Tungsten-silicon nitride toughened ceramic material, method of making and use thereof

Abstract

This application proposes a tungsten-silicon nitride toughened ceramic material, its preparation method, and its application. The method includes the following steps: mixing tungsten powder, silicon nitride powder, and a sintering aid; pre-pressing the mixed powder in a mold; and then sintering to obtain the tungsten-silicon nitride toughened ceramic. This preparation method utilizes the conductive and self-heating properties of tungsten to reduce the sintering temperature and holding time, and uses the sintering aid to form a low-melting-point liquid phase coating of tungsten particles, thereby effectively inhibiting the reaction between tungsten and silicon nitride, ultimately achieving the retention of elemental tungsten in the silicon nitride ceramic matrix under vacuum or atmospheric pressure conditions. This method can introduce a tungsten metal elemental phase into silicon nitride and achieve the construction of a strong silicon nitride-tungsten bonding interface. This structure can facilitate the transfer of tungsten metal dislocations into the ceramic or stress coordination, thereby significantly improving the material's strength, deformation capacity, and fracture toughness. This preparation process is simple, the microstructure is controllable, and it is suitable for the preparation of high-performance silicon nitride structural ceramics.

Description

Technical Field

[0001] This application relates to the field of structural ceramic toughening and plasticizing and metal-ceramic composite materials, specifically to a tungsten-silicon nitride toughened ceramic material, its preparation method and application. Background Technology

[0002] In high-reliability and long-life applications such as aerospace, stringent requirements are placed on Si3N4 ceramic materials: related components must have extremely high structural integrity and damage tolerance. Typically, the material is required to maintain excellent high-temperature strength while also having good fracture toughness and even a certain degree of deformation capacity to cope with the risk of crack initiation and propagation under extreme thermo-mechanical coupling loads.

[0003] However, the strong covalent bond intrinsic characteristics of Si3N4 ceramics make it typically brittle at room temperature, with low fracture toughness and sensitivity to defects. This is fundamentally contradictory to the service requirements of aerospace and other fields for key components to be highly reliable, impact-resistant, and long-lasting.

[0004] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0005] This application addresses the fundamental problem of insufficient toughness in silicon nitride ceramics as mentioned in the background art, as well as the limitations of existing toughening technologies, by providing a tungsten-silicon nitride toughened ceramic material, its preparation method, and its applications. This tungsten-silicon nitride toughened ceramic material retains elemental tungsten metal through rapid low-temperature sintering technology, while simultaneously constructing an interface structure between silicon nitride and tungsten metal that can transfer dislocations or coordinate stresses. This synergistically enhances the material's strength and toughness, overcoming the problem of the "strength-toughness contradiction" in traditional composite materials.

[0006] This application provides a method for preparing tungsten-silicon nitride toughened ceramic materials, comprising the following steps: Tungsten powder, silicon nitride powder, and sintering aid are mixed evenly to obtain a mixed powder. The tungsten powder is uniformly distributed in the form of particles in the silicon nitride powder, and the sintering aid is dispersed between the tungsten powder and the silicon nitride powder. The mixed powder is pre-pressed in a sintering mold and sintered at low temperature under an electric field. The sintering aid reacts with the silicon oxide on the surface of the silicon nitride powder, forming a silicate liquid phase coating layer on the surface of the tungsten powder particles. Low-temperature sintering is achieved by utilizing the electrical conductivity of tungsten. During sintering, the heating rate and holding time are controlled, and the sintering aid forms a low-melting-point liquid phase coating on the tungsten particles, effectively suppressing tungsten diffusion and its reaction with silicon nitride. This yields the tungsten-silicon nitride toughened ceramic material, with a sintering aid film separating the metallic tungsten and the silicon nitride substrate, forming a coherent interface. The fracture toughness of the tungsten-silicon nitride toughened ceramic is ≥6.28 MPa•m. 1 / 2 The low-temperature sintering temperature is 1400℃-1800℃, the heating rate is 100℃ / min-900℃ / min, the low-temperature sintering pressure is 10MPa-100MPa, and the low-temperature sintering time is 1min-20min.

[0007] This application utilizes the conductive and self-heating properties of tungsten metal by incorporating tungsten powder into silicon nitride powder. By controlling the heating rate, sintering temperature, and holding time, it achieves rapid sintering preparation of tungsten-silicon nitride toughened ceramic materials at relatively low temperatures. Introducing metallic tungsten as a second phase, thanks to its intrinsic high conductivity, effectively enhances the overall conductivity of the system during sintering under an electric field. This characteristic allows for faster Joule heating and conduction within the material under the same electric field, significantly increasing the overall heating rate. This rapid heating significantly shortens the material's residence time within the high-temperature reaction window, providing a crucial kinetic advantage for suppressing the interfacial reaction between tungsten and silicon nitride. Ultimately, the introduction of the tungsten phase into the densified silicon nitride ceramic and the formation of a strongly bonded interface structure provide channels for the propagation of dislocations generated by tungsten metal into the ceramic, thereby significantly improving the deformation capacity and fracture toughness of the ceramic material.

[0008] Preferably, the low-temperature sintering method includes discharge plasma sintering, and the atmosphere of the low-temperature sintering is nitrogen or vacuum.

[0009] Preferably, the sintering aid includes at least one of metal oxides, intermetallic compounds, composite sintering aids, and non-oxide aids. The initial particle size D of the sintering aid... 50 The particle size is 30nm-3μm; the mass ratio of the sintering aid to the silicon nitride powder is (0.03-0.15):1.

[0010] Preferably, the initial particle size D of the tungsten powder 50 The initial particle size D of the silicon nitride powder is 100 nm-4 μm. 50 The 100nm and above; the mass ratio of the tungsten powder and silicon nitride powder is (0.03-1.5):1.

[0011] Preferably, the heating rate of the low-temperature sintering is 300℃ / min-900℃ / min, and the low-temperature sintering time is 4min-6min.

[0012] Preferably, the mixing method includes wet mixing, wherein the liquid phase in the wet mixing includes ethanol and / or deionized water, and the mass ratio of the liquid phase to the mixed powder is (0.6-1.5):1.

[0013] Preferably, the sintering mold includes a high-strength graphite mold, and the compressive strength of the sintering mold is above 50 MPa.

[0014] In a second aspect, this application provides a tungsten-silicon nitride toughened ceramic material, obtained by the aforementioned preparation method, wherein the fracture toughness of the tungsten-silicon nitride toughened ceramic material is ≥6.28 MPa•m. 1 / 2 The tungsten-silicon nitride toughened ceramic material also satisfies at least one of the following characteristics: (1) Density ≥ 99.2%; (2) Compressive strength ≥ 3329 MPa; (3) Compressive strain ≥ 1.4%; (4) Hardness ≥ 1705HV1.0; (5) Pore size ≤200nm.

[0015] In a third aspect, this application provides the application of the above-mentioned tungsten-silicon nitride toughened ceramic material in aero-engine bearings, turbine rotors, and sealing rings. Attached Figure Description

[0016] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein, Figure 1 This is a sample diagram of Embodiment 1 of this application; Figure 2 This is a SEM image of Embodiment 1 of this application; Figure 3 This is the XRD pattern of Embodiment 1 of this application; Figure 4 (a), (b), (c), and (d) are XRD patterns of comparative examples 1-4 of this application, respectively; Figure 5 This is a hardness indentation diagram of Example 1 of this application; Figure 6 This is a hardness indentation diagram of Comparative Example 1 of this application; Figure 7 This is a test compression curve diagram of Embodiment 1 of this application; Figure 8This is a test compression curve for Comparative Example 1 of this application. Detailed Implementation

[0017] The following detailed description, with appropriate reference to the accompanying drawings, discloses the tungsten-silicon nitride toughened ceramic material, its preparation method, and embodiments of its application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0018] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0019] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0020] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0021] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0022] To address the toughness issue of silicon nitride ceramic materials, existing technologies mainly employ two toughening pathways: First, introducing a hard second phase (such as TiN or SiC) or fibers / whiskers to toughen the silicon nitride ceramic material. However, this method, while improving toughness, usually leads to a decrease in material strength, failing to fundamentally solve the problem of brittle fracture in ceramics. Second, introducing ductile tungsten (W) as a toughening phase. Since preparing W / Si3N4 composite materials using pressureless or hot-press sintering processes requires extremely high sintering temperatures (>1800℃) and long holding times (>60min) to achieve dense sintering, this process exacerbates the diffusion and interfacial reactions between tungsten and silicon nitride. Therefore, the final product of pressureless or hot-press sintering is a brittle tungsten-silicon compound, unable to retain the elemental tungsten phase. Therefore, in order to retain the elemental tungsten phase in silicon nitride ceramics, the existing technology usually adopts the "gas pressure sintering" process, which uses extremely high nitrogen pressure (up to 10 MPa) to suppress the silicide reaction of tungsten. However, this leads to problems such as complex equipment, high cost, and limited sample size. Moreover, this approach mainly relies on the physical addition of tungsten particles in material design, which is insufficient for the structural control of the metal-ceramic interface. This results in weak interfacial bonding between tungsten and the silicon nitride matrix. Under stress, the interface cracks, leading to a decrease in the strength and toughness of the ceramic.

[0023] Our previous work proposed a "dislocation borrowing" toughening strategy, which enabled the transfer of metal dislocations to ceramics in the La2O3 / Mo system by controlling the metal-ceramic coherent interface structure, providing a novel approach to ceramic toughening. However, applying this mechanism to the W-Si3N4 system still faces many challenges: under vacuum or ambient pressure, Si3N4 and W undergo interfacial reactions to form brittle silicides, making toughening difficult; there is a lack of mature processes for constructing strongly bonded, dislocation-transferable ordered interfaces in this system; and how to synergistically improve toughness and strength remains an unsolved problem.

[0024] Therefore, developing a preparation method that can effectively achieve "borrowed dislocation" toughening and simultaneously improve the overall performance of the material in the W-Si3N4 system is crucial. This application addresses the shortcomings of the existing technology by innovatively proposing a tungsten-silicon nitride toughened ceramic material, its preparation method, and its applications. The core of this application is to form a liquid-phase coating layer on the surface of tungsten particles using sintering aids, and to employ spark plasma sintering (SPS) technology. Utilizing its ultra-fast heating rate (100℃ / min-900℃ / min) and extremely short holding time (1min-20min), the interfacial reaction between the tungsten particles and the silicon nitride ceramic matrix is ​​kinetically avoided. This ultimately achieves stable and efficient retention of the elemental tungsten phase at lower temperatures (1400℃-1800℃) and conventional pressures (10MPa-100MPa) without the need for high-pressure conditions, thus laying a new technological foundation for resolving the "toughening contradiction" in the W-Si3N4 system and improving material performance. The preparation method includes the following steps: After tungsten powder, silicon nitride powder and sintering aid are mixed evenly, a mixed powder is obtained. The tungsten powder is uniformly distributed in the silicon nitride powder in the form of particles, and the sintering aid is dispersed between the tungsten powder and the silicon nitride powder. The mixed powder is passed through a 200-mesh sieve; The mixed powder is pre-pressed in a sintering mold and sintered at low temperature under an electric field. The electrical conductivity of tungsten is utilized to achieve low-temperature sintering. During sintering, the heating rate and holding time are controlled, and a sintering aid reacts with the silicon oxide on the surface of the silicon nitride powder, forming a silicate liquid-phase coating layer on the surface of the tungsten powder particles. This effectively inhibits tungsten diffusion and its reaction with silicon nitride, resulting in the tungsten-silicon nitride toughened ceramic material. A coherent interface is formed between the metallic tungsten and the silicon nitride substrate. The fracture toughness of the tungsten-silicon nitride toughened ceramic is ≥6.28 MPa•m. 1 / 2 The low-temperature sintering temperature is 1400℃-1800℃, the heating rate is 100℃ / min-900℃ / min, the low-temperature sintering pressure is 10MPa-100MPa, and the low-temperature sintering time is 1min-20min.

[0025] This preparation method rapidly reaches relatively low sintering temperatures (1400℃-1800℃) through an extremely rapid heating rate (100-900℃ / min) coupled with an extremely short holding time (1min-20min), kinetically shortening the material's residence time within the high-temperature reaction window. This effectively inhibits interfacial diffusion and reaction between tungsten and silicon nitride. In this rapid sintering system, the low-melting-point liquid phase formed by the sintering aid helps to encapsulate tungsten particles, further preventing their contact with the silicon nitride matrix. Through this synergistic process—centered on rapid heating and short holding time, supplemented by liquid-phase physical isolation—the densification of the silicon nitride matrix is ​​achieved while successfully preserving the highly ductile metallic tungsten phase. This lays a crucial foundation for constructing a "borrowed dislocation" interfacial structure during stress and achieving a synergistic improvement in material strength and toughness.

[0026] Preferably, the particle size D of the tungsten powder is... 50 The particle size D of the silicon nitride powder is 100 nm-4 μm. 50 The 100nm and above; the mass ratio of the tungsten powder and silicon nitride powder is (0.03-1.5):1.

[0027] Preferably, the heating rate of the low-temperature sintering is 300℃ / min-900℃ / min, and the low-temperature sintering time is 4min-6min.

[0028] Preferably, the sintering aid includes at least one of metal oxides, intermetallic compounds, composite sintering aids, and non-oxide aids. The initial particle size D of the sintering aid... 50 The particle size is 30nm-3μm; the mass ratio of the sintering aid to the silicon nitride powder is (0.03-0.15):1.

[0029] Preferably, the uniform mixing method includes wet mixing; the liquid phase in the wet mixing includes ethanol and / or deionized water, the mass ratio of the liquid phase to the mixed powder is (0.6-1.5):1, and the sieving is a 200-mesh sieve.

[0030] Preferably, the sintering mold includes a high-strength graphite mold and a carbon-carbon mold, and the compressive strength of the sintering mold is above 50 MPa.

[0031] Preferably, the low-temperature sintering method includes discharge plasma sintering, and the atmosphere of the low-temperature sintering is high-purity nitrogen or vacuum.

[0032] In a second aspect, this application provides a tungsten-silicon nitride toughened ceramic material, obtained by the aforementioned preparation method, wherein the fracture toughness of the tungsten-silicon nitride toughened ceramic is ≥6.28 MPa•m. 1 / 2 The ultra-high purity silicon carbide dense ceramic also satisfies at least one of the following characteristics: (1) Density ≥ 99.2%; (2) Compressive strength ≥ 3329 MPa; (3) Compressive strain ≥ 1.4%; (4) Hardness ≥ 1705HV1.0; (5) Pore size ≤200nm.

[0033] In a third aspect, this application provides the application of the above-mentioned tungsten-silicon nitride toughened ceramic material in aero-engine bearings, turbine rotors, and sealing rings.

[0034] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0035] Example 1: The mixed powder in this embodiment is made from the following raw materials: silicon nitride powder, tungsten powder, and sintering aid; The silicon nitride powder is α-SiC, with an initial particle size D. 50 It is around 200nm.

[0036] The initial particle size of the tungsten powder is D. 50 The particle size is 2 μm; the mass ratio of the tungsten powder to the silicon nitride powder is 0.7:1; The sintering aid is a composite powder of MgO and Al2O3, and the initial particle size D of the sintering aid is... 50 The particle size is approximately 50 nm, and the purity is ≥99.9%; the mass ratio of the composite sintering aid is 1:1, and the mass ratio of the sintering aid to the silicon nitride powder is 0.08:1.

[0037] The preparation steps of the tungsten-silicon nitride toughened ceramic material in this embodiment are as follows: (1) Silicon nitride powder, tungsten powder and sintering aid are uniformly mixed by wet ball milling. The mass ratio of the mixed powder to alcohol is 0.9:1 and the ball milling time is 24h. The ball milling medium is silicon nitride balls. (2) After drying the uniformly mixed powder, grind it and pass it through a 200-mesh sieve to obtain powder with uniform size; (3) The obtained powder is loaded into a graphite mold and pre-pressed into shape; (4) The pre-pressed sample was placed in SPS and heated to 1500℃ at a heating rate of 700℃ / min under normal pressure nitrogen atmosphere. The pressure was 60MPa. After holding for 4min, it was cooled with the furnace to obtain tungsten-silicon nitride toughened ceramic material with tungsten element. (5) The obtained sample is processed and then applied.

[0038] The composite additive (MgO-Al2O3) reacts with SiO2 on the surface of Si3N4 at 1500℃ to generate a magnesium aluminum silicate liquid phase. This liquid phase encapsulates tungsten particles and inhibits interfacial reactions, providing a dense and controllable microstructure for the subsequent construction of dislocation-borrowed interfaces.

[0039] In this embodiment, appropriate sintering aids maintain a suitable amount of liquid phase generation. This liquid phase wets the grain boundaries and fills the pores, promoting particle rearrangement through capillary force, thereby sintering the tungsten-silicon nitride toughened ceramic material into a dense structure. Sufficiently fast heating rate and sufficiently short holding time are used to suppress the reaction between tungsten and silicon nitride. A suitable high-temperature sintering temperature is selected to ensure sufficient densification driving force and prevent instability of the tungsten-silicon nitride interface structure.

[0040] The tungsten-silicon nitride toughened ceramic material prepared in this embodiment has a uniform and dense microstructure with a density of 99.4% and a pore size of ≤200nm. The high-temperature sintering equipment in this embodiment is a plasma discharge sintering equipment, and the high-temperature sintering atmosphere is nitrogen or vacuum; preferably, high-temperature sintering is carried out in a nitrogen atmosphere to suppress the decomposition of silicon nitride.

[0041] The sintering mold selected in this embodiment is a high-strength graphite mold (compressive strength ≥50MPa), and high-purity carbon paper is inserted into the inner wall to isolate contamination.

[0042] The tungsten-silicon nitride toughened ceramic material prepared by the method in this embodiment has a density of 99.4%, a compressive strength of 3526 MPa, and a fracture toughness of 8.74 MPa·m. 1 / 2 The hardness is 1751HV1.0 and the compressive strain is 3.95%.

[0043] Example 2: In Example 2, the mass ratio of tungsten powder to silicon nitride powder used in the preparation of the tungsten-silicon nitride toughened ceramic material was 1.5:1, and the particle size D of the tungsten powder was... 50 The sintering temperature was 1600℃, the heating rate was 900℃ / min, the sintering pressure was 40MPa, and the holding time was 15min. Other preparation methods were the same as in Example 1. The tungsten-silicon nitride toughened ceramic material prepared by this method achieved a density of 99.2%, a compressive strength of 3329MPa, and a fracture toughness of 8.37MPa·m. 1 / 2The hardness is 1705HV1.0 and the compressive strain is 2.99%.

[0044] Example 3: In Example 3, the mass ratio of tungsten powder to silicon nitride powder used in the preparation of the tungsten-silicon nitride toughened ceramic material was 0.3:1, and the particle size D of the silicon nitride powder was... 50 The particle size D of the tungsten powder is 100 nm. 50 The particle size was 1 μm. The sintering aids were Y₂O₃ and Al₂O₃, with a yttrium oxide:aluminum oxide ratio of 1:1 and a total content of 10 wt.%. The heating rate was 500 °C / min, the sintering temperature was 1700 °C, the sintering pressure was 30 MPa, and the holding time was 8 min. Other preparation methods were the same as in Example 1. The tungsten-silicon nitride toughened ceramic material prepared by this method achieved a density of 99.6%, a compressive strength of 3680 MPa, and a fracture toughness of 6.28 MPa·m. 1 / 2 The hardness is 1827HV1.0 and the compressive strain is 1.40%.

[0045] Example 4: In Example 4, the mass ratio of tungsten powder to silicon nitride powder used in the preparation of the tungsten-silicon nitride toughened ceramic material was 0.1:1, and the particle size D of the tungsten powder was... 50 The thickness was 4 μm. The sintering aids were Y₂O₃ and Yb₂O₃, with a yttrium oxide:ytterbium oxide ratio of 1:1 and a total content of 3 wt.%. The heating rate was 400 °C / min, the sintering temperature was 1800 °C, the sintering pressure was 10 MPa, and the holding time was 1 min. Other preparation methods were the same as in Example 1. The tungsten-silicon nitride toughened ceramic material prepared by the method in this example had a density of 99.3%, a compressive strength of 3423 MPa, and a fracture toughness of 6.64 MPa·m. 1 / 2 The hardness is 2293HV1.0 and the compressive strain is 2.22%.

[0046] Example 5: In Example 5, the mass ratio of tungsten powder to silicon nitride powder used in the preparation of the tungsten-silicon nitride toughened ceramic material was 0.03:1, and the particle size D of the tungsten powder was... 50 The sintering parameters were: 500 nm, heating rate 300 °C / min, sintering aids Re₂O₃ and MgO, rhenium oxide:magnesium oxide = 1:1, total content 15 wt.%, sintering temperature 1400 °C, sintering pressure 100 MPa, holding time 20 min, and other preparation methods were the same as in Example 1. The tungsten-silicon nitride toughened ceramic material prepared by this method achieved a density of 99.4%, a compressive strength of 3555 MPa, and a fracture toughness of 7.49 MPa·m. 1 / 2 The hardness is 2303HV1.0 and the compressive strain is 2.57%.

[0047] The tungsten-silicon nitride toughened ceramic materials prepared in Examples 2-5 were processed and tested for mechanical properties such as hardness, fracture toughness and compressive properties, as well as for microstructure and XRD structure characterization. It was found that these tungsten-silicon nitride toughened ceramic materials maintained high density with a density of more than 99% under the premise of containing tungsten element. The fracture toughness, compressive properties and hardness all met the requirements of the component. The sintering results produced by different raw materials and processes vary.

[0048] In Example 1, medium-sized tungsten powder was matched with α-Si3N4 powder, and MgO-Al2O3 was selected as a sintering aid. This combination can form a magnesium aluminosilicate liquid phase with suitable viscosity at 1500℃, effectively coating the tungsten particles and promoting matrix densification. The appropriate heating rate and holding time effectively suppressed the interfacial reaction between tungsten and silicon nitride while achieving high density, thus obtaining excellent comprehensive properties with a balance of strength, toughness, and hardness.

[0049] In Example 2, the proportion of tungsten powder was significantly increased and its particle size reduced to 100 nm, while the heating rate and sintering temperature were also improved. The higher tungsten content provided a more sufficient reserve of ductile phase for the borrowed dislocation mechanism, while the large specific surface area of ​​the nano-sized tungsten powder enhanced its interfacial effect with the matrix. The faster heating significantly shortened the reaction window, allowing the fine tungsten particles to be retained kinetically even at a higher temperature of 1600 °C. As a result, the material maintained high density while exhibiting a more tortuous crack propagation path, thus improving fracture toughness.

[0050] In Example 3, the silicon nitride powder was refined to 100 nm and Y2O3-Al2O3 was used as the sintering aid. The finer matrix powder exhibits higher sintering activity, while the Y-Al-Si-ON liquid phase system possesses higher high-temperature stability and better wettability, facilitating the growth of better long columnar β-Si3N4 grains at 1700 °C, thereby enhancing the toughness of the matrix itself. Simultaneously, the combination with coarser (1 μm) tungsten powder forms a microstructure of "fine matrix + coarse toughening phase," further dissipating energy through mechanisms such as crack bridging.

[0051] In Example 4, an extremely low tungsten content and coarse tungsten powder were used, along with Y₂O₃-Yb₂O₃ additives and a sintering temperature increased to 1800℃. The low tungsten content reduced the total amount of the ductile phase, but the coarse particles still effectively deflected cracks even at this low content. The high temperature combined with the Y₂O₃-Yb₂O₃ dual rare earth additive helped purify grain boundaries and reduce the glassy phase, thereby significantly improving the high-temperature strength and hardness of the material. The extremely short 1-minute holding time was crucial to suppressing excessive interfacial reactions at high temperatures.

[0052] Example 5 employs a process involving sintering at low temperature and high pressure using extremely low tungsten content, fine tungsten powder, and a high content of rare earth additives (Re2O3-MgO). The low temperature of 1400℃ significantly inhibits diffusion and harmful interfacial reactions between tungsten and silicon nitride, providing the most fundamental thermodynamic guarantee for preserving the chemically pure tungsten elemental phase. Simultaneously, the extremely high pressure of 100MPa provides a strong densification driving force, compensating for the insufficient sintering activity at low temperatures.

[0053] Table 1. Differences in Raw Materials and Sintering Aids

[0054] Comparative Example 1: In this comparative example, the sintering temperature was changed to 1600℃, and other conditions were the same as in Example 1, resulting in a tungsten-silicon nitride toughened ceramic material.

[0055] Increasing the sintering temperature promotes the interfacial reaction between tungsten and silicon nitride, with some tungsten participating in the reaction to form tungsten silicide, which reduces the fracture toughness and compressive strength of the sample.

[0056] The tungsten-silicon nitride toughened ceramic material prepared by this comparative method has a density of 99.5%, a compressive strength of 3026 MPa, and a fracture toughness of 5.14 MPa·m. 1 / 2 Its hardness is 1834HV1.0.

[0057] Comparative Example 2: In this comparative example, the heat preservation time was changed to 30 min, and other conditions were the same as in Example 1, resulting in tungsten-silicon nitride toughened ceramic material.

[0058] The 30-minute holding time provided more reaction time for the interfacial reaction between tungsten and silicon nitride. Some of the tungsten was reacted to form tungsten silicide, which reduced the fracture toughness and compressive strength of the sample.

[0059] The tungsten-silicon nitride toughened ceramic material prepared by this comparative method has a density of 99.3%, a compressive strength of 3134 MPa, and a fracture toughness of 5.86 MPa·m. 1 / 2 Its hardness is 1794HV1.0.

[0060] Comparative Example 3: The high-temperature sintering process of this comparative example differs from that of Example 1: the pre-pressed sample is placed in an atmospheric pressure sintering furnace, and under an atmospheric pressure nitrogen atmosphere with a nitrogen pressure of 1 MPa, the temperature is raised to 1500°C at a heating rate of 40°C / min, held for 60 min, and then cooled down with the furnace. Other conditions are the same as in Example 1, and tungsten-silicon nitride composite ceramics are obtained.

[0061] The method did not reach the sintering densification temperature, and the slow diffusion inside the powder made it difficult to completely sinter and densify. However, due to the limited heating rate and excessive holding time, tungsten and silicon nitride did not react completely and could not form borrowed dislocation structures.

[0062] The tungsten-silicon nitride composite ceramic prepared by this comparative method does not contain elemental tungsten, has a density of 96.5%, a compressive strength of 1697 MPa, and a hardness of 1503 HV1.0.

[0063] Comparative Example 4: This comparative example uses tungsten powder particle size D. 50 The nm wavelength was changed to 50 nm, and other conditions were the same as in Example 1, to obtain tungsten-silicon nitride toughened ceramic material.

[0064] Finer tungsten powder particles have higher activity and react more violently with silicon nitride, making it difficult to suppress the reaction with low temperature and short time. Therefore, tungsten reacts with silicon nitride to form tungsten silicide.

[0065] The tungsten-silicon nitride toughened ceramic material prepared by this comparative method has a density of 99.0%, a compressive strength of 3219 MPa, and a fracture toughness of 5.45 MPa·m. 1 / 2 Its hardness is 1831HV1.0.

[0066] Table 2 Performance of each embodiment and comparative example

[0067] like Figure 1 and Figure 2 As shown, the tungsten-silicon nitride toughened ceramic sample prepared in this application is uniform overall, with a dense microstructure and no pores; combined with Figure 2 , Figure 4 The XRD results of each comparative example show that this application effectively suppressed the interfacial reaction between tungsten and silicon nitride through precise process design, avoided the formation of harmful phases such as brittle tungsten silicide, and successfully preserved the metallic tungsten elemental phase as a toughening source. Figure 5 , Figure 6 The fracture toughness test results show that the crack propagation path of the sample in the example is significantly shorter and more tortuous, which directly proves its excellent crack resistance and higher fracture toughness. Figure 7 , Figure 8 The compression performance test results show that the compressive strain of Example 1 is as high as 3.95%, which is much higher than that of Comparative Example 1 (0.35%). This directly reflects the improved macroscopic plastic deformation capacity of the material due to the retention of the ductile tungsten phase. Experimental results show that the ceramics prepared by this method achieve a synergistic improvement in strength, toughness, and deformation capacity (with a maximum fracture toughness of 8.74 MPa·m) while ensuring high density (≥99.2%). 1 / 2The optimal compressive strain is 3.95%, the highest compressive strength reaches 3680 MPa, and the highest hardness is 2293 HV1.0. This confirms that this method effectively solves the fundamental contradiction of the difficulty in achieving both "strength" and "strain" in traditional tungsten-silicon nitride composites by inhibiting harmful reactions and retaining and utilizing elemental tungsten.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a tungsten-silicon nitride toughened ceramic material, characterized in that, Includes the following steps: Tungsten powder, silicon nitride powder, and sintering aid are mixed evenly to obtain a mixed powder. The tungsten powder is uniformly distributed in the form of particles in the silicon nitride powder, and the sintering aid is dispersed between the tungsten powder and the silicon nitride powder. The mixed powder is pre-pressed in a sintering mold and sintered at low temperature under an electric field. The sintering aid reacts with the silicon oxide on the surface of the silicon nitride powder, forming a silicate liquid phase coating layer on the surface of the tungsten powder particles, thus obtaining the tungsten-silicon nitride toughened ceramic material. A sintering aid film is spaced between the metallic tungsten and the silicon nitride substrate, forming a coherent interface. The fracture toughness of the tungsten-silicon nitride toughened ceramic material is ≥6.28 MPa•m. 1 / 2 The low-temperature sintering temperature is 1400℃-1800℃, the heating rate is 100℃ / min-900℃ / min, the low-temperature sintering pressure is 10MPa-100MPa, and the low-temperature sintering time is 1min-20min. The low-temperature sintering method includes discharge plasma sintering, and the atmosphere of the low-temperature sintering is nitrogen or vacuum.

2. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 1, characterized in that, The sintering aid includes at least one of metal oxides, intermetallic compounds, composite sintering aids, and non-oxide aids.

3. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 2, characterized in that, The initial particle size D of the sintering aid 50 The particle size is 30nm-3μm; the mass ratio of the sintering aid to the silicon nitride powder is (0.03-0.15):

1.

4. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 1, characterized in that, The initial particle size D of the tungsten powder 50 The initial particle size D of the silicon nitride powder is 100nm-4μm. 50 The 100nm or larger; the mass ratio of the tungsten powder to the silicon nitride powder is (0.03-1.5):

1.

5. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 1, characterized in that, The heating rate for the low-temperature sintering is 300℃ / min-900℃ / min, and the sintering time is 4min-6min.

6. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 1, characterized in that, The mixing method includes wet mixing, wherein the liquid phase in the wet mixing includes ethanol and / or deionized water, and the mass ratio of the liquid phase to the mixed powder is (0.6-1.5):

1.

7. The method for preparing the tungsten-silicon nitride toughened ceramic material according to claim 1, characterized in that, The sintering mold includes a graphite mold and a carbon-carbon mold, and the compressive strength of the sintering mold is above 50 MPa.

8. A tungsten-silicon nitride toughened ceramic material, characterized in that, The tungsten-silicon nitride toughened ceramic material obtained by the preparation method according to any one of claims 1-7 has a fracture toughness ≥ 6.28 MPa•m. 1 / 2 The tungsten-silicon nitride toughened ceramic material also satisfies at least one of the following characteristics: (1) Density ≥ 99.2%; (2) Compressive strength ≥ 3329 MPa; (3) Compressive strain ≥ 1.4%; (4) Hardness ≥ 1705HV1.0; (5) Pore size ≤200nm.

9. The application of a tungsten-silicon nitride toughened ceramic material obtained by any one of the preparation methods of claims 1-7 or the tungsten-silicon nitride toughened ceramic material as described in claim 8 in aero-engine bearings, turbine rotors, and sealing rings.

Images