Cemented carbide and cutting tool

Abstract

To provide cemented carbide which enables provision of a cutting tool having a long tool life, particularly in working of a hard-to-machine material, even when used as tool material, and to provide a cutting tool having a long tool life.SOLUTION: Cemented carbide 3 includes 80 vol.% or more of tungsten carbide particles 1 and a binding phase 2 in total, the cemented carbide 3 includes 0.1 vol.% or more and 20 vol.% or less of the binding phase 2, the cemented carbide 3 includes at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium and boron, the cemented carbide 3 includes 0.01 atom% or more and 20 atom% or less of the total of the first elements, the cemented carbide 3 includes 0.5 mass% or more and 1.5 mass% or less of chromium, the binding phase 2 includes 50 mass% or more of cobalt, and the plurality of tungsten carbide particles 1 include first carbide tungsten particles and second carbide tungsten particles which are adjacent to each other.SELECTED DRAWING: Figure 1

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 [Problem to be solved by the invention]

[0004] In recent years, work materials have become increasingly difficult to cut in cutting processes. 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 when machining difficult-to-cut materials, and a cutting tool having a long tool life. [Means for solving the problem]

[0005] The present disclosure provides 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 cemented carbide contains 0.5% by mass or more and 1.5% by mass or less of chromium, The binder phase contains 50% by mass or more of cobalt, the plurality of tungsten carbide particles include adjacent first tungsten carbide particles and second tungsten carbide particles, a first graph showing a result of a line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from a position X1 inside the first tungsten carbide particle toward a position X2 inside the second tungsten carbide particle, the result being plotted on a coordinate system in which the X axis represents the distance from the position X1 and the Y axis represents normalized intensity; Between the first peak and the second peak of the first element, there is a maximum peak of chromium; the first peak is a maximum peak of the first element, The second peak is the second largest peak of the first element, the cemented carbide. Effect of the Invention

[0006] 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 machining difficult-to-cut materials, and a cutting tool having a long tool life. [Brief description of the drawings]

[0007] [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

[0008] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) The present disclosure provides 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 cemented carbide contains 0.5% by mass or more and 1.5% by mass or less of chromium, The binder phase contains 50% by mass or more of cobalt, the plurality of tungsten carbide particles include adjacent first tungsten carbide particles and second tungsten carbide particles, a first graph showing a result of a line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from a position X1 inside the first tungsten carbide particle toward a position X2 inside the second tungsten carbide particle, the result being plotted on a coordinate system in which the X axis represents the distance from the position X1 and the Y axis represents normalized intensity; Between the first peak and the second peak of the first element, there is a maximum peak of chromium; the first peak is a maximum peak of the first element, The second peak is the second largest peak of the first element, the cemented carbide.

[0009] 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 machining difficult-to-cut materials, and a cutting tool having a long tool life.

[0010] (2) In the above (1), a maximum peak of cobalt may be present between the first peak and the second peak in the first graph.

[0011] (3) In the above (1) or (2), the cemented carbide may contain 18 volume % or less of the binder phase, which further improves the hardness and wear resistance of the cemented carbide, thereby further improving the tool life of a cutting tool using the cemented carbide as a material.

[0012] (4) A cutting tool according to the present disclosure is a cutting tool having a cutting edge made of the cemented carbide according to any one of (1) to (3) above.

[0013] According to the present disclosure, a cutting tool having a long tool life can be provided.

[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 specification, the expression "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 specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and is not necessarily 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] 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, 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 cemented carbide contains 0.5% by mass or more and 1.5% by mass or less of chromium, The binder phase contains at least 50% by mass of cobalt, the plurality of tungsten carbide particles includes adjacent first tungsten carbide particles and adjacent second tungsten carbide particles, a first graph showing a result of a line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from a position X1 inside the first tungsten carbide particle toward a position X2 inside the second tungsten carbide particle, the result being plotted in a coordinate system in which the X axis represents the distance from position X1 and the Y axis represents normalized intensity; a maximum peak of chromium is present between the first peak and the second peak of the first element; the first peak is the maximum peak of the first element, The second peak is the second largest peak of the first element, the 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 machining 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 to 20% by volume, and the binder phase contains 50% by mass or more of cobalt. This allows the cemented carbide to have high toughness, and a cutting tool including a cutting edge made of the cemented carbide to have excellent 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 cemented carbide of the first embodiment, in a first graph obtained by performing a line analysis along a first direction from a position X1 provided inside the first tungsten carbide particle toward a position X2 provided inside the second tungsten carbide particle, a maximum peak of chromium exists between the first peak and the second peak of the first element. This indicates that a region with a high concentration of the first element exists near the surface of both the first tungsten carbide particle and the second tungsten carbide particle. More specifically, it indicates that the first element penetrates both the first tungsten carbide particle and the second tungsten carbide particle, and the first element exists near the surface of each tungsten carbide particle. In such a cemented carbide, the first element is easily dispersed and exists throughout the cemented carbide, and the chemical reaction between the cemented carbide and the workpiece is suppressed. Therefore, a cutting tool including a cutting edge made of this cemented carbide is less susceptible to wear and chipping caused by chemical reactions during cutting.

[0023] The cemented carbide of the first embodiment contains 0.5% by mass or more and 1.5% by mass or less of chromium. In a first graph obtained by performing line analysis on the cemented carbide of the first embodiment, the maximum peak of chromium exists between the first peak and the second peak of the first element. This indicates that the maximum concentration region of chromium exists in the binder phase. Such a cemented carbide has excellent corrosion resistance and an improved tool life.

[0024] <Composition of cemented carbide> 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 in the cemented carbide 3 is 80 volume % or more. The total content of the WC particles and the binder phase in the cemented carbide may be 80 volume % or more and 100 volume % or less, 82 volume % or more and 100 volume % or less, 84 volume % or more and 100 volume % or less, 85 volume % or more and 99 volume % or less, or 86 volume % or more and 98 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, B2O3, and NbC.

[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 permitted within a range that does not impair the effects of the present disclosure. For example, the content of the 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 the WC particles and the binder phase 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 tungsten carbide particle content of the cemented carbide of embodiment 1 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, may be 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, may be 19 volume % or less, may be 18 volume % or less, may be 17 volume % or less, may be 16 volume % or less, or may be 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, may be 1 volume % or more and 18 volume % or less, may be 3 volume % or more and 17 volume % or less, may be 5 volume % or more and 16 volume % or less, or may be 8 volume % or more and 15 volume % or less.

[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 in (C1) above is analyzed using SEM-EDX to identify the distribution of the elements identified in (B1) above in the photographed region, and an element mapping image is obtained.

[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 the present disclosure, the average of the area percentages of tungsten carbide particles in the five measurement fields corresponds to the content (volume %) of tungsten carbide particles in the cemented carbide, and the average of the area percentages of the binder phase in the five measurement fields corresponds to the content (volume %) of the binder phase in the cemented carbide.

[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, it has been confirmed that, as long as measurements are performed on the same sample, there is almost no variation in the measurement results, even when the cut-out location of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field of view described in (G1) above are arbitrarily set, and the tungsten carbide particle content and binder phase content of the cemented carbide are measured multiple times according to the above procedure.

[0041] <Tungsten carbide particles> In the first embodiment, the tungsten carbide particles may include tungsten carbide and at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, cerium, yttrium, and boron. The tungsten carbide particles may include impurity elements as long as the effects of the present disclosure are not impaired. Examples of impurity elements include iron (Fe), manganese (Mn), sulfur (S), and calcium (Ca). The tungsten carbide particles may be composed of tungsten carbide, a first element, and an impurity 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% by mass. The content of the impurity elements in the tungsten carbide particles is measured by ICP emission spectrometry.

[0042] 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.

[0043] <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 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, 70% by mass or more and 95% by mass or less, or 75% by mass or more and 90% by mass or less.

[0044] 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.

[0045] As far as the applicant has measured, it has been confirmed that, as long as the measurements are performed on the same sample, there is almost no variation in the measurement results even when the cut-out portion 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.

[0046] In the first embodiment, the binder phase may contain at least one secondary 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 secondary element and an impurity element. Examples of the impurity element include manganese (Mn), magnesium (Mg), calcium (Ca), and sulfur (S). The content of the impurity element in the binder phase is less than 0.1% by mass. The content of the impurity element in the binder phase is measured by ICP emission spectrometry.

[0047] <First 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 the first elements contained in the cemented carbide when the cemented carbide contains two or more types of first elements.

[0048] 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, may be 0.09 atomic % or more, may be 0.10 atomic % or more, may be 0.50 atomic % or more, may be 1.0 atomic % or more, may be 3.0 atomic % or more, may be 5.0 atomic % or more, or may be 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, may be 15.0 atomic % or less, may be 14.0 atomic % or less, or may be 10.0 atomic % or less, from the viewpoint of suppressing the 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 %.

[0049] 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.

[0050] <Chrome> The cemented carbide of the first embodiment contains 0.5% by mass or more and 1.5% by mass or less of chromium. The lower limit of the chromium content of the cemented carbide may be 0.7% by mass or more, or 1.0% by mass or more, from the viewpoint of improving the corrosion resistance of the cemented carbide. The upper limit of the chromium content of the cemented carbide may be 1.3% by mass or less, or 1.1% by mass or less, from the viewpoint of suppressing deterioration of the basic physical properties of the cemented carbide. The chromium content of the cemented carbide may be 0.7% by mass or more and 1.2% by mass or less, or 0.9% by mass or more and 1.1% by mass or less.

[0051] The chromium content in the cemented carbide is measured by ICP emission spectrometry.

[0052] <Line Analysis> The plurality of tungsten carbide particles of the cemented carbide of the first embodiment include adjacent first tungsten carbide particles and second tungsten carbide particles. The results of line analysis of the cemented carbide of the first embodiment, performed along a first direction from a position X1 provided inside the first tungsten carbide particle toward a position X2 provided inside the second tungsten carbide particle, 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 the first embodiment, tungsten, cobalt, the first element (titanium in FIG. 2) and chromium, which are elements contained in the cemented carbide, in a coordinate system in which the X axis is the distance from the position X1 and the Y axis is the normalized intensity. In the cemented carbide shown in the first graph of FIG. 2, the binder phase includes cobalt. In the first graph, the normalized intensity is the intensity of each element shown relatively to the maximum intensity in the area where the line analysis is performed, which is set to 100.

[0053] As shown in FIG. 2, the maximum peak of chromium P is between the first peak P1, which is the maximum peak of the first element, and the second peak P2, which is the second largest peak of the first element. Cr That is, there exists a distance L1 at the maximum peak intensity I1 of the first peak P1, a distance L2 at the maximum peak intensity I2 of the second peak P2, and a maximum peak PCr The maximum peak intensity I Cr of the distance L Cr means that L1 < L Cr < L2. In the present disclosure, the peak intensity of each element in the first graph means the normalized intensity of the peak of each element.

[0054] As shown in FIG. 2, between the first peak P1 and the second peak P2, there may be a maximum peak P of cobalt Co That is, the distance L1, the distance L2, and the maximum peak P of cobalt Cо The maximum peak intensity I Cо of the distance L Cо means that L1 < L Cо < L2 may be shown.

[0055] In at least a part of the first graph of the cemented carbide of Embodiment 1, it is confirmed that the peaks of tungsten periodically exist along the X-axis. The region where the peaks of tungsten periodically exist along the X-axis indicates the region where tungsten carbide particles exist. Further, in the first graph, the peak of the first element is confirmed in the region where the clearly confirmed periodic peaks of tungsten disappear. For example, in FIG. 2, the clearly confirmed periodic peaks of tungsten exist in the region indicated by W1, and the first peak P1 of the first element is confirmed in the region where the periodic peaks disappear. The first peak P1 of the first element is closer to the region W1 where the clearly confirmed periodic peaks of tungsten exist than the maximum peak P Cr of chromium and the maximum peak P Co of cobalt. This indicates that there is a region with a high concentration of the first element near the surface of the first tungsten carbide particles. More specifically, it indicates that the first element penetrates into the first tungsten carbide particles and the first element exists near the surface of the first tungsten carbide particles.

[0056] In the first graph of FIG. 2, the normalized intensity of tungsten increases in the region of approximately 2.5 to 4 nm on the X-axis (the region indicated by W2 in FIG. 2). This region also corresponds to the region where tungsten carbide particles are present, but no clear periodic peaks are observed. This is because the direction of the line analysis is not consistent with the direction of atomic arrangement in the tungsten carbide particles being measured. Even in this case, the second peak P2 of the first element is the maximum peak P of chromium. Cr and the maximum peak of cobalt, P Co The first element is closer to the region W2 where the tungsten intensity is increased than the first element. This indicates that a region with a high concentration of the first element exists near the surface of the second tungsten carbide particle. More specifically, this indicates that the first element penetrates into the second tungsten carbide particle and exists near the surface of the second tungsten carbide particle.

[0057] 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.

[0058] In the first image, the tungsten carbide particles are observed as white regions, and the binder phase is observed as black regions. In the first image, a region is arbitrarily selected in which one tungsten carbide particle (corresponding to the first tungsten carbide particle, hereinafter referred to as the "first tungsten carbide particle"), another tungsten carbide particle adjacent to the first tungsten carbide particle (corresponding to the second tungsten carbide particle, hereinafter also referred to as the "second tungsten carbide particle"), and the binder phase existing between the first tungsten carbide particle and the second tungsten carbide particle can be clearly confirmed. In this case, the distance between the outer edge of the first tungsten carbide particle and the outer edge of the second tungsten carbide particle (corresponding to the width of the binder phase) is selected to be 0.7 nm or more.

[0059] Next, in the selected region, the binder phase is placed near the center of the image, and a second image is obtained by adjusting the observation magnification so that the field of view size is 10 nm x 10 nm. In the second image, a line analysis is performed using an energy dispersive X-ray spectrometer (TEM-EDX) attached to a transmission electron microscope along a first direction from a position X1 inside the first tungsten carbide particle to a position X2 inside the second tungsten carbide particle to measure the distribution of tungsten, cobalt, the first element, and chromium.

[0060] Positions X1 and X2 are set so as to satisfy the following conditions. (a) Regarding position X1, the distance between an arbitrary point E1 on the outer edge of the first tungsten carbide particle and position X1 is 0.5 nm or more and 2 nm or less. (b) The distance between position X2 and any point E2 on the outer edge of the second tungsten carbide particle is 0.5 nm or more and 2 nm or less. (c) Point E1 and point E2 face each other via a binder phase. A straight line connecting point E1 and point E2 does not intersect with any outer edge of the first tungsten carbide particle other than point E1 and any outer edge of the second tungsten carbide particle other than point E2.

[0061] The conditions for EDX were an accelerating 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.

[0062] A first graph is obtained by plotting the measurement results of tungsten, cobalt, the first element and chromium in a coordinate system in which the X-axis represents the distance from position X1 and the Y-axis represents the normalized intensity.

[0063] For the 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. If "the maximum peak of chromium exists between the first peak and the second peak of the first element" in four or more first graphs, it is determined that "the maximum peak of chromium exists between the first peak and the second peak of the first element" in the first graph of the cemented carbide.

[0064] In order to obtain the above criteria, the inventors performed multiple line analyses on each of multiple cemented carbide alloys. As a result, it was confirmed that, among the cemented carbide alloys, when "the maximum peak of chromium exists between the first peak and the second peak of the first element" in 80% or more of the first graphs, the cemented carbide alloy exhibits the effect of the present disclosure. Considering the manufacturing method of the cemented carbide alloy, it is presumed that the existence forms of the first element and chromium are almost the same in the same cemented carbide alloy.

[0065] 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. If the cemented carbide has a "maximum peak of cobalt between the first peak and the second peak" in four or more first graphs, it is determined that the cemented carbide has a "maximum peak of cobalt between the first peak and the second peak" in the first graph. Considering the manufacturing method of the cemented carbide, it is presumed that the existence forms of the first element and chromium are almost the same in the same cemented carbide.

[0066] <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.

[0067] <Preparation process> In the preparation step, raw material powders are prepared. Examples of the raw material powders include first element-added tungsten carbide powder (hereinafter also referred to as "first element-added WC powder"), cobalt (Co) powder, chromium carbide (Cr3C2) powder, and chromium oxide (Cr2O3) powder.

[0068] The first element-added WC powder is produced by sintering a first mixed powder containing tungsten (W) powder, carbon (C) powder, and at least one first element-containing powder selected from the group consisting of TiCN, TiC, TiO2, TaC, Ta2O5, NbC, ZrC, ZrO2, CeC2, CeO2, YC, Y2O3, B4C, and B2O3, and then pulverizing the sintered powder. The sintering conditions are a temperature of 1400°C and a holding time of 60 minutes. The ratio of each powder in the first mixed powder is appropriately adjusted so that the total content of the first element in the cemented carbide produced using the first element-added WC powder obtained by sintering the first mixed powder is 0.01 atomic % or more and 20 atomic % or less.

[0069] In addition to the above raw material powders, nickel (Ni) powder and the like can be prepared. Raw material powders other than the first element-added WC powder can be commercially available. The average particle size of the 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 powders refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size is measured using a Fisher Scientific "Sub-Sieve Sizer Model 95" (trademark).

[0070] <Mixing process> In the mixing step, the raw material powders prepared in the preparation step are mixed in a predetermined ratio to obtain a second mixed powder. The ratio of the raw material powders in the second mixed powder is appropriately adjusted depending on the composition of the target cemented carbide.

[0071] For the mixing of each raw material powder, a ball mill can be used. The mixing conditions can be a media diameter of 6 mm, a rotation speed of 100 rpm, and a mixing time of 20 hours.

[0072] After the mixing step, the second mixed powder may be granulated as necessary. By granulating the second mixed powder, it is easier to fill the mixed powder into the die or mold during the subsequent molding step. For granulation, known granulation methods can be applied. For example, commercially available granulators such as spray dryers can be used.

[0073] <Molding Step> The molding step is a step of molding the second mixed powder obtained in the mixing step into the shape of a cutting tool to obtain a molded body. For the molding method and molding conditions in the molding step, general methods and conditions may be adopted and are not particularly limited.

[0074] <Sintering Step> In the sintering step, the molded body obtained in the molding step is sintered to obtain a cemented carbide intermediate. The sintering conditions are a pressure of 0.1 MPa and a temperature of 1400 °C in Ar gas, with a holding time of 400 minutes.

[0075] <Cooling Step> The cooling step is a step of cooling the cemented carbide intermediate after the sintering step. For example, the cemented carbide intermediate is quenched in Ar gas under the condition of a pressure of 100 - 400 KPaG.

[0076] <HIP Step> To the cemented carbide intermediate after the cooling step, a pressure of 50 MPa is applied for 60 minutes using a hot isostatic pressing (HIP) device. Thereby, a cemented carbide can be obtained.

[0077] <Features of the Method for Manufacturing Cemented Carbide of the Present Embodiment> In the method for producing a cemented carbide according to the present embodiment, a first element-added WC powder is used as a raw material powder. In the first element-added WC powder, a first element-containing powder containing the first element is present between WC particles. Therefore, in the cemented carbide after sintering, a region with a high concentration of the first element can be present near the surface of each WC particle. Therefore, in the cemented carbide obtained by the method for producing a cemented carbide according to the present embodiment, a first peak and a second peak of the first element are present in the first graph. In addition, the chromium powder is mixed with other raw material powders in the mixing step, and is present in the binder phase in the cemented carbide after sintering. Therefore, in the first graph of the cemented carbide, a maximum peak of chromium is present between the first peak and the second peak of the first element.

[0078] In the first element-added WC powder, the first element-containing powder containing the first element is present between WC particles. Therefore, in the sintering process, the grain growth of tungsten carbide particles is likely to be uniform. Therefore, in the cemented carbide after sintering, the grain size of the tungsten carbide particles is likely to be uniform, and the cutting tool including the cutting edge made of the cemented carbide is expected to have improved breakage resistance, crack resistance and chipping resistance, and thus improved tool life.

[0079] In a conventional method for manufacturing a cemented carbide, a raw material powder of the first element (e.g., a powder containing the first element) is prepared separately from WC, and in a mixing step, the raw material powder of the first element, WC powder, and other raw material powders are mixed to obtain a mixed powder. When the mixed powder is sintered, the first element penetrates into the interface region between the WC particles in the sintering step, and precipitates only on the surface of one of the two WC particles that form the interface. For this reason, in the cemented carbide obtained by the conventional method for manufacturing a cemented carbide, only one peak of the first element is present in the first graph.

[0080] [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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The cutting tool of this embodiment can be obtained by forming the cemented carbide of embodiment 1 into a desired shape. EXAMPLES

[0085] The present embodiment will be described more specifically with reference to examples, although the present embodiment is not limited to these examples.

[0086] [Preparation of cemented carbide] <Preparation process> As raw material powders, first element-added WC powder, tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder (average particle size: 1 μm), chromium carbide (Cr3C2) powder (average particle size: 1 μm), and chromium oxide (Cr2O3) powder (average particle size: 1 μm) were prepared. Furthermore, as first element-containing powders, TiCN powder, TaC powder, NbC powder, ZrC powder, CeO2 powder, Y2O3 powder, and B4C powder were prepared. The average particle size of the first element-containing powders was 1 μm.

[0087] The first element-added WC powder (average particle size: 1 μm) used in each sample was prepared by sintering a first mixed powder containing tungsten powder, carbon powder, and a powder containing the first element, followed by pulverization. The sintering conditions were a temperature of 1400°C and a holding time of 60 minutes. The respective contents (mass%) of tungsten powder, carbon powder, and powder containing the first element in the first mixed powder used in each sample are shown in the "W", "C", and "Powder containing first element" columns of "First mixed powder" in Tables 1 to 3. Note that in samples with "-" in the "Powder containing first element" column, the WC powder was prepared without using the powder containing the first element.

[0088] <Mixing process> The raw material powders prepared in the preparation step were mixed in a predetermined ratio to obtain a second mixed powder. The mixing conditions were a media diameter of 6 mm, a rotation speed of 100 rpm, and a mixing time of 20 hours. The content (mass%) of each raw material powder in the second mixed powder of each sample is shown in the "second mixed powder" column of Tables 1 to 3.

[0089] <Forming process> The mixed powder was pressed to obtain a rod-shaped compact.

[0090] <Sintering process> The compact obtained in the compacting step was sintered to obtain a cemented carbide intermediate body. The sintering conditions were a pressure of 0.1 MPa, a temperature of 1400°C in Ar gas, and a holding time of 400 minutes.

[0091] <Cooling process> The cemented carbide intermediate body after the sintering step was quenched in Ar gas under a pressure of 300 KPaG.

[0092] <HIP Process> After the cooling process, a pressure of 50 MPa was applied to the cemented carbide intermediate by a hot isostatic pressing (HIP) apparatus for 60 minutes. As a result, the cemented carbide of each sample was obtained.

[0093]

Table 1

[0094]

Table 2

[0095]

Table 3

[0096] [Evaluation of Cemented Carbide] <Volume% of tungsten carbide particles and volume% of binder phase in cemented carbide> The volume% of tungsten carbide particles and the volume% of the binder phase of the cemented carbide of each sample were measured. The specific measurement method is as described in Embodiment 1. The results are shown in the "WC particle content" and "binder phase content" columns of "Cemented Carbide" in Tables 4 to 6. Furthermore, the total of the volume% of tungsten carbide particles and the volume% of the binder phase of the cemented carbide is shown in the "WC particles + binder phase content" column. It was confirmed that the cemented carbide with a "WC particles + binder phase content" column of less than 100% by volume further contains a phase composed of at least one selected from the group consisting of TiCN, TaC, NbC, ZrC, CeO2, Y2O3, and B4C.

[0097] <Cobalt content of binder phase> In the cemented carbide of each sample, the cobalt content of the binder phase 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 Tables 4 to 6.

[0098] <Type and total content of first element in cemented carbide> The type and total content of the first element in each sample of cemented carbide were measured by ICP emission spectrometry. The results are shown in the "Type" and "Total Content" columns of "First Element" in Tables 4 to 6.

[0099] <Chromium content in cemented carbide> The chromium content of each sample of cemented carbide was measured by ICP emission spectrometry. The results are shown in the "Cr content" column of Tables 4 to 6.

[0100] [Table 4]

[0101] [Table 5]

[0102] [Table 6]

[0103] <Line Analysis> For each sample of cemented carbide, the line analysis shown in the first embodiment was performed to obtain a first graph. In the first graph for each sample, the maximum peak P1 of chromium is between the first peak P1, which is the maximum peak of the first element, and the second peak P2, which is the second largest peak of the first element. Cr The results are shown in the first graph of Tables 7 to 9, "P1 / P Cr The results are shown in the "Yes / No" column of " / P2". "Yes" indicates that there is a maximum chromium peak P between the first peak P1 and the second peak P2 of the first element. Cr If "No", the presumed reason is given in "P1 / P Cr The reasons A to D are as follows: A: The content of the first element in the cemented carbide was too low, so the peak of the first element was not confirmed. B: In the mixing process, WC particles were used instead of the first element-added WC powder, so only one peak of the first element was confirmed. C: There was a large amount of binder phase, the distance between WC particles was large, and the proportion of Cr was reduced, so no Cr peak was observed. D: The content of the first element in the cemented carbide was too high, so the Cr peak was not confirmed, or the first and second peaks could not be distinguished.

[0104] In the first graph of each sample, the maximum peak of cobalt P is between the first peak P1, which is the maximum peak of the first element, and the second peak P2, which is the second largest peak of the first element. Co The results are shown in the first graph of Tables 7 to 9, "P1 / P Co "Yes" indicates that there is a maximum peak P of cobalt between the first peak P1 and the second peak P2 of the first element. Co If "No", the presumed reason is given in "P1 / P Cr The reasons E to H are as follows: E: The content of the first element in the cemented carbide was too low, so the peak of the first element was not confirmed. F: In the mixing process, WC particles were used instead of the first element-added WC powder, so only one peak of the first element was confirmed. G: There was a large amount of binder phase, the distance between WC particles was large, and the proportion of Co was reduced, so no Co peak was observed. H: The content of the first element in the cemented carbide was too high, so the Co peak was not confirmed, or the first peak and the second peak could not be distinguished.

[0105] [Table 7]

[0106] [Table 8]

[0107] [Table 9]

[0108] [Cutting test] A round bar made of cemented carbide of each sample was machined to produce an end mill with a blade diameter of φ6 mm. The end mill was used to machine the side surface of SUS316. The machining conditions were cutting speed Vc200m / min, feed per blade fz0.1mm / blade, cutting depth (axial direction) ap0.2mm, cutting depth (radial direction) ae0.2mm, wet. The cutting length was measured until the damage width due to wear and chipping on the flank reached 0.1mm. The longer the cutting length, the longer the tool life. The results are shown in the "Cutting length" column of "Cutting test" in Tables 7 to 9. The above machining conditions apply to cutting difficult-to-cut materials.

[0109] [Consideration] The cemented carbide and cutting tools of Samples 1 to 48 correspond to Examples. The cemented carbide and cutting tools of Samples 101 to 128 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 1 to 48 had longer tool lives than the cutting tools of Samples 101 to 128.

[0110] 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. 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]

[0111] 1 Tungsten carbide particles 2 Bonded phase 3. Cemented carbide 10 cutting tools 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 cemented carbide contains 0.5% by mass or more and 1.5% by mass or less of chromium, The binder phase contains 50% by mass or more of cobalt, the plurality of tungsten carbide particles include adjacent first tungsten carbide particles and second tungsten carbide particles, a first graph showing a result of a line analysis performed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope along a first direction from a position X1 inside the first tungsten carbide particle toward a position X2 inside the second tungsten carbide particle, the result being plotted on a coordinate system in which the X axis represents the distance from the position X1 and the Y axis represents normalized intensity; Between the first peak and the second peak of the first element, there is a maximum peak of chromium; the first peak is a maximum peak of the first element, The second peak is the second largest peak of the first element.

2. 2. The cemented carbide of claim 1, wherein in the first graph, a maximum peak of cobalt is present between the first peak and the second peak.

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

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

Images