Preparation method for spheroidizing flaky metal powder

Abstract

The invention provides a preparation method for spheroidizing flaky metal powder, which comprises the following steps: step 1, weighing large-particle-size grinding balls and small-particle-size grinding balls with different sizes according to a preset mass ratio of the large grinding balls to the small grinding balls; weighing a certain amount of grinding balls and flaky metal powder according to a preset ball material mass ratio; 2, a mixture of the grinding balls and the flaky metal powder which are weighed according to the proportion is put into a ball milling tank to be sealed; and 3, a planetary ball milling technology with optimized kinetic parameters is adopted, and the metal powder of the sheet structure is converted into the metal powder of the spherical structure.

Description

Technical Field

[0001] The invention relates to the application fields of material protection and high-temperature plasma spraying technology, and in particular to a preparation method for spheroidizing flaky metal powder. Background Art

[0002] Metal components widely used in aerospace, energy, and power generation often experience severe high-temperature oxidation, wear, and corrosion during their service life, leading to failure. This significantly reduces the service life of mechanical equipment and limits the widespread application of related materials. To ensure that metal components can operate reliably in extreme environments such as high-temperature oxidation, corrosion, and wear, applying protective coatings to improve surface properties is particularly important. This is one of the most effective ways to extend their service life.

[0003] As an important surface engineering technology, high-temperature plasma spraying technology is widely used to deposit various metal coatings to increase the service life of metal parts in harsh environments due to its simple process, low cost and high spraying efficiency. Due to its process characteristics, plasma spraying has strict requirements on the morphology of the spraying raw material powder. In the high-temperature plasma jet, spherical powders are ideal spray powders due to their excellent fluidity and uniform heating characteristics. Specifically, spherical particles can ensure stable and continuous powder delivery during the powder feeding process, avoiding blockage of the powder feeding pipeline; in addition, they can also ensure a uniform heating trajectory in the plasma jet, ensuring the uniformity of the molten state, thereby forming a dense, low-porosity protective coating on the surface of the metal parts.

[0004] The preparation of metal-based powders used in plasma spraying presents significant technical challenges. Traditional mechanical ball milling (particularly for plastic metals such as copper and aluminum) tends to produce flaky powders. This morphological characteristic stems from the plastic deformation mechanism of metals. During conventional ball milling, metal particles undergo ductile deformation rather than brittle fracture under the impact energy. Research data shows that after 24 hours of ball milling, the proportion of flaky particles in copper powder can exceed 90%, with an average aspect ratio exceeding 8:1. This flaky structure severely restricts the application of metal powders in plasma spraying. Due to their poor flowability, the powder feeder often pulsates during the spraying process, resulting in a pronounced layered structure in the final coating. Furthermore, the random orientation of flaky metal powders in the plasma jet can easily lead to uneven heating of the powder, resulting in the inclusion of unmelted particles. Moreover, due to its large specific surface area, flake-structured metal powder is prone to significant in-flight oxidation during the spraying process, resulting in a large number of oxide inclusions in the deposited coating. Due to the large difference in linear expansion coefficient between the oxide and the surrounding metal coating, the porosity of the coating deposited using flake metal powder is usually as high as 15-20% (the coating deposited by spherical powder is less than 5%). Compared with the dense metal coating prepared by spherical metal powder, the bonding strength of the coating deposited by flake metal powder is reduced by 40-60%. Tests on aircraft engine blade coatings show that the thermal cycle life of the coating deposited by flake metal powder is less than 1 / 3 of the thermal cycle life of the coating deposited by spherical metal powder.

[0005] While specialized preparation processes such as gas atomization and plasma spheroidization can produce spherical metal powders, their equipment costs are high (often 10-15 times more expensive than conventional ball milling equipment). More importantly, for metal-based powders, the high temperature of the plasma jet causes the powder to react with air entrained in the jet during the powder heating process, resulting in severe oxidation of the metal powder. This is especially true for low-melting-point aluminum-based metal powders, where not only oxidation but also elemental evaporation of the metal powder often occurs. While planetary ball milling is widely used for powder refinement, conventional process parameters still struggle to overcome the flaking tendency of plastic metals.

[0006] Therefore, in the field of material protection and high-temperature plasma spraying technology applications, how to find a low-cost preparation method for spheroidizing flaky metal powder, so as to use plasma spraying technology to spray and prepare high-bonding strength metal coatings with dense organizational structure to ensure that metal parts maintain excellent mechanical properties in harsh working conditions, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In order to solve the problems of difficult-to-control powder shape and metal powder oxidation caused by high-temperature heat sources in traditional flaky metal powder spheroidization preparation methods, the embodiments of the present invention disclose a flaky metal powder spheroidization preparation method to solve the technical difficulties of traditional preparation methods, thereby preparing a high-bonding strength metal coating with a dense organizational structure through plasma spraying technology, thereby ensuring that metal parts maintain excellent mechanical properties when serving in harsh working conditions.

[0008] The present invention is achieved through the following technical solution: a preparation method for spheroidizing flaky metal powder, comprising: Step 1: Weigh large-sized grinding balls and small-sized grinding balls of different sizes according to the preset mass ratio of large grinding balls to small grinding balls; weigh a certain amount of grinding balls and flake metal powder according to the preset ball-to-material mass ratio; Step 2: Place the mixture of grinding balls and flake metal powder weighed in proportion into a ball mill jar and seal it; Step 3: Use planetary ball milling technology with optimized kinetic parameters to transform the flake-structured metal powder into spherical-structured metal powder.

[0009] Specifically, the preset mass ratio of large grinding balls to small grinding balls is 3:7; the preset mass ratio of balls to materials is 10:1.

[0010] Specifically, the grinding balls are 304 stainless steel grinding balls, the diameter of the large-sized grinding balls is in the range of 6mm-10mm, and the diameter of the small-sized grinding balls is in the range of 2mm-4mm.

[0011] Specifically, the flaky metal powder is Al-based, Ni-based, Cu-based or other metal-based powder with good plastic deformation ability.

[0012] Specifically, the thickness of the flake powder ranges from 0.5 μm to 10 μm, and the volume ranges from 400 μm. 3 -1x10 -4 mm 3 .

[0013] Specifically, the planetary ball milling technology for optimizing kinetic parameters has a ball milling speed of 80 r / min-200 r / min and a ball milling time of 10 min-60 min.

[0014] Specifically, the particle size of the spheroidized metal powder ranges from 10 μm to 100 μm. The spheroidized metal powder is mainly used in high-temperature plasma spraying technology, and a high-performance metal protective coating is deposited by plasma spraying the spheroidized metal powder.

[0015] Specifically, after step 3, the method further includes: step 4: using plasma spraying technology to heat and melt the obtained spherical metal powder, and spraying it layer by layer on the surface of the component to form a high-performance coating to improve the service life of the technical components in harsh environments.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Avoid high-temperature oxidation during metal powder preparation and improve coating quality. This invention achieves spheroidization of flaky powders at conventional temperatures by optimizing the kinetic parameters of the planetary ball mill, avoiding oxidation issues in high-temperature environments and thus ensuring the purity and performance of the metal powder. Because the spherical powder is more evenly transported in the plasma flame, it can be precisely heated to the appropriate temperature, avoiding overburning or undermelting, ultimately resulting in a higher-quality, more bonded metal coating.

[0017] The process is simple, efficient, low-cost, and widely applicable. The present invention utilizes planetary ball milling technology that optimizes the milling kinetic parameters to spheroidize flaky powders. This eliminates the need for additional high-temperature heating equipment, simplifies the process flow, reduces energy consumption and equipment investment costs, and significantly lowers overall production costs. The present invention is applicable not only to Al-, Ni-, and Cu-based metal powders, but also to other metal powders with good plasticity, demonstrating its broad applicability.

[0018] Through the above technical advantages, the present invention provides a low-cost, high-efficiency solution for the spheroidization of flaky metal powders, while significantly improving the coating quality of the plasma spraying process, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 This is a flow chart of the preparation method for spheroidizing flake metal powder according to the present invention; Figure 2 A scanning electron microscope image of the Al-based flake metal powder described in Example 1 of the present invention; Figure 3 This is a scanning electron microscope image of spherical Al-based powder produced by planetary ball milling with optimized planetary ball milling kinetic parameters in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0022] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the prior art. The reagents and other instruments used, if the manufacturers are not specified, are all commercially available conventional reagents.

[0023] In order to facilitate understanding of the technical solution proposed by the present invention, a brief description of the relevant preparation technology for spheroidization of flaky metal powders is first given here.

[0024] The main preparation processes for spheroidizing flaky metal powders include gas atomization and plasma spheroidization. Gas atomization is a physical powder-making technique that uses a high-speed airflow to break up a molten metal stream and rapidly solidify it into spherical particles. The resulting powder has good sphericity and can even produce hollow spherical powders. However, its material adaptability is poor. Metals with high surface tension (such as copper and gold) are prone to forming satellite spheres (small particles adhering to larger particles). Metals with low melting points (such as tin) are prone to over-oxidation. Furthermore, the gas atomization method is very expensive. Plasma spheroidization is a secondary processing technology for irregular powders. Essentially, it involves high-temperature remelting. The extremely high heat source temperature of the plasma jet is capable of spheroidizing some refractory metals (such as tungsten and molybdenum). However, for powders smaller than 5μm, the spheroidization efficiency is less than 30% (powders are easily carried out by the airflow, resulting in unmelted powders and inability to spheroidize), and the energy consumption of plasma spheroidization equipment is abnormally high. More importantly, for metal powders, the use of plasma spheroidization is prone to in-flight oxidation of metal elements and evaporation of some alloying elements, resulting in changes in the powder composition.

[0025] Compared to other technologies, the planetary ball milling technology proposed in this paper, with optimized kinetic parameters, uses a solid-state mechanical spheroidization process, circumventing the energy consumption of gas atomization smelting and the limitations of plasma processes. It is particularly suitable for the large-scale production of spherical powders for plastic flake metal powders such as aluminum, nickel, and copper. Its technological value lies in: 1) shortening the process flow; 2) reducing overall costs; and 3) perfectly adapting to the raw material requirements of plasma spraying technology.

[0026] Based on the above description, the technical solutions of the embodiments of the present application are introduced as follows.

[0027] Example 1 The present invention discloses a preparation method for spheroidizing flaky metal powder, comprising the following steps: Step 1: Weigh large-sized grinding balls and small-sized grinding balls of different sizes according to the preset mass ratio of large grinding balls to small grinding balls; weigh a certain amount of grinding balls and flake metal powder according to the preset ball-to-material mass ratio; Among them, the preset mass ratio of large grinding balls to small grinding balls is 3:7.

[0028] Among them, the preset ball-to-material mass ratio is 10:1.

[0029] Furthermore, the grinding balls are 304 stainless steel grinding balls, the diameter of the large-size grinding balls is in the range of 6mm-10mm, and the diameter of the small-size grinding balls is in the range of 2mm-4mm.

[0030] Furthermore, the flaky metal powder is a metal-based powder such as Al-based, Ni-based, Cu-based, etc., which has good plastic deformation ability.

[0031] Furthermore, the thickness of the flake powder is in the range of 0.5 μm to 10 μm, and the volume is in the range of 400 μm. 3 -1x10 -4 mm 3 .

[0032] Step 2: Place the mixture of grinding balls and flake metal powder weighed in proportion into a ball mill jar and seal it; Step 3: Use planetary ball milling technology with optimized kinetic parameters to transform the flake-structured metal powder into spherical-structured metal powder.

[0033] Furthermore, the planetary ball milling technology for optimizing kinetic parameters has a ball milling speed of 80 r / min-200 r / min and a ball milling time of 10 min-60 min.

[0034] It should be noted that flaky metal powder is spheroidized by adjusting the ratio of different grinding ball sizes and adjusting the planetary ball milling parameters. The grinding balls are a mixture of large and small grinding balls in different proportions. The large grinding balls achieve welding and crushing of the metal powder, while the small grinding balls shape the outer layer of the spheroidized metal powder to remove small particles on the outer surface.

[0035] Furthermore, the particle size of the spheroidized metal powder ranges from 10 μm to 100 μm. The spheroidized metal powder is mainly used in high-temperature plasma spraying technology, and a high-performance metal protective coating is deposited by plasma spraying the spheroidized metal powder.

[0036] Specifically, after step 3, the method further includes: Step 4: Use plasma spraying technology to heat and melt the obtained spherical metal powder, and spray it layer by layer on the surface of the component to form a high-performance coating to increase the service life of the technical components in harsh environments.

[0037] In summary, the present invention innovatively optimizes the kinetic parameters of planetary ball milling and establishes a synergistic mechanism of "high-energy crushing-surface reconstruction." While maintaining the low-cost advantage of planetary ball milling technology, it achieves the spheroidization of flaky metal powders, provides a new process path for the efficient spheroidization of plastic metal powders, and offers a powder raw material solution for plasma spraying.

[0038] Example 2 An embodiment of the present invention provides a low-cost preparation method for spheroidizing flaky metal powder. The method is a planetary ball milling technology with optimized kinetic parameters. The metal powder is an Al-based, Ni-based, Cu-based metal-based powder with good plastic deformation ability, and is mainly used in the field of high-temperature plasma spraying technology.

[0039] In the embodiment of the present invention, spherical metal powder with excellent sphericity is prepared by shaping flaky metal powder using a planetary ball milling technology with optimized kinetic parameters. Figure 1 The figure is a flow chart of the low-cost preparation method for spheroidizing the flake metal powder. Figure 1 As shown, first, large-particle grinding balls and small-particle grinding balls of different sizes are weighed in a ratio of 3:7, and a certain amount of grinding balls and metal powder are weighed in a mass ratio of 10:1. Then, the mixture of grinding balls and flaky metal powder weighed in proportion is placed in a ball mill and sealed. Finally, the flaky structured metal powder is converted into spherical structured metal powder through planetary ball milling technology with optimized kinetic parameters.

[0040] In this embodiment, the flaky metal powder is Al-based, Ni-based, Cu-based or other metal powder, and the thickness of the flaky powder ranges from 0.5 μm to 10 μm, and the volume ranges from 400 μm. 3 -1x10 -4 mm 3 .

[0041] In this embodiment, the diameter of the large grinding balls is in the range of 6mm-10mm, the diameter of the small grinding balls is in the range of 2mm-4mm, and the mass ratio of the large grinding balls to the small grinding balls is 3:7.

[0042] In this embodiment, the planetary ball milling speed for optimizing the kinetic parameters is 80 r / min-200 r / min, and the planetary ball milling time is 10 min-60 min.

[0043] In this embodiment, the particle size of the spherical metal powder prepared by the planetary ball milling with optimized kinetic parameters is in the range of 10 μm to 100 μm.

[0044] In this embodiment, the prepared spherical powder is mainly used in the field of plasma spraying, and a high-performance protective coating is deposited on the surface of metal parts through plasma spraying technology.

[0045] Combine Figure 1 The present invention implements a low-cost preparation and application of spheroidized flaky Al-based metal powder, comprising the following steps: Step 1: Weigh 304 stainless steel grinding balls with diameters of 3 mm and 8 mm, respectively, and mix them in a mass ratio of 3:7 to obtain mixed grinding balls; Step 2: weigh a certain amount of Figure 2 The flaky Al-based metal powder is mixed with the mixing grinding balls described in step 1 at a ratio of 1:10 to obtain a mixture of grinding balls and flaky Al-based metal powder; Step 3: Place the mixture of the grinding balls and the flaky Al-based metal powder in step 2 into a ball mill jar, which is then filled with argon and sealed; Step 4: Set the ball mill speed to 120r / min, set the ball milling time to 40min, set the ball milling process to rotate forward and reverse for 1min, and then rest for 1min respectively to ensure that the temperature in the ball mill is lower than 200 o C, thereby avoiding alloying reaction between the elements in the Al-based metal powder due to excessively high temperature, and preparing the same composition as the flaky Al-based metal powder as Figure 3 Spherical Al-based metal powder shown; Step five: using plasma spraying technology to spray the spherical Al-based metal powder prepared in step four to prepare a coating.

[0046] The above is a detailed introduction to the preparation method of spheroidizing flaky metal powder provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core concept. At the same time, for those skilled in the art, according to the concept of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing spheroidized flaky metal powder, characterized in that: include: Step 1: Weigh large-sized grinding balls and small-sized grinding balls of different sizes according to the preset mass ratio of large grinding balls to small grinding balls; weigh a certain amount of grinding balls and flake metal powder according to the preset ball-to-material mass ratio; Step 2: Place the mixture of grinding balls and flake metal powder weighed in proportion into a ball mill jar and seal it; Step 3: Use planetary ball milling technology with optimized kinetic parameters to transform the flake-structured metal powder into spherical-structured metal powder.

2. The preparation method according to claim 1, characterized in that The preset mass ratio of large grinding balls to small grinding balls is 3:7; the preset mass ratio of balls to materials is 10:

1.

3. The preparation method according to claim 1, characterized in that The grinding balls are 304 stainless steel grinding balls, the diameter of the large-sized grinding balls is in the range of 6mm-10mm, and the diameter of the small-sized grinding balls is in the range of 2mm-4mm.

4. The preparation method according to claim 1, characterized in that The flaky metal powder is Al-based, Ni-based, Cu-based or other metal-based powder with good plastic deformation ability.

5. The preparation method according to claim 1, characterized in that The thickness of the flake powder ranges from 0.5 μm to 10 μm, and the volume ranges from 400 μm. 3 -1x10 -4 mm 3 .

6. The preparation method according to claim 1, characterized in that The planetary ball milling technology for optimizing kinetic parameters has a ball milling speed of 80 r / min-200 r / min and a ball milling time of 10 min-60 min.

7. The preparation method according to claim 1, characterized in that The particle size of the spheroidized metal powder ranges from 10 μm to 100 μm. The spheroidized metal powder is mainly used in high-temperature plasma spraying technology, and a high-performance metal protective coating is deposited by plasma spraying the spheroidized metal powder.

8. The preparation method according to claim 1, characterized in that After step 3, the method further includes: Step 4: Use plasma spraying technology to heat and melt the obtained spherical metal powder, and spray it layer by layer on the surface of the component to form a high-performance coating to increase the service life of the technical components in harsh environments.

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