A method for preparing high-temperature alloy spherical powder for additive manufacturing

Abstract

The present invention discloses a method for preparing spherical high-temperature alloy powder for additive manufacturing. The method comprises the following steps: weighing metal powder according to a specific ratio, adding rare earth nitrate and a dispersant, adjusting the volume solids content of the slurry to 35-50% with anhydrous ethanol, and grinding the resulting slurry; adding the ground slurry to a high-speed disperser, adding polyvinyl butyral, and dispersing the powder at high speed; spray granulating the dispersed slurry, and calcining the resulting spherical metal powder with wet hydrogen at a temperature of 400-600°C for 4-6 hours; the hydrogen source is 95% nitrogen-hydrogen gas, and the moisture source is saturated water vapor; the inlet ratio of nitrogen-hydrogen gas to water vapor is 1:1; and sieving the resulting powder to obtain the spherical high-temperature alloy powder for additive manufacturing. This method utilizes cold-state preparation, which is energy-efficient and environmentally friendly. The resulting spherical high-temperature alloy powder has high sphericity, low oxygen content, good fluidity, and excellent mechanical and thermal processing properties.

Description

Technical Field

[0001] The present invention belongs to the field of advanced high-temperature alloy powder preparation, and specifically relates to a method for preparing high-temperature alloy spherical powder for additive manufacturing. Background Art

[0002] Laser additive manufacturing (AM) technology can directly transform complex 3D data models into physical parts. Time magazine listed it as one of the ten fastest-growing industries in the United States, and The Economist believes it will drive the Third Industrial Revolution, transforming existing production models. Compared to traditional manufacturing techniques, metal AM offers the advantage of reduced reliance on molds and fixtures, shortening product development cycles and manufacturing processes. Currently, laser sintering with selected powder bed stacking and laser deposition with simultaneous powder feeding have become the mainstream approaches and primary application methods for metal laser AM.

[0003] However, as the application of metal additive manufacturing expands, traditional metal alloy powders or intermetallic compound powders are no longer sufficient for the complex and harsh environments required for additive manufacturing of parts. For high-performance metal parts produced using laser additive manufacturing, metal powder performance parameters such as particle size, morphology, oxygen, nitrogen, and hydrogen content, impurities, and sphericity directly impact the product's performance. Therefore, academia and industry believe that powders are the technological foundation of the metal additive manufacturing industry and the foundation for producing high-performance metal and alloy parts.

[0004] To achieve the production of high-quality alloy powders, Russia uses the plasma rotating electrode (PREP) method to produce metal powders. However, the powders produced have application defects such as a wide particle size distribution range, poor purity, and high oxygen content. European and American countries use the argon atomization (AA) method to produce high-quality metal powders, but this method requires high purity of the parent metal rod. CN104858440A discloses a method for preparing spherical metal powders for additive manufacturing. Although it achieves the production of alloy powders with high sphericity and low oxygen content, this method is very prone to inclusions for high-temperature alloy powders with complex compositions, and the preparation process causes powder adhesion, which affects the subsequent additive manufacturing process. CN113102747A discloses a method for preparing metal powders for additive manufacturing by doping them with rare earth oxides. Although it achieves the production of composite powders and achieves the purpose of strengthening the alloy matrix, the prepared metal powders are very prone to cracking during the additive manufacturing process. Moreover, the preparation process requires the use of preparation processes such as ball milling, which easily leads to problems such as increased powder surface roughness and decreased fluidity, which is not conducive to the subsequent additive manufacturing process. Therefore, other methods must be used to prepare spherical metal powders for additive manufacturing. Summary of the Invention

[0005] In response to the technical deficiencies in the above-mentioned multi-metal high-temperature alloy powder, the purpose of the present invention is to provide a method for preparing spherical high-temperature alloy powder for additive manufacturing. This method is cold-prepared, and the preparation process is energy-saving and environmentally friendly. The prepared spherical high-temperature alloy powder has high sphericity, low oxygen content, good fluidity, and excellent mechanical properties and thermal processing properties. It solves the preparation problems faced by traditional multi-dimensional component powder preparation, such as high inclusions, adhesion, and uneven composition. In addition, the prepared alloy powder is not prone to cracking during the additive manufacturing process, greatly improving the yield rate of alloy products.

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

[0007] A method for preparing high-temperature alloy spherical powder for additive manufacturing comprises the following steps:

[0008] S1: Weigh metal powder according to the ratio, add rare earth nitrate, the rare earth nitrate is 0.1-0.8% of the total weight of the metal powder; add polyethyleneimine as a dispersant, the dispersant is 0.1-1.0% of the total weight of all powders; add anhydrous ethanol to adjust the volume solid content of the slurry system to 35-50 vol.%, and add the resulting slurry to a sand mill for grinding;

[0009] S2: adding the slurry ground in step S1 to a high-speed disperser, adding polyvinyl butyral, wherein the polyvinyl butyral is 3-6% by weight of the powder; entering a high-speed dispersion state, the high-speed disperser has a dispersion speed of 10,000-15,000 rpm, the explosion-proof barrel temperature is 15-35°C, and the high-speed dispersion time is 3-5 hours;

[0010] S3: spray granulating the slurry obtained in step S2, with the rotation speed of the spray granulation tower being 8000-10000 r / min, the slurry pumping rate being 0.2-0.5 L / min, and the drying temperature of the granulation tower being 70-90°C; the pressurized gas flow being nitrogen, and the gas pressure being 1-3 MPa; and the protective gas nitrogen being introduced into the tower;

[0011] S4: The spherical metal powder obtained in step S3 is wet-hydrogen calcined at a temperature of 400-600° C. for a calcination holding time of 4-6 hours; the hydrogen source is 95% hydrogen in nitrogen, and the moisture source is saturated water vapor; the intake rate of hydrogen in nitrogen and water vapor is 1:1; the obtained powder is sieved to obtain a high-temperature alloy spherical powder for additive manufacturing.

[0012] Furthermore, in step (1), the metal powder is composed of Cr, Co, Mo, W, Al, Ti, Nb, Zr, Ni, C, and B, and is proportioned according to the required high-temperature alloy formula.

[0013] Furthermore, in step (1), the rare earth nitrate is yttrium nitrate.

[0014] Furthermore, in step S1, the obtained slurry is ground for 3 to 5 hours; the balls used in the sand mill are metal balls, and the metal balls include two specifications: large balls and small balls. The diameter of the large balls is 1 mm, and the diameter of the small balls is 0.8 mm.

[0015] Furthermore, in step S1, the mass ratio of the large balls to the small balls is 1-2:1, and the total volume of the metal balls accounts for 75-85% of the volume of the sanding chamber of the sand mill.

[0016] Furthermore, in step S2, the polyvinyl butyral is prepared into a 10% PVB ethanol solution, the high-speed disperser speed is 100 r / min, and the PVB ethanol solution is added to the slurry by dropwise addition; after the addition is completed, the dispersion speed is maintained at 300-800 r / min, the dispersion time is 30-60 minutes, and then the high-speed disperser is adjusted to a high-speed dispersion state.

[0017] Furthermore, in step S4, the powder accumulation thickness does not exceed 8 mm, and calcination is performed in a heat flow circulation mode.

[0018] The beneficial effects of the present invention are:

[0019] 1. The method for preparing spherical high-temperature alloy powder for additive manufacturing disclosed in the present invention does not require preparation processes such as mother metal smelting, mother metal purification, and ionization separation. No inclusions such as ceramics, organic matter, or foreign metals are introduced during the preparation process. The prepared spherical high-temperature alloy powder has product characteristics such as high sphericity, low oxygen content, and good fluidity.

[0020] 2. Compared with the traditional alloy powder preparation process, the present invention belongs to cold preparation, which does not require all alloy materials to be heated to the low-viscosity melting temperature (alloy superheat is 200-300°C). The preparation process is energy-saving and environmentally friendly, and overcomes the defects of the traditional alloy powder preparation process such as uneven alloy powder composition, severe alloy segregation, uneven structure and deterioration of thermal process performance. The alloy powder of the present invention can be used to prepare high-temperature alloys with good mechanical properties and thermal process performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1The SEM test results of the spherical high-temperature alloy powder prepared in Example 1;

[0023] Figure 2 This is a screenshot of the CNAS test report for the high-temperature alloy powder product prepared in Example 2;

[0024] Figure 3 These are the SEM test results of the high-temperature alloy powder product prepared in Example 3. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1

[0027] (1) Commercial metal powders were prepared according to the mass ratio of Cr 10.87%, Co 17.76%, Mo 14.00%, W 3.95%, Al 2.26%, Ti 3.77%, Nb 0.75%, Zr 0.04%, C 0.05%, B 0.016%, and Ni 46.53%. Yttrium nitrate was added at a concentration of 0.8% of the total mass of the metal powders. Polyethyleneimine was added as a dispersant at a concentration of 1.0% of the total mass of the powders. Anhydrous ethanol was added. The volume solid content of the slurry system was adjusted to 50%.

[0028] (2) adding the slurry obtained in step (1) to a sand mill for grinding for 5 hours; the balls used in the sand mill are tungsten steel alloy balls; the metal balls used are of two specifications, the large ball has a diameter of 1 mm, and the small ball has a specification of 0.8 mm; the metal balls used in the sand mill are tungsten steel alloy balls, the mass ratio of the large and small balls is 1, the inner layer of the sand mill is made of stainless steel, and the total volume of the balls used accounts for 80% of the volume of the sand mill chamber of the sand mill;

[0029] (3) Add the slurry obtained in step (2) to a high-speed disperser, add 3% of the mass of the metal powder polyvinyl butyral (PVB-B98), and add PVB in the form of a 10% ethanol solution; set the disperser speed to 100 r / min during the addition, and add it dropwise; after the addition of PVB is completed, maintain the dispersion speed at 500 r / min and the dispersion time for 40 minutes, then adjust the disperser to a high-speed disperser dispersion speed of 15,000 rpm, set the explosion-proof barrel temperature to 25°C, and the high-speed dispersion time for 5 hours;

[0030] (4) The slurry obtained in step (3) was subjected to spray granulation, the speed of the spray granulation tower was set to 8000 r / min, the slurry pumping rate was set to 0.5 L / min, and the drying temperature of the granulation tower was set to 90°C; the pressurized air flow was nitrogen, and the gas pressure was 2 MPa; protective gas nitrogen was introduced into the tower;

[0031] (5) The spherical metal powder obtained in step (4) is wet hydrogen calcined, the powder stacking thickness is 6 mm, the calcination temperature is 600°C, and the calcination holding time is 4 h; the hydrogen gas source used is 95% hydrogen gas in nitrogen; the wet gas source is saturated water vapor; the intake rate of hydrogen gas in nitrogen and water vapor is maintained at 1:1; the obtained powder is sieved to obtain the spherical high-temperature alloy powder required for additive manufacturing.

[0032] Example 2

[0033] (1) Commercial metal powders were prepared according to the mass ratio of Cr 25.87%, Co 22.76%, Mo 3.80%, W 3.95%, Al 2.46%, Ti 3.72%, Nb 0.8%, Zr 0.04%, C 0.05%, B 0.016%, and Ni 36.53%. Yttrium nitrate was added at a concentration of 0.4% of the total mass of the metal powders. Polyethyleneimine was added as a dispersant at a concentration of 0.1% of the total mass of the powders. Anhydrous ethanol was added. The volume solid content of the slurry system was adjusted to 45%.

[0034] (2) adding the slurry obtained in step (1) to a sand mill for grinding for 4 hours; the balls used in the sand mill are tungsten steel alloy balls; the metal balls used are of two specifications, the large ball has a diameter of 1 mm, and the small ball has a specification of 0.8 mm; the metal balls used in the sand mill are tungsten steel alloy balls, the mass ratio of the large and small balls is 1, the inner layer of the sand mill is made of stainless steel, and the total volume of the balls used accounts for 80% of the volume of the sand mill chamber of the sand mill;

[0035] (3) Add the slurry obtained in step (2) to a high-speed disperser, add 4% of the mass of the metal powder polyvinyl butyral (PVB-B98), and add PVB in the form of a 10% ethanol solution; set the disperser speed to 100 r / min during the addition, and add it dropwise; after the addition of PVB is completed, maintain the dispersion speed at 500 r / min, and the dispersion time is 40 minutes, then adjust the disperser to a high-speed disperser dispersion speed of 10,000 rpm, set the explosion-proof barrel temperature to 20°C, and the high-speed dispersion time is 4 hours;

[0036] (4) The slurry obtained in step (3) was subjected to spray granulation, the speed of the spray granulation tower was set to 8000 r / min, the slurry pumping rate was set to 0.5 L / min, and the drying temperature of the granulation tower was set to 90°C; the pressurized air flow was nitrogen, and the gas pressure was 2 MPa; protective gas nitrogen was introduced into the tower;

[0037] (5) The spherical metal powder obtained in step (4) is wet hydrogen calcined, the powder stacking thickness is 6 mm, the calcination temperature is 600°C, and the calcination holding time is 4 h; the hydrogen gas source used is 95% hydrogen gas in nitrogen; the wet gas source is saturated water vapor; the intake rate of hydrogen gas in nitrogen and water vapor is maintained at 1:1; the obtained powder is sieved to obtain the spherical high-temperature alloy powder required for additive manufacturing.

[0038] Example 3

[0039] (1) Commercial metal powders were prepared according to the following mass ratios: Cr 15.87%, Co 12.76%, Mo 4.00%, W 3.95%, Al 2.26%, Ti 3.77%, Nb 0.75%, Zr 0.04%, C 0.05%, B 0.016%, and Ni 56.53%. Yttrium nitrate was added at a concentration of 0.5% by mass of the total metal powders. Polyethyleneimine was added as a dispersant at a concentration of 0.5% by mass of the total powders. Anhydrous ethanol was added. The volume solid content of the slurry was adjusted to 40%.

[0040] (2) adding the slurry obtained in step (1) to a sand mill for grinding for 4 hours; the balls used in the sand mill are tungsten steel alloy balls; the metal balls used are of two specifications, the large ball has a diameter of 1 mm, and the small ball has a specification of 0.8 mm; the metal balls used in the sand mill are tungsten steel alloy balls, the mass ratio of the large and small balls is 1, the inner layer of the sand mill is made of stainless steel, and the total volume of the balls used accounts for 80% of the volume of the sand mill chamber of the sand mill;

[0041] (3) Add the slurry obtained in step (2) to a high-speed disperser, add 4% of the mass of the metal powder polyvinyl butyral (PVB-B98), and add PVB in the form of a 10% ethanol solution; set the disperser speed to 100 r / min during the addition, and add it dropwise; after the addition of PVB is completed, maintain the dispersion speed at 500 r / min, and the dispersion time is 40 minutes, then adjust the disperser to a high-speed disperser dispersion speed of 10,000 rpm, set the explosion-proof barrel temperature to 20°C, and the high-speed dispersion time is 4 hours;

[0042] (4) The slurry obtained in step (3) was subjected to spray granulation, the speed of the spray granulation tower was set to 10000 r / min, the slurry pumping rate was set to 0.5 L / min, and the drying temperature of the granulation tower was set to 90°C; the pressurized air flow was nitrogen, and the gas pressure was 1 MPa; protective gas nitrogen was introduced into the tower;

[0043] (5) The spherical metal powder obtained in step (4) is wet hydrogen calcined, the powder stacking thickness is 3 mm, the calcination temperature is 600°C, and the calcination holding time is 6 h; the hydrogen gas source used is 95% hydrogen gas in nitrogen; the wet gas source is saturated water vapor; the intake rate of hydrogen gas in nitrogen and water vapor is maintained at 1:1; the obtained powder is sieved to obtain the spherical high-temperature alloy powder required for additive manufacturing.

[0044] Figure 1 The SEM test results of the spherical high-temperature alloy powder prepared in Example 1 show that the powder has good sphericity, no adhesion, uniform particle size distribution, and good fluidity;

[0045] Figure 2 This is a screenshot of the CNAS test report for the high-temperature alloy powder product prepared in Example 2. The spherical powder has good fluidity and is suitable for additive manufacturing of high-temperature alloy products.

[0046] Figure 3 This is the SEM test result of the high-temperature alloy powder product prepared in Example 3. It can be seen from the figure that the spherical powder has good sphericity, no adhesion, uniform particle size distribution, and good fluidity.

[0047] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing spherical high-temperature alloy powder for additive manufacturing, characterized in that: The following steps are involved: S1: Weigh metal powder according to the ratio, add rare earth nitrate, the rare earth nitrate is 0.1-0.8% of the total weight of the metal powder; add polyethyleneimine as a dispersant, the dispersant is 0.1-1.0% of the total weight of the metal powder; add anhydrous ethanol to adjust the volume solid content of the slurry system to 35-50 vol.%, and add the resulting slurry to a sand mill for grinding; S2: adding the slurry ground in step S1 to a high-speed disperser, adding polyvinyl butyral, wherein the polyvinyl butyral is 3-6% of the mass of the metal powder; entering a high-speed dispersion state, the high-speed disperser has a dispersion speed of 10,000-15,000 rpm, the explosion-proof barrel temperature is 15-35°C, and the high-speed dispersion time is 3-5 hours; wherein, the polyvinyl butyral is prepared into a 10% PVB ethanol solution, the high-speed disperser speed is 100 r / min, and the 10% PVB ethanol solution is added to the slurry by dropwise addition; after the addition is completed, the dispersion speed is maintained at 300-800 r / min, the dispersion time is 30-60 minutes, and then the high-speed disperser is adjusted to a high-speed dispersion state; S3: spray granulating the slurry obtained in step S2, with the rotation speed of the spray granulation tower being 8000-10000 r / min, the slurry pumping rate being 0.2-0.5 L / min, and the drying temperature of the granulation tower being 70-90°C; the pressurized gas flow being nitrogen at a gas pressure of 1-3 MPa; and the protective gas nitrogen being introduced into the tower; S4: The spherical metal powder obtained in step S3 is wet hydrogen calcined at a calcination temperature of 400-600°C and a calcination holding time of 4-6 hours; the hydrogen gas source is 95% hydrogen gas in nitrogen, and the moisture source is saturated water vapor; the intake rate of hydrogen gas in nitrogen and water vapor is 1:1; the obtained powder is sieved to obtain a high-temperature alloy spherical powder for additive manufacturing; wherein the powder stacking thickness of the wet hydrogen calcined powder does not exceed 8 mm, and the calcination is performed in a heat flow circulation mode.

2. The method for preparing high-temperature alloy spherical powder for additive manufacturing according to claim 1, characterized in that: In step (1), the metal powder is composed of Cr, Co, Mo, W, Al, Ti, Nb, Zr, Ni, C, and B, and is proportioned according to the required high-temperature alloy formula.

3. The method for preparing high-temperature alloy spherical powder for additive manufacturing according to claim 1, characterized in that: In step (1), the rare earth nitrate is yttrium nitrate.

4. The method for preparing high-temperature alloy spherical powder for additive manufacturing according to claim 1, characterized in that: In step S1, the obtained slurry is ground for 3 to 5 hours; the balls used in the sand mill are metal balls, and the metal balls include two specifications: large balls and small balls. The diameter of the large balls is 1 mm, and the diameter of the small balls is 0.8 mm.

5. The method for preparing high-temperature alloy spherical powder for additive manufacturing according to claim 4, characterized in that: In step S1, the mass ratio of the large balls to the small balls is 1-2:1, and the total volume of the metal balls accounts for 75-85% of the volume of the sanding chamber of the sand mill.

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