Cemented carbide

Abstract

The cemented carbide is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains 89% by volume or more in total of the tungsten carbide particles and the binder phase, the cemented carbide contains 1.8% by volume or more and 20.0% by volume or less of the binder phase, the binder phase contains cobalt, the cemented carbide contains 1.0% by mass or more of cobalt, and the hardness of the binder phase at 25°C measured by the nanoindentation method is 7.0 GPa or more.

Description

Technical Field

[0001] The present disclosure relates to cemented carbide.

Background Art

[0002] Conventionally, a cemented carbide including a plurality of tungsten carbide particles and a binder phase has been used as a material for cutting tools (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The cemented carbide of the present disclosure is a cemented carbide including a plurality of tungsten carbide particles and a binder phase, the cemented carbide contains 89% by volume or more in total of the tungsten carbide particles and the binder phase, the cemented carbide contains 1.8% by volume or more and 20.0% by volume or less of the binder phase, the binder phase contains cobalt, the cemented carbide contains 1.0% by mass or more of cobalt, the hardness of the binder phase at 25°C measured by the nanoindentation method is 7.0 GPa or more.

Brief Description of the Drawings

[0005]

Figure 1

Modes for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] In recent years, the work material has become more difficult to machine in cutting, and the operating conditions of cutting tools have become severe. For this reason, various improvements are also required for cemented carbide used as the base material of cutting tools. In particular, even when used as the material of a cutting tool for machining a high-hardness material, a cemented carbide that enables the tool to have a long life is required.

[0007] Therefore, an object of the present disclosure is to provide a cemented carbide that enables the tool to have a long life even when used as the material of a cutting tool for machining a high-hardness material.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables the tool to have a long life even when used as the material of a cutting tool for machining a high-hardness material.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The cemented carbide of the present disclosure is a cemented carbide including a plurality of tungsten carbide particles and a binder phase, the cemented carbide contains 89% by volume or more in total of the tungsten carbide particles and the binder phase, the cemented carbide contains 1.8% by volume or more and 20.0% by volume or less of the binder phase, the binder phase contains cobalt, the cemented carbide contains 1.0% by mass or more of cobalt, the hardness of the binder phase at 25°C measured by the nanoindentation method is 7.0 GPa or more.

[0010] According to the present disclosure, it is possible to provide a cemented carbide that enables the tool to have a long life even when used as the material of a cutting tool for machining a high-hardness material.

[0011] (2) In the above (1), the binder phase further contains a first element, The first element may be at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. This makes it possible to provide a cemented carbide that can further extend the tool life of a cutting tool, especially in the cutting of high-hardness materials.

[0012] (3) In the above (2), in the binder phase, the percentage {M1 / (M1 + M2)}×100 of the mass M1 of the first element with respect to the total mass M1 + M2 of the mass M1 of the first element and the mass M2 of cobalt may be 1% or more and 6% or less. This makes it possible to provide a cemented carbide that can further extend the tool life of a cutting tool, especially in the cutting of high-hardness materials.

[0013] [Details of Embodiments of the Present Disclosure] A specific example of a cutting tool according to an embodiment of the present disclosure (hereinafter also referred to as "this embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Also, dimensional relationships such as length, width, thickness, and depth are appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0014] In the present disclosure, the notation in the form of "A to B" means the upper and lower limits of the range (i.e., A or more and B or less). When there is no unit description for A and a unit is described only for B, the units of A and B are the same.

[0015] In the present disclosure, when representing a compound or the like by a chemical formula, when the atomic ratio is not particularly limited, it includes all conventionally known atomic ratios and should not necessarily be limited only to those within the stoichiometric range.

[0016] [Embodiment 1: Cemented Carbide] The cemented carbide according to an embodiment of the present disclosure will be described with reference to FIG. 1. An embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is A cemented carbide 3 comprising a plurality of tungsten carbide particles 1 and a binder phase 2, the cemented carbide 3 contains 89% by volume or more in total of the tungsten carbide particles 1 and the binder phase 2, the cemented carbide 3 contains 1.8% by volume or more and 20.0% by volume or less of the binder phase 2, the binder phase 2 contains cobalt, the cemented carbide 3 contains 1.0% by mass or more of cobalt, the hardness of the binder phase 2 at 25°C measured by the nanoindentation method is 7.0 GPa or more.

[0017] According to the present disclosure, it is possible to provide a cemented carbide 3 that enables the tool to have a long life even when used as a material for a cutting tool for cutting a particularly high-hardness material. The reason is presumed as follows.

[0018] The cemented carbide 3 of the present embodiment includes a plurality of tungsten carbide particles 1 (hereinafter, also referred to as "WC particles 1") and a binder phase 2, and the total content of the WC particles 1 and the binder phase 2 of the cemented carbide 3 is 89% by volume or more. According to this, the cemented carbide 3 has high hardness and strength, and a cutting tool using the cemented carbide 3 can have excellent wear resistance and chipping resistance.

[0019] The cemented carbide 3 of Embodiment 1 contains 1.8% by volume or more and 20.0% by volume or less of the binder phase 2. The binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0% by mass or more of cobalt. Furthermore, the hardness of the binder phase 2 at 25°C measured by the nanoindentation method is 7.0 GPa or more, and the binder phase 2 can have excellent hardness under the condition of 25°C (in other words, under room temperature conditions). According to this, the hardness of the cemented carbide 3 is improved, and a cutting tool using the cemented carbide 3 can have excellent wear resistance even in the processing of a particularly high-hardness material.

[0020] ≪Composition of Cemented Carbide≫ The cemented carbide 3 contains at least 89% by volume in total of tungsten carbide particles 1 and a binder phase 2. Thereby, the hardness of the cemented carbide 3 can be increased. The cemented carbide 3 may contain 90% by volume or more, 91% by volume or more, or 92% by volume or more in total of the tungsten carbide particles 1 and the binder phase 2. In the cemented carbide 3, the upper limit of the total content ratio of the tungsten carbide particles 1 and the binder phase 2 may be, for example, 100% by volume or less, 99% by volume or less, or 98% by volume or less. The cemented carbide 3 may contain 90% by volume or more and 100% by volume or less, 91% by volume or more and 100% by volume or less, or 92% by volume or more and 100% by volume or less in total of the tungsten carbide particles 1 and the binder phase 2.

[0021] The cemented carbide 3 contains the binder phase 2 in an amount of 1.8% by volume or more and 20.0% by volume or less. Thereby, in the cemented carbide 3, the hardness and toughness can be increased. The lower limit of the content ratio of the binder phase 2 in the cemented carbide 3 may be 2.0% by volume or more, 3.0% by volume or more, or 4.0% by volume or more. The upper limit of the content ratio of the binder phase 2 in the cemented carbide 3 may be 19.0% by volume or less, 18.0% by volume or less, or 17.0% by volume or less. The cemented carbide 3 may contain the binder phase 2 in an amount of 2.0% by volume or more and 19.0% by volume or less, the binder phase 2 in an amount of 3.0% by volume or more and 18.0% by volume or less, or the binder phase 2 in an amount of 4.0% by volume or more and 17.0% by volume or less.

[0022] The cemented carbide 3 of Embodiment 1 can be composed of a plurality of tungsten carbide particles 1 and a binder phase 2. The cemented carbide 3 of the present embodiment can contain other phases (not shown) in addition to the tungsten carbide particles 1 and the binder phase 2. Examples of the other phases include carbides, nitrides, or carbonitrides containing at least one second element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). The composition of the other phases is, for example, TiCN, TaC, NbC, ZrC, HfC, Mo2C.

[0023] The cemented carbide 3 of Embodiment 1 can be composed of tungsten carbide particles 1, a binder phase 2, and other phases. The content rate of other phases in the cemented carbide 3 is allowed within a range that does not impair the effects of the present disclosure. For example, the content rate of other phases in the cemented carbide 3 may be more than 0% by volume and 20% by volume or less, may be more than 0% by volume and 18% by volume or less, or may be more than 0% by volume and 16% by volume or less. In this case, the total content rate of the tungsten carbide particles 1 and the binder phase 2 in the cemented carbide 3 may be 80% by volume or more and less than 100% by volume, may be 82% by volume or more and less than 100% by volume, or may be 84% by volume or more and less than 100% by volume.

[0024] The cemented carbide 3 of Embodiment 1 can contain impurities. Examples of the impurities include iron (Fe), calcium (Ca), oxygen (O), and sulfur (S). The content rate of impurities in the cemented carbide 3 is allowed within a range that does not impair the effects of the present disclosure. For example, the content rate of impurities in the cemented carbide 3 may be 0% by mass or more and less than 0.1% by mass. The content rate of impurities in the cemented carbide 3 is measured by inductively coupled plasma emission spectroscopy (measurement device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0025] The measuring method for the content rate [volume%] of the tungsten carbide particles 1 in the cemented carbide 3 and the content rate [volume%] of the binder phase 2 in the cemented carbide 3 is as follows.

[0026] (A1) Cut out an arbitrary position of the cemented carbide 3 to expose a cross-section. Mirror-finish the cross-section with a cross-section polisher (manufactured by JEOL Ltd.).

[0027] (B1) Analyze the mirror-finished surface of the cemented carbide 3 by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) (device: "Gemini450" (trademark) manufactured by Carl Zeiss) to identify the elements contained in the cemented carbide 3.

[0028] (C1) Photograph the mirror-finished surface of the cemented carbide 3 with a scanning electron microscope (SEM) to obtain a backscattered electron image. The imaging area of the captured image is set at the center of the cross-section of the cemented carbide 3, that is, a position that does not include a portion where the properties are clearly different from the bulk portion such as near the surface of the cemented carbide 3 (a position where the entire imaging area is the bulk portion of the cemented carbide 3). The observation magnification is 5000 times. The measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[0029] (D1) Analyze the imaging area in (C1) using an energy-dispersive X-ray analyzer (SEM-EDX) attached to the SEM to identify the distribution of the elements specified in (B1) in the imaging area and obtain an elemental mapping image.

[0030] (E1) Import the backscattered electron image obtained in (C1) into a computer and perform binarization processing using image analysis software (OpenCV, SciPy). In the image after binarization processing, the tungsten carbide particles 1 are shown in white, and the binder phase 2 is shown in gray to black. Note that since the binarization threshold value varies depending on the contrast, it is set for each image.

[0031] (F1) By overlapping the elemental mapping image obtained in (D1) and the image after binarization processing obtained in (E1), identify the existence regions of the tungsten carbide particles 1 and the binder phase 2 on the image after binarization processing. Specifically, in the image after binarization processing, the region shown in white and where tungsten (W) and carbon (C) exist in the elemental mapping image corresponds to the existence region of the tungsten carbide particles 1. In the image after binarization processing, the region shown in gray to black and where cobalt (Co) exists in the elemental mapping image corresponds to the existence region of the binder phase 2.

[0032] (G1) Set one measurement field of view of a rectangle of 24.9 μm × 18.8 μm in the image after binarization processing. Using the above image analysis software, measure the area percentage of each of the tungsten carbide particles 1 and the binder phase 2 with the total area of the measurement field of view as the denominator.

[0033] (H1) The measurement of (G1) is performed in five different non-overlapping measurement fields. In this specification, the average of the area percentages of tungsten carbide particles 1 in the five measurement fields corresponds to the content rate [volume%] of tungsten carbide particles 1 in the cemented carbide 3 and the average of the area percentages of the binder phase 2 in the five measurement fields corresponds to the content rate [volume%] of the binder phase 2 in the cemented carbide 3.

[0034] When the cemented carbide 3 contains other phases in addition to the tungsten carbide particles 1 and the binder phase 2, the content rate of the other phases of the cemented carbide 3 can be obtained by subtracting the content rate [volume%] of the tungsten carbide particles 1 and the content rate [volume%] of the binder phase 2 measured by the above procedure from the whole of the cemented carbide 3 (100 volume%).

[0035] As long as the applicant has measured, and as long as it is measured on the same sample, the cutting position of the cross-section of the cemented carbide 3 is arbitrarily set, the imaging region described in (C1) above is arbitrarily set on the cross-section, and according to the above procedure, even if the measurement of the content rate of the tungsten carbide particles 1 and the content rate of the binder phase 2 of the cemented carbide 3 is performed multiple times, it has been confirmed that the variation in the measurement results is small and not arbitrary.

[0036] ≪Binder Phase≫ The binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0 mass% or more of cobalt. Thereby, excellent toughness can be imparted to the cemented carbide 3. Note that the binder phase 2 may contain 50 mass% or more of cobalt, 60 mass% or more of cobalt, 70 mass% or more of cobalt, 80 mass% or more of cobalt, 90 mass% or more of cobalt, or 95 mass% or more of cobalt. The binder phase 2 may consist of cobalt. Further, the binder phase 2 may consist of cobalt and a first element described later. Also, the cobalt in the cemented carbide 3 may exist only in the binder phase 2. The lower limit of the content of cobalt in the cemented carbide 3 may be 2.0 mass% or more, 3.0 mass% or more, or 4.0 mass% or more. The upper limit of the content of cobalt in the cemented carbide 3 may be 20 mass% or less, 15 mass% or less, 12 mass% or less, or 10 mass% or less. The cemented carbide 3 may contain 1.0 mass% or more and 20 mass% or less of cobalt, 2.0 mass% or more and 15 mass% or less of cobalt, or 3.0 mass% or more and 12 mass% or less of cobalt.

[0037] The method for measuring the cobalt content in the cemented carbide 3 is as follows. First, set the imaging area in the same manner as (A1) to (C1) of the method for measuring the content of tungsten carbide particles 1 and the content of the binder phase 2 in the above cemented carbide 3. Next, perform an analysis on the imaging area using SEM-EDX to identify the distribution of the elements specified in (B1) in the imaging area, obtain an elemental mapping image, and at the same time, identify the cobalt content in the cemented carbide 3. The method for measuring the "cobalt content in the binder phase 2" is as follows. First, identify the existing area of the binder phase 2 on the binarized image in the same manner as (A1) to (F1) of the method for measuring the content of tungsten carbide particles 1 and the content of the binder phase 2 in the above cemented carbide 3. Next, perform an analysis on the existing area of the binder phase 2 using SEM-EDX to measure the "cobalt content in the binder phase 2". The method for identifying that "the cobalt in the cemented carbide 3 exists only in the binder phase 2" is as follows. First, identify the existing area of the tungsten carbide particles 1 and the existing area of the binder phase 2 on the binarized image in the same manner as (A1) to (F1) of the method for measuring the content of tungsten carbide particles 1 and the content of the binder phase 2 in the above cemented carbide 3. Next, based on the elemental mapping image, the existing area of the tungsten carbide particles 1, and the existing area of the binder phase 2, identify that "the cobalt in the cemented carbide 3 exists only in the binder phase 2".

[0038] As far as the applicant measured, as long as the measurement is carried out on the same sample, even if the cutting location of the cross-section of the cemented carbide 3 and the imaging area described in (C1) are arbitrarily set and the above measurement is carried out multiple times according to the above procedure, it was confirmed that the variation in the measurement results is small and not arbitrary.

[0039] The binding phase 2 further contains a first element, and the first element may be at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. Thereby, it is possible to provide a cemented carbide 3 that can further extend the tool life of a cutting tool even in the cutting of particularly hard materials.

[0040] The content of the first element in the cemented carbide 3 may be 0.01% by mass or more and 1.0% by mass or less. Thereby, the binding phase 2 can have both better hardness and better toughness. Note that the content of the first element in the binding phase 2 may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. The first element in the cemented carbide 3 may be present only in the binding phase 2. The lower limit of the content of the first element in the cemented carbide 3 may be 0.01% by mass or more, 0.04% by mass or more, or 0.1% by mass or more. The upper limit of the content of the first element in the cemented carbide 3 may be 1.0% by mass or less, 0.8% by mass or less, or 0.6% by mass or less. The content of the first element in the cemented carbide 3 may be 0.04% by mass or more and 0.8% by mass or less, or 0.1% by mass or more and 0.6% by mass or less.

[0041] The method for measuring the content ratio of the first element in the cemented carbide 3 is as follows. Except that "cobalt" is read as "the first element", it is carried out in the same way as the method for measuring the cobalt content ratio in the cemented carbide 3. The method for measuring the content ratio of the first element in the binder phase 2 is as follows. Except that "Next, ··· measure the "cobalt" content ratio in the binder phase 2." is read as "Next, ··· measure the "first element" content ratio in the binder phase 2.", it is carried out in the same way as the method for measuring the cobalt content ratio in the binder phase 2. The method for specifying that "the first element in the cemented carbide 3 exists only in the binder phase 2" is as follows. Except that "Next, ··· specify that "cobalt" in the cemented carbide 3 exists only in the binder phase 2." is read as "Next, ··· specify that "the first element" in the cemented carbide 3 exists only in the binder phase 2.", it is carried out in the same way as the method for specifying that "cobalt in the cemented carbide 3 exists only in the binder phase 2".

[0042] As long as the applicant measures, as long as it is measured in the same sample, even if the cutting position of the cross-section of the cemented carbide 3 and the imaging region described in (C1) above are arbitrarily set and the above measurement is performed multiple times according to the above procedure, it has been confirmed that the variation in the measurement results is small and not arbitrary.

[0043] In the bonding phase 2, the percentage {M1 / (M1 + M2)}×100 of the mass M1 of the first element with respect to the total mass M1 + M2 of the mass M1 of the first element and the mass M2 of cobalt may be 1% or more and 6% or less. Thereby, since the bonding phase 2 can have both better hardness and better toughness, it is possible to provide a cemented carbide 3 that can further extend the tool life of a cutting tool, especially in the cutting of high-hardness materials. Here, when the bonding phase contains two or more types of first elements, the mass M1 of the first element means the total mass of all types of first elements. The lower limit of the percentage {M1 / (M1 + M2)}×100 may be 1% or more, may be 2% or more, or may be 3% or more. The upper limit of the percentage {M1 / (M1 + M2)}×100 may be 6% or less, may be 5% or less, or may be 4% or less. The percentage {M1 / (M1 + M2)}×100 may be 2% or more and 5% or less, or may be 3% or more and 4% or less.

[0044] The measuring method of the above percentage {M1 / (M1 + M2)}×100 is as follows. In the same manner as (A1) to (F1) of the measuring method of the content rate of the tungsten carbide particles 1 and the content rate of the bonding phase 2 in the above cemented carbide 3, the existing region of the bonding phase 2 is specified on the image after binarization processing. Analysis is performed on the existing region of the bonding phase 2 using SEM-EDX to measure the cobalt content rate and the first element content rate in the bonding phase 2, and based on these, the percentage {M1 / (M1 + M2)}×100 is calculated. The above measurement is performed in five different measurement fields that do not overlap with each other. In this specification, the average of the percentage {M1 / (M1 + M2)}×100 in the five measurement fields corresponds to the "percentage {M1 / (M1 + M2)}×100" in the bonding phase 2.

[0045] As long as the applicant has measured, as long as it is measured in the same sample, even if the cutting position of the cross-section of the cemented carbide 3 and the imaging region described in (C1) above are arbitrarily set and the measurement of the percentage {M1 / (M1 + M2)}×100 is performed multiple times according to the above procedure, it has been confirmed that the variation in the measurement results is small and not arbitrary.

[0046] <Hardness of the bonding phase> The hardness of the bonding phase 2 at 25°C measured by the nanoindentation method is 7.0 GPa or more. Thus, the bonding phase 2 can have excellent hardness under the condition of 25°C (in other words, at room temperature). The lower limit of the hardness may be 7.1 GPa or more, 7.2 GPa or more, or 7.4 GPa or more. The upper limit of the hardness may be 9 GPa or less, 8.5 GPa or less, or 8 GPa or less. The hardness may be 7.0 GPa or more and 9 GPa or less, 7.1 GPa or more and 8.5 GPa or less, or 7.2 GPa or more and 8 GPa or less.

[0047] The hardness of the bonding phase 2 at 25°C measured by the nanoindentation method is measured by the nanoindentation method (the "Hysitron TI 980 Triboindenter" manufactured by Bruker). The nanoindentation method is a method compliant with ISO14577, and is executed under the conditions that the measurement load is 0.5 mN, the loading time is 0.1 second, the load holding time is 0.1 second, and the unloading time is 0.1 second. The measurement target is each of any 10 bonding phases 2 exposed by polishing the surface of the cemented carbide 3 using a cross-section polisher (CP) processing apparatus (the "IB-19500CP Cross-Section Specimen Preparation Apparatus" (trademark) manufactured by JEOL Ltd.). The average value of the hardness of each of the 10 bonding phases 2 is defined as the "hardness of the bonding phase 2" above.

[0048] As long as the applicant measures, and as long as it is measured in the same sample, it has been confirmed that even if the measurement of the hardness of the bonding phase 2 is performed multiple times by arbitrarily setting 10 bonding phases 2, the variation in the measurement results is small and not arbitrary.

[0049] ≪Tungsten carbide particles≫ In Embodiment 1, the tungsten carbide particles 1 include at least one of "pure WC particles (WC that does not contain any impurity elements, and WC with an impurity element content less than the detection limit)" and "WC particles that intentionally or unavoidably contain impurity elements as long as the effects of the present disclosure are not impaired". The impurity content rate of the tungsten carbide particles (when there are two or more elements constituting the impurities, their total content rate) is less than 0.1% by mass. The content rate of the impurity elements of the tungsten carbide particles is measured by ICP emission analysis (Inductively Coupled Plasma Emission Spectroscopy, measuring device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0050] In Embodiment 1, the average particle size of the tungsten carbide particles 1 is not particularly limited. The average particle size of the tungsten carbide particles 1 can be, for example, 0.5 μm or more and 3 μm or less. It has been confirmed that the cemented carbide 3 of Embodiment 1 can have a long tool life regardless of the average particle size of the tungsten carbide particles 1.

[0051] ≪Applications of Cemented Carbide≫ The cemented carbide 3 of the present embodiment can be used for cutting tools. Examples of the cutting tools include cutting tools for general machining. More specifically, cutting tools such as drills, end mills, drill tip-exchangeable cutting tips, end mill tip-exchangeable cutting tips, milling cutter tip-exchangeable cutting tips, turning tool tip-exchangeable cutting tips, metal saws, tooth cutting tools, reamers, taps, etc. can be mentioned.

[0052] [Embodiment 2: Manufacturing Method of Cemented Carbide] The cemented carbide of the present embodiment can be manufactured by performing the raw material powder preparation step, mixing step, molding step, sintering step, cooling step, and HIP (Hot Isostatic Pressing) step in the above order. Hereinafter, each step will be described.

[0053] <Preparation Step> The preparation process is a process of preparing raw material powders of the materials constituting the cemented carbide. Examples of the raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder") and cobalt (Co) powder. In addition to these raw material powders, first element powder, niobium carbide (NbC) powder, Tantalum tantalum carbide (TaC) powder, titanium carbonitride (TiCN) powder, zirconium carbide (ZrC) powder, etc. can be prepared. Commercially available ones can be used for these raw material powders. The average particle size of these raw material powders is not particularly limited, and for example, it can be 0.5 to 2 μm. The average particle size of the raw material powder means the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size is measured using "Sub-Sieve Sizer model 95" (trademark) manufactured by Fisher Scientific.

[0054] <Mixing process> The mixing process is a process of mixing each raw material powder prepared in the preparation process at a predetermined ratio. By the mixing process, a mixed powder in which each raw material powder is mixed is obtained. The mixing ratio of each raw material powder is appropriately adjusted according to the composition of the target cemented carbide. First element powder may be used as the raw material powder. As a result, since the first element is sufficiently dissolved in the binder phase, it becomes easier for the cemented carbide to have a desired "hardness at 25°C measured by the nano-indentation method of the binder phase". From the viewpoint of making the total of the content rate of tungsten carbide particles and the content rate of the binder phase within a desired range, in the mixed powder, the total content rate of powders other than WC powder, Co powder, and first element powder may be less than 5% by mass. By appropriately adjusting the charged amount of each raw material powder, the content rate of the binder phase and the content rate of WC particles can each be within a desired range.

[0055] For mixing each raw material powder, conventionally known mixing methods such as an attritor, a ball mill, and a bead mill can be used. Conventional known conditions can also be used for the mixing conditions. The mixing time can be, for example, 2 hours or more and 20 hours or less.

[0056] After the mixing process, the mixed powder may be granulated if necessary. By granulating the mixed powder, it becomes easier to fill the die or mold with the mixed powder during the subsequent molding process. Known granulation methods can be applied for granulation. For example, commercially available granulators such as spray dryers can be used.

[0057] <Molding Process> The molding process is a process of molding the mixed powder obtained in the mixing process into the shape of a cutting tool to obtain a molded body. General methods and conditions can be adopted for the molding method and molding conditions in the molding process, and there are no particular restrictions.

[0058] <Sintering Process> The sintering process is a process of sintering the molded body obtained in the molding process to obtain a cemented carbide intermediate. The sintering conditions in this embodiment are as follows. The molded body is heated to 1360 °C and held at 1360 °C for 1 hour.

[0059] <Cooling Process> The cooling process is a process of cooling the cemented carbide intermediate after the sintering process. More specifically, the cemented carbide intermediate is cooled to 800 °C (hereinafter, also referred to as "the first cooling"). The cooling rate of the first cooling is, for example, 20 °C / min.

[0060] <HIP Process> The HIP process is a process of performing HIP treatment on the cemented carbide intermediate after the cooling process. The conditions of the HIP process in this embodiment are as follows. The cemented carbide intermediate is held for 2 hours under the condition that the pressure is 100 MPa. Thereby, the cemented carbide of Embodiment 1 can be obtained.

[0061] <Features of the Method for Manufacturing the Cemented Carbide of this Embodiment> In this embodiment, the sintering process is carried out by heating the compact to 1360°C and holding it at 1360°C for 1 hour. Further, the cooling process is carried out by setting the cooling rate up to 800°C to 20°C / min. Further, the HIP process is carried out under the conditions that the pressure is 100 MPa and the time is 2 hours. By these processes, it is possible to manufacture a cemented carbide in which the hardness at 25°C measured by the nanoindentation method of the binder phase is 7.0 GPa or more. The fact that the cemented carbide of the present disclosure can be realized by such sintering conditions, cooling process, and HIP process is newly found as a result of the inventors' intensive studies.

[0062] [Appendix 1] In the cemented carbide of Embodiment 1, the nanoindentation method can be carried out under the conditions that it is a method conforming to ISO14577, the measurement load is 0.5 mN, the loading time is 0.1 second, the load holding time is 0.1 second, and the unloading time is 0.1 second.

Examples

[0063] This embodiment will be described more specifically with reference to examples. However, this embodiment is not limited by these examples.

[0064] ≪Fabrication of Cemented Carbide≫ Cemented carbides according to Samples 1 to 19 and 101 to 114 were fabricated as follows.

[0065] <Preparation Step> As raw material powders, WC powder (average particle size: 1 μm), Co powder (average particle size: 1 μm), a first element powder, and TiCN powder (average particle size: 1 μm) were prepared. As the first element powder, Si powder (average particle size: 1 μm), Ge powder (average particle size: 1 μm), Sn powder (average particle size: 1 μm), Os powder (average particle size: 1 μm), Ir powder (average particle size: 1 μm), Pt powder (average particle size: 1 μm), P powder (average particle size: 1 μm), Re powder (average particle size: 1 μm), and Ru powder (average particle size: 1 μm) were prepared.

[0066] <Mixing Step> The respective raw material powders were mixed for 10 hours using an attritor at the ratios described in Tables 1 and 2 to obtain a mixed powder.

[0067] <Forming step> A cylindrical shaped formed body was obtained by press forming or extrusion forming the mixed powder.

[0068] <Sintering step> The formed body was heated to the temperatures described in Tables 1 and 2 and held at that temperature for the holding times described in Tables 1 and 2 to obtain a cemented carbide intermediate.

[0069] <Cooling step> The cemented carbide intermediate was cooled to 800 °C at the cooling rates described in Tables 1 and 2.

[0070] <HIP step> A cemented carbide was obtained by performing HIP treatment on the cemented carbide intermediate after the cooling step under the conditions described in Tables 1 and 2.

[0071] Cemented carbides according to Samples 1 to 19 and 101 to 114 were produced by the above procedure.

[0072]

Table 1

[0073]

Table 2

[0074]

Table 3

[0075]

Table 4

[0076] ≪Characteristics Evaluation of Cemented Carbide≫ <Content Ratio of Tungsten Carbide Particles> For the cemented carbide related to each sample, the content ratio of tungsten carbide particles was determined by the method described in Embodiment 1. The obtained results are described in the columns of "Content Ratio of WC Particles [Volume %]" in Tables 3 and 4. Note that the description of "remainder" in the columns of "Content Ratio of WC Particles [Volume %]" in Tables 3 and 4 means that the content ratio of tungsten carbide particles is equal to the numerical value obtained by subtracting the numerical value described in the column of "Content Ratio of Binder Phase [Volume %]" in Tables 3 and 4 from the numerical value described in the column of "Total [Volume %]" in Tables 3 and 4.

[0077] <Content Ratio of Binder Phase> For the cemented carbide related to each sample, the content ratio of the binder phase was determined by the method described in Embodiment 1. The obtained results are described in the columns of "Content Ratio of Binder Phase [Volume %]" in Tables 3 and 4.

[0078] <Hardness of Binder Phase> For the cemented carbide related to each sample, the hardness of the binder phase was determined by the method described in Embodiment 1. The obtained results are described in the columns of "Hardness of Binder Phase [GPa]" in Tables 3 and 4.

[0079] <Content Ratio of Cobalt in Cemented Carbide> For the cemented carbide related to each sample, the content ratio of cobalt in the cemented carbide was determined by the method described in Embodiment 1. The obtained results are described in the columns of "Co Content Ratio [Mass %]" in Tables 3 and 4. Note that for the cemented carbide related to each sample, it was confirmed by the method described in Embodiment 1 that "cobalt in cemented carbide 3 exists only in binder phase 2".

[0080] <Content Ratio of First Element in Cemented Carbide> Regarding the cemented carbide for each sample, the content rate of the first element in the cemented carbide was determined by the method described in Embodiment 1. The obtained results are described in the columns of "Content rate of the first element [mass%]" in Tables 3 and 4. Note that, for the cemented carbide for each sample, when the "Content rate of the first element [mass%]" is not 0 mass%, it was confirmed by the method described in Embodiment 1 that "the first element in the cemented carbide 3 exists only in the binder phase 2".

[0081] <{M1 / (M1+M2)}×100> Regarding the cemented carbide for each sample, {M1 / (M1+M2)}×100 was determined by the method described in Embodiment 1. The obtained results are described in the columns of "{M1 / (M1+M2)}×100 [%]" in Tables 3 and 4.

[0082] ≪Cutting test≫ First, by processing round bars made of the cemented carbide for each sample, three end mills (GSXB20000 type) with a cutting edge diameter of φ6 mm were produced as cutting tools for each sample. Next, using the end mills of each sample, cutting was performed under the following cutting conditions, and the cutting distance until 0.05 mm of wear occurred on the end mill was measured. For each sample, the cutting length was obtained by calculating the average value of the cutting distances of each of the three end mills. The obtained results are described in the columns of "Cutting length [m]" in Tables 3 and 4. Note that the longer the cutting length, the longer the tool life. <Cutting conditions> Workpiece material: SKD51 (high hardness material) Cutting speed Vc: 180 m / min Feed per tooth Fz: 0.15 mm / t Cutting depth Ap: 0.5 mm Cutting fluid: Yes (Wet) The above cutting conditions are applicable to the cutting of high hardness materials.

[0083] Samples 1 to 11、13~ The cemented carbide related to Samples 1 to 19 corresponds to the examples. The cemented carbide related to Samples 101 to 114 corresponds to the comparative examples. The cemented carbide related to Sample 12 corresponds to the reference example. From the results in Tables 3 and 4, Samples 1 to 11、13~The cemented carbide according to 19 has been found to enable the tool to have a longer life even when used as a material for a cutting tool for cutting a high-hardness material, as compared with the cemented carbides according to Samples 101 to 114.

[0084] As described above, Samples 1 to 11、13~ The cemented carbide according to 19 has been found to enable the tool to have a longer life even when used as a material for a cutting tool for cutting a high-hardness material.

[0085] As described above, the embodiments and examples of the present disclosure have been described. However, it has been planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples or to variously modify them.

[0086] The embodiments and examples disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiments and examples but by the claims, and it is intended that all meanings equivalent to the claims and all changes within the scope are included.

Explanation of Reference Numerals

[0087] 1 tungsten carbide particle, 2 binder phase, 3 cemented carbide

Claims

1. A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains 89% by volume or more in total of the tungsten carbide particles and the binder phase, the cemented carbide contains 1.8% by volume or more and 20.0% by volume or less of the binder phase, the binder phase contains cobalt, the cemented carbide contains 1.0% by mass or more of cobalt, the hardness of the binder phase at 25°C measured by nanoindentation is 7.1 GPa or more and 8 GPa or less, the cemented carbide.

2. the binder phase further contains a first element, the first element is at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, the cemented carbide according to claim 1.

3. In the binder phase, the percentage {M1 / (M1 + M2)}×100 of the mass M1 of the first element with respect to the total M1 + M2 of the mass M1 of the first element and the mass M2 of cobalt is 1% or more and 6% or less, the cemented carbide according to claim 2.

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