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 ((Y2 / Y1)×100) of the Young's modulus Y2 GPa at 600°C to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase is 50% or more. Cemented carbide.

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 ((Y2 / Y1)×100) of the Young's modulus Y2 GPa at 600°C to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase is 50% or more.

Brief Description of the Drawings

[0005]

Figure 1

Embodiments 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 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 difficult-to-machine materials with high tensile strength, a cemented carbide that enables the tool to have a long service 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 service life, even when used as a material for cutting tools for high-speed machining of difficult-to-machine materials 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 tool to have a long service life, even when used as a material for cutting tools for high-speed machining of difficult-to-machine materials 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 comprising 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 ((Y2 / Y1)×100) of the Young's modulus Y2 GPa at 600°C to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase is 50% or more.

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

[0011] (2) In the above (1), the percentage (Y2 / Y1)×100 may be 70% 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 difficult-to-cut materials with particularly high tensile strength.

[0012] (3) In the above (1) or (2), the Young's modulus Y1 may be 170 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 difficult-to-cut materials with particularly high tensile strength.

[0013] (4) In any one of the above (1) to (3), 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 difficult-to-cut materials with particularly high tensile strength.

[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 difficult-to-cut materials with particularly high tensile strength.

[0015] [Details of Embodiments of the Present Disclosure] Specific examples of cutting tools according to an embodiment of the present disclosure (hereinafter, also referred to as "the present 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, depth, etc. have been 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 a unit is described only for B, the unit of A and the unit of 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 ((Y2 / Y1)×100) of the Young's modulus Y2 GPa at 600°C to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase 2 is 50% 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 difficult-to-machine materials with particularly high tensile strength. 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 of the WC particles 1 and the binder phase 2 in 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% by volume or more and 20.0% by volume or less. 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 (Y2 / Y1)×100 of the Young's modulus Y2 GPa at 600°C to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase 2 is 50% or more, and the "decrease in the Young's modulus of the cemented carbide 3" accompanying the change from the condition at 25°C (in other words, room temperature condition) to the condition at 600°C (in other words, high temperature condition) can be suppressed. According to this, the "decrease in the Young's modulus of the cemented carbide 3" is suppressed, and a cutting tool using the cemented carbide 3 can have excellent chipping resistance even in the high-speed machining of difficult-to-cut materials with particularly high tensile strength.

[0022] ≪Composition of Cemented Carbide≫ The cemented carbide 3 contains the tungsten carbide particles 1 and the binder phase 2 in a total amount of 89% by volume or more. Thereby, the hardness of the cemented carbide 3 can be increased. The cemented carbide 3 may contain the tungsten carbide particles 1 and the binder phase 2 in a total amount of 90% by volume or more, 91% by volume or more, or 92% by volume or more. In the cemented carbide 3, the upper limit of the total content 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 the tungsten carbide particles 1 and the binder phase 2 in a total amount of 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.

[0023] The cemented carbide 3 contains the binder phase 2 in an amount of 1.8% to 20.0% by volume. Thereby, in the cemented carbide 3, the Young's modulus and toughness 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% to 19.0% by volume, may contain the binder phase 2 in an amount of 3.0% to 18.0% by volume, or may contain the binder phase 2 in an amount of 4.0% to 17.0% by volume.

[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 allowed 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 such 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 mass% or more and less than 0.1 mass%. The content rate of 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 measuring methods for the content rate [volume%] of tungsten carbide particles 1 in the cemented carbide 3 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 area of the photographed image is set at a position in the central part of the cross-section of the cemented carbide 3, that is, a position that does not include a part with clearly 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.

[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 binarization processing is performed 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 ratio of the other phases of the cemented carbide 3 can be obtained by subtracting the content ratio [volume%] of the tungsten carbide particles 1 and the content ratio [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, 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 ratio of the tungsten carbide particles 1 and the content ratio 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.

[0038] ≪Binder Phase≫ The binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0% by 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% by mass or more of cobalt, 60% by mass or more of cobalt, 70% by mass or more of cobalt, 80% by mass or more of cobalt, 90% by mass or more of cobalt, 95% by 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 ratio of cobalt in the cemented carbide 3 may be 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more. The upper limit of the content ratio of cobalt in the cemented carbide 3 may be 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less. The cemented carbide 3 may contain 1.0% by mass or more and 20% by mass or less of cobalt, 2.0% by mass or more and 15% by mass or less of cobalt, 3.0% by mass or more and 12% by 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 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 and the existing areas of the tungsten carbide particles 1 and the binder phase 2, identify that "the cobalt in the cemented carbide 3 exists only in the binder phase 2".

[0040] 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.

[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 difficult-to-cut materials with particularly high tensile strength.

[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 a more excellent Young's modulus and a more excellent toughness. Note that 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 read as "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 bonding phase 2 is as follows. Except that "Next, ··· measure the "cobalt" content rate in the bonding phase 2." is read as "Next, ··· measure the "first element" content rate in the bonding phase 2.", it is carried out in the same manner as the method for measuring the cobalt content rate in the bonding phase 2. The method for specifying that "the first element in the cemented carbide 3 exists only in the bonding phase 2" is as follows. Except that "Next, ··· specify that "cobalt" in the cemented carbide 3 exists only in the bonding phase 2." is read as "Next, ··· specify that "the first element" in the cemented carbide 3 exists only in the bonding 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 bonding 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 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.

[0045] 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. As a result, the bonding phase 2 can have both a better Young's modulus 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, especially in high-speed machining of difficult-to-cut materials with high tensile strength. 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, 2% or more, or 3% or more. The upper limit of the percentage {M1 / (M1 + M2)}×100 may be 6% or less, 5% or less, or 4% or less. The percentage {M1 / (M1 + M2)}×100 may be 2% or more and 5% or less, or 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 bonding phase 2 in the above cemented carbide 3, the existence region of the bonding phase 2 is specified on the binarized image. Analysis is performed on the existence 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.

[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] <Young's modulus of the bonding phase> The percentage ((Y2 / Y1)×100) of the Young's modulus Y2 GPa at 600 °C to the Young's modulus Y1 GPa at 25 °C measured by the nanoindentation method of the bonding phase 2 is 50% or more. Thereby, it is possible to suppress "the decrease in the Young's modulus of cemented carbide 3" accompanying the change from the condition of 25 °C (in other words, room temperature condition) to the condition of 600 °C (in other words, high temperature condition). The lower limit of the percentage ((Y2 / Y1)×100) may be 55% or more, may be 60% or more, or may be 70% or more. The upper limit of the percentage ((Y2 / Y1)×100) may be 85% or less, may be 80% or less, or may be 75% or less. The percentage ((Y2 / Y1)×100) may be 50% or more and 85% or less, may be 55% or more and 80% or less, or may be 60% or more and 75% or less.

[0049] The Young's modulus Y1 may be 170 GPa or more. Thereby, cemented carbide 3 can have better flaw resistance. The lower limit of the Young's modulus Y1 may be 170 GPa or more, may be 175 GPa or more, or may be 180 GPa or more. The upper limit of the Young's modulus Y1 may be 200 GPa or less, may be 195 GPa or less, or may be 193 GPa or less. The Young's modulus Y1 may be 170 GPa or more and 200 GPa or less, may be 175 GPa or more and 195 GPa or less, or may be 180 GPa or more and 193 GPa or less.

[0050] The Young's modulus Y2 may be 85 GPa or more. Thereby, cemented carbide 3 can have better flaw resistance. The lower limit of the Young's modulus Y2 may be 85 GPa or more, may be 90 GPa or more, or may be 95 GPa or more. The upper limit of the Young's modulus Y2 may be 140 GPa or less, may be 137 GPa or less, or may be 134 GPa or less. The Young's modulus Y2 may be 85 GPa or more and 140 GPa or less, may be 90 GPa or more and 137 GPa or less, or may be 95 GPa or more and 134 GPa or less.

[0051] The above Young's modulus Y1 GPa and the above Young's modulus Y2 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 target is each of a total of 10 arbitrary binder phases 2 exposed by polishing the surface of 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 Young's modulus of each of the total 10 binder phases 2 measured under the condition of 25°C is defined as the above Young's modulus Y1 GPa. Also, the average value of the Young's modulus of each of the total 10 binder phases 2 measured under the condition of 600°C is defined as the above Young's modulus Y2 GPa.

[0052] 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 Young's modulus of the binder phase 2 is performed multiple times by arbitrarily setting 10 binder phases 2, 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 one of "pure WC particles (WC containing no impurity elements at all, and WC with the content of impurity elements 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 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 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, cutting tips for drills with replaceable cutting edges, cutting tips for end mills with replaceable cutting edges, cutting tips for milling with replaceable cutting edges, cutting tips for turning with replaceable cutting edges, hacksaws, 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, carbide Tantalum(TaC) powder, titanium carbonitride (TiCN) powder, zirconium carbide (ZrC) powder, etc. can be prepared. These raw material powders can be commercially available ones. 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, in relation to making it easier to align the crystal orientation of the binder phase, it becomes easier for the cemented carbide to have a desired "percentage (Y2 / Y1)×100". 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.

[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. The mixing conditions can also use conventionally known 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 is easier to fill the mixed powder into a die or a mold during the subsequent forming step. For granulation, a known granulation method can be applied, and for example, a commercially available granulator such as a spray dryer can be used.

[0061] <Forming step> 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 1340 °C and held at 1340 °C for 2 hours.

[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 4 hours under the condition that the pressure is 10 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 2 °C / min. Thereby, 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 green compact to 1340°C and holding it at 1340°C for 2 hours. 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 hours. Further, the HIP process is carried out under the conditions that the pressure is 10 MPa and the time is 4 hours. Further, the second cooling process is carried out by setting the cooling rate up to 800°C to 2°C / min. By these processes, it is possible to manufacture a cemented carbide in which the percentage (Y2 / Y1)×100 of the Young's modulus Y2 GPa at 600°C with respect to the Young's modulus Y1 GPa at 25°C measured by the nanoindentation method of the binder phase is 50% 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 a newly found 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 of a method conforming to ISO14577, a measurement load of 0.5 mN, a loading time of 0.1 second, a load holding time of 0.1 second, and an unloading time of 0.1 second.

Examples

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

[0070] ≪Fabrication of Cemented Carbide≫ By carrying out the following steps in the following order, cemented carbides according to Samples 1 to 21 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), 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.

[0072] <Mixing step> 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 step> A round bar-shaped formed body was obtained by press-forming or extrusion-forming the mixed powder.

[0074] <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.

[0075] <First cooling step> 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 step" column, it means that the "First cooling step" was not performed.

[0076] <Heating step> A heating step 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 step" column, it means that the "Heating step" was not performed.

[0077] <HIP step> 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 related to Samples 1 to 21 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 description "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] <Young's modulus of the binder phase> For each cemented carbide sample, the Young's modulus Y1 of the binder phase was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Young's modulus Y1 of the binder phase [GPa]" in Tables 5 and 6. Also, for each cemented carbide sample, the Young's modulus Y2 of the binder phase was determined by the method described in Embodiment 1. The obtained results are recorded in the columns of "Young's modulus Y2 of the binder phase [GPa]" 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".

[0089] <Cobalt content in 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 cemented carbide> For each cemented carbide related to 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 5 and 6. In addition, for each cemented carbide related to 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 cemented carbide 3 exists only in the binder phase 2".

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

[0092] ≪Cutting test≫ First, by processing a round bar made of the cemented carbide related to each sample, an end mill with a cutting edge diameter of φ8 mm was produced as a cutting tool related to 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 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: "Waspalloy" (trademark) manufactured by Hanshin Metallix Co., Ltd. (difficult-to-machine material with high tensile strength) Cutting speed Vc: 60 m / min Feed per tooth Fz: 0.1 mm / t Axial depth of cut ap: 1 mm Radial depth of cut ae: 0.3 mm Cutting fluid: MQL (Minimum Quantity Lubrication) The above cutting conditions correspond to high-speed machining of difficult-to-machine materials with high tensile strength.

[0093] The cemented carbides according to Samples 1 to 21 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 21 can achieve a longer tool life even when used as a material for a cutting tool for high-speed machining of difficult-to-machine materials with high tensile strength, 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 21 can achieve a longer tool life even when used as a material for a cutting tool for high-speed machining of difficult-to-machine materials with high tensile strength.

[0095] 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 and to make various modifications.

[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 meanings equivalent to the claims and all modifications within the scope 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 (Y2 / Y1)×100 of the Young's modulus Y2 GPa at 600 °C to the Young's modulus Y1 GPa at 25 °C measured by the nanoindentation method of the binder phase is 50% or more. A cemented carbide.

2. The cemented carbide according to claim 1, wherein the percentage (Y2 / Y1)×100 is 70% or more.

3. The cemented carbide according to claim 1 or claim 2, wherein the Young's modulus Y1 is 170 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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