Cemented carbide

Abstract

This cemented carbide comprises a plurality of tungsten carbide particles and a binder phase. The cemented carbide includes 89% by volume or more of the tungsten carbide particles and the binder phase in total; the cemented carbide includes 1.8%-20.0% by volume of the binder phase; the binder phase includes cobalt; the cemented carbide includes 1.0% by mass or more of cobalt; and the percentage (Y2 / Y1) × 100 of the Young's modulus Y2 GPa of the binder phase at 600°C with respect to the Young's modulus Y1 GPa of the binder phase at 25°C measured by a nanoindenter method is 50% or more.

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 percentage (Y2 / Y1) x 100 of the Young's modulus Y2GPa at 600°C to the Young's modulus Y1GPa at 25°C measured by a nanoindenter method of the binder phase is 50% 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 the substrate of cutting tools. In particular, cemented carbide alloys that enable tool life extension are being sought, even when used as materials for cutting tools for high-speed machining of difficult-to-cut materials with high tensile strength.

[0007] Therefore, an object of the present disclosure is to provide a cemented carbide that enables a longer tool life, even when used as a material for cutting tools for high-speed machining of difficult-to-cut materials, particularly those with high tensile strength.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables a longer tool life, even when used as a material for cutting tools for high-speed machining of difficult-to-cut materials, particularly those with high tensile strength.

[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 percentage (Y2 / Y1) x 100 of the Young's modulus Y2GPa at 600°C relative to the Young's modulus Y1GPa at 25°C measured by a nanoindenter 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 a longer tool life, even when used as a material for cutting tools for high-speed machining of difficult-to-cut materials, particularly those with high tensile strength.

[0011] (2) In the above (1), the percentage (Y2 / Y1) x 100 may be 70% or more, thereby providing a cemented carbide that can further extend the tool life of cutting tools, especially in high-speed machining of difficult-to-cut materials with high tensile strength.

[0012] (3) In the above (1) or (2), the Young's modulus Y1 may be 170 GPa or more, thereby providing a cemented carbide that can further extend the tool life of cutting tools, especially in high-speed machining of difficult-to-cut materials with high tensile strength.

[0013] (4) In any one of (1) to (3) above, 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 cutting tools, especially in high-speed machining of difficult-to-cut materials with high tensile strength.

[0014] (5) In the above (4), 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 in high-speed machining of difficult-to-cut materials with high tensile strength.

[0015] [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.

[0016] 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.

[0017] 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.

[0018] [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 percentage (Y2 / Y1) x 100 of the Young's modulus Y2GPa at 600°C relative to the Young's modulus Y1GPa at 25°C measured by a nanoindenter 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 a longer tool life, even when used as a material for cutting tools for high-speed machining of difficult-to-cut materials, particularly those with high tensile strength. The reason for this is presumed to be as follows.

[0020] 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.

[0021] The cemented carbide 3 of the first embodiment contains 1.8 to 20.0 volume % of 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 percentage (Y2 / Y1) × 100 of the Young's modulus Y2GPa at 600°C relative to the Young's modulus Y1GPa at 25°C of the binder phase 2 measured by the nanoindenter method is 50% or more, and the "decrease in Young's modulus of the cemented carbide 3" caused by the change from 25°C (i.e., room temperature) to 600°C (i.e., high-temperature) can be suppressed. As a result, the "decrease in Young's modulus of the cemented carbide 3" is suppressed, and a cutting tool using the cemented carbide 3 can have excellent chipping resistance, especially in high-speed machining of difficult-to-cut materials with high tensile strength.

[0022] <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%.

[0023] 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 an increased Young's modulus 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.

[0024] 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.

[0025] 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%.

[0026] 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)).

[0027] 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.

[0028] (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.).

[0029] (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.

[0030] (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.

[0031] (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.

[0032] (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.

[0033] (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.

[0034] (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.

[0035] (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.

[0036] 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 %).

[0037] 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.

[0038] <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.

[0039] 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."

[0040] 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.

[0041] 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 cutting tools, especially in high-speed machining of difficult-to-cut materials with 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. This allows the binder phase 2 to have both a superior Young's modulus 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.

[0043] 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 ".

[0044] 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.

[0045] 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 a superior Young's modulus and superior toughness, thereby providing a cemented carbide 3 that can further extend the tool life of cutting tools, especially in high-speed machining of difficult-to-cut materials with high tensile strength. 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.

[0046] 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.

[0047] 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.

[0048] <Young's Modulus of Binder Phase> The percentage (Y2 / Y1) × 100 of the Young's modulus Y2GPa at 600°C relative to the Young's modulus Y1GPa at 25°C of the binder phase 2 measured by the nanoindenter method is 50% or more. This makes it possible to suppress the "decrease in the Young's modulus of the cemented carbide 3" that occurs when the temperature changes from 25°C (i.e., room temperature) to 600°C (i.e., high temperature). The lower limit of the percentage (Y2 / Y1) × 100 may be 55% or more, 60% or more, or 70% or more. The upper limit of the percentage (Y2 / Y1) × 100 may be 85% or less, 80% or less, or 75% or less. The percentage (Y2 / Y1) x 100 may be 50% or more and 85% or less, 55% or more and 80% or less, or 60% or more and 75% or less.

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

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

[0051] The Young's modulus Y1GPa and the Young's modulus Y2GPa are measured by a nanoindenter method (using a Hysitron TI 980 Triboindenter manufactured by Bruker). 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 (an IB-19500CP cross-section specimen preparation device (trademark) manufactured by JEOL Ltd.). The Young's modulus Y1GPa is the average value of the Young's modulus of the 10 binder phases 2 measured under conditions of 25°C. The average value of the Young's modulus of each of the ten binder phases 2 measured under the condition of 600° C. is defined as the Young's modulus Y2GPa.

[0052] As far as the applicant has measured, it has been confirmed that, as long as measurements are made on the same sample, even if 10 binder phases 2 are arbitrarily set and the Young's modulus of the binder phase 2 is measured multiple times, the measurement results vary little and are not arbitrary.

[0053] <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).

[0054] 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.

[0055] <<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.

[0056] [Embodiment 2: Manufacturing method of cemented carbide] The cemented carbide of this embodiment can be manufactured by carrying out the steps of preparing raw material powder, mixing, molding, sintering, first cooling, heating, HIP (hot isostatic pressing), and second cooling in the above order. Each step will be described below.

[0057] <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.

[0058] <Mixing Process> The mixing process is a process of mixing the raw material powders prepared in the preparation process in a predetermined ratio. A mixed powder is obtained by mixing the raw material powders. The mixing ratio of the raw material powders is adjusted appropriately depending on the target composition of the cemented carbide. A first element powder may be used as the raw material powder. This makes it easier to align the crystal orientation of the binder phase, making it easier to provide the cemented carbide with the desired "percentage (Y2 / Y1) x 100". By appropriately adjusting the amount of each raw material powder charged, the binder phase content and the WC particle content can each be set within the desired range.

[0059] 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.

[0060] 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.

[0061] <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.

[0062] <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 1340°C and held at 1340°C for 2 hours.

[0063] <First Cooling Step> The first cooling step is a step 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 may be, for example, 20° C. / min.

[0064] <Heating Step> The heating step is a step of heating the cemented carbide intermediate. More specifically, the heating temperature is 1200°C, and the temperature is maintained for 0.25 hours.

[0065] <HIP Step> The HIP step is a step of performing HIP treatment on a cemented carbide intermediate. The conditions for the HIP step in this embodiment are as follows: The cemented carbide intermediate is held under a pressure of 10 MPa for 4 hours.

[0066] <Second Cooling Step> The second cooling step is a step of cooling the cemented carbide intermediate. More specifically, the cemented carbide intermediate is cooled to 800°C. The cooling rate is 2°C / min. In this way, the cemented carbide of the first embodiment can be obtained.

[0067] <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 1340°C and holding it at 1340°C for 2 hours. Furthermore, the first cooling step is performed by cooling the cemented carbide intermediate to 1000°C. Furthermore, the heating step is performed under conditions of a temperature of 1200°C and a holding time of 0.25 hours. Furthermore, the HIP step is performed under conditions of a pressure of 10 MPa and a time of 4 hours. Furthermore, the second cooling step is performed by setting the cooling rate to 800°C at 2°C / min. These steps can produce a cemented carbide in which the percentage (Y2 / Y1) x 100 of the Young's modulus Y2GPa at 600°C to the Young's modulus Y1GPa at 25°C of the binder phase measured by the nanoindenter method is 50% or more. The inventors have newly discovered, as a result of extensive research, that the cemented carbide of the present disclosure can be realized by such sintering conditions, first cooling step, heating step, HIP step, and second cooling step.

[0068] [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.

[0069] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0070] <<Preparation of Cemented Carbide>> The cemented carbide samples 1 to 21 and 101 to 114 were prepared by carrying out the following steps in the following order.

[0071] <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.

[0072] <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.

[0073] <Molding Step> The mixed powder was press-molded or extrusion-molded to obtain a round bar-shaped molded body.

[0074] <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.

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

[0076] <Heating Step> The cemented carbide intermediate was subjected to a heating step under the conditions shown in Tables 3 and 4. In the "Heating Step" column, "Temperature [°C]" and "Retention Time [hours]" contain "-" which means that the "heating step" was not performed.

[0077] <HIP Step> The cemented carbide intermediate was subjected to HIP treatment under the conditions shown in Tables 3 and 4.

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

[0079] By the above procedure, cemented carbide samples 1 to 21 and 101 to 114 were produced.

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] <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 5 and 6. Note that the notation "balance" in the "Content of WC Particles [Volume %]" column of Tables 5 and 6 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 5 and 6 from the value listed in the "Total [Volume %]" column of Tables 5 and 6.

[0087] <Binder Phase Content> For each cemented carbide sample, the binder phase content was determined by the method described in Embodiment 1. The results obtained are shown in the column "Binder Phase Content [vol %]" in Tables 5 and 6.

[0088] <Young's modulus of binder phase> For the cemented carbide of each sample, the Young's modulus Y1 of the binder phase was determined by the method described in embodiment 1. The results obtained are shown in the column "Young's modulus Y1 [GPa] of binder phase" in Tables 5 and 6. Furthermore, for the cemented carbide of each sample, the Young's modulus Y2 of the binder phase was determined by the method described in embodiment 1. The results obtained are shown in the column "Young's modulus Y2 [GPa] of binder phase" in Tables 5 and 6. Note that for the cemented carbide of 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."

[0089] <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 5 and 6. 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."

[0090] <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 5 and 6. 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."

[0091] <{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 5 and 6.

[0092] <Cutting Test> First, a round bar made of cemented carbide alloy for each sample was machined to produce an end mill with a cutting diameter of 8 mm as a cutting tool for each sample. Next, cutting was performed using the end mill for each sample under the following cutting conditions, and the cutting length until chipping occurred in the end mill was measured. The results are shown in the "Cutting Length [m]" column of Tables 5 and 6. Note that a longer cutting length indicates a longer tool life. <Cutting Conditions> Workpiece: "Waspaloy" (trademark) manufactured by Hanshin Metallics Co., Ltd. (high tensile strength, difficult-to-cut material) Cutting speed Vc: 60 m / min Feed per tooth Fz: 0.1 mm / t Axial cutting depth ap: 1 mm Radial cutting depth ae: 0.3 mm Cutting fluid: MQL (Minimum Quantity Lubrication) The above cutting conditions correspond to high-speed machining of high tensile strength, difficult-to-cut materials.

[0093] The cemented carbide alloys according to Samples 1 to 21 correspond to Examples. The cemented carbide alloys according to Samples 101 to 114 correspond to Comparative Examples. The results in Tables 5 and 6 show that the cemented carbide alloys according to Samples 1 to 21 enable longer tool life than the cemented carbide alloys according to Samples 101 to 114, even when used as materials for cutting tools for high-speed machining of difficult-to-cut materials with high tensile strength.

[0094] From the above, it was found that the cemented carbide alloys of Samples 1 to 21 enable the tool to have a long life even when used as materials for cutting tools for high-speed machining of difficult-to-cut materials with high tensile strength.

[0095] 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.

[0096] 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.

[0097] 1 Tungsten carbide particles, 2 Binder phase, 3 Cemented carbide

Claims

1. A cemented carbide alloy comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide alloy contains a total of 89 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide alloy contains 1.8 volume % or more and 20.0 volume % or less of the binder phase, the binder phase contains cobalt, the cemented carbide alloy contains 1.0 mass % or more of cobalt, and the percentage (Y2 / Y1) x 100 of the Young's modulus Y2GPa at 600°C to the Young's modulus Y1GPa at 25°C measured by a nanoindenter method of the binder phase is 50% or more.

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

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

4. The cemented carbide according to any one of claims 1 to 3, wherein the binder phase further contains a first element, and 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. The cemented carbide according to claim 4, 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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