Method for preparing EBSD sample through WC powder hot inlaying

Abstract

The invention belongs to the technical field of EBSD preparation, and particularly relates to a method for preparing an EBSD sample through WC powder hot inlaying. According to the method, stirring and mixing are conducted after grinding, the dispersion uniformity degree of the WC powder in the conductive resin is improved, the integrity and original morphology of WC grains are kept, and the fastening degree of the subsequent WC powder in hot inlaying is improved. A hot inlaying process is adopted, mixed powder of WC and resin which are uniformly stirred is poured into the bottom of an inlaying cavity of a hot inlaying machine, and then conductive resin which is not ground is added, so that the tight combination degree of the WC and the resin powder is facilitated, meanwhile, the WC powder is not prone to falling off in the grinding and polishing process, and the problems that a powder sample is difficult to fasten and difficult to grind and polish are solved. The method is simple in process and easy to operate, the processes of pressing, sintering and the like in the WC powder sample preparation process are greatly simplified, the original morphology of the WC powder is kept, meanwhile, energy consumption is reduced, and cost is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of EBSD preparation, and more specifically relates to a method for preparing EBSD samples by hot embedding WC powder. Background Art

[0002] WC powder is the raw material of cemented carbide, and its particle size is usually obtained by FSSS, BET or laser particle size. By studying the powder, the process and product quality can be better controlled. A powder particle usually contains multiple grains. The EBSD technology can utilize crystallographic information to automatically calibrate grain boundaries through grain orientation, making the particle size result more accurate and reliable. However, there are few reports on the EBSD sample preparation method for ultrafine WC powder (<0.5μm) in the literature and patents. Due to the small size, light weight and easy agglomeration of the powder material, the fine powder adhered and fixed on the surface of the sample holder is difficult to be fastened during grinding and polishing, and is easy to fall off, which is not conducive to obtaining high-quality diffraction patterns and greatly limits the application effect.

[0003] For example, Chinese invention patent CN107228870A discloses a method for preparing EBSD samples of cemented carbide powder. The cemented carbide powder and electrolytic Cu powder are mixed in a certain proportion, pressed, sintered, then embedded, ground and polished, and surface cleaned to finally obtain an EBSD specimen. However, in the sintering process of this method, the mixture of cemented carbide powder and copper powder will be solidified, and this process may change the original microstructure of the powder, which is not conducive to analyzing the original state of the powder. Moreover, in the grinding and polishing process, electrolytic Cu powder and cemented carbide powder are mixed, and the hardness difference between the two materials is too large, which is easy to cause scratches and affect the EBSD data acquisition effect. In addition, the whole sample preparation process is relatively cumbersome, involving multiple steps such as pressing and sintering, which not only increases energy consumption but also raises costs. At the same time, in the ordinary hot embedding technology, the cemented carbide powder and the resin powder are not evenly mixed by general mixing means, and the resin powder cannot be dispersed by grinding technology, so the cemented carbide powder will agglomerate and fall off, affecting the sample preparation and EBSD data acquisition effect.

[0004] Therefore, how to provide a method for preparing EBSD samples by hot embedding WC powder is a technical problem that those skilled in the art need to solve urgently. Summary of the Invention

[0005] In order to overcome the disadvantages and deficiencies in the prior art, the present invention proposes a method for preparing EBSD samples by hot embedding WC powder. The EBSD samples of WC powder are prepared by grinding, stirring and mixing, hot embedding, grinding and polishing, and mechanical polishing in sequence. After resin grinding and mixing, the WC powder is uniformly dispersed in the conductive resin, and at the same time, the original morphology of the WC powder is ensured. The hot embedding method is adopted to improve the tight bonding degree between the WC powder and the conductive resin, which is beneficial to the grinding and polishing of the sample, so as to obtain a sample with good EBSD sample preparation effect.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing EBSD samples by hot embedding WC powder, comprising the following steps:

[0008] S1. Grinding: Using a micro planetary ball mill to grind the conductive resin particles to obtain fine and uniform resin powder;

[0009] S2. Stirring and mixing: Using a small plow blade stirring mixer to stir and mix the resin powder and ultra-fine WC powder to obtain a mixed powder;

[0010] S3. Hot embedding: Spreading the well-stirred mixed powder on the bottom of the embedding cavity of the hot embedding machine, and then adding unground conductive resin particles to make up the height of the sample, and starting the hot embedding program;

[0011] S4. Grinding and polishing: Grinding the hot-embedded sample, then using a polishing cloth and adding polishing paste for polishing, and finally rinsing the surface of the sample with deionized water;

[0012] S5. Mechanical polishing: Using a vibratory polisher to polish the ground and polished sample, rinsing the sample with deionized water after completion, and drying it with compressed air to obtain an ultra-fine WC powder EBSD sample.

[0013] Preferably, in step S1, the ball-to-material ratio of the grinding is 5:1, the rotation speed is 120-150 r / min, the grinding time is 1-4 h, and the particle size of the resin powder is <1 μm.

[0014] The beneficial effects of the above technical solutions are: The grinding process of the present invention can effectively grind the conductive resin into fine and uniform powder, laying a good foundation for subsequent mixing and embedding, ensuring that the particle size and uniformity of the resin powder meet the preparation requirements, thereby improving the conductivity of the sample and the uniformity of the microstructure.

[0015] Preferably, in step S2, the mass ratio of the resin powder to the ultra-fine WC powder is 1:1-5.

[0016] Preferably, in step S2, the stirring speed is 500 r / min, and the stirring time is 1-4 h.

[0017] The beneficial effects of the above technical solution are as follows: The mixing process of the present invention can fully and evenly mix the resin powder and WC powder to form a uniform composite material system, avoiding the differences in electrical conductivity and microstructural defects caused by uneven mixing, and laying a foundation for the subsequent hot embedding and grinding and polishing processes.

[0018] Preferably, the mass ratio of the unground conductive resin particles to the mixed powder in step S3 is 1-2:3.

[0019] Preferably, the temperature of the hot embedding in step S3 is 140-160°C, the pressure is 200-250 mbar, and the time is 10-20 min.

[0020] The beneficial effects of the above technical solution are as follows: The hot embedding process of the present invention can maintain the original morphology of the WC powder without damaging the physical structure at an appropriate temperature, pressure and time, enabling the mixed powder and the conductive resin to be fully combined to form a dense and stable inlay, ensuring the structural integrity of the sample and the stability of the electrical conductivity.

[0021] Preferably, the specific operation of the grinding in step S4 is: grinding the sample with grinding discs of 200 mesh and 800 mesh in sequence.

[0022] Preferably, the particle size of the polishing paste in step S4 is 1.0-2.5 μm, and the polishing cloth is a woolen polishing cloth.

[0023] The beneficial effects of the above technical solution are as follows: The grinding and polishing process can quickly remove the defects on the surface of the WC powder, reduce its surface roughness, improve the smoothness, facilitate maintaining a relatively regular particle shape, and improve the quality of the powder.

[0024] Preferably, the polishing liquid in step S5 is a silica solution, and the polishing time is 2-5 h.

[0025] The present invention also provides an EBSD sample prepared according to the above method.

[0026] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a method for preparing an EBSD sample by hot embedding WC powder, having the following beneficial effects:

[0027] 1. The present invention uses stirring and mixing after grinding, improving the degree of uniform dispersion of WC powder in the conductive resin, and maintaining the integrity and morphology of WC grains, which is beneficial to the fastening degree of WC powder in hot embedding.

[0028] 2. The present invention adopts a hot embedding process. The mixed powder of WC and resin after being stirred evenly is poured into the bottom of the embedding cavity of a hot embedding machine, and then unground conductive resin is added, which is beneficial to the tight combination degree of WC and resin powder, and at the same time makes the WC powder not easy to fall off during the grinding and polishing process, solving the problems of difficult fastening and difficult grinding and polishing of powder samples.

[0029] 3. The process of the present invention is simple and easy to operate, greatly simplifies the processes such as pressing and sintering in the sample preparation process of WC powder, maintains the original morphology of WC powder, reduces energy consumption and saves costs at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0031] Figure 1 In the figure, a, b, and c are respectively the SEM image of the polished section, the Kikuchi diffraction pattern, and the BC map of the EBSD sample obtained in Example 1.

[0032] Figure 2 In the figure, a and b are respectively the SEM images of the EBSD sample obtained in Comparative Example 1 at magnifications of 1000 and 3000.

[0033] Figure 3 In the figure, a and b are respectively the SEM images of the EBSD sample obtained in Comparative Example 2 at magnifications of 1000 and 3000.

[0034] Figure 4 It is the SEM image of the EBSD sample obtained in Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing an EBSD sample by hot embedding WC powder includes the following steps:

[0038] S1. Grinding: Use a micro planetary ball mill to grind the metallographic special (thermal) conductive resin to obtain fine and uniform resin powder with a particle size less than 1 μm, a ball-to-material ratio of 5:1, a rotation speed of 150 r / min, and a grinding time of 2 h;

[0039] S2. Stirring and mixing: Use a small plow knife stirring mixer to fully stir and mix 5 g of the ground metallographic special (thermal) conductive resin powder and 10 g of ultra-fine WC powder with a particle size of 0.4 μm. The stirring speed is 500 r / min and the stirring time is 2 h to obtain a mixed powder;

[0040] S3. Hot embedding: Spread the well-stirred mixed powder evenly on the bottom of the embedding cavity of the hot embedding machine, and then add 10 g of unground metallographic special (thermal) conductive resin to make up for the sample height. Start the embedding program, with an embedding temperature of 150 °C, a pressure of 225 mbr, and a time of 15 min;

[0041] S4. Grinding and polishing: Grind and polish the sample after hot embedding. First, use grinding disks with 200 meshes and 800 meshes to polish the sample, with a pressure of 1.5 MPa and a polishing time of 10 min. Then, use a wool polishing cloth and add diamond polishing paste with a particle size of 1.0 μm to polish for 10 min. Finally, rinse the surface of the sample with a large amount of clean water.

[0042] S5. Mechanical polishing: Use a vibratory polisher to polish the ground and polished sample. The polishing liquid is a silica solution, the polishing frequency is 30%, and the time is 3 h; After polishing, rinse the sample with deionized water and dry it with compressed air to obtain a WC powder EBSD sample.

[0043] The detection effect of the WC powder EBSD sample prepared in Example 1 is as Figure 1 shown. It is Figure 1 observed that the phase is single and no obvious scratches will be left during the grinding and polishing process. The WC powder is evenly dispersed and flat, while maintaining a good original powder morphology, and its Kikuchi diffraction pattern has a high quality.

[0044] Comparative Example 1

[0045] A method for preparing an EBSD sample by hot embedding WC powder, without grinding and directly stirring and mixing, includes the following steps:

[0046] S1. Stirring and mixing: Use a small plow knife stirring mixer to fully stir and mix 5 g of unground metallographic special (thermal) conductive resin particles and 10 g of WC powder with a particle size of 0.4 μm. The stirring speed is 500 r / min and the stirring time is 2 h to obtain a mixed powder;

[0047] S2. Hot embedding: Spread the well - stirred mixed powder evenly on the bottom of the embedding cavity of the hot embedding machine, then add 10 g of unground special (hot) conductive resin for metallography to make up for the sample height. Start the embedding program, with an embedding temperature of 150 °C, a pressure of 225 mbr, and a time of 15 min;

[0048] S3. Grinding and polishing: Grind and polish the sample after hot embedding. Select grinding disks of 200 mesh and 800 mesh in sequence to polish the sample, with a pressure of 1.5 MPa and a polishing time of 10 min. Then use a woolen polishing cloth and add 1.0 μm diamond polishing paste to polish for 10 min. Finally, rinse the surface of the sample with a large amount of clear water;

[0049] S4. Mechanical polishing: Use a vibration polishing machine to polish the ground and polished sample. The polishing liquid is a silica solution, the polishing frequency is 30%, and the time is 3 h. After polishing, rinse the sample with deionized water and dry it with compressed air to obtain the WC powder EBSD sample.

[0050] The detection effect of the WC powder EBSD sample prepared in Comparative Example 1 is as Figure 2 shown. Observed at a morphology magnification of 1000 times and 3000 times, the larger resin particles are not completely integrated with the WC powder. The WC powder cannot be dispersed, and it is extremely easy to fall off during the grinding and polishing process, and a powder sample cannot be prepared.

[0051] Comparative Example 2

[0052] A method for preparing an EBSD sample of WC powder by hot embedding, using manual stirring after grinding, includes the following steps:

[0053] S1. Manual stirring: Use a micro - planetary ball mill to grind the special (hot) conductive resin particles for metallography into powder form, with a particle size less than 1 μm, a ball - to - material ratio of 5:1, a rotation speed of 150 r / min, and a grinding time of 2 h;

[0054] S2. Hot embedding: Spread the manually well - stirred mixed powder evenly on the bottom of the embedding cavity of the hot embedding machine, then add 10 g of unground special (hot) conductive resin particles for metallography to make up for the sample height. Start the embedding program, with an embedding temperature of 150 °C, a pressure of 225 mbr, and a time of 15 min;

[0055] S3. Grinding and polishing: Grind and polish the sample after hot embedding. Select grinding disks of 200 mesh and 800 mesh in sequence to polish the sample, with a pressure of 1.5 MPa and a polishing time of 10 min. Then use a woolen polishing cloth and add 1.0 μm diamond polishing paste to polish for 10 min. Finally, rinse the surface of the sample with a large amount of clear water;

[0056] S4. Mechanical polishing: Use a vibratory polisher to polish the polished sample. The polishing solution is a silica solution. The polishing frequency is 30%, and the time is 3 h. After polishing, rinse the sample with deionized water and dry it with compressed air to obtain the WC powder EBSD sample.

[0057] The detection effect of the WC powder EBSD sample prepared in Comparative Example 2 is as Figure 3 shown. When observed at a magnification of 1000 times and 3000 times of the morphology, the WC powder stirred manually is not easily dispersed and is prone to agglomeration and falling off during the grinding and polishing process.

[0058] Comparative Example 3

[0059] A method for preparing an EBSD sample of WC powder, comprising the following steps:

[0060] S1. Mixing: Weigh 10 g of WC powder and copper powder each using an electronic balance, and then mix them in a mortar;

[0061] S2. Compression molding: Pour the mixed powder into a mold and press it into shape on a hydraulic press. The pressing pressure is 400 MPa, and the diameter of the WC powder green body is 30 mm;

[0062] S3. Furnace loading: Put the pressed green body into a copper infiltration furnace, introduce nitrogen to remove the air in the furnace. The ventilation time is 12 min to prevent oxidation reaction during heating. Then close the nitrogen valve, open the hydrogen valve, and introduce hydrogen as a protective gas to ensure that the inside of the furnace is in a reducing atmosphere during the entire copper infiltration process;

[0063] S4. Heating and copper infiltration: Heat up at a rate of 20 °C / min to gradually increase the temperature in the furnace. When the temperature reaches 1083 °C, the copper powder melts and infiltrates into the pores of the WC powder, playing a role in fixing the WC powder. The holding time is 60 min to make the copper and WC powder fully contact and penetrate, ensuring uniform distribution of copper and WC particles;

[0064] S5. Cooling and furnace unloading: After the holding is completed, stop heating, let the sample cool naturally in the furnace to room temperature, then close the hydrogen valve, introduce nitrogen to replace the hydrogen in the furnace with nitrogen, and then open the furnace door to take out the copper-infiltrated sample;

[0065] S6. Grinding and polishing: First, use grinding disks of 200 mesh and 800 mesh to polish the sample. The pressure is 1.5 MPa, and the polishing time is 10 min. Then use a woolen polishing cloth and add diamond polishing paste of 1.0 μm to polish for 10 min. Finally, rinse the surface of the sample with a large amount of clean water;

[0066] S7. Mechanical polishing: The polished sample is polished using a vibration polishing machine. The polishing liquid is a silica solution, the polishing frequency is 30%, the time is 3 h. After polishing, the sample is rinsed with deionized water and dried with compressed air to obtain the WC powder EBSD sample.

[0067] The detection effect of the WC powder EBSD sample prepared in Comparative Example 3 is as Figure 4 shown. The hardness difference between copper and WC powder is large, and scratches are likely to be generated during the grinding and polishing process, affecting the accuracy of EBSD data acquisition.

[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing EBSD samples by hot embedding WC powder, characterized in that, It includes the following steps: S1. Grinding: Use a micro planetary ball mill to grind the conductive resin particles to obtain fine and uniform resin powder; S2. Stirring and mixing: Use a small plow knife stirrer to stir and mix the resin powder and ultrafine WC powder to obtain a mixed powder; S3. Hot embedding: Spread the well-stirred mixed powder evenly on the bottom of the embedding cavity of the hot embedding machine, then add unground conductive resin particles to make up the height of the sample, and start the hot embedding program; S4. Grinding and polishing: Grind the hot-embedded sample, then use a polishing cloth and add polishing paste for polishing, and finally rinse the surface of the sample with deionized water; S5. Mechanical polishing: Use a vibratory polisher to polish the ground and polished sample, rinse the sample with deionized water after finishing, and dry it with compressed air to obtain an ultrafine WC powder EBSD sample.

2. The method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that In step S1, the ball-to-material ratio of the grinding is 5:1, the rotation speed is 120 - 150 r / min, the grinding time is 1 - 4 h, and the particle size of the resin powder is <1 μm.

3. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S2, the mass ratio of the resin powder to the ultrafine WC powder is 1:1 - 5.

4. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S2, the stirring speed is 500 r / min, and the stirring time is 1 - 4 h.

5. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S3, the mass ratio of the unground conductive resin particles to the mixed powder is 1 - 2:

3.

6. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S3, the temperature of the hot embedding is 140 - 160 °C, the pressure is 200 - 250 mbar, and the time is 10 - 20 min.

7. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S4, the specific operation of the grinding is: successively use 200-mesh and 800-mesh grinding discs to grind the sample.

8. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S4, the particle size of the polishing paste is 1.0 - 2.5 μm, and the polishing cloth is a woolen polishing cloth.

9. A method for preparing an EBSD sample by hot embedding WC powder according to claim 1, characterized in that, In step S5, the polishing liquid is a silica solution, and the polishing time is 2 - 5 h.

10. An EBSD sample prepared by the method according to any one of claims 1 - 9.

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