cutting tools

Abstract

A cutting tool comprising a substrate and a coating disposed on the substrate, the coating including a first layer, the first layer comprising a plurality of hard particles, the hard particles comprising titanium, silicon, carbon, and nitrogen, the hard particles having a cubic crystal structure, the first layer having a columnar structure, and a number N of titanium atoms in the first layer. Ti and the number of silicon atoms, N Si The number of silicon atoms N Si Ratio of N Si / (N Ti +N Si ) is 0.010 or more and 0.10 or less, the hard particles have a lamellar structure in which the silicon content changes periodically, and the results obtained by performing line analysis of the hard particles along the lamellar structure stacking direction using an energy dispersive X-ray spectrometer attached to a transmission electron microscope are plotted as follows: the X axis represents the distance from an arbitrary point P1 in the hard particle, and the Y axis represents the ratio N Si / (N Ti +N Si ), the ratio N Si / (N Ti +N Si ) includes, along the positive direction of the X-axis, a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and an average of the second minimums is greater than an average of the first minimum and the third minimum.

Description

[Technical Field]

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

[0002] Conventionally, cutting tools have been developed in which a TiSiCN film is formed on a substrate in order to improve the wear resistance of cutting tools (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 230363 Summary of the Invention

[0004] A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating disposed on the substrate, the coating including a first layer, the first layer being composed of a plurality of hard particles, the hard particles being composed of titanium, silicon, carbon, and nitrogen, the hard particles having a cubic crystal structure, the first layer being a columnar structure, and the number of titanium atoms in the first layer being N Ti and the number of silicon atoms, N Si The number of silicon atoms N Si Ratio of N Si / (N Ti +N Si ) is 0.010 or more and 0.10 or less, the hard particles have a lamellar structure in which the silicon content changes periodically, and the results obtained by performing line analysis of the hard particles along the lamellar structure stacking direction using an energy dispersive X-ray spectrometer attached to a transmission electron microscope are plotted as follows: the X axis represents the distance from an arbitrary point P1 in the hard particle, and the Y axis represents the ratio N Si / (N Ti +N Si ), the ratio N Si / (N Ti +N Si) includes, along the positive direction of the X-axis, a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and an average of the second minimums is greater than an average of the first minimum and the third minimum. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic view showing an example of a cross section of a cutting tool according to a first embodiment. [Figure 2] FIG. 2 is a schematic view showing another example of a cross section of the cutting tool according to the first embodiment. [Figure 3] FIG. 3 is a schematic view showing another example of a cross section of the cutting tool according to the first embodiment. [Figure 4] FIG. 4 is a schematic view showing another example of a cross section of the cutting tool according to the first embodiment. [Figure 5] FIG. 5 is an example of a first graph obtained in the cutting tool according to the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view of an example of a CVD apparatus used in the method for manufacturing a cutting tool according to the second embodiment. [Figure 7] FIG. 7 is an enlarged view of region VII in FIG. [Figure 8] FIG. 8 is a cross-sectional view of the nozzle 56 taken along line XVII-XVII of FIG. [Figure 9] FIG. 9 is a cross-sectional view of the nozzle used in Sample 1-3. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] Cutting tools with a high-hardness TiSiCN film have excellent wear resistance. However, when such cutting tools are used to perform intermittent cutting of chromium-molybdenum steel (SCM435), the tool life may be shortened due to damage to the coating. Therefore, there is a demand for cutting tools that can have a long tool life, especially when used for intermittent cutting of chromium-molybdenum steel.

[0007] Therefore, an object of the present disclosure is to provide a cutting tool that can have a long tool life, particularly when used for interrupted cutting of chromium-molybdenum steel.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide a cutting tool that can have a long tool life, particularly when used for interrupted cutting of chromium-molybdenum steel.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating disposed on the substrate, the coating including a first layer, the first layer being composed of a plurality of hard particles, the hard particles being composed of titanium, silicon, carbon, and nitrogen, the hard particles having a cubic crystal structure, the first layer being a columnar structure, and the number of titanium atoms in the first layer being N Ti and the number of silicon atoms, N Si The number of silicon atoms N Si Ratio of N Si / (N Ti +N Si ) is 0.010 or more and 0.10 or less, the hard particles have a lamellar structure in which the silicon content changes periodically, and the results obtained by performing line analysis of the hard particles along the lamellar structure stacking direction using an energy dispersive X-ray spectrometer attached to a transmission electron microscope are plotted as follows: the X axis represents the distance from an arbitrary point P1 in the hard particle, and the Y axis represents the ratio N Si / (N Ti +N Si ), the ratio N Si / (N Ti +N Si ) includes, along the positive direction of the X-axis, a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and an average of the second minimums is greater than an average of the first minimum and the third minimum.

[0010] According to the present disclosure, it is possible to provide a cutting tool that can have a long tool life, particularly when used for interrupted cutting of chromium-molybdenum steel.

[0011] (2) In the above (1), the periodic width of the first graph in the direction along the X-axis may be 3 nm or more and 20 nm or less, which further improves the tool life.

[0012] (3) In the above (1) or (2), the difference between the average of the first maximum value and the second maximum value and the average of the second minimum value may be 0.005 or more and 0.040 or less, thereby further improving the tool life.

[0013] (4) In any one of the above (1) to (3), the thickness of the first layer may be 1.0 μm or more and 15 μm or less, thereby further improving the tool life.

[0014] (5) In any of the above (1) to (4), the coating may include a second layer disposed between the substrate and the first layer, and the second layer may include at least one layer selected from the group consisting of a TiN layer, a TiC layer, a TiCN layer, a TiBN layer, a TiCNO layer, and an Al2O3 layer.

[0015] This further improves the tool life.

[0016] (6) In any of the above (1) to (5), the coating includes a third layer disposed on the outermost surface of the coating, and the third layer may be a TiN layer, a TiC layer, a TiCN layer, a TiBN layer, a TiCNO layer, or an Al2O3 layer.

[0017] This makes it easier to identify the used portion of the cutting tool after cutting, and further improves the tool life.

[0018] [Details of the embodiments of the present disclosure] The cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals 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.

[0019] In the present disclosure, the notation in the form "A to B" means greater than or equal to A and less than or equal to B, and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same.

[0020] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0021] In this disclosure, when one or more numerical values ​​are listed as the lower limit and upper limit of a numerical range, the combination of any one numerical value listed in the lower limit and any one numerical value listed in the upper limit is also disclosed.

[0022] In this disclosure, "comprises," "includes," "has," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even a configuration expressed in closed terms may include additional elements that are normally incidental impurities or unrelated to the subject technology.

[0023] [Embodiment 1: Cutting tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described with reference to Figures 1 to 4. The cutting tool 1 of the present embodiment is a cutting tool 1 including a substrate 10 and a coating disposed on the substrate 10, the coating 15 including a first layer 11, the first layer 11 being made of a plurality of hard particles, the hard particles being made of titanium, silicon, carbon, and nitrogen, the hard particles having a cubic crystal structure, the first layer 11 having a columnar structure, and the number of titanium atoms N in the first layer 11 being 0. Ti and the number of silicon atoms, N Si The number of silicon atoms, N, Si Ratio of N Si / (N Ti +N Si ) is 0.010 or more and 0.10 or less, and the hard particles have a lamellar structure in which the silicon content changes periodically. The results obtained by performing line analysis of the hard particles along the lamellar structure stacking direction using an energy dispersive X-ray spectrometer attached to a transmission electron microscope are shown in the form of a graph in which the X axis represents the distance from an arbitrary point P1 in the hard particle and the Y axis represents the ratio N Si / (N Ti +N Si ), the ratio N Si / (N Ti +N Si ) includes, along the positive direction of the X-axis, a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and the average of the second minimums is greater than the average of the first minimum and the third minimum.

[0024] The cutting tool of this embodiment has a long tool life, especially when used for interrupted cutting of chromium-molybdenum steel. The reason for this is not clear, but is presumed to be as follows.

[0025] (i) In the cutting tool of this embodiment, the coating includes a first layer made of a plurality of hard particles. The hard particles are made of titanium, silicon, carbon, and nitrogen and have a cubic crystal structure, so that the first layer has high hardness. Therefore, the cutting tool has excellent wear resistance.

[0026] (ii) The hard particles of the cutting tool of this embodiment have a lamellar structure in which the silicon content changes periodically, which causes lattice distortion due to the change in silicon content within the hard particles, and even if cracks occur during cutting, the propagation of the cracks in the lamellar structure is suppressed.

[0027] (iii) In the first graph of the hard particles of the cutting tool of this embodiment, the ratio N Si / (N Ti +N Si ) along the positive direction of the X-axis includes a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and the average of the second minimum is greater than the average of the first minimum and the third minimum. The presence of the second minimum makes the ratio N Si / (N Ti +N Si ) is relatively smallest at the first and third minimums, and the ratio N Si / (N Ti +N Si ) is relatively large, the lattice strain due to the difference between the first maximum and the second maximum is moderately alleviated, and the propagation of cracks in the direction perpendicular to the lamellar structure stacking direction is suppressed. Therefore, the cutting tool has excellent fracture resistance.

[0028] <Cutting tools> As shown in FIG. 1, the cutting tool 1 of this embodiment includes a substrate 10 and a coating 15 disposed on the substrate 10. FIG. 1 illustrates a case in which the coating 15 is composed only of a first layer 11. The coating 15 may cover at least a portion of the substrate that is involved in cutting, or may cover the entire surface of the substrate. The portion of the substrate that is involved in cutting refers to an area on the substrate surface that is within 500 μm of the cutting edge ridge. As long as the effects of the present disclosure are not impaired, it does not depart from the scope of the present disclosure even if a portion of the substrate is not coated with a coating or the coating configuration is partially different.

[0029] <Types of cutting tools> The cutting tool of the present disclosure may be, for example, a drill, an end mill (e.g., a ball end mill), an indexable cutting insert for a drill, an indexable cutting insert for an end mill, an indexable cutting insert for milling, an indexable cutting insert for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.

[0030] <Base material> In this embodiment, the substrate can be a conventionally known material. For example, the substrate can be made of cemented carbide (for example, a WC-based cemented carbide containing tungsten carbide and cobalt, which can contain carbonitrides of Ti, Ta, Nb, 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, or diamond sintered body.

[0031] The substrate is made of a cemented carbide containing tungsten carbide and cobalt, and the cobalt content in the cemented carbide may be 5% by mass or more and 11% by mass or less. This provides an excellent balance of hardness and strength at high temperatures, and has excellent properties as a substrate for cutting tools for the above-mentioned applications. When a WC-based cemented carbide is used as the substrate, its structure may contain free carbon and abnormal phases called η phase or ε phase.

[0032] The surface of the substrate may be modified. For example, in the case of cemented carbide, a de-β layer may be formed on the surface, and in the case of cermet, a surface-hardened layer may be formed. Even if the surface of the substrate is modified, the desired effect can be achieved.

[0033] When the cutting tool is an indexable cutting insert, the substrate may or may not have a chip breaker. The shape of the cutting edge ridge can be any of a sharp edge (the ridge where the rake face and the flank intersect), a honed edge (a sharp edge with a radius), a negative land (a chamfered edge), or a combination of a honed edge and a negative land.

[0034] <Coating> <Coating composition> In this embodiment, the coating includes a first layer. The coating of this embodiment may include other layers as long as it includes the first layer.

[0035] As shown in FIG. 2, the coating 15 of the cutting tool 1 may include a second layer 12 disposed between the substrate 10 and the first layer 11 .

[0036] As shown in FIG. 3, the coating 15 of the cutting tool 1 may include a third layer 13 disposed on the outermost surface of the coating 15 .

[0037] The first, second and third layers will be described in detail below.

[0038] <Coating thickness> In this embodiment, the thickness of the coating may be 1 μm or more and 30 μm or less. Here, the thickness of the coating refers to the thickness of the entire coating. When the thickness of the entire coating is 1 μm or more, excellent wear resistance can be obtained. On the other hand, when the thickness of the entire coating is 30 μm or less, peeling or breakage of the coating can be suppressed when a large stress is applied between the coating and the substrate during cutting. The thickness of the entire coating may be 5 μm or more and 25 μm or less, or 8 μm or more and 20 μm or less.

[0039] In the present disclosure, the thickness of a coating is measured by the following procedure: A cutting tool is cut into a cross section parallel to the normal direction of the surface to obtain a measurement sample with the cross section of the coating exposed. The measurement sample is observed with a scanning transmission electron microscope (STEM) to measure the thickness of the coating. The measurement sample is a thin section sample processed using an ion slicer or the like. An example of a scanning transmission electron microscope is the JEM-2100F (trademark) manufactured by JEOL Ltd. The measurement conditions are an acceleration voltage of 200 kV and a current of 0.3 nA.

[0040] The measurement sample was observed at a magnification of 10,000x, and a rectangular measurement field of view was set in the electron microscope image, with a length parallel to the cutting tool surface of 100 μm and a length equal to or greater than the entire thickness of the coating. The thickness of the coating was measured at 10 points within the field of view, and the average value was taken as the "coating thickness." The thickness (average thickness) of each layer described below was also measured and calculated in the same manner.

[0041] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the selected location of the measurement field is changed arbitrarily and measurements are performed multiple times.

[0042] <First layer> <Composition of the first layer> In this embodiment, the first layer is made of a plurality of hard particles, and the hard particles are made of titanium, silicon, carbon, and nitrogen. In the first layer of this embodiment, the number of titanium atoms N Ti and the number of silicon atoms, N Si The number of silicon atoms, N, Si Ratio of N Si / (N Ti +N Si ) is between 0.010 and 0.10. Si / (N Ti +N Si When the average of N is 0.010 or more, the wear resistance is improved. Si / (N Ti +N Si ) is 0.10 or less, good welding resistance can be obtained.

[0043] N Si / (N Ti +N Si ) may be 0.02 or more and 0.09 or less, or 0.02 or more and 0.07 or less, or 0.02 or more and 0.05 or less.

[0044] In the present disclosure, N in the first layer Si / (N Ti +N Si The average of is measured by the following procedure.

[0045] (A1) The cutting tool is cut with a diamond wire along the normal to the surface of the cutting tool to expose the cross section of the first layer. The exposed cross section is then subjected to focused ion beam processing (hereinafter also referred to as "FIB processing") to make the cross section mirror-finished.

[0046] (A2) A rectangular analysis is performed on the cross section of the first layer using an energy dispersive X-ray spectroscope (EDX) (TEM-EDX) attached to a transmission electron microscope (TEM) to identify the composition of the first layer. The rectangular analysis is performed on three non-overlapping rectangular measurement areas of 0.5 μm × 2 μm set in the cross section of the first layer. In each of the three measurement areas, N Si / (N Ti +N Si ) is calculated from the three measurement areas. Si / (N Ti +N Si ) is calculated. The average is calculated based on the N Si / (N Ti +N Si ) corresponds to the average.

[0047] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the selected location of the measurement field is changed arbitrarily and measurements are made multiple times.

[0048] <First Layer Organization> In this embodiment, the first layer has a columnar structure. This makes the first layer resistant to shear stress and improves wear resistance. Furthermore, the first layer has fewer grain boundaries in the direction perpendicular to the film thickness, which reduces fracture origins and improves chipping resistance.

[0049] In the present disclosure, the first layer having a columnar structure means that the percentage (N1 / N)×100 of the number N1 of first hard particles having an aspect ratio of 3 or more to the number N of all hard particles constituting the first layer is 60% or more. Specifically, the columnar structure of the first layer can be confirmed by the following procedure.

[0050] (B1) The cutting tool is cut with a diamond wire along the normal to the surface of the cutting tool to expose the cross section of the first layer. The exposed cross section is then subjected to FIB processing to create a mirror-finished cross section.

[0051] (B2) The FIB-processed cross section is subjected to EBSD analysis under the following measurement conditions using a field emission scanning electron microscope (FE-SEM) (product name: "SUPRA35VP", manufactured by Carl Zeiss) equipped with an electron backscatter diffraction (EBSD) device. The regions where EBSD analysis is performed (hereinafter also referred to as analysis regions) are three non-overlapping rectangular regions provided within the first layer. The size of the analysis regions is a rectangle with a length of 20 μm or more in the direction parallel to the substrate. The length of the analysis regions in the thickness direction of the coating can be set appropriately depending on the thickness of the first layer. The length of the analysis regions in the thickness direction of the coating is set, for example, to be 90% or more of the thickness of the first layer. (Measurement conditions) Accelerating voltage: 15 kV Current value: 1.8nA Probe current: 60 μm (with HC) Exp:Long 0.03s Binning: 8×8 WD: 15mm Tilt: 70° Step size: 0.02 μm BKD :Background Subtraction, Dynamic Background Subtraction, Normalize Intensity Histogram Magnification: 20,000x Grain boundary definition: 15° or more

[0052] (B3) For data collected by EBSD analysis, a cleanup process is performed by using the CI Dilation method (single Interaction) and Grain CI Standardization to identify only data that satisfy CI > 0.1. The CI value is calculated using the Voting method. Specifically, it is calculated as CI = (V1 - V2) / Videal (V1, 2: 1, second solution, Videal: ideal solution).

[0053] (B4) The EBSD analysis results were analyzed using commercially available software (product name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.), and an IPF map (Inverse Pole Graph) of the analysis area was obtained. F An IPF map (inverse pole figure orientation map) is created. In creating the IPF map, a grain boundary is defined as a misorientation angle of 15° or more between adjacent measurement points. The IPF map shows the shape of each grain and the orientation of each grain, using different colors.

[0054] (B5) The above software ("O IM 7.1") is used to measure the aspect ratio of each of all hard particles in the IPF map of each analysis region. The aspect ratio of a hard particle is the ratio b / a of the long diameter a to the short diameter b of the hard particle. In the present disclosure, the long diameter a is the maximum diameter across of the hard particle observed in the cross section, and the short diameter b is the maximum diameter of the hard particle along a direction perpendicular to the long diameter a. In the present disclosure, hard particles in the IPF map of the analysis region include both hard particles whose entirety exists in the IPF map of the analysis region and hard particles whose at least a portion exists in the IPF map of the analysis region.

[0055] (B6) Calculate the percentage (n1 / n) × 100 of the number n1 of first hard particles with an aspect ratio of 3 or more relative to the number n of all hard particles in the IPF map of each analysis region. In the present disclosure, the average of the percentages (n1 / n) × 100 in the IPF maps of three analysis regions corresponds to the percentage (N1 / N) × 100 of the number N1 of first hard particles with an aspect ratio of 3 or more relative to the number N of all hard particles constituting the first layer. If the percentage (N1 / N) × 100 is 60% or more, it is confirmed that the first layer has a columnar structure.

[0056] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if measurements are made multiple times by changing the cutting tool cut-out position or measurement area.

[0057] <Hard particles> <Hard particle composition> In this embodiment, the hard particles are composed of titanium, silicon, carbon, and nitrogen. The hard particles may contain inevitable impurity elements in addition to titanium, silicon, carbon, and nitrogen, as long as the effects of the present disclosure are not impaired. The hard particles may be composed of titanium, silicon, carbon, nitrogen, and inevitable impurity elements. Examples of inevitable impurity elements include chlorine, cobalt, tungsten, and oxygen. The content of inevitable impurity elements in the hard particles may be, for example, 0.5 atomic % or less. The content of inevitable impurity elements in the hard particles is measured by TEM-EDX.

[0058] <Crystal structure of hard particles> In this embodiment, the hard particles have a cubic crystal structure. When the hard particles have a cubic crystal structure, the first layer can have both excellent wear resistance and high toughness. The fact that the hard particles have a cubic crystal structure can be confirmed by pattern analysis of selected area electron diffraction.

[0059] <First graph> In this embodiment, the hard particles have a lamellar structure in which the silicon content changes periodically. The results obtained by performing line analysis of the hard particles along the lamellar structure stacking direction using an energy dispersive X-ray spectrometer (TEM-EDX) attached to a transmission electron microscope are plotted as follows: the X axis is the distance from an arbitrary point P1 in the hard particle, and the Y axis is the ratio N Si / (N Ti +N Si ), the ratio N Si / (N Ti +N Si ) includes a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum along the positive direction of the X-axis, and the average of the second minimum is greater than the average of the first minimum and the third minimum. The first minimum, the first maximum, the second minimum, the second maximum, and the third minimum are each in the ratio N Si / (N Ti +N Si The first graph is obtained by the following procedure.

[0060] (C1) The cutting tool is cut with a diamond wire along the normal to the surface of the cutting tool to expose the cross section of the first layer. The exposed cross section is then subjected to FIB processing to create a mirror finish.

[0061] (C2) The FIB-processed cross section is observed using a bright-field scanning electron microscope (BF-SEM) to identify a single hard particle. Next, a BF-STEM image of the identified single hard particle is obtained.

[0062] (C3) In the BF-STEM image, the measurement area (size: 100 nm × 100 nm) is set to include a region where 10 or more layers of white layers (hereinafter also referred to as "white layers") and black layers (hereinafter also referred to as "black layers") are stacked. The white layers are regions with a low silicon content. The black layers are regions with a high silicon content.

[0063] (C4) The stacking direction of the white layer and the black layer is identified within the measurement region in the BF-STEM image. Specifically, the electron beam diffraction pattern of the selected visual field region is superimposed on the stacking orientation of the white layer and the black layer, and the stacking direction is identified from the orientation indicated by the diffraction spots. This stacking direction corresponds to the stacking direction of the lamellar structure.

[0064] (C5) In the measurement area in the BF-STEM image, line analysis is performed along the lamellar structure stacking direction using TEM-EDX to measure the composition. The beam diameter for line analysis is 0.5 nm or less, the scan interval is 0.5 nm, and the line length is 50 nm.

[0065] (C6) The results of the line analysis are shown as follows: the X axis is the distance from an arbitrary point P1 within the hard particle, and the Y axis is the ratio N Si / (N Ti +N Si ) to create the first graph.

[0066] In the first graph, if maximum and minimum values ​​alternate with an increase in distance from point P1, the hard particles are determined to have a lamellar structure in which the silicon content changes periodically.

[0067] 5 is an example of a first graph obtained in this embodiment. In the first graph of FIG. 5, the X axis represents the distance from an arbitrary point P1 in the hard particle, and the Y axis represents the ratio N Si / (N Ti +N Si ) is shown. As shown in the first graph of FIG. 5, the first graph obtained in this embodiment shows the ratio N Si / (N Ti +N Si ) are relatively smallest among the minimum values ​​a1 to a8, and among the minimum values ​​a1 to a8, the intervals d1 to d7 between adjacent minimum values ​​are each smaller than the ratio N Si / (N Ti +N Si ) corresponds to one period.

[0068] Ratio N Si / (N Ti +N Si) includes a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum along the positive direction of the X-axis. For example, the ratio N Si / (N Ti +N Si ) includes, along the positive direction of the X-axis, a minimum value a1, a maximum value b1, a minimum value c1, a maximum value b2, and a minimum value a2. The minimum value a1 corresponds to the first minimum value, the maximum value b1 corresponds to the first maximum value, the minimum value c1 corresponds to the second minimum value, the maximum value b2 corresponds to the second maximum value, and the minimum value a2 corresponds to the third minimum value. Note that the minimum value a2 corresponds to the third minimum value in one period d1, and to the first minimum value in one period d2.

[0069] In the present disclosure, the average of the second minimum value and the average of the first minimum value and the third minimum value are calculated by identifying any five adjacent cycles in the first graph and based on the second minimum value, the first minimum value, and the third minimum value included in the five cycles.

[0070] The average of the first maximum value and the second maximum value may be 0.010 or more and 0.120 or less, 0.020 or more and 0.110 or less, or 0.030 or more and 0.100 or less.

[0071] The average of the second minimum values ​​may be 0.008 or more and 0.100 or less, 0.010 or more and 0.090 or less, or 0.020 or more and 0.080 or less.

[0072] The average of the first minimum value and the third minimum value may be 0.003 or more and 0.090 or less, 0.005 or more and 0.080 or less, or 0.010 or more and 0.070 or less.

[0073] The difference between the average of the first maximum and second maximum and the average of the second minimum may be 0.005 to 0.040, 0.010 to 0.040, or 0.010 to 0.025, which makes it easier to obtain the effect of relaxing lattice strain due to the presence of the second minimum.

[0074] The difference between the average of the first minimum and third minimum and the average of the first maximum and second maximum may be 0.007 to 0.050, 0.010 to 0.050, or 0.010 to 0.030, which makes it easier to suppress crack growth due to lattice distortion caused by changes in silicon content.

[0075] The above-mentioned average of the first maximum and second maximum values, the average of the second minimum values, the average of the first minimum values ​​and the third minimum values, the difference between the average of the first maximum and second maximum values ​​and the average of the second minimum values, and the difference between the average of the first minimum values ​​and the third minimum values ​​and the average of the first maximum values ​​and the second maximum values ​​can be any combination of the above ranges.

[0076] In the hard particle, the region near the first minimum and the third minimum is the layer with the relatively lowest silicon content (hereinafter also referred to as the "low-silicon layer"), the region near the first maximum and the second maximum is the layer with the relatively highest silicon content (hereinafter also referred to as the "high-silicon layer"), and the region near the second minimum can also be expressed as a medium-silicon layer having a silicon concentration between the high-silicon layer and the low-silicon layer. That is, one period of the lamellar structure of the hard particle can also be expressed as including, along the stacking direction of the lamellar structure, a low-silicon layer, a high-silicon layer, a medium-silicon layer, a high-silicon layer, and a low-silicon layer.

[0077] In this embodiment, the periodic width along the X-axis of the first graph may be 3 nm or more and 20 nm or less. This makes it easier to maintain lattice distortion within the hard particles, further suppressing crack propagation in the coating and further improving the chipping resistance of the cutting tool. The periodic width of the silicon concentration may be 3 nm or more and 15 nm or less, or 5 nm or more and 10 nm or less.

[0078] In the present disclosure, the period width corresponds to the average of period widths of any five adjacent periods in the first graph.

[0079] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results for each of the above items, even if measurements are made multiple times while changing the hard particles specified in (C2) above.

[0080] <First layer thickness> The thickness of the first layer in this embodiment may be 1.0 μm or more and 15 μm or less. When the thickness of the first layer is 1.0 μm or more, excellent wear resistance can be obtained. On the other hand, when the thickness of the first layer is 15 μm or less, peeling or breakage of the coating can be suppressed when a large stress is applied between the coating and the substrate during cutting. The thickness of the first layer may be 4 μm or more and 15 μm or less, or 6 μm or more and 10 μm or less.

[0081] <Second layer> The coating of this embodiment may include a second layer disposed between the substrate and the first layer, and the second layer may include at least one layer selected from the group consisting of a TiN layer, a TiC layer, a TiCN layer, a TiBN layer, a TiCNO layer, and an Al2O3 layer.

[0082] By placing a TiN layer, TiC layer, TiCN layer, TiBN layer, or TiCNO layer directly on the substrate as the second layer, the adhesion between the substrate and the coating can be improved. By using an Al2O3 layer as the second layer, the oxidation resistance of the coating can be improved. The average thickness of the second layer may be 0.1 μm or more and 20 μm or less. This allows the coating to have excellent wear resistance and chipping resistance.

[0083] <Third layer> The coating of embodiment 1 may include a third layer disposed on the outermost surface of the coating. The third layer may be a TiN layer, a TiC layer, a TiCN layer, a TiBN layer, a TiCNO layer, or an Al2O3 layer. Because the TiN layer has a clear color (golden), its use as the third layer has the advantage of making it easy to identify the used portion of the cutting tool after cutting. Using a TiC layer, a TiCN layer, a TiBN layer, or a TiCNO layer as the third layer can improve the sliding properties of the coating. Using an Al2O3 layer as the third layer can improve the oxidation resistance of the coating.

[0084] The average thickness of the third layer may be 0.5 μm or more and 10 μm or less, which improves the adhesion between the third layer and the adjacent layer.

[0085] [Embodiment 2: Method for manufacturing a cutting tool] A description will be given of an example of a method for manufacturing the cutting tool according to embodiment 1. The method for manufacturing the cutting tool according to embodiment 1 can include a first step of preparing a substrate and a second step of forming a coating on the substrate to obtain the cutting tool.

[0086] <First step> In the first step, a substrate is prepared. Details of the substrate are described in the first embodiment, and therefore, the description thereof will not be repeated.

[0087] <Second process> Next, in the second step, a coating is formed on the substrate to obtain a cutting tool. The coating is formed using, for example, a CVD apparatus shown in FIG. 6. A plurality of substrate setting jigs 52 holding substrates 10 can be placed inside the CVD apparatus 50, and these are covered by a reaction vessel 53 made of heat-resistant alloy steel. In addition, a temperature control device 54 is arranged around the reaction vessel 53, and this temperature control device 54 can control the temperature inside the reaction vessel 53.

[0088] A nozzle 56 having three gas flow paths (a first gas flow path 55, a second gas flow path 57, and the other gas flow path not shown) through which source gases pass is disposed in the CVD apparatus 50. The nozzle 56 is disposed so as to penetrate the area in which the substrate setting jig 52 is disposed. A plurality of injection holes are formed in the nozzle 56 in the vicinity of the substrate setting jig 52 to inject the gas that has passed through the gas flow paths.

[0089] Fig. 8 is a cross-sectional view of the nozzle 56 taken along line XVII-XVII in Fig. 7. As shown in Fig. 8, the nozzle 56 is provided with a first gas flow passage 55, a second gas flow passage 57, and a third gas flow passage 58. SiCl4 gas passes through the first gas flow passage 55, TiCl4 gas passes through the second gas flow passage 57, and CH3CN gas passes through the third gas flow passage 58.

[0090] The first gas flow path 55 communicates with two first injection holes 55a and one second injection hole 55b. The gas that has passed through the first gas flow path 55 is injected toward the substrate from the first injection hole 55a and the second injection hole 55b. The hole diameter of the first injection hole 55a is larger than the hole diameter of the second injection hole 55b.

[0091] The second gas flow passage 57 communicates with the third injection hole 57a. The gas that has passed through the second gas flow passage 57 is injected from the third injection hole 57a toward the substrate. The third gas flow passage 58 communicates with the fourth injection hole 58a, and the gas that has passed through the third gas flow passage 58 is injected from the fourth injection hole 58a toward the substrate.

[0092] The carrier gas may be H2 gas, N2 gas, Ar gas, or the like. The carrier gas is injected from each of the first injection hole, the second injection hole, the third injection hole, and the fourth injection hole. In this disclosure, a gas containing a raw material gas and a carrier gas is referred to as a reaction gas.

[0093] When forming the first layer, the nozzle is rotated while the film is being formed. The first injection holes 55a and the second injection holes 55b through which the SiCl4 gas is injected have different hole diameters. Therefore, the hard particles contained in the first layer can have a lamellar structure in which the silicon content changes periodically. Furthermore, in the first graph obtained for the hard particles, the ratio N Si / (N Ti +N Si ) includes, along the positive direction of the X-axis, a first minimum, a first maximum, a second minimum, a second maximum, and a third minimum, and the average of the second minimums is greater than the average of the first minimum and the third minimum.

[0094] In this process, the substrate temperature in the reaction vessel is 800°C to 900°C, and the pressure in the reaction vessel is 50 hPa to 140 hPa. The thickness of the first layer can be controlled by adjusting the flow rate of the source gas and the deposition time. The periodic width in the direction along the X-axis of the first graph can be controlled by adjusting the rotation speed of the nozzle and the deposition time.

[0095] During the formation of the first layer, the total flow rate of the reactive gas is set to 90 L / min to 150 L / min. Here, the "total gas flow rate" refers to the total volumetric flow rate introduced into the CVD furnace per unit time, assuming that the gas is an ideal gas under standard conditions (0°C, 1 atmosphere).

[0096] When the coating includes at least one of the second layer, intermediate layer, and third layer, these layers can be formed by a conventionally known method.

[0097] (Other processes) The substrate on which the coating is formed is then cooled, for example, at a cooling rate not exceeding 5°C / min, and the cooling rate slows as the temperature of the substrate decreases.

[0098] In addition to the above steps, a heat treatment step such as annealing, and a surface treatment step such as surface grinding or shot blasting may be carried out.

[0099] The cutting tool of the first embodiment can be obtained by the above-described manufacturing method. [Example]

[0100] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0101] <Preparing the substrate> A substrate made of cemented carbide was prepared as the substrate. The composition of the substrate was 6 mass % Co, 1.5 mass % NbC, and the remainder was WC. The shape of the substrate was CNMG120408N-GU.

[0102] <Coating formation> A coating was formed on the surface of the substrate by CVD. The composition of the coating and the thickness of each layer for each sample are shown in Tables 1 and 2. A "-" in the table indicates that no layer is present. The first layer is composed of multiple hard particles, which consist of titanium, silicon, carbon, and nitrogen. The second and third layers are layers formed by conventional CVD methods.

[0103] [Table 1]

[0104] [Table 2]

[0105] The first layer of each sample was formed using the CVD apparatus shown in FIG. 6. For samples marked with "A" in the "Type" column of "Nozzle" in Tables 3 and 4, a nozzle 56 shown in FIG. 8 was used. Nozzle 56 is provided with a first gas flow path 55, a second gas flow path 57, and a third gas flow path 58. SiCl4 gas passes through first gas flow path 55, TiCl4 gas passes through second gas flow path 57, and CH3CN gas passes through third gas flow path 58.

[0106] The first gas flow path 55 communicates with two first injection holes 55a and one second injection hole 55b. The gas that passes through the first gas flow path 55 is injected toward the substrate from the first injection holes 55a and the second injection holes 55b. The diameters φ of the first injection holes 55a and the second injection holes 55b are shown in Tables 3 and 4.

[0107] The second gas flow passage 57 communicates with the third injection hole 57a. The gas that has passed through the second gas flow passage 57 is injected from the third injection hole 57a toward the substrate. The third gas flow passage 58 communicates with the fourth injection hole 58a, and the gas that has passed through the third gas flow passage 58 is injected from the fourth injection hole 58a toward the substrate.

[0108] For samples with "B" in the "Type" column of "Nozzle" in Tables 3 and 4, a nozzle 56 shown in Fig. 9 was used. Nozzle 56 is provided with a first gas flow path 55, a second gas flow path 57, and a third gas flow path 58. SiCl4 gas passes through first gas flow path 55, TiCl4 gas passes through second gas flow path 57, and CH3CN gas passes through third gas flow path 58.

[0109] The first gas flow passage 55 communicates with one second injection hole 55b. The gas that has passed through the first gas flow passage 55 is injected toward the substrate from the second injection hole 55b. The second gas flow passage 57 communicates with a third injection hole 57a. The gas that has passed through the second gas flow passage 57 is injected toward the substrate from the third injection hole 57a. The third gas flow passage 58 communicates with a fourth injection hole 58a, and the gas that has passed through the third gas flow passage 58 is injected toward the substrate from the fourth injection hole 58a.

[0110] Tables 3 and 4 show the percentage (V1 / V) x 100 of the volumetric flow rate V1 of SiCl4 relative to the volumetric flow rate V of the entire reaction gas during the formation of the first layer, the nozzle rotation speed, the substrate temperature, and the pressure for each sample.

[0111] The substrate was then cooled to obtain a cutting tool for each sample.

[0112] [Table 3]

[0113] [Table 4]

[0114] <First layer configuration> When the first layer of each cutting tool sample was observed using a bright-field scanning electron microscope (BF-SEM), it was confirmed that the first layer consisted of multiple hard particles.

[0115] <Crystal structure of hard particles> The crystalline structure of the hard particles in the first layer of each cutting tool sample was confirmed by selected area electron diffraction pattern analysis. The results are shown in Tables 5 and 6. In the tables, "cubic" indicates that the hard particles have a cubic structure. In the tables, "cubic + amorphous" indicates that the hard particles have a cubic structure that includes amorphous material.

[0116] <First layer organization> In the first layer of each sample cutting tool, the percentage (N1 / N) × 100 of the number N1 of first hard particles with an aspect ratio of 3 or more relative to the number N of all hard particles constituting the first layer was measured. The specific measurement method is as described in embodiment 1. If the value of the percentage (N1 / N) × 100 is 60% or more, the first layer is determined to have a columnar structure, and if the value of the percentage (N1 / N) × 100 is less than 60%, the first layer is determined to be composed of granular crystals. The results are shown in Tables 5 and 6.

[0117] <Composition of the first layer> In each sample cutting tool, the number of titanium atoms in the first layer, N Ti and the number of silicon atoms, N Si The number of silicon atoms, N, Si Ratio of N Si / (N Ti +N Si ) was measured by TEM-EDX. The specific measurement method is as described in embodiment 1. The results are shown in Tables 1 and 2.

[0118] <Presence or absence of lamellar structure> The hard particles of each cutting tool sample consisted of titanium, silicon, carbon, and nitrogen. The hard particles of each cutting tool sample were checked for the presence or absence of a lamellar structure in which the silicon content periodically changed. The specific checking method was as described in embodiment 1. The results are shown in Tables 5 and 6.

[0119] <First graph> Line analysis was performed using TEM-EDX on the hard particles of the cutting tools of each sample to obtain the first graph. Tables 5 and 6 show the "average of the first and third minimum values," "average of the second minimum value," "average of the first and second maximum values," and the "period width" along the X-axis of the first graph for each sample. Note that for Samples 1-2 and 2-2, only one maximum value (first maximum value) was present between the two minimum values ​​(within one period) with the lowest silicon content, and neither a second minimum value nor a second maximum value was present. Therefore, the "average of the first and second maximum values" column in the table lists the average silicon content of the first maximum values.

[0120] [Table 5]

[0121] [Table 6]

[0122] <Cutting test> Using the cutting tools of each sample, cutting was performed under the cutting conditions described in Cutting Test 1 or Cutting Test 2 below, and the cutting time until the flank damage width reached 0.3 mm was measured. A longer cutting time indicates a longer tool life. The results are shown in Tables 7 and 8.

[0123] <Cutting test 1: Samples 1 to 15, Samples 1-1 to 1-3> Work material: SCM435 grooved round bar material Holder: DCLNR2525M12 Insert: CNMG120408N-GU Cutting speed Vc:200m / min Feed: 0.3 mm / rev Cutting depth ap: 1.5 mm Cutting fluid: Yes (WET)

[0124] [Table 7]

[0125] <Cutting test 2: Samples 21 to 35, Samples 2-1 to 2-3> Work material: SCM435 grooved round bar material Holder: DCLNR2525M12 Insert: CNMG120408N-GU Cutting speed Vc:400m / min Feed: 0.15mm / rev Cutting depth ap: 1.5 mm Cutting fluid: Yes (WET)

[0126] [Table 8]

[0127] <Considerations based on cutting condition 1> The cutting tools of Samples 1 to 15 correspond to Examples, and the cutting tools of Samples 1-1 to 1-3 correspond to Comparative Examples. The results of Cutting Test 1 confirmed that the cutting tools of the Examples had longer tool life than the cutting tools of the Comparative Examples, particularly in the intermittent cutting of chromium-molybdenum steel, which is relatively prone to welding at low speeds.

[0128] For sample 1-2, there was no second minimum within one cycle in graph 1. Therefore, it is presumed that the lattice strain relaxation effect due to the difference between the first and third minimums and the first maximum was not achieved, cracks tended to propagate in a direction perpendicular to the lamellar structure stacking direction, and tool life was reduced.

[0129] <Considerations based on cutting condition 2> The cutting tools of Samples 21 to 35 correspond to Examples, and the cutting tools of Samples 2-1 to 2-3 correspond to Comparative Examples. The results of Cutting Test 2 confirmed that the cutting tools of the Examples had longer tool life than the cutting tools of the Comparative Examples, particularly in intermittent cutting of chromium-molybdenum steel, which is susceptible to wear at high speeds.

[0130] For sample 2-2, there was no second minimum within one cycle in graph 1. Therefore, it is presumed that the lattice strain relaxation effect due to the difference between the first and third minimums and the first maximum was not achieved, cracks tended to propagate in a direction perpendicular to the lamellar structure stacking direction, and tool life was reduced.

[0131] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0132] 1 cutting tool, 10 substrate, 11 first layer, 12 second layer, 13 third layer, 15 coating, 50 CVD apparatus, 52 substrate setting jig, 53 reaction vessel, 54 temperature control device, 55 first gas flow path, 55a first injection hole, 55b second injection hole, 56 nozzle, 57 second gas flow path, 57a third injection hole, 58 third gas flow path, 58a fourth injection hole, 59 exhaust pipe, 60 exhaust port.

Claims

1. A cutting tool comprising a base material and a coating disposed on the base material, The coating includes a first layer, The aforementioned first layer consists of a plurality of hard particles, The hard particles consist of titanium, silicon, carbon, and nitrogen. The hard particles have a cubic crystal structure, The aforementioned first layer is a columnar structure, In the above layer, the number of titanium atoms N Ｔｉ and the number of silicon atoms N Ｓｉ The number of silicon atoms N relative to the total Ｓｉ Ratio N Ｓｉ / (N Ｔｉ +N Ｓｉ The average of ) is between 0.010 and 0.

10. The hard particles have a lamellar structure in which the silicon content changes periodically. In the hard particles, the result obtained by performing line analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along the stacking direction of the lamellar structure, where the X-axis is the distance from an arbitrary point P1 within the hard particles and the Y-axis is the ratio N Ｓｉ / (N Ｔｉ + N Ｓｉ ) is shown in a first graph in a coordinate system where The ratio N Ｓｉ / (N Ｔｉ +N Ｓｉ Each of the periods of the X-axis includes a first local minimum, a first local maximum, a second local minimum, a second local maximum, and a third local minimum along the positive direction of the X-axis. A cutting tool in which the average of the second minimum is greater than the average of the first minimum and the third minimum.

2. The cutting tool according to claim 1, wherein the periodic width in the direction along the X-axis of the first graph is 3 nm or more and 20 nm or less.

3. The cutting tool according to claim 1 or claim 2, wherein the difference between the average of the first maximum value and the second maximum value and the average of the second minimum value is 0.005 or more and 0.040 or less.

4. The cutting tool according to claim 1 or claim 2, wherein the thickness of the first layer is 1.0 μm or more and 15 μm or less.

5. The coating includes a second layer disposed between the substrate and the first layer. The second layer consists of a TiN layer, a TiC layer, a TiCN layer, a TiBN layer, a TiCNO layer, and an Al layer. ２ O ３ A cutting tool according to claim 1 or claim 2, comprising at least one selected from the group consisting of layers.

6. The coating includes a third layer disposed on the outermost surface of the coating, The third layer is a TiN layer, TiC layer, TiCN layer, TiBN layer, TiCNO layer, or Al ２ O ３ A cutting tool according to claim 1 or claim 2, which is a layer.

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