Tungsten carbide powder and tungsten carbide mixed powder

Abstract

The purpose of the present disclosure is to provide a tungsten carbide powder and a tungsten carbide mixed powder that, when used as a raw material of a cemented carbide, allow a PCB drill which comprises the cemented carbide to have a long tool life.　The present disclosure relates to a tungsten carbide powder comprising first tungsten carbide particles to which a first element has been added, wherein the first element is at least one element selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and in a first graph on which a result that is obtained by using an energy dispersive X-ray spectrometer attached to a transmission electron microscope to perform line analysis from a position X1, which is set inside the first tungsten carbide particles and which is at a distance of not less than 6 nm from the outer edge of the first tungsten carbide particles to a position X2, which is set outside the first tungsten carbide particles and which is at a distance of not less than 6 nm from the outer edge of the first tungsten carbide particles is shown in a coordinate system where the X-axis represents the distance from the position X1 and the Y-axis represents a net strength, a first range in which the total net strength of the first element is greater than the net strength of tungsten is present at a distance from the point of origin that is greater than a distance P1, at which the net strength of tungsten is 0.5 times the maximum net strength of tungsten.

Description

Tungsten carbide powder and tungsten carbide mixed powder

[0001] This disclosure relates to tungsten carbide powder and tungsten carbide mixed powder.

[0002] Conventionally, cemented carbide alloys obtained by firing a mixed powder of tungsten carbide powder and cobalt powder have been used as materials for cutting tools (Patent Document 1).

[0003] International Publication No. 2024 / 005017

[0004] The tungsten carbide powder of this disclosure is a tungsten carbide powder comprising first tungsten carbide particles to which a first element is added, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and is provided inside the first tungsten carbide particles and at a distance of 6 nm or more from the outer edge of the first tungsten carbide particles, and is provided outside the first tungsten carbide particles and at a distance of 6 nm or more from the outer edge of the first tungsten carbide particles. In a first graph showing the results obtained by performing line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope toward a position X2 at a distance of 6 nm or more, in a coordinate system where the X axis is the distance from the position X1 and the Y axis is the net intensity, there exists a first range where the sum of the net intensities of the first element is greater than the net intensity of tungsten, at a distance P1 from the origin where the net intensity of tungsten is 0.5 times the maximum net intensity of tungsten.

[0005] Figure 1 is an example of a first graph obtained by performing line analysis on the first tungsten carbide particles of Embodiment 1.

[0006] [Problems this disclosure aims to solve] In recent years, technologies have been developed to improve the heat resistance of printed circuit boards in order to cope with the increasing amount of information they can hold. On the other hand, this has made printed circuit boards more difficult to machine. As a result, cutting tools used for drilling holes in printed circuit boards (hereinafter also referred to as "PCB drills") tend to break or chip easily.

[0007] Therefore, the present disclosure aims to provide tungsten carbide powder and tungsten carbide mixed powder that, when used as raw materials for cemented carbide, enable PCB drills equipped with the cemented carbide to have a long tool life.

[0008] [Effects of this disclosure] According to this disclosure, it is possible to provide tungsten carbide powder and tungsten carbide mixed powder that, when used as a raw material for cemented carbide, enable PCB drills equipped with the cemented carbide to have a long tool life.

[0009] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. (1) The tungsten carbide powder of the Disclosure is a tungsten carbide powder comprising first tungsten carbide particles to which a first element has been added, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and is provided inside the first tungsten carbide particles and from a position X1 at a distance of 6 nm or more from the outer edge of the first tungsten carbide particles to the outside of the first tungsten carbide particles and from the outer edge of the first tungsten carbide particles In a first graph showing the results obtained by performing line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope toward a position X2 where the distance from the line is 6 nm or more, in a coordinate system where the X axis is the distance from the position X1 and the Y axis is the net intensity, there exists a first range where the sum of the net intensities of the first element is greater than the net intensity of tungsten, at a distance P1 that is further from the origin than the distance where the net intensity of tungsten is 0.5 times the maximum net intensity of tungsten, which is the tungsten carbide powder.

[0010] According to this disclosure, it is possible to provide tungsten carbide powder that, when used as a raw material for cemented carbide, enables PCB drills equipped with the cemented carbide to have a long tool life. The reason for this is presumed to be as follows.

[0011] The first element can improve the reactivity resistance of cemented carbide. Conventionally, when mixing tungsten carbide powder and cobalt powder, the raw material powder of the first element was added and mixed, and then the mixed powder was fired to produce cemented carbide containing the first element. In this cemented carbide, a coarse hard phase containing the first element was formed, which reduced the bending strength of the cemented carbide. With conventional cemented carbide, it was difficult to achieve both improved reactivity resistance and improved bending strength.

[0012] In the tungsten carbide powder of this disclosure, the first element is present on the surface of the first tungsten carbide particles. When manufacturing cemented carbide using the tungsten carbide powder of this disclosure, it is not necessary to add raw material powder of the first element. Therefore, in cemented carbide manufactured using the tungsten carbide powder of this disclosure, the hard phase containing the first element can be finely dispersed in the cemented carbide structure without becoming coarse. This suppresses grain growth of tungsten carbide particles in the cemented carbide, resulting in an alloy structure with uniform particle size. Furthermore, since the hard phase containing the coarse first element, which is the starting point for fracture and chipping, is reduced, the flexural strength of the cemented carbide is improved. Therefore, a PCB drill equipped with a cemented carbide manufactured using the tungsten carbide powder of this disclosure as a raw material can have a long tool life.

[0013] (2) In (1) above, the content of the first element in the tungsten carbide powder may be 0.01% by mass or more and 2% by mass or less. If the content of the first element in the tungsten carbide powder is 0.01% by mass or more, the flexural strength of the cemented carbide made from the tungsten carbide powder is further improved. If the content of the first element in the tungsten carbide powder is 2% by mass or less, the cemented carbide has excellent flexural strength and damage due to wear of the cemented carbide is suppressed.

[0014] (3) In (1) or (2) above, the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles may be 0.05 or more and 0.7 or less.

[0015] When the D10 / D90 ratio is 0.05 or higher, the balance between fine primary tungsten carbide particles and coarse primary tungsten carbide particles in the tungsten carbide powder is good, resulting in a dense cemented carbide structure. When the D10 / D90 ratio is 0.7 or lower, the particle size of the cemented carbide produced using the tungsten carbide powder as a raw material becomes more uniform, further improving the flexural strength of the cemented carbide.

[0016] (4) In any of (1) to (3) above, the 50% cumulative particle size D50 based on the number of first tungsten carbide particles may be 0.2 μm or more and 3.0 μm or less. When D50 is 0.2 μm or more, the cemented carbide made from the tungsten carbide powder tends to have toughness suitable for PCB drills. When D50 is 3.0 μm or less, the cemented carbide tends to have hardness suitable for PCB drills.

[0017] (5) The tungsten carbide mixed powder of the present disclosure is a tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in any of (1) to (4) above.

[0018] For the same reasons as in (1) above, the present disclosure makes it possible to provide a tungsten carbide mixed powder that, when used as a raw material for a cemented carbide, enables a PCB drill equipped with the cemented carbide to have a long tool life.

[0019] (6) In (5) above, the tungsten carbide mixed powder may contain 20% by mass or more of the first tungsten carbide particles. This further improves the tool life of a cutting tool made of cemented carbide manufactured using the tungsten carbide mixed powder as a raw material.

[0020] [Details of Embodiments of the Disclosure] Specific examples of the tungsten carbide powder and tungsten carbide mixed powder of the Disclosure will be described below with reference to the drawings. In the drawings of the Disclosure, the same reference numerals indicate the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0021] In this disclosure, the notation "A to B" means A or greater and B or less. If no unit is specified for A, and only a unit is specified for B, then the unit for A and the unit for B are the same.

[0022] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0023] In this disclosure, if one or more numerical values ​​are listed as the lower limit and upper limit of a numerical range, any combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit shall also be disclosed.

[0024] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0025] [Embodiment 1: Tungsten Carbide Powder] The tungsten carbide powder according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a tungsten carbide powder comprising first tungsten carbide particles to which a first element has been added, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and is provided inside the first tungsten carbide particles and is provided outside the first tungsten carbide particles from a position X1 that is 6 nm or more away from the outer edge of the first tungsten carbide particles, and the first tungsten carbide In the first graph, which shows the results obtained by line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope toward position X2, where the distance from the outer edge of the tungsten carbide particles is 6 nm or more, in a coordinate system where the X axis is the distance from position X1 and the Y axis is the net intensity, there exists a first range where the sum of the net intensities of the first element is greater than the net intensity of tungsten, at a distance P1 where the net intensity of tungsten is 0.5 times the maximum net intensity of tungsten, and this range is indicative of tungsten carbide powder.

[0026] The tungsten carbide powder of Embodiment 1 consists of primary tungsten carbide particles to which a primary element has been added. The tungsten carbide powder of Embodiment 1 may consist of one primary tungsten carbide particle or a plurality of primary tungsten carbide particles. The tungsten carbide powder of Embodiment 1 may contain unavoidable impurities as long as the effects of the present disclosure are not impaired. Examples of unavoidable impurities include Al, Ca, Cr, V, Cu, Fe, Mg, Mn, Mo, Ni, Si, Sn, etc.

[0027] <First Tungsten Carbide Particles> <First Graph> First tungsten carbide particles are tungsten particles to which the first element has been added. The first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium.

[0028] In tungsten carbide particles, the first element is present on the surface of the tungsten carbide particle. Specifically, in the first graph above, there exists a first range where the sum of the net strengths of the first element is greater than the net strength of tungsten, at a distance P1 from the origin where the net strength of tungsten is 0.5 times the maximum net strength of tungsten.

[0029] In this disclosure, the first graph is prepared by the following procedure. Tungsten carbide powder is embedded in resin, and a sample for measurement is prepared by thinning it 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 a finishing voltage of 2 kV. A general resin used for alloy observation can be used as the resin.

[0030] Next, the sample for measurement is observed at 200,000x magnification under an acceleration voltage of 200V using a transmission electron microscope (TEM) ("JEM-ARM300F2" trademark, manufactured by JEOL Ltd.) to obtain a dark-field image (hereinafter also referred to as "first image"). In the first image, tungsten carbide particles are observed as white to gray regions, and the resin is observed as a black region. In the first image, the interface between the tungsten carbide particles and the resin is arbitrarily selected. This interface corresponds to the outer edge of the tungsten carbide particles.

[0031] Next, the selected interface is positioned so that it passes near the center of the image, and the observation magnification is adjusted so that the field of view size is 10 nm × 10 nm to obtain a second image. In the second image, a position X1 is set inside the tungsten carbide particle, at a distance of 6 nm or more from the interface along a direction perpendicular to the extension direction of the interface. Here, the direction perpendicular to the extension direction of the interface means the direction along a straight line that intersects the tangent to the extension direction at an angle of 90° ± 5°. Furthermore, in the second image, a position X2 is set on the line along the direction perpendicular to the extension direction of the interface that passes through position X1, and outside the tungsten carbide particle, but located inside the resin. The distance between the interface and position X2 is 6 nm or more.

[0032] Perform line analysis using an energy-dispersive X-ray spectrometer (TEM-EDX) attached to a transmission electron microscope along the first direction from position X1 to position X2, and measure the distribution of tungsten and the first element. The conditions during EDX implementation are an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel number of 128×128 pixels, and a dwell time of 0.02 - 3 s / pixel.

[0033] Obtain a first graph by showing the line analysis results in a coordinate system where the X-axis is the distance from position X1 and the Y-axis is the net intensity. When the first tungsten carbide particles contain two or more first elements, the net intensity of the first graph is the sum of the net intensities of all the first elements.

[0034] FIG. 1 is an example of a first graph obtained by performing line analysis on the first tungsten carbide particles of Embodiment 1. In FIG. 1, the horizontal axis (X-axis) indicates the distance [nm] from position X1, and the vertical axis (Y-axis) indicates the net intensity [a.u.]. In FIG. 1, the first element is titanium (Ti).

[0035] In the first graph, identify the maximum net intensity W of tungsten (W). max In the first graph, identify the distance P1 where tungsten shows a net intensity W that is 0.5 times the maximum net intensity W. max In FIG. 1, there is a first range where the net intensity of titanium (the first element) is greater than the net intensity of tungsten at a distance from the origin farther than distance P1. 0.5max It has been confirmed that as long as the same first tungsten carbide particles are measured by the above procedure, there is almost no variation in the line analysis results even if the measurement location of the line analysis is changed.

[0036] It has been confirmed that as long as the same first tungsten carbide particles are measured by the above procedure, there is almost no variation in the line analysis results even if the measurement location of the line analysis is changed.

[0037] <<Particle Size of First Tungsten Carbide Particles>> In the case where the tungsten carbide powder of Embodiment 1 consists of a plurality of first tungsten carbide particles, the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles is 0.05 or more and 0.7 or less, and may also be 0.10 or more and 0.5 or less, 0.15 or more and 0.45 or less, or 0.2 or more and 0.4 or less.

[0038] In the case where the tungsten carbide powder of Embodiment 1 consists of a plurality of primary tungsten carbide particles, the 50% cumulative particle size D50 based on the number of primary tungsten carbide particles may be 0.2 μm or more and 3.0 μm or less, 0.3 μm or more and 2.0 μm or less, 0.4 μm or more and 1.0 μm or less, or 0.5 μm or more and 0.8 μm or less.

[0039] In this disclosure, the cumulative particle size distribution based on the number of primary tungsten carbide particles is measured using a laser diffraction / scattering particle size distribution analyzer, the "MT3000EXII" (trademark) manufactured by MicrotracBEL. The amount of primary tungsten carbide particles to be measured is approximately 0.05 g to 2 g, or 30 million or more.

[0040] <Tungsten Carbide Powder> <Content of the First Element> The content of the first element in the first tungsten carbide powder of Embodiment 1 may be 0.01% by mass or more and 2% by mass or less, 0.1% by mass or more and 1.4% by mass or less, 0.3% by mass or more and 1.2% by mass or less, 0.4% by mass or more and 1.1% by mass or less, or 0.5% by mass or more and 1.0% by mass or less.

[0041] The content of element I in tungsten carbide powder is measured by ICP (Inductively Coupled Plasma) emission spectrometry (measuring device: Shimadzu Corporation's "ICPS-8100" trademark).

[0042] <Method for producing tungsten carbide powder> The method for producing tungsten carbide powder according to Embodiment 1 may include a raw material preparation step, a mixing step, a carbonization step, and a crushing step.

[0043] <<Raw Material Preparation Step>> In the raw material preparation step, metallic tungsten powder (hereinafter also referred to as "W powder"), carbon powder (hereinafter also referred to as "C powder"), and oxide powder of a first element are prepared. As the oxide powder of the first element, TiO ２ powder, ZrO ２ powder, Nb ２ O ５ powder, Ta ２ O ５ powder, MoO ２ powder, CeO ２ powder, and Y ２ O ３ powder, at least one selected from the group consisting thereof is prepared.

[0044] <<Mixing Step>> In the mixing step, the W powder, C powder, and the oxide powder of the first element are strongly mixed using a dry attritor, and then weakly mixed using a wet ball mill to obtain a mixed powder. The mixing conditions of the dry attritor are: cemented carbide media diameter: 3 mm, rotation speed: 40 rpm, mixing time: 1 hour. The mixing conditions of the wet ball mill are: cemented carbide media diameter: 6 mm, rotation speed 30 rpm, mixing time: 6 hours.

[0045] <<Carbonization Step>> In the carbonization step, the mixed powder is charged into a batch furnace and heated at 1500 °C for 2 hours under a vacuum atmosphere.

[0046] <<Crushing Step>> In the crushing step, the mixed powder after the carbonization step is crushed using a dry ball mill to obtain the tungsten carbide powder of Embodiment 1. The conditions of the dry ball mill are: cemented carbide media diameter: 6 mm, rotation speed 5 rpm, crushing time: 2 hours.

[0047] <<Features of the Method for Producing Tungsten Carbide Powder of Embodiment 1>> In the mixing step of the method for producing tungsten carbide powder of Embodiment 1, the oxide powder of the first element is strongly mixed using a dry attritor, and then mixed using a wet ball mill to obtain a mixed powder. By using the dry attritor and the wet ball mill, the oxide powder of the first element can be uniformly adhered to the surface of the W powder. In the conventional mixing step, since it was generally carried out using a mixer, the oxide powder of the first element could not be uniformly adhered to the surface of the W powder.

[0048] In the carbonization step of the method for producing tungsten carbide powder in Embodiment 1, the mixed powder is heated at 1500°C for 2 hours. This carbonizes the W powder, forming WC particles with the first element added. Because high temperature and short duration heating are employed, aggregation of the first element oxide powder is suppressed. In the mixed powder of Embodiment 1, since the first element oxide powder is uniformly attached to the surface of the W powder, even with high temperature and short duration heating, particle growth of WC particles is suppressed, and WC particles with uniform particle size can be obtained. Conventional carbonization steps were generally carried out at low temperatures and for long durations (for example, 1300°C for 6 hours) to suppress particle growth of WC particles. As a result, aggregation of the first element oxide powder was likely to occur.

[0049] The method for producing tungsten carbide powder according to Embodiment 1 includes a crushing step. The crushing step allows the first element to adhere more strongly to the surface of the WC particles.

[0050] [Embodiment 2: Tungsten Carbide Mixed Powder] The tungsten carbide mixed powder according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in Embodiment 1.

[0051] The tungsten carbide mixed powder of Embodiment 2 consists of the first tungsten carbide particles described in Embodiment 1 and a different type of tungsten carbide particles. The different type of tungsten carbide particles is not particularly limited as long as it does not impair the effects of the present disclosure. The different type of tungsten carbide particles may be, for example, tungsten carbide particles consisting only of tungsten carbide, or conventionally known tungsten carbide particles containing additive elements (such as Ti, Nb, Hf, Mo, Ta, Zr). In conventionally known tungsten carbide particles containing additive elements, the form of the additive element is different from the form of the first element in the first tungsten carbide particles.

[0052] The content of primary tungsten carbide particles in the tungsten carbide mixed powder of Embodiment 2 may be 20% by mass or more, 20% by mass or more but less than 100% by mass, 22% by mass or more but less than 100% by mass, 40% by mass or more but less than 100% by mass, 60% by mass or more but less than 100% by mass, or 80% by mass or more but less than 100% by mass.

[0053] The content of primary tungsten carbide particles in the above-mentioned tungsten carbide mixed powder is measured by the following procedure. The tungsten carbide mixed powder is embedded in resin and thinned to obtain a sample for measurement in the same manner as when creating the first graph in Embodiment 1. The sample for measurement is observed using a TEM at an acceleration voltage of 200 V and magnification of 200,000 to obtain a dark-field image (first image). Line analysis is performed on any 10 tungsten carbide particles in the acquired first image in the same manner as when creating the first graph in Embodiment 1 to confirm whether each tungsten carbide particle corresponds to a primary tungsten carbide particle. The equivalent diameter of a circle is calculated from the cross-sectional area of ​​each tungsten carbide particle in the first image. Each tungsten carbide particle is considered a sphere, and the volume ratio of the 10 tungsten particles is calculated based on the equivalent diameter. The ratio of the total volume of primary tungsten carbide particles to the total volume of the 10 tungsten carbide particles is calculated. In this disclosure, the ratio corresponds to the content of primary tungsten carbide particles in the tungsten carbide mixed powder. In the above measurement, primary tungsten carbide particles and other tungsten carbide particles can be considered to have the same density.

[0054] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0055] [Preparation of Tungsten Carbide Powder] Tungsten carbide powder was prepared for each sample using the following procedure. <<Raw Material Preparation Process>> Metallic tungsten powder (W powder), carbon powder (C powder), and oxide powder of the first element were prepared. The oxide powder of the first element was TiO ２ Powder, ZrO ２ powder, Nb ２ O ５ Powder, Ta２ O ５ Powder, MoO ２ powder, CeO ２ Powder, and Y ２ O ３ At least one sample was prepared from the group consisting of powders. The specific surface area of ​​the W powder used in each sample, measured by the BET method, is shown in Tables 1 to 3. The mass ratios of the W powder, C powder, and the first element oxide powder are shown in Tables 1 to 3.

[0056]

[0057]

[0058]

[0059] ≪Mixing Process≫ W powder, C powder, and the oxide powder of the first element were mixed using the method described in A or B below to obtain a mixed powder. A: W powder, C powder, and the oxide powder of the first element were strongly mixed using a dry attritor, and then weakly mixed using a wet ball mill to obtain a mixed powder. The mixing conditions for the dry attritor were: carbide media diameter: 3 mm, rotation speed: 40 rpm, mixing time: 1 hour. The mixing conditions for the wet ball mill were: carbide media diameter: 6 mm, rotation speed: 30 rpm, mixing time: 6 hours. B: W powder, C powder, and the oxide powder of the first element were weakly mixed using a mixer. The mixing conditions for the mixer were: mixing speed: 20 m / s.

[0060] ≪Carbonization Process≫ The mixed powder was placed in a batch furnace and heated at 1500°C for 2 hours under a vacuum atmosphere.

[0061] ≪Disintegration Process≫ The mixed powder after the carbonization process was disintegrated using a dry ball mill to obtain tungsten carbide powder for each sample. The conditions for the dry ball mill were: carbide media diameter: 6 mm, rotation speed: 25 rpm, disintegration time: 2 hours.

[0062] [Measurement of Tungsten Carbide Powder] For each sample of tungsten carbide powder, line analysis was performed on the tungsten carbide particles to confirm the type of first element contained in the tungsten carbide particles and the presence or absence of the first range in the first graph using the method described in Embodiment 1. The results are shown in Tables 4 to 6. For all samples, all tungsten carbide particles in the measurement sample showed the results described in Tables 4 to 6.

[0063] The D50, D10 / D90 of tungsten carbide particles, and the first element content of tungsten carbide powder were measured using the method described in Embodiment 1. The specific surface area of ​​the tungsten carbide particles was measured by the BET method. The results are shown in Tables 4 to 6.

[0064] For each sample, tungsten carbide particles in the tungsten carbide powder were analyzed by TOF-SIMS using the method described in International Publication No. 2024 / 005017

[0052] to

[0054] , and the depth-direction distribution of the intensity ratio (SUM / W) between the sum of the secondary ionic intensities of the first element (SUM) and the secondary ionic intensity of tungsten (W) was determined. The minimum values ​​of (SUM / W) in the region from the outermost surface of the tungsten carbide particles to a depth of 5 nm are shown in Tables 4 to 6.

[0065]

[0066]

[0067]

[0068] In samples 1 to 46, the tungsten carbide particles contain the first element, and their first graph includes the first range. That is, the tungsten carbide powders of samples 1 to 46 consist of first tungsten carbide particles and were confirmed to correspond to the examples. In samples 1 to 46, the minimum value of (SUM / W) in the region from the outermost surface to a depth of 5 nm was 30 or greater. This value is more than 30 times greater than the value of (SUM / W) in the region from the outermost surface to a depth of 5 nm described in International Publication No. 2024 / 005017 (approximately 0.9 or less in Figure 4). Therefore, the mode of existence of the first element in the tungsten carbide particles of samples 1 to 50 is different from the mode of existence of Ti, Zr, Nb, Ta, and Mo in the tungsten carbide grains described in International Publication No. 2024 / 005017.

[0069] In samples 51 to 57, the tungsten carbide particles contain the first element, but their first graph does not include the first range. In other words, the tungsten carbide powders of samples 51 to 57 do not contain the first tungsten carbide particles and are confirmed to be in the comparative example category.

[0070] [Preparation of cemented carbide] Using the tungsten carbide powder from each sample, cemented carbide was prepared according to the following procedure. The WC powder prepared from each sample (referred to as "First WC Powder" in Tables 7 to 9), commercially available tungsten carbide powder (Allied Material Co., Ltd. "WC02NR"), and Co powder (average particle size 0.5 μm) were mixed in a ball mill in the mass ratios shown in Tables 7 to 9 to obtain a mixed powder. The mixing conditions in the ball mill were: media diameter: 6 mm, rotation speed: 100 rpm, mixing time: 20 hours.

[0071] A round bar-shaped molded body was obtained by pressing the mixed powder. The molded body was heated at 1400°C for 1 hour, and then rapidly cooled to obtain a cemented carbide intermediate.

[0072] Next, the cemented carbide intermediates were subjected to HIP treatment. Specifically, the cemented carbide intermediates were subjected to 1320°C and a pressure of 30 MPa for 60 minutes using Ar gas as the pressure medium. After that, they were slowly cooled to obtain the cemented carbide alloys of each sample.

[0073]

[0074]

[0075]

[0076] [Cutting Test] Round bars made of cemented carbide for each sample were processed to create PCB drills with a cutting diameter of φ0.15 mm. Using the PCB drills, holes were drilled in commercially available printed circuit boards (0.8 mm thick) for semiconductor packaging. The processing conditions were a rotation speed of 120 krpm, and drilling was performed until breakage occurred or up to 10,000 hits. Based on the number of hits at which breakage occurred, the breakage resistance rate was calculated using the following formula: Breakage resistance rate (%) = (Number of hits at which breakage occurred / 10,000) × 100

[0077] If drilling can be performed up to 10,000 hits without breakage, the breakage resistance rate is 100%. Drilling was performed with 10 PCB drills and the breakage resistance rate was measured. The average breakage resistance rate of the 10 PCB drills was calculated. This average is shown in the "Breakage Resistance Rate" column of Tables 7 to 9. A higher breakage resistance rate indicates higher bending strength of the cemented carbide and a longer tool life for the cutting tool.

[0078] [Discussion] The tungsten carbide powders of Samples 1 to 46 correspond to the examples. The tungsten carbide powders of Samples 51 to 57 correspond to the comparative examples. It was confirmed that PCB drills made with cemented carbide alloys using the tungsten carbide powders of Samples 1 to 46 as raw materials had a longer tool life than PCB drills made with cemented carbide alloys using the tungsten carbide powders of Samples 51 to 57 as raw materials.

[0079] While embodiments and examples of this disclosure have been described above, it is intended from the outset that the configurations of each of the embodiments and examples described above may be combined or modified in various ways as appropriate. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalences.

Claims

1. A tungsten carbide powder comprising first tungsten carbide particles to which a first element has been added, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and the results obtained by line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope, from a position X1 located inside the first tungsten carbide particles and at a distance of 6 nm or more from the outer edge of the first tungsten carbide particles toward a position X2 located outside the first tungsten carbide particles and at a distance of 6 nm or more from the outer edge of the first tungsten carbide particles, are shown in a first graph in a coordinate system where the X axis is the distance from position X1 and the Y axis is the net intensity, wherein there exists a first range where the sum of the net intensities of the first element is greater than the net intensity of tungsten, at a distance P1 from the origin where the net intensity of tungsten is 0.5 times the maximum net intensity of tungsten.

2. The tungsten carbide powder according to claim 1, wherein the content of the first element in the tungsten carbide powder is 0.01% by mass or more and 2% by mass or less.

3. The tungsten carbide powder according to claim 1 or claim 2, wherein the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles is 0.05 or more and 0.7 or less.

4. The tungsten carbide powder according to any one of claims 1 to 3, wherein the 50% cumulative particle size D50 based on the number of the first tungsten carbide particles is 0.2 μm or more and 3.0 μm or less.

5. A tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in any one of claims 1 to 4.

6. The tungsten carbide mixed powder according to claim 5, wherein the tungsten carbide mixed powder contains 20% by mass or more of the first tungsten carbide particles.

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