Cemented carbide

Abstract

Provided is a cemented carbide which comprises a plurality of tungsten carbide grains and a binder phase. The cemented carbide contains the tungsten carbide grains and the binder phase in a combined amount of 89% by volume or more. The cemented carbide contains the binder phase in an amount of 1.8% by volume to 20.0% by volume inclusive. The binder phase contains cobalt. The cemented carbide contains 1.0% by mass or more cobalt. The hardness of the binder phase at 25°C is 7.0 GPa or more as measured by a nanoindenter-based method.

Description

cemented carbide

[0001] The present disclosure relates to cemented carbide.

[0002] Conventionally, cemented carbide alloys comprising a plurality of tungsten carbide particles and a binder phase have been used as materials for cutting tools (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2004-131769

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

[0005] FIG. 1 is a diagram schematically illustrating a cross section of a cemented carbide according to an embodiment of the present disclosure.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, workpiece materials have become increasingly difficult to cut in cutting processes, and the conditions under which cutting tools are used have become more severe. For this reason, improvements in various properties are being sought for cemented carbide alloys used as base materials for cutting tools. In particular, cemented carbide alloys that enable tool life extension are being sought, even when used as materials for cutting tools for cutting high-hardness materials.

[0007] Therefore, an object of the present disclosure is to provide a cemented carbide that enables a longer tool life, especially when used as a material for cutting tools for cutting high-hardness materials.

[0008] [Advantages of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables a longer tool life, particularly when used as a material for cutting tools for cutting high-hardness materials.

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

[0010] According to the present disclosure, it is possible to provide a cemented carbide that enables a longer tool life, especially when used as a material for cutting tools for cutting high-hardness materials.

[0011] (2) In the above (1), the binder phase may further contain 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. This makes it possible to provide a cemented carbide that can further extend the tool life of a cutting tool, especially when cutting high-hardness materials.

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

[0013] [Details of the embodiment of the present disclosure] A specific example of a cutting tool according to one 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 symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been changed as appropriate for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

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

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

[0016] [Embodiment 1: Cemented Carbide] A cemented carbide according to one embodiment of the present disclosure will be described with reference to Figure 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, wherein the cemented carbide 3 contains a total of 89 volume % or more of the tungsten carbide particles 1 and the binder phase 2, the cemented carbide 3 contains 1.8 volume % or more and 20.0 volume % or less of the binder phase 2, the binder phase 2 contains cobalt, the cemented carbide 3 contains 1.0 mass % or more of cobalt, and the hardness of the binder phase 2 at 25°C measured by a nanoindenter method is 7.0 GPa or more.

[0017] According to the present disclosure, it is possible to provide a cemented carbide 3 that enables a longer tool life, especially when used as a material for cutting tools for cutting high-hardness materials. The reason for this is presumed to be as follows.

[0018] The cemented carbide 3 of this embodiment comprises 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 volume % or more. As a result, the cemented carbide 3 has high hardness and strength, and a cutting tool using the cemented carbide 3 can have excellent wear resistance and chipping resistance.

[0019] The cemented carbide 3 of the first embodiment contains 1.8 volume % or more and 20.0 volume % or less of the binder phase 2, and the binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0 mass % or more of cobalt. Furthermore, the hardness of the binder phase 2 at 25°C measured by the nanoindenter method is 7.0 GPa or more, and the binder phase 2 can have excellent hardness under conditions of 25°C (in other words, under room temperature conditions). As a result, the hardness of the cemented carbide 3 is improved, and a cutting tool using the cemented carbide 3 can have excellent wear resistance, especially when machining high-hardness materials.

[0020] <Composition of Cemented Carbide> The cemented carbide 3 contains tungsten carbide particles 1 and binder phase 2 in total at 89 vol% or more. This increases the hardness of the cemented carbide 3. The cemented carbide 3 may contain tungsten carbide particles 1 and binder phase 2 in total at 90 vol% or more, 91 vol% or more, or 92 vol% or more. In the cemented carbide 3, the upper limit of the total content of tungsten carbide particles 1 and binder phase 2 may be, for example, 100 vol% or less, 99 vol% or less, or 98 vol% or less. The cemented carbide 3 may contain tungsten carbide particles 1 and binder phase 2 in total at 90 vol% to 100 vol%, 91 vol% to 100 vol%, or 92 vol% to 100 vol%.

[0021] The cemented carbide 3 contains 1.8 vol% or more and 20.0 vol% or less of the binder phase 2. This allows the cemented carbide 3 to have increased hardness and toughness. The lower limit of the content of the binder phase 2 in the cemented carbide 3 may be 2.0 vol% or more, 3.0 vol% or more, or 4.0 vol% or more. The upper limit of the content of the binder phase 2 in the cemented carbide 3 may be 19.0 vol% or less, 18.0 vol% or less, or 17.0 vol% or less. The cemented carbide 3 may contain 2.0 vol% or more and 19.0 vol% or less of the binder phase 2, 3.0 vol% or more and 18.0 vol% or less of the binder phase 2, or 4.0 vol% or more and 17.0 vol% or less of the binder phase 2.

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

[0023] The cemented carbide 3 of the first embodiment can be composed of tungsten carbide particles 1, a binder phase 2, and other phases. The content of the other phases in the cemented carbide 3 is acceptable as long as it does not impair the effects of the present disclosure. For example, the content of the other phases in the cemented carbide 3 may be more than 0 vol% and less than 20 vol%, more than 0 vol% and less than 18 vol%, or more than 0 vol% and less than 16 vol%. In this case, the total content of the tungsten carbide particles 1 and the binder phase 2 in the cemented carbide 3 may be 80 vol% or more and less than 100 vol%, 82 vol% or more and less than 100 vol%, or 84 vol% or more and less than 100 vol%.

[0024] The cemented carbide 3 of the first embodiment may contain impurities. Examples of such impurities include iron (Fe), calcium (Ca), oxygen (O), and sulfur (S). The impurity content of the cemented carbide 3 is acceptable as long as it does not impair the effects of the present disclosure. For example, the impurity content of the cemented carbide 3 may be 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide 3 is measured by ICP optical emission spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0025] The content [vol %] of the tungsten carbide particles 1 in the cemented carbide 3 and the content [vol %] of the binder phase 2 in the cemented carbide 3 were measured as follows.

[0026] (A1) An arbitrary position of the cemented carbide 3 is cut out to expose a cross section, which is then mirror-polished using a cross-section polisher (manufactured by JEOL Ltd.).

[0027] (B1) The mirror-finished surface of the cemented carbide 3 is analyzed by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) (apparatus: Carl Zeiss "Gemini 450" (trademark)) to identify the elements contained in the cemented carbide 3.

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

[0029] (D1) The photographed region of (C1) above is analyzed using an energy dispersive X-ray analyzer (SEM-EDX) attached to an SEM, the distribution of the elements identified in (B1) above in the photographed region is identified, and an element mapping image is obtained.

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

[0031] (F1) By superimposing the element mapping image obtained in (D1) above on the binarized image obtained in (E1) above, the regions where tungsten carbide particles 1 and binder phase 2 are present are identified on the binarized image. Specifically, the regions shown in white in the binarized image and where tungsten (W) and carbon (C) are present in the element mapping image correspond to the regions where tungsten carbide particles 1 are present. The regions shown in gray to black in the binarized image and where cobalt (Co) is present in the element mapping image correspond to the regions where binder phase 2 is present.

[0032] (G1) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the image after the binarization process. Using the image analysis software, the area percentages of the tungsten carbide particles 1 and the binder phase 2 are measured, with the area of ​​the entire measurement field being used as the denominator.

[0033] (H1) The measurement of (G1) above is carried out 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 [volume %] of tungsten carbide particles 1 in cemented carbide 2, and the average of the area percentages of binder phase 2 in the five measurement fields corresponds to the content [volume %] of binder phase 2 in cemented carbide 3.

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

[0035] As far as the applicant has measured, it has been confirmed that, as long as measurements are made on the same sample, even if the cut-out location of the cross section of the cemented carbide 3 is arbitrarily set, the photographing area described in (C1) above is arbitrarily set on the cross section, and the content of the tungsten carbide particles 1 and the content of the binder phase 2 of the cemented carbide 3 are measured multiple times according to the above procedure, there is little variation in the measurement results and they are not arbitrary.

[0036] <Binder Phase> The binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0 mass% or more of cobalt. This allows the cemented carbide 3 to have excellent toughness. The binder phase 2 may contain 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more of cobalt. The binder phase 2 may consist of cobalt. Alternatively, the binder phase 2 may consist of cobalt and a first element described below. Alternatively, the cobalt in the cemented carbide 3 may be present only in the binder phase 2. The lower limit of the cobalt content 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 cobalt content 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% to 20 mass% of cobalt, 2.0 mass% to 15 mass% of cobalt, or 3.0 mass% to 12 mass% of cobalt.

[0037] The method for measuring the cobalt content in the cemented carbide 3 is as follows. First, a photographed region is set using the same method as in (A1) to (C1) of the method for measuring the content of tungsten carbide particles 1 and the content of binder phase 2 in the cemented carbide 3 described above. Next, the photographed region is analyzed using SEM-EDX to identify the distribution of the elements identified in (B1) above in the photographed region, and an element mapping image is obtained, while simultaneously identifying the cobalt content in the cemented carbide 3. The method for measuring the "cobalt content in binder phase 2" is as follows. First, a region where binder phase 2 exists is identified on the image after binarization processing using the same method as in (A1) to (F1) of the method for measuring the content of tungsten carbide particles 1 and the content of binder phase 2 in the cemented carbide 3 described above. Next, the region where binder phase 2 exists is analyzed using SEM-EDX to measure the "cobalt content in binder phase 2." The method for identifying that "cobalt in cemented carbide 3 is present only in binder phase 2" is as follows. First, using the same methods as (A1) to (F1) of the method for measuring the content of tungsten carbide particles 1 and the content of binder phase 2 in cemented carbide 3 described above, the regions where tungsten carbide particles 1 and the binder phase 2 are present are identified on the image after binarization processing. Next, based on the element mapping image and the regions where tungsten carbide particles 1 and the binder phase 2 are present, it is identified that "cobalt in cemented carbide 3 is present only in binder phase 2."

[0038] As far as the applicant has measured, it has been confirmed that, as long as measurements are taken on the same sample, even if the cut-out location of the cross section of the cemented carbide 3 and the photographing area described in (C1) above are arbitrarily set and the above measurements are taken multiple times according to the above procedure, there is little variation in the measurement results and they are not arbitrary.

[0039] The binder phase 2 may further contain a first element, which may be at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, thereby providing a cemented carbide 3 that can further extend the tool life of a cutting tool, especially when cutting high-hardness materials.

[0040] The content of the first element in the cemented carbide 3 may be 0.01% by mass or more and 1.0% by mass or less. This allows the binder phase 2 to have both superior hardness and superior toughness. The content of the first element in the binder 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 binder 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 mass % or more and 0.8 mass % or less, or 0.1 mass % or more and 0.6 mass % or less.

[0041] The method for measuring the content of the first element in the cemented carbide 3 is as follows. Except for the point where "cobalt" is read as "first element", the method is the same as the method for measuring the content of cobalt in the cemented carbide 3. The method for measuring the "content of the first element in the binder phase 2" is as follows. Except for the point where "Next, ... measure the 'cobalt' content in the binder phase 2." is read as "Next, ... measure the 'first element' content in the binder phase 2."", the method for specifying that "the first element in the cemented carbide 3 is present only in the binder phase 2" is as follows. "Next, ... specify that 'cobalt' in the cemented carbide 3 is present only in the binder phase 2." specifies that "the 'first element' in the cemented carbide 3 is present only in the binder phase 2." " is read as " the cobalt in the cemented carbide 3 is present only in the binder phase 2 ", except that " the cobalt in the cemented carbide 3 is present only in the binder phase 2 " is read as " the cobalt in the cemented carbide 3 is present only in the binder phase 2 ".

[0042] As far as the applicant has measured, it has been confirmed that, as long as measurements are taken on the same sample, even if the cut-out location of the cross section of the cemented carbide 3 and the photographing area described in (C1) above are arbitrarily set and the above measurements are taken multiple times according to the above procedure, there is little variation in the measurement results and they are not arbitrary.

[0043] In the binder phase 2, the percentage {M1 / (M1+M2)}×100 of the mass M1 of the first element relative to the total mass M1+M2 of the mass M1 of the first element and the mass M2 of cobalt may be 1% or more and 6% or less. This allows the binder phase 2 to have both superior hardness and superior toughness, thereby providing a cemented carbide 3 that can further extend the tool life of a cutting tool, particularly when cutting high-hardness materials. Here, when the binder phase contains two or more types of first elements, the mass M1 of the first element refers to 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 may be 3% or more and 4% or less.

[0044] The method for measuring the percentage {M1 / (M1+M2)}×100 is as follows. The region where the binder phase 2 exists is identified on the image after binarization processing using the same methods as (A1) to (F1) of the method for measuring the content of the tungsten carbide particles 1 and the content of the binder phase 2 in the cemented carbide 3. The region where the binder phase 2 exists is analyzed using SEM-EDX to measure the cobalt content and the first element content in the binder phase 2, and the percentage {M1 / (M1+M2)}×100 is calculated based on these. The above measurement is performed in five different, non-overlapping measurement fields. 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 binder phase 2.

[0045] As far as the applicant has measured, it has been confirmed that, as long as measurements are made on the same sample, even if the cut-out location of the cross section of the cemented carbide 3 and the photographing area described in (C1) above are arbitrarily set and the percentage {M1 / (M1+M2)}×100 is measured multiple times according to the above procedure, the measurement results have little variation and are not arbitrary.

[0046] <Hardness of Binder Phase> The hardness of the binder phase 2 at 25°C measured by the nanoindenter method is 7.0 GPa or more. This allows the binder phase 2 to have excellent hardness under conditions at 25°C (in other words, under room temperature conditions). The lower limit of the hardness may be 7.1 GPa or more, 7.2 GPa or more, or 7.4 GPa or more. The upper limit of the hardness may be 9 GPa or less, 8.5 GPa or less, or 8 GPa or less. The hardness may be 7.0 GPa or more and 9 GPa or less, 7.1 GPa or more and 8.5 GPa or less, or 7.2 GPa or more and 8 GPa or less.

[0047] The hardness of the binder phase 2 at 25°C measured by the nanoindenter method is measured by the nanoindenter method (Bruker's "Hysitron TI 980 Triboindenter"). The nanoindenter method is performed in accordance with ISO 14577 under the following conditions: a measurement load of 0.5 mN, a loading time of 0.1 seconds, a load holding time of 0.1 seconds, and an unloading time of 0.1 seconds. The measurement targets are any 10 binder phases 2 exposed by polishing the surface of the cemented carbide 3 using a cross-section polisher (CP) processing device (JEOL Ltd.'s "IB-19500CP Cross-Section Sample Preparation Device" (trademark)). The average hardness of the 10 binder phases 2 is defined as the "hardness of binder phase 2."

[0048] As far as the applicant has measured, it has been confirmed that, as long as measurements are made on the same sample, even if ten binder phases 2 are arbitrarily set and the hardness of the binder phases 2 is measured multiple times, the measurement results vary little and are not arbitrary.

[0049] <Tungsten Carbide Particles> In the first embodiment, the tungsten carbide particles 1 include at least one of "pure WC particles (including WC containing no impurity elements and WC containing impurity elements below the detection limit)" and "WC particles containing impurity elements intentionally or unavoidably contained therein, as long as the effects of the present disclosure are not impaired." The impurity content of the tungsten carbide particles (when two or more elements constitute the impurities, the total content of these elements) is less than 0.1% by mass. The impurity element content of the tungsten carbide particles is measured by ICP optical emission spectroscopy (Inductively Coupled Plasma Emission Spectroscopy, measuring device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0050] In the first embodiment, 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 the first embodiment can have a long tool life regardless of the average particle size of the tungsten carbide particles 1.

[0051] <<Uses of Cemented Carbide>> The cemented carbide 3 of this embodiment can be used in cutting tools. Examples of such cutting tools include cutting tools for general-purpose machining. More specifically, examples of such cutting tools include drills, end mills, indexable cutting tips for drills, indexable cutting tips for end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, and taps.

[0052] [Embodiment 2: Manufacturing method of cemented carbide] The cemented carbide of this embodiment can be manufactured by carrying out a raw material powder preparation step, a mixing step, a molding step, a sintering step, a cooling step, and a HIP (hot isostatic pressing) step in the above order. Each step will be described below.

[0053] <Preparation Step> The preparation step is a step of preparing raw material powders of materials constituting the cemented carbide. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder") and cobalt (Co) powder. In addition to these raw material powders, first element powder, niobium carbide (NbC) powder, tungsten carbide (TaC) powder, titanium carbonitride (TiCN) powder, and zirconium carbide (ZrC) powder can also be prepared. These raw material powders can be commercially available. 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 refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size is measured using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0054] <Mixing Process> The mixing process is a process of mixing the raw material powders prepared in the preparation process in a predetermined ratio. The mixing process results in a mixed powder obtained by mixing the raw material powders. The mixing ratio of the raw material powders is appropriately adjusted depending on the target composition of the cemented carbide. A first element powder may be used as the raw material powder. This allows the first element to be sufficiently dissolved in the binder phase, making it easier to provide the cemented carbide with the desired "hardness at 25°C as measured by the nanoindenter method of the binder phase." In order to keep the total content of the tungsten carbide particles and the binder phase within the desired range, the total content of powders other than the WC powder, Co powder, and the first element powder in the mixed powder may be less than 5% by mass. By appropriately adjusting the amount of each raw material powder charged, the binder phase content and the WC particle content can each be kept within the desired range.

[0055] The raw material powders can be mixed using a conventionally known mixing method such as an attritor, a ball mill, or a bead mill. Conventional known mixing conditions can also be used. The mixing time can be, for example, from 2 hours to 20 hours.

[0056] After the mixing step, the mixed powder may be granulated as necessary. Granulating the mixed powder makes it easier to fill the mixed powder into a die or mold during the molding step described below. A known granulation method can be applied to the granulation, and for example, a commercially available granulator such as a spray dryer can be used.

[0057] <Molding step> The molding step is a step of molding the mixed powder obtained in the mixing step into a shape for a cutting tool to obtain a molded body. The molding method and molding conditions in the molding step are not particularly limited and may be general methods and conditions.

[0058] <Sintering Step> The sintering step is a step of sintering the compact obtained in the compacting step to obtain a cemented carbide intermediate. The sintering conditions in this embodiment are as follows: The compact is heated to 1360°C and held at 1360°C for 1 hour.

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

[0060] <HIP step> The HIP step is a step of performing HIP treatment on the cemented carbide intermediate body after the cooling step. The conditions of the HIP step in this embodiment are as follows: The cemented carbide intermediate body is held under a pressure of 100 MPa for 2 hours. This allows the cemented carbide of embodiment 1 to be obtained.

[0061] <Features of the Manufacturing Method of the Cemented Carbide of the Present Embodiment> In the present embodiment, the sintering step is performed by heating the compact to 1360°C and holding it at 1360°C for 1 hour. Furthermore, the cooling step is performed by cooling to 800°C at a rate of 20°C / min. Furthermore, the HIP step is performed under conditions of a pressure of 100 MPa and a time of 2 hours. These steps make it possible to manufacture a cemented carbide whose binder phase has a hardness of 7.0 GPa or more at 25°C as measured by the nanoindenter method. The fact that the cemented carbide of the present disclosure can be realized by such sintering conditions, cooling step, and HIP step is a new discovery made by the present inventors after extensive research.

[0062] [Supplementary Note 1] In the cemented carbide of embodiment 1, the nanoindenter method can be performed in accordance with ISO 14577 under the following conditions: a measurement load of 0.5 mN, a loading time of 0.1 seconds, a load holding time of 0.1 seconds, and an unloading time of 0.1 seconds.

[0063] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0064] <<Preparation of Cemented Carbide>> Cemented carbide samples 1 to 19 and 101 to 114 were prepared as follows.

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

[0066] <Mixing Step> The raw material powders were mixed in the proportions shown in Tables 1 and 2 for 10 hours using an attritor to obtain mixed powders.

[0067] <Molding Step> The mixed powder was press-molded or extrusion-molded to obtain a round bar-shaped molded body.

[0068] <Sintering Step> The compact was heated to a temperature shown in Tables 1 and 2 and held at that temperature for a holding time shown in Tables 1 and 2 to obtain a cemented carbide intermediate.

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

[0070] <HIP Step> The cemented carbide intermediate body after the cooling step was subjected to HIP treatment under the conditions shown in Tables 1 and 2 to obtain a cemented carbide.

[0071] By the above procedure, cemented carbide samples 1 to 19 and 101 to 114 were produced.

[0072]

[0073]

[0074]

[0075]

[0076] <Characteristic Evaluation of Cemented Carbide Alloys> <Content of Tungsten Carbide Particles> The content of tungsten carbide particles for each cemented carbide alloy sample was determined by the method described in embodiment 1. The results obtained are shown in the "Content of WC Particles [Volume %]" column of Tables 3 and 4. Note that the notation "balance" in the "Content of WC Particles [Volume %]" column of Tables 3 and 4 means that the content of tungsten carbide particles is equal to the value obtained by subtracting the value listed in the "Content of Binder Phase [Volume %]" column of Tables 3 and 4 from the value listed in the "Total [Volume %]" column of Tables 3 and 4.

[0077] <Binder Phase Content> The binder phase content of each cemented carbide sample was determined by the method described in Embodiment 1. The results obtained are shown in the column "Binder Phase Content [vol %]" in Tables 3 and 4.

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

[0079] <Cobalt Content in Cemented Carbide> For the cemented carbide according to each sample, the cobalt content in the cemented carbide was determined by the method described in embodiment 1. The results obtained are shown in the column "Co content [mass%]" in Tables 3 and 4. Note that for the cemented carbide according to each sample, it was confirmed by the method described in embodiment 1 that "cobalt in cemented carbide 3 is present only in binder phase 2."

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

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

[0082] <Cutting Test> First, three end mills (GSXB20000 type) with a cutting diameter of 6 mm were fabricated as cutting tools for each sample by machining round bars made of cemented carbide alloy for each sample. Next, cutting was performed using the end mills of each sample under the following cutting conditions, and the cutting distance until the end mills were worn down to 0.05 mm was measured. For each sample, the cutting length was obtained by calculating the average cutting distance of each of the three end mills. The results are shown in the "Cutting Length [m]" column of Tables 3 and 4, respectively. Note that a longer cutting length indicates a longer tool life. <Cutting Conditions> Workpiece: SKD51 (high-hardness material); Cutting Speed ​​Vc: 180 m / min; Feed per Tooth Fz: 0.15 mm / t; Depth of Cut Ap: 0.5 mm; Cutting Fluid: Yes (Wet). The above cutting conditions correspond to cutting of high-hardness material.

[0083] The cemented carbide alloys of Samples 1 to 19 correspond to Examples. The cemented carbide alloys of Samples 101 to 114 correspond to Comparative Examples. The results in Tables 3 and 4 show that the cemented carbide alloys of Samples 1 to 19 enable longer tool life than the cemented carbide alloys of Samples 101 to 114, even when used as materials for cutting tools for cutting high-hardness materials.

[0084] From the above, it was found that the cemented carbide according to Samples 1 to 19 can extend the life of cutting tools even when used as materials for cutting high-hardness materials.

[0085] Although the embodiments and examples of the present disclosure have been described above, it is originally intended that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0086] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0087] 1 Tungsten carbide particles, 2 Binder phase, 3 Cemented carbide

Claims

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

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

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

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