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 Young's modulus at 25 °C measured by the nanoindentation method of the binder phase is 170 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 Young's modulus at 25°C measured by the nanoindentation method of the binder phase is 170 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 workpieces to be machined have become more difficult to machine in cutting, and the operating conditions of cutting tools have become severe. Therefore, various improvements are required for cemented carbides used as the base materials of cutting tools. In particular, even when used as a material for cutting tools for high-efficiency machining of difficult-to-machine materials with high tensile strength, cemented carbides that enable the cutting tools to have a long service life are required.

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

[0008] [Effect of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables the cutting tool to have a long service life even when used as a material for a cutting tool for high-efficiency machining of a difficult-to-machine material with high tensile strength.

[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 Young's modulus of the binder phase measured by the nanoindentation method at 25°C is 170 GPa or more.

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

[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 extend the tool life of a cutting tool even in the high-efficiency machining of difficult-to-cut materials with particularly high tensile strength.

[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 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 extend the tool life of a cutting tool even in the high-efficiency machining of difficult-to-cut materials with particularly high tensile strength.

[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 have been appropriately changed for the 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 there is a unit description 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 a total of 89% by volume or more 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 Young's modulus of the binder phase 2 at 25°C measured by the nanoindentation method is 170 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 high-efficiency machining of difficult-to-cut materials with particularly high tensile strength. The reason is speculated 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 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 Young's modulus of the binder phase 2 at 25°C measured by the nanoindentation method is 170 GPa or more, and the binder phase 2 can have an excellent Young's modulus under the condition of 25°C (in other words, under room temperature conditions). According to this, the Young's modulus of the cemented carbide 3 is improved, and a cutting tool using the cemented carbide 3 can have excellent chipping resistance even in high-efficiency machining of difficult-to-cut materials with particularly high tensile strength.

[0020] ≪Composition of Cemented Carbide≫ The cemented carbide 3 contains a total of 89% by volume or more of tungsten carbide particles 1 and a binder phase 2. Thereby, the Young's modulus of the cemented carbide 3 can be increased. The cemented carbide 3 may contain a total of 90% by volume or more of tungsten carbide particles 1 and a binder phase 2, may contain 91% by volume or more, and may contain 92% by volume or more. 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, may be 99% by volume or less, and may be 98% by volume or less. The cemented carbide 3 may contain a total of 90% by volume or more and 100% by volume or less of tungsten carbide particles 1 and a binder phase 2, may contain 91% by volume or more and 100% by volume or less, and may contain 92% by volume or more and 100% by volume or less.

[0021] The cemented carbide 3 contains 1.8% by volume or more and 20.0% by volume or less of the binder phase 2. Thereby, in the cemented carbide 3, the Young's modulus 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, may be 3.0% by volume or more, and may be 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, may be 18.0% by volume or less, and may be 17.0% by volume or less. The cemented carbide 3 may contain 2.0% by volume or more and 19.0% by volume or less of the binder phase 2, may contain 3.0% by volume or more and 18.0% by volume or less of the binder phase 2, and may contain 4.0% by volume or more and 17.0% by volume or less of the binder phase 2.

[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 may 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 phase 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 of 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 of 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, and 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 of 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, and 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 the impurities of 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 the impurities of the cemented carbide 3 may be 0% by mass or more and less than 0.1% by mass. The content rate of the impurities of the cemented carbide 3 is measured by inductively coupled plasma emission spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0025] The measuring method of 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. The cross section is polished to a mirror finish by 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-polished 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 central part of the cross-section of the cemented carbide 3, that is, a position that does not include a portion with significantly different properties from the bulk part such as the vicinity of the surface of the cemented carbide 3 (a position where the imaging area is entirely the bulk part 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 respective 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 measurement fields that do not overlap with each other. In this specification, the average of the area percentages of tungsten carbide particles 1 in the five measurement fields corresponds to the content [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 [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 of the other phases of the cemented carbide 3 can be obtained by subtracting the content [volume%] of the tungsten carbide particles 1 and the content [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 of the tungsten carbide particles 1 and the content 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, may contain 60 mass% or more of cobalt, may contain 70 mass% or more of cobalt, may contain 80 mass% or more of cobalt, may contain 90 mass% or more of cobalt, or may contain 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 be present 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, may be 3.0 mass% or more, or may be 4.0 mass% or more. The upper limit of the content of cobalt in the cemented carbide 3 may be 20 mass% or less, may be 15 mass% or less, may be 12 mass% or less, or may be 10 mass% or less. The cemented carbide 3 may contain 1.0 mass% or more and 20 mass% or less of cobalt, may contain 2.0 mass% or more and 15 mass% or less of cobalt, or may contain 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 analysis on the imaging area using SEM-EDX, 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. Note that the method for measuring the "cobalt content in the binder phase 2" is as follows. First, identify the existence 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 analysis on the existence area of the binder phase 2 using SEM-EDX to measure the "cobalt content in the binder phase 2". Also, the method for identifying that "cobalt in the cemented carbide 3 exists only in the binder phase 2" is as follows. First, identify the existence area of the tungsten carbide particles 1 and the existence 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 and the existence areas of the tungsten carbide particles 1 and the binder phase 2, identify that "cobalt in the cemented carbide 3 exists only in the binder phase 2".

[0038] As long as the applicant has 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 has been confirmed that the variation in the measurement results is small and not arbitrary.

[0039] The bonding 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 the cemented carbide 3 that can further extend the tool life of the cutting tool even in the high-efficiency machining of difficult-to-cut materials with particularly high tensile strength.

[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 bonding phase 2 can have both a more excellent Young's modulus and a more excellent toughness. The content of the first element in the bonding 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 bonding 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 rate of the first element in the cemented carbide 3 is as follows. Except that "cobalt" is replaced with "the first element", it is carried out in the same manner as the method for measuring the cobalt content rate in the cemented carbide 3. The method for measuring the content rate of the first element in the binder phase 2 is as follows. Except that "Next, ··· measure the "cobalt" content rate in the binder phase 2." is replaced with "Next, ··· measure the "first element" content rate in the binder phase 2.", it is carried out in the same manner as the method for measuring the cobalt content rate 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 replaced with "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 manner 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, and 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 region described in (C1) above are arbitrarily set and the above measurement is carried out 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 binding 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. As a result, the binding phase 2 can have both a better Young's modulus and better toughness, so that it is possible to provide a cemented carbide 3 that can further extend the tool life of a cutting tool even in high-efficiency machining of difficult-to-cut materials with particularly high tensile strength. Here, when the binding 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 binding phase 2 in the above cemented carbide 3, the existence region of the binding phase 2 is specified on the image after binarization processing. The binding phase 2 is analyzed using SEM-EDX to measure the cobalt content rate and the first element content rate in the binding 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 binding 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] <Young's modulus of the bonding phase> The Young's modulus at 25 °C measured by the nanoindentation method for the bonding phase 2 is 170 GPa or more. Accordingly, the bonding phase 2 can have an excellent Young's modulus under the condition of 25 °C (in other words, at room temperature). The lower limit of the Young's modulus may be 180 GPa or more, 190 GPa or more, or 200 GPa or more. The upper limit of the Young's modulus may be 230 GPa or less, 220 GPa or less, 210 GPa or less, or 198 GPa or less. The Young's modulus may be 170 GPa or more and 230 GPa or less, 180 GPa or more and 220 GPa or less, or 190 GPa or more and 210 GPa or less.

[0047] The Young's modulus at 25 °C measured by the nanoindentation method for the bonding phase 2 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 object 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 device (the "IB-19500CP Cross-Section Specimen Preparation Device" (trademark) manufactured by JEOL Ltd.). The average value of the Young's modulus of each of the 10 bonding phases 2 is defined as the "Young's modulus of the bonding phase 2" described above.

[0048] As long as the applicant measures, as long as it is measured in the same sample, even if 10 bonding phases 2 are arbitrarily set and the measurement of the Young's modulus of the bonding phase 2 is performed multiple times, it has been confirmed that 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 containing no impurity elements and WC with an impurity element content less than the detection limit)" and "WC particles containing impurity elements intentionally or unavoidably 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, hacksaws, gear 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 a raw material powder preparation step, a mixing step, a molding step, a sintering step, a cooling step, and a 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 (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 set to 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 of the raw material powders 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. This makes it easier to align the crystal orientations of the binder phase, and thus it becomes easier for the cemented carbide to have a desired "Young's modulus at 25°C measured by the nanoindentation method of the binder phase". By appropriately adjusting the charged amount of each raw material powder, the content of the binder phase and the content 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 as necessary. By granulating the mixed powder, it becomes easier to fill the mixed powder into a die or mold 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 1340 °C and held at 1340 °C for 2 hours.

[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, 2 °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 4 hours under the condition that the pressure is 10 MPa. Thereby, the cemented carbide of Embodiment 1 can be obtained.

[0061] <Features of the Manufacturing Method of the Cemented Carbide of this Embodiment> In this embodiment, the sintering process is carried out by heating the green compact to 1340°C and holding it at 1340°C for 2 hours. Further, the cooling process is carried out by setting the cooling rate up to 800°C to 2°C / min. Further, the HIP process is carried out under the conditions that the pressure is 10 MPa and the time is 4 hours. By these processes, it is possible to produce a cemented carbide in which the Young's modulus at 25°C measured by the nanoindentation method of the binder phase is 170 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 intensive studies by the inventors.

[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 compliant with 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 further specifically described by way of examples. However, this embodiment is not limited by these examples.

[0064] ≪Fabrication of Cemented Carbide≫ Cemented carbides according to Samples 1 to 20 and 101 to 112 were fabricated as follows.

[0065] <Preparation Process> 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 Process> The mixed powder was obtained by mixing the raw material powders at the ratios described in Tables 1 and 2 using an attritor for 10 hours.

[0067] <Forming process> A round bar-shaped compact was obtained by press-forming or extrusion-forming the mixed powder.

[0068] <Sintering process> The compact 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 process> The cemented carbide intermediate was cooled to 800 °C at the cooling rates described in Tables 1 and 2.

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

[0071] Cemented carbides according to Samples 1 to 20 and 101 to 112 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 value obtained by subtracting the value described in the column of "Content Ratio of Binder Phase [Volume %]" in Tables 3 and 4 from the 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] <Young's Modulus of Binder Phase> For the cemented carbide related to each sample, the Young's modulus of the binder phase was determined by the method described in Embodiment 1. The obtained results are described in the column of "Young's Modulus [GPa]" in the column of "Binder Phase" 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. In addition, regarding 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 a round bar made of the cemented carbide for each sample, an end mill with a cutting edge diameter of φ6 mm was produced as a cutting tool for each sample. Next, using the end mill of each sample, cutting was performed under the following cutting conditions, and the cutting length until a defect occurred in the end mill was measured. The obtained results are respectively 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: "Hastelloy C276" (trademark) manufactured by Osaka Stainless Steel Co., Ltd. (a difficult-to-machine material with high tensile strength) Cutting speed Vc: 45 m / min Feed per tooth Fz: 0.2 mm / t Axial depth of cut ap: 1 mm Radial depth of cut ae: 0.3 mm Cutting fluid: Yes (Wet) The above cutting conditions are applicable to high-efficiency machining of difficult-to-machine materials with high tensile strength.

[0083] The cemented carbides according to Samples 1 to 20 correspond to the examples. The cemented carbides according to Samples 101 to 112 correspond to the comparative examples. From the results in Tables 3 and 4, it was found that even when the cemented carbides according to Samples 1 to 20 are used as a material for a cutting tool for high-efficiency machining of difficult-to-cut materials with high tensile strength, it is possible to extend the tool life.

[0084] From the above, it was found that the cemented carbides according to Samples 1 to 20 can extend the tool life even when used as a material for a cutting tool for high-efficiency machining of difficult-to-cut materials with high tensile strength.

[0085] Although the embodiments and examples of the present disclosure have been described as above, 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 as 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 modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0087] 1 Tungsten carbide particles, 2 Bonding 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 Young's modulus at 25°C measured by the nanoindentation method of the binder phase is 170 GPa or more, 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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