Ti al alloy cyclone and injection molding method for preparing the same

Abstract

The application provides a TiAl alloy swirler and an injection forming preparation method thereof. In the preparation method, a swirler mold for injection forming adopts a design method of a water-soluble mold core, a difficult mold opening area is filled with a water-soluble material, a swirler green body with a mold core is formed, and a manual insert mold opening mode is used to enhance the demolding capacity of the injection blank, so that the green body quality is maximally ensured, the size precision of the TiAl alloy swirler is effectively improved, and technical problems such as high cost, long cycle, and difficult surface quality control of a swirler sample of an existing preparation method are solved.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a TiAl alloy hydrocyclone and its injection molding preparation method. Background Technology

[0002] Swirlers are crucial components in aero-engines, creating a recirculation zone at the flame tube head to reduce gas velocity and stabilize the combustion chamber. TiAl alloys, with their lightweight, high strength, excellent oxidation resistance, and high-temperature mechanical properties, are the preferred material for aero-engine swirler fabrication. Currently, aero-engine swirlers are typically manufactured using a combination of precision casting and machining. However, aero-engines have high quality requirements for components, and swirler blades often have complex surfaces with varying curvatures, making surface machining of the prototypes difficult. Furthermore, casting requires high-precision molds, which are relatively expensive. For thin-walled, complex structures like swirlers, traditional precision casting techniques struggle to control metallurgical defects such as porosity and shrinkage cavities, resulting in poor dimensional stability, low yield, poor assemblability, and reduced combustion chamber lifespan, which is detrimental to the long-term normal operation of the aero-engine.

[0003] Powder injection molding (PIM) technology combines traditional plastic injection molding with powder metallurgy, overcoming metallurgical defects inherent in precision casting. It facilitates the near-net-shape mass production of complex-shaped parts, producing samples with uniform and fine microstructures and high dimensional accuracy. PIM typically includes processes such as feedstock preparation, injection molding, debinding, and sintering. A high-quality injection-molded preform is crucial for ensuring the dimensional accuracy of the final part. Hydrocyclone components exhibit significant cross-sectional dimension variations, with thin, continuous blades distributed along an annular profile. The sides of the profile are solid walls of varying thicknesses, and one side features an inverted T-shaped structure. For PIM components, excessive thickness variations and the annular convex structure make demolding extremely difficult, leading to deformation, cracks, and other defects during demolding, severely impacting product quality and dimensional accuracy.

[0004] In summary, there is an urgent need to propose a hydrocyclone mold design method with good demolding ability, and to use injection molding technology to achieve near-net-shape preparation of engine hydrocyclones, so as to solve the problems of low dimensional accuracy and poor assemblability of hydrocyclones caused by traditional casting processes. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, the main objective of this invention is to provide a TiAl alloy hydrocyclone and its injection molding preparation method. In this preparation method, the hydrocyclone mold used for injection molding adopts a water-soluble mold core design method, which fills the difficult-to-open mold area with water-soluble material to form a hydrocyclone blank with a mold core, thereby maximizing the quality of the blank and effectively improving the dimensional accuracy of the TiAl alloy hydrocyclone.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing a TiAl alloy hydrocyclone by injection molding is provided.

[0007] The injection molding method for preparing the TiAl alloy hydrocyclone includes the following steps:

[0008] Preparation of granular feed;

[0009] Injection molding yields a hydrocyclone preform with a mold core;

[0010] The hydrocyclone blank with mold core is subjected to degreasing, pre-sintering, sintering and hot isostatic pressing without cladding in sequence to obtain the hydrocyclone part.

[0011] Furthermore, the injection molding process for obtaining a hydrocyclone preform with a mold core includes:

[0012] Obtain the mold core and use water-soluble materials for injection molding to obtain the mold core;

[0013] Obtain the hydrocyclone mold and assemble the mold core onto the hydrocyclone mold;

[0014] The cyclone preform with mold core is obtained by injection molding using the granular feed.

[0015] Furthermore, the water-soluble material is at least one of water-soluble paraffin, polyethylene glycol, and polystyrene;

[0016] Preferably, the injection molding process parameters of the mold core are: injection temperature of 60-150℃, injection pressure of 50-100MPa, holding pressure of 40-90MPa, holding time of 5-25s, mold temperature of 40-70℃, and injection speed of 40-70% of the maximum injection speed of the injection molding machine.

[0017] Furthermore, the injection molding process parameters for the cyclone separator preform with mold core are as follows: injection temperature is 170-200℃, injection pressure is 100-130MPa, holding pressure is 90-120MPa, holding time is 5-25s, mold temperature is 80-120℃, and injection speed is 50-80% of the maximum injection speed of the injection molding machine.

[0018] Furthermore, the degreasing treatment includes solvent degreasing, catalytic degreasing, and thermal degreasing;

[0019] The solvent degreasing uses at least one of n-heptane, anhydrous ethanol, trichloroethylene, and trichloroethane as the solvent;

[0020] The catalytic defatting is oxalic acid-catalyzed defatting;

[0021] The thermal degreasing is carried out under vacuum conditions, with the temperature increased from room temperature to 450-600°C at a rate of 1-5°C / min under a protective atmosphere, and held at that temperature for 0.5-2 hours.

[0022] Preferably, the solvent degreasing temperature is 35-65℃ and the time is 6-12h; after degreasing, it is dried in a vacuum drying oven at 40-60℃ for 4-8h.

[0023] Preferably, the catalytic degreasing uses a nitrogen degreasing atmosphere, with a nitrogen flow rate of 20-100 L / min, a degreasing temperature of 110-150℃, an acid inlet rate of 2-6 g / min, and a degreasing time of 6-14 h;

[0024] Preferably, the thermal degreasing uses high-purity argon as a protective gas, and the vacuum degree is 1-40 Pa.

[0025] Furthermore, the pre-sintering treatment is carried out at a temperature of 900–1100°C, for a holding time of 0.5–2 h, and at a heating rate of 5–10°C / min.

[0026] Furthermore, the sintering process is carried out under vacuum conditions. First, the temperature is increased from room temperature to 900-1100°C at a rate of 5-10°C / min and held for 0.5-1h to carry out the first stage of sintering. Then, the temperature is increased to 1300-1400°C at a rate of 1-3°C / min and held for 1-6h to carry out the second stage of sintering.

[0027] Preferably, the vacuum degree is 10. -2 ~10 -4 Pa.

[0028] Furthermore, the uncoated hot isostatic pressing treatment is carried out under vacuum conditions at a temperature of 1200–1300°C for 1–6 hours and a holding pressure of 160–200 MPa.

[0029] Preferably, the vacuum degree is 10. -2 ~10 -4 Pa.

[0030] Furthermore, the granular feed is prepared by mixing TiAl-based pre-alloyed powder and binder as raw materials and then crushing them.

[0031] Preferably, the powder loading of the feed is 60-65%;

[0032] Preferably, the TiAl-based pre-alloyed powder has a particle size distribution of 0–20 μm;

[0033] Preferably, the mixing temperature is 170–200℃, the rotation speed is 5–30 r / min, and the time is 0.5–2 h.

[0034] Preferably, the composition of the TiAl-based pre-alloyed powder, by atomic percentage, is: Al 45-49 at.%, Cr 0-5 at.%, Nb 0-5 at.%, with the balance being Ti;

[0035] Preferably, the adhesive comprises the following components by weight percentage: 78-85% polyoxymethylene, 2-6% high-density polyethylene, 3-8% ethylene-vinyl acetate copolymer, 5-10% stearic acid, and 2-5% microcrystalline wax.

[0036] To achieve the above objectives, according to a second aspect of the present invention, a TiAl alloy cyclone separator is provided.

[0037] The TiAl alloy cyclone was fabricated using the injection molding method described above; wherein,

[0038] The density of the TiAl alloy hydrocyclone is 99% to 99.8%, the dimensional accuracy is ±0.1% to ±0.5%, the dimensional deviation of key parts is 0.1 to 0.3 mm, and the surface roughness of the sample is Ra1.6 μm to Ra3.2 μm.

[0039] In this invention, the amount of microcrystalline wax added is 2-5%. If the content is too low, the reduction in viscosity of the entire feeding system will be limited, making it difficult to fill the hydrocyclone cavity in a uniform state. If the content is too high, the viscosity of the entire feeding system will be greatly reduced. Although the cavity can be filled smoothly, defects such as flash will be generated, which will seriously reduce the dimensional accuracy of the parts.

[0040] The beneficial effects of this invention are:

[0041] (1) A water-soluble mold core was designed for injection molding to prepare TiAl alloy hydrocyclones, which improved the demolding ability of the injection blank, the shape retention of the green blank, and the dimensional accuracy of the final part.

[0042] (2) Powder injection molding technology was used to realize the near-net-shape preparation of TiAl alloy hydrocyclones with thin walls and complex shapes for aero engines. Compared with existing casting and machining methods, the cost is significantly reduced, the material utilization rate is high, and it is easy to realize the mass production of hydrocyclone parts.

[0043] (3) The TiAl alloy hydrocyclone parts prepared by injection molding technology have good surface quality, high dimensional accuracy, and small dimensional deviation in key parts, which reduces the subsequent machining allowance and shortens the preparation cycle of the hydrocyclone. Attached Figure Description

[0044] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0045] Figure 1 This is a schematic diagram of the mold core structure in an embodiment provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the structure of the hydrocyclone preform with a mold core in an embodiment provided by the present invention;

[0047] Figure 3 This is a schematic diagram of the structure of the TiAl alloy hydrocyclone provided in the embodiments of the present invention. Detailed Implementation

[0048] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0049] Currently, aero-engine cyclones are typically manufactured using a combination of single-piece precision casting and machining. However, their complex structural features pose significant challenges to high-precision fabrication. On one hand, the cyclone's complex shape, with blades exhibiting intricate profiles and varying curvatures, makes direct machining difficult. On the other hand, the annular sections of the edge blades have numerous profiles, are thin, and have a small overall volume. During casting, the fluidity of the molten metal easily leads to unavoidable metallurgical defects such as porosity and shrinkage cavities. These defects not only result in poor dimensional accuracy, affecting the selection of datum surfaces and the determination of machining allowances in subsequent precision machining, but also lead to low yield rates, increased manufacturing costs, and reduced service life due to metallurgical defects. TiAl alloys possess lightweight, high strength, and excellent high-temperature performance, making them highly promising for the fabrication of aero-engine cyclones. However, precision casting, as the primary method for cyclone fabrication, suffers from defects such as porosity, shrinkage cavities, coarse grains, and uneven composition, which hinder the utilization of TiAl alloy's material advantages. Furthermore, TiAl alloys, as intermetallic compounds with both metallic and covalent bonds, exhibit inherent room-temperature brittleness, making them difficult to machine. For small, complex structural components like hydrocyclones, the machining difficulty is significantly increased.

[0050] Powder injection molding (PIM) is a near-net-shape forming technology that incorporates powder metallurgy into plastic injection molding. It achieves nearly 100% raw material utilization and is suitable for mass production of small, complex-shaped parts. The resulting parts exhibit uniform microstructure, fine grains, excellent mechanical properties, and high dimensional accuracy. However, in the case of hydrocyclone parts, the cross-sectional dimensions of the hydrocyclone sample vary significantly. The annular profile features thin, continuous blades running vertically, with solid walls of varying thickness on both sides of the profile, and an inverted T-shaped feature on one side of the annular profile. For PIM parts, this large thickness variation and the annular convex structure make demolding extremely difficult, leading to defects such as deformation and cracks during demolding, severely impacting product quality and dimensional accuracy.

[0051] To address this, the present invention employs a water-soluble mold core design method. Water-soluble materials are used to fill the difficult-to-open areas to form a hydrocyclone blank with a mold core. The excess mold core is then removed using a subsequent solvent degreasing process, thereby avoiding the adverse effects of the "inverted T-shaped" structure on the demolding process. In addition, a manual insert mold opening method is used to enhance the demolding ability of the injection blank and maximize the quality of the green blank.

[0052] In addition, the present invention utilizes low-viscosity microcrystalline wax components to adjust the flowability of the polyoxymethylene-based binder system, which not only allows the feed to uniformly fill the entire hydrocyclone at a lower viscosity, but also reduces the friction between the die core and the hydrocyclone contact area, thereby improving the surface quality of the part.

[0053] According to a specific embodiment of the present invention, a method for injection molding preparation of a TiAl alloy hydrocyclone is provided, comprising the following steps:

[0054] 1) Prepare granular feed;

[0055] TiAl-based pre-alloyed powder and binder are used as raw materials, and the mixture is kneaded at a powder loading of 60-65% and then crushed to obtain granular feed.

[0056] In this embodiment of the invention, the mixing temperature is 170-200℃, the rotation speed is 5-30 r / min, and the time is 0.5-2 h.

[0057] In this embodiment of the invention, after the mixing is completed, the material is fed into granules using a metal-specific crushing mechanism.

[0058] In this embodiment of the invention, the particle size distribution of the TiAl-based pre-alloyed powder is 0–20 μm.

[0059] In this embodiment of the invention, the composition of the TiAl-based pre-alloyed powder, by atomic percentage, is: Al 45-49 at.%, Cr 0-5 at.%, Nb 0-5 at.%, with the balance being Ti.

[0060] It is worth mentioning that the atomic percentages of Cr and Nb are not both taken as 0.

[0061] In embodiments of the present invention, the adhesive comprises the following components by weight percentage: 78-85% polyoxymethylene, 2-6% high-density polyethylene, 3-8% ethylene-vinyl acetate copolymer, 5-10% stearic acid, and 2-5% microcrystalline wax.

[0062] 2) Injection molding is used to obtain a hydrocyclone preform with a mold core, specifically including the following steps:

[0063] 2-1) Obtain the mold core and use water-soluble material for injection molding to obtain the mold core, such as... Figure 1 As shown.

[0064] In an embodiment of the present invention, the mold core is made of SKD11 high wear-resistant mold steel, which has a heat treatment hardness of 62-65 HRC.

[0065] In an embodiment of the present invention, the core is an inverted T-shaped structure at the annular position of the hydrocyclone to be manufactured.

[0066] In embodiments of the present invention, the water-soluble material is at least one of water-soluble paraffin, polyethylene glycol, and polystyrene.

[0067] In an embodiment of the present invention, the injection molding process parameters of the mold core are as follows: injection temperature is 60-150°C, injection pressure is 50-100MPa, holding pressure is 40-90MPa, holding time is 5-25s, mold temperature is 40-70°C, and injection speed is 40-70% of the maximum injection speed of the injection molding machine.

[0068] 2-2) Obtain the hydrocyclone mold and assemble the mold core onto the hydrocyclone mold.

[0069] In an embodiment of the present invention, the hydrocyclone injection mold is made of SKD11 high wear-resistant mold steel, which has a heat treatment hardness of 62-65 HRC.

[0070] In an embodiment of the present invention, the core molded by injection molding is assembled with the hydrocyclone mold through a positioning device / component, thereby enabling injection molding and demolding of the hydrocyclone blank with the core mold. Then, the core mold is removed by degreasing treatment, thereby avoiding the adverse effects of the "inverted T-shaped" structure on the demolding process and obtaining a hydrocyclone blank with high dimensional accuracy.

[0071] 2-3) Granular feed injection molding is used to obtain a hydrocyclone preform with a mold core, such as... Figure 2 As shown.

[0072] In an embodiment of the present invention, the injection molding process parameters for the hydrocyclone preform with mold core are as follows: injection temperature is 170-200°C, injection pressure is 100-130MPa, holding pressure is 90-120MPa, holding time is 5-25s, mold temperature is 80-120°C, and injection speed is 50-80% of the maximum injection speed of the injection molding machine.

[0073] It is worth mentioning that the hydrocyclone mold in this embodiment of the invention is equipped with a manually operated insert. The structure and number of the insert can be determined according to the size characteristics of the fan blades in the hydrocyclone. The insert is distributed in a ring in the hydrocyclone. After the injection molding of the preform, the insert is removed using a demolding tool, and the injection molding is demolded. During the next round of injection molding, the insert is repositioned on the mold using a matching tool. It can be recycled and repeated, so as to quickly produce hydrocyclone preforms with mold cores in batches. After sintering, combined with unencased hot isostatic pressing, a fully dense TiAl alloy hydrocyclone with uniform microstructure and high dimensional accuracy can be obtained.

[0074] 3) Degrease the hydrocyclone preform with mold core, wherein the degreasing treatment includes solvent degreasing, catalytic degreasing and thermal degreasing.

[0075] In embodiments of the present invention, solvent degreasing uses at least one of n-heptane, anhydrous ethanol, trichloroethylene, and trichloroethane as the solvent.

[0076] Solvent degreasing is performed at a temperature of 35–65°C for 6–12 hours. After degreasing, the product is dried in a vacuum drying oven at 40–60°C for 4–8 hours, followed by catalytic degreasing.

[0077] In an embodiment of the present invention, catalytic degreasing is oxalic acid catalytic degreasing, using a nitrogen degreasing atmosphere with a nitrogen flow rate of 20–100 L / min, a degreasing temperature of 110–150 °C, an acid inlet rate of 2–6 g / min, and a degreasing time of 6–14 h. Thermal degreasing is then performed.

[0078] In an embodiment of the present invention, thermal degreasing is carried out under vacuum conditions, with high-purity argon as the protective atmosphere and a vacuum degree of 1 to 40 Pa; the temperature is increased from room temperature to 450 to 600°C at a rate of 1 to 5°C / min and held for 0.5 to 2 hours.

[0079] 4) After hot degreasing, pre-sintering is carried out to obtain the pre-sintered billet of the hydrocyclone.

[0080] In an embodiment of the present invention, after thermal degreasing is completed, the temperature is increased to 900-1100°C at a rate of 5-10°C / min and held for 0.5-2 hours.

[0081] 5) Sinter the pre-sintered billet of the hydrocyclone.

[0082] In an embodiment of the present invention, the sintering process is performed under vacuum conditions, with a vacuum degree of 10. -2 ~10 -4 Pa, firstly, the temperature is increased from room temperature to 900-1100℃ at 5-10℃ / min and held for 0.5-1h for the first stage of sintering; then, the temperature is increased to 1300-1400℃ at 1-3℃ / min and held for 1-6h for the second stage of sintering.

[0083] 6) Unencased hot isostatic pressing is used to produce nearly fully dense (density > 99%) hydrocyclone components.

[0084] In an embodiment of the present invention, the uncoated hot isostatic pressing process is performed under vacuum conditions, with a vacuum degree of 10. -2 ~10 -4 Pa, temperature 1200~1300℃, heat preservation 1~6h, pressure preservation 160~200MPa.

[0085] According to a specific embodiment of the present invention, a TiAl alloy cyclone separator is also provided, such as... Figure 3 As shown.

[0086] The TiAl alloy hydrocyclone of this invention is prepared by the above-mentioned injection molding method. Its density is 99% to 99.8%, its dimensional accuracy is ±0.1% to ±0.5%, the dimensional deviation of key parts is 0.1 to 0.3 mm, and the surface roughness of the sample is Ra1.6 μm to Ra3.2 μm.

[0087] The following detailed description of the TiAl alloy hydrocyclone and its injection molding preparation method in this invention will be provided through specific embodiments.

[0088] Example 1:

[0089] Using 0-20μm Ti-48Al-2Cr-2Nb pre-alloyed powder as raw material, with a solid powder loading of 62%, 80% polyoxymethylene, 4% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 8% stearic acid, and 3% microcrystalline wax were weighed out to form a binder system. First, the pre-alloyed powder was mixed evenly with polyoxymethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, stearic acid, and microcrystalline wax, and then added to a mixer. After mixing at 180℃ and 30r / min for 1.5h, the mixture was taken out and placed in a metal crusher to be made into granular feed.

[0090] Using water-soluble paraffin wax as raw material, injection molding is used to obtain... Figure 1The mold core shown is injected at a temperature of 70°C, with an injection pressure of 90MPa, a holding pressure of 80MPa, a holding time of 25s, a mold temperature of 50°C, and an injection speed of 50% of the maximum injection speed of the injection molding machine. After cooling, the mold core is assembled into the corresponding position of the same shape in the hydrocyclone mold using a positioning device. Using the above-mentioned feed material as raw material, a hydrocyclone blank with a mold core is obtained by injection using the hydrocyclone mold. The injection temperature is 190°C, the injection pressure is 120MPa, the holding pressure is 110MPa, the holding time is 5s, the mold temperature is 110°C, and the injection speed is 65% of the maximum injection speed of the injection molding machine.

[0091] Take the hydrocyclone blank with the mold core, such as Figure 2 As shown, the core was immersed in n-heptane at 45°C until it was completely dissolved. After being removed, it was dried in a vacuum drying oven at 45°C for 8 hours to obtain a hydrocyclone blank. Then, the hydrocyclone blank was placed in an oxalic acid degreasing furnace for catalytic degreasing. The catalytic atmosphere was high-purity nitrogen, the gas flow rate was 50 L / min, the degreasing temperature was 135°C, the acid inlet rate was 5 g / min, and the degreasing time was 10 hours. Subsequently, the degreased blank was placed in a vacuum degreasing sintering furnace for thermal degreasing. The protective atmosphere was high-purity argon, the vacuum degree was 30 Pa, the heating rate was 2°C / min, the degreasing temperature was 500°C, and the holding time was 2 hours. Then, the temperature was increased to 1000°C at 5°C / min and held for 1 hour for pre-sintering.

[0092] The pre-sintered green body was placed in a vacuum sintering furnace for sintering treatment at a vacuum degree of 10. -3 The specific process is as follows: First-stage sintering is performed by heating from room temperature to 1000℃ at a rate of 8℃ / min and holding for 0.5h; second-stage sintering is performed by heating to 1400℃ at a rate of 2℃ / min and holding for 3h to obtain a sintered blank; finally, the sintered blank is subjected to unclad hot isostatic pressing (HIP) at a temperature of 1280℃, a pressure of 170MPa, and a holding time of 4h, thereby obtaining a fully dense TiAl alloy hydrocyclone component, such as... Figure 3 As shown.

[0093] Examples 2 to 6 use the same preparation method as Example 1, but differ in the core material used, the designed binder composition, and the parameters of the powder injection molding process. The core material, binder composition, and injection molding process parameters of Examples 1 to 6 are summarized in Tables 1 to 5.

[0094] Table 1. Mold core materials and their preparation process parameters in Examples 1-6

[0095]

[0096] Table 2. Preparation process parameters of the adhesive

[0097]

[0098]

[0099] Table 3 summarizes the process parameters for mixing and injection molding in Examples 1-6.

[0100]

[0101] Table 4 summarizes the degreasing process parameters in Examples 1-6.

[0102]

[0103]

[0104] Table 5 Summary of process parameters for pre-sintering, sintering and hot isostatic pressing in Examples 1-6

[0105]

[0106]

[0107] In Examples 1-6 of this invention, a typical cyclone with a complex shape is used as a specific example. Through the designed mold core, a TiAl alloy cyclone with high density, high dimensional accuracy and good surface quality is prepared by powder injection molding technology, which shows the feasibility of preparing cyclones for aero-engines by injection molding method proposed in this invention.

[0108] The following comparative experiments will illustrate the advantages of the TiAl alloy hydrocyclone preparation method of this invention and the specific range of the main parameters in the injection molding process.

[0109] I. Experimental Subjects

[0110] The TiAl alloy hydrocyclone components prepared in Examples 1-6 and the TiAl alloy hydrocyclone components prepared in Comparative Examples 1-10, wherein:

[0111] Comparative Example 1:

[0112] Using TiAl-based pre-alloyed powder with the same composition as in Example 1, and selecting a solid powder loading of 62%, 80% polyoxymethylene, 4% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 8% stearic acid, and 3% microcrystalline wax were weighed to form a binder system. Then, conventional solid injection molds were used to sequentially perform injection molding, debinding, pre-sintering, sintering, and hot isostatic pressing.

[0113] Comparative Example 2:

[0114] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 1, except that the particle size range of the pre-alloyed powder used was 0–45 μm.

[0115] Comparative Example 3:

[0116] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 1, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was lower. The binder system was composed of 85% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 6% stearic acid, and 1% microcrystalline wax by mass ratio.

[0117] Comparative Example 4:

[0118] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 1, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was higher. The binder system was composed of 82% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 4% stearic acid, and 6% microcrystalline wax by mass ratio.

[0119] Comparative Example 5:

[0120] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 3, except that the particle size range of the pre-alloyed powder used was 0–45 μm.

[0121] Comparative Example 6:

[0122] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 3, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was lower. The binder system was composed of 85% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 6% stearic acid, and 1% microcrystalline wax by mass ratio.

[0123] Comparative Example 7:

[0124] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 3, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was higher. The binder system was composed of 82% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 4% stearic acid, and 6% microcrystalline wax by mass ratio.

[0125] Comparative Example 8:

[0126] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 5, except that the particle size range of the pre-alloyed powder used was 0–45 μm.

[0127] Comparative Example 9:

[0128] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 5, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was lower. The binder system was composed of 85% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 6% stearic acid, and 1% microcrystalline wax by mass ratio.

[0129] Comparative Example 10:

[0130] TiAl alloy hydrocyclone components were prepared using the same preparation process as in Example 5, except that the contents of each component in the binder system were different, especially the content of microcrystalline wax was higher. The binder system was composed of 82% polyoxymethylene, 3% high-density polyethylene, 5% ethylene-vinyl acetate copolymer, 4% stearic acid, and 6% microcrystalline wax by mass ratio.

[0131] II. Experimental Methods

[0132] The performance of the TiAl alloy hydrocyclone components prepared in Examples 1-6 and Comparative Examples 1-10 was determined using conventional testing methods in the prior art.

[0133] Performance testing:

[0134] (1) Relative density test: The relative density of the parts prepared in Examples 1-6 and Comparative Examples 1-10 was determined using an analytical balance.

[0135] (2) Dimensional deviation test: The dimensional accuracy and dimensional deviation of key parts of the parts prepared by Examples 1 to 6 and Comparative Examples 1 to 10 were measured by using vernier calipers.

[0136] (3) Surface roughness test: The surface roughness of the parts prepared in Examples 1-6 and Comparative Examples 1-10 was measured using a laser confocal microscope.

[0137] III. Experimental Results

[0138] Testing revealed that the TiAl alloy hydrocyclones prepared in Examples 1-6 were nearly fully dense and possessed high assembly precision; the density was 99%-99.8%; the dimensional accuracy was ±0.1%-±0.5%; the dimensional deviation of key parts was 0.1-0.3 mm; and the surface roughness was Ra1.6 μm-Ra3.2 μm.

[0139] The experimental results of Examples 1-6 and Comparative Examples 1-10 are summarized below, as detailed in Table 6.

[0140] Table 6. Performance comparison of hydrocyclone components prepared in Examples 1-6 and Comparative Examples 1-10

[0141]

[0142] Through testing and data comparison, it was found that in Comparative Example 1, the injection molding preform was hindered by the "inverted T-shaped" structure during the injection molding stage, making it difficult to demold smoothly and produce a high-quality hydrocyclone preform. However, in Examples 1-6 of this invention, an innovative water-soluble mold core design method was used to fill the difficult-to-open areas with water-soluble substances, avoiding the obstruction of the annular "inverted T-shaped" structure, thus successfully forming a hydrocyclone preform with a mold core. Therefore, the design of the mold core structure in this invention directly affects the quality of the injection-molded preform.

[0143] Comparative Examples 2, 5, and 8 used TiAl pre-alloyed powder with a relatively large particle size (0–45 μm) as raw material to prepare hydrocyclone components. After uncoated hot isostatic pressing densification treatment, the density of the components was still at a low level (<96%). In contrast, Examples 1–6 of this invention used finer 0–20 μm TiAl pre-alloyed powder as raw material, which allowed for a higher level of sintering activity of the raw material powder. After vacuum sintering, the open pores could be completely closed, and after hot isostatic pressing, the closed pores could be closed, ultimately achieving a near-fully dense hydrocyclone component.

[0144] Furthermore, in Comparative Examples 3, 6, and 9, the low content of microcrystalline wax resulted in excessively high viscosity of the injection feed material, preventing it from filling the entire hydrocyclone cavity smoothly. This led to severe underfill defects during injection, resulting in the inability to produce high-quality hydrocyclone green parts. In Comparative Examples 4, 7, and 10, the excessively high content of microcrystalline wax resulted in low viscosity of the injection feed material, leading to defects such as flash and uneven density distribution during injection molding. Even after hot isostatic pressing, the final part's density was still below 99%, and its dimensional accuracy was low. In contrast, Examples 1-6 of this invention use an appropriate amount of microcrystalline wax to adjust the flowability of the binder system. This not only allows the feed material to fill the entire hydrocyclone uniformly at a lower viscosity but also reduces friction between the mold core and the hydrocyclone, improving the surface quality of the part. Therefore, it is evident that the absence or alteration of any component in the raw material powder or the binder, or changes in the proportions between the components, will prevent the successful preparation of high-quality injection-molded parts.

[0145] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for injection molding a TiAl alloy hydrocyclone, characterized in that, Includes the following steps: Granular feedstock is prepared by mixing TiAl-based pre-alloyed powder and binder as raw materials and then crushing them; the composition of the TiAl-based pre-alloyed powder, by atomic percentage, is: Al 45~49 at.%, Cr 0~5 at.%, Nb 0~5 at.%, with the balance being Ti; the binder, by mass percentage, comprises the following components: polyoxymethylene 78~85%, high-density polyethylene 2~6%, ethylene-vinyl acetate copolymer 3~8%, stearic acid 5~10%, and microcrystalline wax 2~5%; A hydrocyclone preform with a mold core is obtained by injection molding. The injection temperature is 170~200℃, the injection pressure is 100~130MPa, the holding pressure is 90~120MPa, the holding time is 5~25s, the mold temperature is 80~120℃, and the injection speed is 50~80% of the maximum injection speed of the injection molding machine. The mold core is an inverted T-shaped structure at the annular position of the hydrocyclone to be produced. The mold core is obtained by injection molding using a water-soluble material, which is water-soluble paraffin or polyethylene glycol. The hydrocyclone preform with the mold core is then subjected to degreasing, pre-sintering, sintering, and hot isostatic pressing without cladding to obtain the hydrocyclone part.

2. The injection molding preparation method according to claim 1, characterized in that, Injection molding to obtain a hydrocyclone preform with a mold core includes: Obtain the mold core and use water-soluble materials for injection molding to obtain the mold core; Obtain the hydrocyclone mold and assemble the mold core onto the hydrocyclone mold; The cyclone preform with mold core is obtained by injection molding using the granular feed.

3. The injection molding preparation method according to claim 1, characterized in that, The injection molding process parameters for the mold core are as follows: injection temperature is 60~150℃, injection pressure is 50~100MPa, holding pressure is 40~90MPa, holding time is 5~25s, mold temperature is 40~70℃, and injection speed is 40~70% of the maximum injection speed of the injection molding machine.

4. The injection molding preparation method according to claim 1, characterized in that, The degreasing process includes solvent degreasing, catalytic degreasing, and thermal degreasing; The solvent degreasing uses at least one of n-heptane, anhydrous ethanol, trichloroethylene, and trichloroethane as the solvent; The catalytic defatting is oxalic acid-catalyzed defatting; The thermal degreasing is carried out under vacuum conditions, with the temperature increased from room temperature to 450-600°C at a rate of 1-5°C / min under a protective atmosphere, and held at that temperature for 0.5-2 hours.

5. The injection molding preparation method according to claim 4, characterized in that, The solvent degreasing temperature is 35~65℃, and the time is 6~12h; after degreasing, it is dried in a vacuum drying oven at 40~60℃ for 4~8h.

6. The injection molding preparation method according to claim 4, characterized in that, The catalytic degreasing uses a nitrogen degreasing atmosphere with a nitrogen flow rate of 20~100L / min, a degreasing temperature of 110~150℃, an acid inlet rate of 2~6g / min, and a degreasing time of 6~14h.

7. The injection molding preparation method according to claim 4, characterized in that, The thermal degreasing process uses high-purity argon as a protective gas, with a vacuum degree of 1~40Pa.

8. The injection molding preparation method according to claim 1, characterized in that, The pre-sintering treatment is performed at a temperature of 900~1100℃, with a holding time of 0.5~2h and a heating rate of 5~10℃ / min.

9. The injection molding preparation method according to claim 1, characterized in that, The sintering process is carried out under vacuum conditions. First, the temperature is increased from room temperature to 900-1100℃ at a rate of 5-10℃ / min and held for 0.5-1h to carry out the first stage of sintering. Then, the temperature is increased to 1300-1400℃ at a rate of 1-3℃ / min and held for 1-6h to carry out the second stage of sintering.

10. The injection molding preparation method according to claim 9, characterized in that, Vacuum degree is 10 -2 ~10 -4 Pa.

11. The injection molding preparation method according to claim 1, characterized in that, The uncoated hot isostatic pressing process is carried out under vacuum conditions at a temperature of 1200~1300℃ for 1~6 hours and a holding pressure of 160~200MPa.

12. The injection molding preparation method according to claim 11, characterized in that, Vacuum degree is 10 -2 ~10 -4 Pa.

13. The injection molding preparation method according to claim 1, characterized in that, The powder loading of the feed is 60-65%.

14. The injection molding preparation method according to claim 1, characterized in that, The TiAl-based pre-alloyed powder has a particle size distribution of 0~20μm.

15. The injection molding preparation method according to claim 1, characterized in that, The mixing temperature is 170~200°C, the rotation speed is 5~30 r / min, and the time is 0.5~2h.

16. A TiAl alloy hydrocyclone, characterized in that, It is manufactured using the injection molding method according to any one of claims 1-15; wherein, The density of the TiAl alloy hydrocyclone is 99%~99.8%, the dimensional accuracy is ±0.1%~±0.5%, the dimensional deviation of key parts is 0.1~0.3mm, and the surface roughness of the sample is Ra1.6μm~Ra3.2μm.

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