COATING AND THE COATING-COMPREHENSIVE COATED CUTTING TOOL

Abstract

Coating, comprehensive: a layer comprising an aluminum oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains in the aluminum oxide matrix, wherein a mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is 100 nm or less, characterized in that the at least one of the zirconium oxide grains and the hafnium oxide grains is primarily arranged within grains of the aluminum oxide matrix.

Description

TECHNICAL AREA

[0001] The present application relates to the field of coatings and in particular coatings for cutting tools. BACKGROUND

[0002] Cutting tools, including carbide cutting tools, have been used in both coated and uncoated states for machining various metals and alloys. To increase the wear resistance, performance, and service life of these cutting tools, one or more layers of refractory material have been applied to their surfaces. For example, TiC, TiCN, TiN, and / or Al₂O₃ have been deposited onto carbide substrates by chemical vapor deposition (CVD) and physical vapor deposition (PVD). While effectively preventing wear and extending tool life in a wide range of applications, refractory coatings based on single- or multi-layer structures of the aforementioned refractory materials have increasingly reached their performance limits, necessitating the development of new coating architectures for cutting tools.

[0003] US Patent 2006 / 0257691A1 discloses a cutting insert on which at least a thin, adhesive, hard, and resistant coating is applied. The coating comprises a metal oxide / oxide composite layer consisting of two components with grain sizes ranging from approximately 1 to approximately 100 nm.

[0004] US Patent 5,827,570 A discloses a method for depositing a wear-resistant composite ceramic coating on a substrate, in which a wear-resistant two-phase composite ceramic coating is deposited on the substrate. SUMMARY

[0005] In one embodiment, a coating comprises a layer with an aluminum oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains embedded in the aluminum oxide matrix. The mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is 100 nm or less. The at least one of the zirconium oxide grains and the hafnium oxide grains is primarily arranged within grains of the aluminum oxide matrix.

[0006] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 1 nm to 80 nm.

[0007] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 1 nm to 40 nm.

[0008] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 40 nm to 80 nm.

[0009] At least one of the zirconium oxide grains and the hafnium oxide grains may comprise grains with at least one of a tetragonal, monoclinic or orthorhombic crystal structure.

[0010] The layer can have a thickness of 0.1 µm to 25 µm.

[0011] In a further embodiment, a coated cutting tool comprises a substrate and a coating bonded to the substrate. The substrate has a rake face, a flank face, and a cutting edge formed at the intersection of the rake face and the flank face. The coating comprises a layer with an aluminum oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains embedded in the aluminum oxide matrix. The mean grain size of the at least one of the zirconium oxide grains and hafnium oxide grains is 100 nm or less. The at least one of the zirconium oxide grains and hafnium oxide grains is primarily arranged within grains of the aluminum oxide matrix.

[0012] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 1 nm to 80 nm.

[0013] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 1 nm to 40 nm.

[0014] The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 40 nm to 80 nm.

[0015] At least one of the zirconium oxide grains and the hafnium oxide grains may comprise grains with at least one of a tetragonal, monoclinic or orthorhombic crystal structure.

[0016] The layer can have a thickness of 0.1 µm to 25 µm.

[0017] Further embodiments of the disclosed coating and the coated cutting tool will become apparent from the following detailed description, the accompanying drawings and the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig.Figure 1 illustrates a cutting insert substrate according to an example from the present description. The Fig. 2A and Fig. Figures 2B are TEM images of the Al2O3-ZrO2 nanocomposite coatings described herein. The Fig. 3A, Fig. 3B and Fig. 3C are SEM images of ZrO2 in the micrometer range, which is formed by continuously introducing Zr into a coating system. The Fig. 4A, Fig. 4B and Fig. 4C are SEM images of ZrO2 in the nanometer range, formed by pulsed introduction of Zr into a coating system, wherein the ZrO2 formed is preferably segregated at the grain boundary. The Fig. 5A, Fig. 5B and Fig.5C are SEM images of ZrO2 in the nanometer range, formed by pulsed introduction of Zr into a coating system, where the formed ZrO2 exhibits intragranular grain formation and the mean grain size of the ZrO2 is less than 100 nm. DETAILED DESCRIPTION

[0018] The embodiments described herein may be more easily understood with reference to the following detailed description and the examples and their preceding and subsequent descriptions. However, the elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments merely illustrate the principles of the present description. Numerous modifications and adaptations are readily apparent to a person skilled in the art without deviating from the meaning and scope of the present description.

[0019] According to the present description, a coating comprises a layer with an aluminum oxide matrix and at least one zirconium oxide grain and at least one hafnium oxide grain within the aluminum oxide matrix. The coating can be a single-layer coating on a substrate or a multi-layer coating on a substrate with at least one layer of an aluminum oxide matrix and at least one zirconium oxide grain and at least one hafnium oxide grain within the aluminum oxide matrix, and optionally one or more other layers.

[0020] The aluminum oxide matrix is ​​resistant to oxidation even at high temperatures. Pure aluminum oxide is susceptible to cracking. At least one zirconium oxide grain and one hafnium oxide grain are added to the aluminum oxide matrix to increase its resistance to crack propagation.

[0021] The mean grain size of at least one of the zirconium oxide grains and hafnium oxide grains is 100 nm or less. This small grain size can provide high hardness based on Hall-Petch effects. Simultaneously, grain refinement can produce the zirconium oxide in a preferred phase, such as tetragonal. This phase can then contribute to the toughness of the aluminum oxide matrix. The mean grain size of at least one of the zirconium oxide grains and hafnium oxide grains is preferably in the range of 1 nm to 80 nm.The mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can, for example, be in a range of 1 nm to 40 nm, or the mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains can be in a range of 40 nm to 80 nm.

[0022] At least one of the zirconium oxide grains and hafnium oxide grains can comprise grains with a tetragonal, monoclinic, or orthorhombic crystal structure. Zirconium oxide or hafnium oxide grains refined to the nanometer scale preferentially form the tetragonal crystal structure. The tetragonal phase is favored for the toughness of the aluminum oxide matrix.

[0023] At least one of the zirconium oxide grains and hafnium oxide grains is primarily located within the grains of the aluminum oxide matrix. Positioning at least one of the zirconium oxide grains and hafnium oxide grains within the grains of the aluminum oxide matrix is ​​advantageous for the toughness of the aluminum oxide matrix against intragranular cracking. Positioning at least one of the zirconium oxide grains and hafnium oxide grains at grain boundaries of the aluminum oxide matrix is ​​advantageous for the toughness of the aluminum oxide matrix against intergranular cracking. The strengthening mechanism can be based on grain boundary strengthening due to the dispersed nanoscale secondary phase of zirconium oxide. The positioning of at least one of the zirconium oxide grains and hafnium oxide grains can be determined based on the overall architecture of the coating.The positioning of at least one of the zirconium oxide grains and the hafnium oxide grains can be selected by controlling the deposition conditions.

[0024] The mean grain size of the aluminum oxide matrix is ​​larger than the mean grain size of at least one of the zirconium oxide grains and the hafnium oxide grains. In one aspect, the mean grain size of the aluminum oxide matrix is ​​200 nm or larger. In another aspect, the mean grain size of the aluminum oxide matrix is ​​500 nm or larger. In yet another aspect, the mean grain size of the aluminum oxide matrix is ​​1 micrometer or larger. However, a small mean grain size of the aluminum oxide matrix is ​​preferred.

[0025] The layer, consisting of the aluminum oxide matrix and containing at least one zirconium oxide grain and one hafnium oxide grain within the aluminum oxide matrix, can have any thickness that is not inconsistent with the purposes of the coating. For example, the layer can have a thickness of 0.1 µm to 25 µm.

[0026] The layer with the aluminum oxide matrix and the at least one of zirconium oxide grains and hafnium oxide grains in the aluminum oxide matrix can be coated in any way that is not inconsistent with the purposes of the present description.

[0027] This description provides the following approaches for producing the layer by chemical vapor deposition (CVD).

[0028] By controlling the zirconium introduction methods, the selection of the Al / Zr introduction ratios, and other processing conditions, a uniformly distributed ZrO2 grain in the nanometer range (at least in one dimension smaller than 100 nm) can be produced. In one case, the formed ZrO2 grains preferentially settle / segregate at the grain boundary. In the other case, the formed ZrO2 grains can be uniformly embedded in the Al2O3 matrix to form mixed Al2O3-ZrO2 composite grains with alternative deposition conditions. As described in the Fig. 2A and Fig. Figure 2B shows that transmission electron microscopy (TEM) observation revealed ZrO2 grains in the range of 50 nm to some 10 nm.

[0029] To create a layer with an aluminum oxide matrix and at least one zirconium oxide grain and one hafnium oxide grain within the aluminum oxide matrix, a secondary phase beyond the matrix was introduced into a coating system. The method of introducing the secondary raw material determines the final products. As described in the Fig. 3A, Fig. 3B and Fig. As shown in Figure 3C, a composition of Al2O3 and ZrO2 with ZrO2 grains in the micrometer range can be formed by continuously introducing Zr into the coating system.

[0030] To achieve refinement of the secondary phase of ZrO₂, the Zr source was introduced using pulse patterns, and the Al / Zr ratio was chosen to be 1.5 or greater. Preferably, the Al / Zr ratio can be above 2. Additionally, after the introduction of the Al / Zr mixture, a pure Al environment was used for ZrO₂ grain refinement. This pure Al environment provides a pure Al₂O₃ deposition step, which achieves ZrO₂ grain refinement by terminating the ZrO₂ grains formed with the Al / Zr mixture.

[0031] CVD deposition combines temperature, gas flow, and partial pressures in the reactor, so the coating growth kinetics are also dominated by these factors. At 850 to 950 °C, ZrO2 grains formed with a mean grain size of less than 100 nm, more preferentially with a mean grain size of 40 to 80 nm, with the decrease in grain boundary segregation, as seen in the Fig. 4A, Fig. 4B and Fig. 4C is shown.

[0032] As in the Fig. 5A, Fig. 5B and Fig. As shown in Figure 5C, the formation of nanoscale intragranular grains of secondary-phase ZrO2 in an Al2O3 matrix was achieved directly by CVD. By controlling the deposition conditions, a high ZrO2 density of over 300 per square micrometer and ZrO2 grains with a mean grain size in the range of 40 to 100 nm were formed.

[0033] The Al / Al+Zr ratios for the pulsed step compared to the pure Al step, the deposition time, the temperature, the gas flow rate, and the introduction of other gas streams, including H₂S and CO₂, can all play a role in coating microstructure formation. Al / Al+Zr ratios and short deposition times result in fine ZrO₂ grains. Temperature can control atomic diffusion and segregation, leading to grain boundary enrichment and aluminum oxide matrix inclusion. CO₂ flux controls H₂O formation, which determines the reaction kinetics. H₂S promotes crystal growth and also influences nucleation density and grain growth behavior.

[0034] The following Table 1 describes, by way of example and without limitation, parameters for the deposition of an aluminum oxide matrix and of zirconium oxide grains and hafnium oxide grains in nanosize in the aluminum oxide matrix using CVD. Table 1 Layer composition Gas mixture Temperature (°C) Print duration (Torr) (minutes) Al2O3 AlCl3 + H2 +CO2 + H2S(optional) + HCl(optional) 800-1050 30-500 3-600 MeAl2O3 / MeO2 [(AlCl3 + TiCl4 or ZrCl4 or HfCl4) or (their combination)] + H2 + CO2 + H2S (optional) + HCl (optional) 800-950 or 1020-1050 40-60 1-15

[0035] According to the present description, a coated cutting tool comprises a substrate and the coating bonded to the substrate. The substrate of the coated cutting tool typically has a rake face, a flank face, and a cutting edge formed at the intersection of the rake face and the flank face.

[0036] One aspect describes cutting tools that incorporate refractory coatings using composite architectures. Cutting tools with such refractory coatings are, in some embodiments, suitable for applications with high wear and / or abrasion, such as metal cutting operations.

[0037] With regard to specific components, a coated cutting tool comprises a substrate. A coated article may comprise any substrate that is not inconsistent with the purposes of this description. The cutting tools include, without limitation, indexable inserts, end mills, saw blades, or drills.

[0038] Indexable inserts can have any desired ANSI standard geometry for milling or turning applications. The substrates of the coated articles described herein can be made of cemented carbide, carbide, polycrystalline diamond, polycrystalline cubic boron nitride, ceramic, cermet, steel, or any other alloy.

[0039] In some embodiments, a cemented carbide substrate comprises tungsten carbide (WC). WC may be present in a cutting tool substrate in any amount that is not inconsistent with the purposes of this description. For example, WC may be present in an amount of at least 70% by weight, at least 80% by weight, or at least 85% by weight. Additionally, the cemented carbide metallic binder may comprise cobalt or a cobalt alloy. For example, cobalt may be present in a cemented carbide substrate in an amount of 1% to 15% by weight. In some embodiments, cobalt is present in a cemented carbide substrate in an amount in the range of 5% to 12% by weight or 6% to 10% by weight. Furthermore, a cemented carbide substrate may have a binder enrichment zone that begins at the surface of the substrate and extends inwards from it.

[0040] Hard metal substrates may also include one or more additives, such as one or more of the following elements and / or their compounds: titanium, niobium, vanadium, tantalum, chromium, zirconium, and / or hafnium. In some embodiments, titanium, niobium, vanadium, tantalum, chromium, zirconium, and / or hafnium form solid solution carbides with the substrate's core material. In such embodiments, the substrate may comprise one or more solid solution carbides in an amount ranging from 0.1 to 5 percent by weight. Additionally, a hard metal substrate may include nitrogen.

[0041] The cutting tool substrate typically comprises one or more cutting edges formed at the junction of a rake face and at least one flank face of the substrate. Fig. Figure 1 illustrates a cutting insert substrate according to an example described herein. As in Fig.As illustrated in Figure 1, the substrate 10 has cutting edges 12 formed at the junctions of the rake face 14 and the flank face 16 of the substrate. The substrate 10 also includes an opening 18 for attaching the substrate 10 to a tool holder. The substrate 10 has several geometries and configurations, e.g., with or without a chip breaker, a mounting hole, or a positive or negative rake angle.

[0042] The layer with the aluminum oxide matrix and at least one zirconium oxide grain and at least one hafnium oxide grain in the aluminum oxide matrix can be deposited directly onto the substrate surface. Alternatively, a multilayer coating with at least one layer containing an aluminum oxide matrix and at least one zirconium oxide grain and at least one hafnium oxide grain in the aluminum oxide matrix can further comprise one or more inner layers between the substrate and the layer containing an aluminum oxide matrix and at least one zirconium oxide grain and at least one hafnium oxide grain in the aluminum oxide matrix.

[0043] In some embodiments, one or more inner layers may comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB, and VIB of the periodic table, and one or more non-metallic elements selected from groups IIIA, IVA, VA, and VIA of the periodic table. In particular, the one or more inner layers may comprise a carbide, nitride, carbonitride, oxycarbonitride, oxide, or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB, and VIB of the periodic table.

[0044] One or more inner layers can be selected, for example, from the group consisting of titanium nitride, titanium carbonitride, titanium oxycarbonitride, titanium carbide, zirconium nitride, zirconium carbonitride, zirconium oxycarbonitride, zirconium carbide, hafnium nitride, and hafnium carbonitride. Furthermore, a layer of titanium oxycarbonitride can be used as a connecting layer between one or more inner layers and the layer containing the aluminum oxide matrix and at least one of the zirconium oxide grains and hafnium oxide grains in the aluminum oxide matrix.

[0045] The one or more inner layers of the coating can have any thickness that is not inconsistent with the purposes of this description. For example, a single inner layer can have a thickness of at least 1.5 µm. Alternatively, several inner layers together can achieve a thickness of at least 1.5 µm.

[0046] The following Table 2 describes exemplary parameters for the deposition of exemplary inner layers using CVD. Table 2 Composition of the inner layer Gas mixture Temperature (°C) Pressure (Torr) Duration (minutes) TiN H2, N2, TiCl4 800-900 60-300 20-120 TiCN(MT) H2, N2, TiCl4, CH3CN 750-900 30-300 60-300 TiCN(HT) H2, N2, TiCl4, CH4 900-1050 30-300 30-200 TiC H2, TiCl4, CH4 900-1050 30-300 30-200 TiOCN H2, N2, TiCl4, CH4, CO 900-1050 60-500 30-300 ZrN H2, N2 / NH3, ZrCl4 800-900 60-300 20-120 ZrCN(MT) H2, N2, ZrCl4, CH3CN 750-900 30-300 60-300 ZrCN(HT) H2, N2, ZrCl4, CH4 900-1050 30-300 30-200 ZrC H2, ZrCl4, CH4 900-1050 30-300 30-200 ZrOCN H2, N2, ZrCl4, CH4, CO 900-1050 60-500 30-300

[0047] The layer containing the aluminum oxide matrix and at least one zirconium oxide grain and hafnium oxide grain within the aluminum oxide matrix can be the outermost layer of the coating. Alternatively, a coating described herein can comprise one or more outer layers above the layer containing the aluminum oxide matrix and the at least one zirconium oxide grain and hafnium oxide grain within the aluminum oxide matrix. The one or more outer layers can comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB, and VIB of the periodic table, and one or more nonmetallic elements selected from groups IIIA, IVA, VA, and VIA of the periodic table.In particular, one or more outer layers may comprise a carbide, nitride, carbonitride, oxycarbonitride, oxide, or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB, and VIB of the periodic table. For example, one or more outer layers may be selected from the group consisting of titanium nitride, titanium carbonitride, titanium oxycarbonitride, titanium carbide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride, and aluminum oxide, and mixtures thereof.

[0048] The one or more outer layers described herein may have any thickness that is not inconsistent with the purposes of this description. In some embodiments, an outer layer of the coating may have a thickness of 0.2 µm to 5 µm.

[0049] The coatings described herein can be subjected to post-coating treatments. For example, the coatings can be blasted with various wet and / or dry particle compositions. Post-coating blasting can be performed in any desired manner. In some embodiments, post-coating blasting includes shot peening or pressure blasting. Pressure blasting can be applied in several forms, including compressed air blasting, wet compressed air blasting, hydraulic pressure blasting, wet blasting, and steam blasting. Wet blasting, for example, is achieved using a slurry of inorganic and / or ceramic particles, such as aluminum oxide, and water. The particle slurry can be pneumatically directed onto a surface of the coated cutting tool body so that it impacts the surface of the coating.The size of the inorganic and / or ceramic particles can generally range between 20 µm and 100 µm.

[0050] The blasting parameters include pressure, impact angle, distance to the workpiece surface, and duration. In some embodiments, the impact angle can range from 5 degrees to 90 degrees, meaning the particles strike the coating surface at an angle between 5 and 90 degrees. Suitable pressures can range from 30 to 55 pounds per square inch (psi) at a distance of 1 to 6 inches from the coating surface. Furthermore, the blasting duration can generally range from 1 to 10 seconds or longer. Blasting can generally be performed over the coating surface or applied to selected locations, such as a workpiece contact area of ​​the cutting tool. A workpiece contact area can be a honed region of the cutting tool.

[0051] In other embodiments, a coating undergoes a grinding treatment after application. Grinding can be performed with a paste of diamond or ceramic grains of a suitable size. The grain size of the paste in some embodiments ranges from 1 µm to 10 µm. In one embodiment, a diamond grain paste with a grain size of 5 to 10 µm is used for grinding the coating. Furthermore, the grain paste can be applied to the coating with any device that is not inconsistent with the purposes of this description, such as a brush. In one embodiment, for example, a flat brush is used to apply the grain paste to the coating in a workpiece contact area of ​​the cutting tool.

[0052] A coating described herein can be blasted or ground over a period of time sufficient to achieve a desired surface roughness and / or other parameters, such as the reduction of tensile residual stress in the coating.

[0053] Furthermore, in some embodiments, a post-coating treatment does not remove one or more outer layers of the coating, such as outer layers of TiN, TiCN, TiOCN, TiC, ZrN, ZrC, ZrCN, ZrOCN, ZrOCN, HaN, HaC, HaCN and / or HaOCN. Alternatively, a post-coating treatment may remove or partially remove one or more outer layers.

[0054] The following Table 3 describes exemplary properties for coatings comprising the layer with the aluminium oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains in the aluminium oxide matrix with a mean grain size of 100 nm or less. Table 3 Example A B TiN thickness (µm) 0,4 0,4 MT-TiCN 7,9 8,6 Thickness (µm) HT-TiCN / TiOCN thickness (µm) 1,0 0,9 Al2O3-ZrO2 nanocompound thickness (µm) 8,2 8,8 Total (µm) 17,5 18,7 Zr / (Zr+Al) ratio 0,3-0,6 0,4-0,8 Temperature (°C) 850-950 1020-1050 H2S / CO2 ratio 0,04 0,02

[0055] Example A demonstrates the case of grain boundary inclusion and example B the case of secondary phase inclusion in an Al2O3 matrix.

[0056] Although various embodiments of the disclosed coating and the coated cutting insert have been shown and described, modifications may occur to a person skilled in the art when reading the patent specification. The present application includes these modifications and is limited only by the scope of the appended claims.

Claims

[1] Coating, comprising: a layer with an aluminium oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains in the aluminium oxide matrix, wherein a mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is 100 nm or less, characterized by , that at least one of the zirconium oxide grains and the hafnium oxide grains is primarily arranged within grains of the aluminum oxide matrix. [2] Coating according to claim 1, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 1 nm to 80 nm. [3] Coating according to claim 1 or 2, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 1 nm to 40 nm. [4] Coating according to claim 1 or 2, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 40 nm to 80 nm. [5] Coating according to one of the preceding claims, wherein the at least one of the zirconium oxide grains and the hafnium oxide grains comprises grains having at least one of a tetragonal, monoclinic and orthorhombic crystal structure. [6] Coating according to any of the preceding claims, wherein the layer has a thickness of 0.1 µm to 25 µm. [7] Coated cutting tool, comprising: a substrate (10) with a rake face (14), a clearance face (16) and a cutting edge (12) formed at the meeting of the rake face (14) and the clearance face (16); and a coating bonded to the substrate, wherein the coating comprises a layer with an aluminum oxide matrix and at least one of zirconium oxide grains and hafnium oxide grains in the aluminum oxide matrix, wherein a mean grain size of the at least one of the zirconium oxide grains and hafnium oxide grains is 100 nm or less, characterized by , that at least one of the zirconium oxide grains and the hafnium oxide grains is primarily arranged within grains of the aluminum oxide matrix. [8] Coated cutting tool according to claim 7, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 1 nm to 80 nm. [9] Coated cutting tool according to claim 7 or 8, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 1 nm to 40 nm. [10] Coated cutting tool according to claim 7 or 8, wherein the mean grain size of the at least one of the zirconium oxide grains and the hafnium oxide grains is in a range of 40 nm to 80 nm. [11] Coated cutting tool according to claim 7, wherein the at least one of the zirconium oxide grains and the hafnium oxide grains comprises grains having at least one of a tetragonal, monoclinic and orthorhombic crystal structure. [12] Coated cutting tool according to any one of claims 7 to 11, wherein the coating has a thickness of 0.1 µm to 25 µm.

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