WC-based cemented carbide

Abstract

This WC-based cemented carbide is characterized by containing a total of 4.0-12.0 mass% of Co, Ni, and Fe and 0.0-1.0 mass% of Cr with a (Cr content (mass%)) / (total content (mass%) of Co, Ni, and Fe) value being 0.10 or less, and also containing 0.0-12.0 mass% of M (M is one or more of Ta, Nb, and Ti) and 5.4-8.0 mass% of C, with the balance being made up of W and unavoidable impurities. This WC-based cemented carbide is also characterized by including a main hard phase that contains a carbide of W as a main component, an auxiliary hard phase that contains a carbide of M as a main component, and a binder phase that contains Co and / or Ni as a main component, wherein: the main hard phase is composed of crystal grains having an average grain size in the range of 0.8-3.0 µm; the crystal grains include first crystal grains that have a grain size in the range of 0.2 µm to 6.0 µm and an average value (GOSave) of grain orientation spread (GOS) in the range of 0.85° to 1.50°; and the area ratio A1 / A of the area A1 occupied by the first crystal grains to the area A occupied by the crystal grains is 0.20-1.00.

Description

WC-based cemented carbide

[0001] The present invention relates to WC-based cemented carbide, and more particularly to WC-based cemented carbide suitable for cutting tool substrates including surface-coated cutting tool substrates. This application claims priority under Japanese Patent Application No. 2024-231674, filed on 27 December 2024, and Japanese Patent Application No. 2025-50646, filed on 25 March 2025. All provisions contained in said Japanese Patent Applications are incorporated herein by reference.

[0002] Conventionally, WC-based cemented carbide alloys containing a hard phase mainly composed of tungsten carbide and a binder phase mainly composed of Co have been used as the base material for cutting tools. In addition to strength, toughness, hardness, resistance to plastic deformation and wear resistance, this base material is required to have resistance to chipping, chipping and thermal cracking.

[0003] For example, in addition to proposals to improve chipping resistance and fracture resistance by increasing the CO content or coarsening the tungsten carbide particles, there have also been proposals to improve chipping resistance and fracture resistance by methods and means other than increasing the CO content or coarsening the tungsten carbide particles.

[0004] For example, Patent Document 1 describes a WC-based cemented carbide in which the number of tungsten carbide particles with an inter-grain orientation difference of 0.75° or less accounts for 70% or more of the total number of tungsten carbide particles, and this WC-based cemented carbide is said to be less prone to thermal cracking and less likely to experience chipping.

[0005] Patent No. 5835305

[0006] The present invention has been made based on the above circumstances and proposals, and in particular aims to provide a WC-based cemented carbide that exhibits excellent resistance to plastic deformation, wear resistance, chipping resistance, and fracture resistance in wet cutting of various stainless steels, including austenitic stainless steel, and Ni-based alloys when used as a base material for cutting tools (with or without a coating layer).

[0007] Here, both chipping and chipping refer to the phenomenon where a portion of the cutting edge locally breaks off during cutting. The difference between the two is as follows: Chipping is a small-scale fracture that allows cutting to continue, while chipping is a large-scale fracture that makes cutting impossible. Furthermore, the process leading to chipping can involve gradual fracture after chipping, or sudden chipping due to mechanical stress during cutting without any prior chipping.

[0008] It should be noted that chipping resistance and chipping resistance represent the likelihood of chipping and chipping occurring, respectively, and the boundary between the two is ambiguous; therefore, this distinction is not necessarily clear in this specification.

[0009] The following six types of WC-based cemented carbide are examples of the embodiments of the present invention.

[0010] (Embodiment 1) The WC-based cemented carbide according to Embodiment 1 contains: Total of Co and / or Ni and an optional component Fe: 4.0 to 12.0 mass%, Cr: 0.0 to 1.0 mass%, where [Cr content (mass%)] / [Total content of Co, Ni and Fe (mass%)] is 0.10 or less, M (M is at least one selected from the group consisting of Ta, Nb and Ti): 0.0 to 12.0 mass%, C: 5.4 to 8.0 mass%, the remainder being W and unavoidable impurities, and comprises a main hard phase mainly composed of W carbides, a secondary hard phase mainly composed of M carbides, and a binder phase mainly composed of Co and / or Ni, the main hard phase is composed of crystal grains having an average particle size in the range of 0.8 to 3.0 μm, and the crystal grains are The grain size is in the range of X1 μm to X2 μm, and the average value of the mean orientation difference within the crystal grain (GOS) is... ａｖｅ ) includes a first crystal grain whose angle is in the range of 0.85 to 1.50°, and X1 and X2 satisfy 0.2 ≤ X1 < X2 ≤ 6.0, and the area ratio A １ / A is between 0.20 and 1.00, where A １ is the area occupied by the first crystal grain, and A is the area occupied by the aforementioned crystal grain.

[0011] (Embodiment 2) The WC-based cemented carbide according to Embodiment 2, in the above Embodiment 1, the crystal grains have a particle size in the range of X3 μm to X4 μm, and the average value of the average orientation difference (GOS) within the crystal grains (GOS ａｖｅ ) further includes second crystal grains in the range of 0.30 to 0.80°, where X1, X2, X3, and X4 satisfy 0.2 ≦ X1 < X2 < X3 < X4 ≦ 6.0 or 0.2 ≦ X3 < X4 < X1 < X2 ≦ 6.0, and the area ratio A ２ / A is 0.20 to 0.40, where A ２ is the area occupied by the second crystal grains.

[0012] (Embodiment 3) The WC-based cemented carbide according to Embodiment 3, in the above Embodiment 1, X1 is 0.2 and X2 is 2.0.

[0013] (Embodiment ④) The WC-based cemented carbide according to Embodiment 4, in the above Embodiment 1, X1 is 2.5 and X2 is 6.0.

[0014] (Embodiment 5) The WC-based cemented carbide according to Embodiment 5, in the above Embodiment 2, X1 is 0.2, X2 is 2.0, X3 = 2.5, and X4 is 6.0.

[0015] (Embodiment ⑥) The WC-based cemented carbide according to Embodiment 6, in the above Embodiment 2, X1 is 2.5, X2 is 6.0, X3 is 0.2, and X4 is 2.0.

[0016] When the WC-based cemented carbide according to each of the above embodiments is used as a cutting tool substrate (which may or may not have a coating layer), it has excellent plastic deformation resistance, wear resistance, chipping resistance, and defect resistance in the wet cutting of various stainless steels including austenitic stainless steel and Ni-based alloys.

[0017] A schematic explanatory diagram of the measurement points of the average orientation difference (GOS) within the crystal grains is shown. It is a schematic diagram showing an example of the plastic deformation amount of the flank face of the cutting edge. Note that the upper figure (rake face) is a plan view, and the lower figure (flank face) is a side view.

[0018] The inventors first examined the prior art. As a result, the following matters (1) to (2) were recognized.

[0019] (1) In order to improve the chipping resistance and crater wear resistance required for a WC-based cemented carbide used as a cutting tool substrate, increasing the Co content or coarsening the tungsten carbide particles may sacrifice the plastic deformation resistance and wear resistance.

[0020] (2) If the proportion of the number of tungsten carbide grains having an intragranular orientation difference within a specific range as described in Patent Document 1 is controlled, it is possible to some extent improve the chipping resistance and crater wear resistance, but it may not be sufficient to improve the plastic deformation resistance and wear resistance.

[0021] Therefore, the present inventors have conducted intensive studies, and when the average value (GOS ａｖｅ ) of the average orientation difference (GOS) of grains within a predetermined grain size range among the tungsten carbide grains is within a specific range, novel findings have been obtained that the plastic deformation resistance, wear resistance, crater wear resistance, and chipping resistance are improved in wet cutting of various stainless steels including austenitic stainless steel and Ni-based alloys.

[0022] The present invention is based on this finding. Hereinafter, the present invention will be described by explaining in more detail the WC-based cemented carbide according to an embodiment of the present invention. In the description of this specification and the claims, when a numerical range is expressed as "K to L", it is synonymous with "K or more and L or less", and the range includes the numerical values of the upper limit value (L) and the lower limit value (K). Also, when only the upper limit value (L) is described with a unit, the upper limit value (L) and the lower limit value (K) are in the same unit.

[0023] 1. Composition The composition of the WC-based cemented carbide according to Embodiments 1 to 6 will be described below. The composition of the WC-based cemented carbide according to Embodiments 1 to 6 is as follows: Total of Co and / or Ni and an optional component Fe: 4.0 to 12.0 mass%, Cr: 0.0 to 1.0 mass%, where [Cr content (mass%)] / [Total content of Co, Ni and Fe (mass%)] is 0.100 or less, M (M is at least one element selected from the group consisting of Ta, Nb and Ti): 0.0 to 12.0 mass%, C: 5.4 to 8.0 mass%, and the remainder is W and unavoidable impurities. The content of each element will be described below in order.

[0024] (1) Co, Ni, Fe The total content of Co and / or Ni and the optional component Fe is 4.0 to 12.0 mass%. The reason is as follows: When the WC-based cemented carbide of Embodiments 1 to 6 is used as the base material for a cutting tool, if it is less than 4.0 mass%, the fracture resistance and chipping resistance are insufficient, while if it exceeds 12 mass%, the plastic deformation resistance and wear resistance become insufficient. It is more preferable that the total content be 6.0 to 10.0 mass%.

[0025] Note that Co and / or Ni are the main components of the crystal grains that constitute the bonded phase (Fe is mainly contained in the bonded phase but does not constitute a main component). Here, the main component of a crystal grain means that the main component accounts for 50% or more by mass of the total amount of all elements contained in that crystal grain. This definition of the main component also applies to the definition of the main component of other crystal grains.

[0026] (2) Cr The inclusion of Cr is optional. That is, Cr does not have to be included, and if it is included, it should be 1.0% by mass or less. Cr has the effect of suppressing the growth of W carbides, and if the amount exceeds the upper limit, when the WC-based cemented carbide of Embodiments 1 to 6 is used as a base material for cutting tools, the fracture resistance and chipping resistance will not be sufficient. A Cr content of 0.2 to 0.8% by mass is more preferable.

[0027] Furthermore, it is preferable that the ratio of [Cr content (mass%)] / [total content of Co, Ni, and Fe (mass%)] is 0.10 or less (the lower limit may be 0.0%). If this content ratio is not satisfied, when the WC-based cemented carbide of Embodiments 1 to 6 is used as a base material for a cutting tool, the fracture resistance and chipping resistance will not be sufficient. It is more preferable that this content ratio is 0.40 to 0.80.

[0028] (3) M (M is at least one element selected from the group consisting of Ta, Nb, and Ti) The inclusion of M, which is at least one element selected from the group consisting of Ta, Nb, and Ti, is optional. That is, M does not have to be included, and if it is included, the total content of Ta, Nb, and Ti is 12.0 mass% or less. M is the main component of the secondary hard phase, and if it is included in an amount exceeding the upper limit of the total content, when the WC-based cemented carbide of Embodiments 1 to 6 is used as a base material for a cutting tool, the fracture resistance and chipping resistance will not be sufficient. The content of M is more preferably 2.0 to 8.0 mass%.

[0029] (4) The C content is 5.4 to 8.0% by mass. If the C content is within this range, an appropriate amount of carbides will be formed in the WC-based cemented carbide of Embodiments 1 to 6.

[0030] (5) W constitutes the remainder of the composition together with unavoidable impurities that are unintentionally included in the raw materials for manufacturing the WC-based cemented carbide of Embodiments 1 to 6 and unavoidable impurities that are unintentionally included in the manufacturing process (hereinafter, these two types of unavoidable impurities are collectively referred to as unavoidable impurities).

[0031] 2. Microstructure The microstructure of the WC-based cemented carbide will be described below. The WC-based cemented carbide of Embodiments 1 to 6 includes a main hard phase, a secondary hard phase, and a binder phase. In addition to the main hard phase, secondary hard phase, and binder phase, voids, free carbon phase, η phase, and amorphous phase may be unintentionally present. These voids, free carbon phase, η phase, and amorphous phase will be collectively referred to as the X phase. Each phase will be described below.

[0032] (1) Main hard phase The main hard phase is an aggregate of crystal grains with carbides of W (carbides mainly composed of WC, but not limited to the stoichiometric composition of W and C) as the main component. In addition to Co, Ni, and Fe contained in the bonding phase, the main hard phase may contain a component M (M is at least one element selected from the group consisting of Ta, Nb, and Ti), Cr, and further inevitable impurities. Also, the crystal structure of the crystal grains that are the main component of the main hard phase is a hexagonal (hcp) structure.

[0033] (2) Secondary hard phase The secondary hard phase is an aggregate of crystal grains with carbides of M (M is at least one element selected from the group consisting of Ta, Nb, and Ti) (carbides formed by the combination of M and C not limited to the stoichiometric composition and / or composite carbides are applicable) as the main component. In addition to Co, Ni, Fe, and Cr contained in the bonding phase, the secondary hard phase may contain W mainly contained in the main hard phase, and further inevitable impurities. Also, since the crystal structure of the crystal grains that are the main component of the secondary hard phase is a face-centered cubic (fcc) structure, it is different from the crystal structure of the crystal grains that are the main component of the main hard phase. Note that the secondary hard phase does not exist when the M component is not contained.

[0034] (3) Bonding phase The bonding phase is an aggregate of crystal grains with Co and / or Ni as the main component (Fe is also mainly contained in the bonding phase but is not the main component). In the bonding phase, there may be further contained W, which is a component of the main hard phase, M (M is at least one element selected from the group consisting of Ta, Nb, and Ti), which is a component of the secondary hard phase, Cr, C, and further inevitable impurities. When these elements exist in the bonding phase, it is presumed that they are in a solid-solved state in the bonding phase. Also, the crystal structure of the crystal grains that are the main component of the bonding phase is an hcp structure or an fcc structure.

[0035] 3. Crystal grain size (1) Definition of crystal grain size and average crystal grain size (average particle size) In the claims and the description of the specification, the crystal grain size is the equivalent circle diameter (the diameter of a circle equal to the area of the crystal grain), and the average crystal grain size (average particle size) is the area-averaged equivalent circle diameter and is defined by the following formula. Average crystal grain size (average particle size) = Σ(d ｉ ×S ｉ ) / ΣS ｉHere, d ｉ : Equivalent circular diameter of each crystal grain S ｉ : This represents the area of ​​each crystal grain.

[0036] (2) Average grain size of the crystal grains constituting the main hard phase The average grain size of the crystal grains constituting the main hard phase is 0.8 to 3.0 μm. The reason for this is that if the average grain size of the crystal grains constituting the main hard phase is less than 0.8 μm, when the WC-based cemented carbide of Embodiments 1 to 6 is used as a cutting tool substrate, the fracture resistance and chipping resistance will not be sufficient, and if it exceeds 3.0 μm, the wear resistance and plastic deformation resistance will not be sufficient. It is more preferable that the average grain size of the crystal grains constituting the main hard phase is 1.5 to 2.5 μm.

[0037] 4. Average orientation difference and proportion of crystal grains with a specific grain size that constitute the main hard phase. ａｖｅ It is preferable that they exist in a specific proportion (area proportion) depending on the circumstances.

[0038] (Embodiment 1) In Embodiment 1, the first crystal grains in a specific grain size range constituting the main hard phase are as follows: The first crystal grains have a grain size of X1 μm or more and X2 μm or less, provided that X1 and X2 satisfy 0.2 ≤ X1 < X2 ≤ 6.0, and the average value of the grain mean orientation difference (GOS) is ａｖｅ The angle is 0.85 to 1.50°, and the area ratio A of the first crystal grain is １ / A is between 0.20 and 1.00, where A is the area of ​​all the crystal grains constituting the main hard phase, A １ This is the area occupied by the first crystal grain, which has a grain size of X1 μm or more and X2 μm or less, among all the crystal grains constituting the main hard phase.

[0039] The reason for setting the average value of the intra-grain average orientation difference of the first crystal grain to 0.85 to 1.50° is as follows: If it is less than 0.85°, the plastic deformation resistance is insufficient when the WC-based cemented carbide of this embodiment 1 is used as a cutting tool substrate, while if it exceeds 1.50°, the fracture resistance and chipping resistance become insufficient. A more preferable average value of the intra-grain average orientation difference of the first crystal grain is 1.00 to 1.40°.

[0040] Area ratio A １ The reason why / A is between 0.20 and 1.00 is as follows: When the WC-based cemented carbide of Embodiment 1 is used as the base material for a cutting tool, if the area ratio is less than 0.20, the resistance to plastic deformation and wear resistance will be insufficient, while up to 1.00, the resistance to plastic deformation, wear resistance, chipping resistance, and fracture resistance will be excellent. Area ratio A １ / A is more preferably between 0.40 and 0.80.

[0041] (Embodiment 2) In Embodiment 2, in addition to the first crystal grains in a specific particle size range that constitute the main hard phase, there are second crystal grains in a specific particle size range that constitute the main hard phase. That is, in addition to the first crystal grains in a specific particle size range that constitute the main hard phase of Embodiment 1, the average value of the mean orientation difference (GOS) (GOS ａｖｅ ) has a second crystal grain with a temperature of 0.30 to 0.80° and a particle size of X3 μm or more and X4 μm or less, and X1, X2, X3 and X4 satisfy 0.2 ≤ X1 < X2 < X3 < X4 ≤ 6.0 or 0.2 ≤ X3 < X4 < X1 < X2 ≤ 6.0 and area ratio A ２ / A is between 0.20 and 0.40, where A is the area of ​​all the crystal grains constituting the main hard phase. ２ This is the area occupied by the second crystal grain, which has a grain size of X3 μm or more and X4 μm or less, among all the crystal grains that make up the main hard phase.

[0042] The reason for setting the average value of the intra-grain average orientation difference of the second crystal grain to 0.30 to 0.80° is as follows: If it is less than 0.30°, when the WC-based cemented carbide of this embodiment is used as a cutting tool substrate, the resistance to plastic deformation, or the resistance to chipping and fracture, will be insufficient depending on the cutting conditions. On the other hand, if it exceeds 0.80°, the resistance to chipping and fracture, or the resistance to plastic deformation, will be insufficient depending on the cutting conditions. A more preferable average value of the intra-grain average orientation difference of the second crystal grain is 0.40 to 0.70°.

[0043] Area ratio A ２The reason why / A is between 0.20 and 0.40 is as follows: If the area ratio of the second crystal grain is less than 0.20, when the WC-based cemented carbide of this embodiment is used as a cutting tool substrate, depending on the cutting conditions, the fracture resistance, chipping resistance, or plastic deformation resistance will be insufficient. On the other hand, if it exceeds 0.40, depending on the cutting conditions, the plastic deformation resistance, fracture resistance, and chipping resistance will also be insufficient. Area ratio A ２ / A is more preferably 0.25 to 0.35.

[0044] (Embodiment 3) In Embodiment 3, the particle size of the first crystal grains in a specific particle size range constituting the main hard phase is as follows: That is, in Embodiment 1, X1 is 0.2 and X2 is 2.0.

[0045] (Embodiment 4) In Embodiment 4, the grain size of the first crystal grains in a specific grain size range constituting the main hard phase is as follows: In Embodiment 1, X1 is 2.5 and X2 is 6.0.

[0046] (Embodiment 5) In Embodiment 5, the particle sizes of the first and second crystal grains in a specific particle size range that constitute the main hard phase are as follows: In Embodiment 2, X1 is 0.2, X2 is 2.0, X3 is 2.5, and X4 is 6.0.

[0047] (Embodiment 6) In Embodiment 6, the grain sizes of the first and second crystal grains in a specific grain size range that constitute the main hard phase are as follows: In Embodiment 2, X1 is 2.5, X2 is 6.0, X3 is 0.2, and X4 is 2.0.

[0048] Herein, in the claims and in this specification, the mean grain orientation difference (GOS) is as described below.

[0049] Definition of Grain Orientation Spread (GOS) The grain orientation spread (GOS) is defined as follows: When observing the inside of a crystal grain using EBSD (Electron Beam Spectroscopy), and setting the observation points within the crystal grain as regular hexagonal pixels, the orientation difference between a specific regular hexagonal pixel and all other pixels within the same crystal grain is calculated and averaged (Figure 1). The grain orientation spread (GOS) can be expressed mathematically by the following formula (Formula 1). Here, n is the number of pixels within the same crystal grain, i and j are the numbers assigned to different pixels within the same crystal grain (where 1 ≤ i, j ≤ n), and α is the crystal orientation difference obtained from the crystal orientation at pixel i and the crystal orientation at pixel j. ｉｊ（ｉ≠ｊ） This is how it is expressed.

[0050]

[0051] The average value of the mean orientation difference (GOS) within each crystal grain (GOS) ａｖｅ The mean of the mean orientation difference (GOS) within a crystal grain is defined by the following formula: ａｖｅ ) = Σ(GOS ｉ ×S ｉ ) / ΣS ｉ Here, GOS ｉ : The average orientation difference within each crystal grain S ｉ : This represents the area of ​​each crystal grain.

[0052] 5. Average value of the average orientation difference within a crystal grain (GOS) ａｖｅ ) Average value of the average orientation difference within the crystal grain (GOS) ａｖｅ The average grain orientation difference (GOS) is measured after identifying the crystal grains constituting the main hard phase, secondary hard phase, and binder phase, as described below. ａｖｅ During the measurement process, the average grain size of the crystal grains constituting the main hard phase is also determined. Details will be described later.

[0053] 1) Observation by EDS and EBSD: Fine irregularities on any cross-section or surface of the WC-based cemented carbide according to the 1-6 embodiments are smoothed by grinding so as not to interfere with measurement by backscatter electron diffraction (EBSD). An observation field is set on the smoothed surface and observed. The size and number of observation fields can be appropriately determined according to the specifications of the EBSD device used. Setting five observation fields with dimensions of 24 μm vertically x 72 μm horizontally will yield highly accurate measurement results. Of course, the size of the observation fields can be larger, and the number can exceed five.

[0054] Then, the cross-section or surface of the WC-based cemented carbide is observed using a field emission scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an EBSD measuring device, and the SEM image, characteristic X-ray data of each measurement point (pixel) described later, and crystal orientation (IPF) data based on the inverse pole figure are obtained.

[0055] Observation conditions should be determined according to the specifications of the equipment used. An example of observation conditions is shown below. Observation is performed at an accelerating voltage of 15 kV, EBSD pattern and EDS data are simultaneously acquired, and analysis is performed using software such as AMETEK's OIM Data Collection. A crystal orientation map based on the inverse pole figure is then drawn using software such as AMETEK's OIM Analysis Ver. 7.3.1. The working distance (distance between the bottom surface of the objective lens and the sample) is set to 15 mm, the measurement count rate to 41000 cps, and the pixel spacing to 50 nm.

[0056] As shown in Figure 1, measurement points (pixels) P exist discretely, but the measurement result of a measurement point is used to represent the region up to the midpoint between adjacent measurement points (assuming it is a regular hexagon). When there is an orientation difference of 5° or more between adjacent measurement points, the end of the aforementioned midpoint region is defined as a grain boundary B. However, measurement points that have an orientation difference of 5° or more from all adjacent measurement points, or measurement points that exist alone without adjacent measurement points, are not considered crystal grains, while crystal grains are considered to be those where two or more measurement points are connected.

[0057] 2) Identification of each crystal grain For example, the measurement data is read using the AMETEK OIM Analysis ver. 7.3.1 software, and for each crystal grain, the EDS count values ​​obtained from each measurement point inside the crystal grain corresponding to each element are averaged to obtain the EDS measurement value for each element in each crystal grain, and the composition of each crystal grain is derived from the obtained measurement values. Follow the procedure below for details.

[0058] First, the average EDS counts for all elements—W, Co, Ni, Fe, Ta, Nb, Ti, Cr, and other elements—are calculated across the entire observation field. Next, the EDS count values ​​for each element at each pixel within each crystal grain are averaged to derive the composition of each crystal grain.

[0059] From the interband angle information obtained from the diffraction plane of the acquired EBSD pattern, the crystal structure and orientation of each crystal grain are identified using software such as OIM Data Collection from AMETEK.

[0060] The main hard phase is considered to be an aggregate of crystal grains having an hcp crystal structure, mainly composed of W carbide; the secondary hard phase is considered to be an aggregate of crystal grains having an fcc crystal structure, mainly composed of M (where M is at least one element selected from the group consisting of Ta, Nb, and Ti); and the bonding phase is considered to be an aggregate of crystal grains having an fcc crystal structure or an hcp crystal structure, mainly composed of Co and / or Ni. The region that does not fall under any of the main hard phase, secondary hard phase, or bonding phase is considered to be the X phase. The X phase is one of voids, free carbon phase, η phase, or amorphous phase. When manufactured by the method exemplified in this specification, which will be described later, the area ratio of the X phase is less than 1%, and the influence of the presence of the X phase on the wear resistance, chipping resistance, and fracture resistance when the WC-based cemented carbide of Embodiments 1 to 6 is used as a cutting tool substrate is negligible, so no further mention is made.

[0061] 3) Grain size and average grain size of the crystal grains constituting the main hard phase For each of the crystal grains constituting the main hard phase identified in 2) above, calculate the equivalent circle diameter. At this time, it is preferable to calculate the equivalent circle diameter for 500 or more crystal grains constituting the main hard phase (with the size and number of observation fields exemplified above, 500 or more crystal grains can be observed). Then, determine the average grain size according to the formula above.

[0062] 4) Calculation of average orientation difference For each of the crystal grains constituting the main hard phase identified in 2) above, the average value of the average orientation difference (GOS) is calculated according to the formula described above. ａｖｅ The calculation is performed on 300 to 500 crystal grains (with the size and number of observation fields exemplified above, 300 to 500 crystal grains can be observed).

[0063] 6. Composition Measurement The composition of the WC-based cemented carbide is measured using an electron beam microanalyzer (EPMA). Any cross section of the substrate is processed to be smooth by removing fine irregularities so as not to interfere with EPMA measurement. Since there is a possibility that the bonding phase components on the substrate surface may evaporate during sintering, three or more observation fields of view with a size of 100 μm (vertical) × 100 μm (horizontal) are set up in a region at least 500 μm inward from the substrate surface on this smooth surface (one side of one adjacent observation field of view and one side of the other observation field of view are parallel and the distance between them is 100 μm or more). The substrate composition is determined from the characteristic X-rays obtained by irradiating each observation field of view with an electron beam, and the average content is obtained by arithmetic mean. Note that the size and number of observation fields of view mentioned above are examples.

[0064] 7. Manufacturing Method An example of a manufacturing method will be described. First, the manufacturing method common to Embodiments 1 to 6 will be described, and the differences between each embodiment will be described later.

[0065] 7-1. Manufacturing method common to each embodiment: predetermined raw material powder (WC powder as the main hard phase raw material powder, Co powder, Ni powder, Fe powder as the binding phase raw material powder, TiC powder, TaC powder, NbC powder, and Cr as the secondary hard phase raw material powder) ３ C ２Prepare the powder. Here, two types of main hard phase raw material powder (WC powder) are prepared, as described later: a first main hard phase raw material powder with a large average particle size (Fischer diameter) and a second main hard phase raw material powder with a small average particle size (Fischer diameter). Then, (1) raw material powder pretreatment process, (2) mixing and drying process, (3) molding process, (4) sintering process, (5) finishing process, and (6) coating process as needed are carried out in order. These will be explained in order below. Note that an appropriate amount of graphite powder may be prepared separately as a carbon source.

[0066] (1) Pre-treatment process of raw material powder The following pre-grinding process, slurry extraction process, and drying process are carried out.

[0067] 1) Preliminary Grinding Process: In the preliminary grinding process, the first main hard raw material powder is ground to an average particle size (Fischer diameter) of 1 / 10 to 3 / 5. The preliminary grinding process is carried out using an attritor, for example, with ethanol as the solvent and a rotation speed of 60 to 100 mins. －１ Mix under these conditions for 9 to 12 hours.

[0068] 2) Slurry Aspiration Process The slurry aspiration process is a process to remove powder that remains with a large particle size because it was not sufficiently pulverized in the preliminary grinding process. This process involves pouring the slurry prepared in the preliminary grinding process into, for example, a graduated cylinder, letting it stand for a predetermined time, and then aspirating a portion of the slurry from the top. Since powders with smaller particle sizes have a lower settling velocity, aspirating from the top of the slurry leaves only the small-particle powder that has been pulverized to the aforementioned average particle size (Fischer diameter) of 1 / 10 to 3 / 5. By setting the standing time to 30 to 40 minutes and the slurry aspiration rate to 50 to 60% by volume, it is possible to collect the main hard raw material powder that has been pulverized to the average particle size (Fischer diameter) of 1 / 10 to 3 / 5.

[0069] 3) Drying Process The drying process involves evaporating the ethanol solvent to obtain the main hard raw material powder. Examples of processing conditions for this process include placing the slurry obtained in the slurry extraction process under a vacuum atmosphere of 1 Pa or less and holding it at 80-100°C for 2-3 hours.

[0070] (2) Mixing and drying process The first mixing process, the second mixing process, and the drying process described below are carried out.

[0071] 1) First mixing step In the first mixing step, the following are mixed: a secondary hard phase raw material powder with an average particle size (Fischer diameter) of 1.0 to 1.5 μm, a binding phase raw material powder of 1.0 to 1.5 μm, and Cr of 1.0 to 1.5 μm. ３ C ２ The three types of raw material powders are blended to achieve the composition of the cemented carbide to be manufactured, and then the first main hard phase raw material powder is added to uniformly disperse each raw material powder. The first main hard phase raw material powder has undergone a raw material powder pretreatment process and is added in an amount that is 0.15 to 0.90 in mass ratio to the mass ratio of the composition of the cemented carbide to be manufactured.

[0072] The first mixing step involves using an attritor, for example, with ethanol as the solvent, and rotating at a speed of 60-100 mins. －１ Mix under these conditions for 5 to 7 hours to obtain a slurry.

[0073] 2) Second Mixing Step In the second mixing step, a second main hard phase raw material powder, which has not undergone the raw material powder pretreatment step and has a predetermined average particle size (Fischer diameter), is added to the slurry obtained in the first mixing step and uniformly dispersed so that the main hard raw material powder has the compound composition of the cemented carbide to be manufactured. The second mixing step is carried out using an attritor, for example, with ethanol as the solvent and a rotation speed of 60 to 100 mins. －１ Mix under these conditions for 1 to 3 hours. In the following description, the second main hard phase raw material powder that has not undergone the raw material powder pretreatment process may be referred to as unground powder.

[0074] 3) Granulation and Drying Process: The granulation and drying process involves granulating and drying the slurry obtained in the second mixing process, for example, using a spray dryer. The size of the granulated powder is such that it can be easily press-molded into the desired shape in the molding process.

[0075] (3) Molding Process The granulated powder that has undergone the mixing and drying process is molded into a molded body that can become a base body of a predetermined shape (an insert shape of CNMG120408 as defined in ISO standard 1832:2017 is an example, but is not limited to this). Molding can be exemplified by press molding at a pressure of 100 MPa.

[0076] (4) Sintering process Sintering is performed, for example, 10 －１After holding the material in a vacuum atmosphere below Pa at a temperature range of 1360 to 1420°C for 50 to 100 minutes, it is furnace-cooled to room temperature.

[0077] (5) Finishing process The molded body that has gone through the sintering process is subjected to grinding to obtain the predetermined base shape.

[0078] (6) Coating step A coating layer having a known composition and layer structure is formed by known means. Forming the coating layer is optional.

[0079] 7-2. Manufacturing Method for Each Embodiment The manufacturing method common to each embodiment described above is modified as follows according to the embodiment (manufacturing methods not described below are not modified).

[0080] (1) Embodiment 1 In Embodiment 1, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 8.0 to 12.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 0.9 to 7.0 μm and is blended in an amount that is 0.20 to 0.80 in mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 0.8 to 5.0 μm.

[0081] (2) Embodiment 2 In Embodiment 2, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 8.0 to 12.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 1.9 to 7.0 μm and is blended in an amount that is 0.30 to 0.60 in mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 0.8 to 5.0 μm and is blended in an amount that is 0.40 to 0.70 in mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured.

[0082] (3) Embodiment 3 In Embodiment 3, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 8.0 to 10.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 0.7 to 4.0 μm and is blended in an amount that is 0.15 to 0.90 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 3.0 to 5.0 μm and is blended in an amount that is 0.10 to 0.85 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured.

[0083] (4) Embodiment 4 In Embodiment 4, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 11.0 to 12.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 2.5 to 7.0 μm and is blended in an amount that is 0.30 to 0.60 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 0.8 to 1.5 μm and is blended in an amount that is 0.40 to 0.70 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured.

[0084] (5) Embodiment 5 In Embodiment 5, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 8.0 to 10.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 1.9 to 2.1 μm and is blended in an amount that is 0.30 to 0.60 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 3.0 to 5.0 μm and is blended in an amount that is 0.40 to 0.70 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured.

[0085] (6) Embodiment 6 In Embodiment 6, 1) As raw material powder, the first main hard raw material powder has an average particle size (Fischer diameter) of 11.0 to 12.0 μm and is subjected to the raw material powder pretreatment process. 2) In the mixing and drying process, the first main hard phase raw material powder that has undergone the raw material powder pretreatment process has an average particle size (Fischer diameter) of 2.5 to 7.0 μm and is blended in an amount that is 0.30 to 0.60 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured. 3) In the second mixing process, the second main hard phase raw material powder that has not undergone the pretreatment process has an average particle size (Fischer diameter) of 0.8 to 1.5 μm and is blended in an amount that is 0.45 to 0.68 by mass ratio to the mass ratio of the WC composition of the cemented carbide to be manufactured.

[0086] The above description includes the following characteristics: (Note 1) Total of Co and / or Ni and an optional component Fe: 4.0 to 12.0 mass%, Cr: 0.0 to 1.0 mass%, where [Cr content (mass%)] / [Total content of Co, Ni and Fe (mass%)] is 0.10 or less, M (M is at least one selected from the group consisting of Ta, Nb and Ti): 0.0 to 12.0 mass%, C: 5.4 to 8.0 mass%, the remainder being W and unavoidable impurities, the main hard phase is composed of crystal grains having an average particle size in the range of 0.8 to 3.0 μm, the crystal grains have a particle size in the range of X1 μm to X2 μm, and the average value of the mean orientation difference within the crystal grain (GOS) is ａｖｅ ) includes a first crystal grain whose angle is in the range of 0.85 to 1.50°, and X1 and X2 satisfy 0.2 ≤ X1 < X2 ≤ 6.0, and the area ratio A １ / A is between 0.20 and 1.00, where A １ A is the area occupied by the first crystal grain, and A is the area occupied by the said crystal grain, characterized in that (Note 2) The WC-based cemented carbide according to Note 1, characterized in that the [Cr content (mass%)] / [total content of Co, Ni and Fe (mass%)] is 0.40 to 0.80. (Note 3) The average value of the mean orientation difference (GOS) within the first crystal grain (GOS) ａｖｅ WC-based cemented carbide as described in Appendix 1 or 2, characterized in that the angle is 1.00 to 1.40°. (Appendix 4) Area ratio A １ A WC-based cemented carbide alloy according to any one of appendices 1 to 3, characterized in that A is 0.40 to 0.80. (Appendix 5) A WC-based cemented carbide alloy according to any one of 1 to 4, characterized in that X1 is 0.2 and X2 is 2.0. (Appendix 6) A WC-based cemented carbide alloy according to any one of 1 to 4, characterized in that X1 is 2.5 and X2 is 6.0. (Appendix 7) The crystal grains have a grain size in the range of X3 μm to X4 μm, and the average value of the mean orientation difference within the crystal grain (GOS) is ａｖｅThe material further includes a second crystal grain whose angle is in the range of 0.30 to 0.80°, and X1, X2, X3, and X4 satisfy 0.2 ≤ X1 < X2 < X3 < X4 ≤ 6.0 or 0.2 ≤ X3 < X4 < X1 < X2 ≤ 6.0, and the area ratio A ２ / A is between 0.20 and 0.40, where A ２ The WC-based cemented carbide according to claim 1, characterized in that is the area occupied by the second crystal grain. (Note 8) The WC-based cemented carbide according to note 7, characterized in that the [Cr content (mass%)] / [total content of Co, Ni and Fe (mass%)] is 0.40 to 0.80. (Note 9) The average value of the mean orientation difference (GOS) within the crystal grain of the first crystal grain (GOS ａｖｅ WC-based cemented carbide as described in Appendix 7 or 8, characterized in that the angle is 1.00 to 1.40°. (Appendix 10) Area ratio A １ A WC-based cemented carbide as described in any of Appendix 7 to 9, characterized in that A is 0.40 to 0.80. (Appendix 11) The average value of the intra-grain mean orientation difference (GOS) of the second crystal grain (GOS ａｖｅ WC-based cemented carbide as described in Appendix 7 to 10, characterized in that the area ratio A is 0.40 to 0.70°. (Appendix 12) The area ratio A ２ A WC-based cemented carbide alloy according to appendices 7 to 11, characterized in that A is 0.25 to 0.35. (Appendix 13) A WC-based cemented carbide alloy according to any one of appendices 7 to 12, characterized in that X1 is 0.2, X2 is 2.0, X3 is 2.5 and X4 is 6.0. (Appendix 14) A WC-based cemented carbide alloy according to any one of appendices 7 to 12, characterized in that X1 is 2.5, X2 is 6.0, X3 is 0.2 and X4 is 2.0.

[0087] The present invention will be specifically described by examples when the WC-based cemented carbide of the present invention is used as a base material (insert) for a coated tool, but the present invention is not limited to these examples.

[0088] 1. Manufacturing of WC-based cemented carbide in the example (1) Raw material powders In order to produce mixed powders with the blending ratios shown in Table 1, the raw material powders are as follows: First main hard phase raw material powder (WC powder (8.2 μm), WC powder (9.1 μm), WC powder (10.0 μm), WC powder (10.5 μm), WC powder (11.1 μm), WC powder (12.0 μm)), Second main hard phase raw material powder (WC powder (0.8 μm), WC powder (1.0 μm), WC powder (1.2 μm), WC powder (1.5 μm), WC powder (2.1 μm), WC powder (3.1 μm), WC powder (4.2 μm)), binder phase raw material powder (Co powder (1. 0 μm), Ni powder (1.0 μm), Fe powder (1.0 μm)), secondary hard phase raw material powder (TiC powder (1.0 μm), TaC powder (1.2 μm), NbC powder (1.2 μm), Cr ３ C ２ Powder (1.2 μm) was prepared. Here, the number in parentheses after each powder name represents the average particle size of each powder, indicating the Fischer diameter of the raw material powder measured by air permeation using a Fischer subsieve sizer.

[0089] (2) Raw material powder pretreatment process (slurry extraction process, drying process), mixing and drying process, molding process, sintering process, finishing process As described above, the raw material powder pretreatment process (slurry extraction process, drying process), mixing and drying process, molding process, sintering process, and finishing process were carried out in order.

[0090] In the raw material powder pretreatment process, the first hard phase raw material powders (WC raw material powders) with average particle sizes (Fischer diameters) of 8.2 μm, 9.1 μm, 10.0 μm, 10.5 μm, 11.1 μm, and 12.0 μm were subjected to the raw material powder pretreatment process shown in Table 3. After a slurry extraction process and a drying process, WC powders with average particle sizes (Fischer diameters) of 0.9 to 7.2 μm, as shown in Table 4, were obtained. Subsequently, based on the blending ratios shown in Table 1, the first and second mixing processes shown in Tables 3 and 4 were performed. In the molding process, the obtained raw material powders were press-molded at a pressure of 100 MPa to form an insert shape of CNMG120408. After that, sintering was performed in the sintering process at the holding temperature and holding time shown in Table 4, and grinding was performed in the finishing process to form an insert shape of the predetermined CNMG120408 shape. The results of the analysis of these inserts using the method described above are shown in Tables 7 and 8.

[0091] 2. To compare the manufacturing process of the comparative WC-based cemented carbide, in addition to the same raw material powder as in the example, unground WC powder with an average particle size (Fischer diameter) of 15.4 μm was prepared for the first mixing step, unground WC powder with average particle sizes (Fischer diameters) of 0.3 μm, 3.2 μm, and 6.2 μm, respectively, and graphite powder with average particle sizes (Fischer diameters) of 45 μm and 10 μm were prepared for the second mixing step. Subsequently, the raw material powder pretreatment step, mixing step, molding step, sintering step, and finishing step shown in Tables 5 and 6 were carried out in order.

[0092] As shown in Tables 5 and 6, the comparative examples include those in which the mixing time in the raw material powder pretreatment step was longer or shorter than the range shown in the example of the manufacturing method, and those in which the raw material powder pretreatment step was not performed; those in which the ratio of WC powder that had undergone the raw material powder pretreatment step was higher or lower than the range shown in the example in the first mixing step; those in which the rotation speed was higher or lower than the range shown in the example; and those in which the mixing time was longer or shorter than the range shown in the example of the manufacturing method (in Table 5, comparative example steps where the raw material powder pretreatment step is indicated as "-" mean that the raw material powder pretreatment step was not performed). However, for comparative examples in which the raw material powder pretreatment step was not performed, WC powder that had not undergone the raw material powder pretreatment step with the particle size shown in Table 6 was blended in the WC powder mass ratio of the cemented carbide to be manufactured. The raw material powder after the mixing step was press-molded at a pressure of 100 MPa to form an insert shape of the CNMG120408 shape. In the sintering process, as shown in Table 6, some samples had holding temperatures that were higher than the range indicated in the example manufacturing method. Subsequently, grinding was performed to create inserts of the predetermined shape of CNMG120408. The results of analyzing these inserts using the method described above are shown in Tables 9 and 10.

[0093] 3. Formation of the coating layer Subsequently, coating layers shown in Tables 12 and 13 were formed on each insert of the Examples and Comparative Examples by chemical vapor deposition under the film formation conditions shown in Table 11, thereby obtaining Example coating tools 1 to 26 (hereinafter referred to as Examples 1 to 26) and Comparative Example coating tools 1' to 28' (hereinafter referred to as Comparative Examples 1' to 28').

[0094] Examples 21 and 24 are cutting tools made of WC-based cemented carbide according to Embodiment 1, Examples 22, 23, 25 and 26 are according to Embodiment 2, Examples 2, 3, 4, 6, 7 and 9 are according to Embodiment 3, Examples 11, 13 and 17 are according to Embodiment 4, Examples 1, 5, 8 and 10 are according to Embodiment 5, and Examples 12, 14, 15, 16, 18, 19 and 20 are cutting tools made of WC-based cemented carbide according to Embodiment 6.

[0095]

[0096]

[0097] In Tables 1 and 2, "-" indicates that the component was not included, and column "C" shows the composition (mass%) of graphite.

[0098]

[0099]

[0100]

[0101]

[0102] In Tables 4, 5, and 6, "-" indicates that there were no matching results.

[0103]

[0104] In Tables 7 and 9, "-" indicates that the component was not present or did not exist; "○" in the Main Hard Phase column indicates that the main component is a W carbide; "○" in the Secondary Hard Phase column indicates that the main component is one or more carbides selected from Ti, Ta, and Nb; and "○" in the Binder Phase column indicates that the main components are Co and Ni. In addition, the content of unavoidable impurities was 0.3% by mass or less as an extra-mass percentage of 100% by mass.

[0105]

[0106] In Table 8, "-" indicates that there were no matching results.

[0107]

[0108]

[0109] In Table 10, "-" indicates that there were no matching results.

[0110]

[0111]

[0112]

[0113] Next, cutting tests 1, 2, 3, and 4 were performed on Examples 1 to 26 and Comparative Examples 1' to 28', respectively, to measure the amount of plastic deformation or wear on the flank surface of the cutting edge, and to observe the wear state of the cutting edge. The results are shown in Tables 14, 15, 16, and 17.

[0114] Cutting Test 1: Wet external turning of a hexagonal prism-shaped workpiece made of stainless steel (regular hexagonal cross-section with sides of 20 mm). Workpiece material: SUS304. Cutting speed: 150 m / min. Depth of cut: 2.0 mm. Feed rate per revolution: 0.5 mm. Cutting time: 5 minutes.

[0115] Cutting Test 2: Wet outer diameter turning of a stainless steel round bar workpiece with a single groove slit (round bar with outer diameter of 100 mm) Workpiece material: SUS630 Cutting speed: 120 m / min Depth of cut: 2.0 mm Feed rate per revolution: 0.45 mm Cutting time: 10 minutes

[0116] Cutting Test 3 Wet outer diameter turning of a round bar workpiece made of Ni-based alloy (round bar with outer diameter of 100 mm) Workpiece material: Ni-based alloy with composition (mass%) of Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1(Nb+Ta) Cutting speed: 60 m / min Depth of cut: 0.5 mm Feed per revolution: 0.10 mm Cutting time: 10 minutes

[0117] Cutting Test 4 Wet outer diameter turning of a round bar workpiece made of Ni-based alloy with a single groove slit (round bar with outer diameter of 100 mm) Workpiece material: Ni-based alloy with composition (mass%) of Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1(Nb+Ta) Cutting speed: 40 m / min Depth of cut: 0.5 mm Feed per revolution: 0.10 mm Cutting time: 10 minutes

[0118] In the cutting tests 1 and 2 described above, cutting was interrupted every 30 seconds to observe the cutting edge, measure the amount of plastic deformation of the flank face of the cutting edge, and observe the wear condition. The amount of plastic deformation of the flank face of the cutting edge was measured by drawing a line segment on the ridge where the main cutting edge side flank face (21) and the rake face (20) intersect at a position sufficiently far from the cutting edge (22) on the main cutting edge side flank face of the tool, extending this line segment in the direction of the cutting edge, and measuring the point where the distance between the extended line segment (24) and the cutting edge ridge (perpendicular to the extended line segment) was greatest, and this was defined as the amount of plastic deformation of the flank face of the cutting edge (23) (see Figure 2). Furthermore, if the amount of plastic deformation of the flank face was 0.050 mm or more, the wear condition was described as cutting edge deformation, if chipping with a width of 50 μm or more occurred, it was described as chipping, and if chipping with a width of 10 μm or more and less than 50 μm occurred, it was described as minute chipping. When chipping occurred at the cutting edge, it was noted as chipping. Because it was difficult to distinguish the ridge line (making measurement impossible), the amount of wear on the flank surface could not be measured.

[0119] In cutting tests 3 and 4, cutting was interrupted every 30 seconds to observe the cutting edge, measure the wear width of the flank surface of the cutting edge, and observe the wear condition. When the amount of flank surface wear exceeded 0.30 mm, it was determined that the tool had reached the end of its lifespan, and the cutting test was stopped at that point. When chipping with a width of 50 μm or more occurred, it was labeled as "chipping," and the amount of flank surface wear at the time of chipping was measured. When chipping with a width of 10 μm or more but less than 50 μm occurred, allowing the cutting test to continue until the end of the 10-minute cutting time, it was labeled as "minor chipping." When a chip occurred at the cutting edge, it was labeled as "chip," and the amount of flank surface wear could not be measured because it was difficult to distinguish the edge (making measurement impossible).

[0120] In Tables 14, 15, 16, and 17, a "-" in the "Cutting time to life" column indicates that cutting was possible up to the cutting time (5 minutes in Cutting Test 1, and 10 minutes in Cutting Tests 2, 3, and 4).

[0121]

[0122]

[0123]

[0124]

[0125] As is clear from Table 14 showing the results of cutting test 1 and Table 15 showing the results of cutting test 2, although some samples of the examples showed minute chipping of 50 μm width or less (chipping that did not hinder the continuation of the cutting test), all exhibited excellent toughness and resistance to plastic deformation with minimal plastic deformation and no chipping. In contrast, the comparative examples showed large plastic deformation of the tool and chipping of 50 μm width or more during the predetermined cutting time, or chipping of the cutting edge, making it difficult to perform machining to obtain the predetermined dimensions of the workpiece.

[0126] As is clear from Table 16 showing the results of cutting test 3 and Table 17 showing the results of cutting test 4, the examples exhibited excellent toughness and wear resistance without any chipping occurring, although some of them showed minute chipping of less than 50 μm in width (chipping that did not hinder the continuation of the cutting test). In contrast, the comparative examples showed significant wear on the flank surface of the tool and chipping of 50 μm or more in width, or chipping of the cutting edge, during a predetermined cutting time.

[0127] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described herein, and all modifications within the scope are intended to be included in the meaning of equivalences of the claims.

Claims

1. The total of Co and / or Ni and an optional component Fe: 4.0 to 12.0 mass%, Cr: 0.0 to 1.0 mass%, where [Cr content (mass%)] / [total content of Co, Ni and Fe (mass%)] is 0.100 or less, M (M is at least one selected from the group consisting of Ta, Nb and Ti): 0.0 to 12.0 mass%, C: 5.4 to 8.0 mass%, the remainder being W and unavoidable impurities, comprising a main hard phase mainly composed of W carbides, a secondary hard phase mainly composed of M carbides, and a binding phase mainly composed of Co and / or Ni, the main hard phase being composed of crystal grains with an average particle size in the range of 0.8 to 3.0 μm, and the crystal grains are The grain size is in the range of X1 μm to X2 μm, and the average value of the mean orientation difference (GOS) within the crystal grain is (GOS ａｖｅ ) includes a first crystal grain whose angle is in the range of 0.85 to 1.50°, and X1 and X2 satisfy 0.2 ≤ X1 < X2 ≤ 6.0, and the area ratio A １ / A is between 0.20 and 1.00, where A １ A WC-based cemented carbide is characterized in that A is the area occupied by the first crystal grain, and A is the area occupied by the said crystal grain.

2. The crystal grains have a particle size in the range of X3 μm to X4 μm, and the average value of the intra-grain mean orientation difference (GOS) is (GOS ａｖｅ The material further includes a second crystal grain whose angle is in the range of 0.30 to 0.80°, and X1, X2, X3, and X4 satisfy 0.2 ≤ X1 < X2 < X3 < X4 ≤ 6.0 or 0.2 ≤ X3 < X4 < X1 < X2 ≤ 6.0, and the area ratio A ２ / A is between 0.20 and 0.40, where A ２ The WC-based cemented carbide according to claim 1, wherein is the area occupied by the second crystal grain.

3. The WC-based cemented carbide according to claim 1, characterized in that X1 is 0.2 and X2 is 2.

0.

4. The WC-based cemented carbide according to claim 1, characterized in that X1 is 2.5 and X2 is 6.

0.

5. The WC-based cemented carbide according to claim 2, characterized in that X1 is 0.2, X2 is 2.0, X3 is 2.5, and X4 is 6.

0.

6. The WC-based cemented carbide according to claim 2, characterized in that X1 is 2.5, X2 is 6.0, X3 is 0.2, and X4 is 2.0.

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