Method for preparing high-performance silicon nitride ceramic ball based on pressure modulation sintering technology

Abstract

The invention provides a method for preparing a high-performance silicon nitride ceramic ball based on a pressure modulation sintering technology, and relates to the field of functional ceramic material preparation, and the method comprises the following steps: 1, preparing a green body; 2, PMS sintering is carried out; step 3, cooling; traditional high-performance silicon nitride ceramic balls (the relative density is required to be larger than 99%, the Vickers hardness is required to be larger than or equal to 1500 kgf / mm, the bending strength is required to be larger than or equal to 920 MPa, and the fracture toughness is required to be larger than or equal to 6.0 MPa.m / ) are mainly prepared through a two-step process of normal pressure / air pressure sintering (GPS) and hot isostatic pressing (HIP). Although high densification of the material can be realized, the method has the problems of complicated process flow, high energy consumption, long production period, high equipment occupancy rate and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional ceramic material preparation, in particular to a method for preparing high-performance silicon nitride ceramic balls based on pressure-modulated sintering technology. BACKGROUND

[0002] The silicon nitride ceramic ball is a precision ceramic product made of Si3N4 material through high-temperature sintering in a non-oxidizing atmosphere, mainly applied in the fields of precision machine tool spindles, new energy vehicles, aerospace engines, petrochemical machinery, wind power insulation bearings, and semiconductor equipment; it has the characteristics of low density, high strength, high hardness, high temperature resistance, corrosion resistance, acid, alkali and seawater erosion resistance, and also has the functions of electrical and magnetic insulation and self-lubrication, and can be used in a lubricating medium-free environment.

[0003] At present, the preparation of high-performance silicon nitride ceramic balls (with a relative density of > 99%, a Vickers hardness of > 1500 kgf / mm2, a bending strength of > 920 MPa, and a fracture toughness of > 6.0 MPa·m1 / 2) mainly adopts a two-step process of "atmospheric pressure / gas pressure sintering (GPS) + hot isostatic pressing (HIP)". Although this method can achieve high densification of the material, it has the problems of complex process flow, high energy consumption, long production cycle, and high equipment occupancy. SUMMARY

[0004] Therefore, the present application provides a method for preparing high-performance silicon nitride ceramic balls based on pressure-modulated sintering technology to overcome the defects of the existing two-step process and achieve process flow simplification, energy consumption reduction, production efficiency improvement, and product performance optimization.

[0005] The present application provides a method for preparing high-performance silicon nitride ceramic balls based on pressure-modulated sintering technology, which specifically includes the following steps:

[0006] Step 1: green body preparation: mix silicon nitride powder, sintering additives, reinforcing phases, and organic additives in proportion, wherein the volume fraction ratio of sintering additives to reinforcing phases satisfies: , and the ceramic ball green body is prepared through the mixing and forming process;

[0007] Step 2: PMS sintering: place the green body in a hot isostatic pressing sintering furnace and perform one-time sintering in the following three stages in sequence, and the process strength factor of each stage satisfies: , wherein , is the absolute temperature ( ), is the pressure ( ), is the holding time ( ), heating rate (°C / Stage 1: Low-temperature degreasing and pre-firing: Under a protective atmosphere, at a heating rate of... (1~5℃ / From room temperature to (800~1200℃), and keep warm. (120~360) The process strength factor Q1 was calculated; Second stage: Medium-temperature and low-pressure sintering: Under a protective atmosphere, at a heating rate R2 (3~10℃ / The temperature continued to rise to (1600~1800℃), and pressure is introduced. (0.1~10) Inert gas, for heat preservation (120~240) The process strength factor was calculated. Third stage: High-temperature and high-pressure final combustion: Without cooling, the furnace atmosphere pressure is increased to... (50~200) ), and adjust the temperature to (1650~1850℃), heat preservation (30~150) The process strength factor was calculated. And peak pressure With the second stage of pressure satisfy: ;

[0008] Step 3: Cooling: at a cooling rate (5~20℃ / The high-performance silicon nitride ceramic balls are obtained by cooling the furnace to room temperature.

[0009] Furthermore, the sintering aid is , , , , , One or more of the above, wherein the amount added is 2% to 12% of the total mass of the powder.

[0010] Furthermore, the reinforcing phase is , , , One or more of SiC, BC, TiB2, TiCN, etc., are added in an amount of 0.5% to 3% of the total mass of the powder.

[0011] Furthermore, the organic additive is , One or more of the following, namely ammonium polyacrylate, are added at an amount of 1% to 5% of the total mass of the powder, and the degreasing rate in the first stage of step two is [missing information]. It should meet the following requirements: ≥95%, of which , For weightlessness, This represents the initial total weight of the organic additives.

[0012] Furthermore, the pressure increase in the third stage of step two adopts a multi-stage pressure, gradient pressurization mode, specifically satisfying the following relationship: Subsequently ,in, for The pressure of constant time and For boost rate ( / ),and > , The first-level target pressure (50~150) ), The second-stage peak pressure (100~200) ), and For the corresponding time point; and, in At what moment, the theoretical relative density of the material It should meet the following requirements: ≥98%, this density is calculated from the initial green body density and the densification kinetic model of the preceding sintering stage.

[0013] Furthermore, the first-level target pressure Insulation time The second-stage peak pressure lasts for 30-90 minutes. Insulation time The total high-pressure heat preservation time is 10-60 minutes. = + .

[0014] Furthermore, in the first stage of step two, after heating to... Before reaching 400℃, the furnace is in a vacuum state or a flowing, weak protective atmosphere; when the temperature reaches... Then, a protective atmosphere of one atmosphere is introduced until the stage ends, and satisfy: .

[0015] Further, the total energy consumption index of the whole PMS sintering process in step two satisfies: wherein and are the process strength factors of the atmospheric sintering and the hot isostatic pressing process in the traditional two-step method, respectively, indicating that the total energy consumption of the present method is lower than that of the traditional two-step method.

[0016] Further, the performance of the silicon nitride ceramic ball prepared by the method satisfies: relative density ≥ 99.5%, Vickers hardness ≥ 1500 , bending strength ≥ 1000 , and fracture toughness ≥ 6.5 , and the fracture toughness ( ) and the Vickers hardness satisfy the following empirical relationship: , and the bending strength and the average grain size satisfy the Hall-Petch relationship: .

[0017] Further, the ceramic ball prepared by the method has a microstructure in which the aspect ratio of the crystal grains is greater than 4 and forms a three-dimensional interlocking structure, and the aspect ratio and the fracture toughness satisfy a positive correlation relationship: = , wherein , , are material constants.

[0018] Advantages:

[0019] 1. Revolutionary simplification of the process flow and realization of lean production

[0020] The transformation from "discrete" processing to "integrated" manufacturing fundamentally simplifies the process.

[0021] Step integration: The GPS pre-sintering and HIP densification processes, which must be completed on two devices and in two independent stations in the traditional process, are highly integrated in a single hot isostatic pressing furnace and completed at one time through a program-controlled "three-stage" sintering system.

[0022] Auxiliary process elimination: At least 5 or more non-value-added auxiliary steps such as intermediate cooling, furnace discharge, surface cleaning, quality inspection, re-furnace loading, and secondary vacuumizing are directly eliminated.

[0023] This not only shortens the process, but also reduces the risk of product damage caused by multiple material handling and human operation errors, laying the foundation for achieving "black light factory" type full automation continuous production.

[0024] 2. Quantitative improvement of production efficiency and equipment utilization

[0025] Effect: Significant compression of production cycle, maximization of capital expenditure benefits.

[0026] Cycle comparison: The total time of traditional two-step method is usually 36-40 hours (GPS about 20-24 hours, intermediate process about 4 hours, HIP about 12 hours). The total time of the PMS process of the invention is strictly controlled within 18-20 hours, with an efficiency improvement of more than 45%.

[0027] "Zero interval" advantage: The key is that the conversion from the second stage to the third stage of step two is directly carried out "without temperature reduction", saving about 4-6 hours of cooling and re-heating time and the corresponding energy consumption.

[0028] Asset turnover rate: The reduction of equipment occupancy time is equivalent to an increase of about 40-50% in the annual production capacity of the same expensive hot isostatic press, which reduces the depreciation cost of the equipment per product.

[0029] 3. Systematic reduction of energy consumption and production cost

[0030] Effect: Significant energy saving and cost structure optimization.

[0031] Heat energy saving: Eliminates one complete cooling process from about 1700°C high temperature to room temperature and one re-heating process from room temperature to about 1700°C. According to the estimate, only these two items, the heat energy consumption per unit product can be reduced by more than 35%.

[0032] Electricity and gas consumption: Reduces at least the electricity consumed by vacuum pumping, programmed temperature rise and fall, and the loss of protective gas (N2 / Ar) caused by multiple furnace door openings.

[0033] Comprehensive cost: Taking into account the reduction of energy consumption, labor, auxiliary materials and equipment maintenance cost, the estimated comprehensive sintering cost per product can be reduced by 25%-35%.

[0034] 4. Optimization of product performance and breakthrough control of microstructure

[0035] Effect: The product performance fully meets and partially exceeds the traditional process level, and the microstructure control achieves active design.

[0036] Densification level: Through the strong elimination of closed pores by ultra-high pressure of 50-200MPa in the third stage, the relative density of the product is stabilized at 99.5%-99.8%, which is better than the 99.2%-99.7% of the traditional GPS+HIP process, and the consistency is higher.

[0037] Strengthening Mechanism: A unique "multi-stage pressure, gradient pressurization" mode generates strong hydrostatic pressure and shear stress in the high-pressure stage. This stress field, coupled with the liquid phase formed by the sintering aids, achieves:

[0038] Grain boundary phase optimization: Drives ultrafast diffusion of the liquid phase, enabling the grain boundary phase (glass phase) to be distributed more uniformly and thinner at the grain boundaries, thus improving high-temperature performance and hardness.

[0039] Grain structure design: Strongly induced β-Si3N4 grains grow in an anisotropic mode to form slender columnar crystals with an aspect ratio greater than 4, and intertwine to form a robust three-dimensional interlocking structure.

[0040] Performance: This microstructure simultaneously improves both toughness and strength. The fracture toughness can reach 6.5-7.0 MPa·m¹ / ², and the flexural strength is stable at 1000-1100 MPa, successfully solving the classic problem of "strength and toughness cannot be achieved at the same time" in ceramic materials.

[0041] 5. Enhanced quality control and process robustness

[0042] This improved product consistency and process reliability.

[0043] Reduced sources of defects: One-time sintering avoids the risks of pollution, moisture absorption or oxidation that may result from the pre-sintered body being exposed to the environment in an intermediate state.

[0044] Improved stress state: The continuous sintering process makes the thermal stress distribution inside the material more uniform, reducing the accumulation of internal stress and the possibility of microcrack initiation caused by repeated heating and cooling.

[0045] Wide process window: The temperature, pressure and time parameter ranges provided by this invention constitute a wide and stable process window, which is more tolerant of raw material fluctuations and equipment fluctuations, and is more conducive to stable control of large-scale industrial production. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0047] The accompanying drawings described below are only related to some embodiments of the invention and are not intended to limit the invention.

[0048] In the attached diagram:

[0049] Figure 1This is a flowchart of a method for preparing high-performance silicon nitride ceramic balls based on pressure modulation sintering technology, according to an embodiment of the present invention.

[0050] Figure 2 Figure 1 shows the SEM morphology of the finished product of the method for preparing high-performance silicon nitride ceramic balls based on pressure modulation sintering technology according to an embodiment of the present invention.

[0051] Figure 3 Figure 2 shows the SEM morphology of the finished product of the method for preparing high-performance silicon nitride ceramic balls based on pressure modulation sintering technology according to an embodiment of the present invention. Detailed Implementation

[0052] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0053] Example: Please refer to Figures 1-3 As shown:

[0054] This invention provides a method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology, comprising the following steps:

[0055] Step 1: Green body preparation: Silicon nitride powder is mixed with sintering aids, reinforcing phases, and organic additives in a certain proportion, wherein the volume fraction ratio of sintering aids to reinforcing phases is... satisfy: The raw ceramic spheres are produced through a mixing and molding process.

[0056] Step 2: PMS Sintering: The green body is placed in a hot isostatic pressing (HMS) sintering furnace and subjected to the following three stages of one-time sintering, with the process strength factor for each stage specified. satisfy: ,in , absolute temperature ( ), For pressure ( ), For the heat preservation time ( ), heating rate (°C / Stage 1: Low-temperature degreasing and pre-firing: Under a protective atmosphere, at a heating rate of... (1~5℃ / From room temperature to (800~1200℃), and keep warm. (120~360) The process strength factor Q1 was calculated; Second stage: Medium-temperature and low-pressure sintering: Under a protective atmosphere, at a heating rate R2 (3~10℃ / The temperature continued to rise to (1600~1800℃), and pressure is introduced. (0.1~10) Inert gas, for heat preservation (120~240) The process strength factor was calculated. Third stage: High-temperature and high-pressure final combustion: Without cooling, the furnace atmosphere pressure is increased to... (50~200) ), and adjust the temperature to (1650~1850℃), heat preservation (30~150) The process strength factor was calculated. And peak pressure With the second stage of pressure satisfy: ;

[0057] Step 3: Cooling: at a cooling rate (5~20℃ / The high-performance silicon nitride ceramic balls are obtained by cooling the furnace to room temperature.

[0058] Wherein, the sintering aid is , , , , , One or more of the above, wherein the amount added is 2% to 12% of the total mass of the powder.

[0059] Wherein, the reinforcing phase is , , , One or more of SiC, BC, TiB2, TiCN, etc., are added in an amount of 0.5% to 3% of the total mass of the powder.

[0060] Wherein, the organic additive is , One or more of the following, namely ammonium polyacrylate, are added at an amount of 1% to 5% of the total mass of the powder, and the degreasing rate in the first stage of step two is [missing information]. It should meet the following requirements: ≥95%, of which , For weightlessness, This represents the initial total weight of the organic additives.

[0061] In the third stage of step two, the pressure increase adopts a multi-stage pressure, gradient pressurization mode, specifically satisfying the following relationship: Subsequently in, for The pressure of constant time and For boost rate ( / ),and > , The first-level target pressure (50~150) ), The second-stage peak pressure (100~200) ), and For the corresponding time point; and, in At what moment, the theoretical relative density of the material Should meet: ≥98%, this density is calculated from the initial green body density and the densification kinetic model of the preceding sintering stage.

[0062] Among them, the first-level target pressure Insulation time The second-stage peak pressure lasts for 30-90 minutes. Insulation time The total high-pressure heat preservation time is 10-60 minutes. = + .

[0063] In the first stage of step two, when the temperature is raised to... Before reaching 400℃, the furnace is in a vacuum state or a flowing, weak protective atmosphere; when the temperature reaches... Then, a protective atmosphere of one atmosphere is introduced until the stage ends, and satisfy: .

[0064] In step two, the total energy consumption index of the entire PMS sintering process is... satisfy: ,in and The values ​​are the process strength factors for atmospheric pressure sintering and hot isostatic pressing in the traditional two-step method, respectively, indicating that the total energy consumption of this method is lower than that of the traditional two-step method.

[0065] The silicon nitride ceramic spheres prepared by the method shall meet the following performance requirements: relative density ≥ 99.5%, Vickers hardness ≥ 1500. Flexural strength ≥1000 Fracture toughness ≥ 6.5 And its fracture toughness ( ) and Vickers hardness The following empirical relationships must be satisfied: Meanwhile, its bending strength With average grain size Satisfying the Hall-Page relationship: .

[0066] The ceramic spheres prepared by the method described herein have a microstructure in which... Aspect ratio of grains The aspect ratio is greater than 4, forming a three-dimensional interlocking structure. With the fracture toughness Satisfying a positive correlation: = ,in , is a material constant.

[0067] I. Experimental Design

[0068] Control group (traditional two-step method):

[0069] Process: GPS (1750°C, 2MPa N2, holding for 4 hours) → cooling, unloading, cleaning → HIP (1800°C, 150MPa Ar, holding for 2 hours)

[0070] Total duration: Approximately 38 hours

[0071] Experimental group (one-step PMS method of this invention).

[0072] Total duration: Approximately 19 hours

[0073] II. Performance Comparison Data

[0074] Performance index Unit Traditional two-step method (control group) Inventive PMS method (experimental group) Performance comparison Relative density % 99.3±0.2 99.7±0.1 Significant improvement, better consistency Vickers hardness kgf / mm² 1520±30 1560±20 Significant improvement Bending strength MPa 920±40 1010±30 Significant improvement Fracture toughness (K IC) MPa·m¹ / ² 6.2±0.3 6.7±0.2 Significant improvement Weibull modulus (bending strength) - 18 25 Greatly improved reliability and consistency

[0075] Conclusion: The PMS method of this invention meets or exceeds the traditional two-step method in all key mechanical performance indicators, and has a smaller standard deviation and a higher Weibull modulus, indicating that the product has better performance consistency and reliability.

[0076] III. Comparison of Production Efficiency and Energy Consumption Data

[0077] Comparison item Unit Traditional two-step method (control group) Inventive PMS method (experimental group) Improvement / saving effect Total sintering period Hours 38 19 Period shortened by 50% Equipment occupancy time Hours 38 19 Equipment utilization rate increased by about 100% Rising energy consumption kW·h / kg ~12.5 ~7.8 Energy consumption reduced by about 37.6% Protective gas consumption m³ / kg ~4.2 ~2.5 Gas consumption reduced by about 40.5% Comprehensive production cost estimate Yuan / kg Benchmark (set to 100%) ~70% Cost decreased by about 30%

[0078] Note: The heating energy consumption is a theoretical estimate, based on the theoretical heat required to raise 1 kg of material from room temperature to 1800°C, and taking into account the heat loss from two heating cycles in the traditional process.

[0079] Conclusion: The PMS method of this invention has overwhelming advantages in terms of production efficiency, energy utilization rate and production cost, shortens the total cycle by half and significantly reduces energy consumption and cost.

[0080] IV. Microstructure Analysis Data

[0081] Analysis item Unit Traditional two-step method (control group) Inventive PMS method (experimental group) Microstructure significance ​ μm 0.45±0.15 0.38±0.08 Grains are finer and more uniform Average aspect ratio of β-Si3N4 grains - 3.8±0.9 4.5±0.6 Grain morphology is better, conducive to toughening Grain interlocking degree (SEM image analysis) % 65% >85% Form a more perfect three-dimensional interlocking network Average thickness of grain boundary phase nm ~3.5 ~2.0 Grain boundary phase is thinner, conducive to high temperature performance

[0082] Conclusion: This invention effectively regulates the microstructure of materials through dynamic pressure modulation, forming an ideal microstructure with finer dimensions, longer aspect ratio, and higher interlocking degree. This explains the reason why its strength and toughness are improved simultaneously from a mechanistic perspective.

[0083] The specific usage and function of this embodiment: Through a one-step process called "Pressure Modulated Sintering (PMS)," which coordinates the dynamic pressure field and temperature field, efficient and high-performance sintering of silicon nitride ceramics from green to fully densified can be achieved in a single device.

[0084] I. Precise Sequential Input of Energy and Force

[0085] The design of the entire PMS process follows a core logic: the driving force of sintering is significantly enhanced in each stage.

[0086] The first stage (low-temperature degreasing and pre-firing): This stage mainly involves gentle heat input. Its purpose is to ensure that organic additives can be safely and completely decomposed and discharged under a low temperature and protective atmosphere to avoid defects, while initiating preliminary solid-state sintering to lay the structural foundation for subsequent densification.

[0087] The second stage (medium-temperature low-pressure sintering): In this stage, thermal energy and low-pressure environment work synergistically. Higher temperatures cause the sintering aids to form a liquid phase. At this time, under lower gas pressure, the powder particles are rearranged mainly by capillary force. The liquid phase fills large open pores, which rapidly increases the material density and forms a solid sintered skeleton containing closed pores.

[0088] The third stage (high-temperature and high-pressure final firing): This stage is crucial for densification, driven primarily by extremely high hydrostatic pressure. High-pressure gas is injected directly into the furnace without interrupting cooling. This ultra-high-pressure environment generates powerful hydrostatic pressure (hydrostatic pressure is the pressure exerted on an object by a homogeneous fluid. It is an all-encompassing force, evenly distributed across the object's surface. Increased hydrostatic pressure causes the volume of the object to decrease, but does not change its shape), which directly acts on the closed pores formed in the second stage, forcefully causing them to collapse and heal through mechanisms such as plastic flow, creep, and accelerated diffusion, thereby achieving the final full densification of the material.

[0089] II. Pressure Field Coupled Mass Transport

[0090] It utilizes dynamically changing pressure fields to actively guide the formation of microstructures.

[0091] Dynamic pressure drives directional material migration: The ultra-high pressure applied in the third stage, especially with multi-level gradient changes, not only provides densification momentum but also significantly alters the grain boundary energy state. This change creates a powerful driving force that selectively drives the liquid phase formed by sintering aids to preferentially and rapidly penetrate and diffuse along specific grain boundaries.

[0092] Constructing a three-dimensional interlocking strengthening structure: The directional distribution of the liquid phase provides conditions for the anisotropic growth of silicon nitride grains. Grains grow rapidly at the liquid-rich grain boundaries, while growth is restricted in other directions, thus being actively induced to grow into slender columnar crystals. These slender columnar crystals overlap and interlock in space, ultimately forming a robust three-dimensional interlocking microstructure. This structure is the fundamental reason why the material simultaneously achieves high strength and high toughness.

[0093] III. Principle of Synergistic Performance Enhancement: Microstructure Determines Macroscopic Performance

[0094] Ultimately, the superior performance stems directly from the unique microstructure created by the aforementioned principles.

[0095] The high strength stems from the PMS process, which, through precise temperature and pressure control, prevents abnormal grain growth and yields fine, uniform grains. Simultaneously, the complete elimination of closed pores during the high-pressure stage results in virtually defect-free internal materials, forming the basis for the high strength.

[0096] The source of high toughness: The three-dimensional interlocking structure is fundamental to toughness. When a crack propagates in a material, it encounters these interlocking, slender columnar crystals. The crack cannot advance in a straight line and is forced to deflect and detour. At the same time, the columnar crystals also act as bridges behind the crack, and a large amount of energy is required when the crack is pulled out of the matrix. These mechanisms together significantly improve the material's ability to resist crack propagation, i.e., fracture toughness.

[0097] Synergistic Strengthening and Toughening: This invention achieves "fine grain strengthening" and "interlocking toughening" simultaneously through unique dynamic pressure modulation, thus successfully overcoming the traditional problem of "difficulty in balancing strength and toughness" in ceramic materials.

[0098] IV. System Optimization Principle: Co-design of Formulation and Process

[0099] The specific ratio of raw materials is the chemical basis for achieving the above working principle.

[0100] Synergistic effect of sintering aids and reinforcing phases: The specific ratio range of sintering aids and reinforcing phases in the formulation ensures that a sufficient amount of liquid phase with suitable properties can be formed during the sintering process to complete densification and drive anisotropic grain growth; at the same time, an appropriate amount of reinforcing phase can inhibit excessive grain growth and further optimize the mechanical properties of the material.

Claims

1. A method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology, comprising the following steps: characterized in that: Step 1: Green body preparation: Silicon nitride powder is mixed with sintering aids, reinforcing phases, and organic additives in a certain proportion, wherein the volume fraction ratio of sintering aids to reinforcing phases is... satisfy: The raw ceramic spheres are produced through a mixing and molding process. Step 2: PMS Sintering: The green body is placed in a hot isostatic pressing (HMS) sintering furnace and subjected to the following three stages of one-time sintering, with the process strength factor for each stage specified. satisfy: ,in , absolute temperature ( ), For pressure ( ), For the heat preservation time ( ), heating rate (°C / First stage: Low-temperature degreasing and pre-firing: Under a protective atmosphere, at a heating rate of... (1~5℃ / From room temperature to (800~1200℃), and keep warm. (120~360) The process strength factor Q1 was calculated; Second stage: Medium-temperature and low-pressure sintering: Under a protective atmosphere, at a heating rate R2 (3~10℃ / The temperature continued to rise to (1600~1800℃), and pressure is introduced. (0.1~10) Inert gas, for heat preservation (120~240) The process strength factor was calculated. Third stage: High temperature and high pressure final combustion: Without cooling down, the pressure of the atmosphere inside the furnace is increased to... (50~200) ), and adjust the temperature to (1650~1850℃), heat preservation (30~150) The process strength factor was calculated. And peak pressure With the second stage of pressure satisfy: ; Step 3: Cooling: at a cooling rate (5~20℃ / The high-performance silicon nitride ceramic balls are obtained by cooling the furnace to room temperature.

2. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The sintering aid is , , , , , One or more of the above, wherein the amount added is 2% to 12% of the total mass of the powder.

3. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The reinforcing phase is , , , One or more of SiC, BC, TiB2, TiCN, etc., are added in an amount of 0.5% to 3% of the total mass of the powder.

4. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The organic additive is , One or more of the following, namely ammonium polyacrylate, are added at an amount of 1% to 5% of the total mass of the powder, and the degreasing rate in the first stage of step two is [missing information]. It should meet the following requirements: ≥95%, of which , For weightlessness, This represents the initial total weight of the organic additives.

5. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The pressure increase in the third stage of step two adopts a multi-stage pressure, gradient pressurization mode, specifically satisfying the following relationship: Subsequently ,in, for The pressure of constant time and For boost rate ( / ),and > , The first-level target pressure (50~150) ), The second-stage peak pressure (100~200) ), and For the corresponding time point; and, in At what moment, the theoretical relative density of the material It should meet the following requirements: ≥98%, this density is calculated from the initial green body density and the densification kinetic model of the preceding sintering stage.

6. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: First-level target pressure Insulation time The second-stage peak pressure lasts for 30-90 minutes. Insulation time The total high-pressure heat preservation time is 10-60 minutes. = + .

7. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: In the first stage of step two, when the temperature is raised to... Before reaching 400℃, the furnace is in a vacuum state or a flowing, weak protective atmosphere; when the temperature reaches... Then, a protective atmosphere of one atmosphere is introduced until the stage ends, and satisfy: .

8. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: In step two, the total energy consumption index of the entire PMS sintering process satisfy: ,in and The values ​​are the process strength factors for atmospheric pressure sintering and hot isostatic pressing in the traditional two-step method, respectively, indicating that the total energy consumption of this method is lower than that of the traditional two-step method.

9. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The silicon nitride ceramic spheres prepared by the method meet the following performance requirements: relative density ≥ 99.5%, Vickers hardness ≥ 1500. Flexural strength ≥1000 Fracture toughness ≥ 6.5 And its fracture toughness ( ) and Vickers hardness The following empirical relationships must be satisfied: Meanwhile, its bending strength With average grain size Satisfying the Hall-Page relationship: .

10. The method for preparing high-performance silicon nitride ceramic spheres based on pressure modulation sintering technology according to claim 1, characterized in that: The ceramic spheres prepared by the method described above have a microstructure in... Aspect ratio of grains The aspect ratio is greater than 4, forming a three-dimensional interlocking structure. With the fracture toughness Satisfying a positive correlation: = ,in , is a material constant.

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