Method for testing strength of powder for spraying based on ultrasonic crushing

Abstract

The invention provides a method for testing the strength of powder for spraying based on ultrasonic pulverization, which comprises the following steps: selecting spraying powder to be tested, and uniformly mixing with water to obtain a test raw material; performing ultrasonic cell crushing on the test raw material to obtain a crushed sample; and testing the particle size distribution of the crushed sample, calculating the powder crushing degree according to the particle size distribution, and evaluating the powder strength according to the powder crushing degree. According to the powder strength testing method provided by the invention, the process condition is closer to the actual working condition of a dynamic impact environment in the powder spraying process, the overall strength state of the powder is accurately evaluated, the operation is simpler and more convenient, the testing efficiency is high, the strength evaluation is accurate, and the method has great engineering application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of spraying, and relates to a method for testing spraying powder, in particular to a method for testing the strength of spraying powder based on ultrasonic crushing. Background Art

[0002] As an important process means in the field of surface engineering, the principle of plasma spraying technology is to ionize inert gas through a DC arc to form a high-temperature plasma (the highest temperature can reach 16,000 K), and use a high-speed flame flow (the flow velocity can reach 800 m / s) to heat metal or ceramic powder to a molten or semi-molten state, and form a dense coating on the substrate surface through high-speed impact. With the advantages of a wide range of processable materials, high coating bonding strength, and small heat-affected zone, this technology plays an irreplaceable role in high-end manufacturing fields such as aerospace, mechanical manufacturing, and energy devices. Among them, the powder properties have a key impact on the coating quality.

[0003] In the powder property parameter system, particle strength is the core index affecting the stability of the spraying process. Ideal spraying powder needs to meet multiple index requirements such as particle size distribution, sphericity, and fluidity. Among them, mechanical strength directly determines the structural integrity of the powder during high-speed transportation. During the acceleration of the plasma flame flow, the powder particles need to withstand extremely high acceleration and collision frequency. When the mechanical strength of the particles is too low, the powder breakage rate is relatively high, which will lead to serious defects such as an increase in the coating porosity and a decrease in the bonding strength. Therefore, establishing a reliable powder strength testing method has important engineering significance for ensuring the coating performance.

[0004] The existing powder test strength system is mainly based on the quasi-static compression principle, and a single-particle compression test is carried out by using a material testing machine in combination with an optical microscope. The specific method is to select a single particle, compress it at a certain loading rate until it breaks, record the load and calculate the particle strength. For example, CN103760029A discloses a hollow powder compressive strength tester, which includes a pressurizing device, a pressurizing main unit, a precision pressurizing cylinder, a measuring device and a control device. The measuring device includes a low-pressure test device and a high-pressure test device, and adopts a single pressurization and dual pressure control system, which can measure the crushing rate of hollow powder inorganic materials under different pressures. CN114414374A discloses an ultra-fine ceramic powder crushing strength test device and method, which includes a sample stage, an observation component and a test component. The observation component includes a high-power objective lens and a low-power objective lens, and the test component includes a pressing head for applying pressure. Although the above methods can obtain accurate mechanical parameters, they have significant defects: a large number of repeated operations are required for single-particle testing, which is time-consuming, and the technical operation requirements are strict, and the equipment cost is high; more importantly, the traditional quasi-static loading test method has a magnitude difference from the dynamic impact environment in the plasma spraying process, and the correlation between its test results and the actual working conditions is insufficient. This damages the engineering guiding value of the existing test methods, especially for powders with a hollow structure, and the true bearing capacity cannot be accurately characterized due to contact stress concentration.

[0005] Therefore, these technical bottlenecks severely restrict the R & D process of high-performance spraying powders, and it is urgent to develop a new test method to achieve rapid evaluation of powder strength. Summary of the Invention

[0006] The purpose of the present invention is to provide a test method for the strength of spraying powder based on ultrasonic crushing. By means of ultrasonic crushing, the overall fragmentation parameter under dynamic conditions of the powder is calculated, and the powder strength is evaluated by the powder fragmentation degree.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] The present invention provides a test method for the strength of spraying powder based on ultrasonic crushing, and the test method includes the following steps:

[0009] (1) Select the spraying powder to be tested, test the particle size distribution of the spraying powder, and mix the spraying powder with water evenly to obtain a test raw material;

[0010] (2) Perform ultrasonic cell crushing on the test raw material to obtain a crushed sample;

[0011] (3) Test the particle size distribution of the crushed sample, calculate the powder fragmentation degree through the particle size distribution, and evaluate the powder strength by the powder fragmentation degree.

[0012] The method provided by the present invention performs high-frequency ultrasonic cell crushing on a certain amount of powder in total, calculates the degree of fragmentation of the sprayed powder through the particle size distribution before and after crushing, and evaluates the powder strength with the degree of fragmentation. On the one hand, the ultrasonic crushing method is used for powder crushing, and its process conditions are closer to the actual working conditions of the dynamic impact environment during powder spraying, and the obtained degree of fragmentation is more valuable for reference and guiding significance. On the other hand, crushing a certain amount of powder in total can better characterize the overall strength state of the powder compared with the compression test of single particles, and the operation is simpler, more convenient, with high test efficiency and accurate strength evaluation, having great engineering application value.

[0013] Preferably, the material of the sprayed powder in step (1) includes any one or a combination of at least two of oxides, carbides, nitrides or cermet composites.

[0014] Exemplarily, the oxides include any one or a combination of at least two of Al2O3, Y2O3, Cr2O3 or TiO2.

[0015] Exemplarily, the carbides include WC and / or Cr3C2.

[0016] Exemplarily, the nitrides include TiN and / or BN.

[0017] Exemplarily, the cermet composites include WC-Co and / or Cr3C2-NiCr.

[0018] Preferably, the purity of the sprayed powder in step (1) is 2N - 4N. For example, it can be 2N, 2N5, 3N, 3N5 or 4N, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the particle size range of the sprayed powder in step (1) is 5 - 100μm. For example, it can be 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, preferably 10 - 80μm.

[0020] Preferably, the particle size distribution of the sprayed powder in step (1) is measured by a laser particle size analyzer.

[0021] Preferably, the liquid-solid ratio of the water to the spraying powder in step (1) is (4 - 60):1 mL / g. For example, it can be 4:1 mL / g, 10:1 mL / g, 15:1 mL / g, 20:1 mL / g, 25:1 mL / g, 30:1 mL / g, 35:1 mL / g, 40:1 mL / g, 45:1 mL / g, 50:1 mL / g, 55:1 mL / g or 60:1 mL / g. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] Preferably, the ultrasonic power of the ultrasonic cell disruption in step (2) is 900 - 1000 W. For example, it can be 900 W, 910 W, 920 W, 930 W, 940 W, 950 W, 960 W, 970 W, 980 W, 990 W or 1000 W. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the ultrasonic frequency of the ultrasonic cell disruption in step (2) is 15 - 25 kHz. For example, it can be 15 kHz, 16 kHz, 17 kHz, 18 kHz, 19 kHz, 20 kHz, 21 kHz, 22 kHz, 23 kHz, 24 kHz or 25 kHz. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the time of the ultrasonic cell disruption in step (2) is 10 - 30 min. For example, it can be 10 min, 15 min, 20 min, 25 min or 30 min. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the particle size distribution of the crushed sample in step (3) is measured by a laser particle size analyzer.

[0026] Preferably, the calculation method of the powder fragmentation degree in step (3) is: the difference between the proportion of the number of particles with a particle size below 8 μm in the crushed sample in the total number of particles and the proportion of the number of particles with a particle size below 8 μm in the spraying powder in the total number of particles.

[0027] In the present invention, 8 μm is used as the critical particle size for characterizing the powder fragmentation degree. On the one hand, in the actual spraying process, the particle size of the spraying powder is generally in the range of 8 - 100 μm. When the particle size of the powder is less than 8 μm, its flowability significantly decreases, directly affecting the stability of the spraying process. Therefore, choosing 8 μm as the critical particle size conforms to the industrial application specifications and has good effectiveness in process characterization. On the other hand, under this numerical standard, the test results of the fragmentation degree obtained can show significant numerical gradients, thereby ensuring the sensitivity and accuracy of the powder strength evaluation. If the selected particle size is too large, the fragmentation degree values will tend to converge, ultimately leading to a decrease in the accuracy of the evaluation system.

[0028] As a preferred technical solution of the test method provided by the present invention, the test method includes the following steps:

[0029] (1) Select spraying powder with a particle size range of 10 - 80 μm, use a laser particle size analyzer to test the particle size distribution of the spraying powder, mix the spraying powder and deionized water according to a liquid-solid ratio of (4 - 60):1 mL / g, and stir evenly to obtain a test raw material;

[0030] (2) Perform ultrasonic cell crushing on the test raw material. The ultrasonic power of the ultrasonic cell crushing is 900 - 1000 W, the ultrasonic frequency is 15 - 25 kHz, and the time of ultrasonic cell crushing is 10 - 30 min. After completion, a crushed sample is obtained;

[0031] (3) Use a laser particle size analyzer to test the particle size distribution of the crushed sample, independently calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles of the spraying powder and the crushed sample respectively, calculate the difference between the proportions of the crushed sample and the spraying powder as the powder fragmentation degree, and evaluate the powder strength from the powder fragmentation degree.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The powder strength test method provided by the present invention has process conditions closer to the actual working conditions of the dynamic impact environment during powder spraying. The powder fragmentation degree and the powder strength conform to a good linear relationship, and R 2 is close to 1. Thus, the overall strength state of the powder can be directly and accurately evaluated through the powder fragmentation degree, and the operation is simpler, more convenient, the test efficiency is high, and it has great engineering application value. Description of the Drawings

[0034] Figure 1 is the metallographic micrograph of the spraying powder of the test method provided in Example 1;

[0035] Figure 2 is the Malvern particle size distribution result graph of the spraying powder of the test method provided in Example 1;

[0036] Figure 3 It is the metallographic micrograph of the crushed sample of the test method provided in Example 1;

[0037] Figure 4 It is the Malvern particle size distribution result graph of the crushed sample of the test method provided in Example 1. Detailed implementation manners

[0038] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0039] Example 1

[0040] This example provides a test method for the strength of spraying powder based on ultrasonic crushing. The test method includes the following steps:

[0041] (1) Select the spraying powder to be tested with a particle size range of 5 - 100 μm, and use a laser particle size analyzer to test the spraying powder to be tested to obtain the particle size distribution of the spraying powder;

[0042] (2) Add 3 g of spraying powder into a beaker, add 30 mL of deionized water, stir evenly, and the liquid - solid ratio is 10:1 mL / g to obtain the test raw material;

[0043] (3) Put the test raw material into an ultrasonic cell crusher for ultrasonic crushing. The parameters of ultrasonic crushing are: power 950 W, ultrasonic frequency 20 kHz, treatment time 15 min. After the ultrasonic crushing is completed, a crushed sample is obtained;

[0044] (4) Use a laser particle size analyzer to test the crushed sample to obtain the particle size distribution of the crushed sample. Calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the spraying powder, calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the crushed sample, and the difference between the proportion of the spraying powder and the proportion of the crushed sample is the powder breakage degree.

[0045] Example 2

[0046] This example provides a test method for the strength of spraying powder based on ultrasonic crushing. The test method includes the following steps:

[0047] (1) Select the spraying powder to be tested with a particle size range of 5 - 100 μm, and use a laser particle size analyzer to test the spraying powder to be tested to obtain the particle size distribution of the spraying powder;

[0048] (2) Add 1 g of the spraying powder into a beaker, add 60 mL of deionized water, stir evenly, with a liquid-solid ratio of 60:1 mL / g, to obtain the test raw material;

[0049] (3) Put the test raw material into an ultrasonic cell disrupter for ultrasonic comminution. The parameters of ultrasonic comminution are: power 900 W, ultrasonic frequency 25 kHz, treatment time 10 min. After the ultrasonic comminution is completed, a comminuted sample is obtained;

[0050] (4) Test the comminuted sample with a laser particle size analyzer to obtain the particle size distribution of the comminuted sample. Calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the spraying powder, calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the comminuted sample, and the difference between the proportion of the spraying powder and the proportion of the comminuted sample is the powder fragmentation degree.

[0051] Example 3

[0052] This example provides a method for testing the strength of spraying powder based on ultrasonic comminution. The testing method includes the following steps:

[0053] (1) Select the spraying powder to be tested with a particle size range of 5 - 100 μm, and test the spraying powder to be tested with a laser particle size analyzer to obtain the particle size distribution of the spraying powder;

[0054] (2) Add 5 g of the spraying powder into a beaker, add 20 mL of deionized water, stir evenly, with a liquid-solid ratio of 4:1 mL / g, to obtain the test raw material;

[0055] (3) Put the test raw material into an ultrasonic cell disrupter for ultrasonic comminution. The parameters of ultrasonic comminution are: power 1000 W, ultrasonic frequency 15 kHz, treatment time 30 min. After the ultrasonic comminution is completed, a comminuted sample is obtained;

[0056] (4) Test the comminuted sample with a laser particle size analyzer to obtain the particle size distribution of the comminuted sample. Calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the spraying powder, calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the comminuted sample, and the difference between the proportion of the spraying powder and the proportion of the comminuted sample is the powder fragmentation degree.

[0057] Example 4

[0058] This example provides a method for testing the strength of spraying powder based on ultrasonic comminution. Compared with Example 1, the ultrasonic power of ultrasonic cell comminution is 800 W, and the rest are the same as in Example 1.

[0059] Example 5

[0060] This embodiment provides a method for testing the strength of powder for spraying based on ultrasonic comminution. Compared with Embodiment 1, the ultrasonic power of the ultrasonic cell crusher is 1200 W, and the rest are the same as in Embodiment 1.

[0061] Embodiment 6

[0062] This embodiment provides a method for testing the strength of powder for spraying based on ultrasonic comminution. Compared with Embodiment 1, the calculation method of powder fragmentation degree is as follows: independently calculate the proportion of the number of particles with a particle size below 3 μm in the total number of particles of the spraying powder and the comminuted sample respectively, and calculate the difference between the proportions of the spraying powder and the comminuted sample. The rest are the same as in Embodiment 1.

[0063] Embodiment 7

[0064] This embodiment provides a method for testing the strength of powder for spraying based on ultrasonic comminution. Compared with Embodiment 1, the calculation method of powder fragmentation degree is as follows: independently calculate the proportion of the number of particles with a particle size below 20 μm in the total number of particles of the spraying powder and the comminuted sample respectively, and calculate the difference between the proportions of the spraying powder and the comminuted sample. The rest are the same as in Embodiment 1.

[0065] To evaluate the accuracy of the method for testing the strength of powder for spraying based on ultrasonic comminution provided in Embodiments 1 - 7, three different powders are provided, namely Powder A, Powder B, and Powder C. Powder A: The plasma thermal spraying powder of alumina with a purity of 4N is kept at 1300 °C for 3 hours, and the obtained spraying powder is used as the test object. The compressive strength of Powder A is 3.5 N. Powder B: The plasma thermal spraying powder of alumina with a purity of 4N is kept at 1400 °C for 3 hours, and the obtained spraying powder is used as the test object. The compressive strength of Powder B is 6.8 N. Powder C: The plasma thermal spraying powder of alumina with a purity of 4N is kept at 1500 °C for 3 hours, and the obtained spraying powder is used as the test object. The compressive strength of Powder C is 10.4 N. The compressive strength of the above powders is tested by the method of Standard GB / T 44750 - 2024.

[0066] Powder A is tested by the test method provided in Embodiment 1. Figure 1 is the metallographic micrograph of the spraying powder (i.e., before ultrasonic cell comminution). Figure 2 is the Malvern particle size distribution result graph of the spraying powder. Figure 3 is the metallographic micrograph of the comminuted sample (i.e., after ultrasonic comminution). Figure 4 is the Malvern particle size distribution result graph of the comminuted sample.

[0067] The test method provided in the examples was repeated three times, and the average crushing rate was calculated. The results are listed in Table 1. In Table 1, the "proportion of particles in the sprayed powder" refers to the proportion of the number of particles with a particle size below the corresponding critical particle size in the total number of particles in the sprayed powder to be tested (i.e., before ultrasonic cell disruption).

[0068] Table 1

[0069]

[0070]

[0071] As can be seen from Table 1, by fitting the numerical relationships of the powder strength data and the average fragmentation degree data in Examples 1 - 3, the average fragmentation degree and the powder strength respectively satisfy the relationships y = -0.084x + 10.64, y = -0.085x + 10.57, y = -0.083x + 10.69. It can be seen that there is a stable linear relationship between the average fragmentation degree and the powder strength. At the same time, calculate R 2 (coefficient of determination) are 0.9991, 0.9986, 0.9994 respectively. R 2 is close to 1, and the residual sum of squares (RSS) are 0.020, 0.033, 0.014 respectively, with extremely small values, indicating that the average fragmentation degree and the powder strength values of each data point conform to a good linear relationship. The average fragmentation degree value can be used to evaluate the powder strength well. And further, the unknown powder strength can be evaluated based on the good linear relationship through the known powder strength.

[0072] Compared with Example 1, in Examples 4 and 5, by fitting the linear relationship of the corresponding data, the calculated R 2 are 0.9528 and 0.9536 respectively. R 2 is on the small side, and the residual sum of squares (RSS) are 1.124 and 1.103 respectively. RSS becomes larger. When the ultrasonic power is too small, the powder is not broken sufficiently. When the ultrasonic power is too large, the degree of powder fragmentation is too large, which will make the numerical discrimination degree of the fragmentation degree not significant, thus reducing its linear accuracy; in Examples 6 and 7, by fitting the linear relationship of the corresponding data, the calculated R 2 are 0.9755 and 0.9230 respectively. R 2 is on the small side, and the residual sum of squares (RSS) are 0.582 and 1.833 respectively. RSS is on the large side. When the particle size critical value is too small, the powder proportion is too small. When the particle size critical value is too large, the difference in the average fragmentation degree is too small, thus making the final numerical discrimination degree smaller and the fitting accuracy rate decrease, thereby affecting the accuracy and sensitivity of the strength evaluation.

[0073] In summary, the powder strength testing method provided by the present invention has process conditions that are closer to the actual working conditions of the dynamic impact environment during powder spraying. There is a good linear relationship between the powder fragmentation degree and the powder strength, and R 2 is close to 1. Thus, the overall strength state of the powder can be directly and accurately evaluated through the powder fragmentation degree, and the operation is simpler, more convenient, with high testing efficiency, and has great engineering application value.

[0074] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A test method for the strength of powder used in spraying based on ultrasonic comminution, characterized in that, The described testing method includes the following steps: (1) Select the spraying powder to be tested, test the particle size distribution of the spraying powder, and mix the spraying powder evenly with water to obtain a test raw material; (2) Perform ultrasonic cell crushing on the test raw material to obtain a crushed sample; (3) Test the particle size distribution of the crushed sample, calculate the powder fragmentation degree through the particle size distribution, and evaluate the powder strength from the powder fragmentation degree.

2. The test method according to claim 1, characterized in that, In step (1), the particle size range of the spraying powder is 5 - 100 μm.

3. The test method according to claim 1 or 2, characterized in that, In step (1), the particle size distribution of the spraying powder is measured by a laser particle size analyzer.

4. The test method according to any one of claims 1-3, characterized in that, In step (1), the liquid-solid ratio of water to the spraying powder is (4 - 60):1 mL / g.

5. The testing method according to any one of claims 1-4, characterized in that In step (2), the ultrasonic power of the ultrasonic cell crushing is 900 - 1000 W.

6. The test method according to any one of claims 1-5, characterized in that In step (2), the ultrasonic frequency of the ultrasonic cell crushing is 15 - 25 kHz.

7. The testing method according to any one of claims 1-6, characterized in that, In step (2), the time of the ultrasonic cell crushing is 10 - 30 min.

8. The test method according to any one of claims 1-7, characterized in that, In step (3), the particle size distribution of the crushed sample is measured by a laser particle size analyzer.

9. The test method according to any one of claims 1-8, characterized in that, The calculation method of the powder fragmentation degree in step (3) is: the difference between the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the crushed sample and the proportion of the number of particles with a particle size below 8 μm in the total number of particles in the spraying powder.

10. The test method according to any one of claims 1-9, characterized in that, The described testing method includes the following steps: (1) Select a spraying powder with a particle size range of 5 - 100 μm, use a laser particle size analyzer to test the particle size distribution of the spraying powder, mix the spraying powder with deionized water according to a liquid-solid ratio of (4 - 60):1 mL / g, and stir evenly to obtain a test raw material; (2) Perform ultrasonic cell crushing on the test raw material, the ultrasonic power of the ultrasonic cell crushing is 900 - 1000 W, the ultrasonic frequency is 15 - 25 kHz, and the time of the ultrasonic cell crushing is 10 - 30 min. After completion, a crushed sample is obtained; (3) Use a laser particle size analyzer to test the particle size distribution of the crushed sample, independently calculate the proportion of the number of particles with a particle size below 8 μm in the total number of particles of the spraying powder and the crushed sample respectively, and calculate the difference between the proportions of the crushed sample and the spraying powder as the powder fragmentation degree, and evaluate the powder strength from the powder fragmentation degree.

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