HARD METAL AND COATED TOOLS AND CUTTING TOOLS USING THEREBY

Abstract

A cemented carbide in a non-limiting embodiment of the present disclosure comprises a hard phase with W and C, a solid solution phase with W, C, and Ti, and a binder phase with an iron group metal. The cemented carbide has a β-free layer formed only of WC and an iron group metal on a surface of a cutting area of ​​a rake face and a flank face in the cemented carbide. The average thickness of the β-free layer of the rake face in the cutting area is "a", and the average thickness of the β-free layer of the flank face in the cutting area is "b". A relationship between "a" and "b" satisfies b < a. A coated tool in a non-limiting embodiment of the present disclosure comprises the cemented carbide and a coating layer arranged on a surface of the cemented carbide.A cutting tool in a non-restrictive embodiment of the present disclosure has a holder extending from a first end to a second end and having a pocket on one side of the first end, and the coated tool is located in the pocket.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2022-051034, filed on March 28, 2022. The contents of this application are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present disclosure relates to a cemented carbide, as well as a coated tool and a cutting tool each using the cemented carbide. BACKGROUND

[0003] Cemented carbide, which contains WC (tungsten carbide) as a hard phase, is used for a base body, etc., in a coated tool, and is used in a cutting tool such as an end mill. Cemented carbide requires fracture toughness, etc.

[0004] For example, as a cemented carbide with excellent fracture toughness, Japanese Patent No. 3235259 (Patent Document 1) describes that a β-free layer is present at a portion of the ridge line of the cutting edge of the cemented carbide and also describes a thickness of the β-free layer. Japanese Patent No. 3656838 (Patent Document 2) does not describe that a β-free layer is present at a portion of the ridge line of the cutting edge of the cemented carbide, but describes the adjustment of the thickness of the β-free layer on each of the rake face and flank face. BRIEF EXPLANATION

[0005] A cemented carbide in one non-limiting embodiment of the present disclosure includes a hard phase including W and C, a solid solution phase including W, C, and Ti, and a binder phase including an iron group metal. The cemented carbide has a β-free layer formed only of WC and an iron group metal at a surface of an intersection of a rake face and a flank face in the cemented carbide. An average thickness of the β-free layer of the rake face in the intersection area is "a," and an average thickness of the β-free layer of the flank face in the intersection area is "b." A relationship between "a" and "b" satisfies the condition of b < a.

[0006] A coated tool in one non-limiting embodiment of the present disclosure includes the cemented carbide and a coating layer disposed on a surface of the cemented carbide.

[0007] A cutting tool in one non-limiting embodiment of the present disclosure includes a holder extending from a first end to a second end and having a pocket on a side of the first end, and the coated tool is disposed in the pocket. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a cemented carbide in a non-limiting embodiment of the present disclosure, Fig. 2 is a sectional view along the line II-II in the Fig. 1 shown hard metal, in particular a sectional view orthogonal to a cutting area in a top view (top view) of a chip surface, Fig. 3 is a sectional view showing a vicinity of a surface of a coated tool in a non-limiting embodiment of the present disclosure, Fig.4 is a sectional view showing a vicinity of a surface of a coated tool in a non-limiting embodiment of the present disclosure, and Fig. 5 is a perspective view showing a cutting tool in a non-limiting embodiment of the present disclosure. EMBODIMENT <hartmetall>

[0008] A cemented carbide 1 in a non-limiting embodiment of the present disclosure will be described in detail below with reference to the drawings. For convenience of description, the drawings referred to below show, in a simplified form, only the main elements necessary for describing the embodiments. Therefore, the cemented carbide 1 may include any structural element not shown in the referenced drawings. The dimensions of the elements in the drawings do not reflect the dimensions of the actual structural elements, nor do they reflect the size ratios of these elements. These points also apply to a coated tool and a cutting tool, which will be described later.

[0009] The cemented carbide 1 may have a hard phase, a solid solution phase and a binder phase.

[0010] The hard phase may contain W (tungsten) and C (carbon). In other words, the hard phase may contain WC. The hard phase may contain WC as a major component. The term "major component" as used herein may mean a component with the largest mass fraction compared to other components. In particular, the components that have the two highest values ​​in mass % among those contained in the hard phase may be W and C.

[0011] The solid solution phase may contain W, C, and Ti (titanium). The solid solution phase may contain W, C, and Ti as a major component. This means that the total mass % of W, C, and Ti may be the largest in the solid solution phase. The components that have the three highest mass % values ​​among the components contained in the solid solution phase may be W, C, and Ti.

[0012] The binder phase may comprise an iron group metal. Examples of an iron group metal include Co (cobalt) and Ni (nickel). The binder phase may comprise at least one of Co and Ni. The binder phase may comprise the iron group metal as a major component. The binder phase may serve as a phase that connects the adjacent hard phases. The iron group metals, including Co and Ni as examples, may have the largest mass % value among the components contained in the binder phase.

[0013] The individual compositions of the hard phase, the solid solution phase, and the binder phase can be measured, for example, using energy-dispersive X-ray spectroscopy (EDS). The measurements can be performed using the EDS contained in an electron microscope. Examples of electron microscopes include a scanning electron microscope (SEM) and a transmission electron microscope (TEM).

[0014] The hard metal 1 may have a rake face 3 and a flank face 5, as in a non-limiting embodiment shown in the Fig. 1 and Fig. 2. That is, the cemented carbide 1 may have the shape of a cutting tool. The cemented carbide 1 may have the shape of a plate. For example, the cemented carbide 1 may have the shape of a square plate, as shown in Fig. 1. In this case, an upper surface can be the rake face 3 and a side surface can be the flank face 5. The shape of the cemented carbide 1 is not limited to the shape of a square plate. The rake face 3 can, for example, have a triangular, pentagonal, hexagonal, or circular shape.

[0015] The cemented carbide 1 is not limited to specific dimensions. For example, the width D1 of the rake face 3 can be set to 3-20 mm. The width D2 of the flank face 5 can be set to 5-20 mm. The widths D1 and D2 can be dimensions in a direction orthogonal to an intersecting ridge line portion of the rake face 3 and the flank face 5.

[0016] The cemented carbide 1 may have an intersection area 7 of the rake face 3 and the flank face 5. Namely, the intersection area 7 is a part of the ridge line of the cutting edge, and a cutting edge may be subjected to honing as cutting edge processing. A part of the cutting edge subjected to cutting edge processing may be the ridge line part. Honing may be a machining method in which the cutting edge is polished by pressing a hone against the cutting edge while rotating and reciprocating the hone. In other words, the intersection area 7 may be an area subjected to honing in the intersection area of ​​the ridge line part of the rake face 3 and the flank face 5.In particular, in a top view (plan view) of the rake face 3, a region of a range S1 from a boundary part L1 on one side of the rake face 3 to the flank face 5 of the part of the ridge line of the cutting edge, and in a top view (plan view) of the flank face 5, a region S2 from a boundary part L2 on one side of the flank face 5 to the rake face 3 of the part of the ridge line of the cutting edge, the cutting area 7 may be (see . Fig. 2).

[0017] If it is difficult to determine the boundary part L1, a position 80 µm away from the flank surface 5 in the plan view of the rake face 3 can be regarded as the boundary part L1. If it is difficult to determine the boundary part L2, a position 60 µm away from the rake face 3 in the plan view of the flank surface 5 can be regarded as the boundary part L2.

[0018] The cutting area 7 may have a convex curved surface shape. The shape of the cutting area 7 is not limited to the shape of a convex curved surface. For example, the cutting area 7 may have a flat shape that is subjected to chamfering. The cutting area 7 with the flat shape is inclined with respect to the rake surface 3 and the flank surface 5. Therefore, it is easy to determine an end part on one side of the rake surface 3 in the cutting area 7 and an end part on one side of the flank surface 5 in the cutting area 7. When the cutting area 7 has the convex curved surface shape, it is easy to determine the end part on the rake surface 3 side in the cutting area 7 and the end part on the flank surface 5 side in the cutting area 7 from a difference between the rake surface 3 and the flank surface 5, each having the flat shape, and the cutting area 7 having the convex curved surface shape.

[0019] The cutting area 7 can be located on part or all of the intersecting ridge line of the rake face 3 and the flank face 5. The cutting area 7 can be used for machining a workpiece.

[0020] The cemented carbide 1 may have a β-free layer 9 on a surface of the cutting region 7 formed only of WC and an iron group metal, as in the non-limiting embodiment shown in Fig. 2. The β-free layer 9 is a layer rich in an iron group metal such as Co, which has excellent toughness and can serve as a layer that absorbs a shock caused between it and a workpiece to prevent fracture. Therefore, when the cemented carbide 1 has the β-free layer 9 on the surface of the cutting portion 7, the cutting portion 7 is less likely to fracture.

[0021] As used herein, "the β-free layer 9 formed only of WC and the iron group metal" means that almost all of the components constituting the β-free layer 9 are WC and the iron group metal. The β-free layer 9 may contain impurities that are unavoidable during the manufacturing process. A total content of the impurities may be 3 mass% or less, in other words, a total value of WC and the iron group metal may be 97 mass% or more.

[0022] The cemented carbide 1 can have the β-free layer 9 on the entire surface of the cutting area 7. In other words, the entire surface of the cutting area 7 can be the β-free layer 9 in the cemented carbide 1. The cemented carbide 1 can also have the β-free layer 9 on a surface other than the cutting area 7. The iron group metal in the β-free layer 9 can have the same composition as the iron group metal in the binder phase. The β-free layer 9 can be identified, for example, using EDS.

[0023] Here, an average thickness of the β-free layer 9 on the rake face 3 in the cutting area 7 can be denoted as "a," and an average thickness of the β-free layer 9 on the flank face 5 in the cutting area 7 can be denoted as "b." A relationship between "a" and "b" can satisfy b < a. In this case, the cutting area 7 is less susceptible to cracks, chipping, etc., and the probability of the cutting area 7 breaking is significantly lower. Consequently, the cemented carbide 1 has increased fracture strength.

[0024] The relationship between "a" and "b" can satisfy 1 < a / b ≤ 2.5. In this case, it is easy to improve the fracture toughness of cemented carbide 1.

[0025] The relationship between "a" and "b" can be 1.5 ≤ a / b ≤ 2.5. In this case, it is easier to improve the fracture toughness of cemented carbide 1.

[0026] The average thickness of the β-free layer 9 of the rake face 3 in the cutting region 7 can indicate, as viewed from the rake face 3, the average thickness of the β-free layer 9 at an end part on one side of the rake face 3 in the cutting region 7. Therefore, the average thickness of the β-free layer 9 of the rake face 3 in the cutting region 7 can be expressed as the average thickness of the β-free layer 9 in a region S1a located at the end part on the side of the rake face 3 in the cutting region 7. The region S1a can be, for example, a region extending 10 μm from the boundary part L1.

[0027] The average thickness of the β-free layer 9 of the flank surface 5 in the intersection region 7, viewed from the flank surface 5, can indicate the average thickness of the β-free layer 9 at an end part on one side of the flank surface 5 in the intersection region 7. Therefore, the average thickness of the β-free layer 9 of the flank surface 5 in the intersection region 7 can be expressed as the average thickness of the β-free layer 9 in a region S2a located at the end part on the side of the flank surface 5 in the intersection region 7. The region S2a can be, for example, a region extending by 5 μm from the boundary part L2.

[0028] The thickness of the β-free layer 9 can be measured by cross-sectional observation using an electron microscope. A cross-section to be observed can, for example, be a cross-section as shown in Fig. 2. That is, the cross section to be observed may be a cross section orthogonal to the cutting area 7 in the top view (plan view) of the rake face 3. The thickness of the β-free layer 9 may be measured at 5 or more measuring points at intervals of 1 μm with a width of 5 μm or more at any position of the area S1a or the area S2a in the cross section, and an average value may be calculated therefrom.

[0029] Here, "a" and "b" are not limited to a specific thickness. For example, "a" can be set to 7.3-14.3 µm and "b" can be set to 2.9-13 µm.

[0030] An average thickness of the β-free layer 9 in the cutting area 7 may decrease monotonically from one side of the rake face 3 to one side of the flank face 5. When the average thickness of the β-free layer 9 has the above configuration, the cutting area 7 is much less prone to cracking and chipping, and the cutting area 7 is much less likely to break.

[0031] The cutting region 7 may further include a region located between an end part on one side of the rake face 3 and an end part on one side of the flank face 5, in which the average thickness of the β-free layer 9 is "c." In other words, the cutting region 7 may further include another region between the region S1a and the region S2a, and the average thickness of the β-free layer 9 in the region may be "c." In this case, "c" may be smaller than either of "a" and "b." When the average thickness of the β-free layer 9 has the above configuration, the β-free layer 9 can be made thin at a cutting edge, thereby maintaining the cutting performance of the cutting edge.

[0032] In cases where the section area 7 in the section view has the convex curved surface shape as in the Fig. 2, the region where the average thickness of the β-free layer 9 is "c" may be located at a part with a minimum radius of curvature in the cutting region 7. Specifically, the radius of curvature of the cutting region 7 in the region where the average thickness of the β-free layer 9 is "c" may be smaller than a radius of curvature of the cutting region 7 in each of the regions S1a and S2a. When the cutting region 7 has the above configuration, the cutting edge can be made sharp, thereby maintaining the cutting performance of the cutting edge.

[0033] The region where the average thickness of the β-free layer 9 is "c" may be located on one side of the flank surface 5 rather than on one side of the rake surface 3. In other words, the region where the average thickness of the β-free layer 9 is "c" may be located closer to the flank surface 5 than to the rake surface 3. In this case, the thickness of the β-free layer 9 of the rake surface 3 may be increased to improve the fracture strength.

[0034] A width of the cutting area 7 in a plan view of the rake face 3 may be larger than a width of the cutting area 7 in a plan view of the flank face 5. In this case, an increase in the radius of curvature of the honing of the rake face 3 leads to an improvement in the performance against chipping. <Verfahren zur Herstellung von Hartmetall>

[0035] A method for producing a cemented carbide in a non-limiting embodiment of the present disclosure will be described below using the example of producing a cemented carbide 1.

[0036] Initially, WC powder, Co powder, and TiC powder can be produced as raw material powders. The proportion of Co powder can be 4-12 mass%. The proportion of TiC powder can be 0.5-15 mass%. The remainder can be WC powder.

[0037] The average particle diameters of the raw material powders can be conveniently selected within a range of 0.1–10 µm. The average particle diameters of the raw material powders can be values ​​measured using a micro-tracking method.

[0038] A molded article can be obtained by mixing the prepared raw material powders and then molding them to have a rake face 3 and a flank face 5. This may include pre-molding into a shape obtained by chamfering a ridgeline cut portion of the rake face 3 and the flank face 5 by a metal forming press. In this case, it is easy to form a β-free layer 9 on a surface of a cut portion 7. The chamfering may include forming the ridgeline cut portion into a convex curved surface shape and a flat shape.

[0039] A cemented carbide 1 can be obtained by subjecting the resulting molded body to a debinding treatment, followed by sintering. Sintering can be carried out in a non-oxidizing atmosphere, such as vacuum, argon, or nitrogen. A sintering temperature can be 1450-1600°C. A sintering time can be 0.5-3 hours. It is easy to form the β-free layer 9 on a surface of the cemented carbide 1 when sintering is carried out at the above-mentioned sintering temperature and for the above-mentioned sintering time.

[0040] The resulting cemented carbide 1 can be subjected to honing to form the cutting area 7 of the rake face 3 and the flank face 5. Subsequently, the thickness of the β-free layer 9 can be adjusted by polishing the cutting area 7 such that a ratio between "a" and "b" b < a is sufficient. Polishing can be performed, for example, by brushing, blasting, and barrel treatment.

[0041] The above manufacturing method is one embodiment of the method for manufacturing the cemented carbide 1. Therefore, it is needless to say that the cemented carbide 1 is not limited to one manufactured by the above method. <Beschichtetes Werkzeug>

[0042] A coated tool 101 in a non-limiting embodiment of the present disclosure is described below with reference to the Fig. 3 and Fig. 4, wherein the case is shown as an example in which it has the hard metal 1 described above.

[0043] The coated tool 101 may comprise the cemented carbide 1 and a coating layer 103 disposed on a surface of the cemented carbide 1, as in the non-limiting embodiment shown in the Fig. 3 and Fig. 4. The coated tool 101 may include the cemented carbide 1 as a base body. When the coated tool 101 includes the cemented carbide 1, it is easy to improve the cutting performance, e.g., the intermittent performance, due to the high fracture toughness of the cemented carbide 1. This results in a long service life of the coated tool 101.

[0044] The coating layer 103 can be arranged on all or part of the surface of the cemented carbide 1. That is, the coating layer 103 can be arranged on at least part of the surface of the cemented carbide 1.

[0045] The coating layer 103 may be deposited using the chemical vapor deposition (CVD) method. In other words, the coating layer 103 may be a CVD layer. Alternatively, the coating layer 103 may be a PVD layer deposited using the physical vapor deposition (PVD) method.

[0046] The coating layer 103 may be configured as a single layer or may be configured with a plurality of laminated layers. Examples of the composition of the coating layer 103 may include TiCN (titanium carbonitride), Al2O3 (aluminum oxide), and TiN (titanium nitride).

[0047] The coating layer 103 may comprise a TiCN layer 105 and an Al2O3 layer 107, which follow one another from one side of the cemented carbide 1, as shown in the Fig. 3. The TiCN layer 105 may be in contact with the cemented carbide 1. The Al2O3 layer 107 may be in contact with the TiCN layer 105.

[0048] The coating layer 103 may comprise a TiN layer 109, the TiCN layer 105 and the Al2O3 layer 107, in sequence from one side of the cemented carbide 1, as shown in Fig. 4. The TiN layer 109 may be in contact with the cemented carbide 1. The TiCN layer 105 may be in contact with the TiN layer 109. The Al2O3 layer 107 may be in contact with the TiCN layer 105.

[0049] The coating layer 103 is not limited to a specific thickness. For example, the thickness of the TiCN layer 105 may be set to approximately 1.0-15 µm. A thickness of the Al2O3 layer 107 may be set to approximately 1-15 µm. A thickness of the TiN layer 109 may be set to approximately 0.1-5 µm. The thickness of the coating layer 103 can be measured by cross-sectional observation using an electron microscope. The thickness of the coating layer 103 may be an average value. For example, the thickness may be measured at 10 or more measuring points at intervals of 1 µm with a width of 10 µm or more at any position of each layer, and an average value may be calculated therefrom.

[0050] The coated tool 101 may have a through hole 111. For the sake of simplicity, Fig. 1, the through hole 111. The through hole 111 can be used for attaching a fastening screw or a clamping part when the coated tool 101 is held in a holder. The through hole 111 can be formed from an upper surface (chip surface 3) to a lower surface located on a side opposite the upper surface, and the through hole 111 can open into these surfaces. It is also not a problem if the through hole 111 is configured to open into areas that are opposite each other in a side surface (clearance surface 5). <Verfahren zur Herstellung eines beschichteten Werkzeugs>

[0051] A method for producing a coated tool in a non-limiting embodiment of the present disclosure is described below using the example of producing a coated tool 101.

[0052] The coated tool 101 can be obtained by depositing a coating layer 103 on a surface of a cemented carbide 1 by a CVD method.

[0053] A TiCN layer 105 can be deposited as follows. First, a gas mixture consisting of 0.1-10 vol% titanium tetrachloride (TiCl4) gas, 10-60 vol% nitrogen (N2) gas, 0.1-15 vol% methane (CH4) gas, and the remainder hydrogen (H2) gas can be prepared as the reaction gas composition. The gas mixture can be introduced into a chamber to deposit the TiCN layer 105, with a temperature of 800-1100°C and a pressure of 5-30 kPa.

[0054] An Al2O3 layer 107 can be deposited as follows. First, a gas mixture consisting of 0.5-5 vol% aluminum trichloride (AlCl3) gas, 0.5-3.5 vol% hydrogen chloride (HCl) gas, 0.5-5 vol% carbon dioxide (CO2) gas, 0.5 vol% or less hydrogen sulfide (H2S) gas, and the remainder hydrogen (H2) gas can be prepared as the reaction gas composition. The gas mixture can be introduced into the chamber to deposit the Al2O3 layer 107 by setting a temperature of 930-1010°C and a pressure of 5-10 kPa.

[0055] A TiN layer 109 can be deposited as follows. First, a gas mixture consisting of 0.1-10 vol% titanium tetrachloride (TiCl4) gas, 10-60 vol% nitrogen (N2) gas, and the remainder hydrogen (H2) gas can be prepared as the reaction gas composition. The gas mixture can be introduced into the chamber to deposit the TiN layer 109, with a temperature of 800-1010°C and a pressure of 10-85 kPa.

[0056] The above method is one embodiment of the method for manufacturing the coated tool 101. Therefore, it is needless to say that the coated tool 101 is not limited to one manufactured by the above method. <schneidwerkzeug>

[0057] A cutting tool 201 in a non-limiting embodiment of the present disclosure will be described below with reference to Fig. 5 by exemplifying the case of having the coated tool 101.

[0058] The cutting tool 201 may include a holder 203 extending from a first end 203a to a second end 203b and having a pocket 205 on one side of the first end 203a, and the coated tool 101 is disposed in the pocket 205. When the cutting tool 201 includes the coated tool 101, the cutting tool 201 has high wear resistance and is capable of stable machining due to the high durability of the coated tool 101.

[0059] The pocket 205 may be a part to which the coated tool 101 is attached. The pocket 205 may open into an outer peripheral surface of the holder 203 and an end surface on one side of the first end 203a.

[0060] The coated tool 101 may be fixed to the pocket 205 such that a cutting portion 7 may protrude outward from the holder 203. The coated tool 101 may also be fixed to the pocket 205 by a fixing screw 207. That is, the coated tool 101 may be fixed to the pocket 205 by inserting the fixing screw 207 into a through hole 111 of the coated tool 101 and inserting a front end of the fixing screw 207 into a screw hole formed in the pocket 205 to ensure engagement between screw parts. In this case, a lower surface of the coated tool 101 may directly contact the pocket 205, or alternatively, a plate may be held between the coated tool 101 and the pocket 205.

[0061] For example, steel and cast iron can be used as the material of the holder 203. If the material of the holder 203 is steel, the holder 203 has high toughness.

[0062] In the Fig. In the embodiment shown in Figure 5, the cutting tool 201 is used for a so-called turning process. Examples of the turning process may include internal machining, external machining, and grooving. The use of the cutting tool 201 is not limited to the turning process. For example, it is not a problem if the cutting tool 201 is also used for a milling process.

[0063] Although the present disclosure will be described in detail below by way of examples, the present disclosure is not limited to the following examples. EXAMPLES[Examples No. 1 to 6]<Herstellung von Hartmetall>

[0064] First, WC powder with an average particle diameter of 9 µm, Co powder with an average particle diameter of 1.5 µm, and TiC powder with an average particle diameter of 1.5 µm were prepared as raw material powders. The average particle diameters of the raw material powders were measured using the micro-track method.

[0065] Subsequently, a molded body was prepared by mixing the respective proportions of 7 mass% of Co powder, 2 mass% of TiC powder, and the remainder being WC powder. It was then pressed into a cutting tool mold (CNMG120408) to form a rake face and a flank face. Samples Nos. 1 to 5 were formed by chamfering an intersecting ridge line portion of the rake face and flank face into a convex curved surface shape using a metal forming press.

[0066] Each of the resulting molded bodies was subjected to debinding treatment and sintered at 1500°C for one hour to obtain a cemented carbide. The resulting cemented carbide was subjected to honing to form a cutting area of ​​the rake face and flank face.

[0067] The composition of the resulting cemented carbide was measured using an EDS. Specifically, a cross-sectional observation was performed using the EDS mounted on an SEM, and measurements were taken under conditions where five locations were measured at 5000-20000x magnification to obtain an average value.

[0068] The results of the EDS measurements showed that all the obtained cemented carbides had a hard phase containing W and C as a main component, a solid solution phase containing W, C, and Ti as a main component, and a binder phase containing an iron group metal (Co) as a main component. The cemented carbides of Samples Nos. 1 to 5 had a β-free layer composed only of WC and an iron group metal (Co) on the entire surface of the cutting area.

[0069] For each of Samples Nos. 1 to 5, the cut area was polished (brushing or blasting treatment), so that "a" and "b" can assume the values ​​shown in Table 1. The values ​​of "a" and "b" shown in the column "average thickness of the β-free layer in the cut area" in Table 1 are values ​​measured according to the method described above. <auswertung>

[0070] The obtained cemented carbides were subjected to machining evaluation. Specifically, a coated tool was fabricated by successively depositing a 1 µm thick TiN layer, a 10 µm thick TiCN layer, and a 6 µm thick Al2O3 layer on one side of the cemented carbide (base body) using the CVD process. Cutting performance was then evaluated under the following conditions. The thickness of each of these layers is an average value. Machining type: Turning Cutting speed: 150 m / min Feed: 0.4 mm / revolution Cutting depth: 0.5 mm Workpiece: SCM440 ϕ200 round bar Processing condition: Wet

[0071] The evaluation results are shown in Table 1. The term "number of impacts until cutting edge fracture occurs" indicates the number of impacts until the cutting edge fractures during a machining operation. This is also referred to as intermittent performance evaluation. [Table 1] Sample No. Average thickness of the β-free layer in the cutting area (µm) Evaluation results a b away Number of impacts until a break in the cutting edge occurs (number) 1 7,3 2,9 2,5 30,000 or more 2 8,6 6,6 1,3 25000 3 11,4 5,7 2 30,000 or more 4 14,3 13 1,1 9000 5 11,4 11,4 1 900 6 0 0 0 650

[0072] Samples Nos. 1 to 4 showed obviously improved stability compared with samples Nos. 5 and 6. In particular, sample No. 6 had no β-free layer on the surface of the cutting area, had the least number of impacts, low wear resistance at the cutting edge, and it was difficult to perform stable machining as a cutting tool. Reference symbol 1 carbide 3 chip surface 5 open space 7 Cutting area 9 β-free layer 101 Coated tool 103 Coating layer 105 TiCN layer 107 Al2O3 layer 109 TiN layer 111 Through hole 201 cutting tool 203 holders 203a first end 203b second end 205 Bag 207 fixing screw QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-051034

[0001] JP 3235259

[0004] JP 3656838

[0004] < / auswertung> < / schneidwerkzeug> < / hartmetall>

Claims

[1] A hard metal comprising: a hard phase containing W and C, a solid solution phase comprising W, C and Ti, and a binder phase comprising an iron group metal, wherein the cemented carbide has a β-free layer formed only from WC and an iron group metal on a surface of an intersection area of ​​a rake face and a flank face in the cemented carbide, is an average thickness of the β-free layer of the rake face in the cutting area “a”, and is an average thickness of the β-free layer of the flank in the section area “b”, and a relationship between “a” and “b” satisfies the condition b < a. [2] The cemented carbide according to claim 1, wherein the ratio between “a” and “b” satisfies the value 1 < a / b ≤ 2.

5. [3] The cemented carbide according to claim 1, wherein the average thickness of the β-free layer in the cutting area monotonically decreases from one side of the rake face to one side of the flank face. [4] The hard metal according to claim 1, wherein the cutting area has an area lying between an end part on one side of the rake face and an end part on one side of the flank face and in which the average thickness of the β-free layer is ‘c’, and the “c” is smaller than any “a” and “b”. [5] The cemented carbide according to claim 4, wherein the region where the average thickness of the β-free layer is “c” is located at a part having a minimum radius of curvature in the cutting region. [6] The cemented carbide according to claim 4, wherein the region in which the average thickness of the β-free layer is “c” is closer to a side of the flank surface than to a side of the rake surface. [7] The cemented carbide according to claim 1, wherein a width of the cutting area in plan view of the rake face is larger than a width of the cutting area in plan view of the flank face. [8] A coated tool comprising: the hard metal according to one of claims 1 to 7 and a coating layer disposed on a surface of the cemented carbide. [9] The coated tool according to claim 8, wherein the coating layer comprises a TiCN layer and an Al2O3 layer in this sequence from one side of the cemented carbide. [10] The coated tool according to claim 8, wherein the coating layer comprises a TiN layer, a TiCN layer and an Al2O3 layer in this sequence from one side of the cemented carbide. [11] A cutting tool comprising: a holder extending from a first end to a second end and having a pocket on one side of the first end, and the coated tool according to any one of claims 8 to 10, which is arranged in the pocket.

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