Cutting Tools

Abstract

A cutting tool comprising a substrate and a coating disposed on the substrate, the coating being comprised of hexagonal W(C 1-a N a ) x wherein a is equal to or greater than 0.3 and equal to or less than 0.8, and x is equal to or greater than 0.8 and equal to or less than 1.2.

Description

[Technical field]

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

[0002] Various studies have been conducted with the aim of extending the life of cutting tools. JP 2022-095116 A (Patent Document 1) discloses a cutting tool having a substrate and a coating disposed on the substrate, the coating including a first layer made of metallic tungsten and hexagonal ditungsten carbide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-095116 Summary of the Invention

[0004] The cutting tool of the present disclosure comprises: 1. A cutting tool comprising a substrate and a coating disposed on the substrate, The coating is made of hexagonal W(C 1-a N a ) x A first layer consisting of The a is 0.3 or more and 0.8 or less, The cutting tool, wherein x is equal to or greater than 0.8 and equal to or less than 1.2. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view illustrating one embodiment of a cutting tool. [Diagram 2] FIG. 2 is a schematic enlarged cross-sectional view of an example of the cutting tool according to the first embodiment. [Diagram 3] FIG. 3 is a schematic enlarged cross-sectional view of another example of the cutting tool according to the first embodiment. [Figure 4]FIG. 4 is a schematic enlarged cross-sectional view of another example of the cutting tool according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] There is a demand for cutting tools that have a long tool life even in environments with high thermal loads, such as when turning titanium alloys.

[0007] Therefore, an object of the present disclosure is to provide a cutting tool having a long tool life, especially even under an environment of high thermal load such as during turning of titanium alloys.

[0008] [Effects of this disclosure] The cutting tool of the present disclosure can have a long tool life, especially in an environment of high thermal load such as during turning of titanium alloys.

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0010] (1) The cutting tool of the present disclosure comprises: 1. A cutting tool comprising a substrate and a coating disposed on the substrate, The coating is made of hexagonal W(C 1-a N a ) x A first layer consisting of The a is 0.3 or more and 0.8 or less, The cutting tool, wherein x is equal to or greater than 0.8 and equal to or less than 1.2.

[0011] The cutting tool of the present disclosure can have a long tool life, especially in an environment of high thermal load such as during turning of titanium alloys.

[0012] (2) In the above (1), in the X-ray diffraction spectrum of the first layer, a peak may exist in the range of a diffraction angle 2θ of 46.0° or more and 47.0° or less.

[0013] The peak in the range of the diffraction angle 2θ of 46.0° to 47.0° (hereinafter also referred to as the "first peak") is a peak caused by the (105) plane of hexagonal tungsten nitride. When the first peak is present in the X-ray diffraction spectrum of the first layer, the heat resistance of the coating is further improved.

[0014] (3) In the above (1) or (2), the first layer may have a thickness of 0.3 μm or more and 4.0 μm or less, thereby further improving the tool life.

[0015] (4) In any of (1) to (3) above, The coating further includes a second layer disposed on an opposite side of the first layer from the substrate, The second layer can be made of at least one element selected from a first group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum, and silicon of the periodic table, or a compound consisting of at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

[0016] This further improves the tool life.

[0017] (5) In any of (1) to (4) above, the coating further includes a third layer disposed between the substrate and the first layer; The third layer can be made of at least one element selected from a first group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum, and silicon of the periodic table, or a compound consisting of at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

[0018] This further improves the tool life.

[0019] (6) In any of (1) to (5) above, The substrate may include at least one selected from the group consisting of cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body, and the tool has excellent hardness and strength at high temperatures.

[0020] [Details of the embodiment of the present disclosure] A specific example of a cutting tool according to an embodiment of the present disclosure (hereinafter also referred to as the "present embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0021] In this specification, the expression in the form "A to B" means the upper and lower limits of a range (i.e., greater than or equal to A and less than or equal to B). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0022] In the present specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and is not necessarily limited to only those within the stoichiometric range.

[0023] [Embodiment 1: Cutting tool] A cutting tool according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. FIG. As shown in FIG. 2, a cutting tool 10 according to one embodiment of the present disclosure (hereinafter also referred to as “embodiment 1”) includes: A cutting tool comprising a substrate 11 and a coating 14 disposed on the substrate 11, The coating is made of hexagonal W(C 1-a N a ) x a first layer 12 consisting of The a is 0.3 or more and 0.8 or less, The cutting tool, wherein x is equal to or greater than 0.8 and equal to or less than 1.2.

[0024] The cutting tool of the present embodiment has a long tool life even in an environment of high thermal load, such as during turning of titanium alloys, for which the reason is presumably as follows.

[0025] The first layer is hexagonal W(C 1-a N a ) x Since the first layer contains C (carbon), the friction coefficient at the contact interface with the workpiece is reduced, and cutting resistance can be reduced. As a result, cutting tools that include the first layer have improved wear resistance and longer tool life.

[0026] The first layer contains nitrogen (N), which improves heat resistance compared to WC. As a result, cutting tools that contain the first layer have improved oxidation resistance and longer tool life in processes where the cutting edge becomes hot, such as dry cutting.

[0027] <Cutting tools> The cutting tool of this embodiment may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for milling, an indexable cutting tip for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.

[0028] FIG. 1 is a perspective view illustrating one embodiment of a cutting tool. A cutting tool having such a shape is used, for example, as an indexable cutting tip. The cutting tool 10 has a rake face 1, a flank face 2, and a cutting edge ridge 3 where the rake face 1 and the flank face 2 intersect. That is, the rake face 1 and the flank face 2 are surfaces that are connected to each other with the cutting edge ridge 3 in between. The cutting edge ridge 3 constitutes the cutting edge tip of the cutting tool 10. The shape of such a cutting tool 10 can also be understood as the shape of the base material of the cutting tool. That is, the base material has a rake face, a flank face, and a cutting edge ridge that connects the rake face and the flank face.

[0029] <Base material> The substrate of this embodiment can be any substrate known in the art.For example, the substrate is preferably selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide containing carbonitrides such as Cr, Ti, Ta, Nb in addition to WC, etc.), cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body (cBN sintered body) and diamond sintered body, and more preferably selected from the group consisting of cemented carbide, cermet and cBN sintered body.

[0030] In addition, when a cemented carbide is used as the substrate, the effect of this embodiment is exhibited even if such a cemented carbide contains free carbon or an abnormal phase called an η phase in the structure. The substrate used in this embodiment may have a modified surface. For example, in the case of a cemented carbide, a de-β layer may be formed on the surface, and in the case of a cermet, a surface hardened layer may be formed. Even if the surface is modified in this way, the effect of this embodiment is exhibited.

[0031] When the cutting tool is an indexable cutting tip (such as an indexable cutting tip for milling), the substrate may or may not have a chip breaker. The shape of the ridge of the cutting edge may be any of the following: sharp edge (the ridge where the rake face and the flank intersect), honing (shape in which a radius is added to the sharp edge), negative land (chamfered shape), and a combination of honing and negative land.

[0032] <Coating> The "coating" according to this embodiment has the effect of improving various properties of the cutting tool, such as chipping resistance and wear resistance, by covering at least a part of the substrate (for example, a part involved in cutting that comes into contact with the workpiece during cutting). The coating can cover at least the part involved in cutting. The coating may cover the entire surface of the substrate. Even if the configuration of the coating is partially different, it does not deviate from the scope of this embodiment. The part involved in cutting of the substrate means, for example, a region on the surface of the substrate that is within 50 μm from the cutting edge line. The coating may cover the entire surface of the part involved in cutting of the substrate. As long as the effect of the cutting tool of the present disclosure is not impaired, even if a coating is not formed on a part of the part involved in cutting of the substrate, it does not deviate from the scope of this embodiment.

[0033] The coating is hexagonal W(C 1-a N a ) x 2 is a schematic cross-sectional view of a cutting tool according to one aspect of this embodiment. As shown in FIG. 2, the first layer 12 may be provided directly on the substrate 11.

[0034] The coating may include other layers in addition to the first layer 12. The other layers include a third layer 15 disposed between the substrate 11 and the first layer 12 as shown in Fig. 4, and a second layer 13 provided on the side of the first layer 12 opposite the substrate 11 as shown in Figs. 3 and 4.

[0035] The thickness of the coating may be 0.3 μm or more and 10 μm or less, 0.5 μm or more and 10 μm or less, 1 μm or more and 6 μm or less, or 1.5 μm or more and 4 μm or less. If the thickness of the coating is less than 0.1 μm, the wear resistance tends to decrease. If the thickness of the coating is more than 10 μm, for example, when a large stress is applied between the coating and the substrate during interrupted processing, the coating tends to peel off or break frequently.

[0036] In this specification, the thickness of the coating refers to the sum of the thicknesses of the layers constituting the coating, such as the first layer, the second layer, and the third layer, which will be described later. The thickness of the coating is measured by measuring three arbitrary points on a cross-sectional sample parallel to the normal direction of the surface of the substrate using a transmission electron microscope (TEM) and averaging the thicknesses of the three measured points. An example of a transmission electron microscope is a spherical aberration corrector "JEM-2100F (trademark)" manufactured by JEOL Ltd. The thickness of each layer described later is also measured in the same manner unless otherwise specified.

[0037] <1st layer> The coating is hexagonal W(C 1-a N a ) x (wherein a is 0.3 or more and 0.8 or less, and x is 0.8 or more and 1.2 or less). 1-a N a ) x It is a hexagonal crystal structure of W(C 1-a N a ) x The hexagonal crystal structure of the first layer suppresses the diffusion reaction between the coating and the work material, reduces adhesion of the work material, and improves tool life. The first layer can improve the heat resistance, oxidation resistance, and wear resistance of the coating.

[0038] The first layer is made of hexagonal W(C 1-a N a ) x In addition, the first layer may contain unavoidable impurities. Examples of the unavoidable impurities include iron (Fe), calcium (Ca), zinc (Zn), sodium (Na), fluorine (F), nickel (Ni), molybdenum (Mo), and chromium (Cr). The content of the unavoidable impurities is preferably 0% by mass or more and 0.2% by mass or less with respect to the total mass of the first layer. The content of the unavoidable impurities is measured by glow discharge mass spectrometry. Similarly, the "second layer" and the "third layer" described later may contain unavoidable impurities to the extent that the effects of the cutting tool of the present disclosure are not impaired.

[0039] <Crystal structure of the first layer> The first layer is W(C 1-a N a ) x It can be confirmed by analysis using XRD measurement that the first layer is made up of W(C) having a hexagonal crystal structure. Specifically, an arbitrary region of the first layer is analyzed by irradiating the surface of each sample opposite to the substrate with X-rays, and X-ray diffraction measurement (XRD measurement) is performed. If both the peaks shown in JCPDS (ICDD) cards 01-076-7103 and 01-77-2001 are observed in the obtained XRD spectrum, and both the peaks shown in JCPDS (ICDD) cards 01-075-1012 and 00-042-0853 are not observed, the first layer is made up of W(C) having a hexagonal crystal structure. 1-a N a ) x It is confirmed that it consists of.

[0040] When the coating contains layers other than the first layer, such as a second layer, a third layer, or an intermediate layer, peaks derived from layers other than the first layer or from the substrate (hereinafter also referred to as "other peaks") may be detected in the XRD spectrum. In this case, the peak derived from the first layer is identified by the following method.

[0041] X-rays are irradiated onto the surface of the measurement sample opposite the substrate, and an XRD measurement is performed on the coating to obtain a diffraction pattern A. A layer on the surface side (X-ray irradiated side) of the measurement sample that is closer to the surface than the first layer is mechanically removed to expose the first layer. X-rays are irradiated onto the exposed surface of the first layer to obtain an XRD measurement on the first layer to obtain a diffraction pattern B. The first layer of the measurement sample is mechanically removed to expose a layer closer to the substrate than the first layer. X-rays are irradiated onto the surface of the exposed layer to obtain an XRD measurement on the exposed layer to obtain a diffraction pattern C. The peaks originating from the first layer are identified by comparing the diffraction patterns A, B, and C. In the present disclosure, the X-ray diffraction spectrum in which the peaks originating from the first layer have been identified by the above-mentioned procedure is referred to as the "X-ray diffraction spectrum of the first layer." line This is referred to as "diffraction spectrum."

[0042] Apparatuses used for the X-ray diffraction measurement include "SmartLab" (product name) manufactured by Rigaku Corporation and "X'pert" (product name) manufactured by PANalytical Corporation.

[0043] In this specification, the conditions for XRD measurement are as follows. (XRD measurement conditions) Scanning axis: 2θ-θ X-ray source: Cu-Kα ray (1.541862Å) Detector: 0-dimensional detector (scintillation counter) Tube voltage: 45kV Tube current: 40mA Incident optical system: Use of mirrors Receiving optical system: Use of analyzer crystal (PW3098 / 27) Step: 0.03° Accumulation time: 2 seconds Scan range (2θ): 10°~120°

[0044] In the X-ray diffraction spectrum of the first layer, a peak may be present in the range of diffraction angle 2θ of 46.0° or more and 47.0° or less. The peak in the range of diffraction angle 2θ of 46.0° or more and 47.0° or less (hereinafter also referred to as the "first peak") is a peak due to hexagonal tungsten nitride. When the first peak is present in the X-ray diffraction spectrum of the first layer, that is, when the first layer contains hexagonal tungsten nitride, diffusion between the coating and the workpiece is suppressed, and the heat resistance of the coating is further improved.

[0045] Furthermore, as far as the applicant has measured, it has been confirmed that, as long as the above analysis is performed on the same sample, there is almost no variation in the analysis results even if the measurement area is changed and the analysis is performed multiple times, and that setting the measurement area arbitrarily is not arbitrary.

[0046] <Composition of the first layer> The first layer is hexagonal W(C 1-a N a ) xwherein a is equal to or greater than 0.3 and equal to or less than 0.8, and x is equal to or greater than 0.8 and equal to or less than 1.2.

[0047] The lower limit of a is 0.3 or more, may be 0.4 or more, or may be 0.5 or more. The upper limit of a is 0.8 or less, may be 0.7 or less, or may be 0.6 or less. a may be 0.4 or more and 0.7 or less, or may be 0.5 or more and 0.6 or less.

[0048] The lower limit of x is 0.8 or more, and may be 0.9 or more. The upper limit of x is 1.2 or less, and may be 1.1 or less. stomach x may be 0.9 or more and 1.1 or less, or may be 1.0.

[0049] In this disclosure, "the first layer is a hexagonal W(C 1-a N a ) x "consisting of" means that the first layer is made of W(C 1-a N a ) x In addition to the above, inevitable impurities may be included. Examples of inevitable impurities include oxygen and carbon. 1 layer The total content of unavoidable impurities in 12 may be greater than 0 atomic % and less than 1 atomic %. In this disclosure, "atomic %" refers to the ratio (%) of the number of atoms to the total number of atoms constituting the layer.

[0050] The above a is measured by using electron energy loss spectroscopy (TEM-EELS). The specific measurement method is as follows.

[0051] The cutting tool is cut in a direction normal to the surface of the coating using an argon ion slicer to prepare a slice having a thickness of 3 to 100 nm including the cross section of the coating. The slice is observed at 100,000 to 1,000,000 times magnification using a transmission electron microscope (TEM, product name: "JEM-2100F / Cs", manufactured by JEOL Ltd.) to obtain a cross-sectional transmission image of the coating. The cross-sectional transmission image is subjected to electron energy loss spectroscopy (EELS) and scanned with an observation spot of 10 nm square to observe the energy loss curve associated with the excitation of carbon and nitrogen electrons. In the energy loss curve, the parallel intensity of 270 to 280 eV for carbon and 385 to 395 eV for nitrogen are defined as background intensity, and the ratio of the energy of carbon to that of nitrogen is calculated. This allows the above a to be obtained.

[0052] In this disclosure, the composition of the first layer W(C 1-a N a ) x In this case, the number of W atoms is A M1 The total number of C and N atoms for N1 Ratio of A N1 / A M1 is 0.8 or more and 1.2 or less. N1 / A M1 can be measured by the Rutherford backscattering (RBS) method. N1 / A M1 It has been confirmed that the effect of the present disclosure is not impaired if the amount is within the above range.

[0053] <Average thickness of first layer> The lower limit of the thickness of the first layer may be 0.2 μm or more. This suppresses the diffusion reaction between the first layer and the workpiece. The lower limit of the thickness of the first layer may be 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 0.9 μm or more. The upper limit of the thickness of the first layer may be 5.0 μm or less. This provides a coating with high hardness and good wear resistance. The upper limit of the thickness of the first layer may be 4.0 μm or less, 2.0 μm or less, or 1.5 μm or less. The thickness of the first layer may be 0.2 μm or more and 5.0 μm or less, 0.3 μm or more and 4.0 μm or less, 0.5 μm or more and 2.0 μm or less, or 0.7 μm or more and 1.5 μm or less.

[0054] <Second layer> As shown in Figures 3 and 4, the coating 14 can further include a second layer 13 provided on the side of the first layer 12 opposite the substrate 11. Here, "provided on the side of the first layer opposite the substrate" means that the second layer 13 is provided on the upper side (the side away from the substrate) of the first layer 12, and the first layer 12 and the second layer 13 do not need to be in contact with each other. In other words, another layer may be provided between the first layer 12 and the second layer 13. The second layer 13 may be provided directly on the first layer 12. The second layer 13 may be the outermost layer.

[0055] The second layer may be made of at least one element selected from the first group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si), or a compound consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon (C), nitrogen (N), oxygen (O) and boron (B). Examples of Group 4 elements include titanium (Ti), zirconium (Zr), hafnium (Hf), etc. Examples of Group 5 elements include vanadium (V), niobium (Nb), tantalum (Ta), etc. Examples of Group 6 elements include chromium (Cr), molybdenum (Mo), tungsten (W), etc. As long as the effect of the present disclosure is not impaired, the second layer may contain impurities in addition to at least one element selected from Group 1 or the above compound.

[0056] The second layer may consist of at least one element selected from Group 1A consisting of Cr, Al, Ti and Si, or a compound consisting of at least one element selected from Group 1A and at least one element selected from Group 2 consisting of carbon, nitrogen, oxygen and boron.

[0057] Examples of compounds constituting the second layer include AlTiBN, TiAlN, TiAlON, Al2O3, TiAlSiN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrON, AlCrSiN, AlCrBN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlVN, AlTiVN, TiB2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiCN, TiCON, ZrN, and ZrCN. These compounds can reduce the friction coefficient of the coating and extend the life of the cutting tool.

[0058] The thickness of the second layer may be 0.1 μm or more. When the thickness of the second layer is 0.1 μm or more, the lubricity imparting effect of the second layer is easily obtained. On the other hand, the upper limit of the thickness of the second layer is not particularly limited, but when it exceeds 2 μm, the above-mentioned lubricity imparting effect tends not to be further improved. Therefore, in consideration of the cost aspect, the thickness of the second layer may be 2 μm or less.

[0059] <3rd layer> 4, the coating 14 may further include a third layer 15 disposed between the substrate 11 and the first layer 12. This may increase the adhesion between the substrate 11 and the coating 14.

[0060] The third layer may be made of at least one element selected from the first group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si), or a compound consisting of at least one element selected from the first group and at least one element selected from the second group consisting of carbon (C), nitrogen (N), oxygen (O) and boron (B). Examples of Group 4 elements include titanium (Ti), zirconium (Zr), hafnium (Hf), etc. Examples of Group 5 elements include vanadium (V), niobium (Nb), tantalum (Ta), etc. Examples of Group 6 elements include chromium (Cr), molybdenum (Mo), tungsten (W), etc. As long as the effect of the present disclosure is not impaired, the third layer may contain impurities in addition to at least one element selected from Group 1 or the above compound.

[0061] The third layer can be composed of at least one element selected from Group 1A consisting of Cr, Al, Ti, and Si, or a compound consisting of at least one element selected from Group 1A and at least one element selected from Group 2 consisting of carbon, nitrogen, oxygen, and boron.

[0062] Examples of compounds constituting the third layer include TiWCN, TiN, TiAlN, TiAlON, Al2O3, TiAlSiN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrON, AlCrSiN, AlCrBN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlVN, AlTiVN, TiB2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiCN, TiCON, ZrN, and ZrCN.

[0063] The thickness of the third layer is not particularly limited as long as the effects of this embodiment are not impaired, and can be, for example, 0.1 μm or more and 2 μm or less.

[0064] <Middle Class> The coating may include an intermediate layer disposed between the second layer and the first layer or between the first layer and the third layer. Examples of intermediate layers include TiAlCeN, AlTiN, AlTiBN, AlTiSiN, AlTiYN, AlTiLaN, etc. The thickness of the intermediate layer may be 0.1 μm to 2 μm, 0.3 μm to 1.5 μm, or 0.4 μm to 1.0 μm.

[0065] [Embodiment 2: Manufacturing method of cutting tool] An example of a method for manufacturing the cutting tool of the first embodiment will be described below. The method for manufacturing the cutting tool according to this embodiment includes a first step of preparing a substrate and a second step of forming a coating on the substrate. The second step includes a step of forming a first layer. Each step will be described below.

[0066] <1st process> In the first step, a substrate is prepared. The substrate described in the first embodiment can be used.

[0067] When using a cemented carbide as the substrate, a commercially available substrate may be used, or the substrate may be manufactured by a general powder metallurgy method. When manufacturing by a general powder metallurgy method, WC powder and Co powder are mixed by a ball mill or the like to obtain a mixed powder. The mixed powder is dried and then molded into a predetermined shape to obtain a molded body. The molded body is further sintered to obtain a WC-Co-based cemented carbide (sintered body). Next, the sintered body is subjected to a predetermined cutting edge processing such as honing to manufacture a substrate made of a WC-Co-based cemented carbide. Substrates other than those mentioned above can also be prepared as long as they are conventionally known as substrates of this type.

[0068] <Second process> In the second step, a coating is formed on the substrate. The second step includes a step of forming a first layer. Examples of a method for forming the first layer include a physical vapor deposition method (PVD method).

[0069] Examples of physical vapor deposition methods include sputtering, ion plating, arc ion plating, electron ion beam deposition, etc. In particular, the use of cathodic arc ion plating or sputtering, which has a high ionization rate of the raw material element, is preferred because it enables metal or gas ion bombardment treatment of the substrate surface before forming the coating, thereby significantly improving the adhesion between the coating and the substrate.

[0070] When the first layer is formed by the arc ion plating method, the following conditions can be mentioned, for example. First, WC targets (for example, binderless WC with a composition containing 93 mass% or more of WC and a sintered target with a C content of 3 to 6.1 mass%) are set in two opposing arc-type evaporation sources in the device. The substrate temperature is set to 400 to 550°C, and the gas pressure in the device is set to 1.5 to 5.5 Pa.

[0071] As the gas, only nitrogen (N2) gas or a mixture of nitrogen gas and argon gas is introduced.

[0072] While maintaining the substrate (negative) bias voltage at 10 to 150 V and DC or pulse DC (frequency 20 to 50 kHz), an arc current of 80 to 150 A is supplied to the cathode electrode, and metal ions and the like are generated from the arc evaporation source to form a first layer on the substrate. The tungsten filament also discharges during film formation (emission current 30 to 45 A). This allows the ions in the plasma to be increased. An example of an apparatus used in the arc ion plating method is AIP (product name) manufactured by Kobe Steel, Ltd. The substrate temperature, gas pressure, bias voltage, frequency, arc current, and emission current during film formation are constant within the above ranges.

[0073] By forming the film under the above conditions, hexagonal W(C 1-a N a ) x(wherein a is 0.3 or more and 0.8 or less, and x is 0.8 or more and 1.2 or less). The above conditions were newly discovered by the present inventors as a result of extensive research. By adjusting the gas composition, gas pressure, arc current, and bias voltage within the above ranges, the composition of the first layer and the presence or absence of the first peak (peak in the range of diffraction angle 2θ of 46.0° or more and 47.0° or less) in the XRD spectrum of the first layer can be adjusted. For example, when the amount of nitrogen in the gas is large or the bias voltage is large, the ratio of carbon (C) in the coating tends to decrease. Also, when the gas pressure is low and the partial pressure of nitrogen is low, the first peak tends not to exist.

[0074] The second step may include a step of forming the first layer, as well as a step of surface treatment of the coating, such as grinding and shot blasting. The second step may also include a step of forming other layers, such as the second layer, the third layer, and an intermediate layer. The other layers may be formed by a conventionally known chemical vapor deposition method or physical vapor deposition method. From the viewpoint that the other layers can be formed continuously with the first layer in one physical vapor deposition apparatus, it is preferable to form the other layers by physical vapor deposition. EXAMPLES

[0075] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these.

[0076] <Cutting tool manufacturing> [Samples 1 to 22, Samples 101 to 105] <1st process> In the first step, a JIS standard K10 cemented carbide (shape: JIS standard CNMG120408) was prepared as a substrate. Next, the substrate was set at a predetermined position in an arc ion plating device (manufactured by Kobe Steel, Ltd., product name: AIP).

[0077] <Second process> In the second step, a coating including a first layer was formed on the substrate by arc ion plating to obtain each sample cutting tool. The first layer was formed by the following method. First, WC targets (binderless WC with a composition containing 93 mass% or more of WC and a sintered target with a C content of 3 to 6.1 mass%) were set in two opposing arc-type evaporation sources in the device. The substrate temperature was set to 400 to 550°C, and the gas pressure in the device was set to 1.5 to 5.5 Pa.

[0078] As the gas, only nitrogen (N2) gas or a mixture of nitrogen gas and argon gas was introduced.

[0079] In Samples 1 to 22, the substrate (negative) bias voltage was maintained at 10 to 150 V and DC or pulse DC (frequency 20 to 50 kHz), and an arc current of 80 to 150 A was supplied to the cathode electrode to generate metal ions and the like from the arc-type evaporation source, forming a first layer on the substrate. A tungsten filament was also discharged during film formation (emission current 30 to 45 A). The substrate temperature, gas pressure, bias voltage, frequency, and emission current during film formation were kept constant within the above ranges. In each sample, the gas composition, gas pressure, arc current, and bias voltage were adjusted within the above ranges to adjust the composition of the first layer and the presence or absence of the first peak in the XRD spectrum of the first layer (a peak in the range where the diffraction angle 2θ is 46.0° or more and 47.0° or less).

[0080] In sample 20, a third layer was provided between the substrate and the first layer. The third layer was formed directly on the substrate by the following procedure before the formation of the first layer. A target (sintered target) containing the metal composition in the column for the composition of the third layer in Table 1 was set in the arc-type evaporation source of the arc ion plating device. Next, the substrate temperature was set to 600°C, and the gas pressure in the device was set to 3.5 Pa. A mixed gas of nitrogen gas, methane gas, and argon gas was introduced as the reactive gas. Then, an arc current of 130 A was supplied to the cathode electrode. The third layer was formed to the thickness listed in Table 1 by generating metal ions and the like from the arc-type evaporation source by supplying the arc current.

[0081] In sample 19, a second layer was provided on the first layer. The second layer was formed directly on the first layer after the formation of the first layer by the following procedure. A target (sintered target) containing the metal composition in the column of the composition of the second layer in Table 1 was set in the arc type evaporation source of the arc ion plating device. Next, the substrate temperature was set to 550°C and the gas pressure in the device was set to 4.0 Pa. Nitrogen was introduced as the reactive gas. Then, an arc current of 150 A was supplied to the cathode electrode. The second layer was formed to the thickness listed in Table 1 by generating metal ions and the like from the arc type evaporation source by supplying the arc current.

[0082] For Sample 101, the gas pressure was set to 1.0 Pa, a mixed gas of nitrogen gas and argon gas was introduced, the bias voltage was set to 100 V, and the other conditions were the same as for Samples 1 to 22 when the film was formed.

[0083] For samples 102 and 103, the gas pressure was set to 1.0 Pa, and only nitrogen gas was introduced. 1-a N a ) x The arc current and bias voltage were changed so that a and x in the above were the values ​​shown in Table 1, and the other conditions were the same as those for Samples 1 to 22.

[0084] For sample 104, the gas pressure was set to 4.0 Pa, a mixed gas of nitrogen gas and argon gas was introduced, the bias voltage was set to 200 V, the arc current was set to 150 A, and the other conditions were the same as for samples 1 to 22 when the film was formed.

[0085] For Sample 105, the gas pressure was set to 5.0 Pa, a mixed gas of nitrogen gas and argon gas was introduced, the bias voltage was set to 500 V, the arc current was set to 190 A, and the other conditions were the same as for Samples 1 to 22 when the film was formed.

[0086] [Sample 106] A substrate identical to that of Sample 1 was prepared, and a coating was formed on the substrate in the same manner as that of Sample 15 of Patent Document 1 to obtain a cutting tool of Sample 106.

[0087] <Evaluation of cutting tool characteristics> For each sample cutting tool, the crystal structure of the first layer, the presence or absence of the first peak, the composition of the first layer, and the thickness of each layer were evaluated.

[0088] <Crystal structure of the first layer and presence or absence of the first peak> The crystal structure of the first layer of each sample was identified by XRD. The specific measurement method is described in the first embodiment, and therefore the description will not be repeated. The results are shown in the "Crystal Structure" column of "First Layer" in Table 1.

[0089] The notation "hexagonal" in the "Crystal Structure" column indicates that the first layer does not contain tungsten carbide or tungsten nitride, which have a cubic crystal structure, and that the first layer is a hexagonal W(C 1-a N a ) x It indicates that it consists of.

[0090] The notation "Hexagonal + Cubic" in the "Crystal Structure" column indicates that the first layer contained a mixture of hexagonal tungsten nitride (hexagonal WN), hexagonal tungsten carbide (hexagonal WC), and at least one of cubic WN and W3C. If at least one of the peaks shown in JCPDS (ICDD) Card 01-075-1012 (WN) and 00-042-0853 (W3C) is observed in the XRD spectrum of the first layer, the first layer contains a cubic crystal structure.

[0091] The “W+hW2C” in the “Crystal Structure” column for Sample 106 indicates that the first layer is composed of metallic tungsten and hexagonal ditungsten carbide.

[0092] In the X-ray diffraction spectrum of the first layer obtained for each sample, it was confirmed whether or not a peak was present in the range of diffraction angle 2θ of 46.0° to 47.0°. The results are shown in the "XRD spectrum first peak" column of "First layer" in Table 1. "Present" indicates that the first peak was present, and "Absent" indicates that the first peak was not present.

[0093] <Composition of the 1st, 2nd and 3rd layers> The composition of the first layer of each sample was measured using electron energy loss spectroscopy (TEM-EELS) and Rutherford backscattering (RBS). When the second and third layers were formed, their compositions were also measured. The specific measurement method is described in the first embodiment, and therefore the description will not be repeated. The results are shown in Table 1 under "First layer (W(C 1-a N a ) x )” column, the “Composition” column of the “2nd Layer” and the “Composition” column of the “3rd Layer”.

[0094] <Thickness of each layer> The thicknesses of the first layer, the second layer, the third layer, and the coating were measured using a transmission electron microscope (TEM) (manufactured by JEOL Ltd., product name: JEM-2100F). The specific measurement method is described in embodiment 1, so the description will not be repeated. The results are shown in the "Thickness" column of each layer in Table 1.

[0095] In Table 1, the notation "-" next to "Second Layer" and "Third Layer" indicates that the corresponding layer is not present in the coating.

[0096] [Table 1]

[0097] <Cutting test> Using each sample cutting tool, the cutting time (tool life) was measured under the following cutting conditions until the cutting tool was chipped or the flank wear amount reached 0.15 mm. The results are shown in the "Tool life" column of "Cutting test" in Table 2.

[0098] <Cutting conditions> Work material (material): Ti-6Al-4V Speed:V70m / min Feed: 0.2mm / rev Cutting depth: 1mm The above cutting conditions apply to turning of titanium alloys, and high thermal loads are applied to the cutting tool during machining.

[0099] [Table 2]

[0100] The cutting tools of Samples 1 to 22 correspond to Examples, and the cutting tools of Samples 101 to 106 correspond to Comparative Examples. From the results of the cutting tests, it was confirmed that the cutting tools of Samples 1 to 22 have a longer tool life than the cutting tools of Samples 101 to 106 even under an environment of high thermal load.

[0101] Although the embodiments and examples of the present invention have been described above, it is also intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0102] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0103] 1 cutting face, 2 flank face, 3 cutting edge portion, 10 cutting tool, 11 base material, 12 first layer, 13 second layer, 14 coating, 15 third layer.

Claims

1. 1. A cutting tool comprising a substrate and a coating disposed on the substrate, The coating is made of hexagonal W(C １－ａ N ａ ) ｘ A first layer consisting of The a is 0.3 or more and 0.8 or less, The cutting tool, wherein x is equal to or greater than 0.8 and equal to or less than 1.

2.

2. 2. The cutting tool according to claim 1, wherein an X-ray diffraction spectrum of the first layer has a peak in a diffraction angle 2θ range of 46.0° or more and 47.0° or less.

3. The cutting tool according to claim 1 or 2, wherein the first layer has an average thickness of 0.3 μm or more and 4.0 μm or less.

4. The coating further includes a second layer disposed on an opposite side of the first layer from the substrate, 3. The cutting tool according to claim 1, wherein the second layer is made of at least one element selected from a first group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound containing at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

5. the coating further includes a third layer disposed between the substrate and the first layer; 3. The cutting tool according to claim 1, wherein the third layer is made of at least one element selected from a first group consisting of Group 4 elements, Group 5 elements, Group 6 elements of the periodic table, aluminum, and silicon, or a compound containing at least one element selected from the first group and at least one element selected from a second group consisting of carbon, nitrogen, oxygen, and boron.

6. 3. The cutting tool according to claim 1, wherein the substrate comprises at least one material selected from the group consisting of cemented carbide, cermet, high speed steel, ceramics, a cubic boron nitride sintered body, and a diamond sintered body.

Images