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 a total of 89% by volume or more 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 percentage (H2 / H1)×100 of the hardness H2 GPa at 600 °C to the hardness H1 GPa at 25 °C measured by the nanoindentation method of the binder phase is 25% 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 percentage (H2 / H1)×100 of the hardness H2 GPa at 600°C to the hardness H1 GPa at 25°C measured by the nanoindentation method of the binder phase is 25% 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 a material for cutting tools for high-speed machining of high-hardness materials, 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 a material for cutting tools for high-speed machining of high-hardness materials.

[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 a material for cutting tools for high-speed machining of high-hardness materials.

[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 percentage (H2 / H1)×100 of the hardness H2 GPa at 600°C to the hardness H1 GPa at 25°C measured by the nanoindentation method of the binder phase is 25% 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 a material for cutting tools for high-speed machining of high-hardness materials.

[0011] (2) In the above (1), the percentage (H2 / H1) × 100 may be 50% or more. By this, it is possible to provide a cemented carbide that can further extend the tool life of a cutting tool even in high-speed machining of particularly high-hardness materials.

[0012] (3) In the above (1) or (2), the hardness H1 may be 7.0 GPa or more. By this, it is possible to provide a cemented carbide that can further extend the tool life of a cutting tool even in high-speed machining of particularly high-hardness materials.

[0013] (4) In any one of (1) to (3) above, 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. By this, it is possible to provide a cemented carbide that can further extend the tool life of a cutting tool even in high-speed machining of particularly high-hardness materials.

[0014] (5) In the above (4), 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. By this, it is possible to provide a cemented carbide that can further extend the tool life of a cutting tool even in high-speed machining of particularly high-hardness materials.

[0015] [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 the sake of clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0016] 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.

[0017] 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.

[0018] [Embodiment 1: Cemented carbide] The cemented carbide according to an embodiment of the present disclosure will be described with reference to FIG. 1. One embodiment of the present disclosure (hereinafter, also referred to as "this embodiment") is a cemented carbide 3 including 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 percentage (H2 / H1)×100 of the hardness H2 GPa at 600 °C with respect to the hardness H1 GPa at 25 °C measured by the nanoindentation method of the binder phase 2 is 25% or more.

[0019] 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-speed machining of particularly high-hardness materials. The reason is presumed as follows.

[0020] The cemented carbide 3 of this 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 rate 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.

[0021] The cemented carbide 3 of Embodiment 1 contains the binder phase 2 in an amount of 1.8% to 20.0% by volume. The binder phase 2 contains cobalt, and the cemented carbide 3 contains cobalt in an amount of 1.0% by mass or more. Further, the percentage (H2 / H1)×100 of the hardness H2 GPa at 600°C to the hardness H1 GPa at 25°C measured by the nanoindentation method of the binder phase 2 is 25% or more, and the "decrease in the hardness of the cemented carbide 3" accompanying the change from the condition at 25°C (in other words, at room temperature) to the condition at 600°C (in other words, at high temperature) can be suppressed. According to this, the "decrease in the hardness of the cemented carbide 3" is suppressed, and the cutting tool using the cemented carbide 3 can have excellent wear resistance even in the high-speed machining of high-hardness materials.

[0022] ≪Composition of Cemented Carbide≫ The cemented carbide 3 contains a total of 89% by volume or more of tungsten carbide particles 1 and the binder phase 2. Thereby, the hardness 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 the binder phase 2, may contain 91% by volume or more, or 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, or 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 the binder phase 2, may contain 91% by volume or more and 100% by volume or less, or may contain 92% by volume or more and 100% by volume or less.

[0023] 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, the hardness and toughness of the cemented carbide 3 can be increased. The lower limit of the content 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, or may be 4.0% by volume or more. The upper limit of the content 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, or may be 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, may contain the binder phase 2 in an amount of 3.0% by volume or more and 18.0% by volume or less, or may contain the binder phase 2 in an amount of 4.0% by volume or more and 17.0% by volume or less.

[0024] 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 phase is, for example, TiCN, TaC, NbC, ZrC, HfC, Mo2C.

[0025] The cemented carbide 3 of Embodiment 1 can be composed of tungsten carbide particles 1, a binder phase 2, and other phases. The content of the other phases of the cemented carbide 3 is acceptable within a range that does not impair the effects of the present disclosure. For example, the content of the 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, or may be more than 0% by volume and 16% by volume or less. In this case, the total content 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, or may be 84% by volume or more and less than 100% by volume.

[0026] 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 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 the impurities in the cemented carbide 3 may be 0 mass% or more and less than 0.1 mass%. The content rate of the impurities in the cemented carbide 3 is measured by ICP emission analysis (Inductively Coupled Plasma Emission Spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark))).

[0027] The measurement methods for the content rate [volume%] of the tungsten carbide particles 1 and the content rate [volume%] of the binder phase 2 in the cemented carbide 3 are as follows.

[0028] (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.).

[0029] (B1) Analyze the mirror-finished surface of the cemented carbide 3 by scanning electron microscope - energy dispersive X-ray spectroscopy (SEM-EDX) (device: "Gemini450" (trademark) manufactured by Carl Zeiss) to identify the elements contained in the cemented carbide 3.

[0030] (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 region of the photographed image is set at a position in the center of the cross-section of the cemented carbide 3, that is, a position that does not include a portion with clearly different properties from the bulk portion such as near the surface of the cemented carbide 3 (a position where the entire imaging region 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.

[0031] (D1) For the imaging area of (C1) above, analysis is performed 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.

[0032] (E1) The backscattered electron image obtained in (C1) above is imported into a computer and subjected to binarization processing using image analysis software (OpenCV, SciPy). In the image after binarization processing, tungsten carbide particles 1 are shown in white and the bonding phase 2 is shown in gray to black. Note that since the binarization threshold changes depending on the contrast, it is set for each image.

[0033] (F1) By overlapping the elemental mapping image obtained in (D1) above and the image after binarization processing obtained in (E1) above, the respective existence regions of tungsten carbide particles 1 and the bonding phase 2 are identified 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 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 bonding phase 2.

[0034] (G1) In the image after binarization processing above, one measurement field of a rectangle of 24.9 μm × 18.8 μm is set. Using the above image analysis software, the area percentage of each of tungsten carbide particles 1 and the bonding phase 2 is measured with the total area of the measurement field as the denominator.

[0035] (H1) The measurement in (G1) above 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 bonding phase 2 in the five measurement fields corresponds to the content rate [volume%] of the bonding phase 2 in the cemented carbide 3.

[0036] 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% by volume).

[0037] As long as the applicant measures and as long as it is measured in the same sample, the cutting position of the cross-section of the cemented carbide 3 is arbitrarily set, the imaging region described in the above (C1) 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 is confirmed that the variation in the measurement results is small and not arbitrary.

[0038] ≪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. 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 the 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 rate 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 rate 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.

[0039] 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 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. Note that 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 analysis on the existing 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 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 and the existing 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".

[0040] As far 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.

[0041] 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 a cemented carbide 3 that can further extend the tool life of a cutting tool even in high-speed machining of particularly hard materials.

[0042] 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 better hardness and better 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.

[0043] 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. Also, 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."

[0044] As long as the applicant has measured and as long as the measurement is made 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 performed multiple times according to the above procedure, it has been confirmed that the variation in the measurement results is small and not arbitrary.

[0045] 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 better hardness and better toughness, and thus it is possible to provide a cemented carbide 3 that can further extend the tool life of a cutting tool even in high-speed machining of high-hardness materials. 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.

[0046] 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. Analysis is performed on the existence region of the binding phase 2 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.

[0047] As long as the applicant has measured, as long as the measurement is performed on the same sample, even if the cutting position of the cross-section of the cemented carbide 3 and the imaging region described in the above (C1) 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.

[0048] <Hardness of the bonding phase> The percentage (H2 / H1)×100 of the hardness H2 GPa at 600 °C with respect to the hardness H1 GPa at 25 °C measured by the nanoindentation method of the bonding phase 2 is 25% or more. Thereby, it is possible to suppress "the decrease in the hardness of the cemented carbide 3" accompanying the change from the condition at 25 °C (in other words, at room temperature) to the condition at 600 °C (in other words, at high temperature). The lower limit of the percentage (H2 / H1)×100 may be 50% or more, may be 60% or more, or may be 70% or more. The upper limit of the percentage (H2 / H1)×100 may be 85% or less, may be 80% or less, may be 75% or less, or may be 61% or less. The percentage (H2 / H1)×100 may be 25% or more and 85% or less, may be 50% or more and 80% or less, or may be 60% or more and 75% or less.

[0049] The hardness H1 may be 7.0 GPa or more. Thereby, the cemented carbide 3 can have more excellent wear resistance. The lower limit of the hardness H1 may be 7.0 GPa or more, may be 7.1 GPa or more, or may be 7.2 GPa or more. The upper limit of the hardness H1 may be 8.2 GPa or less, may be 8.0 GPa or less, or may be 7.8 GPa or less. The hardness H1 may be 7.0 GPa or more and 8.2 GPa or less, may be 7.1 GPa or more and 8.0 GPa or less, or may be 7.2 GPa or more and 7.8 GPa or less.

[0050] The hardness H2 may be 1.8 GPa or more. Thereby, the cemented carbide 3 can have more excellent wear resistance. The lower limit of the hardness H2 may be 1.8 GPa or more, may be 1.9 GPa or more, or may be 2.0 GPa or more. The upper limit of the hardness H2 may be 4.0 GPa or less, may be 3.9 GPa or less, or may be 3.7 GPa or less. The hardness H2 may be 1.8 GPa or more and 4.0 GPa or less, may be 1.9 GPa or more and 3.9 GPa or less, or may be 2.0 GPa or more and 3.7 GPa or less.

[0051] The above hardness H1 GPa and the above hardness H2 GPa are 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 binder phases 2 exposed by polishing the surface of the cemented carbide 3 using a cross-section polisher (CP) 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 binder phases 2 measured under the condition of 25°C is defined as the above hardness H1 GPa. Further, the average value of the hardness of each of the 10 binder phases 2 measured under the condition of 600°C is defined as the above hardness H2 GPa.

[0052] As far as the applicant has measured, as long as the measurement is made on the same sample, even if the measurement of the hardness of the binder phase 2 is performed multiple times by arbitrarily setting 10 binder phases 2, it has been confirmed that the variation in the measurement results is small and not arbitrary.

[0053] ≪Tungsten Carbide Particles≫ In Embodiment 1, the tungsten carbide particles 1 include at least any one of "pure WC particles (WC containing no impurity element at all, and WC with the content of the impurity element being less than the detection limit)" and "WC particles containing impurity elements intentionally or unavoidably therein 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 impurity, their total content rate) is less than 0.1 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 apparatus: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0054] 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.

[0055] ≪Applications of Cemented Carbide≫ The cemented carbide 3 of this 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.

[0056] [Embodiment 2: Manufacturing Method of Cemented Carbide] The cemented carbide of this embodiment can be manufactured by performing a raw material powder preparation step, a mixing step, a molding step, a sintering step, a first cooling step, a heating step, a HIP (Hot Isostatic Pressing) step, and a second cooling step in this order. Hereinafter, each step will be described.

[0057] <Preparation Step> The preparation step is a step 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, a first element powder, niobium carbide (NbC) powder, carbonized TantalumPowders such as (TaC) powder, titanium carbonitride (TiCN) powder, and zirconium carbide (ZrC) powder can be prepared. Commercially available products can be used as these raw material powders. The average particle size of these raw material powders is not particularly limited, and can be, for example, 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.

[0058] <Mixing step> The mixing step is a step of mixing each raw material powder prepared in the preparation step at a predetermined ratio. By the mixing step, 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. The 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 the 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 the first element powder may be less than 5% by mass. By appropriately adjusting the charged amount of each raw material powder, each of the content rate of the binder phase and the content rate of WC particles can be within a desired range.

[0059] The mixing of each raw material powder can use a conventionally known mixing method such as an attritor, a ball mill, and a bead mill. 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.

[0060] After the mixing step, 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 a mold during the molding step described later. Known granulation methods can be applied to granulation, and for example, commercially available granulators such as a spray dryer can be used.

[0061] <Forming Process> The forming process is a process of forming the mixed powder obtained in the mixing process into the shape of a cutting tool to obtain a formed body. The forming method and forming conditions in the forming process may adopt general methods and conditions and are not particularly limited.

[0062] <Sintering Process> The sintering process is a process of sintering the formed body obtained in the forming process to obtain a cemented carbide intermediate. The sintering conditions in this embodiment are as follows. The formed body is heated to 1360 °C and held at 1360 °C for 1 hour.

[0063] <First Cooling Process> The first cooling process is a process of cooling the cemented carbide intermediate. More specifically, the cemented carbide intermediate is cooled to 1000 °C. The cooling rate is not particularly limited, but can be, for example, 20 °C / min.

[0064] <Heating Process> The heating process is a process of heating the cemented carbide intermediate. More specifically, the heating temperature is 1200 °C and the holding time at this temperature is 0.25 hours.

[0065] <HIP Process> The HIP process is a process of performing HIP treatment on the cemented carbide intermediate. 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.

[0066] <Second Cooling Process> The second cooling process is a process of cooling the cemented carbide intermediate. More specifically, the cemented carbide intermediate is cooled to 800 °C. The cooling rate is 20 °C / min. Thus, the cemented carbide of Embodiment 1 can be obtained.

[0067] <Features of the Manufacturing Method of 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 first cooling process is carried out by cooling the cemented carbide intermediate to 1000°C. Further, the heating process is carried out under the conditions that the temperature is 1200°C and the holding time is 0.25 hour. Further, the HIP process is carried out under the conditions that the pressure is 100 MPa and the time is 2 hours. Further, the second cooling process is carried out by setting the cooling rate up to 800°C to 20°C / min. By these processes, it is possible to manufacture a cemented carbide in which the percentage (H2 / H1)×100 of the hardness H2 GPa at 600°C with respect to the hardness H1 GPa at 25°C measured by the nanoindentation method of the binder phase is 25% or more. The fact that the cemented carbide of the present disclosure can be realized by such sintering conditions, the first cooling process, the heating process, the HIP process, and the second cooling process is newly found as a result of the inventors' intensive studies.

[0068] [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

[0069] The present embodiment will be described more specifically by way of examples. However, the present embodiment is not limited by these examples.

[0070] ≪Fabrication of Cemented Carbide≫ By performing the following steps in the following order, cemented carbides according to Samples 1 to 20 and 101 to 114 were fabricated.

[0071] <Preparation Step> As raw material powders, WC powder (average particle size: 1 μm), Co powder (average particle size: 1 μm), the 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.

[0072] <Mixing Process> Each raw material powder was mixed for 10 hours using an attritor at the ratios described in Tables 1 and 2 to obtain a mixed powder.

[0073] <Forming Process> A round bar-shaped formed body was obtained by press-forming or extrusion-forming the mixed powder.

[0074] <Sintering Process> 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.

[0075] <First Cooling Process> The cemented carbide intermediate was cooled to the temperatures described in Tables 3 and 4. Note that when "-" is described in the "Temperature [°C]" column in the "First Cooling Process" column, it means that the "First Cooling Process" was not performed.

[0076] <Heating Process> The heating process was performed on the cemented carbide intermediate under the conditions described in Tables 3 and 4. Note that when "-" is described in each of the "Temperature [°C]" column and the "Holding Time [hours]" column in the "Heating Process" column, it means that the "Heating Process" was not performed.

[0077] <HIP Process> The HIP treatment was performed on the cemented carbide intermediate under the conditions described in Tables 3 and 4.

[0078] <Second Cooling Process> The cemented carbide intermediate after the HIP process was cooled to 800 °C at the cooling rates described in Tables 3 and 4 to obtain a cemented carbide.

[0079] Cemented carbides according to Samples 1 to 20 and 101 to 114 were produced by the above procedure.

[0080]

Table 1

[0081]

Table 2

[0082]

Table 3

[0083]

Table 4

[0084]

Table 5

[0085]

Table 6

[0086] ≪Characteristic Evaluation of Cemented Carbide≫ <Content of Tungsten Carbide Particles> For each cemented carbide sample, the content of tungsten carbide particles was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "WC particle content [volume %]" in Tables 5 and 6. Note that the notation "remainder" in the columns of "WC particle content [volume %]" in Tables 5 and 6 means that the content of tungsten carbide particles is equal to the value obtained by subtracting the value described in the column of "Binder phase content [volume %]" in Tables 5 and 6 from the value described in the column of "Total [volume %]" in Tables 5 and 6.

[0087] <Binder phase content> For each cemented carbide sample, the content of the binder phase was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Binder phase content [volume %]" in Tables 5 and 6.

[0088] <Hardness of the binder phase> For each cemented carbide sample, the hardness H1 of the binder phase was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Hardness H1 of the binder phase [GPa]" in Tables 5 and 6. Also, for each cemented carbide sample, the hardness H2 of the binder phase was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Hardness H2 of the binder phase [GPa]" in Tables 5 and 6.

[0089] <Cobalt content in the cemented carbide> For each cemented carbide sample, the cobalt content in the cemented carbide was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Co content [mass %]" in Tables 5 and 6. Note that for each cemented carbide sample, it was confirmed by the method described in Embodiment 1 that "cobalt in cemented carbide 3 exists only in binder phase 2".

[0090] <Content of the first element in the cemented carbide> For each of the cemented carbides related to the samples, 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 5 and 6. Note that for each of the cemented carbides related to the samples, 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 cemented carbide 3 exists only in the binder phase 2".

[0091] <{M1 / (M1+M2)}×100> For each of the cemented carbides related to the samples, {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 5 and 6.

[0092] ≪Cutting test≫ First, by processing round bars made of the cemented carbides related to the samples, three end mills (GSXB20000 type) with a cutting edge diameter of φ8 mm were produced for each of the cutting tools related to the samples. 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 the three end mills. The obtained results are described in the columns of "Cutting length [m]" in Tables 5 and 6 respectively. Note that the longer the cutting length, the longer the tool life. <Cutting conditions> Workpiece material: SKD11 (high-hardness material) Cutting speed Vc: 250 m / min Feed per tooth Fz: 0.15 mm / t Cutting depth Ap: 0.5 mm Cutting fluid: None (Dry) The above cutting conditions correspond to high-speed machining of high-hardness materials.

[0093] The cemented carbides according to Samples 1 to 20 correspond to the examples. The cemented carbides according to Samples 101 to 114 correspond to the comparative examples. From the results in Tables 5 and 6, it was found that the cemented carbides according to Samples 1 to 20 can enable the tool to have a longer service life even when used as a material for a cutting tool for high-speed machining of high-hardness materials, as compared with the cemented carbides according to Samples 101 to 114.

[0094] From the above, it was found that the cemented carbides according to Samples 1 to 20 can enable the tool to have a longer service life even when used as a material for a cutting tool for high-speed machining of high-hardness materials.

[0095] 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.

[0096] 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

[0097] 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 percentage (H2 / H1)×100 of the hardness H2 GPa at 600 °C to the hardness H1 GPa at 25 °C measured by the nanoindentation method of the binder phase is 25% or more. Cemented carbide.

2. The cemented carbide according to claim 1, wherein the percentage (H2 / H1)×100 is 50% or more.

3. The cemented carbide according to claim 1 or claim 2, wherein the hardness H1 is 7.0 GPa or more.

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

5. In the binder phase, the percentage {M1 / (M1 + M2)}×100 of the mass M1 of the first element to the total mass 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 4.

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