A method for detecting the number of inclusions in alloy powder

Abstract

This invention relates to a method for detecting the number of inclusions in alloy powders, and relates to the field of materials analysis technology. The main technical solution employed is as follows: the method comprises the following steps: performing a first pressing process on the powder to be tested to obtain a first pressed sample; then, under a protective atmosphere, performing a second pressing process on the first pressed sample to obtain a test sample; and testing one or more of the test samples using a radiographic detection method to determine the number of inclusions contained in the test sample. This invention is primarily intended to improve the accuracy, efficiency, and comprehensiveness of inclusion detection in alloy powders.

Description

Technical Field

[0001] The present invention relates to the technical field of material analysis, in particular to a method for detecting the number of inclusions in alloy powder. Background Art

[0002] Powder inclusions are an important indicator of powder materials and a key factor in ensuring the mechanical properties of formed parts. Inclusions in alloy powders for additive manufacturing can be divided into two main categories: metallic inclusions and non-metallic inclusions. Metallic inclusions mainly come from stainless steel screens, powder storage tanks, and powder storage bottles. Non-metallic inclusions mainly come from the master alloy; specifically, non-metallic inclusions in slag, insulation materials, and furnace charges during vacuum melting can all become possible sources of inclusions; therefore, non-metallic inclusions in the original powder are mainly ceramics, slag, and other inclusions, which vary in shape, and their main chemical components are Al, Si, Ca, Ti, Mg, and C, with sizes ranging from thousands of microns to hundreds of microns.

[0003] Factors such as the type, quantity, and size of inclusions in powders directly affect the mechanical properties and service life of finished parts. Currently, the national standard GB / T 39251-2020 (Methods for Characterizing Metal Powder Properties for Additive Manufacturing) primarily specifies three testing methods: microscopy, scanning electron microscopy, and industrial CT scanning. However, all three methods have significant limitations in practice, leading to significant deviations in test results.

[0004] For the existing microscopy method, the detection process is as follows: "Use visual inspection and stereo microscope to inspect. Take 100g of the powder to be tested and place it in a glass container with a diameter of 50-100mm. First, perform a visual inspection, and then use a stereo microscope to carefully inspect the inclusions of the powder sample." However, the stereo microscope distinguishes inclusions by the difference in the light reflection ability of powders of different components. Through research, it was found that when using a stereo microscope for detection, only powder samples perpendicular to the light source can show normal powder morphology. Powders at other angles will more or less reflect the light source (such as Figure 1 ), making it impossible to discern the presence of inclusions.

[0005] Existing scanning electron microscopy (SEM) testing is generally conducted in accordance with the "JY / T 010-1996 General Rules for Analytical Scanning Electron Microscopy Methods." However, this method first requires morphological differentiation between the test powder and suspected inclusions, followed by determination of the inclusion composition using an energy spectrum analyzer. In other words, if the test powder and suspected inclusions cannot be distinguished morphologically, the presence of inclusions can be easily lost. For mixed alloy powders containing other components, the particle size and sphericity of the test powder and inclusions are very similar, resulting in low accuracy and efficiency in the test results. Furthermore, a related patent (201811204036.6) discloses a method for measuring the inclusion content in ultrafine titanium alloy powders used in selective laser melting. The accuracy of this method's test results relies on the powder sample preparation process. However, this method, on the one hand, requires a small sample size, making the test unrepresentative. On the other hand, during the sample preparation process (here, the sample preparation refers to spreading the powder on a conductive adhesive), inclusions can be lost, leading to biased test results. Therefore, this method cannot meet the detection requirements of inclusions.

[0006] The existing industrial CT scanning method (GB / T 39251-2020 Method for Characterization of Metal Powder Properties for Additive Manufacturing) for direct powder inclusion detection also has two shortcomings: insufficient detection capability and extremely low detection efficiency. Regarding detection capability, since industrial CT technology is used for testing, and its detection accuracy limit is 50μm, powder inclusions smaller than 50μm are difficult to detect. Furthermore, post-processing is required (this complex image processing includes: reconstruction software to reconstruct 2D CT images into 3D information; processing software to adjust global and local contrast and brightness for easier observation; fractional software to measure the sample's 3D surface information and filter out unnecessary matter, such as air; analysis software to perform layered observation of the sample's 3D information; and selection of grayscale values ​​for the powder sample and identification of inclusions). This reduces the stability of the test results. Furthermore, using industrial CT equipment to test powder inclusion rates is costly and inefficient. Regarding testing efficiency, the standard stipulates that the powder to be tested must be pre-conditioned in the testing environment for 12 hours before testing can be performed. Industrial production often requires more than a dozen heats to produce the same batch of powder, and each heat must be tested. This results in a testing time of at least 180 hours per batch, severely impacting powder production schedules.

[0007] In addition, related art (CN108043586) proposes a method for detecting the content of non-metallic inclusions in metal powder. Although this method can improve detection efficiency, since it uses the electrostatic principle to detect inclusions, this method can only detect non-metallic inclusions and still cannot efficiently and accurately inspect metal inclusions.

[0008] In summary, there is an urgent need for a method to detect the number of inclusions in alloy powders used in additive manufacturing to improve detection accuracy and efficiency. Summary of the Invention

[0009] In view of this, the present invention provides a method for detecting the number of inclusions in alloy powder, the main purpose of which is to improve detection accuracy and detection efficiency.

[0010] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0011] An embodiment of the present invention provides a method for detecting the number of inclusions in alloy powder for additive manufacturing, comprising the following steps:

[0012] The test sample preparation step includes: performing a first pressing process on the powder to be tested to obtain a first pressed sample; then, performing a second pressing process on the first pressed sample under a protective atmosphere to obtain a test sample;

[0013] Detection step: using a radiographic detection method to detect one or more of the test samples to obtain the number of inclusions contained in the test samples.

[0014] Preferably, in the step of preparing the test sample: the powder to be tested is placed in a package and subjected to a first pressing process and a second pressing process, and the package is removed to obtain the test sample.

[0015] Preferably, the first pressing process is cold pressing.

[0016] Preferably, the temperature of the first pressing treatment is room temperature, the deformation amount of the first pressing treatment is 40-60%, the pressure of the first pressing treatment is 300-500 MPa, and the time of the first pressing treatment is 30-60 min.

[0017] Preferably, the temperature of the second pressing treatment is 300-600° C.; the pressure of the second pressing treatment is 400-600 MPa; the time of the second pressing treatment is 1-4 hours; and the deformation amount of the second pressing treatment is 10-30%.

[0018] Preferably, the mass of the powder to be tested is not less than 600 g.

[0019] Preferably, the mass of the powder to be tested is not higher than 900 g.

[0020] Preferably, in the test sample preparation step: the powder to be tested is divided into multiple portions, and then the multiple portions of the powder to be tested are subjected to a first pressing process and a second pressing process to obtain multiple test samples.

[0021] Preferably, in the step of preparing the test sample: the powder to be tested is divided into 3-6 portions.

[0022] Preferably, in the detection step: one or more detection samples are detected based on the principle of radiographic detection, the gaps in the detected image are filled, and the filled image is observed to obtain the number of inclusions contained in the sample.

[0023] Preferably, in the detection step: the detection method adopted is an X-ray detection method or a micro-CT detection method.

[0024] Preferably, the particle size of the powder to be tested is less than 250 μm.

[0025] Preferably, the powder to be tested is titanium alloy powder.

[0026] Preferably, the powder to be tested is an alloy powder for additive manufacturing.

[0027] Compared with the prior art, the method for detecting the number of inclusions in alloy powders of the present invention has at least the following beneficial effects:

[0028] An embodiment of the present invention provides a method for detecting inclusion counts in alloy powders, comprising the following steps: performing a first pressing process on the powder to be tested to obtain a first pressed sample; then, performing a second pressing process on the first pressed sample under a protective atmosphere to obtain a test sample; and testing the test sample using a radiographic inspection method to determine the number of inclusions contained in the test sample. Regarding these steps, the present invention only requires pressing the powder to be tested into a test sample for testing. In terms of testing efficiency, the present invention can simultaneously test multiple test samples, while other existing methods require multiple tests. In terms of accuracy, the present method can compress at least 600g of powder to prepare a test sample for testing, while other existing methods typically test samples weighing less than 50g. Due to the small sample mass, inclusions may be missed during sampling. Furthermore, the present method is scientifically sound, as the pressing process does not result in powder loss. Other methods, such as spreading the powder on a conductive adhesive, can easily result in powder particle loss during sample preparation, leading to inaccurate inclusion counts. As can be seen, compared with existing detection methods, the method of the present invention is more scientific and accurate during the sample preparation process, and does not cause deviations in the results due to sample preparation. Furthermore, the present invention significantly improves detection efficiency, accuracy, and comprehensiveness over existing methods, enabling a more convenient, accurate, comprehensive, and rapid determination of inclusion counts in additive manufacturing powders.

[0029] Furthermore, an embodiment of the present invention provides a method for detecting the number of inclusions in alloy powder. By controlling the temperature (room temperature), pressure and deformation of the first pressing treatment, and controlling the atmosphere, temperature, pressure and deformation of the second pressing treatment, not only can the gaps between powder particles be eliminated as much as possible, but also test samples of corresponding sizes can be prepared according to the requirements of the detection equipment, thereby effectively controlling the sample size, so that more samples can be tested at a single time, thereby improving detection efficiency.

[0030] Furthermore, an embodiment of the present invention provides a method for detecting the number of inclusions in alloy powder. The powder to be tested is randomly selected and evenly divided into multiple portions, and then a first pressing treatment and a second pressing treatment are performed respectively to obtain multiple test samples. By testing the multiple test samples, it can be ensured that the sample preparation process will not affect the accuracy of the test results.

[0031] Furthermore, an embodiment of the present invention provides a method for detecting the number of inclusions in alloy powder, which uses X-ray (DR technology) or micro-CT detection to achieve high detection accuracy; the present invention can realize large-scale powder detection with high detection efficiency. At the same time, the single detection time of the present invention is only about 1 hour; the sample preparation process of the present invention is more scientific and will not cause deviation in the detection results due to sample preparation.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is an image of inclusion detection of powder using a stereo microscope in the prior art;

[0034] Figure 2 is the detection image of Example 1 of the present invention; Figure 2 Figure (a) is the detection image of the first detection sample in Example 1. Figure 2 Figure (b) is the detection image of the second detection sample in Example 1; Figure 2 Figure (c) is the detection image of the third detection sample in Example 1; Figure 2 Figure (d) is the detection image of the fourth detection sample in Example 1;

[0035] Figure 3 is the detection image of Example 2 of the present invention; Figure 3 Figure (a) is the detection image of the first detection sample in Example 2. Figure 3 Figure (b) is the detection image of the second detection sample in Example 2; Figure 3 Figure (c) is the detection image of the third detection sample in Example 2;

[0036] Figure 4 is the detection image of Example 3 of the present invention; Figure 4 Figure (a) is the detection image of the first detection sample in Example 3; Figure 4 Figure (b) is the detection image of the second detection sample in Example 3; Figure 4 Figure (c) is the detection image of the third detection sample in Example 3; Figure 4 Figure (d) is the detection image of the fourth detection sample in Example 3; Figure 4 Figure (e) is the detection image of the fifth detection sample in Example 3; Figure 4 Figure (f) is the detection image of the sixth detection sample in Example 3;

[0037] Figure 5 These are morphology diagrams of the powder after paving in Comparative Example 1 of the present invention; wherein, (a) is a macroscopic morphology diagram; and (b) is a microscopic morphology diagram. DETAILED DESCRIPTION

[0038] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0039] An embodiment of the present invention provides a method for detecting inclusions in alloy powder. This method proposes, for the first time, subjecting the powder to be tested to a first pressing process to obtain a first pressed sample. Next, under a protective atmosphere, the first pressed sample is subjected to a second pressing process to obtain a test sample. This ensures the scientific and accurate preparation of the powder to be tested. The test sample is then inspected using X-ray (DR) or industrial CT technology, enabling efficient and accurate detection of powder inclusions. This method offers the advantages of simple operation, high detection efficiency and accuracy, and comprehensive testing. The specific implementation of the present invention is as follows:

[0040] An embodiment of the present invention provides a method for detecting the number of inclusions in alloy powder, which mainly includes the following steps:

[0041] 1) Preparation of test samples: Randomly sample the powder to be tested and place it in a package for a first pressing process to obtain a first pressed sample; then, under a protective atmosphere, perform a second pressing process on the first pressed sample and remove the package to obtain a test sample.

[0042] Preferably, the mass of the powder to be tested is not less than 600 g, preferably not more than 900 g.

[0043] Preferably, the powder to be tested is evenly divided into multiple portions (3-6 portions), and then subjected to a first pressing process and a second pressing process respectively to obtain multiple test samples.

[0044] Preferably, the first pressing process is a cold pressing process (temperature is room temperature), the deformation is 40-60%, the pressure of the first pressing process is 300-500 MPa, and the time of the first pressing process is 30-60 minutes.

[0045] Preferably, the temperature of the second pressing treatment is 300-600° C., the pressure is 400-600 MPa, the time is 1-4 h, the deformation is 10-30%, and the protective atmosphere is an inert gas, preferably argon or helium.

[0046] Preferably, the powder to be tested has a particle size of less than 250 μm. Preferably, the powder to be tested is a titanium alloy powder. Preferably, the powder to be tested is an alloy powder for additive manufacturing.

[0047] 2) Detection step: using a radiographic detection method to detect the test sample to obtain the number of inclusions contained in the test sample.

[0048] Preferably, in this step, the test sample is tested based on the principle of radiographic testing, the gaps in the image after testing are filled, and the processed image is observed to obtain the number of inclusions contained in the test sample.

[0049] It should be noted that: (1) the voids in the detected image come from the uncompacted part; (2) the voids are filled using image processing software (e.g., Photoshop, Image Editing Assistant, Adobe Lightroom, etc.) so that the voids have the same contrast as the material matrix, i.e., the voids are black and the inclusions are bright; the inclusions are judged by brightness (contrast), and inclusions are those with a significant brightness difference from the matrix; (4) all types of inclusions can be detected, based on the fact that the contrast between inclusions and the matrix is ​​different under X-rays.

[0050] It should also be noted that the present invention only needs to perform filling processing on the detection image, and the operation is simple.

[0051] Preferably, the radiation detection method is X-ray (DR technology) or micro-CT detection, which can detect inclusions of several microns.

[0052] The following is further described by specific experimental examples:

[0053] Example 1

[0054] This embodiment detects the number of inclusions in TC4 alloy powder for additive manufacturing, including the following steps:

[0055] (1) Randomly sample 800g of powder to be tested, with a particle size range of 10-53μm. Divide the powder to be tested into 4 portions. Each of the 4 portions of powder to be tested is placed in a bag and subjected to a first pressing process (cold pressing). The temperature of the first pressing process is room temperature, the pressure is 500MPa, the pressing time is 45min, and the pressing deformation is 50%. Four first pressing samples are obtained. Under an argon atmosphere, the four first pressing samples are subjected to a second pressing process. The temperature of the second pressing process is 500℃, the pressure of the second pressing process is 450MPa, the pressing time is 2h, and the pressing deformation is 20%. Four test samples are obtained.

[0056] (2) Micro-CT technology was used to perform X-ray inspection on four test samples. The gaps in the images after inspection were filled, and then the processed images were observed to obtain the number of inclusions contained in the test samples.

[0057] In this example, one inclusion was detected in four test samples. Figure 2 As shown in Figures (a), (b), (c), and (d), only one inclusion was detected in the first sample tested.

[0058] Example 2

[0059] This embodiment detects the number of inclusions in Ti60 alloy powder for additive manufacturing, including the following steps:

[0060] (1) Randomly select 600g of the powder to be tested (particle size 75-180 microns) and evenly divide the powder into three parts. The three parts of the powder to be tested are respectively placed in a bag and subjected to the first pressing process. The temperature of the first pressing process is room temperature, the pressure is 550MPa, the pressing time is 60min, and the pressing deformation is 60%. Three first pressing samples are obtained. In a helium atmosphere, the three first pressing samples are respectively subjected to the second pressing process. The temperature of the second pressing process is 550℃, the pressure of the second pressing process is 550MPa, the pressing time is 1.5h, and the pressing deformation is 15%. Three test samples are obtained.

[0061] (2) Industrial CT technology was used to perform radiographic inspection on three test samples. The gaps in the images after inspection were filled, and then the processed images were observed to obtain the number of inclusions contained in the test samples.

[0062] In this example, three inclusions were detected in three test samples. Figure 3 As shown, see Figure 3 In Figures (a), (b), and (c), two inclusions were detected in the first test sample, one inclusion was detected in the second test sample, and no inclusions were detected in the third test sample.

[0063] Example 3

[0064] This embodiment detects the number of inclusions in Ti2AlNb alloy powder for additive manufacturing, including the following steps:

[0065] (1) Randomly select 900 g of the powder to be tested (particle size 75-250 μm) and evenly divide the powder into 6 portions. Each of the 6 portions of powder to be tested is placed in a bag and subjected to a first pressing process. The temperature of the first pressing process is room temperature, the pressure of the first pressing process is 485 MPa, and the deformation of the first pressing process is 55%. Six first pressing samples are obtained. Under an argon atmosphere, the six first pressing samples are subjected to a second pressing process. The temperature of the second pressing process is 600°C, the pressure of the second pressing process is 575 MPa, the time of the second pressing process is 2.5 h, and the deformation of the pressing process is 10%. Six test samples are obtained.

[0066] (2) X-ray (DR technology) was used to perform radiographic inspection on 6 test samples. The gaps in the images after inspection were filled and the images after filling were observed to obtain the number of inclusions contained in the samples.

[0067] No inclusions were detected in any of the 6 samples tested in this example. Figure 4 As shown in Figures (a), (b), (c), (d), (e) and (f).

[0068] Comparative Example 1

[0069] Comparative Example 1: Inclusions in TC4 titanium alloy ultrafine powder were detected using a conventional method, which mainly includes the following steps:

[0070] 1) Detect inclusions in TC4 titanium alloy ultrafine powder. The particle size range of TC4 titanium alloy ultrafine powder is below 63μm. Use a sampler to randomly remove 1kg of powder in an argon-protected device. Wear powder-free rubber gloves when sampling to prevent the introduction of contaminants that may affect the test results.

[0071] 2) Randomly take out 20g of the powder to be tested from 1kg of powder in an argon-protected device and divide the powder into 5 equal portions, each 4g. Wear powder-free rubber gloves when sampling to prevent the introduction of contaminants that may affect the test results.

[0072] 3) Stick the conductive glue on the stage and spread the powder evenly on the conductive glue to avoid excessive overlap of the powder;

[0073] 4) Place the sample carrier with the powder to be tested into the gold spraying equipment for gold spraying. The gold spraying parameters are: current 20~30mA, vacuum degree <10Pa;

[0074] 5) Place the prepared powder under test in a scanning electron microscope with the following equipment parameters: voltage 20 kV, current 128-133 mA;

[0075] 6) Observe the powder morphology using a scanning electron microscope with a field of view of 10-8000 times to identify suspicious powder inclusions;

[0076] 7) After the suspicious powder inclusions are identified, the energy spectrum analyzer that comes with the scanning electron microscope is used to perform energy spectrum analysis on the suspicious powder inclusions to determine whether they are powder inclusions. The equipment parameters of the energy spectrum analyzer are: voltage 20KV, magnification 500 times;

[0077] 8) Repeat the above steps 4 times, conduct a comprehensive test on 20g of powder, and record the amount of included powder to evaluate the inclusion content in the 20g powder, so as to determine whether the TC4 titanium alloy ultrafine powder meets the use requirements.

[0078] The above steps of Comparative Example 1 include at least the following steps:

[0079] 1. Regarding Step 2): 20g of powder was finally sampled for testing in Comparative Example 1, which is not representative of the 1kg sample. The sample needs to be divided into five portions for testing. During the sample subpackaging process, inclusions may be lost, affecting the test results.

[0080] 2. For step 3): The macroscopic appearance of the powder after spreading is as follows: Figure 5 As shown in Figure (a); no matter how the powder is spread, it will still overlap, and the bottom inclusions may be blocked by the upper powder (see Figure 5 (B) shows that the bottom layer of powder is obscured by the upper layer. Furthermore, since the SEM can only examine the powder from a fixed viewing angle, inclusions in the bottom layer cannot be detected. Furthermore, since only the bottom layer of powder adheres securely, loose inclusions in the upper layer can fall off during sample loading.

[0081] 3. For step 4): During the gold spraying process, the included powder that is not firmly adhered will fall off, resulting in inaccurate test results.

[0082] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for detecting the number of inclusions in alloy powder, characterized in that: It includes the following steps: The test sample preparation step includes: performing a first pressing process on the powder to be tested to obtain a first pressed sample; then, performing a second pressing process on the first pressed sample under a protective atmosphere to obtain a test sample; wherein the first pressing process is a cold pressing process; the temperature of the first pressing process is room temperature; the deformation of the first pressing process is 40-60%; the pressure of the first pressing process is 300-500 MPa; and the time of the first pressing process is 30-60 minutes; the temperature of the second pressing process is 300-600° C.; the pressure of the second pressing process is 400-600 MPa; the time of the second pressing process is 1-4 hours; the deformation of the second pressing process is 10-30%; the protective atmosphere is an inert gas; wherein the mass of the powder to be tested is not less than 600 g; Detection step: using a radiographic detection method to detect one or more of the test samples to obtain the number of inclusions contained in the test samples; wherein, based on the radiographic detection principle, one or more of the test samples are detected, the gaps in the image after detection are filled, and the filled image is observed to obtain the number of inclusions contained in the sample.

2. The method for detecting the number of inclusions in alloy powder according to claim 1, characterized in that: In the preparation of test samples: The powder to be tested is placed in a package and subjected to a first pressing process and a second pressing process. After the package is removed, a test sample is obtained.

3. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: The mass of the powder to be tested is not higher than 900 g.

4. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: In the step of preparing the test sample: The powder to be tested is divided into multiple portions, and then the multiple portions of the powder to be tested are subjected to a first pressing process and a second pressing process to obtain multiple test samples.

5. The method for detecting the number of inclusions in alloy powder according to claim 4, characterized in that: In the step of preparing the test sample: the powder to be tested is divided into 3-6 portions.

6. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: In the detection step: the detection method used is an X-ray detection method or a micro-CT detection method.

7. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: The particle size of the powder to be tested is less than 250 μm.

8. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: The powder to be tested is titanium alloy powder.

9. The method for detecting the number of inclusions in alloy powder according to claim 1, wherein: The powder to be tested is an alloy powder for additive manufacturing.

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