Tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating and preparation method of tungsten alloy material

Abstract

The invention discloses a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating and a preparation method of the tungsten alloy material, and belongs to the field of ceramic material preparation. The method comprises the following steps: ball-milling and mixing powder raw materials containing modified silicon carbide, aluminum oxide, silicon dioxide and lead oxide with a solvent, and defoaming to obtain ceramic slurry; the ceramic slurry is brushed on the surface of a tungsten alloy matrix subjected to surface pretreatment, and after drying, vacuum sintering is performed to obtain the tungsten alloy. The compact silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating is introduced to the surface of a tungsten alloy matrix, the hardness, the high-temperature oxidation resistance and the high-temperature carburization resistance of a tungsten alloy material are remarkably improved, the stability of the coating can be improved through the silicon carbide distributed in a dispersed point shape, the thermal expansion coefficient of the coating is evenly reduced, and the hardness, the high-temperature oxidation resistance and the high-temperature carburization resistance of the tungsten alloy material are improved. The thermal expansion coefficient difference value between the multiphase ceramic coating and a tungsten alloy matrix is reduced, and the thermal shock resistance of the coating is improved.

Description

Technical Field

[0001] The present invention relates to a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating and a preparation method thereof, and in particular to a method for preparing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating on the surface of a tungsten alloy material by using a slurry sintering method, belonging to the field of ceramic material preparation. Background Art

[0002] Tungsten alloys, with their high strength, hardness, and excellent thermal stability, hold a crucial position in the defense and military sectors (e.g., armor-piercing projectile cores and armor protection), the energy and chemical industries (e.g., coal-water slurry gasifier components), and the aerospace sector (e.g., high-temperature engine components). In particular, in coal-water slurry gasification technology, tungsten alloys are the preferred material for burner shrouds due to their ability to withstand extreme mechanical loads and thermal shock. However, when subjected to long-term high-temperature environments of 1250–1400°C, these shrouds face severe challenges from high-temperature oxidation and carburization corrosion. High-temperature oxidation causes a loose, porous WO3 oxide layer to form on the tungsten alloy surface. This layer is susceptible to cracking and flaking due to repeated thermal stress, further accelerating matrix oxidation. Furthermore, carbon atoms in the carbon-containing atmosphere diffuse into the tungsten alloy, forming a brittle carbide phase that destroys the matrix structure and significantly reduces strength and toughness. This coupled oxidation-carburization corrosion severely shortens equipment life.

[0003] To address these challenges, preparing high-performance ceramic coatings on tungsten alloy surfaces is crucial. Existing coating preparation technologies, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), suffer from high equipment costs and complex processes. Slurry sintering, however, is the preferred process for preparing these composite ceramic coatings due to its suitability for complex substrates, controllable microstructure (through dispersants to regulate particle distribution and phase composition), and low cost. Incorporating slurry sintering technology into the preparation of tungsten alloy coatings is expected to further improve the overall performance of tungsten alloy workpieces.

[0004] Introducing silicon carbide into an Al2O3-SiO2 matrix to form a composite ceramic coating is expected to be an ideal choice for tungsten alloy burners in water-coal slurry gasifiers. However, the preparation process faces two major technical bottlenecks: first, micron-sized silicon carbide powder tends to agglomerate in the ceramic slurry, resulting in poor slurry fluidity and difficulty in forming; second, the significant difference in the coefficient of thermal expansion (CTE) between the tungsten alloy and the ceramic coating can easily lead to cracking and shedding of the coating due to interfacial thermal stress. Therefore, a preparation method that can perfectly address these difficulties is essential. Summary of the Invention

[0005] In view of the problems in the prior art of tungsten alloy materials in high-temperature service environments, which lead to the shortened life of tungsten alloy material equipment, the first object of the present invention is to provide a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating. The material significantly improves the hardness, high-temperature oxidation resistance and high-temperature carburization resistance of the tungsten alloy material by introducing a dense silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating on the surface of the tungsten alloy substrate. The dispersed point-distributed silicon carbide can improve the stability of the coating, uniformly reduce the thermal expansion coefficient of the coating, reduce the difference in thermal expansion coefficient between the multiphase ceramic coating and the tungsten alloy substrate, and improve the thermal shock resistance of the coating.

[0006] The second object of the present invention is to provide a method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating. This method avoids the agglomeration problem of silicon carbide by synergistically treating silicon carbide with a silane coupling agent and polyethyleneimine grafting, while promoting the formation of a continuous interface phase in the aluminosilicate liquid phase, significantly improving the interface bonding strength and density of the coating. In addition, the slurry sintering method does not require a complex mold and can meet the surface protection requirements of parts with special shapes.

[0007] In order to achieve the above technical objectives, the present invention provides a method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating. According to the method, powder raw materials including modified silicon carbide, aluminum oxide, silicon dioxide and lead oxide are mixed with a solvent by ball milling and then defoamed to obtain a ceramic slurry; the ceramic slurry is brushed on the surface of a tungsten alloy substrate after surface pretreatment, dried and vacuum sintered to obtain the obtained material; the preparation process of the modified silicon carbide is as follows: silicon carbide powder is sequentially subjected to spheroidization treatment, silane coupling agent treatment and polyethyleneimine grafting treatment; the silicon carbide in the composite ceramic coating is distributed in the Al2O3-SiO2 matrix in the form of dispersed points.

[0008] The key idea of ​​the technical solution of the present invention is to first modify silicon carbide and then use a slurry sintering method to metallurgically and mechanically bond a layer of silicon carbide reinforced Al2O3-SiO2 based composite ceramic coating on the surface of the tungsten alloy substrate. As a result, the silicon carbide in the composite ceramic coating can be distributed in the Al2O3-SiO2 matrix in a dispersed point shape, forming a "SiC particle-matrix" composite structure, thereby significantly improving the stability of the coating, uniformly reducing the thermal expansion coefficient of the coating, reducing the difference in thermal expansion coefficient between the composite ceramic coating and the tungsten alloy substrate, improving the thermal shock resistance of the coating, and improving the high-temperature comprehensive performance of the tungsten alloy material.

[0009] In the modification process of silicon carbide, the present invention firstly spheroidizes the silicon carbide powder to increase the force uniformity and density of the composite ceramic coating by utilizing the spherical morphology of the silicon carbide powder, thereby reducing the occurrence of microcracks caused by stress concentration; secondly, the silicon carbide powder after spheroidization is treated with a silane coupling agent and then grafted with polyethyleneimine, which has a significant synergistic effect and is also the key to improving the overall performance of tungsten alloy materials. Specifically: before sintering, the silane chain of the silane coupling agent and the amino chain of the polyethyleneimine can be combined through hydrogen bonds to form a more stable particle coating layer, which significantly improves the dispersibility of silicon carbide, inhibits sintering obstacles caused by agglomeration, and improves the stability of the slurry; and as the sintering temperature rises to 300°C, the polyethyleneimine will gradually decompose and release gases such as ammonia and hydrogen. The residual nitrogen-containing intermediates (such as amine derivatives) can react with lead oxide to form lead amine complexes, lowering its melting point (from 888°C to 750°C) and forming liquid phase channels in advance. Its amino group and Al 3+ The coordination effect of the silane coupling agent promotes the dissolution of Al2O3 in the liquid phase, allowing the aluminosilicate glass phase to more evenly fill the intergranular gaps and reduce local porosity. As the sintering temperature rises to 600-800°C, the organic chain segments (aminoalkanes) of the silane coupling agent gradually decompose. However, the remaining silicon-oxygen skeleton (Si-O-Si) is stable at high temperatures and can serve as an interfacial reaction site, pre-reacting with the hydroxyl groups on the surfaces of the alumina and silica particles in the slurry to form initial Si-O-Al or Si-O-Si bonds, providing reaction seeds for interfacial fusion during the high-temperature stage. At higher sintering temperatures, the residual silicon-oxygen structure of the silane coupling agent can be dissolved in the low-melting-point liquid phase formed by the decomposition of polyethyleneimine, promoting the penetration of the liquid phase into the gaps between silicon carbide particles through the bridging effect of Si-O bonds, accelerating the rearrangement and densification of particles, and reacting with alumina to form an aluminosilicate transition phase (such as mullite precursor 3 Al2O3•2SiO2). The thermal expansion coefficient of this phase is between that of silicon carbide and Al2O3, which can relieve interfacial thermal stress and reduce sintering cracking. At the same time, it anchors the silicon carbide particles in the ceramic matrix and improves the interfacial bonding strength.

[0010] Experiments have found that without the addition of lead oxide to the slurry, a sufficient amount of low-melting-point liquid phase cannot be formed during high-temperature sintering, resulting in difficulty in sintering and insufficient densification, which in turn leads to a surge in the material's porosity. However, the vacuum sintering method employed in this invention can also inhibit oxidation of the tungsten alloy substrate to a certain extent, maintaining the stability of the original composition of the coating and substrate. It also isolates impurities in the air (such as N2 and CO2) from reacting with the coating to form brittle phases (such as silicon nitride and carbonates), maintaining interfacial bonding strength.

[0011] As a preferred solution, the particle size of silicon carbide in the multiphase ceramic coating is 1-5 μm.

[0012] As a preferred embodiment, the mass ratio of modified silicon carbide, aluminum oxide, silicon dioxide, and lead oxide in the ceramic slurry is (5-15): (15-21): (14-18): (2-5). When the amount of modified silicon carbide in the ceramic slurry is excessive, although the silicon carbide particles in the final composite ceramic coating are still dispersed in the matrix, the dense distribution of the silicon carbide particles will cause a small amount of silicon carbide particles to slightly agglomerate, thereby reducing the overall performance of the coating. At the same time, the amount of aluminum oxide cannot be excessive. When it is excessive, the excessive lead silicate glass phase formed by it and silicon dioxide at high temperature will cause a sudden drop in the overall hardness of the coating and a simultaneous decrease in wear resistance. It is further preferred that the mass ratio of modified silicon carbide, aluminum oxide, silicon dioxide, and lead oxide in the ceramic slurry is (5-10): (18-21): (16-18): (2-5).

[0013] As a preferred solution, the powder raw material further includes a dispersant, such as tetramethylammonium hydroxide and polyvinylpyrrolidone (PVP); and the solvent includes at least one of methanol, ethanol, acetone and toluene.

[0014] As a preferred embodiment, the spheroidization treatment conditions are as follows: After soaking the silicon carbide powder in HF, pre-oxidizing it in air at 700-900°C for 2-4 hours, followed by HF pickling and drying. During the spheroidization process, pre-oxidizing it in air facilitates preferential oxidation of sharp areas on the silicon carbide surface to silicon dioxide, which is then removed with hydrofluoric acid, resulting in a silicon carbide powder with higher sphericity. Furthermore, the pre-oxidation and pickling are repeated 2-4 times.

[0015] As a preferred embodiment, the silane coupling agent treatment conditions are as follows: at least one silane coupling agent selected from KH792 and KH550, spheroidized silicon carbide powder, and water are mixed for 1-4 hours and then washed with water. The amount of silane coupling agent added is 5-15 wt% relative to the total amount of silane coupling agent, spheroidized silicon carbide powder, and water. The viscosity of the slurry decreases and then stabilizes with increasing silane coupling agent addition. Therefore, the amount of silane coupling agent added is preferably 10-15 wt% relative to the total amount of silane coupling agent, spheroidized silicon carbide powder, and water.

[0016] As a preferred solution, the conditions for the polyethyleneimine grafting treatment are: soaking the silicon carbide powder treated with a silane coupling agent in a polyethyleneimine aqueous solution with a pH of 3-4 for 1-3 hours, wherein the concentration of the polyethyleneimine aqueous solution is 6-8 wt%.

[0017] As a preferred solution, the spheroidization treatment also includes pickling and impurity removal treatment before the spheroidization treatment.

[0018] Furthermore, the pickling and impurity removal process is as follows: the silicon carbide powder is soaked in hydrochloric acid, ultrasonicated every 15 to 20 minutes, and then filtered and washed with water several times to remove surface impurities such as Ca 2+ Mg 2+ 、Fe 3+ wait.

[0019] As a preferred solution, the vacuum sintering procedure is: first heat to 700~900℃ and keep warm for 20~40min, heat to 1000~1200℃ at 1~5℃ / min and keep warm for 20~40min, then heat to 1300~1400℃ at 1~5℃ / min and keep warm for 1~2h, cool to 700~900℃ and cool to room temperature with the furnace, and the vacuum degree is 0.1~1MPa.

[0020] As a preferred solution, the amount of the brush coating is used to control the thickness of the silicon carbide reinforced Al2O3-SiO2 based composite ceramic layer after high temperature vacuum sintering to be 50-120 μm.

[0021] The present invention also provides a tungsten alloy material containing a silicon carbide-reinforced Al2O3-SiO2-based multiphase ceramic coating, which is obtained by the above-mentioned preparation method.

[0022] The silicon carbide in the tungsten alloy composite ceramic coating prepared by this method is distributed as dispersed dots within the Al2O3-SiO2 matrix, significantly impacting the overall coating performance. Experiments have found that if this distribution is disrupted, such as by agglomeration or localized segregation, the agglomerated SiC particles prevent the liquid from fully filling the gaps, forming numerous pores and microcracks and disrupting the coating's continuity. Simultaneously, the SiC's reinforcing effect is lost, significantly reducing wear resistance. Agglomerates easily peel from the matrix, exacerbating wear. Crucially, thermal expansion coefficient matching is disrupted, significantly reducing thermal shock resistance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses a silane coupling agent and polyethyleneimine grafting synergistic treatment on silicon carbide to avoid the agglomeration problem of silicon carbide while promoting the formation of a continuous interface phase in the aluminosilicate liquid phase, significantly improving the interface bonding strength and density of the coating. In addition, the slurry of the present invention has good fluidity and can be evenly applied to the surface of a complex-shaped tungsten alloy substrate by spraying, brushing, dipping, etc., without the need for complex molds, and can meet the surface protection requirements of special-shaped parts. In addition, the raw material utilization rate is high during the slurry coating process, and the unsintered slurry can be recycled or re-coated, reducing production costs and being suitable for industrial mass production.

[0025] (2) The process of the present invention is not only applicable to Al2O3-SiO2-based composite ceramic systems, but is also compatible with other ceramic matrices and can flexibly add reinforcing phases such as carbon fibers and nanoparticles to further expand the wear resistance, oxidation resistance, and carburization resistance of the coating.

[0026] (3) The tungsten alloy material of the present invention significantly improves the hardness, high-temperature oxidation resistance and high-temperature carburization resistance of the tungsten alloy material by introducing a dense silicon carbide-reinforced Al2O3-SiO2-based multiphase ceramic coating on the surface of the tungsten alloy substrate. The dispersed point-distributed silicon carbide can improve the stability of the coating, uniformly reduce the thermal expansion coefficient of the coating, reduce the difference in thermal expansion coefficient between the multiphase ceramic coating and the tungsten alloy substrate, and improve the thermal shock resistance of the coating.

[0027] (4) The surface hardness of the silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating in the tungsten alloy material of the present invention is 1756 HV, which is 123% higher than that of the bare tungsten alloy sample (786 HV). In an oxidizing environment at 1400°C, the coating sample only gained 0.006 g, while the bare tungsten alloy sample gained 0.563 g. The coating can effectively inhibit oxidation. In a carburizing experiment at 1400°C, the coating sample only gained 0.092 g (0.46%), while the bare sample gained 1.116 g (5.84%). The coating can effectively block the penetration of carbon atoms. Before the introduction of silicon carbide powder reinforcement, the surface hardness of the Al2O3-SiO2-based composite ceramic coating was 1324 HV, and after reinforcement, it can reach 1756 HV. The introduction of silicon carbide powder can reduce the thermal expansion coefficient of the coating, narrow the difference in thermal expansion coefficient between the coating and the tungsten alloy substrate, and improve the thermal shock resistance of the coating. In a 1400°C air-cooled thermal shock cycle test, the silicon carbide-reinforced coating of the present invention achieved 28 critical failure cycles, significantly higher than the 12 cycles for the unreinforced coating, effectively slowing damage evolution. Furthermore, the coating of the present invention bonded tightly to the tungsten alloy substrate, achieving excellent surface smoothness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 a and b are surface SEM images of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 1, wherein, Figure 1 b in Figure 1 A partial enlarged view of a in .

[0029] Figure 2 This is the XRD pattern of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 1.

[0030] Figure 3This is a surface EDS point scanning image of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 1.

[0031] Figure 4 a and b are surface SEM images of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 2, wherein, Figure 4 b in Figure 1 A partial enlarged view of a in .

[0032] Figure 5 This is the XRD pattern of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 2.

[0033] Figure 6 a and b are surface SEM images of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 3, wherein, Figure 6 b in Figure 6 A partial enlarged view of a in .

[0034] Figure 7 This is the XRD pattern of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Example 3.

[0035] Figure 8 This is the effect of the addition amount of coupling agent KH550 on the viscosity of ceramic slurry.

[0036] Figure 9 This is the effect of the addition amount of coupling agent KH792 on the viscosity of ceramic slurry.

[0037] Figure 10 The effect of PEI concentration on the viscosity of ceramic slurry.

[0038] Figure 11 This is the XRD pattern of the Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the Al2O3-SiO2-based multiphase ceramic coating prepared in Comparative Example 1.

[0039] Figure 12 This is an SEM image of the surface of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Comparative Example 2.

[0040] Figure 13 This is an SEM image of the surface of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in Comparative Example 3.

[0041] Figure 14 This is the surface SEM image of the Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the Al2O3-SiO2-based multiphase ceramic coating prepared in Comparative Example 5. DETAILED DESCRIPTION

[0042] The present invention is further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by professionals in this field without making creative efforts are still within the scope of protection of the present invention.

[0043] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0044] The tungsten alloy substrate used in the embodiments and comparative examples of the present invention is 95W-3Co-2Ni cemented carbide, and other tungsten alloy substrates can also be applied to the method of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating, comprising the following steps:

[0047] 1. Silicon carbide powder modification

[0048] (1) Surface acid pickling and purification: Soak the silicon carbide powder in 15wt% hydrochloric acid for 1 hour, ultrasonicate it once every 15 minutes, and ultrasonicate it for 15 minutes each time, then filter it, wash it with water twice, and dry it for later use to remove surface impurities.

[0049] (2) Spheroidization treatment of silicon carbide powder: First, soak the silicon carbide powder in 15wt% HF for 5 minutes, filter and dry it, and then keep it in air at 800℃ for 2 hours for pre-oxidation treatment. Then, carry out HF pickling and drying treatment. Repeat the pre-oxidation-pickling process 3 times to improve the sphericity of the powder and reduce the internal resistance of the slurry flow.

[0050] (3) Silane coupling agent treatment: The spheroidized silicon carbide powder, KH792, and deionized water were ultrasonically mixed and stirred at a mass ratio of 9:2:9 for 1 hour, and then allowed to stand. The mixture was then washed with 5 times the volume of deionized water, allowed to stand, and the supernatant was collected and filtered. This process was repeated twice, and the KH792-adsorbed silicon carbide powder was obtained after drying.

[0051] (4) Polyethyleneimine (PEI) grafting treatment: 10 g of silicon carbide powder adsorbed with KH792 was added to a PEI aqueous solution (PEI concentration of 6 wt%, volume of 100 mL) at pH = 3 under magnetic stirring. After soaking for 1 h, filtering, and drying, silicon carbide powder adsorbed with KH792 and grafted with PEI (i.e., modified silicon carbide powder) was obtained.

[0052] 2. Preparation of ceramic slurry

[0053] While maintaining magnetic stirring, 5 g of modified silicon carbide powder, 21 g of alumina powder, 18 g of silicon dioxide powder, 6 g of tetramethylammonium hydroxide (TMAH) and 2 g of lead oxide were added to 100 mL of methanol in sequence, and the mixture was placed in an XQM-2 variable frequency planetary ball mill (rotation 180 r / min, revolution 200 r / min) for 6 h. A ZKT-6020 vacuum degassing machine was used to remove bubbles in the slurry to obtain a ceramic slurry.

[0054] 3. Tungsten alloy substrate pretreatment

[0055] A tungsten alloy block (15 mm × 15 mm × 5 mm) was polished on 120#, 240#, 400#, and 600# silicon carbide sandpaper in succession, and then ultrasonically cleaned with anhydrous ethanol and acetone for 15 min in sequence and dried.

[0056] 4. Surface brushing

[0057] Use a brush to evenly apply the prepared ceramic slurry on the surface of the pretreated tungsten alloy substrate to ensure uniform coating thickness. After application, place the sample in a constant temperature drying oven and dry it at 80°C for 2 hours.

[0058] 5. Vacuum sintering

[0059] The dried sample was placed in a muffle furnace with a vacuum degree of 0.5 MPa, heated to 900℃ and kept warm for 30 minutes, heated to 1200℃ at 3℃ / min and kept warm for 30 minutes, heated to 1400℃ at 2℃ / min and kept warm for 2 hours, cooled to 900℃, and then cooled to room temperature with the furnace to obtain a tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2 based composite ceramic coating.

[0060] Figure 1This is the SEM image of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in this embodiment, wherein Figure 1 b in Figure 1 A partial enlarged view of a in Figure 1. The black phase in the figure is silicon carbide (SiC) particles, and the grayish-white matrix is ​​the Al2O3-SiO2 composite ceramic matrix. Figure 1 As can be seen in a, SiC particles are distributed in the matrix in the form of dispersed points, forming a composite structure of "SiC particles-matrix". Figure 1 As can be seen in Figure b, the SiC particles are mainly concentrated in the 1-5μm range, belonging to the submicron-micron range, and some particles are irregular polyhedrons. The thickness of the silicon carbide reinforced Al2O3-SiO2 composite ceramic layer is 100μm.

[0061] Figure 2 The XRD pattern of the silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating prepared in this example shows that discrete diffraction peaks appear in the spectrum and their positions are the same as those in the silicon carbide standard PDF card, indicating that SiC particles have been successfully introduced into the coating and also confirming that the silane coupling agent and PEI have decomposed during the sintering process.

[0062] Figure 3 This is an EDS scan of the surface of the silicon carbide-reinforced Al2O3-SiO2-based composite ceramic coating in the tungsten alloy material containing the silicon carbide-reinforced Al2O3-SiO2-based composite ceramic coating prepared in this example. As can be seen from the figure, the presence of oxygen in the elemental composition at point 1 is due to diffusion of oxygen from the matrix into the silicon carbide particles during high-temperature sintering. The presence of carbon at point 2 is also due to diffusion of carbon from the silicon carbide particles into the matrix during high-temperature sintering. This demonstrates that significant interfacial interaction occurs between the silicon carbide particles and the Al2O3-SiO2 matrix during high-temperature sintering. Carbon from the silicon carbide particles diffuses into the matrix, and oxygen from the matrix diffuses into the silicon carbide particles. This diffusion is not a simple physical contact, but rather a chemical bond achieved through atomic-level interpenetration. This directly demonstrates the existence of a tight interfacial bond between the silicon carbide and the matrix, rather than a loose mechanical stacking. This interfacial interdiffusion effectively weakens the interfacial energy between the silicon carbide and the matrix, alleviating stress concentration caused by the difference in thermal expansion coefficients between the two.

[0063] Example 2

[0064] The difference between this embodiment and embodiment 1 is only the change in the amount of each component in the ceramic slurry: while maintaining magnetic stirring, 10 g of modified silicon carbide powder, 18 g of aluminum oxide powder, 16 g of silicon dioxide powder, 6 g of tetramethylammonium hydroxide (TMAH) and 2 g of lead oxide are added in sequence to 100 mL of methanol. The remaining steps and conditions are the same as those in embodiment 1, and a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating is obtained.

[0065] Figure 4 This is a surface SEM image of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in this embodiment, wherein Figure 4 b in Figure 4 A partial enlarged view of a in Figure 1. The black phase in the figure is silicon carbide (SiC) particles, and the grayish-white matrix is ​​the Al2O3-SiO2 composite ceramic matrix. Figure 4 As can be seen from the figure, SiC particles are distributed in the matrix in the form of dispersed points and the amount of modified silicon carbide powder increases compared to Figure 1 More dense.

[0066] Figure 5 The XRD pattern of the silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating prepared in this embodiment also shows the diffraction peak of silicon carbide and the relative intensity of the diffraction peak is increased.

[0067] Example 3

[0068] The only difference between this embodiment and Example 1 is that the amount of each component in the ceramic slurry is changed: while maintaining magnetic stirring, 15 g of modified silicon carbide powder, 15 g of aluminum oxide powder, 14 g of silicon dioxide powder, 6 g of tetramethylammonium hydroxide (TMAH) and 2 g of lead oxide are added in sequence to 100 mL of methanol. The remaining steps and conditions are the same as those in Example 1, and a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating is obtained.

[0069] Figure 6 This is a surface SEM image of the silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating in the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2 based multiphase ceramic coating prepared in this embodiment, wherein Figure 6 b in Figure 6 A partial enlarged view of a in Figure 1. The black phase in the figure is silicon carbide (SiC) particles, and the grayish-white matrix is ​​the Al2O3-SiO2 composite ceramic matrix. Figure 6It can be seen that the SiC particles are distributed in the matrix in the form of dispersed points and are very dense, but due to the large amount of silicon carbide used, the silicon carbide particles appear to be slightly agglomerated.

[0070] Figure 7 The XRD spectrum of the silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating prepared in this embodiment also shows the diffraction peak of silicon carbide and the relative intensity of the diffraction peak is the largest.

[0071] Example 4 (Exploration of the dosage of KH550 as a silane coupling agent)

[0072] Soak the silicon carbide powder in 15wt% hydrochloric acid for 1 hour, ultrasonicate it every 15 minutes, and then filter it, wash it twice with water, and dry it for later use. Soak the silicon carbide powder in 15wt% HF for 5 minutes, filter it and dry it, then pre-oxidize it at 800℃ in air for 2 hours, then HF pickle it and dry it, and repeat the pre-oxidation-pickling process 3 times.

[0073] When the spheroidized silicon carbide powder, KH550 and deionized water were mixed, the effect of the addition amount of coupling agent KH550 on the viscosity of the ceramic slurry was investigated, with the other conditions being the same as in Example 1. The results are shown in FIG. Figure 8 shown.

[0074] The results show that when the KH550 addition level is 0, the viscosity is 1452 mPa·s. With other process conditions remaining unchanged, the viscosity decreases as the KH550 addition level increases. When the KH550 addition level is 10 wt%, the viscosity drops to approximately 1124 mPa·s. These results indicate that the viscosity of the ceramic slurry initially decreases significantly with increasing KH550 addition. As the KH550 addition level increases, dispersing effects such as steric hindrance within the system gradually take effect, causing the viscosity to decrease. Due to limited data points, a plateau is not observed. However, it is speculated that with continued increases in KH550 addition, the system's dispersing effects may reach relative saturation, and the viscosity change will become more gradual.

[0075] Example 5 (Exploration of the dosage of KH792 as a silane coupling agent)

[0076] Soak the silicon carbide powder in 15wt% hydrochloric acid for 1 hour, ultrasonicate it every 15 minutes, and then filter it, wash it twice with water, and dry it for later use. Soak the silicon carbide powder in 15wt% HF for 5 minutes, filter it and dry it, then pre-oxidize it at 800℃ in air for 2 hours, then HF pickle it and dry it, and repeat the pre-oxidation-pickling process 3 times.

[0077] When the spheroidized silicon carbide powder, KH792 and DW (deionized water) were mixed, the effect of the addition amount of coupling agent KH792 relative to the total amount of spheroidized silicon carbide powder, KH792 and deionized water on the viscosity of the ceramic slurry was investigated. The other conditions were the same as those in Example 1. The results are shown in FIG. Figure 9 shown.

[0078] The results show that when the amount of KH792 added is 0, the viscosity is 1452mPa•s. When other process conditions remain unchanged, the viscosity decreases as the amount of KH792 added increases. When the amount of KH792 added is 10wt%, the viscosity drops to 892mPa•s and tends to be stable. The above results show that the viscosity of the ceramic slurry first decreases significantly and then tends to be stable as the amount of KH792 added increases. When the amount of KH792 added reaches a certain level, the dispersion effects such as steric hindrance in the system reach relative saturation. Continuing to increase the amount of KH792 added will have a smaller effect on the viscosity, so the viscosity tends to be stable. At the same time, through Figure 9 It can be seen that the addition amount of KH792 needs to be greater than 10wt%, and the preferred addition amount of KH792 is 10~15wt%.

[0079] Example 6 (Exploration of PEI Concentration)

[0080] Under the condition of maintaining magnetic stirring, 10g of the silicon carbide powder adsorbed with KH792 prepared in Example 1 was mixed with 100ml of PEI aqueous solution with different concentrations and pH = 3 to investigate the effect of PEI concentration on the viscosity of the ceramic slurry. The other conditions were the same as in Example 1. The results are shown in FIG. Figure 10 shown.

[0081] The results show that as the concentration of PEI increases, the viscosity of the ceramic slurry first decreases significantly, reaches the lowest when it reaches 6wt%, and then increases slightly when the PEI concentration increases further.

[0082] Example 7

[0083] This embodiment provides a method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating, comprising the following steps:

[0084] 1. Silicon carbide powder modification

[0085] (1) Surface acid pickling and purification: Soak the silicon carbide powder in 15wt% hydrochloric acid for 1 hour, ultrasonicate it once every 15 minutes, and ultrasonicate it for 15 minutes each time, then filter it, wash it with water twice, and dry it for later use to remove surface impurities.

[0086] (2) Spheroidization treatment of silicon carbide powder: First, soak the silicon carbide powder in 15wt% HF for 5 minutes, filter and dry it, and then keep it in air at 900℃ for 1 hour for pre-oxidation treatment. Then, carry out HF pickling and drying treatment. Repeat the pre-oxidation-pickling process 3 times to improve the sphericity of the powder and reduce the internal resistance of the slurry flow.

[0087] (3) Silane coupling agent treatment: The spheroidized silicon carbide powder, KH792, and deionized water were ultrasonically mixed and stirred for 2 hours at a mass ratio of 9:2:9, and then allowed to stand. The mixture was then washed with 5 times the volume of deionized water, allowed to stand, and the supernatant was collected and filtered. This process was repeated twice, and the KH792-adsorbed silicon carbide powder was obtained after drying.

[0088] (4) Polyethyleneimine (PEI) grafting treatment: 10 g of silicon carbide powder adsorbed with KH792 was added to a PEI aqueous solution (PEI concentration of 6 wt%, volume of 100 mL) with a pH of 3 under magnetic stirring. After soaking (immersion time of 3 h), filtering and drying, silicon carbide powder adsorbed with KH792 and grafted with PEI (i.e., modified silicon carbide powder) was obtained.

[0089] 2. Preparation of ceramic slurry

[0090] While maintaining magnetic stirring, 5 g of modified silicon carbide powder, 20 g of alumina powder, 18 g of silicon dioxide powder, 6 g of polyvinyl pyrrolidone (PVP) and 3 g of lead oxide were added to 100 mL of methanol in sequence, and the mixture was placed in an XQM-2 variable frequency planetary ball mill for ball milling (rotation 180 r / min, revolution 200 r / min) for 7 h. A ZKT-6020 vacuum degassing machine was used to remove bubbles in the slurry to obtain a ceramic slurry.

[0091] 3. Tungsten alloy substrate pretreatment

[0092] A tungsten alloy block (15 mm × 15 mm × 5 mm) was polished on 120#, 240#, 400#, and 600# silicon carbide sandpaper in succession, and then ultrasonically cleaned with anhydrous ethanol and acetone for 15 min in sequence and dried.

[0093] 4. Surface brushing

[0094] Use a brush to evenly apply the prepared ceramic slurry on the surface of the pretreated tungsten alloy substrate to ensure uniform coating thickness. After application, place the sample in a constant temperature drying oven and dry it at 80°C for 2 hours.

[0095] 5. Vacuum sintering

[0096] The dried sample was placed in a muffle furnace with a vacuum degree of 0.5 MPa, heated to 800℃ and kept warm for 40 minutes, heated to 1000℃ at 3℃ / min and kept warm for 30 minutes, heated to 1300℃ at 2℃ / min and kept warm for 2 hours, cooled to 900℃, and then cooled to room temperature with the furnace to obtain a tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2 based composite ceramic coating.

[0097] Comparative Example 1

[0098] The only difference between this comparative example and Example 1 is that silicon carbide powder is not added to the ceramic slurry. The other steps and conditions are the same. Only the Al2O3-SiO2-based multiphase ceramic coating is combined on the tungsten alloy substrate to obtain a tungsten alloy material containing an Al2O3-SiO2-based multiphase ceramic coating.

[0099] Figure 11 The XRD spectrum of the Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the Al2O3-SiO2-based multiphase ceramic coating prepared in this comparative example has only one broad diffuse scattering peak in the spectrum, and a "halo peak" phenomenon appears, indicating that the coating is amorphous.

[0100] Comparative Example 2

[0101] The only difference between this comparative example and Example 1 is that no silane coupling agent is used for modification of the silicon carbide powder. The remaining steps and conditions are the same, and a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating is obtained.

[0102] Figure 12 This is a surface SEM image of the Al2O3-SiO2-based composite ceramic coating in the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating prepared in this comparative example. It can be seen from the figure that the silicon carbide particles have serious agglomeration and obvious cracks have appeared in the coating.

[0103] Comparative Example 3

[0104] The only difference between this comparative example and Example 1 is that polyethyleneimine (PEI) grafting treatment is not used when modifying the silicon carbide powder. The remaining steps and conditions are the same, and a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating is obtained.

[0105] Figure 13 This is the surface SEM image of the Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating prepared in this comparative example. It can be seen from the figure that the silicon carbide particles have serious segregation and there are local loose areas.

[0106] Comparative Example 4

[0107] The only difference between this comparative example and Example 1 is that the vacuum sintering procedure is replaced by: processing for the same time at a sintering temperature of 600°C, and the other steps and conditions are the same. The obtained Al2O3-SiO2-based composite ceramic coating reinforced with silicon carbide powder is not completely sintered, but is only a loose mechanical stacking. The coating is loose and porous and can be easily scraped off with tweezers.

[0108] Comparative Example 5

[0109] The only difference between this comparative example and Example 1 is that the silicon carbide powder is not modified, and the remaining steps and conditions are the same, thereby obtaining a tungsten alloy material containing an Al2O3-SiO2-based multiphase ceramic coating.

[0110] Figure 14 This is a surface SEM image of the Al2O3-SiO2-based multiphase ceramic coating in the tungsten alloy material containing the Al2O3-SiO2-based multiphase ceramic coating prepared in this comparative example. It can be seen from the image that the silicon carbide particles have serious agglomeration and the coating has obvious cracks.

[0111] The coating surface and substrate hardness of the tungsten alloy materials containing silicon carbide reinforced Al2O3-SiO2-based composite ceramic coatings prepared in Examples 1 to 3 and Example 7, the tungsten alloy materials prepared in Comparative Examples 1 to 5, and the bare tungsten alloy substrate (not subjected to vacuum sintering treatment) were tested respectively. The results are shown in Table 1.

[0112] ;

[0113] The thermal shock resistance of the tungsten alloy material containing silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating and the tungsten alloy material containing Al2O3-SiO2-based composite ceramic coating prepared in Example 1 and Comparative Example 1 under 1400°C air-cooled thermal shock cycle was tested respectively. The results are shown in Table 2.

[0114] ;

[0115] The oxidation resistance of the tungsten alloy material containing the silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating prepared in Example 1 and the bare sample coating surface of the tungsten alloy substrate in an oxidizing environment of 1400°C for 15 hours and the carburizing performance at 1400°C for 15 hours were tested respectively. The results are shown in Tables 3 and 4.

[0116] ;

[0117] .

Claims

1. A method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating, characterized in that: The powder raw materials including modified silicon carbide, aluminum oxide, silicon dioxide and lead oxide are ball-milled with a solvent and then defoamed to obtain a ceramic slurry; the ceramic slurry is brush-coated on the surface of the tungsten alloy substrate after surface pretreatment, dried and then vacuum sintered to obtain the ceramic slurry; The preparation process of the modified silicon carbide is as follows: silicon carbide powder is sequentially subjected to spheroidization treatment, silane coupling agent treatment and polyethyleneimine grafting treatment; In the multiphase ceramic coating, silicon carbide is distributed in the Al2O3-SiO2 matrix in the form of dispersed dots.

2. The method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 1, characterized in that: The mass ratio of modified silicon carbide, aluminum oxide, silicon dioxide and lead oxide in the ceramic slurry is (5-15): (15-21): (14-18): (2-5).

3. The method for preparing a tungsten alloy material containing a silicon carbide-reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 2, characterized in that: The powder raw material also includes a dispersant; and the solvent includes at least one of methanol, ethanol, acetone and toluene.

4. The method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 1, characterized in that: The conditions for the spheroidization treatment are as follows: soaking the silicon carbide powder in HF, pre-oxidizing it in air at 700-900° C. for 1-2 hours, and then washing it with HF acid and drying it.

5. The method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 4, characterized in that: The silane coupling agent treatment conditions are as follows: at least one silane coupling agent selected from KH792 and KH550, the spheroidized silicon carbide powder and water are mixed for 1 to 4 hours and then washed with water, wherein the amount of the silane coupling agent added is 5 to 15 wt % relative to the total amount of the silane coupling agent, the spheroidized silicon carbide powder and water; The conditions for the polyethyleneimine grafting treatment are: soaking the silicon carbide powder treated with a silane coupling agent in a polyethyleneimine aqueous solution with a pH of 3-4 for 1-3 hours, wherein the concentration of the polyethyleneimine aqueous solution is 6-8 wt %.

6. The method for preparing a tungsten alloy material containing silicon carbide-enhanced Al2O3-SiO2-based multiphase ceramic coating according to any one of claims 2 to 5, wherein: The spheroidization process also includes pickling and impurity removal process before the spheroidization process.

7. The method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 6, characterized in that: The vacuum sintering procedure is as follows: first, heat to 700-900°C and keep warm for 20-40 minutes, then heat to 1000-1200°C at a rate of 1-5°C / min and keep warm for 20-40 minutes, then heat to 1300-1400°C at a rate of 1-5°C / min and keep warm for 1-2 hours, then cool to 700-900°C and cool to room temperature with the furnace, with a vacuum degree of 0.1-1 MPa.

8. The method for preparing a tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based multiphase ceramic coating according to claim 7, characterized in that: The amount of the brush coating is used to control the thickness of the silicon carbide reinforced Al2O3-SiO2 based composite ceramic layer after high temperature vacuum sintering to be 50-120 μm.

9. A tungsten alloy material containing a silicon carbide reinforced Al2O3-SiO2-based composite ceramic coating, characterized in that: Obtained by the preparation method according to any one of claims 1 to 8.

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