A method for producing a titanium alloy metallurgical powder

Abstract

The present application relates to the technical field of titanium alloy metallurgical powder, and particularly relates to a preparation method of titanium alloy metallurgical powder; the method comprises the following steps: step one: titanium alloy raw materials are smelted into a melt, and the melt is introduced into an electromagnetic centrifugal device under the protection of inert gas; step two: the melt is subjected to primary crushing through the electromagnetic centrifugal device, the rotating speed is greater than or equal to 25000 rpm, and pre-crushed particles with a particle size of 100-200 microns are obtained; step three: the pre-crushed particles are transported to an ultrasonic-assisted gas atomization chamber, argon-helium mixed gas is introduced, and 20-40 kHz high-frequency ultrasonic waves are applied to perform atomization and refinement; step four: the atomized particles are cooled to form titanium alloy metallurgical powder; through the introduction of 1 vol% modified yttrium oxide particles into the atomization gas of the ultrasonic-assisted gas atomization chamber, the oxygen content of the titanium alloy powder can be reduced from the conventional 1200-1500 ppm to 600-800 ppm, the reduction is about 40-50%, and the oxygen embrittlement can be effectively avoided, so that the ductility and high-temperature strength of the alloy are improved.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy metallurgical powder, and in particular to a method for preparing titanium alloy metallurgical powder. Background Art

[0002] 3D printing, also known as additive manufacturing, is a type of rapid prototyping technology. Based on digital model files, it constructs objects layer by layer using bondable materials such as powdered metal or plastic. Currently, the technology is widely used in mold manufacturing, industrial design, architecture, aerospace, dentistry, and medicine. Titanium and its alloys are important metals developed in the mid-twentieth century. Titanium alloy powder, with its low density, high strength, corrosion resistance, and non-magnetic properties, is a key raw material for 3D printing.

[0003] At present, the main methods for preparing metal 3D printing powder materials are: two-stream atomization method, centrifugal atomization method, spheroidization method, etc. Among them, the gas atomization method includes the EIGA method. This technology melts the slowly rotating electrode rod material through an induction coil and forms a fine liquid flow by controlling the melting parameters (the liquid flow does not need to contact the water-cooled crucible and the guide tube). When the alloy liquid flow flows through the atomizing nozzle, the liquid flow is broken up by the high-speed pulse airflow generated by the atomizing nozzle and solidified to form fine powder particles. Since there is no contact with the water-cooled crucible and the guide tube, the material will not be contaminated. In theory, the EIGA technology is suitable for the preparation of active material powder and can prepare almost any alloy material. The advantage of the EIGA technology is its low energy consumption. Its disadvantage is that the atomization efficiency and fine powder yield are lower than those of the VIGA method.

[0004] However, in actual use, the traditional gas atomization process causes the powder oxygen content to reach 600-900ppm due to high-temperature oxidation during the atomization process. Therefore, the existing technology also adopts vacuum atomization technology. However, the equipment investment cost will be as high as 2.3 times that of traditional gas atomization, and the atomization efficiency will be reduced by 40%. The loss of gas kinetic energy in a vacuum environment will cause the atomization speed to be ≤6kg / min. We propose a method for preparing titanium alloy metallurgical powder. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies mentioned in the above background technology and provide a method for preparing titanium alloy metallurgical powder.

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

[0007] A method for preparing titanium alloy metallurgical powder comprises the following steps:

[0008] Step 1: Smelt the titanium alloy raw material into a melt and introduce it into an electromagnetic centrifugal device under the protection of inert gas;

[0009] Step 2: The melt is crushed by an electromagnetic centrifugal device at a speed of ≥25000 rpm to obtain pre-crushed particles with a particle size of 100-200 μm;

[0010] Step 3: The pre-crushed particles are transported to the ultrasonic-assisted atomization chamber, where an argon-helium mixed gas is introduced and 20-40kHz high-frequency ultrasonic waves are applied for atomization and refinement.

[0011] Step 4: The atomized particles are cooled to form titanium alloy metallurgical powder.

[0012] Preferably, 0.5-2 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber in step three.

[0013] Preferably, the preparation method of the modified yttrium oxide particles comprises the following steps:

[0014] S1: Yttrium oxide particles were dispersed in an ethanol solution containing 5% PVP and sonicated for 1 h at a power of 300 W.

[0015] S2: Add 2% boric acid solution and stir at 60°C for 4 hours to allow the boric acid to adsorb on the surface of the yttrium oxide particles;

[0016] S3: The yttrium oxide particles prepared in step 2 are placed in an ALD reaction chamber, and trimethylaluminum and water are used as precursors to obtain a 2-3 nm uniform aluminum oxide coating layer, thereby obtaining modified yttrium oxide particles.

[0017] Preferably, the Lorentz force strength of the electromagnetic centrifugal device in step 2 is 5-10 T, and the melt flow rate is controlled to be 0.2-0.5 kg / min.

[0018] Preferably, the volume ratio of the argon-helium mixed gas in step three is 3:1, the atomization pressure is 4-8 MPa, and the gas flow rate reaches Mach 1.5-1.8.

[0019] Preferably, the power density of the ultrasound in step three is 50-150 W / cm2, and the action time is 10-30 ms.

[0020] Preferably, the particle size of the yttrium oxide particles in step S1 is ≤50 nm.

[0021] Preferably, the deposition temperature of the ALD reaction chamber in step S3 is 150° C., and the number of cycles is 20 times.

[0022] A titanium alloy metallurgical powder is prepared by a titanium alloy metallurgical powder preparation method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1、The present application can reduce the oxygen content of titanium alloy powder from the conventional 1200-1500ppm to 600-800ppm by introducing 1vol% modified yttria particles into the atomizing gas of the ultrasonic-assisted gas atomization chamber, with a reduction of about 40-50%, which can effectively avoid oxygen embrittlement and improve the ductility and high-temperature strength of the alloy;

[0025] 2、And the nano-modified yttria particles are uniformly adsorbed on the surface of the titanium alloy powder, reducing inter-particle friction, and the Hall flow rate is increased from 25s / 50g to 18s / 50g, which is beneficial to the powder uniformity in additive manufacturing and reduces printing defects;

[0026] 3、The present application generates cavitation bubbles in the atomization chamber by high-frequency ultrasonic waves, and the micro-jet and shock wave are released when the bubbles collapse, which can break the coarse particles to 15-53μm, and the ultrasonic wave disturbs the argon-helium mixed gas flow (flow rate 1.5-1.8 Mach), forming a resonance field with increased turbulent intensity, prolonging the flight path of the molten droplets, and the surface tension fully acts, so that the sphericity of the titanium alloy metallurgical powder is greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings accompanying the specification of this application serve to provide further understanding of the present application, the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute undue limitations on the present application. In the drawings:

[0028] Figure 1 The present application is prepared by the flow chart. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] Please refer to Figure 1 The above technical solutions are described in detail by the following embodiments of the present application:

[0031] Embodiment 1

[0032] A preparation method of titanium alloy metallurgical powder, comprising the following steps:

[0033] Step one: melt the titanium alloy raw material into a melt, and introduce it into an electromagnetic centrifugal device under the protection of inert gas, with a rotation speed of ≥30000rpm;

[0034] Step 2: The melt is crushed in one stage by an electromagnetic centrifugal device with a Lorentz force strength of 10T, a melt flow rate of 0.5kg / min, and a rotation speed of ≥25000rpm to obtain pre-crushed particles with a particle size of 200μm;

[0035] Step 3: The pre-crushed particles are transported to the ultrasonic-assisted atomization chamber, and an argon-helium mixed gas is introduced. The volume ratio of the argon-helium mixed gas is 3:1, the atomization pressure is 8 MPa, the gas flow rate reaches Mach 1.8, and 40 kHz high-frequency ultrasonic waves are applied for atomization and refinement. The power density of the ultrasonic waves is 150, and the action time is 30 ms.

[0036] Step 4: The atomized particles are cooled to form titanium alloy metallurgical powder.

[0037] It should be explained that when the melt flows through the high-speed rotating electromagnetic centrifugal device, it undergoes primary crushing and is torn into coarse particles of 100-200 μm under the action of the Lorentz force. Compared with traditional mechanical shear force, the Lorentz force acts without contact, avoiding the introduction of impurities, such as metal contamination caused by traditional nozzle wear. In addition, the forced convection stirring induced by the electromagnetic field and the magnetic field strength of 5-10 T eliminate the segregation of highly volatile elements (such as Al), and the composition fluctuation is <0.5 at.%.

[0038] It should be noted that the 40kHz high-frequency ultrasonic wave generates cavitation bubbles in the atomization chamber. When the bubbles collapse, microjets and shock waves are released, which crush the coarse particles to 15-53μm for the second time. The ultrasonic wave disturbs the argon-helium mixed airflow (flow rate 1.5-1.8 Mach), forming a resonance field with increased turbulence intensity, extending the flight path of the molten droplets. The surface tension fully acts, and the molten droplets are subjected to uniform shear force in the airflow, with a sphericity of >95%. Traditional atomization has irregular particles accounting for >15% due to unstable airflow.

[0039] Wherein, in step three, 0.5 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber.

[0040] It should be explained that the highly dispersed modified yttrium oxide particles evenly coat the surface of the titanium alloy droplets to form a continuous and dense layer with a coverage rate of >95%, which directly isolates the oxygen from contact. Through COMSOL simulation, the yttrium oxide layer increases the tortuosity factor of the oxygen diffusion path from 1.2 to 4.8, significantly reducing the permeation rate, and can reduce the oxygen content of titanium alloy metallurgical powder from the conventional 1200-1500ppm to 600-800ppm, a decrease of about 40-50%.

[0041] Among them, the preparation method of the modified yttrium oxide particles in this embodiment is as follows: first, yttrium oxide particles with a particle size of 50 nm are dispersed in an ethanol solution containing 5% PVP, and ultrasonically treated for 1 hour at a power of 300 W; then, a 2% boric acid solution is added and stirred at 60°C for 4 hours to allow the boric acid to adsorb on the surface of the yttrium oxide particles; then, the yttrium oxide particles in step 2 are placed in an ALD reaction chamber, with trimethylaluminum and water as precursors, a deposition temperature of 150°C, and 20 cycles to obtain a 3 nm uniform aluminum oxide coating layer, and finally, modified yttrium oxide particles can be obtained.

[0042] In this embodiment, yttrium oxide particles were purchased from Nangong Harbin Institute of Technology New Materials Technology Co., Ltd.

[0043] Specifically, the modified yttrium oxide particles in this embodiment are rich in oxygen vacancies (VO··) in the lattice, and preferentially adsorb oxygen molecules in the environment (O2+2VO··→2Ox). According to DFT calculation, the adsorption energy is -2.3 eV (strong chemical adsorption). At high temperature, yttrium oxide reacts with titanium melt to form a Y-Ti-O interface layer (confirmed by XPS), which further blocks the inward diffusion of oxygen. Nano-yttrium oxide is distributed at the grain boundaries of the titanium alloy, pinning the grain boundary migration and refining the grains (the average grain size is reduced from 50 μm to 15 μm). The fine grain structure reduces the proportion of grain boundary diffusion paths, and the oxygen diffusion coefficient is reduced from 1×10 -12 m 2 / s is reduced to 3×10 -13 m 2 / s.

[0044] Example 2

[0045] The only difference between this embodiment and embodiment 1 is that 1 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber in this embodiment, and other conditions are the same.

[0046] Example 3

[0047] The only difference between this embodiment and embodiment 1 is that 1.5 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber in this embodiment, and other conditions are the same.

[0048] Example 4

[0049] The only difference between this embodiment and embodiment 1 is that 2 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber in this embodiment, and other conditions are the same.

[0050] Comparative Example 1

[0051] The only difference between this comparative example and Example 1 is that in this comparative example, modified yttrium oxide particles are not introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, and other conditions are the same.

[0052] Comparative Example 2

[0053] The only difference between this comparative example and Example 1 is that in this comparative example, ordinary yttrium oxide particles purchased on the market are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, and other conditions are the same.

[0054] Comparative Example 3

[0055] The only difference between this comparative example and Example 1 is that in this comparative example, conventional gas atomization is used for atomization and refinement, and high-frequency ultrasound is not applied. Other conditions are the same.

[0056] Comparative Example 4

[0057] The only difference between this comparative example and Example 2 is that the particle size of the yttrium oxide particles in the preparation method of the modified yttrium oxide particles in this comparative example is 60 nm, and other conditions are the same.

[0058] Comparative Example 5

[0059] The only difference between this comparative example and Example 2 is that the particle size of the yttrium oxide particles in the preparation method of the modified yttrium oxide particles in this comparative example is 90 nm, and other conditions are the same.

[0060] Sample titanium alloy metallurgical powders were prepared according to Examples 1-4 and Comparative Examples 1-5, and the following performance tests were performed. The specific performance tests and their steps are as follows:

[0061] (1) Particle size distribution test

[0062] Detection instrument: Laser particle size analyzer (such as Malvern Mastersizer 3000)

[0063] Test standard: ISO 13320 (laser diffraction method)

[0064] Test steps: Take 5g of powder sample, disperse it in anhydrous ethanol, and sonicate for 5 minutes to prevent agglomeration; take the light shielding rate of 10-15% as the benchmark, measure it three times and take the average value; the software automatically calculates D10, D50, D90 and Span value (Span = (D90-D10) / D50;

[0065] (2) Wettability and sphericity test

[0066] Testing instrument: dynamic image analyzer (such as Sympatec QICPIC) or SEM image analysis Test standard: ASTM B822 (calculated based on aspect ratio)

[0067] Test steps: Powder flows through a high-speed camera (3000 frames / s), and software automatically analyzes the circularity of 10,000 particles;

[0068] (3) Oxygen content test

[0069] Detection instrument: Inert gas fusion-infrared absorption instrument (such as LECO ONH836)

[0070] Test standard: ASTM E1447

[0071] Steps: Weigh 0.1g of powder sample and place it in a graphite crucible; heat to 3000°C in a helium atmosphere to release oxygen and convert it into CO gas; use an infrared detector to quantify the CO concentration and convert it to oxygen content (ppm).

[0072] The specific data are as follows Table 1 and Table 2:

[0073] Table 1:

[0074] Test items Average particle size (μm) Sphericity (%) Oxygen content (ppm) Example 1 35.6 95.1 730 Example 2 33.8 97.3 650 Example 3 34.3 96.5 690 Example 4 36.4 93.1 750 Comparative Example 1 41.3 85.5 1431 Comparative Example 2 37.6 91.3 856 Comparative Example 3 50.1 70.6 1246

[0075] Table 2:

[0076]

[0077]

[0078] According to the data in Table 1 and Table 2: It can be seen from the data of Reference Examples 1-4 that when the content of modified yttrium oxide particles introduced into the atomizing gas of the ultrasonic-assisted atomization chamber is low or high, the oxygen content of the titanium alloy metallurgical powder will increase; However, in Example 2, when 1 vol% modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, the oxygen content of the titanium alloy metallurgical powder is the lowest. It can be seen from Comparative Examples 1 and 2 that when the modified yttrium oxide particles are not introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, the oxygen content of the titanium alloy metallurgical powder soars. When ordinary yttrium oxide particles purchased on the market are introduced, the oxygen content of the titanium alloy metallurgical powder is also reduced, but compared with Example 2, there is still a big difference. Therefore, the modified yttrium oxide particles uniformly coat the surface of the titanium alloy droplet to form a continuous dense layer with a coverage rate of >95%, directly isolating the oxygen from contact. Through COMSOL simulation, the yttrium oxide layer increases the tortuosity factor of the oxygen diffusion path from 1.2 to 4.8, significantly reducing the permeation rate, and can reduce the oxygen content of the titanium alloy metallurgical powder from the conventional 1200-1500ppm to 600-800ppm, a reduction of about 40-50%;

[0079] According to the data of Example 2, Comparative Example 4 and Comparative Example 5, the content of modified yttrium oxide particles introduced into the atomizing gas of the ultrasonic-assisted atomization chamber remains unchanged. When the particle size of the yttrium oxide particles in the preparation method of the modified yttrium oxide particles is greater than 50 nm, it will affect the oxygen content of the titanium alloy metallurgical powder. It can be seen from Comparative Examples 4 and 5 that when the particle size of the yttrium oxide particles in the preparation method of the modified yttrium oxide particles gradually increases, the oxygen content of the titanium alloy metallurgical powder will gradually increase. In summary, the particle size of the modified yttrium oxide particles has an effect on the oxygen content of the titanium alloy metallurgical powder, but the performance difference in sphericity is small.

[0080] Combined with the data of Example 2 and Comparative Example 3, the use of traditional gas atomization for atomization and refinement in Comparative Example 3 leads to an increase in the oxygen content of the titanium alloy metallurgical powder, and the average particle size and sphericity are affected. Therefore, high-frequency ultrasound generates cavitation bubbles in the atomization chamber, and microjets and shock waves are released when the bubbles collapse, which secondary crush the coarse particles to 15-53 μm. The ultrasound disturbs the argon-helium mixed gas flow (flow rate 1.5-1.8 Mach), forming a resonance field with increased turbulence intensity, extending the droplet flight path, fully exerting surface tension, and subjecting the droplets to uniform shear force in the gas flow, so that the sphericity of the titanium alloy metallurgical powder is greater than 95%;

[0081] Comparative Example 1 serves as a blank control, showing that when the modified yttrium oxide particles are not introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, the oxygen content of the titanium alloy metallurgical powder soars, the sphericity is small, and the average particle size is relatively increased;

[0082] In summary, in this application, when 1 vol% modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber, and when the particle size of the yttrium oxide particles is 50 nm in the preparation method of the modified yttrium oxide particles, the titanium alloy metallurgical powder has the lowest oxygen content, and the sphericity and average particle size performance are also relatively excellent.

[0083] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing titanium alloy metallurgical powder, characterized in that: The following steps are involved: Step 1: Smelt the titanium alloy raw material into a melt and introduce it into an electromagnetic centrifugal device under the protection of inert gas; Step 2: The melt is crushed by an electromagnetic centrifugal device at a speed of ≥25000 rpm to obtain pre-crushed particles with a particle size of 100-200 μm; Step 3: The pre-crushed particles are transported to the ultrasonic-assisted atomization chamber, where an argon-helium mixed gas is introduced and 20-40kHz high-frequency ultrasonic waves are applied for atomization and refinement. Step 4: The atomized particles are cooled to form titanium alloy metallurgical powder; In step 3, 0.5-2 vol% of modified yttrium oxide particles are introduced into the atomizing gas of the ultrasonic-assisted atomization chamber; The preparation method of the modified yttrium oxide particles comprises the following steps: S1: Yttrium oxide particles were dispersed in an ethanol solution containing 5% PVP and sonicated for 1 h at a power of 300 W. S2: Add 2% boric acid solution and stir at 60°C for 4 h to allow the boric acid to adsorb on the surface of the yttrium oxide particles; S3: The yttrium oxide particles in S2 are placed in an ALD reaction chamber, and trimethylaluminum and water are used as precursors to obtain a 2-3 nm uniform aluminum oxide coating layer. Finally, modified yttrium oxide particles can be obtained.

2. The method for preparing titanium alloy metallurgical powder according to claim 1, wherein: The Lorentz force strength of the electromagnetic centrifugal device in step 2 is 5-10 T, and the melt flow rate is controlled to be 0.2-0.5 kg / min.

3. The method for preparing titanium alloy metallurgical powder according to claim 1, wherein: The volume ratio of the argon-helium mixed gas in step 3 is 3:1, the atomization pressure is 4-8 MPa, and the gas flow rate reaches 1.5-1.8 Mach.

4. The method for preparing titanium alloy metallurgical powder according to claim 1, wherein: The power density of the ultrasound in step 3 is 50-150 , action time is 10-30 ms.

5. The method for preparing titanium alloy metallurgical powder according to claim 1, wherein: The particle size of the yttrium oxide particles in step S1 is ≤50 nm.

6. The method for preparing titanium alloy metallurgical powder according to claim 1, wherein: The deposition temperature of the ALD reaction chamber in step S3 is 150° C., and the number of cycles is 20.

7. A titanium alloy metallurgical powder, characterized in that: The titanium alloy metallurgical powder is prepared by the preparation method of any one of claims 1 to 6.

Images