Hardmetal and cutting tools

Abstract

A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, the cemented carbide containing 80 volume % or more of the tungsten carbide particles and the binder phase, the cemented carbide containing 0.1 volume % or more and 20 volume % or less of the binder phase, the cemented carbide containing at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron, the cemented carbide containing 0.01 atomic % or more and 20 atomic % or less of the first element, the binder phase containing 50 mass % or more of cobalt, and a diffraction grating was performed using an energy dispersive X-ray microscope attached to a transmission electron microscope along a first direction from the binder phases adjacent to each other toward the tungsten carbide particles. In a first graph showing the results of line analysis using a line spectrometer 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 present between a tungsten peak W1 that is closest to the origin and another tungsten peak W2 that is 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.

Description

[Technical field]

[0001] The present disclosure relates to hardmetals and cutting tools. [Background technology]

[0002] 2. Description of the Related Art Cemented carbide having tungsten carbide (WC) particles and a binder phase mainly composed of cobalt or the like has been used as a material for cutting tools (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-098393 A [Patent Document 2] JP 2021-110010 A Summary of the Invention

[0004] The cemented carbide of the present disclosure is A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, The cemented carbide contains 80% by volume or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by 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 amount of 0.01 atomic % or more and 20 atomic % or less, The binder phase contains 50% by mass or more of cobalt, 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 adjacent binder phases toward the tungsten carbide particles, in a coordinate system in which the X-axis represents the distance from the position where cobalt has the maximum intensity and the Y-axis represents normalized intensity; A 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, For each of the first elements, a ratio IB / IA of an intensity IB of the maximum peak M to a maximum peak intensity IA is 0.5 or less; The intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the distance P1 of the maximum peak intensity IA toward the opposite side to the origin, and is a cemented carbide. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view of a cemented carbide according to a first embodiment. [Diagram 2] FIG. 2 shows an example of a first graph of the cemented carbide according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram of a cutting tool according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] In recent years, work materials have become increasingly difficult to cut. Furthermore, the demand for improved processing efficiency has 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 having a long tool life, particularly in high-speed machining of difficult-to-cut materials, and a cutting tool having a long tool life.

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

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The cemented carbide disclosed herein is A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, The cemented carbide contains 80% by volume or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by 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 amount of 0.01 atomic % or more and 20 atomic % or less, The binder phase contains 50% by mass or more of cobalt, 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 adjacent binder phases toward the tungsten carbide particles, in a coordinate system in which the X-axis represents the distance from the position where cobalt has the maximum intensity and the Y-axis represents normalized intensity; A 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, For each of the first elements, a ratio IB / IA of an intensity IB of the maximum peak M to a maximum peak intensity IA is 0.5 or less; The intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the distance P1 of the maximum peak intensity IA toward the opposite side to the origin, and is a cemented carbide.

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

[0011] (2) In the above (1), the cemented carbide may contain 18 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 according to (1) or (2) above.

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

[0014] [Details of the embodiment 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 this disclosure, an expression in the form "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[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 described as the lower limit and the upper limit of a numerical range, a combination of any one numerical value described as the lower limit and any one numerical value described as the upper limit is also disclosed. For example, when a1 or more, b1 or more, and c1 or more are described as the lower limit, and a2 or less, b2 or less, and c2 or less are described 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 disclosed.

[0018] [Embodiment 1: Carbide] The 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, The cemented carbide contains 80% by volume or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains 0.1% by volume or more and 20% by volume or less of the binder phase, The cemented carbide comprises 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 amount of 0.01 atomic % or more and 20 atomic % or less, The binder phase contains at least 50% by mass of cobalt, 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 adjacent binder phases toward the tungsten carbide particles, in a coordinate system in which the X-axis represents the distance from the position where cobalt has the maximum intensity and the Y-axis represents normalized intensity; a 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; For each of the first elements, a ratio IB / IA of an intensity IB of the maximum peak M to a maximum peak intensity IA is 0.5 or less; The intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the distance P1 of the maximum peak intensity IA toward the opposite side to the origin, and is a cemented carbide.

[0019] When used as a tool material, the cemented carbide of embodiment 1 can provide a cutting tool having a long tool life, particularly in high-speed machining of difficult-to-cut materials, and can provide a cutting tool having 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 includes 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 the 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 or more and 20% by volume or less, and the binder phase contains 50% by mass or more of cobalt. Thus, the cemented carbide has high hardness and strength, and a cutting tool using the cemented carbide can have excellent wear resistance and chipping resistance.

[0022] The cemented carbide of the first embodiment contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron in a total amount of 0.01 atomic % to 20 atomic %. In the first graph obtained by performing line analysis on the cemented carbide of the first embodiment, the maximum peak M of each first element exists between the tungsten peak W1 closest to the origin and another tungsten peak W2 closest to the peak W1. This indicates that the maximum concentration region of the first element exists in the surface layer portion 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 exists only in the surface layer portion of the tungsten carbide particle and does not penetrate deep inside the tungsten carbide particle.

[0023] In the cemented carbide of the first embodiment, the first element is present only in the surface layer of the tungsten carbide particles, so that the adhesion resistance of the cemented carbide is improved. As a result, when the cemented carbide of the first embodiment is used in a cutting tool, the occurrence of damage such as chipping caused by adhesion during cutting is suppressed. In addition, in the cemented carbide of the first embodiment, the first element does not penetrate deep into the inside of the tungsten carbide particles, so that 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 FIG. 1, the cemented carbide 3 of the first embodiment 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 the binder phase of the cemented carbide 3 is 80% by volume or more. The lower limit of the total content of the WC particles and the binder phase of the cemented carbide 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 binder phase of the cemented carbide may be 100% by volume or less. From the viewpoint of manufacturing, the upper limit of the total content of the WC particles and the binder phase of the cemented carbide may be 99% by volume or less, or 98% by volume or less. The total content of the WC particles and the binder phase of the cemented carbide may be 80% by volume or more and 100% by volume or less, 82% by volume or more and 100% by volume or less, or 84% by volume or more and 100% by volume or less.

[0025] The cemented carbide of the first embodiment can be composed of a plurality of tungsten carbide particles and a binder phase. The cemented carbide of the present embodiment can include other phases in addition to the tungsten carbide particles and the binder phase. The other phases can include at least one phase selected from the group consisting of TiCN, TiC, TiO2, TaC, Ta2O5, ZrC, ZrO2, CeC2, CeO2, YC, Y2O3, B4C and B2O3.

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

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

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

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

[0030] The method 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 is as follows.

[0031] (A1) An arbitrary position of the cemented carbide is cut out to expose a cross section, which is then mirror-finished 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 Gemini450 (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 is set to the center of the cross section of the cemented carbide, that is, a position that does not include areas with properties that are clearly different from the bulk part, such as the surface area 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 3kV, a current value of 2nA, and a working distance (WD) of 5mm.

[0034] (D1) The photographed region of (C1) above is analyzed using an energy dispersive X-ray analyzer attached to a SEM (SEM-EDX), 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 bond phase is shown in gray to black. Note that the binarization threshold changes depending on the contrast, so it is set for each image.

[0036] (F1) By superimposing the element mapping image obtained in (D1) above and the image after the binarization process obtained in (E1) above, the respective regions of the tungsten carbide particles and the binder phase are identified on the image after the binarization process. Specifically, the regions shown in white in the image after the binarization process and in which tungsten (W) and carbon (C) exist in the element mapping image correspond to the regions of the tungsten carbide particles. The regions shown in gray to black in the image after the binarization process and in which cobalt (Co) exists in the element mapping image correspond to the regions of the binder phase.

[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 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] If the cemented carbide contains other phases in addition to the WC particles and the binder phase, the content of the other phases in the cemented carbide can be obtained by subtracting the content (volume %) of the tungsten carbide particles 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 performed on the same sample, the cut-out location of the cemented carbide cross section, the photographing area described in (C1) above, and the measurement field of view described in (G1) above can be arbitrarily set, and even if 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 the cut-out location of the cemented carbide cross section, the photographing area, and the measurement field of view can be arbitrarily set without being 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 the maximum peak M of each of the first elements is between the tungsten peak W1 closest to the origin and another tungsten peak W2 closest to the peak W1 in a first graph obtained by performing line analysis on the cemented carbide.

[0042] As long as the effect of the present disclosure is not impaired, the tungsten carbide particles may contain impurity elements other than carbon, tungsten, and the first element. The content of the impurities in the tungsten carbide particles (when the impurities are composed of two or more elements, the total concentration of the elements) is less than 0.1 mass%. The content of the impurity elements in the tungsten carbide particles is measured by ICP 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] <Binded 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 and less than 100% by mass, 60% by mass or more and 99% by mass or less, 65% by mass or more and 98% by mass or less, 65% by mass or more and 95% by mass or less, or 65% by mass or more and 90% by mass or less.

[0045] The method for measuring the cobalt content of the binder phase is as follows. Using the same method as (A1) to (F1) for measuring the tungsten carbide particle content and binder phase content of the cemented carbide, the binder phase-existing region is identified on the image after the binarization process. The binder phase-existing region 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 the same sample is measured, even if the cut-out portion of the cross section of the cemented carbide and the photographed 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 portion of the cross section of the cemented carbide and the photographed area is not arbitrary.

[0047] In the first embodiment, the binder phase may contain 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) in addition to cobalt. The binder phase may be composed of cobalt, a 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 emission spectrometry.

[0048] <1st element> The cemented carbide of the first embodiment 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, may be 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 the adhesion resistance. The upper limit of the content of the first element in the cemented carbide is 20.0 atomic % or less, may be 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 from 0.07 atomic % to 17.0 atomic %, from 0.09 atomic % to 15.0 atomic %, from 0.10 atomic % to 15.0 atomic %, from 0.50 atomic % to 15.0 atomic %, from 1.0 atomic % to 14.0 atomic %, from 3.0 atomic % to 14.0 atomic %, from 5.0 atomic % to 10.0 atomic %, or from 7.0 atomic % to 10.0 atomic %.

[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 optical emission spectrometry.

[0051] <Line Analysis> In the cemented carbide of the first embodiment, the results of line analysis performed along the first direction from the adjacent binder phases toward the 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 performed on the cemented carbide of the first embodiment for tungsten, cobalt, and the first element (titanium in FIG. 2), which are elements contained in the cemented carbide, in a coordinate system in which the X-axis is the distance [nm] from the position where cobalt shows the maximum intensity, and the Y-axis is the normalized intensity (normalized intensity) [au]. 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 away from 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 shown relatively to the maximum intensity in the area where the line analysis was performed, which is set to 100.

[0052] As shown in FIG. 2, the maximum peak M of the first element is 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 away from the origin O than the peak W1. That is, the maximum peak intensity I of the peak W1 is 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 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 of the maximum peak M to the maximum peak intensity IA is 0.5 or less. distance The distance from P1 to the opposite side of the origin is 0.2 nm. distanceP2 is the intensity of the first element. 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 maximum peaks of the first element are present in the same number as the types of elements, all peaks are present between peaks W1 and W2, and the ratio IB / IA of each peak is 0.5 or less.

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

[0055] In the present disclosure, the line analysis of the cemented carbide and the acquisition of the 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.) under conditions of an acceleration voltage of 6 kV and finishing of 2 kV to prepare a measurement sample. Next, the measurement sample is observed at 200,000 times magnification using a TEM (Transmission Electron Microscopy) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) under conditions of 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 as to pass through the center of the image, and the observation magnification is adjusted so that the field of view size is 10 nm x 10 nm, and a second image is obtained (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 and extending from a position X1 in the bonding phase to a position X2 in a tungsten carbide particle adjacent to the bonding phase, and the distribution of tungsten, cobalt, and the first element is measured. Here, the direction perpendicular to the extension direction of the interface means a direction along a straight line intersecting the tangent of the extension direction at an angle of 90°±5°. The position X1 in the bonding phase is set to a position in the first graph where the distance from the distance P1 of the peak M to the origin side is 0.5 nm or more and 5 nm or less, and where the peak of cobalt can be confirmed. Position X2 in the tungsten carbide particle is set to a position where the distance from the distance P1 of the peak M to the opposite side of the origin is 2 nm or more and 5 nm or less in the first graph. The conditions for carrying out 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 has the maximum intensity and the Y-axis represents the normalized intensity.

[0059] For a cemented carbide, five mutually non-overlapping first images are arbitrarily obtained, and the above-mentioned analysis is performed based on each of the first images to obtain five first graphs. When "the maximum peak M of each of the first elements is between the peak W1 and the peak W2, and the ratio IB / IA is 0.5 or less" in four or more first graphs, it is determined that "the maximum peak M of each of the first elements is between the peak W1 and the peak W2, and the ratio IB / IA is 0.5 or less" in the first graph of the cemented carbide. In order to obtain this judgment criterion, the inventors performed multiple line analyses on each of multiple cemented carbide. As a result, it was confirmed that when "the maximum peak M of each of the first elements is between the peak W1 and the peak W2, and the ratio IB / IA is 0.5 or less" is shown in 80% or more of the first graphs of the cemented carbide, the cemented carbide exhibits the effect of the present disclosure. Considering the manufacturing method of the cemented carbide, it is presumed that the existence forms of tungsten and the first element in the interface region between the WC particles and the binder phase will be approximately the same within the same cemented carbide.

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

[0061] <Preparation process> 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 powder containing the first element. Examples of powder containing the first element include TiCN powder, TaC powder, NbC powder, ZrC powder, CeC2 powder, Y2O3 powder, and B4C 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. The average particle size of these raw material powders is not particularly limited and can be, for example, 0.1 to 3.0 μm. The average particle size of the raw material powder means 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 process> The mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio. A mixed powder in which the raw material powders are mixed is obtained by the mixing step. The mixing ratio of the raw material powders is appropriately adjusted depending on the composition of the target 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. By granulating the mixed powder, it becomes easier to fill the mixed powder into a die or a mold during the molding step described below. For granulation, a known granulation method can be applied, and for example, a commercially available granulator such as a spray dryer can be used.

[0065] <Forming process> 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] <Sintering process> In the sintering process, the compact obtained in the forming process is sintered to obtain a cemented carbide. In the method for manufacturing a cemented carbide of the present disclosure, first, it is held at a pressure of 0.1 MPa and a temperature of 1400 °C for 400 minutes in Ar gas (hereinafter, also referred to as the "first sintering process"), and then, it is held at a pressure of 5 MPa and a temperature of 1350 °C for 300 minutes in Ar gas (hereinafter, also referred to as the "second sintering process") to sinter the compact and obtain a cemented carbide intermediate.

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

[0068] <HIP process> A pressure of 10 MPa is applied to the cooled cemented carbide intermediate with a hot isostatic pressing (HIP) device for 60 minutes. Thereby, a cemented carbide can be obtained.

[0069] <Features of the method for manufacturing a cemented carbide of the present embodiment> In the present embodiment, the mixing process is performed for 20 hours using a ball mill, and the sintering process is performed in two steps: first, it is held at a pressure of 0.1 MPa and a temperature of 1400 °C for 400 minutes (the first sintering process), and then, it is held at a pressure of 5 MPa and a temperature of 1350 °C for 300 minutes (the second sintering process). As a result, it is presumed that the first graph of the obtained cemented carbide shows that "between peak W1 and peak W2, there is a maximum peak M of each of the first elements, and the ratio IB / IA is 0.5 or less". The fact that the cemented carbide of the present disclosure can be realized under such mixing conditions and sintering conditions is newly found as a result of the inventors' intensive studies. Note that the mixing conditions and sintering conditions used in the present embodiment are not those adopted by those skilled in the art because the production efficiency decreases.

[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 heating 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 particles and the binder phase, and in the first graph, the maximum peak M of each of the first elements does not exist between the peaks W1 and W2.

[0071] [Embodiment 2: Cutting tool] The cutting tool of this embodiment includes a cutting edge made of the cemented carbide of embodiment 1. In this disclosure, the cutting edge means a part involved in cutting. More specifically, the cutting edge means a region surrounded by a cutting edge ridge and a virtual surface that is 0.5 nm or 2 mm away from the cutting edge ridge toward the cemented carbide side.

[0072] Examples of cutting tools include cutting tools, drills, end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, taps, etc. In particular, as shown in Fig. 3, the cutting tool 10 of this embodiment can exhibit excellent effects in the case of a small diameter drill for processing printed circuit boards. The cutting edge 11 of the cutting tool 10 shown in Fig. 3 is made of the cemented carbide of the first embodiment.

[0073] The cemented carbide of the present embodiment may constitute the entirety of these tools, or may constitute a part of them. Here, "constitute a part" refers to a mode in which the cemented carbide of the present 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 covering at least a part of the surface of the substrate made of cemented carbide. The hard film may be made of, for example, diamond-like carbon or diamond.

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

[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] Each sample of cemented carbide was 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), CeC2 powder (average particle size 0.5 μm), Y2O3 powder (average particle size 0.5 μm), and B4C powder (average particle size 0.5 μm) were prepared in the proportions listed in the "Raw material powder" column of Tables 1 to 3.

[0079] [Table 1]

[0080] [Table 2]

[0081] [Table 3]

[0082] The raw material powders were mixed in a bead mill to obtain a mixed powder. The mixing conditions (media diameter, rotation speed, packing ratio, and time) were as follows. "Packing ratio" refers to the bead packing ratio. <Sample 1 to Sample 48> Media diameter 6 mm, rotation speed 100 rpm, filling rate 40%, mixing time 20 hours. <Sample 49 to Sample 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 having a cutting chip shape. Next, the green body was sintered to obtain a cemented carbide intermediate. The sintering conditions for each sample were as follows: <Sample 1 to Sample 48> First sintering process: Maintain in Ar gas at a pressure of 0.1 MPa and a temperature of 1400°C for 400 minutes. Second sintering process: Maintain in Ar gas at a pressure of 5 MPa and a temperature of 1350°C for 300 minutes. <Sample 49 to Sample 76> First sintering process: Maintain in Ar gas at a pressure of 0.1 MPa and a temperature of 1400°C for 60 minutes. Second sintering process: 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 at 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] [Cutting tool manufacturing] The obtained cemented carbide was machined to produce an indexable cutting tool (shape: end mill).

[0086] [Evaluation of cemented carbide] <Content (volume %) of tungsten carbide particles and binder phase (volume %) of cemented carbide> The content (volume %) of tungsten carbide particles and the content (volume %) of the binder phase in the cemented carbide of each sample were measured. The specific measurement method is as described in the first embodiment. The results are shown in the "WC particle content" and "binder phase content" columns of "carbide" in Tables 4 to 6. Furthermore, the total content of tungsten carbide particles and the binder phase in the cemented carbide are shown in the "WC particle + binder phase content" column of "carbide" in Tables 4 to 6. In Tables 4 to 6, it was confirmed that the cemented carbide with the "WC particle + binder phase content" column of less than 100 volume % contained precipitates or solid solutions of compounds containing the first element (e.g., TiCN and 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> For each sample of cemented carbide, the line analysis shown in embodiment 1 was performed 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 exists between the tungsten peak W1 closest to the origin and another tungsten peak W2 closest to the 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, "present" is indicated when all the maximum peaks exist between W1 and W2.

[0090] In the sample in which the "maximum peak M" exists, the ratio IB / IA of the intensity IB of the maximum peak M to the maximum peak intensity IA was measured. Here, the intensity IB is the maximum peak intensity. distance The distance from P1 to the opposite side of the origin of the first graph is 0.2 nm. distance The results are shown in the "IB / IA" column of "Cemented Carbide" in Tables 7 to 9.

[0091] [Table 4]

[0092] [Table 5]

[0093] [Table 6]

[0094] [Table 7]

[0095] [Table 8]

[0096] [Table 9]

[0097] <Cutting test> End milling was performed using the cutting tools of each sample under the following conditions, and the damage width on the flank was measured every 0.01 m of cutting distance. 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≫ Work material: Inconel Processing: Side processing Cutting speed: 120m / min Feed per tooth fz: 0.1mm / t Axial cutting depth ap: 0.2mm Radial cutting depth ae: 0.2mm Cutting fluid: Water-soluble cutting oil The above cutting conditions apply to high-speed machining of difficult-to-cut materials.

[0099] <Consideration> 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 a peak M and a ratio IB / IA of 0.5 or less, improving resistance to welding and suppressing the occurrence of wear and chipping due to welding.

[0100] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset 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 as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0102] 1 tungsten carbide particle, 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, The cemented carbide contains 80 volume % or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by 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 amount of 0.01 atomic % or more and 20 atomic % or less, The binder phase contains 50% by mass or more of cobalt, 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 adjacent binder phases toward the tungsten carbide particles, the results being plotted on a coordinate system in which the X-axis represents the distance from the position where cobalt has the maximum intensity and the Y-axis represents normalized intensity; A 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, 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; The intensity IB is the intensity of the first element at a distance P2 that is 0.2 nm away from the distance P1 of the maximum peak intensity IA toward the opposite side to the origin.

2. 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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