Preparation method and application of spherical yttrium aluminum garnet / silicon carbide composite powder for spraying

Abstract

The application discloses a preparation method and application of a spherical yttrium aluminum garnet / silicon carbide composite powder for spraying, and belongs to the technical field of thermal spraying materials. Al(NO3)3.9H2O and Y(NO3)3.6H2O are weighed and dispersed in deionized water, a chelating agent is added, and heating and stirring are conducted to form a yttrium aluminum precursor sol; SiC particles are added into the sol, heating and stirring are conducted, and a three-dimensional network YAG gel is formed; the three-dimensional network YAG gel is aged at constant temperature, is transferred into a vacuum heating furnace, is subjected to staged heating calcination, cooling and airflow crushing, and YAG / SiC composite powder is obtained; the composite powder is ball milled with a binder to form slurry, spray drying is conducted, and agglomerated YAG / SiC composite powder is obtained; the agglomerated YAG / SiC composite powder is transferred into a vacuum heating furnace, is heated and kept warm, is cooled to room temperature, and YAG / SiC composite powder is obtained through screening. The YAG / SiC composite powder is directly synthesized through a liquid phase method, the yttrium aluminum garnet particles are nanoscale, are uniformly distributed with silicon carbide, the composite powder has high sphericity, and the problems of powder agglomeration and composition segregation are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of thermal spraying materials technology, specifically relating to a method for preparing and applying spherical yttrium aluminum garnet / silicon carbide composite powder for spraying. Background Technology

[0002] Silicon carbide (SiC) ceramics exhibit excellent mechanical properties at both room and high temperatures due to their strong intrinsic intermolecular bonding, making them ideal candidates for harsh service environments such as extreme wear, high-temperature oxidation, and corrosion. However, the inherent physicochemical properties of pure SiC powder are incompatible with the high-temperature spraying process. During the extreme transient heating processes of conventional plasma or supersonic jets, pure SiC powder particles do not undergo the ideal melting-spreading process but instead experience severe thermal decomposition and sublimation (~2500℃). This results in a large number of sprayed particles vaporizing or transforming into silicon-rich vapor and free carbon before reaching a fully melted or plastically softened state, directly affecting the efficiency of coating deposition. Furthermore, SiC particles have extremely high surface tension and viscosity, resulting in poor wettability to most metal or ceramic substrates. This makes it difficult for molten particles to spread and overlap properly with adjacent particles after impacting the substrate, easily leading to incomplete interlayer bonding during microsecond-level solidification. The coating is prone to leaving a large number of unhealed micropores, voids and microcracks, which seriously weakens the overall protective effectiveness of the SiC coating as a physical and chemical barrier.

[0003] To address the fundamental technological challenge of thermal decomposition and sublimation of pure silicon carbide (SiC) during high-temperature thermal spraying, domestic and international research has primarily focused on two key technologies: doping SiC powder with a second phase and surface modification of SiC powder. Based on these, various SiC-based composite coating material systems have been developed. Regarding second-phase doping modification, Al / SiC, Si / SiC, and ZrB2 / SiC systems have been used as case studies to introduce second-phase materials with relatively low melting points or high thermal stability. By allowing Al or Si to melt first during spraying, consuming heat, the instantaneous heating temperature of SiC particles is reduced to some extent, thus inhibiting their decomposition. Studies have shown that such composite powders can indeed be successfully deposited on substrates such as high-temperature alloys, stainless steel, and magnesium alloys to form coatings. However, the proportion of silicon carbide in this type of composite powder is usually low, making it difficult to fully inherit and utilize the high hardness and high wear resistance inherent in SiC. At the same time, the physical differences between SiC and the second phase can easily lead to micro-agglomeration, resulting in poor continuity of SiC phase distribution in the coating and the formation of local enriched or depleted areas.

[0004] Regarding surface coating modification, the first step is to construct a ceramic coating layer on the surface of SiC particles that has a high melting point, good high-temperature stability, and is physically compatible with SiC. For example, existing research uses yttrium aluminum garnet (Y3Al5O4) as an example. 12Using YAG as the coating phase, composite powder materials of 20-50 wt.% YAG / SiC were prepared by liquid-phase precipitation. Subsequent ball milling, sieving, and controlled agglomeration treatment yielded spherical powder suitable for thermal spraying. During spraying, the outer YAG layer (melting point approximately 1940℃) preferentially melts upon reaching the high-temperature zone of the flame, forming a molten liquid shell that effectively encapsulates and isolates the internal SiC core. The molten YAG shell plays a dual crucial role: firstly, it significantly reduces the direct impact of high-temperature heat flow on the SiC core, thereby fundamentally inhibiting the decomposition of SiC at extreme temperatures; secondly, as a "binder," the molten YAG liquid phase possesses superior spreadability and wettability compared to SiC, effectively filling the voids between adjacent particles after impacting the substrate, promoting metallurgical bonding and densification between particles, and significantly reducing micropores and cracks in the coating caused by the poor spreadability of SiC itself. Studies have shown that coatings prepared by this method exhibit significantly reduced porosity, improved bonding strength and toughness, and superior overall thermodynamic performance with a longer potential service life. However, the traditional liquid-phase precipitation method for preparing YAG / SiC composite powder is extremely sensitive to changes in concentration, temperature, and pH, easily leading to hard agglomeration and uneven composition of the powder. Furthermore, it relies on cumbersome washing steps, making large-scale production difficult. Summary of the Invention

[0005] To overcome the difficulties of existing technologies, this invention innovatively integrates the "sol-gel-calcination" and "spray granulation-sintering" processes. First, through a controllable sol-gel method, yttrium and aluminum precursors are formed into a uniform three-dimensional network gel around nano-SiC particles, achieving uniform composite at the nanoscale and fundamentally solving the problems of incomplete coating and component segregation.

[0006] To address the issues of powder agglomeration and poor morphology and flowability after calcination, this invention innovatively introduces centrifugal spray granulation technology. After the composite powder is slurried, it is atomized at high speed to form uniform micron-sized droplets. After drying, YAG / SiC composite powder with high sphericity, concentrated particle size, and excellent flowability is directly obtained. This continuous process is stable and efficient, laying a solid foundation for large-scale production.

[0007] Therefore, the purpose of this invention is to provide a method for preparing and applying spherical yttrium aluminum garnet / silicon carbide composite powder for spraying.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying, comprising the following steps: S1. Weigh Al(NO3)3·9H2O and Y(NO3)3·6H2O according to the stoichiometric ratio, add deionized water and disperse by ultrasonication, then add citric acid as a chelating agent under magnetic stirring, and heat and stir at a constant temperature to form a uniform and transparent yttrium aluminum precursor sol. S2. Add SiC powder to the yttrium aluminum precursor sol in step S1 at a final composite powder ratio of 70 wt.% and form a three-dimensional network yttrium aluminum garnet gel coated with silicon carbide under the "stirring-heating" condition. S3. The three-dimensional network yttrium aluminum garnet gel is placed in a sealed environment and aged at a constant temperature. The aged gel is then transferred to a vacuum heating furnace and calcined in stages to obtain yttrium aluminum garnet / silicon carbide composite powder. S4. The obtained YAG / SiC composite powder is crushed and then ball-milled with deionized water and organic binder to form a uniform slurry. The slurry is then pumped into a centrifugal spray dryer for granulation and drying to obtain agglomerated composite powder. S5. The agglomerated YAG / SiC composite powder is transferred to a vacuum heating furnace for high-temperature treatment, and after cooling, it is sieved to obtain spherical YAG / SiC composite powder.

[0009] Furthermore, in step S1, the stoichiometric ratio of Al(NO3)3·9H2O and Y(NO3)3·6H2O is 5:3, and the amount of deionized water added is 20 to 80 times the total stoichiometric ratio of the above powders; the citric acid is AR analytical grade.

[0010] Furthermore, in step S1, the ultrasonic dispersion time is 15~30 min; the constant temperature heating temperature is 50~80℃, and the heating and stirring time is 20~50 min.

[0011] Furthermore, in step S2, the D50 particle size of the SiC is 0.5~10μm, and the purity is 4N or 5N.

[0012] Furthermore, in step S2, when the "stirring-heating" mode is used, the heating temperature range is 60-120℃ and the heating time is 3-6 hours.

[0013] Furthermore, in step S3, the constant temperature aging temperature is 100~120℃, and the aging time is 12~24h; Furthermore, in step S3, the segmented heating and calcination process is divided into: the first stage, heating to 350-450°C at a rate of 5-8°C / min and holding for 1-2 hours to remove organic chelating agents and moisture from the gel; and the second stage, heating to 750-1050°C at a rate of 10-15°C / min and holding for 2-5 hours.

[0014] Furthermore, in step S4, the organic binder is polyvinyl alcohol, accounting for 2‰~5‰ of the total mass of the powder, and the specification is PVA1788. The ball milling speed is 350~500 rpm / min, and the ball milling time is 2~4h.

[0015] Furthermore, in step S5, the vacuum heating temperature is 1500~1800℃, and the holding time is 2~5h.

[0016] Furthermore, in step S5, the particle size range of the sieved composite powder is 20–80 μm.

[0017] Furthermore, the composite powder is suitable for components with stringent requirements for wear resistance, high-temperature corrosion resistance, and structural stability, specifically including: shafts and wear-resistant parts of high-load mechanical systems, protective coatings for graphite crucibles used in high-temperature melting or crystal growth, and cavity lining components resistant to plasma etching in semiconductor manufacturing.

[0018] The beneficial effects of this invention are as follows: 1. To address the problems of yttrium aluminum garnet (YAG) agglomeration and uneven coating on the silicon carbide surface caused by transient heterogeneous nucleation in traditional precipitation methods, this invention achieves a more uniform and denser adhesion of the YAG phase to the SiC particle surface through controlled hydrolysis-condensation to form a three-dimensional gel network, realizing uniform composite of the two phases at the nanoscale. Furthermore, traditional methods require multiple washings to remove residual ions, resulting in a cumbersome process; while the reaction byproducts of this invention are easily volatile, and the gel network has a strong complexing effect on metal ions, reducing the introduction of impurities and the washing burden, thus improving product purity and batch consistency.

[0019] 2. The core technical solution of this invention lies in the creative coupling of an integrated continuous process of "gel sol-liquid phase method-calcination" and "spray granulation-sintering". Traditional precipitates are mostly irregular aggregates with poor sphericity and flowability. This invention, combined with spray granulation technology, allows for precise control of atomization parameters, directly obtaining YAG / SiC composite powders with high sphericity and good flowability, meeting the requirements of thermal spraying processes and improving deposition efficiency. This provides a feasible path for the low-cost, large-scale, and stable production of high-performance YAG / SiC composite powders and coatings.

[0020] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0021] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 The X-ray diffraction patterns of the spherical yttrium aluminum garnet / silicon carbide composite powders prepared in Examples 1-4 and Comparative Example 1 of this invention are shown below. Figure 2 This is a particle size distribution diagram of the spherical yttrium aluminum garnet / silicon carbide composite powder prepared in Example 2 of the present invention; Figure 3 Secondary electron diagrams of the surface microstructure of yttrium aluminum garnet / silicon carbide composite powder prepared in step S3 of Example 2 and Comparative Example 2 of the present invention; Figure 4 Secondary electron diagram and elemental distribution diagram of the surface microstructure of the spherical yttrium aluminum garnet / silicon carbide composite powder prepared in Example 2 of the present invention; Figure 5 The images show the secondary electron diagram and elemental distribution diagram of the cross-sectional microstructure of the spherical yttrium aluminum garnet / silicon carbide composite powder prepared in Example 2 of this invention. Detailed Implementation

[0022] like Figure 1-5 As shown, this invention discloses a method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying and its application.

[0023] Example 1 S1. Weigh Al(NO3)3·9H2O and Al(NO3)3·9H2O separately according to a stoichiometric ratio of 5:3. Add deionized water at a total stoichiometric ratio of 20 times that of the two powders. Place them in an ultrasonic cleaner and ultrasonically disperse for 15 minutes. Then transfer them to a magnetic stirrer and add citric acid at a total stoichiometric ratio of 0.5 times that of the powders as a chelating agent. Heat to 50°C and stir for 20 minutes to form a uniform and transparent yttrium aluminum precursor sol. S2. Weigh SiC particles with a D50 of 0.5 μm according to the final composite powder having a SiC content of 70 wt.% and slowly add them to the yttrium aluminum precursor sol. Then, use the "stirring-heating" mode to heat to 60°C and stir for 3 hours to allow the yttrium aluminum precursor to be directionally deposited on the surface of the SiC particles and in the surrounding space to form a three-dimensional network YAG gel. S3. The three-dimensional network gel is placed in a sealed container and aged at 100℃ for 12 hours to remove residual air bubbles inside the gel. Then, the aged gel is transferred to a vacuum heating furnace and subjected to a segmented heating and calcination process: in the first stage, the temperature is increased to 350℃ at a rate of 5℃ / min and held for 1 hour to remove organic chelating agents and moisture from the gel; in the second stage, the temperature is increased to 750℃ at a rate of 10℃ / min and held for 2 hours to complete the full formation of the YAG crystal phase and the fusion of the YAG / SiC interface. After cooling, the gel is pulverized and classified by airflow to obtain spherical yttrium aluminum garnet / silicon carbide composite powder for spraying. S4. The crushed YAG / SiC composite powder is added to deionized water and 2‰ binder and ball-milled for 2 hours to form a slurry. The slurry is then pumped into a centrifugal spray dryer, where the rotation speed of the physicochemical disc is 20Hz, the drying inlet temperature is 205℃, and the outlet temperature is 105℃. After drying, agglomerated YAG / SiC composite powder is obtained. S5. Transfer the agglomerated YAG / SiC composite powder to a vacuum heating furnace and heat it to 1500℃. Hold it at that temperature for 2 hours and then cool it to room temperature with the furnace. After sieving, obtain spherical YAG / SiC composite powder.

[0024] Example 2 S1. Weigh Al(NO3)3·9H2O and Al(NO3)3·9H2O according to a stoichiometric ratio of 5:3. Add deionized water at a total stoichiometric ratio of 40 times that of the two powders. Place the mixture in an ultrasonic cleaner and ultrasonically disperse for 15 minutes. Then transfer it to a magnetic stirrer and add citric acid at a total stoichiometric ratio of 1 as a chelating agent. Heat the mixture to 50°C and stir for 20 minutes to form a uniform and transparent yttrium aluminum precursor sol. S2. Weigh SiC particles with a D50 of 0.5μm according to the final composite powder having a SiC content of 70wt.% and slowly add them to the yttrium aluminum precursor sol. Then, use the "stirring-heating" mode to heat to 60℃ and stir for 3h to allow the yttrium aluminum precursor to be directionally deposited on the surface of the SiC particles and in the surrounding space to form a three-dimensional network YAG gel. S3. The three-dimensional network gel is placed in a sealed container and aged at 100℃ for 12 hours to remove residual air bubbles inside the gel. Then, the aged gel is transferred to a vacuum heating furnace and subjected to a segmented heating and calcination process: in the first stage, the temperature is increased to 350℃ at a rate of 5℃ / min and held for 1 hour to remove organic chelating agents and moisture from the gel; in the second stage, the temperature is increased to 850℃ at a rate of 10℃ / min and held for 3 hours to complete the full formation of the YAG crystal phase and the fusion of the YAG / SiC interface. After cooling, the gel is pulverized and classified by airflow to obtain spherical yttrium aluminum garnet / silicon carbide composite powder for spraying. S4. The crushed YAG / SiC composite powder is added to deionized water and 2‰ binder and ball-milled for 2 hours to form a slurry. The slurry is then pumped into a centrifugal spray dryer, where the rotation speed of the physicochemical disc is 20Hz, the drying inlet temperature is 205℃, and the outlet temperature is 105℃. After drying, agglomerated YAG / SiC composite powder is obtained. S5. The agglomerated YAG / SiC composite powder is transferred to a vacuum heating furnace and heated to 1600℃, held for 3 hours, cooled to room temperature with the furnace, and then sieved to obtain spherical YAG / SiC composite powder. The difference between Example 2 and Example 1 is that, in Example 2, step S2 is heated to 60°C and stirred for 3 hours; in step S3, the gel is calcined at 850°C and held for 3 hours, but both are within the protection scope of this invention.

[0025] Example 3 S1. Weigh Al(NO3)3·9H2O and Al(NO3)3·9H2O separately according to a stoichiometric ratio of 5:3. Add deionized water at a total stoichiometric ratio of 60 times that of the two powders. Place them in an ultrasonic cleaner and ultrasonically disperse for 30 minutes. Then transfer them to a magnetic stirrer and add citric acid at a total stoichiometric ratio of 1.5 times that of the powders as a chelating agent. Heat to 70°C and stir for 40 minutes to form a uniform and transparent yttrium aluminum precursor sol. S2. Weigh SiC particles with a D50 of 5μm according to the final composite powder with a SiC content of 70wt.% and slowly add them to the yttrium aluminum precursor sol. Then, use the "stirring-heating" mode to heat to 100℃ and stir for 5h to allow the yttrium aluminum precursor to be directionally deposited on the surface of SiC particles and in the surrounding space to form a three-dimensional network YAG gel. S3. The three-dimensional network gel is placed in a sealed container and aged at 115℃ for 20 hours to remove residual air bubbles inside the gel. Then, the aged gel is transferred to a vacuum heating furnace and subjected to a segmented heating and calcination process: in the first stage, the temperature is increased to 350℃ at a rate of 5℃ / min and held for 1 hour to remove organic chelating agents and moisture from the gel; in the second stage, the temperature is increased to 950℃ at a rate of 10℃ / min and held for 5 hours to complete the full formation of the YAG crystal phase and the fusion of the YAG / SiC interface. After cooling, the gel is pulverized and classified by airflow to obtain spherical yttrium aluminum garnet / silicon carbide composite powder for spraying. S4. The crushed YAG / SiC composite powder is added to deionized water and 4‰ binder and ball-milled for 4 hours to form a slurry. The slurry is then pumped into a centrifugal spray dryer, where the rotation speed of the physicochemical disc is 40Hz, the drying inlet temperature is 215℃, and the outlet temperature is 115℃. After drying, agglomerated YAG / SiC composite powder is obtained. S5. The agglomerated YAG / SiC composite powder is transferred to a vacuum heating furnace and heated to 1700℃, held for 4 hours, cooled to room temperature with the furnace, and then sieved to obtain spherical YAG / SiC composite powder.

[0026] The difference between Example 3 and Example 1 is that the SiC particle size selected in step S2 of Example 3 is 5 μm, and the parameters designed in each stage of the preparation process are different, but all are within the protection scope of this invention.

[0027] Example 4 S1. Weigh Al(NO3)3·9H2O and Al(NO3)3·9H2O according to a stoichiometric ratio of 5:3. Add deionized water at a ratio of 80 times the total stoichiometric ratio of the two powders. Place the mixture in an ultrasonic cleaner and ultrasonically disperse for 30 minutes. Then transfer it to a magnetic stirrer and add citric acid at a ratio of 2 times the total stoichiometric ratio of the powders as a chelating agent. Heat the mixture to 80°C and stir for 50 minutes to form a uniform and transparent yttrium aluminum precursor sol. S2. Weigh SiC particles with a D50 of 10μm according to the final composite powder with a SiC content of 70wt.% and slowly add them to the sol in capture S1. Then, use the "stirring-heating" mode to heat to 120℃ and stir for 6h to allow the yttrium aluminum precursor to be directionally deposited on the surface of SiC particles and in the surrounding space to form a three-dimensional network YAG gel. S3. The three-dimensional network gel is placed in a sealed container and aged at 120℃ for 24 hours to remove residual air bubbles inside the gel. Then, the aged gel is transferred to a vacuum heating furnace and a segmented heating and calcination process is adopted: in the first stage, the temperature is increased to 350℃ at a rate of 5℃ / min and held for 1 hour to remove organic chelating agents and moisture in the gel; in the second stage, the temperature is increased to 1050℃ at a rate of 10℃ / min and held for 5 hours to complete the full formation of the YAG crystal phase and the fusion of the YAG / SiC interface. After cooling, it is pulverized and classified by airflow to obtain spherical yttrium aluminum garnet / silicon carbide composite powder for spraying. S4. The crushed YAG / SiC composite powder is added to deionized water and 5‰ binder and ball-milled for 5 hours to form a slurry. The slurry is then pumped into a centrifugal spray dryer, where the rotation speed of the physicochemical disc is 50 Hz, the drying inlet temperature is 235 ℃, and the outlet temperature is 120 ℃. After drying, agglomerated YAG / SiC composite powder is obtained. S5. The agglomerated YAG / SiC composite powder is transferred to a vacuum heating furnace and heated to 1800℃, held for 4 hours, cooled to room temperature with the furnace, and then sieved to obtain spherical YAG / SiC composite powder.

[0028] The difference between Example 4 and Example 1 is that the SiC particle size selected in step S2 of Example 3 is 10 μm, and the parameters designed in each stage of the preparation process are different, but all are within the protection scope of this invention.

[0029] To verify the superiority of the present invention, comparative examples 1-2 are provided here.

[0030] Comparative Example 1: The only difference from Example 1 is that the second stage calcination process in step S3 is to keep the temperature at 750°C for 2 hours; the rest is the same as in Example 1.

[0031] from Figure 1The X-ray diffraction pattern shown indicates that the gel after high-temperature treatment and aging did not form a YAG phase, and only the SiC phase was detected in the composite powder, without the formation of a YAG phase, indicating that the gel did not undergo thermal decomposition at this temperature.

[0032] Comparative Example 2: The only difference from Example 2 is that SiC particles with a D50 of 10 μm are added in step S2; otherwise, it is the same as Example 1.

[0033] like Figure 2 As shown, the secondary electronic morphology of the composite powder after calcination and crushing in step S3 shows that when the SiC particles are 10 μm, the formed YAG is not uniformly coated on the SiC surface, indicating that when the SiC particle size is larger, the ideal coated composite powder cannot be obtained.

[0034] The working principle and process of this invention application are as follows: In step S1, ultrasonic dispersion can quickly break up nitrate aggregates and increase the dissolution rate; citric acid forms stable chelate complexes with Y³⁺ and Al³⁺, avoiding premature hydrolysis and precipitation of metal ions, reducing the critical gelation temperature of the sol, and improving the stability of the precursor solution, laying the foundation for subsequent uniform coating.

[0035] In step S2, the "stirring-heating" mode can avoid localized uneven concentration caused by single stirring, and at the same time prevent damage to the particle surface structure by prolonged ultrasound, ensuring that the yttrium aluminum precursor is uniformly coated on the SiC particle surface and forms a continuous three-dimensional network gel.

[0036] In step S3, constant-temperature aging allows the moisture and residual solvent inside the gel to slowly diffuse and overflow, avoiding gel cracking caused by rapid drying, while also promoting further densification of the gel network structure. In the segmented calcination process, slow heating at low temperatures prevents the rapid decomposition of organic components from generating a large amount of gas that could lead to gel disintegration, ensuring that organic impurities are fully removed. Rapid heating and holding at high temperatures promotes the solid-state reaction of the yttrium aluminum precursor to generate pure-phase YAG crystals, while reducing the oxidation of SiC particles in a vacuum environment and improving the bonding strength between the SiC and YAG interfaces. Airflow pulverization and classification removes a small amount of agglomerates, ensuring the particle size uniformity of the composite powder and preparing it for the next step of spray granulation to prepare spherical agglomerated powder.

[0037] In step S4, ball milling the composite powder after slurry preparation for a certain period of time can further break down the particle size of the composite powder, preventing large particles from forming uneven areas. At the same time, the binder can play a role in bonding between particles, improving the shear strength of the slurry, and enabling the formation of agglomerated spherical powders during high-speed centrifugation and drying processes.

[0038] In step S5, heating to a certain temperature and time in a vacuum furnace allows the organic binder from step S4 to volatilize, thereby improving the purity of the composite powder. Simultaneously, the composite powder undergoes a densification process during the subsequent high-temperature process, characterized by a further increase in the loose density and flowability of the composite powder, resulting in spherical YAG / SiC composite powder suitable for thermal spraying, thus laying the foundation for subsequent industrial applications of thermal spraying.

[0039] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying, characterized in that: Includes the following steps, S1. Weigh Al(NO3)3·9H2O and Y(NO3)3·6H2O according to the stoichiometric ratio, add deionized water and disperse by ultrasonication, then add citric acid as a chelating agent under magnetic stirring, and heat and stir at a constant temperature to form a uniform and transparent yttrium aluminum precursor sol. S2. Add SiC powder to the yttrium aluminum precursor sol in step S1 at a final composite powder ratio of 70 wt.% and form a three-dimensional network yttrium aluminum garnet gel coated with silicon carbide under the "stirring-heating" condition. S3. The three-dimensional network yttrium aluminum garnet gel is placed in a sealed environment and aged at a constant temperature. The aged gel is then transferred to a vacuum heating furnace and calcined in stages to obtain yttrium aluminum garnet / silicon carbide composite powder. S4. The obtained YAG / SiC composite powder is crushed and then ball-milled with deionized water and organic binder to form a uniform slurry. The slurry is then pumped into a centrifugal spray dryer for granulation and drying to obtain agglomerated composite powder. S5. The agglomerated YAG / SiC composite powder is transferred to a vacuum heating furnace for high-temperature treatment, and after cooling, it is sieved to obtain spherical YAG / SiC composite powder.

2. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S1, the stoichiometric ratio of Al(NO3)3·9H2O and Y(NO3)3·6H2O is 5:3; the amount of deionized water added is 20 to 80 times the total stoichiometric ratio of the above powders; and the citric acid is AR analytical grade.

3. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S1, the ultrasonic dispersion time is 15-30 min; the constant temperature heating temperature is 50-80℃, and the heating and stirring time is 20-50 min.

4. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S2, the D50 particle size of the SiC is 0.5~10μm, and the purity is 4N or 5N.

5. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S2, during the "stirring-heating" mode, the heating temperature range is 60-120℃, and the heating time is 3-6 hours.

6. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S3, the constant temperature aging temperature is 100~120℃, and the aging time is 12~24h.

7. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S3, the segmented heating and calcination process is divided into: the first stage, heating to 350-450°C at a rate of 5-8°C / min and holding for 1-2 hours to remove organic chelating agents and moisture from the gel; and the second stage, heating to 750-1050°C at a rate of 10-15°C / min and holding for 2-5 hours.

8. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S4, the organic binder is polyvinyl alcohol, accounting for 2‰~5‰ of the total mass of the powder, and the specification is PVA1788. The ball mill speed is 350~500 rpm / min, and the ball milling time is 2~4h.

9. The method for preparing spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S5, the vacuum heating temperature is 1500~1800℃, and the holding time is 2~5h.

10. The method for preparing a spherical yttrium aluminum garnet / silicon carbide composite powder for spraying according to claim 1, characterized in that: In step S5, the particle size range of the sieved composite powder is 20–80 μm.

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