results, the results of all other samples tested together with the reference in the test runs were correlated with the reference.

[0136]

[0137] Reference sample 7 had generally quite good performance in all tests, but the aluminum content of its TiAlN coating was quite low. The object of the present invention is a TiAlN coating with a higher aluminum content than the reference, and generally, the higher the aluminum content of TiAlN, the more difficult it tends to be to maintain cutting performance.

[0138] The conclusion is that sample 1 within the scope of the present invention has a good level of flank wear resistance, and at the same time, the crater wear resistance is very good.

[0139] The conclusion is that sample 3 within the scope of the present invention has a good level of flank wear resistance, and at the same time, the crater wear resistance is very good.

[0140] The conclusion is that sample 4 within the scope of the present invention has extremely high flank wear resistance, and at the same time, the crater wear resistance is also at a good level. The anti-comb crack resistance is about 80% of the reference level, and is actually quite good.

[0141] The comparative samples showed poorer results in one or both of the flank wear resistance test and the crater wear resistance test.

[0142] It can also be noted that example sample 3, as the most preferred embodiment of the present invention, showed the best anti-comb crack resistance among all the samples.

Claims

1. A coated cutting tool (1) for metal machining, the coated cutting tool (1) comprising: a rake face (2) and a flank face (3) and a cutting edge (4) therebetween, the coated cutting tool further comprising: a substrate (5) and a coating (6) thereon, wherein on both the rake face (2) and the flank face (3), the coating (6) comprises a Ti 1-x Al x N layer, 0.60 ≤ x ≤ 0.77, - The Ti 1-x Al x N layer on the rake face (2) comprises: grains having an average grain size of 40 nm to 200 nm, preferably 50 nm to 150 nm, measured parallel to the surface of the substrate (5) in the upper 50% portion of the Ti 1-x Al x N layer, - The Ti 1-x Al x N layer on the flank face (3) comprises: grains having an average grain size of 10 nm to 100 nm, preferably 20 nm to 80 nm, measured parallel to the surface of the substrate (5) in the upper 50% portion of the Ti 1-x Al x N layer, - The ratio of the average grain size in the upper 50% portion of the Ti 1-x Al x N layer on the flank face (3) to the average grain size in the upper 50% portion of the Ti 1-x Al x N layer on the rake face (2) is 0.15 to 0.

90.

2. The coated cutting tool (1) according to claim 1, wherein in the Ti 1-x Al x N layer on both the rake face (2) and the flank face (3), 0.63 ≤ x ≤ 0.75, preferably 0.66 ≤ x ≤ 0.75, most preferably 0.68 ≤ x ≤ 0.

73.

3. The coated cutting tool (1) according to claim 1, wherein in the Ti 1-x Al x N layer on both the rake face (2) and the flank face (3), 0.66 ≤ x ≤ 0.77, preferably 0.68 ≤ x ≤ 0.77, most preferably 0.68 ≤ x ≤ 0.

75.

4. The coated cutting tool (1) according to any one of claims 1 - 3, wherein the Ti 1-xAl x The average grain size in the upper 50% portion of the N layer and the Ti on the rake face (2) 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer is from 0.15 to 0.75, preferably from 0.20 to 0.

60.

5. The coated cutting tool (1) according to any one of claims 1 - 3, wherein the Ti on the flank face (3) 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer and the Ti on the rake face (2) 1-x Al x The ratio of the average grain size in the upper 50% portion of the N layer is from 0.20 to 0.75, preferably from 0.25 to 0.

60.

6. The coated cutting tool (1) according to any one of claims 1 - 5, wherein the Ti on the rake face (2) and the flank face (3) 1-x Al x The grains in the N layer have a cubic structure.

7. The coated cutting tool (1) according to any one of claims 1 - 6, wherein the ratio of the peak area intensities of I(111) and I(200) in the θ - 2θ XRD analysis of the Ti 1-x Al x N layer on the rake face (2) is from 0.2 to 3.

0.

8. The coated cutting tool (1) according to any one of claims 1 - 7, wherein in the Ti 1-x Al x N layer on the rake face (2), the grains have a columnar microstructure throughout the entire Ti 1-x Al x N layer.

9. The coated cutting tool (1) according to any one of claims 1 - 8, wherein the upper 50% portion of the Ti 1-x Al x N layer on the flank face (3), in the cross - section cutting area perpendicular to the surface of the substrate (5), mainly comprises a nanocrystalline microstructure of grains.

10. The coated cutting tool (1) according to any one of claims 1 - 9, wherein the coating comprises one or more other layers below the Ti 1-x Al x N layer, and the other layers are layers of metal nitrides.

11. The coated cutting tool (1) according to any one of claims 1 - 10, wherein the Ti 1-x Alx The N layer is the outermost layer of the coating, and the Ti 1-x Al x The thickness of the N layer is from 0.2 µm to 1.5 µm.

12. The coated cutting tool (1) according to any one of claims 1 - 10, wherein the Ti 1-x Al x The thickness of the N layer on both the rake face (2) and the flank face (3) is from 0.5 μm to 8 μm, or from 1 μm to 6 μm.

13. The coated cutting tool (1) according to any one of claims 1 - 12, wherein the ratio of the thickness of the Ti 1-x Al x N layer on the rake face to the thickness of the Ti 1-x Al x N layer on the flank face is from 0.20 to 0.

95.

14. The coated cutting tool (1) according to any one of claims 1 - 13, wherein the Ti 1-x Al x N layer is a cathodic arc evaporation deposition layer.

15. The coated cutting tool (1) according to any one of claims 1 - 14, wherein the substrate (5) of the coated cutting tool (1) is made of cemented carbide, cermet, ceramic, cubic boron nitride or high - speed steel.

16. The coated cutting tool (1) according to any one of claims 1 - 15, wherein the coated cutting tool (1) is a cutting tool insert for metal machining, preferably a milling, drilling or turning insert.

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