Super hard alloy and cutting tool using same

Abstract

This invention relates to a superhard alloy comprising a plurality of tungsten carbide particles and a bonding phase. The superhard alloy comprises a total of 80% or more of the tungsten carbide particles and the bonding phase. The superhard alloy comprises 0.1% to 20% of the bonding phase. The superhard alloy comprises at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum. The superhard alloy comprises a total of 0.01 atomic% to 10.0 atomic% of the first element. The bonding phase comprises 50% or more of cobalt. In the first interface region between adjacent tungsten carbide particles, the first element is not segregated. Provided is a super hard alloy comprising a plurality of tungsten carbide particles and a binding phase, wherein: the super hard alloy contains a total of 80 vol% or more of the tungsten carbide particles and the binding phase; the super hard allow contains the binding phase in an amount of 0.1 to 20 vol%; the super hard alloy contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum; the super hard alloy contains a total of from 0.01 atom% to 10.0 atom% of the first element; the binding phase contains 50 mass% or more of cobalt; and the first element is not segregated in a first interface region between the tungsten carbide particles adjacent to each other.

Description

[Technical Field]

[0001] This invention relates to a superhard alloy and a cutting tool using the same. [Previous Technology]

[0002] Previously, superhard alloys containing tungsten carbide (WC) particles and cobalt or similar composite phases have been used as materials for cutting tools (Patent Documents 1, 2). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-098393 [Patent Document 2] Japanese Patent Application Publication No. 2021-110010 [Summary of the Invention]

[0004] The superhard alloy of the present invention comprises a plurality of tungsten carbide particles and a bonding phase. The superhard alloy comprises a total of 80% or more of the tungsten carbide particles and the bonding phase. The superhard alloy comprises 0.1% or more and 20% or less of the bonding phase. The superhard alloy comprises at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium and molybdenum. The superhard alloy comprises a total of 0.01% or more and 10.0% or less of the first element. The bonding phase comprises 50% or more of cobalt. In the first interface region between the adjacent tungsten carbide particles, the first element is not segregated.

Implementation Method

[0006] [Problem to be Solved by the Invention] In recent years, with the expansion of 5G (5th generation mobile communication system) and the advancement of high-capacity information, the heat resistance of printed circuit boards (PCBs) has become increasingly important. To improve the heat resistance of PCBs, technologies have been developed to enhance the heat resistance of the resins or glass fillers constituting the PCBs. However, this also makes the PCBs more difficult to cut. When considering the materials used for cutting tools in drilling holes in such PCBs, there is a need for superhard alloys that can extend tool life.

[0007] Therefore, the object of the present invention is to provide a superhard alloy that can extend tool life, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, and a cutting tool having the same.

[0008] [Effects of the Invention] According to the present invention, a superhard alloy that can extend tool life, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, can be provided, as well as a cutting tool having the same.

[0009] [Description of Embodiments of the Invention] First, embodiments of the present invention will be described. (1) The superhard alloy of the present invention comprises a plurality of tungsten carbide particles and a bonding phase. The superhard alloy comprises a total of 80% or more of the tungsten carbide particles and the bonding phase. The superhard alloy comprises 0.1% or more and 20% or less of the bonding phase. The superhard alloy comprises at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium and molybdenum. The superhard alloy comprises a total of 0.01% or more and 10.0% or less of the first element. The bonding phase comprises 50% or more of cobalt. In the first interface region between the adjacent tungsten carbide particles, the first element is not segregated.

[0010] According to the present invention, a superhard alloy that can extend tool life, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, can be provided, as well as a cutting tool having the same.

[0011] (2) In (1) above, the total content of the first element in the superhard alloy can also be 0.1 atomic% or more and 5 atomic% or less. In this way, the tool life is further improved.

[0012] (3) In (1) or (2) above, the superhard alloy may also contain less than 18% by volume of the above-mentioned bonding phase. Thereby, the tool life is further improved.

[0013] (4) In any of the above (1) to (3), when the above-mentioned adjacent tungsten carbide particles are designated as the first tungsten carbide particle and the second tungsten carbide particle, the first tungsten carbide particle and the second tungsten carbide particle form a first interface, and the first interface region includes a first A region within 1.2 nm of the distance from the first interface to the side of the first tungsten carbide particle and a first B region within 1.2 nm of the distance from the first interface to the side of the second tungsten carbide particle.

[0014] (5) The cutting tool of the present invention has a cutting tip comprising a superhard alloy as described in any one of (1) to (4) above.

[0015] The cutting tool of the present invention can also have a longer tool life, especially when used for drilling holes in printed circuit boards.

[0016] [Details of Embodiments of the Invention] Specific examples of the superhard alloy and cutting tools of the present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or equivalent parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately modified to make the drawings clear and simplified, and do not necessarily represent actual dimensional relationships.

[0017] In this invention, the expression "A~B" means the upper and lower limits of the range (i.e., above A and below B). When only the unit of B is recorded, but not A, the unit of A is the same as the unit of B.

[0018] In this invention, when compounds are represented by chemical formulas, the atomic ratio is not specifically limited, and all previously known atomic ratios are included, and should not be limited to only the stoichiometric range.

[0019] In this invention, when one or more values ​​are recorded as the lower limit and the upper limit of the numerical range, the combination of any one value recorded as the lower limit and any one value recorded as the upper limit is 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 above a2 and below, a1 and above b2 and below, a1 and above c2 and below, b1 and above a2 and below, b1 and above b2 and below, b1 and above c2 and below, c1 and above a2 and below, c1 and above b2 and below, c1 and above c2 and below.

[0020] [Embodiment 1: Superhard Alloy] An ultrahard alloy according to one embodiment of the present invention (hereinafter also referred to as "Embodiment 1") comprises a plurality of tungsten carbide particles and a bonding phase. The ultrahard alloy comprises a total of 80% or more of the tungsten carbide particles and the bonding phase. The ultrahard alloy comprises 0.1% or more and 20% or less of the bonding phase. The ultrahard alloy comprises at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium and molybdenum. The ultrahard alloy comprises a total of 0.01% or more and 10.0% or less of the first element. The bonding phase comprises 50% or more of cobalt. The first element is not segregated in the first interface region between adjacent tungsten carbide particles.

[0021] Embodiment 1 provides a superhard alloy that can extend tool life, particularly when used as a material for cutting tools for drilling holes in printed circuit boards, and a cutting tool equipped with the same. The reason for this is not clear, but it is speculated as follows.

[0022] The superhard alloy of Embodiment 1 comprises a plurality of 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 of the superhard alloy is 80% by volume or more. Thereby, the superhard alloy can have high hardness and strength, and the cutting tool using the superhard alloy can have excellent wear resistance and fracture resistance.

[0023] The superhard alloy of Embodiment 1 contains a binding phase of 0.1% to 20% by volume, and the binding phase contains 50% by mass or more cobalt. Therefore, the superhard alloy can have high hardness and strength, and cutting tools using this superhard alloy can have excellent wear resistance and fracture resistance.

[0024] The superhard alloy of Embodiment 1 includes at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, and the superhard alloy includes the first element in a total of 0.01 atomic% to 10.0 atomic% or more. This improves the heat resistance and reactivity of the superhard alloy.

[0025] In the superhard alloy of Embodiment 1, the first element does not segregate in the first interface region between adjacent tungsten carbide particles. Therefore, the interfacial strength between tungsten carbide particles in the superhard alloy is increased, and the shedding of tungsten carbide particles during machining is suppressed. Consequently, cutting tools using this superhard alloy as a material can have a longer tool life. Furthermore, the hole position accuracy of the cutting tool is also improved.

[0026] <Composition of the Superhard Alloy> As shown in Figure 1, the superhard alloy 3 of Embodiment 1 comprises a plurality of tungsten carbide particles 1 (hereinafter also referred to as "WC particles") and a binding phase 2, wherein the total content of the WC particles and the binding phase of the superhard alloy 3 is 80% by volume or more. The lower limit of the total content of the WC particles and the binding phase of the superhard alloy may be 82% by volume or more, 84% by volume or more, 85% by volume or more, or 86% by volume or more. The upper limit of the total content of the WC particles and the binding phase of the superhard alloy may also be 100% by volume or less. From a manufacturing point of view, the upper limit of the total content of the WC particles and the binding phase of the superhard alloy may be 99% by volume or less, or 98% by volume or less. In this superhard alloy, the total content of WC particles and bonding phases can be above 80% to below 100% by volume, above 82% to below 100% by volume, or above 84% to below 100% by volume.

[0027] The superhard alloy of Embodiment 1 may contain a plurality of tungsten carbide particles and a bonding phase. In addition to tungsten carbide particles and the bonding phase, the superhard alloy of this embodiment may contain other phases. Examples of other phases include carbides, nitrides, or carbonitrides of at least one first element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). The composition of other phases may be, for example, TiCN, TaC, NbC, ZrC, HfC, or Mo₂C.

[0028] The superhard alloy of Embodiment 1 may contain tungsten carbide particles, a bonding phase, and other phases. The content of other phases in the superhard alloy is allowed to be within a range that does not impair the effects of the present invention. For example, the content of other phases in the superhard alloy may be more than 0% by volume and less than 20% by volume, more than 0% by volume and less than 18% by volume, or more than 0% by volume and less than 16% by volume. In this case, the total content of WC particles and the bonding phase in the superhard alloy may be more than 80% by volume and less than 100% by volume, more than 82% by volume and less than 100% by volume, or more than 84% by volume and less than 100% by volume.

[0029] The superhard alloy of Embodiment 1 may contain impurities. Examples of such impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the superhard alloy is allowed to be within a range that does not impair the effects of the present invention. For example, the impurity content of the superhard alloy is preferably 0% by mass or more and less than 0.1% by mass. The impurity content of the superhard alloy is determined by ICP luminescence analysis (Inductively Coupled Plasma Emission Spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0030] The lower limit of the tungsten carbide particle content of the superhard alloy in Embodiment 1 can be 60% by volume or more, 62% by volume or more, 64% by volume or more, or 68% by volume or more. The upper limit of the tungsten carbide particle content of the superhard alloy can be 99.9% by volume or less, 99.2% by volume or less, 99% by volume or less, 98% by volume or less, 97% by volume or less, or 90% by volume or less. The tungsten carbide particle content of the superhard alloy can be 60% by volume or more and 99.9% by volume or less, 60% by volume or more and 99.2% by volume or less, 64% by volume or more and 97% by volume or less, or 68% by volume or more and 90% by volume or less.

[0031] The superhard alloy of Embodiment 1 contains a binding phase of 0.1% to 20% by volume. From the viewpoint of improving toughness, the lower limit of the content of the binding phase in the superhard alloy is 0.1% by volume or more, and can be 0.4% by volume or more, 1% by volume or more, 1.5% by volume or more, 2% by volume or more, 3% by volume or more, or 8% by volume or more. From the viewpoint of improving hardness, the upper limit of the content of the binding phase in the superhard alloy is 20% by volume or less, and can be 18% by volume or less, 16% by volume or less, or 15% by volume or less. The content of the binding phase in the superhard alloy can be 0.1% by volume or more and 18% by volume, 0.4% by volume or more and 18% by volume, 1.5% by volume or more and 16% by volume, or 8% by volume or more and 14% by volume. If the content of the bonding phase in the superhard alloy is less than 18% by volume, the hardness and wear resistance of the superhard alloy are further improved, thus further increasing the tool life of cutting tools made from the superhard alloy. The Rockwell hardness (HRC) of the superhard alloy in this embodiment is, for example, 90 to 95, or 91 to 95.

[0032] The methods for determining the content (volume %) of tungsten carbide particles and the content (volume %) of the bonding phase in superhard alloys are as follows.

[0033] (A1) Cut at any position on the superhard alloy to expose the cross section. Perform mirror finishing on the cross section using a cross section polishing machine (manufactured by Nippon Electronics Co., Ltd.).

[0034] (B1) The mirror-finished surface of the superhard alloy was analyzed using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) (device: Gemini450 (trademark) manufactured by Carl Zeiss), and the elements contained in the superhard alloy were identified.

[0035] (C1) Reflected electron images were obtained by photographing the mirror-finished surface of the superhard alloy using a scanning electron microscope (SEM). The image area was set to the central part of the cross-section of the superhard alloy, excluding areas near the surface of the superhard alloy that have significantly different properties from the main body (the image area was the main body of the superhard alloy). The magnification was 5000x. The measurement conditions were: accelerating voltage 3 kV, current 2 nA, and working distance (WD) 5 mm.

[0036] (D1) The image area (C1) above is analyzed using an energy dispersive X-ray analyzer with SEM attached (SEM-EDX) to identify the distribution of the elements identified in (B1) above in the image area and obtain an element mapping image.

[0037] (E1) The reflected electron image obtained in (C1) above is input into a computer and binarized using image analysis software (OpenCV, SciPy). In the binarized image, tungsten carbide particles are represented in white, and the bound phase is represented in gray to black. Furthermore, the binarization threshold varies with contrast, and is therefore set separately for each image.

[0038] (F1) The elemental mapping image obtained in (D1) above is overlaid with the binarized image obtained in (E1) above, thereby identifying the respective regions where tungsten carbide particles and the bonding phase exist on the binarized image. Specifically, the regions in the binarized image represented in white, where tungsten (W) and carbon (C) are present in the elemental mapping image, correspond to the regions where tungsten carbide particles exist. The regions in the binarized image represented in gray to black, where cobalt (Co) is present in the elemental mapping image, correspond to the regions where the bonding phase exists.

[0039] (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 of ​​the entire measurement field of view is set as the denominator to determine the area percentage of each tungsten carbide particle and the bound phase.

[0040] (H1) The above (G1) determination is performed in five different non-overlapping measurement fields. In this specification, the average area percentage of tungsten carbide particles in the five measurement fields corresponds to the content (volume %) of tungsten carbide particles in the superhard alloy, and the average area percentage of the bound phase in the five measurement fields corresponds to the content (volume %) of the bound phase in the superhard alloy.

[0041] When the superhard alloy contains other phases besides WC particles and the bonding phase, the content of other phases of the superhard alloy can be obtained by subtracting the content of tungsten carbide particles (volume%) and the content of the bonding phase (volume%) measured according to the above procedure from the total superhard alloy (100 volume%).

[0042] According to the applicant's measurement, based on the measurement performed on the same sample, even if the cutting part of the cross section of the superhard alloy, the shooting area described in (C1) above, and the measurement field of view described in (G1) above are arbitrarily set, and the content of tungsten carbide particles and the content of the bound phase of the superhard alloy are measured multiple times according to the above procedure, the deviation of the measurement results is also small, confirming that even if the cutting part of the cross section of the superhard alloy, the shooting area, and the measurement field of view are arbitrarily set, it is not arbitrary.

[0043] <Tungsten Carbide Particles> In Embodiment 1, the tungsten carbide particles include at least one of "pure WC particles (including WC completely free of impurity elements and WC with impurity element content not reaching the detection limit)" and "WC particles that intentionally or unavoidably contain impurity elements within them without impairing the effects of the present invention." The impurity content of the tungsten carbide particles (when there are two or more elements constituting the impurities, it is their total concentration) does not reach 0.1% by mass. The impurity element content of the tungsten carbide particles is determined by ICP-luminescence analysis.

[0044] 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 superhard alloy of Embodiment 1 can have a long tool life regardless of the average particle size of the tungsten carbide particles.

[0045] <Binding Phase> In Embodiment 1, the binding phase contains 50% by mass or more of cobalt. This imparts excellent toughness to the superhard alloy. The lower limit of the cobalt content in the binding phase can be 52% by mass or more, 60% by mass or more, 66% by mass or more, or 70% by mass or more. The upper limit of the cobalt content in the binding phase can be 100% by mass or less, less than 100% by mass, 95% by mass or less, 93% by mass or less, or 90% by mass or less. The cobalt content in the binding phase can be 50% by mass or more and less than 100% by mass, 60% by mass or more and 95% by mass or less, or 70% by mass or more and 90% by mass or less.

[0046] The method for determining the cobalt content of the bound phase is as follows. Using the same method as (A1) to (F1) for determining the content of tungsten carbide particles and the bound phase in the above-mentioned superhard alloy, the region where the bound phase exists is identified on the binarized image. The region where the bound phase exists is analyzed using SEM-EDX to determine the cobalt content of the bound phase.

[0047] According to the applicant’s measurement, based on the measurement of the same sample, even if the cutting part of the cross section of the superhard alloy and the shooting area described in (C1) are arbitrarily set, and the cobalt content of the binding phase is measured multiple times according to the above procedure, the deviation of the measurement results is small, confirming that even if the cutting part of the cross section of the superhard alloy and the shooting area are arbitrarily set, it is not arbitrary.

[0048] In Embodiment 1, the bonding phase, in addition to cobalt, may contain at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum. In addition to cobalt and the first element, the bonding phase may further contain at least one second element selected from the group consisting of nickel (Ni), chromium (Cr), iron (Fe), aluminum (Al), ruthenium (Ru), and rhenium (Re). The bonding phase may contain cobalt and the first element. The bonding phase may contain cobalt, the first element, and the second element. The bonding phase may contain cobalt, the first element, the second element, and unavoidable impurities. Examples of unavoidable impurities include manganese (Mn), magnesium (Mg), calcium (Ca), and sulfur (S).

[0049] <First Element> The superhard alloy of Embodiment 1 includes at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, and the superhard alloy includes a total of 0.01 atomic% to 10 atomic% of the first element. From the viewpoint of improving tool life, the lower limit of the content of the first element in the superhard alloy is 0.01 atomic% or more, which can be 0.03 atomic% or more, 0.1 atomic% or more, 0.8 atomic% or more, 1 atomic% or more, 2 atomic% or more, or 2.3 atomic% or more. From the viewpoint of maintaining strength, the upper limit of the content of the first element in the superhard alloy is 10.0 atomic% or less, which can be 9 atomic% or less, 8.2 atomic% or less, 8 atomic% or less, 7.7 atomic% or less, or 5 atomic% or less. The content of the first element in superhard alloys can also be above 0.1 atomic% and below 5 atomic%.

[0050] The atomic number of the first element in the superhard alloy was determined by ICP (Inductively Coupled Plasma) luminescence analysis (measuring device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0051] In the superhard alloy of Embodiment 1, the first element does not segregate in the first interface region between adjacent tungsten carbide particles. This increases the interfacial strength between the tungsten carbide particles, and the superhard alloy exhibits excellent wear resistance and fracture resistance.

[0052] In this invention, FIG2 is used to describe the method for confirming that the first element does not segregate in the first interface region between adjacent tungsten carbide particles of the superhard alloy.

[0053] Using an argon ion slicer (Cryo Ion Slicer IB-09060BCIS, a trademark manufactured by JEOL Ltd.), ultrahard alloy sheets were sliced ​​to a thickness of 30–100 nm to prepare a sample for measurement under conditions of accelerating voltage 6 kV and final accelerating voltage 2 kV. Subsequently, the sample for measurement was observed at 200,000x magnification using a TEM (Transmission Electron Microscopy) (JEM-ARM300F2, a trademark manufactured by JEOL Ltd.), under conditions of accelerating voltage 200 V, thereby obtaining the first image (not shown).

[0054] In the first image, tungsten carbide particles are observed as white areas, the bonding phase as black areas, and the interface as black areas. In the first image, the interfaces between tungsten carbide particles are arbitrarily selected. In this invention, adjacent tungsten carbide particles forming interfaces are also referred to as the first tungsten carbide particle and the second tungsten carbide particle.

[0055] Next, the selected interface is positioned near the center of the image, and the observation magnification is adjusted to a field of view size of 5 nm × 5 nm to obtain a second image (not shown). In the second image, the elongation direction of the interface is identified. Linear analysis is performed using EDX in a direction perpendicular to this elongation direction and from the first tungsten carbide particle toward the second tungsten carbide particle to obtain a curve (hereinafter also referred to as the first curve) showing the distribution of cobalt, tungsten, and the first element. When the superhard alloy contains two or more first elements, the distribution of each element is measured. Here, the direction perpendicular to the elongation direction of the interface means the direction of a straight line intersecting the tangent to the elongation direction at an angle of 90° ± 5°. The measurement conditions for obtaining the second image are: accelerating voltage 200 kV, camera distance 10 cm, pixel count 128 × 128 pixels, and dwell time 0.02–3 s / pixel.

[0056] Figure 2 is an example of the first curve. In Figure 2, the horizontal axis (X-axis) represents the distance (nm) from the starting point of the measurement, and the vertical axis (Y-axis) represents the NET intensity (unitless). In the superhard alloy shown in Figure 2, the first element is tantalum (Ta).

[0057] The peak position of cobalt is specifically identified in the first curve. In this invention, the peak position of cobalt is denoted as the first interface. The first interface is formed by adjacent first tungsten carbide particles and second tungsten carbide particles. In the first curve of Figure 2, the position of the first interface is 4.15 nm on the X-axis.

[0058] In the first curve diagram, region 1A, within 1.20 nm of the distance from the first interface to the side of the first tungsten carbide particle, and region 1B, within 1.20 nm of the distance from the first interface to the side of the second tungsten carbide particle, are specifically identified. In this invention, the region composed of region 1A and region 1B is the first interface region. In the first curve diagram of Figure 2, the position of the first interface region is 2.95–5.35 nm along the X-axis.

[0059] In the first curve diagram, region 2A, where the distance from the first interface to the first tungsten carbide particle side is 1.50 nm to 3.50 nm, and region 2B, where the distance from the first interface to the second tungsten carbide particle side is 1.50 nm to 3.50 nm, are specifically identified. In the first curve diagram of Figure 2, region 2A is located at 0.65–2.65 nm on the X-axis, and region 2B is located at 5.65–7.65 nm on the X-axis.

[0060] Based on the first curve, the average value B of the NET intensity of the first element in the baseline region composed of region 2A and region 2B is calculated. In the first curve, the maximum value A of the NET intensity of the first element in the first interface region is measured. When the ratio A / B of the maximum value A to the average value B is less than 3, it can be confirmed that the first element has not segregated in the first interface region between adjacent tungsten carbide particles of the superhard alloy. In the first curve of Figure 2, the average value B of the NET intensity of tantalum (the first element) in the baseline region including region 2A and region 2B is 78.7 (the average value of the NET intensity in region 2A is 97.6, and the average value of the NET intensity in region 2B is 59.7), and the maximum value A of the NET intensity of tantalum (the first element) in the first interface region is 112.6. In the superhard alloy shown in Figure 2, since A / B is 1.43, it can be confirmed that the first element does not segregate in the first interface region between the adjacent tungsten carbide particles of the superhard alloy.

[0061] In the superhard alloy, five non-overlapping first images of the field of view are randomly acquired. The above analysis is repeatedly performed based on each first image. When the segregation of the first element is not confirmed in the first interface region in four or more fields of view, it is determined that the first element is not segregated in the first interface region between adjacent tungsten carbide particles of the superhard alloy.

[0062] According to the applicant's measurements, based on measurements performed on the same sample, even if the cut portion of the cross-section of the superhard alloy is arbitrarily set, and the first image is arbitrarily acquired on that cross-section, and the area of ​​line analysis is changed repeatedly according to the above procedure to confirm whether the first element segregates in the first interface region, it can be confirmed that the result of whether the first element segregates in the first interface region is almost without deviation. Therefore, as long as the superhard alloy is subjected to the above-mentioned method for confirming the segregation of the first element, and it is confirmed that the first element does not segregate in the first interface region, it can be inferred that the interfacial strength between the tungsten carbide particles of the superhard alloy is improved.

[0063] In the superhard alloy of the present invention, the first element may exist in the other phases mentioned above or in cobalt.

[0064] <Manufacturing Method of Superhard Alloy> The superhard alloy of this embodiment can be manufactured by sequentially performing the following steps: raw material powder preparation, mixing, molding, sintering, and cooling. Each step will be described below.

[0065] <Preparation Steps> The preparation steps are the steps of preparing the raw material powders that constitute the superhard alloy. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder, and powders containing a first metallic element. Examples of powders containing a first metallic element include titanium carbonitride (TiCN) powder, tantalum carbide (TaC) powder, niobium carbide (NbC) powder, zirconium carbide (ZrC) powder, hafnium carbide (HfC) powder, molybdenum carbide (Mo2C) powder, etc. Commercially available raw material powders can be used. There is no particular limitation on the average particle size of these raw material powders, for example, it can be set to 0.1 to 3.0 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. This average particle size is measured using the "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific. The particle size distribution of the WC powder was measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

[0066] <Mixing Step> The mixing step is a step in which the raw material powders prepared in the preparation step are mixed in a specified ratio. Through the mixing step, a mixed powder of the raw material powders is obtained. The mixing ratio of the raw material powders is appropriately adjusted according to the composition of the target superhard alloy.

[0067] The mixing of the various raw material powders can be performed using previously known mixing methods such as grinding mills, ball mills, and bead mills. The mixing conditions can also be previously known conditions. For example, the mixing time can be set to more than 2 hours and less than 20 hours.

[0068] After the mixing step, the mixed powder may also be granulated as needed. By granulating the mixed powder, it is easier to fill the nozzle or mold during the forming step below. Granulation can be performed using known granulation methods, such as commercially available granulators such as spray dryers.

[0069] <Forming Step> The forming step is the step of forming the mixed powder obtained in the mixing step into a shape for use as a cutting tool (e.g., a round rod shape) to obtain a shaped body. The forming method and forming conditions in the forming step can be general methods and conditions, and there are no particular limitations.

[0070] <Sintering Step> The sintering step is a step to obtain an ultrahard alloy intermediate by sintering through a sintering HIP (Hot Isostatic Pressing) process that simultaneously sintersects and pressurizes the shaped body obtained through the forming step.

[0071] The sintering step may include a first sintering step and a second sintering step. First, in the first sintering step, the sintering temperature is maintained at 1300°C and the sintering pressure is maintained at 7 MPa for 240 minutes. Second, in the second sintering step, the sintering pressure is maintained at 7 MPa while the temperature is raised to 1360°C and held at 1360°C for 15 minutes to obtain an ultra-hard alloy intermediate.

[0072] There are no special restrictions on the atmosphere during sintering. For example, a nitrogen atmosphere or an inert gas atmosphere such as Ar can be used.

[0073] <Cooling Step> The cooling step is the step of cooling the superhard alloy intermediate after the sintering step. For example, the superhard alloy intermediate can be rapidly cooled in argon gas under a pressure of 100 to 400 MPaG to obtain the superhard alloy.

[0074] <Features of the Manufacturing Method of the Superhard Alloy of this Embodiment> The sintering temperature of 1300°C in the first sintering step is lower than that of conventional superhard alloys. Furthermore, the sintering time of 240 minutes in the first sintering step is longer than that of conventional superhard alloys (30-60 minutes). It is speculated that by advancing the diffusion and rearrangement of atoms during sintering, the superhard alloy of the present invention, in which the first element is not segregated in the first interface region between adjacent tungsten carbide particles, can be obtained. The superhard alloy of the present invention, which can be achieved by means of such sintering conditions, is a new discovery obtained by the inventors through their efforts. Furthermore, the sintering temperature and sintering time in the first sintering step have not been adopted by manufacturers due to low production efficiency.

[0075] [Embodiment 2: Cutting Tool] The cutting tool of this embodiment includes a cutting tip made of superhard alloy as described in Embodiment 1. In this invention, the cutting tip refers to the part related to cutting. More specifically, the cutting tip refers to the area enclosed by the cutting tip ridge and an imaginary surface with a distance of 2 mm from the cutting tip ridge to the superhard alloy side.

[0076] Examples of cutting tools include cutting tools, drills, end mills, milling inserts with interchangeable tips, turning inserts with interchangeable tips, metal saws, gear cutting tools, reamers, and taps. In particular, as shown in FIG3, when the cutting tool 10 of this embodiment is a small-diameter drill for printing circuit board processing, it exhibits excellent performance. The tip 11 of the cutting tool 10 shown in FIG3 comprises the superhard alloy of Embodiment 1.

[0077] The superhard alloy of this embodiment can form the entire tool or a part of it. Here, "forms a part" means that the tip of the tool is formed by hard soldering the superhard alloy of this embodiment to a specified position on any substrate.

[0078] The cutting tool of this embodiment may further have a hard film covering at least a portion of the surface of the substrate containing the superhard alloy. As the hard film, for example, diamond-like carbon or diamond can be used.

[0079] The cutting tool of this embodiment can shape the superhard alloy of Embodiment 1 into the desired shape. [Example]

[0080] This embodiment will be further described in detail with reference to the embodiments. However, this embodiment is not limited to these embodiments.

[0081] [Preparation of superhard alloys] Superhard alloys for each sample are prepared according to the following procedure.

[0082] WC powder (average particle size 0.3 μm), Co powder (average particle size 1.0 μm), TiCN powder (average particle size 1.0 μm), TaC powder (average particle size 1.0 μm), NbC powder (average particle size 1.0 μm), ZrC powder (average particle size 1.0 μm), HfC powder (average particle size 1.0 μm), and Mo₂C powder (average particle size 1.0 μm) were prepared and mixed according to the ratios listed in the "Raw Material Powder" column of Table 1 to obtain a mixed powder. For example, in Sample 1, WC powder, Co powder, and TiCN powder were prepared and mixed in a mass ratio of 81.8:11.7:6.5 to obtain a mixed powder. For all samples, the mixing process was carried out using a mill for 10 hours.

[0083] [Table 1] Table 1 Sample No. raw material powder WC Co TiCN TaC NbC ZrC HfC MO2C quality% quality% quality% quality% quality% quality% quality% quality% 1 81.8 11.7 6.5 - - - - - 2 94.0 3.3 2.8 - - - - - 3 91.4 5.2 - 3.4 - - - - 4 99.1 0.3 - - 0.7 - - - 5 88.5 8.5 - - - 3.1 - - 6 89.6 10.4 - - - - 0.01 - 7 87.3 9.8 - - - - - 3.0 8 84.5 6.5 7.9 - 1.1 - - - 9 91.3 3.9 - 3.3 1.5 - - - 10 92.6 1.0 5.9 - - - 0.6 - 11 83.7 10.4 - - 5.2 - - 0.7 12 99.92 0.07 0.01 - - - - - 13 75.0 13.0 12.0 - - - - - 1-1 79.0 13.7 7.3 - - - - - 1-2 91.4 0.0 8.6 - - - - - 1-3 89.60 10.40 0.00 - - - - - 1-4 80.4 7.2 12.5 - - - - - 1-5 88.4 5.2 6.4 - - - - - 1-6 89.0 3.3 7.8 - - - - - 1-7 81.8 11.7 6.5 - - - - - 1-8 81.8 11.7 6.5 - - - - -

[0084] Next, a cylindrical rod-shaped molded body is prepared by pressing the mixed powder into shape. Then, a first sintering step is performed on the molded body in argon gas. The temperature, pressure, and time in the first sintering step are shown in the "First Sintering Step" column of Table 2. Then, while maintaining the pressure, the temperature is changed to 1360°C and a second sintering step is performed to obtain an ultrahard alloy intermediate. The holding time in the second sintering step is shown in the "Second Sintering Step" column of Table 2. Then, the ultrahard alloy intermediate is rapidly cooled in argon gas at a pressure of 200 MPaG to obtain ultrahard alloy samples.

[0085] [Table 2] Table 2 Sample No. First sintering step 2nd sintering step temperature time pressure Duration ℃ minute MPa minute 1 1300 240 7 15 2 1300 240 7 15 3 1300 240 7 15 4 1300 240 7 15 5 1300 240 7 15 6 1300 240 7 15 7 1300 240 7 15 8 1300 240 7 15 9 1300 240 7 15 10 1300 240 7 15 11 1300 240 7 15 12 1300 240 7 15 13 1300 240 7 15 1-1 1300 240 7 15 1-2 1300 240 7 15 1-3 1300 240 7 15 1-4 1300 240 7 15 1-5 1300 240 7 15 1-6 1380 240 7 15 1-7 1380 240 7 15 1-8 1300 60 7 20

[0086] [Manufacturing of cutting tools] A drill bit for PCB (Printed Circuit Board) processing with a cutting diameter of 0.3 mm is manufactured by machining a round rod containing the obtained superhard alloy.

[0087] [Evaluation of Superhard Alloys] <Tungsten Carbide Particle Content (Volume %) and Bonded Phase Content (Volume %) of Superhard Alloys> The tungsten carbide particle content (volume %) and bonded phase content (volume %) of each superhard alloy sample were determined. The specific determination method is as described in Embodiment 1. The results are shown in the "WC Particle Content" and "Bonded Phase Content" columns of "Superhard Alloys" in Table 3. Furthermore, the sum of the tungsten carbide particle content and bonded phase content of the superhard alloys is shown in the "WC Particle + Bonded Phase Content" column of "Superhard Alloys" in Table 3. In Table 3, it can be confirmed that superhard alloys with a "WC particle + bound phase content" column of less than 100% by volume include at least one of the groups consisting of carbides, nitrides and carbonitrides containing the first element.

[0088] <Co content in the bonding phase> The cobalt content in the bonding phase was determined in each superhard alloy sample. The specific determination method is as described in Embodiment 1. The results are shown in the "Co content in the bonding phase" column of "Superhard Alloy" in Table 3. For all samples, it was also confirmed that the bonding phase contains, in addition to cobalt, the same first element as the first element listed in the "First Element Type" column of "Superhard Alloy" in Table 3.

[0089] <Content of the First Element in the Superhard Alloy> In each superhard alloy sample, the types of the first element contained in the superhard alloy and the total content (atomic %) of the first element in the superhard alloy were determined. The specific determination method is as described in Embodiment 1. The results are shown in the "Types of First Element" and "Content of First Element" columns of "Superhard Alloy" in Table 3. When there is only one type of first element, "Content of First Element" means the content of one type of first element. When there are two types of first elements, "Content of First Element" means the total content of the two types of first elements.

[0090] <Presence or absence of first element segregation in the first interface region> In each sample of the superhard alloy, it was confirmed whether there was first element segregation in the first interface region between adjacent tungsten carbide particles. The specific confirmation method is as described in Embodiment 1. The results are shown in the "First element segregation" column of "Superhard Alloy" in Table 3.

[0091] <Rockwell Hardness> The Rockwell hardness (HRC) of each specimen of the superhard alloy was determined according to "JIS Z 2245:2016 Rockwell Hardness Test - Test Method". The test conditions were room temperature (23℃±5℃), test force 60 N, and holding time 4 seconds. The results are shown in the "Rockwell Hardness" column of Table 3.

[0092] [Evaluation of Cutting Tools] <Cutting Test> PCB drills for each sample were used to drill holes in commercially available automotive printed circuit boards, and the hole position accuracy was evaluated. The drilling conditions were set as follows: rotation speed 120 krpm, feed rate 2 m / min, and pull-out speed 25 m / min. The number of drilling hits was measured when the hole position accuracy (ave + 3σ (μm)) exceeded 70 μm. The results are shown in the "Cutting Test" column of Table 3. The values ​​in Table 3 are obtained by rounding down the actual number of drilling hits to the tens place. For example, if the actual number of drilling hits is 6250, it is recorded as 6200 hits in the "Cutting Test" column. A higher number of drilling hits indicates better hole position accuracy and longer tool life.

[0093] [Table 3] Table 3 Sample No. super carbide Cutting test WC particle content Combined phase content WC particle + bound phase content Combined with the Co content in the phase Type of Element 1 Element 1 content rate Element 1 segregation Rockwell hardness Number of holes volume% volume% volume% quality% atom% Yes / No HRC hit 1 64.0 18.0 82.0 85.0 Ti 5.40 none 91 6500 2 90.0 5.0 95.0 93.0 Ti 2.30 none 93 7400 3 84.0 8.0 92.0 70.0 Ta 7.30 none 92 6400 4 99.2 0.4 99.6 66.0 Nb 0.80 none 94 6600 5 74.0 13.0 87.0 52.0 Zr 3.60 none 93 7200 6 68.0 16.0 84.0 75.0 Hf 0.03 none 92 6200 7 70.0 15.0 85.0 79.0 Mo 6.80 none 92 6200 8 80.0 10.0 90.0 91.0 Ti, Nb 8.20 none 93 6500 9 88.0 6.0 94.0 88.0 Ta、Zr 9.00 none 93 6600 10 97.0 1.5 98.5 79.0 Ti, Hf 6.10 none 94 6400 11 68.0 16.0 84.0 83.0 Nb, Mo 7.70 none 92 6300 12 93.9 0.1 94.0 94.0 Ti 0.01 none 94 7900 13 77.0 20.0 97.0 50.0 Ti 10.00 none 90 6000 1-1 58.0 21.0 79.0 67.0 Ti 6.10 none 90 2900 1-2 100.0 0.0 100.0 79.0 Ti 7.20 none 94 4900 1-3 68.0 16.0 84.0 94.0 Ti 0.00 none 92 3600 1-4 78.0 11.0 89.0 52.0 Ti 10.40 none 93 4000 1-5 84.0 8.0 92.0 48.0 Ti 5.30 none 93 4200 1-6 90.0 5.0 95.0 66.0 Ti 6.50 have 93 3500 1-7 64.0 18.0 82.0 85.0 Ti 12.40 have 91 1600 1-8 64.0 18.0 82.0 85.0 Ti 11.00 have 91 1700

[0094] <Investigation> The superhard alloys and cutting tools of Specimens 1 to 13 correspond to the Examples. The superhard alloys and cutting tools of Specimens 1-1 to 1-8 correspond to the Comparative Examples. It can be confirmed that compared with the cutting tools of Specimens 1-1 to 1-8 (Comparative Examples), the cutting tools of Specimens 1 to 13 (Examples) have excellent hole position accuracy and longer tool life. It is speculated that the reason is that the superhard alloys of Specimens 1 to 13 have excellent wear resistance and fracture resistance.

[0095] The embodiments and examples of the present invention have been described as above, but it is also intended from the outset that the above embodiments and examples be appropriately combined or varied. It should be considered that the embodiments and examples disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above embodiments and examples, and is intended to include all changes within the scope and meaning equivalent to the claims. 1: Tungsten carbide particles 2: Binding phase 3: Superhard alloy 10: Cutting tool 11: Tool tip [Simplified Explanation of the Diagram]

[0005] Figure 1 is a schematic cross-sectional view of the superhard alloy of Embodiment 1. Figure 2 is a diagram illustrating the method for confirming that the first element does not segregate in the first interface region, and shows the first curve. Figure 3 is a schematic diagram of the cutting tool of Embodiment 2.

Claims

1. A superhard alloy comprising a plurality of tungsten carbide particles and a bonding phase, wherein the superhard alloy comprises a total of 80% by volume or more of the tungsten carbide particles and the bonding phase, wherein the superhard alloy comprises 0.1% by volume or more and 20% by volume of the bonding phase, wherein the superhard alloy comprises at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium and molybdenum, wherein the superhard alloy comprises a total of 0.01 atomic% by atomic% or more of the first element, wherein the bonding phase comprises 50% by mass or more of cobalt, and wherein the first element is not segregated in the first interface region between adjacent tungsten carbide particles.

2. The superhard alloy as claimed in claim 1, wherein the total content of the first element in the superhard alloy is more than 0.1 atomic% and less than 5 atomic%.

3. The superhard alloy as claimed in claim 1 or 2, wherein the superhard alloy contains less than 18% by volume of the aforementioned bonding phase.

4. The superhard alloy of claim 1 or 2, wherein when the adjacent tungsten carbide particles are designated as a first tungsten carbide particle and a second tungsten carbide particle, the first tungsten carbide particle and the second tungsten carbide particle form a first interface, the first interface region including a first A region within 1.2 nm of the distance from the first interface to the side of the first tungsten carbide particle, and a first B region within 1.2 nm of the distance from the first interface to the side of the second tungsten carbide particle.

5. A cutting tool having a cutting tip comprising a superhard alloy as claimed in any one of claims 1 to 4.

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