cutting tools

Abstract

A cutting tool comprising: a substrate and a hard carbon film disposed on the substrate; when a cross-section of the hard carbon film is observed using a high-angle scattering annular dark-field scanning transmission electron microscope, the area ratio of black regions having an equivalent circular diameter of 10 nm or more is 0.7% or less, and the hydrogen content of the hard carbon film is 5 atomic % or less.

Description

Technical Field

[0001] The present disclosure relates to cutting tools. Background Art

[0002] Hard carbon films such as amorphous carbon and diamond-like carbon have excellent wear resistance and lubricity and are therefore used as coating materials for cutting tools, molds, and machine parts.

[0003] Japanese Patent Application Laid-Open No. 2003-62706 (Patent Document 1) discloses an amorphous carbon-coated tool including a WC-based substrate and an amorphous carbon film coating the substrate.

[0004] International Publication No. 2016 / 190443 (Patent Document 2) discloses a cutting tool including a substrate and a DLC layer located on a surface of the substrate and containing diamond-like carbon.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-62706

[0008] Patent Document 2: International Publication No. 2016 / 190443 Summary of the Invention

[0009] The cutting tool disclosed herein comprises:

[0010] a substrate and a hard carbon film disposed on the substrate,

[0011] When a cross section of the hard carbon film is observed using a high-angle scattering annular dark-field scanning transmission electron microscope, the area ratio of black regions having a circle-equivalent diameter of 10 nm or more is 0.7% or less.

[0012] The hard carbon film has a hydrogen content of 5 atomic % or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] [ Figure 1 ] Figure 1 This is a cross-sectional view of an example of a cutting tool according to an embodiment of the present disclosure.

[0014] [ Figure 2 ] Figure 2 This is a cross-sectional view of another example of a cutting tool according to an embodiment of the present disclosure.

[0015] [ Figure 3 ] Figure 3This is an image showing the results of observing a cross section of a hard carbon film of a cutting tool according to one embodiment of the present disclosure using a high-angle scattering annular dark-field scanning transmission electron microscope.

[0016] [ Figure 4 ] Figure 4 The images show the results of observing a cross section of a hard carbon film on a conventional cutting tool using a high-angle scattering annular dark-field scanning transmission electron microscope.

[0017] [ Figure 5 ] Figure 5 A diagram for explaining a method for measuring a black region of a hard carbon film.

[0018] [ Figure 6 ] Figure 6 This is a schematic diagram showing an example of a film forming apparatus used for manufacturing a cutting tool according to an embodiment of the present disclosure.

[0019] [ Figure 7 ] Figure 7 This is a diagram showing an example of a target material used in the production of a cutting tool according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] [Problems to be Solved by the Present Disclosure]

[0021] In recent years, the diversity of materials being cut has continued to grow, and soft metals such as aluminum alloys, non-ferrous metals such as titanium, magnesium, and copper, organic materials, materials containing hard particles such as graphite, and carbon fiber reinforced plastics (CFRP) have been processed.

[0022] When using cutting tools with hard carbon coatings to cut these materials, the material being cut can adhere to the tool's cutting edge, increasing cutting resistance or causing damage to the cutting edge, which can reduce tool life. This is particularly common when the material being cut is soft metal. Therefore, cutting tools with a long tool life are in high demand, even when used to cut soft metals.

[0023] The object is therefore to provide a cutting tool which has a long tool life, in particular even when used for cutting soft metals.

[0024] [Effects of the Present Disclosure]

[0025] According to the present disclosure, it is possible to provide a cutting tool capable of having a long tool life even when used for cutting soft metals in particular.

[0026] [Description of Embodiments of the Present Disclosure]

[0027] First, embodiments of the present disclosure will be listed and described.

[0028] (1) The cutting tool disclosed herein comprises:

[0029] a substrate and a hard carbon film disposed on the substrate,

[0030] When a cross section of the hard carbon film is observed using a high-angle scattering annular dark-field scanning transmission electron microscope, the area ratio of black regions having a circle-equivalent diameter of 10 nm or more is 0.7% or less.

[0031] The hard carbon film has a hydrogen content of 5 atomic % or less.

[0032] The cutting tool of the present disclosure can have a long tool life, particularly even when used for cutting soft metals.

[0033] (2) The thickness of the portion of the hard carbon film involved in cutting is preferably 0.1 μm to 3 μm. This can suppress peeling and chipping of the hard carbon film.

[0034] (3) It is preferable that the substrate and the hard carbon film are in contact with each other. This improves the adhesion between the substrate and the hard carbon film.

[0035] (4) Preferably, the cutting tool includes an interface layer disposed between the substrate and the hard carbon film.

[0036] The interface layer comprises:

[0037] At least one selected from the group consisting of: a single element selected from the first group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Group 13 elements, and Group 14 elements excluding carbon of the periodic table; an alloy or a first compound containing at least one element selected from the first group; and a solid solution derived from the first compound; or

[0038] a second compound composed of at least one element selected from the first group and carbon, and one or both of a solid solution derived from the second compound;

[0039] The thickness of the interface layer is greater than or equal to 0.5 nm and less than or equal to 10 nm.

[0040] Thus, the substrate and the hard carbon film are firmly adhered to each other via the interface layer, and the interface layer balances the hardness difference between the substrate and the hard carbon film, that is, acts as a buffer, thereby improving impact resistance.

[0041] (5) The substrate is preferably made of WC-based cemented carbide or cermet. Thus, the cutting tool is suitable for cutting non-ferrous alloys, particularly aluminum alloys, copper alloys, magnesium alloys, and the like.

[0042] (6) The substrate is preferably made of cubic boron nitride. Thus, the cutting tool is suitable for cutting non-ferrous alloys, particularly aluminum alloys, copper alloys, magnesium alloys, and the like.

[0043] [Details of the embodiments of the present disclosure]

[0044] Specific examples of the cutting tool disclosed herein are described below with reference to the accompanying drawings. In the drawings disclosed herein, identical reference numerals denote identical or equivalent parts. Furthermore, for clarity and simplicity of the drawings, the dimensional relationships of length, width, thickness, depth, etc., have been appropriately altered and do not necessarily represent actual dimensional relationships.

[0045] In this specification, expressions in the form of "A to B" refer to the upper and lower limits of a range (i.e., greater than A and less than B). When no unit is described in A and only in B, the unit of A is the same as that of B.

[0046] [Embodiment 1: Cutting Tool]

[0047] use Figures 1 to 3 A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as “this embodiment”) will be described. Figure 1 This is a cross-sectional view of an example of the cutting tool according to this embodiment. Figure 2 This is a cross-sectional view of another example of the cutting tool according to this embodiment. Figure 3 This is an image showing the results of observing a cross section of a hard carbon film of a cutting tool according to one embodiment of the present disclosure using a high-angle annular dark-field scanning transmission electron microscope (hereinafter also referred to as “HAADF-STEM”).

[0048] like Figure 1 As shown, the cutting tool 30 of this embodiment is a cutting tool 30 comprising a substrate 5 and a hard carbon film 20 arranged on the substrate 5. When a cross-section of the hard carbon film is observed using a high-angle scattering annular dark-field scanning transmission electron microscope, the area ratio of black regions with a circular equivalent diameter of 10 nm or more is less than 0.7%, and the hydrogen content of the hard carbon film is less than 5 atomic %.

[0049] The cutting tool of this embodiment can have a long tool life, especially when used for cutting soft metals. The reason for this is unclear, but it is presumed to be as follows (i) and (ii).

[0050] (i) When observing a cross section of the hard carbon film on the cutting tool of this embodiment using HAADF-STEM, the area ratio of black regions with an equivalent circular diameter of 10 nm or greater was 0.7% or less. Black regions with an equivalent circular diameter of 10 nm or greater in the hard carbon film are believed to be caused by film defects such as macroscopic particles, voids, and abnormal film growth. Therefore, in the hard carbon film on the cutting tool of this embodiment, the defect content is believed to be reduced to 0.7% or less based on area.

[0051] When cutting soft metals such as aluminum alloys using a cutting tool with a coating on its surface, the cut material repeatedly welds to and detaches from the coating. It is believed that when the welded cut material detaches from the coating, stress acting in the direction of peeling the coating and shear stress acting approximately parallel to the coating surface act on the coating. At this point, if there are defects in the coating, it is believed that the coating will break, starting from the defect, causing damage to the coating to progress.

[0052] In the cutting tool of this embodiment, since the number of defects in the hard carbon film is reduced, it is difficult for the defects to cause damage. Therefore, the cutting tool of this embodiment can have a long tool life, especially when used for cutting soft metals.

[0053] (ii) In the cutting tool of this embodiment, the hydrogen content of the hard carbon film is 5 atomic % or less. 3 The bond ratio increases, and the hardness increases. In addition, the oxidation resistance of the hard carbon film is also improved. Therefore, the cutting tool of this embodiment can have a long tool life.

[0054] exist Figure 1 In the embodiment, the substrate 5 is in contact with the hard carbon film 20, but the cutting tool of this embodiment is not limited thereto. Figure 2 As shown, the cutting tool 31 of this embodiment can include an interface layer 21 disposed between the substrate 5 and the hard carbon film 20. Furthermore, a mixed composition layer (not shown) in which the compositions of these films are mixed, or a gradient composition layer (not shown) in which the composition continuously changes, can be provided between the substrate 5 and the interface layer 21. Furthermore, a base layer (not shown) can be provided between the substrate 5 and the interface layer 21 to improve adhesion therebetween.

[0055] The hard carbon film 20 can be arranged to cover the entire surface of the substrate 5 or only a portion thereof. When the hard carbon film is arranged to cover a portion of the substrate, it is preferably arranged to cover at least the surface of the portion of the substrate that participates in cutting. In this specification, the portion of the substrate that participates in cutting refers to the area of the substrate enclosed by a virtual plane having a distance of 2 mm between the cutting edge ridgeline and a perpendicular line extending from the cutting edge ridgeline toward the substrate and along the cutting edge ridgeline.

[0056] <Base material>

[0057] As the substrate 5, a metal or ceramic substrate can be used. Specific examples include substrates made of iron, heat-treated steel, WC-based cemented carbide, cermet, stainless steel, nickel, copper, aluminum alloy, titanium alloy, alumina, cubic boron nitride, and silicon carbide. Among them, substrates made of WC-based cemented carbide, cermet, or cubic boron nitride are preferably used.

[0058] Hard Carbon Film

[0059] (composition)

[0060] In this specification, hard carbon films generally refer to carbon films referred to as diamond-like carbon (DLC), amorphous carbon, or diamond-like carbon. Hard carbon films are believed to contain carbon as their primary component and are structurally classified as amorphous rather than crystalline. They contain a mixture of single bonds (C-C) like those observed in diamond crystals and double bonds (C=C) like those observed in graphite crystals. Depending on the production method, they may also contain hydrogen such as CH.

[0061] The hard carbon film containing carbon as a main component means that the carbon content of the hard carbon film is 95 atomic % or more. The carbon content in the hard carbon film can be measured using an X-ray photoelectron spectroscopy analyzer (XPS measuring apparatus: "PHI5000 VersaProbe III" (trademark) manufactured by ULVAC-PHI, Inc.). Specifically, the composition of the elements constituting the sample surface is analyzed by irradiating the sample surface with X-rays and measuring the kinetic energy of the photoelectrons emitted from the sample surface. It should be noted that, with respect to the measurements conducted by the applicant, it has been confirmed that, as long as the measurement is performed on the same sample, even if the selected position of the measurement field of view is changed and the carbon content measurement results are calculated multiple times, there is almost no deviation in the measurement results. Even if the measurement field of view is arbitrarily set, the measurement results are not random.

[0062] Whether the hard carbon film is amorphous can be confirmed by, for example, X-ray diffraction measurement. The specific confirmation method is described below.

[0063] (A1) A hard carbon film formed on a substrate was subjected to X-ray diffraction measurement under the following conditions (measurement apparatus: "SmartLab" (trademark) manufactured by Rigaku Corporation) to obtain an X-ray diffraction pattern.

[0064] X-ray source: Cu-kα line

[0065] X-ray output power: 45kV, 200mA

[0066] Detector: One-dimensional semiconductor detector

[0067] Diffraction angle 2θ measurement range: 15 to 140°

[0068] Scanning speed: 0.2° / min

[0069] (A2) In the obtained diffraction pattern, when there are no peaks attributable to graphite or diamond other than the peak derived from the substrate and a broad peak is observed, it is determined that the hard carbon film is an amorphous phase.

[0070] (Area ratio of black area)

[0071] When a cross section of the hard carbon film 20 is observed using HAADF-STEM, the area ratio of black regions having an equivalent circle diameter of 10 nm or more (hereinafter also referred to as “area ratio of black regions”) is 0.7% or less.

[0072] When the area ratio of the black region is 0.7% or less, the hard carbon film is less susceptible to damage, and tool life is improved. The upper limit of the area ratio of the black region is 0.7% or less, preferably 0.5% or less, more preferably 0.3% or less, and even more preferably 0.2% or less. The lower limit of the area ratio of the black region is preferably 0% or more. From a manufacturing perspective, the lower limit of the area ratio of the black region can be set to 0.05% or more. The area ratio of the black region is preferably 0% or more and 0.7% or less, preferably 0% or more and 0.5% or less, more preferably 0% or more and 0.3% or less, and even more preferably 0% or more and 0.2% or less.

[0073] The area ratio of the black region of the hard carbon film can be measured by HAADF-STEM observation. The specific measurement method is described below.

[0074] (B1) Cut the cutting tool along the normal direction of the surface to produce a sample containing a cross section of the hard carbon film. Cut at 10 random locations within the cutting tool, including the portion involved in cutting. Ten samples are produced. Cutting is performed using a focused ion beam system, cross-section polishing equipment, or the like.

[0075] (B2) A cross section of each sample was observed at a magnification of 200,000 times using HAADF-STEM to obtain a dark field image.

[0076] (B3) Specifying the Hard Carbon Film in the Obtained Dark Field Image: By performing cross-sectional mapping analysis using energy dispersive X-ray analysis (EDX) with HAADF-STEM, the carbon-based hard carbon film, the interface layer, and the substrate can be specified.

[0077] (B4) A rectangular measurement field of view is set within the hard carbon film region in the dark field image. A pair of opposite sides of this rectangle are parallel to the main surface of the substrate on the hard carbon film side and are 800 nm long. The distance between the opposite sides on the substrate side and the main surface of the substrate on the hard carbon film side is 30 nm. The distance between the opposite sides on the surface side of the hard carbon film and the surface of the hard carbon film is 30 nm.

[0078] use Figure 5 The above-mentioned measurement visual field will be described in detail. Figure 5 This is a dark-field image of a cutting tool cross-section observed using HAADF-STEM at a magnification of 200,000x. In this dark-field image, the area enclosed by line segments a, b, c, and d corresponds to the rectangular measurement field of view. A pair of opposite sides of this rectangle (line segments a and b) are parallel to the main surface S1 of the hard carbon film side of the substrate 5 and are 800 nm long. The distance between the opposite side (line segment b) on the substrate side and the main surface S1 of the hard carbon film 20 side of the substrate 5 is 30 nm. The distance between the opposite side (line segment a) on the surface S2 of the hard carbon film 20 and the surface S2 of the hard carbon film 20 is also 30 nm.

[0079] If the hard carbon film-side main surface of the substrate 5 has irregularities, the hard carbon film-side main surface S1 of the substrate is defined as follows. Within the measurement field of view, the portion of the substrate where the amount of protrusion toward the hard carbon film is greatest is identified. A line parallel to the average line of the irregularities on the substrate's main surface is drawn through this portion. This line is defined as the hard carbon-side main surface S1 of the substrate.

[0080] If the surface of the hard carbon film 20 has irregularities, the surface S2 of the hard carbon film is defined as follows. Within the measurement field of view, the portion of the hard carbon film where the surface irregularities are greatest is identified. A line parallel to the average line of the irregularities on the hard carbon film surface is drawn through this portion. This line is defined as the surface S2 of the hard carbon film.

[0081] The reason for excluding the region where the hard carbon film 20 is 30 nm or less from the main surface S1 of the substrate 5 and the region where the hard carbon film 20 is 30 nm or less from the surface S2 of the substrate 5 in setting the measurement field of view is to eliminate the influence of sample adjustment and the influence of the interface layer.

[0082] (B5) The dark field image was processed using image analysis software ("WinROOF" (trademark) from Mitani Shoji Co., Ltd.) to convert it into a 256-grayscale monochrome image. Adjustments were made to the image after conversion to a 256-grayscale monochrome image so that no contrast difference occurred in the white area within the measurement field of view.

[0083] (B6) In the monochromatic image, the average density within the measurement visual field is determined, and the monochromatic image is binarized using the average density as a threshold.

[0084] Figure 3 FIG. 2 shows an example of an image obtained by binary processing of a cross section of a hard carbon film of a cutting tool disclosed in the present invention. Figure 3 As shown, almost no black region is confirmed in the hard carbon film of the cutting tool of the present disclosure.

[0085] Figure 4 An example of an image obtained by binary processing of a cross section of a hard carbon film of a conventional cutting tool is shown. Figure 4 As shown, a black region indicated by symbol B exists in the hard carbon film of the conventional cutting tool.

[0086] (B7) Particle analysis is performed on the binarized image to determine the area of the black region with an equivalent circular diameter of 10 nm or more. The ratio of the black region with an equivalent circular diameter of 10 nm or more to the total area of the measurement field is calculated.

[0087] (B8) The area ratio of the black region is measured for each of the ten samples. The average of the area ratios of the black regions measured for the ten samples is defined as the "area ratio of the black region of the hard carbon film." Specifically, if the average of the area ratios of the black regions measured for the ten samples is 0.7% or less, it is determined that the "area ratio of the black region of the hard carbon film is 0.7% or less."

[0088] It should be noted that, as far as the applicant's measurements are concerned, it can be confirmed that as long as the measurements are performed on the same sample, even if the selected position of the cut surface or the selected position of the measurement field of view is changed to calculate the measurement results of the area ratio of the black area multiple times, there is almost no deviation in the measurement results. Even if the measurement field of view is set arbitrarily, the measurement results are not arbitrary.

[0089] (thickness)

[0090] The thickness of the portion of the hard carbon film 20 involved in cutting (hereinafter also referred to as the "thickness of the hard carbon film") is preferably 0.1 μm to 3 μm. In this specification, the portion of the hard carbon film involved in cutting refers to the area of the hard carbon film enclosed by the cutting edge ridgeline of the cutting tool and a virtual plane perpendicular to a tangent line extending from the cutting edge ridgeline toward the cutting tool, with a distance of 2 mm. The thickness of the portion of the hard carbon film involved in cutting refers to the thickness of the hard carbon film in the region involved in cutting, measured from the surface of the hard carbon film along the direction normal to the surface.

[0091] When the thickness of the hard carbon film is 0.1 μm or more, wear resistance is improved. When the thickness of the hard carbon film is 3 μm or less, an increase in internal stress accumulated in the hard carbon film can be suppressed, thereby suppressing peeling and chipping of the hard carbon film.

[0092] The lower limit of the thickness of the hard carbon film is preferably 0.1 μm or greater, more preferably 0.5 μm or greater, and even more preferably 1.0 μm or greater. The upper limit of the thickness of the hard carbon film is preferably 3 μm or less, more preferably 2.0 μm or less, and even more preferably 1.5 μm or less. The thickness of the hard carbon film can be set to 0.1 μm or greater and 3 μm or less, 0.5 μm or greater and 2.0 μm or less, or 1.0 μm or greater and 1.5 μm or less.

[0093] The thickness of the hard carbon film can be measured by observing the cross section of the hard carbon film using a SEM (scanning electron microscope, measuring device: "JSM-6610 series" (trademark) manufactured by JEOL Ltd.). Specifically, the cross section sample is observed at a magnification of 5000 to 10000 times and an observation area of 100 to 500 μm. 2 , measure the thickness at three randomly selected locations within a field of view, and use the average value as the "thickness." It should be noted that, with respect to the applicant's measurements, it has been confirmed that, as long as the measurements are performed on the same sample, even if the selected location of the measurement field of view is changed and the thickness measurement results are calculated multiple times, there is almost no deviation in the measurement results. Even if the measurement field of view is arbitrarily set, the measurement results are not arbitrary.

[0094] (Hydrogen content)

[0095] The hard carbon film 20 is basically composed of carbon and inevitable impurities, but may contain hydrogen. This hydrogen is believed to originate from hydrogen and moisture remaining in the film forming apparatus that enter the hard carbon film during film formation.

[0096] The hydrogen content of the hard carbon film 20 is 5 atomic % or less. 3The higher the bond ratio, the higher the hardness. Furthermore, the oxidation resistance of the hard carbon film is also improved. The upper limit of the hydrogen content of the hard carbon film is more preferably 4 atomic % or less, and even more preferably 2 atomic % or less. The lower limit of the hydrogen content of the hard carbon film is preferably 0 atomic %, but from a manufacturing perspective, it can be 0 atomic % or more, 1 atomic % or more, or 2 atomic % or more. The hydrogen content of the hard carbon film can be set to 0 atomic % or more and 5 atomic % or less, 0 atomic % or more and 4 atomic % or less, 0 atomic % or more and 2 atomic % or less, 1 atomic % or more and 5 atomic % or less, 1 atomic % or more and 4 atomic % or less, 1 atomic % or more and 2 atomic % or less, 2 atomic % or more and 5 atomic % or less, or 2 atomic % or more and 4 atomic % or less.

[0097] The hydrogen content of the hard carbon film is measured using ERDA (Elastic Rebound Particle Detection, measuring device: "HRBS500" manufactured by Kobe Steel). This method is a method in which hydrogen ions that collide with He ions incident at a low angle of incidence are rebounded in the forward direction and the energy of the rebounded hydrogen particles is analyzed to measure the hydrogen content. It should be noted that, with respect to the measurements made by the applicant, it can be confirmed that as long as the measurement is performed on the same sample, even if the selected position of the measurement field is changed and the measurement results of the hydrogen content are calculated multiple times, there is almost no deviation in the measurement results. Even if the measurement field is arbitrarily set, the measurement results are not arbitrary.

[0098] (hardness)

[0099] The hardness of the hard carbon film 20 is preferably 35 GPa or more and 75 GPa or less. When the hardness of the hard carbon film is 35 GPa or more, wear resistance is improved. When the hardness of the hard carbon film is 75 GPa or less, defect resistance is improved. The lower limit of the hardness of the hard carbon film is preferably 35 GPa or more, more preferably 45 GPa or more, and even more preferably 55 GPa or more. The upper limit of the hardness of the hard carbon film is preferably 75 GPa or less, and even more preferably 73 GPa or less. The hardness of the hard carbon film is preferably 35 GPa or more and 75 GPa or less, more preferably 45 GPa or more and 73 GPa or less, and even more preferably 55 GPa or more and 73 GPa or less.

[0100] The hardness of a hard carbon film can be measured using nanoindentation (measurement device: "Nano IndenterXP" (trademark) manufactured by MTS). Specifically, the hardness is measured at three locations on the surface of the hard carbon film, and the average value is used as the "hardness." It should be noted that the applicant's measurements confirmed that, as long as the measurement is performed on the same sample, even if the selected position of the measurement field of view is changed and the hardness measurement results are calculated multiple times, there is little deviation in the measurement results. Even if the measurement field of view is arbitrarily set, the measurement results are not random.

[0101] <Interface layer>

[0102] like Figure 2 As shown, the cutting tool 31 of this embodiment may include an interface layer 21 disposed between the substrate 5 and the hard carbon film 20. Thus, the substrate and the hard carbon film are firmly adhered to each other via the interface layer.

[0103] (composition)

[0104] The composition of the interface layer 5 may be as described below in (K1) or (K2).

[0105] (K1) contains at least one selected from the group consisting of: a single element selected from Group 1 consisting of Group 4 elements, Group 5 elements, Group 6 elements, Group 13 elements, and Group 14 elements excluding carbon of the periodic table, an alloy containing at least one element selected from the first group, a first compound, and a solid solution derived from the first compound; or

[0106] (K2) contains one or both of a second compound composed of at least one element selected from the above-mentioned first group and carbon, and a solid solution derived from the second compound.

[0107] That is, the interface layer may be any of the following forms (k1) to (k4).

[0108] (k1) It is composed of at least one selected from the group consisting of a single substance selected from the first group, an alloy containing at least one element selected from the first group, a first compound, and a solid solution derived from the first compound.

[0109] (k2) Contains at least one selected from the group consisting of a single element selected from the first group, an alloy containing at least one element selected from the first group, a first compound, and a solid solution derived from the first compound.

[0110] (k3) A second compound composed of at least one element selected from the first group and carbon, and one or both of a solid solution derived from the second compound.

[0111] (k4) Contains one or both of a second compound composed of at least one element selected from the first group and carbon, and a solid solution derived from the second compound.

[0112] Here, Group 4 elements of the periodic table include, for example, titanium (Ti), zirconium (Zr), and hafnium (Hf). Group 5 elements include, for example, vanadium (V), niobium (Nb), and tantalum (Ta). Group 6 elements include, for example, chromium (Cr), molybdenum (Mo), and tungsten (W). Group 13 elements include, for example, boron (B), aluminum (Al), gallium (Ga), and indium (In). Group 14 elements other than carbon include, for example, silicon (Si), germanium (Ge), and tin (Sn). Hereinafter, elements contained in Group 4 elements, Group 5 elements, Group 6 elements, Group 13 elements, and Group 14 elements other than carbon are also referred to as "first elements."

[0113] Examples of alloys containing the first element include Ti—Zr, Ti—Hf, Ti—V, Ti—Nb, Ti—Ta, Ti—Cr, and Ti—Mo. Examples of intermetallic compounds containing the first element include TiCr 2 and Ti 3 Al.

[0114] Examples of the first compound containing the first element include titanium boride (TiB2), zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), niobium boride (NbB2), tantalum boride (TaB2), chromium boride (CrB), molybdenum boride (MoB), tungsten boride (WB), and aluminum boride (AlB2).

[0115] The solid solution derived from the first compound mentioned above refers to a state in which two or more first compounds are dissolved in each other's crystal structures, and refers to an intrusive solid solution or a substitutional solid solution.

[0116] Examples of the second compound composed of the first element and carbon include titanium carbide (TiC), zirconium carbide (ZrC), hafnium carbide (HfC), vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr3C2), molybdenum carbide (MoC), tungsten carbide (WC), and silicon carbide (SiC).

[0117] The solid solution derived from the second compound mentioned above refers to a state in which two or more second compounds are dissolved in each other's crystal structures, and refers to an intrusive solid solution or a substitutional solid solution.

[0118] The total content of one monomer selected from the first group, an alloy containing at least one selected from the first group, a first compound, and a solid solution derived from the first compound in the interface layer (hereinafter also referred to as "the content of the first compound, etc.") is preferably greater than 70 volume % and less than 100 volume %, more preferably greater than 80 volume % and less than 100 volume %, further preferably greater than 90 volume % and less than 100 volume %, and most preferably 100 volume %.

[0119] The total content of the second compound in the interface layer and the solid solution derived from the second compound (hereinafter also referred to as "the content of the second compound, etc.") is preferably greater than 70 volume % and less than 100 volume %, more preferably greater than 80 volume % and less than 100 volume %, further preferably greater than 90 volume % and less than 100 volume %, and most preferably 100 volume %.

[0120] The composition of the interface layer, the content of the first compound, etc., and the content of the second compound, etc. can be measured using a transmission electron microscope-energy dispersive X-ray analysis (TEM-EDX: Transmission Electron Microscopy-Energy Dispersive X-ray spectrometry) method. Specifically, a cutting tool is cut using a FIB (focused ion beam device) to expose the interface layer, and the composition of the elements constituting the interface layer, the content of the first compound, etc., and the content of the second compound, etc. are measured while observing the cross section using a TEM. It should be noted that, as far as the applicant's measurements are concerned, it can be confirmed that as long as the measurements are performed on the same sample, even if the selected position of the measurement field is changed and the measurement results are calculated multiple times, there is almost no deviation in the measurement results, and even if the measurement field is arbitrarily set, the measurement results are not arbitrary.

[0121] (thickness)

[0122] The thickness of the interface layer 5 is preferably 0.1 nm or greater and less than 10 nm. When the thickness of the interface layer falls within this range, the adhesion between the substrate and the hard carbon film is enhanced. The thickness of the interface layer is more preferably 0.6 nm or greater and 8.0 nm or less, and even more preferably 1.0 nm or greater and 5.0 nm or less.

[0123] The thickness of the interface layer can be measured by observing the cross section of the hard carbon film using a SEM (scanning electron microscope). Specifically, the cross section sample is observed at a magnification of 5000 to 10000 times and an observation area of 100 to 500 μm. 2 , measure the thickness at three randomly selected locations within a field of view, and use the average value as the "thickness." It should be noted that, with respect to the measurements performed by the applicant, it has been confirmed that, as long as the measurements are performed on the same sample, even if the selected location of the measurement field of view is changed and the thickness measurement results are calculated multiple times, there is almost no deviation in the measurement results. Even if the measurement field of view is arbitrarily set, the measurement results are not arbitrary.

[0124] <Other floors>

[0125] The cutting tool of this embodiment preferably includes a mixed composition layer formed by mixing the compositions of these films, or a gradient composition layer with continuously changing compositions, between the interface layer and the hard carbon film. This further improves the adhesion between the substrate and the hard carbon film.

[0126] Mixed layers and gradient composition layers cannot always be clearly distinguished. When manufacturing conditions change from forming the interface layer to forming the hard carbon film, the compositions of the interface layer and the hard carbon film often slightly intermingle, forming mixed or gradient composition layers. While direct identification of these layers is difficult, their presence can be reasonably estimated from results such as XPS (X-ray Photoelectron Spectroscopy) and AES (Auger Electron Spectroscopy).

[0127] <Applications of Cutting Tools>

[0128] The cutting tool of this embodiment has excellent wear resistance and welding resistance, and is therefore particularly suitable for processing aluminum and its alloys. In addition, it is also suitable for processing non-ferrous materials such as titanium, magnesium, and copper. In addition, it is also suitable for cutting materials containing hard particles such as graphite, organic materials, etc., printing circuit board processing, and co-cutting of iron-based materials and aluminum. In addition, the hard carbon film of the cutting tool of this embodiment has a very high hardness, so it can be used not only for non-ferrous materials, but also for processing steel such as stainless steel or castings.

[0129] <Types of Cutting Tools>

[0130] The cutting tool of this embodiment can be used as, for example, a drill, an end mill, an indexable cutting insert for end milling, an indexable cutting insert for milling, an indexable cutting insert for turning, a metal saw, a gear cutting tool, a reamer, and a tap.

[0131] [Embodiment 2: Method for manufacturing a cutting tool]

[0132] The cutting tool of the present disclosure can be used, for example, Figure 6 The film forming apparatus 1 shown forms a hard carbon film on a substrate. Hereinafter, an example of a method for manufacturing a cutting tool according to the present disclosure will be described.

[0133] (Preparation of substrate)

[0134] Prepare a substrate 5. The substrate may be any of the materials described in Embodiment 1. For example, the substrate is preferably made of WC-based cemented carbide, cermet, or cubic boron nitride.

[0135] The substrate 5 is mounted on the substrate holder 4 in the film forming apparatus 1. The substrate holder 4 rotates between the targets 2 and 3 with the center point of the targets 2 and 3 as the center.

[0136] The substrate 5 was heated to 200° C. using the substrate heater 6, and the vacuum degree in the film forming apparatus 1 was set to 5×10 - 4 Pa atmosphere. Subsequently, the set temperature of the substrate heater 6 was lowered to 100°C, and then argon gas was introduced and maintained at 2×10 -1 Pa atmosphere, while simultaneously applying a voltage of -1000 V to the substrate holder 4 via the film forming bias power supply 9 to perform argon plasma cleaning on the substrate surface. The argon gas is then exhausted. In the film forming apparatus 1, gas is supplied via a gas supply port 10 and exhausted via an exhaust port 11.

[0137] Next, a target 2 composed of a Group 4 element, a Group 5 element, or a Group 6 element of the periodic table is placed in the film forming apparatus 1 .

[0138] The target material 2 is evaporated and ionized, and a voltage of -600 V is applied to the substrate holder 4 by the bias power supply 9 to perform metal ion bombardment. This etches the surface of the substrate, improving adhesion with the subsequently formed interface layer or hard carbon film.

[0139] It should be noted that the formation of the interface layer and the formation of the hard carbon film described later may be performed without subjecting the substrate to the metal ion bombardment treatment.

[0140] (Formation of Interface Layer)

[0141] Next, a target 2 composed of an element selected from the group consisting of Group 4, Group 5, Group 6, and Group 13 elements of the periodic table, and Group 14 elements excluding carbon, is placed within film-forming apparatus 1. With or without the introduction of a hydrocarbon gas, target 2 is evaporated and ionized by vacuum arc discharge. A voltage of -100V to -800V is applied to substrate holder 4 by bias power supply 9 to form an interface layer on the substrate. The hydrocarbon gas is then exhausted.

[0142] Note that the hard carbon film described later may be formed without forming an interface layer on the substrate.

[0143] (Formation of Hard Carbon Film)

[0144] Next, a target material 3 made of glassy carbon is placed in the film forming apparatus 1. Argon gas is introduced at a flow rate of 15cc / minute, and simultaneously, a vacuum arc discharge (cathode current of 120A) is used to evaporate and ionize the target material 3. A bias power supply 9 applies a voltage of -100V to the substrate holder 4 to form a hard carbon film on the interface layer, thereby obtaining a cutting tool. A hydrocarbon gas may be introduced along with the argon gas. During film formation, the temperature of the substrate heater 6 is set to 180°C.

[0145] Commercially available glassy carbon can be used. Glassy carbon is a high-purity carbonaceous material and, unlike conventional sintered carbon (e.g., sintered graphite) used in cathodes, is free of metallic contamination. In particular, Hitachi Chemical's glassy carbon contains no aluminum (Al), making it particularly suitable for cutting aluminum alloys. Furthermore, the use of glassy carbon suppresses the formation of macroscopic particles in the hard carbon film, resulting in a smoother hard carbon film and improved cutting performance.

[0146] The target is usually cylindrical, disc-shaped or rectangular. However, the present inventors have made a new discovery after intensive research: from the perspective of improving the film quality of the hard carbon film, Figure 7 The triangular prism shape shown is preferred. High currents are sometimes required to flow through the target, but using a V-shaped electrode and closely contacting the target's sides with the electrode allows for stable power supply to the target. Furthermore, since the target and electrode are closely contacted, cooling is also improved. Effective target cooling reduces electrical resistance, facilitating arc point movement. This suppresses defects in the hard carbon film, improving film quality.

[0147] From the perspective of improving the purity of hard carbon films, it is preferable to form the film in a vacuum without introducing Ar gas. However, the present inventors have conducted extensive research and discovered that, compared to vacuum, flowing Ar gas at a flow rate of 15 cc / min stabilizes arc discharge and improves film quality.

[0148] Example

[0149] This embodiment will be described in more detail with reference to examples, but this embodiment is not limited to these examples.

[0150] Example 1

[0151] [Manufacturing of cutting tools]

[0152] <<Sample 1 to Sample 3>>

[0153] In Samples 1 to 3, glassy carbon was used as a raw material, and a hard carbon film was formed on a substrate by a cathode arc ion plating method (represented as "arc method" in Table 1) to produce a cutting tool.

[0154] (Preparation of substrate)

[0155] A 6 mm diameter WC (grain size: 1 μm)-based cemented carbide drill was prepared as a base material. This base material contained 8% by mass of Co as a bonding material.

[0156] Install the substrate Figure 6 In the film forming apparatus 1 shown, the substrate is heated to 200° C. using the substrate heater 6 and the vacuum degree in the film forming apparatus 1 is set to 5×10-4 Pa atmosphere. Subsequently, the set temperature of the substrate heater 6 was lowered to 100°C, and then argon gas was introduced and maintained at 2×10 -1 Pa atmosphere, and simultaneously a voltage of -1000 V was applied to the substrate holder 4 by the film forming bias power supply 9 to perform argon plasma cleaning on the substrate surface.

[0157] (Formation of Hard Carbon Film)

[0158] Next, argon gas was introduced into the film-forming apparatus 1 at a flow rate of 15 cc / min. A triangular prism-shaped target material composed of glassy carbon ("Glassy Carbon" manufactured by Hitachi Chemical Co., Ltd.) was evaporated and ionized by vacuum arc discharge (cathode current 120 A). A voltage of -100 V was applied to the substrate holder 4 by a bias power supply 9 to form a hard carbon film on the substrate, thereby producing a cutting tool. The set temperature of the substrate heater 6 during the formation of the hard carbon film was set to 180°C. The thickness of the hard carbon film for each sample is shown in the "Thickness (μm)" column of the "Hard Carbon Film" section in Table 1.

[0159] <<Sample 4 to Sample 7>>

[0160] In Samples 4 to 7, an interface layer and a hard carbon film were sequentially formed on a substrate by cathodic arc ion plating to produce cutting tools.

[0161] <Sample 4>

[0162] (Preparation of substrate)

[0163] A substrate was prepared in the same manner as in Sample 1.

[0164] (Formation of Interface Layer)

[0165] Next, hydrocarbon gas was introduced into the film-forming apparatus 1 at a flow rate of 15 cc / min. Simultaneously, a triangular prism-shaped target material composed of chromium (Cr) was evaporated and ionized by vacuum arc discharge (cathode current 80 A). A voltage of -100 V was applied to the substrate holder 4 by a bias power supply 9, thereby forming a 5 nm thick interface layer composed of chromium carbide (CrC) on the substrate. The hydrocarbon gas was then exhausted.

[0166] (Formation of Hard Carbon Film)

[0167] Next, argon gas at a flow rate of 15 cc / min and hydrocarbon gas at a flow rate of 5 cc / min were introduced into the film forming apparatus 1. Simultaneously, a triangular prism-shaped target material composed of glassy carbon ("Glassy Carbon" manufactured by Hitachi Chemical) was evaporated and ionized by vacuum arc discharge (cathode current 120 A). A voltage of -100 V was applied to the substrate holder 4 via a bias power supply 9 to form a 0.6 μm thick hard carbon film on the interface layer, thereby producing a cutting tool. During the formation of the hard carbon film, the set temperature of the substrate heater 6 was set to 180°C.

[0168] Sample 5

[0169] (Preparation of substrate)

[0170] A substrate was prepared in the same manner as in Sample 1.

[0171] (Formation of Interface Layer)

[0172] Next, without introducing gas into the film forming device 1, the target material composed of chromium (Cr) is evaporated and ionized by vacuum arc discharge (cathode current 80A), and a voltage of -800V is applied to the substrate holder 4 by the bias power supply 9 to form an interface layer with a thickness of 5nm composed of (Cr) on the substrate.

[0173] (Formation of Hard Carbon Film)

[0174] Next, argon gas at a flow rate of 15 cc / min and hydrocarbon gas at a flow rate of 20 cc / min were introduced into the film forming apparatus 1. Simultaneously, a triangular prism-shaped target material composed of glassy carbon ("Glassy Carbon" manufactured by Hitachi Chemical) was evaporated and ionized by vacuum arc discharge (cathode current 120 A). A voltage of -100 V was applied to the substrate holder 4 via a bias power supply 9 to form a 0.4 μm thick hard carbon film on the interface layer, thereby producing a cutting tool. During the formation of the hard carbon film, the set temperature of the substrate heater 6 was set to 180°C.

[0175] Sample 6

[0176] (Preparation of substrate)

[0177] A substrate was prepared in the same manner as in Sample 1.

[0178] (Formation of Interface Layer)

[0179] Next, hydrocarbon gas was introduced into the film-forming apparatus 1 at a flow rate of 15 cc / min. Simultaneously, a triangular prism-shaped target material composed of titanium (Ti) was evaporated and ionized by vacuum arc discharge (cathode current 80 A). A voltage of -100 V was applied to the substrate holder 4 by a bias power supply 9, thereby forming a 5 nm thick interface layer composed of titanium carbide (TiC) on the substrate. The hydrocarbon gas was then exhausted.

[0180] (Formation of Hard Carbon Film)

[0181] Next, argon gas was introduced into the film forming apparatus 1 at a flow rate of 15 cc / min. Simultaneously, a triangular prism-shaped target material composed of glassy carbon ("Glassy Carbon" manufactured by Hitachi Chemical) was evaporated and ionized by vacuum arc discharge (cathode current 120 A). A voltage of -100 V was applied to the substrate holder 4 via a bias power supply 9 to form a 0.6 μm thick hard carbon film on the interface layer, thereby producing a cutting tool. During the formation of the hard carbon film, the set temperature of the substrate heater 6 was set to 180°C.

[0182] Sample 7

[0183] (Preparation of substrate)

[0184] A substrate was prepared in the same manner as in Sample 1.

[0185] (Formation of Interface Layer)

[0186] Next, without introducing gas into the film forming device 1, the target material composed of titanium (Ti) is evaporated and ionized by vacuum arc discharge (cathode current 80A), and a voltage of -100V is applied to the substrate holder 4 by the bias power supply 9 to form an interface layer composed of titanium (Ti) with a thickness of 5nm on the substrate.

[0187] (Formation of Hard Carbon Film)

[0188] Next, argon gas was introduced into the film forming apparatus 1 at a flow rate of 15 cc / min. Simultaneously, a triangular prism-shaped target material composed of glassy carbon ("Glassy Carbon" manufactured by Hitachi Chemical) was evaporated and ionized by vacuum arc discharge (cathode current 120 A). A voltage of -100 V was applied to the substrate holder 4 via a bias power supply 9 to form a 0.9 μm thick hard carbon film on the interface layer, thereby producing a cutting tool. During the formation of the hard carbon film, the set temperature of the substrate heater 6 was set to 180°C.

[0189] <<Sample 8 to Sample 11>>

[0190] In Samples 8 to 11, sintered graphite was used as a raw material, and a hard carbon film was formed on a substrate by cathodic arc ion plating to produce cutting tools.

[0191] (Preparation of substrate)

[0192] A substrate was prepared in the same manner as in Sample 1.

[0193] (Formation of Hard Carbon Film)

[0194] Next, argon gas at a flow rate of 15 cc / min (Samples 8, 10, and 11), or argon gas at a flow rate of 15 cc / min and a hydrocarbon gas at a flow rate of 5 cc / min (Sample 9), was introduced into the film forming apparatus 1. Simultaneously, a triangular prism-shaped target made of sintered graphite ("IG-510" manufactured by Toyo Tanso Co., Ltd.) was evaporated and ionized by vacuum arc discharge (cathode current: 180 A for Sample 8; 120 A for Samples 9 and 10; 150 A for Sample 11). A voltage of -100 V was applied to the substrate holder 4 via a bias power supply 9 to form a 0.5 μm thick hard carbon film on the substrate, thereby producing a cutting tool. The set temperature of the substrate heater 6 during the formation of the hard carbon film was set to 180°C.

[0195] <<Sample 12>>

[0196] In Sample 12, a hard carbon film having a thickness of 0.5 μm was formed on the same substrate as that of Sample 1 by a plasma CVD method using methane gas as a raw material, thereby producing a cutting tool.

[0197] [evaluate]

[0198] (Measurement of the Area Ratio of Black Region)

[0199] The area ratio of the black region was measured for each sample of the hard carbon film. The method for measuring the area ratio of the black region is described in Embodiment 1, so its description is not repeated here. The results are shown in the "Area Ratio of Black Region (%)" column of Table 1.

[0200] (Determination of hydrogen content)

[0201] The hydrogen content of the hard carbon film of each sample was measured. The method for measuring the hydrogen content is described in Embodiment 1, so its description will not be repeated. The results are shown in the "Hydrogen Content (Atom %)" column of Table 1.

[0202] (Determination of hardness)

[0203] The hardness of the hard carbon film of each sample was measured. The hardness measurement method is described in Embodiment 1, so its description will not be repeated. The results are shown in the "Hardness (GPa)" column of Table 1.

[0204] (Cutting test)

[0205] Using the cutting tool of each sample, drilling was performed under the following cutting conditions.

[0206] Cutting material: ADC12 (Al-Si-Cu alloy)

[0207] Cutting speed: 200m / min

[0208] Feed speed: 0.4mm / rev

[0209] Hole depth: 23mm stop

[0210] Coolant: Internal oil supply 1.9MPa

[0211] The number of holes machined from the drill tip wearing out and aluminum alloy deposition to a defect (500 μm or greater) was measured. A greater number of holes machined indicates superior wear resistance and longer tool life. The results are shown in the "Number of holes machined" column under "Cutting Test" in Table 1.

[0212] [Table 1]

[0213]

[0214] <Discussion>

[0215] The cutting tools of samples 1 to 7 correspond to Examples, and the cutting tools of samples 8 to 12 correspond to Comparative Examples.

[0216] Compared to Samples 8 to 12 (Comparative Examples), Samples 1 to 7 (Examples) demonstrated a greater number of machined holes, superior wear resistance, and longer tool life. It should be noted that while the hard carbon films of Samples 1 to 3 and Samples 6 and 7 were formed under identical conditions, the area ratios of the black regions differed. This is believed to be due to manufacturing variations.

[0217] It is considered that since the area ratio of the black region of the hard carbon films of Samples 8 to 11 exceeded 0.7% and the crystallinity exceeded 6.5%, the hardness was low, the wear resistance was reduced, and the tool life was short.

[0218] It is considered that since the hydrogen content of the hard carbon film of Sample 12 exceeded 5 atomic %, the hardness was low, the wear resistance was reduced, and the tool life was short.

[0219] Example 2

[0220] <<Sample 2-1>>

[0221] (Preparation of substrate)

[0222] As a substrate, a cermet insert having an insert number of DCGT11T308N-AG was prepared, and the surface of the substrate was cleaned with argon plasma in the same manner as in Sample 1.

[0223] (Formation of Hard Carbon Film)

[0224] Next, a hard carbon film having a thickness of 0.4 μm was formed on the substrate under the same conditions as those of Sample 1, thereby obtaining a cutting tool.

[0225] <<Sample 2-2>>

[0226] Sample 2-2 is the same insert made of cermet as that prepared in Sample 2-1. Sample 2-2 does not have a hard carbon film.

[0227] [evaluate]

[0228] (Measurement of black area ratio, hydrogen content, and hardness)

[0229] The hard carbon film of Sample 2-1 was measured for the black area ratio, hydrogen content, and hardness. The measurement methods are described in Embodiment 1, so their descriptions are omitted. The results are shown in the "Black Area Ratio (%)," "Hydrogen Content (Atom %)," and "Hardness (GPa)" columns of Table 2.

[0230] (Cutting test)

[0231] Using the cutting tool for each sample, round bar turning was performed under the following cutting conditions.

[0232] Cutting material: ADC12 (Al-Si-Cu alloy) round bar

[0233] Cutting speed: 300m / min

[0234] Feed speed: 0.2mm / rev

[0235] Cutting depth: 2.0mm

[0236] Cutting oil: dry

[0237] The cutting length (km) until the tool was chipped (500 μm or greater) due to cutting edge adhesion was measured. A longer cutting length indicates better chipping resistance and longer tool life. The results are shown in the "Cutting Length" column of the "Cutting Test" section in Table 2.

[0238] [Table 2]

[0239]

[0240] <Discussion>

[0241] The cutting tool of Sample 2-1 corresponds to the Example. The cutting tool of Sample 2-2 corresponds to the Comparative Example. It was confirmed that Sample 2-1 (Example) had a longer cutting length, excellent chipping resistance, and longer tool life than Sample 2-2 (Comparative Example).

[0242] Example 3

[0243] <<Sample 3-1>>

[0244] (Preparation of substrate)

[0245] As a substrate, a cubic boron nitride insert with an insert number of VBGW160408 was prepared. The substrate surface was cleaned with argon plasma in the same manner as in Sample 1.

[0246] (Formation of Hard Carbon Film)

[0247] Next, a hard carbon film having a thickness of 0.4 μm was formed on the substrate under the same conditions as those of Sample 1, thereby obtaining a cutting tool.

[0248] <<Sample 3-2>>

[0249] Sample 3-2 is the same insert made of cubic boron nitride as that prepared in Sample 3-1. Sample 3-2 does not have a hard carbon film.

[0250] [evaluate]

[0251] (Measurement of black area ratio, hydrogen content, and hardness)

[0252] The hard carbon film of Sample 3-1 was measured for the black area ratio, hydrogen content, and hardness. The measurement methods are described in Embodiment 1, so their descriptions are omitted. The results are shown in the "Black Area Ratio (%)," "Hydrogen Content (Atom %)," and "Hardness (GPa)" columns of Table 3.

[0253] (Cutting test)

[0254] Using the cutting tool for each sample, round bar turning was performed under the following cutting conditions.

[0255] Cutting material: ADC12 (Al-Si-Cu alloy) round bar

[0256] Cutting speed: 400m / min

[0257] Feed speed: 0.05mm / rev

[0258] Cutting depth: 2.0mm

[0259] Cutting oil: wet

[0260] The cutting length (km) until the tool was chipped (500 μm or greater) due to cutting edge adhesion was measured. A longer cutting length indicates better chipping resistance and longer tool life. The results are shown in the "Cutting Length" column of the "Cutting Test" section in Table 3.

[0261] [Table 3]

[0262]

[0263] <Discussion>

[0264] The cutting tool of Sample 3-1 corresponds to the Example. The cutting tool of Sample 3-2 corresponds to the Comparative Example. It was confirmed that Sample 3-1 (Example) had a longer cutting length, excellent chipping resistance, and longer tool life than Sample 3-2 (Comparative Example).

[0265] As described above, the embodiments and examples of the present disclosure have been described. However, it is initially intended that the configurations of the above-described embodiments and examples may be appropriately combined or various modifications may be made.

[0266] The embodiments and examples disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is not limited to the embodiments and examples described above, but is indicated by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0267] Explanation of symbols

[0268] 1 Film-forming apparatus, 2, 3 target, 4 substrate holder, 5 substrate, 6 substrate heater, 7, 8 power supply, 9 film-forming bias power supply, 10 gas supply port, 11 exhaust port, 20 hard carbon film, 21 interface layer, 30, 31 cutting tool, line segments a, b, c, d, B black area, S1 main surface of substrate, S2 surface of hard carbon film.

Claims

1. A cutting tool comprising: a substrate and a hard carbon film disposed on the substrate, When a cross section of the hard carbon film is observed using a high-angle scattering annular dark-field scanning transmission electron microscope, the area ratio of black regions having a circle-equivalent diameter of 10 nm or more is 0.7% or less. The hydrogen content of the hard carbon film is 5 atomic % or less, The area ratio of the black region of the hard carbon film is measured by the following method: (B1) cutting the cutting tool along the normal direction of the surface to produce a sample including a cross section of the hard carbon film, with the cutting position set at any 10 locations including the portion of the cutting tool involved in cutting, to produce 10 samples; (B2) A cross-section of each sample was observed using a high-angle scattering annular dark-field scanning transmission electron microscope at a magnification of 200,000 times to obtain a dark-field image; (B3) Designation of the hard carbon film in the resulting dark field image; (B4) A rectangular measurement field of view is set within the hard carbon film region in the dark field image. A pair of opposite sides of the rectangle are parallel to the main surface of the substrate on the hard carbon film side and are 800 nm in length. The distance between the opposite sides on the substrate side and the main surface of the substrate on the hard carbon film side is 30 nm, and the distance between the opposite sides on the surface side of the hard carbon film and the surface of the hard carbon film is 30 nm. When the main surface of the substrate on the hard carbon film side has irregularities, the main surface of the substrate on the hard carbon film side is set as follows: within the measurement field of view, a portion of the substrate where the amount of protrusion toward the hard carbon film side is the largest is designated, and a line is drawn through this portion parallel to the average line of the irregularities of the main surface of the substrate, and this line is defined as the main surface of the substrate on the hard carbon film side. When the surface of the hard carbon film has irregularities, the surface of the hard carbon film is defined as follows: a portion of the hard carbon film surface having the largest irregularities is specified in a measurement field, a line is drawn through the portion parallel to an average line of the irregularities on the hard carbon film surface, and the line is defined as the surface of the hard carbon film; (B5) The dark field image was processed using image analysis software and converted into a 256-grayscale monochrome image; (B6) in the monochromatic image, obtaining an average density within the measurement field, using the average density as a threshold value, and performing binarization processing on the monochromatic image; (B7) Particle analysis is performed on the binarized image to determine the area of black regions with an equivalent circular diameter of 10 nm or more, and the ratio of the area of black regions with an equivalent circular diameter of 10 nm or more to the total area of the measurement field of view is calculated; (B8) The area ratio of the black region is measured for each of the ten samples, and the average of the area ratios of the black regions measured for the ten samples is defined as the "area ratio of the black region of the hard carbon film." 2. The cutting tool according to claim 1, wherein The area ratio of the black region is 0% or more and 0.7% or less.

3. The cutting tool according to claim 2, wherein The area ratio of the black region is not less than 0% and not more than 0.5%.

4. The cutting tool according to claim 3, wherein The area ratio of the black region is 0% or more and 0.3% or less.

5. The cutting tool according to any one of claims 1 to 4, wherein: The hydrogen content is not less than 0 atomic % and not more than 5 atomic %.

6. The cutting tool according to claim 5, wherein The hydrogen content is not less than 0 atomic % and not more than 4 atomic %.

7. The cutting tool according to claim 6, wherein The hydrogen content is not less than 0 atomic % and not more than 2 atomic %.

8. The cutting tool according to any one of claims 1 to 4, wherein: The thickness of the portion of the hard carbon film involved in cutting is not less than 0.1 μm and not more than 3 μm.

9. The cutting tool according to any one of claims 1 to 4, wherein: The substrate is in contact with the hard carbon film.

10. The cutting tool according to any one of claims 1 to 4, comprising an interface layer disposed between the substrate and the hard carbon film, The interface layer comprises: At least one selected from the group consisting of: a single element selected from Group 1 consisting of Group 4 elements, Group 5 elements, Group 6 elements, Group 13 elements, and Group 14 elements excluding carbon of the periodic table, an alloy containing at least one element selected from the first group, a first compound containing at least one element selected from the first group, and a solid solution derived from the first compound; or a second compound composed of at least one element selected from the first group and carbon, and one or both of a solid solution derived from the second compound, The thickness of the interface layer is greater than or equal to 0.5 nm and less than or equal to 10 nm.

11. The cutting tool according to any one of claims 1 to 4, wherein: The carbon content of the hard carbon film is 95 atomic % or more, The hard carbon film is amorphous.

12. The cutting tool according to any one of claims 1 to 4, wherein: The hardness of the hard carbon film is 35 GPa or more and 75 GPa or less. The hardness is measured by nanoindentation.

13. The cutting tool according to claim 12, wherein The hardness is greater than or equal to 45 GPa and less than or equal to 73 GPa.

14. The cutting tool according to any one of claims 1 to 4, wherein: The substrate is made of WC-based hard alloy or metal ceramic.

15. The cutting tool according to any one of claims 1 to 4, wherein: The substrate is composed of cubic boron nitride.

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