Hard coating and hard coating–coated tool

Abstract

Provided are: a hard coating that has a novel structure and has excellent wear resistance and deposition resistance with respect to a wide range of work materials; and a hard coating–coated tool.　A hard coating according to the present invention is formed by layering a first layer group 34 and an alternating nanolayer layer 36 that is a second layer group. The alternating nanolayer layer 36 is an alternating stack of at least three layers from among a nanolayer A layer 36a, a nanolayer B layer 36b, a nanolayer C layer 36c, and a nanolayer D layer 36d. The relationship between the hardness and the toughness of the coating can be optimized and the durability of the coating improved by varying the growth of particles at each layer by selecting the compositional ratio and additional elements of each layer to control crystal size and the relationship between crystal orientation (200) and orientation (111).

Description

Hard coatings and hard coating-coated tools

[0001] The present invention relates to hard coatings and hard coating-coated tools, and more particularly to hard coatings having excellent wear resistance and welding resistance.

[0002] Conventionally, attempts have been made to improve wear resistance and welding resistance by applying a hard coating to the surface of tools. For example, the tools described in Patent Documents 1 and 2, and Non-Patent Document 1 are examples of this. Patent Documents 1 and 1 disclose a drill coated with a nanolayer coating (a coating layer with a thickness in the nanometer range) having an AlCr-based / TiAlCrSi-based / TiSi-based composition. Patent Document 2 also describes applying a coating having a multilayer structure of AlCr-based, TiSi-based, and TiAl-based coatings.

[0003] Patent No. 5648078 Patent No. 6687390

[0004] Jie Liu et al., Properties and Performance of TiAlSiN and AlCrN Monolayer and Multilayer Coatings for Turning Ti-6Al-4V, Coatings 2023,13,1229

[0005] However, even with tools coated with such a hard film, for example, the technologies described in Patent Document 1 and Non-Patent Document 1 sometimes did not provide sufficient wear resistance when used for cutting carbon steel or cast iron. Furthermore, while the technology described in Patent Document 2 improved wear resistance, its poor resistance to welding meant that sufficient performance could not be obtained when drilling alloy steel or stainless steel.

[0006] The present invention was made against the above circumstances, and its objective is to provide a new hard coating and hard coating-coated tool with excellent wear resistance and welding resistance for a wide range of workpiece materials such as carbon steel, cast iron, alloy steel, stainless steel, and titanium alloy.

[0007] Based on the above circumstances, the inventors conducted various experiments and studies, and as a result, they found that the first layer has composition A, which is a nitride of AlCrα (α is one or more elements selected from the group consisting of B, C, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W), the first layer has composition B, which is a nitride of AlCrCβ (β is one or more elements selected from the group consisting of B, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W), and the first layer has composition C, which is a nitride of TiSiCγ (γ is one or more elements selected from the group consisting of B, Al, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W). We have found that abrasion resistance and welding resistance can be obtained by a hard coating having a structure in which a first layer group having at least one of the following layers, a first layer group having composition D which is a nitride of TiAlCδ (δ is one or more elements selected from the group consisting of B, Si, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W), and a second layer group which is an alternating nanolayer layer in which at least three of the following are laminated at least once: nanolayer A having composition A, nanolayer B having composition B, nanolayer C having composition C, and nanolayer D having composition D, are laminated alternately at least once. The present invention is based on this finding.

[0008] The first invention is a hard coating having a structure in which a first layer group and a second layer group are alternately laminated at least once on the surface of a substrate, (b) the first layer group has at least one layer from among a first layer having composition A, a first layer having composition B, a first layer having composition C, and a first layer having composition D, and (c) composition A is Al ａ Cr ｂ α ｃ (However, a, b, and c are atomic ratios of 0.30 ≤ a ≤ 0.85, 0.15 ≤ b ≤ 0.60, 0 ≤ c ≤ 0.1 and a + b + c = 1, and α is one or more elements selected from the group consisting of B, C, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is present in an amount of 10 at% or less.) The nitride is (d) the composition of B is Al ｄ Cr ｅ C ｆ β ｇ(where d, e, f, and g are each in an atomic ratio of 0.30 ≤ d ≤ 0.85, 0.14 ≤ e ≤ 0.60, 0 < f ≤ 0.10, 0 ≤ g ≤ 0.1, and d + e + f + g = 1, and β is one or more elements selected from the group consisting of B, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) nitride, (e) the C composition is Ti ｈ Si ｉ C ｊ γ ｋ (where h, i, j, and k are each in an atomic ratio of 0.45 ≤ h ≤ 0.85, 0.05 ≤ i ≤ 0.45, 0 ≤ j ≤ 0.10, 0 ≤ k ≤ 0.10, 0 ≤ j + k ≤ 0.10, and h + i + j + k = 1, and γ is one or more elements selected from the group consisting of B, Al, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) nitride, (f) the D composition is Ti ｌ Al ｍ C ｎ δ ｏ (where l, m, n, and o are each in an atomic ratio of 0.30 ≤ l ≤ 0.75, 0.15 ≤ m ≤ 0.70, 0 ≤ n ≤ 0.10, 0 ≤ o ≤ 0.10, 0 ≤ n + o ≤ 0.10, and l + m + n + o = 1, and δ is one or more elements selected from the group consisting of B, Si, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) nitride, (g) the second layer group is a nano-layer alternating layer in which at least three of nano-layer A, nano-layer B, nano-layer C, and nano-layer D are laminated, (h) the nano-layer A has the A composition and a film thickness of 1 to 200 nm, (i) the nano-layer B has the B composition and a film thickness of 1 to 200 nm, (j) the nano-layer C has the C composition and a film thickness of 1 to 200 nm, (k) the nano-layer D has the D composition and a film thickness of 1 to 200 nm, which is a characteristic hard film.

[0009] The second invention is characterized in that, in the hard coating of the first invention, when the diffraction line intensities of the highest peaks of the rock salt structure type (111) plane and (200) plane, measured by X-ray diffraction using the θ-2θ method with Kα rays of (l)Cu, are I(111) and I(200), respectively, these values ​​satisfy equation (1): 0.3 ≤ I(111) / I(200) ≤ 2.5 ... (1).

[0010] The third invention is characterized in that, in the hard coating of the second invention, in the X-ray diffraction, the diffraction line intensity peak appears in the range of 37° to 38° for the diffraction angle of the (111) plane diffraction line, and the diffraction line intensity peak appears in the range of 43.5° to 44.5° for the diffraction angle of the (200) plane diffraction line.

[0011] The fourth invention is characterized in that, in any one of the first to third inventions, the total thickness of the hard coating is 0.5 to 15 μm.

[0012] The fifth invention is a hard-coated tool in which part or all of the tool base material is covered with a hard coating according to any one of the first to fourth inventions.

[0013] According to the first invention, in the hard coating, at least three layers from among the nanolayer A, nanolayer B, nanolayer C, or nanolayer D are alternately deposited in the alternating nanolayer layer. When forming each nanolayer, strain occurs due to the influence of the surface energy of the underlying coating. Furthermore, the difference between the strain energy and the surface energy of the nanolayer affects the orientation, resulting in a different orientation ratio of (200) planes to (111) planes compared to when a single layer is formed. This effect further suppresses crystal growth, leading to refinement of the microstructure. As a result, it is possible to control the relationship between crystal size and crystal orientation (200) and orientation (111) in each layer, and to optimize the relationship between hardness and toughness in the coating properties, leading to further improvement in durability. In addition, by laminating the single layer group and the alternating nanolayer layer, cracking of the coating is suppressed, and the overall durability of the coating is improved. Furthermore, in general, in alternating nanolayer layers, as the crystal grains are refined, internal stress increases, resulting in an unstable coating. However, by sandwiching the aforementioned single layer, the internal stress is relieved, stabilizing the coating and resulting in a stable coating with high toughness and adhesion. In addition, since the aforementioned single layer and the alternating nanolayer layers are stacked alternately, and in the alternating nanolayer layers, each nanolayer is stacked in a predetermined order, the strain between layers is relieved, suppressing delamination. Moreover, as the crystals are refined, the hardness increases, resulting in a coating with gradually changing hardness within the film, improving toughness and wear resistance.

[0014] According to the second invention, in the first invention, when the diffraction line intensities of the highest peaks of the (111) plane and the (200) plane of the rock salt structure type, measured by X-ray diffraction using the θ-2θ method with Cu Kα rays, are denoted as I(111) and I(200), respectively, these values ​​satisfy the relationship 0.3 ≤ I(111) / I(200) ≤ 2.5. Therefore, in the NaCl structure, the balance between wear resistance and toughness can be controlled by optimizing the crystals of the (111) orientation and the (200) orientation, and excellent performance can be obtained. As a result, a hard coating with excellent wear resistance can be obtained, and flank wear and rake face wear can be suppressed during machining.

[0015] According to the third invention, in the second invention, the diffraction line intensity peak appears in the range of 37° to 38° for the diffraction angle of the (111) plane diffraction line in the X-ray diffraction, and the diffraction line intensity peak appears in the range of 43.5° to 44.5° for the diffraction angle of the (200) plane diffraction line. By making the lattice spacing of the crystal grains of each periodic laminate closer together, the misfit of the lattice spacing between layers is reduced, and the strain between layers is suppressed, resulting in a tough coating.

[0016] According to the fourth invention, in any one of the first to third inventions, the total thickness of the hard coating is 0.5 to 15 μm, so a coating with excellent lubricity and wear resistance can be obtained.

[0017] According to the fifth invention, since the hard-coated tool is partially or completely covered by the hard coating of the first to fourth inventions, it exhibits excellent wear resistance and oxidation resistance, and high wear resistance, toughness, lubricity, and welding resistance are obtained even when processing various materials such as carbon steel, cast iron alloy steel, and stainless steel. Furthermore, because the coating has relaxed internal stress, it is possible to achieve a longer tool life in both dry and wet machining.

[0018] This is a front view showing an example of a drill to which the present invention is applied. This is an enlarged bottom view of the drill in Figure 1, viewed from the tip side. This is a schematic diagram illustrating the coating structure of the hard coating applied to the drill in Figure 1. This is a schematic diagram illustrating another example of the coating structure of the hard coating applied to the drill in Figure 1. This is a schematic diagram illustrating yet another example of the coating structure of the hard coating applied to the drill in Figure 1. This is a schematic diagram illustrating yet another example of the coating structure of the hard coating applied to the drill in Figure 1. This is a schematic diagram illustrating an arc ion plating apparatus, which is an example of a physical deposition apparatus for forming the hard coatings of Figures 3 to 6 on a tool base material. This is a diagram showing the types and content ratios of constituent elements of composition A that make up the hard coatings of test samples 01 to 06 and development products 01 to 22 used in cutting tests. This is a diagram showing the types and content ratios of constituent elements of composition B that make up the hard coatings of test samples 01 to 06 and development products 01 to 22. This figure shows the types and content ratios of constituent elements of the C composition that makes up the hard coating of test samples 01 to 06 and development products 01 to 22. This figure shows the types and content ratios of constituent elements of the D composition that makes up the hard coating of test samples 01 to 06 and development products 01 to 22. This figure explains the total film thickness, film structure, and film hardness of the hard coating of test samples 01 to 06 and development products 01 to 22, based on the results of X-ray diffraction using the θ-2θ method with Cu Kα rays. This figure explains in detail the results of X-ray diffraction for each of test samples 01, 01, 02, and 03. This figure shows the number of machinable holes and the judgment results measured by drilling tests for the hard coatings of test samples 01 to 06 and development products 01 to 22. This figure shows in detail the results of the drilling test in Figure 14 for each of test samples 01, 01, and 02. Figure 15 shows the changes in the tip's second surface during the drilling test process, as captured by a scanning electron microscope (SEM). The figure also shows the results of the toughness tests performed on test sample 01 and development sample 01, as captured by a scanning electron microscope (SEM).

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings illustrate the essential parts related to the invention, and the dimensions and shapes are not necessarily depicted accurately.

[0020] Figures 1 and 2 show a drill 10, which is an example of a part coated with a hard carbon coating according to one embodiment of the present invention. Figure 1 is a front view seen from a direction perpendicular to the axis O, and Figure 2 is an enlarged bottom view seen from the tip side where the cutting edge 12 is provided. The drill 10 is made of a tool base material 12 which is made of cemented carbide or high-speed tool steel (HSS). This drill 10 is a two-blade twist drill, with a shank 14 and a body 16 integrally provided in the axial direction, and a pair of grooves 18 twisted clockwise around the axis O are formed in the body 16. A pair of cutting edges 12 are provided at the tip of the body 16 corresponding to the grooves 18, and when viewed from the shank 14 side, the cutting edges 12 cut a hole, and chips are discharged through the grooves 18 to the shank 14 side. In Figure 1, the shaded portion of the blade 16 indicates the portion coated (adhered) with the hard carbon coating 30. It is also possible to cover the entire drill 10, including the shank 14, with the hard coating 30.

[0021] The hard coating 30 has a multilayer structure in which the second layer group 36 and the first layer group 34 are stacked in at least one period. In the example in Figure 3, the hard coating 30 is stacked in multiple sets (number of times) of alternating nanolayer layers 36, which are the second layer group 36, in alternating order from the side closest to the tool base material 12, with the first layer 34a having composition A as the first layer group 34 (hereinafter referred to as layer A 34a) and the second layer group 36. The alternating nanolayer layers 36 consist of four layers, nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d, which are stacked in this order for a predetermined number of times. Thus, in the example in Figure 3, the first layer group 34 and the second layer group 36 are repeatedly stacked on the surface of the tool base material 12 in that order. Furthermore, in the second layer group 36, four layers, nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d, are repeatedly laminated in this order a predetermined number of times from the tool base material 12 side. The total thickness T of the hard coating 30 is preferably appropriately determined within the range of 0.5 to 15 μm, but may be outside this range.

[0022] The first layer 34 is composed of at least one of the following layers: a first layer 34a composed of composition A, a first layer 34b composed of composition B, a first layer 34c composed of composition C, and a first layer 34d composed of composition D. In other words, the first layer group 34 may be composed of any one of the following layers: first layer 34a composed of composition A, first layer 34b composed of composition B, first layer 34c composed of composition C, or first layer 34d composed of composition D; any two of the following layers may be stacked together: first layer 34a composed of composition A, first layer 34b composed of composition B, first layer 34c composed of composition C, and first layer 34d composed of composition D; any three of the following layers may be stacked together: first layer 34a composed of composition A, first layer 34b composed of composition B, first layer 34c composed of composition C, and first layer 34d composed of composition D; or all four layers may be stacked together: first layer 34a composed of composition A, first layer 34b composed of composition B, first layer 34c composed of composition C, and first layer 34d composed of composition D. Furthermore, when the first layer group 34 is composed of multiple first layers, the stacking order can be arbitrarily selected. Furthermore, if the first layer group 34 is established multiple times, the same configuration and order are used.

[0023] The second layer group 36 is constructed by laminating at least three types of nanolayers from among nanolayer A layer 36a composed of composition A, nanolayer 36b composed of composition B, nanolayer C layer 36c composed of composition C, and nanolayer D layer 36d composed of composition D. That is, the second layer group 36 may be constructed by laminating any three types of nanolayers from among nanolayer A layer 36a composed of composition A, nanolayer 36b composed of composition B, nanolayer C layer 36c composed of composition C, or nanolayer D layer 36d composed of composition D, or it may be constructed by laminating four layers: nanolayer A layer 36a composed of composition A, nanolayer 36b composed of composition B, nanolayer C layer 36c composed of composition C, and nanolayer D layer 36d composed of composition D. Furthermore, the order in which the multiple nanolayers in the second layer group 36 are laminated can be arbitrarily selected. Also, if the second layer group 36 is provided multiple times, the same configuration and order are used. Furthermore, the film thicknesses of the nanolayer A layer 36a, composed of composition A, the nanolayer B layer 36b, composed of composition C, the nanolayer C layer 36c, and composed of composition D layer 36d are preferably selected from within the range of 1 to 200 nm, but may exceed this range.

[0024] The above composition A is Al ａ Cr ｂ α ｃ (However, a, b, and c are nitrides with atomic ratios of 0.30 ≤ a ≤ 0.85, 0.15 ≤ b ≤ 0.60, 0 ≤ c ≤ 0.1, and a + b + c = 1.) α is one or more elements selected from the group consisting of B, C, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is present in an atomic ratio of 10 at% or less. Figure 8 shows specific examples of the content (at%) of each element in composition A, where a blank space means content (at%) = 0. In Figure 8, the product labeled "development product" meets the requirements of composition A, while the product labeled "test product" does not meet the requirements of composition A.

[0025] The first layer 34a or nanolayer A layer 36a, which is composed of such A composition, contains, as α, one or more elements selected from the group consisting of B, C, Si, Ti, V, Y, Zr, Nb, Mo, Ta, and W in a proportion of 10 at% or less in the AlCr nitride. The nitride having the above A composition becomes a coating with excellent wear resistance and lubricity. In particular, to meet the requirements for high-speed machining and to improve high-temperature stability, by including one or more elements selected from α in the AlCr nitride in a proportion of 10 at% or less, solid solution strengthening occurs in the A layer, thereby increasing the hardness of the A layer. Furthermore, by including element α, the coating structure is maintained even when high temperatures are reached due to heat generation during cutting. In addition, oxides are formed on the surface of the coating, resulting in a good balance between wear resistance and welding resistance, thus extending the life of tools having a coating including the first layer 34a or nanolayer A layer 36a composed of such A composition. Note that the same composition A is used for the first layer group 34 and the second layer group 36.

[0026] The aforementioned composition B is Al ｄ Cr ｅ C ｆ β ｇ (However, d, e, f, and g are nitrides with atomic ratios of 0.30 ≤ d ≤ 0.85, 0.14 ≤ e ≤ 0.60, 0 < f ≤ 0.10, 0 ≤ g ≤ 0.1, and d + e + f + g = 1.) β is one or more elements selected from the group consisting of B, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is present in an atomic ratio of 10% or less. Figure 9 shows specific examples of the content (at%) of each element in the B composition, where a blank space means the content (at%) = 0. The product labeled "Development Product" meets the requirements of the B composition, while the product labeled "Test Product" does not meet the requirements of the B composition.

[0027] The first layer 34b or nanolayer B layer 36b, composed of composition B, contains, as β, one or more elements selected from the group consisting of B, Si, V, Y, Nb, Mo, Hf, Ta, and W in a proportion of 10 at% or less within the AlCrC nitride. By containing carbides in the nitride of composition B, ultra-fine granular crystals are achieved, significantly improving wear resistance and lubricity. As a dense structure containing carbon is formed, improved hardness and low friction are obtained, enabling high-speed machining and extended tool life in machining difficult-to-machine materials with a coating containing the first layer 34b or nanolayer B layer 36b composed of composition B. In particular, when toughness of the coating is required for machining high-strength workpieces, including one or more elements selected from β in a proportion of 10 at% or less allows for finer crystalline particles of the coating, further improving wear resistance.

[0028] The above C composition is Ti ｈ Si ｉ C ｊ γ ｋ (However, h, i, and j are nitrides with atomic ratios of 0.45 ≤ h ≤ 0.85, 0.05 ≤ i ≤ 0.45, 0 ≤ j ≤ 0.10, 0 ≤ k ≤ 0.10, 0 ≤ j + k ≤ 0.10, and h + i + j + k = 1.) γ is one or more elements selected from the group consisting of B, Al, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is present in an atomic ratio of 10 at% or less. Figure 10 shows specific examples of the content (at%) of each element in the C composition, with blank spaces indicating a content (at%) = 0. In Figure 10, those labeled "Development Product" meet the requirements for the C composition, while those labeled "Test Product" do not meet the requirements for the C composition.

[0029] The first layer 34c or nanolayer C layer 36c, composed of C composition, has a composition containing TiSiC nitride, which exists in the form of a compound called TiSi, has low bonding affinity to oxygen, and Si is covalently bonded. Therefore, it has high hardness, little decrease in mechanical strength even above 1000°C, excellent wear resistance, and good sliding properties, resulting in a coating with high hardness and excellent oxidation resistance, improving wear resistance. Si oxide film SiO formed on the surface of the C layer２ In order to suppress the progress of oxidation inside, oxidation resistance can be obtained. Particularly when there are further requirements for wear resistance, by including 10 at% or less of one or more elements selected from γ in the nitride of TiSi constituting the C composition, the crystal grains of the coating are refined in the C layer, the hardness is improved, and the wear resistance is also improved. By including these elements, an improvement in high hardness, toughness, and lubricity can be obtained, and since it has excellent wear resistance and oxidation resistance, a surface-coated cutting tool capable of achieving a further longer life in high-speed machining and dry machining of tools can be obtained.

[0030] The D composition is Ti ｌ Al ｍ C ｎ δ ｏ (where l, m, n, o are atomic ratios of 0.30 ≤ l ≤ 0.75, 0.15 ≤ m ≤ 0.70, 0 ≤ n ≤ 0.10, 0 ≤ o ≤ 0.10 and 0 ≤ n + o ≤ 0.10 and l + m + n + o = 1). δ is one or more elements selected from the group consisting of B, Si, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is included at 10 at% or less in atomic ratio. FIG. 11 is a diagram showing specific examples of the content (at%) of each element of the D composition, and the blank spaces indicate that the content (at%) = 0. In FIG. 11, those described as development products satisfy the requirements of the D composition, and those described as test products do not satisfy the requirements of the D composition.

[0031] The first layer 34d or the nanolayer D layer 36d composed of such a D composition contains, as an element δ in the nitride of TiAlC, one or more selected from the group consisting of B, Si, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W at an atomic ratio of 10 at% or less. The nitride composed of the D composition is a coating excellent in toughness and adhesion. Particularly when it is desired to further strengthen the strength of the coating, solid solution strengthening occurs in the layer by containing one or more selected from the above δ at an atomic ratio of 10 at% or less, and the hardness of the TiAl nitride can be increased. In particular, when the ratio (atomic ratio) o of the element δ to the total amount with Ti and Al is 0 ≤ o ≤ 0.1, solid solution strengthening occurs in the nitride of TiAl, and the hardness can be increased. Further, when V, Y, Nb, Mo, W, etc. are particularly selected as the element δ, a self-lubricating effect is exhibited by the oxide due to the heat generation during cutting, and further extension of the tool life can be expected.

[0032] In such a hard coating 30, since the first layer group 34 and the second layer group 36 are alternately laminated at least once each, the thickness, the number of lamination times, and the composition of each coating layer constituting the first layer group 34 and the second layer group 36 can be accurately controlled. Further, in the second layer group 36, at least three of the nanolayer A layer 36a, the nanolayer B layer 36b, the nanolayer C layer 36c, or the nanolayer D layer 36d are alternately deposited, so that the coating is formed under the influence of the surface energy and lattice spacing of the underlying coating during the formation of each nanolayer, resulting in distortion and affecting the crystal orientation and grain growth. Therefore, by selecting the composition ratio and additive elements of each layer and controlling the relationship between the crystal size and the crystal orientations (200) and (111) in each layer, as the characteristics of the coating, the relationship between hardness and toughness can be optimized, and further improvement in durability can be obtained. When such a hard coating 30 is applied to a carbide tool, excellent wear resistance is exhibited during cutting.

[0033] Furthermore, in the first layer 34a having composition A, the first layer 34b having composition B, the first layer 34c having composition C, and the first layer 34d having composition D in the first layer group 34, and in the nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d in the second layer group 36, the crystal grains are refined and each layer is stacked, so that film fracture due to cracks is suppressed and the abrasion resistance of the entire film is improved. In addition, when the crystal grains are refined, the internal stress increases and the film becomes unstable, but the internal stress is relieved by the interposition of the aforementioned layer group 34, improving the stability of the hard film 30 and providing excellent durability.

[0034] Furthermore, when a first layer 34a having composition A, which is mainly composed of AlCr, a first layer 34b having composition B, which is mainly composed of AlCr, and a second layer group 36 are laminated, the first layer 34b having composition B contains carbon and therefore has a finer crystal structure than the first layer 34a having composition A, and the second layer group 36 has an even finer crystal structure than the first layer group 34, when laminated in this order, the film structure becomes one in which the crystals gradually become finer, and delamination is suppressed. In addition, as the crystals become finer, the hardness increases, resulting in a film in which the hardness gradually changes within the film, and toughness is improved.

[0035] Figures 4 to 6 illustrate another embodiment of this model. The example in Figure 4 differs from the example in Figure 3 in that the first layer group 34 of the hard coating 50 includes a first layer 34b composed of composition B and a first layer 34c composed of composition C, in that order, from the side closest to the tool base material 12, and the second layer group 36 is constructed by laminating nanolayer A layer 36a, nanolayer B layer 36b, and nanolayer C layer 36c in that order a predetermined number of times, from the side closest to the tool base material 12. Note that all of the second layer group 36 in the hard coating 50, namely nanolayer A layer 36a, nanolayer B layer 36b, and nanolayer C layer 36c, are provided in that order.

[0036] In the hard coating 50 shown in Figure 4, the total thickness of the hard coating 50 is preferably 0.5 to 15 μm, but it may be in other ranges.

[0037] In the example in Figure 5, the hard coating 60 differs from the examples in Figures 3 and 4 in that the first layer group 34 and the second layer group 36 are repeatedly provided in the order of first layer group 34 and second layer group 36 from the side closer to the tool base material 12, the first layer group 34 is composed of a first layer 34a made of composition A, a first layer 34d made of composition D, and a first layer 34b made of composition B in that order from the side closer to the tool base material 12, and the second layer group 36 is composed of nanolayer C layer 36c, nanolayer B layer 36b, and nanolayer D layer 36d stacked a predetermined number of times in that order from the side closer to the tool base material 12. Note that the composition of all second layer groups 36 in the hard coating 60 is common.

[0038] In the example in Figure 6, the first layer group 34 of the hard coating 70 differs from the example in Figure 3 in that it is composed of a first layer 34a made of composition A, a first layer 34b made of composition B, a first layer 34c made of composition C, and a first layer 34d made of composition D, which are laminated together. Also, the second layer group 36 differs from the examples in Figures 3 to 5 in that it is composed of nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d, which are laminated together in that order a predetermined number of times from the side closest to the tool base material 12. Note that the composition of all second layer groups 36 in the hard coating 70 is common. Furthermore, the interface layer can be changed to a general coating that can enhance adhesion, including coatings of other compositions (composition A, composition B, and composition C), depending on the tool base material and shape.

[0039] Figure 7 is a schematic diagram illustrating the apparatus 100 used when coating a tool base material 12 with the hard coatings 30, 50, 60, 70, or the hard coatings of the developed products described in Figures 8 to 13 (hereinafter, unless otherwise specified, simply referred to as hard coating 30, etc.). The apparatus 100 coats the surface of the tool base material 12 with the hard coatings 30, etc. by arc ion plating, a type of PVD method. By switching the evaporation source (target) and reaction gas, multiple types of layers with different compositions can be continuously formed with predetermined film thicknesses. For example, in the case of the hard coating 30 shown in Figure 3, a second layer group 36 is formed on the surface of the tool base material 12 by repeatedly laminating nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d a predetermined number of times, and a first layer 34a composed of composition A is provided as the first layer group 34. The operation of forming the second layer group 36 and the first layer group 34 is repeated a predetermined number of times, or until a predetermined thickness is achieved. Figure 7 corresponds to a plan view of the apparatus 100 from above.

[0040] The apparatus 100 includes a rotary table 154 that holds multiple workpieces, i.e., tool base materials 12 to be coated with a hard film 30, etc., and is driven to rotate around a substantially vertical rotation center S; a bias power supply 156 that applies a negative bias voltage to the tool base materials 12; a chamber 158 that serves as a processing container housing the tool base materials 12, etc.; a supply device 160 that supplies a predetermined reaction gas into the chamber 158; an exhaust device 162 that discharges the gas in the chamber 158 using a vacuum pump or the like to reduce the pressure; a first arc power supply 164; a second arc power supply 166; a third arc power supply 168; a fourth arc power supply 170, etc. The rotary table 154 has a disc shape centered on the rotation center S, and multiple tool base materials 12 are arranged on the outer circumference of the rotary table 154 in a position substantially parallel to the rotation center S. The tool base materials 12 can also be rotated on their own axis while revolving around the rotation center S by the rotary table 154. The supply device 160 supplies nitrogen gas into the chamber 158 when coating nitrides such as layers 34a, 36a composed of composition A, layers 34b, 36b composed of composition B, layers 34c, 36c composed of composition C, and layers 34d, 36d composed of composition D. The chamber 158 is kept under vacuum, for example, 2 to 10 Pa, by the exhaust device 162, and heated to a deposition processing temperature of, for example, 300 to 600°C by the heater 185 or the like.

[0041] The first arc power supply 164, the second arc power supply 166, the third arc power supply 168, and the fourth arc power supply 170 each use the first evaporation source 172, the second evaporation source 176, the third evaporation source 180, and the fourth evaporation source 184, all made of deposition material, as cathodes. By selectively applying a predetermined arc current between these cathodes and the anodes 174, 178, 182, and 186, an arc discharge is caused, thereby selectively evaporating the evaporation material from these first evaporation sources 172, 176, 180, and 184. The evaporated evaporation material becomes positive ions and is deposited onto the tool base material 12 to which a negative bias voltage is applied. That is, the evaporation sources 172, 176, 180, and 184 are each composed of one of the alloys of composition A, composition B, composition C, and composition D. In addition to these compositions A, B, C, and D, if a layer is to be composed of yet another composition, this can be achieved by using the alloy of the other composition as a fifth evaporation source, and further providing a corresponding arc power supply and anode. Furthermore, for example, when producing the hard coating 50 shown in Figure 4, the hard coating 50 does not include layers 34a and 36a composed of composition A, so the configuration does not include an anode, arc power supply, or evaporation source related to composition A.

[0042] Then, by appropriately switching the arc power supplies 164, 166, 168, and 170 to sequentially coat layers of a predetermined composition, the hard coating 30 or the like with a predetermined coating structure can be obtained. The thickness of each layer can be adjusted by the rotation speed of the rotary table 154, the energizing time of the arc power supplies 164, 166, 168, and 170, etc. A mixed layer of two different compositions may be formed at the boundary between multiple layers of different compositions.

[0043] Furthermore, although not shown in the illustrations, the hard coating can be constructed in yet another manner. For example, in the hard coating 30, the first layer group 34 used was a first layer 34a composed of composition A, but instead, it may be composed of other compositions, such as a first layer 34b composed of composition B, or a first layer 34 having multiple different compositions may be used. In the hard coating 50, the first layer group 34 was constructed by laminating a first layer 34b composed of composition B and a first layer 34c composed of composition C, but the first layer 34b composed of composition B and the first layer 34c composed of composition C may be used individually. That is, in the hard coating 30, etc., the first layer group 34 only needs to have at least one layer from among the first layer 34a having composition A, the first layer 34b having composition B, the first layer 34c having composition C, and the first layer 34d having composition D. Furthermore, the second layer group 36 may have any configuration that includes three or all four of the nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, and nanolayer D layer 36d.

[0044] Furthermore, in the hard coatings 30, 50, 60, and 70, the first layer group 34 and the second layer group 36 are stacked alternately in units of one cycle, but it is arbitrary whether the top layer of the hard coatings 30, 50, 60, and 70 is the first layer group 34 or the second layer group 36. In other words, in the hard coatings 30, 50, 60, 70, and 80, when stacking begins with the first layer group 34 on the base material 12, the surface may be configured to show either the second layer group 36 or the first layer group 34. The same applies when stacking begins with the second orthotic device 36.

[0045] Figure 12 is a table showing the ratio of the diffraction line intensities of the peaks (highest values) of the (111) plane and the (200) plane of the rock salt structure type, measured when X-ray diffraction is performed using the θ-2θ method with Cu Kα rays on the hard coating 30 etc. of development products 01 to 22 and test products 01 to 06. More specifically, it is a table showing the value of I(111) / I(200) when the diffraction line intensity of the peak of the (111) plane is I(111) and the diffraction line intensity of the peak of the (200) plane is I(200). This figure specifically explains the coating structure. As shown in Figure 12, all development products 01 to 22 satisfy the range 0.3 ≤ I(111) / I(200) ≤ 2.5, while test products 02, 03, and 06 do not satisfy this range.

[0046] Furthermore, Figure 12 is a table showing the values ​​of angle 2θ 2θ(111) at which the diffraction line intensity peak I(111) of the (111) plane was produced, and the values ​​of angle 2θ 2θ(200) at which the diffraction line intensity peak I(200) of the (200) plane was produced, when X-ray diffraction was performed using the θ-2θ method with Cu Kα rays on the hard coating 30 etc. of development products 01 to 22 and test products 01 to 06.As shown in Figure 12, all development products 01 to 22 satisfy both the ranges of 37° ≤ 2θ(111) ≤ 38° and 43.5° ≤ 2θ(200) ≤ 44.5°, while test products 02 and 03 do not satisfy the above range for 2θ(111), and test product 05 does not satisfy the above range for 2θ(200).

[0047] Figure 13 shows the XRD measurement data obtained when X-ray diffraction was performed using the θ-2θ method with Cu Kα rays for test product 01, development products 01, 02, and 03, which are among the development products 01 to 22 and test products 01 to 06 shown in Figures 8 to 12. Figure 13(a) shows the range 35° ≤ 2θ ≤ 65°, and Figure 14(b) is a magnified view of the area around 35° ≤ 2θ ≤ 45° in Figure 13(a). As shown in Figure 13, it can be seen that, particularly for the developed product, the angle 2θ value 2θ(111) that produced the diffraction line intensity peak I(111) of the (111) plane and the angle 2θ value 2θ(200) that produced the diffraction line intensity peak I(200) of the (200) plane satisfy the meshed range in Figure 13(b), namely, the range 37° ≤ 2θ(111) ≤ 38° and 43.5° ≤ 2θ(200) ≤ 44.5°, respectively.

[0048] Returning to Figure 12, it shows the total film thickness of the hard coating 30, etc., for development products 01 to 22 and test products 01 to 06. For development products 01 to 22, the total film thickness is within the preferred range of 0.5 to 15 μm, while test product 05 falls below the lower limit of that range, and test product 06 exceeds the upper limit.

[0049] Next, we will explain the results of performance tests of hard coatings on drills similar to the drill 10, which has a diameter of 2 mm and two blades, with a tool base material 12 made of ultrafine grain cemented carbide. Test samples 01 to 06 and development samples 01 to 22 were prepared, each fitted with a hard coating with the coating structure shown in Figures 8 to 12. Figure 13 shows the test results, where the coating hardness is the value of the HV value (Vickers hardness) of the hard coating measured under conditions indicated by the hardness symbol HV 0.025, according to the Vickers hardness test method (JIS G0202, Z2244). Development samples 01 to 22, which correspond to the embodiments of the present invention, generally have a coating hardness of about 2600 to 2900, and excellent wear resistance and impact resistance (strength against cracking and peeling due to intermittent cutting) can be expected, while test samples 01 to 06 have a coating hardness of 2600 or less. Furthermore, the number of machinable holes was investigated when drilling was performed using test samples 01 to 06 and development samples 01 to 22 according to the following cutting test conditions, and the coating performance (durability) was determined. Specifically, the wear width of the second-to-last surface at the tip was measured every 100 holes drilled consecutively, and the number of machinable holes until the wear width reached 0.15 mm was determined. Figure 14 is a table showing these results. In Figure 14, in addition to the number of machinable holes, the judgment result was that if the number of machinable holes until the wear width reached 0.15 mm was 600 or more, it was judged as a pass (○), and if it was less than that, it was judged as a fail (×), and the results are shown. The flank surface wear width was observed and measured using a measuring microscope (MM-400 / LM) manufactured by Nikon Corporation. 《Drilling Test Conditions》 ・Workpiece material: S50C ・Cutting fluid: FGE360 manufactured by Yushiro Chemical Industry Co., Ltd. (diluted 20 times) ・Cutting speed: 50 m / min ・Feed rate: 0.05 mm / rev ・Machining depth: 16 mm stop ・Step amount: 0.6 mm As is clear from Figure 14, all of the inventive products, development products 01 to 22, were capable of drilling 600 or more holes and demonstrated excellent durability. In contrast, the comparative test products 01 to 06 all had fewer than 600 machined holes.

[0050] Figure 15 shows the wear width of the second tip surface measured every 100 drilling cycles for each of the drills with hard coatings applied to test samples 01 to 06 and development samples 01 to 22 shown in Figures 8 to 12, specifically for test sample 01, development samples 01 and 02. Compared to test sample 01, development samples 01 and 02 show a slower rate of increase in wear width relative to the number of drilled holes, indicating improved durability and lifespan.

[0051] Figure 16 shows scanning electron microscope (SEM) images of the tip of the drill 10 in this embodiment. Of these, Figure 16(a) shows the entire tip of the drill 10 before processing. Figures 16(b), 16(c), and 16(d) are magnified views of the area around the second surface of the tip at the end of drilling 100 holes for test sample 01, development sample 01, and development sample 02, respectively. In Figure 16(b), the length L corresponding to the wear width of the second surface of the tip is shown. Furthermore, Figures 16(e), 16(f), and 16(g) are magnified views of the area around the second surface of the tip at the end of drilling 100 holes for test sample 01, development sample 01, and development sample 02, respectively. As shown in Figures 16(b) to 16(g), at the completion of drilling 100 holes and 200 holes, the wear width of the second tip surface of test product 01 is greater than that of development product 01 and development product 02. In other words, it can be seen that the drills of development product 01 and development product 02, which are embodiments of the present invention, have improved wear resistance and, consequently, durability compared to test product 01, which is a comparative example.

[0052] Next, the results of experiments conducted by the inventors to confirm the toughness of the hard coating of the present invention are shown. In the toughness confirmation test, a Rockwell hardness test was performed on cemented carbide tool materials coated with the hard coating 30 of test sample 01 and development product 01 shown in Figures 8 to 12 above, under the conditions of scale C as defined in JIS Z 2245, and the indentations formed on the surface of the samples were observed with a scanning electron microscope. Figure 17 shows the results of this toughness confirmation test. Of these, Figures 17(a) to (c) are images of cemented carbide tool materials coated with development product 01 in the embodiment of the present application, and Figures 17(d) to (f) are images of cemented carbide tool materials coated with test sample 01. Also, Figures 17(a) and (d) show the entire contact area between the diamond indenter and the cemented carbide tool material, and Figures 17(b) and (e) are enlarged views of the portions corresponding to the ends of the contact area in Figures 17(a) and (d), respectively. Figures 17(c) and (f) are enlarged views of the areas indicated by rectangles in Figures 17(b) and (e), respectively.

[0053] As shown in Figures 17(a) to (c) and (d) to (f), respectively, an annular recess is observed at the contact point between the diamond indenter and the carbide tool material, and a crack extends radially outward from this annular recess. On the other hand, as can be seen particularly in Figures 17(e) and (d), in the coating of test sample 01, there are areas where the coating has peeled off at the outer edge of the annular recess, exposing the carbide tool material. In contrast, in the coating of development sample 01 corresponding to the embodiment of the present application, no peeling is observed in the images of Figures 17(a) to (c).

[0054] In the hard coatings 30, 50, 60, and 70 of this embodiment, at least three layers from among the nanolayer A layer 36a, nanolayer B layer 36b, nanolayer C layer 36c, or nanolayer D layer 36d are alternately deposited in the nanolayer alternating layer 36. Therefore, when each nanolayer is formed, the coating is affected by the surface energy and lattice spacing of the underlying coating, causing strain and affecting the crystal orientation and grain growth. Thus, by selecting the composition ratio and additive elements of each layer, the growth of particles in each layer changes, and by controlling the relationship between crystal size and crystal orientation (200) and orientation (111), the relationship between the hardness and toughness of the coating can be optimized, resulting in further improvement in durability. Furthermore, by laminating the single layer group 34 and the nanolayer alternating layer 36, crack-induced coating failure is suppressed, and the overall wear resistance of the coatings 30, 50, 60, and 70 is improved. Furthermore, in the alternating nanolayer layers 36, as the crystal grains are refined, internal stress increases, resulting in an unstable coating. However, by sandwiching the single layer group 34, the internal stress is relieved, improving the stability of the coating and providing excellent durability. In addition, since the single layer group 34 and the alternating nanolayer layers 36 are stacked alternately, and in the alternating nanolayer layers 36, each of the nanolayer layers 36a, 36b, 36c, and 36d is stacked in a predetermined order, a coating structure with refined crystals is achieved, suppressing delamination between layers. Moreover, as the crystals are refined, the hardness increases, resulting in a coating with gradually changing hardness within the coating, improving toughness.

[0055] Furthermore, with the hard coatings 30, 50, 60, and 70 of this embodiment, when the diffraction line intensities of the highest peaks of the (111) plane and (200) plane of the rock salt structure type, measured by X-ray diffraction using the θ-2θ method with Cu Kα rays, are denoted as I(111) and I(200), respectively, these values ​​satisfy the relationship 0.3 ≤ I(111) / I(200) ≤ 2.5. As a result, hard coatings 30, 50, 60, and 70 with excellent wear resistance are obtained, and flank wear and rake face wear can be suppressed during machining.

[0056] Furthermore, according to the hard coatings 30, 50, 60, and 70 of this embodiment, the diffraction line intensity peak appears in the range of 37° to 38° for the diffraction angle of the (111) plane diffraction line in the X-ray diffraction, and the diffraction line intensity peak appears in the range of 43.5° to 44.5° for the diffraction angle of the (200) plane diffraction line. Therefore, by adjusting the orientation effect, or in other words, the orientation of the refined crystal grains, the hardness, toughness, lubricity, and wear resistance of the hard coating are improved.

[0057] Furthermore, according to the hard coatings 30, 50, 60, and 70 of this embodiment, the total film thickness of the hard coatings 30, 50, 60, and 70 is 0.5 to 15 μm, so a coating with excellent lubricity and wear resistance can be obtained.

[0058] Furthermore, the drill 10, which is a hard-coated tool provided with the hard coatings 30, 50, 60, and 70 of this embodiment, is partially or completely covered by the hard coatings 30, 50, 60, and 70, resulting in excellent wear resistance and oxidation resistance. High wear resistance, toughness, lubricity, and anti-welding properties can be obtained even when processing various materials such as carbon steel, cast iron alloy steel, and stainless steel. In addition, extended tool life can be achieved in both dry and wet machining.

[0059] Although embodiments of the present invention have been described in detail above with reference to the drawings, these are merely examples, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[0060] For example, in the above-described embodiment, the tool coated with the hard coating 30 was a drill 10, but it is not limited to this. For example, it is suitably applied to hard coatings provided on the surface of various processing tools, such as rotary cutting tools like milling cutters, taps, and end mills, as well as non-rotary cutting tools like cutting tools, or non-cutting tools like rake taps, rolling tools, and press dies. It can also be applied to hard coatings provided on the surface of components other than processing tools that require wear resistance, lubricity, oxidation resistance, etc., such as bearing members and surface protective films for semiconductor devices. It can also be applied to cutting edge tips used attached to various processing tools. As the tool base material for hard-coated tools, cemented carbide, high-speed tool steel, cermet, ceramics, polycrystalline diamond (PCD), single-crystal diamond, and CBN are suitably used, but other tool materials can also be used. As the means for forming the hard coating, PVD methods (physical vapor deposition) such as arc ion plating, sputtering, and PLD (Pulse Laser Deposition) are suitably used.

[0061] The hard coating 30 of the present invention is suitably used in cutting tools for machining other workpiece materials such as carbon steel, stainless steel, cast iron, and alloy steel, but is also suitably used in cutting tools for machining titanium alloys, for example. It can also be used in cutting tools that perform machining under harsh machining conditions such as high-speed machining and dry machining.

[0062] Furthermore, in the above-described embodiment, the hard coating 30, etc., was directly applied to the surface of the tool base material 12, but the embodiment is not limited to this configuration. For example, an interface layer may be provided on the tool base material 12, and the hard coating 30, etc., of this embodiment may be provided on the interface layer. This interface layer may have any one of the compositions A to D described above, or any other composition. Also, when an interface layer is provided, the total film thickness of the hard coating 30, etc., may be defined as including the thickness of the interface layer.

[0063] Furthermore, in addition to the hard coating 30 in the above-described embodiment, it is also possible to have a configuration in which a surface layer is provided on top of it. In this embodiment, the surface layer, rather than the hard coating 30, is exposed on the surface of the tool 10. The surface layer may have any one of the compositions A to D described above, or any other composition. Also, when a surface layer is provided, the total film thickness of the hard coating 30, etc., may be defined as including the thickness of the surface layer.

[0064] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[0065] 10: End mill 12: Tool base material 30, 50, 60, 70: Hard coating 34: First layer group 34a: First layer composed of composition A 34b: First layer composed of composition B 34c: First layer composed of composition C 34d: First layer composed of composition D 36: Second layer group 36a: Second layer composed of composition A 36b: Second layer composed of composition B 36c: Second layer composed of composition C 36d: Second layer composed of composition C

Claims

1. A hard film having a structure in which a first layer group and a second layer group are alternately laminated on the surface of a substrate at least once, wherein the first layer group has at least one layer selected from a first layer having a composition A, a first layer having a composition B, a first layer having a composition C, and a first layer having a composition D, wherein the composition A is a nitride of Al ａ Cr ｂ α ｃ (where a, b, c are atomic ratios of 0.30 ≤ a ≤ 0.85, 0.15 ≤ b ≤ 0.60, 0 ≤ c ≤ 0.1 and a + b + c = 1, and α is one or more elements selected from the group consisting of B, C, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) wherein the composition B is a nitride of Al ｄ Cr ｅ C ｆ β ｇ (where d, e, f, g are atomic ratios of 0.30 ≤ d ≤ 0.85, 0.14 ≤ e ≤ 0.60, 0 < f ≤ 0.10, 0 ≤ g ≤ 0.1 and d + e + f + g = 1, and β is one or more elements selected from the group consisting of B, Si, Ti, V, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) wherein the composition C is a nitride of Ti ｈ Si ｉ C ｊ γ ｋ (where h, i, j are atomic ratios of 0.45 ≤ h ≤ 0.85, 0.05 ≤ i ≤ 0.45, 0 ≤ j ≤ 0.10, 0 ≤ k ≤ 0.10, 0 ≤ j + k ≤ 0.10, and h + i + j + k = 1, and γ is one or more elements selected from the group consisting of B, Al, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is contained at 10 at% or less.) wherein the composition D is a nitride of Ti ｌ Al ｍ C ｎ δ ｏ (where l, m, n, and o are nitrides of the following atomic ratios: 0.30 ≤ l ≤ 0.75, 0.15 ≤ m ≤ 0.70, 0 ≤ n ≤ 0.10, 0 ≤ o ≤ 0.10, and 0 ≤ n + o ≤ 0.10 and l + m + n + o = 1, and δ is one or more elements selected from the group consisting of B, Si, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W, and is present in an amount of 10 at% or less.) The second layer group is an alternating nanolayer layer in which at least three of nanolayer A, nanolayer B, nanolayer C, and nanolayer D are laminated, the nanolayer A has the composition of A and a film thickness of 1 to 200 nm, the nanolayer B has the composition of B and a film thickness of 1 to 200 nm, the nanolayer C has the composition of C and a film thickness of 1 to 200 nm. The hard coating is characterized in that the nanolayer D layer has the composition D and a film thickness of 1 to 200 nm.

2. When the diffraction line intensities of the highest peaks of the (111) plane and the (200) plane of the rock salt structure type, measured by X-ray diffraction using the θ-2θ method with Cu Kα rays, are denoted as I(111) and I(200), respectively, these values ​​satisfy equation (1): 0.3 ≤ I(111) / I(200) ≤ 2.5 ... (1) - a hard coating according to claim 1.

3. The hard coating according to claim 2, characterized in that, in the X-ray diffraction, the diffraction angle of the diffraction line of the (111) plane shows a peak in diffraction line intensity within the range of 37° to 38°, and the diffraction angle of the diffraction line of the (200) plane shows a peak in diffraction line intensity within the range of 43.5° to 44.5°.

4. The hard coating according to any one of claims 1 to 3, characterized in that the total thickness of the hard coating is 0.5 to 15 μm.

5. A hard-coated tool characterized in that part or all of the tool base material is covered with a hard coating according to any one of claims 1 to 4.

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