Coated Cutting Tools

Abstract

The present invention relates to a coated cutting tool comprising a substrate and a coating comprising first, second and third layers, wherein i) the first layer is a (Ti,Al)N layer bonded to the substrate, the first layer having a. an atomic ratio Al / (Ti+Al) of 0.3 to 0.65, b. a fracture toughness in the range of 3.5 to 6 MPa√m, c. a substantially uniform residual stress σ in the range of +100 to -1000 MPa. 1 and ii) a second layer is a (Ti,Al)N layer bonded to the first layer, the (Ti,Al)N layer having a. an atomic ratio Al / (Ti+Al) between 0.3 and 0.85 and b. a .about.σ at the interface with the first layer. 1 From the above, σ at the interface with the third layer 3 Residual stress σ in the range 2 Where σ 2 increases gradually from the interface with the first layer to the interface with the third layer bonded to the second layer, and the residual stress at the interface with the third layer, σ 2 is substantially the same as that of the third layer, 2 and iii) a third layer is made of a nitride of one or more elements from group 4, 5 or 6 of the periodic table of the elements or of a nitride of Al and / or Si with one or more elements from group 4, 5 or 6 of the periodic table of the elements, the third layer having a substantially uniform residual stress σ 3 <-1200MPa.

Description

[Technical Field]

[0001] The present invention relates to a coated cutting tool comprising a substrate and a coating comprising first, second, and third layers. [Background technology]

[0002] There is a continuing need to extend the service life of metalworking cutting tools and to withstand higher cutting speeds and / or other increasingly demanding cutting operations. Typically, metalworking cutting tools include a hard substrate material, such as a cemented carbide, coated with a thin, hard, wear-resistant coating, such as a titanium aluminum nitride (Ti,Al)N coating deposited by a physical vapor deposition (PVD) process. While a single-phase cubic crystal structure is generally desired, there exists a threshold aluminum content for providing such a single-phase cubic crystal structure, as opposed to a mixed structure containing both cubic and hexagonal crystal structures, which may vary to some extent depending, for example, on the deposition conditions. Furthermore, it is well known that thicker coatings may provide a longer service life, up to a certain limit at which, for example, undesirable high stress concentrations occur at the coating-substrate interface.

[0003] It is an object of the present invention to provide a coated cutting tool having a single-phase cubic structure (Ti,Al)N coating that has high fracture toughness and low residual compressive stress while providing improved adhesion between the coating and substrate.

[0004] It is a further object of the present invention to provide a coated cutting tool having excellent flank wear resistance.It is a further object of the present invention to provide a versatile tool such as a solid carbide drill that can be applied to all machining operations, including drilling various steel grades. Summary of the Invention

[0005] The present invention provides a coated cutting tool comprising a substrate and a coating having first, second, and third layers, i) the first layer is a (Ti,Al)N layer adhered to a substrate, said first layer comprising: a. An atomic ratio Al / (Ti+Al) of 0.3 to 0.65, preferably 0.4 to 0.65, and more preferably 0.5 to 0.65 b. Fracture toughness in the range of 3.5 to 6 MPa√m, preferably 4 to 5 MPa√m c. A substantially uniform residual stress σ1 in the range of +100 to -1000 MPa, preferably -300 to -700 MPa It has ii) the second layer is a (Ti,Al)N layer adhered to the first layer; a. an atomic ratio Al / (Ti+Al) of 0.3 to 0.85, preferably 0.4 to 0.85 b. a residual stress σ2 ranging from about σ1 at the interface with the first layer to σ3 at the interface with the third layer, σ2 gradually increasing from the interface with the first layer to the interface with the third layer adhered to the second layer, and the residual stress σ2 at the interface with the third layer being substantially the same as the residual stress in the third layer. a (Ti,Al)N layer having ii) the third layer is made of a nitride of one or more elements belonging to group 4, 5 or 6 of the periodic table of the elements, or a nitride of Al and / or Si with one or more elements belonging to group 4, 5 or 6 of the periodic table of the elements, and said third layer has a substantially uniform residual stress of σ3<-1200 MPa, preferably σ3<-1400 MPa, more preferably -5000 MPa<σ3<-1500 MPa; This relates to coated cutting tools.

[0006] According to one embodiment, substantially uniform residual stress means that the residual stress has a maximum variation of 15% from the mean value, or preferably a maximum variation of 5%.

[0007] The term "gradually / incrementally" also means that the increase may be stepwise and not necessarily a continuous increase. However, "gradual / incremental" preferably means a continuous and regular increase, e.g., a continuous linear increase.

[0008] According to one embodiment, the second layer is a cubic (Ti,Al)N layer.

[0009] According to one embodiment, the third layer, which may be single or multi-layered, is composed of a nitride containing at least one of Al, Zr, Ti, Nb and Cr, or a nitride of Al and / or Si with at least one of Zr, Ti, Nb and Cr. The third layer may suitably be composed of (Ti,Al)N, (Cr,Al)N, (Ti,Si)N, CrN, TiN or NbN.

[0010] According to one embodiment, the third layer is a cubic (Ti, Al)N or (Ti, Si)N layer with an atomic ratio Al / (Ti+Al) between 0.67 and 0.85 or an atomic ratio Si / (Ti+Si) between 0.05 and 0.2.

[0011] According to one embodiment, the atomic ratio Al / (Ti+Al) of the second layer gradually increases from the interface with the first layer towards the interface with the third layer, for example between 0.5 and 0.8, or between 0.55 and 0.75.

[0012] The gradual increase in Al content in the second layer can be achieved in several ways. For example, the increase in Al content can be achieved by selecting the type and number of targets containing certain amounts of Al and Ti during the deposition process. Furthermore, the Al and Ti content of the deposited coating layer can be varied by changing deposition conditions such as bias voltage and arc current.

[0013] According to one embodiment, at least one of the first, second, and third layers is a multilayer consisting of two or more alternating (Ti,Al)N sublayer types differing in composition, with overall atomic ratios as specified herein.

[0014] According to one embodiment, at least one of the first, second and third (Ti,Al)N layers is a multilayer of two or more compositionally different alternating (Ti,Al)N sublayer types, at least one of which (Ti,Al)N sublayer type has an atomic ratio Al / (Ti+Al) between 0.50 and 0.67, preferably between 0.55 and 0.67, most preferably between 0.60 and 0.67, and at least one of which (Ti,Al)N sublayer type has an atomic ratio Al / (Ti+Al) between 0.70 and 0.90, preferably between 0.75 and 0.85.

[0015] The multilayer (Ti,Al)N sublayer type is suitably a nanolayer which may have an average thickness of 1-100 nm, preferably 1.5 to 50 nm, most preferably 2-20 nm.

[0016] According to one embodiment, the first, second and third layers are single layers.

[0017] According to one embodiment, the third layer is a (Ti, Al)N layer with an atomic ratio Al / (Ti+Al) in the range of 0.70 to 0.85.

[0018] According to one embodiment, the second layer has an atomic ratio Al / (Al+Ti) of 0.7 to 0.85.

[0019] According to one embodiment, the average particle size of the first layer is in the range of 50 to 500 nm, preferably 50 to 200 nm, most preferably 70 to 150 nm.

[0020] According to one embodiment, the thickness of the first layer is in the range of 1 μm to 20 μm, such as 2 μm to 10 μm, for example 3 μm to 8 μm.

[0021] According to one embodiment, the coating has a thickness of 3 to 25 μm, preferably 5 to 15 μm, most preferably 7 to 12 μm.

[0022] According to one embodiment, the first layer exhibits a distribution of misorientation angles 311. The misorientation angles 311 are the angle between the normal vector to the surface of the first layer and the angle closest to the normal vector to the surface of the first layer. <311> Preferably, the cumulative frequency distribution of the misorientation angles 311 is such that 40% or more are less than 12.5°.

[0023] The term misorientation angle refers to the smallest angle, i.e., the angle between the normal vector to the (Ti,Al)N layer and the vector closest to the normal vector to the (Ti,Al)N layer. <311> It means the angle between the direction.

[0024] According to one embodiment, the cumulative frequency distribution of 311 misorientation angles is such that more than 50%, for example more than 55%, are less than 12.5°.

[0025] According to one embodiment, the cumulative frequency distribution of 311 misorientation angles is such that 95% or less, such as less than 85% or less than 75%, are less than 12.5°.

[0026] According to one embodiment, the cumulative frequency distribution of 311 misorientation angles is such that 40-85%, for example 50-75%, is less than 12.5°.

[0027] According to one embodiment, the cumulative frequency distribution of 311 misorientation angles is such that 5-40%, such as 8-25% or such as 10-15% are less than 5°.

[0028] The distribution of 311 misorientation angles can be determined by electron backscattering analysis (EBSD). However, the width of the columnar grains generally increases with increasing (Ti,Al)N layer thickness, especially in the first few micrometers of the (Ti,Al)N layer, and EBSD analysis may not be suitable if the grain width is too small. Therefore, for (Ti,Al)N layers with a thickness of 2 μm or less, the distribution of 311 misorientation angles is preferably determined by transmission electron microscope (TEM) analysis if the grain size is considered too small for EBSD analysis. EBSD or TEM analysis is suitably performed within a distance of 0.7 mm from the cutting edge.

[0029] According to one embodiment, the third layer is the outermost layer.

[0030] According to one embodiment, the first layer (Ti,Al)N has a Vickers hardness of 2400 HV or more (15 mN load), preferably 2500 to 2800 HV (15 mN load).

[0031] According to one embodiment, the first (Ti,Al)N layer has a plane strain modulus of 450 GPa or more, preferably 500 GPa or more, for example 450-550, or 450-500 GPa. The third (Ti,Al)N layer preferably has a plane strain modulus of 450-530 GPa, more preferably 480-510 GPa.

[0032] The substrate of the coated cutting tool can be of any type common in the field of cutting tools for metalworking. The substrate is suitably selected from cemented carbide, cermet, cubic boron nitride (cBN), ceramic, polycrystalline diamond (PCD), and high speed steel (HSS). In one preferred embodiment, the substrate is cemented carbide.

[0033] The coated cutting tool of the present invention, obtained by the process further described herein, has a first layer with low residual stress. This is achieved by depositing the first layer on a substrate at selected process conditions, including high temperatures. This process also provides improved fracture toughness to the first layer. This process also includes depositing a second layer during a linear temperature ramp, as further described in the Examples. This also creates a residual stress gradient throughout the second layer. The third layer is deposited at the lowest temperature used for the second layer, allowing a single-phase cubic crystal structure with a high aluminum content (Ti,Al)N composition to be deposited as the outermost layer. Wet blasting and drag finishing can be performed to improve surface roughness and reduce surface adhesion of workpiece material. The coated cutting tool produced is preferably a drilling insert, such as a solid carbide drill, turning insert, end mill insert, or other indexable insert. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a schematic diagram of an embodiment of a cutting tool that is a milling insert; [Figure 2] Schematic of the coated cutting tool and the temperatures used during the deposition of the three layers. DETAILED DESCRIPTION OF THE INVENTION

[0035] Figure 1 shows a schematic diagram of one embodiment of a cutting tool (1) having a rake face (2), a flank face (3), and a cutting edge (4). The cutting tool (1) is a milling insert in this embodiment. Figure 2 shows a schematic diagram of a cross section of one embodiment of a coated cutting tool of the present invention having a substrate body (5) and first (6), second (7), and third (8) coating layers.

[0036] method Electron Backscatter Diffraction (EBSD): The cumulative frequency distribution of the 311 misorientation angles was calculated as follows: for each spot measurement across the entire EBSD scan (representing the incremental surface area across the analyzed surface area), the crystallographic direction perpendicular to the surface plane of the (Ti,Al)N layer is derived from the measured absolute crystallographic orientation (i.e., Euler angle direction data).

[0037] Next, the crystal direction closest to this <311> Calculate the vector angle between the type direction, where "closest" includes the smallest possible angle with the surface normal (among all 12 crystallographically equivalent possibilities). <311> This angle is defined as the 311 misorientation angle. Because each measurement point constitutes an equal proportion of the analyzed area, the relative frequency distribution of these angular misorientation values ​​characterizes the overall degree of 311 surface texture.

[0038] Electron diffraction by transmission electron microscope (TEM): The sample is suitably analyzed in cross section, i.e., the incident electron beam is parallel to the film plane. To exclude amorphization during sample preparation, various methods can be used: i) conventional preparation, including mechanical cutting, gluing, grinding, and ion polishing; and ii) cutting the sample using FIB, followed by removal and final polishing. The location of analysis is, for example, near the substrate, approximately 200 nm from the substrate.

[0039] Next, SAED data for the sample is acquired. The SAED data provides a diffraction intensity profile along the 311 ring, centered at an angular position corresponding to the coating normal. Normalized integration is then performed on both the 311 and -3-1-1 diffraction points, each up to a misorientation angle of 45 degrees. The two integrals are then combined into a single intensity distribution curve. To increase the number of data points, intensity distribution data from both the 311 and -3-1-1 diffraction points is used, thereby reducing the signal-to-noise ratio as much as possible.

[0040] The intensity at a particular misorientation angle is directly proportional to the sample volume exhibiting this misorientation. Thus, the intensity distribution curve corresponds to the distribution of 311 misorientation angles. Correspondingly, the cumulative intensity curve obtained from the intensity distribution curve then corresponds to the cumulative frequency distribution of 311 misorientation angles.

[0041] Vickers hardness Vickers hardness was measured by nanoindentation (force-depth curve) using a Picodentor HM500 from Helmut Fischer GmbH, Sindelfingen, Germany. The Oliver-Pharr evaluation algorithm was applied for measurements and calculations. Vickers diamond specimens were pressed into the layer and the force-path curve was recorded during the measurement. The maximum load used was 15 mN (HV 0.0015), and the load increase and decrease times were 20 seconds each. The hardness was calculated from this curve.

[0042] Plane strain coefficients: The elastic properties of the coated samples were measured using the so-called plane strain modulus E obtained by nanoindentation using the Oliver-Pharr method. ps Nanoindentation data were obtained by indentation as described above for Vickers hardness.

[0043] Particle size: The average grain size is determined from SEM images by the following stereo line intersection method: a line grid is overlaid on the micrograph of interest and the intersections of the lines with the grain boundary network are marked. The statistics of the distances between adjacent intersections reflect the size of the grains in three dimensions (e.g., H.E. Exner, Quantitative Description of Microstructures by Image Analysis, in: Mater. Sci. Technol., Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2006 (including section 15.3.5 "Size and spacing" - https: / / doi.org / 10.1002 / 9783527603978.mst0024).

[0044] To account for the morphological characteristics of the PVD hard coatings (mainly elongated columnar grains), the spacing between grain boundaries was evaluated only on lines parallel to the film plane, resulting in data reflecting the grain width parallel to the coating surface.

[0045] Each SEM micrograph was taken from the flank face of a triple-rotated test insert made of cemented carbide (the substrate surface repeatedly faces the arc source during deposition). They were taken from a distance of 100 μm from the edge of the substrate. Grain widths were measured at a defined coating height of 2 μm. At least 380 spaced measurements were collected.

[0046] Residual stress: Residual stress was measured using a Seifert / GE (PTS 3003) diffractometer. 2The Ψ method was followed. CuKα radiation was used for the analysis (high voltage 40 kV, current 40 mA) using a polycapillary lens (to generate a parallel beam). The incident beam was defined by a 2.0 mm pinhole. An energy dispersive detector (Meteor 0D) was used in the diffraction beam path. An Euler cradle was used to tilt the sample at an angle of Ψ (Ψ = angle between the normal to the sample surface and the diffraction vector). The {111}-cubic-TiAlN reflection was used to measure the residual stress in the sample. To determine the residual stress value of the coating, the angle -60°<Ψ<60° (sin 2 Fifteen Ψ angles were considered in the interval (equidistant in Ψ). Assuming a rotationally symmetric distribution of residual stress, only one φ direction was used. For stress evaluation of TiAlN, the X-ray elastic constant -s1=0,491 TPa -1 and 0,5s2=2,780TPa -1 To perform peak fitting, Rachinger's correction (to correct for Kα2) and pseudo-Voigt function were applied to perform peak fitting.

[0047] For measuring the residual stress of a coating layer that has a further layer deposited on it, the coating material is removed from above the layer to be measured. Care must be taken to select and apply a material removal method that does not significantly alter the residual stress in the remaining nitride multilayer material. A suitable method for removing the deposited coating material can be polishing, but gentle, slow polishing using fine abrasives should be applied. As is known in the art, aggressive polishing using coarse abrasives will actually increase the residual stress. Other methods suitable for removing deposited coating material are ion etching and laser ablation.

[0048] Thickness: The layer thickness was determined by carrot grinding, using a 30 mm diameter steel ball to grind a dome-shaped recess, and the diameter of the ring was measured and the layer thickness calculated from that. The layer thickness measurements on the rake face (RF) of the cutting tool were carried out at a distance of 2000 μm from the corner, and the measurements on the flank face (FF) were carried out at the center of the flank face.

[0049] Fracture toughness: To quantify the fracture toughness of the investigated coatings, the micropillar splitting technique developed by Sebastiani et al. [1, 2, and 4] was applied. In this test method, the tip of a sharp indenter is placed at the center of the top surface of a micron-scale pillar of the sample material. When the pillar is subjected to the indenter load, the force increases continuously until the pillar breaks, i.e., cracks. The critical stress concentration factor at which a crack initiates from the indenter contact, i.e., the cracking fracture toughness, Kc, is determined by the critical cracking force, P. c is derived from the following formula: K c =γ(E / H)P c / R 3 / 2 (1) where γ represents a proportionality coefficient that depends on the elastic-plastic properties of the tested material (the ratio of Young's modulus E to hardness H), and R represents the pillar radius. The above equation is based on an analytical model of a semi-elliptical surface crack and is verified by cohesive zone finite element modeling (CZ-FEM) [2].

[0050] Pillars were microfabricated from the target coating by focused ion beam (FIB) milling. To minimize pillar taper, a single-pass milling strategy was used, utilizing a concentric circular pattern with successively decreasing diameter. The FIB probe current was accordingly reduced continuously from 15 nA (initial roughing) to 300 pA for the final polishing current. All tested pillars had a diameter of 7 μm and an aspect ratio of approximately 1.3 (height-to-diameter ratio, required for pillar splitting techniques to be greater than 1 [2]). Prior to FIB milling, the sample surface to be structured was carefully polished using a colloidal silica suspension with a nominal particle size of 40 nm (Struers OPS 0.04 μm). This step was performed to remove any roughness present on the deposited coating surface. Less than 100 nm of the top coating was removed by this procedure.

[0051] After this surface treatment, the micropillars were consistently positioned at a distance of approximately 120 μm from the cutting edge, i.e., near the "nose radius" of the carrier substrate.

[0052] Pillar loading was performed with a Fischer Picodenter HM500 nanoindentation system (Helmut Fischer GmbH, Sindelfingen, Germany) using a three-sided pyramidal cube-corner diamond indenter (nominal surface angle 35.26°). Experiments were performed in a load-controlled manner using a constant loading rate of 1 mN / s. For each coating and specimen condition, a minimum of 12 tests were performed (20 tests in most cases) to account for the inherent variability of fracture experiments. The accuracy of the specimen stage and tip positioning was experimentally verified to be within 10% of the pillar radius used to avoid distorting the measurement results [3]. To calculate the fracture toughness according to equation (1), the coating-specific γ coefficient was derived from data published by Ghidelli et al. [4]. Measurements can be performed by preparing cross sections of already coated tools or by carefully removing the top layer by mechanical polishing or focused ion beam machining.

[0053] [1] M. Sebastiani, KE Johanns, EG Herbert, F. Carassiti, GM Pharr, A novel Pillar indentation splitting test for measuring fracture toughness of thin ceramic coatings, Philos. Mag. 95 (2015) 1928-1944. https: / / doi.org / 10.1080 / 14786435.2014.913110.

[0054] [2] M. Sebastiani, K.E.Johanns, E.G. Herbert, G.M. Pharr, Measurement of fracture toughness by nanoindentation methods: Recent advances and future challenges, Curr. Opin. Solid State Mater. Sci. 19 (2015) 324-333. https: / / doi.org / 10.1016 / j.cossms.2015.04.003.

[0055] [3] C.M. Lauener, L. Petho, M. Chen, Y. Xiao, J. Michler, J.M. Wheeler, Fracture of Silicon: Influence of rate, positioning accuracy, FIB machining, and elevated temperatures on toughness measured by pillar indentation splitting, Mater. Des. 142 (2018) 340-349. https: / / doi.org / 10.1016 / j.matdes.2018.01.015.

[0056] [4] M. Ghidelli, M. Sebastiani, K.E. Johanns, G.M. Pharr, Effects of indenter angle on micro‐scale fracture toughness measurement by pillar splitting, J. Am. Ceram. Soc. 100 (2017) 5731-5738. https: / / doi.org / 10.1111 / jace.15093.

Example

[0057] Example 1 The WC-Co substrates were pretreated with plasma etching (center beam etching) before the deposition of the coating to remove approximately 1 μm to eliminate organic residues and to reduce surface damage and residual stress due to pre-polishing of the substrate. The etching was carried out at a temperature of 600° C. with the following additional process conditions: I: 140A U bias : 170V p Ar : 0.21Pa t etch : 65 minutes

[0058] Arc-deposited (Ti,Al)N three-layer coatings were prepared by depositing a first base layer, a second middle layer, and a third top layer on a cemented carbide substrate in the above order. 0.40 Al 0.60 The first and second layers were prepared from targets. The substrate had a composition of 6 wt. % Co and the remainder WC. Deposition was carried out using cathodic arc deposition in a Balzers Innova Arc-PVD system (Oerlikon Balzers Coating AG, Balzers, Liechtenstein) with the following process parameters:

[0059] First (base) layer of (Ti,Al)N: Target material: Ti 0.40 Al 0.60 Target size: 150mm circle Arc current: 4 x 200A Pressure: 5Pa Temperature: 600℃ Total pressure: 5Pa (N2) Argon pressure: 0 Pa (0 sccm Ar) Bias potential: -40V Both double and triple rotation Source configuration APO, mag 14

[0060] A layer thickness of approximately 3.1 μm was deposited.

[0061] Second (intermediate) layer of (Ti,Al)N: Target material: Ti 0.40 Al 0.60 Target size: 150mm circle Arc current: 2 x 200A Pressure: 5Pa(N2) Temperature: 600~300℃ Total pressure: 5Pa (N2 pressure) Argon pressure: 0 Pa (0 Ar sccm) Bias potential: -40V Source configuration APO, mag 14

[0062] The temperature was linearly decreased during the coating process from 600° C. to 300° C. The second layer was grown to a thickness of 1.5 μm.

[0063] Third (top) layer of (Ti,Al)N: Target material: Ti 0.27 Al 0.73 Target size: 150mm circle Arc current: 2 x 120A Temperature: 300℃ Total pressure: 2Pa Argon flow rate: 300sccm Bias potential: -80V Source configuration APO, mag 14

[0064] A layer thickness of 1.4 μm was deposited, thus preparing a coating with a total thickness of 6 μm.

[0065] Residual stress in the first layer: -600MPa Fracture toughness of the first layer: 4.1MPa√m First layer hardness: 2600HV Plane strain modulus of the first layer: 520GPa

[0066] Electron backscatter diffraction (EBSD) analysis was performed on the (Ti,Al)N first (base) layer. The cumulative frequency distribution of the 311 misorientation angles was calculated as described in the Methods section. The (Ti,Al)N first (base) layer exhibits a cumulative frequency distribution of the 311 misorientation angles in which approximately 62% of the 111 misorientation angles are less than 12.5 degrees and approximately 13% of the 311 misorientation angles are less than 5 degrees.

[0067] The third (top) layer of (Ti,Al)N exhibits a 111 texture. The cumulative frequency distribution of the 111 misorientation angles of the third (top) layer of (Ti,Al)N is estimated to be such that >50% of the 111 misorientation angles are less than 10 degrees.

[0068] Example 2 (Comparative) A comparative base layer was prepared according to the preparation of the first (base) layer of Example 1, except that it was prepared at a thickness of 5.9 μm to provide a coating thickness equivalent to the total coating thickness of Example 1.

[0069] Example 3 Drilling tests on various workpiece materials were carried out on a DMG MORI DMU65 MonoBlock vertical 3-axis machine according to the following: In this Example 3, steel was machined with coated cutting tools prepared with coatings prepared according to the coatings of Examples 1 and 2. The number of holes to critical flank wear for the tested tools is shown in Table 1 below:

[0070] Workpiece material: Steel C45, 1.1191 (705N / mm 2 ) Cutting speed, v c : 200m / min Feed / rpm: 0.28mm / rpm Drilling depth: 30mm Hole Type: Through Hole KSS: Emulsion, 7%; 40bar TIFF2025513585000001.tif22170

[0071] As can be seen from Table 1, the three layer tool with the coating according to Example 1 (invention) has a longer tool life compared to the single layer coating of Example 2 (reference).

[0072] Example 4 In Example 4, an analog test was carried out on 42CrMo4 steel.

[0073] Workpiece material: 42CrMo4, (EN-JL1040; 215HB) Cutting speed, V c :105m / min Feed / rotation speed: 0.2 mm / rotation speed Drilling depth: 30 mm Hole Type:Through Hole KSS: Emulsion, 6%; 40 bar TIFF2025513585000002.tif22170

[0074] Table 2 shows significantly higher wear resistance for critical flank wear for the present invention compared to the same reference.

Claims

1. 1. A coated cutting tool comprising a substrate and a coating comprising first, second, and third layers, i) the first layer is a (Ti,Al)N layer adhered to a substrate, said first layer comprising: a. Atomic ratio Al / (Ti+Al) of 0.3 to 0.65 b. Fracture toughness in the range of 3.5 to 6 MPa√m c. A substantially uniform residual stress σ in the range of +100 to −1000 MPa １ and ii) the second layer is a (Ti,Al)N layer bonded to the first layer; a. Atomic ratio Al / (Ti+Al) of 0.3 to 0.85 b. Approximately σ at the interface with the first layer １ From this, σ at the interface with the third layer ３ Residual stress σ in the range ２ and σ ２ gradually increases from the interface with the first layer to the interface with the third layer bonded to the second layer, and the residual stress σ ２ is substantially the same as that of the third layer, ２ a (Ti,Al)N layer having iii) the third layer is made of a nitride of one or more elements belonging to group 4, 5 or 6 of the periodic table of the elements, or a nitride of Al and / or Si with one or more elements belonging to group 4, 5 or 6 of the periodic table of the elements, and the third layer has a substantially uniform residual stress σ ３ <-1200 MPa, Coated cutting tools.

2. 2. The coated cutting tool of claim 1, wherein the third layer is a cubic (Ti,Al)N layer or a (Ti,Si)N layer having an atomic ratio Al / (Ti+Al) of 0.67 to 0.85 or an atomic ratio Si / (Ti+Si) of 0.05 to 0.

2.

3. The coated cutting tool of claim 1, wherein the first layer has a fracture toughness in the range of 4 to 5 MPa√m.

4. 2. The coated cutting tool according to claim 1, wherein the atomic ratio Al / (Ti+Al) of the second layer gradually increases from the interface with the first layer toward the interface with the third layer.

5. 2. The coated cutting tool of claim 1, wherein at least one of the first, second, and third layers is a multilayer consisting of two or more alternating (Ti,Al)N sub-layer types differing in composition, with overall atomic ratios as defined in claim 1.

6. 10. The coated cutting tool of claim 1, wherein the cumulative frequency distribution of 311 misorientation angles in the first layer is such that ≥ 40% are less than 12.5°.

7. The coated cutting tool of claim 1 , wherein the first, second, and third layers are single layers.

8. 2. The coated cutting tool of claim 1, wherein the third layer is a (Ti,Al)N layer having an atomic ratio Al / (Ti+Al) in the range of 0.70 to 0.

85.

9. 2. The coated cutting tool of claim 1, wherein the first layer has a residual stress in the range of −300 to −700 MPa.

10. The coated cutting tool of claim 1 , wherein the tool is a carbide drill, an end mill, or an indexable insert.

11. 2. The coated cutting tool according to claim 1, wherein the atomic ratio Al / (Al+Ti) of the second layer is 0.7 to 0.

85.

12. The coated cutting tool of claim 1, wherein the first layer has an average grain size in the range of 50 to 500 nm.

13. The coated cutting tool of claim 1, wherein the first layer has a thickness in the range of 1 to 20 μm.

14. 2. The coated cutting tool of claim 1, wherein the coating has a thickness in the range of 3 to 25 μm.

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