Method for evaluating grain size of tungsten carbide powder and tungsten carbide powder

Abstract

The application provides a tungsten carbide powder grain size evaluation method and a tungsten carbide powder. The evaluation method comprises the following steps: (1) obtaining grain size data of the tungsten carbide powder based on the Fisher particle size method and EBSD analysis, and calculating effective grain size D mgs ; (2) combining the Fisher particle size FSSS of the tungsten carbide powder with the effective grain size D mgs , and evaluating the grain size of the tungsten carbide powder; wherein, in the formula of the effective grain size, the evaluation method provided by the application utilizes the grain size data obtained by EBSD analysis for weighted average processing, and the coefficient is corrected according to tungsten carbide powder samples with different Fisher particle sizes, so that the microstructure performance difference of tungsten carbide powder from different sources can be accurately characterized and evaluated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical measurement technology, and relates to a grain size evaluation method, in particular to a tungsten carbide powder grain size evaluation method and tungsten carbide powder. BACKGROUND

[0002] Electron backscatter diffraction (EBSD) analysis technology is a characterization technology for analyzing the microstructure characteristics of materials such as metal or metal compound powder, alloy, etc. by using the diffraction phenomenon of backscattered electrons. For alloy powder with tungsten carbide (WC) as the hard phase component, the EBSD analysis technology can be used to identify and analyze the crystallographic structure characteristics of the hard phase grains in the material, such as the morphology, size, crystal axis orientation, grain boundary type and distribution, etc.

[0003] Since the above characteristics are directly related to the application performance of the hard alloy powder, accurately characterizing and evaluating the grain distribution state of the hard alloy powder, especially the effective grain size value, can help researchers master the microstructure performance level of the material. The tungsten carbide powder cannot be finely divided by using the traditional Fisher particle size, laser particle size distribution, scanning electron microscope, etc. characterization method, and more accurate quantitative evaluation can be made, and more scientific prediction and inference can be made on the application performance of the product.

[0004] CN103902841A discloses a method for quantitatively analyzing the grain size of a body-centered cubic alloy solidification structure by EBSD measurement, which comprises the following steps: 1. obtaining EBSD data; 2. establishing a two-dimensional array; 3. establishing a rotation matrix and a growth orientation matrix; 4. assigning attributes to the first precipitated phase elements; 5. evolving the dendritic structure into a grain structure; 6. calculating the equivalent diameter of the grains; and 7. calculating the average equivalent diameter of the grains in the gravity direction. The invention can analyze both grain structure and dendritic structure, evaluate the grain size and distribution characteristics, and then evaluate the mechanical properties by using the grain size grade standard. However, the invention is to solve the technical problem that the EBSD measurement is for dendritic structure rather than grain structure, and cannot evaluate the grain size, and is not applicable to the evaluation of tungsten carbide powder grain size.

[0005] Therefore, it is an urgent problem for the present technical personnel in the field to provide a tungsten carbide powder grain size evaluation method to accurately characterize and evaluate the microstructure performance difference of tungsten carbide powder from different sources. SUMMARY

[0006] The application aims to provide a tungsten carbide powder grain size evaluation method and a tungsten carbide powder.

[0007] To achieve the above object, the application adopts the following technical solutions.

[0008] In the first aspect, the application provides a tungsten carbide powder grain size evaluation method, which comprises the following steps:

[0009] (1) obtaining the grain size data of the tungsten carbide powder based on the Fisher particle size method and EBSD analysis, and calculating the effective grain size D mgs .

[0010] (2) combining the Fisher particle size FSSS of the tungsten carbide powder with the effective grain size D mgs obtained in step (1) to evaluate the grain size of the tungsten carbide powder.

[0011] In the first aspect, the application provides a tungsten carbide powder grain size evaluation method, which comprises the following steps: and D i is the equivalent circle diameter of the i-th effective statistical grain obtained based on EBSD analysis, n is the number of effective statistical grains, and c is the correction coefficient.

[0012] The application proposes an effective grain size D mgs for characterizing the tungsten carbide powder, which is different from the general metal powder average grain size (the calculation method is described in detail in GB / T 36165-2018 Metal Average Grain Size Determination Electron Backscatter Diffraction (EBSD) Method).

[0013] In the application, the Fisher particle size method is a conventional powder particle size test method in the field (the test method is described in detail in GB / T 3249-2022 Metal and Compound Powder Fisher Particle Size Determination Method), which can achieve accurate measurement of the tungsten carbide powder Fisher particle size, so the specific steps of the Fisher particle size method are not particularly limited.

[0014] ​In the present application, the calculation method of the circumscribed circle diameter of the i-th effective statistical grain refers to GB / T 36165-2018 Metal Average Grain Size Determination Electron Backscatter Diffraction (EBSD) Method, and the specific calculation formula is: Wherein, A i is the scanning area of the i-th effective statistical grain.

[0015] Preferably, the value range of the correction coefficient c is 0.88-0.98, for example, it can be 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97 or 0.98, but not only limited to the listed values, other values not listed in this value range are also applicable.

[0016] Preferably, step (1) determines the value of the correction coefficient c according to the Fisher particle size FSSS of the tungsten carbide powder, specifically:

[0017] When FSSS∈[0.01μm, 1.0μm), the correction coefficient c=0.88.

[0018] When FSSS∈[1.0μm, 3.0μm), the correction coefficient c=0.92.

[0019] When FSSS∈[3.0μm, 10.0μm), the correction coefficient c=0.95.

[0020] When FSSS∈[10.0μm, 25.0μm), the correction coefficient c=0.98.

[0021] Preferably, the EBSD analysis in step (1) includes sample preparation, sample loading, step selection, field selection, EBSD scanning and data processing in sequence.

[0022] Preferably, the sample preparation includes sampling, glue mixing, shaping, curing and polishing in sequence.

[0023] Preferably, the mass ratio of the glue mixing is m 样品 :m 胶水 =1:(2-4), for example, it can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8 or 1:4, but not only limited to the listed values, other values not listed in this value range are also applicable.

[0024] In the present application, the glue used in the glue mixing can be G2 commercial glue, as long as it can realize the shaping of the sample, so the specific type of glue is not particularly limited here.

[0025] Preferably, the size of the shaped sample is (6-8) mm x (6-8) mm x (2-4) mm, for example, it can be 6 mm x 6 mm x 2 mm, 7 mm x 7 mm x 2 mm, 8 mm x 8 mm x 2 mm, 6 mm x 6 mm x 3 mm, 7 mm x 7 mm x 3 mm, 8 mm x 8 mm x 3 mm, 6 mm x 6 mm x 4 mm, 7 mm x 7 mm x 4 mm or 8 mm x 8 mm x 4 mm, but not limited to the listed values, other values not listed in the range are also applicable.

[0026] Preferably, the temperature of the solidification is 100-140℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ or 140℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0027] Preferably, the time of the solidification is 4-6 min, for example, it can be 4 min, 4.2 min, 4.4 min, 4.6 min, 4.8 min, 5 min, 5.2 min, 5.4 min, 5.6 min, 5.8 min or 6 min, but not limited to the listed values, other values not listed in the range are also applicable.

[0028] Preferably, the polishing comprises mechanical polishing and / or focused ion beam etching.

[0029] The present application removes the surface stress of the sample by polishing and improves the flatness of the sample surface.

[0030] In the present application, the sample loading is specifically fixing the sample on a sample stage inclined at 70° to ensure that the test sample is stable and has good conductivity, then loading the sample stage into the sample chamber, selecting an appropriate magnification, and dynamically focusing on the upper, middle and lower three regions in the field of view of the sample, so that each point can be clearly displayed.

[0031] Preferably, the selection step length is specifically adjusting the test step length to 1 / 50-1 / 10 of the FSSS of the tungsten carbide powder according to the FSSS of the tungsten carbide powder, for example, it can be 1 / 50, 1 / 40, 1 / 30, 1 / 20 or 1 / 10, but not limited to the listed values, other values not listed in the range are also applicable.

[0032] Preferably, the selection field of view is specifically selecting at least 2 fields of view to scan the measured sample, and determining the sample quantity according to the FSSS of the tungsten carbide powder.

[0033] Preferably, the determination standard of the sample quantity is:

[0034] When FSSS∈[0.01μm, 1.0μm), it is guaranteed that each field of view contains at least 750 complete grains, and all fields of view contain at least 1500 complete grains, for example, the number of complete grains contained in each field of view can be 750, 760, 770, 780, 790 or 800, and the number of complete grains contained in all fields of view can be 1500, 1520, 1540, 1560, 1580 or 1600, but not limited to the listed values, other unlisted values within the range of values are also applicable.

[0035] When FSSS∈[1.0μm, 3.0μm), it is guaranteed that each field of view contains at least 500 complete grains, and all fields of view contain at least 1000 complete grains, for example, the number of complete grains contained in each field of view can be 500, 510, 520, 530, 540 or 550, and the number of complete grains contained in all fields of view can be 1000, 1020, 1040, 1060, 1080 or 1100, but not limited to the listed values, other unlisted values within the range of values are also applicable.

[0036] When FSSS∈[3.0μm, 10.0μm), it is guaranteed that each field of view contains at least 300 complete grains, and all fields of view contain at least 600 complete grains, for example, the number of complete grains contained in each field of view can be 300, 310, 320, 330, 340 or 350, and the number of complete grains contained in all fields of view can be 600, 620, 640, 660, 680 or 700, but not limited to the listed values, other unlisted values within the range of values are also applicable.

[0037] When FSSS∈[10.0μm, 25.0μm), it is guaranteed that each field of view contains at least 250 complete grains, and all fields of view contain at least 500 complete grains, for example, the number of complete grains contained in each field of view can be 250, 260, 270, 280, 290 or 300, and the number of complete grains contained in all fields of view can be 500, 520, 540, 560, 580 or 600, but not limited to the listed values, other unlisted values within the range of values are also applicable.

[0038] Preferably, the data processing includes sequentially acquiring original grain size data, removing noise points and acquiring processed grain size data.

[0039] In the present application, the detailed steps of the data processing refer to GB / T 36165-2018 Metal Average Grain Size Determination Electron Backscatter Diffraction (EBSD) Method, and therefore will not be repeated here.

[0040] Preferably, the grain size evaluation standard of the tungsten carbide powder in step (2) is:

[0041] When FSSS∈[0.01μm, 1.0μm), if D mgs ∈[0.8×FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not.

[0042] When FSSS∈[1.0μm, 3.0μm), if D mgs ∈[0.78×FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not.

[0043] When FSSS∈[3.0μm, 10.0μm), if D mgs ∈[0.75×FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not.

[0044] When FSSS∈[10.0μm, 25.0μm), if D mgs ∈[0.72×FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not.

[0045] As a preferred technical solution of the present application, the evaluation method comprises the following steps:

[0046] (1) Obtain the grain size data of the tungsten carbide powder based on the Fisher particle size method and EBSD analysis, and calculate the effective grain size D wherein, and D i is the circumscribed circle diameter of the ith effective statistical grain obtained based on EBSD analysis, n is the number of effective statistical grains, and c is the correction coefficient.

[0047] The value of the correction coefficient c is determined according to the Fisher particle size FSSS of the tungsten carbide powder, specifically:

[0048] When FSSS∈[0.01μm, 1.0μm), the correction coefficient c = 0.88.

[0049] When FSSS∈[1.0μm, 3.0μm), the correction coefficient c = 0.92.

[0050] When FSSS∈[3.0μm, 10.0μm), the correction coefficient c = 0.95.

[0051] When FSSS∈[10.0μm, 25.0μm), the correction coefficient c = 0.98.

[0052] The EBSD analysis includes sample preparation, sample loading, step selection, field selection, EBSD scanning and data processing in sequence.

[0053] (2) Fisher particle size FSSS of the tungsten carbide powder combined with effective grain size D of step (1) mgs The grain size of the tungsten carbide powder is evaluated, and the evaluation standard is:

[0054] When FSSS ∈ [0.01 μm, 1.0 μm), if D mgs ∈ [0.8 × FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not meet the standard.

[0055] When FSSS ∈ [1.0 μm, 3.0 μm), if D mgs ∈ [0.78 × FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not meet the standard.

[0056] When FSSS ∈ [3.0 μm, 10.0 μm), if D mgs ∈ [0.75 × FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not meet the standard.

[0057] When FSSS ∈ [10.0 μm, 25.0 μm), if D mgs ∈ [0.72 × FSSS, +∞), the tungsten carbide powder meets the high-quality grain size standard; otherwise, it does not meet the standard.

[0058] In a second aspect, the application provides a tungsten carbide powder meeting the high-quality grain size standard obtained by the evaluation method of the first aspect.

[0059] Compared with the prior art, the application has the following beneficial effects:

[0060] The application proposes an effective grain size D mgs Compared with the average grain size of metal powder in general sense, the main difference of the application is that the grain size data obtained by EBSD analysis is weighted and averaged, and the coefficient is corrected according to tungsten carbide powder samples with different Fisher particle sizes, so that the microstructure and performance differences of tungsten carbide powder from different sources can be accurately characterized and evaluated. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 is an EBSD scanning image provided in Example 1;

[0062] Figure 2 is an EBSD scanning image provided in Example 2;

[0063] Figure 3 is an EBSD scanning image provided in Example 3;

[0064] Figure 4 is an EBSD scanning image provided in Example 4. DETAILED DESCRIPTION

[0065] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0066] Example 1

[0067] The present embodiment provides an evaluation method for grain size of tungsten carbide powder and tungsten carbide powder, the evaluation method comprising the following steps:

[0068] (1) The Fisher particle size FSSS of the tungsten carbide powder is measured by Fisher particle size method, FSSS = 0.8 μm, and the Fisher particle size method specifically refers to GB / T 3249-2022 Metal and its compound powder Fisher particle size determination method;

[0069] (2) EBSD analysis, specifically:

[0070] (2.1) Sample preparation, including sampling, glue mixing, shaping, curing and polishing in sequence; wherein the mass ratio of glue mixing is m 样品 :m 胶水 = 1:3, and the glue used is G2 commercial glue; the size of shaping is 7mm x 7mm x 3mm; the curing temperature is 120℃, and the time is 5min; the polishing includes low-speed mechanical polishing and focused ion beam etching in sequence, so as to remove the surface stress of the sample and improve the flatness of the sample surface;

[0071] (2.2) Sample loading, specifically fixing the sample on a sample stage inclined at an angle of 70° to ensure that the test sample is stable and well conductive, then loading the sample stage into the sample chamber, selecting an appropriate magnification, and dynamically focusing the upper, middle and lower three regions in the sample field, so that each point can be clearly displayed;

[0072] (2.3) Selecting step, specifically adjusting the test step to 1 / 16 of the Fisher particle size FSSS of the tungsten carbide powder, i.e. 0.05 μm, according to the Fisher particle size FSSS of the tungsten carbide powder;

[0073] (2.4) Selecting field of view, specifically selecting 2 fields of view to scan the measured sample, and determining the number of samples according to the Fisher particle size FSSS of the tungsten carbide powder; since FSSS = 0.8 μm ∈ [0.01 μm, 1.0 μm), at least 750 complete grains are ensured in each field of view, and at least 1500 complete grains are ensured in all fields of view.

[0074] (2.5) Adjust the test conditions of the scanning electron microscope and the EBSD, perform the EBSD scanning, and obtain a high-quality scanning image as shown in FIG. 2B; Figure 1 ;

[0075] (2.6) Data processing, including sequentially obtaining raw grain size data, removing noise points, and obtaining processed grain size data;

[0076] (2.7) Based on the grain size data of the tungsten carbide powder obtained in step (2.6), calculating the effective grain size wherein, and D i is the circumscribed circle diameter of the i-th effective statistical grain obtained based on the EBSD analysis, and the number of complete grains in this embodiment is 2174;

[0077] (3) Since FSSS = 0.8 μm ∈ [0.01 μm, 1.0 μm), and D mgs = 0.655 μm ∈ [0.8 × FSSS, +∞) = [0.64 μm, +∞), the tungsten carbide powder meets the high-quality grain size standard.

[0078] Example 2

[0079] The present embodiment provides an evaluation method for the grain size of a tungsten carbide powder and a tungsten carbide powder, the evaluation method comprising the following steps:

[0080] (1) The Fisher particle size FSSS of the tungsten carbide powder is measured by the Fisher particle size method, FSSS = 1.5 μm, and the Fisher particle size method specifically refers to GB / T 3249-2022 Metal and Compound Powder Fisher Particle Size Determination Method;

[0081] (2) EBSD analysis, specifically:

[0082] (2.1) Sample preparation, including sequentially taking samples, mixing glue, shaping, curing, and polishing; wherein the mass ratio of the mixed glue is m 样品 :m 胶水 = 1:2, and the glue used is G2 commercial glue; the size of the shaping is 6 mm × 6 mm × 2 mm; the curing temperature is 100℃, and the time is 6 min; the polishing includes sequentially low-speed mechanical polishing and focused ion beam etching to remove the surface stress of the sample and improve the flatness of the sample surface;

[0083] (2.2) sample loading, specifically, fixing the sample on a sample stage with an inclination of 70° to ensure that the sample is stable and has good electrical conductivity, then loading the sample stage into the sample chamber, selecting an appropriate magnification, and dynamically focusing on the upper, middle and lower three regions in the sample field of view to ensure that each point can be clearly displayed;

[0084] (2.3) selecting a step size, specifically, adjusting the test step size to 1 / 10 of the FSSS of the tungsten carbide powder, i.e. 0.15 μm, according to the FSSS of the tungsten carbide powder;

[0085] (2.4) selecting a field of view, specifically, selecting 2 fields of view to scan the sample, and determining the number of samples according to the FSSS of the tungsten carbide powder; since FSSS = 1.5 μm ∈ [1.0 μm, 3.0 μm), it is ensured that each field of view contains at least 500 complete grains, and all fields of view contain at least 1000 complete grains;

[0086] (2.5) adjusting the test conditions of the scanning electron microscope and EBSD, performing EBSD scanning, and obtaining a high-quality scanning image as shown in Figure 2 ;

[0087] (2.6) data processing, including sequentially obtaining raw grain size data, removing noise points, and obtaining processed grain size data;

[0088] (2.7) based on the grain size data of the tungsten carbide powder obtained in step (2.6), calculating the effective grain size wherein, and D i is the circumscribed circle diameter of the i-th effective statistical grain obtained based on EBSD analysis, and the number of complete grains in this embodiment is 1735;

[0089] (3) since FSSS = 1.5 μm ∈ [1.0 μm, 3.0 μm), and D mgs = 1.217 μm ∈ [0.78 × FSSS, +∞) = [1.17 μm, +∞), the tungsten carbide powder meets the high-quality grain size standard.

[0090] Example 3

[0091] The present embodiment provides a method for evaluating the grain size of a tungsten carbide powder and a tungsten carbide powder, the method comprising the following steps:

[0092] (1) measuring the FSSS of the tungsten carbide powder by the FSS method, FSSS = 6.0 μm, and the FSS method specifically refers to GB / T 3249-2022 Metal and its compounds Powder FSS method for measuring grain size;

[0093] (2) EBSD analysis, specifically:

[0094] (2.1) sample preparation, including sampling, glue mixing, shaping, curing and polishing in sequence; wherein the mass ratio of the glue mixing is m 样品 :m 胶水 = 1:4, and the glue used is G2 commercial glue; the size of the shaping is 8mm x 8mm x 4mm; the curing temperature is 140℃, and the time is 4min; the polishing includes low-speed mechanical polishing and focused ion beam etching in sequence to remove the surface stress of the sample and improve the flatness of the sample surface;

[0095] (2.2) sample loading, specifically fixing the sample on a sample stage inclined at 70° to ensure stable and good conductivity of the sample, then loading the sample stage into the sample chamber, selecting an appropriate magnification, and dynamically focusing the upper, middle and lower three regions in the sample field to ensure that each point can be clearly displayed;

[0096] (2.3) selecting the step size, specifically adjusting the test step size to 1 / 30 of the FSSS of the tungsten carbide powder, i.e. 0.2μm, according to the FSSS of the tungsten carbide powder;

[0097] (2.4) selecting the field of view, specifically selecting 2 fields of view to scan the measured sample, and determining the sample quantity according to the FSSS of the tungsten carbide powder; since FSSS = 6.0μm ∈ [3.0μm, 10.0μm), it is ensured that each field of view contains at least 300 complete grains, and all fields of view contain at least 600 complete grains;

[0098] (2.5) adjusting the test conditions of the scanning electron microscope and EBSD, performing EBSD scanning, and obtaining a high-quality scanning image as Figure 3 ;

[0099] (2.6) data processing, including obtaining original grain size data, removing noise points and obtaining processed grain size data in sequence;

[0100] (2.7) based on the grain size data of the tungsten carbide powder obtained in step (2.6), calculating the effective grain size wherein, and D i is the circumscribed circle diameter of the i-th effective statistical grain based on the EBSD analysis, and the number of complete grains in this embodiment is 1236;

[0101] (3) since FSSS = 6.0μm ∈ [3.0μm, 10.0μm), and D mgs= 4.683 pm ∈ [0.75 * FSSS, +∞) = [4.5 pm, +∞), the tungsten carbide powder meets the high-quality grain size standard.

[0102] Example 4

[0103] The present embodiment provides an evaluation method for the grain size of a tungsten carbide powder and a tungsten carbide powder, the evaluation method comprising the following steps:

[0104] (1) The Fisher particle size FSSS of the tungsten carbide powder is measured by the Fisher particle size method, and the Fisher particle size method specifically refers to GB / T 3249-2022 Metal and Compound Powder Determination Method for Fisher Particle Size;

[0105] (2) EBSD analysis, specifically:

[0106] (2.1) Sample preparation, including sampling, glue mixing, shaping, curing and polishing in sequence; wherein the mass ratio of glue mixing is m 样品 :m 胶水 = 1:3, and the glue used is G2 commercial glue; the size of shaping is 7 mm x 7 mm x 3 mm; the curing temperature is 120°C, and the time is 5 min; the polishing includes low-speed mechanical polishing and focused ion beam etching in sequence to remove the surface stress of the sample and improve the flatness of the sample surface;

[0107] (2.2) Sample loading, specifically fixing the sample on a sample stage inclined at an angle of 70° to ensure stable and good conductivity of the sample, then loading the sample stage into the sample chamber, selecting an appropriate magnification, and dynamically focusing the upper, middle and lower three regions in the sample field, so that each point can be clearly displayed;

[0108] (2.3) Selecting the step size, specifically adjusting the test step size to 1 / 40 of the Fisher particle size FSSS of the tungsten carbide powder, i.e. 0.5 pm;

[0109] (2.4) Selecting the field of view, specifically selecting 2 fields of view to scan the measured sample, and determining the number of samples according to the Fisher particle size FSSS of the tungsten carbide powder; since FSSS = 20.0 pm ∈ [10.0 pm, 25.0 pm), at least 250 complete grains are ensured in each field of view, and at least 500 complete grains are ensured in all fields of view;

[0110] (2.5) Adjusting the test conditions of the scanning electron microscope and EBSD, performing EBSD scanning, and obtaining a high-quality scanning image as shown in Figure 4 ;

[0111] (2.6) Data processing, including sequentially obtaining raw grain size data, removing noise points, and obtaining processed grain size data;

[0112] (2.7) Based on the grain size data of the tungsten carbide powder obtained in step (2.6), calculate the effective grain size wherein, and D i is the circumscribed circle diameter of the i-th effective statistical grain obtained based on EBSD analysis, and the number of complete grains in this embodiment is 915;

[0113] (3) Since FSSS = 20.0 μm ∈ [10.0 μm, 25.0 μm), and D mgs = 15.509 μm ∈ [0.72 × FSSS, +∞) = [14.4 μm, +∞), the tungsten carbide powder meets the high-quality grain size standard.

[0114] Comparative Example 1

[0115] This comparative example provides a tungsten carbide powder, the FSSS of which is measured by the Fisher particle size method to be 0.8 μm, and the EBSD analysis as described in Example 1 shows that D mgs = Therefore, the tungsten carbide powder does not meet the high-quality grain size standard.

[0116] Comparative Example 2

[0117] This comparative example provides a tungsten carbide powder, the FSSS of which is measured by the Fisher particle size method to be 1.5 μm, and the EBSD analysis as described in Example 2 shows that D mgs = Therefore, the tungsten carbide powder does not meet the high-quality grain size standard.

[0118] Comparative Example 3

[0119] This comparative example provides a tungsten carbide powder, the FSSS of which is measured by the Fisher particle size method to be 6.0 μm, and the EBSD analysis as described in Example 3 shows that D mgs = Therefore, the tungsten carbide powder does not meet the high-quality grain size standard.

[0120] Comparative Example 4

[0121] This comparative example provides a tungsten carbide powder, the FSSS of which is measured by the Fisher particle size method to be 20 μm, and the EBSD analysis as described in Example 4 shows that D mgs = Therefore, the tungsten carbide powder does not meet the high-quality grain size standard.

[0122] The tungsten carbide-based hard alloy is prepared by using the tungsten carbide powder described in examples 1-4 and comparative examples 1-4 under the same process, and the specific preparation process comprises the following steps:

[0123] (1) Material preparation: the material preparation is performed by using a ball milling method, and the specific material preparation process is shown in Table 1.

[0124] Table 1

[0125]

[0126]

[0127] (2) Pressing: the pressing process is shown in Table 2.

[0128] Table 2

[0129] Pressing parameters Dimensions (mm) Pressing pressure (N / mm 2 )]]> Shrinkage factor Parameter values 25×5×5 2 x 10 4 ]] 1.24

[0130] (3) Sintering: the sintering process is shown in Table 3.

[0131] Table 3

[0132] Process steps Temperature interval (°C) Interval time (min) 1 25～1000 810 2 1000 30 3 1000～1500 150 4 1500 30 5 1500～25 240

[0133] The performance parameters of the tungsten carbide-based hard alloy prepared by using the tungsten carbide powder described in examples 1-4 and comparative examples 1-4 are shown in Table 4.

[0134] Table 4

[0135]

[0136]

[0137] As shown in Table 4, under the condition of using the same material preparation, pressing and sintering process, and under the premise that the hardness and density of the hard alloy obtained from examples 1-4 are equivalent to those of the hard alloy obtained from comparative examples 1-4, the bending strength of the former is generally higher than that of the latter, and the improvement range is about 10%, which indicates that the effective grain size value of the hard alloy powder within the high-quality grain size standard range is higher, and the hard alloy substrate with higher toughness and comprehensive performance can be produced.

[0138] Therefore, the effective grain size D mgs of the tungsten carbide powder is proposed in the present application, and compared with the average grain size of the metal powder in the general sense, the main difference of the present application is that the grain size data obtained by using EBSD analysis is processed by weighted average, and the coefficient correction is performed according to the tungsten carbide powder samples with different Fisher grain sizes, so that the microstructure performance difference of the tungsten carbide powder from different sources can be accurately characterized and evaluated.

[0139] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for evaluating the grain size of tungsten carbide powder, characterized in that, The evaluation method includes the following steps: (1) Based on the Fisher particle size distribution method and EBSD analysis, the grain size data of tungsten carbide powder were obtained, and the effective grain size was calculated. ; (2) Combining the Fisher's Score (FSSS) of tungsten carbide powder with the effective grain size obtained in step (1) The grain size of the tungsten carbide powder was evaluated. Among them, the effective grain size mentioned in step (1) In the formula, , ,and Based on the results of EBSD analysis The diameter of the circle of equal area of ​​an effective statistical grain. It is an effective count of the number of grains. It is a correction factor; The correction coefficient The value range is 0.88-0.98; Step (1) determines the value of the correction coefficient c based on the Fisher particle size (FSSS) of the tungsten carbide powder, specifically: When FSSS When, the correction coefficient ; when When, the correction coefficient ; when When, the correction coefficient ; when When, the correction coefficient .

2. The evaluation method according to claim 1, characterized in that, Step (1) of the EBSD analysis includes sample preparation, sample loading, step size selection, field of view selection, EBSD scanning and data processing performed sequentially.

3. The evaluation method according to claim 2, characterized in that, The sample preparation includes sampling, mixing, shaping, curing and polishing in sequence.

4. The evaluation method according to claim 3, characterized in that, The mass ratio of the mixed adhesive is m 样品 :m 胶水 =1:(2-4).

5. The evaluation method according to claim 3, characterized in that, The dimensions of the molded part are (6-8)mm × (6-8)mm × (2-4)mm.

6. The evaluation method according to claim 3, characterized in that, The curing temperature is 100-140℃.

7. The evaluation method according to claim 3, characterized in that, The curing time is 4-6 minutes.

8. The evaluation method according to claim 3, characterized in that, The polishing includes mechanical polishing and / or focused ion beam etching.

9. The evaluation method according to claim 2, characterized in that, The selection step size is specifically adjusted to 1 / 50-1 / 10 of the FSSS based on the Fisher's Score of tungsten carbide powder.

10. The evaluation method according to claim 2, characterized in that, The selection of the field of view specifically involves selecting at least two fields of view to scan the sample under test, and determining the number of samples based on the Fisher's Score (FSSS) of the tungsten carbide powder.

11. The evaluation method according to claim 10, characterized in that, The criteria for determining the sample size are as follows: when At the same time, ensure that each field of view contains at least 750 complete grains, and that all fields of view contain at least 1500 complete grains; when At the same time, ensure that each field of view contains at least 500 complete grains, and that all fields of view contain at least 1000 complete grains; when At the same time, ensure that each field of view contains at least 300 complete grains, and that all fields of view contain at least 600 complete grains; when At the same time, ensure that each field of view contains at least 250 complete grains, and that all fields of view contain at least 500 complete grains.

12. The evaluation method according to claim 2, characterized in that, The data processing includes sequentially acquiring the original grain size data, removing noise, and acquiring the processed grain size data.

13. The evaluation method according to claim 1, characterized in that, The grain size evaluation standard for the tungsten carbide powder in step (2) is as follows: when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder has a high grain size, then it meets the high-quality grain size standard; otherwise, it does not.

14. The evaluation method according to claim 1, characterized in that, The evaluation method includes the following steps: (1) Based on the Fisher particle size distribution method and EBSD analysis, the grain size data of tungsten carbide powder were obtained, and the effective grain size was calculated. In the formula, , ,and Based on the results of EBSD analysis The diameter of the circle of equal area of ​​an effective statistical grain. It is an effective count of the number of grains. It is a correction factor; The value of the correction factor c is determined based on the Fisher's Score (FSSS) of the tungsten carbide powder, specifically as follows: When FSSS When, the correction coefficient ; when When, the correction coefficient ; when When, the correction coefficient ; when When, the correction coefficient ; The EBSD analysis includes sample preparation, sample loading, step size selection, field of view selection, EBSD scanning, and data processing performed sequentially. (2) Combining the Fisher's Score (FSSS) of tungsten carbide powder with the effective grain size obtained in step (1) The grain size of the tungsten carbide powder is evaluated, and the evaluation criteria are as follows: when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder meets the high-quality grain size standard, then it does not; otherwise, it does not. when At that time, if If the tungsten carbide powder has a high grain size, then it meets the high-quality grain size standard; otherwise, it does not.

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