A silicon nitride combined silicon carbide material with wear resistance and anti-coking functions for waste incinerator

Abstract

The application belongs to the technical field of protective materials for household garbage incinerator high-temperature working conditions, and discloses a silicon nitride combined silicon carbide material with wear resistance and anti-coking functions for garbage incinerator, and application of the material to high-temperature key components in household garbage incinerator. The raw material is added in the following weight fractions: 66-72 parts of high-purity silicon carbide powder, 28-34 parts of elemental silicon powder, 6-9% of the total weight of the raw material of a composite modifier, and 8-11% of the raw material of a resin binder. The application realizes comprehensive optimization in wear resistance, anti-coking property and chlorine and sulfur corrosion resistance through gradient temperature structure evolution regulation and control of silicon carbide, synergistic construction of main phase and multi-element functional phase, and synergistic regulation and control of preparation process, and can meet the long-term stable service requirements of garbage incinerator under high-temperature harsh working conditions.

Description

Technical Field

[0001] This invention relates to the field of protective materials for high-temperature operation of municipal solid waste incinerators, specifically to a silicon nitride-bonded silicon carbide material for waste incinerators that combines wear resistance and anti-coking properties, and its application in key high-temperature components of municipal solid waste incinerators. Background Technology

[0002] Municipal solid waste incineration technology has become the mainstream technology for municipal solid waste disposal in China due to its advantages such as significant volume reduction, thorough harmless treatment, and resource recyclability, and has been widely applied in engineering projects across the country. However, the operating environment inside the waste incinerator is extremely harsh. The furnace operating temperature is maintained at 865℃~1070℃ for a long time. The heated surfaces inside the furnace are not only subjected to high-speed erosion and wear from high-concentration dust-laden flue gas, but are also exposed to highly corrosive atmospheres such as HCl, chloride salts, and sulfates for a long time, making the material surfaces prone to severe chemical corrosion. More importantly, the ash of municipal solid waste is rich in alkali metal oxides and heavy metal components, which are prone to forming low-melting-point eutectic compounds under high-temperature incineration. These compounds adhere to the heated surfaces and form a dense and difficult-to-clean slag layer. The coupled effects of high temperature, wear, corrosion, and coking significantly shorten the service life of key components inside the furnace, seriously affecting the continuity and stability of the incineration system, and have become the core technical bottleneck restricting the efficient development of the waste incineration industry.

[0003] Currently, in engineering practice, the main protective measures for the heated surfaces of waste incinerators are heat-resistant alloys, traditional refractory materials, and surface functional coatings. However, all of these materials have significant performance defects in actual use: While heat-resistant alloys possess excellent mechanical and processing properties, they lack a dedicated anti-coking and wear-resistant phase. Their corrosion resistance, resistance to solid particle erosion, and resistance to ash adhesion and coking are all poor under high-temperature chlorine-sulfur composite atmospheres. Long-term use can easily lead to problems such as localized corrosion thinning, wear perforation, and slag blockage on the heated surfaces. Conventional silicon carbide refractories consist of only a single silicon carbide phase, lacking a whisker-reinforced composite main phase, and are not designed with a multi-component synergistic composition system. The structural evolution of silicon carbide under gradient temperatures has not been studied. Relying solely on a single silicon carbide phase results in insufficient adaptability to the complex atmosphere of waste incineration, poor anti-slagging effect, and easy wetting of the surface under high-temperature alkali metal salt corrosion, further aggravating ash adhesion and coking. Existing commercial anti-slagging coatings mostly rely on surface physical modification to reduce ash adhesion, without optimizing from the perspective of the main phase construction, introduction of multiple functional phases, new composition design, and temperature structural evolution of silicon carbide. However, their high-temperature erosion resistance is limited, and the bonding strength with the substrate is insufficient. Under the coupled effect of long-term high temperature and wear, they are prone to cracking, peeling and other failure phenomena, and cannot achieve long-term stable protection of the heated surface.

[0004] Silicon nitride-bonded silicon carbide ceramics, as a high-performance non-oxide composite ceramic material, possesses a high hardness of 9 on the Mohs scale, excellent high-temperature structural stability, and good chemical inertness. Its wear resistance is more than 3.3 times that of traditional wear-resistant cast steel, and it can form a dense oxide protective film in situ under high-temperature oxidizing atmospheres. Currently, it has found some applications in wear-resistant structural components and high-temperature kiln furniture. However, when directly applied to waste incineration environments, it suffers from problems such as strong ash adhesion, difficulty in self-removal of the slag layer, and insufficient long-term service stability. These issues prevent it from meeting the long-term use requirements of high-temperature components in incinerators, thus limiting the large-scale engineering application of this type of material in the waste incineration field. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects of existing high-temperature protective materials for waste incinerators, such as severe wear, difficulty in removing coking, and aggravated corrosion by chlorine and sulfur media. This invention provides a method for constructing a protective structure through controllable crystal transformation and in-situ whisker growth. A new silicon carbide-based multi-component synergistic system was designed by introducing a corundum-hexagonal boron nitride composite functional phase into the whisker-SiC particle composite main phase. The structural evolution law of silicon carbide under gradient temperature was clarified. At the same time, a silicon nitride-silicon carbide composite material with high wear resistance, coking resistance and corrosion resistance was combined with interface modification, and its application method in key components in the furnace was clarified.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The raw materials added in this invention are: 66-72 parts of high-purity silicon carbide powder, 28-34 parts of elemental silicon powder, 6%-9% of the total weight of the composite modifier, and 8%-11% of the raw materials.

[0008] The resin binder is phenolic resin;

[0009] The high-purity silicon carbide powder has a purity of ≥96%, and particle sizes of ≤2.57mm, ≤0.4mm, and ≤47μm, respectively, with a weight ratio of 3~4:3~4:3 for the three particle size grades.

[0010] The purity of the elemental silicon powder is ≥99.3%, and the particle size is ≤47μm;

[0011] The composite modifier is a composite of corundum and hexagonal boron nitride, with a weight ratio of 1.3-2.0:1.

[0012] The silicon carbide particles are graded in a 3:4:3:4:3 ratio: coarse particles (≤2.57mm) provide the main structural support, medium particles (≤0.4mm) fill the large gaps between coarse particles, and fine particles (≤47μm) fill the micro gaps between medium particles, achieving the densest packing of particles, maximizing the initial density of the green body, reducing shrinkage deformation during sintering, and the gradient particle size distribution can effectively disperse external impact stress, improving the flexural strength and impact toughness of the material.

[0013] The weight ratio of corundum to hexagonal boron nitride is controlled at 1.3-2.0:1. When the proportion of corundum is below this range, it cannot completely neutralize the alkali metal salts in the incinerator ash, and low-melting-point eutectics will still be generated in large quantities. When the proportion of corundum is above this range, it will lead to a decrease in the sintering density of the material and a reduction in mechanical properties. If the proportion of hexagonal boron nitride is too low, a continuous low surface energy interface cannot be formed, resulting in insufficient anti-coking effect. If the proportion is too high, it will hinder the bonding between β-Si3N4 whiskers and the silicon carbide matrix, reducing the wear resistance of the material.

[0014] The preparation method of this invention, which combines high wear resistance and anti-coking properties of silicon nitride-bonded silicon carbide material, is as follows:

[0015] Step 1, Ingredients and Mixing: Weigh out the high-purity silicon carbide, elemental silicon powder, composite modifier and binder according to the above proportions; add the high-purity silicon carbide, elemental silicon powder and composite modifier to the binder, and put them into a planetary mixer together. Stir for 50 minutes to obtain a uniform mixed composite raw material.

[0016] Step 2: Load the thoroughly mixed composite raw materials into a custom steel mold and use a fully automatic hydraulic forming machine to press and hold the material under a constant forming pressure of 120MPa for 30 seconds to ensure that the raw material particles are tightly bound and there are no voids inside. Finally, a high-strength and dense blank with a regular shape and precise dimensions of 24mm×24mm×160mm is prepared.

[0017] Step 3: The pressed dense green body is transferred into an electrically heated constant-temperature drying oven and dried continuously at a constant temperature of 120℃ for 50 hours to completely remove volatile components such as adsorbed water and bound water inside the green body, avoiding cracking and deformation defects during subsequent sintering. After drying, the green body is smoothly transferred to a closed nitrogen atmosphere high-temperature sintering furnace, and high-purity nitrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The pressure inside the furnace is maintained at a slightly positive pressure of 0.06MPa. Gradual temperature control is performed at a heating rate of 65℃ / h: 320℃ for 1 hour; 610℃ for 1.5 hours; 810℃ for 2 hours; and 1440℃ for constant-temperature sintering for 6 hours. After sintering, the nitrogen atmosphere is kept constant, and the sample is allowed to cool slowly to room temperature naturally with the furnace, finally obtaining this silicon nitride-bonded silicon carbide material with both high wear resistance and anti-coking properties.

[0018] In step three, during the process of gradient temperature control of silicon carbide structural evolution and construction of a new composite phase, the furnace pressure is maintained at a slightly positive pressure of 0.06 MPa, and gradient temperature control is carried out at a heating rate of 65℃ / h, holding at 320℃ for 1h; rising to 610℃ and holding for 1.5h; rising to 810℃ and holding for 2h.

[0019] The temperature was raised to 1435±10℃ and sintered at a constant temperature for 6 hours to achieve the structural evolution of silicon carbide from an inert framework to a dense framework. This process was simultaneously completed... Towards Controllable crystal form transformation, In-situ directional growth of whiskers, crystal development, and overall material densification result in materials with an aspect ratio ≥10. Whiskers interwoven with a dense silicon carbide framework A novel whisker-SiC particle composite phase and a three-dimensional network interlocking structure were developed. After sintering, the nitrogen atmosphere was kept constant, and the sample was allowed to cool slowly to room temperature naturally in the furnace. Finally, a silicon nitride-bonded silicon carbide composite material with high wear resistance, high coking resistance and high temperature corrosion resistance was prepared with the novel composite phase as the core.

[0020] This invention achieves a significant improvement in the overall performance of composite materials by synergistically optimizing the new composition of raw materials, the ratio system, the evolution law of silicon carbide gradient temperature structure, the modification mechanism of corundum-hexagonal boron nitride composite and the preparation process parameters. It realizes the overall performance improvement of composite materials from five core dimensions: main phase construction, introduction of multi-functional phases, new composition design, silicon carbide temperature structure evolution and interface control. It creatively proposes an integrated technology solution for wear resistance and coking prevention, which is "controllable crystal form + structural reinforcement + interface modification + main phase construction + synergistic effect of multi-functional phases + silicon carbide temperature control".

[0021] This invention uses high-purity silicon carbide powder (≥96% purity) and elemental silicon powder as the core raw materials, and corundum-hexagonal boron nitride composite modifier to construct a new silicon carbide-based multi-element synergistic system. Through precise temperature gradient control (320℃~610℃~810℃~1400℃), the structural evolution of silicon carbide in different temperature ranges is clarified: at 320℃~610℃, silicon carbide forms a chemically inert initial framework to resist corrosive media; at 610℃~810℃, silicon carbide particles undergo pre-densification bonding, providing a basis for whisker growth; at 810℃~1400℃, silicon carbide forms a dense, hard framework, simultaneously achieving a directional reaction between elemental silicon and nitrogen, completing... Towards long columnar Controllable crystal transformation allows for in-situ directional growth of fibrous structures within the material. The structure features a whisker-reinforced structure with a whisker aspect ratio ≥10. The whiskers are uniformly distributed between and on the surface of the silicon carbide particles, forming a hard framework of silicon carbide particles. Whiskers are ductile The whisker-SiC particle composite main phase constructs a three-dimensional network interlocking structure, achieving structural densification, ceramic-like grain boundary bonding, and tight interfacial bonding. Simultaneously, corundum and hexagonal boron nitride in the new system serve as composite modifying components. During service, corundum reacts in situ with alkali metal salts in the incinerator ash to generate a high-melting-point aluminosilicate phase, preventing the formation of low-melting-point eutectic binders. Hexagonal boron nitride, as a chemically inert phase, is uniformly distributed on the material surface and grain boundaries, significantly reducing surface energy and ash adhesion. The coking layer can then detach autonomously under flue gas scouring and thermal stress, inhibiting ash adhesion and coking layer formation through its mechanism. Combined with a special resin binder, the forming strength of the green body is enhanced, ensuring dimensional stability and structural integrity throughout the forming, drying, and high-temperature sintering processes.

[0022] Anti-coking principle: The anti-coking effect of this material is achieved through a three-pronged mechanism: ① Low surface energy wetting inhibition: The whisker-SiC particle composite main phase has extremely low surface free energy, preventing molten slag from wetting and spreading, with a contact angle ≥120°, thus blocking adhesion from an interfacial thermodynamic perspective; ② Structural barrier: The three-dimensional network interlocking structure is dense and without through pores, preventing corrosive slag from penetrating and forming a firm coking substrate; ③ Synergistic effect of modifiers: Corundum and alkali metal salts generate high-melting-point phases in situ, preventing the formation of low-melting-point eutectic bonding phases; Hexagonal boron nitride significantly reduces surface energy, resulting in a significant decrease in slag adhesion, allowing the coking layer to detach autonomously.

[0023] Through the above-mentioned new composition design, the regulation of silicon carbide gradient temperature structure evolution, and the synergistic construction and preparation process of the main phase and multiple functional phases, the present invention achieves comprehensive optimization in terms of wear resistance, coking resistance and chlorine and sulfur corrosion resistance, and can meet the requirements for long-term stable service under the high temperature and harsh conditions of waste incinerator. Attached Figure Description

[0024] Figure 1 The image shows the microstructure of the silicon nitride-bonded silicon carbide material obtained in Example 1, which exhibits both high wear resistance and anti-coking properties. Detailed Implementation

[0025] The following examples illustrate the implementation and features of the present invention, but the present invention is not limited to the following embodiments.

[0026] Example 1:

[0027] The raw materials are added in the following weight proportions: 66 parts of high-purity silicon carbide (of which particles with a particle size ≤2.57mm, ≤0.4mm, and ≤47μm are in a weight ratio of 4:3:3), 34 parts of elemental silicon powder, and 9% of the total weight of the composite modifier (corundum and hexagonal boron nitride in a weight ratio of 1.3:1), and 8% of the total weight of the raw materials is prepared as phenolic resin.

[0028] Example 2:

[0029] The raw materials added are as follows by weight: 72 parts of high-purity silicon carbide (of which particles with a particle size ≤2.57mm, ≤0.4mm, and ≤47μm are in a weight ratio of 3:3:4), 28 parts of elemental silicon powder, and 6% of the total weight of the composite modifier (corundum and hexagonal boron nitride in a weight ratio of 2.0:1), and phenolic resin accounting for 11% of the total weight of the raw materials is also prepared.

[0030] Example 3:

[0031] The raw materials are added in the following weight proportions: 70 parts of high-purity silicon carbide (of which particles with a particle size ≤2.57mm, ≤0.4mm, and ≤47μm are in a weight ratio of 3:3:3), 30 parts of elemental silicon powder, and 8% of the total weight of the composite modifier (corundum and hexagonal boron nitride in a weight ratio of 1.5:1), and 10% of the total weight of the raw materials is prepared as phenolic resin.

[0032] The preparation methods for Examples 1, 2, and 3 are as follows:

[0033] Step 1, Ingredients and Mixing: Weigh out the high-purity silicon carbide, elemental silicon powder, composite modifier and binder according to the above proportions; add the high-purity silicon carbide, elemental silicon powder and composite modifier to the phenolic resin, put them into a planetary mixer and stir for 50 minutes to obtain a uniform mixed composite raw material.

[0034] Step 2: Load the thoroughly mixed composite raw materials into a custom steel mold and use a fully automatic hydraulic forming machine to press and hold the material under a constant forming pressure of 120MPa for 30 seconds to ensure that the raw material particles are tightly bound and there are no gaps inside. Finally, a high-strength and dense blank with a regular shape and precise dimensions of 24mm×24mm×160mm is prepared.

[0035] Step 3: The pressed dense green body is transferred into an electrically heated constant-temperature drying oven and dried continuously at a constant temperature of 120℃ for 50 hours to completely remove volatile components such as adsorbed water and bound water inside the green body, avoiding cracking and deformation defects during subsequent sintering. After drying, the green body is smoothly transferred to a closed nitrogen atmosphere high-temperature sintering furnace, and high-purity nitrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The pressure inside the furnace is maintained at a slightly positive pressure of 0.06MPa. Gradual temperature control is performed at a heating rate of 65℃ / h: 320℃ for 1 hour; 610℃ for 1.5 hours; 810℃ for 2 hours; and 1440℃ for constant-temperature sintering for 6 hours. After sintering, the nitrogen atmosphere is kept constant, and the sample is allowed to cool slowly to room temperature naturally with the furnace, finally obtaining this silicon nitride-bonded silicon carbide material with both high wear resistance and anti-coking properties.

[0036] Application Example 1: Furnace Lining Application

[0037] The silicon nitride-bonded silicon carbide material prepared in Example 1, which features a novel β-Si3N4 whisker-SiC particle composite phase and exhibits both high wear resistance and anti-coking properties, was processed into refractory bricks with dimensions of 230mm × 114mm × 65mm. These bricks were then used to construct the sidewalls of a 500-ton-per-day waste incinerator, extending from 1 meter above the grate to the furnace outlet, with a thickness of 105mm. After 12 months of continuous operation, the furnace lining surface showed no obvious wear marks. The silicon carbide maintained a dense, hard skeleton structure at furnace temperatures of 865℃~1070℃. The novel composite phase did not undergo structural damage. The coking layer thickness was ≤4.8mm, and the coking layer could be easily detached by mechanical vibration. No adhesion or blockage occurred in the furnace lining.

[0038] Application Example 2: Nozzle Application

[0039] The silicon nitride-bonded silicon carbide material prepared in Example 2, which possesses both high wear resistance and anti-coking properties, was installed in the nozzle of the secondary air injection system of a waste incinerator. This nozzle... The nozzle uses a whisker-SiC particle composite phase as its core, operates within a temperature range of 860℃-940℃, and works on high-temperature flue gas containing ash particles. Silicon carbide maintains structural stability at this temperature. After eight months of operation, the nozzle's inner wall wear was ≤0.75mm, the composite phase remained intact, there was no obvious coking on the nozzle surface, and the injection flow rate remained stable. The service life of this nozzle is 4.2 times longer than that of traditional metal nozzles.

[0040] Application Example 3: Heat-receiving surface protection application

[0041] For the surface protection treatment process of waste incinerator equipment, the silicon nitride-bonded silicon carbide material with high wear resistance and anti-coking properties, which retains the new composite phase of β-Si3N4 whiskers-SiC particles obtained in Example 3 of this invention, is ground into a composite fine powder as a spraying raw material. Using supersonic flame spraying technology, a protective coating is prepared on the surface of the metal tube wall of the superheater of the waste incinerator boiler. By precisely controlling the process parameters such as spraying distance, powder feeding rate and flame power, a dense protective coating with high bonding strength and no obvious internal pores is obtained on the tube wall surface. The average thickness of the coating is stably controlled at 2.1 mm. The new composite phase in the coating remains continuous. The silicon carbide does not undergo structural deformation during the spraying thermal process and the service temperature of 320℃~1430℃. The coated superheater tubes were assembled into an actual waste incinerator for six consecutive months of industrial operation testing. After the operation period, the appearance, bonding condition, and structural integrity of the coating were assessed offline. The results showed that the coating maintained its overall morphology, the interface with the metal substrate was stable, and no coating peeling, cracking, warping, or localized powdering occurred. This protective coating significantly improves the high-temperature performance of the superheater tubes. Specifically, the amount of molten ash coking and deposits on the tube surface is reduced by more than 70% compared to the untreated tube surface. The wear resistance of the coated area is improved by 3.1 times or more compared to the original uncoated tube substrate, effectively extending the service life and maintenance cycle of the superheater tubes.

[0042] Comparative Example 1

[0043] The difference between this comparative example and Example 1 is that the modifier used in step one is only corundum (without hexagonal boron nitride), lacking the synergistic effect of the silicon carbide-based multi-component new composition. The remaining process parameters and operating conditions are the same as in Example 1.

[0044] Comparative Example 2

[0045] The difference between this comparative example and Example 1 is that the amount of elemental silicon powder added in step one is 21%, resulting in... The new phase structure of whisker-SiC particle composite was incomplete, but the remaining process parameters and operating conditions were consistent with those in Example 1.

[0046] Comparative Example 3

[0047] The difference between this comparative example and Example 1 is that gradient temperature control was not used in step three, and the temperature was directly raised to 1370°C. As a result, the silicon carbide did not complete the complete gradient structure evolution and the densification was insufficient. The other process parameters and operating conditions are the same as those in Example 1.

[0048] Performance testing

[0049] The present invention prepares with The silicon nitride-bonded silicon carbide materials with whisker-SiC particle composite novel phase as the core were tested for performance according to national standards and industry testing methods: wear resistance was determined according to GB / T26545-2011, room temperature flexural strength was determined according to GB / T3002-2017, ash particle contact angle was evaluated using the seat drop method, and high temperature corrosion behavior was evaluated according to GB / T1954-2008 with weight loss as the indicator. Simultaneously, the structural integrity of silicon carbide and the stability of the composite novel phase were tested at different temperatures. Detailed test results of the materials prepared in Examples 1-3 and Comparative Examples 1-3 are summarized in Table 1.

[0050] Table 1 Performance Test Results

[0051]

[0052] The above description is only a part of the specific embodiments of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A silicon nitride-bonded silicon carbide material for waste incinerators, characterized by: The raw materials added are: 66-72 parts of high-purity silicon carbide powder, 28-34 parts of elemental silicon powder, 6%-9% of the total weight of the composite modifier, and 8%-11% of the raw materials. The composite modifier is a composite of corundum and hexagonal boron nitride with a weight ratio of 1.3-2.0:

1.

2. The silicon nitride-bonded silicon carbide material for waste incinerators with both wear resistance and anti-coking properties as described in claim 1, characterized in that: The purity of the high-purity silicon carbide powder is ≥96%, and the particle sizes are ≤2.57mm, ≤0.4mm, and ≤47μm, respectively, with a weight ratio of 3~4:3~4:3 for the three particle size grades.

3. The silicon nitride-bonded silicon carbide material for waste incinerators with both wear resistance and anti-coking properties as described in claim 1, characterized in that: The purity of elemental silicon powder is ≥99.3%, and the particle size is ≤47μm.

4. The silicon nitride-bonded silicon carbide material for waste incinerators with both wear resistance and anti-coking properties as described in claim 1, characterized in that: The resin binder is phenolic resin.

5. A method for preparing a silicon nitride-bonded silicon carbide material for a waste incinerator that combines wear resistance and anti-coking properties, as described in claim 1, characterized in that: Step 1, Ingredients and Mixing: Weigh out the high-purity silicon carbide, elemental silicon powder, composite modifier and binder according to the above proportions; add the high-purity silicon carbide, elemental silicon powder and composite modifier to the binder, and put them into a planetary mixer together. Stir for 50 minutes to obtain a uniform mixed composite raw material. Step 2: Load the thoroughly mixed composite raw materials into a custom steel mold and use a fully automatic hydraulic forming machine to press and hold the material under a constant forming pressure of 120MPa for 30 seconds to ensure that the raw material particles are tightly bound and there are no voids inside. Finally, a high-strength and dense blank with a regular shape and precise dimensions of 24mm×24mm×160mm is prepared. Step 3: The pressed dense green body is transferred into an electrically heated constant-temperature drying oven and dried continuously at a constant temperature of 120℃ for 50 hours to completely remove volatile components such as adsorbed water and bound water inside the green body, avoiding cracking and deformation defects during subsequent sintering. After drying, the green body is smoothly transferred to a closed nitrogen atmosphere high-temperature sintering furnace, and high-purity nitrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The pressure inside the furnace is maintained at a slightly positive pressure of 0.06MPa. Gradual temperature control is performed at a heating rate of 65℃ / h: 320℃ for 1 hour; 610℃ for 1.5 hours; 810℃ for 2 hours; and 1440℃ for constant-temperature sintering for 6 hours. After sintering, the nitrogen atmosphere is kept constant, and the sample is allowed to cool slowly to room temperature naturally with the furnace, finally obtaining this silicon nitride-bonded silicon carbide material with both high wear resistance and anti-coking properties.

6. The method for preparing a silicon nitride-bonded silicon carbide material for a waste incinerator with both wear resistance and anti-coking properties according to claim 5, characterized in that: In step three, gradient temperature control is performed to achieve the structural evolution of silicon carbide from an inert framework to a dense, hard framework. After reaching the target temperature, it is sintered at a constant temperature for 6 hours. During this process, the process is completed simultaneously. Towards Controllable crystal form transformation, In-situ directional growth of whiskers, crystal development, and overall material densification result in materials with an aspect ratio ≥10. Whiskers interwoven with a dense silicon carbide framework A novel phase composed of whiskers and SiC particles and a three-dimensional interlocking network structure.

7. The method for preparing a silicon nitride-bonded silicon carbide material for a waste incinerator with both wear resistance and anti-coking properties according to claim 6, characterized in that: Step 3 yields a silicon nitride-bonded silicon carbide material with both high wear resistance and anti-coking properties. This material is ground into fine powder and used as a spraying raw material. A protective coating is prepared on the surface of the metal tube wall of the superheater in a waste incineration boiler using supersonic flame spraying technology. A dense protective coating with high bonding strength and no obvious internal pores is obtained on the tube wall surface. The average thickness of the coating is stably controlled at 2.1 mm. The composite new phase in the coating remains continuous. The silicon carbide does not undergo structural deformation during the spraying thermal process and at service temperatures of 320℃~1430℃.

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