Tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing and preparation method of tungsten-aluminum alloy spherical powder

Abstract

The invention discloses tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing and a preparation method of the tungsten-aluminum alloy spherical powder, and belongs to the technical field of refractory metal and additive manufacturing. Small-particle-size tungsten powder and aluminum powder are assembled into spherical alloy powder particles in a spray drying and segmented heat treatment mode, in the heat treatment process, organic matter in the tungsten alloy powder is firstly removed at the low temperature, then heat preservation is conducted at the high temperature, and the spherical alloy powder particles are obtained. And intermetallic compounds are formed through reaction diffusion among the raw material powder components, so that the density of the powder is improved. The particle size distribution of the powder is controlled by adjusting the frequency of the atomizer in the spray granulation process, the powder particles with the particle size within the range of 15-53 microns obtained after airflow classification can reach 90% or above, and compared with a plasma rotating electrode atomization method, the yield of the powder with the target particle size is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory metals and additive manufacturing, and specifically relates to a tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing and a preparation method thereof. Background Art

[0002] Tungsten has a high melting point (3695K), high strength (yield strength at room temperature is greater than 1GPa), high thermal conductivity, and a very low thermal expansion coefficient (4.3×10 -6 K -1 ) and excellent resistance to radiation damage, so tungsten alloys have important applications in radiation collimators, nuclear fusion first wall materials, and hypersonic vehicles. However, tungsten has a high melting point and poor room temperature plasticity, and conventional processing methods are difficult to process tungsten alloys with complex shape requirements.

[0003] At present, tungsten alloys are generally prepared by powder metallurgy. The high melting point of tungsten makes it difficult to densify it, and due to mold limitations, this method is difficult to prepare components with complex shapes. Laser additive manufacturing technology uses high-energy-density lasers as energy sources to prepare refractory metal materials, especially to achieve the preparation and processing of complex structural parts, and is expected to provide a new solution for the preparation of tungsten alloys. However, there are still problems in obtaining spherical tungsten alloy powders suitable for laser additive manufacturing. The method of directly mixing spherical printing powders cannot ensure the uniform distribution of alloying elements and tungsten, thereby affecting the uniformity of the composition after printing. Although good-quality tungsten alloy powders for laser additive manufacturing can be obtained through plasma rotating electrode atomization technology and plasma spheroidization technology, they are limited by the preparation of high-quality alloy rods, the high cost of equipment, and the low yield of fine powders in the particle size range (15-53μm) required for selective laser melting. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing, comprising the following steps:

[0007] (1) Using tungsten powder and aluminum powder as raw materials and ethanol as a ball milling medium, ball milling is performed to obtain a mixed powder;

[0008] (2) mixing the mixed powder, the binder and water and then ball-milling to obtain a slurry;

[0009] (3) agglomerating and granulating the slurry to obtain spherical powder;

[0010] (4) The spherical powder is dewaxed, ground and screened in sequence to obtain tungsten aluminum alloy spherical powder suitable for laser additive manufacturing.

[0011] Preferably, in the step (1), the purity of the tungsten powder and the aluminum powder is independently ≥99.9wt.%, and the average particle size is independently 1-3μm; in the raw materials composed of tungsten powder and aluminum powder, aluminum powder accounts for 2-10wt.%, and the rest is tungsten powder; the amount of ethanol added is 70-90% of the total mass of the tungsten powder and aluminum powder; the ball-to-material ratio of ball milling is (1-3):1.

[0012] Preferably, in step (1), the ball milling speed is 200 to 300 r / min, and the ball milling time is 18 to 20 h.

[0013] Preferably, in step (2), the solid content of the mixture obtained by mixing is 60-80wt.%, the binder is polyethylene glycol (PEG-10000), and the content of the binder in the mixture obtained by mixing is 1.5-5wt.%; the ball-to-material ratio of ball milling is (1-3):1.

[0014] Preferably, in step (2), the ball milling speed is 200-300 r / min, and the ball milling time is 1.5-2 h.

[0015] Preferably, in step (3), the agglomeration granulation method is spray drying; the atomizer frequency is set to 30 to 60 Hz.

[0016] Preferably, in the step (4), the dewaxing includes a first dewaxing and a second sintering; the parameters of the first dewaxing are as follows: argon protection, a heating rate of 3 to 5°C / min, a temperature of 300 to 500°C, and a holding time of 1 to 2h; the parameters of the second sintering are as follows: vacuum state, air pressure ≤10Pa, a heating rate of 5 to 10°C / min, a temperature of 1100 to 1150°C, and a holding time of 1.5 to 3h.

[0017] Preferably, in step (4), the particle size distribution of the obtained tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing is such that particles with a particle size of 15 to 53 μm account for more than 90%.

[0018] The present invention also provides tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing, which is prepared by the preparation method of the tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing.

[0019] The beneficial technical effects of the present invention are as follows:

[0020] (1) The present invention develops a new type of tungsten aluminum alloy spherical powder suitable for laser additive manufacturing. The method has outstanding scalability and can be used to prepare tungsten alloy spherical powders of other components.

[0021] (2) The present invention assembles small-size tungsten powder and aluminum powder into spherical alloy powder particles by spray drying and segmented heat treatment. During the heat treatment process, organic matter in the tungsten alloy powder is first removed at a relatively low temperature, and then the powder is kept at a relatively high temperature to form intermetallic compounds by reaction and diffusion between the components of the raw powder to improve the density of the powder.

[0022] (3) Compared with the simple mechanical mixing method of coarse-grained powder, the composition distribution in the tungsten-aluminum alloy powder particles prepared by the present invention is more uniform.

[0023] (4) The present invention controls the powder particle size distribution by adjusting the atomizer frequency during the spray granulation process. After airflow classification, the powder particles with a particle size in the range of 15 to 53 μm can reach more than 90%. Compared with the plasma rotating electrode atomization method, the target particle size powder yield is significantly improved.

[0024] (5) This method does not require smelting to prepare master alloy rods, and the powder yield is high, which effectively improves production efficiency and reduces powder preparation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The morphology of the tungsten aluminum alloy powder after spray drying in Example 1; (a) and (b) are morphology images at different magnifications;

[0026] Figure 2 is a morphology diagram of the tungsten aluminum alloy powder after airflow classification in Example 1;

[0027] Figure 3 The morphology and composition distribution diagram of the tungsten aluminum alloy powder particles after heat treatment in Example 1;

[0028] Figure 4 is the X-ray diffraction pattern of the tungsten aluminum alloy powder after heat treatment in Example 1;

[0029] Figure 5 is a morphology diagram of the tungsten aluminum alloy powder particles after heat treatment in Example 2;

[0030] Figure 6 is the X-ray diffraction pattern of the tungsten aluminum alloy powder after heat treatment in Example 2;

[0031] Figure 7 is a morphology diagram of the tungsten aluminum alloy powder particles after heat treatment in Example 3;

[0032] Figure 8 This is the X-ray diffraction pattern of the tungsten aluminum alloy powder after heat treatment in Example 3. DETAILED DESCRIPTION

[0033] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0034] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0035] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] (1) Tungsten powder and aluminum powder with a purity of more than 99.9wt.%, an average particle size of 2.0μm and uniform particle size distribution are used as raw materials. The above powders are weighed at a mass ratio of tungsten to aluminum of 96.4:3.4. A cemented carbide ball mill is used to mix the powders at a mass ratio of grinding balls to powders of 3:1 and anhydrous ethanol is added. The ball milling speed is 200r / min and the ball milling time is 18h. The mixed powder is dried.

[0039] (2) The mixed powder prepared in step (1), polyethylene glycol (PEG-10000) and deionized water are placed in a carbide ball mill, mixed in a mass ratio of grinding balls to powder of 3:1, wherein the solid content is 70 wt.%, the PEG-10000 content is 3 wt.%, the rotation speed is 200 r / min, and the ball milling time is 1.5 h to prepare a slurry.

[0040] (3) The slurry obtained in step (2) is agglomerated and granulated by spray drying at an atomizer frequency of 45 Hz to obtain spherical powder with a particle size of 15-53 μm (the particle size range required for selective laser melting).

[0041] (4) The powder obtained in step (3) is dewaxed in a vacuum heat treatment furnace. Argon protection is used to prevent oxidation of the powder during the dewaxing process. In the first step, the temperature is raised to 400°C at a heating rate of 3°C / min and kept warm for 2 hours. After this step is completed, the atmosphere in the furnace is evacuated and kept below 10Pa. In the second step, the temperature is further raised to 1130°C at a heating rate of 5°C / min under high temperature and vacuum conditions, kept warm for 1.5 hours, and then cooled to room temperature. The obtained powder is ground and crushed, and the crushed small particles are removed by airflow classification to obtain tungsten aluminum alloy spherical powder in the target particle size range.

[0042] The morphology of the spray-dried tungsten aluminum alloy powder prepared in step (3) of Example 1 is shown in FIG. Figure 1 (a), (b), the morphology of the tungsten aluminum alloy powder after airflow classification in step (4) is shown in Figure 2 , showing that the powder has good sphericity and the particle size distribution is in the range of 15 to 53 μm.

[0043] The morphology and composition distribution of tungsten aluminum alloy powder particles after heat treatment are shown in Figure 3 , indicating that the density of the powder particles is improved after heat treatment, and aluminum is distributed more evenly in the particles.

[0044] The XRD spectrum of the tungsten aluminum alloy powder prepared in Example 1 is as follows: Figure 4 , forming tungsten-aluminum intermetallic compounds during heat treatment.

[0045] Example 2

[0046] (1) Tungsten powder and aluminum powder with a purity of more than 99.9wt.%, an average particle size of 2.0μm and uniform particle size distribution are used as raw materials. The above powders are weighed at a mass ratio of tungsten to aluminum of 96.4:3.4. A cemented carbide ball mill is used to mix the powders at a mass ratio of grinding balls to powders of 3:1 and anhydrous ethanol is added. The ball milling speed is 200r / min and the ball milling time is 18h. The mixed powder is dried.

[0047] (2) The mixed powder prepared in step (1), polyethylene glycol (PEG-10000) and deionized water are placed in a carbide ball mill, mixed in a mass ratio of grinding balls to powder of 3:1, wherein the solid content is 70 wt.%, the PEG-10000 content is 3 wt.%, the rotation speed is 200 r / min, and the ball milling time is 1.5 h to prepare a slurry.

[0048] (3) The slurry obtained in step (2) is agglomerated and granulated by spray drying at an atomizer frequency of 45 Hz to obtain spherical powder with a particle size of 15 to 53 μm (the particle size range required for selective laser melting).

[0049] (4) The powder obtained in step (3) is dewaxed in a vacuum heat treatment furnace. Argon protection is used to prevent oxidation of the powder during the dewaxing process. In the first step, the temperature is raised to 400°C at a heating rate of 3°C / min and kept warm for 2 hours. After this step is completed, the atmosphere in the furnace is evacuated and kept below 10Pa. In the second step, the temperature is further raised to 1100°C at a heating rate of 5°C / min under high temperature and vacuum conditions, kept warm for 1.5 hours, and then cooled to room temperature. The obtained powder is ground and crushed to obtain tungsten aluminum alloy spherical powder in the target particle size range.

[0050] The morphology of the tungsten aluminum alloy powder after heat treatment in step (4) of Example 2 is shown in FIG. Figure 5 , showing that the powder has good sphericity and the particle size distribution is in the range of 15 to 53 μm.

[0051] The XRD spectrum of the tungsten aluminum alloy powder prepared in Example 2 is as follows: Figure 6 , forming tungsten-aluminum intermetallic compounds during heat treatment.

[0052] Example 3

[0053] (1) Tungsten powder and aluminum powder with a purity of more than 99.9wt.%, an average particle size of 2.0μm and uniform particle size distribution are used as raw materials. The above powders are weighed at a mass ratio of tungsten to aluminum of 96.4:3.4. A cemented carbide ball mill is used to mix the powders at a mass ratio of grinding balls to powders of 3:1 and anhydrous ethanol is added. The ball milling speed is 200r / min and the ball milling time is 18h. The mixed powder is dried.

[0054] (2) The mixed powder prepared in step (1), polyethylene glycol (PEG-10000) and deionized water are placed in a carbide ball mill, mixed in a mass ratio of grinding balls to powder of 3:1, wherein the solid content is 70 wt.%, the PEG-10000 content is 3 wt.%, the rotation speed is 200 r / min, and the ball milling time is 1.5 h to prepare a slurry.

[0055] (3) The slurry obtained in step (2) is agglomerated and granulated by spray drying at an atomizer frequency of 45 Hz to obtain spherical powder with a particle size of 15 to 53 μm (the particle size range required for selective laser melting).

[0056] (4) The powder obtained in step (3) is dewaxed in a vacuum heat treatment furnace. Argon protection is used to prevent oxidation of the powder during the dewaxing process. In the first step, the temperature is raised to 400°C at a heating rate of 3°C / min and kept warm for 2 hours. After this step is completed, the atmosphere in the furnace is evacuated and kept below 10Pa. In the second step, the temperature is further raised to 1150°C at a heating rate of 5°C / min under high temperature and vacuum conditions, kept warm for 1.5 hours, and then cooled to room temperature. The obtained powder is ground and crushed to obtain tungsten aluminum alloy spherical powder in the target particle size range.

[0057] The morphology of the tungsten aluminum alloy powder after heat treatment in step (4) of Example 3 is shown in FIG. Figure 7 , showing that the powder has good sphericity and the particle size distribution is in the range of 15 to 53 μm.

[0058] The XRD spectrum of the tungsten aluminum alloy powder prepared in Example 3 is as follows: Figure 8 , forming tungsten-aluminum intermetallic compounds during heat treatment.

[0059] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing, characterized in that: The steps include: (1) Using tungsten powder and aluminum powder as raw materials and ethanol as a ball milling medium, ball milling is performed to obtain a mixed powder; (2) mixing the mixed powder, the binder and water and then ball-milling to obtain a slurry; (3) agglomerating and granulating the slurry to obtain spherical powder; (4) The spherical powder is dewaxed, ground and screened in sequence to obtain tungsten aluminum alloy spherical powder suitable for laser additive manufacturing.

2. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 1, characterized in that: In the step (1), the purity of tungsten powder and aluminum powder is independently ≥99.9wt.%, and the average particle size is independently 1-3μm; in the raw materials composed of tungsten powder and aluminum powder, aluminum powder accounts for 2-10wt.%, and the rest is tungsten powder; the amount of ethanol added is 70-90% of the total mass of tungsten powder and aluminum powder; the ball-to-material ratio of ball milling is (1-3):

1.

3. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 2, characterized in that: In the step (1), the ball milling speed is 200 to 300 r / min, and the ball milling time is 18 to 20 h.

4. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to any one of claims 1 to 3, characterized in that: In the step (2), the solid content of the mixture obtained by mixing is 60-80wt.%, the binder is polyethylene glycol, and the content of the binder in the mixture obtained by mixing is 1.5-5wt.%; the ball-to-material ratio of ball milling is (1-3):

1.

5. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 4, characterized in that: In the step (2), the ball milling speed is 200 to 300 r / min, and the ball milling time is 1.5 to 2 h.

6. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 5, characterized in that: In the step (3), the agglomeration granulation method is spray drying; the atomizer frequency is set to 30 to 60 Hz.

7. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 5 or 6, characterized in that: In the step (4), the dewaxing includes a first dewaxing and a second sintering; the parameters of the first dewaxing are as follows: argon protection, a heating rate of 3 to 5°C / min, a temperature of 300 to 500°C, and a holding time of 1 to 2 hours; the parameters of the second sintering are as follows: vacuum state, air pressure ≤10Pa, a heating rate of 5 to 10°C / min, a temperature of 1100 to 1150°C, and a holding time of 1.5 to 3 hours.

8. The method for preparing tungsten aluminum alloy spherical powder suitable for laser additive manufacturing according to claim 5 or 6, characterized in that: In the step (4), the particle size distribution of the obtained tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing is that particles with a particle size of 15 to 53 μm account for more than 90%.

9. Tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing obtained by the preparation method of tungsten-aluminum alloy spherical powder suitable for laser additive manufacturing according to any one of claims 1 to 8.

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