Coated tool and cutting tool

Abstract

This coated tool comprises a base material and a coating layer positioned on the base material. The base material has an outer-side region including a surface in contact with the coating layer, and an inner-side region positioned on the side opposite from the coating-layer side with respect to the outer-side region. The coating layer has a lower-side region including a surface in contact with the base material, and an upper-side region positioned on the side opposite from the base-material side with respect to the lower-side region. The base material contains tungsten. The coating layer contains tungsten and a light metal element. The outer-side region contains at least one light metal element. The average tungsten content in the lower-side region is greater than the average tungsten content of the coating layer. The average tungsten content in the upper-side region is less than the average tungsten content of the coating layer. The thickness of the outer-side region is greater than the thickness of the lower-side region.

Description

Coated and cutting tools

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to coated tools and cutting tools.

[0002] BACKGROUND ART As a tool used in cutting processes such as turning or milling, a coated tool is known in which the surface of a substrate made of cemented carbide, cermet, ceramics, or the like is coated with a coating layer to improve wear resistance and the like.

[0003] For example, in a surface-coated sintered alloy in which a base material made of cemented carbide is coated with a hard film, it is known to use a surface-coated sintered alloy with excellent adhesion in which a diffusion element-containing layer is formed in which one or more of the iron group elements constituting the base material and the diffusion elements, tungsten and carbon, are diffused almost uniformly in the hard film (see, for example, JP 2000-355777 A).

[0004] A coated tool according to one aspect of this embodiment includes a substrate and a coating layer located on the substrate, the substrate having an outer region including a surface in contact with the coating layer and an inner region located on the opposite side of the outer region from the coating layer, the coating layer having a lower region including a surface in contact with the substrate and an upper region located on the opposite side of the substrate from the lower region, the substrate containing tungsten, the coating layer containing tungsten and a light metal element, the outer region containing at least one light metal element, the average tungsten content in the lower region being greater than the average tungsten content in the coating layer, the average tungsten content in the upper region being less than the average tungsten content in the coating layer, and the thickness of the outer region being greater than the thickness of the lower region.

[0005] FIG. 1 is a perspective view showing an example of a coated tool according to the present embodiment. FIG. 2 is a cross-sectional view showing an example of an insert according to the present embodiment. FIG. 3 is a cross-sectional view showing an example of a coated tool according to the present embodiment. FIG. 4 is a diagram showing an example of a tungsten atom content distribution in the coated tool according to the present embodiment. FIG. 5 is a cross-sectional view showing an example of a coating layer according to the present embodiment. FIG. 6 is a diagram showing an example of an atom content distribution in the coating layer according to the present embodiment. FIG. 7 is a front view showing an example of a cutting tool according to the present embodiment. FIG. 8 is a diagram showing an atom content distribution in the coated tool according to Sample No. 1 of the Example. FIG. 9 is a diagram showing an atom content distribution in the coated tool according to Sample No. 7 of the Comparative Example. FIG. 10 is a diagram showing an atom content distribution in the coating layer according to Sample No. 1 of the Example.

[0006] Hereinafter, modes for carrying out the coated tool and cutting tool disclosed herein (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. The coated tool and cutting tool disclosed herein are not limited to the embodiments described below. In the following embodiments, the same components are designated by the same reference numerals, and redundant description will be omitted.

[0007] For example, when the above-mentioned surface-coated sintered alloy is used for machining with high cutting resistance, the adhesion between the base material and the hard film is insufficient, and the hard film is likely to peel off from the base material or chip, resulting in the tool reaching the end of its useful life in a relatively short period of time.

[0008] As described above, the prior art has room for further improvement in terms of improving wear resistance and chipping resistance.

[0009] Therefore, there is a need for a technology that can overcome the above-mentioned problems and improve wear resistance and fracture resistance.

[0010] <Coated Tool> Fig. 1 is a perspective view showing an example of a coated tool according to this embodiment. As shown in Fig. 1, the coated tool 1 according to this embodiment has an insert 11.

[0011] (Insert 11) The insert 11 has, for example, a hexahedral shape in which the upper and lower surfaces (surfaces intersecting with the Z axis shown in Fig. 1) are shaped like a substantially parallelogram.

[0012] One corner portion of the insert 11 functions as a cutting edge portion. The cutting edge portion has a first surface (e.g., an upper surface) and a second surface (e.g., a side surface) that is connected to the first surface. In this embodiment, the first surface functions as a "rake face," and the second surface functions as a "flank face." A cutting edge is located on at least a portion of the ridge where the first surface and the second surface intersect, and the coated tool 1 cuts the workpiece by bringing this cutting edge into contact with the workpiece.

[0013] A through-hole 15 is located in the center of the insert 11, penetrating the insert 11 from top to bottom. The central axis of the through-hole 15 may pass through the center of the upper surface and the center of the lower surface. A screw 75 is inserted into the through-hole 15 to attach the coated tool 1 to a holder 70 (described later) (see FIG. 7 ).

[0014] 1 is merely an example and does not limit the shape of the coated tool according to the present disclosure. The coated tool according to the present disclosure may have, for example, a rod-shaped body having a rotation axis and extending from a first end to a second end, a cutting edge located at the first end of the body, and a groove extending spirally from the cutting edge toward the second end of the body.

[0015] Fig. 2 is a cross-sectional view showing an example of an insert according to this embodiment. The cross section shown in Fig. 2 may be a cross section parallel to the central axis of the through hole 15. As shown in Fig. 2, the insert 11 has a base body 2 and a coating layer 3.

[0016] (Substrate 2) The substrate 2 is formed of, for example, a cemented carbide. The cemented carbide contains a hard phase containing at least W (tungsten), specifically WC (tungsten carbide). The cemented carbide may contain a binder phase containing at least one iron group element such as Ni (nickel) and Co (cobalt). As an example, the substrate 2 may be a WC-based cemented carbide whose main component is hard particles made of WC. Here, the main component refers to a cemented carbide containing 80 mass % or more of hard particles made of WC. When the substrate 2 is the above-mentioned cemented carbide, the substrate 2 has better heat resistance.

[0017] (Coating layer 3) The coating layer 3 coats the substrate 2 for the purpose of improving the abrasion resistance, heat resistance, etc. of the substrate 2. In the example of FIG. 2, the coating layer 3 coats the entire substrate 2. The coating layer 3 is not particularly limited as long as it is located at least on the surface of the substrate 2. When the coating layer 3 is located on the first surface (here, the upper surface) of the substrate 2, the abrasion resistance and heat resistance of the first surface are high. When the coating layer 3 is located on the second surface (here, the side surface) of the substrate 2, the abrasion resistance and heat resistance of the second surface are high.

[0018] <Coated tool 1> An example of a coated tool according to this embodiment will now be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a cross-sectional view showing an example of a coated tool according to this embodiment. Fig. 4 is a diagram showing an example of the distribution of tungsten atomic content in the coated tool according to this embodiment. In Fig. 4, the horizontal axis represents the distance from the surface of the coated tool 1 in the thickness direction of the coating layer 3, i.e., the position in the thickness direction of the coating layer 3. In Fig. 4, the vertical axis represents the tungsten atomic content (atomic %).

[0019] As shown in FIG. 3 , the coated tool 1 according to this embodiment includes a substrate 2 and a coating layer 3 located on the substrate 2. As will be described later, an outer region 21 of the substrate 2 is a region containing at least one light metal element. An inner region 22 of the substrate 2 is a region not containing any light metal element. The term "not containing" as used above does not strictly mean not containing any light metal element, but rather means being below the measurement limit that cannot be detected by normal measurement. For example, a content (atomic %) of less than 0.1% may be considered to be free of the component to be evaluated. In the measurement method using a combination of sputtering and X-ray photoelectron spectroscopy (XPS) described later, a component is considered to be "not containing" if it is not determined to be contained.

[0020] The substrate 2 has an outer region 21 including a surface in contact with the coating layer 3, and an inner region 22 located on the opposite side of the outer region 21 from the coating layer 3 side. Hereinafter, the "opposite side of the outer region 21 from the coating layer 3 side" may also be referred to as the center side.

[0021] The coating layer 3 has a lower region 31 including a surface in contact with the substrate 2, and an upper region 32 located on the opposite side of the lower region 31 from the substrate 2. As will be described later, the lower region 31 of the coating layer 3 is a region in which the average tungsten content is higher than the average tungsten content in the coating layer 3. The upper region 32 of the coating layer 3 is a region in which the average tungsten content is lower than the average tungsten content in the coating layer 3.

[0022] The surface of the substrate 2 in contact with the coating layer 3, i.e., the interface between the substrate 2 and the coating layer 3, is identified, for example, by taking a photograph of a cross section of the coated tool 1 including the substrate 2 and the coating layer 3 using a scanning electron microscope (STEM). When using a measurement method that combines sputtering and XPS, as in this embodiment, the position of the interface between the substrate 2 and the coating layer 3 may be identified, for example, by calculating the average thickness of the coating layer 3, i.e., the average distance from the surface of the coating layer 3 to the interface between the substrate 2 and the coating layer 3, in a photograph of a cross section of the coated tool 1 including the substrate 2 and the coating layer 3. When the surface of the coating layer 3 is flat, the thickness direction refers to the direction perpendicular to the surface of the coating layer 3. When the direction cannot be uniquely identified, the thickness direction refers to the direction perpendicular to the interface between the substrate 2 and the coating layer 3.

[0023] The substrate 2 contains tungsten. The substrate 2 is mainly composed of hard particles made of WC, for example. Here, the term "main component" means that the main component is 80% or more by mass.

[0024] The coating layer 3 contains tungsten and a light metal element. The light metal element contained in the coating layer 3 may be one type or two or more types. Examples of the light metal element include aluminum, titanium, and silicon. For example, the coating layer 3 may contain Al ａ Ti ｂ W ｃ M ｄand at least one nonmetal selected from carbon, nitrogen, and oxygen. M is at least one metal selected from Groups 4, 5, and 6 (excluding Cr and W) of the periodic table of elements and Si. a, b, c, and d are 0≦a≦65, 0≦b<100, and 0<c≦5, and a+b+c+d=100. As an example, the composition of the coating layer 3 may be AlTiWNbSiN. The notation AlTiWNbSiN indicates the types of constituent elements and does not indicate that the atomic ratio of the constituent elements is equal. The coating layer 3 does not necessarily need to contain M. In this case, the composition of the coating layer 3 may be, for example, AlTiWN. The notation AlTiWN indicates the types of constituent elements and does not indicate that the atomic ratio of the constituent elements is equal. The coating layer 3 has high hardness at high temperatures (e.g., 1100°C) and high oxidation resistance.

[0025] The thickness of the coating layer 3 may be 1.0 μm or more and 7.0 μm or less. In particular, when the thickness of the coating layer 3 is 1.5 μm or more, the wear resistance of the coated tool 1 is easily improved. When the thickness of the coating layer 3 is 3.0 μm or less, the fracture resistance of the coating layer 3 is easily improved. Therefore, when the thickness of the coating layer 3 is 1.5 μm or more and 3.0 μm or less, the wear resistance and fracture resistance of the coating layer 3 can be improved.

[0026] The outer region 21 of the substrate 2 is a region containing at least one type of light metal element. The light metal element contained in the outer region 21 may be one type or two or more types. In this embodiment, the light metal element contained in the coating layer 3 is diffused into the outer region 21, thereby causing the light metal element to be contained in the outer region 21. Therefore, the light metal element contained in the outer region 21 may partially overlap with the light metal element contained in the coating layer 3. The inner region 22 of the substrate 2 is a region that does not contain a light metal element. In this embodiment, the inner region 22 is a region that does not have the light metal element contained in the coating layer 3.

[0027] The tungsten and light metal elements contained in the coating layer 3 and the light metal elements contained in the outer region 21 of the substrate 2 are detected, for example, by a combination of sputtering and X-ray photoelectron spectroscopy (XPS). Specifically, a sputtering device is used to scrape the surface of the coated tool 1 from the coating layer 3 toward the substrate 2, and XPS is applied to the atoms that are ejected from the surface of the coated tool 1, thereby identifying the type of atoms.

[0028] As mentioned above, "containing light metal elements" means that a material is determined to contain light metal elements when the content (atomic %) of the light metal elements is detected to be 0.1% or more.

[0029] When using a measurement method combining sputtering and XPS as described above, as in this embodiment, if light metal elements are not detected closer to the center than the region at a distance of D x 0.5 of the coating layer thickness from the interface between the substrate 2 and the coating layer 3 toward the center, it is determined that the inner region 22 of the substrate 2 does not contain light metal elements.

[0030] For example, when the light metal element is not determined to be contained when the combination of sputtering and XPS as described above is applied, it is determined that the light metal element is not contained.

[0031] 4 , the average tungsten content in the lower region 31 of the coating layer 3 is greater than the average tungsten content in the coating layer 3. The average tungsten content in the upper region 32 of the coating layer 3 is less than the average tungsten content in the coating layer 3. The average atomic content refers to the average value of atomic contents measured at multiple positions in the thickness direction of the coated tool 1. For example, the coating layer 3 may be divided into five regions evenly in the thickness direction of the coated tool 1, and the average of the atomic contents measured in each region may be used as the "average content."

[0032] The thickness of the outer region 21 of the substrate 2 is greater than the thickness of the lower region 31 of the covering layer 3 .

[0033] In the coated tool 1, the coating layer 3 contains a light metal element, and the outer region 21 of the substrate 2 contains at least one type of light metal element. This means that diffusion of at least one type of light metal element contained in the coating layer 3 from the coating layer 3 to the outer region 21 of the substrate 2 is significantly promoted.

[0034] The diffusion of at least one light metal element contained in the coating layer 3 from the coating layer 3 to the outer region 21 of the substrate 2 is significantly promoted, which tends to reduce the difference between the thermal expansion coefficient of the substrate 2 and the thermal expansion coefficient of the coating layer 3. In this case, the residual stress caused by the difference between the thermal expansion coefficient of the substrate 2 and the thermal expansion coefficient of the coating layer 3 tends to be reduced. This tends to improve the adhesion between the substrate 2 and the coating layer 3 in the coated tool 1. As a result, it becomes possible to improve the fracture resistance of the coated tool 1, for example, in turning stainless steel (SUS) or the like.

[0035] The diffusion of at least one light metal element from the coating layer 3 to the outer region 21 of the substrate 2 is significantly promoted, and thus the at least one light metal element diffuses into the binder phase contained in the substrate 2. In this case, the hardness of the binder phase contained in the substrate 2 is likely to increase. This tends to reduce the occurrence of shedding of hard particles contained in the substrate 2. As a result, the wear resistance of the coated tool 1 can be improved.

[0036] In the coated tool 1, the substrate 2 contains tungsten. The average tungsten content in the lower region 31 of the coating layer 3 is greater than the average tungsten content in the coating layer 3, and the average tungsten content in the upper region 32 of the coating layer 3 is less than the average tungsten content in the coating layer 3. This means that diffusion of tungsten contained in the substrate 2 from the substrate 2 to the lower region 31 of the coating layer 3 is significantly promoted.

[0037] The diffusion of tungsten contained in the substrate 2 from the substrate 2 to the lower region 31 of the coating layer 3 is significantly promoted, which tends to improve the oxidation resistance of the lower region 31 of the coating layer 3 near the interface between the substrate 2 and the coating layer 3. The generation of strain within the crystals constituting the lower region 31 of the coating layer 3 tends to increase the hardness of the lower region 31 of the coating layer 3 near the interface between the substrate 2 and the coating layer 3. Residual stress caused by the difference between the thermal expansion coefficients of the substrate 2 and the coating layer 3 tends to be reduced. This tends to improve the adhesion between the substrate 2 and the coating layer 3 in the coated tool 1. As a result, for example, it becomes possible to improve the fracture resistance of the coated tool 1.

[0038] Because the thickness of the outer region 21 of the substrate 2 is greater than the thickness of the lower region 31 of the coating layer 3, the residual stress in the outer region 21 of the substrate 2 is likely to be further reduced regardless of the length or width of the outer region 21 of the substrate 2. This tends to further improve the adhesion between the substrate 2 and the coating layer 3 in the coated tool 1. As a result, it becomes possible to improve the fracture resistance of the coated tool 1. If the length or width of the outer region 21 of the substrate 2 is increased, it becomes possible to further improve the fracture resistance and oxidation resistance of the coated tool 1.

[0039] When the substrate 2 is mainly composed of hard particles made of WC, the diffusion of at least one light metal element from the coating layer 3 to the outer region 21 of the substrate 2 is significantly promoted, which tends to improve the oxidation resistance of the outer region 21 of the substrate 2. This tends to reduce the rate of wear of the substrate 2 after the coating layer 3 is worn away. As a result, it becomes possible to prevent the need to suddenly replace the coated tool 1 after the coating layer 3 is worn away.

[0040] The coating layer 3 contains titanium and aluminum as light metal elements, and the outer region 21 of the substrate 2 may contain titanium and aluminum as at least one of the light metal elements.

[0041] In this case, the diffusion of aluminum and titanium contained in the coating layer 3 from the coating layer 3 to the outer region 21 of the substrate 2 is significantly promoted. As a result, the wear resistance, fracture resistance, and oxidation resistance of the coated tool 1 can be further improved.

[0042] <Coating Layer> Next, an example of the coating layer according to this embodiment will be described with reference to Figs. 5 and 6. Fig. 5 is a cross-sectional view showing an example of the coating layer according to this embodiment. Fig. 6 is a diagram showing an example of the distribution of atomic content in the coating layer according to this embodiment. In Fig. 6, the horizontal axis represents the distance from the surface of the coated tool 1 in the thickness direction of the coating layer 3 (the stacking direction of the coating layer 3), i.e., the position in the thickness direction of the coating layer 3 (the stacking direction of the coating layer 3). In Fig. 6, the vertical axis represents the atomic content (atomic %). The atomic content in the coating layer 3 shown in Fig. 6 is measured, for example, by an energy dispersive X-ray spectroscopy (EDS) device attached to an electron microscope.

[0043] In the coated tool 1, the coating layer 3 further contains niobium. The coating layer 3 includes a stack 33 in which a plurality of layers each containing niobium are stacked. For example, as shown in Fig. 5 , the coating layer 3 includes a stack 33 in which a plurality of high-content layers 33a and a plurality of low-content layers 33b are alternately stacked.

[0044] As shown in Fig. 6, each of the multiple high-concentration layers 33a has a maximum niobium content in the stacking direction. Each of the multiple low-concentration layers 33b has a minimum niobium content in the stacking direction. As shown in Fig. 6, each of the multiple high-concentration layers 33a has a maximum tungsten content in the stacking direction. Each of the multiple low-concentration layers 33b has a minimum tungsten content in the stacking direction.

[0045] Since the coating layer 3 includes the laminate 33 in which a plurality of high content layers 33 a and a plurality of low content layers 33 b are alternately stacked, the laminate 33 tends to reduce the growth of cracks that occur in the coating layer 3 during cutting using the coated tool 1. This makes it possible to improve the wear resistance of the coated tool 1 as well as the fracture resistance of the coated tool 1.

[0046] A plurality of high-content layers 33a having a maximum niobium content in the stacking direction and a plurality of low-content layers 33b having a minimum niobium content in the stacking direction are alternately stacked. This tends to increase the hardness of the coating layer 3. The stacking of the plurality of high-content layers 33a and low-content layers 33b containing niobium, which form an oxidation protective coating, tends to reduce the progression of oxidation of the coating layer 3. As a result, the oxidation resistance of the coated tool 1 can be improved.

[0047] As shown in FIG. 6, the maximum value of the niobium content in the high content layer 33a is greater than the maximum value of the tungsten content in the high content layer 33a.

[0048] In this case, the niobium content of the oxidation protective coating is higher than the tungsten content in the plurality of high-content layers 33 a. The locally high niobium content in the coating layer 3 tends to reduce the progress of oxidation of the coating layer 3. As a result, the oxidation resistance of the coated tool 1 can be further improved.

[0049] As shown in FIG. 6, the minimum value of the niobium content in the low content layer 33b is greater than the minimum value of the tungsten content in the low content layer 33b.

[0050] In this case, the niobium content of the low-content layers 33b, which form the oxidation protective coating, is higher than the tungsten content. The locally high niobium content in the coating layer 3 thus tends to reduce the progress of oxidation of the coating layer 3. As a result, the oxidation resistance of the coated tool 1 can be further improved.

[0051] 6, attention is focused on the high-content layer 33a and the low-content layer 33b adjacent in the stacking direction. As shown in FIG. 6, the difference between the maximum value of the niobium content in the high-content layer 33a and the minimum value of the niobium content in the low-content layer 33b is larger than the difference between the maximum value of the tungsten content in the high-content layer 33a and the minimum value of the tungsten content in the low-content layer 33b. Specifically, as shown in FIG. 6, the multiple high-content layers 33a include a first layer 33c, and the multiple low-content layers 33b include a second layer 33d adjacent to the first layer 33c in the stacking direction. The difference between the maximum value of the niobium content in the first layer 33c and the minimum value of the niobium content in the second layer 33d is larger than the difference between the maximum value of the tungsten content in the first layer 33c and the minimum value of the tungsten content in the second layer 33d.

[0052] In this case, the difference in the niobium content of the oxidation protective coating between the high-content layer 33a and the low-content layer 33b adjacent in the stacking direction is greater than the difference in the tungsten content. The locally high niobium content in the coating layer 3 tends to reduce the progress of oxidation of the coating layer 3. As a result, the oxidation resistance of the coated tool 1 can be further improved.

[0053] By arranging the high niobium content layer 33 a and the low niobium content layer 33 b adjacent to each other in the stacking direction, the hardness of the coating layer 3 formed by stacking the multiple high niobium content layers 33 a and the multiple low niobium content layers 33 b is likely to increase. In this way, by further increasing the hardness of the coating layer 3, it is possible to improve the wear resistance of the coated tool 1.

[0054] <Method for manufacturing coated tool 1> Next, an example of a method for manufacturing the coated tool 1 according to this embodiment will be described. The method for manufacturing the coated tool 1 according to this embodiment is not limited to the following method.

[0055] The coated tool 1 is manufactured by forming a coating layer 3 on a substrate 2. The coating layer 3 may be formed by, for example, a physical vapor deposition (PVD) method. For example, when the coating layer 3 is formed by using physical vapor deposition while the substrate 2 is held on the inner circumferential surface of the through hole 15, the coating layer 3 can be formed so as to cover the entire surface of the substrate 2 except for the inner circumferential surface of the through hole 15.

[0056] Examples of physical vapor deposition methods include ion plating methods such as arc ion plating (AIP) and sputtering. The arc ion plating method uses arc discharge in a vacuum atmosphere to evaporate a target metal, and nitrogen (N ２ ) gas, etc. to form a film of metal or metal nitride.

[0057] For example, when the coating layer 3 is formed on the substrate 2 by arc ion plating, the coated tool 1 can be produced by the following method.

[0058] As an example, a metal target of Ti, Al, or M, or a composite alloy target, or a sintered target is prepared, where M is at least one metal selected from Groups 4, 5, and 6 (excluding Cr) of the periodic table of elements, and Si.

[0059] Next, the target, which is the metal source, is evaporated and ionized by arc discharge or glow discharge. The ionized metal is then evaporated with nitrogen (N ２ ) gas and is deposited on the surface of the substrate 2. As a result, the coating layer 3 can be formed on the substrate 2.

[0060] Here, in order to diffuse the tungsten contained in the substrate 2 into the lower region 31 of the coating layer 3 and to diffuse at least one of the light metal elements contained in the coating layer 3 into the outer region 21 of the substrate 2, the plasma density and plasma energy of the ionized metal are increased. Methods for increasing the plasma density and plasma energy of the ionized metal include, for example, setting the temperature of the substrate 2 to a temperature in the range of 600°C to 800°C, setting the gas pressure of nitrogen gas or the like to a pressure in the range of 1.0 Pa to 3.0 Pa, setting the distance between the target and the substrate 2 to a distance in the range of 150 mm to 200 mm, setting the bias voltage applied to the substrate 2 to a voltage in the range of 50 V to 100 V, forming a linear magnetic field in the target direction, setting the distance between the cathodes to a distance in the range of 150 mm to 250 mm, and setting the magnetic flux density of the magnet to a magnetic flux density in the range of 20 mT to 60 mT.

[0061] By using two targets with different compositions and alternately depositing them under the above conditions, two layers with different metal components can be formed. By applying a pulsed bias voltage, it is also possible to adjust the time or distance that metal ions travel from the target to the substrate 2. This makes it possible to create a difference in the composition of the metal components during film formation.

[0062] <Cutting Tool> Next, a cutting tool including the above-described coated tool 1 will be described with reference to Fig. 7. Fig. 7 is a front view showing an example of a cutting tool according to this embodiment.

[0063] As shown in FIG. 7, a cutting tool 100 according to this embodiment includes a coated tool 1 and a holder 70 for fixing the coated tool 1 .

[0064] The holder 70 is a rod-shaped member extending from a first end (the upper end in FIG. 7 ) to a second end (the lower end in FIG. 7 ). The holder 70 is made of, for example, steel or cast iron. Among these materials, steel, which has high toughness, may be used.

[0065] The holder 70 has a pocket 73 at the end on the first end side. The pocket 73 is a portion where the coated tool 1 is attached, and has a seating surface that intersects with the rotation direction of the workpiece and a constraint side surface that is inclined relative to the seating surface. The seating surface is provided with a screw hole into which a screw 75, which will be described later, is threaded.

[0066] The coated tool 1 is positioned in a pocket 73 of the holder 70 and attached to the holder 70 by a screw 75. That is, the screw 75 is inserted into the through hole 5 of the coated tool 1, and the tip of the screw 75 is inserted into a threaded hole formed in the seating surface of the pocket 73 to screw the threaded portions together. In this way, the coated tool 1 is attached to the holder 70 so that the cutting edge portion protrudes outward from the holder 70.

[0067] In this embodiment, a cutting tool 100 used for so-called turning is illustrated. Examples of turning include internal diameter machining, external diameter machining, and grooving. The cutting tool is not limited to that used for turning. For example, the coated tool 1 may be used as a cutting tool used for milling. Examples of cutting tools used for milling include milling cutters such as flat milling cutters, face milling cutters, side milling cutters, and groove milling cutters, and end mills such as single-blade end mills, multi-blade end mills, tapered-blade end mills, and ball end mills.

[0068] Examples of the present disclosure will be specifically described below, but the present disclosure is not limited to the examples shown below.

[0069] (Example) First, a coating layer was formed on a substrate by arc ion plating under the conditions shown in Table 1, and a coated tool including the substrate and the coating layer located on the substrate was produced. Here, a WC-based cemented carbide was used as the substrate. The deposition time was adjusted under various conditions so that the thickness of the coating layer formed on the substrate was 2.0 μm. The average composition of the coating layer formed on the substrate is shown in Table 1. In Table 1, two targets with different compositions are referred to as "Target 1" and "Target 2," respectively.

[0070] Next, a photograph of a cross section including the substrate and the coating layer of the coated tool produced as an example was taken using a scanning transmission electron microscope. The interface between the substrate and the coating layer was identified from the photograph of the cross section including the substrate and the coating layer.

[0071] Next, the distribution of atomic content in the coated tool manufactured as an example was measured using a sputtering device and an XPS device. The analysis conditions using the XPS device are as follows: Device name: Quantera II manufactured by PHI X-ray source: Monochrome AlKα (200 μm 15 kV) Measurement area: Approximately 200 μmφ Pass energy: 224.0 eV Step size: 0.400 eV Sputtering conditions Ion species: Ar ＋ Acceleration voltage: 4 kV HP Sputtering rate: 15.41 nm / min (equivalent to the thickness of the ultra-hard material)

[0072] Fig. 8 is a diagram showing the distribution of atomic content in the coated tool according to Example Sample No. 1. In Fig. 8, the horizontal and vertical axes represent sputtering thickness (nm) and atomic content (atomic %), respectively. The distribution of atomic content of tungsten, aluminum, titanium, and niobium in the coated tool according to Example Sample No. 1 was measured.

[0073] 8, in the coated tool according to Example Sample No. 1, it was confirmed that the substrate contained tungsten, the coating layer contained tungsten, titanium, and aluminum, and the outer region of the substrate contained titanium and aluminum.

[0074] As shown in FIG. 8, it was confirmed that the average tungsten content in the lower region of the coating layer was greater than the average tungsten content in the coating layer, and the average tungsten content in the upper region of the coating layer was smaller than the average tungsten content in the coating layer.

[0075] The average thickness of the outer region of the substrate and the average thickness of the lower region of the coating layer were about 2500 nm and about 500 nm, respectively.

[0076] Among the examples, in at least Samples No. 1 to No. 6, the coated tool includes a substrate and a coating layer located on the substrate, the substrate having an outer region including a surface in contact with the coating layer and an inner region located on the opposite side of the outer region from the coating layer, the coating layer having a lower region including a surface in contact with the substrate and an upper region located on the opposite side of the substrate from the lower region, the substrate contains tungsten, the coating layer contains tungsten and a light metal element, the outer region contains at least one light metal element, the average tungsten content in the lower region is greater than the average tungsten content in the coating layer, the average tungsten content in the upper region is less than the average tungsten content in the coating layer, and the thickness of the outer region is greater than the thickness of the lower region.

[0077] Among the examples, in at least Samples No. 1 to No. 5, the coating layer includes a laminate in which a plurality of layers each containing niobium are stacked, and the laminate includes a plurality of high-content layers each having a maximum niobium content in the stacking direction and a plurality of low-content layers each having a minimum niobium content in the stacking direction, and the plurality of high-content layers and the plurality of low-content layers are alternately stacked in the laminate.

[0078] Among the examples, in at least Samples No. 1 to No. 4, each of the multiple high-content layers includes a maximum value of the tungsten content in the stacking direction, and the maximum value of the niobium content in the high-content layer is greater than the maximum value of the tungsten content in the high-content layer.

[0079] Among the examples, in at least Samples No. 1 to No. 3 and No. 5, each of the plurality of low-content layers includes a minimum value of the tungsten content in the stacking direction, and the minimum value of the niobium content in the low-content layer is greater than the minimum value of the tungsten content in the low-content layer.

[0080] Among the examples, in at least Samples No. 1, No. 2, and No. 4, the plurality of high-content layers includes a first layer, the plurality of low-content layers includes a second layer adjacent to the first layer in the stacking direction, and the difference between the maximum value of the niobium content in the first layer and the minimum value of the niobium content in the second layer is larger than the difference between the maximum value of the tungsten content in the first layer and the minimum value of the tungsten content in the second layer.

[0081] Among the examples, in at least Samples No. 1 and Nos. 3 to 6, the coating layer contains titanium and aluminum as light metal elements, and the outer region contains titanium and aluminum as at least one of the light metal elements.

[0082] Similarly, the atomic content distribution of a conventional coated tool as a comparative example was measured. Figure 9 is a diagram showing the atomic content distribution of the coated tool according to comparative example sample No. 7. In Figure 9, the horizontal and vertical axes represent sputtering thickness (nm) and atomic content (atomic %), respectively. The atomic content distributions of tungsten, aluminum, titanium, and niobium in the coated tool according to comparative example sample No. 7 were measured.

[0083] 9 , in the coated tool according to Sample No. 7 of the comparative example, it was confirmed that the substrate contained tungsten, the coating layer contained tungsten, aluminum, and titanium, but the substrate contained neither aluminum nor titanium.

[0084] It was confirmed that the average tungsten content in each of the lower region of the coating layer and the upper region of the coating layer was approximately the same as the average tungsten content in the coating layer.

[0085] Next, the distribution of atomic content in the coating layer included in the coated tool fabricated as an example was measured using an energy dispersive X-ray analyzer attached to a transmission electron microscope for the coated tool fabricated as an example. Figure 10 is a diagram showing the distribution of atomic content in the coating layer of Example Sample No. 1. In Figure 10, the horizontal and vertical axes represent relative position and relative intensity in the thickness direction (stacking direction), respectively. The relative intensity is proportional to the atomic content (atomic %). The distribution of atomic content of niobium and tungsten in the coating layer included in Example Sample No. 1 was measured.

[0086] Specifically, a cross-sectional slice of the coating layer was first prepared using a focused ion beam (FIB) processing machine. Next, C vapor deposition was applied to the slice of the coating layer as a pretreatment. The slice of the coating layer was then observed using a scanning transmission electron microscope (STEM). The atomic content at each position in the coating layer was then measured using an energy dispersive X-ray analyzer (EDS) attached to the scanning transmission electron microscope. Based on the results obtained, the average content of each atom in a region of 30 nm in the planar direction of the coating layer × 0.25 nm in the thickness direction (stacking direction) of the coating layer was analyzed over a range of approximately 65 nm in the thickness direction (stacking direction) of the coating layer. Furthermore, a 10-point moving average was applied to the measured values ​​of the atomic content in each obtained region to obtain the data shown in Figure 10. The equipment and measurement conditions used for each analysis are shown below. <Apparatus> FIB: Focused ion beam processing and observation apparatus JIB-4700F (manufactured by JEOL) STEM: Atomic resolution analytical electron microscope JEM-ARM200F NEOARM (manufactured by JEOL) EDS: Energy dispersive X-ray spectrometer JED-2300T (manufactured by JEOL) <Conditions> FIB Acceleration voltage: 30.3 kV Deposition film: C STEM Acceleration voltage: 200 kV EDS Acceleration voltage: 200 kV Time constant: T4 Probe current: approx. 40 pA Dwell time; area analysis: 0.1 msec Sweep; area analysis: 200 times

[0087] As shown in Fig. 10, it was confirmed that the coating layer contained niobium. It was confirmed that the coating layer included a laminate in which a plurality of high-content layers having a maximum niobium content in the stacking direction and a plurality of low-content layers having a minimum niobium content in the stacking direction were alternately stacked.

[0088] The high-content layer 33a may be a layer having a higher relative intensity of niobium than the average relative intensity of niobium contained in the laminate, and the low-content layer 33b may be a layer having a lower relative intensity of niobium than the average relative intensity of niobium contained in the laminate. More specifically, the relative intensity of niobium in the high-content layer 33a may always be higher than the average relative intensity of niobium in the laminate, and the relative intensity of niobium in the low-content layer 33b may always be lower than the average relative intensity of niobium in the laminate. In such cases, maximum and minimum values ​​can be observed after excluding very slight peaks.

[0089] As shown in FIG. 10, it was confirmed that the maximum value of the niobium content in the high content layer was greater than the maximum value of the tungsten content in the high content layer.

[0090] As shown in FIG. 10, it was confirmed that the minimum value of the niobium content in the low content layer was greater than the minimum value of the tungsten content in the low content layer.

[0091] 10 , it was confirmed that, in a high-content layer and a low-content layer adjacent to each other in the thickness of the coating layer, the difference between the maximum value of the niobium content in the high-content layer and the minimum value of the niobium content in the low-content layer was larger than the difference between the maximum value of the tungsten content in the high-content layer and the minimum value of the tungsten content in the low-content layer. Specifically, it was confirmed that the multiple high-content layers had a first layer, and the multiple low-content layers had a second layer adjacent to the first layer in the stacking direction, and the difference between the maximum value of the niobium content in the first layer and the minimum value of the niobium content in the second layer was larger than the difference between the maximum value of the tungsten content in the first layer and the minimum value of the tungsten content in the second layer.

[0092] Next, cutting tests were conducted on the coated tools of the example and the comparative example. The cutting test conditions are shown below. Cutting conditions Workpiece material: SCM420 Cutting speed: Vc = 120 m / min (low speed) and 200 m / min (high speed) Feed: f = 0.1 mm / rev Depth of cut: ae = 1.5 mm Cutting state: Wet Cutting tool shape: GBA43R300-030GM Evaluation method: Turning was performed for 120 minutes under the above conditions, and the wear width of the front flank after cutting was measured.

[0093] Table 2 shows the results of cutting tests on the coated tools according to Example Samples No. 1 to No. 6 and Comparative Example Samples No. 7 to No. 9. More specifically, Table 2 shows the wear width (mm) of the leading flank of the coated tools when low-speed and high-speed cutting was performed under the above-mentioned cutting conditions.

[0094] As shown in Table 2, the wear width of the front flank of the coated tools according to Samples No. 1 to No. 6 of the Examples was smaller than the wear width of the front flank of the coated tools according to Samples No. 7 to No. 9 of the Comparative Examples, in both low-speed cutting and high-speed cutting. Thus, it was confirmed that the wear resistance and fracture resistance of the coated tools according to Samples No. 1 to No. 6 of the Examples were improved compared to the coated tools according to Samples No. 7 to No. 9 of the Comparative Examples.

[0095] <Note> (1): A coated tool comprising: a base; and a coating layer located on the base; wherein the base has an outer region including a surface in contact with the coating layer, and an inner region located on the opposite side of the outer region from the coating layer; the coating layer has a lower region including a surface in contact with the base, and an upper region located on the opposite side of the base from the lower region; the base contains tungsten; the coating layer contains tungsten and a light metal element; the outer region contains at least one of the light metal elements; an average tungsten content in the lower region is greater than an average tungsten content in the coating layer; an average tungsten content in the upper region is less than the average tungsten content in the coating layer; and the thickness of the outer region is greater than a thickness of the lower region. (2): The coated tool according to (1), wherein the coating layer includes a laminate formed by laminating a plurality of layers each containing niobium, the laminate including a plurality of high-content layers each including a maximum value of niobium content in the lamination direction, and a plurality of low-content layers each including a minimum value of niobium content in the lamination direction, and the plurality of high-content layers and the plurality of low-content layers are alternately laminated in the laminate. (3): The coated tool according to (2), wherein the plurality of high-content layers each include a maximum value of tungsten content in the lamination direction, and the maximum value of niobium content in the high-content layer is greater than the maximum value of tungsten content in the high-content layer. (4): The coated tool according to (2) or (3), wherein the plurality of low-content layers each include a minimum value of tungsten content in the lamination direction, and the minimum value of niobium content in the low-content layer is greater than the minimum value of tungsten content in the low-content layer.(5): The coated tool according to any one of (2) to (4), wherein the plurality of high content layers includes a first layer, and the plurality of low content layers includes a second layer adjacent to the first layer in the stacking direction, and a difference between a maximum value of the niobium content in the first layer and a minimum value of the niobium content in the second layer is greater than a difference between a maximum value of the tungsten content in the first layer and a minimum value of the tungsten content in the second layer. (6): The coated tool according to any one of (1) to (5), wherein the coating layer contains titanium and aluminum as the light metal elements, and the outer region contains titanium and aluminum as at least one of the light metal elements. (7): A cutting tool comprising: a rod-shaped holder having a pocket at an end; and the coated tool according to any one of (1) to (6) positioned in the pocket.

[0096] Further advantages and / or modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0097] 1 Covered tool 11 Insert 15 Through hole 2 Base body 21 Outer region 22 Inner region 3 Covering layer 31 Lower region 32 Upper region 33 Laminated body 33a High content layer 33b Low content layer 33c First layer 33d Second layer 70 Holder 73 Pocket 75 Screw 100 Cutting tool D Covering layer thickness

Claims

1. A coated tool comprising: a substrate; and a coating layer located on the substrate, wherein the substrate has an outer region including a surface in contact with the coating layer, and an inner region located on the opposite side of the outer region from the coating layer, the coating layer having a lower region including a surface in contact with the substrate, and an upper region located on the opposite side of the substrate from the lower region, the substrate contains tungsten, the coating layer contains tungsten and a light metal element, the outer region contains at least one of the light metal elements, the average tungsten content in the lower region is greater than the average tungsten content in the coating layer, the average tungsten content in the upper region is less than the average tungsten content in the coating layer, and the thickness of the outer region is greater than the thickness of the lower region.

2. The coated tool according to claim 1, wherein the coating layer comprises a laminate in which a plurality of layers each containing niobium are stacked, the laminate comprising a plurality of high-content layers each having a maximum niobium content in the stacking direction, and a plurality of low-content layers each having a minimum niobium content in the stacking direction, and the plurality of high-content layers and the plurality of low-content layers are stacked alternately in the laminate.

3. The coated tool according to claim 2, wherein each of the plurality of high tungsten content layers includes a maximum value of the tungsten content in the stacking direction, and the maximum value of the niobium content in the high tungsten content layer is greater than the maximum value of the tungsten content in the high tungsten content layer.

4. The coated tool according to claim 2 or 3, wherein each of the plurality of low-content layers includes a minimum value of the tungsten content in the stacking direction, and the minimum value of the niobium content in the low-content layer is greater than the minimum value of the tungsten content in the low-content layer.

5. The coated tool according to any one of claims 2 to 4, wherein the plurality of high niobium content layers includes a first layer, and the plurality of low niobium content layers includes a second layer adjacent to the first layer in the stacking direction, and a difference between the maximum value of the niobium content in the first layer and the minimum value of the niobium content in the second layer is greater than a difference between the maximum value of the tungsten content in the first layer and the minimum value of the tungsten content in the second layer.

6. The coated tool according to any one of claims 1 to 5, wherein the coating layer contains titanium and aluminum as the light metal elements, and the outer region contains titanium and aluminum as at least one of the light metal elements.

7. A cutting tool comprising: a rod-shaped holder having a pocket at an end thereof; and a coated tool according to any one of claims 1 to 6 positioned in said pocket.

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