Cemented carbide and cutting tool

Abstract

Provided is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, the cemented carbide containing the tungsten carbide particles and the binder phase in a total amount of 89-100 vol%, and the binder phase in an amount of 0.5-25 vol%, wherein: the binder phase contains cobalt in an amount of 40 mass% or greater, and further contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum; and in a rectangular measurement region, which is provided in a TEM-HAADF image obtained by observing a (110) plane of the cobalt having an fcc structure by a magnification of 5 million times using an atomic resolution transmission electron microscope, and in which 31 cobalt atoms are contained in a first direction and 5 to 10 cobalt atoms are contained in a second direction orthogonal to the first direction, a frequency of mismatch of an atomic array of the cobalt atoms is from 8% to 30.0%.

Description

Cemented Carbide and Cutting Tools

[0001] The present disclosure relates to cemented carbides and cutting tools.

[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 the tungsten carbide particles and the binder phase in a total amount of 89 volume % or more and 100 volume % or less, the cemented carbide contains the binder phase in an amount of 0.5 volume % or more and 25 volume % or less, the binder phase contains 40 mass % or more of cobalt, and the binder phase further contains silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and / or platinum. The cemented carbide contains at least one first element selected from the group consisting of: (a) a first element selected from the group consisting of (b) a first element selected from the group consisting of (c) a first element selected from the group consisting of (d) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (e) a first element selected from the group consisting of (f) a first element selected from the group consisting of (f) a first element selected from the group consisting of (f) a second element selected from the group consisting of (e) a second element selected from the group consisting of (e) a second element selected from the group consisting of (e) a first element selected from the group consisting of (f ... first element selected from the group consisting of (f) a second element selected from the group consisting of

[0005] Fig. 1 is an example of an IPF map of the cemented carbide of embodiment 1. Fig. 2 is an example of a TEM-HAADF image of the cemented carbide of embodiment 1. Fig. 3 is an example showing an extracted measurement region set in the TEM-HAADF image of Fig. 2. Fig. 4 is a schematic diagram of a cutting tool of embodiment 2.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, technologies for improving the heat resistance of printed circuit boards have been developed to accommodate the increasing volume of information. However, this has made printed circuit boards increasingly difficult to cut. As a result, cutting tools tend to break easily when processing printed circuit boards.

[0007] Therefore, an object of the present disclosure is to provide a cemented carbide alloy that enables a longer life of cutting tools, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, and a cutting tool including the same.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables a longer life of a cutting tool, particularly when used as a material for the cutting tool for drilling holes in printed circuit boards, and a cutting tool including the same.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (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 the tungsten carbide particles and the binder phase in a total amount of 89% by volume or more and 100% by volume or less, the cemented carbide contains the binder phase in an amount of 0.5% by volume or more and 25% by volume or less, the binder phase contains 40% by mass or more of cobalt, and the binder phase further contains silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. The cemented carbide contains at least one first element selected from the group consisting of: wherein the (110) plane of the cobalt having an fcc structure is observed at 5 million magnifications using an atomic resolution transmission electron microscope, and in a rectangular measurement region provided in the TEM-HAADF image, the region contains 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction, the frequency of mismatch in the atomic arrangement of the cobalt atoms is 8% to 30.0%.

[0010] According to the present disclosure, it is possible to provide a cemented carbide that enables a longer life of cutting tools, particularly when used as a material for cutting tools for drilling holes in printed circuit boards. The reason for this is presumed to be as follows.

[0011] The cemented carbide of the present disclosure comprises a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles") and a binder phase. The total content of the WC particles and binder phase in the cemented carbide is 89 volume % or more and 100 volume % or less. This allows the cemented carbide to have high hardness and strength, and cutting tools including the cemented carbide to have excellent wear resistance and breakage resistance.

[0012] The cemented carbide of the present disclosure contains a binder phase of 0.5% by volume or more and 25% by volume or less. The binder phase contains 40% by mass or more of cobalt. When the binder phase content of the cemented carbide is 0.5% by volume or more, the toughness of the cemented carbide is improved. When the binder phase content of the cemented carbide is 25% by volume or less, the hardness of the cemented carbide is improved. Therefore, a cutting tool including the cemented carbide can have excellent wear resistance and breakage resistance.

[0013] In the cemented carbide of the present disclosure, the binder phase further contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. This improves the strength of the binder phase itself, the interface strength between tungsten carbide particles, and the interface strength between the tungsten carbide particles and the binder phase. Therefore, in a cutting tool including this cemented carbide, wear of the binder phase and shedding of tungsten carbide particles are suppressed during cutting, and the cutting tool can have a long tool life.

[0014] In the cemented carbide disclosed herein, in a TEM-HAADF image obtained by observing the (110) plane of cobalt having an FCC structure in the binder phase at 5 million times magnification using an atomic resolution transmission electron microscope, the frequency of mismatch in the atomic arrangement of cobalt atoms in a rectangular measurement region containing 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction is 8% to 30.0%. When the frequency of mismatch in the atomic arrangement of cobalt atoms is 8% or more, dislocation propagation is likely to be inhibited at the locations where the atomic arrangement of cobalt atoms is mismatched, improving the toughness and fatigue strength of the cemented carbide. When the frequency of mismatch in the atomic arrangement of cobalt atoms is 30% or less, the strength of the cemented carbide can be maintained. Therefore, cutting tools including this cemented carbide have improved fatigue breakage resistance during cutting while maintaining their strength, thereby improving tool life. Here, fatigue breakage refers to breakage that occurs after a certain amount of processing time has elapsed since the cutting tool began to be used.

[0015] (2) In the above (1), the frequency of mismatch in the atomic arrangement of the cobalt atoms may be 10% or more, thereby further improving the fatigue breakage resistance during cutting of a cutting tool including the cemented carbide, and further improving the tool life.

[0016] (3) In the above (1) or (2), the percentage of the mass M1 of the first element relative to the total mass M1+M2 of the first element and the cobalt, {M1 / (M1+M2)}×100, may be 0.2% or more and 25% or less. Here, the units of mass M1 and mass M2 are the same. When {M1 / (M1+M2)}×100 is 0.2% or more, the strength of the binder phase itself, the interfacial strength between tungsten carbide particles, and the interfacial strength between tungsten carbide particles and the binder phase in the cemented carbide alloy are further improved. Therefore, in a cutting tool including the cemented carbide, wear of the binder phase and shedding of tungsten carbide particles during cutting are further suppressed, further improving the tool life of the cutting tool. When {M1 / (M1+M2)}×100 is 25% or less, the strength of the cemented carbide alloy is improved.

[0017] (4) In any of (1) to (3) above, the average particle size of the tungsten carbide particles may be 0.2 μm or more and 3 μm or less. When the average particle size of the WC particles is 0.2 μm or more, the hardness and strength of the cemented carbide are improved. When the average particle size of the WC particles is 3 μm or less, the hardness of the cemented carbide is improved. Therefore, the wear resistance of a cutting tool including the cemented carbide is improved, and the tool life is extended.

[0018] (5) In any one of the above (1) to (4), the frequency of mismatch in the atomic arrangement of the cobalt atoms is a percentage of the number of boundaries between the atomic arrangements of the cobalt atoms where the atomic arrangements of adjacent cobalt atoms are mismatched, relative to the total number of boundaries between the atomic arrangements of the cobalt atoms in the measurement region, where the boundaries between the atomic arrangements of the cobalt atoms in the measurement region are boundaries extending in a direction along the second direction.

[0019] (6) A cutting tool according to the present disclosure is a cutting tool having a cutting edge made of the cemented carbide according to any one of (1) to (5) above.

[0020] This makes it possible to provide a cutting tool that has a long tool life, especially when used for drilling holes in printed circuit boards.

[0021] [Details of the Embodiments of the Present Disclosure] Specific examples of the cemented carbide and cutting tool of the present disclosure 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. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0022] In the present disclosure, the notation in the form of "A to B" means A or more and B or less, and when no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0023] 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.

[0024] In the present disclosure, when one or more numerical values ​​are listed as the lower limit and the upper limit of a numerical range, the combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit is also considered to be disclosed.

[0025] In this disclosure, "comprises," "includes," "has," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even a configuration expressed in closed terms may include additional elements that are normally incidental impurities or unrelated to the subject technology.

[0026] [Embodiment 1: Cemented Carbide] A cemented carbide according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cemented carbide including a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains 89 volume % or more and 100 volume % or less of the tungsten carbide particles and the binder phase in total, the cemented carbide contains 0.5 volume % or more and 25 volume % or less of the binder phase, the binder phase contains 40 mass % or more of cobalt, and the binder phase further contains silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium and platinum, and at least one first element selected from the group consisting of cobalt having an fcc structure, wherein the frequency of mismatch in the atomic arrangement of the cobalt atoms is 8% or more and 30.0% or less in a rectangular measurement region in a TEM-HAADF image obtained by observing the (110) plane of cobalt having an fcc structure at 5 million magnifications using an atomic resolution transmission electron microscope, the region containing 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction.

[0027] <Composition of Cemented Carbide> The cemented carbide of embodiment 1 contains 89 to 100 volume % of tungsten carbide particles and a binder phase in total. The cemented carbide may contain 90 to 100 volume % of tungsten carbide particles and a binder phase in total, or 92 to 100 volume % of tungsten carbide particles and a binder phase in total.

[0028] The cemented carbide of embodiment 1 includes a binder phase in an amount of 0.5 to 25% by volume. The binder phase content of the cemented carbide may be 1 to 20% by volume, 1 to 15% by volume, or 1 to 13% by volume.

[0029] The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles and a binder phase. The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles, a binder phase, and impurities, as long as the effects of the present disclosure are not impaired.

[0030] In addition to the tungsten carbide particles and binder phase, the cemented carbide may contain other phases (not shown). The other phases may include carbides, nitrides, or carbonitrides containing at least one element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). The compositions of the other phases may be, for example, TiCN, TaC, NbC, ZrC, HfC, and Mo. ２ C.

[0031] The content of other phases in the cemented carbide is permitted within a range that does not impair the effects of the present disclosure. The content of other phases in the cemented carbide may be more than 0 vol% and not more than 11 vol%, more than 0 vol% and not more than 10 vol%, or more than 0 vol% and not more than 8 vol%.

[0032] The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles, a binder phase, and other phases. The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles, a binder phase, other phases, and impurities, as long as the effects of the present disclosure are not impaired.

[0033] Examples of the impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the cemented carbide is acceptable within a range that does not impair the effects of the present disclosure. For example, the impurity content of the cemented carbide may be 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide is measured by inductively coupled plasma emission spectroscopy (ICP optical emission spectroscopy). The measuring device that can be used is the "ICPS-8100" (trademark) manufactured by Shimadzu Corporation.

[0034] The content of tungsten carbide particles in the cemented carbide of embodiment 1 may be 75% by volume or more and 99.5% by volume or less, 80% by volume or more and 99% by volume or less, 85% by volume or more and 99% by volume or less, or 87% by volume or more and 99% by volume or less.

[0035] The methods for measuring the content (volume %) of tungsten carbide particles in the cemented carbide and the content (volume %) of the binder phase in the cemented carbide are as follows.

[0036] (A1) A cemented carbide alloy is cut out at an arbitrary position to expose a cross section, which is then polished to a mirror finish using a cross section polisher (manufactured by JEOL Ltd.).

[0037] (B1) The mirror-finished surface of the cemented carbide is analyzed using an energy dispersive X-ray spectrometer (SEM-EDX) attached to a scanning electron microscope (apparatus: Carl Zeiss Gemini 450 (trademark)) to identify the elements contained in the cemented carbide.

[0038] (C1) The mirror-finished surface of the cemented carbide is photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image. The photographed area is set at the center of the cross section of the cemented carbide, i.e., a position that does not include areas with properties clearly different from the bulk part, such as the surface vicinity of the cemented carbide (a position where the photographed area is entirely the bulk part of the cemented carbide). 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.

[0039] (D1) The photographed region of (C1) above 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.

[0040] (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, tungsten carbide particles are shown in white and the binder phase is shown in black. Note that the binarization threshold varies depending on the contrast, so it is set for each image.

[0041] (F1) By superimposing the elemental mapping image obtained in (D1) above on the binarized image obtained in (E1) above, the regions where tungsten carbide particles and binder phase exist are identified on the binarized image. Specifically, the regions shown in white in the binarized image and where tungsten (W) and carbon (C) exist in the elemental mapping image correspond to the regions where tungsten carbide particles exist. The regions shown in black in the binarized image and where cobalt (Co) exists in the elemental mapping image correspond to the regions where binder phase exists.

[0042] (G1) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the binarized image, and the area percentages of the tungsten carbide particles and the binder phase are measured using the area of ​​the entire measurement field as the denominator using the image analysis software.

[0043] (H1) The measurement of (G1) above is carried out in five different, non-overlapping measurement fields. In the present disclosure, the average of the area percentages of tungsten carbide particles in the five measurement fields corresponds to the content (volume %) of tungsten carbide particles in the cemented carbide, and the average of the area percentages of the binder phase in the five measurement fields corresponds to the content (volume %) of the binder phase in the cemented carbide.

[0044] When the cemented carbide contains other phases in addition to the WC grains and binder phase, the content of the other phases in the cemented carbide can be obtained by subtracting the content (volume %) of the tungsten carbide grains and the content (volume %) of the binder phase measured by the above procedure from the total cemented carbide (100 volume %).

[0045] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view described in (G1) above are arbitrarily set and the tungsten carbide particle content and the binder phase content of the cemented carbide are measured multiple times according to the above procedure.

[0046] <Tungsten Carbide Particles> In the cemented carbide of the first embodiment, the tungsten carbide particles 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 concentration of these elements) is less than 0.1 mass%. The impurity element content of the tungsten carbide particles is measured by ICP optical emission spectrometry.

[0047] In embodiment 1, the average particle size of the tungsten carbide particles is not particularly limited. It has been confirmed that the cemented carbide of embodiment 1 enables a longer tool life when used as a cutting tool material, regardless of the average particle size of the tungsten carbide particles. From the viewpoint of improving tool life, the average particle size of the tungsten carbide particles may be 0.2 μm or more and 3 μm or less, 0.2 μm or more and 2.8 μm or less, or 0.2 μm or more and 2.5 μm or less.

[0048] The average particle size of tungsten carbide particles is measured as follows. Using the same method as (A1) to (G1) in the methods for measuring the tungsten carbide particle content and binder phase content of cemented carbide, a rectangular measurement field of 24.9 μm × 18.8 μm is set in the binarized image. Using the image analysis software, the circle-equivalent diameter (Heywood diameter: diameter equivalent to a circle with an equal area) of each of all tungsten carbide particles in the measurement field is measured. The above measurement is performed in three different, non-overlapping measurement fields. In the present disclosure, the 50% cumulative particle size (circle-equivalent diameter) D50 on an area basis is calculated based on all tungsten carbide particles in the three measurement fields. This D50 corresponds to the average particle size of the tungsten carbide particles.

[0049] As long as measurements were performed on the same sample, it was confirmed that there was almost no variation in the measurement results even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view were arbitrarily set and the average particle size of tungsten carbide particles was measured multiple times according to the above procedure.

[0050] <Binder Phase> <Cobalt> In the cemented carbide of embodiment 1, the binder phase contains 40 mass% or more of cobalt. This allows the cemented carbide to have excellent toughness. The cobalt content of the binder phase may be 40 mass% or more but less than 100 mass%, 50 mass% or more but 90 mass% or less, or 60 mass% or more but 80 mass% or less.

[0051] The method for measuring the cobalt content of the binder phase is as follows. An elemental mapping image and a binarized image are obtained by the same methods as (A1) to (E1) of the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide described above. The elemental mapping image and the binarized image are superimposed to identify the region where the binder phase exists in the elemental mapping image. A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the elemental mapping image. The cobalt content is measured in the region where the binder phase exists in the measurement field of view. The above measurement is performed in five different, non-overlapping measurement fields of view. In the present disclosure, the average of the cobalt contents in the regions where the binder phase exists in the five measurement fields of view corresponds to the cobalt content of the binder phase.

[0052] As long as the measurement is performed on the same sample, it has been confirmed that there is almost no variation in the measurement results even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view are arbitrarily set and the cobalt content of the binder phase is measured multiple times according to the above procedure.

[0053] <<First Element>> In the cemented carbide of embodiment 1, the binder phase further contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum.

[0054] The inclusion of the first element in the binder phase is confirmed by the following procedure. An element mapping image and a binarized image are obtained by the same methods as steps (A1) to (E1) of the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide described above. The element mapping image and the binarized image are superimposed to identify the region in which the binder phase exists in the element mapping image. If the first element is present in the region in which the binder phase exists in the element mapping, it is confirmed that the binder phase contains the first element.

[0055] In the binder phase of the cemented carbide of embodiment 1, 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, {M1 / (M1+M2)}×100, may be 0.2% or more and 25% or less, 2% or more and 5% or less, or 3% or more and 4% or less. Here, the units of the mass M1 and the mass M2 are the same. When the binder 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.

[0056] The method for measuring the percentage {M1 / (M1+M2)} x 100 is as follows. An element mapping image and a binarized image are obtained using the same methods as steps (A1) to (E1) of the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide. The element mapping image and the binarized image are superimposed to identify the binder phase region in the element mapping image. A rectangular measurement field of view of 24.9 μm x 18.8 μm is set in the element mapping image. In the binder phase region in the measurement field of view, the percentage {m1 / (m1+m2)} x 100 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 is calculated. The above measurement is performed in five different, non-overlapping measurement fields of view. In the present disclosure, the average of the percentages {m1 / (m1+m2)}×100 in the five measurement fields corresponds to the "percentage {M1 / (M1+M2)}×100" in the binder phase of the cemented carbide.

[0057] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view are arbitrarily set and the percentage {M1 / (M1+M2)}×100 is measured multiple times according to the above procedure.

[0058] In the cemented carbide of embodiment 1, the binder phase may contain, in addition to cobalt and the first element, at least one second element selected from the group consisting of iron (Fe), nickel (Ni), and chromium (Cr). The binder phase may consist of cobalt, the first element, and the second element. The binder phase may consist of cobalt, the first element, the second element, and inevitable impurities. Examples of the inevitable impurities include iron (Fe), nickel (Ni), and sulfur (S).

[0059] <<Mismatch in atomic arrangement of cobalt atoms>> In a rectangular measurement region in a TEM-HAADF image obtained by observing the (110) plane of the fcc structure of the binder phase of the cemented carbide of embodiment 1 at 5 million magnifications using an atomic resolution transmission electron microscope, which contains 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction, the frequency of mismatch in atomic arrangement of cobalt atoms is 8% to 30.0%. The frequency of mismatch in atomic arrangement of cobalt atoms may be 8.0% to 29.2%, 8.1% to 25.0%, or 9.0% to 20.0%.

[0060] The method for measuring the frequency of mismatch in the atomic arrangement of cobalt atoms will be described with reference to FIGS.

[0061] (A2) Using an argon ion slicer ("IB-09060CIS Cryo-Ion Slicer" (trademark) manufactured by JEOL Ltd.), the cemented carbide is sliced ​​to a thickness of 30 to 100 nm under conditions of an acceleration voltage of 6 kV and a finishing voltage of 2 kV to prepare a measurement sample.

[0062] The measurement sample is subjected to EBSD analysis using a field emission scanning electron microscope (FE-SEM) (Zeiss "Gemini 450" (trademark)) equipped with an electron backscatter diffraction (EBSD) device under the following measurement conditions. <Measurement conditions> Acceleration voltage: 30 kV Magnification: 10,000 times Current value: 22 nA WD: 4 mm Tilt: 20° Step size: 0.02 μm

[0063] (B2) The EBSD analysis results are analyzed using a crystal orientation analyzer (analysis software "AZtecCrystal Version 3.1" manufactured by Oxford Instruments Ltd.), and an IPF map (inverse pole figure orientation map) of the analysis region is created. In creating the IPF map, a grain boundary is defined as a boundary where the misorientation angle between adjacent measurement points is 15° or more. In the IPF map, the crystal orientation of each crystal grain is indicated by a different color. Figure 1 shows an example of an IPF map of the cemented carbide of embodiment 1.

[0064] (C2) Identifying cobalt having an fcc structure on the IPF map. In FIG. 1, an example of cobalt having an fcc structure is shown as Co-fcc phase. Generally, in cemented carbide, the main crystal structure of cobalt is an fcc structure. For example, in the cemented carbide of embodiment 1, more than 50 volume % of cobalt may have an fcc structure, or 60 volume % or more may have an fcc structure. It has been confirmed that, in the cemented carbide of embodiment 1, as long as more than 50 volume % of cobalt has an fcc structure and the frequency of mismatch in the atomic arrangement of cobalt atoms is 8% or more, the effects of the present disclosure derived from the frequency of mismatch in the atomic arrangement of cobalt atoms can be obtained.

[0065] (D2) The (110) plane of cobalt having the fcc structure identified on the IPF map is observed at 5,000,000 magnification using an atomic resolution transmission electron microscope ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) to obtain a TEM-HAADF image. Figure 2 is an example of a TEM-HAADF image of the cemented carbide of embodiment 1.

[0066] (E2) In the TEM-HAADF image, a rectangular measurement area is set containing 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction. FIG. 3 is an example showing an extracted measurement area set in the TEM-HAADF image of FIG. 2. In FIG. 3, the boundaries between the atomic arrangements of cobalt atoms are indicated by dotted lines and solid lines. In FIG. 3, the solid lines indicate the boundaries between atomic arrangements where the atomic arrangements of adjacent cobalt atoms are inconsistent. The boundaries between atomic arrangements where the atomic arrangements of adjacent cobalt atoms are inconsistent correspond to the boundaries between the fcc structure and hcp structure of cobalt observed in the TEM-HAADF image. In the cemented carbide of embodiment 1, when cobalt having an fcc structure identified on the IPF map is observed at a magnification of 5,000,000 times in a TEM-HAADF image, an fcc structure and an hcp structure are present.

[0067] In a measurement region set in the TEM-HAADF image, the total number of boundaries between atomic arrangements of cobalt atoms (the total number of boundaries is 30) and the number of boundaries between atomic arrangements where the atomic arrangements of adjacent cobalt atoms are inconsistent are counted. Here, the boundaries between atomic arrangements of cobalt atoms are boundaries extending in the second direction. The percentage of the number of boundaries between atomic arrangements of adjacent cobalt atoms where the atomic arrangements are inconsistent with respect to the total number of boundaries between atomic arrangements of cobalt atoms is calculated. This percentage corresponds to the frequency of inconsistencies in the atomic arrangements of cobalt atoms. For example, in the TEM-HAADF image of FIG. 3, the total number of boundaries between atomic arrangements of cobalt atoms is 30, and the number of boundaries between atomic arrangements where the atomic arrangements of adjacent cobalt atoms are inconsistent with respect to the total number of boundaries between atomic arrangements of cobalt atoms is 5, and the percentage of the number of boundaries between atomic arrangements of adjacent cobalt atoms where the atomic arrangements are inconsistent with respect to the total number of boundaries between atomic arrangements of cobalt atoms is 16.7%.

[0068] In the present disclosure, the measurement of (E2) above is performed in three different non-overlapping measurement areas, and if the frequency of mismatch in the atomic arrangement of cobalt atoms is 8% or more in two or more measurement areas, the frequency of mismatch in the atomic arrangement of cobalt atoms in the measurement area of ​​the cemented carbide is determined to be 8% or more. The frequency of other mismatch in the atomic arrangement of cobalt atoms (for example, 10% or more) is also determined by whether two or more measurement areas among the three measurement areas satisfy that frequency.

[0069] As long as measurements are performed on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the cut-out location of the cemented carbide cross section, the location where the IPF map and TEM-HAADF image are created, and the measurement area described in (E2) above are arbitrarily set.

[0070] <Method for manufacturing cemented carbide> The cemented carbide of embodiment 1 can be manufactured by carrying out a raw material powder preparation step, a mixing step, a molding step, a sintering step, and a cooling step in the above order. Each step will be described below.

[0071] <Preparation Step> The preparation step is a step of preparing a raw material powder for the cemented carbide. Examples of the raw material powder include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt powder, first element powder, and alloy powder of the first element and cobalt. Examples of the first element powder include silicon powder, phosphorus powder, germanium powder, tin powder, rhenium powder, ruthenium powder, osmium powder, iridium powder, and platinum powder.

[0072] As the raw material powder, nickel powder, vanadium carbide powder, titanium carbonitride powder, etc. can also be prepared. These raw material powders can be commercially available products.

[0073] The average particle size of the raw material powder is not particularly limited and may be, for example, 0.5 to 5 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.

[0074] <Mixing Step> The mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio. By the mixing step, a mixed powder in which the raw material powders are mixed is obtained. The mixing ratio of the raw material powders is appropriately adjusted depending on the target composition of the cemented carbide.

[0075] An attritor is used to mix the raw material powders. First, the raw material powders of the binder phase (cobalt powder, first element powder, alloy powder of the first element and cobalt, and nickel powder) are charged into the attritor and subjected to intense pulverization (conditions: 300 rpm for 2 hours). Subsequently, the other raw material powders are charged into the attritor and mixed (conditions: 200 rpm for 6 hours).

[0076] 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.

[0077] <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.

[0078] <Sintering Step> The sintering step is a step of sintering the compact obtained in the compacting step to obtain a cemented carbide intermediate body. The sintering conditions are holding in an Ar atmosphere at 1350°C and 7 MPa for 2 hours.

[0079] <Cooling Step> The cooling step is a step of cooling the cemented carbide intermediate body after the sintering step to obtain a cemented carbide. Specifically, the cemented carbide intermediate body is cooled at -50°C / min.

[0080] [Embodiment 2: Cutting Tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a cutting tool equipped with a cutting edge made of the cemented carbide of Embodiment 1. In this disclosure, the cutting edge refers to the portion involved in cutting. More specifically, the cutting edge refers to the region surrounded by the cutting edge ridge and an imaginary plane that is 0.5 mm or 2 mm away from the cutting edge ridge toward the cemented carbide.

[0081] Examples of cutting tools include cutting tools, drills, end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metal saws, gear cutting tools, reamers, taps, etc. In particular, as shown in Figure 4, the cutting tool 10 of the second embodiment is highly effective in the case of small-diameter drills for machining printed circuit boards. The cutting edge 11 of the cutting tool 10 shown in Figure 4 is made of the cemented carbide of the first embodiment.

[0082] In the cutting tool of Embodiment 2, the cemented carbide of Embodiment 1 may constitute the entire tool or may constitute a part of the tool. Here, "constitute a part" refers to a mode in which the cemented carbide of Embodiment 1 is brazed to a predetermined position of an arbitrary substrate to form a cutting edge.

[0083] The cutting tool of the second embodiment may further include a hard film that covers at least a part of the surface of the substrate made of cemented carbide. The hard film may be made of, for example, diamond-like carbon or diamond.

[0084] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0085] [Preparation of Cemented Carbide] Each sample of cemented carbide was prepared according to the following procedure. <Preparation Step> As raw material powders, WC powder (average particle size: as shown in Table 1), Co powder (average particle size: 1 μm), first element powder, Ni powder (average particle size: 1 μm), VC powder (average particle size: 1 μm), and TiCN powder (average particle size: 1 μm) were prepared. As first element powders, silicon (Si) powder (average particle size: 1 μm), phosphorus (P) powder (average particle size: 1 μm), germanium (Ge) powder (average particle size: 1 μm), tin (Sn) powder (average particle size: 1 μm), rhenium (Re) powder (average particle size: 1 μm), ruthenium (Ru) powder (average particle size: 1 μm), osmium (Os) powder (average particle size: 1 μm), iridium (Ir) powder (average particle size: 1 μm), and platinum (Pt) powder (average particle size: 1 μm) were prepared. The raw material powders were prepared in the proportions shown in Table 1. The proportions (mass%) of the raw material powders shown in Table 1 are the proportions when the total raw material powder is taken as 100 mass%. The "balance" in the "mass%" column for "WC powder" refers to the value obtained by subtracting the proportion of raw material powders other than WC powder from the total raw material powder (100 mass%).

[0086]

[0087] <Mixing Step> For samples with "Strongly pulverized → mixed" in the "Mixing" column in Table 2, mixing was performed using the following procedure. First, the raw material powders of the binder phase (cobalt powder, first element powder) were placed in the attritor and strongly pulverized (conditions: 300 rpm for 2 hours). Subsequently, the other raw material powders were placed in the attritor and mixed (conditions: 200 rpm for 6 hours).

[0088] For the samples marked "normal mixing" in the "mixing" column of Table 2, all raw material powders were simultaneously charged into the attritor and mixed for 10 hours.

[0089] <Molding Step> The mixed powder was pressed to obtain a molded body in the shape of a round bar or an insert (CNMG120408N-GU).

[0090] <Sintering Step> The compact was sintered in an Ar atmosphere under the conditions shown in the "Sintering" column in Table 2 to obtain a cemented carbide intermediate.

[0091] <Cooling Step> The cemented carbide intermediate was cooled at the cooling rate shown in the "Cooling" column of Table 2 to obtain a cemented carbide.

[0092]

[0093] [Evaluation of Cemented Carbide] <Content (volume %) of Tungsten Carbide Particles and Content (volume %) of Binder Phase in Cemented Carbide> The content (volume %) of tungsten carbide particles and the content (volume %) of binder phase in the cemented carbide of each sample were measured by the method described in embodiment 1. The results are shown in Table 3. Furthermore, the total content (WC particle + binder phase content) of the tungsten carbide particles and the binder phase in the cemented carbide is shown in Table 3. It was confirmed that cemented carbide alloys with a "WC particle + binder phase content" column of less than 100% by volume contained TiCN or VC.

[0094] <Cobalt Content in Binder Phase> The cobalt content in the binder phase of each cemented carbide sample was measured by the method described in embodiment 1. The results are shown in Table 3.

[0095] <Type of First Element and {M1 / (M1+M2)}×100> In the binder phase of the cemented carbide of each sample, the type and content of the first element, as well as the percentage {M1 / (M1+M2)}×100 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, were measured by the method described in embodiment 1. The results are shown in Table 3. Samples with "-" in the "First Element" column indicate that they did not contain the first element.

[0096] <Average particle size of tungsten carbide particles> In each sample of cemented carbide alloy, the average particle size of tungsten carbide particles was measured by the method described in embodiment 1. The results are shown in Table 3.

[0097] <Mismatch in atomic arrangement of cobalt atoms> In each sample of cemented carbide, the frequency of mismatch in atomic arrangement of cobalt atoms was measured by the method described in embodiment 1. Among the frequencies of mismatch in atomic arrangement of cobalt atoms measured in each of the three measurement regions, the second smallest value is shown in Table 3. Note that, when the three frequencies A, B, and C are A = B < C, the value of B is shown in Table 3; when A = B = C, the value of B is shown; and when A < B = C, the value of B is shown. Note that, in all samples, it was confirmed that more than 50% by volume of cobalt had an fcc structure.

[0098]

[0099] [Cutting Test 1] A round bar made of cemented carbide alloy from each sample was machined to produce a drill for machining printed circuit boards (PCB (Printed Circuit Board) drill) with a cutting diameter of 0.18 mm. Using the PCB drill, holes were drilled into commercially available printed circuit boards for semiconductor packages, and the breakage rate was evaluated. First, two 0.8 mm thick printed circuit boards were stacked, and these were drilled using a PCB drill at a rotation speed of 250 krpm up to 10,000 hits. Next, three 0.8 mm thick printed circuit boards were stacked, and these were drilled using the same PCB drill at a rotation speed of 250 krpm up to 10,000 hits. The above drilling was performed using 10 PCB drills, and the breakage rate was calculated. A lower breakage rate indicates better fatigue breakage resistance and a longer tool life of the cutting tool. The results are shown in Table 4.

[0100] [Cutting test 2] An 8 μm thick TiCN layer and an 8 μm thick Al layer were formed by CVD on the surface of the cemented carbide insert (CNMG120408N-GU) of each sample. ２ O ３ The layers were formed in the above order to obtain a surface-coated cutting tool. Using each sample of the surface-coated cutting tool, the end face of a notched round bar made of SCM435 was machined, and the time until chipping occurred at the cutting edge was evaluated. The machining conditions were a cutting speed (vc) of 250 m / min, a feed rate (f) of 0.3 mm / rev, and a depth of cut (ap) of 1.5 mm. The longer the time until chipping occurred at the cutting edge, the better the chipping resistance of the cutting tool and the longer the tool life. The results are shown in Table 4.

[0101]

[0102] [Discussion] The cemented carbide alloys and cutting tools of Samples 1 to 21 correspond to Examples. The cemented carbide alloys and cutting tools of Samples 1-1 to 1-7 correspond to Examples. It was confirmed that the cutting tools of Samples 1 to 21 had longer tool life in drilling holes in printed circuit boards and in machining the end faces of notched round bars made of SCM435 than the cutting tools of Samples 1-1 to 1-7.

[0103] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and modified in various ways. 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 above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0104] 10 cutting tool, 11 cutting edge

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 to 100 volume % of the tungsten carbide particles and the binder phase, the cemented carbide alloy contains 0.5 to 25 volume % of the binder phase, the binder phase contains 40 mass % or more of cobalt, and the binder phase further contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, The cemented carbide alloy has a (110) plane of the cobalt having an fcc structure, and in a TEM-HAADF image obtained by observing the (110) plane at 5 million magnifications using an atomic resolution transmission electron microscope, the rectangular measurement region contains 31 cobalt atoms in a first direction and 5 to 10 cobalt atoms in a second direction perpendicular to the first direction. In this rectangular measurement region, the frequency of mismatch in the atomic arrangement of the cobalt atoms is 8% to 30.0%.

2. The cemented carbide according to claim 1, wherein the frequency of mismatch in the atomic arrangement of the cobalt atoms is 10% or more.

3. The cemented carbide according to claim 1 or 2, wherein in the binder phase, 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 the cobalt, {M1 / (M1+M2)}×100, is 0.2% or more and 25% or less.

4. A cemented carbide alloy according to any one of claims 1 to 3, wherein the average particle size of the tungsten carbide particles is 0.2 μm or more and 3 μm or less.

5. The cemented carbide according to any one of claims 1 to 4, wherein the frequency of mismatch in the atomic arrangement of the cobalt atoms is the percentage of the number of boundaries between the atomic arrangements of the cobalt atoms where the atomic arrangements of adjacent cobalt atoms are mismatched, relative to the total number of boundaries between the atomic arrangements of the cobalt atoms in the measurement region.

6. A cutting tool having a cutting edge made of the cemented carbide according to any one of claims 1 to 5.

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