Cemented carbide and cutting tool

Abstract

This cemented carbide is provided with a plurality of multiple tungsten carbide particles and a binding phase. The cemented carbide contains a total of 80 vol% or more of the tungsten carbide particles and the binding phase. The cemented carbide contains 0.1-20 vol% of the binding phase. The cemented carbide contains one or more first elements selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron. The cemented carbide contains a total of 0.01-20 at% of the first elements. The binding phase contains 50 mass% or more of cobalt. In a first graph indicating, in a coordinate system in which the X-axis represents the distance from a position at which cobalt exhibits the maximum intensity and the Y-axis represents the standardized intensity, the result obtained through a line analysis performed in a first direction from the binding phase to an adjacent one of the tungsten carbide particles by using an energy dispersion type X-ray spectroscopy device that is accessory to a transmission electron microscope, the maximum peak M of each of the first elements exists between a peak W1 of tungsten located closest to the point of origin and another peak W2 of tungsten located closest to the peak W1, and the ratio IB / IA of an intensity IB with respect to the maximum peak intensity IA of the maximum peak M for each of the first elements is 0.5 or less, where the intensity IB is the intensity of the first element at a distance P2 which is 0.2 nm beyond a distance P1 of the maximum peak intensity IA toward the opposite side with respect to the point of origin.

Description

Cemented Carbide and Cutting Tools

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

[0002] Conventionally, cemented carbide alloys comprising tungsten carbide (WC) particles and a binder phase containing cobalt or the like as a main component have been used as materials for cutting tools (Patent Documents 1 and 2).

[0003] JP 2016-098393 A JP 2021-110010 A

[0004] The cemented carbide of the present disclosure is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains the tungsten carbide particles and the binder phase in a total of 80 volume % or more, the cemented carbide contains the binder phase in an amount of 0.1 volume % or more and 20 volume % or less, the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron, the cemented carbide contains the first element in a total of 0.01 atomic % or more and 20 atomic % or less, and the binder phase contains 50 mass % or more of cobalt, and in a first graph showing the results of line analysis performed along a first direction from the binder phases adjacent to each other toward the tungsten carbide particles using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the results being plotted on a coordinate system in which the X axis represents the distance from the position where cobalt shows the maximum intensity and the Y axis represents normalized intensity, the cemented carbide wherein a maximum peak M of each of the first elements exists between a peak W1 of tungsten closest to the origin and another peak W2 of tungsten closest to the peak W1, and for each of the first elements, a ratio IB / IA of an intensity IB to a maximum peak intensity IA of the maximum peak M is 0.5 or less, and the intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the origin from a distance P1 of the maximum peak intensity IA.

[0005] Fig. 1 is a schematic cross-sectional view of a cemented carbide according to embodiment 1. Fig. 2 shows an example of a first graph of the cemented carbide according to embodiment 1. Fig. 3 is a schematic view of a cutting tool according to embodiment 2.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, workpiece materials have become increasingly difficult to cut in cutting processes. Furthermore, demands for improved processing efficiency have led to stricter processing conditions, such as increased cutting speeds.

[0007] Therefore, an object of the present disclosure is to provide a cemented carbide that, when used as a tool material, can provide a cutting tool with a long tool life, particularly in high-speed machining of difficult-to-cut materials, and to provide a cutting tool with a long tool life.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that, when used as a cutting tool material, can provide a cutting tool with a long tool life, particularly in high-speed machining of difficult-to-cut materials, and a cutting tool with a long tool life.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The presently disclosed cemented carbide alloy is a cemented carbide alloy comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide alloy contains the tungsten carbide particles and the binder phase in a total of 80% by volume or more, the cemented carbide alloy contains the binder phase in an amount of 0.1% by volume or more and 20% by volume or less, the cemented carbide alloy contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron, the cemented carbide alloy contains the first element in a total of 0.01 atomic % or more and 20 atomic % or less, and the binder phase contains 50% by mass or more of cobalt, and in a first graph showing the results of line analysis performed along a first direction from the binder phases adjacent to each other toward the tungsten carbide particles using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, the results being plotted on a coordinate system in which the X axis represents the distance from a position where cobalt shows the maximum intensity and the Y axis represents normalized intensity, the cemented carbide wherein a maximum peak M of each of the first elements exists between a peak W1 of tungsten closest to the origin and another peak W2 of tungsten closest to the peak W1, and for each of the first elements, a ratio IB / IA of an intensity IB to a maximum peak intensity IA of the maximum peak M is 0.5 or less, and the intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the origin from a distance P1 of the maximum peak intensity IA.

[0010] According to the present disclosure, it is possible to provide a cemented carbide that, when used as a cutting tool material, can provide a cutting tool with a long tool life, particularly in high-speed machining of difficult-to-cut materials, and a cutting tool with a long tool life.

[0011] (2) In the above (1), the cemented carbide may contain 18% by volume or less of the binder phase, which further improves the tool life.

[0012] (3) A cutting tool according to the present disclosure is a cutting tool having a cutting edge made of the cemented carbide alloy described in (1) or (2) above.

[0013] The cutting tools of the present disclosure can have a long tool life.

[0014] [Details of the Embodiments of the Present Disclosure] Specific examples of the cemented carbide and cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0015] In the present disclosure, the notation in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the units of A and B are the same.

[0016] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0017] In the present disclosure, when one or more numerical values ​​are recited as the lower limit and the upper limit of a numerical range, a combination of any one numerical value recited as the lower limit and any one numerical value recited as the upper limit is also considered to be disclosed. For example, when a1 or more, b1 or more, and c1 or more are recited as the lower limit and a2 or less, b2 or less, and c2 or less are recited as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are considered to be disclosed.

[0018] [Embodiment 1: Cemented Carbide] A cemented carbide according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains a total of 80 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide contains 0.1 volume % or more and 20 volume % or less of the binder phase, the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron, the cemented carbide contains a total of 0.01 atomic % or more and 20 atomic % or less of the first element, the binder phase contains 50 mass % or more of cobalt, The cemented carbide alloy is characterized in that, in a first graph showing the results of line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from the adjacent binder phases toward the tungsten carbide particles, the X axis represents the distance from the position where cobalt exhibits the maximum intensity and the Y axis represents normalized intensity, the maximum peak M of each of the first elements is present between a peak W1 of tungsten closest to the origin and another peak W2 of tungsten closest to the peak W1, the ratio IB / IA of the intensity IB to the maximum peak intensity IA of the maximum peak M of each of the first elements is 0.5 or less, and the intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the origin from the distance P1 of the maximum peak intensity IA.

[0019] When used as a tool material, the cemented carbide of embodiment 1 can provide a cutting tool with a long tool life, particularly in high-speed machining of difficult-to-cut materials, and can provide a cutting tool with a long tool life. The reason for this is not clear, but is presumed to be as follows.

[0020] The cemented carbide of the first embodiment comprises a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles") and a binder phase, and the total content of the WC particles and binder phase in the cemented carbide is 80 volume % or more. As a result, the cemented carbide has high hardness and strength, and a cutting tool using the cemented carbide can have excellent wear resistance and chipping resistance.

[0021] The cemented carbide of the first embodiment contains a binder phase of 0.1% by volume to 20% by volume, and the binder phase contains 50% by mass or more of cobalt. This allows the cemented carbide to have high hardness and strength, and a cutting tool using the cemented carbide to have excellent wear resistance and chipping resistance.

[0022] The cemented carbide of embodiment 1 contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron in a total content of 0.01 atomic % to 20 atomic %. In a first graph obtained by performing line analysis on the cemented carbide of embodiment 1, a maximum peak M of each first element is present between the tungsten peak W1 closest to the origin and another tungsten peak W2 closest to peak W1. This indicates that a maximum concentration region of the first element exists in the surface layer of the tungsten carbide particle. Furthermore, the ratio IB / IA of the intensity IB to the maximum peak intensity IA is 0.5 or less. This indicates that the first element is present only in the surface layer of the tungsten carbide particle and does not penetrate deep into the interior of the tungsten carbide particle.

[0023] In the cemented carbide of embodiment 1, the first element is present only in the surface layer portion of the tungsten carbide particles, thereby improving the adhesion resistance of the cemented carbide. As a result, when the cemented carbide of embodiment 1 is used in a cutting tool, the occurrence of damage such as chipping due to adhesion during cutting is suppressed. Note that in the cemented carbide of embodiment 1, the first element does not penetrate deep into the tungsten carbide particles, so the basic physical properties of the tungsten carbide particles, such as high hardness and strength, are not significantly changed and are maintained.

[0024] <Composition of Cemented Carbide> As shown in Figure 1, the cemented carbide 3 of embodiment 1 includes a plurality of tungsten carbide particles 1 (hereinafter also referred to as "WC particles") and a binder phase 2, and the total content of the WC particles and binder phase in the cemented carbide 3 is 80 volume % or more. The lower limit of the total content of the WC particles and binder phase in the cemented carbide may be 82 volume % or more, 84 volume % or more, 85 volume % or more, or 86 volume % or more. The upper limit of the total content of the WC particles and binder phase in the cemented carbide may be 100 volume % or less. From a manufacturing standpoint, the upper limit of the total content of the WC particles and binder phase in the cemented carbide may be 99 volume % or less, or 98 volume % or less. The total content of WC grains and binder phase in the cemented carbide may be 80% by volume to 100% by volume, 82% by volume to 100% by volume, or 84% by volume to 100% by volume.

[0025] The cemented carbide of the first embodiment may be composed of a plurality of tungsten carbide particles and a binder phase. In addition to the tungsten carbide particles and the binder phase, the cemented carbide of the present embodiment may contain other phases, such as TiCN, TiC, and TiO. ２ , TaC, Ta ２ O ５ , ZrC, ZrO ２ , CeC ２ , CeO ２ , Y.C., Y. ２ O ３ , B ４ C and B ２ O ３ The phase may be at least one selected from the group consisting of:

[0026] The cemented carbide of the first embodiment may be composed of tungsten carbide particles, a binder phase, and other phases. The content of the other phases in the cemented carbide is acceptable as long as it does not impair the effects of the present disclosure. For example, the content of the other phases in the cemented carbide may be 0% to 20% by volume, 0% to 18% by volume, or 0% to 16% by volume. In this case, the total content of the WC particles and binder phase in the cemented carbide may be 80% to less than 100% by volume, 82% to less than 100% by volume, or 84% to less than 100% by volume.

[0027] The cemented carbide of the first embodiment may contain impurities. Examples of such impurities include manganese (Mn), magnesium (Mg), calcium (Ca), and sulfur (S). The impurity content of the cemented carbide is acceptable as long as it does not impair the effects of the present disclosure. For example, the impurity content of the cemented carbide is preferably 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide is measured by ICP optical emission spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0028] The lower limit of the tungsten carbide particle content of the cemented carbide alloy of embodiment 1 may be 60 vol% or more, 65 vol% or more, 66 vol% or more, or 68 vol% or more. The upper limit of the tungsten carbide particle content of the cemented carbide alloy may be 99.9 vol% or less, 99.8 vol% or less, 99 vol% or less, 98 vol% or less, 96 vol% or less, or 94 vol% or less. The tungsten carbide particle content of the cemented carbide alloy may be 60 vol% or more and 99.9 vol% or less, 65 vol% or more and 99.8 vol% or less, 66 vol% or more and 99 vol% or less, or 68 vol% or more and 98 vol% or less.

[0029] The cemented carbide of embodiment 1 contains a binder phase in an amount of 0.1 vol% or more and 20 vol% or less. From the viewpoint of improving toughness, the lower limit of the binder phase content of the cemented carbide is 0.1 vol% or more, and may be 1 vol% or more, 2 vol% or more, 3 vol% or more, 5 vol% or more, or 8 vol% or more. From the viewpoint of improving hardness, the upper limit of the binder phase content of the cemented carbide is 20 vol% or less, 19 vol% or less, 18 vol% or less, 17 vol% or less, 16 vol% or less, or 15 vol% or less. The binder phase content of the cemented carbide may be 0.1 vol% or more and 18 vol% or less, 1 vol% or more and 18 vol% or less, 3 vol% or more and 17 vol% or less, 5 vol% or more and 16 vol% or less, or 8 vol% or more and 15 vol% or less. When the content of the binder phase in the cemented carbide is 18% by volume or less, the hardness and wear resistance of the cemented carbide are further improved, and therefore the tool life of cutting tools using the cemented carbide as a material is further improved.

[0030] The methods for measuring the content (volume %) of tungsten carbide particles in the cemented carbide and the content (volume %) of the binder phase in the cemented carbide are as follows.

[0031] (A1) A cemented carbide alloy is cut out at an arbitrary position to expose a cross section, which is then polished to a mirror finish using a cross section polisher (manufactured by JEOL Ltd.).

[0032] (B1) The mirror-finished surface of the cemented carbide is analyzed using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) (apparatus: Carl Zeiss Gemini 450 (trademark)) to identify the elements contained in the cemented carbide.

[0033] (C1) The mirror-finished surface of the cemented carbide is photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image. The photographed area of ​​the photographed image is set to the center of the cross section of the cemented carbide, i.e., a position that does not include areas with properties clearly different from the bulk part, such as the surface vicinity of the cemented carbide (a position where the entire photographed area is the bulk part of the cemented carbide). The observation magnification is 5000x. The measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[0034] (D1) The photographed region of (C1) above is analyzed using an energy dispersive X-ray analyzer (SEM-EDX) attached to an SEM, the distribution of the elements identified in (B1) above in the photographed region is identified, and an element mapping image is obtained.

[0035] (E1) The backscattered electron image obtained in (C1) above is imported into a computer and binarized using image analysis software (OpenCV, SciPy). In the binarized image, tungsten carbide particles are shown in white, and the binder phase is shown in gray to black. Note that the binarization threshold varies depending on the contrast, so it is set for each image.

[0036] (F1) By superimposing the elemental mapping image obtained in (D1) above on the binarized image obtained in (E1) above, the regions where tungsten carbide particles and binder phase exist are identified on the binarized image. Specifically, the regions shown in white in the binarized image and where tungsten (W) and carbon (C) exist in the elemental mapping image correspond to the regions where tungsten carbide particles exist. The regions shown in gray to black in the binarized image and where cobalt (Co) exists in the elemental mapping image correspond to the regions where binder phases exist.

[0037] (G1) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the image after the binarization process. Using the image analysis software, the area percentages of the tungsten carbide particles and the binder phase are measured, with the area of ​​the entire measurement field being used as the denominator.

[0038] (H1) The measurement of (G1) above is carried out in five different, non-overlapping measurement fields. In this specification, the average of the area percentages of tungsten carbide particles in the five measurement fields corresponds to the content (volume %) of tungsten carbide particles in the cemented carbide, and the average of the area percentages of the binder phase in the five measurement fields corresponds to the content (volume %) of the binder phase in the cemented carbide.

[0039] When the cemented carbide contains other phases in addition to the WC grains and binder phase, the content of the other phases in the cemented carbide can be obtained by subtracting the content (volume %) of the tungsten carbide grains and the content (volume %) of the binder phase measured by the above procedure from the total cemented carbide (100 volume %).

[0040] As far as the applicant has measured, as long as measurements are made on the same sample, even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view described in (G1) above are arbitrarily set, and the tungsten carbide particle content and the binder phase content of the cemented carbide are measured multiple times according to the above procedure, there is little variation in the measurement results, and it has been confirmed that arbitrarily setting the cut-out location of the cross section of the cemented carbide, the photographing area, and the measurement field of view is not arbitrary.

[0041] <Tungsten Carbide Particles> In embodiment 1, the tungsten carbide particles include tungsten carbide and a first element. In the present disclosure, the inclusion of the first element in the tungsten carbide particles is indicated by confirming that a maximum peak M of each of the first elements exists between a tungsten peak W1 closest to the origin and another tungsten peak W2 closest to peak W1 in a first graph obtained by performing line analysis on the cemented carbide.

[0042] The tungsten carbide particles may contain impurity elements other than carbon, tungsten, and the first element, as long as the effects of the present disclosure are not impaired. The impurity content of the tungsten carbide particles (when two or more elements constitute the impurities, the total concentration of these elements) is less than 0.1 mass%. The impurity element content of the tungsten carbide particles is measured by ICP optical emission spectrometry.

[0043] In the first embodiment, the average particle size of the tungsten carbide particles is not particularly limited. The average particle size of the tungsten carbide particles can be, for example, 0.1 μm or more and 3.5 μm or less. It has been confirmed that the cemented carbide of the first embodiment can have a long tool life regardless of the average particle size of the tungsten carbide particles.

[0044] <Binder Phase> In the first embodiment, the binder phase contains 50% by mass or more of cobalt. This can impart excellent toughness to the cemented carbide. The lower limit of the cobalt content of the binder phase may be 55% by mass or more, 60% by mass or more, or 65% by mass or more. The upper limit of the cobalt content of the binder phase may be 100% by mass or less, less than 100% by mass, 99% by mass or less, 98% by mass or less, 95% by mass or less, or 90% by mass or less. The cobalt content of the binder phase may be 50% by mass or more but less than 100% by mass, 60% by mass or more but 99% by mass or less, 65% by mass or more but 98% by mass or less, 65% by mass or more but 95% by mass or less, or 65% by mass or more but 90% by mass or less.

[0045] The method for measuring the cobalt content of the binder phase is as follows: The region where the binder phase exists is identified on the image after binarization processing using the same methods as (A1) to (F1) for measuring the content of tungsten carbide particles and the content of the binder phase in the cemented carbide. The region where the binder phase exists is analyzed using SEM-EDX to measure the cobalt content of the binder phase.

[0046] As far as the applicant has measured, as long as measurements are made on the same sample, even if the cut-out location of the cross section of the cemented carbide and the photographing area described in (C1) above are arbitrarily set and the cobalt content of the binder phase is measured multiple times according to the above procedure, there is little variation in the measurement results, and it has been confirmed that arbitrarily setting the cut-out location of the cross section of the cemented carbide and the photographing area is not arbitrary.

[0047] In embodiment 1, the binder phase may contain, in addition to cobalt, at least one second element selected from the group consisting of boron (B), aluminum (Al), silicon (Si), iron (Fe), nickel (Ni), germanium (Ge), ruthenium (Ru), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), tantalum (Ta), and niobium (Nb). The binder phase may consist of cobalt, the second element, and inevitable impurities. Examples of the inevitable impurities include manganese (Mn), magnesium (Mg), calcium (Ca), and sulfur (S). The content of the inevitable impurities in the binder phase is less than 0.1% by mass. The content of the impurity elements in the binder phase is measured by ICP atomic emission spectrometry.

[0048] <First Element> The cemented carbide of embodiment 1 contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron. The total content of the first elements in the cemented carbide is 0.01 atomic % or more and 20 atomic % or less. Here, the total content of the first elements means the content of one type of first element when the cemented carbide contains one type of first element, and means the total content of all first elements contained in the cemented carbide when the cemented carbide contains two or more types of first elements.

[0049] The lower limit of the total content of the first element in the cemented carbide is 0.01 atomic % or more, 0.07 atomic % or more, 0.09 atomic % or more, 0.10 atomic % or more, 0.50 atomic % or more, 1.0 atomic % or more, 3.0 atomic % or more, 5.0 atomic % or more, or 7.0 atomic % or more from the viewpoint of improving adhesion resistance. The upper limit of the content of the first element in the cemented carbide is 20.0 atomic % or less, 17.0 atomic % or less, 15.0 atomic % or less, 14.0 atomic % or less, or 10.0 atomic % or less from the viewpoint of suppressing deterioration of the basic physical properties of the cemented carbide. The total content of the first element in the cemented carbide may be 0.07 atomic % or more and 17.0 atomic % or less, 0.09 atomic % or more and 15.0 atomic % or less, 0.10 atomic % or more and 15.0 atomic % or less, 0.50 atomic % or more and 15.0 atomic % or less, 1.0 atomic % or more and 14.0 atomic % or less, 3.0 atomic % or more and 14.0 atomic % or less, 5.0 atomic % or more and 10.0 atomic % or less, or 7.0 atomic % or more and 10.0 atomic % or less.

[0050] The type of the first element contained in the cemented carbide and the content of the first element contained in the cemented carbide are identified by ICP emission spectrometry.

[0051] <Line Analysis> The results of line analysis of the cemented carbide of embodiment 1, performed along a first direction from adjacent binder phases toward tungsten carbide particles using an energy dispersive X-ray spectrometer attached to a transmission electron microscope, will be described with reference to FIG. 2. FIG. 2 is an example of a first graph showing the results of line analysis of the cemented carbide of embodiment 1, which are elements contained in the cemented carbide, tungsten, cobalt, and the first element (titanium in FIG. 2), in a coordinate system in which the X axis represents the distance [nm] from the position where cobalt shows the maximum intensity, and the Y axis represents the normalized intensity (normalized intensity) [a.u.]. In the cemented carbide shown in the first graph of FIG. 2, the binder phase is cobalt. In the first graph, the origin O is 0 nm along the X axis, and corresponds to the position where cobalt shows the maximum intensity in the line analysis results. The normalized intensity is the intensity relative to the maximum intensity within the region where the line analysis was performed, which is set to 100.

[0052] 2, the maximum peak M of the first element is located between the peak W1 of tungsten closest to the origin O of the first graph and another peak W2 of tungsten closest to the peak W1. The peak W2 is located farther from the origin O than the peak W1. That is, the maximum peak intensity I of the peak W1 ｗ１ Distance P at ｗ１ and the maximum peak intensity I of peak W2 ｗ２ Distance P at ｗ２ and the distance P1 at the maximum peak intensity IA of the maximum peak M is P ｗ１ <P1<P ｗ２ In the present disclosure, the peak intensity of the peak of each element in the first graph means the normalized intensity of the peak of each element.

[0053] The ratio IB / IA of the intensity IB to the maximum peak intensity IA of the maximum peak M is 0.5 or less. The intensity IB is the intensity of the first element at position P2, which is 0.2 nm away from the position P1 of the maximum peak intensity on the opposite side of the origin. In FIG. 2, the first element is one type of element (titanium), so there is one peak M. When the first element contains two or more types of elements, the number of maximum peaks of the first element is the same as the number of elements, and all peaks are between peaks W1 and W2, with the ratio IB / IA being 0.5 or less for each peak.

[0054] The upper limit of the ratio IB / IA is 0.5 or less, and may be 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The lower limit of the ratio IB / IA may be 0 or more, 0.001 or more, 0.002 or more, 0.003 or more, 0.005 or more, 0.01 or more, 0.02 or more, or 0.05 or more. The ratio IB / IA may be 0 or more and 0.5 or less, 0.001 or more and 0.5 or less, 0.005 or more and 0.4 or less, 0.01 or more and 0.3 or less, or 0.05 or more and 0.2 or less.

[0055] In the present disclosure, line analysis of a cemented carbide and acquisition of a first graph based on the analysis results are performed as follows: The cemented carbide is sliced ​​to a thickness of 30 to 100 nm using an argon ion slicer ("Cryo-ion Slicer IB-09060BCIS" (trademark) manufactured by JEOL Ltd.) at an acceleration voltage of 6 kV and a finishing voltage of 2 kV to prepare a measurement sample. Next, the measurement sample is observed at 200,000 magnification using a TEM (Transmission Electron Microscopy) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) at an acceleration voltage of 200 V to obtain a first image (not shown).

[0056] In the first image, the tungsten carbide particles are observed as white areas and the binder phase is observed as black areas. In the first image, the interface between the tungsten carbide particles and the binder phase is arbitrarily selected.

[0057] Next, the selected interface is positioned so that it passes near the center of the image, and the observation magnification is adjusted so that the field of view is 10 nm × 10 nm, thereby obtaining a second image (not shown). In the second image, the extension direction of the interface is confirmed. Line analysis is performed using an energy dispersive X-ray spectrometer (TEM-EDX) attached to a transmission electron microscope along a first direction perpendicular to the extension direction, from position X1 in the binder phase to position X2 in the tungsten carbide particle adjacent to the binder phase, to measure the distribution of tungsten, cobalt, and the first element. Here, the direction perpendicular to the extension direction of the interface refers to the direction along a straight line intersecting the tangent to the extension direction at an angle of 90° ± 5°. Position X1 in the binder phase is set to a position in the first graph that is 0.5 nm or more and 5 nm or less from the distance P1 of peak M toward the origin, where the cobalt peak can be confirmed. Position X2 within the tungsten carbide particle is set to a position in graph 1 where the distance from the distance P1 of peak M to the opposite side of the origin is 2 nm or more and 5 nm or less. The conditions for EDX are an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel count of 128 × 128 pixels, and a dwell time of 0.02 to 3 s / pixel.

[0058] A first graph is obtained by plotting the measurement results for tungsten, cobalt, and the first element in a coordinate system in which the X axis represents the distance from the position where cobalt shows the maximum intensity and the Y axis represents the normalized intensity.

[0059] Five non-overlapping first images of a cemented carbide are randomly acquired, and the above-described analysis is performed based on each of the first images to obtain five first graphs. If, in four or more of the first graphs, "the maximum peak M of each first element exists between peak W1 and peak W2, and the ratio IB / IA is 0.5 or less," it is determined that "the maximum peak M of each first element exists between peak W1 and peak W2, and the ratio IB / IA is 0.5 or less" in the first graph of the cemented carbide. To obtain this determination criterion, the inventors performed multiple line analyses on each of multiple cemented carbide alloys. As a result, it was confirmed that, when 80% or more of the first graphs of a cemented carbide show "the maximum peak M of each first element exists between peak W1 and peak W2, and the ratio IB / IA is 0.5 or less," the cemented carbide exhibits the effects of the present disclosure. Considering the manufacturing method of cemented carbide, it is presumed that the state of existence of tungsten and the first element in the interface region between the WC grains and the binder phase will be almost the same within the same cemented carbide.

[0060] <Method for manufacturing cemented carbide> The cemented carbide of this embodiment can be manufactured by carrying out a raw material powder preparation step, a mixing step, a molding step, a sintering step, a cooling step, and a HIP step in the above order. Each step will be described below.

[0061] <Preparation Step> The preparation step is a step of preparing raw material powders of materials constituting the cemented carbide material. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder, and powders containing a first element. Examples of powders containing a first element include TiCN powder, TaC powder, NbC powder, ZrC powder, and CeC powder. ２ Powder, Y ２ O ３ powder, B ４Examples of the raw material powder include C powder. In addition to these raw material powders, nickel (Ni) powder and the like can be prepared. These raw material powders can be commercially available. There are no particular limitations on the average particle size of these raw material powders, and they can be, for example, 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. The average particle size is measured using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0062] <Mixing Step> The mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio. By the mixing step, a mixed powder in which the raw material powders are mixed is obtained. The mixing ratio of the raw material powders is appropriately adjusted depending on the target composition of the cemented carbide.

[0063] The raw material powders can be mixed using a ball mill under the following mixing conditions: media diameter: 6 mm, rotation speed: 100 rpm, and mixing time: 20 hours.

[0064] After the mixing step, the mixed powder may be granulated as necessary. Granulating the mixed powder makes it easier to fill the mixed powder into a die or mold during the molding step described below. A known granulation method can be applied to the granulation, and for example, a commercially available granulator such as a spray dryer can be used.

[0065] <Molding step> The molding step is a step of molding the mixed powder obtained in the mixing step into a shape for a cutting tool to obtain a molded body. The molding method and molding conditions in the molding step are not particularly limited and may be general methods and conditions.

[0066] In the sintering step, the compact obtained in the compacting step is sintered to obtain a cemented carbide. In the method for producing a cemented carbide according to the present disclosure, the compact is first sintered in Ar gas at a pressure of 0.1 MPa and a temperature of 1400°C for 400 minutes (hereinafter also referred to as the "first sintering step"), and then sintered in Ar gas at a pressure of 5 MPa and a temperature of 1350°C for 300 minutes (hereinafter also referred to as the "second sintering step") to obtain a cemented carbide intermediate.

[0067] <Cooling Step> The cooling step is a step of cooling the cemented carbide intermediate body after the sintering step. For example, the cemented carbide intermediate body can be quenched in Ar gas under a pressure of 100 to 400 MPaG.

[0068] <HIP step> After cooling, the cemented carbide intermediate body is subjected to a pressure of 10 MPa for 60 minutes in a hot isostatic pressing (HIP) apparatus, thereby obtaining a cemented carbide.

[0069] <Features of the Manufacturing Method of the Cemented Carbide of the Present Embodiment> In the present embodiment, the mixing step is performed using a ball mill for 20 hours, and the sintering step is performed in two stages: first, a pressure of 0.1 MPa and a temperature of 1400°C are held for 400 minutes (first sintering step), and then a pressure of 5 MPa and a temperature of 1350°C are held for 300 minutes (second sintering step). It is presumed that the first graph of the resulting cemented carbide shows that "the maximum peak M of each first element is present between peaks W1 and W2, and the ratio IB / IA is 0.5 or less." The inventors have newly discovered, as a result of extensive research, that the cemented carbide of the present disclosure can be realized under such mixing and sintering conditions. The mixing and sintering conditions used in the present embodiment would not have been adopted by those skilled in the art because they would reduce production efficiency.

[0070] In a conventional method for manufacturing a cemented carbide, the mixing time is about 10 hours, and the sintering process is performed in one step by raising the temperature to a predetermined temperature and maintaining it for a predetermined time. In the cemented carbide obtained by the conventional method for manufacturing a cemented carbide, the first element is randomly arranged in the interface region between the WC grains and the binder phase, and in Graph 1, there is no maximum peak M of each of the first elements between Peak W1 and Peak W2.

[0071] [Embodiment 2: Cutting Tool] A cutting tool of this embodiment includes a cutting edge made of the cemented carbide of embodiment 1. In this disclosure, the cutting edge refers to a portion involved in cutting. More specifically, the cutting edge refers to a region surrounded by a cutting edge ridge and an imaginary plane that is 0.5 nm or 2 mm away from the cutting edge ridge toward the cemented carbide.

[0072] Examples of cutting tools include cutting tools, drills, end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metal saws, gear cutting tools, reamers, taps, etc. In particular, as shown in Figure 3, the cutting tool 10 of this embodiment is highly effective in the case of small-diameter drills for machining printed circuit boards. The cutting edge 11 of the cutting tool 10 shown in Figure 3 is made of the cemented carbide of embodiment 1.

[0073] The cemented carbide of this embodiment may constitute the entire tool or may constitute a part of the tool. Here, "constitute a part" refers to a mode in which the cemented carbide of this embodiment is brazed to a predetermined position of any substrate to form a cutting edge.

[0074] The cutting tool of this embodiment may further include a hard film that covers at least a portion of the surface of the substrate made of cemented carbide. The hard film may be made of, for example, diamond-like carbon or diamond.

[0075] The cutting tool of this embodiment can be obtained by forming the cemented carbide of embodiment 1 into a desired shape.

[0076] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0077] [Preparation of Cemented Carbide] Cemented carbide samples were prepared according to the following procedure.

[0078] WC powder (average particle size 0.5 μm), Co powder (average particle size 1.0 μm), TiCN powder (average particle size 0.1 μm), TaC powder (average particle size 0.3 μm), NbC powder (average particle size 0.3 μm), ZrC powder (average particle size 0.5 μm), CeC ２ Powder (average particle size 0.5 μm), Y ２ O ３ Powder (average particle size 0.5 μm), B ４ C powder (average particle size 0.5 μm) was prepared in the proportions shown in the “raw material powder” column of Tables 1 to 3.

[0079]

[0080]

[0081]

[0082] The raw material powders were mixed in a bead mill to obtain mixed powders. The mixing conditions (media diameter, rotation speed, filling rate, and time) were as follows. "Filling rate" refers to the bead filling rate. <Samples 1 to 48> Media diameter 6 mm, rotation speed 100 rpm, filling rate 40%, mixing time 20 hours. <Samples 49 to 76> Media diameter 6 mm, rotation speed 100 rpm, filling rate 40%, mixing time 10 hours.

[0083] Next, the mixed powder was press-molded to produce a green body in the shape of a cutting tip. The green body was then sintered to obtain a cemented carbide intermediate. The sintering conditions for each sample were as follows: <Samples 1 to 48> First sintering step: held in Ar gas at a pressure of 0.1 MPa and a temperature of 1400°C for 400 minutes. Second sintering step: held in Ar gas at a pressure of 5 MPa and a temperature of 1350°C for 300 minutes. <Samples 49 to 76> First sintering step: held in Ar gas at a pressure of 0.1 MPa and a temperature of 1400°C for 60 minutes. Second sintering step: none.

[0084] The "first sintering step" refers to a sintering step carried out immediately after the start of sintering. The "second sintering step" refers to a second sintering step carried out after the first sintering step. The entry "none" for the second sintering step indicates that the second sintering step was not carried out. Next, the cemented carbide intermediate was quenched in Ar gas under a pressure of 200 MPaG. A pressure of 10 MPa was applied to the cooled cemented carbide intermediate for 60 minutes in a hot isostatic pressing (HIP) device. This resulted in the production of each cemented carbide sample.

[0085] [Fabrication of Cutting Tools] The obtained cemented carbide alloy was machined to fabricate indexable cutting tools (shape: end mills).

[0086] [Evaluation of Cemented Carbide] <Content (volume %) of Tungsten Carbide Particles and Content (volume %) of Binder Phase in Cemented Carbide> The content (volume %) of tungsten carbide particles and the content (volume %) of binder phase in the cemented carbide of each sample were measured. Specific measurement methods are as described in Embodiment 1. The results are shown in the "WC Particle Content" and "Binder Phase Content" columns of "Cemented Carbide" in Tables 4 to 6. Furthermore, the total content of tungsten carbide particles and binder phase in the cemented carbide is shown in the "WC Particle + Binder Phase Content" column of "Cemented Carbide" in Tables 4 to 6. In Tables 4 to 6, cemented carbides with a "WC Particle + Binder Phase Content" column of less than 100% by volume were confirmed to contain precipitates or solid solutions of compounds containing the first element (e.g., TiCN or TaC).

[0087] <Cobalt content in binder phase> The cobalt content in the binder phase of each cemented carbide sample was measured. The specific measurement method is as described in embodiment 1. The results are shown in the "Co content in binder phase" column of "Cemented carbide" in Tables 4 to 6.

[0088] <Total Content of First Element in Cemented Carbide> The type and total content of the first element in each sample of cemented carbide was measured. The specific measurement method is as described in embodiment 1. The results are shown in the "Type of First Element" and "Total Content of First Element" columns of "Cemented Carbide" in Tables 7 to 9.

[0089] <Line Analysis> The line analysis shown in embodiment 1 was performed on each cemented carbide sample to obtain the first graph. In the first graph of each sample, it was confirmed whether or not the maximum peak M of each first element existed between the tungsten peak W1 closest to the origin and another tungsten peak W2 closest to peak W1. The results are shown in the "Maximum Peak M" column of "Cemented Carbide" in Tables 7 to 9. "Present" indicates that the maximum peak M exists, and "Absent" indicates that the maximum peak M does not exist. When multiple maximum peaks M exist, if all of the maximum peaks exist between W1 and W2, it is indicated as "present."

[0090] In samples having a "maximum peak M," the ratio IB / IA of the intensity IB to the maximum peak intensity IA of the maximum peak M was measured. Here, the intensity IB is the normalized intensity of the first element at position P2, which is 0.2 nm away from the position P1 of the maximum peak intensity on the opposite side of the origin of the first graph. The results are shown in the "IB / IA" column of "Cemented Carbide" in Tables 7 to 9.

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] <Cutting test> End milling was performed using the cutting tool of each sample under the following conditions, and the damage width on the flank was measured every 0.01 m of cutting distance. The damage width refers to the maximum length of damage on the flank caused by wear or chipping. In the case of wear, the maximum length corresponds to the maximum amount of wear, and in the case of chipping, it corresponds to the maximum loss length. The cutting distance at which the damage width reaches 0.1 mm is taken as the tool life. The results are shown in the "Cutting test" column of Tables 7 to 9. The longer the cutting distance, the longer the tool life.

[0098] <Cutting conditions> Workpiece: Inconel Processing: Side processing Cutting speed: 120 m / min Feed per tooth fz: 0.1 mm / t Axial depth of cut ap: 0.2 mm Radial depth of cut ae: 0.2 mm Cutting fluid: Water-soluble cutting oil The above cutting conditions apply to high-speed machining of difficult-to-cut materials.

[0099] <Discussion> The cemented carbide alloys and cutting tools of Samples 1 to 48 correspond to Examples. The cemented carbide alloys and cutting tools of Samples 49 to 76 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 1 to 48 (Examples) exhibited longer tool life in high-speed machining of difficult-to-cut materials than the cutting tools of Samples 49 to 76 (Comparative Examples). This is presumably because the cemented carbide alloys of Samples 1 to 48 (Examples) have Peak M and a ratio IB / IA of 0.5 or less, which improves adhesion resistance and suppresses the occurrence of wear and chipping due to adhesion.

[0100] Although the embodiments and examples of the present disclosure have been described above, it is originally intended that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0101] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0102] 1 tungsten carbide particles, 2 binder phase, 3 cemented carbide, 10 cutting tool, 11 cutting edge.

Claims

1. A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains a total of 80 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide contains 0.1 volume % or more and 20 volume % or less of the binder phase, the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium and boron, the cemented carbide contains a total of 0.01 atomic % or more and 20 atomic % or less of the first element, and the binder phase contains 50 mass % or more of cobalt, and a first graph showing the results of a line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from the binder phases adjacent to each other toward the tungsten carbide particles, the first graph being plotted in a coordinate system in which the X axis represents the distance from the position where cobalt shows the maximum intensity and the Y axis represents normalized intensity, a maximum peak M of each of the first elements is between a peak W1 of tungsten closest to the origin and another peak W2 of tungsten closest to the peak W1; for each of the first elements, a ratio IB / IA of an intensity IB to a maximum peak intensity IA of the maximum peak M is 0.5 or less; and the intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the origin from a distance P1 of the maximum peak intensity IA.

2. The cemented carbide of claim 1, wherein the cemented carbide comprises up to 18% by volume of the binder phase.

3. A cutting tool having a cutting edge made of the cemented carbide according to claim 1 or 2.

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