An electrically fused rare earth silicate environmental barrier coating powder, a preparation method and application thereof

Abstract

The application provides an electric melting rare earth silicate environmental barrier coating powder and a preparation method and application thereof, and relates to the technical field of high-temperature thermal spraying ceramic powder.The electric melting rare earth silicate is obtained by electric melting liquid phase one-time synthesis with rare earth oxide and SiO2 as raw materials, and the electric melting rare earth silicate has low porosity, high phase purity, and is basically free of free SiO2 and rare earth oxide residues; the thermal spraying powder with different morphologies and structural characteristics is further prepared by taking the electric melting rare earth silicate as a mother powder source, the systematic preparation of the rare earth silicate environmental barrier coating powder from the high-purity dense mother powder to the multi-process adaptive spraying powder is realized, and the application prospect of the rare earth silicate environmental barrier coating powder is good in SiC / SiC ceramic matrix composite environmental barrier coatings for aeroengines, gas turbines and other high-temperature water-vapor corrosion environments.

Description

Technical Field

[0001] This invention relates to the field of high-temperature thermal spray ceramic powder technology, and in particular to an electrofused rare earth silicate environmental barrier coating powder, its preparation method, and its application. Background Technology

[0002] SiC / SiC ceramic matrix composites possess characteristics such as low density, good high-temperature resistance, high specific strength, and excellent retention of high-temperature mechanical properties, making them important candidate structural materials for high-temperature hot-end components such as aero-engines and gas turbines. However, when SiC-based composites operate in high-temperature water vapor environments, the material surface is prone to oxidation reactions, potentially generating volatile silanol species. This leads to continuous wear of the matrix surface, interface degradation, and a decline in mechanical properties. To improve the long-term service stability of SiC / SiC ceramic matrix composites in high-temperature water vapor environments, it is typically necessary to prepare an environmental barrier coating on their surface to prevent water vapor, oxidizing gases, and corrosive media from penetrating into the matrix.

[0003] Rare earth silicate materials have become an important material system for environmental barrier ceramic coatings due to their good high-temperature phase stability, resistance to water vapor corrosion, and thermal expansion properties that are relatively well-matched with the SiC matrix. In order to meet the requirements of thermal spraying for preparing environmental barrier coatings, rare earth silicates usually need to be prepared into sprayable powders with specific particle size, morphology, flowability, and phase composition before forming a coating through plasma spraying, flame spraying, or other thermal spraying processes.

[0004] Existing rare earth silicate spray coating powders can generally be prepared through solid-state sintering, spray granulation sintering, or spheroidization. Solid-state sintering has relatively low equipment requirements, but the reaction mainly relies on solid-state diffusion. The uniformity and completeness of the reaction between raw materials are affected by factors such as diffusion distance, sintering temperature, holding time, and raw material particle size, which can easily lead to problems such as incomplete reaction, localized component segregation, and residual free rare earth oxides or free SiO2. These residual phases may cause phase transformation, volume changes, interfacial stress concentration, or coating cracking during subsequent thermal spraying and high-temperature service, thus affecting the long-term stability of the environmental barrier coating.

[0005] Furthermore, the powder obtained after crushing traditional sintered green bodies often still contains certain pores or loose structures. During the spraying process, the powder's melting, spreading, and stacking behavior is unstable, easily leading to increased coating porosity, insufficient density, and decreased water vapor barrier capacity. Although spray granulation sintering can improve the external sphericity and powder feeding stability of the powder, and plasma spheroidization can further improve powder sphericity and flowability, if the primary powder used as the master powder source itself has insufficient phase purity, residual impurities, or high internal porosity, subsequent morphology control alone cannot fundamentally improve the phase stability and service reliability of environmental barrier coating materials.

[0006] Meanwhile, for silicon-containing oxide systems such as rare earth disilicates, the SiO2 component may be lost to some extent through volatilization during high-temperature melting or heat treatment. If the batching is still carried out entirely according to the theoretical stoichiometric ratio, it may lead to problems such as silicon deficiency, rare earth phase enrichment, or reduced content of the target rare earth disilicate phase in the final product, thereby affecting the consistency of powder composition and coating performance.

[0007] Therefore, how to improve the purity of the target phase of rare earth silicates, reduce the residue of free oxides, obtain low-porosity and high-density master powder materials, and further take into account the different requirements of different thermal spraying processes for powder morphology and flowability, remains a technical problem to be solved in the preparation of rare earth silicate environmental barrier coating powders. Summary of the Invention

[0008] In view of this, the present invention provides an electrofused rare earth silicate environmental barrier coating powder, its preparation method, and its application. The present invention achieves a low-porosity, high-phase-purity electrofused rare earth silicate with virtually no free SiO2 or rare earth oxide residues through a one-step electrofused liquid-phase synthesis using rare earth oxides and SiO2 as raw materials. Furthermore, the electrofused rare earth silicate is used as a masterbatch source to prepare thermal spraying powders with different morphologies and structural characteristics. This realizes the systematic preparation of rare earth silicate environmental barrier coating powders from high-purity, dense masterbatch to multi-process adaptable spraying powders, showing promising application prospects in SiC / SiC ceramic matrix composite environmental barrier coatings for aero-engines, gas turbines, and other high-temperature, water-vapor-corrosion environments.

[0009] The first aspect of this invention provides an electrofused rare earth silicate environmental barrier coating powder, the powder being obtained from electrofused rare earth silicate through post-processing; The fused rare earth silicate is synthesized in one step from raw materials containing rare earth oxides and SiO2 via an fused liquid phase reaction. The rare earth silicate is rare earth monosilicate RE2SiO5 and / or rare earth disilicate RE2Si2O7; The target phase of the fused rare earth silicate has a purity of ≥75% and is free of or essentially free of SiO2 and rare earth oxide residues. The powder is: Irregular polygonal powder obtained from fused rare earth silicates through crushing, grading, and sieving; or, Spherical agglomerated powder obtained by wet mixing, spray granulation or other pelletizing processes of finely crushed rare earth silicate powder, followed by high-temperature sintering; or, Highly dense solid spherical powder obtained by plasma flame spheroidization treatment of finely crushed rare earth silicate powder.

[0010] Preferably, the RE is Y, Yb, Y / Yb composite rare earth, or a combination thereof with at least one rare earth element selected from La, Gd, Er, and Lu.

[0011] Preferably, when synthesizing rare earth monosilicate RE2SiO5, the molar ratio of rare earth oxides RE2O3 to SiO2 is 1:(1~1.2); when synthesizing rare earth disilicate RE2Si2O7, the molar ratio of rare earth oxides RE2O3 to SiO2 is 1:(2~2). . 2); The excessive addition of SiO2 is used to compensate for the volatilization loss of SiO2 during the electrofusion process.

[0012] Preferably, the electrofused liquid phase reaction is carried out in an electric arc furnace, the melting temperature is 1800~2600℃, the holding time is 1~10 h, the melting atmosphere is air or inert atmosphere, and after melting, the dense electrofused rare earth silicate frit is obtained by cooling.

[0013] Preferably, the D of the irregular polygonal powder 50 The thickness is 20~40 μm, preferably 30 μm.

[0014] Preferably, the spherical agglomerated powder is obtained by spray granulation and sintering of a slurry containing fused rare earth silicate crushed fine powder, deionized water, organic binder and dispersant; the solid content of the slurry is 20-80 wt%; the organic binder is polyvinyl alcohol; the dispersant is polyacrylic acid dispersant; the spray granulation drying inlet temperature is 120-250℃; the sintering temperature is 1100-1500℃, and the holding time is 1-5 h.

[0015] Preferably, the high-density solid spherical powder is obtained by spheroidization using an argon-hydrogen mixed plasma heat source. The finely crushed rare earth silicate powder is fed into the plasma flame and melted and then rapidly cooled and spheroidized. The resulting powder has a sphericity ≥95% and a volumetric density ≥95%.

[0016] A second aspect of the present invention provides a method for preparing the electrofused rare earth silicate environmental barrier coating powder, comprising the following steps: S1. Ingredient mixing: Weigh rare earth oxides and SiO2 according to the composition of the target rare earth monosilicate RE2SiO5 or rare earth disilicate RE2Si2O7, and mix them by dry ball milling to obtain a mixture. S2. High-temperature electric melting: The mixture obtained in step S1 is put into an electric arc melting furnace and melted and held at 1800~2600℃ for 1~10 h to allow the raw material to undergo an electric melting liquid phase reaction. After cooling, an electric fused rare earth silicate briquette is obtained. S3. Crushing and refining: The fused rare earth silicate frit obtained in step S2 is subjected to coarse crushing, medium crushing and ultrafine grinding in sequence to obtain fused rare earth silicate crushed fine powder. S4. Post-processing based on morphology: The fused rare earth silicate powder obtained in step S3 is crushed into fine powder, and then subjected to multi-stage airflow classification, sieving, and iron removal to obtain irregular polygonal powder; or, The crushed fine powder is mixed with deionized water, organic binder, and dispersant to form a suspension slurry. This slurry is then subjected to spray granulation or other pelletizing processes to obtain green pellets. Finally, it is subjected to high-temperature sintering and sieving to obtain spherical agglomerated powder; or... The crushed fine powder is fed into a plasma spheroidizing device, where it is melted and rapidly cooled and spheroidized in a plasma flame. After cooling and sieving, a highly dense solid spherical powder is obtained.

[0017] Preferably, the target phase of the fused rare earth silicate obtained in step S2 has a purity of ≥75%, more preferably ≥99%, and has no or essentially no free SiO2 and rare earth oxide residues.

[0018] Preferably, when preparing Yb₂Si₂O₇ powder, the molar ratio of Yb₂O₃ to SiO₂ is 1:2. . 18; The theoretical molar ratio of Yb₂O₃ to SiO₂ is 1:2 . Compared to 0, excess SiO2 is used to compensate for the volatilization loss of SiO2 during the electrofusion process (to be confirmed by the inventor), in order to improve the purity of the target phase Yb2Si2O7 and reduce the residue of free Yb2O3.

[0019] A third aspect of the present invention provides the application of the electrofused rare earth silicate environmental barrier coating powder in the preparation of SiC / SiC ceramic matrix composite environmental barrier coatings (EBCs).

[0020] Preferably, the environmental barrier coating is used for high-temperature water vapor environment protection of hot-end components of aero-engines or gas turbines.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention employs an electrofused liquid-phase reaction to synthesize rare-earth silicate materials in a single step, allowing rare-earth oxides and SiO2 to fully mix and react in a molten state. Compared to traditional solid-state sintering processes that primarily rely on solid-phase diffusion, electrofused liquid-phase reaction shortens the reaction path, improves component uniformity and reaction completeness, thereby increasing the purity of the target rare-earth silicate phase, reducing the residue of free SiO2, free rare-earth oxides, and other non-target impurity phases, and minimizing the risk of volume changes, cracking, and performance degradation in subsequent coatings during high-temperature service due to impurity phase reactions or phase transformations.

[0022] The fused rare earth silicate obtained by this invention has high density and low internal porosity, with the porosity controllable at a low level. When using this fused rare earth silicate as a masterbatch source to prepare spray powder, it can reduce the internal pores and loose structure of the powder from the source, improve the melting, spreading and deposition behavior of the powder during the spraying process, and facilitate the acquisition of an environmental barrier coating with a denser structure and lower pore connectivity, thereby improving the coating's barrier ability against high-temperature water vapor and oxidizing media.

[0023] This invention uses the same fused rare earth silicate as a base material to prepare irregular polygonal powder, spherical agglomerated powder, and highly dense solid spherical powder according to different spraying process requirements. Irregular polygonal powder can be directly obtained through crushing, grading, and sieving, resulting in a simple process route. Spherical agglomerated powder can be obtained through wet mixing, spray granulation, or other spheroidizing processes followed by sintering, exhibiting good flowability and powder delivery stability. Highly dense solid spherical powder can be obtained through plasma spheroidization treatment, possessing high sphericity and density. Therefore, this invention not only improves the phase reliability of the powder itself but also enhances its adaptability to different thermal spraying equipment, powder delivery methods, and coating preparation processes.

[0024] For the preparation of rare earth disilicate powders, this invention can compensate for the possible SiO2 volatilization loss during high-temperature electrofusion by appropriately increasing the SiO2 proportion, thereby reducing the formation of non-target phases such as rare earth enriched phases or monosilicates due to silicon depletion. This is beneficial for further improving the content and compositional stability of the target phase in rare earth disilicates. Combining this proportioning compensation method with the one-step electrofused liquid phase synthesis process can improve the stoichiometric consistency of the final electrofused molten block and powder, providing a more stable process basis for the preparation of high-purity rare earth disilicate environmental barrier coating powders.

[0025] When using the powder of this invention to prepare environmental barrier coatings, the resulting coatings exhibit better density, resistance to water vapor penetration, and high-temperature service stability due to the powder's high purity of the target phase, low residual free oxides, low internal porosity, and controllable morphology. Especially in high-temperature, water-vapor-containing, and highly oxidizing service environments such as aero-engines and gas turbines, the powder of this invention is beneficial for improving the anti-scraping ability, corrosion resistance, and long-term service reliability of SiC / SiC ceramic matrix composite environmental barrier coatings. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] Figure 1 This is a scanning electron microscope image of the irregular polygonal sprayed powder of fused ytterbium bisilicate prepared in Example 1 of the present invention. Figure 2This is a scanning electron microscope image of the spherical agglomerates of electrofused Y / Yb composite disilicate spray-granulated sintered powder obtained in Example 2 of the present invention. Figure 3 This is a scanning electron microscope image of the surface morphology of spherical powder obtained by plasma flame spheroidization treatment of fused yttrium monosilicate prepared in Example 3 of the present invention. Figure 4 The X-ray diffraction pattern of the fused rare earth silicate powder in this embodiment of the invention is shown below. The fused rare earth silicate powder is ytterbium bissilicate, with ytterbium bissilicate as the main phase, containing 100% of the powder and no other phases present. Figure 5 This is a cross-sectional morphology diagram of the fused rare earth silicate block in Embodiment 1 of the present invention; Figure 6 The X-ray diffraction pattern of the rare earth silicate powder prepared by the conventional solid-state sintering process in Comparative Example 1 of the present invention is shown. The rare earth silicate powder is ytterbium disilicate, and the pattern shows that in addition to the target phase, it also contains non-target phases such as ytterbium monosilicate, ytterbium oxide, and cristobalite. Figure 7 The X-ray diffraction pattern of the rare earth silicate powder prepared by the electric melting process in Comparative Example 2 of the present invention without SiO2 overcompensation is shown. The rare earth silicate powder is ytterbium disilicate, and the pattern shows that in addition to the target phase, it also contains non-target phases such as ytterbium monosilicate and ytterbium oxide. Figure 8 The X-ray diffraction pattern of the spherical agglomerated powder obtained by spray granulation and sintering of solid-phase sintering master powder in Comparative Example 3 of the present invention is shown. The spherical agglomerated powder is ytterbium disilicate, and the pattern shows that in addition to the target phase, it also contains non-target phases such as ytterbium monosilicate, ytterbium oxide, and cristobalite. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0030] Example 1: Irregularly Sprayed Fused Yb₂Si₂O₇ Disilicate Powder Ingredients: Weigh out Yb₂O₃ and quartz SiO₂ to make a molar ratio of Yb₂O₃ to SiO₂ of 1:2. . 1. Dry ball milling for 2 hours.

[0031] Electrofusion: The mixture is put into an electric arc furnace, heated to 2200℃, and held for 2 hours to allow the raw materials to melt completely and undergo a liquid phase reaction. Then, it is water-cooled and quenched to obtain a dense Yb2Si2O7 electrofused ingot.

[0032] Crushing and refining: The obtained fused molten metal was subjected to jaw crusher, cone crusher and air jet ultrafine mill in sequence to obtain fused ytterbium bisilicate crushed powder with a median particle size D50 of 30 μm.

[0033] Classification and impurity removal: The crushed powder is subjected to air classification, iron removal and sieving to directly obtain irregular multi-angle spray powder.

[0034] The obtained powder is a single Yb2Si2O7 phase, without any impurities; Figure 5 The black area in the middle is mainly the inlaid resin filling area / cutting gap formed during the cross-section sample preparation process; the porosity of the electrofused fused agglomerate obtained in Example 1 was 0.6% as measured by the Archimedes method.

[0035] In this embodiment, the molar ratio of Yb2O3 to SiO2 is 1:2.1, which is higher than the theoretical stoichiometric ratio of Yb2Si2O7 (1:2.0). This ratio is used to compensate for the volatilization loss of SiO2 during the high-temperature electrofusion process.

[0036] Example 2: Electrofused Y 1.2 Yb 0.8 Si2O7 spray granulation sintered spherical powder The difference from Example 1 is that: The raw material ratio is: Y2O3 and Yb2O3 in a molar ratio of 1:1. . 2:0 . Mix 8 parts together and then mix them with SiO2 in the required proportion for the target silicate phase.

[0037] The electrofusion temperature is 2000℃, and the holding time is 1 day. . After 5 hours of quenching, the material is crushed to D. 50 It is an electrofused fine powder with a diameter of 2 μm.

[0038] Slurry preparation: Mix fused fine powder, deionized water, polyvinyl alcohol binder and polyacrylic acid dispersant to prepare a suspension slurry with a solid content of 60 wt%.

[0039] Spray granulation: The slurry is spray granulated at an inlet air temperature of 180℃ to obtain green pellets with a particle size of 10~45 μm.

[0040] Sintering and sieving: The green pellets are sintered at 1300℃ for 2 h to remove organic matter and strengthen particle bonding, and then sieved to obtain agglomerated spherical spray powder.

[0041] The resulting powder had a flowability of 32 s / 50g.

[0042] Example 3: Electrofused Yttrium Monosilicate Y2SiO5 Plasma Spheroidization High-Density Spherical Powder The difference from Example 1 is that: Y2O3 and SiO2 were used as raw materials, and the mixture was prepared according to a molar ratio of Y2O3:SiO2=1:1.

[0043] The mixture was electrofused at 2000℃ and then quenched to obtain electrofused yttrium monosilicate frit.

[0044] The fused ingot is ultra-finely ground and graded to D. 50 It is a fine powder with a particle size of 35 μm.

[0045] The fine powder is fed into an argon-hydrogen plasma flame for plasma spheroidization, where it melts and rapidly cools to form spheroids. D is then obtained by sieving. 50 It is a solid spherical powder with a diameter of 32 μm.

[0046] This powder was used for plasma spraying on CMCs substrate materials. An F4-MB spray gun was used, and the binder layer was made of silicon metal powder. The spraying power was 44 kW, the argon flow rate was 42 L / min, the hydrogen flow rate was 5.5 L / min, the carrier gas argon flow rate was 3.2 L / min, the powder feed rate was 20 g / min, the spraying distance was 105 mm, and the spraying thickness was 130 μm. The coating was annealed at 1300℃ for 8 h. The resulting coating was tested according to GB / Z45463-2025, the method for metallographic specimen preparation and porosity determination. The porosity of the coating was 6%, and it showed no failure after 1000 h of water vapor circulation at 1400℃.

[0047] Example 4: Multi-rare earth doped fused bisilicate composite powder The difference from Example 1 is that: Rare earth oxides in the formula Gd₂O₃:Y₂O₃:Yb₂O₃=0 . 2:0 . 4:0 . The ingredients are prepared in a molar ratio of 4 and mixed with SiO2 according to the required molar ratio of rare earth disilicates.

[0048] The mixture was electrofused at 2200℃ and then quenched to obtain a multi-rare earth-doped electrofused disilicate frit.

[0049] The obtained molten metal is crushed into fine powder, and then the crushed fine powder is subjected to multi-stage airflow classification, sieving, and iron removal to obtain D. 50 The powder, which is an irregular polygonal particle with a diameter of 30 μm, is fed into a plasma spray gun for plasma densification and spheroidization to obtain D. 50 Highly dense solid spherical powder with a diameter of 28 μm.

[0050] The resulting powder is suitable for use in medium-temperature gas turbine environments as a barrier coating.

[0051] Comparative Example 1: Irregularly Sprayed Yb2Si2O7 Powder Based on Traditional Solid-State Sintering The difference from Example 1 is that the Yb2Si2O7 irregular spray powder is prepared by traditional solid-state sintering process instead of electric arc melting process.

[0052] The specific steps are as follows: Ingredients: Weigh out Yb₂O₃ and quartz SiO₂ to make a molar ratio of Yb₂O₃ to SiO₂ of 1:2. . 1. Consistent with Example 1.

[0053] Mixing: The above raw materials are dry ball milled and mixed for 2 hours to obtain a uniformly mixed solid-phase reaction raw material.

[0054] Solid-state sintering: The mixed raw materials are placed in an alumina crucible and heated to 1550℃ in an air atmosphere. The temperature is maintained for 6 h to allow Yb2O3 and SiO2 to undergo a solid-state reaction. After cooling, a solid-state sintered block is obtained.

[0055] Crushing and refining: The obtained solid sintered block is subjected to jaw crusher, cone crusher and airflow ultrafine mill in sequence.

[0056] Classification and impurity removal: The crushed powder is subjected to air classification, iron removal, and sieving to obtain the median particle size D. 50 The powder used was a conventional solid-state sintered Yb₂Si₂O₇ irregularly sprayed powder with a particle size of 30 μm, with the same particle size as the powder obtained in Example 1. Figure 6 The crystal phase results show that, in addition to the presence of 25% mono-ytterbium silicate, there are a large amount of free, unsynthesized ytterbium oxide and silicon dioxide. The proportion of the ytterbium disilicate main phase is less than 70%, which cannot meet the requirements for spraying.

[0057] Comparative Example 2: Electrofused Yb2Si2O7 spray powder without SiO2 compensation The difference from Example 1 is that Yb₂O₃ and SiO₂ are in a theoretical molar ratio of 1:2. . The weighing was 0, and no SiO2 excess compensation was set. The remaining steps of electric melting, crushing, air classification, iron removal, and screening were the same as in Example 1.

[0058] Testing revealed that the electrofused molten block obtained in Comparative Example 2 contained a low content of the target phase Yb2Si2O7, with 35% Yb2SiO5 and 1%-3% free ytterbium oxide present. The product did not meet the requirements for spraying.

[0059] Comparative Example 3: Preparation of Spray-Granulated Sintered Spherical Powder from Solid-Phase Sintering Master Powder The difference from Example 2 is that the primary particles used to prepare the spray granulation slurry are not electrofused crushed fine powder, but rare earth silicate fine powder prepared by the conventional solid-state sintering method described in Comparative Example 1; the remaining steps of slurry preparation, spray granulation, sintering, and sieving are the same as in Example 2.

[0060] Testing revealed that the agglomerated spherical powder obtained in Comparative Example 3 contained less than 55% of the target Yb2Si2O7 phase, 35% of Yb2SiO5, 10% of free ytterbium oxide, and a small amount of cristobalite phase. The product did not meet the requirements for spraying.

[0061] Comparative Example 4: Spherical powder prepared by plasma spheroidization of solid-state sintering masterbatch The difference from Example 3 is that the fine powder used for plasma spheroidization is not electrofused crushed fine powder, but Y2SiO5 prepared by solid-state sintering.

[0062] The specific steps are as follows: Ingredients: Weigh out Y2O3 and SiO2 to make the molar ratio of Y2O3 to SiO2 1:1.

[0063] Mixing: The above raw materials are dry ball-milled and mixed for 2 hours.

[0064] Solid-state sintering: The mixed raw materials are placed in an alumina crucible and heated to 1550℃ in an air atmosphere. The temperature is maintained for 6 h to allow Y2O3 and SiO2 to undergo a solid-state reaction. After cooling, solid-state sintered Y2SiO5 bulk material is obtained.

[0065] Crushing and Refining: The obtained solid-phase sintered mass is subjected to crushing and ultrafine grinding to obtain D. 50 The solid-state sintered Y2SiO5 fine powder is 35 μm, with a particle size that is the same as or substantially the same as the electrofused crushed fine powder in Example 3.

[0066] Plasma spheroidization: The above-mentioned solid-phase sintered Y2SiO5 fine powder is fed into an argon-hydrogen plasma flame for plasma spheroidization treatment, so that the powder melts in the flame and is rapidly cooled to spheroidize.

[0067] Sieving: The spheroidized powder was cooled and sieved to obtain a high-density solid spherical powder with a particle size of 33 μm.

[0068] Testing revealed that the hollowness rate of the spherical powder obtained in Comparative Example 4 was as high as 45%, and the porosity of the coating obtained by spraying with this powder was 6.5%, with the coating density failing to meet the requirements.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A fused rare earth silicate environmental barrier coating powder, characterized in that, The powder is obtained by post-processing of fused rare earth silicates. The fused rare earth silicate is synthesized in one step from raw materials containing rare earth oxides and SiO2 via an fused liquid phase reaction. The rare earth silicate is rare earth monosilicate RE2SiO5 and / or rare earth disilicate RE2Si2O7; RE is a rare earth element; The powder is an irregular polygonal powder, a spherical agglomerated powder, or a highly dense solid spherical powder.

2. The fused rare earth silicate environmental barrier coating powder according to claim 1, characterized in that, The RE is Y, Yb, Y / Yb composite rare earth and its combination with at least one rare earth element selected from La, Gd, Er, and Lu.

3. The fused rare earth silicate environmental barrier coating powder according to claim 1, characterized in that, When synthesizing rare earth monosilicate RE2SiO5, the molar ratio of rare earth oxide RE2O3 to SiO2 is 1:(1~1.2); when synthesizing rare earth disilicate RE2Si2O7, the molar ratio of rare earth oxide RE2O3 to SiO2 is 1:(2~2). . 2).

4. The fused rare earth silicate environmental barrier coating powder according to claim 1, characterized in that, The irregular polygonal powder is obtained by crushing, classifying and sieving the fused rare earth silicate. The median particle size D of the irregular polygonal powder is... 50 The range is 1~100 μm.

5. The fused rare earth silicate environmental barrier coating powder according to claim 1, characterized in that, The spherical agglomerated powder is obtained by wet mixing, spray granulation or pelletizing of electrofused rare earth silicate fine powder, followed by high-temperature sintering; the median particle size D of the spherical agglomerated powder is... 50 The range is 5~80 μm.

6. The fused rare earth silicate environmental barrier coating powder according to claim 1, characterized in that, The high-density solid spherical powder is obtained by plasma flame spheroidization treatment of finely crushed rare earth silicate powder.

7. The method for preparing the electrofused rare earth silicate environmental barrier coating powder according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Ingredient Mixing: Weigh rare earth oxides and SiO2 according to the composition of the target rare earth monosilicate RE2SiO5 or rare earth disilicate RE2Si2O7, and mix them to obtain a mixture. S2. High-temperature electro-melting: The mixture obtained in step S1 is put into an electro-melting furnace or induction furnace and melted and held at 1800~2600℃ for 1~10 h to allow rare earth oxides and SiO2 to undergo an electro-melting liquid phase reaction. After blowing or natural cooling, electro-melted rare earth silicate frit is obtained. S3. Crushing and refining: The fused rare earth silicate frit obtained in step S2 is crushed and ground to obtain fused rare earth silicate crushed fine powder. S4. Post-processing based on morphology: The fused rare earth silicate powder obtained in step S3 is classified, sieved, and iron-removed to obtain irregular polygonal powder; or... The fused rare earth silicate powder obtained in step S3 is mixed with deionized water, organic binder, and dispersant to form a suspension slurry. This slurry is then subjected to spray granulation or pelletizing to obtain green pellets, followed by high-temperature sintering and sieving to obtain spherical agglomerated powder; or... The fused rare earth silicate powder obtained in step S3 is fed into a plasma spheroidizing device, where it is melted and rapidly cooled and spheroidized in a plasma flame. After cooling and sieving, highly dense solid spherical powder is obtained.

8. The preparation method according to claim 7, characterized in that, In step S2, the electric furnace is an electric arc furnace, and the molten liquid phase reaction is carried out in an air atmosphere or an inert atmosphere.

9. The preparation method according to claim 7, characterized in that, When preparing spherical agglomerated powder, the solid content of the suspension slurry is 20~80wt%, the organic binder is polyvinyl alcohol, the dispersant includes polyacrylic acid dispersant, the spray granulation drying inlet temperature is 110~250℃, the sintering temperature is 1100~1500℃, and the holding time is 1~5 h; when preparing highly dense solid spherical powder, plasma spheroidization treatment is carried out using an argon-hydrogen mixed plasma heat source.

10. The application of the fused rare earth silicate environmental barrier coating powder according to any one of claims 1 to 6 or the fused rare earth silicate environmental barrier coating powder prepared by the preparation method according to any one of claims 7 to 9 in the preparation of environmental barrier coatings for SiC / SiC ceramic matrix composites.

Images