A low-cost preparation method and application of high-quality gamma-TiAl alloy powder

Abstract

This invention belongs to the field of titanium alloy powder preparation technology, and relates to a low-cost method for preparing high-quality γ-TiAl alloy powder and its application. The method includes the following steps: Step 1: In an electrode block pressing mold, pure aluminum is distributed on both the upper and lower sides of the raw material for pressing into a γ-TiAl alloy electrode block. The raw material includes HTi particles. Step 2: The γ-TiAl alloy electrode block is welded into a consumable electrode, and the consumable electrode is repeatedly melted to obtain a γ-TiAl alloy ingot. Step 3: The γ-TiAl alloy ingot is machined to obtain a powder-making rod; the rod is then subjected to plasma rotating electrode atomization to obtain γ-TiAl alloy powder. This method can promote the full alloying of various raw materials during the VAR melting process, preventing the formation of infusible substances from HTi and other high-melting-point elements.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy powder preparation technology, and relates to a low-cost preparation method and application of high-quality γ-TiAl alloy powder. Background Technology

[0002] γ-TiAl alloy is a lightweight, high-temperature structural material that combines high specific strength, high specific stiffness, and excellent creep and oxidation resistance. Within the service temperature range of 650℃ to 900℃, this alloy, with its near-high-temperature alloy performance and low density, is gradually replacing high-temperature alloys in the aerospace field to achieve component lightweighting. It has already been successfully applied to low-pressure turbine blades in several advanced international aero engines. Notably, the GE9X engine on the Boeing 777 MAX was the first to use electron beam additive manufacturing technology to produce γ-TiAl alloy low-pressure turbine blades (the traditional process is precision casting). This breakthrough has greatly promoted research and industrial development in the field of γ-TiAl alloy additive manufacturing, and the market demand for high-quality, low-cost γ-TiAl alloys continues to rise.

[0003] Currently, the mainstream methods for preparing γ-TiAl alloy powders include plasma rotating electrode atomization (PREP), electrode induction melting gas atomization (EIGA), vacuum induction melting gas atomization (VIGA), and plasma atomization (PA). Among these, the PREP method produces powders with core advantages such as high purity, excellent sphericity, and virtually no hollow or satellite powders. It is the preferred powder material for applications with stringent requirements for fatigue life, material purity, and reliability, such as critical load-bearing components in aerospace and long-term implantable medical devices. However, the high production cost of this method limits its large-scale application.

[0004] The core reason for the high cost of γ-TiAl alloy powder lies in the extreme difficulty of preparing powder rods, specifically in the following three aspects: 1. Strict quality requirements for bar stock During PREP powder production, the bar stock needs to rotate at high speed, requiring it to be free of internal metallurgical defects, have a smooth external surface, and high coaxiality accuracy. This places higher process standards on the γ-TiAl alloy, which exhibits significant room-temperature brittleness. If coaxiality deviation causes vibration, or if cracks initiate at defects, the electrodes can easily disintegrate during high-speed rotation, causing equipment damage. Other powder production methods, such as induction melting (suspension melting) and arc melting casting, can prepare bar stock. Although these methods are inexpensive, cast bar stock generally suffers from porosity and shrinkage defects, failing to meet the quality requirements of PREP powder production.

[0005] 2. The alloy smelting process is difficult. γ-TiAl alloys have a melting point of 1450℃~1550℃, which is lower than that of ordinary titanium alloys. When using traditional vacuum arc remelting (VAR), incomplete fusion of titanium blocks and high-melting-point intermediate alloys is likely to occur. Currently, a multi-process melting method combining induction solidification melting and arc solidification melting is required to eliminate incomplete fusion defects inside the ingot. This process requires a large investment in equipment, which directly increases production costs.

[0006] 3. Low production efficiency of bar stock. High-quality ingots can be produced by combining VAR (Vacuum-Anaerobic Reduction) with induction shell melting, but the production capacity is strictly limited by the induction shell melting equipment. Currently, the world's largest induction shell melting equipment has a single-furnace capacity of only 114 kg, far lower than that of VAR equipment; increasing production capacity requires purchasing more expensive induction shell melting equipment, further exacerbating the pressure on production costs.

[0007] Therefore, there is an urgent need to develop a low-cost method for preparing high-quality γ-TiAl alloy powder. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a low-cost preparation method for high-quality γ-TiAl alloy powder and its application.

[0009] This invention discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, such as... Figure 1 As shown, it includes the following steps: Step 1: In the electrode block pressing mold, pure aluminum is distributed on the upper and lower sides of the raw material to form a γ-TiAl alloy electrode block. The raw material includes HTi particles. Step 2: Weld 5 to 10 γ-TiAl alloy electrode blocks into one consumable electrode, and perform multiple meltings on the consumable electrode to obtain a γ-TiAl alloy ingot. Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0010] Furthermore, in step one, the particle size of the HTi particles is ≤12.7mm, and the purity of the pure aluminum is ≥99.7%.

[0011] Furthermore, in step one, the fabric application method specifically includes: First, pure aluminum is divided into pure aluminum A and pure aluminum B. Then, pure aluminum A, raw material and pure aluminum B are placed in the electrode block pressing mold from bottom to top.

[0012] Furthermore, in step two, the welding adopts plasma beam welding process, which mainly includes: pre-vacuum ≤10Pa, welding box leakage rate ≤2Pa / min, argon filling pressure ≥10000Pa, argon flow rate ≥5L / min, welding current 200-500A, and welding voltage 35-70V.

[0013] Furthermore, the smelting in step two adopts the VAR smelting process: pre-vacuum ≤5Pa, leakage rate ≤1Pa / min, 2-3 smelting times, smelting current 2-5kA, smelting voltage 25-32V, argon charging pressure 0-50kPa, finished ingot diameter 200-300mm, finished ingot length ≥800mm.

[0014] Furthermore, the machining process in step three includes the following steps: Step 3.1: Use wire electrical discharge machining to process powder rod blanks with a diameter of 55-75mm and a length of ≥700mm from γ-TiAl alloy finished ingots. The wire feed speed is 100-120mm / s, the pulse width is 30-40μs, and the peak current is 5-15A. Step 3.2: Use a lathe to machine the powder-making rod blank into powder-making rods with a diameter of 50-70mm and a length of 695-700mm. The surface roughness of the powder-making rod shall not exceed Ra1.6. Carbide tools are used for turning, the cutting speed is 20-50mm / min, and the feed rate is ≤0.1mm / rev. Furthermore, in plasma rotating electrode atomization powder production, the argon purging pressure is ≤1 kPa, the electrode rotation speed is 20000-40000 rpm, and the plasma beam generation power is 40-80 kW.

[0015] Furthermore, the chemical element mass percentage of the γ-TiAl alloy powder includes: Al: 29-34%, Nb: 3-6%, Mn: 0-4%, Cr: 0-3%, B: 0-0.3%, O≤0.06%, with the remainder being Ti and unavoidable impurities.

[0016] On the other hand, the present invention discloses the application of γ-TiAl alloy powder prepared by the above preparation method in the preparation of low-pressure turbine blades.

[0017] Compared with the prior art, the present invention has the following beneficial effects: First, by selecting small-particle HTi and special-component intermediate alloys whose thermophysical properties are better matched with γ-TiAl alloys, the alloying of each raw material can be fully promoted during the VAR melting process, thus preventing HTi and other high-melting-point elements from forming infusible substances from the source.

[0018] Secondly, regarding the problem that HTi lumps can easily fall off during the melting process when using traditional titanium alloy uniform distribution for γ-TiAl alloys with high aluminum content, the aluminum content weakens the strength of the electrode block, leading to HTi lumps falling off. This invention adopts an aluminum-concentrated external arrangement scheme, concentrating the aluminum material on the outside of the electrode to avoid the weakening of the strength of the HTi main mixture by pure aluminum, ensuring the structural stability of the mixture after pressing and molding, and completely eliminating the hidden danger of infusible material formation caused by HTi lumps falling off.

[0019] Third, the TiAl alloy ingots are prepared using a multi-stage VAR melting process, which has significant advantages over other processes, including high metallurgical quality, controllable cost, and high production efficiency, enabling mass production of γ-TiAl alloy ingots. At the same time, exclusive melting parameters are developed for the characteristics of γ-TiAl alloys to ensure complete alloying of all raw materials and completely solve the problem of non-melting of HTi and high-melting-point master alloys. Fourth, γ-TiAl alloy powder is prepared using the PREP method. The finished powder has the core characteristics of low impurity element content, excellent sphericity, and extremely low hollow powder ratio, which can accurately meet the stringent application requirements of high-end equipment additive manufacturing and powder metallurgy. Attached Figure Description

[0020] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the process for preparing γ-TiAl alloy powder in this invention; Figure 2 This is a schematic diagram of the fabric making method using aluminum briquettes as raw materials in Example 1; Figure 3 This is a schematic diagram of the fabric application method using aluminum plates as raw materials in Example 2; Figure 4 This is a schematic diagram of the morphology of the γ-TiAl alloy powder prepared in Example 1; Figure 5 This is a schematic diagram of the morphology of the γ-TiAl alloy powder prepared in Example 2; Figure 6 This is a schematic diagram of the morphology of the γ-TiAl alloy powder prepared in Example 3; Figure 7This is a schematic diagram of the morphology of the γ-TiAl alloy powder prepared in Example 4; Figure 8 This is a schematic diagram of the morphology of the γ-TiAl alloy powder prepared in Example 5; Figure 9 The results of X-ray inspection of the γ-TiAl alloy powder rod billet in Comparative Example 2 are shown. Figure 10 A schematic diagram of the morphology of γ-TiAl alloy powder prepared by VIGA for Comparative Example 2. Detailed Implementation

[0023] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0024] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example 1 This embodiment discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, using aluminum granules as raw materials, such as... Figure 2 As shown, the main steps include: Step 1: In the electrode block pressing mold, a γ-TiAl alloy electrode block is pressed by a material distribution method in which pure aluminum is respectively placed on the upper and lower sides of the raw material. The raw material includes HTi particles. Specifically, HTi particles (particle size 3-12.7mm), aluminum granules, NbCrAl alloy, and Cr70Al alloy are used as raw materials for preparing γ-TiAl alloy, with a ratio of 6:3.2:0.8:0.002. The aluminum granules are divided into two portions and wrapped in pure aluminum foil to form package A and package B, respectively. The HTi particles, NbCrAl alloy, and Cr70Al alloy are thoroughly mixed using a mixer to obtain a mixture. Package A is placed at the bottom of the electrode block pressing mold, and then the mixture is completely covered on top of package A. Then, package B is placed on top of the mixture. The γ-TiAl alloy electrode block is pressed using a hydraulic press. Multiple γ-TiAl alloy electrode blocks are prepared using the above method. Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum was 5 Pa, the leakage rate of the welding box was 1.3 Pa / min, the argon purging pressure during welding was 20000 Pa, the argon flow rate was 7.5 L / min, the welding current was 320 A, and the welding voltage was 40 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for VAR melting to prepare γ-TiAl alloy ingots. The total number of melting cycles was 3. The pre-vacuum levels before the first, second, and third melting cycles were 5 Pa, 2.5 Pa, and 0.5 Pa, respectively, and the leakage rates were 0.5 Pa / min, 0.4 Pa / min, and 0.25 Pa / min, respectively. The argon purging pressure during all three melting cycles was 0 Pa. The melting currents for the first, second, and third melting cycles were 2.5 kA, 3.0 kA, and 3.5 kA, respectively, and the melting voltages for the first, second, and third melting cycles were 28 V, 26 V, and 30 V, respectively. A γ-TiAl alloy ingot with a diameter of 280 mm and a length of 1 m was obtained. Step 3: Machining the γ-TiAl alloy ingot to obtain a powder casting rod; then subjecting the casting rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder. Specifically, a γ-TiAl alloy ingot was longitudinally cut into powder-making rod blanks with a diameter of 58 mm and a length of 850 mm using an electrical discharge wire (EDM) system. The wire feed rate was 110 mm / s, the pulse width was 32 μm, and the peak current was 9 A. The prepared powder-making rod blanks were then machined on a lathe to obtain finished powder-making rods with a diameter of 55 mm and a length of 695 mm. The cutting speed was 25 mm / min, the feed rate was 0.06 mm / rev, and the surface roughness of the finished product was Ra1.2. The prepared γ-TiAl alloy powder rods were then processed into powder using a PREP (Preparative Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 500 Pa, the electrode rotation speed was 25000 rpm, and the plasma beam generation power was 55 kW. The resulting γ-TiAl alloy powder had a composition of Ti-32.34Al-4.54Nb-2.54Cr (wt.%) and an oxygen content of 540 ppm. The morphology of the prepared γ-TiAl alloy powder is as follows: Figure 4 As shown.

[0026] Example 2 This embodiment discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, using aluminum plate as raw material, such as... Figure 3 As shown, it includes the following steps: Step 1: In the electrode block pressing mold, a γ-TiAl alloy electrode block is pressed by a material distribution method in which pure aluminum is respectively placed on the upper and lower sides of the raw material. The raw material includes HTi particles. Specifically, HTi particles (particle size 3-5mm), pure aluminum plates, NbMnAl alloy, Mn65Al alloy, and TiB2 powder are used as raw materials for preparing γ-TiAl alloy, with a ratio of 6.2:3.1:0.6:0.08:0.01. Each electrode block uses two pure aluminum plates, namely pure aluminum plate A and pure aluminum plate B. The HTi particles, NbMnAl alloy, and Mn65Al alloy are thoroughly mixed using a mixer to obtain a mixture. Pure aluminum plate A is placed at the center of the bottom of the electrode block pressing mold. Then, the mixture is completely filled to the top of pure aluminum plate A. Pure aluminum plate B is then placed in the center of the top of the mixture. A hydraulic press is used to press the γ-TiAl alloy electrode block. Several γ-TiAl alloy electrode blocks are prepared using this method.

[0027] Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum was 3.5 Pa, the welding box leakage rate was 0.9 Pa / min, the argon purging pressure during welding was 25000 Pa, the argon flow rate was 6.5 L / min, the welding current was 280 A, and the welding voltage was 36 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for VAR melting to prepare γ-TiAl alloy ingots. The total number of melting operations was three. The pre-vacuum levels before the first, second, and third melting operations were respectively... A γ-TiAl alloy ingot with a diameter of 300 mm and a length of 950 mm was prepared by applying pressures of 4.5 Pa / 3.1 Pa / 0.3 Pa and leakage rates of 0.48 Pa / min / 0.37 Pa / min / 0.31 Pa / min, respectively, argon charging pressures of 0 Pa / 20 kPa / 20 kPa during the first / second / third melting process, currents of 2.8 kA / 3.5 kA / 3.2 kA during the first / second / third melting process, and voltages of 28 V / 32 V / 29 V during the first / second / third melting process.

[0028] Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0029] Specifically, a γ-TiAl alloy ingot was longitudinally cut into powder-making rod blanks with a diameter of 75 mm and a length of 800 mm using an electrical discharge wire (EDM) system. The wire feed rate was 105 mm / s, the pulse width was 36 μm, and the peak current was 12 A. The prepared powder-making rod blanks were then machined on a lathe to obtain finished powder-making rods with a diameter of 70 mm and a length of 700 mm. The cutting speed was 30 mm / min, the feed rate was 0.05 mm / rev, and the surface roughness of the finished product was Ra1.5. The prepared γ-TiAl alloy powder rods were then processed into powder using a PREP (Preparative Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 800 Pa, the electrode rotation speed was 30,000 rpm, and the plasma beam generation power was 65 kW. The resulting γ-TiAl alloy powder had a composition of Ti-30.75Al-4.43Nb-2.35Mn-0.23B (wt.%) and an oxygen content of 480 ppm. The morphology of the prepared γ-TiAl alloy powder is as follows: Figure 5 As shown.

[0030] Example 3 This embodiment discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, including the following steps: Step 1: In the electrode block pressing mold, a γ-TiAl alloy electrode block is pressed by a material distribution method in which pure aluminum is respectively placed on the upper and lower sides of the raw material. The raw material includes HTi particles. Specifically, HTi particles (particle size 3-12.7 mm), aluminum granules, NbCrAl alloy, Cr70Al alloy, and TiB2 powder were used as raw materials for preparing γ-TiAl alloy, with a ratio of 6.05:3.1:0.85:0.002:0.01. The materials were wrapped in pure aluminum foil to form wrappers C and D. The HTi particles, NbCrAl alloy, Cr70Al alloy, and TiB2 powder were thoroughly mixed using a mixer to obtain a mixture. Wrapper C was placed at the bottom of an electrode block pressing mold, and then the mixture was completely covered on top of wrapper C. Wrapper D was then placed on top of the mixture. A hydraulic press was used to press the γ-TiAl alloy electrode block. Multiple γ-TiAl alloy electrode blocks were prepared using this method.

[0031] Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum was 2 Pa, the leakage rate of the welding box was 0.8 Pa / min, the argon purging pressure during welding was 15000 Pa, the argon flow rate was 8.5 L / min, the welding current was 280 A, and the welding voltage was 38 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for VAR melting to prepare γ-TiAl alloy ingots. The total number of melting operations was two. The pre-vacuum levels before the first and second melting operations were 3.2 Pa and 0.8 Pa, respectively, with leakage rates of 0.38 Pa / min and 0.26 Pa / min, respectively. The argon purging pressure during both melting operations was 0 Pa. The first and second melting currents were 2.6 kA and 3.2 kA, respectively, and the first and second melting voltages were 28 V and 29 V, respectively. A γ-TiAl alloy ingot with a diameter of 200 mm and a length of 1.2 m was obtained.

[0032] Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0033] Specifically, a γ-TiAl alloy ingot was longitudinally cut into powder-making rod blanks with a diameter of 55 mm and a length of 900 mm using an electrical discharge wire (EDM) system. The wire feed rate was 100 mm / s, the pulse width was 40 μm, and the peak current was 15 A. The prepared powder-making rod blanks were then machined on a lathe to obtain finished powder-making rods with a diameter of 50 mm and a length of 700 mm. The cutting speed was 40 mm / min, the feed rate was 0.04 mm / rev, and the surface roughness of the finished product was Ra1.1. The prepared γ-TiAl alloy powder rods were then processed into powder using a PREP (Preparative Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 900 Pa, the electrode rotation speed was 35000 rpm, and the plasma beam generation power was 60 kW. The resulting γ-TiAl alloy powder had a composition of Ti-31.95Al-4.78Nb-2.83Cr-0.24B (wt.%) and an oxygen content of 390 ppm. The morphology of the prepared γ-TiAl alloy powder is as follows: Figure 6 As shown.

[0034] Example 4 This embodiment discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, mainly including the following steps: Step 1: In the electrode block pressing mold, a γ-TiAl alloy electrode block is pressed by a material distribution method in which pure aluminum is respectively placed on the upper and lower sides of the raw material. The raw material includes HTi particles. Specifically, HTi particles (particle size 3-12.7mm), aluminum granules, NbCrAl alloy, and Cr70Al alloy were used as raw materials for preparing γ-TiAl alloy, with a ratio of 6.48:2.78:0.54:0.19. The aluminum granules were divided into two portions and wrapped with pure aluminum foil to form packages E and F, respectively. The HTi particles, NbCrAl alloy, and Cr70Al alloy were thoroughly mixed using a mixer to obtain a mixture. Package E was placed at the bottom of the electrode block pressing mold, and then the mixture was completely covered on top of package E. Then, package F was placed on top of the mixture. The γ-TiAl alloy electrode block was pressed using a hydraulic press. Multiple γ-TiAl alloy electrode blocks were prepared using the above method.

[0035] Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum before welding was 5 Pa, the leakage rate of the welding box was 1 Pa / min, the argon purging pressure during welding was 20000 Pa, the argon flow rate was 7.5 L / min, the welding current was 200 A, and the welding voltage was 70 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for VAR melting to prepare γ-TiAl alloy ingots. The total number of melting times was 3. The pre-vacuum levels before the first, second, and third meltings were 5 Pa, 2.5 Pa, and 0.5 Pa, respectively, and the leakage rates were 0.5 Pa / min, 0.4 Pa / min, and 0.25 Pa / min, respectively. The argon purging pressure during the three meltings was 50 kPa, the melting currents for the first, second, and third meltings were 2 kA, 3.5 kA, and 5 kA, respectively, and the melting voltages for the first, second, and third meltings were 28 V, 26 V, and 32 V, respectively. A γ-TiAl alloy ingot with a diameter of 250 mm and a length of 1 m was obtained.

[0036] Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0037] Specifically, a wire EDM process was used to longitudinally cut a γ-TiAl alloy ingot into powder-making rod blanks with a diameter of 65 mm and a length of 700 mm. The wire feed rate was 120 mm / s, the pulse width was 30 μm, and the peak current was 5 A. The prepared powder-making rod blanks were then machined on a lathe to obtain finished powder-making rods with a diameter of 60 mm and a length of 695 mm. The cutting speed was 50 mm / min, the feed rate was 0.08 mm / rev, and the surface roughness of the finished product was Ra1.6. The prepared γ-TiAl alloy powder rods were then processed into powder using a PREP (Preparative Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 700 Pa, the electrode rotation speed was 40,000 rpm, and the plasma beam generation power was 80 kW. The resulting γ-TiAl alloy powder had a composition of Ti-29.1Al-3.1Nb-2.95Cr (wt.%) and an oxygen content of 540 ppm. The morphology of the prepared γ-TiAl alloy powder is as follows: Figure 7 As shown.

[0038] Example 5 This embodiment discloses a low-cost method for preparing high-quality γ-TiAl alloy powder, mainly including the following steps: Step 1: In the electrode block pressing mold, a γ-TiAl alloy electrode block is pressed by a material distribution method in which pure aluminum is respectively placed on the upper and lower sides of the raw material. The raw material includes HTi particles. Specifically, HTi particles (particle size 3-5mm), pure aluminum plates, NbMnAl alloy, Mn65Al alloy, and TiB2 powder were used as raw materials for preparing γ-TiAl alloy, with a ratio of 5.31:3.03:1.09:0.49:0.09. Two pure aluminum plates, C and D, were used for each electrode block. The HTi particles, NbMnAl alloy, and Mn65Al alloy were thoroughly mixed using a mixer to obtain a mixture. A pure aluminum plate C was placed at the center of the bottom of the electrode block pressing mold. Then, the mixture was completely filled to the top of the pure aluminum plate C. Finally, pure aluminum plate D was placed in the center of the top of the mixture. A hydraulic press was used to press the γ-TiAl alloy electrode block. Several γ-TiAl alloy electrode blocks were prepared using this method.

[0039] Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum was 5 Pa, the welding box leakage rate was 1 Pa / min, the argon purging pressure during welding was 20000 Pa, the argon flow rate was 7.5 L / min, the welding current was 500 A, and the welding voltage was 35 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for VAR melting to prepare γ-TiAl alloy ingots. The total number of melting cycles was 3. The pre-vacuum levels before the first, second, and third melting cycles were 5 Pa, 2.5 Pa, and 0.5 Pa, respectively, and the leakage rates were 0.5 Pa / min, 0.4 Pa / min, and 0.25 Pa / min, respectively. The argon purging pressure during each of the three melting cycles was 35 kPa. The melting currents for the first, second, and third melting cycles were 2 kA, 2.3 kA, and 2.5 kA, respectively, and the melting voltages for the first, second, and third melting cycles were 28 V, 25 V, and 30 V, respectively. A γ-TiAl alloy ingot with a diameter of 250 mm and a length of 1 m was obtained.

[0040] Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0041] Specifically, a wire EDM process was used to longitudinally cut a γ-TiAl alloy ingot into powder-making rod blanks with a diameter of 63 mm and a length of 830 mm. The wire feed rate was 110 mm / s, the pulse width was 34 μm, and the peak current was 5 A. The prepared powder-making rod blanks were then machined on a lathe to obtain finished powder-making rods with a diameter of 55 mm and a length of 698 mm. The cutting speed was 20 mm / min, the feed rate was 0.09 mm / rev, and the surface roughness of the finished product was Ra1.6. The prepared γ-TiAl alloy powder rods were then processed into powder using a PREP (Prepared Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 600 Pa, the electrode rotation speed was 20000 rpm, and the plasma beam generation power was 40 kW. The resulting γ-TiAl alloy powder had a composition of Ti-33.75Al-5.98Nb-3.85Mn-0.28B (wt.%) and an oxygen content of 480 ppm. The morphology of the prepared γ-TiAl alloy powder is as follows: Figure 8 As shown.

[0042] Comparative Example 1 This comparative example discloses a method for preparing γ-TiAl alloy ingots using the suspension melting (ISM) + VAR process route and preparing powders using the PREP route, mainly including the following steps: Step 1: Use an ISM melting equipment with mid-process feeding function to alloy and melt the raw materials in multiple heats; Specifically, HTi particles (particle size 3-25.4 mm), aluminum briquettes, Nb70Al alloy, and Cr70Al alloy were used as raw materials for preparing γ-TiAl alloy, with a ratio of 6.1:3.04:0.57:0.29. The HTi, Nb70Al, and Cr70Al raw materials were placed inside a water-cooled copper crucible of the ISM melting equipment. A portion of the aluminum briquettes was initially placed in the remaining space of the water-cooled copper crucible, and the remaining aluminum briquettes were placed in the feeding hopper of the ISM melting equipment. Before melting, a pre-vacuum of 0.6 Pa was applied, and 50 kPa of argon gas was introduced into the melting furnace for a single melting operation. After the raw materials were completely melted, the melt was refined for 15 minutes using a melting power of 400 kW. Then, the melting power was turned off, and the melt was allowed to solidify in the water-cooled copper pot. After cooling for more than 3 hours, the ingot is removed from the water-cooled copper crucible, inverted, and placed back into the water-cooled copper crucible. The ISM melting furnace is then sealed for a second melting process, with the same process parameters as the first melting. The difference is that after refining the melt for 15 minutes, the water-cooled copper crucible is tilted and the melt is poured into a steel mold. After cooling, the φ160mm 20kg TiAl alloy ingot is obtained.

[0043] Step 2: Weld multiple φ160mm ingots into electrodes, and use a VAR melting furnace to prepare TiAl alloy finished ingots; Specifically, five 20kg TiAl alloy ingots with a diameter of 160mm were welded into electrodes using an in-furnace welding method. The pre-vacuum for welding was 5Pa, the welding current was 3.6kA, and the welding time was 1min. TiAl alloy ingots were prepared using a single-stage VAR method. The pre-vacuum before melting was 0.2Pa, the leakage rate was 0.21Pa / min, the melting current was 4.5kA, and the melting voltage was 32V, resulting in a finished TiAl alloy ingot with a diameter of 220×1000mm.

[0044] Step 3: Machining the γ-TiAl alloy ingot to obtain a powder casting rod; then subjecting the casting rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

[0045] Specifically, an electrical discharge machining (EDM) wire cutter was used to longitudinally cut a γ-TiAl alloy ingot into powder-making rod blanks with a diameter of 60 mm and a length of 800 mm. The wire feed rate was 120 mm / s, the pulse width was 40 μm, and the peak current was 6.5 A. The processed powder-making rod blanks were then machined on a lathe to obtain powder-making rods with a diameter of 55 mm and a length of 700 mm. The cutting speed was 25 mm / min, the feed rate was 0.08 mm / rev, and the surface roughness of the finished product was Ra1.8. The prepared γ-TiAl alloy powder rods were then used to prepare powder using a PREP (Preparative Phosphate Extraction) device. During the preparation process, the argon purging pressure inside the device was 650 Pa, the electrode rotation speed was 25000 rpm, and the plasma beam generation power was 45 kW. The resulting γ-TiAl alloy powder had a composition of Ti-33.05Al-3.98Nb-2.12Cr (wt.%) and an oxygen content of 450 ppm.

[0046] Compared to Examples 1-5, Comparative Example 1's ingot production efficiency is directly limited by the melting capacity of the ISM melting equipment, requiring 11 melting cycles to produce a 100kg TiAl alloy ingot with a diameter of φ220mm. In contrast, Example 3 achieved the production of ingots of similar specifications with only 3 VAR melting cycles. Therefore, the comparative example has lower ingot production efficiency. Furthermore, the cost per melting cycle of the ISM melting equipment is much higher than that of the VAR melting equipment, resulting in a significantly higher cost for the product produced using this method compared to Examples 1-5.

[0047] Comparative Example 2 This comparative example discloses a method for preparing γ-TiAl alloy ingots using the VAR+Electric Arc Shell Melting (VAR SK) process route and preparing TiAl powder using VIGA, which mainly includes the following steps: Step 1: Pressing γ-TiAl alloy electrode blocks in an electrode block pressing mold using a uniform mixing and material distribution method. Specifically, HTi particles (particle size 3-12.7 mm), Al beads, Nb70Al alloy, and Cr70Al alloy were used as raw materials for preparing γ-TiAl alloy, with a ratio of 6.1:3.04:0.57:0.29. A V-type mixer was used to mix the raw materials for 5 minutes. After mixing, the mixture was placed into a pressing mold, and a hydraulic press was used to press the γ-TiAl alloy electrode blocks. Several γ-TiAl alloy electrode blocks were prepared using this method.

[0048] Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform a single melting of the consumable electrode to obtain a γ-TiAl alloy primary ingot. Specifically, the electrode blocks were welded using a plasma beam welding box. The pre-vacuum was 5.5 Pa, the leakage rate of the welding box was 0.8 Pa / min, the argon purging pressure during the welding process was 40000 Pa, the argon flow rate was 8.5 L / min, the welding current was 320 A, and the welding voltage was 32 V. Multiple γ-TiAl alloy electrode blocks were welded into consumable electrodes. The welded consumable electrodes were then used for a single VAR melting process to prepare a γ-TiAl alloy primary ingot. The pre-vacuum was 2.4 Pa, the leakage rate was 0.6 Pa / min, the melting current was 3.5 kA, and the melting voltage was 32 V. A γ-TiAl alloy primary ingot with a diameter of 200 mm and a length of 1 m was obtained.

[0049] Step 3: Prepare powder rod blanks by centrifugal casting of γ-TiAl alloy primary ingots using the VAR SK method; Specifically, the pre-vacuum before melting is 0.4 Pa, the melting current is 15 kA, and the melting voltage is 35 V. After the molten pool reaches the predetermined pouring volume, the electric arc is extinguished, the copper crucible is tilted, and the alloy melt is poured into a rotating steel mold. The crucible tilt angle is 110°, the pouring time is 5 seconds, and the mold rotation speed is 120 r / min. After cooling and removal from the furnace, the mold is opened to obtain several pre-prepared billets with a diameter of 35 mm and a length of 315 mm.

[0050] Step 4: Machining the γ-TiAl alloy powder-making rod blank to obtain a casting rod for powder making; subjecting the casting rod to induction heating and gas atomization powder making to obtain γ-TiAl alloy powder.

[0051] Specifically, the powder-making rod blank was machined on a lathe to obtain a finished powder-making rod with a diameter of 30 mm and a length of 300 mm; then, γ-TiAl alloy powder was prepared using the VIGA method, and the morphology of the γ-TiAl alloy powder is as follows. Figure 10 As shown, the powder-making rod blank prepared by the VAR+VARSK+centrifugal casting method has a large number of shrinkage cavities in its core, making it unsuitable as a raw material for PREP powder production. The γ-TiAl alloy powder obtained by gas atomization has a high void ratio and poor quality. From... Figure 9 It can be clearly seen that there are a large number of dispersed shrinkage cavities, shrinkage porosity and loose structures in the core of the billet. These casting defects will become crack sources due to the centrifugal force and vibration generated by the high speed rotation of the billet during the plasma rotating electrode atomization (PREP) powder production process. This can easily lead to the billet cracking or even disintegration. It cannot meet the stringent requirements of PREP powder production for the internal density and defect-free nature of the billet. This further illustrates that the billet prepared by this process route is only suitable for the gas atomization (VIGA) powder production method with relatively low quality requirements, and cannot be used for the preparation of high-quality γ-TiAl alloy powder.

[0052] The γ-TiAl alloy powders prepared in Examples 1-5 of this invention ( Figures 4-8 Compared to powders prepared by traditional methods, the powder obtained by this invention exhibits significantly superior morphological characteristics: the powder particles obtained by this invention have high sphericity, regular and rounded shapes, smooth and clean surfaces without obvious pits, cracks or rough textures, narrow particle size distribution, and good size uniformity; while Comparative Example 2 (e.g.) Figure 10 The powder particles prepared (as shown) are irregular in shape, mostly spherical or polyhedral, with rough and porous surfaces, cellular structures and shrinkage defects, and a wide particle size distribution with a mixture of large and small particles. It is evident that this invention can effectively improve the stability and forming density of subsequent processing technologies such as additive manufacturing and powder metallurgy, significantly improve the mechanical properties and dimensional accuracy of the final parts, and solve the industry pain points of poor sphericity and numerous forming defects in traditional γ-TiAl alloy powders.

[0053] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0054] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A low-cost method for preparing high-quality γ-TiAl alloy powder, characterized in that, Includes the following steps: Step 1: In the electrode block pressing mold, pure aluminum is placed on the upper and lower sides of the raw material for material distribution, and then pressed into γ-TiAl alloy electrode blocks. The raw material includes HTi particles. Step 2: Weld the γ-TiAl alloy electrode block into a consumable electrode, and perform multiple melting processes on the consumable electrode to obtain a γ-TiAl alloy ingot. Step 3: Machining the γ-TiAl alloy ingot to obtain a powder-making rod; then subjecting the rod to plasma rotating electrode atomization to obtain γ-TiAl alloy powder.

2. The method for preparing high-quality γ-TiAl alloy powder at low cost according to claim 1, characterized in that, In step one, the particle size of the HTi particles is ≤12.7mm, and the purity of the pure aluminum is ≥99.7%.

3. The low-cost preparation method for high-quality γ-TiAl alloy powder according to claim 1, characterized in that, In step one, the fabric application method is specifically as follows: First, pure aluminum is divided into pure aluminum A and pure aluminum B. Then, pure aluminum A, raw material and pure aluminum B are placed in the electrode block pressing mold from bottom to top.

4. The low-cost preparation method for high-quality γ-TiAl alloy powder according to claim 1, characterized in that, In step two, the welding process adopts plasma beam welding technology, which mainly includes: pre-vacuum ≤10Pa, welding box leakage rate ≤2Pa / min, argon filling pressure ≥10000Pa, argon flow rate ≥5L / min, welding current 200-500A, and welding voltage 35-70V.

5. The low-cost preparation method for high-quality γ-TiAl alloy powder according to claim 1, characterized in that, The smelting in step two adopts the VAR smelting process: pre-vacuum ≤5Pa, leakage rate ≤1Pa / min, 2-3 smelting times, smelting current 2-5kA, smelting voltage 25-32V, argon purging pressure 0-50kPa, finished ingot diameter 200-300mm, finished ingot length ≥800mm.

6. The method for low-cost preparation of high-quality γ-TiAl alloy powder according to claim 1, characterized in that, The machining process in step three includes the following steps: Step 3.1: Use wire electrical discharge machining to process powder rod blanks with a diameter of 55-75mm and a length of ≥700mm from γ-TiAl alloy finished ingots. The wire feed speed is 100-120mm / s, the pulse width is 30-40μs, and the peak current is 5-15A. Step 3.2: Use a lathe to machine the powder-making rod blank into powder-making rods with a diameter of 50-70mm and a length of 695-700mm. The surface roughness of the powder-making rod is ≤Ra1.

6. Carbide tools are used for turning, the cutting speed is 20-50mm / min, and the feed rate is ≤0.1mm / rev.

7. The low-cost preparation method for high-quality γ-TiAl alloy powder according to claim 1, characterized in that, In plasma rotating electrode atomization powder production, the argon purging pressure is ≤1kPa, the electrode rotation speed is 20000-40000rpm, and the plasma beam generation power is 40-80kW.

8. The method for preparing high-quality γ-TiAl alloy powder at low cost according to claim 1, characterized in that, The chemical element mass percentage of the γ-TiAl alloy powder includes: Al: 29-34%, Nb: 3-6%, Mn: 0-4%, Cr: 0-3%, B: 0-0.3%, O≤0.06%, with the remainder being Ti and unavoidable impurities.

9. The application of γ-TiAl alloy powder prepared by the preparation method according to any one of claims 1 to 8 in the preparation of low-pressure turbine blades.

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