A single-phase solid-solution oxide thermal spray powder and coating and method of making the same

Abstract

The application provides a single-phase solid-solution oxide thermal spraying powder and coating and a preparation method thereof. The composition of the powder and the coating material is ZrO2-X mol% Yb2O3, wherein X=8-30. The coating has no phase transition in the range of room temperature to 2400 DEG C, and has a heat protection capacity of more than 240 seconds in an arc plasma ablation process at 2400 DEG C. The preparation method of the powder and the coating comprises the following steps: taking ZrO2 and Yb2O3 with a purity of 99.9% as raw materials, and adopting a roller ball milling, spray granulation, vacuum sintering and plasma spheroidization method to prepare a single-phase Yb2O3 fully stabilized ZrO2 powder with high flowability and bulk density; and finally, adopting a plasma spraying technology to prepare a single-phase Yb2O3 fully stabilized ZrO2 heat protection coating. The prepared powder and the coating have high-temperature phase stability, and the coating has an oxidation ablation resistance performance at an ultra-high temperature for a long time.

Description

Technical Field

[0001] This invention belongs to the field of surface coating preparation technology, specifically relating to a wide-temperature-range single-phase solid solution oxide thermal spray powder and coating and its preparation method. Background Technology

[0002] When flight speeds reach a certain level, the temperature of materials in some heated parts of an aircraft can exceed 2000℃. At this point, these materials must also withstand severe airflow erosion and intense oxidation, posing a significant challenge to the safe operation of the aircraft. Therefore, preparing a thermal protective coating on the surface of these materials is essential to improving the aircraft's service performance. This coating not only effectively blocks the erosion from high-temperature airflow but also prevents oxygen penetration into the substrate during oxidation, significantly improving its resistance to oxidation and ablation without compromising the substrate's performance. While there are many types of thermal protectants, such as ultra-high temperature ceramics (e.g., TaC, ZrC, HfB2, HfN), which have advantages such as high melting points (>3000℃), high-temperature strength, and good ablation resistance, they undergo significant oxidation within tens of seconds in ultra-high temperature and oxygen-rich environments. This causes all compounds to transform into oxides, thus the thermal properties of the oxides determine the upper limit of the thermal protective coating's operating temperature.

[0003] Under extremely high heat flux and thermal ablation, ultra-high temperature ceramic coatings are oxidized to form corresponding refractory metal oxides. Those with relatively low melting points (such as TiO2, Nb2O5, and Ta2O5) soften, melt, and liquefy, and are eventually carried away by the high-temperature gas flow. Those with even lower melting and boiling points (such as MoO3 and WO3) are preferentially vaporized during oxidation and ablation, causing coating bulging defects and ultimately accelerating coating failure. Although the melting points of the oxides of refractory metals Zr and Hf (ZrO2 and HfO2, approximately 2725℃ and 2809℃, respectively) are higher than conventional high-temperature ablation temperatures, they both undergo phase transformations, from a room-temperature monoclinic phase to a mid-temperature tetragonal phase and a high-temperature cubic phase, resulting in 5%–8% volume expansion and contraction during heating and cooling. Furthermore, ultra-high temperature ceramic coatings also generate B2O3(g) and CO during ablation. x Gases such as (g) can also cause coating blistering.

[0004] Therefore, developing coating materials that combine wide-temperature-range phase-change resistance with long-term anti-oxidation and ablation performance at ultra-high temperatures and preparing corresponding coatings can replace existing ultra-high temperature ceramic coatings, reduce problems such as coating bulging and cracking caused by gases and phase changes, further improve the high-temperature stability of the coating itself, and extend the service life of materials in the heated parts of the aircraft. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] This invention proposes a single-phase solid solution oxide thermal spray powder and coating and its preparation method to solve the technical problem of how to achieve wide-temperature-range phase-change-free and ultra-high-temperature long-term anti-oxidation and ablation performance.

[0007] (II) Technical Solution

[0008] To address the aforementioned technical problems, this invention proposes a method for preparing single-phase solid solution oxide thermal spray powder, which includes the following steps:

[0009] S1. ZrO2 powder and Yb2O3 powder are doped and mixed at a molar ratio of (2-12):1 to obtain mixed powder; the particle size of ZrO2 powder is 100nm-500nm and the purity is 99.9%; the particle size of Yb2O3 powder is 100nm-500nm and the purity is 99.9%.

[0010] S2. Prepare 10% PVA adhesive in an electrically heated constant temperature water bath; weigh 90℃ hot water as solvent according to 40% to 48% of the mass of the mixed powder; add PVA adhesive to the solvent, the amount of PVA adhesive added is 6% to 8% of the mass of the solvent; stir evenly by electromagnetic stirring.

[0011] S3. Add the mixed powder to the solvent, add the defoamer n-butanol and 1% by weight of the solvent dispersant PEG to the solvent, and stir by roller ball milling to obtain the slurry for spray drying;

[0012] S4. The slurry is spray-granulated using a centrifugal spray dryer. During the spray granulation process, the slurry is continuously stirred by a mechanical stirring paddle to obtain ZrO2-Yb2O3 powder with a concave center on the surface.

[0013] S5. The ZrO2-Yb2O3 powder is subjected to high-temperature sintering treatment to remove residual PVA colloid in the powder and obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization.

[0014] S6. High-purity ZrO2-Yb2O3 powder is subjected to atmospheric plasma spheroidization solid solution to achieve atomic-level complete solid solution and densification of ZrO2-Yb2O3 powder, thereby obtaining single-phase solid solution ZrO2-Yb2O3 powder.

[0015] S7. The single-phase solid solution ZrO2-Yb2O3 powder is dried and ultrasonically sieved to obtain micron-sized spherical dense wide-temperature-range single-phase solid solution oxide thermal spray powder for high-energy plasma spraying.

[0016] Further, in step S2, the electromagnetic stirring speed is 300 rpm and the time is 10 min; in step S3, the drum ball mill speed is 600 rpm and the time is 8 h, the grinding balls are ZrO2 small balls, the ball-to-material ratio is 1:2, and the ratio of large, medium and small balls is 1:2:4.

[0017] Further, in step S4, the mechanical stirring paddle rotates at 1600 rpm, the inlet temperature of the centrifugal spray dryer is 200℃~240℃, the outlet temperature is 120℃~140℃, the atomizer frequency is 48Hz~50Hz, the peristaltic pump speed is 8rpm~10rpm, and then an ultrasonic-assisted vibrating screen is used with a 180-mesh sieve for sieving, the ultrasonic frequency is 37kHz, and the time is 5 minutes.

[0018] Further, in step S5, the ZrO2-Yb2O3 powder is subjected to high-temperature sintering in a muffle furnace to obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization. The heating rate of the muffle furnace is 8℃ / min, the holding temperature is 1100℃~1300℃, the holding time is 4h, and then the powder is cooled with the furnace. Then, the powder treated by high-temperature sintering is sieved through a 600-mesh sieve, the ultrasonic frequency is 37kHz, and the time is 5 minutes.

[0019] Furthermore, in step S6, the plasma spheroidizing current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min; during the spheroidizing process, the plasma beam after powder feeding is vertically directed into a stainless steel tank containing distilled water.

[0020] Further, in step S7, the single-phase solid solution ZrO2-Yb2O3 powder is dried at 155℃ for 4 hours; then it is sieved using an ultrasonic-assisted vibrating sieve with a 280-mesh sieve at an ultrasonic frequency of 37kHz for 5 minutes.

[0021] In addition, the present invention also proposes a single-phase solid solution oxide thermal spray powder, which is prepared by the above method.

[0022] In addition, the present invention also proposes a method for preparing an ultra-high temperature thermal protective coating. The method involves using high-energy plasma spraying technology to spray the above-mentioned single-phase solid solution oxide thermal spraying powder onto the substrate surface to prepare a Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating.

[0023] Furthermore, the process parameters for high-energy plasma spraying are as follows: the flow rate of the main gas argon is 58L / min to 62L / min, the flow rate of the secondary gas nitrogen is 22L / min to 28L / min; the voltage is 88V to 92V, the current is 720A, the powder feeding speed is 10.2g / min, and the spraying distance is 80mm to 100mm.

[0024] In addition, the present invention also proposes an ultra-high temperature thermal protection coating, which is prepared by the above method.

[0025] (III) Beneficial Effects

[0026] This invention proposes a single-phase solid solution oxide thermal spray powder and coating, and its preparation method. The powder and coating materials are composed of ZrO2-X mol% Yb2O3, where X = 8-30. The coating exhibits no phase change in the temperature range from room temperature to 2400℃ and possesses thermal protection capabilities that can withstand arc plasma ablation at 2400℃ for more than 240 seconds. The preparation method of the powder and coating involves using ZrO2 and Yb2O3 with a purity of 99.9% as raw materials, and preparing a single-phase Yb2O3 fully stable ZrO2 powder with high flowability and bulk density through methods such as roller ball milling, spray granulation, vacuum sintering, and plasma spheroidization. Finally, a single-phase Yb2O3 fully stable ZrO2 thermal protective coating is prepared using high-energy plasma spraying technology. The prepared powder and coating exhibit high-temperature phase stability, and the coating possesses ultra-high temperature long-term anti-oxidation and ablation performance.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Compared to conventional methods of preparing spray granulation slurry using planetary ball milling and mechanical stirring, this invention employs a drum ball milling method, which makes it easier to achieve uniform slurry mixing, prevents slurry stratification due to large differences in powder density, and yields a macroscopically particle-free slurry with a high collection rate, which is beneficial for the normal operation of the peristaltic pump during subsequent spray granulation. Furthermore, drum ball milling has a simpler process than planetary ball milling and mechanical stirring, is not limited by the total amount of material required, and can produce at least 2 kg of prepared slurry in a single batch, thus improving work efficiency.

[0029] 2. Compared to conventional plasma spraying methods that directly use spray-granulated powder, this invention performs high-temperature sintering and plasma spheroidization treatment on the spray-granulated powder. High-temperature sintering not only promotes complete solid solution of the powder but also eliminates PVA colloids remaining in the powder due to spray granulation, reducing powder impurities and improving powder quality. It also improves the agglomeration of the granulated powder, resulting in a more concentrated plasma spheroidization beam and higher powder utilization. Plasma spheroidization treatment not only improves the powder's flowability and bulk density, facilitating subsequent spraying, but also enhances coating quality and reduces the formation of coating pores and cracks.

[0030] 3. After high-temperature sintering, the powder undergoes high-temperature heat treatment and rapid solidification via plasma spheroidization and plasma spraying, maintaining the same composition and single-phase structure as the powder itself. This demonstrates compositional and phase stability across a wide temperature range from the powder to the coating. Existing ultra-high temperature ceramic or oxide coatings undergo chemical changes or phase transitions in the presence of oxygen and over a wide temperature range. Changes in coating composition lead to variations in coating performance; phase transitions cause shrinkage and expansion of the coating, resulting in defects such as cracks and reduced coating quality.

[0031] 4. Compared to existing ultra-high temperature ceramic coatings, the coating prepared by the powder of this invention has fewer defects and a higher density (approximately 95%). It is less prone to melting during plasma ablation, mitigating problems such as melt flow and evaporation of coating components. It is also resistant to oxidation under high-temperature, oxygen-rich conditions, resulting in improvements in both ablation temperature and time. (ZrO) 2- The Yb2O3 coating can withstand continuous ablation by electric arc plasma at 2400℃ for up to 240 seconds, exhibiting excellent ablation resistance. Attached Figure Description

[0032] Figure 1 The scanning electron microscope morphology of the spray-granulated ZrO2-Yb2O3 powder in Example 1 of this invention;

[0033] Figure 2 This is an X-ray diffraction pattern of the spray-granulated ZrO2-Yb2O3 powder in Example 1 of the present invention;

[0034] Figure 3 This is a scanning electron microscope image of the isoionic spheroidized Yb₂O₃ fully stable ZrO₂ powder in Example 1 of the present invention;

[0035] Figure 4 This is an X-ray diffraction pattern of isoionic spheroidized Yb₂O₃ fully stable ZrO₂ powder in Example 1 of the present invention;

[0036] Figure 5 This is a cross-sectional scanning electron microscope image of the Yb2O3 fully stable ZrO2 ultra-high temperature thermal protection coating in Embodiment 1 of the present invention;

[0037] Figure 6 The image shows the ablation curve of the Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating in Example 1 of this invention. Detailed Implementation

[0038] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0039] Example 1

[0040] S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of 87:13 to obtain a mixed powder of the two substances. The ZrO2 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%.

[0041] S2. Dissolve and prepare 10% PVA (polyvinyl alcohol) adhesive in an electrically heated constant temperature water bath. Weigh out 90℃ hot water as solvent, which is 45% of the mass of the mixed powder; add the PVA adhesive to the solvent, with the amount of PVA adhesive added being 8% of the mass of the solvent; stir evenly using an electromagnetic stirrer.

[0042] S3. Add the mixed powder to the solvent, add 1 ml of n-butanol defoamer, and add 1% (by solvent weight) of PEG (polyethylene glycol) dispersant. The slurry is stirred using a ball mill to obtain a slurry for spray drying.

[0043] S4. The slurry was spray-dried using a centrifugal spray dryer. During the spray granulation process, a mechanical agitator continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a centrally recessed surface. The inlet air temperature was 200℃, the outlet air temperature was 130℃, the atomizer frequency was 50Hz, and the peristaltic pump speed was 10rpm. The scanning electron microscope image and X-ray diffraction phase pattern are shown below. Figure 1 and 2 As shown. The powder's flowability is 65.6 s / 50 g, and its loose density is 1.41 g / cm³. 3 .

[0044] S5. The spray-granulated ZrO2-Yb2O3 powder was sintered and solution treated in a muffle furnace at 1300℃ for 4 hours, while removing residual PVA colloids from the granulated powder, thereby obtaining ZrO2-Yb2O3 powder for the next step of plasma spheroidization.

[0045] S6. The powder after high-temperature sintering is subjected to atmospheric plasma spheroidization and solid solution treatment to achieve atomic-level complete solid solution of ZrO2-Yb2O3 powder. The plasma spheroidization current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min. During the spheroidization process, the plasma beam after powder feeding is vertically directed into a large stainless steel tank containing distilled water.

[0046] S7. The spheroidized single-phase solid solution ZrO2-Yb2O3 powder was dried and ultrasonically sieved to obtain micron-sized, dense, wide-temperature-range single-phase solid solution oxide thermal spraying powder for plasma spraying. After spheroidization, the powder was dried at 155℃ for 4 hours, and the calculated plasma spheroidization collection rate was 83.2%. Its scanning electron microscopy morphology image and X-ray diffraction phase pattern are shown below. Figure 3 and 4 As shown. The powder's flowability is 19.8 s / 50 g, and its loose density is 5.20 g / cm³. 3 .

[0047] S8. A fully stabilized Yb₂O₃ ZrO₂ ultra-high temperature thermal protective coating was prepared on the substrate surface using high-energy plasma spraying technology. The main gas argon flow rate was 60 L / min, the secondary gas nitrogen flow rate was 25 L / min; the voltage was 90 V, the current was 720 A, the powder feed rate was 10.2 g / min, and the spraying distance was 100 mm. Figure 5 As shown, this is a cross-section of a coating prepared using high-energy plasma spraying technology. This coating cross-section is relatively dense and has few defects. Figure 6 As shown, the ultra-high temperature thermal protection coating obtained through this step can withstand an arc plasma ablation test at 2400℃ for 250 seconds.

[0048] Example 2

[0049] S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of 82:18 to obtain a mixed powder of the two substances. The ZrO2 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%.

[0050] S2. Dissolve and prepare 10% PVA (polyvinyl alcohol) adhesive in an electrically heated constant temperature water bath. Weigh out 90℃ hot water as solvent, which is 48% of the mass of the mixed powder; add the PVA adhesive to the solvent, with the amount of PVA adhesive added being 6% of the mass of the solvent; stir evenly using an electromagnetic stirrer.

[0051] S3. Add the mixed powder to the solvent, add 1 ml of n-butanol defoamer, and add 1% (by solvent weight) of PEG (polyethylene glycol) dispersant. The slurry is stirred using a ball mill to obtain a slurry for spray drying.

[0052] S4. The slurry was spray-dried using a centrifugal spray dryer. During the spray granulation process, a mechanical agitator continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a centrally recessed surface. The inlet air temperature was 210℃, the outlet air temperature was 140℃, the atomizer frequency was 48Hz, and the peristaltic pump speed was 8rpm. The powder's flowability was 67.2s / 50g, and its loose packing density was 1.37g / cm³. 3 .

[0053] S5. The spray-granulated ZrO2-Yb2O3 powder was subjected to high-temperature sintering treatment at 1300℃ for 4 hours using a muffle furnace, while removing residual PVA colloids from the granulated powder, thereby obtaining ZrO2-Yb2O3 powder for the next step of plasma spheroidization.

[0054] S6. The powder after high-temperature sintering is subjected to atmospheric plasma spheroidization and solid solution treatment to achieve atomic-level complete solid solution of ZrO2-Yb2O3 powder. The plasma spheroidization current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min. During the spheroidization process, the plasma beam after powder feeding is vertically directed into a large stainless steel tank containing distilled water.

[0055] S7. The spheroidized single-phase solid solution ZrO2-Yb2O3 powder was dried and ultrasonically sieved to obtain micron-sized, dense, wide-temperature-range single-phase solid solution oxide thermal spraying powder for plasma spraying. After spheroidization, the powder was dried at 155℃ for 4 hours, and the calculated plasma spheroidization collection rate was 81.4%; the powder flowability was 21.6 s / 50 g, and the loose packing density was 5.14 g / cm³. 3 .

[0056] S8. A fully stabilized Yb₂O₃ ZrO₂ ultra-high temperature thermal protective coating was prepared on the substrate surface using high-energy plasma spraying technology. The main gas argon flow rate was 62 L / min, the secondary gas nitrogen flow rate was 28 L / min; the voltage was 92 V, the current was 720 A, the powder feed rate was 10.2 g / min, and the spraying distance was 90 mm. The ultra-high temperature thermal protective coating obtained through this step can withstand an arc plasma ablation test at 2400℃ for 245 seconds.

[0057] Example 3

[0058] S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of 92:8 to obtain a mixed powder of the two substances. The ZrO2 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%.

[0059] S2. Dissolve and prepare 10% PVA (polyvinyl alcohol) adhesive in an electrically heated constant temperature water bath. Weigh out 40% of the mass of the mixed powder and use 90℃ hot water as a solvent; add the PVA adhesive to the solvent, the amount of PVA adhesive added is 7% of the mass of the solvent; stir evenly using an electromagnetic stirrer.

[0060] S3. Add the mixed powder to the solvent, add 1 ml of n-butanol defoamer, and add 1% (by solvent weight) of PEG (polyethylene glycol) dispersant. The slurry is stirred using a ball mill to obtain a slurry for spray drying.

[0061] S4. The slurry was spray-dried using a centrifugal spray dryer. During the spray granulation process, a mechanical agitator continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a centrally recessed surface. The inlet air temperature was 240℃, the outlet air temperature was 120℃, the atomizer frequency was 49Hz, and the peristaltic pump speed was 9rpm. The powder's flowability was 67.9 g / cm³. 3 The loose bulk density is 1.36 g / cm³. 3 .

[0062] S5. The spray-granulated ZrO2-Yb2O3 powder was subjected to high-temperature sintering treatment at 1300℃ for 4 hours using a muffle furnace, while removing residual PVA colloids from the granulated powder, thereby obtaining ZrO2-Yb2O3 powder for the next step of plasma spheroidization.

[0063] S6. The powder after high-temperature sintering is subjected to atmospheric plasma spheroidization and solid solution treatment to achieve atomic-level complete solid solution of ZrO2-Yb2O3 powder. The plasma spheroidization current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min. During the spheroidization process, the plasma beam after powder feeding is vertically directed into a large stainless steel tank containing distilled water.

[0064] S7. The spheroidized single-phase solid solution ZrO2-Yb2O3 powder was dried and ultrasonically sieved to obtain micron-sized, dense, wide-temperature-range single-phase solid solution oxide thermal spraying powder for plasma spraying. After spheroidization, the powder was dried at 155℃ for 4 hours. The calculated plasma spheroidization collection rate was 80.2%, the powder flowability was 20.9 s / 50 g, and the loose packing density was 5.13 g / cm³. 3 .

[0065] S8. A fully stabilized Yb₂O₃ ZrO₂ ultra-high temperature thermal protective coating was prepared on the substrate surface using high-energy plasma spraying technology. The main gas argon flow rate was 58 L / min, the secondary gas nitrogen flow rate was 22 L / min; the voltage was 88 V, the current was 720 A, the powder feed rate was 10.2 g / min, and the spraying distance was 80 mm. The ultra-high temperature thermal protective coating obtained through this step can withstand an arc plasma ablation test at 2400℃ for 242 seconds.

[0066] The ZrO2-Yb2O3 coatings in all the above embodiments can withstand ultra-high temperature long-term thermal protection for more than 240 seconds during the arc plasma ablation process at 2400℃, and have excellent phase stability and anti-oxidation ablation performance.

[0067] Comparative Example 1

[0068] S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of 87:13 to obtain a mixed powder of the two substances. The ZrO2 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%.

[0069] S2. Dissolve and prepare 10% PVA (polyvinyl alcohol) adhesive in an electrically heated constant temperature water bath. Weigh out 90℃ hot water as solvent, which is 45% of the mass of the mixed powder; add the PVA adhesive to the solvent, with the amount of PVA adhesive added being 8% of the mass of the solvent; stir evenly using an electromagnetic stirrer.

[0070] S3. Add the mixed powder to the solvent, add 1 ml of n-butanol defoamer, and add 1% (by solvent weight) of PEG (polyethylene glycol) dispersant. The slurry is stirred using a ball mill to obtain a slurry for spray drying.

[0071] S4. The slurry is spray-granulated using a centrifugal spray dryer. During the spray granulation process, a mechanical agitator continuously stirs the slurry to obtain ZrO2-Yb2O3 powder with a concave center on the surface. The inlet temperature is 200℃, the outlet temperature is 130℃, the atomizer frequency is 50Hz, and the peristaltic pump speed is 10rpm.

[0072] S5. The spray-granulated ZrO2-Yb2O3 powder was subjected to high-temperature sintering at 1400℃ for 4 hours using a muffle furnace. This process simultaneously removed residual PVA colloids from the granulated powder, thus obtaining ZrO2-Yb2O3 powder for the subsequent plasma spheroidization. After the high-temperature sintering, the powder agglomerated and was difficult to disperse even with ultrasonic sieving, indicating that the sintering temperature was too high and the powder had already formed, making subsequent plasma spheroidization impossible.

[0073] Therefore, the loosely connected powder obtained by holding at 1300℃ for 4 hours in Comparative Example 1 still has good fluidity after ultrasonic sieving and does not affect the subsequent plasma spheroidization treatment. Sintering at 1400℃ for 4 hours is not easy to form powder for the next step of plasma spheroidization.

[0074] Comparative Example 2

[0075] S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of 87:13 to obtain a mixed powder of the two substances. The ZrO2 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100 nm to 500 nm and a purity of 99.9%.

[0076] S2. Dissolve and prepare 10% PVA (polyvinyl alcohol) adhesive in an electrically heated constant temperature water bath. Weigh out 50% of the mass of the mixed powder and use 90℃ hot water as a solvent; add the PVA adhesive to the solvent, the amount of PVA adhesive added is 8% of the mass of the solvent; stir evenly using an electromagnetic stirrer.

[0077] S3. Add the mixed powder to the solvent, add 1 ml of n-butanol defoamer, and add 1% (by solvent weight) of PEG (polyethylene glycol) dispersant. The slurry is stirred using a ball mill to obtain a slurry for spray drying.

[0078] S4. The slurry is spray-granulated using a centrifugal spray dryer. During the spray granulation process, a mechanical agitator continuously stirs the slurry to obtain ZrO2-Yb2O3 powder with a concave center on the surface. The inlet temperature is 200℃, the outlet temperature is 130℃, the atomizer frequency is 50Hz, and the peristaltic pump speed is 10rpm.

[0079] S5. The spray-granulated ZrO2-Yb2O3 powder is subjected to high-temperature sintering in a muffle furnace to remove residual PVA colloids from the granulated powder, thereby obtaining ZrO2-Yb2O3 powder for the next step of plasma spheroidization.

[0080] S6. The powder after high-temperature sintering is subjected to atmospheric plasma spheroidization and solid solution treatment to achieve atomic-level complete solid solution of ZrO2-Yb2O3 powder. The plasma spheroidization current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min. During the spheroidization process, the plasma beam after powder feeding is vertically directed into a large stainless steel tank containing distilled water.

[0081] S7. The spheroidized single-phase solid solution ZrO2-Yb2O3 powder was dried and ultrasonically sieved to obtain micron-sized, dense, wide-temperature-range single-phase solid solution oxide thermal spraying powder for plasma spraying. After spheroidization, the powder was dried at 155℃ for 4 hours, and the plasma spheroidization collection rate was calculated to be 80.0%. The phase composition of the -280 mesh (less than 53 microns) powder after ultrasonic sieving was determined by X-ray diffraction. It was found that under the same plasma spheroidization conditions, there were still undissolved peaks in the spectrum (2θ in the range of 84-95°), indicating that Yb2O3 was not completely dissolved in ZrO2.

[0082] Therefore, the spray granulation slurry with excessively high solid content in Comparative Example 1 is prone to producing spherical spray granulation powder. Compared with the spray granulation powder with a concave center on the surface in Example 1, the spherical spray granulation powder is not easy to form a single-phase fully stable cubic fluorite structure ultra-high temperature oxide powder, and cannot be used for subsequent coating preparation experiments.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing single-phase solid solution oxide thermal spray powder, characterized in that, The method for preparing the single-phase solid solution oxide thermal spray powder includes the following steps: S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of (2~12):1 to obtain a mixed powder; the ZrO2 powder has a particle size of 100nm~500nm and a purity of 99.9%; the Yb2O3 powder has a particle size of 100nm~500nm and a purity of 99.9%. S2. Prepare 10% PVA adhesive in an electrically heated constant temperature water bath; weigh 90℃ hot water as solvent according to 40%~48% of the mass of the mixed powder; add PVA adhesive to the solvent, the amount of PVA adhesive added is 6%~8% of the mass of the solvent; stir evenly by electromagnetic stirring; the electromagnetic stirring speed is 300 rpm and the time is 10 min; S3. Add the mixed powder to the solvent, add the defoamer n-butanol and 1% by weight of the solvent dispersant PEG to the solvent, and stir by roller ball milling to obtain a slurry for spray drying; the roller ball milling speed is 600 rpm, the time is 8 h, the grinding balls are ZrO2 small balls, the ball-to-powder ratio is 1:2, and the ratio of large, medium and small balls is 1:2:

4. S4. The slurry is spray-granulated using a centrifugal spray dryer. During the spray granulation process, the slurry is continuously stirred by a mechanical agitator to obtain ZrO2-Yb2O3 powder with a concave center on the surface. The rotation speed of the mechanical agitator is 1600 rpm, the inlet temperature of the centrifugal spray dryer is 200℃~240℃, the outlet temperature is 120℃~140℃, the atomizer frequency is 48Hz~50Hz, and the peristaltic pump speed is 8rpm~10rpm. Subsequently, an ultrasonic-assisted vibrating screener is used to sieve the slurry through a 180-mesh sieve at a frequency of 37kHz for 5 minutes. S5. The ZrO2-Yb2O3 powder was subjected to high-temperature sintering to remove residual PVA colloids and obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization. The ZrO2-Yb2O3 powder was subjected to high-temperature sintering in a muffle furnace to obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization. The heating rate of the muffle furnace was 8℃ / min, the holding temperature was 1100℃~1300℃, the holding time was 4h, and then the powder was cooled with the furnace. The powder was then sieved through a 600-mesh sieve, and the ultrasonic frequency was 37kHz for 5 minutes. S6. High-purity ZrO2-Yb2O3 powder is subjected to atmospheric plasma spheroidization and solid solution treatment to achieve atomic-level complete solid solution and densification of ZrO2-Yb2O3 powder, thereby obtaining single-phase solid solution ZrO2-Yb2O3 powder; the plasma spheroidization current is 780A, the voltage is 90V, the main gas argon flow rate is 60L / min, and the secondary gas nitrogen flow rate is 25L / min; during the spheroidization process, the plasma beam after powder feeding is vertically directed into a stainless steel tank containing distilled water; S7. The single-phase solid solution ZrO2-Yb2O3 powder was dried and ultrasonically sieved to obtain micron-sized spherical dense wide-temperature-range single-phase solid solution oxide thermal spraying powder for high-energy plasma spraying; the single-phase solid solution ZrO2-Yb2O3 powder was dried at 155℃ for 4 hours; then it was sieved through an ultrasonic-assisted vibrating sieve with a 280-mesh sieve at an ultrasonic frequency of 37kHz for 5 minutes.

2. A single-phase solid solution oxide thermal spray powder, characterized in that, The single-phase solid solution oxide thermal spray powder is prepared by the method described in claim 1.

3. A method for preparing an ultra-high temperature thermal protective coating, characterized in that, The method for preparing the ultra-high temperature thermal protection coating is as follows: using high-energy plasma spraying technology, the single-phase solid solution oxide thermal spraying powder as described in claim 2 is sprayed onto the substrate surface to prepare a Yb2O3 fully stable ZrO2 ultra-high temperature thermal protection coating.

4. The method for preparing an ultra-high temperature thermal protective coating as described in claim 3, characterized in that, The process parameters for high-energy plasma spraying are as follows: the flow rate of the main gas argon is 58L / min~62L / min, the flow rate of the secondary gas nitrogen is 22L / min~28L / min; the voltage is 88V~92V, the current is 720A, the powder feeding speed is 10.2g / min, and the spraying distance is 80mm~100mm.

5. An ultra-high temperature thermal protection coating, characterized in that, The ultra-high temperature thermal protection coating is prepared using the method described in claim 3 or 4.

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