Cemented carbide and cutting tool

Abstract

A cemented carbide provided with a plurality of tungsten carbide particles and a binding phase, the cemented carbide containing a total of 89 vol% or more of the tungsten carbide particles and the binding phase, the cemented carbide containing 1.5 vol% or more and 23 vol% or less of the binding phase, the binding phase containing 40 mass% or more of cobalt, 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 first element being not segregated in a first interface region between the tungsten carbide particles adjacent to each other, and being not segregated in a second interface region between the tungsten carbide particles adjacent to each other. In a second interface region between the tungsten carbide particles and the bonding phase adjacent to each other, the first element is not segregated.

Description

Technical Field

[0001] This disclosure relates to cemented carbide and cutting tools. Background Technology

[0002] Previously, cemented carbide containing multiple tungsten carbide particles and a bonding phase was used as a material for cutting tools (Patent Document 1).

[0003] Existing technical documents Patent documents Patent document 1: Japanese Patent Application Publication No. 2004-131769. Summary of the Invention

[0004] The disclosed cemented carbide comprises multiple tungsten carbide particles and a bonding phase, wherein, The cemented carbide comprises a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide comprises 1.5% by volume and 23% by volume of the bonding phase. The bonding phase contains more than 40% by mass of cobalt. The bonding phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. In the first interface region between adjacent tungsten carbide particles, the first element does not segregate, and, In the second interface region between the adjacent tungsten carbide particles and the bound phase, the first element does not segregate. Attached Figure Description

[0005] Figure 1 This is a schematic cross-sectional view of the cemented carbide involved in Embodiment 1.

[0006] Figure 2 This is an example of a first image of the cemented carbide involved in Embodiment 1.

[0007] Figure 3 It is a graph used to illustrate the method of confirming that the first element in the first interface area has no bias, and it represents the first curve.

[0008] Figure 4 This is a graph used to illustrate the method for confirming that the first element in the second interface region has no bias, representing the second curve.

[0009] Figure 5 This is a schematic diagram of the cutting tool involved in Embodiment 2. Detailed Implementation

[0010] [The problem this disclosure aims to solve] In recent years, the machining of materials has become increasingly difficult, and the operating conditions of cutting tools have become more demanding. For example, in printed circuit boards (PCBs), with the expansion of 5G (fifth-generation mobile communication systems) and the continued development of high-capacity information, there is a growing demand for higher heat resistance in PCBs. To improve the heat resistance of PCBs, technologies are being developed to enhance the heat resistance of the resins and glass fillers that constitute the PCBs. On the other hand, this has further exacerbated the difficulty in machining PCBs. Consequently, there is a tendency for cutting tools to wear and break during PCB processing.

[0011] Therefore, the object of this disclosure is to provide a cemented carbide material that enables a long service life of the cutting tool, particularly when used as a material for cutting tools for making openings in printed circuit boards, and a cutting tool incorporating the cemented carbide.

[0012] [Effects of this disclosure] According to this disclosure, a cemented carbide, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, can achieve a long service life for the cutting tool, as well as a cutting tool incorporating the cemented carbide.

[0013] [Description of embodiments of this disclosure] First, embodiments of this disclosure will be described.

[0014] (1) The cemented carbide disclosed herein comprises multiple tungsten carbide particles and a bonding phase, wherein, The cemented carbide comprises a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide comprises 1.5% by volume and 23% by volume of the bonding phase. The bonding phase contains more than 40% by mass of cobalt. The bonding phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. In the first interface region between adjacent tungsten carbide particles, the first element does not segregate, and, In the second interface region between the adjacent tungsten carbide particles and the bound phase, the first element does not segregate.

[0015] According to this disclosure, cemented carbide can be provided, especially when it is used as a material for cutting tools for drilling holes in printed circuit boards, to achieve a long service life for cutting tools.

[0016] (2) In (1) above, it is also possible that the percentage of the mass M1 of the first element relative to the total mass M1+M2 of the first element and the mass M2 of cobalt, {M1 / (M1+M2)}×100, in the bonding phase is 1% or more and 6% or less. Here, the units of mass M1 and mass M2 are the same. As a result, it is possible to provide a cemented carbide that can extend the tool life of cutting tools.

[0017] (3) In either (1) or (2) above, it could also be that... The cemented carbide does not contain: An intermetallic compound composed 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.

[0018] Here, the first compound does not contain tungsten carbide.

[0019] This helps to suppress the reduction in the strength of cemented carbide.

[0020] (4) The cutting tool disclosed herein is a cutting tool having a cutting tip made of cemented carbide as described in any one of (1) to (3) above.

[0021] Therefore, it is possible to provide cutting tools with long tool life, especially in the case of drilling holes in printed circuit boards.

[0022] [Details of the embodiments disclosed herein] Specific examples of the cemented carbide and cutting tools of this disclosure will be described below with reference to the accompanying drawings. In the drawings of this disclosure, the same reference numerals denote the same or equivalent parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplicity in the drawings and do not necessarily represent actual dimensional relationships.

[0023] In this disclosure, the expression "A~B" refers to the upper and lower limits of the range (i.e., above A and below B). If there is no unit recorded in A, but only in B, the unit of A is the same as the unit of B.

[0024] In this disclosure, when compounds are represented by chemical formulas, the atomic ratio is not limited to any particular range unless otherwise specified. All previously known atomic ratios are included.

[0025] In this disclosure, when one or more values ​​are recorded as the lower limit and upper limit of the numerical range, combinations of any value recorded as the lower limit and any value recorded as the upper limit are also disclosed. For example, when a1 and above, b1 and above, and c1 and above are recorded as the lower limit, and a2 and below, b2 and below, and c2 and below are recorded as the upper limit, the following combinations are disclosed: a1 and below, a1 and below, a1 and below, a1 and below, c1 and below, b1 and below, b1 and below, b1 and below, b1 and below, c1 and below, c1 and below, c1 and below, c1 and below, c1 and below, c1 and below, c2 and below.

[0026] [Implementation Method 1: Hard Alloy] use Figure 1 The cemented carbide involved in one embodiment of the present disclosure will be described.

[0027] One embodiment of this disclosure (hereinafter also referred to as "Embodiment 1") involves a cemented carbide 3 comprising a plurality of tungsten carbide particles 1 and a bonding phase 2, wherein, The cemented carbide 3 contains a total of more than 89% by volume tungsten carbide particles 1 and a bonding phase 2. The cemented carbide 3 contains more than 1.5% by volume and less than 23% by volume of the bonding phase 2. Phase 2 contains more than 40% by mass of cobalt. 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. In the first interface region between adjacent tungsten carbide particles 1, the first element does not segregate, and, In the second interface region between adjacent tungsten carbide particles 1 and the bound phase 2, the first element does not segregate.

[0028] The cemented carbide of Embodiment 1 provides a cemented carbide that can achieve a long life of cutting tools, especially when used as a material for cutting tools for drilling holes in printed circuit boards, as well as a cutting tool equipped with the cemented carbide. The reason for this is not clear, but it is speculated as follows.

[0029] The cemented carbide of Embodiment 1 comprises multiple tungsten carbide particles (hereinafter also referred to as "WC particles") and a bonding phase, wherein the total content of the WC particles and the bonding phase in the cemented carbide is 89% by volume or more. Therefore, the cemented carbide exhibits high hardness and strength, and cutting tools made from this cemented carbide possess excellent wear resistance and breakage resistance.

[0030] The cemented carbide of Embodiment 1 contains 1.5% by volume and 23% by volume of a binding phase, wherein the binding phase contains 40% by mass and 40% by mass of cobalt. Therefore, the cemented carbide exhibits high hardness and strength, and cutting tools made from this cemented carbide possess excellent wear resistance and breakage resistance.

[0031] In the cemented carbide of Embodiment 1, the bonding phase comprises 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 also does not segregate in the second interface region between adjacent tungsten carbide particles and the bonding phase. Therefore, the interfacial strength between tungsten carbide particles and the interfacial strength between tungsten carbide particles and the bonding phase are further improved in the cemented carbide, suppressing the shedding of tungsten carbide particles during machining. Thus, 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.

[0032] <Composition of cemented carbide> The cemented carbide of Embodiment 1 comprises 89% by volume or more tungsten carbide particles and a bonding phase. This increases the hardness of the cemented carbide. The cemented carbide may comprise 89% by volume or more and 100% by volume or less tungsten carbide particles and a bonding phase, may comprise 90% by volume or more and 100% by volume or less tungsten carbide particles and a bonding phase, may comprise 91% by volume or more and 100% by volume or less tungsten carbide particles and a bonding phase, or may comprise 92% by volume or more and 100% by volume or less tungsten carbide particles and a bonding phase.

[0033] The cemented carbide of Embodiment 1 contains 1.5 vol% or more and 23 vol% or less of a bonding phase. This improves the hardness and toughness of the cemented carbide. The content of the bonding phase in the cemented carbide can be 2.0 vol% or more and 19.0 vol% or less, 3.0 vol% or more and 18.0 vol% or less, or 4.0 vol% or more and 17.0 vol% or less.

[0034] The cemented carbide of Embodiment 1 can be composed of multiple tungsten carbide particles and a bonding phase. In this case, the cemented carbide can contain impurities without impairing the effects of this disclosure.

[0035] Hard alloys can contain other phases (not shown) in addition to tungsten carbide particles and a bonding phase. Examples of other phases 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). Other phase compositions may also include, for example, at least one element selected from the group consisting of TiCN, TaC, NbC, ZrC, HfC, and Mo2C.

[0036] The cemented carbide of Embodiment 1 can be composed of tungsten carbide particles, a bonding phase, and other phases. In this case, the cemented carbide can contain impurities without impairing the effects of this disclosure.

[0037] The content of other phases in cemented carbide is permitted to the extent that it does not impair the effects of this disclosure. For example, the content of other phases in cemented carbide may be more than 0 vol% and less than 11 vol%, more than 0 vol% and less than 7 vol%, or more than 0 vol% and less than 4 vol%.

[0038] The cemented carbide of Embodiment 1 can contain impurities. Examples of impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the cemented carbide is permitted within a range that does not impair the effects of this disclosure. For example, the impurity content of the cemented carbide can be 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide is determined by ICP (Inductively Coupled Plasma Emission Spectroscopy). The measuring apparatus can be the "ICPS-8100" (trademark) manufactured by Shimadzu Corporation.

[0039] The content of tungsten carbide particles in the cemented carbide of Embodiment 1 can be 67% or more and 98.5% or less by volume, 70% or more and 97% or less by volume, or 75% or more and 96% or less by volume.

[0040] The methods for determining the content (volume%) of tungsten carbide particles and the content (volume%) of the bonding phase in cemented carbide are as follows.

[0041] (A1) Cut at any point on the cemented carbide to expose the cross-section. Perform mirror finishing on the cross-section using a cross-section polishing machine (manufactured by Nippon Egis Corporation).

[0042] (B1) The mirror-finished surface of the cemented carbide was analyzed using an energy-dispersive X-ray spectrometer (SEM-EDX) attached to a scanning electron microscope (device: Gemini 450 (trademark) manufactured by Carl Zeiss) to determine the elements contained in the cemented carbide.

[0043] (C1) Reflected electron images were obtained by scanning electron microscopy (SEM) of the mirror-finished surface of cemented carbide. The imaging area was set to the central part of the cross-section excluding the cemented carbide, i.e., the area near the surface of the cemented carbide, where the properties are significantly different from the bulk part (the imaging area consists entirely of the bulk part of the cemented carbide). The magnification was 5000x. The measurement conditions were: accelerating voltage 3kV, current 2nA, and working distance (WD) 5mm.

[0044] (D1) Use SEM-EDX to analyze the shooting area in (C1) above, determine the distribution of the elements in the shooting area determined by (B1) above, and obtain the element mapping image.

[0045] (E1) The reflected electron image obtained through (C1) above is imported into a computer and binarized using image analysis software (OpenCV, SciPy). In the binarized image, white represents tungsten carbide particles, and gray to black represent the bound phase. Furthermore, since the binarization threshold varies depending on the contrast, it is set for each image.

[0046] (F1) The elemental mapping image obtained by (D1) above is overlaid with the binarized image obtained by (E1) above, thereby determining the respective regions where tungsten carbide particles and the bonding phase exist on the binarized image. Specifically, the regions represented in white in the binarized image and containing tungsten (W) and carbon (C) in the elemental mapping image correspond to the regions where tungsten carbide particles exist. The regions represented in gray to black in the binarized image and containing cobalt (Co) in the elemental mapping image correspond to the regions where the bonding phase exists.

[0047] (G1) In the image after binarization, a rectangular measurement field of view of 24.9 μm × 18.8 μm is set. Using the image analysis software described above, the area percentage of each tungsten carbide particle and the bound phase is determined with the total area of ​​the measurement field of view as the denominator.

[0048] (H1) The above (G1) determination is performed in five distinct measurement fields. In this disclosure, the average area percentage of tungsten carbide particles in the five measurement fields corresponds to the content (volume %) of tungsten carbide particles in cemented carbide, and the average area percentage of the bound phase in the five measurement fields corresponds to the content (volume %) of the bound phase in cemented carbide.

[0049] When cemented carbide contains other phases in addition to WC particles and the bonding phase, the content of other phases in the cemented carbide can be obtained by subtracting the content of tungsten carbide particles (volume%) and the content of the bonding phase (volume%) determined by the above steps from the total cemented carbide (100 vol%).

[0050] It was confirmed that as long as the measurement is performed on the same sample, even if the cutting part of the cemented carbide section, the shooting 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 content of the bonding phase of the cemented carbide are measured multiple times following the above steps, there is almost no deviation in the measurement results.

[0051] The cobalt content of the cemented carbide in Embodiment 1 may be 1.0% by mass or more and 20% by mass or less, 2.0% by mass or more and 15% by mass or less, or 3.0% by mass or more and 12% by mass or less.

[0052] The method for determining the cobalt content in cemented carbide is as follows. Elemental mapping images are obtained by SEM-EDX analysis using the same methods (A1) to (D1) as those used in the methods for determining the content of tungsten carbide particles and the content of the bound phase in cemented carbide described above. Based on the elemental mapping images, regions of cobalt in the cemented carbide are identified, and the cobalt content is determined. This determination is performed in five distinct imaging regions. In this disclosure, the average cobalt content in the five imaging regions corresponds to the cobalt content of the cemented carbide.

[0053] It was confirmed that as long as the measurement is performed on the same sample, even if the cutting part of the cross section of the cemented carbide is arbitrarily set, the shooting area described in (C1) above is used, and the cobalt content of the cemented carbide is measured multiple times following the above steps, there is almost no deviation in the measurement results.

[0054] <Tungsten carbide particles> In the cemented carbide of Embodiment 1, the tungsten carbide particles comprise at least one of "pure WC particles (including WC free of all impurity elements, or WC with impurity element content below the detection limit)" and "WC particles that intentionally or unavoidably contain impurity elements therein, provided that the effects of this disclosure are not impaired." The impurity content of the tungsten carbide particles (the total concentration of the impurity elements if there are two or more) is less than 0.1% by mass. The impurity element content of the tungsten carbide particles is determined by ICP-luminescence analysis.

[0055] In Embodiment 1, there is no particular limitation on the average particle size of the tungsten carbide particles. For example, the average particle size of the tungsten carbide particles can be set to 0.1 μm or more and 3.5 μm or less. It has been confirmed that the cemented carbide of Embodiment 1 is independent of the average particle size of the tungsten carbide particles, and a long tool life can be achieved even when it is used as a material for cutting tools.

[0056] <Binding Phase> In the cemented carbide of Embodiment 1, the bonding phase contains 40% or more cobalt. Therefore, the cemented carbide exhibits excellent toughness. The cobalt content in the bonding phase can be 40% or more and less than 100% by mass, 50% or more and less than 90% by mass, or 60% or more and less than 80% by mass.

[0057] The method for determining the cobalt content of the bound phase is as follows. An elemental mapping image and a binarized image are obtained using the same method (A1) to (E1) as described in the method for determining the content of tungsten carbide particles and the bound phase in cemented carbide. The region where the bound phase exists is determined in the elemental mapping image by overlaying the elemental mapping image and the binarized image. A measurement field of view of 24.9 μm × 18.8 μm rectangle is set in the elemental mapping image. The cobalt content is measured in the region where the bound phase exists within the measurement field of view. The above measurement is performed in five distinct measurement fields. In this disclosure, the average cobalt content in the region where the bound phase exists in the five measurement fields corresponds to the cobalt content of the bound phase.

[0058] It was confirmed that as long as the measurement is performed on the same sample, even if the cutting part of the cross section of the cemented carbide, the shooting area described in (C1) above, and the measurement field of view above are arbitrarily set, and the cobalt content of the bound phase is measured multiple times following the above steps, there is almost no deviation in the measurement results.

[0059] In the cemented carbide of Embodiment 1, the bonding phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium and platinum.

[0060] The presence of the first element in the bonding phase was confirmed by the following steps. An elemental mapping image and a binarized image were obtained using the same methods (A1) to (E1) as described above for determining the content of tungsten carbide particles and the content of the bonding phase in cemented carbide. The region where the bonding phase exists was determined in the elemental mapping image by overlaying the elemental mapping image with the binarized image. It was confirmed that if the first element is present in the region where the bonding phase exists in the elemental mapping, then the bonding phase contains the first element.

[0061] In the cemented carbide bonding phase 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 mass M2 of cobalt, {M1 / (M1+M2)}×100, can be 1% or more and 6% or less. Here, the units of mass M1 and mass M2 are the same. Therefore, since the bonding phase can possess both superior hardness and superior toughness, cutting tools equipped with cemented carbide containing this bonding phase can have a longer tool life. Here, when the bonding phase contains two or more 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 can be 2% or more and 5% or less, or 3% or more and 4% or less.

[0062] The method for determining the percentage {M1 / (M1+M2)}×100 is as follows. Using the same method (A1)~(E1) as described above for determining the content of tungsten carbide particles and the content of the bound phase in cemented carbide, an elemental mapping image and a binarized image are obtained. The region where the bound phase exists is determined in the elemental mapping image by overlaying the elemental mapping image and the binarized image. A measurement field of view of a rectangle measuring 24.9 μm × 18.8 μm is set in the elemental mapping image. In the region where the bound phase exists in the measurement field of view, the percentage {m1 / (m1+m2)}×100 of the total m1+m2 of the mass m1 of the first element and the mass m2 of cobalt is calculated in the region where the bound phase exists. The above determination is performed in five distinct measurement fields. In this disclosure, the average of the percentages {m1 / (m1+m2)}×100 in the five measurement fields corresponds to the percentages {M1 / (M1+M2)}×100 in the bonding phase of the cemented carbide.

[0063] It was confirmed that as long as the measurement is performed on the same sample, even if the cutting part of the cross section of the cemented carbide, the shooting area described in (C1) above, and the measurement field of view above are arbitrarily set, and the percentage measurement {M1 / (M1+M2)}×100 is performed multiple times following the above steps, there is almost no deviation in the measurement results.

[0064] In the cemented carbide of Embodiment 1, the bonding phase may include at least one second element selected from the group consisting of iron (Fe), nickel (Ni), and chromium (Cr), in addition to cobalt and the first element. The bonding phase may consist of cobalt, the first element, and the second element. Alternatively, the bonding phase may consist of cobalt, the first element, the second element, and unavoidable impurities. Examples of unavoidable impurities include iron (Fe), nickel (Ni), and sulfur (S).

[0065] <First interface area and second interface area> In the cemented carbide of Embodiment 1, the first element does not segregate in the first interface region between adjacent tungsten carbide particles, and also does not segregate in the second interface region between adjacent tungsten carbide particles and the bonding phase. As a result, the interfacial strength between tungsten carbide particles and the interfacial strength between tungsten carbide particles and the bonding phase are improved, thus enhancing the wear resistance and breakage resistance of the cemented carbide.

[0066] In this disclosure, the use Figure 2 as well as Figure 3 A method for confirming that there is no segregation of the first element in the first interface region between adjacent tungsten carbide particles in cemented carbide is described.

[0067] (A2) Using an argon ion slicer (Cryo Ion Slicer IB-09060BCIS, a trademark manufactured by JEOL Ltd.), cemented carbide sheets were sliced ​​to a thickness of 30-100 nm to prepare a test sample. The test sample was observed at 200,000x magnification using a TEM (Transmission Electron Microscopy) (JEM-ARM300F2, a trademark manufactured by JEOL Ltd.), with an accelerating voltage of 200V, thereby obtaining a first image. An example of the first image is shown below. Figure 2 .

[0068] (B2) In the first image, tungsten carbide particles 1 are observed as white to gray areas, the bonding phase 2 is observed as a black area, and the interface 4 between adjacent tungsten carbide particles 1 is observed as a black area. In the first image, the width of the interface 4 is, for example, 2 nm or less. In the first image, the interface between adjacent tungsten carbide particles is arbitrarily selected. Hereinafter, in this disclosure, adjacent tungsten carbide particles are also referred to as first tungsten carbide particles and second tungsten carbide particles.

[0069] (C2) Next, the selected interface is positioned near the center of the image, and the magnification is adjusted to make the field of view size 5nm × 5nm for observation, thereby obtaining a second image. In the second image, the elongation direction of the interface is identified. Linear analysis is performed using an energy-dispersive X-ray analyzer (TEM-EDX) attached to the TEM in a direction perpendicular to this elongation direction and from the first tungsten carbide particle toward the second tungsten carbide particle, obtaining a curve (hereinafter also referred to as the first curve) that measures the distribution of cobalt, tungsten, and the first element. In the case where the cemented carbide contains two or more first elements, the distribution of each element is measured. Here, the direction perpendicular to the elongation direction of the interface refers to the direction of a straight line that intersects the tangent to the elongation direction at an angle of 90° ± 5°. For example, in Figure 2 In the diagram, the arrow indicates a direction perpendicular to the elongation direction of the interface. The measurement conditions for acquiring the second image were: accelerating voltage 200kV, camera length 10cm, pixel count 128×128 pixels, and dwell time 0.02~3s / pixel.

[0070] Figure 3 This is an example of the first curve graph. In Figure 3 In the diagram, the horizontal axis (X-axis) represents the distance (nm) from the starting point of the measurement, and the vertical axis (Y-axis) represents the content of each element (atomic %). Figure 3 In the cemented carbide shown, the first element is silicon (Si).

[0071] (D2) In the first graph, the peak position of cobalt is determined. In this disclosure, the peak position of cobalt is denoted as the first interface. The first interface is formed between adjacent first and second tungsten carbide particles. Figure 3 In the first curve plot, the first interface is located at 5.98nm on the X-axis.

[0072] In the first graph, a first region A is defined as being within 1.20 nm from the first interface towards the first tungsten carbide particle side, and a first region B is defined as being within 1.20 nm from the first interface towards the second tungsten carbide particle side. In this disclosure, the region formed by regions 1A and 1B is the first interface region. Figure 3 In the first curve diagram, the first interface region is located in the region of 4.78~7.18 nm on the X-axis. In this disclosure, the first interface region between adjacent tungsten carbide particles can also be described as the first interface region between adjacent tungsten carbide particles.

[0073] In the first curve diagram, region 2A, located at a distance of 1.50 nm or more and 3.50 nm or less from the first interface toward the first tungsten carbide particle side, and region 2B, located at a distance of 1.50 nm or more and 3.50 nm or less from the first interface toward the second tungsten carbide particle side, are defined. Figure 3 In the first curve, region 2A is located in the region of 2.48~4.48nm on the X-axis, and region 2B is located in the region of 7.48~9.48nm on the X-axis.

[0074] (E2) Based on the first curve, calculate the average B (atomic %) of the content of the first element in the baseline region formed by region 2A and region 2B. In the first curve, determine the maximum value A (atomic %) of the content of the first element in the first interface region. It was confirmed that when the ratio A / B of the maximum value A to the average B is less than 3, there is no segregation of the first element in the first interface region between adjacent tungsten carbide particles of the cemented carbide.

[0075] exist Figure 3 In the first curve plot, the average content of silicon (the first element) in the baseline region formed by regions 2A and 2B is 7.68 atoms (B), and the maximum content of silicon (the first element) in the first interface region is 6.75 atoms (A). The following was confirmed: In Figure 3 In the cemented carbide shown, since A / B is 0.9, the first element does not segregate in the first interface region between adjacent tungsten carbide particles in the cemented carbide.

[0076] (F2) In cemented carbide, five unique first images are obtained, and a first curve is obtained based on each first image. The above analysis is repeatedly performed. If the segregation of the first element is not confirmed in the first interface region in four or more first curves, it is determined that the first element is not segregated in the first interface region between adjacent tungsten carbide particles in the cemented carbide.

[0077] In this disclosure, the use Figure 4 A method for confirming that there is no segregation of the first element in the second interface region between adjacent tungsten carbide particles and the bound phase is described.

[0078] (A3) In the first interface region described above, a first image is obtained by the same method as (A2) described in the confirmation method for the absence of segregation of the first element. In the first image, the interface between adjacent tungsten carbide particles and the bound phase is arbitrarily selected.

[0079] (B3) Next, the selected interface is positioned near the center of the image, and the magnification is adjusted to obtain a field of view of 5 nm × 5 nm, thus obtaining a third image. In the third image, the elongation direction of the interface is confirmed. Linear analysis is performed by TEM-EDX in the direction perpendicular to this elongation direction and from the tungsten carbide particles toward the bonding phase to obtain a curve (hereinafter also referred to as the second curve) that measures the distribution of cobalt, tungsten, and the first element. In the case where the cemented carbide contains two or more first elements, the distribution of each element is measured. Here, the direction perpendicular to the elongation direction of the interface refers to the direction of a straight line that intersects the tangent to the elongation direction at an angle of 90° ± 5°. The measurement conditions for obtaining the third image were: accelerating voltage 200 kV, camera length 10 cm, pixel count 128 × 128 pixels, and dwell time 0.02~3 s / pixel.

[0080] Figure 4 This is an example of the second curve. In Figure 4 In the diagram, the horizontal axis (X-axis) represents the distance (nm) from the starting point of the measurement, and the vertical axis (Y-axis) represents the content of each element (atomic %). Figure 4 In the cemented carbide shown, the first element is silicon (Si).

[0081] In the second graph, the intersection of the tungsten and cobalt contents is determined. In this disclosure, the intersection of the tungsten and cobalt contents is denoted as the second interface. The second interface forms between adjacent tungsten carbide particles and the bonding phase. Figure 4 In the second curve, the second interface is located at 5.97 nm on the X-axis.

[0082] In the second curve diagram, a first C region with a distance of less than 1.20 nm from the second interface toward the tungsten carbide particle side and a first D region with a distance of less than 1.20 nm from the second interface toward the bonding phase side are defined. In this disclosure, the region formed by the first C region and the first D region is the second interface region. Figure 4 In the second curve diagram, the second interface region is located in the region of 4.76~7.16 nm on the X-axis. In this disclosure, the second interface region between adjacent tungsten carbide particles and the bonding phase can also be described as the second interface region located between adjacent tungsten carbide particles and the bonding phase.

[0083] In the second curve diagram, the second C region, with a distance of 1.50 nm or more and 3.50 nm or less from the second interface toward the tungsten particle side, and the second D region, with a distance of 1.50 nm or more and 3.50 nm or less from the second interface toward the bonding phase side, are defined. Figure 4In the second curve, region 2C is located in the region of 2.46~4.46nm on the X-axis, and region 2D is located in the region of 7.46~9.46nm on the X-axis.

[0084] Based on the second curve, the average D (atomic %) of the first element content in the baseline region formed by region 2C and region 2D was calculated. The maximum C (atomic %) of the first element content in the second interface region was determined in the second curve. It was confirmed that when the ratio C / D of the maximum C to the average D is less than 3, there is no segregation of the first element in the second interface region between adjacent tungsten carbide particles and the bonding phase in the cemented carbide.

[0085] (C3) In cemented carbide, five unique first images are obtained, and the above analysis is repeatedly performed based on the second curve obtained from each first image. If the segregation of the first element is not confirmed in the second interface region in four or more second curves, it is determined that the first element is not segregated in the second interface region between the adjacent tungsten carbide particles and the bonding phase in the cemented carbide.

[0086] It was confirmed that, as long as the measurement is performed on the same sample, even if the cut location of the cemented carbide section is arbitrarily set, the first image is arbitrarily obtained on that section, and the presence or absence of segregation of the first element in the first interface region and the second interface region is repeatedly confirmed by changing the linear analysis area according to the above steps, there is almost no deviation 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 it is confirmed that the above method for confirming the segregation of the first element in cemented carbide does not result in segregation of the first element in the first interface region and the second interface region, it is presumed that the interfacial strength between the tungsten carbide particles and the interfacial strength between the tungsten carbide particles and the bonding phase of the cemented carbide are improved.

[0087] <Intermetallic Compounds and First Compounds> The cemented carbide of Embodiment 1 may also not contain an intermetallic compound (hereinafter also referred to as "first intermetallic 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 a 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 contain tungsten carbide. This suppresses the reduction in the strength of the cemented carbide.

[0088] Examples of first intermetallic compounds include Co2Si, Co3Si, and CoSi.

[0089] Examples of first compounds include, for example, Co3W3C and Co6W6C.

[0090] In this disclosure, microstructure observation of the cross-section of the cemented carbide and EDX analysis confirmed that the cemented carbide does not contain the first intermetallic compound or any of the first compounds.

[0091] <Manufacturing Methods of Hard Alloys> The cemented carbide of Embodiment 1 can be manufactured by performing the following steps in the order described above: raw material powder preparation, mixing, molding, sintering, first cooling, HIP (Hot Isostatic Pressing) and second cooling. Each step will be described below.

[0092] <Preparation Process> The preparation process involves preparing the raw material powder for cemented carbide. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder, first element powder, and alloy powders of the first element and cobalt. Examples of first element powders 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. Further raw material powders can be prepared such as nickel (Ni) powder, niobium carbide (NbC) powder, tungsten carbide (TaC) powder, and titanium carbonitride (TiCN) powder. Commercially available raw material powders can be used. There are no particular limitations on the average particle size of these raw material powders; for example, it can be set to 0.5~5 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 was determined using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0093] <Mixed Process> The mixing process is a process of mixing the raw material powders prepared in the preparation process in a predetermined ratio. Through the mixing process, a mixed powder containing the raw material powders is obtained. The mixing ratio of the raw material powders can be appropriately adjusted according to the composition of the target cemented carbide.

[0094] In mixing the various raw material powders, conventionally known mixing methods such as grinding mills, ball mills, and bead mills can be used. Conventionally known conditions can also be used for mixing. The mixing time can be set, for example, to be more than 2 hours and less than 20 hours.

[0095] After the mixing process, the mixed powder can be granulated as needed. Granulation of the mixed powder facilitates filling the die or mold during the forming process described later. For granulation, known granulation methods can be used; for example, commercially available granulators such as spray dryers can be employed.

[0096] <Forming Process> The forming process is the process of shaping the mixed powder obtained through the mixing process into a shape suitable for cutting tools to obtain a molded body. The forming methods and conditions in the forming process can use general methods and conditions, without special restrictions.

[0097] <Sintering Process> The sintering process is a process of sintering the shaped body obtained through the forming process to obtain a cemented carbide intermediate. The sintering conditions in Embodiment 1 are as follows: The shaped body is heated to 1360°C at a heating rate of 30°C / min and held at 1360°C for 15 minutes.

[0098] <First Cooling Process> The first cooling process is to cool the cemented carbide intermediate after the sintering process. Specifically, the cemented carbide intermediate is cooled to 800°C. The cooling rate is -20°C / minute.

[0099] <HIP process> The HIP process is a process for treating the cemented carbide intermediate after the first cooling process. The conditions for the HIP process are as follows: The cemented carbide intermediate is held at 200 MPa and 1310°C for 15 minutes.

[0100] <Second Cooling Process> The second cooling step is to cool the cemented carbide intermediate after the HIP process. Specifically, the cemented carbide intermediate is cooled to 800°C. The cooling rate is -30°C / minute. After that, the cemented carbide of Embodiment 1 can be obtained by slow cooling. The cooling rate during slow cooling can be set under general conditions and is not particularly limited.

[0101] <Features of the cemented carbide manufacturing method of Embodiment 1> In the cemented carbide manufacturing method of Embodiment 1, the heating rate in the sintering process is 30°C / min, which is higher than the general heating rate. Furthermore, the cooling rate in the second cooling process is -30°C / min, which is higher than the general cooling rate. Under these conditions, it is possible to manufacture the cemented carbide of Embodiment 1, in which the bonding phase contains at least 40% by mass of cobalt, and contains 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 fact that the cemented carbide of this disclosure can be achieved by employing such heating rates in the sintering process and cooling rates in the second cooling process is a result of the inventors' in-depth research.

[0102] [Implementation Method 2: Cutting Tool] One embodiment of this disclosure (hereinafter also referred to as "Embodiment 2") includes a cutting tool comprising a cutting tip made of cemented carbide as in Embodiment 1. In this disclosure, the cutting tip refers to the portion involved in cutting. More specifically, the cutting tip refers to the area enclosed by a cutting tip ridge and an imaginary surface extending 0.5 mm or 2 mm from that cutting tip ridge towards the cemented carbide side.

[0103] Examples of cutting tools include cutting tools, drills, end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metalworking saws, gear cutting tools, reamers, or taps. In particular, such as Figure 5 As shown, the cutting tool 10 of Embodiment 2 can perform excellently when used as a small-diameter drill bit for processing printed circuit boards. Figure 5 The cutting tool 10 shown has a cutting tip 11 made of cemented carbide as described in Embodiment 1.

[0104] In the cutting tool of Embodiment 2, the cemented carbide of Embodiment 1 can form the entire tool or a part of it. Here, "forms a part" means, for example, brazing the cemented carbide of Embodiment 1 to a predetermined position on any substrate to form the tool tip.

[0105] The cutting tool of embodiment 2 may also include a hard film covering at least a portion of the surface of a substrate made of cemented carbide. For example, diamond-like carbon or diamond can be used as the hard film.

[0106] The cutting tool of Embodiment 2 can shape the cemented carbide of Embodiment 1 into the desired shape.

[0107] [Appendix 1] In the cemented carbide disclosed herein, when adjacent tungsten carbide particles are first tungsten carbide particles and second tungsten carbide particles, a first interface may be formed between the first tungsten carbide particles and the second tungsten carbide particles. The first interface region is composed of a first A region within 1.2 nm from the first interface toward the first tungsten carbide particle side and a first B region within 1.2 nm from the first interface toward the second tungsten carbide particle side.

[0108] [Appendix 2] In the cemented carbide disclosed herein, a second interface may also be formed between adjacent tungsten carbide particles and the bonding phase. The second interface region consists of a first C region extending within 1.2 nm from the second interface toward the tungsten carbide particle side and a first D region extending within 1.2 nm from the second interface toward the bonding phase side.

[0109] Example This embodiment will be further described in detail through examples. However, this embodiment is not limited to these examples.

[0110] [The production of cemented carbide] The cemented carbide samples were fabricated using the following steps.

[0111] <Preparation Process> 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 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.

[0112] <Mixed Process> The raw material powders were mixed in a grinder for 10 hours according to the proportions shown in Table 1 to obtain a mixed powder. The proportions (mass%) of the raw material powders shown in Table 1 are based on the condition that the total mass of the mixed powder is 100%.

[0113]

[0114] <Forming Process> By stamping the mixed powder, a cylindrical shaped body was obtained.

[0115] <Sintering Process> The molded body is heated to the temperature recorded in the "Holding Temperature" column at the heating rate recorded in the "Sintering Process" column of Table 2, and held at that temperature for the time recorded in the "Holding Time" column. Thus, a cemented carbide intermediate is obtained.

[0116] <First Cooling Process> The cemented carbide intermediate after the sintering process was cooled to 800°C at the cooling rate recorded in the "Cooling Rate" column of the "First Cooling Process" in Table 2.

[0117]

[0118] <HIP process> The cemented carbide intermediate after the first cooling process was subjected to HIP treatment. During the HIP treatment, the pressure recorded in the "Pressure" column and the temperature recorded in the "Temperature" column of "HIP Process" in Table 3 were maintained for the time recorded in the "Time" column.

[0119] <Second Cooling Process> The cemented carbide intermediate after the HIP process was cooled to 800°C at the cooling rate specified in the "Cooling Rate" column of the "Second Cooling Process" in Table 3. Afterwards, it was slowly cooled to obtain the cemented carbide for each sample.

[0120]

[0121] [Evaluation of cemented carbide] <Content (volume %) of tungsten carbide particles and content (volume %) of the bonding phase in cemented carbide> The content (volume %) of tungsten carbide particles and the content (volume %) of the bonding phase in the cemented carbide of each sample were determined. The specific determination method is as described in Embodiment 1. The results are shown in the "WC Particle Content" and "Bonding Phase Content" columns of "Cemented Carbide" in Table 4. Furthermore, the total content of tungsten carbide particles and the content of the bonding phase in the cemented carbide are shown in the "WC Particle + Bonding Phase Content" column of "Cemented Carbide" in Table 4. In Table 4, it was confirmed that cemented carbide with a "WC Particle + Bonding Phase Content" column of less than 100% by volume also contains TiCN, TaC, or NbC.

[0122] <The first intermetallic compound and the presence or absence of the first compound> In the cemented carbide samples, the presence or absence of the first intermetallic compound and the first compound was confirmed by microstructural 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. "None" was recorded when neither the first intermetallic compound nor either the first compound was confirmed, and "Present" was recorded when at least one of the first intermetallic compound and the first compound was confirmed.

[0123] <Cobalt content in cemented carbide> The cobalt content of the cemented carbide in each sample was determined. The specific determination method is as described in Example 1. The results are shown in the "Co Content" column of "Cemented Carbide" in Table 4.

[0124]

[0125] <Cobalt content in the bound phase> The cobalt content of the bonding phase was determined in the cemented carbide samples. The specific determination method is as described in Example 1. The results are shown in the "Co Content" column of "Bonding Phase" in Table 5.

[0126] <The types of the first element and {M1 / (M1+M2)}×100> The type of the first element and the percentage of the mass M1 of the first element relative to the total mass M1 of the first element and the mass M2 of cobalt, M1 + M2, were determined in the cemented carbide bonding phase of each sample, denoted as {M1 / (M1+M2)} × 100. The specific determination method is as described in Embodiment 1. The results are shown in the "First Element" column and the "{M1 / (M1+M2)} × 100" column under "Binding Phase" in Table 5. A "-" in the "First Element" column indicates that the sample does not contain the first element.

[0127] <The presence or absence of bias in the first element of the first interface area and the second interface area> In the cemented carbide samples, the presence or absence of segregation of the first element in the first interface region and the second interface region 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 the First Element" in Table 5.

[0128] [Cutting Test] A 0.10 mm diameter drill bit for PCB (Printed Circuit Board) machining was fabricated by machining round bars made of cemented carbide from each sample. Using the PCB drill bit, hole-making was performed on commercially available semiconductor packaging PCBs, and the hole position accuracy was evaluated. The PCB used was a PCB formed by overlapping two 0.4 mm thick substrates. The hole-making conditions were set as follows: rotational speed 160 rpm, feed rate 2.0 m / min, and pull-out speed 25 m / min. The hole position accuracy (ave + 3σ (μm)) was measured after 8000 holes (8000 hits). The measurement was performed three times, and the average hole position accuracy was calculated. The results are shown in the "Cutting Test" column of Table 5. A smaller hole position accuracy value indicates better hole position accuracy and longer tool life.

[0129]

[0130] [Inspection] The carbide and cutting tools of specimens 1 to 17 correspond to the examples. The carbide and cutting tools of specimens 101 to 104 correspond to the comparative examples. It was confirmed that, compared with the cutting tools of specimens 101 to 104, the cutting tools of specimens 1 to 17 have excellent hole position accuracy and long tool life.

[0131] The embodiments and examples of this disclosure have been described above. However, it is also intended from the outset that the above embodiments and examples may be appropriately combined or modified.

[0132] The embodiments and examples disclosed herein should be considered exemplary in all respects, and not restrictive. The scope of the invention is defined not by the foregoing embodiments and examples, but by the claims, and is intended to include all modifications equivalent to and within the scope of the claims.

[0133] Explanation of reference numerals in the attached figures: 1: Tungsten carbide particles; 2: Binding phase; 3: Cemented carbide; 4: Interface; 10: Cutting tool; 11: Tool tip.

Claims

1. A cemented carbide comprising multiple tungsten carbide particles and a bonding phase, wherein, The cemented carbide comprises a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide comprises 1.5% by volume and 23% by volume of the bonding phase. The bonding phase contains more than 40% by mass of cobalt. The bonding phase further comprises at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. In the first interface region between adjacent tungsten carbide particles, the first element does not segregate, and, In the second interface region between the adjacent tungsten carbide particles and the bound phase, the first element does not segregate.

2. The cemented carbide according to claim 1, wherein, In the combined phase, the percentage of the mass M1 of the first element relative to the total mass M1+M2 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 composed 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. The first compound does not contain tungsten carbide.

4. A cutting tool, wherein, The cutting tool has a cutting tip made of cemented carbide as described in any one of claims 1 to 3.

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