Preparation method of micro low-oxygen spherical TiAl alloy powder

Abstract

The invention provides a preparation method of micro low-oxygen spherical TiAl alloy powder, and relates to the technical field of spherical titanium-based alloy powder. The preparation method comprises the steps of raw material selection and treatment of a wire material, preparation of a TiAl composite wire, preparation of a TiAl alloy wire, treatment of the TiAl alloy wire, establishment of a gas system, high-frequency induction preheating, radio frequency plasma smelting and atomization powder preparation which are sequentially carried out. According to the method, through multiple wire twisting, multiple continuous hot drawing, diffusion homogenization annealing, high-frequency induction preheating, radio frequency plasma smelting and atomization powder preparation, the TiAl alloy wire with the evenly-distributed components can be directly prepared at the low temperature, then the TiAl alloy fine powder with the low oxygen content and the evenly-distributed components is prepared, the TiAl alloy fine powder is suitable for additive manufacturing, and the method is suitable for being used for additive manufacturing. The method is high in flexibility, simple to operate, wide in application, low in cost and 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 0-25μm) and additive manufacturing (powder 15-53μm), the performance of the finished product depends largely on the TiAl alloy powder raw material. Generally speaking, the powder raw material for manufacturing high-performance finished products should have high sphericity, fluidity, purity, low hollow rate and fine powder particle size. Due to the room temperature brittleness of TiAl alloy, there are still technical bottlenecks in the preparation of TiAl alloy wire, and it is easy to react with other substances at high temperatures. Therefore, the preparation of spherical TiAl alloy powder mainly uses rods as raw materials and adopts non-contact melting, such as plasma rotating electrode (PREP) method, electrode induction melting gas atomization (EIGA) method, etc.

[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 then is thrown out under the action of high-speed rotating centrifugal force to form fine droplets. The small droplets are quickly cooled and solidified into spherical powders under the action of surface tension. However, TiAl alloy is an intermetallic compound with poor plasticity, so it is very easy for the rod to crack during the powder making process. In addition, TiAl alloy itself has poor thermal conductivity, the solidification speed of the molten droplet 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 20000r / min, which makes the centrifugal force of the molten droplet dispersion atomization smaller, and the viscosity of the molten droplet 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 materials, and uses high-frequency induction current to melt the surface of the rods and form a molten liquid flow that falls into the atomizing nozzle. Under the action of high-speed airflow, dispersed molten droplets are formed and quickly cooled and solidified into fine particles. Compared with the PREP method, the powder particle size produced by the EIGA method is finer, but the fine powder yield that meets the requirements of injection molding and additive manufacturing is low, less than 40%. In addition, the TiAl alloy droplets after induction melting will leave the high-temperature zone too quickly, resulting in insufficient temperature and time during the gas atomization condensation process to ensure that the droplets shrink into balls under the action of surface tension. The sphericity of the powder produced is low, and hollow balls are easily produced.

[0005] Chinese patent CN114309621A discloses a method for preparing fine TiAl alloy spherical powder containing refractory metal elements, which uses TiH2, Al and MHx as main raw materials, performs high-energy ball milling in a hydrogen atmosphere, and feeds the ground materials into an inductively coupled plasma torch for dehydrogenation, melting, and alloying and spheroidization to obtain alloy spherical powder. Obviously, this method has a complex device structure and is difficult to operate. It requires multiple powder making 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 method for preparing low-cost fine-grained low-oxygen titanium and titanium alloy powders, which 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 hydrogenated titanium 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 sphericity of the alloy powder finally obtained is not high, the surface is not smooth, and the powder particle size range is wide.

[0007] Chinese patent CN116984605A discloses a method for preparing a gas atomized TiAl alloy powder for additive manufacturing, wherein the key to improving the quality of the powder lies in the quality of the smelted rod for preparing the powder, and the smelted rod is prepared by a complex method using a gas atomized TiAl alloy of selected composition whose particle size is not suitable for powder, requiring forging and hot isostatic pressing. The composition distribution of the smelted rod prepared by these methods is not uniform, as is the composition of the heated molten alloy liquid, and even more so the prepared powder.

[0008] In addition to the above problems, the PREP and EIGA methods also have limitations in preparing TiAl alloy spherical powders, such as complex raw material bar preparation, slow melting rate, low powder yield, and electrode contamination. Therefore, it is urgent to invent a method for preparing high-quality and high-yield fine TiAl alloy spherical powders to meet the requirements of high-performance complex shape near-net forming of existing TiAl alloys. Summary of the invention

[0009] In order to solve the problem that the TiAl alloy powder for additive manufacturing in the prior art has poor plasticity at room temperature and cannot be drawn, most of the current powder making technologies can only use TiAl alloy rods as raw materials. However, the existing powder making technology does not have a crucible for holding titanium liquid, which leads to low superheat of TiAl alloy liquid, resulting in high viscosity of TiAl alloy droplets, which in turn leads to poor atomization or rotation dispersion effect, and the powder particle size after cooling is coarse, which is suitable for injection molding, additive manufacturing, etc. The fine powder yield rate does not exceed 40%, and 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 raw material rod preparation is complex, the rod melting rate is slow, and other problems also make the powder yield low and the production cost high. Therefore, the embodiment of the present invention provides a method for preparing a fine low-oxygen spherical TiAl alloy powder with a small particle size (0-60μm), a smooth surface, a high sphericity, good fluidity, no hollow powder, a 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 raw materials for wire: according to the mass ratio of the components of the target TiAl alloy wire, select a plurality of corresponding Ti wires and a plurality of Al wires as wire raw materials; and use commercially available cleaning agents to ultrasonically clean the wire raw materials to obtain wire raw materials with clean surfaces;

[0012] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and hot-drawn continuously for multiple times. After the first round of hot-drawing, the obtained wire is divided into multiple equal parts along the cross section, twisted by a twisting machine, and then hot-drawn for the second time, and then the process of dividing into multiple equal parts-twisting-drawing is 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, and the whole process is automatically transmitted until the target pass is stopped. The extrusion target 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 the TiAl alloy wire;

[0014] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned on the surface 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: adopt radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated, and then filled with inert gas to establish the gas system and adjust the system pressure.

[0016] S6, high-frequency induction preheating: the TiAl alloy wire whose surface is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain the 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 uses existing brands of wire, or a customized design is performed to adjust the composition; the diameter of the wire material is 1-5 mm; the frequency of ultrasonic cleaning is 20-60 kHz, and the power is 240-720 W.

[0020] Optionally, the speed of the stranding machine in S2 is greater than 500rmp, 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: the drawing temperature is 250-500°C, the drawing rate is 5-30m / min, and according to the uniformity of the TiAl composite wire, the total number of drawing passes is 2-10 rounds, and the total deformation of the multi-pass drawing is 20-90%; the tensile strength of the uniform TiAl composite wire is 100-700MPa, the yield strength is 50-600MPa, and the elongation is 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 by 0.2-1mm gradually 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 whole 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 30-100kW, the oscillation frequency is 2-150MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and 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.

[0025] Optionally, the high-pressure gas flow for the atomization reaction treatment in S8 is an argon gas flow or a helium gas flow, the gas purity is ≥99.999%, the pressure is 5-20 MPa, and the gas flow rate is 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 the 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 selectable raw materials is wide, and additive manufacturing can prepare more complex shapes of titanium alloys with different compositions, 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 a single metal wire of the alloy to be compounded, and forms a tight spiral structure with two or more of the single metal wires through a twisting method. Combined with a multi-pass continuous warm drawing process, the pre-alloying of the single metal alloy 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 has a low cost, and can be applied to the additive manufacturing of alloys with complex shapes with different performance requirements; in particular, thinner wire raw materials are easier to melt during the powder making process, the formed molten droplets have a low viscosity, the atomization and dispersion effect is good, and the obtained powder 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, the present invention 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 fine 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 component distribution as raw material, replacing the traditional radio frequency plasma with 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 component 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, thereby ensuring that the prepared spherical TiAl alloy powder is pollution-free and free of inclusions.

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

[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, a high sphericity, good fluidity, no hollow powder, a low impurity content (oxygen content ≤ 1000 ppm), and a high production efficiency. It can improve the performance of injection molding and additive manufacturing TiAl alloy finished products 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 700MPa, and the maximum can be close to 720MPa; similarly, the yield strength ratio is above 0.9, and the maximum can be close to 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 "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0043] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express are the same. "of", "corresponding" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they want to express 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 more clear, 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 comprises the following steps:

[0047] S1. Selection and processing of raw materials for wire: according to the mass ratio of the components of the target TiAl alloy wire, select a plurality of corresponding Ti wires and a plurality of Al wires as wire raw materials; and use commercially available cleaning agents to ultrasonically clean the wire raw materials to obtain wire raw materials with clean surfaces;

[0048] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and hot-drawn continuously for multiple times. After the first round of hot-drawing, the obtained wire is divided into multiple equal parts along the cross section, twisted by a twisting machine, and then hot-drawn for the second time, and then the process of dividing into multiple equal parts-twisting-drawing is 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, and the whole process is automatically transmitted until the target pass is stopped. The extrusion target 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 the TiAl alloy wire;

[0050] S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned on the surface 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: adopt radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated, and then filled with inert gas to establish the gas system and adjust the system pressure.

[0052] S6, high-frequency induction preheating: the TiAl alloy wire whose surface is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain the 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 customizes the design and composition; 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 speed of the stranding machine in S2 is greater than 500rmp, 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: the drawing temperature is 250-500°C, the drawing rate is 5-30m / min, and according to the uniformity of the TiAl composite wire, the total number of drawing passes is 2-10 rounds, and the total deformation of the multi-pass drawing is 20-90%; the tensile strength of the uniform TiAl composite wire is 100-700MPa, the yield strength is 50-600MPa, and the elongation is 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 by 0.2-1mm gradually 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 after evacuation 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 whole 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%, and 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 an argon gas flow or a helium gas flow, the gas purity is ≥99.999%, the pressure is 5-20MPa, and the gas flow rate is 4-20m 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 content of the TiAl alloy wire is as follows: Ti 52%, Al 48% by mass percentage; the method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0066] S1. Selection and processing of raw materials for wires: According to the mass ratio of the target TiAl alloy wire components, 5 Ti wires and 5 Al wires with a diameter of 2 mm were selected as raw materials for wires; and commercially available cleaning agents were used to ultrasonically clean the raw materials for wires, respectively, at a frequency of 40 kHz and a power of 360 W to obtain raw materials for wires with clean surfaces;

[0067] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and continuous multiple hot drawing is performed. After the first round of hot drawing, the total number of hot drawing rounds is determined to be 2 according to the uniformity of the TiAl composite wire, and then the obtained wire is divided into four equal parts along the cross section, and then twisted by a twisting machine, and then two rounds of hot drawing are performed, and then the multiple division-twisting-drawing process is repeated until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 315MPa, a yield strength of 252MPa, a yield strength ratio of 0.800, an elongation of 7%, and a strength-ductility product of 2.21GPa·%; wherein the drawing temperature is 380-400℃, the drawing rate is 9-15m / 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 is continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature is 850°C, the extrusion rate is 15m / min, the extrusion die diameter is 3mm and the diameter decreases by 0.5mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10 -1 Pa, heating temperature is 800℃, holding time is 75min, and a TiAl alloy wire with uniform composition distribution and a diameter of 1mm is obtained; the tensile strength of the TiAl alloy wire is 668MPa, the yield strength is 621MPa, the yield strength ratio is 0.930, the elongation is 5%, and the strength-ductility product is 3.34GPa·%;

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

[0070] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, the preheating temperature is 600°C, and the preheated TiAl alloy wire is obtained; wherein, 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 80kW, the oscillation frequency is 20MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13L / min, the side gas flow rate is 110L / min, and low-viscosity TiAl alloy droplets are obtained; the viscosity of the TiAl alloy droplets is 15mPa·s;

[0073] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

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

[0075] Example 2

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

[0077] S1. Selection and processing of raw materials for wire: According to the mass ratio of the target TiAl alloy wire, 6 Ti wires and 4 Al wires with a diameter of 3 mm were selected as raw materials for wire; and the raw materials for wire were ultrasonically cleaned with commercially available cleaning agents, with a frequency of 60 kHz and a power of 720 W to obtain raw materials for wire with clean surfaces;

[0078] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and continuous multiple hot drawing is performed. 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, and then the obtained wire is divided into three equal parts along the cross section, and then twisted by a twisting machine, and then two rounds of hot drawing are performed, and then the wire obtained in the second round is divided into four equal parts along the cross section, and then twisted by a twisting machine, and then three rounds of drawing are performed. Four 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 447MPa, a yield strength of 366MPa, a yield strength ratio of 0.819, an elongation of 7%, and a strength-ductility product of 3.13GPa·%; wherein the drawing temperature is 270-350℃, the drawing rate is 6-8m / 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 is continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature is 900°C, the extrusion rate is 18m / min, the extrusion die diameter is 4mm and the diameter decreases by 0.2mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10 -2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with uniform composition distribution and a diameter of 3mm 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 on the surface with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0081] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, the preheating temperature is 800°C, and the preheated TiAl alloy wire is obtained; wherein, 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 90kW, the oscillation frequency is 30MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 25L / min, the side gas flow rate is 200L / min, and a TiAl alloy droplet with low viscosity is obtained; the viscosity of the TiAl alloy droplet is 38mPa·s;

[0084] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

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

[0086] Comparative Example 1

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

[0088] S1. Selection and processing of raw materials for wires: According to the mass ratio of the target TiAl alloy wire components, 5 Ti wires and 5 Al wires with a diameter of 2 mm were selected as raw materials for wires; and commercially available cleaning agents were used to ultrasonically clean the raw materials for wires, respectively, at a frequency of 40 kHz and a power of 360 W to obtain raw materials for wires with clean surfaces;

[0089] S2. Preparation of TiAl composite wire: The wire materials in S1 are tightly twisted together by a stranding machine, and are continuously hot-drawn for multiple passes to obtain TiAl composite wire. The tensile strength of the TiAl composite wire is 310 MPa, the yield strength is 232 MPa, the yield strength ratio is 0.748, the elongation is 10%, and the strength-ductility product is 3.10 GPa·%; wherein the drawing temperature is 380°C, the drawing rate is 9 m / min, and the total deformation after drawing is 60%;

[0090] 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 wire drawing machine temperature is 850°C, the extrusion rate is 15m / min, the extrusion die diameter is 3mm and the diameter decreases by 0.5mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 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 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 on the surface with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0092] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 whole system is >20ppm;

[0093] S6, high-frequency induction preheating: the TiAl alloy wire whose surface is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, and the preheating temperature is 600°C; wherein, 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 80kW, the oscillation frequency is 20MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13L / min, the side gas flow rate is 110L / min, and low-viscosity TiAl alloy droplets are obtained; the viscosity of the TiAl alloy droplets is 15mPa·s;

[0095] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is 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), but due to insufficient continuous warm drawing passes in the preparation process 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 fine spherical TiAl alloy powder obtained has a high impurity content (oxygen content is 2483ppm).

[0097] Comparative Example 2

[0098] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition content of the TiAl alloy wire is as follows: Ti 53%, Al 47% 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 raw materials for wire: According to the mass ratio of the target TiAl alloy wire, 6 Ti wires and 4 Al wires with a diameter of 3 mm were selected as raw materials for wire; and the raw materials for wire were ultrasonically cleaned with commercially available cleaning agents, with a frequency of 60 kHz and a power of 720 W to obtain raw materials for wire with clean surfaces;

[0100] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and continuous multiple hot drawing is performed. 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, and then the obtained wire is divided into three equal parts along the cross section, and then twisted by a twisting machine, and then two rounds of hot drawing are performed, and then the wire obtained in the second round is divided into four equal parts along the cross section, and then twisted by a twisting machine, and then three rounds of drawing are performed. Four 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 447MPa, a yield strength of 366MPa, a yield strength ratio of 0.819, an elongation of 7%, and a strength-ductility product of 3.13GPa·%; wherein the drawing temperature is 270-350℃, the drawing rate is 6-8m / 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 is continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature is 900°C, the extrusion rate is 18m / min, the extrusion die diameter is 4mm and the diameter decreases by 0.2mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10-2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with uniform composition distribution and a diameter of 3mm 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 on the surface with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0103] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, and the preheating temperature is 300°C; wherein, 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, the side gas flow rate is 90L / min, and low-viscosity TiAl alloy droplets are obtained; 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 gas flow or helium gas 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 is obtained after cooling and solidification.

[0107] The spherical TiAl alloy powder obtained in this comparative example has a low impurity content (oxygen content is 382ppm), but due to the low high-frequency induction pretreatment temperature and radio frequency melting power, the superheat of the TiAl alloy droplets is insufficient, the viscosity of the molten droplets is too large, the particle size of the obtained TiAl alloy powder is relatively coarse (~200μm), and the recovery rate of 0-50μm 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 component segregation in the fine low-oxygen spherical TiAl alloy powder; the control of the impurity content of the system directly affects the impurity content of the final spherical TiAl alloy powder; 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 content of the TiAl alloy wire is as follows: Ti 54%, Al 46% by mass percentage; the method for preparing the fine low-oxygen spherical TiAl alloy powder comprises the following steps:

[0111] S1. Selection and processing of raw materials for wires: According to the mass ratio of the target TiAl alloy wire components, three Ti wires and three Al wires with a diameter of 4 mm were selected as raw materials for wires; and commercially available cleaning agents were used to ultrasonically clean the raw materials for wires, respectively, at a frequency of 20 kHz and a power of 240 W to obtain raw materials for wires with clean surfaces;

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

[0113] 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 wire drawing machine temperature is 770°C, the extrusion rate is 10 m / min, the extrusion die diameter is 5 mm and the diameter decreases by 0.5 mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 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 tensile strength of the TiAl alloy wire is 711MPa, the yield strength is 645MPa, the yield strength ratio is 0.907, the elongation is 8%, and the strength-ductility product is 5.69GPa·%;

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

[0115] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, the preheating temperature is 900°C, and the preheated TiAl alloy wire is obtained; wherein, 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 50kW, the oscillation frequency is 8MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10L / min, the side gas flow rate is 150L / min, and low-viscosity TiAl alloy droplets are obtained; the viscosity of the TiAl alloy droplets is 50mPa·s;

[0118] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

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

[0120] Example 4

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

[0122] S1. Selection and processing of raw materials for wires: According to the mass ratio of the target TiAl alloy wire components, 5 Ti wires and 5 Al wires with a diameter of 2 mm were selected as raw materials for wires; and the raw materials for wires were ultrasonically cleaned using commercially available cleaning agents, with a frequency of 60 kHz and a power of 720 W to obtain raw materials for wires with clean surfaces;

[0123] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and continuous multiple hot drawing is performed. 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, and then the obtained wire is divided into two equal parts along the cross section, and then twisted by a twisting machine, and then two rounds of hot drawing are performed, and then the wire obtained in the second round is divided into four equal parts along the cross section, and then twisted by a twisting machine, and then three rounds of drawing are performed until a uniform TiAl composite wire is obtained. The uniform TiAl composite wire has a tensile strength of 466MPa, a yield strength of 370MPa, a yield strength ratio of 0.794, an elongation of 7.3%, and a strength-ductility product of 3.40GPa·%; wherein the drawing temperature is 380-400°C, the drawing rate is 9-15m / 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 is continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature is 850°C, the extrusion rate is 15m / min, the extrusion die diameter is 3mm and the diameter decreases by 0.5mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10 -1 Pa, heating temperature is 800℃, holding time is 75min, and a TiAl alloy wire with uniform composition distribution and a diameter of 1mm is obtained; the tensile strength of the TiAl alloy wire is 698MPa, the yield strength is 649MPa, the yield strength ratio is 0.930, the elongation is 2.4%, and the strength-ductility product is 1.68GPa·%;

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

[0126] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, and the preheating temperature is 820°C; wherein, 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 90kW, the oscillation frequency is 30MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 25L / min, the side gas flow rate is 200L / min, and a TiAl alloy droplet with low viscosity is obtained; the viscosity of the TiAl alloy droplet is 11mPa·s;

[0129] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

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

[0131] Example 5

[0132] A method for preparing fine low-oxygen spherical TiAl alloy powder, wherein the composition content of the TiAl alloy wire is as follows: Ti 53%, Al 47% 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 raw materials for wires: According to the mass ratio of the target TiAl alloy wire components, three Ti wires and three Al wires with a diameter of 4 mm were selected as raw materials for wires; and commercially available cleaning agents were used to ultrasonically clean the raw materials for wires, respectively, at a frequency of 20 kHz and a power of 240 W to obtain raw materials for wires with clean surfaces;

[0134] S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and continuous multiple hot drawing is performed. 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, and then the obtained wire is divided into four equal parts along the cross section, and then twisted by a twisting machine, and then two rounds of hot drawing are performed, and then the multi-equal division-twisting-drawing process is repeated until the three rounds are completed to obtain a uniform TiAl composite wire. The uniform TiAl composite wire has a tensile strength of 542MPa, a yield strength of 439MPa, a yield strength ratio of 0.810, an elongation of 6.8%, and a strength-ductility product of 3.69GPa·%; wherein the drawing temperature is 450°C, the drawing rate is 18-20m / 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 is continuously drawn and extruded through a continuous wire drawing machine. The wire drawing machine temperature is 770°C, the extrusion rate is 10 m / min, the extrusion die diameter is 5 mm and the diameter decreases by 0.5 mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10 -3 Pa, heating temperature is 680℃, holding time is 120min, and a TiAl alloy wire with uniform composition distribution and a diameter of 2mm 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 .34GPa·%;

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

[0137] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, and the preheating temperature is 650°C; wherein, 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 75kW, the oscillation frequency is 18MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 13L / min, the side gas flow rate is 110L / min, and low-viscosity TiAl alloy droplets are obtained; the viscosity of the TiAl alloy droplets is 29mPa·s;

[0140] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

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

[0142] Example 6

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

[0144] S1. Selection and processing of raw materials for wire: According to the mass ratio of the target TiAl alloy wire, 6 Ti wires and 4 Al wires with a diameter of 3 mm were selected as raw materials for wire; and the raw materials for wire were ultrasonically cleaned with commercially available cleaning agents, with a frequency of 60 kHz and a power of 720 W to obtain raw materials for wire with clean surfaces;

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

[0146] 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 wire drawing machine temperature is 900°C, the extrusion rate is 18m / min, the extrusion die diameter is 4mm and the diameter decreases by 0.2mm each time. The whole process is automatically transmitted until the target pass stops. The extrusion target pass is related to the diameter of the TiAl alloy wire, the extrusion die diameter and the diameter reduction of each pass. The obtained wire is placed in a vacuum furnace for heating and heat preservation. The vacuum degree is 10 -2 Pa, heating temperature is 750℃, holding time is 100min, and a TiAl alloy wire with uniform composition distribution and a diameter of 3mm 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 on the surface with a commercially available cleaning agent to remove oxide scale and impurities, thereby obtaining a TiAl alloy wire with a clean surface;

[0148] S5. Establishment of gas system: Use radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated 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 is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5, and the preheating temperature is 910°C; wherein, 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 50kW, the oscillation frequency is 8MHz, the inert gas is argon or helium, the gas purity is ≥99.999%, and the main gas flow rate is 10L / min, the side gas flow rate is 150L / min, and low-viscosity TiAl alloy droplets are obtained; the viscosity of the TiAl alloy droplets is 62Pa·s;

[0151] S8, atomization powder making: S7 low viscosity TiAl alloy droplets are sent into the atomization reaction chamber for atomization reaction treatment, wherein the high pressure gas flow is argon gas flow or helium gas 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 is obtained.

[0152] The fine low-oxygen spherical TiAl alloy powder obtained in this embodiment has a smooth surface, high sphericity, good fluidity, no hollow powder, low impurity content (oxygen content is 459ppm), small particle size and narrow distribution range (0-60μm), sphericity ≥95%, spheroidization rate of about 100%, and 0-50μm fine powder recovery rate ≥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 the 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 selectable raw materials is wide, and additive manufacturing can prepare more complex shapes of titanium alloys with different compositions, 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 a single metal wire of the alloy to be compounded, and forms a tight spiral structure with two or more of the single metal wires through a twisting method. Combined with a multi-pass continuous warm drawing process, the pre-alloying of the single metal alloy 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 has a low cost, and can be applied to the additive manufacturing of alloys with complex shapes with different performance requirements; in particular, thinner wire raw materials are easier to melt during the powder making process, the formed molten droplets have a low viscosity, the atomization and dispersion effect is good, and the obtained powder 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, the present invention 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 fine 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 component distribution as raw material, replacing the traditional radio frequency plasma with 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 component 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, thereby ensuring that the prepared spherical TiAl alloy powder is pollution-free and free of inclusions.

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

[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, a high sphericity, good fluidity, no hollow powder, a low impurity content (oxygen content ≤ 1000 ppm), and a high production efficiency. It can improve the performance of injection molding and additive manufacturing TiAl alloy finished products 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 700MPa, and the maximum can be close to 720MPa; similarly, the yield strength ratio is above 0.9, and the maximum can be close to 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" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0164] In the present invention, "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 items or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[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 is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope 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 raw materials for wire: according to the mass ratio of the components of the target TiAl alloy wire, select a plurality of corresponding Ti wires and a plurality of Al wires as wire raw materials; and use commercially available cleaning agents to ultrasonically clean the wire raw materials to obtain wire raw materials with clean surfaces; S2, preparation of TiAl composite wire: the wire raw materials in S1 are tightly twisted together by a twisting machine, and hot-drawn continuously for multiple times. After the first round of hot-drawing, the obtained wire is divided into multiple equal parts along the cross section, twisted by a twisting machine, and then hot-drawn for the second time, and then the process of dividing into multiple equal parts-twisting-drawing is 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, and the whole process is automatically transmitted until the target pass is stopped. The extrusion target 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 the TiAl alloy wire; S4. Treatment of TiAl alloy wire: The TiAl alloy wire prepared in S3 is cleaned on the surface 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: adopt radio frequency plasma combined with gas atomization powder making equipment for powder making. Before powder making, the whole powder making system needs to be evacuated, and then filled with inert gas to establish the gas system and adjust the system pressure. S6, high-frequency induction preheating: the TiAl alloy wire whose surface is cleaned in S4 is preheated by the high-frequency induction heating equipment adjusted in S5 to obtain the 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 customizes the design and composition; 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 500rmp, 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 5-30m / min, and the total number of drawing passes is 2-10 rounds according to the uniformity of the TiAl composite wire, and the total deformation of the multi-pass drawing is 20-90%; the tensile strength of the uniform TiAl composite wire is 100-700MPa, the yield strength is 50-600MPa, and the elongation is 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 0.8-5mm, and the diameter decreases by 0.2-1mm until the target pass stops; The heating and heat preservation is heating to 600-900°C and keeping the temperature 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%.

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 whole 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%, and 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 5-20MPa, and a gas flow rate of 4-20m 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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