A high-entropy ceramic aerospace seal with high airtightness, temperature resistance and wear resistance and a preparation method thereof

Abstract

The application discloses a high-entropy ceramic aerospace sealing element with high airtightness, temperature resistance and wear resistance and a preparation method thereof, and relates to the technical field of aerospace sealing elements. The high-entropy ceramic aerospace sealing element comprises the following raw materials in parts by weight: 10-15 parts of carbonized tantalum, 15-17 parts of carbonized titanium, 8-10 parts of aluminum nitride, 5-8 parts of yttrium oxide, 15-18 parts of aluminum oxide, 20-22 parts of high-entropy ceramic powder, 5-8 parts of carbon fiber, 1-3 parts of ceramic stabilizer, 1-3 parts of ceramic reinforcing agent, 1-3 parts of toughening agent, 1-3 parts of coupling agent, 1-5 parts of ceramic lubricant, 1-2 parts of active carbon and 1-3 parts of surfactant. The application effectively solves the problem of insufficient airtightness of the existing aerospace sealing element by optimizing the raw material formula and designing the preparation process, and the application has excellent mechanical properties, high-temperature resistance and chemical stability, thereby meeting the harsh requirements of the aerospace field on the sealing element.

Description

Technical Field

[0001] This invention relates to the field of aerospace sealing technology, specifically to a high-entropy ceramic aerospace sealing component with high airtightness, temperature resistance, and wear resistance, and its preparation method. Background Technology

[0002] In the aerospace field, the airtightness of seals is crucial, directly affecting the operational performance and reliability of spacecraft, as well as the safety of astronauts. However, existing aerospace seals suffer from limitations in material properties and manufacturing processes, resulting in certain performance constraints. For example, due to inherent material properties and manufacturing issues, seals struggle to maintain a good sealing effect for extended periods under extreme environments. Furthermore, high temperatures can cause material deformation, and frequent friction and vibration can lead to rapid wear, severely degrading seal performance or even causing failure. Poor high-temperature resistance and wear resistance fail to meet increasingly stringent aerospace requirements.

[0003] In addition, existing methods for preparing seals also have certain defects. For example, it is difficult to achieve uniform mixing in the raw material mixing stage, resulting in unstable product performance; the pressure and temperature control in the hot pressing process is not precise enough, affecting the shape and performance of the seal; unreasonable setting of the heating rate and holding time in the vacuum sintering stage may lead to uneven internal structure and affect airtightness; and the surface treatment process is rough and cannot meet the high precision requirements, thus affecting the sealing effect.

[0004] Due to the shortcomings of the aforementioned materials and manufacturing processes, the airtightness of existing aerospace seals in extreme environments cannot be effectively guaranteed. This could not only lead to gas leakage inside the spacecraft, interfering with its normal operation, but also shorten the spacecraft's service life, posing significant risks and losses to space missions. Therefore, providing a high-entropy ceramic aerospace seal with excellent mechanical properties, high-temperature resistance, and chemical stability, along with its manufacturing method, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a high-entropy ceramic aerospace seal with high airtightness, high temperature resistance, and wear resistance, along with its preparation method. By optimizing the raw material formulation, including multiple components such as tantalum carbide, titanium carbide, aluminum nitride, yttrium oxide, and alumina, and by carefully designing the preparation process—such as precisely controlling the preparation of the mixed powder, the conditions for hot pressing, the heating rate and holding time of vacuum sintering, and the precision of surface treatment—this invention effectively solves the problem of insufficient airtightness in existing aerospace seals. Simultaneously, it possesses excellent mechanical properties, high-temperature resistance, and chemical stability, meeting the stringent requirements of the aerospace field for seals.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance, comprising the following parts by weight of raw materials:

[0008] The composition includes 10-15 parts tantalum carbide, 15-17 parts titanium carbide, 8-10 parts aluminum nitride, 5-8 parts yttrium oxide, 15-18 parts alumina, 20-22 parts high-entropy ceramic powder, 5-8 parts carbon fiber, 1-3 parts ceramic stabilizer, 1-3 parts ceramic reinforcing agent, 1-3 parts toughening agent, 1-3 parts coupling agent, 1-5 parts ceramic lubricant, 1-2 parts activated carbon, and 1-3 parts surfactant.

[0009] Tantalum carbide, titanium carbide, aluminum nitride, yttrium oxide, and alumina are the core ceramic matrix raw materials of this invention. The selection and compounding of these raw materials are based on the core requirements of aerospace sealing components for high airtightness, high temperature resistance, high mechanical properties, and chemical stability. The reasons for the selection of each raw material and the advantages of compounding are as follows:

[0010] Tantalum carbide (TaC): With a melting point as high as 3880℃ and a hardness of 9-10 Mohs, it is an ultra-high hardness, ultra-high temperature ceramic material with extremely strong chemical stability. It can maintain structural stability at temperatures above 1800℃, while also improving the density of the ceramic matrix, reducing gas permeation channels, and ensuring high airtightness.

[0011] Titanium carbide (TiC): melting point 3140℃, hardness 9-9.5 Mohs, has excellent wear resistance and electrical conductivity, and has good compatibility with TaC, which can form TaC-TiC solid solution, reduce the sintering temperature of ceramic matrix and improve sintering density.

[0012] Aluminum nitride (AlN): It has high thermal conductivity, low coefficient of thermal expansion, and better toughness than pure carbide ceramics, which can alleviate the brittleness of carbide ceramics. At the same time, the nitrogen bond of AlN can form a covalent bond with carbide, which can improve the structural stability of the matrix. It does not decompose at high temperature, ensuring the airtightness of the seal at high temperature.

[0013] Yttrium oxide (Y2O3): As a sintering aid, it can reduce the sintering activation energy of ceramics, promote grain densification, inhibit the high-temperature oxidation of carbide ceramics, improve chemical stability, and form a composite phase with alumina to improve the toughness of the matrix.

[0014] Alumina (Al2O3): melting point 2030℃, hardness 5-9 Mohs, relatively low cost, and excellent wear resistance, insulation and chemical stability. As the base phase of ceramic matrix, it can form a composite system with other high melting point carbides and nitrides to balance material performance and preparation cost.

[0015] This invention uses the above-mentioned raw materials to form a multi-component composite ceramic matrix. TaC and TiC are ultra-high hardness and ultra-high temperature phases, AlN and Al2O3 are toughening phases, and Y2O3 is a sintering aid. The phases form a microstructure of solid solution and composite phase, which not only ensures the high temperature resistance above 1800℃ and high wear resistance of the sealing parts, but also alleviates the brittleness of pure carbide ceramics and improves fracture toughness.

[0016] Meanwhile, the compounding of raw materials in this invention can improve sintering density and ensure high airtightness. The complementary particle sizes of the raw materials (TaC 1-5μm, TiC 3-5μm, AlN 2-4μm, Al2O3 1-3μm, Y2O3 4-6μm) achieve close packing. Combined with the sintering fluxing effect of Y2O3, the matrix density after sintering is ≥98.5%, significantly reducing porosity and grain boundary defects, blocking gas permeation paths, and making the airtightness <1×10 -11 Pa・m 3 / s.

[0017] The composite ceramic matrix exhibits excellent chemical stability. Under the high temperature, high vacuum, and strong radiation environment of the aerospace field, it does not react with aerospace propellants or atomic oxygen in the space environment, thus avoiding material degeneration and failure and extending the service life of the seals.

[0018] The core raw materials and high-entropy ceramic powder are highly compatible in composition, synergistically enhancing each other and forming a continuous solid solution phase. This further improves the high-temperature stability and density of the ceramic matrix, achieving a performance improvement effect of 1+1>2.

[0019] Preferably, the ceramic stabilizer is calcium oxide and magnesium oxide, and the mass ratio of calcium oxide to magnesium oxide is 1.5-2.5:1, more preferably 2:1;

[0020] The ceramic reinforcing agent is zirconium oxide and silicon nitride, and the mass ratio of zirconium oxide to silicon nitride is 1-2:1, more preferably 1.5:1;

[0021] The ceramic lubricant is graphite and molybdenum disulfide, and the mass ratio of graphite to molybdenum disulfide is 0.8-1.2:1, more preferably 1:1.

[0022] The ceramic stabilizers (calcium oxide and magnesium oxide), ceramic reinforcing agents (zirconia and silicon nitride), and ceramic lubricants (graphite and molybdenum disulfide) used in this invention cannot be used as single components alone. The combination of two components creates a synergistic effect; the absence of any single component will lead to a significant decrease in the performance of the sealing components, failing to meet the stringent requirements of the aerospace field. Specifically:

[0023] Ceramic stabilizers: calcium oxide (CaO) and magnesium oxide (MgO). CaO can effectively inhibit the excessive growth of grain boundary phases in the ceramic matrix and reduce grain boundary defects; MgO can refine ceramic grains and improve matrix density. Both are alkaline oxides, which can react with trace acidic impurities in ceramic raw materials, reducing the impact of impurities on airtightness. At the same time, MgO can compensate for the high volatility of CaO at high temperatures, and CaO can alleviate the problem of poor dispersibility of MgO. They synergistically improve the chemical stability and high-temperature structural stability of the ceramic matrix, reduce the generation of pores during sintering, and ensure the high airtightness of the seals. Using CaO alone can easily lead to high-temperature grain boundary cracking in ceramics, while using MgO alone results in poor grain refinement and insufficient density.

[0024] Ceramic reinforcing agents: Zirconia (ZrO2) and silicon nitride (Si3N4). ZrO2 has a phase transformation toughening effect, undergoing a martensitic phase transformation under stress, absorbing crack energy, and improving the fracture toughness of ceramics. Si3N4 is a high-hardness, high-modulus ceramic phase that can form a hard reinforcing phase in the matrix, improving surface hardness and wear resistance. Moreover, the whisker-like structure of Si3N4 can form a composite reinforcing system with the granular structure of ZrO2, synergistically improving the mechanical properties of ceramics. The combination of the two has both phase transformation toughening and hard phase reinforcement effects, simultaneously improving the fracture toughness, wear resistance, and compressive strength of the sealing components. Using ZrO2 alone can only improve toughness, with limited improvement in wear resistance. Using Si3N4 alone can easily lead to increased brittleness of ceramics, making them prone to cracking at low temperatures.

[0025] Ceramic lubricants: graphite and molybdenum disulfide (MoS2). Graphite has a layered structure with weak interlayer bonding, which can form a solid lubricating film, making it suitable for high-temperature oxidizing environments. MoS2 has better layered slip properties and a lower lubrication coefficient, making it suitable for high-vacuum aerospace environments. The combination of the two can achieve complementary lubrication effects under different aerospace conditions, and graphite can inhibit the oxidative decomposition of MoS2 at high temperatures. It can still maintain excellent lubrication performance in the extreme aerospace environment of 1800℃ high temperature and high vacuum, reducing friction and wear between seals and mating parts and extending service life. Graphite alone has a high lubrication coefficient, while MoS2 alone is prone to failure at high temperatures and cannot meet the wear resistance requirements of aerospace seals.

[0026] The toughening agent of this invention is selected from one or two of phenolic resin and polyimide resin. After high-temperature pyrolysis, polyimide can controllably precipitate 0.8% to 2.0% dispersed carbon phase, which is uniformly distributed in the ceramic grain boundary, thereby achieving crack deflection and grain boundary pinning and playing a toughening role.

[0027] This invention uses epoxy resin as a green body binder, added externally during the slurry preparation stage. During the debinding stage at 300–500℃, most of the epoxy resin undergoes pyrolysis and volatilization, leaving only trace amounts of residual carbon (<0.3wt%). This carbon cannot form an effective toughening phase at the ceramic grain boundaries and therefore lacks matrix toughening effect.

[0028] The coupling agent is a silane or a titanate, and the mass ratio of the silane to the titanate is 1.5-2.5:1, preferably 2:1;

[0029] The surfactant is at least one of sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and Tween-80.

[0030] Preferably, the silane is at least one of silane coupling agents KH550, KH560, and KH570; and the titanate is at least one of titanate coupling agents NDZ-101 and NDZ-201.

[0031] Preferably, the high-entropy ceramic powder is a TiC-TaC-ZrC-SiC-AlN powder with a molar ratio of 1:1:1:1:1; a melting point of 3000℃; a hardness of 7-9 Mohs; a particle size of 2-5 μm; a face-centered cubic crystal form; a density of ≥98%; and a high-temperature thermal expansion coefficient of 4.0-5.0 × 10⁻⁶. -6 / ℃ (25-1800℃).

[0032] Preferably, the method for preparing the high-entropy ceramic powder is as follows:

[0033] (1) Weigh TiC, TaC, ZrC, SiC and AlN powders (particle size 1-3μm) by molar ratio, add anhydrous ethanol as dispersant and epoxy resin as binder, and ball mill for 24-36h (ball-to-material ratio 10:1, rotation speed 300r / min) to obtain mixed powder;

[0034] (2) The mixed powder is dried at 80-100℃, passed through a 200-mesh sieve, placed in a vacuum furnace, and vacuum sintered at 1800-2000℃ and 10-20MPa pressure for 4-6 hours; after sintering, it is crushed and sieved to obtain TiC-TaC-ZrC-SiC-AlN pentagonal carbon nitride-based high entropy ceramic powder with a particle size of 2-5μm.

[0035] Preferably, the airtightness of the high-entropy ceramic aerospace seal is <1×10⁻⁶. -11 Pa·m 3 / s, high temperature resistance test temperature above 1800℃, wear resistance <0.10mm 3 / N·m.

[0036] This invention uses carbonitride-based high-entropy ceramic powder, which is a pentagonal high-entropy ceramic. This component is compatible with the raw materials such as tantalum carbide, titanium carbide, and aluminum nitride in the sealing component of this invention, and can form a solid solution, which improves the density and high-temperature stability of the ceramic matrix. The melting point is stable at about 3000℃ and the hardness is 7-9 Mohs, which meets the original technical requirements.

[0037] The preparation method of the high-entropy ceramic aerospace seal with high airtightness, high temperature resistance, and wear resistance described above specifically includes the following steps:

[0038] (1) Weigh the raw materials according to the stated weight proportions and set aside;

[0039] (2) The raw materials are mixed evenly and then hot-pressed to obtain a green blank of the sealing component;

[0040] (3) After the green blank of the sealing component is subjected to vacuum sintering and surface treatment in sequence, a high-entropy ceramic aerospace sealing component with high airtightness, temperature resistance and wear resistance is obtained.

[0041] Preferably, the specific steps of mixing in step (2) are as follows: anhydrous ethanol and epoxy resin are added to the raw materials and stirred until they are in the form of a slurry. Then, the mixture is ball-milled for 6-10 hours and then dried and sieved to obtain the mixed powder.

[0042] Preferably, the molar concentration of the raw materials in the slurry is 0.003-0.005 mol / L.

[0043] This range is the optimal range, which can achieve uniform dispersion of powder, ensure ball milling effect, and at the same time take into account drying efficiency and avoid powder agglomeration. If the concentration is <0.003mol / L, the amount of anhydrous ethanol is too large, the powder concentration is too low, the probability of powder collision during ball milling is small, the mixing uniformity is poor, and the energy consumption and time during drying are high, which can easily lead to powder agglomeration. If the concentration is >0.005mol / L, the amount of anhydrous ethanol is too small, the slurry viscosity is high, the fluidity is poor, and uniform dispersion of powder cannot be achieved during ball milling. It is easy to cause ball sticking and can sticking, resulting in local segregation of mixed powder. After sintering, the ceramic matrix will produce pores and cracks, affecting the airtightness.

[0044] Preferably, the parameters for the ball milling process are: ball milling speed 250-350 r / min, ball-to-material ratio 8-12:1, and time 6-10 h.

[0045] Preferably, the parameters for hot pressing in step (2) are: pressure of 20-35MPa, temperature of 1600-1800℃, the powder is first pre-pressed at room temperature at 15MPa and then hot-pressed at high temperature.

[0046] Preferably, the vacuum sintering step in step (3) is as follows: placing the green blank of the sealing component in a vacuum furnace and reducing the pressure inside the furnace to 1-5×10⁻⁶. -3 Pa, first heat to 1000-1200℃ at a heating rate of 80-120℃ / min, then heat to 2000-2200℃ at a heating rate of 120-150℃ / min, hold at that temperature for 3-5 hours, and then cool to room temperature by introducing inert gas.

[0047] Preferably, the inert gas is argon (Ar) with a flow rate of 50-100 mL / min.

[0048] The high vacuum environment used in this invention can prevent the ceramic powder from oxidizing at high temperatures, reduce the formation of pores and impurity phases, and use argon gas, which is highly inert and does not react with the ceramic matrix. The uniform flow of argon gas during cooling can achieve gradient cooling and prevent the ceramic from cracking due to thermal stress.

[0049] Preferably, the surface treatment step in step (3) is as follows: the vacuum sintered green seal blank is polished on a polishing machine, and polishing agent is added to the surface to improve the polishing effect and reduce friction damage, so as to ensure that the surface roughness Ra of the seal is Ra=0.05~0.08μm. After polishing, water-based cleaning agent is used for cleaning.

[0050] Preferably, the polishing agent is a W0.5 specification water-based diamond micro powder polishing agent: after polishing, the surface of the workpiece is cleaned with a water-based cleaner (pH=6.5~7.5). The water-based cleaner is specifically a polyethylene glycol type neutral degreasing cleaner with a concentration of 5%~10% and a cleaning temperature of 40-60℃. Strong acid / alkali cleaners should be avoided to prevent corrosion of the sealing surface and affect the sealing effect.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) By optimizing the formula design and introducing high-entropy ceramic powder and other components, this invention effectively solves the problem of insufficient air tightness of existing aerospace sealing components, enhances the high temperature resistance and wear resistance of the sealing components, and enables them to maintain excellent air tightness in extreme environments.

[0053] (2) This invention improves the success rate of sealing component preparation by optimizing the formula design and preparation process. It uses high-strength tantalum carbide, high-hardness titanium carbide, and high-toughness aluminum nitride as main components. The high-temperature carbon toughening effect of polyimide enhances the fracture toughness of the matrix, while epoxy resin optimizes the powder molding process and improves the integrity of the green blank. The combination of these two components yields a highly dense and tough aerospace sealing ceramic, with an airtightness of <1×10⁻⁶. -11 Pa·m 3 / s, operating temperature (°C) > 1800, abrasion resistance < 0.10mm 3 / N·m, (hardness (HV)) > 2000, fracture toughness (MPam) 1 / 2 >6, effectively solving the problem that existing seals cannot maintain excellent performance in many aspects. Attached Figure Description

[0054] 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. The drawings in this description are merely embodiments of the present invention.

[0055] Figure 1 This is a process flow diagram of a high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance according to the present invention. Detailed Implementation

[0056] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0057] Raw materials: High-entropy ceramic powder with a molar ratio of 1:1:1:1:1 (TiC-TaC-ZrC-SiC-AlN), melting point 3000℃, hardness 7-9 Mohs, particle size 2-5 μm; crystal form: face-centered cubic; density ≥98%; high-temperature thermal expansion coefficient: 4.0-5.0 × 10⁻⁶. -6 / ℃ (25-1800℃);

[0058] The carbon fiber is T700 grade PAN-based carbon fiber (7μm in diameter, 4.9GPa tensile strength).

[0059] The coupling agent is KH560 γ-glycidyl etheroxypropyltrimethoxysilane and NDZ-201 isopropyltris(dioctylpyrophosphate)titanate.

[0060] The surfactant is sodium dodecyl sulfate (SDS, industrial grade 99%, model K12).

[0061] The diamond polishing agent is a W0.5 micro-powder diamond polishing agent (water-based);

[0062] The water-based cleaner is a polyethylene glycol-based neutral degreasing cleaner (model PE-60, pH=7.0).

[0063] The activated carbon is nano-sized activated carbon (particle size 1-4μm, specific surface area 1500m² / g).

[0064] The preparation method of high-entropy ceramic powder is as follows:

[0065] (1) Weigh TiC, TaC, ZrC, SiC and AlN powders (all with a particle size of 1-3 μm) by molar ratio, add anhydrous ethanol as a dispersant and epoxy resin as a binder, and ball mill for 30 h (ball-to-material ratio 10:1, rotation speed 300 r / min) to obtain mixed powder;

[0066] (2) The mixed powder is dried at 80-100℃, passed through a 200-mesh sieve, placed in a vacuum furnace, and vacuum sintered at 1800-2000℃ and 10-20MPa pressure for 5h; after sintering, it is crushed and sieved to obtain TiC-TaC-ZrC-SiC-AlN pentagonal carbonitride-based high-entropy ceramic powder with a particle size of 2-5μm.

[0067] This invention provides a method for preparing a high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance, such as... Figure 1 As shown, the steps are as follows:

[0068] (1) Preparation of mixed powder

[0069] Weigh the raw materials according to their composition, mix them, add anhydrous ethanol and epoxy resin and stir until they form a slurry (the concentration of raw materials in the slurry is 0.003-0.005 mol / L). Then, put them into a ball mill and ball mill them for 6-10 hours. Then, use a spray dryer to dry the ball-milled particles at a temperature of 100-120℃ to make the moisture content reach 3-5%. Remove impurities and particles that do not meet the requirements by screening through a sieve to obtain a mixed powder.

[0070] (2) Hot pressing

[0071] After the mixed powder is sieved, it is first pre-formed into a green blank by dry pressing at room temperature at 15MPa, then filled into a graphite mold, and held under pressure of 20-35MPa and temperature of 1600-1800℃ for 15-20 minutes, and then cooled to obtain the green blank of the sealing part.

[0072] (3) Vacuum sintering

[0073] The above-mentioned green sealing component is placed in a vacuum furnace and heated to 1000℃ at a heating rate of 80-120℃ / min, and then heated to 2000-2200℃ at a heating rate of 120-150℃ / min. The holding time is 3-5 hours. After the holding time is completed, the furnace is cooled to room temperature to obtain the sintered sealing component blank.

[0074] (4) Surface treatment

[0075] The sintered sealing blank is fixed on the worktable of the polishing machine for polishing. An appropriate amount of diamond polishing agent is continuously added to the surface to improve the polishing effect and reduce friction damage to ensure that the requirement of 0.05-0.08μm is met. After polishing, the surface is cleaned to remove the polishing agent and impurities.

[0076] (5) Performance testing

[0077] The surface-treated seals were subjected to performance testing, including tests for air tightness, high-temperature resistance, and wear resistance. Air tightness test results were <1×10⁻⁶. -11 Pa·m3 / s, high temperature resistance test temperature is above 1800℃, wear resistance test wear resistance <0.10mm 3 The product is deemed qualified if the required N·m is met, resulting in a high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance.

[0078] The specific detection method is as follows:

[0079] I. Air tightness test

[0080] Test method: Helium mass spectrometry leak detection method (national standard test method for airtightness of aerospace sealing components, GB / T15823-2021).

[0081] Test equipment: ZLJ-27 helium mass spectrometer leak detector (CAS Instruments).

[0082] Test conditions: test pressure 0.1MPa, test temperature 25℃, helium partial pressure 50%, test time 30min.

[0083] II. High Temperature Resistance Test

[0084] Test method: High-temperature thermogravimetric-differential thermal analysis (TG-DTA) combined with high-temperature pressure resistance test;

[0085] Testing equipment: STA449F3 synchronous thermal analyzer (Netzsch), high temperature vacuum pressure tester (Shenyang Kejing);

[0086] Test conditions: Heat to the specified temperature at a heating rate of 10℃ / min, hold for 2 hours, and observe whether the sample shows deformation, cracking, or oxidation. After holding, the airtightness must still meet the requirement of < 1×10⁻¹¹Pa・m³ / s.

[0087] III. Wear Resistance Test

[0088] Test method: Ball-disc friction and wear test method (GB / T 30834-2014).

[0089] Testing equipment: UMT-3 friction and wear testing machine (Brook);

[0090] Test conditions: The friction pair is a Si3N4 ball (6mm in diameter), the load is 5N, the rotation speed is 300r / min, the sliding distance is 1000m, the test temperature is 25℃, and the vacuum degree is 1×10⁻³Pa.

[0091] IV. Hardness (HV) Test

[0092] Test method: Vickers hardness test method (GB / T 4340.1-2009).

[0093] Testing equipment: HV-1000 micro Vickers hardness tester (Shanghai Lianer);

[0094] Test conditions: test force 10N, holding time 15s, average value of 5 test points at different locations of the sample.

[0095] V. Fracture Toughness Test

[0096] Test method: Single-sided notched beam method (SENB) (GB / T 23806-2009);

[0097] Testing equipment: WDW-100 electronic universal testing machine (Jinan Shijin);

[0098] Test conditions: Sample size 2mm×4mm×20mm, cut depth 2mm, loading rate 0.5mm / min, span 16mm.

[0099] Examples 1-3

[0100] This invention provides a method for preparing a high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance, specifically including the following steps:

[0101] (1) Weigh the raw materials according to Tables 1 and 2 and set aside;

[0102] Table 1 Performance parameters of raw materials used in high-entropy ceramic aerospace seals in Examples 1-3

[0103] Table 2. Raw material ratios used in high-entropy ceramic aerospace seals in Examples 1-3

[0104] (2) Preparation parameters are shown in Table 3;

[0105] Table 3. Fabrication parameters of high-entropy ceramic aerospace seals in Examples 1-3

[0106] The test results of the high-entropy ceramic aerospace seals prepared in each embodiment are shown in Table 4.

[0107] Table 4 Performance test results of high-entropy ceramic aerospace seals in Examples 1-3

[0108] The results in Table 4 show that the performance of the three groups of samples with different ratios fluctuates reasonably. Example 2 has the best overall performance, while the performance of the high and low ratios drops slightly. The formula range is set scientifically and reasonably.

[0109] Example 4

[0110] Raw material ratio range adjustment:

[0111] Example 4-1: The stabilizer mass ratio is CaO:MgO = 1.5:1, and the other proportions and preparation process are the same as in Example 2;

[0112] Example 4-2: The stabilizer mass ratio is CaO:MgO = 2.5:1, and the other proportions and preparation process are the same as in Example 2;

[0113] Example 4-3: The reinforcing agent mass ratio is ZrO2:Si3N4=1:1, and the other proportions and preparation process are the same as in Example 2;

[0114] Example 4-4: The reinforcing agent mass ratio is ZrO2:Si3N4=2:1, and the other proportions and preparation process are the same as in Example 2;

[0115] Examples 4-5: The mass ratio of the lubricant was graphite:MoS2 = 0.8:1, and the other proportions and preparation process were the same as in Example 2;

[0116] Examples 4-6: The mass ratio of lubricant is graphite:MoS2 = 1.2:1, and the other proportions and preparation process are the same as in Example 2;

[0117] The product performance test results for Example 4 are shown in Table 5:

[0118] Table 5 Performance test results of Example 4

[0119] Example 4-1 <![CDATA[6×10 -12 ]]> 2010 0.06 6.8 qualified Example 4-2 <![CDATA[7×10 -12 ]]> 1990 0.07 6.7 qualified Example 4-3 <![CDATA[5×10 -12 ]]> 2030 0.06 6.9 qualified Example 4-4 <![CDATA[6×10 -12 ]]> 2000 0.07 6.8 qualified Examples 4-5 <![CDATA[5×10 -12 ]]> 2020 0.06 6.9 qualified Examples 4-6 <![CDATA[6×10 -12 ]]> 2010 0.07 6.8 qualified Example 2 <![CDATA[5×10 -12 ]]> 2060 0.05 7.1 qualified

[0120] As can be seen from the data in the table above, the finished products can be successfully prepared at the endpoints of each auxiliary agent ratio range defined in the claims of this invention. The performance fluctuates slightly but all meet the standards, verifying that the protection range of the formula is reasonable and feasible.

[0121] To further demonstrate the advantages of the technical solution of this invention, comparative examples of raw material exploration (Table 6) and comparative examples of preparation process exploration (Table 7) were added. By comparing the performance data with those of the comparative examples, the innovation and superiority of the formulation and process of this invention are highlighted. The test methods for all comparative examples are consistent with those of the examples, as detailed below:

[0122] Raw material exploration and comparison

[0123] A single-component missing / replacement comparison ratio was set up, and the proportions of other raw materials and preparation processes were the same as in Example 2 (the optimal example), and the core performance was tested.

[0124] Comparative Example 1

[0125] Comparative Example 1-1: No CaO+MgO stabilizer was added; the remaining proportions and preparation process were the same as in Example 2.

[0126] Comparative Examples 1-2: CaO was used as the stabilizer alone, and the other proportions and preparation process were the same as in Example 2;

[0127] Comparative Examples 1-3: MgO was used as the stabilizer alone, and the other proportions and preparation process were the same as in Example 2;

[0128] Comparative Examples 1-4: No ZrO2+Si3N4 reinforcing agent was added; the remaining proportions and preparation processes were the same as in Example 2.

[0129] Comparative Examples 1-5: ZrO2 was used alone as the reinforcing agent, and the other proportions and preparation process were the same as in Example 2;

[0130] Comparative Examples 1-6: The reinforcing agent was Si3N4 alone, and the other proportions and preparation process were the same as in Example 2;

[0131] Comparative Examples 1-7: No graphite + MoS2 reinforcing agent was added; the remaining proportions and preparation processes were the same as in Example 2.

[0132] Comparative Examples 1-8: The lubricant used alone was graphite, and the other proportions and preparation process were the same as in Example 2;

[0133] Comparative Examples 1-9: MoS2 was used as the lubricant alone, and the other proportions and preparation processes were the same as in Example 2;

[0134] The performance test results of Comparative Example 1 are shown in Table 6-1:

[0135] Table 6-1 Performance test results of Comparative Example 1

[0136] Comparative Example 1-1 <![CDATA[4.3×10 -10 ]]> 1710 0.17 1810 4.7 Unqualified Comparative Examples 1-2 <![CDATA[5.2×10 -10 ]]> 1790 0.15 1860 5.0 Unqualified Comparative Examples 1-3 <![CDATA[5.8×10 -10 ]]> 1810 0.16 1870 5.1 Unqualified Comparative Examples 1-4 <![CDATA[4.8×10 -10 ]]> 1690 0.19 1770 4.5 Unqualified Comparative Examples 1-5 <![CDATA[2.1×10 -10 ]]> 1860 0.17 1960 5.3 Unqualified Comparative Examples 1-6 <![CDATA[2.7×10 -10 ]]> 1840 0.18 2000 5.0 Unqualified Comparative Examples 1-7 <![CDATA[5.5×10 -10 ]]> 1930 0.21 2090 5.6 Unqualified Comparative Examples 1-8 <![CDATA[3.9×10 -10 ]]> 1910 0.19 2100 5.7 Unqualified Comparative Examples 1-9 <![CDATA[3.4×10 -10 ]]> 1890 0.16 2120 5.8 Unqualified Example 2 <![CDATA[5×10 -12 ]]> 2055 0.05 2225 7.1 qualified

[0137] Comparative Example 2

[0138] Experiment on the gradient of core auxiliary agent ratio:

[0139] Comparative Example 2-1: The stabilizer mass ratio was CaO:MgO = 1:1 (lower than the protection scope of this invention), and the other proportions and preparation process were the same as in Example 2;

[0140] Comparative Example 2-2: The stabilizer mass ratio was CaO:MgO = 3:1 (higher than the scope of protection of this invention), and the other ratios and preparation process were the same as in Example 2;

[0141] Comparative Examples 2-3: The reinforcing agent mass ratio was ZrO2:Si3N4 = 0.8:1 (lower than the scope of protection of this invention), and the other proportions and preparation process were the same as in Example 2;

[0142] Comparative Examples 2-4: The reinforcing agent mass ratio was ZrO2:Si3N4 = 2.2:1 (higher than the scope of protection of this invention), and the other proportions and preparation process were the same as in Example 2;

[0143] Comparative Examples 2-5: The mass ratio of lubricant was graphite:MoS2 = 0.6:1 (lower than the scope of protection of this invention), and the other proportions and preparation process were the same as in Example 2;

[0144] Comparative Examples 2-6: The mass ratio of lubricant was graphite:MoS2 = 1.4:1 (higher than the scope of protection of this invention), and the other proportions and preparation process were the same as in Example 2;

[0145] The performance test results of Comparative Example 2 are shown in Table 6-2:

[0146] Table 6-2 Performance test results of Comparative Example 2

[0147] Comparative Example 2-1 <![CDATA[7.2×10 -11 ]]> 1970 0.08 2030 6.4 Performance lower than the patented optimal ratio Comparative Example 2-2 <![CDATA[6.5×10 -11 ]]> 1950 0.08 2010 6.2 Performance lower than the patented optimal ratio Comparative Examples 2-3 <![CDATA[7.9×10 -11 ]]> 1930 0.09 1980 6.0 Performance lower than the patented optimal ratio Comparative Examples 2-4 <![CDATA[7.4×10 -11 ]]> 1960 0.09 2020 6.3 Performance lower than the patented optimal ratio Comparative Examples 2-5 <![CDATA[6.8×10 -11 ]]> 2000 0.10 2070 6.5 Performance lower than the patented optimal ratio Comparative Examples 2-6 <![CDATA[6.1×10 -11 ]]> 1990 0.09 2090 6.6 Performance lower than the patented optimal ratio Example 2 <![CDATA[5×10 -12 ]]> 2055 0.05 2225 7.1 Best overall performance

[0148] As can be seen from the data in the table above, when the compound additives are removed or only a single additive is used to prepare the sample, the air tightness of the product decreases by about one order of magnitude compared with the optimal example 2, the high temperature resistance decreases by 12% to 19%, and the wear resistance and fracture toughness decrease by 15% to 25%. The overall performance does not meet the standards for aerospace sealing components.

[0149] When the additive ratio deviates from the specified ratio range of this invention, the airtightness, high-temperature resistance, wear resistance, and toughness of the sample slightly deteriorate. The high-temperature resistance performance decreases by 3% to 7%, and the overall performance is worse than the preferred ratio in Example 2, but still on the edge of passing the test. This verifies that the ratio range of this invention is the optimal performance range. This fully demonstrates the synergistic effect of the compounded additives in terms of high airtightness, high-temperature resistance, and wear resistance, and the ratio range specified by this invention is the optimal performance range for aerospace sealing components. Therefore, the compounding of ceramic stabilizer, reinforcing agent, and lubricant in this invention has significant functional complementarity and synergistic effect. The specific principle and analysis are as follows:

[0150] 1) The stabilizers CaO and MgO are combined. CaO inhibits excessive growth of grain boundaries, while MgO refines grains and compensates for the high-temperature volatility of CaO. After the combination, the air tightness is improved by about one order of magnitude compared with the use of CaO alone, and the fracture toughness is improved by about 18%.

[0151] 2) The reinforcing agent ZrO2 is combined with Si3N4. ZrO2 undergoes phase transformation to toughen the material, while Si3N4 forms a hard reinforcing phase. After the combination, the wear resistance is improved by about 32% compared with ZrO2 alone, which takes into account both toughness and wear resistance.

[0152] 3) The lubricant graphite and MoS2 are compounded. Graphite is suitable for high-temperature oxidation environment, MoS2 is suitable for high vacuum environment, and graphite inhibits the high-temperature oxidation of MoS2. The compound system has significantly better lubrication stability than the single raw material under high-temperature vacuum conditions, effectively reducing friction loss.

[0153] The specified ratios of the three types of additives are the optimal range determined through multiple experiments. Deviating from this range will weaken the synergistic effect of each component, reduce the overall performance of the seal, and fail to meet the stringent requirements of the aerospace field.

[0154] Comparative Example 3

[0155] Experimental exploration of raw material components:

[0156] Comparative Example 3-1: No tantalum carbide (TaC) was added; the remaining proportions and preparation process were the same as in Example 2.

[0157] Comparative Example 3-2: Titanium carbide (TiC) was not added; the remaining proportions and preparation process were the same as in Example 2.

[0158] Comparative Example 3-3: No aluminum nitride (AlN) was added; the remaining proportions and preparation process were the same as in Example 2.

[0159] Comparative Examples 3-4: No alumina (Al2O3) was added; the remaining proportions and preparation process were the same as in Example 2.

[0160] Comparative Examples 3-5: Yttrium oxide (Y2O3) was not added; the remaining proportions and preparation process were the same as in Example 2.

[0161] The performance test results of Comparative Example 3 are shown in Table 6-3:

[0162] Table 6-3 Comparative examples of matrix raw materials lacking single components (same process as Example 2)

[0163] Comparative Example 3-1 <![CDATA[3.7×10 -10 ]]> 1760 0.15 1890 4.9 Unqualified Comparative Example 3-2 <![CDATA[3.1×10 -10 ]]> 1780 0.16 1870 4.8 Unqualified Comparative Example 3-3 <![CDATA[4.9×10 -10 ]]> 1740 0.17 1850 4.6 Unqualified Comparative Examples 3-4 <![CDATA[4.2×10 -10 ]]> 1750 0.14 1900 5.0 Unqualified Comparative Examples 3-5 <![CDATA[5.9×10 -10 ]]> 1700 0.19 1760 4.4 Unqualified Example 2 <![CDATA[5×10 -12 ]]> 2055 0.05 2225 7.1 qualified

[0164] The five-element compound of TaC, TiC, AlN, Al2O3, and Y2O3 in this invention has a significant synergistic effect. The matrix formula lacks any one of the core raw materials, and the air tightness decreases by about one order of magnitude compared with Example 2, the high temperature resistance decreases by 290-355℃, and the fracture toughness decreases by 22%-39%. All performance indicators do not meet the threshold for use in aerospace sealing components.

[0165] Preparation process exploration and comparison

[0166] The key process parameters were set to deviate from the comparative example, while the remaining raw material ratios and preparation processes were the same as in Example 2, and the core performance was tested.

[0167] Comparative Example 4: Hot pressing pressure 18 MPa (lower than the scope of this invention), other proportions and preparation process are the same as in Example 2;

[0168] Comparative Example 5: Vacuum sintering temperature 1800℃ (lower than the range of this invention), other proportions and preparation process are the same as in Example 2;

[0169] Comparative Example 6: Surface roughness Ra = 0.2 μm (higher than the range of this invention), other proportions and preparation process are the same as in Example 2;

[0170] Comparative Example 7: Ball milling time 3h (shorter than the scope of this invention), other proportions and preparation process are the same as in Example 2;

[0171] The performance test results of Comparative Examples 4-7 are shown in Table 7:

[0172] Table 7 Comparative examples and performance test results of the preparation process exploration

[0173] Comparative Example 4 <![CDATA[5.3×10 -10 ]]> 1730 0.11 1910 5.6 Unqualified Comparative Example 5 <![CDATA[7.1×10 -10 ]]> 1620 0.20 1720 4.3 Unqualified Comparative Example 6 <![CDATA[5.1×10 -10 ]]> 2020 0.06 2200 6.9 Unqualified Comparative Example 7 <![CDATA[6.2×10 -10 ]]> 1820 0.13 2010 5.3 Unqualified Example 2 <![CDATA[5×10 -12 ]]> 2055 0.05 2225 7.1 qualified

[0174] As shown in the table, the manufacturing process parameters directly determine the matrix density, microstructure uniformity, and surface adhesion of the high-entropy ceramic aerospace seal. When deviating from the limits defined in this invention, the core performance cannot meet the requirements of high airtightness, high temperature resistance, and wear resistance in aerospace applications. The influence mechanism of each parameter on high temperature resistance and overall performance is as follows:

[0175] 1) Hot pressing pressure (Comparative Example 4, 18MPa): When the hot pressing pressure is reduced to 18MPa (below the lower limit of 20MPa of this invention), the powder is not compacted enough, the sintered matrix has more pores, density <95%, high temperature resistance decreases by about 16%, air tightness decreases by nearly one order of magnitude, and fracture toughness decreases by about 21%.

[0176] 2) Vacuum sintering temperature (Comparative Example 5, 1800℃): The sintering temperature was selected as 1800℃. The powder sintering reaction was incomplete and the grain boundary bonding strength was low. The high temperature resistance decreased by about 21% and the wear resistance decreased by about 75%. It was the condition with the greatest impact on product performance among all process variables and the item with the largest performance decrease among all process deviations.

[0177] 3) Surface roughness (Comparative Example 6, Ra=0.2μm): When the surface roughness increases to 0.2μm, the gap between the sealing mating surfaces increases, and the airtightness deteriorates slightly, decreasing by about 0.9 orders of magnitude. The internal properties of the substrate, such as high temperature resistance and hardness, do not change significantly. This parameter has no significant effect on the microstructure of the substrate. Therefore, the substrate properties such as high temperature resistance and hardness do not decrease significantly. However, if the surface adhesion does not meet the standard, it is still judged as unqualified.

[0178] 4) Ball milling time (Comparative Example 7, 3h): When the ball milling time is shortened to 3h, the raw materials are not mixed evenly and local segregation is easy to occur. The high temperature resistance of the finished product decreases by about 11%, the fracture toughness decreases by about 25%, and the wear resistance deteriorates significantly.

[0179] This invention limits the process parameters to an optimal range. The vacuum sintering temperature is the key process control point that determines the high temperature resistance of the finished product. Strictly controlling it within 2000-2200℃ is the key to ensuring the sealing parts meet the temperature resistance requirements of above 1800℃.

[0180] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance, characterized in that, Including the following parts by weight of raw materials: 10-15 parts tantalum carbide, 15-17 parts titanium carbide, 8-10 parts aluminum nitride, 5-8 parts yttrium oxide, 15-18 parts alumina, 20-22 parts high-entropy ceramic powder, 5-8 parts carbon fiber, 1-3 parts ceramic stabilizer, 1-3 parts ceramic reinforcing agent, 1-3 parts toughening agent, 1-3 parts coupling agent, 1-5 parts ceramic lubricant, 1-2 parts activated carbon, and 1-3 parts surfactant; The carbon fiber is T700 grade PAN-based carbon fiber; The ceramic stabilizer is calcium oxide and magnesium oxide, and the mass ratio of calcium oxide to magnesium oxide is 1.5-2.5:1; The ceramic reinforcing agent is zirconium oxide and silicon nitride, and the mass ratio of zirconium oxide to silicon nitride is 1-2:1; The ceramic lubricant is composed of graphite and molybdenum disulfide, with a mass ratio of graphite to molybdenum disulfide of 0.8-1.2:

1. The toughening agent is a polyimide resin; The coupling agent is a silane or a titanate, and the mass ratio of the silane to the titanate is 2:

1. The surfactant is sodium dodecyl sulfate.

2. The high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance according to claim 1, characterized in that, The high-entropy ceramic powder is TiC-TaC-ZrC-SiC-AlN with a molar ratio of 1:1:1:1:

1.

3. The high-entropy ceramic aerospace seal with high airtightness, temperature resistance, and wear resistance according to claim 1, characterized in that, The airtightness of the high-entropy ceramic aerospace seal is <1×10⁻⁶. -11 Pa·m 3 / s, high temperature resistance test temperature above 1800℃, wear resistance <0.10mm 3 / N·m.

4. The method for preparing a high-airtightness, temperature-resistant, and wear-resistant high-entropy ceramic aerospace seal according to any one of claims 1-3, characterized in that, Specifically, the following steps are included: (1) Weigh the raw materials according to the stated weight proportions and set aside; (2) After adding anhydrous ethanol and epoxy resin to the raw materials and stirring until a slurry is formed, the mixture is ball-milled for 6-10 hours, then dried and sieved to obtain a mixed powder, and then hot-pressed to obtain a green seal blank; the hot-pressing parameters are: pressure of 20-35 MPa, temperature of 1600-1800℃, and holding pressure for 15-20 minutes. After the powder is dried and sieved, it is first pre-formed by dry pressing at room temperature at 15MPa, and then put into a graphite mold for high-temperature hot pressing. (3) After the green blank of the sealing component is subjected to vacuum sintering and surface treatment in sequence, a high-entropy ceramic aerospace sealing component with high airtightness, high temperature resistance and wear resistance is obtained; wherein, the vacuum sintering step is as follows: the green blank of the sealing component is placed in a vacuum furnace, and the pressure inside the furnace is reduced to 1-5×10 -3 Pa, first heat to 1000-1200℃ at a heating rate of 80-120℃ / min, then heat to 2000-2200℃ at a heating rate of 120-150℃ / min, hold at that temperature for 3-5 hours, and then cool to room temperature by introducing inert gas.

5. The method for preparing a high-airtightness, temperature-resistant, and wear-resistant high-entropy ceramic aerospace seal according to claim 4, characterized in that, The surface treatment steps in step (3) are as follows: polish the vacuum sintered green seal on a polishing machine, add polishing agent to the surface at the same time, and clean it with water-based cleaner after polishing.

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