Cemented carbide and cutting tool

Abstract

Provided is a cemented carbide which comprises a plurality of tungsten carbide grains and a binder phase, wherein: the cemented carbide contains the tungsten carbide grains and the binder phase in a combined amount of 89% by volume or more; the cemented carbide contains the binder phase in an amount of 1.5% by volume to 23% by volume inclusive; the binder phase contains 40% by mass or more cobalt; the binder phase additionally contains at least one first element that is selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum; the first element is not segregated in a first interface region between the tungsten carbide grains adjacent to each other; and the first element is not segregated in a second interface region between the binder phase and the tungsten carbide grains adjacent to each other.

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 comprises a total of 89 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide comprises 1.5 volume % or more and 23 volume % or less of the binder phase, the binder phase comprises 40 mass % or more of cobalt, and the binder phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, wherein the first element does not segregate in a first interface region between adjacent tungsten carbide particles, and the first element does not segregate in a second interface region between adjacent tungsten carbide particles and the binder phase.

[0005] Fig. 1 is a schematic cross-sectional view of a cemented carbide according to embodiment 1. Fig. 2 is a diagram showing an example of a first image of the cemented carbide according to embodiment 1. Fig. 3 is a diagram showing a first graph for explaining a method for confirming that a first element does not segregate in a first interface region. Fig. 4 is a diagram showing a second graph for explaining a method for confirming that a first element does not segregate in a second interface region. Fig. 5 is a schematic diagram of a cutting tool according to embodiment 2.

[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 for using cutting tools have become harsher. For example, with the expansion of 5G (fifth-generation mobile communication systems), the amount of information transmitted via printed circuit boards has increased, and printed circuit boards are required to have even greater heat resistance. To improve the heat resistance of printed circuit boards, technologies have been developed to improve the heat resistance of resins and glass fillers that make up printed circuit boards. However, this has made printed circuit boards increasingly difficult to cut. As a result, cutting tools tend to be more susceptible to wear and breakage 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 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.

[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 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 1.5 volume % or more and 23 volume % or less 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, wherein the first element does not segregate in a first interface region between adjacent tungsten carbide particles, and the first element does not segregate in a second interface region between adjacent tungsten carbide particles and the binder phase.

[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.

[0011] (2) In the above (1), 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 cobalt, {M1 / (M1+M2)}×100, may be 1% or more and 6% or less. Here, the units of the mass M1 and the mass M2 are the same. This makes it possible to provide a cemented carbide that can extend the tool life of a cutting tool.

[0012] (3) In the above (1) or (2), the cemented carbide may not contain an intermetallic compound consisting of two or more elements selected from the group consisting of the first element, cobalt, and tungsten, and a first compound consisting of at least one element selected from the group consisting of the first element, cobalt, and tungsten, and at least one element selected from the group consisting of carbon, nitrogen, and oxygen, wherein the first compound does not include tungsten carbide.

[0013] This prevents the strength of the cemented carbide from decreasing.

[0014] (4) 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 (3) above.

[0015] 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.

[0016] [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.

[0017] 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.

[0018] 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.

[0019] In the present disclosure, when one or more numerical values ​​are recited as the lower limit and the upper limit of a numerical range, a combination of any one numerical value recited as the lower limit and any one numerical value recited as the upper limit is also considered to be disclosed. For example, when a1 or more, b1 or more, and c1 or more are recited as the lower limit and a2 or less, b2 or less, and c2 or less are recited as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are considered to be disclosed.

[0020] [Embodiment 1: Cemented Carbide] A cemented carbide according to one embodiment of the present disclosure will be described with reference to FIG. A cemented carbide (3) according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 1") is a cemented carbide (3) comprising a plurality of tungsten carbide particles (1) and a binder phase (2), wherein the cemented carbide (3) comprises a total of 89 volume % or more of the tungsten carbide particles (1) and the binder phase (2), the cemented carbide (3) comprises 1.5 volume % or more and 23 volume % or less of the binder phase (2), the binder phase (2) comprises 40 mass % or more of cobalt, and the binder phase (2) further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, wherein the first element does not segregate in a first interface region between adjacent tungsten carbide particles (1), and the first element does not segregate in a second interface region between adjacent tungsten carbide particles (1) and the binder phase (2).

[0021] The cemented carbide of embodiment 1 can provide a cemented carbide that enables a longer life of a cutting tool, particularly when used as a material for a cutting tool for drilling holes in printed circuit boards, and a cutting tool including the cemented carbide. The reason for this is not clear, but is presumed to be as follows.

[0022] The cemented carbide of the first embodiment comprises a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles") and a binder phase, and the total content of the WC particles and binder phase in the cemented carbide is 89 volume % or more. As a result, the cemented carbide has high hardness and strength, and a cutting tool including the cemented carbide can have excellent wear resistance and breakage resistance.

[0023] The cemented carbide of the first embodiment contains a binder phase of 1.5 to 23 volume % and the binder phase contains 40 mass % or more of cobalt, which provides high hardness and strength, and allows a cutting tool including the cemented carbide to have excellent wear resistance and breakage resistance.

[0024] In the cemented carbide of embodiment 1, the binder phase contains at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. Furthermore, the first element does not segregate in the first interface region between adjacent tungsten carbide particles, and the first element does not segregate in the second interface region between adjacent tungsten carbide particles and the binder phase. This further improves the interfacial strength between the tungsten carbide particles and between the tungsten carbide particles and the binder phase, thereby suppressing the shedding of tungsten carbide particles during cutting. Therefore, cutting tools using this cemented carbide as a material can have a long tool life. Furthermore, the hole position accuracy of the cutting tool is also improved.

[0025] <Composition of Cemented Carbide> The cemented carbide of embodiment 1 contains tungsten carbide particles and a binder phase in a total amount of 89% by volume or more. This increases the hardness of the cemented carbide. The cemented carbide may contain tungsten carbide particles and a binder phase in a total amount of 89% by volume or more and 100% by volume or less, 90% by volume or more and 100% by volume or less, 91% by volume or more and 100% by volume or less, or 92% by volume or more and 100% by volume or less.

[0026] The cemented carbide of the first embodiment contains 1.5 to 23 volume percent of a binder phase, which can enhance the hardness and toughness of the cemented carbide. The binder phase content of the cemented carbide may be 2.0 to 19.0 volume percent, 3.0 to 18.0 volume percent, or 4.0 to 17.0 volume percent.

[0027] The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles and a binder phase. In this case, the cemented carbide may contain impurities within a range that does not impair the effects of the present disclosure.

[0028] 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.

[0029] The cemented carbide of the first embodiment may be composed of tungsten carbide particles, a binder phase, and other phases. In this case, the cemented carbide may contain impurities within a range that does not impair the effects of the present disclosure.

[0030] The content of other phases in the cemented carbide is permitted within a range that does not impair the effects of the present disclosure. For example, 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 7 vol%, or more than 0 vol% and not more than 4 vol%.

[0031] The cemented carbide of embodiment 1 may contain impurities. Examples of impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the cemented carbide is acceptable as long as it 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.

[0032] The content of tungsten carbide particles in the cemented carbide of embodiment 1 may be 67% by volume or more and 98.5% by volume or less, 70% by volume or more and 97% by volume or less, or 75% by volume or more and 96% by volume or less.

[0033] 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.

[0034] (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.).

[0035] (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.

[0036] (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.

[0037] (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.

[0038] (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 gray to black. Note that the binarization threshold varies depending on the contrast, so it is set for each image.

[0039] (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 gray to black in the binarized image and where cobalt (Co) exists in the elemental mapping image correspond to the regions where binder phases exist.

[0040] (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 and the binder phase are measured, with the area of ​​the entire measurement field being used as the denominator.

[0041] (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.

[0042] 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 %).

[0043] 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.

[0044] The cobalt content of the cemented carbide of embodiment 1 may be 1.0 mass % or more and 20 mass % or less, 2.0 mass % or more and 15 mass % or less, or 3.0 mass % or more and 12 mass % or less.

[0045] The method for measuring the cobalt content of a cemented carbide alloy is as follows. Analysis is performed using SEM-EDX to obtain an elemental mapping image using the same methods as (A1) to (D1) of the method for measuring the tungsten carbide particle content and binder phase content of a cemented carbide alloy described above. Based on the elemental mapping image, the cobalt region in the cemented carbide alloy is identified, and the cobalt content is measured. The measurement is performed in five different, non-overlapping imaging regions. In the present disclosure, the average of the cobalt contents in the five imaging regions corresponds to the cobalt content of the cemented carbide alloy.

[0046] 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 and the photographing area described in (C1) above were arbitrarily set and the cobalt content of the cemented carbide was measured multiple times according to the above procedure.

[0047] <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.

[0048] In the first embodiment, the average particle size of the tungsten carbide particles is not particularly limited. The average particle size of the tungsten carbide particles can be, for example, 0.1 μm or more and 3.5 μm or less. It has been confirmed that the cemented carbide of the first embodiment enables the tool to have a long life when used as a cutting tool material, regardless of the average particle size of the tungsten carbide particles.

[0049] <Binder Phase> 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.

[0050] 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.

[0051] 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.

[0052] In the cemented carbide of embodiment 1, the binder phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum.

[0053] 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.

[0054] In the binder phase of the cemented carbide of embodiment 1, 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 1% or more and 6% or less. Here, the units of the masses M1 and M2 are the same. This allows the binder phase to have both superior hardness and superior toughness, thereby enabling a cutting tool including a cemented carbide containing the binder phase to have a longer tool life. 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 percentage {M1 / (M1+M2)}×100 may be 2% or more and 5% or less, or 3% or more and 4% or less.

[0055] 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.

[0056] 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.

[0057] 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).

[0058] <First interface region and second interface region> In the cemented carbide of embodiment 1, the first element does not segregate in the first interface region between adjacent tungsten carbide particles, and the first element does not segregate in the second interface region between adjacent tungsten carbide particles and the binder phase. This improves the interface strength between the tungsten carbide particles and between the tungsten carbide particles and the binder phase, thereby improving the wear resistance and breakage resistance of the cemented carbide.

[0059] In the present disclosure, a method for confirming that the first element is not segregated in the first interface region between adjacent tungsten carbide particles of the cemented carbide will be described with reference to FIGS. 2 and 3 .

[0060] (A2) A measurement sample is prepared by cutting the cemented carbide into thin slices of 30 to 100 nm using an argon ion slicer ("Cryo-ion slicer IB-09060BCIS" (trademark) manufactured by JEOL Ltd.) under conditions of an acceleration voltage of 6 kV and a finishing voltage of 2 kV. The measurement sample is observed at 200,000 magnifications using a TEM (Transmission Electron Microscopy) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) under conditions of an acceleration voltage of 200 V, thereby obtaining a first image. An example of the first image is shown in FIG. 2.

[0061] (B2) In the first image, the tungsten carbide particles 1 are observed as white to gray regions, the binder phase 2 is observed as black regions, and the interfaces 4 located between adjacent tungsten carbide particles 1 are observed as black regions. In the first image, the width of the interfaces 4 is, for example, 2 nm or less. In the first image, the interfaces between adjacent tungsten carbide particles are arbitrarily selected. Hereinafter, in this disclosure, the adjacent tungsten carbide particles are also referred to as first tungsten carbide particles and second tungsten carbide particles.

[0062] (C2) Next, the selected interface is positioned so that it passes near the center of the image, and the observation magnification is adjusted so that the field of view is 5 nm x 5 nm, thereby obtaining a second image. In the second image, the extension direction of the interface is confirmed. Line analysis is performed using an energy dispersive X-ray analyzer (TEM-EDX) attached to the TEM in a direction perpendicular to the extension direction and from the first tungsten carbide particle toward the second tungsten carbide particle to obtain a graph (hereinafter also referred to as the first graph) measuring the distribution of cobalt, tungsten, and the first element. If the cemented carbide contains two or more types of first elements, the distribution of each element is measured. Here, the direction perpendicular to the extension direction of the interface refers to the direction along a straight line intersecting the tangent to the extension direction at an angle of 90°±5°. For example, in Figure 2, the direction indicated by the arrow corresponds to the direction perpendicular to the extension direction of the interface. The measurement conditions for acquiring the second image were an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel count of 128×128 pixels, and a dwell time of 0.02 to 3 s / pixel.

[0063] Fig. 3 is an example of the first graph. In Fig. 3, the horizontal axis (X axis) represents the distance (nm) from the measurement start point, and the vertical axis (Y axis) represents the content (atomic %) of each element. In the cemented carbide shown in Fig. 3, the first element is silicon (Si).

[0064] (D2) Identify the cobalt peak position in the first graph. In this disclosure, the cobalt peak position is referred to as the first interface. The first interface is formed between adjacent first and second tungsten carbide particles. In the first graph of FIG. 3, the first interface is located at 5.98 nm on the X-axis.

[0065] In the first graph, a first A region is identified, the distance from the first interface to the first tungsten carbide particle side being within 1.20 nm, and a first B region is identified, the distance from the first interface to the second tungsten carbide particle side being within 1.20 nm. In the present disclosure, the region consisting of the first A region and the first B region is the first interface region. In the first graph of FIG. 3, the first interface region is located in the region of 4.78 to 7.18 nm on the X axis. In the present disclosure, the first interface region between adjacent tungsten carbide particles can also be expressed as the first interface region located between adjacent tungsten carbide particles.

[0066] In the first graph, a second A region is identified where the distance from the first interface to the first tungsten carbide particle side is 1.50 nm or more and 3.50 nm or less, and a second B region is identified where the distance from the first interface to the second tungsten carbide particle side is 1.50 nm or more and 3.50 nm or less. In the first graph of Figure 3, the second A region is located in the region of 2.48 to 4.48 nm on the X axis, and the second B region is located in the region of 7.48 to 9.48 nm on the X axis.

[0067] (E2) Based on the first graph, calculate the average content B (atomic %) of the first element in the baseline region consisting of the second A region and the second B region. Measure the maximum content A (atomic %) of the first element in the first interface region in the first graph. If the ratio A / B of the maximum value A to the average B is less than 3, it is confirmed that the first element is not segregated in the first interface region between adjacent tungsten carbide particles of the cemented carbide.

[0068] In the first graph of Fig. 3, the average silicon (first element) content B in the baseline region consisting of Regions 2A and 2B is 7.68 atomic %, and the maximum silicon (first element) content A in the first interface region is 6.75 atomic %. In the cemented carbide shown in Fig. 3, A / B is 0.9, which confirms that the first element does not segregate in the first interface region between adjacent tungsten carbide particles of the cemented carbide.

[0069] (F2) For a cemented carbide, five mutually non-overlapping first images are arbitrarily obtained, a first graph is obtained based on each of the first images, and the above-described analysis is repeatedly performed. If no segregation of the first element is confirmed in the first interface region in four or more of the first graphs, it is determined that the first element is not segregated in the first interface region between adjacent tungsten carbide particles of the cemented carbide.

[0070] In the present disclosure, a method for confirming that the first element is not segregated in the second interface region between adjacent tungsten carbide particles and the binder phase will be described with reference to FIG. 4 .

[0071] (A3) A first image is obtained by the same method as (A2) described in the method for confirming that the first element is not segregated in the first interface region. In the first image, an interface between adjacent tungsten carbide particles and the binder phase is arbitrarily selected.

[0072] (B3) Next, the selected interface is positioned so that it passes near the center of the image, and the observation magnification is adjusted so that the field of view is 5 nm x 5 nm, thereby obtaining a third image. In the third image, the extension direction of the interface is confirmed. Line analysis is performed using TEM-EDX perpendicular to the extension direction, in the direction from the tungsten carbide particles toward the binder phase, to obtain a graph (hereinafter also referred to as the second graph) measuring the distribution of cobalt, tungsten, and the first element. If the cemented carbide contains two or more types of first elements, the distribution of each element is measured. Here, the direction perpendicular to the extension direction of the interface refers to the direction along a straight line intersecting the tangent to the extension direction at an angle of 90° ± 5°. The measurement conditions for obtaining the third image were an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel count of 128 x 128 pixels, and a dwell time of 0.02 to 3 s / pixel.

[0073] Fig. 4 is an example of the second graph. In Fig. 4, the horizontal axis (X axis) represents the distance (nm) from the measurement start point, and the vertical axis (Y axis) represents the content (atomic %) of each element. In the cemented carbide shown in Fig. 4, the first element is silicon (Si).

[0074] In the second graph, the position where the tungsten content and the cobalt content intersect is identified. In this disclosure, the position where the tungsten content and the cobalt content intersect is referred to as the second interface. The second interface is formed between adjacent tungsten carbide particles and the binder phase. In the second graph of Figure 4, the second interface is located at 5.97 nm on the X-axis.

[0075] In the second graph, a first C region is identified, the distance from the second interface to the tungsten carbide particle side being within 1.20 nm, and a first D region is identified, the distance from the second interface to the binder phase side being within 1.20 nm. In the present disclosure, the region consisting of the first C region and the first D region is the second interface region. In the second graph of FIG. 4, the second interface region is located in the region of 4.76 to 7.16 nm on the X-axis. In the present disclosure, the second interface region between adjacent tungsten carbide particles and the binder phase can also be expressed as the second interface region located between adjacent tungsten carbide particles and the binder phase.

[0076] In the second graph, a second C region is identified where the distance from the second interface to the tungsten particle side is 1.50 nm or more and 3.50 nm or less, and a second D region is identified where the distance from the second interface to the binder phase side is 1.50 nm or more and 3.50 nm or less. In the second graph of Figure 4, the second C region is located in the region of 2.46 to 4.46 nm on the X axis, and the second D region is located in the region of 7.46 to 9.46 nm on the X axis.

[0077] Based on the second graph, the average content D (atomic %) of the first element in the baseline region consisting of the second C region and the second D region is calculated. In the second graph, the maximum content C (atomic %) of the first element in the second interface region is measured. If the ratio C / D of the maximum C to the average D is less than 3, it is confirmed that the first element is not segregated in the second interface region between adjacent tungsten carbide particles and the binder phase of the cemented carbide.

[0078] (C3) For a cemented carbide, five mutually non-overlapping first images are arbitrarily obtained, and second graphs are obtained based on the respective first images, and the above-described analysis is repeatedly performed. If no segregation of the first element is confirmed in the second interface region in four or more of the second graphs, it is determined that the first element is not segregated in the second interface region between adjacent tungsten carbide particles and the binder phase in the cemented carbide.

[0079] As long as measurements are performed on the same sample, it has been confirmed that even if the cut-out location of the cemented carbide cross section is arbitrarily set, the first image is arbitrarily obtained on the cross section, and the presence or absence of segregation of the first element in the first interface region and the second interface region is confirmed multiple times according to the above procedure while changing the region of line analysis, there is almost no variation in the results regarding the presence or absence of segregation of the first element in the first interface region and the second interface region. Therefore, as long as the above method for confirming the segregation of the first element is performed on a cemented carbide, and it is confirmed that the interfacial strength between the tungsten carbide particles of the cemented carbide and the interfacial strength between the tungsten carbide particles and the binder phase are improved.

[0080] <Intermetallic Compound and First Compound> The cemented carbide of the first embodiment may not include an intermetallic compound (hereinafter also referred to as "first interalloy compound") composed of two or more elements selected from the group consisting of a first element, cobalt, and tungsten, or a first compound composed of at least one element selected from the group consisting of the first element, cobalt, and tungsten and at least one element selected from the group consisting of carbon, nitrogen, and oxygen. Here, the first compound does not include tungsten carbide. This prevents a decrease in the strength of the cemented carbide.

[0081] The first intermetallic compound may be, for example, Co. ２ Si, Co ３ Examples of the material include Si and CoSi.

[0082] The first compound may be, for example, Co ３ W ３ C, Co ６ W ６ C is an example.

[0083] In the present disclosure, the fact that the cemented carbide does not contain either the first intermetallic compound or the first compound is confirmed by structural observation and EDX analysis of a cross section of the cemented carbide.

[0084] <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, a first cooling step, a HIP (hot isostatic pressing) step, and a second cooling step in the above order. Each step will be described below.

[0085] <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 (Co) powder, first element powder, and alloy powder of the first element and cobalt. Examples of the first element powder include silicon (Si) powder, phosphorus (P) powder, germanium (Ge) powder, tin (Sn) powder, rhenium (Re) powder, ruthenium (Ru) powder, osmium (Os) powder, iridium (Ir) powder, and platinum (Pt) powder. Other raw material powders that can be prepared include nickel (Ni) powder, niobium carbide (NbC) powder, tungsten carbide (TaC) powder, and titanium carbonitride (TiCN) powder. 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 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 using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0086] <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.

[0087] 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.

[0088] 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.

[0089] <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.

[0090] <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 embodiment 1 are as follows: The compact is heated to 1360°C at a temperature increase rate of 30°C / min and held at 1360°C for 15 minutes.

[0091] <First Cooling Step> The first cooling step is a step of cooling the cemented carbide intermediate body after the sintering step. Specifically, the cemented carbide intermediate body is cooled to 800° C. The temperature decreasing rate is −20° C. / min.

[0092] <HIP Step> The HIP step is a step of performing HIP treatment on the cemented carbide intermediate body after the first cooling step. The conditions of the HIP step are as follows: The cemented carbide intermediate body is held under conditions of 200 MPa and 1310°C for 15 minutes.

[0093] <Second Cooling Step> The second cooling step is a step of cooling the cemented carbide intermediate body after the HIP step. Specifically, the cemented carbide intermediate body is cooled to 800°C. The temperature drop rate is -30°C / min. Thereafter, the cemented carbide of the first embodiment is obtained by slow cooling. The temperature drop rate during slow cooling may be any general condition and is not particularly limited.

[0094] <Features of the Manufacturing Method of the Cemented Carbide of the First Embodiment> In the manufacturing method of the cemented carbide of the first embodiment, the heating rate in the sintering step is 30°C / min, which is higher than a typical heating rate. Furthermore, the cooling rate in the second cooling step is -30°C / min, which is higher than a typical cooling rate. Under these conditions, the cemented carbide of the first embodiment can be manufactured, in which the binder phase contains 40 mass% or more of cobalt and at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, and the first element does not segregate in the first interface region and the second interface region. The inventors have found, through extensive research, that the cemented carbide of the present disclosure can be realized by adopting such a heating rate in the sintering step and a heating rate in the second cooling step.

[0095] [Embodiment 2: Cutting Tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") includes 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.

[0096] 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 5, 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 5 is made of the cemented carbide of the first embodiment.

[0097] 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.

[0098] 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.

[0099] The cutting tool of the second embodiment can be obtained by forming the cemented carbide of the first embodiment into a desired shape.

[0100] [Supplementary Note 1] In the cemented carbide alloy of the present disclosure, when adjacent tungsten carbide particles are first tungsten carbide particles and second tungsten carbide particles, a first interface is formed between the first tungsten carbide particle and the second tungsten carbide particle, and the first interface region may be composed of a first A region located within 1.2 nm from the first interface toward the first tungsten carbide particle, and a first B region located within 1.2 nm from the first interface toward the second tungsten carbide particle.

[0101] [Supplementary Note 2] In the cemented carbide alloy of the present disclosure, a second interface may be formed between adjacent tungsten carbide particles and a binder phase, and the second interface region may include a first C region located at a distance of 1.2 nm or less from the second interface toward the tungsten carbide particle side, and a first D region located at a distance of 1.2 nm or less from the second interface toward the binder phase side.

[0102] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0103] [Preparation of Cemented Carbide] The cemented carbide samples were prepared according to the following procedure: <Preparation Step> As raw material powders, WC powder (average particle size: 1 μm), Co powder (average particle size: 1 μm), first element powder, Ni powder (average particle size: 1 μm), TiCN powder (average particle size: 1 μm), TaC powder (average particle size: 1 μm), and NbC powder (average particle size: 1 μm) were prepared. As the 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.

[0104] <Mixing Step> A mixed powder was obtained by mixing the raw material powders for 10 hours using an attritor in the proportions shown in Table 1. The proportion (mass %) of each raw material powder shown in Table 1 is the proportion when the total mixed powder is taken as 100 mass %.

[0105]

[0106] <Molding Step> The mixed powder was pressed to obtain a round bar-shaped molded body.

[0107] <Sintering step> The compact was heated to the temperature shown in the "Holding temperature" column at the heating rate shown in the "Heating rate" column of "Sintering step" in Table 2, and held at that temperature for the time shown in the "Holding time" column. This gave a cemented carbide intermediate.

[0108] <First Cooling Step> The cemented carbide intermediate body after the sintering step was cooled to 800°C at the temperature decreasing rate shown in the "Temperature decreasing rate" column of "First cooling step" in Table 2.

[0109]

[0110] <HIP step> The cemented carbide intermediate body after the first cooling step was subjected to HIP treatment. In the HIP treatment, the pressure and the temperature shown in the "Pressure" column and the "Temperature" column of "HIP step" in Table 3 were maintained for the time shown in the "Time" column.

[0111] <Second Cooling Step> The cemented carbide intermediate body after the HIP step was cooled to 800°C at the temperature decreasing rate shown in the "Temperature decreasing rate" column of "Second Cooling Step" in Table 3. Thereafter, the cemented carbide of each sample was obtained by slow cooling.

[0112]

[0113] [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. The specific measurement method is as described in Embodiment 1. The results are shown in the "WC Particle Content" and "Binder Phase Content" columns of "Cemented Carbide" in Table 4. Furthermore, the total content of tungsten carbide particles and binder phase in the cemented carbide is shown in the "WC Particle + Binder Phase Content" column of "Cemented Carbide" in Table 4. In Table 4, it was confirmed that cemented carbides whose "WC Particle + Binder Phase Content" column was less than 100 vol% further contained TiCN, TaC, or NbC.

[0114] <Presence or absence of first intermetallic compound and first compound> The presence or absence of the first intermetallic compound and the first compound in each cemented carbide sample was confirmed by structural observation of the cross section of the cemented carbide and EDX analysis. The results are shown in the "First intermetallic compound / first compound" column of "Cemented carbide" in Table 4. When neither the first intermetallic compound nor the first compound was confirmed, it is recorded as "absent," and when at least one of the first intermetallic compound and the first compound was confirmed, it is recorded as "present."

[0115] <Cobalt Content of Cemented Carbide> The cobalt content of the cemented carbide was measured for each sample of cemented carbide. The specific measurement method is as described in Embodiment 1. The results are shown in the "Co content" column of "Cemented Carbide" in Table 4.

[0116]

[0117] <Cobalt content in binder phase> The cobalt content in the binder phase of each cemented carbide sample was measured. The specific measurement method is as described in embodiment 1. The results are shown in the "Co content" column of "Binder phase" in Table 5.

[0118] <Type of First Element and {M1 / (M1+M2)}×100> In the binder phase of each sample of cemented carbide, the type of first element and the percentage {M1 / (M1+M2)}×100 of the mass of the first element M1 relative to the total mass M1+M2 of the first element M1 and the mass M2 of cobalt were measured. The specific measurement method is as described in embodiment 1. The results are shown in the "First Element" column and the "{M1 / (M1+M2)}×100" column of "Binder Phase" in Table 5. A "-" in the "First Element" column indicates that the sample does not contain the first element.

[0119] <Presence or Absence of Segregation of First Element in First Interface Region and Second Interface Region> The presence or absence of segregation of the first element in the first interface region and the second interface region of each cemented carbide sample was confirmed. The specific confirmation method is as described in Embodiment 1. The results are shown in the "First interface region" and "Second interface region" columns of "Segregation of First Element" in Table 5.

[0120] [Cutting Test] A round bar made of cemented carbide of each sample was machined to prepare a drill for machining printed circuit boards (PCB (Printed Circuit Board) drill) with a cutting diameter of 0.10 mm. Using the PCB drill, holes were drilled into commercially available printed circuit boards for semiconductor packages, and the hole position accuracy was evaluated. The printed circuit board used was composed of two stacked 0.4 mm thick boards. The drilling conditions were a rotation speed of 160 krpm, a feed rate of 2.0 m / min, and a withdrawal rate of 25 m / min. The hole position accuracy (ave + 3σ (μm)) after 8,000 drilling attempts (8,000 hits) was measured. The measurement was performed three times, and the average hole position accuracy of the three attempts was calculated. The results are shown in the "Cutting Test" column in Table 5. A smaller value for hole position accuracy indicates better hole position accuracy of the cutting tool and a longer tool life.

[0121]

[0122] [Discussion] The cemented carbide alloys and cutting tools of Samples 1 to 17 correspond to Examples. The cemented carbide alloys and cutting tools of Samples 101 to 104 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 1 to 17 had better hole position accuracy and longer tool life than the cutting tools of Samples 101 to 104.

[0123] 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 or 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.

[0124] 1 tungsten carbide particle, 2 binder phase, 3 cemented carbide, 4 interface, 10 cutting tool, 11 cutting edge.

Claims

1. A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide comprises a total of 89 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide comprises 1.5 volume % or more and 23 volume % or less of the binder phase, the binder phase comprises 40 mass % or more of cobalt, and the binder phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum, wherein the first element is not segregated in a first interface region between adjacent tungsten carbide particles, and wherein the first element is not segregated in a second interface region between adjacent tungsten carbide particles and the binder phase.

2. The cemented carbide according to claim 1, 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.

3. The cemented carbide according to claim 1 or 2, wherein the cemented carbide does not contain an intermetallic compound consisting of two or more elements selected from the group consisting of the first element, cobalt and tungsten, and a first compound consisting of at least one element selected from the group consisting of the first element, cobalt and tungsten, and at least one element selected from the group consisting of carbon, nitrogen and oxygen, and the first compound does not contain tungsten carbide.

4. A cutting tool having a cutting edge made of the cemented carbide according to any one of claims 1 to 3.

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