Hard coating and element covered with hard coating

Abstract

A hard coating (30; 50; 60; 70; 80; 90) to be applied to the surface of a substrate (12) in such a way as to cover the surface of the substrate (12), wherein the hard coating (30; 50; 60; 70; 80; 90) has a total thickness (Ttotal) in the range of 0.5 - 20 µm and comprises three types of layers (32, 38, 40; 34, 38, 42; 36, 40, 42) stacked alternately, wherein the three types of layers (32, 38, 40; 34, 38, 42; 36, 40, 42) consist of a single-composition layer (32; 34; 36) and two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) consist of the single composition layer (32; 34; 36) being formed by an A composition, a B composition and a C composition, and wherein the two types of nanolayer interlayers (38, 40; 38, 42;40, 42) nanolayers (32n, 34n, 36n) are contained, which are alternately layered on top of each other and which are formed by two of three combinations consisting of a combination of the A composition and the B composition, a combination of the A composition and the C composition and a combination of the B composition and the C composition, such that the nanolayers (32n, 34n; 32n, 36n) contained in one (38; 40) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) are formed by one of the two of the three combinations and that the nanolayers (32n, 36n; 34n, 36n) contained in the other (40; 42) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) are formed by one of the two of the three combinations 36n) are formed by the other of the two of the three combinations; the A composition is a nitride which is given by the composition formula AlaCrbSic&agr;is represented where the atomic ratios a, b, c, d satisfy 0.30 ≤ a ≤ 0.85, 0.10 ≤ b ≤ 0.65, 0.01 ≤ c ≤ 0.45, 0 ≤ d ≤ 0.10 and a + b + c + d = 1 and where the optional additional component Σ at least one type of element is selected from B, C, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W; the B composition is a nitride represented by the composition formula AleTifSig&bgr;hre, satisfying the atomic ratios e, f, g, h 0.01 ≤ e ≤ 0.85, 0.05 ≤ f ≤ 0.90, 0.05 ≤ g ≤ 0.45, 0 ≤ h ≤ 0.10 and e + f + g + h = 1, and where the optional additional component &bgr; at least one type of element is selected from B, C, Cr, V, Y, Zr, Nb, Mo, Hf, Ta and W; the C composition is a nitride defined by the composition formula AliCrj(SiC)k&ggr;l is represented, wherein the atomic ratios i, j, k, l satisfy 0.20 ≤ i ≤ 0.85, 0.10 ≤ j ≤ 0.50, 0.03 ≤ k ≤ 0.45, 0 ≤ l ≤ 0.10 and i + j + k + l = 1 and wherein the optional additional component ↑ is at least one type of element selected from B, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W; the single composition layer (32; 34; 36) has a thickness (T1) in a range of 0.5 - 1000 nm; and each of the nanolayers (32n, 34n, 36n) that form the two types of nanolayer interlayers (38, 40; 38, 42; 40, 42) has a thickness in the range of 0.5 - 500 nm and each of the two types of nanolayer interlayers (38, 40; 38, 42; 40, 42) has a thickness (T2, T3) in the range of 1 - 1000 nm.

Description

Technical field The present invention relates to a hard coating and an element covered with a hard coating, and in particular to such a hard coating which has excellent wear resistance and weld resistance. State of the art A hard coating is used on various elements, such as different machining tools and friction parts that require wear resistance, to cover the surface of a substrate made of cemented carbide, high-speed tool steel, or the like. The various machining tools include cutting tools such as end mills, milling cutters, drills, lathe end mills, and cutting tips, as well as non-cutting tools such as thread formers and rotary tools. For example, JP 2012-35378A proposes a hard coating with a multilayer structure of an AlCrN / AlTiSiN system. JP 2014-79834A proposes a hard coating with a multilayer structure of an AlCrN / CrN system. JP 2008-534297A proposes a hard coating with a multilayer structure of an AlCr / TiSi system.These hard coatings generally have excellent wear resistance and weld resistance. WO 2018 / 078 731 A1, CN 1 06 995 913 A, US 2018 / 0 099 335 A1, DE 10 2010 039 035 A1, JP 2007 - 030 132 A and US 2006 / 0 222 893 A1 reveal further hard coatings. Disclosure of the invention Problem to be solved by the invention However, it is possible that the hard coating described above may not provide sufficiently satisfactory performance, depending on factors such as machining and operating conditions, the type of workpiece material, and cutting speeds, leaving room for improvement. For example, if a cutting tool coated with a conventional hard coating is used for cutting titanium alloys, the tool may not have a sufficient service life due to early peeling or breakage of the hard coating, as titanium alloys have a relatively high degree of toughness. The present invention was developed in light of the prior art discussed above. It is therefore an object of the invention to provide a hard coating and a tool covered with a hard coating that have excellent wear resistance and weld resistance and are capable of providing a certain service life even during cutting operations for, for example, cutting titanium alloys. Means of solving the problem Various experiments and studies carried out in the situation described above by the inventor of the present invention and collaborators have revealed that a hard coating with high toughness and excellent durability can be obtained by using an A composition, a B composition, and a C composition, and layering them, for example, with certain thicknesses, wherein the A composition is a nitride of AlCrSiα, wherein an optional additional component α is at least one type of element selected from B, C, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W; the B composition is a nitride of AlTiSiβ, wherein an optional additional component β is at least one type of element selected from B, C, Cr, V, Y, Zr, Nb, Mo, Hf, Ta, and W; and the C composition is a nitride of AlCr(SiC)γ.wherein an optional additional component γ is at least one type of element selected from B, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W. The present invention is based on the discovered fact. The above problem is solved by a hard coating according to claim 1 and by an element covered with a hard coating according to claim 7. It should be noted that the (SiC) in the C composition of claim 1 means that the (SiC) is present in the form of silicon carbide as a compound. Furthermore, it is difficult to precisely control the thickness of each layer across the entire range. Each of the thicknesses described in this description is an average thickness value, and the actual thickness may deviate from a corresponding value within the ranges described above, as long as the average thickness falls within the corresponding ranges described in claim 1. Subclaims 2 to 6 relate to further developments of the hard coating according to claim 1 and subclaim 8 to a further development of the element covered with a hard coating according to claim 7. The coating hardness (HV0.025) in claim 6 is an HV value (Vickers hardness) of the hard coating, which is measured in accordance with the Vickers hardness test method according to the Japanese Industrial Standard JIS Z 2244: 2009. Vickers hardness test - test method under a condition specified by the hardness symbol HV0.025. It is pointed out that, as long as a rounded value of an actual value lies within a corresponding numerical range defined in the inventions described above, such an actual value is to be interpreted as lying within the corresponding numerical range. Effects of the invention In the hard coating of the present invention described above, the individual composition layer formed by the A composition has, depending on the proportions of Al and Cr, high hardness, oxidation resistance and toughness, and the individual composition layer formed by the B composition has, depending on the proportions of Al and Ti, high toughness, lubricity and oxidation resistance.Furthermore, the single composition layer formed by the carbon composition exhibits low affinity for oxygen, as silicon (Si) in the carbon composition is present as SiC (silicon carbide) compound. It also possesses a high degree of hardness, with minimal reduction in mechanical strength even at temperatures of 1000 °C or higher due to the covalent bond between the SiC and carbon. Consequently, the single composition layer formed by the carbon composition offers excellent heat resistance, wear resistance, and oxidation resistance. Each of the nanolayer interlayers possesses the properties described above, depending on the composition of the nanolayers. Additionally, each nanolayer interlayer has a thickness and smaller crystal particles than the single composition layer, resulting in high hardness and improved wear resistance.Furthermore, each of the nanolayer layers exhibits increased toughness thanks to its multilayer structure. The components α, β, and γ are optionally added to the respective A, B, and C compositions in a ratio of 10 at% (atomic percent) or less. This allows for the micronization of the coating's crystal particles and the control of particle size by adjusting the addition quantity. This, in turn, enables the adjustment of properties such as the coating's hardness, oxidation resistance, toughness, and lubricity. The structure, in which one type of single-composition layer and the two types of nanolayer layers with the properties described above are stacked alternately at predetermined thicknesses, makes it possible to achieve a hard coating with excellent wear resistance, lubricity, weld resistance, and toughness.Thanks to these features, in the case of a cutting tool, for example, it has become possible to increase the tool's service life thanks to its high toughness, which suppresses breakage and peeling of the hard coating, during cutting operations with various workpiece materials such as carbon steel, stainless steel, cast iron, alloy steel and titanium alloy, or under harsh machining conditions such as high-speed machining and dry machining. Since, in the second invention, the ratio T1 / T2 of the thickness T1 of the single composition layer to the thickness T2 of one of the two types of nanolayer alternating layers and the ratio T1 / T3 of the thickness T1 of the single composition layer to the thickness T3 of the other of the two types of nanolayer alternating layers are both in a range of 0.2 - 10, the one type of single composition layer and the two types of nanolayer alternating layers are provided with corresponding thicknesses that ensure certain properties, making it possible to achieve corresponding performance characteristics such as wear resistance and weld resistance. In the third invention, the lowest layer of the three types of layers, which consist of one type of single-composition layer and two types of nanolayer alternating layers that are stacked alternately on top of each other, is arranged directly on a surface of the substrate, so that the coating formation costs can be reduced compared to an arrangement in which an interface layer or the like is provided in a boundary adjacent to the substrate. In the fourth invention, the interface layer is provided in the boundary adjacent to the substrate, which is formed by the predetermined composition or compositions and which has the predetermined thickness, so that it is possible to increase the adhesion strength of the hard coating to the substrate. In the fifth invention, the outermost layer of the hard coating is the surface layer, which is formed by the predetermined composition or compositions and has the predetermined thickness, so that it is possible to improve certain coating performances such as wear resistance and weld resistance by appropriately determining the composition or compositions and the thickness of the surface layer. In the sixth invention, the coating hardness (HV0.025) of the hard coating is in the range of 2700 - 3300 (HV), so that wear resistance and high toughness can be achieved with an excellent balance between them, thereby suppressing breakage and peeling of the hard coating and accordingly achieving excellent durability. In the case of the seventh invention, which relates to the element covered with a hard coating, it is possible, since the hard coating is provided by each of the first to sixth inventions, to achieve essentially the same effects as the corresponding invention. In the eighth invention, the element covered with a hard coating is an intermittent cutting tool, such as an end mill or a cutter, such that the element covered with the hard coating is repeatedly subjected to impact loads and is slightly heated when a cutting process occurs intermittently through the cutting edges. Therefore, the hard coating of the present invention, which is capable of achieving high wear resistance, toughness, lubricity, and weld resistance, is advantageously used for such an intermittently cutting tool. Brief description of the drawings Fig. 1 is a front view showing an exemplary end mill in which the present invention is used. Fig. 2 is an enlarged bottom view from the side of a far end of the end mill of Fig. 1. Fig. 3 is a schematic view illustrating a coating structure of a hard coating provided on the end mill of Fig. 1. Fig. 4 is a schematic view illustrating another example of the coating structure of the hard coating provided on the end mill of Fig. 1. Fig. 5 is a schematic view illustrating yet another example of the coating structure of the hard coating provided on the end mill of Fig. 1. Fig. 6 is a schematic view illustrating yet another example of the coating structure of the hard coating provided on the end mill of Fig. 1.Figure 7 is a schematic view illustrating yet another example of the coating structure of the hard coating applied to the end mill of Figure 1. Figure 8 is a schematic view illustrating yet another example of the coating structure of the hard coating applied to the end mill of Figure 1. Figure 9 is a schematic view illustrating an arc ion plating device as an example of a physical vapor deposition device for forming the hard coating of each of Figures 3-8 on a tool substrate. Types of embodiments of the invention The present invention is advantageously used for a hard coating applied to the surface of one of several machining tools, including rotating cutting tools such as end mills, milling cutters, taps, and drills; non-rotating cutting tools such as lathe cutters; and non-cutting tools such as thread formers, rotary tools, and press tools. However, the present invention can also be used for a hard coating that serves as a surface protection coating for a bearing element, a semiconductor device, or the like, specifically as a hard coating applied to an element other than the machining tools and which must, for example, possess wear resistance, lubricity, and oxidation resistance.Furthermore, the present invention is also applicable to a cutting tip that can be attached to one of several machining tools. Advantageously, cemented carbide, high-speed tool steel, cermet, ceramic, polycrystalline diamond (PCD), monocrystalline diamond, polycrystalline CBN, or monocrystalline CBN are used as the tool substrate of a tool covered with a hard coating, although other tool materials can also be used. Advantageously, a PVD (physical vapor deposition) process such as arc ion plating, sputtering, and PLD (laser beam evaporation) is used as a method for forming the hard coating. The hard coating of the present invention is advantageously used for a cutting tool that performs a cutting operation for cutting, for example, titanium alloy, but it can also advantageously be used for a cutting tool that performs a cutting operation for cutting other workpiece materials such as carbon steel, stainless steel, cast iron and alloy steel, since it has excellent wear resistance, lubricity, weld resistance and toughness. The hard coating contains three types of layers that are stacked alternately on top of each other, wherein the three types of layers consist of a single-composition layer and two types of nanolayer alternating layers, wherein the single-composition layer is formed by an A-composition, a B-composition and a C-composition, wherein the two types of nanolayer alternating layers contain nanolayers that are stacked alternately on top of each other and that are formed by two of three combinations consisting of a combination of the A-composition and the B-composition, a combination of the A-composition and the C-composition and a combination of the B-composition and the C-composition.that the nanolayers contained in one of the two types of nanolayer interlayers are formed by one of the two of the three combinations, and that the nanolayers contained in the other of the two types of nanolayer interlayers are formed by the other of the two of the three combinations. The stacking sequence of the layers is determined accordingly. It is preferable that the three types of layers, consisting of the single-composition layer and the two types of nanolayer interlayers, are stacked on top of each other in the predetermined sequence for at least one cycle, and that the three types of layers are stacked on top of each other for one complete cycle or cycles such that the number of each of the three types of layers is equal. However, the stacking of the three types of layers can be terminated without a topmost layer of the three types of layers completing a corresponding cycle.For example, the top layer may be of the same type as the bottom layer of the three types of layers. This also applies to the types of nanolayer alternating layers, each of which contains the nanolayers of the two compositions stacked alternately. It is preferable that the two types of nanolayers are stacked alternately for at least one cycle. However, the number of nanolayers stacked alternately in each of the two types of nanolayer alternating layers may be odd. If the hard coating contains an interface layer and / or a surface layer, the total thickness of the hard coating includes the thickness of the interface layer and / or the thickness of the surface layer. It is preferable that the ratio T1 / T2 of the thickness T1 of the single composition layer to the thickness T2 of one of the two types of nanolayer interlayers, and the ratio T1 / T3 of the thickness T1 of the single composition layer to the thickness T3 of the other of the two types of nanolayer interlayers, both lie within the range of 0.2 to 10. However, each of the thicknesses T1, T2, and T3 can be set to a value that causes the corresponding ratio to deviate from the corresponding numerical range. The hard coating can, if required, include an interface layer to be placed adjacent to the substrate.It is preferable that the interface layer be formed by a single-composition layer consisting of one of the A, B, and C components, or by an alternating nanolayer layer containing two types of nanolayers, each consisting of two of the A, B, and C components, respectively, stacked alternately. However, the interface layer may be a layer of metal nitride, metal carbonitride, or metal carbide composed of at least one type of element consisting of B, Al, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, and W, or a layer composed of another composition or compositions. The interface layer has a thickness preferably in the range of 5–1000 nm. However, the thickness of the interface layer may be outside the numerical range of 5–1000 nm. The hard coating may, if required, have a surface layer. It is preferable that the surface layer be formed by a single-composition layer consisting of one of the A, one of the B, and one of the C components, or by an alternating nanolayer layer containing two types of nanolayers, each consisting of two of the A, B, and C components, respectively, stacked alternately. However, the surface layer may be a layer consisting of a different composition or compositions. The surface layer has a thickness preferably in the range of 0.5–1000 nm. However, the thickness of the surface layer may be outside this range. Regarding the coating hardness (HV0.025) of the hard coating, insufficient wear resistance could be achieved if it were too low, and the hard coating could easily peel or break if it were excessively high. Therefore, regardless of the presence or absence of the interface and surface layers, it is appropriate for the coating hardness to be in a range of, for example, approximately 2700–3300 (HV), and it is preferable for the coating hardness to be in a range of, for example, approximately 2800–3200 (HV). However, the coating hardness (HV0.025) of the hard coating may be less than 2700 (HV) or greater than 3300 (HV), depending on, for example, the type of workpiece material and the machining and operating conditions. According to the findings obtained by the inventor of the present invention and his collaborators, the hard coating of the present invention, thanks to the alternating layering of the three types of layers—comprising one type of single-composition layer and two types of nanolayer alternating layers—exhibits improved mechanical properties (hardness), wear resistance, oxidation resistance, and shear strength compared to a multilayer coating based on AlCrN or AlCrTiN. Furthermore, high hardness can be achieved due to the inhibition of lattice dislocations, which is facilitated by an interface between each pair of adjacent layers exhibiting different elastic properties (modulus of elasticity and hardness). This interface not only contributes to increased coating hardness but also improves toughness by inhibiting energy dissipation and crack propagation.Since the interface strongly influences the properties of the multilayer coating, the provision of the nanolayer layering, in which a layering cycle of the nanolayers lies in the nanometer range, makes it possible to achieve the effects of an improvement in the mechanical properties and the tribology of the hard coating when the sizes of the crystal particles and the coating density are adjusted accordingly by controlling the thickness of each nanolayer of the nanolayer layering. Furthermore, thanks to the diffusion of a mixture of amorphous alloy phase and crystalline phase, each of the individual nano-, interface-, and nanolayer alternating layers exhibits better wear resistance and toughness than a conventional multilayer coating of coarse particles. Within each of the nanolayer alternating layers, the internal stress is reduced due to particle boundary dislocation and disclination, thereby suppressing cracks and fractures in the coating during machining, such as intermittent cutting. The hard coating of the present invention, thanks to the formation of fine particles, has a smooth surface and a dense surface structure, and consequently, improved wear resistance. Furthermore, numerous boundaries are defined by the interfaces, which, through particle boundary dislocation and disclination, weakens the internal stress across these interfaces. This results in improved toughness and hardness, making it possible to suppress the propagation of cracks and fractures in the coating during machining, such as intermittent cutting processes. Example of implementation In the following, an embodiment of the invention is described in detail with reference to the drawings. Fig. 1 is a front view showing an end mill 10, which is an example of a hard-coated element in which the present invention is used. Fig. 2 is an enlarged bottom view seen from the side of a far end of the end mill 10. The end mill 10 is formed mainly of a tool substrate 12 (see Figs. 3-8) made of carbide, and the tool substrate 12 has a shank section 14 and a cutting edge section 16, which together form a unit. The cutting edge section 16 is provided with five cutting edges arranged at equal intervals around an axis of the end mill 10, each of the cutting edges having a peripheral cutting edge 18 and a terminal cutting edge 20. When the end mill 10 is rotated around the axis, the end mill 10 performs an intermittent cutting operation through the peripheral cutting edge 18 and the end cutting edge 20 of the cutting edge.In this embodiment, the end mill 10 is a radius cutter in which the peripheral cutting edge 18 and the end cutting edge 20 are joined at a corner that is rounded. The end mill 10 is a tool coated with a hard coating and corresponds to an intermittent cutting tool. A hard coating 30, shown in Fig. 3, is provided such that it covers a surface of the blade section 16, which is a section of the tool substrate 12. Fig. 3 is a schematic view, enlarged to show a cross-section of a neighborhood of the surface of the blade section 16 covered by the hard coating 30. The area of ​​the surface covered by the hard coating 30 is represented by a hatched area in Fig. 1. It is also possible to provide the hard coating 30 such that the entire ball end mill 10, including the shank section 14, is covered with the hard coating 30. The hard coating 30 has a multilayer structure and comprises an A-layer 32, a nanolayer interchange layer 38, and a nanolayer interchange layer 40, arranged in that order in one direction from an outer surface of the hard coating 30 to the tool substrate 12. The A-layer 32, the nanolayer interchange layer 38, and the nanolayer interchange layer 40 are stacked on top of each other for at least one cycle. The hard coating 30 also includes an interface layer 44, which is located in its boundary section adjacent to the tool substrate 12. This means that the interface layer 44 is first arranged on a surface of the tool substrate 12, and then the nanolayer interchange layer 40, the nanolayer interchange layer 38, and the A-layer 32 are arranged on the interface layer 44.The nanolayer layer 40, the nanolayer layer 38, and the A-layer 32 are repeatedly stacked on top of each other in the order described, such that the A-layer 32 provides the uppermost section of the hard coating 30. The hard coating 30 with the interface layer 44 has a total thickness Ttotal, which is set to a value in the range of 0.5–20 µm. The A-layer 32 has a thickness T1, which is set to a value in the range of 0.5–1000 nm. The nanolayer layers 38 and 40 each have thicknesses T2 and T3, respectively, each of which is set to a value in the range of 1–1000 nm. Furthermore, the thicknesses T1 - T3 are set to the respective values ​​such that a ratio T1 / T2 of thickness T1 to thickness T2 and a ratio T1 / T3 of thickness T1 to thickness T3 both lie in a range of 0.2 - 10. The A-position 32 is a single-composition layer formed by only one A-composition. The A-composition is a nitride represented by the formula AlaCrbSicAd, where the atomic ratios a, b, c, d satisfy 0.30 ≤ a ≤ 0.85, 0.10 ≤ b ≤ 0.65, 0.01 ≤ c ≤ 0.45, 0 ≤ d ≤ 0.10 and a + b + c + d = 1, and where the optional additional component α is at least one type of element selected from B, C, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W. Table 1 shows the types of constituent elements and their proportions in an A composition forming the hard coating of each of test samples 1 - 50 used in a cutting test.Table 1 shows examples of the content (at%) of each element in the A composition, where each blank space indicates that the content (at%) of the corresponding element is 0, and each gray area (each column with scatter dots) indicates that the atomic ratio corresponding to the content of the respective element deviates from the corresponding numerical range of the composition formula described above. This means that test samples 7-50 meet the requirements of the A composition. The A-layer 32 with this composition has a crystal system in the form of a cubic rock salt structure and is characterized by high hardness and excellent wear resistance. Depending on the ratios of Al and Cr, it provides high hardness, oxidation resistance, and toughness. Furthermore, the heat resistance can be increased by adding Si in a predetermined ratio.Furthermore, the addition of the optional component α at a ratio of no more than 10 at% allows for the micronization of crystal particles and the control of particle size by adjusting the addition quantity, thereby adjusting the coating's hardness, toughness, and lubricity. Additionally, the presence of these elements in A-Layer 32 improves lubricity and oxidation resistance, as well as strength and toughness at high temperatures during heat-generating cutting processes. These characteristics help suppress the occurrence of, for example, chipping and fractures during cutting conditions involving high impacts and mechanical loads.Furthermore, it is possible to reduce oxidation wear due to heat generated during high-speed machining or the like, and to achieve an excellent balance between wear resistance and weld resistance, thus ensuring high durability even during high-speed and dry machining. The nanolayer interlayer 38 has a multilayer structure comprising an A-nanolayer 32n and a B-nanolayer 34n, which are alternately stacked on top of each other for at least one cycle, wherein the A-nanolayer 32n, like the A-layer 32, is formed by the A-composition and the B-nanolayer 34n is formed by the B-composition. In this embodiment, a bottom section of the nanolayer interlayer 38 is provided by the A-nanolayer 32n, while a top section of the nanolayer interlayer 38 is provided by the B-nanolayer 34n. However, the bottom section and the top section of the nanolayer interlayer 38 can each be provided by the B-nanolayer 34n and the A-nanolayer 32n, respectively. The A-nanolayer 32n and the B-nanolayer 34n each have thicknesses that are set to a value in the range of 0.5 - 500 nm.The B composition is a nitride represented by the formula AleTifSigβhre, where the atomic ratios e, f, g, h satisfy 0.01 ≤ e ≤ 0.85, 0.05 ≤ f ≤ 0.90, 0.05 ≤ g ≤ 0.45, 0 ≤ h ≤ 0.10 and e + f + g + h = 1, and where the optional additional component β is at least one type of element selected from B, C, Cr, V, Y, Zr, Nb, Mo, Hf, Ta, and W. Table 2 shows the types of constituent elements and their proportions in a B composition forming the hard coating of each test sample 1–50. Specifically, Table 2 shows examples of the content (at%) of each element in the B composition, where each blank space means that the content (at%) of the corresponding element is 0, and each grey part (each column with scatter dots) means that the atomic ratio corresponding to the content of the corresponding element differs from the corresponding numerical range of the composition formula described above.This means that test samples 7-50 meet the requirements of the B composition. Depending on the proportions of Al and Ti, the B composition provides high toughness, heat resistance, and oxidation resistance. The addition of the optional component β at a ratio of no more than 10 at% gives the coating high hardness and excellent oxidation resistance, leading to improved wear resistance. The B composition has a cubic crystal structure, and the crystal particles are micronized by the addition of the optional component β, further improving hardness and wear resistance. The crystal structure is oriented with higher priority towards the (200) face than the (111) face, and the integral strength of a diffraction line on the (200) face is 1.5 times or more greater than that on the (111) face. The nanolayer interlayer 40 has a multilayer structure comprising the A nanolayer 32n and a C nanolayer 36n stacked on top of each other for at least one cycle, wherein the A nanolayer 32n, like the A layer 32, is formed by the A composition and the C nanolayer 36n is formed by the C composition. In this embodiment, a bottom section of the nanolayer interlayer 40 is provided by the A nanolayer 32n, while a top section of the nanolayer interlayer 40 is provided by the C nanolayer 36n. However, the bottom section and the top section of the nanolayer interlayer 40 can each be provided by the C nanolayer 36n and the A nanolayer 32n, respectively. The A-nanolayer 32n and the C-nanolayer 36n each have thicknesses that are set to a value in the range of 0.5 - 500 nm.The carbon composition is a nitride represented by the formula AliCrj(SiC)kγl, where the atomic ratios i, j, k, l satisfy 0.20 ≤ i ≤ 0.85, 0.10 ≤ j ≤ 0.50, 0.03 ≤ k ≤ 0.45, 0 ≤ l ≤ 0.10 and i + j + k + l = 1, and where the optional additional component γ is at least one type of element selected from B, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W. Table 3 shows the types of constituent elements and their proportions in a carbon composition forming the hard coating of each test sample 1–50. Specifically, Table 3 shows examples of the content (at%) of each element in the C composition, where each blank space means that the content (at%) of the corresponding element is 0, and each grey part (each column with scatter dots) means that the atomic ratio corresponding to the content of the corresponding element differs from the corresponding numerical range of the composition formula described above.This means that test samples 7-50 meet the requirements of the C composition. The C composition has a low bonding capacity with oxygen because Si is present in the form of SiC (silicon carbide) as a compound, and the SiC bond is covalent. This results in high hardness, minimal reduction in mechanical strength even at temperatures of 1000°C or higher, and high lubricity. Thus, the C composition is characterized by high hardness as well as excellent heat resistance, oxidation resistance, and wear resistance. Furthermore, by adding the optional additional component γ in a ratio of no more than 10 at%, it is possible to micronize the crystal particles and control the particle size by adjusting the addition quantity, thereby adjusting the hardness, toughness, and lubricity of the coating.Thanks to its excellent wear and oxidation resistance, it is possible to reduce oxidation wear caused by heat generated during high-speed machining or similar processes and to achieve sufficient wear and weld resistance, thus ensuring high durability even during high-speed and dry machining. Each of the nanolayer layers 38, 40, depending on the composition of the nanolayers 32n, 34n, 36n, provides the properties described above and is characterized by high hardness as well as excellent wear resistance, toughness, and oxidation resistance. The interface between the nanolayers 32n, 34n, 36n contributes to an increase in coating hardness and, thanks to its ability to inhibit energy dissipation and crack propagation, also to an improvement in toughness. Since the deposition cycle of the nanolayers 32n, 34n, 36n is in the nanometer range, it is also possible to achieve improvements in the mechanical properties and tribology of the hard coating by appropriately adjusting the crystal particle size and coating density through control of the thickness of each of the nanolayers 32n, 34n, 36n.Each of the nanolayer layers 38 and 40 exhibits superior wear resistance and toughness compared to a conventional multilayer coating of coarse particles, thanks to the diffusion of a mixture of amorphous alloy phase and crystalline phase. Within each of these nanolayer layers, internal stress is reduced due to particle boundary dislocation and disclination, thereby suppressing cracks and fractures in the coating and their propagation during machining operations such as intermittent cutting. Nanolayer layer 38 offers excellent oxidation resistance and lubricity, with a hardness (measured by nanoindentation) of approximately 38–40 GPa. Nanolayer layer 40 exhibits high hardness, with a hardness (measured by nanoindentation) of approximately 43–45 GPa. Since the A-layer 32 and the two types of nanolayer alternating layers 38 and 40 are stacked alternately, the internal stress can also be balanced by adjusting the hardness of each of the layers 32, 38, and 40 accordingly. This increases the bond strength between the layers 32, 38, and 40, suppressing delamination and achieving excellent chipping and wear resistance, even during high-speed machining of materials of high hardness or other difficult-to-cut materials. The interface layer 44 is a single-composition layer, which, like the A-layer 32, is formed solely by the A-composition. The interface layer 44 has a thickness that is accordingly set to a value in the range of 5–1000 nm. Since the interface layer 44 is located at a boundary adjacent to the tool substrate 12, the adhesion strength of the hard coating 30 to the tool substrate 12 can be increased. Regarding the coating hardness (HV0.025) of the hard coating 30, sufficient wear resistance could not be achieved if it were too low, and the hard coating 30 could easily peel off or break if it were too high. In the exemplary embodiment, the coating hardness is in the range of approximately 2700–3300 (HV). Figures 4-8 are views illustrating further examples of the hard coatings, each of which is to be applied to the surface of the cutting section 16 of the end mill 10. Each of Figures 4-8 is a schematic sectional view corresponding to the view in Figure 3, and the total thickness Ttotal of each hard coating is in the range of 0.5-20 µm. A hard coating 50 of Figure 4 differs from the hard coating 30 described above in that a B-layer 34 is provided instead of the A-layer 32, a nano-layer 42 is provided instead of the nano-layer 40, and an interface layer 52 is provided instead of the interface layer 44. In the hard coating 50 of Figure 4, the B-layer 34 has a thickness T1, which is accordingly set to a value in the range of 0.5-1000 nm.The nanolayer interlayers 38 and 42 each have thicknesses T2 and T3, respectively, each set to a value within a range of 1–1000 nm. Furthermore, the thicknesses T1–T3 are set such that the ratio T1 / T2 of thickness T1 to thickness T2 and the ratio T1 / T3 of thickness T1 to thickness T3 both lie within a range of 0.2–10. It should be noted that while the thickness T1 of the B-layer 34 is determined independently of the thickness T1 of the A-layer 32 described above, layers 32 and 34 are both single-composition layers whose respective numerical ranges are identical. Therefore, the same reference symbol "T1" is used as a common reference symbol for the thicknesses of A-layer 32 and B-layer 34. The same applies to the thicknesses T2, T3 of the nanolayer alternating layers 38, 42. The B-layer 34 is a single-composition layer consisting solely of the B-composition. The nanolayer interlayer 42 has a multilayer structure containing the B-nanolayer 34n and the C-nanolayer 36n, which are alternately stacked on top of each other for at least one cycle. In this embodiment, a bottom section of the nanolayer interlayer 42 is provided by the B-nanolayer 34n, while a top section of the nanolayer interlayer 42 is provided by the C-nanolayer 36n. However, the bottom and top sections of the nanolayer interlayer 42 can also be provided by the C-nanolayer 36n and the B-nanolayer 34n, respectively. The B-nanolayer 34n and the C-nanolayer 36n each have thicknesses, each of which is appropriately set to a value in the range of 0.5–500 nm.The interface layer 52 is a single-composition layer formed solely by the B composition, and its thickness is adjusted to a value within the range of 5–1000 nm. The nanolayer interlayer 42 exhibits excellent oxidation resistance and lubricity, and a hardness (measured by nanoindentation) of approximately 38–40 GPa. A hard coating 60 of Fig. 5 differs from the hard coating 30 described above in that a C-layer 36 is provided instead of the A-layer 32, a nano-layer 42 is provided instead of the nano-layer 38, and an interface layer 62 is provided instead of the interface layer 44. In the hard coating 60 of Fig. 5, the C-layer 36 has a thickness T1, which is set to a value in the range of 0.5–1000 nm. The nano-layer 40 and 42 each have thicknesses T2 and T3, respectively, each of which is set to a value in the range of 1–1000 nm. Furthermore, the thicknesses T1 - T3 are adjusted to their respective values ​​such that the ratio T1 / T2 of thickness T1 to thickness T2 and the ratio T1 / T3 of thickness T1 to thickness T3 both lie within the range of 0.2 - 10. C-layer 36 is a single-composition layer consisting solely of the carbon composition.The interface layer 62 is an alternating nanolayer layer consisting of two types of A-nanolayer 32n, B-nanolayer 34n, and C-nanolayer 36n, layered alternately, with a thickness adjusted to a value within the range of 5–1000 nm. Each of the two types of nanolayers—A-nanolayer 32n, B-nanolayer 34n, and C-nanolayer 36n—has a thickness adjusted to a value within the range of 0.5–500 nm. A hard coating 70 of Fig. 6 differs from the hard coating 30 described above with respect to the layering sequence of the A-layer 32 and the nanolayer alternating layers 38, 40. In the hard coating 70, the A-layer 32 is arranged between the nanolayer alternating layer 40 and the nanolayer alternating layer 38, and the nanolayer alternating layer 40 is provided as an outermost layer of the hard coating 70. Furthermore, instead of the interface layer 44, which is formed by the A-composition, the interface layer 62, which is a nanolayer alternating layer, is provided. It is noted that the stacking sequence of the three types of layers 32, 38, 40, which are stacked alternately on top of each other, can be determined accordingly, for example such that the A-layer 32 is arranged between the nanolayer alternating layer 38 and the nanolayer alternating layer 40, with the nanolayer alternating layer 38 being provided as the outermost layer.The same applies to the other hard coatings 50, 60. In addition, a combination of one type of A-layer 32, B-layer 34 and C-layer 36 and the two types of nanolayer alternating layers 38, 40, 42 can be specified accordingly, for example in such a way that the A-layer 32 and the nanolayer alternating layers 38, 42 are stacked on top of each other, or in such a way that the A-layer 32 and the nanolayer alternating layers 40, 42 are stacked on top of each other. A hard coating 80 of Fig. 7 differs from the hard coating 30 described above in that the interface layer 44 is missing. A hard coating 90 of Fig. 8 differs from the hard coating 30 described above in that a surface layer 92 provides an outermost surface of the hard coating 90 and an interface layer 94 is formed by a composition or compositions that are different from the A composition, B composition, and C composition. The surface layer 92 is provided by a single-composition layer, which, like the A layer 32, B layer 34, or C layer 36, is formed by a composition of the A composition, the B composition, and the C composition, respectively, or, like the interface layer 62 described above, it is an alternating nanolayer layer containing two types of A nanolayer 32n, B nanolayer 34n, and C nanolayer 36n, which are stacked alternately such that each of the two types of nanolayers has a thickness in the range of 0.5–500 nm.Surface layer 92 has a thickness that is appropriately adjusted to a value in the range of 0.5–1000 nm. Interfacial layer 94 is formed by a metal nitride, metal carbonitride, or metal carbide composed of at least one element selected from B, Al, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, and W, and it has a thickness that is appropriately adjusted to a value in the range of 5–1000 nm. Furthermore, the hard coating can be structured in other ways, even if this is not shown in the drawings. For example, in each of the hard coatings 30, 50, 60, 70, 80, 90, the three types of layers, consisting of one type of single-composition layer (provided by A-layer 32, B-layer 34, and C-layer 36) and two of the nanolayer alternating layers 38, 40, 42, are stacked alternately in a predetermined sequence for one or more complete cycles, such that the number of each of the three types of layers is equal. However, the stacking of the three types of layers can be terminated without either the top or bottom layer completing a corresponding cycle, for example, by omitting A-layer 32, which provides the top layer of the hard coating 30.In other words, in each of the hard coatings 30, 50, 60, 70, 80, in which the surface layer is not specified, the outermost layer can be considered a surface layer that is different from the three types of layers that are alternately stacked. Similarly, with regard to each of the nanolayer alternating layers 38, 40, 42, which contains the two types of nanolayers (two each of A-layer 32n, B-nanolayer 34n, and C-nanolayer 36n) that are alternately stacked, the number of stacked nanolayers can also be an odd number, for example, such that nanolayer alternating layer 38 begins and ends with A-nanolayer 32n. Furthermore, it is possible to use a boundary layer that is a single composition layer formed only by the C composition instead of each of the boundary layer positions 44, 52, 62, 94. Table 4 and Table 5 are views for a detailed explanation of a coating structure of the hard coating of each of the test samples 1 - 50 on end mills. In the column "SINGLE COMPOSITION LAYER", "A-LAYER", "B-LAYER", and "C-LAYER" correspond to the A-Layer 32, B-Layer 34, and C-Layer 36 described above, respectively. Furthermore, in the column "NANOLAYER ACROSS LAYER", "A-LAYER", "B-LAYER", and "C-LAYER" correspond to the A-Nanolayer 32n, B-Nanolayer 34n, and C-Nanolayer 36n described above, respectively, and "ACROSS LAYER (AB)", "ACROSS LAYER (AC)", and "BCROSS LAYER (BC)" correspond to the nanolayer alternating layers 38, 40, and 42, respectively. Additionally, "INTERFACIAL LAYER" corresponds to one of the interface layers 44, 52, 62, and 94 described above.Each horizontal dash “-” in “A-LAYER”, “B-LAYER”, and “C-LAYER” in the “SINGLE COMPOSITION LAYER”, “NUMBER OF LAYER PAIRS”, and “THICKNESS” of “CHANGE LAYER (AB)”, “CHANGE LAYER (AC)”, and “CHANGE LAYER (BC)” in the “NANO-LAYER CHANGE LAYER” and “LIMIT LAYER” columns indicates that the corresponding layer or layer is not provided. Furthermore, none of the test specimens 1–50 shown in Tables 4 and 5 are provided with the surface layer. In Table 4, each gray area (each column with scatter dots) indicates that a corresponding requirement regarding the thicknesses of the embodiment (of claim 1 of the invention) is not met, and test specimens 1–6 are comparison products, while test specimens 7–50 are products of the present invention. Fig. 9 is a schematic design view (schematic view) illustrating an arc ion plating device 100 used to form the hard coatings 30, 50, 60, 70, 80, 90 described above, or the hard coatings of the test samples 1-50 described in Figs. 13 and 14 (hereinafter simply referred to as "hard coating 30 or the like" when not distinguished from one another), on the tool substrate 12. The arc ion plating device 100 is configured to form the hard coating 30 or the like on the surface of the tool substrate 12 by arc ion plating as a type of PVD process, and it is capable of continuously forming a variety of types of layers, differing in composition, with predetermined thicknesses by changing an evaporation source (target) and a reaction gas.For example, if the hard coating 30 is to be formed, the nanolayer alternating layers 40, 38 and the A-layer 32 are stacked alternately on top of each other after the interface layer 44 has been formed on the surface of the tool substrate 12. Fig. 9 corresponds to a top view of the arc ion plating device 100 as seen from a top side of the arc ion plating device 100. The arc ion plating device 100 comprises the following: a rotary table 154, which is to be driven to rotate about a rotational axis S extending essentially in a vertical direction, and which is intended to hold a variety of workpieces, i.e.The system comprises a multitude of tool substrates 12, each on which the hard coating 30 or the like is to be formed; a preload current source 156 for applying a negative preload to the tool substrates 12; a process vessel in the form of a chamber 158, which houses the tool substrates 12; a reaction gas supply device 160 for supplying a reaction gas into the chamber 158; a gas discharge device 162 for removing a gas from the interior of the chamber 158, for example by means of a vacuum pump, in order to reduce the pressure inside the chamber 158; a first arc current source 164; a second arc current source 166; a third arc current source 168; and a fourth arc current source 170. The rotary table 154 is a disk-shaped table whose center corresponds to the axis of rotation S described above.The multitude of tool substrates 12 are arranged in an outer circumferential section of the rotary table 154 such that each tool substrate 12 assumes a position that makes each substrate 12 substantially parallel to the axis of rotation S. While the tool substrates 12 are rotated about the axis of rotation S by the rotary table 154, each tool substrate 12 can be rotated about its own axis. When the nitride of A-layer 32, B-layer 34, C-layer 36, or the like is to be formed, the reaction gas supply device 160 introduces nitrogen gas into the chamber 158. The interior of the chamber 158 is, for example, brought into a vacuum state of about 2–10 Pa by the gas discharge device 162 and heated to a vapor deposition temperature of, for example, about 300–600°C by a heater or the like, which is not shown in the drawings. Each of the first arc current source 164, second arc current source 166, third arc current source 168 and fourth arc current source 170 is configured to generate an arc current between a corresponding anode 174, 178, 182, 186 and a corresponding cathode in the form of a first evaporation source 172, second evaporation source 176, third evaporation source 180 and fourth evaporation source 184, which consist of vapor deposition material, in order to bring about an arc discharge, thereby selectively causing evaporation material to evaporate from the corresponding one of the first evaporation source 172, second evaporation source 176, third evaporation source 180 and fourth evaporation source 184. After it has evaporated, the evaporation material becomes positive ions, which are deposited in such a way that they cover each of the tool substrates 12 on which a negative (-) bias is applied.This means that each of the evaporation sources 172, 176, 180, 184 is formed by an alloy of compositions A, B, and C, respectively. One of the evaporation sources can serve as an additional source, formed, for example, by an alloy of compositions A, B, and C, which must be formed with a relatively large thickness to enable efficient coating formation. The number of evaporation sources can be three to correspond to the number of compositions consisting of A, B, and C. The arc current sources 164, 166, 168, 170 described above are changed as needed to successively form layers of predetermined compositions, thereby producing the hard coating 30 or the like with a predetermined coating structure. The thickness of each layer can be adjusted by setting the rotational speed of the rotary table 154 and the switching time of one or more of the corresponding arc current sources 164, 166, 168, 170. A boundary section located between a multitude of layers with different compositions can be provided with a mixed layer formed by a mixture of two types of compositions. The results of a performance test of the hard coatings are now described. This test was carried out by producing test samples 1-50, in which the hard coating with the respective coating structures shown in Figures 10-14 was applied to a radius cutter, which is essentially the same as the end mill 10 described above, has five cutting edges, and is formed by the carbide tool substrate 12, and has a diameter of 16 mm. Table 6 shows the coating hardness of the hard coating for each test sample 1-50, as well as a wear width, a cutting length, and an evaluation result measured or achieved during the cutting test. Specifically, "COATING HARDNESS" in Table 6 represents an HV (Vickers hardness) value for each hard coating, determined in accordance with the Vickers hardness test method according to JIS Z 2244:2009.Vickers hardness test – test procedure performed under a condition specified by the hardness symbol HV0.025. Additionally, a cutting operation was carried out in which each of the test specimens 1–50 was used in accordance with a cutting test condition described below. A cutting distance and a wear width of a flank surface adjacent to the peripheral cutting edge 18 were measured, and coating performance (durability) was assessed. More precisely, the wear width of the flank surface was measured by interrupting the cutting operation as needed and then measuring the cutting distance when the wear width of the flank surface reached 0.2 mm or more. Those achieving a cutting distance of 20 m or more were then rated as successes “0”, while those with a cutting distance of less than 20 m were rated as failures “×”.The wear width was measured visually using a microscope (MM-400 / LM) manufactured by Nikon Corporation. - Cutting test condition - Workpiece material: Titanium alloy; Cutting speed V: 70 m / min; Rotational speed n: 1400 min-1; Feed rate: f = 0.09 mm / t, F = 630 mm / min; Machining form: Side cutting; Axial depth of cut ap: 28.8 mm; Radial depth of cut ae: 3.2 mm; Table 6 Test sample 122303,5×comparison product Test sample 221207×Comparison product Test sample 3220010,5×comparison product Test sample 4199014×Comparison product Test sample 523007×Comparison product Test sample 6226017,5×comparison product Test sample 7299035.6◯Invented product Test sample 8286033,6◯Invented product Test sample 9296029,4◯Invented product Test sample 10301032,2◯Invented product Test sample 11305034.5◯Invented product Test sample 12298025,2◯Invented product Test sample 13301039.6◯Invented product Test sample 14287033,7◯Invented product Test sample 15295028.7◯Invented product Test sample 16287037.8◯Invented product Test sample 17302038,1◯Invented product Test sample 18299035,2◯Invented product Test sample 19285029.8◯Invented product Test sample 20301037.8◯Invented product Test sample 21300029.8◯Invented product Test sample 22298035.6◯Invented product Test sample 23299029,8◯Invented product Test sample 24289028,1◯Invented product Test sample 25280027.9◯Invented product Test sample 26278035,2◯Invented product Test sample 27280031.5◯Invented product Test sample 28302029.6◯Invented product Test sample 29308030,2◯Invented product Test sample 30298030.4◯Invented product Test sample 31296033,9◯Invented product Test sample 32288037.7◯Invented product Test sample 33298040,1◯Invented product Test sample 34300033.7◯Invented product Test sample 35298035,9◯Invented product Test sample 36310033,4◯Invented product Test sample 37320039.6◯Invented product Test sample 38305033.5◯Invented product Test sample 39308036.9◯Invented product Test sample 40299035.5◯Invented product Test sample 41298035.6◯Invented product Test sample 42301036.5◯Invented product Test sample 43296033,1◯Invented product Test sample 44291040,1◯Invented product Test sample 45300039.8◯Invented product Test sample 46305036.7◯Invented product Test sample 47300042,1◯Invented product Test sample 48296038.7◯Invented product Test sample 49298036.8◯Invented product Test sample 50307037.9◯Invented product As can be seen from Table 6, each of the test samples 7-50, as a product of the present invention, exhibits a surface coating hardness (HV0.025) in the range of 2700-3300 (HV) and suggests excellent wear resistance and impact resistance (resistance to breakage and peeling during intermittent cutting). In contrast, test samples 1-6, the comparison products, showed hardness values ​​of approximately 1900-2300 (HV). Regarding the cutting distance, each of the test samples 7-50, as products of the present invention, was able to perform the cutting process over 20 m and demonstrated excellent durability. In contrast, each of the test samples 1-6, the comparison products, had a cutting distance of less than 20 m. As described above, with the hard coating 30 or the like of the end mill 10 according to the exemplary embodiment, in which three types of layers are stacked alternately with predetermined thicknesses, consisting of the single-composition layer provided by A-layer 32, B-layer 34 and C-layer 36, and the two nanolayer alternating layers provided by two nanolayer alternating layers 38, 40, 42 each, are possible with predetermined thicknesses, excellent wear resistance, toughness, lubricity and weld resistance. For example, excellent durability was achieved even during a cutting operation with a titanium alloy.Thanks to these characteristics, it has become possible to suppress breakage and peeling of the hard coating 30 or the like during a cutting operation with a titanium alloy or any other of various workpiece materials such as carbon steel, stainless steel, cast iron and alloy steel, or under hard machining conditions such as high-speed machining and dry machining, due to the high toughness, and accordingly to increase the service life of the tool. Since the ratio T1 / T2 of the thickness T1 of one type of single composition layer to the thickness T2 of one of the two types of nanolayer alternating layers and the ratio T1 / T3 of the thickness T1 of one type of single composition layer to the thickness T3 of the other of the two types of nanolayer alternating layers are both in a range of 0.2 - 10, the one type of single composition layer and the two types of nanolayer alternating layers are also provided with corresponding thicknesses that ensure certain properties, making it possible to achieve corresponding performance characteristics such as wear resistance and weld resistance. Furthermore, the coating hardness (HV0.025) of the hard coating 30 or the like is in the range of 2700 - 3300 (HV), so that wear resistance and high toughness can be achieved with an excellent balance between them, which suppresses breakage and peeling of the hard coating 30 or the like and accordingly achieves excellent durability. Furthermore, the hard coating 80 of Fig. 7, which is not provided with the interface layer, can be produced at reduced coating costs, and the end mill 10 with the hard coating 80 can be manufactured cost-effectively. On the other hand, with the hard coatings 30, 50, 60, 70, 90 and the test samples 7-50, which are provided with the interface layer having the predetermined composition(s) and the predetermined thickness, it is possible in each case to increase the adhesion strength of the adhesive coating 30 or the like to the tool substrate 12. Furthermore, with the hard coating 90 of Fig. 8, which is provided with the surface layer 92 having the predetermined composition or compositions and the predetermined thickness, it is possible to further improve certain coating performances such as wear resistance and weld resistance if the composition or compositions and the thickness of the surface layer 92 are determined accordingly. Furthermore, the end mill 10 is an intermittently cutting tool, designed to perform an intermittent cutting operation via the peripheral cutting edge 18 and the end cutting edge 20. This results in repeated impact loads being applied to the peripheral cutting edge 18 and the end cutting edge 20, causing them to heat up slightly during the cutting process. However, by applying a hard coating 30 or similar material with high wear resistance, toughness, lubricity, and weld resistance, the tool's service life can be extended. Although the embodiment of the invention has been described in detail with reference to the accompanying drawings, it is understood that the described embodiment is merely one embodiment and that the present invention can be carried out with various modifications and improvements based on the knowledge of a person skilled in the art. Reference symbol list 10: End mill (element covered with a hard coating, intermittently cutting tool), 12: Tool substrate (substrate), 14: Shank section, 16: Cutting edge section, 18: Peripheral cutting edge (cutting edge), 20: End cutting edge (cutting edge), 30, 50, 60, 70, 80, 90: Hard coating, 32: A layer (single composition layer), 32n: A nanolayer (nanolayer), 34: B layer (single composition layer), 34n: B nanolayer (nanolayer), 36: C layer (single composition layer), 36n: C nanolayer (nanolayer), 38, 40, 42: Nanolayer alternating layer, 44, 52, 62, 94: Interface layer, 92: Surface layer 100: Arc ion plating device, 154: Rotary table, 156: Preload current source, 158: Chamber, 160: Reaction gas supply device, 162: Gas discharge device, 164, 166, 168, 170: Arc current source, 172, 176, 180, 184: Evaporation source (cathode), 174, 178, 182, 186: Anode, S: Axis of rotation, Ttotal: Total thickness, T1: Thickness of individual composition layer, T2,T3: Thick nanolayer alternating layer,

Claims

A hard coating (30; 50; 60; 70; 80; 90) to be applied to the surface of a substrate (12) in such a way as to cover the surface of the substrate (12), wherein the hard coating (30; 50; 60; 70; 80; 90) has a total thickness (Ttotal) in the range of 0.5 - 20 µm and comprises three types of layers (32, 38, 40; 34, 38, 42; 36, 40, 42) stacked alternately, wherein the three types of layers (32, 38, 40; 34, 38, 42; 36, 40, 42) consist of a single-composition layer (32; 34; 36) and two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) consist of the single composition layer (32; 34; 36) being formed by an A composition, a B composition and a C composition, and wherein the two types of nanolayer interlayers (38, 40; 38, 42;40, 42) nanolayers (32n, 34n, 36n) are contained, which are alternately layered on top of each other and which are formed by two of three combinations consisting of a combination of the A composition and the B composition, a combination of the A composition and the C composition and a combination of the B composition and the C composition, such that the nanolayers (32n, 34n; 32n, 36n) contained in one (38; 40) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) are formed by one of the two of the three combinations and that the nanolayers (32n, 36n; 34n, 36n) contained in the other (40; 42) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) are formed by one of the two of the three combinations 36n) are formed by the other of the two of the three combinations;the A composition is a nitride represented by the formula AlaCrbSicAd, where the atomic ratios a, b, c, d satisfy 0.30 ≤ a ≤ 0.85, 0.10 ≤ b ≤ 0.65, 0.01 ≤ c ≤ 0.45, 0 ≤ d ≤ 0.10 and a + b + c + d = 1, and where the optional additional component α is at least one type of element selected from B, C, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W; the B composition is a nitride represented by the formula AleTifSigβhre, where the atomic ratios e, f, g, h satisfy 0.01 ≤ e ≤ 0.85, 0.05 ≤ f ≤ 0.90, 0.05 ≤ g ≤ 0.45, 0 ≤ h ≤ 0.10 and e + f + g + h = 1 satisfy and where the optional additional component β is at least one type of element selected from B, C, Cr, V, Y, Zr, Nb, Mo, Hf, Ta and W;the C composition is a nitride represented by the composition formula AliCrj(SiC)kγl, where the atomic ratios i, j, k, l satisfy 0.20 ≤ i ≤ 0.85, 0.10 ≤ j ≤ 0.50, 0.03 ≤ k ≤ 0.45, 0 ≤ l ≤ 0.10 and i + j + k + l = 1, and where the optional additional component γ is at least one type of element selected from B, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W; the single composition layer (32; 34; 36) has a thickness (T1) in a range of 0.5 - 1000 nm; and each of the nanolayers (32n, 34n, 36n) that form the two types of nanolayer interlayers (38, 40; 38, 42; 40, 42) has a thickness in the range of 0.5 - 500 nm and each of the two types of nanolayer interlayers (38, 40; 38, 42; 40, 42) has a thickness (T2, T3) in the range of 1 - 1000 nm. Hard coating (30; 50; 60; 70; 80; 90) according to claim 1, wherein a ratio (T1 / T2) of the thickness (T1) of the single composition layer (32; 34; 36) to the thickness (T2) of one (38; 40) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) and a ratio (T1 / T3) of the thickness (T1) of the single composition layer (32; 34; 36) to the thickness (T3) of the other (40; 42) of the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) are both in a range of 0.2 - 10. Hard coating (80) according to claim 1 or 2, wherein a bottom layer of the single composition layer (32; 34; 36) and the two types of nanolayer alternating layers (38, 40; 38, 42; 40, 42) which are stacked alternately on top of each other, is arranged directly on a surface of the substrate (12). A hard coating (30; 50; 60; 70; 90) according to claim 1 or 2, wherein the hard coating (30; 50; 60; 70; 90) comprises an interface layer (44; 52; 62; 94) that is adjacent to the substrate (12); the interface layer (44; 52; 62; 94) has a thickness in the range of 5–1000 nm and is provided by one of three types of layers, which are: a single-composition layer formed by one of the A composition, one of the B composition, and one of the C composition; a nanolayer alternating layer comprising two types of nanolayers, each formed by two of the A composition, one of the B composition, and one of the C composition, and which are alternately stacked such that each of the two types of nanolayers has a thickness of 0.5–500 nm. has;and a layer of metal nitride, metal carbonitride or metal carbide formed by at least one type of element selected from B, Al, Ti, Y, Zr, Hf, V, Nb, Ta, Cr and W; A hard coating (90) according to any one of claims 1-4, wherein the hard coating (90) comprises a surface layer (92) providing an outermost surface of the hard coating (90); the surface layer (92) is provided by a single-composition layer formed by one of the A composition, the B composition and the C composition, or by an alternating nanolayer layer comprising two types of nanolayers, each formed by two of the A composition, the B composition and the C composition, and which are alternately stacked such that each of the two types of nanolayers has a thickness in the range of 0.5-500 nm; and the surface layer (92) has a thickness of 5-1000 nm. Hard coating (30; 50; 60; 70; 80; 90) according to one of claims 1 - 5, wherein the coating hardness of the hard coating (30; 50; 60; 70; 80; 90) is in a range of Vickers hardness of 2700 - 3300 HV0.

025. Element (10) covered with a hard coating, comprising a substrate (12) whose surface is partially or completely covered with the hard coating (30; 50; 60; 70; 80; 90) according to one of claims 1 - 6. A hard-coated element (10) according to claim 7, wherein the hard-coated element (10) is an intermittently cutting tool (10) having cutting edges (18, 20) and being rotated about an axis such that it performs an intermittent cutting operation through the cutting edges (18, 20).

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