A method for preparing fine low-oxygen spherical TiAl alloy powder

Abstract

The present invention provides a method for preparing fine low-oxygen spherical TiAl alloy powder, which relates to the technical field of spherical titanium-based alloy powder. The preparation method includes the following steps: selecting and processing raw materials for wires, preparing TiAl composite wires, preparing TiAl alloy wires, processing TiAl alloy wires, establishing a gas system, high-frequency induction preheating, radio frequency plasma melting and atomization powder making. The present invention can directly prepare TiAl alloy wires with uniform composition distribution at a relatively low temperature through multiple twisting, multiple continuous hot drawing, diffusion homogenization annealing, high-frequency induction preheating, radio frequency plasma melting and atomization powder making, and further prepare TiAl alloy fine powder with low oxygen content and uniform composition distribution, which is suitable for use in additive manufacturing, has high flexibility, simple operation, wide applicability and low cost, and is very suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of spherical titanium-based alloy powder, in particular to a method for preparing fine low-oxygen spherical TiAl alloy powder. Background Art

[0002] For TiAl alloy injection molding (powder size 0-25μm) and additive manufacturing (powder size 15-53μm), the performance of the finished product depends largely on the TiAl alloy powder feedstock. Generally speaking, the powder feedstock for producing high-performance finished products should exhibit high sphericity, flowability, purity, low hollow content, and a fine powder particle size. Due to the room-temperature brittleness of TiAl alloy, the preparation of TiAl alloy wire currently faces technical bottlenecks, and TiAl alloy wire is prone to reaction with other substances at high temperatures. Therefore, the preparation of spherical TiAl alloy powder mainly uses rods as the raw material, using non-contact melting methods such as the plasma rotating electrode (PREP) method and the electrode induction melting gas atomization (EIGA) method.

[0003] Among them, the PREP method is to prepare TiAl alloy into a rod-type consumable electrode. One end of the consumable electrode melts into droplets under the action of plasma heating, and is then thrown out under the action of high-speed rotating centrifugal force to form fine droplets. The small droplets are rapidly cooled and solidified into spherical powders under the action of surface tension. However, TiAl alloy is an intermetallic compound with poor plasticity, so the rod is very likely to crack during the powder making process. In addition, TiAl alloy itself has poor thermal conductivity, the droplet solidification rate is slow, and anisotropic deformation is prone to occur during the solidification process, resulting in a low sphericity of the powder. In addition, the rotation speed of the TiAl alloy rod in this technology is lower than 20,000 r / min, which makes the centrifugal force for the droplet dispersion and atomization smaller, and the droplet viscosity is larger, so the spherical powder obtained is coarse, with a powder particle size of 40-400μm.

[0004] The EIGA method uses TiAl alloy rods as raw material. A high-frequency induction current is used to melt the rod surface, forming a molten stream that falls into an atomizing nozzle. High-speed airflow forms dispersed molten droplets, which rapidly cool and solidify into fine particles. Compared to the PREP method, the EIGA method produces finer powders, but the yield of fine powders suitable for injection molding and additive manufacturing is low, less than 40%. Furthermore, the TiAl alloy droplets after induction melting tend to leave the high-temperature zone too quickly, resulting in insufficient temperature and time during the atomization condensation process to ensure that the droplets shrink into spheres under the action of surface tension. The resulting powder has a low sphericity and is prone to hollow spheres.

[0005] Chinese patent CN114309621A discloses a method for preparing fine TiAl alloy spherical powder containing refractory metal elements. The method uses TiH2, Al and MHx as main raw materials, performs high-energy ball milling in a hydrogen atmosphere, and then feeds the ground powder into an inductively coupled plasma torch for dehydrogenation and melting, followed by alloying and spheroidization to produce alloy spherical powder. Obviously, this method has a complex device structure and is difficult to operate. It requires multiple powdering processes, and the hydrogen content in the prepared TiAl alloy spherical powder is not completely removed. The cost and heat energy consumed are high, and refractory metal elements need to be added.

[0006] Chinese patent CN111151762A discloses a low-cost method for preparing fine-grained, low-oxygen titanium and titanium alloy powders. The method uses sponge titanium and alloy powders as raw materials and obtains the final product through processes such as hydrogenation, crushing, dehydrogenation, pre-alloying, and passivation. This method requires titanium hydride raw materials and other pre-alloyed or elemental powders, and relies on the hydrogenation and dehydrogenation method to prepare titanium and titanium alloy powders. The resulting alloy powder has low sphericity, a rough surface, and a wide range of powder particle sizes.

[0007] Chinese patent CN116984605A discloses a method for preparing aerosolized TiAl alloy powder for additive manufacturing. The key to improving powder quality lies in the quality of the smelted rods used to prepare the powder. The smelted rods are prepared by a complex method using aerosolized TiAl alloy of selected composition, the particle size of which is not suitable for powders. Forging and hot isostatic pressing are required. However, the composition distribution of the smelted rods prepared by these methods is not uniform, as is the composition of the heated molten alloy liquid, and even more so the powder prepared.

[0008] In addition to the aforementioned issues, both the PREP and EIGA methods for preparing TiAl alloy spherical powders face limitations such as complex raw material bar preparation, slow melting rates, low powder yields, and electrode contamination. Therefore, a method for preparing high-quality, high-yield, fine TiAl alloy spherical powders is urgently needed to meet the current requirements for high-performance, complex, near-net-shape forming of TiAl alloys. Summary of the Invention

[0009] To address the problem in the existing technology of preparing TiAl alloy powder for additive manufacturing, which is that the poor room temperature plasticity of TiAl alloy makes it impossible to form a wire drawing, resulting in most current powder making technologies using only TiAl alloy rods as raw materials. However, due to the lack of a crucible for holding the titanium liquid, the superheat of the TiAl alloy liquid is low, resulting in high viscosity of the TiAl alloy droplets, which in turn leads to poor atomization or rotational dispersion. The powder particle size after cooling is relatively coarse, and the fine powder yield rate for injection molding, additive manufacturing, etc. does not exceed 40%. In addition, the prepared powder also has problems such as low sphericity, wide particle size distribution, high impurity content, and hollow powder. At the same time, the complex preparation of the raw material rods and the slow melting rate of the rods also lead to low powder yield and high production costs. Therefore, the embodiment of the present invention provides a method for preparing fine low-oxygen spherical TiAl alloy powder with fine particle size (0-60μm), smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content ≤1000ppm), and high production efficiency. The technical solution is as follows:

[0010] A method for preparing fine low-oxygen spherical TiAl alloy powder, the method for preparing fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0011] S1. Selection and processing of wire raw materials: According to the composition and mass ratio of the target TiAl alloy wire, a plurality of Ti wires and a plurality of Al wires are selected as wire raw materials; and the wire raw materials are ultrasonically cleaned using commercially available cleaning agents to obtain wire raw materials with clean surfaces;

[0012] S2, Preparation of TiAl Composite Wire: The wire materials in S1 are tightly twisted together using a stranding machine and subjected to continuous multiple hot drawing. After the first round of hot drawing, the obtained wires are divided into multiple equal parts along the cross section, twisted again using a stranding machine, and then subjected to a second round of hot drawing. The dividing-twisting-drawing process is then repeated until a uniform TiAl composite wire is obtained.

[0013] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 is continuously drawn and extruded through a continuous wire drawing machine. The entire process is automatically conveyed until the target pass is stopped. The target extrusion pass is related to the diameter of the TiAl alloy wire, the diameter of the extrusion die, and the amount of diameter reduction per pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation to obtain TiAl alloy wire;

[0014] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0015] S5. Establishment of gas system: RF plasma combined with gas atomization powder making equipment is used for powder making. Before powder making, the entire powder making system needs to be evacuated, then filled with inert gas to establish the gas system, and the system pressure is adjusted;

[0016] S6, high-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain a preheated TiAl alloy wire;

[0017] S7, radio frequency plasma melting: sending the TiAl alloy wire preheated in S6 to the radio frequency plasma high temperature area for radio frequency plasma melting treatment to obtain TiAl alloy droplets with low viscosity;

[0018] S8, atomization powder making: the TiAl alloy droplets with low viscosity in S7 are sent into the atomization reaction chamber for atomization reaction treatment, and fine low-oxygen spherical TiAl alloy powder is obtained after cooling and solidification.

[0019] Optionally, the wire material in S1 can use existing brand wire, or be customized to adjust the composition; the wire material diameter is 1-5mm; the frequency of ultrasonic cleaning is 20-60kHz, and the power is 240-720W.

[0020] Optionally, the stranding machine speed in S2 is greater than 500 rpm, and the length of the stranded wire after stranding is 70-90% of the wire raw material; the continuous multi-pass hot drawing is specifically as follows: the drawing temperature is 250-500°C, the drawing rate is 5-30 m / min, the total number of drawing passes is 2-10 rounds depending on the uniformity of the TiAl composite wire, and the total deformation of the multi-pass drawing is 20-90%; the uniform TiAl composite wire has a tensile strength of 100-700 MPa, a yield strength of 50-600 MPa, and an elongation of 6-30%.

[0021] Optionally, the extrusion rate of the continuous drawing extrusion in S3 is 1-20 m / min, and the vacuum degree of the vacuum furnace is 10 -1 ~10 -3 Pa, the diameter of the prepared TiAl alloy wire is 0.8-5mm, and the diameter decreases gradually by 0.2-1mm until the target pass stops; the heating and insulation is heated to 600-900℃ and kept warm for 60-120min; the tensile strength of the TiAl alloy wire is 400-750MPa, the yield strength is 300-650MPa, and the elongation is 3-10%.

[0022] Optionally, the vacuum degree of S5 is 10 -1 ~10 -3 Pa, adjust the system pressure to -55kPa~+55kPa, the gas system has its own oxygen detection device, and the oxygen content of the entire system is ≤20ppm.

[0023] Optionally, the preheating temperature of the preheating treatment in S6 is 500-900° C., the wire feeding speed is 1-20 m / min, the high-frequency induction heating power is 10-50 kW, and the oscillation frequency is 30-250 kHz.

[0024] Optionally, the RF plasma power of the RF plasma melting treatment in S7 is 30-100 kW, the oscillation frequency is 2-150 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10-50 L / min, and the side gas flow rate is 100-300 L / min; the viscosity of the TiAl alloy droplet is 10-100 mPa·s.

[0025] Optionally, the high-pressure gas flow for the atomization reaction treatment in S8 is an argon flow or a helium flow, with a gas purity of ≥99.999%, a pressure of 5-20 MPa, and a gas flow rate of 4-20 m 3 / min.

[0026] Optionally, the oxygen content of the fine low-oxygen spherical TiAl alloy powder in S8 is ≤1000ppm, the powder particle size is 0-60μm, the sphericity is ≥95%, the spheroidization rate is about 100%, and the 0-50μm fine powder recovery rate is ≥90%.

[0027] Optionally, the preparation method described in S1-S8 is not only applicable to TiAl alloys, but also to Ti-Al-Nb alloys, Ti-Al-V alloys, Ti-Cu alloys, Ti-Ni alloys, Ti-Fe alloys and Ti-Mo alloys.

[0028] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0029] The above scheme, the present invention proposes a method for preparing fine low-oxygen spherical TiAl alloy powder, which can solve the problems of the existing powder making technology using TiAl alloy rods as raw materials and no crucible for holding titanium liquid, resulting in high droplet viscosity and coarse powder particle size during the preparation process, as well as other quality problems such as poor sphericity of the prepared powder, wide particle size distribution, high impurity content, hollow powder, etc.; at the same time, it also solves the problem of low preparation efficiency caused by the complex preparation of raw material rods and slow melting rate of rods in the existing powder making technology.

[0030] The present invention is not limited to the preparation of spherical TiAl alloy powder, but is also applicable to the preparation of spherical Ti-Al-Nb alloy powder, spherical Ti-Al-V alloy powder, spherical Ti-Cu alloy powder, spherical Ti-Ni alloy powder, spherical Ti-Fe alloy powder and spherical Ti-Mo alloy powder, etc., and has no special restrictions on the raw material brand, composition, etc., and can be freely adjusted according to the target composition. The range of optional raw materials is wide, and additive manufacturing can prepare a large number of complex shapes and different compositions of titanium alloys, which is conducive to large-scale industrial production and commercial promotion and application.

[0031] The present invention utilizes the good room temperature plasticity of a single metal wire, adopts the alloy single metal wire to be compounded, and forms a tight spiral structure with two or more of the aforementioned single metal wires through a twisting method. Combined with a multi-pass continuous warm drawing process, the pre-alloying of the alloy single metal to be compounded can be achieved at a relatively low temperature. Compared with the TiAl alloy rods used in the existing powder preparation method, the present invention is convenient to operate and low in cost, and can be applied to the additive manufacturing of alloys with complex shapes with different performance requirements; in particular, the thinner wire raw materials are easier to melt during the powder making process, the formed molten droplets have low viscosity, the atomization and dispersion effect is good, and the powder obtained has a fine particle size.

[0032] The present invention combines high-frequency induction heating with radio frequency plasma to achieve segmented continuous heating of TiAl alloy wire. Compared with single induction heating or plasma heating, it can effectively accelerate the melting rate of raw materials, reduce the viscosity of molten droplets, and improve the wire feeding speed and powder yield. The high-temperature plasma can ensure that the molten droplets have high superheat and low viscosity, and use high-pressure gas atomization to atomize low-viscosity TiAl droplets into fine droplets, which are condensed and spheroidized under the action of surface tension. The obtained spherical TiAl alloy powder has a small particle size, good sphericity, high spheroidization rate, no hollow powder, and high yield.

[0033] The present invention uses specially prepared TiAl alloy wire with uniform composition distribution as raw material, replacing the traditional radio frequency plasma powder as raw material. This replacement can effectively reduce the oxidation of the raw material and the adsorption of impurities, and reduce the oxygen content and impurity content of the powder product, thereby obtaining low-oxygen and high-purity spherical TiAl alloy powder with uniform composition distribution.

[0034] The entire powder making process of the present invention is carried out under the protection of inert gas, the oxygen content of the entire gas system is ≤20ppm, and the radio frequency plasma equipment used does not have electrode pollution, ensuring that the prepared spherical TiAl alloy powder is pollution-free and free of inclusions.

[0035] The present invention further disperses the molten droplets after radio frequency plasma atomization through the high-pressure airflow of the atomizing nozzle, thereby avoiding the generation of coarse particle ball powder, ensuring a high fine powder yield of the spherical TiAl alloy powder, high sphericity, and narrow particle size distribution, and avoiding the large-scale generation of hollow balls.

[0036] The fine low-oxygen spherical TiAl alloy powder prepared by the present invention has a small particle size (0-60 μm), a smooth surface, high sphericity, good fluidity, no hollow powder, a low impurity content (oxygen content ≤ 1000 ppm), and high production efficiency. It can improve the performance of TiAl alloy products in injection molding and additive manufacturing while reducing their raw material costs.

[0037] The tensile strength, yield strength and yield strength ratio of the TiAl alloy wire prepared by the present invention gradually increase as the process progresses, and the tensile strength can reach about 700 MPa, and the maximum can approach 720 MPa; similarly, the yield strength ratio is above 0.9, and the maximum can approach 0.94.

[0038] In summary, compared with other traditional methods, the method of the present invention can directly prepare TiAl alloy wires with uniform composition distribution at a lower temperature through multiple wire twisting, multiple continuous hot drawing, diffusion homogenization annealing, high-frequency induction preheating, radio frequency plasma melting and atomization powder making, and then prepare TiAl alloy fine powder with low oxygen content and uniform composition distribution. It is suitable for additive manufacturing, has high flexibility, simple operation, wide applicability, low cost, and is very suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0040] Figure 1 The present invention is a process flow chart of a method for preparing fine low-oxygen spherical TiAl alloy powder. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0042] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0043] In the embodiments of the present invention, "image" and "picture" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same. "of," "corresponding," and "corresponding" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same.

[0044] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0045] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0046] A method for preparing fine low-oxygen spherical TiAl alloy powder, such as Figure 1 As shown, the preparation method of the fine low-oxygen spherical TiAl alloy powder is as follows:

[0047] S1. Selection and processing of wire raw materials: According to the composition and mass ratio of the target TiAl alloy wire, a plurality of Ti wires and a plurality of Al wires are selected as wire raw materials; and the wire raw materials are ultrasonically cleaned using commercially available cleaning agents to obtain wire raw materials with clean surfaces;

[0048] S2, Preparation of TiAl Composite Wire: The wire materials in S1 are tightly twisted together using a stranding machine and subjected to continuous multiple hot drawing. After the first round of hot drawing, the obtained wires are divided into multiple equal parts along the cross section, twisted again using a stranding machine, and then subjected to a second round of hot drawing. The dividing-twisting-drawing process is then repeated until a uniform TiAl composite wire is obtained.

[0049] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 is continuously drawn and extruded through a continuous wire drawing machine. The entire process is automatically conveyed until the target pass is stopped. The target extrusion pass is related to the diameter of the TiAl alloy wire, the diameter of the extrusion die, and the amount of diameter reduction per pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation to obtain TiAl alloy wire;

[0050] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0051] S5. Establishment of gas system: RF plasma combined with gas atomization powder making equipment is used for powder making. Before powder making, the entire powder making system needs to be evacuated, then filled with inert gas to establish the gas system, and the system pressure is adjusted;

[0052] S6, high-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain a preheated TiAl alloy wire;

[0053] S7, radio frequency plasma melting: sending the TiAl alloy wire preheated in S6 to the radio frequency plasma high temperature area for radio frequency plasma melting treatment to obtain TiAl alloy droplets with low viscosity;

[0054] S8, atomization powder making: the TiAl alloy droplets with low viscosity in S7 are sent into the atomization reaction chamber for atomization reaction treatment, and fine low-oxygen spherical TiAl alloy powder is obtained after cooling and solidification.

[0055] In particular, the wire raw material in S1 uses existing brands of wire, or customized design and composition adjustment; the wire raw material diameter is 1-5mm; the frequency of ultrasonic cleaning is 20-60kHz, and the power is 240-720W.

[0056] In particular, the stranding machine speed in S2 is greater than 500 rpm, and the length of the stranded wire after stranding is 70-90% of the wire raw material; the continuous multi-pass hot drawing is specifically as follows: the drawing temperature is 250-500°C, the drawing rate is 5-30 m / min, the total number of drawing passes is 2-10 rounds depending on the uniformity of the TiAl composite wire, and the total deformation of the multi-pass drawing is 20-90%; the uniform TiAl composite wire has a tensile strength of 100-700 MPa, a yield strength of 50-600 MPa, and an elongation of 6-30%.

[0057] In particular, the extrusion rate of the continuous drawing extrusion in S3 is 1-20 m / min, and the vacuum degree of the vacuum furnace is 10 -1 ~10 -3 Pa, the diameter of the prepared TiAl alloy wire is 0.8-5mm, and the diameter decreases gradually by 0.2-1mm until the target pass stops; the heating and insulation is heated to 600-900℃ and kept warm for 60-120min; the tensile strength of the TiAl alloy wire is 400-750MPa, the yield strength is 300-650MPa, and the elongation is 3-10%.

[0058] In particular, the vacuum degree of S5 is 10 -1 ~10 -3 Pa, adjust the system pressure to -55kPa~+55kPa, the gas system has its own oxygen detection device, and the oxygen content of the entire system is ≤20ppm.

[0059] In particular, the preheating temperature of the preheating treatment in S6 is 500-900° C., the wire feeding speed is 1-20 m / min, the high-frequency induction heating power is 10-50 kW, and the oscillation frequency is 30-250 kHz.

[0060] In particular, the RF plasma power of the RF plasma melting treatment in S7 is 30-100kW, the oscillation frequency is 2-150MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, the main gas flow rate is 10-50L / min, and the side gas flow rate is 100-300L / min; the viscosity of the TiAl alloy droplet is 10-100mPa·s.

[0061] In particular, the high-pressure gas flow for the atomization reaction treatment in S8 is argon or helium, with a gas purity of ≥99.999%, a pressure of 5-20 MPa, and a gas flow rate of 4-20 m 3 / min.

[0062] In particular, the oxygen content of the fine low-oxygen spherical TiAl alloy powder in S8 is ≤1000ppm, the powder particle size is 0-60μm, the sphericity is ≥95%, the spheroidization rate is about 100%, and the 0-50μm fine powder recovery rate is ≥90%.

[0063] In particular, the preparation method described in S1-S8 is not only applicable to TiAl alloys, but also to Ti-Al-Nb alloys, Ti-Al-V alloys, Ti-Cu alloys, Ti-Ni alloys, Ti-Fe alloys and Ti-Mo alloys.

[0064] Example 1

[0065] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 52% and Al 48% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0066] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, five Ti wires and five Al wires, each with a diameter of 2 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 40 kHz and a power of 360 W to obtain surface-cleaned wire raw materials.

[0067] S2. Preparation of TiAl composite wire: The wire materials in S1 are tightly twisted together using a stranding machine and subjected to continuous multiple hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be two based on the uniformity of the TiAl composite wire. The obtained wire is then divided into four equal parts along the cross section, twisted again using a stranding machine, and then subjected to two rounds of hot drawing. The multiple division-twisting-drawing process is then repeated until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 315 MPa, a yield strength of 252 MPa, a yield strength ratio of 0.800, an elongation of 7%, and a strength-ductility product of 2.21 GPa·%. The drawing temperature is 380-400°C, the drawing rate is 9-15 m / min, and the total deformation after two rounds of drawing is 70%.

[0068] S3, Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 850 ° C, the extrusion rate was 15 m / min, the extrusion die diameter was 3 mm and the diameter decreased by 0.5 mm each time. The whole process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -1 Pa, heating temperature 800 ℃, holding time 75min, obtained a TiAl alloy wire with a diameter of 1mm and uniform composition distribution; the TiAl alloy wire has a tensile strength of 668MPa, a yield strength of 621MPa, a yield strength ratio of 0.930, an elongation of 5%, and a strength-ductility product of 3.34GPa·%;

[0069] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0070] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -1 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -15kPa~+15kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0071] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 600°C to obtain a preheated TiAl alloy wire. The high-frequency induction heating power is 15kW, the oscillation frequency is 50kHz, and the wire feeding speed is 6m / min.

[0072] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 80 kW, the oscillation frequency is 20 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13 L / min and the side gas flow rate is 110 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 15 mPa·s;

[0073] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 7MPa, and the gas flow rate is 9m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0074] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 704 ppm), small particle size and a narrow distribution range (0-60 μm), sphericity ≥95%, a spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0075] Example 2

[0076] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 53% and Al 47% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0077] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, six Ti wires and four Al wires, each with a diameter of 3 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 60 kHz and a power of 720 W to obtain surface-cleaned wire raw materials.

[0078] S2. Preparation of TiAl composite wire: The wire raw materials in S1 are tightly twisted together by a stranding machine, and are subjected to continuous multiple-pass hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 4 according to the uniformity of the TiAl composite wire. The obtained wire is then divided into three equal parts along the cross section, and then twisted by a stranding machine, and then subjected to two rounds of hot drawing. The wire obtained in the second round is then divided into four equal parts along the cross section, and then twisted by a stranding machine, and then subjected to three rounds of drawing. Four rounds of drawing are performed in this way until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 447 MPa, a yield strength of 366 MPa, a yield strength ratio of 0.819, an elongation of 7%, and a strength-ductility product of 3.13 GPa·%. The drawing temperature is 270-350°C, the drawing rate is 6-8 m / min, and the total deformation after two rounds of drawing is 75%.

[0079] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 900°C, the extrusion rate was 18 m / min, the extrusion die diameter was 4 mm and the diameter decreased by 0.2 mm each time. The entire process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the TiAl alloy wire diameter, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with a diameter of 3mm and uniform composition distribution is obtained; the tensile strength of the TiAl alloy wire is 693MPa, the yield strength is 648MPa, the yield strength ratio is 0.935, the elongation is 6.8%, and the strength-ductility product is 4.71GPa·%;

[0080] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0081] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -2 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -30kPa~+30kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0082] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating device adjusted in S5. The preheating temperature is 800°C to obtain a preheated TiAl alloy wire. The high-frequency induction heating power is 25kW, the oscillation frequency is 100kHz, and the wire feeding speed is 10m / min.

[0083] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 90 kW, the oscillation frequency is 30 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 25 L / min and the side gas flow rate is 200 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 38 mPa·s;

[0084] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 13MPa, and the gas flow rate is 15m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0085] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 558 ppm), small particle size and a narrow distribution range (0-60 μm), sphericity ≥95%, a spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0086] Comparative Example 1

[0087] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 52% and Al 48% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0088] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, five Ti wires and five Al wires, each with a diameter of 2 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 40 kHz and a power of 360 W to obtain surface-cleaned wire raw materials.

[0089] S2. Preparation of TiAl composite wire: The wire materials in S1 were tightly twisted together using a stranding machine and subjected to continuous multi-pass hot drawing to obtain TiAl composite wire. The TiAl composite wire had a tensile strength of 310 MPa, a yield strength of 232 MPa, a yield strength ratio of 0.748, an elongation of 10%, and a strength-ductility product of 3.10 GPa·%; the drawing temperature was 380°C, the drawing rate was 9 m / min, and the total deformation after drawing was 60%.

[0090] S3, Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 850 ° C, the extrusion rate was 15 m / min, the extrusion die diameter was 3 mm and the diameter decreased by 0.5 mm each time. The whole process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -1 Pa, heating temperature is 800℃, holding time is 75min, and TiAl alloy wire with a diameter of 1mm is obtained; the tensile strength of the TiAl alloy wire is 550MPa, the yield strength is 496MPa, the yield strength ratio is 0.902, the elongation is 4%, and the strength-ductility product is 2.20GPa·%;

[0091] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0092] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -1 Pa, then fill with inert gas to establish a gas system, adjust the system pressure to -15kPa~+15kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is greater than 20ppm;

[0093] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 600°C. The high-frequency induction heating power is 15kW, the oscillation frequency is 50kHz, and the wire feeding speed is 6m / min.

[0094] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 80 kW, the oscillation frequency is 20 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13 L / min and the side gas flow rate is 110 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 15 mPa·s;

[0095] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 7MPa, and the gas flow rate is 9m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0096] The fine spherical TiAl alloy powder obtained in this comparative example has a smooth surface, high sphericity, good fluidity, no hollow powder, small particle size and a narrow distribution range (0-60μm). However, due to insufficient continuous warm drawing passes during the preparation of the TiAl alloy wire, the fine spherical TiAl alloy powder obtained has component segregation, and since the oxygen content of the entire system is greater than 20ppm, the impurity content of the fine spherical TiAl alloy powder obtained is relatively high (oxygen content is 2483ppm).

[0097] Comparative Example 2

[0098] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: 53% Ti, 47% Al by mass percentage; the method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0099] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, six Ti wires and four Al wires, each with a diameter of 3 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 60 kHz and a power of 720 W to obtain surface-cleaned wire raw materials.

[0100] S2. Preparation of TiAl composite wire: The wire raw materials in S1 are tightly twisted together by a stranding machine, and are subjected to continuous multiple-pass hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 4 according to the uniformity of the TiAl composite wire. The obtained wire is then divided into three equal parts along the cross section, and then twisted by a stranding machine, and then subjected to two rounds of hot drawing. The wire obtained in the second round is then divided into four equal parts along the cross section, and then twisted by a stranding machine, and then subjected to three rounds of drawing. Four rounds of drawing are performed in this way until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 447 MPa, a yield strength of 366 MPa, a yield strength ratio of 0.819, an elongation of 7%, and a strength-ductility product of 3.13 GPa·%. The drawing temperature is 270-350°C, the drawing rate is 6-8 m / min, and the total deformation after two rounds of drawing is 75%.

[0101] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 900°C, the extrusion rate was 18 m / min, the extrusion die diameter was 4 mm and the diameter decreased by 0.2 mm each time. The entire process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the TiAl alloy wire diameter, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10-2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with a diameter of 3mm and uniform composition distribution is obtained; the tensile strength of the TiAl alloy wire is 693MPa, the yield strength is 648MPa, the yield strength ratio is 0.935, the elongation is 1.8%, and the strength-ductility product is 1.25GPa·%;

[0102] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0103] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -2 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -30kPa~+30kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0104] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 300°C. The high-frequency induction heating power is 7kW, the oscillation frequency is 25kHz, and the wire feeding speed is 5m / min.

[0105] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 20kW, the oscillation frequency is 5MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10L / min and the side gas flow rate is 90L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is much greater than 100mPa·s;

[0106] S8, atomization powder making: the TiAl alloy droplets of S7 are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 13MPa, and the gas flow rate is 15m 3 / min, and low-oxygen TiAl alloy powder was obtained after cooling and solidification.

[0107] The spherical TiAl alloy powder obtained in this comparative example has a low impurity content (oxygen content is 382 ppm). However, due to the low high-frequency induction pretreatment temperature and radio frequency melting power, the TiAl alloy droplets are insufficiently superheated and the droplet viscosity is too high. The obtained TiAl alloy powder has a coarse particle size (~200 μm) and the yield of 0-50 μm fine powder is less than 90%.

[0108] In summary, by comparing the examples with the comparative examples, it can be found that the uniformity of the TiAl alloy wire determines whether there will be composition segregation in the fine low-oxygen spherical TiAl alloy powder; the control of the impurity content in the system directly affects the impurity content of the final spherical TiAl alloy powder; the high-frequency induction preheating temperature, radio frequency plasma melting power, gas flow rate, etc. are important parameters for controlling the particle size and morphology of the TiAl alloy powder.

[0109] Example 3

[0110] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 54% and Al 46% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0111] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, three Ti wires and three Al wires, each with a diameter of 4 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 20 kHz and a power of 240 W to obtain surface-cleaned wire raw materials.

[0112] S2, preparation of TiAl composite wire: The wire raw materials in S1 are tightly twisted together by a stranding machine, and are subjected to continuous multiple-pass hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 5 rounds based on the uniformity of the TiAl composite wire. The obtained wire is then divided into four equal parts along the cross section, twisted again by a stranding machine, and subjected to two rounds of hot drawing. The wire obtained in the second round is then divided into four equal parts along the cross section, twisted again by a stranding machine, and subjected to three rounds of drawing. Four and five rounds of drawing are performed according to this method until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 525 MPa, a yield strength of 435 MPa, a yield strength ratio of 0.829, an elongation of 6.5%, and a strength-ductility product of 3.41 GPa·%; wherein the drawing temperature for the five rounds is 450°C, the drawing rate is 18-20 m / min, and the total deformation after the five rounds of drawing is 87%;

[0113] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 770°C, the extrusion rate was 10 m / min, the extrusion die diameter was 5 mm and the diameter decreased by 0.5 mm each time. The entire process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the TiAl alloy wire diameter, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -3Pa, heating temperature is 680℃, holding time is 120min, and a TiAl alloy wire with a diameter of 2mm and uniform composition distribution is obtained; the TiAl alloy wire has a tensile strength of 711MPa, a yield strength of 645MPa, a yield strength ratio of 0.907, an elongation of 8%, and a strength-ductility product of 5.69GPa·%;

[0114] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0115] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -3 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -50kPa~+50kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0116] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 900°C to obtain the preheated TiAl alloy wire. The high-frequency induction heating power is 40kW, the oscillation frequency is 220kHz, and the wire feeding speed is 18m / min.

[0117] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 50 kW, the oscillation frequency is 8 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10 L / min and the side gas flow rate is 150 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 50 mPa·s;

[0118] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 16MPa, and the gas flow rate is 19m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0119] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 2478 ppm), small particle size and narrow distribution range (0-60 μm), sphericity ≥95%, spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0120] Example 4

[0121] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 54% and Al 46% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0122] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, five Ti wires and five Al wires, each with a diameter of 2 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 60 kHz and a power of 720 W to obtain surface-cleaned wire raw materials.

[0123] S2. Preparation of TiAl composite wire: The wire raw materials in S1 are tightly twisted together by a stranding machine and subjected to continuous multiple-pass hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 3 according to the uniformity of the TiAl composite wire. The obtained wire is then divided into two equal parts along the cross section, twisted again by a stranding machine, and subjected to two rounds of hot drawing. The wire obtained in the second round is then divided into four equal parts along the cross section, twisted again by a stranding machine, and subjected to three rounds of drawing until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 466 MPa, a yield strength of 370 MPa, a yield strength ratio of 0.794, an elongation of 7.3%, and a strength-ductility product of 3.40 GPa·%. The drawing temperature is 380-400°C, the drawing rate is 9-15 m / min, and the total deformation after three rounds of drawing is 75%.

[0124] S3, Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 850 ° C, the extrusion rate was 15 m / min, the extrusion die diameter was 3 mm and the diameter decreased by 0.5 mm each time. The whole process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -1 Pa, heating temperature 800℃, holding time 75min, and a TiAl alloy wire with a diameter of 1mm and uniform composition distribution were obtained; the TiAl alloy wire had a tensile strength of 698MPa, a yield strength of 649MPa, a yield strength ratio of 0.930, an elongation of 2.4%, and a strength-ductility product of 1.68GPa·%;

[0125] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0126] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -1 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -28kPa~+28kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0127] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 820°C. The high-frequency induction heating power is 28kW, the oscillation frequency is 120kHz, and the wire feeding speed is 10m / min.

[0128] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 90 kW, the oscillation frequency is 30 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 25 L / min and the side gas flow rate is 200 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 11 mPa·s;

[0129] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 14MPa, and the gas flow rate is 16m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0130] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 825 ppm), small particle size and a narrow distribution range (0-60 μm), sphericity ≥95%, a spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0131] Example 5

[0132] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: 53% Ti, 47% Al by mass percentage; the method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0133] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, three Ti wires and three Al wires, each with a diameter of 4 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 20 kHz and a power of 240 W to obtain surface-cleaned wire raw materials.

[0134] S2. Preparation of TiAl composite wire: The wire materials in S1 are tightly twisted together using a stranding machine and subjected to continuous multiple hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be three based on the uniformity of the TiAl composite wire. The obtained wire is then divided into four equal parts along the cross section, twisted again using a stranding machine, and then subjected to two rounds of hot drawing. The multiple-equal division-twisting-drawing process is then repeated until three rounds are completed to obtain a uniform TiAl composite wire. The uniform TiAl composite wire has a tensile strength of 542 MPa, a yield strength of 439 MPa, a yield strength ratio of 0.810, an elongation of 6.8%, and a strength-ductility product of 3.69 GPa·%; the drawing temperature is 450°C, the drawing rate is 18-20 m / min, and the total deformation after two rounds of drawing is 73%;

[0135] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 770°C, the extrusion rate was 10 m / min, the extrusion die diameter was 5 mm and the diameter decreased by 0.5 mm each time. The entire process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the TiAl alloy wire diameter, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -3 Pa, heating temperature is 680℃, holding time is 120min, and a TiAl alloy wire with a diameter of 2mm and uniform composition distribution is obtained; the tensile strength of the TiAl alloy wire is 670MPa, the yield strength is 626MPa, the yield strength ratio is 0.934, the elongation is 2%, and the strength-ductility product is 0.34GPa·%;

[0136] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0137] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -3 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -14kPa~+14kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0138] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 650°C. The high-frequency induction heating power is 17kW, the oscillation frequency is 70kHz, and the wire feeding speed is 7m / min.

[0139] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 75 kW, the oscillation frequency is 18 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13 L / min and the side gas flow rate is 110 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 29 mPa·s;

[0140] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 7MPa, and the gas flow rate is 9m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0141] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 202 ppm), small particle size and a narrow distribution range (0-60 μm), sphericity ≥95%, a spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0142] Example 6

[0143] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition of the TiAl alloy wire is as follows: Ti 52% and Al 48% by mass. The method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0144] S1. Selection and processing of wire raw materials: Based on the mass ratio of the target TiAl alloy wire components, six Ti wires and four Al wires, each with a diameter of 3 mm, were selected as wire raw materials. The wire raw materials were ultrasonically cleaned using commercially available cleaning agents at a frequency of 60 kHz and a power of 720 W to obtain surface-cleaned wire raw materials.

[0145] S2, preparation of TiAl composite wire: The wire raw materials in S1 are tightly twisted together by a stranding machine, and are subjected to continuous multiple-pass hot drawing. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 5 rounds based on the uniformity of the TiAl composite wire. The obtained wire is then divided into three equal parts along the cross section, and then twisted by a stranding machine, and then subjected to two rounds of hot drawing. The wire obtained in the second round is then divided into two equal parts along the cross section, and then twisted by a stranding machine, and then subjected to three rounds of drawing. Four and five rounds of drawing are performed according to this method until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 320 MPa, a yield strength of 252 MPa, a yield strength ratio of 0.788, an elongation of 7.4%, and a strength-ductility product of 2.37 GPa·%. The drawing temperature for the five rounds is 270-350°C, the drawing rate is 6-8 m / min, and the total deformation after the five rounds of drawing is 70%.

[0146] S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 was continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature was 900°C, the extrusion rate was 18 m / min, the extrusion die diameter was 4 mm and the diameter decreased by 0.2 mm each time. The entire process was automatically transmitted until the target pass was stopped. The extrusion target pass was related to the TiAl alloy wire diameter, the extrusion die diameter and the diameter reduction of each pass. The obtained wire was placed in a vacuum furnace for heating and heat preservation. The vacuum degree was 10 -2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with a diameter of 3mm and uniform composition distribution is obtained; the tensile strength of the TiAl alloy wire is 662MPa, the yield strength is 615MPa, the yield strength ratio is 0.929, the elongation is 2.2%, and the strength-ductility product is 1.46GPa·%;

[0147] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0148] S5. Gas system establishment: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the entire powder making system needs to be vacuumed to a vacuum degree of 10 -2 Pa, then fill in inert gas to establish a gas system, adjust the system pressure to -50kPa~+50kPa, the gas system is equipped with an oxygen detection device, and the oxygen content of the entire system is ≤20ppm;

[0149] S6. High-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5. The preheating temperature is 910°C. The high-frequency induction heating power is 42kW, the oscillation frequency is 225kHz, and the wire feeding speed is 20m / min.

[0150] S7, radio frequency plasma melting: The TiAl alloy wire preheated in S6 is sent to the radio frequency plasma high temperature area for radio frequency plasma melting treatment. The radio frequency plasma power of the radio frequency plasma melting treatment is 50 kW, the oscillation frequency is 8 MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10 L / min and the side gas flow rate is 150 L / min, to obtain low-viscosity TiAl alloy droplets; the viscosity of the TiAl alloy droplets is 62 Pa·s;

[0151] S8, atomization powder making: send the TiAl alloy droplets with low viscosity in S7 into the atomization reaction chamber for atomization reaction treatment, wherein the high-pressure gas flow is argon flow or helium flow, the gas purity is ≥99.999%, the pressure is 16MPa, and the gas flow rate is 19m 3 / min, and after cooling and solidification, fine, low-oxygen spherical TiAl alloy powder was obtained.

[0152] The fine low-oxygen spherical TiAl alloy powder obtained in this example has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 459 ppm), small particle size and a narrow distribution range (0-60 μm), sphericity ≥95%, a spheroidization rate of approximately 100%, and a 0-50 μm fine powder yield of ≥90%.

[0153] The above scheme, the present invention proposes a method for preparing fine low-oxygen spherical TiAl alloy powder, which can solve the problems of the existing powder making technology using TiAl alloy rods as raw materials and no crucible for holding titanium liquid, resulting in high droplet viscosity and coarse powder particle size during the preparation process, as well as other quality problems such as poor sphericity of the prepared powder, wide particle size distribution, high impurity content, hollow powder, etc.; at the same time, it also solves the problem of low preparation efficiency caused by the complex preparation of raw material rods and slow melting rate of rods in the existing powder making technology.

[0154] The present invention is not limited to the preparation of spherical TiAl alloy powder, but is also applicable to the preparation of spherical Ti-Al-Nb alloy powder, spherical Ti-Al-V alloy powder, spherical Ti-Cu alloy powder, spherical Ti-Ni alloy powder, spherical Ti-Fe alloy powder and spherical Ti-Mo alloy powder, etc., and has no special restrictions on the raw material brand, composition, etc., and can be freely adjusted according to the target composition. The range of optional raw materials is wide, and additive manufacturing can prepare a large number of complex shapes and different compositions of titanium alloys, which is conducive to large-scale industrial production and commercial promotion and application.

[0155] The present invention utilizes the good room temperature plasticity of a single metal wire, adopts the alloy single metal wire to be compounded, and forms a tight spiral structure with two or more of the aforementioned single metal wires through a twisting method. Combined with a multi-pass continuous warm drawing process, the pre-alloying of the alloy single metal to be compounded can be achieved at a relatively low temperature. Compared with the TiAl alloy rods used in the existing powder preparation method, the present invention is convenient to operate and low in cost, and can be applied to the additive manufacturing of alloys with complex shapes with different performance requirements; in particular, the thinner wire raw materials are easier to melt during the powder making process, the formed molten droplets have low viscosity, the atomization and dispersion effect is good, and the powder obtained has a fine particle size.

[0156] The present invention combines high-frequency induction heating with radio frequency plasma to achieve segmented continuous heating of TiAl alloy wire. Compared with single induction heating or plasma heating, it can effectively accelerate the melting rate of raw materials, reduce the viscosity of molten droplets, and improve the wire feeding speed and powder yield. The high-temperature plasma can ensure that the molten droplets have high superheat and low viscosity, and use high-pressure gas atomization to atomize low-viscosity TiAl droplets into fine droplets, which are condensed and spheroidized under the action of surface tension. The obtained spherical TiAl alloy powder has a small particle size, good sphericity, high spheroidization rate, no hollow powder, and high yield.

[0157] The present invention uses specially prepared TiAl alloy wire with uniform composition distribution as raw material, replacing the traditional radio frequency plasma powder as raw material. This replacement can effectively reduce the oxidation of the raw material and the adsorption of impurities, and reduce the oxygen content and impurity content of the powder product, thereby obtaining low-oxygen and high-purity spherical TiAl alloy powder with uniform composition distribution.

[0158] The entire powder making process of the present invention is carried out under the protection of inert gas, the oxygen content of the entire gas system is ≤20ppm, and the radio frequency plasma equipment used does not have electrode pollution, ensuring that the prepared spherical TiAl alloy powder is pollution-free and free of inclusions.

[0159] The present invention further disperses the molten droplets after radio frequency plasma atomization through the high-pressure airflow of the atomizing nozzle, thereby avoiding the generation of coarse particle ball powder, ensuring a high fine powder yield of the spherical TiAl alloy powder, high sphericity, and narrow particle size distribution, and avoiding the large-scale generation of hollow balls.

[0160] The fine low-oxygen spherical TiAl alloy powder prepared by the present invention has a small particle size (0-60 μm), a smooth surface, high sphericity, good fluidity, no hollow powder, a low impurity content (oxygen content ≤ 1000 ppm), and high production efficiency. It can improve the performance of TiAl alloy products in injection molding and additive manufacturing while reducing their raw material costs.

[0161] The tensile strength, yield strength and yield strength ratio of the TiAl alloy wire prepared by the present invention gradually increase as the process progresses, and the tensile strength can reach about 700 MPa, and the maximum can approach 720 MPa; similarly, the yield strength ratio is above 0.9, and the maximum can approach 0.94.

[0162] In summary, compared with other traditional methods, the method of the present invention can directly prepare TiAl alloy wires with uniform composition distribution at a lower temperature through multiple wire twisting, multiple continuous hot drawing, diffusion homogenization annealing, high-frequency induction preheating, radio frequency plasma melting and atomization powder making, and then prepare TiAl alloy fine powder with low oxygen content and uniform composition distribution. It is suitable for additive manufacturing, has high flexibility, simple operation, wide applicability, low cost, and is very suitable for large-scale industrial production.

[0163] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0164] In this disclosure, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0165] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0166] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing fine low-oxygen spherical TiAl alloy powder, characterized in that: The preparation method of the fine low-oxygen spherical TiAl alloy powder comprises the following steps: S1. Selection and processing of wire raw materials: According to the composition and mass ratio of the target TiAl alloy wire, a plurality of Ti wires and a plurality of Al wires are selected as wire raw materials; and the wire raw materials are ultrasonically cleaned using commercially available cleaning agents to obtain wire raw materials with clean surfaces; S2, Preparation of TiAl Composite Wire: The wire materials in S1 are tightly twisted together using a stranding machine and subjected to continuous multiple hot drawing. After the first round of hot drawing, the obtained wires are divided into multiple equal parts along the cross section, twisted again using a stranding machine, and then subjected to a second round of hot drawing. The dividing-twisting-drawing process is then repeated until a uniform TiAl composite wire is obtained. S3. Preparation of TiAl alloy wire: The TiAl composite wire prepared in S2 is continuously drawn and extruded through a continuous wire drawing machine. The entire process is automatically conveyed until the target pass is stopped. The target extrusion pass is related to the diameter of the TiAl alloy wire, the diameter of the extrusion die, and the amount of diameter reduction per pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation to obtain TiAl alloy wire; S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface; S5. Establishment of gas system: RF plasma combined with gas atomization powder making equipment is used for powder making. Before powder making, the entire powder making system needs to be evacuated, then filled with inert gas to establish the gas system, and the system pressure is adjusted; S6, high-frequency induction preheating: The TiAl alloy wire whose surface has been cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain a preheated TiAl alloy wire; S7, radio frequency plasma melting: sending the TiAl alloy wire preheated in S6 to the radio frequency plasma high temperature area for radio frequency plasma melting treatment to obtain TiAl alloy droplets with low viscosity; S8, atomization powder making: the TiAl alloy droplets with low viscosity in S7 are sent into the atomization reaction chamber for atomization reaction treatment, and fine low-oxygen spherical TiAl alloy powder is obtained after cooling and solidification.

2. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The wire material in S1 uses existing brands of wire, or customized design and composition adjustment; the wire material diameter is 1-5mm; the frequency of ultrasonic cleaning is 20-60kHz, and the power is 240-720W.

3. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The speed of the stranding machine in S2 is greater than 500 rpm, and the length of the stranded wire after stranding is 70-90% of the wire raw material; the continuous multi-pass hot drawing is specifically as follows: the drawing temperature is 250-500°C, the drawing rate is 5-30 m / min, the total number of drawing passes is 2-10 rounds depending on the uniformity of the TiAl composite wire, and the total deformation of the multi-pass drawing is 20-90%; the uniform TiAl composite wire has a tensile strength of 100-700 MPa, a yield strength of 50-600 MPa, and an elongation of 6-30%.

4. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The extrusion rate of continuous drawing extrusion in S3 is 1-20m / min, and the vacuum degree of the vacuum furnace is 10 -1 ~10 -3 Pa, the diameter of the prepared TiAl alloy wire is 0.8-5 mm, and the diameter decreases by 0.2-1 mm until the target pass stops; The heating and heat preservation process is heating to 600-900° C. and keeping the temperature for 60-120 minutes. The tensile strength of the TiAl alloy wire is 400-750 MPa, the yield strength is 300-650 MPa, and the elongation is 3-10%.

5. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: After S5 is evacuated, the vacuum degree is 10 -1 ~10 -3 Pa, adjust the system pressure to -55kPa~+55kPa, the gas system has its own oxygen detection device, and the oxygen content of the entire system is ≤20ppm.

6. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The preheating temperature of the preheating treatment in S6 is 500-900°C, the wire feeding speed is 1-20m / min; the high-frequency induction heating power is 10-50kW, and the oscillation frequency is 30-250kHz.

7. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The RF plasma power of the RF plasma melting treatment in S7 is 30-100kW, the oscillation frequency is 2-150MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, the main gas flow rate is 10-50L / min, and the side gas flow rate is 100-300L / min; the viscosity of the TiAl alloy droplet is 10-100mPa·s.

8. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The high-pressure gas flow for atomization reaction treatment in S8 is argon or helium, with a gas purity of ≥99.999%, a pressure of 5-20 MPa, and a gas flow rate of 4-20 m 3 / min.

9. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The oxygen content of the fine low-oxygen spherical TiAl alloy powder in S8 is ≤1000ppm, the powder particle size is 0-60μm, the sphericity is ≥95%, the spheroidization rate is about 100%, and the 0-50μm fine powder recovery rate is ≥90%.

10. The method for preparing fine low-oxygen spherical TiAl alloy powder according to claim 1, characterized in that: The preparation method described in S1-S8 is not only applicable to TiAl alloys, but also to Ti-Al-Nb alloys, Ti-Al-V alloys, Ti-Cu alloys, Ti-Ni alloys, Ti-Fe alloys and Ti-Mo alloys.

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