Cemented carbide, insert, and cutting tool

Abstract

This cemented carbide includes a first phase containing tungsten carbide particles, a second phase containing at least one of a carbide of vanadium and a carbide of chromium, and a third phase containing nickel or cobalt. The ratio MW of the number of tungsten atoms to the number of atoms constituting the first phase, the second phase and the third phase, the ratio MV of the number of vanadium atoms to the number of atoms constituting the first phase, the second phase, and the third phase, and the ratio MCr of the number of chromium atoms to the number of atoms constituting the first phase, the second phase, and the third phase satisfy the relationship (MV / MW) / (NV / NW)+(MCr / MW) / (NCr / NW)>1.

Description

Cemented Carbide, Inserts and Cutting Tools

[0001] The present disclosure relates to cemented carbides, inserts, and cutting tools.

[0002] It is known that the hardness of cemented carbide depends on the amount of carbon contained in the cemented carbide. Specifically, as the amount of carbon contained in the cemented carbide increases, the hardness of the cemented carbide tends to decrease.

[0003] It is believed that an increase in the amount of carbon contained in a cemented carbide promotes abnormal growth of tungsten carbide (WC) particles, which is the main component of the cemented carbide, thereby reducing the hardness of the cemented carbide. Therefore, a technique for suppressing the reduction in hardness of a cemented carbide by adding an inhibitor that suppresses the abnormal growth of WC particles to the raw materials of the cemented carbide is known. For example, Japanese Patent Application Laid-Open No. 2007-191741 discloses that the elements V (vanadium), Cr (chromium), Ta (tantalum), and Nb (niobium) are additives that have the effect of suppressing the grain growth of WC particles.

[0004] Japanese Patent Application Laid-Open No. 2007-191741

[0005] A cemented carbide according to one embodiment of the present disclosure includes a first phase including tungsten carbide particles, a second phase including at least one of vanadium carbide and chromium carbide and covering the first phase, and a third phase including nickel or cobalt. The ratio M of the number of tungsten atoms to the number of atoms constituting the first phase, the second phase, and the third phase is Ｗ , the ratio M of the number of vanadium atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｖ , and the ratio M of the number of chromium atoms to the number of atoms constituting the first phase, the second phase, and the third phase. Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1, and N Ｗ is the number of tungsten atoms constituting the tungsten carbide particle, and NＶ is the number of vanadium atoms required to cover the tungsten carbide particle, and N Ｃｒ is the number of chromium atoms required to cover the tungsten carbide particle.

[0006] FIG. 1 is a perspective view showing an example of an insert according to an embodiment. FIG. 2 is a side cross-sectional view showing an example of an insert according to an embodiment. FIG. 3 is a diagram schematically showing a cross section of a substrate mainly composed of a cemented carbide according to an embodiment. FIG. 4 is a diagram explaining a model of tungsten carbide particles constituting the cemented carbide. FIG. 5 is a diagram explaining a model of vanadium atoms or chromium atoms constituting the cemented carbide. FIG. 6 is a front view showing an example of a cutting tool according to an embodiment. FIG. 7 is a diagram showing the relationship between saturation magnetization and Vickers hardness of the cemented carbide according to Example 1. FIG. 8 is a diagram showing the relationship between saturation magnetization and Vickers hardness of the cemented carbide according to Example 2. FIG. 9 is a diagram showing the relationship between saturation magnetization and Vickers hardness of the cemented carbide according to a comparative example.

[0007] Hereinafter, modes for carrying out the cemented carbide, insert, and cutting tool according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. The cemented carbide, insert, and cutting tool according to the present disclosure are not limited to these embodiments. The embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. In the following embodiments, the same parts are given the same reference numerals, and redundant explanations will be omitted.

[0008] In the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in a strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0009] During the production of cemented carbide, carbon may be added as an inevitable impurity to the raw materials during the kneading, molding, and sintering processes. This may result in variations in the amount of carbon contained in the cemented carbide. As a result, variations in the hardness of the cemented carbide may occur. Therefore, conventional cemented carbide has room for further improvement in terms of reducing variations in the hardness of the cemented carbide.

[0010] Therefore, there is a need to develop a technology that can overcome the above-mentioned problems and reduce the variation in hardness of cemented carbide.

[0011] <Insert> Fig. 1 is a perspective view showing an example of an insert 1 according to an embodiment. Fig. 2 is a side cross-sectional view showing an example of the insert 1 according to an embodiment.

[0012] As shown in FIGS. 1 and 2 , the insert 1 according to the embodiment includes a base body 2 and a coating layer 3 .

[0013] (Base 2) The base 2 has, for example, a hexahedral shape in which the upper and lower surfaces (surfaces intersecting with the Z axis shown in FIG. 1) are parallelograms.

[0014] One corner portion of the base body 2 functions as a cutting edge portion. The cutting edge portion includes a first surface (e.g., an upper surface) and a second surface (e.g., a side surface) connected to the first surface. In the embodiment, the first surface functions as a "rake surface" that scoops up chips generated by cutting, and the second surface functions as a "flank surface." A cutting edge is located on at least a portion of the ridge where the first surface and the second surface intersect, and the insert 1 cuts the workpiece by bringing this cutting edge into contact with the workpiece.

[0015] A through-hole 21 that passes through the base body 2 from top to bottom may be located in the center of the base body 2. In this case, a screw 75 for attaching the insert 1 to a holder 70 (described later) is inserted into the through-hole 21 (see FIG. 6).

[0016] The substrate 2 contains a cemented carbide. As an example, the substrate 2 may be mainly composed of a cemented carbide. Hereinafter, the expression "main component" means that the component accounts for 50% or more of the total number of atoms. The cemented carbide contains a hard phase containing at least W (tungsten), specifically WC (tungsten carbide). The hard phase is an example of a first phase. The cemented carbide contains a grain growth control phase containing at least one of V (vanadium) and Cr (chromium). The grain growth control phase is an example of a second phase. The grain growth control phase covers the hard phase. The cemented carbide may contain a binder phase containing at least one iron group element such as Ni (nickel) or Co (cobalt). The binder phase is an example of a third phase. As an example, the substrate 2 is made of a WC-based cemented carbide having hard particles made of WC particles as the hard phase component, a grain growth control phase containing carbides of V and Cr as the main component and covering the hard phase, and a binder phase containing Co as the main component. When the substrate 2 is made of a cemented carbide, the substrate 2 has better heat resistance properties.

[0017] Fig. 3 is a diagram schematically showing a cross section of a substrate 2 mainly composed of a cemented carbide according to an embodiment. As shown in Fig. 3, the cemented carbide constituting the substrate 2 includes a first phase 5, a second phase 6, and a third phase 7. The first phase 5 is the main component of the cemented carbide.

[0018] The first phase 5 includes at least tungsten carbide particles (WC particles). As an example, the first phase 5 may be mainly composed of WC particles. The first phase 5 improves the hardness of the cemented carbide. The first phase 5 and the WC particles may be referred to as a hard phase and hard particles, respectively.

[0019] The second phase 6 includes at least one of vanadium (V) carbide and chromium (Cr) carbide. The second phase 6 may include both V carbide and Cr carbide. As an example, the second phase 6 may be mainly composed of at least one of V carbide and Cr carbide. The second phase 6 partially or entirely covers the first phase 5. The second phase 6 controls the growth of WC grains covered by the second phase 6. The second phase 6 and at least one of V carbide and Cr carbide are sometimes referred to as a grain growth control phase and a grain growth control agent, respectively. An example of the V carbide is vanadium carbide (VC). An example of the Cr carbide is trichromium dicarbide (Cr ３ C ２ ) are listed.

[0020] The third phase 7 includes at least nickel or cobalt. The third phase 7 may be mainly composed of nickel or cobalt. As an example, the third phase 7 is mainly composed of cobalt. The third phase 7 binds the first phase 5, which is covered with the second phase 6. The third phase 7 is sometimes called a binder phase.

[0021] If the amount of grain growth inhibitor added to a cemented carbide is excessively increased, the toughness of the cemented carbide may decrease. Therefore, a study was conducted to reduce the variation in hardness of the cemented carbide without significantly decreasing the toughness of the cemented carbide. In the cemented carbide according to the embodiment, the amount of at least one of vanadium (V) carbide and chromium (Cr) carbide, which are the main grain growth inhibitors added to the cemented carbide, is set taking into account the size of the WC particles contained in the cemented carbide. Specifically, in order to efficiently control the growth of the WC particles, the entire surfaces of the WC particles are covered with at least one of vanadium (V) carbide and chromium (Cr) carbide.

[0022] From now on, M Ｗ represents the ratio of the number of tungsten atoms to the number of atoms constituting the first phase 5, the second phase 6, and the third phase 7. M Ｖ represents the ratio of the number of vanadium atoms to the number of atoms constituting the first phase 5, the second phase 6, and the third phase 7. M Ｃｒrepresents the ratio of the number of chromium atoms to the number of atoms constituting the first phase 5, the second phase 6, and the third phase 7. Ｗ represents the number of tungsten atoms constituting the tungsten carbide particle. Ｖ represents the number of vanadium atoms required to cover a tungsten carbide particle. Ｃｒ represents the number of chromium atoms required to cover a tungsten carbide particle.

[0023] In the cemented carbide according to the embodiment, M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1 (1) The above relationship (1) generally means that the ratio of the number of vanadium atoms or chromium atoms to the number of tungsten atoms, based on the total number of atoms constituting the first phase 5, the second phase 6, and the third phase 7, is greater than the ratio of the number of vanadium atoms or chromium atoms required to cover the WC grains to the number of tungsten atoms. That is, M Ｗ , M Ｖ , and M Ｃｒ However, when the above relationship (1) is satisfied, it is considered that the number of vanadium atoms or chromium atoms relative to the number of tungsten atoms is greater than the number of vanadium atoms or chromium atoms required to cover the WC particles. Ｗ , M Ｖ , and M Ｃｒ However, when the above relationship (1) is satisfied, it is believed that the WC particles can be sufficiently covered with at least one of vanadium (V) carbide and chromium (Cr) carbide. Ｗ , N Ｖ , and N Ｃｒ To satisfy the above relationship (1), Ｗ , M Ｖ , and M Ｃｒ Set.

[0024] Here, N Ｗ , N Ｖ , and N Ｃｒ The calculation method of N will be explained. Ｗ , N Ｖ , and N Ｃｒ In order to calculate the above, a model of tungsten carbide particles and vanadium or chromium atoms constituting the cemented carbide is used. Fig. 4 is a diagram illustrating a model of tungsten carbide particles constituting the cemented carbide. Fig. 5 is a diagram illustrating a model of vanadium or chromium atoms constituting the cemented carbide.

[0025] For example, as shown in Figure 4, a regular triangular prism having a base that is an equilateral triangle with a side length of d and a side that is a square with a side length of d is used as a model of a WC particle 8 that constitutes a cemented carbide. In this case, the volume V of the regular triangular prism is given by ((1 / 2) x d x (√3d / 2)) x d = (√3 / 4) d ３ The total area S of the regular triangular prism is 2 × ((1 / 2) × d × (√3d / 2)) + 3 × (d × d) = ((√3 / 2) + 3) d ２ It is expressed as:

[0026] For example, as shown in Fig. 5, a sphere with a radius r is used as a model of a V or Cr atom 9 that constitutes a cemented carbide. In this case, the cross-sectional area s of the V or Cr atom 9 is expressed as s = πr ２ When the V or Cr atom 9 is a vanadium atom, the radius r is expressed as r Ｖ When the V or Cr atom 9 is a chromium atom, a sphere of radius r = r is used as the model of the chromium atom. Ｃｒ A ball is used.

[0027] N Ｗ is considered to be roughly the number of tungsten carbide units that make up the tungsten carbide particle. Ｗ is N Ｗ = Volume of a regular triangular prism, which is a model of a tungsten carbide particle, V / Volume of a tungsten carbide unit. Ｗ is N Ｗ = (√3 / 4)d ３The volume of the tungsten carbide unit is calculated by, for example, 2.092 × 10 based on "Material Project MP-1894". －１１ μm ３ In this case, N Ｗ is N Ｗ = (√3 / 4) d ３ / (2.092 x 10 －１１ μm ３ ) is calculated as follows.

[0028] N Ｖ is considered to be roughly the number of cross-sectional areas of vanadium atoms contained in the surface area of ​​tungsten carbide. Ｖ is N Ｖ = Area V of a regular triangular prism, which is a model of a tungsten carbide particle / Cross-sectional area s of a sphere, which is a model of a vanadium atom (r = r Ｖ ) is calculated by N Ｖ is N Ｖ =(((√3 / 2)+3)d ２ ) / (πr Ｖ ２ ) where r Ｖ For example, the metallic bond radius of vanadium is 1.31 × 10 －４ In this case, N Ｖ is N Ｖ =(((√3 / 2)+3)d ２ ) / (π × 1.72 × 10 －８ μm ２ ) is calculated as follows.

[0029] N Ｃｒ is considered to be roughly the number of cross-sectional areas of chromium atoms contained in the surface area of ​​tungsten carbide. Ｃｒ is N Ｃｒ = Area V of a regular triangular prism, which is a model of a tungsten carbide particle / Cross-sectional area s of a sphere, which is a model of a chromium atom (r = r Ｃｒ ) is calculated by N Ｃｒ is N Ｃｒ =(((√3 / 2)+3)d ２ ) / (πr Ｃｒ２ ) where r Ｃｒ For example, the metallic bond radius of chromium is 1.28 × 10 －４ In this case, N Ｃｒ is N Ｃｒ =(((√3 / 2)+3)d ２ ) / (π × 1.64 × 10 －８ μm ２ ) is calculated as follows.

[0030] As mentioned above, N Ｗ , N Ｖ , and N Ｃｒ is a function of d. Ｗ , N Ｖ , and N Ｃｒ For example, the cross section of the substrate 2 is photographed using a scanning electron microscope. Since the size of the WC grains contained in the cemented carbide varies, the average cross-sectional size d of the WC grains contained in the cross section of the substrate 2 is calculated by analyzing the scanning electron microscope photograph of the cross section of the substrate 2. ａｖｅ For example, image processing software "Image-J" can be used to analyze the scanning electron microscope photograph of the cross section of the substrate 2. d is calculated by, for example, using the average value d of the cross section of the WC grains contained in the cross section of the substrate 2 calculated as above. ａｖｅ is used.

[0031] N included in the above relationship (1) Ｖ / N Ｗ and N Ｃｒ / N Ｗ is d －１ When the size of WC grains contained in cemented carbide is reduced, d decreases, and therefore N Ｖ / N Ｗ and N Ｃｒ / N Ｗ will increase.

[0032] M Ｗ , M Ｖ , and M ＣｒHowever, when the above relationship (1) is satisfied, it is believed that the WC particles can be adequately covered with at least one of vanadium (V) carbide and chromium (Cr) carbide. Therefore, the growth of the WC particles can be adequately controlled. This allows the variation in hardness of the cemented carbide to be reduced without significantly reducing the toughness of the cemented carbide.

[0033] The average particle size of the tungsten carbide particles may be 0.5 μm or less, which suppresses abnormal growth of WC particles and thus makes it easier to reduce variations in hardness of the cemented carbide.

[0034] M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ ) > 1.75 (2) may be satisfied. In this case, even if vanadium carbide or chromium carbide that does not cover the WC particles is present in the cemented carbide, it is considered that the WC particles can be covered with the vanadium carbide or chromium carbide contained in the cemented carbide. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0035] M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>2 (3) may be satisfied. In this case, even if vanadium carbide or chromium carbide that does not cover the WC particles is present in the cemented carbide, it is considered that the WC particles can be more reliably covered with the vanadium carbide or chromium carbide contained in the cemented carbide. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0036] M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) > 0.5 (4) may be satisfied. In this case, it is thought that at least the vanadium carbide of the vanadium carbide and the chromium carbide contained in the cemented carbide can cover the WC particles. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0037] M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )>0.5, and (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ ) > 0.5 (5) may be satisfied. In this case, it is considered that each of the vanadium carbide and the chromium carbide contained in the cemented carbide can cover the WC particles. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0038] M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) > 0.75 (6) may be satisfied. In this case, it is believed that at least the vanadium carbide of the vanadium carbide and the chromium carbide contained in the cemented carbide can more reliably cover the WC particles. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0039] In a cross-sectional view of the cemented carbide contained in the substrate 2, the first phase 5 may be surrounded by the second phase 6. In this case, the second phase 6 surrounding the first phase 5 can prevent carbon, an inevitable impurity that may cause abnormal growth of the WC grains contained in the first phase 5, from being contained in the WC grains. Therefore, the variation in hardness of the cemented carbide can be more reliably reduced.

[0040] (Coating layer 3) The coating layer 3 coats the base 2 for the purpose of improving the abrasion resistance, heat resistance, etc. of the base 2. While Fig. 2 shows an example in which the coating layer 3 covers the entire surface of the base 2, the coating layer 3 does not necessarily have to cover the entire surface of the base 2. The coating layer 3 only needs to be located on at least a portion of the surface of the base 2. When the coating layer 3 is located on the first surface (here, the upper surface) of the base 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 base 2, the abrasion resistance and heat resistance of the second surface are high.

[0041] The coating layer 3 may be composed of, for example, at least one metal element selected from Groups 4, 5, and 6 of the periodic table, Al (aluminum), and Si (silicon), and at least one nonmetal element selected from C (carbon), N (nitrogen), and O (oxygen). This configuration improves the oxidation resistance of the coating layer 3, further improving the wear resistance of the coating layer 3. The coating layer 3 may be a single layer. Alternatively, the insert 1 may have a layered coating layer 3, i.e., two or more layers.

[0042] (Manufacturing Method) Next, an example of a manufacturing method for the substrate 2 containing cemented carbide as a main component according to the embodiment will be described.

[0043] First, d of the above model is determined in advance. Next, N Ｗ , N Ｖ , and N Ｃｒ Next, set N Ｗ , N Ｖ , and N Ｃｒ From the above relationship (1), M Ｗ , M Ｖ , and M ＣｒDetermine.

[0044] Next, the determined M Ｗ , M Ｖ , and M Ｃｒ With this as a goal, for example, a mixed powder is obtained by mixing tungsten carbide (WC) powder, at least one powder of vanadium carbide and chromium carbide, and nickel or cobalt powder.

[0045] Next, the resulting mixed powder is mixed with a solvent such as water or an organic solvent, and optionally with an organic binder. The mixed powder is then pulverized using a pulverizer such as a ball mill or a vibration mill. The mixed powder is then dried using a spray dryer to obtain granules of the mixed powder.

[0046] Next, the granules of the resulting mixed powder are molded into the desired shape of the insert as shown in FIG. 1 by a molding method such as press molding, casting, extrusion, or cold isostatic pressing to obtain a compact.

[0047] Next, the obtained molded body is placed in a baking furnace under vacuum or Ar, N ２ The mixture is fired in a non-oxidizing atmosphere such as a sintering temperature of 1350 to 1450°C for 0.5 to 5 hours. Thereafter, HIP sintering is carried out at a temperature 5 to 50°C lower than the firing temperature and at a pressure of 5 to 20 MPa for 0.5 to 3 hours to produce a cemented carbide for inserts.

[0048] Thereafter, a coating layer 3 may be provided on the surface of the substrate 2 as needed. The coating layer 3 may be a so-called hard film, and may be formed, for example, by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method. Examples of PVD methods include ion plating and sputtering. Examples of CVD methods include thermal CVD, plasma CVD, organic CVD, and catalytic CVD. The coating layer 3 may be a single-layer film or a multilayer film.

[0049] <Cutting Tool> Next, the configuration of a cutting tool including the insert 1 described above will be described with reference to Fig. 6. Fig. 6 is a front view showing an example of a cutting tool 100 according to an embodiment.

[0050] As shown in FIG. 6 , a cutting tool 100 according to the embodiment includes an insert 1 and a holder 70 for fixing the insert 1 .

[0051] The holder 70 is a rod-shaped member extending from a first end (the upper end in FIG. 6 ) to a second end (the lower end in FIG. 6 ). The holder 70 is made of, for example, steel or cast iron. Of these materials, it is particularly preferable to use steel, which has high toughness.

[0052] The holder 70 has a pocket 73 located at an end on the first end side. The pocket 73 is a portion into which the insert 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.

[0053] The insert 1 is positioned in the pocket 73 of the holder 70 and is attached to the holder 70 by a screw 75. That is, the screw 75 is inserted into the through hole 21 of the insert 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 insert 1 is attached to the holder 70 so that the cutting edge portion protrudes outward from the holder 70.

[0054] In the embodiment, a cutting tool 100 used for so-called turning is exemplified. 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 insert 1 may be used in 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.

[0055] Examples of the present disclosure will be specifically described below, but the present disclosure is not limited to the examples shown below.

[0056] (Example 1) First, d of the above model was set to 0.15 μm. Next, the above-mentioned N Ｗ = (√3 / 4)d３ / (2.092 x 10 －１１ μm ３ ) by the formula N Ｗ was calculated. Ｖ =(((√3 / 2)+3)d ２ ) / (π × 1.72 × 10 －８ μm ２ ) by the formula Ｖ was calculated. Ｃｒ =(((√3 / 2)+3)d ２ ) / (π × 1.64 × 10 －８ μm ２ ) by the formula Ｃｒ The calculated N Ｗ , N Ｖ , and N Ｃｒ are 6.99 × 10 ７ , 1.61 x 10 ６ , and 1.69 × 10 ６ Accordingly, (N Ｖ / N Ｗ ) and (N Ｃｒ / N Ｗ ) were 0.0230 and 0.0242, respectively.

[0057] Next, add (N Ｖ / N Ｗ ) = 0.0230 and (N Ｃｒ / N Ｗ ) = 0.0242 into the formula (M Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242>1, M Ｗ , M Ｖ , and M Ｃｒ The target value was determined.

[0058] Next, the determined M Ｗ , M Ｖ , and M ＣｒA mixed powder was prepared by mixing tungsten carbide powder, vanadium carbide powder, chromium carbide powder, and cobalt powder with reference to the target values. Next, a solvent and an organic binder were mixed with the obtained mixed powder, and the mixed powder was then pulverized using a ball mill. The mixed powder was then dried using a spray dryer to obtain mixed powder granules.

[0059] Next, the granules of the mixed powder obtained were pressed to obtain a compact. Next, the obtained compact was placed in a sintering furnace under N ２ The mixture was fired in a sintering atmosphere at a firing temperature of 1350 to 1450° C. for 0.5 to 5 hours to obtain a cemented carbide.

[0060] Next, a photograph of the cross section of the obtained cemented carbide was taken using a scanning electron microscope. Next, the image processing software "Image-J" was used to photograph the cross section of the obtained cemented carbide, and the average value of the cross-sectional size of the tungsten carbide particles contained in the cross section of the cemented carbide was calculated as the average particle size of tungsten carbide. The calculated average particle size of tungsten carbide was 0.33 μm.

[0061] Next, the content of tungsten atoms, vanadium atoms, and chromium atoms contained in the cemented carbide was measured for a cross section of the obtained cemented carbide using an EDS (energy dispersive X-ray spectrometer) attached to an STEM (scanning transmission electron microscope). That is, the ratio M of the number of tungsten atoms to the number of atoms constituting the cemented carbide was Ｗ , the ratio M of the number of vanadium atoms to the number of atoms constituting the cemented carbide Ｖ , and the ratio M of the number of chromium atoms to the number of atoms constituting the cemented carbide Ｃｒ The measured M Ｗ , M Ｖ , and M Ｃｒ were 0.49, 0.0052, and 0.014, respectively. Ｖ / M Ｗ ) and (M Ｃｒ / M Ｗ ) were 0.011 and 0.029, respectively. Ｖ / M Ｗ) / 0.0230 + (M Ｃｒ / M Ｗ The value of (M) / 0.0242 was 1.6. Ｖ / M Ｗ ) / 0.0230 and (M Ｃｒ / M Ｗ ) / 0.0242 were 0.46 and 1.2, respectively.

[0062] Next, eleven samples of the cemented carbide according to Example 1 were produced using the method described above. Next, the saturation magnetization of each sample of the cemented carbide according to Example 1 was measured using a vibrating sample magnetometer (VSM) or the like. The saturation magnetization of a cemented carbide depends on the amount of carbon contained in the cemented carbide. Specifically, as the amount of carbon contained in the cemented carbide increases, the saturation magnetization of the cemented carbide tends to decrease. Next, using a microindentation hardness tester "ENT-1100b / a" (manufactured by Elionix Co., Ltd.), the Vickers hardness of each sample of the cemented carbide according to Example 1 was measured with an indenter indentation load of 30 N, with the measurement range being from the surface of the wear-resistant layer (i.e., the surface of the coating layer) to a depth of 20% of the thickness of the wear-resistant layer.

[0063] Fig. 7 is a diagram showing the relationship between the saturation magnetization and Vickers hardness of the cemented carbide according to Example 1. In Fig. 7, the horizontal axis represents the saturation magnetization (Ms) of the cemented carbide, and the vertical axis represents the Vickers hardness (HV) of the cemented carbide. As shown in Fig. 7, it was confirmed that when the saturation magnetization of the cemented carbide according to Example 1 was 103 Ms or more and 138 Ms or less, the Vickers hardness of the cemented carbide according to Example 1 was 2013 HV or more and 2104 HV or less. That is, the variation in the Vickers hardness of the cemented carbide according to Example 1 within the above-described range of saturation magnetization of the cemented carbide according to Example 1 was about 91 HV.

[0064] (Example 2) In the same manner as in Example 1, d and N Ｗ , N Ｖ , and N Ｃｒ was set in the same manner as in Example 1. Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / MＷ ) / 0.0242>1, M Ｗ , M Ｖ , and M Ｃｒ The target value was determined.

[0065] Next, the determined M Ｗ , M Ｖ , and M Ｃｒ A cemented carbide was obtained in the same manner as in Example 1, with reference to the target value of . The average particle size of tungsten carbide in the obtained cemented carbide was 0.29 μm. The M measured for the obtained cemented carbide was Ｗ , M Ｖ , and M Ｃｒ were 0.49, 0.0091, and 0.018, respectively. Ｖ / M Ｗ ) and (M Ｃｒ / M Ｗ ) were 0.019 and 0.037, respectively. Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ The value of (M) / 0.0242 was 2.3. Ｖ / M Ｗ ) / 0.0230 and (M Ｃｒ / M Ｗ ) / 0.0242 were 0.81 and 1.5, respectively.

[0066] Next, six samples of the cemented carbide according to Example 2 were produced by the method described above. Next, in the same manner as in Example 1, the saturation magnetization and the Vickers hardness of each sample of the cemented carbide according to Example 2 were measured.

[0067] Fig. 8 is a diagram showing the relationship between the saturation magnetization and Vickers hardness of the cemented carbide according to Example 2. In Fig. 8, the horizontal axis represents the saturation magnetization (Ms) of the cemented carbide, and the vertical axis represents the Vickers hardness (HV) of the cemented carbide. As shown in Fig. 8, it was confirmed that when the saturation magnetization of the cemented carbide according to Example 2 was 105 Ms or more and 138 Ms or less, the Vickers hardness of the cemented carbide according to Example 2 was 2151 HV or more and 2194 HV or less. That is, the variation in the Vickers hardness of the cemented carbide according to Example 2 within the above-mentioned range of saturation magnetization of the cemented carbide according to Example 2 was about 41 HV.

[0068] (Comparative Example) A conventional cemented carbide was prepared as a comparative example. The average particle size of the tungsten carbide in the conventional cemented carbide was 0.3 μm. Ｗ , M Ｖ , and M Ｃｒ were 0.50, 0.0031, and 0.083, respectively. Ｖ / M Ｗ ) and (M Ｃｒ / M Ｗ ) were 0.0062 and 0.017, respectively. Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242 was 0.96.

[0069] Next, eight samples of the cemented carbide according to the comparative example were manufactured by the method described above. Next, the saturation magnetization and Vickers hardness of each sample of the cemented carbide according to the comparative example were measured.

[0070] Fig. 9 is a diagram showing the relationship between the saturation magnetization and Vickers hardness of the cemented carbide according to the comparative example. In Fig. 9, the horizontal axis represents the saturation magnetization (Ms) of the cemented carbide, and the vertical axis represents the Vickers hardness (HV) of the cemented carbide. As shown in Fig. 9, it was confirmed that when the saturation magnetization of the cemented carbide according to the comparative example was 108 Ms or more and 136 Ms or less, the Vickers hardness of the cemented carbide according to the comparative example was 1927 HV ​​or more and 2081 HV or less. In other words, the variation in the Vickers hardness of the cemented carbide according to the comparative example within the above range of saturation magnetization of the cemented carbide according to the comparative example was about 154 HV.

[0071] As described above, the cemented carbides obtained in each of Examples 1 and 2 had a melting point of 1000 .mu.m. Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242>1. On the other hand, the cemented carbide obtained in the comparative example satisfies the formula (M Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242>1 does not satisfy the formula. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to each of Examples 1 and 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to the comparative example. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to each of Examples 1 and 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to the comparative example. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1, it was confirmed that the variation in hardness of the cemented carbide can be reduced.

[0072] The cemented carbide obtained in Example 2 was (MＶ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242>1.75. On the other hand, the cemented carbide obtained in Example 1 satisfies the formula (M Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ ) / 0.0242>1.75 is not satisfied. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 1. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 1. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1.75 is satisfied, the variation in hardness of the cemented carbide can be further reduced.

[0073] The cemented carbide obtained in Example 2 was (M Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ On the other hand, the cemented carbide obtained in Example 1 satisfies the formula (M Ｖ / M Ｗ ) / 0.0230 + (M Ｃｒ / M Ｗ) / 0.0242>2 does not satisfy the formula. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 1. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 1. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>2 is satisfied, it was confirmed that the variation in hardness of the cemented carbide can be further reduced.

[0074] The cemented carbide obtained in Example 2 was (M Ｖ / M Ｗ ) / 0.0230>0.5. On the other hand, the cemented carbide obtained in Example 1 satisfies the formula (M Ｖ / M Ｗ ) / 0.0230>0.5 is not satisfied. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 1. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 1. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )>0.5, it was confirmed that the variation in hardness of the cemented carbide can be further reduced.

[0075] The cemented carbide obtained in Example 2 was (MＶ / M Ｗ ) / 0.0230>0.5 and (M Ｃｒ / M Ｗ ) / 0.0242>0.5. On the other hand, the cemented carbide obtained in Example 1 satisfies the formula (M Ｖ / M Ｗ ) / 0.0230>0.5 is not satisfied. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 1. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 1. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )>0.5, and (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>0.5, it was confirmed that the variation in hardness of the cemented carbide can be further reduced.

[0076] The cemented carbide obtained in Example 2 was (M Ｖ / M Ｗ On the other hand, the cemented carbide obtained in Example 1 satisfies the formula (M Ｖ / M Ｗ ) / 0.0230>0.75 is not satisfied. The variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in saturation magnetization of the cemented carbide according to Example 1. In other words, the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 2 is smaller than the variation in Vickers hardness relative to the variation in the amount of carbon contained in the cemented carbide according to Example 1. Therefore, M Ｗ , M Ｖ , and M Ｃｒ But, (MＶ / M Ｗ ) / (N Ｖ / N Ｗ )>0.75 is satisfied, it was confirmed that the variation in hardness of the cemented carbide can be further reduced.

[0077] As described above, the cemented carbide according to the embodiment includes a first phase (for example, first phase 5) containing tungsten carbide particles, a second phase (for example, second phase 6) containing at least one of vanadium carbide and chromium carbide and covering the first phase, and a third phase (for example, third phase 7) containing nickel or cobalt, and the ratio M of the number of tungsten atoms to the number of atoms constituting the first phase, the second phase, and the third phase is 0.05. Ｗ , the ratio M of the number of vanadium atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｖ , and the ratio M of the number of chromium atoms to the number of atoms constituting the first phase, the second phase, and the third phase. Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1, and N Ｗ is the number of tungsten atoms constituting the tungsten carbide particle, and N Ｖ is the number of vanadium atoms required to cover the tungsten carbide particle, and N Ｃｒ is the number of chromium atoms required to cover the tungsten carbide particle.

[0078] Therefore, according to the cemented carbide according to the embodiment, the variation in hardness of the cemented carbide can be reduced.

[0079] 1 is merely an example and does not limit the shape of the insert according to the present disclosure. The insert according to the present disclosure may have, for example, a rod-shaped body having a rotation axis and extending from a front end to a rear end, a cutting edge located at a first end of the body, and a groove extending spirally from the cutting edge toward a second end of the body.

[0080] Here, an example has been described in which the cemented carbide is used as a tool, but the use of the cemented carbide according to the present disclosure is not limited to tools.

[0081] Supplementary Note (1): A tungsten alloy alloy comprising a first phase containing tungsten carbide particles, a second phase containing at least one of vanadium carbide and chromium carbide and covering the first phase, and a third phase containing nickel or cobalt, wherein the ratio M of the number of tungsten atoms to the number of atoms constituting the first phase, the second phase, and the third phase is Ｗ , the ratio M of the number of vanadium atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｖ , and the ratio M of the number of chromium atoms to the number of atoms constituting the first phase, the second phase, and the third phase. Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1, and N Ｗ is the number of tungsten atoms constituting the tungsten carbide particle, and N Ｖ is the number of vanadium atoms required to cover the tungsten carbide particle, and N Ｃｒ is the number of chromium atoms required to cover the tungsten carbide particles. Appendix (2): The cemented carbide according to Appendix (1), wherein the average particle size of the tungsten carbide particles is 0.5 μm or less. Appendix (3): M Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1.75. Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>2. Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )>0.5. Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )>0.5, and (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>0.5. Ｗ , M Ｖ , and M Ｃｒ is (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ) > 0.75. Appendix (8): The cemented carbide according to any one of Appendixes (1) to (7), wherein, in a cross-sectional view, the first phase is surrounded by the second phase. Appendix (9): An insert comprising: a substrate containing the cemented carbide according to any one of Appendixes (1) to (8). Appendix (10): A cutting tool comprising: a holder extending from a first end to a second end and having a pocket on the first end side; and the insert according to Appendix (9) located in the pocket.

[0082] 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.

[0083] REFERENCE SIGNS LIST 1 Insert 2 Substrate 3 Coating layer 5 First phase 6 Second phase 7 Third phase 8 WC particles 9 V or Cr atoms 21 Through hole 70 Holder 73 Pocket 75 Screw 100 Cutting tool

Claims

1. A first phase containing tungsten carbide particles, a second phase containing at least one of vanadium carbide and chromium carbide and covering the first phase, and a third phase containing nickel or cobalt, and a ratio M of the number of tungsten atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｗ , a ratio M of the number of vanadium atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｖ , and a ratio M of the number of chromium atoms to the number of atoms constituting the first phase, the second phase, and the third phase Ｃｒ satisfy the relationship of (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ )+(M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ )>1, where N Ｗ is the number of tungsten atoms constituting the tungsten carbide particles, N Ｖ is the number of vanadium atoms required to cover the tungsten carbide particles, and N Ｃｒ is the number of chromium atoms required to cover the tungsten carbide particles, a cemented carbide.

2. The cemented carbide according to claim 1, wherein the average particle size of the tungsten carbide particles is 0.5 μm or less.

3. M Ｗ , M Ｖ , and M Ｃｒ satisfy the relationship of (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ ) > 1.75, and the cemented carbide according to claim 1 or 2.

4. M Ｗ , M Ｖ , and M Ｃｒ satisfy the relationship of ((M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) + ((M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ ) > 2, the cemented carbide according to claim 3.

5. M Ｗ , M Ｖ , and M Ｃｒ satisfy the relationship of (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) > 0.5, and the cemented carbide according to any one of claims 1 to 4.

6. M Ｗ , M Ｖ , and M Ｃｒ satisfy the relationship of (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) > 0.5, and (M Ｃｒ / M Ｗ ) / (N Ｃｒ / N Ｗ ) > 0.

5. The cemented carbide according to claim 5 7. M Ｗ 、M Ｖ 、and M Ｃｒ satisfy the relationship of (M Ｖ / M Ｗ ) / (N Ｖ / N Ｗ ) > 0.75, the cemented carbide according to claim 5 or 6.

8. The cemented carbide according to any one of claims 1 to 7, wherein in a cross-sectional view, the first phase is surrounded by the second phase.

9. An insert comprising a substrate containing the cemented carbide according to any one of claims 1 to 8.

10. A cutting tool comprising a holder extending from a first end to a second end and having a pocket on the first end side, and the insert according to claim 9 positioned in the pocket.

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