Single-phase solid solution oxide thermal spraying powder and coating and preparation method thereof

Abstract

The invention provides single-phase solid solution oxide thermal spraying powder and coating and a preparation method thereof, the powder and coating material comprises ZrO2-Xmol% Yb2O3, and X is equal to 8-30. The coating has no phase change in a range from room temperature to 2400 DEG C, and has a thermal protection capability of bearing 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: by taking ZrO2 and Yb2O3 with the purity of 99.9% as raw materials, preparing single-phase Yb2O3 fully-stable ZrO2 powder with relatively high flowability and apparent density by adopting modes of roller ball milling, spray granulation, vacuum sintering, plasma spheroidization and the like; and finally, the single-phase Yb2O3 fully-stable ZrO2 thermal protection coating is prepared through a plasma spraying technology, the prepared powder and coating have high-temperature phase stability, and the coating has ultra-high-temperature long-time oxidation ablation resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of surface coating preparation, and specifically relates to a wide-temperature-range single-phase solid-solution oxide thermal spraying powder and coating and a preparation method thereof. Background Art

[0002] When the flight speed reaches a certain level, the temperature of some heated parts of the aircraft can reach more than 2000℃. At this time, the materials in this part have to withstand severe airflow scouring and strong oxidation ablation, which makes the safe operation of the aircraft face huge challenges. Therefore, preparing a thermal protection coating on the surface of the material in this part is a necessary way to improve the service performance of the aircraft. It can not only effectively block the scouring of high-temperature airflow, but also prevent oxygen from penetrating into the substrate during the oxidation process. It can significantly improve its anti-oxidation and ablation performance without reducing the performance of the substrate. Although there are many types of thermal protection bodies, such as ultra-high temperature ceramics (such as TaC, ZrC, HfB2, HfN, etc.), which have the advantages of high melting point (>3000℃), high temperature strength, and good ablation resistance, in an ultra-high temperature oxygen environment, as a coating material, it will undergo significant oxidation within tens of seconds, causing all compounds to be converted into oxides. Therefore, the thermal properties of oxides determine the upper limit of the use temperature of thermal protection coatings.

[0003] Under the action of extremely high heat flux and thermal ablation, the ultra-high temperature ceramic coating material is oxidized to generate the corresponding refractory metal oxides. Those with relatively low melting points (such as TiO2, Nb2O5, Ta2O5, etc.) will soften, melt, liquefy, etc., and will eventually be washed away by the high-temperature airflow; those with lower melting points and relatively low boiling points (such as MoO3, WO3) will be preferentially vaporized during the oxidation and ablation process, causing coating bulging defects and ultimately accelerating coating failure. Although the melting points of the refractory metal Zr and Hf oxides ZrO2 and HfO2 (approximately 2725℃ and 2809℃, respectively) are higher than the conventional high-temperature ablation temperature, they will undergo phase changes, that is, from room temperature monoclinic phase to medium temperature tetragonal phase and high temperature cubic phase, which will cause 5% to 8% volume expansion and contraction during the heating and cooling process. In addition, the ultra-high temperature ceramic coating will also generate B2O3(g) and CO during the ablation process. x (g) and other gases can also cause coating bulging.

[0004] Therefore, developing a coating material that has both wide temperature range, no phase change, and ultra-high temperature, long-term anti-oxidation and ablation properties and preparing the corresponding coating can replace the existing ultra-high temperature ceramic coating, reduce problems such as coating bulging and cracks caused by gas, phase change, etc., further improve the high-temperature stability of the coating itself, and extend the service life of the materials in the heated parts of the aircraft. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a single-phase solid solution oxide thermal spray powder and coating and a preparation method thereof, so as to solve the technical problem of how to have a wide temperature range without phase change and ultra-high temperature long-time anti-oxidation and ablation performance.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a method for preparing a single-phase solid solution oxide thermal spray powder, which comprises the following steps:

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

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

[0011] S3. The mixed powder is added to a solvent, a defoamer n-butanol and a dispersant PEG of 1% by mass of the solvent are added to the solvent, and the mixture is stirred by roller milling to obtain a slurry for spray drying;

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

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

[0014] S6. Perform atmospheric plasma spheroidization solid solution on high-purity ZrO2-Yb2O3 powder to achieve complete solid solution and densification of ZrO2-Yb2O3 powder at the atomic level, and obtain single-phase solid solution ZrO2-Yb2O3 powder.

[0015] S7. Dry and ultrasonically vibrate the single-phase solid solution ZrO2-Yb2O3 powder to obtain micron-sized spherical dense single-phase solid solution oxide thermal spraying powder for high-energy plasma spraying.

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

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

[0018] Furthermore, in step S5, a muffle furnace is used to perform high-temperature sintering treatment on the ZrO2-Yb2O3 powder to obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization; the heating rate of the muffle furnace is 8°C / min, the insulation temperature is 1100°C~1300°C, the insulation time is 4h, and then the furnace is cooled, and then a 600-mesh sieve is used to sieve the high-temperature sintered powder, the ultrasonic frequency is 37kHz, and the time is 5 minutes.

[0019] Furthermore, in step S6, 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 delivery is vertically injected into a stainless steel barrel containing distilled water.

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

[0021] In addition, the present invention also provides a single-phase solid solution oxide thermal spraying powder, and the single-phase solid solution oxide thermal spraying powder 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 for preparing the ultra-high temperature thermal protective coating is to use high-energy plasma spraying technology to spray the above-mentioned single-phase solid solution oxide thermal spraying powder on the surface of the substrate to prepare a Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating.

[0023] Furthermore, the process parameters of high-energy plasma spraying are: 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.

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

[0025] (III) Beneficial effects

[0026] The present invention proposes a single-phase solid solution oxide thermal spray powder and coating and a preparation method thereof. The composition of the powder and coating materials is ZrO2-Xmol%Yb2O3, wherein X=8-30. The coating has no phase change in the range of room temperature to 2400°C, and has the ability to withstand thermal protection for more than 240 seconds during arc plasma ablation at 2400°C. The preparation method of the powder and coating comprises using ZrO2 and Yb2O3 with a purity of 99.9% as raw materials, and adopting roller ball milling, spray granulation, vacuum sintering and plasma spheroidization to prepare a single-phase Yb2O3 fully stable ZrO2 powder with high fluidity and loose density; finally, adopting high-energy plasma spraying technology to prepare a single-phase Yb2O3 fully stable ZrO2 thermal protective coating, and the prepared powder and coating have high-temperature phase stability, and the coating has ultra-high temperature and long-term anti-oxidation and ablation performance.

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

[0028] 1. Compared with the conventional planetary ball milling and mechanical stirring method for configuring spray granulation slurry, the present invention adopts a drum ball milling slurry method, which makes it easier to mix the slurry evenly, and does not cause slurry stratification due to large differences in powder density. A slurry with no macroscopic particle feeling and a high collection rate can be obtained, which is conducive to the normal operation of the peristaltic pump in the subsequent spray granulation process. At the same time, compared with the planetary ball milling and mechanical stirring methods, the drum ball milling process is simpler, is not limited by the total amount of materials required, and can obtain at least 2 kg of configured slurry at one time, which can improve work efficiency.

[0029] 2. Compared with the conventional plasma spraying method of directly using spray granulation powder, the present invention performs high-temperature sintering and plasma spheroidization treatment on the powder after spray granulation. High-temperature sintering can not only promote the complete solid solution of the powder, but also eliminate the PVA colloid remaining in the powder due to spray granulation, reduce powder impurities, improve powder quality, and improve the agglomeration of the granulated powder, so that the subsequent plasma spheroidization beam is more concentrated and the powder utilization rate is high; plasma spheroidization treatment can not only improve the fluidity and bulk density of the powder, facilitate subsequent spraying, but also improve the coating quality and reduce the generation of coating holes and cracks.

[0030] 3. After high-temperature sintering, the powder undergoes high-temperature heat treatment and rapid solidification of plasma spheroidization and plasma spraying, and still maintains the same composition and single-phase structure as the powder, showing the stability of the composition and phase stability from powder to coating in a wide temperature range. Existing ultra-high temperature ceramic or oxide coatings will undergo chemical changes or phase changes in the presence of oxygen and a wide temperature range. Changes in the composition of the coating will cause changes in the performance of the coating; the occurrence of phase changes will cause the coating to shrink and expand, resulting in defects such as cracks, reducing the quality of the coating.

[0031] 4. Compared with the existing ultra-high temperature ceramic coating, the coating prepared by the powder of the present invention has fewer defects and higher density, which can reach about 95%. It is difficult to melt during the plasma ablation process, which can alleviate the problems of melting and evaporation of coating components. It is not afraid of oxidation under high temperature and oxygen conditions, and the ablation temperature and ablation time are improved. ZrO 2- The Yb2O3 coating can withstand continuous arc plasma ablation at 2400°C for up to 240 seconds and has excellent anti-ablation properties. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0033] Figure 2 This is the 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 plasma spheroidized Yb2O3 fully stable ZrO2 powder in Example 1 of the present invention;

[0035] Figure 4 The X-ray diffraction pattern of the plasma 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 Example 1 of the present invention;

[0037] Figure 6 This is the ablation curve of the Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the 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, wherein 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%.

[0041] S2. Dissolve 10% PVA (polyvinyl alcohol) glue in an electrically heated constant temperature water bath. Weigh 90°C hot water as a solvent, accounting for 45% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 8% of the mass of the solvent; stir evenly by electromagnetic stirring.

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

[0043] S4. The slurry was sprayed and granulated by a centrifugal spray dryer. During the spray granulation process, the mechanical stirring paddle continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a concave surface in the middle. The air inlet temperature was 200°C, the air outlet temperature was 130°C, the atomizer frequency was 50Hz, and the peristaltic pump speed was 10rpm. The scanning electron microscopy morphology image and X-ray diffraction phase spectrum are shown as follows: Figure 1 and 2 The powder has a fluidity of 65.6s / 50g and a bulk density of 1.41g / cm 3 .

[0044] S5. The spray granulated ZrO2-Yb2O3 powder was sintered and solution treated at 1300°C for 4 hours in a muffle furnace, and the PVA colloid remaining in the granulated powder was removed to obtain ZrO2-Yb2O3 powder for the next plasma spheroidization.

[0045] S6. Perform atmospheric plasma spheroidization and solid solution on the powder after high temperature sintering to achieve complete atomic-level 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 delivery is vertically injected into a stainless steel barrel filled with distilled water.

[0046] S7. Dry and ultrasonically vibrate the single-phase solid-solution ZrO2-Yb2O3 powder after spheroidization to obtain micron-sized spherical dense wide-temperature range single-phase solid-solution oxide thermal spray powder for plasma spraying. After spheroidization, the powder was dried at 155°C for 4 hours, and the plasma spheroidization collection rate was calculated to be 83.2%; its scanning electron microscopy morphology image and X-ray diffraction phase spectrum are shown as follows: Figure 3 and 4 The powder has a fluidity of 19.8s / 50g and a bulk density of 5.20g / cm 3 .

[0047] S8. Use high-energy plasma spraying technology to prepare Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating on the substrate surface. The flow rate of the main gas argon is 60L / min, the flow rate of the secondary gas nitrogen is 25L / min; the voltage is 90V, the current is 720A, the powder feeding speed is 10.2g / min, and the spraying distance is 100mm. Figure 5 As shown in the figure, it is a cross section of a coating prepared by 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 protective coating obtained by this step can withstand the arc plasma ablation test of 2400°C continuous ablation for 250 seconds.

[0048] Example 2

[0049] S1. Mix ZrO2 powder and Yb2O3 powder in a molar ratio of 82:18 to obtain a mixed powder of the two substances, wherein 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%.

[0050] S2. Dissolve 10% PVA (polyvinyl alcohol) glue in an electrically heated constant temperature water bath. Weigh 90°C hot water as a solvent, accounting for 48% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 6% of the mass of the solvent; stir evenly by electromagnetic stirring.

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

[0052] S4. The slurry was sprayed and granulated using a centrifugal spray dryer. During the spray granulation process, the mechanical stirring paddle continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a concave middle surface. The air inlet temperature was 210°C, the air outlet temperature was 140°C, the atomizer frequency was 48Hz, and the peristaltic pump speed was 8rpm. The powder flowability was 67.2s / 50g and the bulk density was 1.37g / cm 3 .

[0053] S5. The spray granulated ZrO2-Yb2O3 powder was subjected to high temperature sintering treatment at 1300°C for 4 hours in a muffle furnace, and the residual PVA colloid in the granulated powder was removed at the same time, thereby obtaining ZrO2-Yb2O3 powder for the next plasma spheroidization step.

[0054] S6. Perform atmospheric plasma spheroidization and solid solution on the powder after high temperature sintering to achieve complete atomic-level 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 delivery is vertically injected into a stainless steel barrel filled with distilled water.

[0055] S7. Dry and ultrasonically vibrate the single-phase solid-solution ZrO2-Yb2O3 powder after spheroidization to obtain micron-sized spherical dense wide-temperature range single-phase solid-solution oxide thermal spray powder for plasma spraying. After spheroidization, the powder was dried at 155°C for 4 hours, and the plasma spheroidization collection rate was calculated to be 81.4%; the powder flowability was 21.6s / 50g, and the bulk density was 5.14g / cm 3 .

[0056] S8. Use high-energy plasma spraying technology to prepare Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating on the substrate surface. The flow rate of the main gas argon is 62L / min, and the flow rate of the secondary gas nitrogen is 28L / min; the voltage is 92V, the current is 720A, the powder feeding speed is 10.2g / min, and the spraying distance is 90mm. The ultra-high temperature thermal protective coating obtained by this step can withstand the arc plasma ablation test of 2400℃ continuous ablation for 245 seconds.

[0057] Example 3

[0058] S1. Mix ZrO2 powder and Yb2O3 powder in a molar ratio of 92:8 to obtain a mixed powder of the two substances, wherein 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%.

[0059] S2. Dissolve 10% PVA (polyvinyl alcohol) glue in an electrically heated constant temperature water bath. Weigh 90°C hot water as a solvent, accounting for 40% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 7% of the mass of the solvent; stir evenly by electromagnetic stirring.

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

[0061] S4. The slurry was sprayed and granulated using a centrifugal spray dryer. During the spray granulation process, the mechanical stirring paddle continuously stirred the slurry to obtain ZrO2-Yb2O3 powder with a concave surface in the middle. The air inlet temperature was 240°C, the air outlet temperature was 120°C, the atomizer frequency was 49Hz, and the peristaltic pump speed was 9rpm. The powder fluidity was 67.9g / cm 3 , bulk density is 1.36g / cm 3 .

[0062] S5. The spray granulated ZrO2-Yb2O3 powder was subjected to high temperature sintering treatment at 1300°C for 4 hours in a muffle furnace, and the residual PVA colloid in the granulated powder was removed at the same time, thereby obtaining ZrO2-Yb2O3 powder for the next plasma spheroidization step.

[0063] S6. Perform atmospheric plasma spheroidization and solid solution on the powder after high temperature sintering to achieve complete atomic-level 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 delivery is vertically injected into a stainless steel barrel filled with distilled water.

[0064] S7. Dry and ultrasonically vibrate the single-phase solid-solution ZrO2-Yb2O3 powder after spheroidization to obtain micron-sized spherical dense wide-temperature range single-phase solid-solution oxide thermal spray powder for plasma spraying. After spheroidization, the powder was dried at 155°C for 4 hours. The plasma spheroidization collection rate was calculated to be 80.2%, the powder fluidity was 20.9s / 50g, and the bulk density was 5.13g / cm 3 .

[0065] S8. Use high-energy plasma spraying technology to prepare Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating on the substrate surface. The flow rate of the main gas argon is 58L / min, and the flow rate of the secondary gas nitrogen is 22L / min; the voltage is 88V, the current is 720A, the powder feeding speed is 10.2g / min, and the spraying distance is 80mm. The ultra-high temperature thermal protective coating obtained by this step can withstand the arc plasma ablation test of 2400℃ continuous ablation for 242 seconds.

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

[0069] S2. Dissolve 10% PVA (polyvinyl alcohol) glue in an electrically heated constant temperature water bath. Weigh 90°C hot water as a solvent, accounting for 45% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 8% of the mass of the solvent; stir evenly by electromagnetic stirring.

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

[0071] S4. The slurry is sprayed and granulated by 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 middle part of the surface. The air inlet temperature is 200°C, the air outlet temperature is 130°C, 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 treatment at 1400℃ for 4h in a muffle furnace, and the residual PVA colloid in the granulated powder was removed at the same time, thereby obtaining ZrO2-Yb2O3 powder for the next plasma spheroidization. After the high temperature sintering treatment, the powder agglomerated and was difficult to disperse by ultrasonic vibration sieve, indicating that the sintering temperature was too high and the powder had been formed, and the subsequent plasma spheroidization treatment could not be carried out.

[0073] Therefore, the virtual contact powder obtained by keeping warm at 1300°C for 4 hours in Comparative Example 1 still has good fluidity after ultrasonic vibration screening, and does not affect the subsequent plasma spheroidization treatment. The sintering at 1400°C for 4 hours is not easy to form powder for the next 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, wherein 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%.

[0076] S2. Dissolve 10% PVA (polyvinyl alcohol) glue in an electrically heated constant temperature water bath. Weigh 90°C hot water as a solvent, accounting for 50% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 8% of the mass of the solvent; stir evenly by electromagnetic stirring.

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

[0078] S4. The slurry is sprayed and granulated by 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 middle part of the surface. The air inlet temperature is 200°C, the air outlet temperature is 130°C, 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 treatment using a muffle furnace, and the PVA colloid remaining in the granulated powder is removed at the same time, thereby obtaining ZrO2-Yb2O3 powder for the next plasma spheroidization step.

[0080] S6. Perform atmospheric plasma spheroidization and solid solution on the powder after high temperature sintering to achieve complete atomic-level 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 delivery is vertically injected into a stainless steel barrel filled with distilled water.

[0081] S7. Dry and ultrasonically vibrate the single-phase solid-solution ZrO2-Yb2O3 powder after spheroidization to obtain micron-level spherical dense wide-temperature range single-phase solid-solution oxide thermal spray powder for plasma spraying. After spheroidization, the powder was dried at 155°C for 4 hours, and the plasma spheroidization collection rate was calculated to be 80.0%. The phase 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 unsolidified 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 too high solid content in Comparative Example 1 is prone to produce spherical spray granulation powder. Compared with the spray granulation powder with a depression in the middle of the surface in Example 1, the spherical spray granulation powder is not easy to form an ultra-high temperature oxide powder with a single-phase fully stable cubic fluorite structure, and subsequent coating preparation experiments cannot be carried out.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a single-phase solid solution oxide thermal spray powder, characterized in that: The single-phase solid solution oxide thermal spray powder preparation method comprises the following steps: S1. ZrO2 powder and Yb2O3 powder are mixed in a molar ratio of (2 to 12): 1 to obtain a mixed powder; the particle size of ZrO2 powder is 100nm to 500nm, and the purity is 99.9%; the particle size of Yb2O3 powder is 100nm to 500nm, and the purity is 99.9%; S2. Prepare 10% PVA glue in an electrically heated constant temperature water bath; weigh 90°C hot water as a solvent according to 40% to 48% of the mass of the mixed powder; add PVA glue to the solvent, the amount of PVA glue added is 6% to 8% of the mass of the solvent; stir evenly by electromagnetic stirring; S3. The mixed powder is added to a solvent, a defoamer n-butanol and a dispersant PEG of 1% by mass of the solvent are added to the solvent, and the mixture is stirred by roller milling to obtain a slurry for spray drying; S4. The slurry is sprayed and granulated by a centrifugal spray dryer. During the spray granulation process, the slurry is continuously stirred by a mechanical stirring paddle to obtain a ZrO2-Yb2O3 powder with a concave surface in the middle; S5. The ZrO2-Yb2O3 powder is subjected to high temperature sintering treatment to remove the residual PVA colloid in the powder to obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization; S6. Perform atmospheric plasma spheroidization solid solution on high-purity ZrO2-Yb2O3 powder to achieve complete solid solution and densification of ZrO2-Yb2O3 powder at the atomic level, and obtain single-phase solid solution ZrO2-Yb2O3 powder. S7. Dry and ultrasonically vibrate the single-phase solid solution ZrO2-Yb2O3 powder to obtain micron-sized spherical dense single-phase solid solution oxide thermal spraying powder for high-energy plasma spraying.

2. The method for preparing a single-phase solid solution oxide thermal spray powder according to claim 1, characterized in that: In step S2, the electromagnetic stirring speed is 300 rpm and the time is 10 min; in step S3, the roller ball milling speed is 600 rpm and the time is 8 h. The grinding balls are small ZrO2 balls, the ball-to-material ratio is 1:2, and the ratio of large, medium and small balls is 1:2:

4.

3. The method for preparing a single-phase solid solution oxide thermal spray powder according to claim 1, characterized in that: In step S4, the speed of the mechanical stirring paddle is 1600rp, the air inlet temperature of the centrifugal spray dryer is 200°C~240°C, the air outlet temperature is 120°C~140°C, the atomizer frequency is 48Hz~50Hz, the peristaltic pump speed is 8rpm~10rpm, and then an ultrasonic-assisted vibrating sieve machine is used with a 180-mesh sieve for sieving, the ultrasonic frequency is 37kHz, and the time is 5 minutes.

4. The method for preparing a single-phase solid solution oxide thermal spray powder according to claim 1, characterized in that: In step S5, a muffle furnace is used to perform high-temperature sintering treatment on the ZrO2-Yb2O3 powder to obtain high-purity ZrO2-Yb2O3 powder for plasma spheroidization; the heating rate of the muffle furnace is 8°C / min, the insulation temperature is 1100°C~1300°C, the insulation time is 4h, and then the furnace is cooled, and then a 600-mesh sieve is used to sieve the high-temperature sintered powder, the ultrasonic frequency is 37kHz, and the time is 5 minutes.

5. The method for preparing a single-phase solid solution oxide thermal spray powder according to claim 1, characterized in that: In step S6, 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 delivery is vertically injected into a stainless steel barrel containing distilled water.

6. The method for preparing a single-phase solid solution oxide thermal spray powder according to claim 1, characterized in that: In step S7, the single-phase solid solution ZrO2-Yb2O3 powder is dried at 155°C for 4 hours; then it is sieved using an ultrasonic-assisted vibrating sieve machine with a 280-mesh sieve, the ultrasonic frequency is 37 kHz, and the time is 5 minutes.

7. A single-phase solid solution oxide thermal spray powder, characterized in that: The single-phase solid solution oxide thermal spraying powder is prepared by the method according to any one of claims 1 to 6.

8. A method for preparing an ultra-high temperature thermal protective coating, characterized in that: The method for preparing the ultra-high temperature thermal protective coating is to use high-energy plasma spraying technology to spray the single-phase solid solution oxide thermal spraying powder as described in claim 7 on the surface of the substrate to prepare the Yb2O3 fully stable ZrO2 ultra-high temperature thermal protective coating.

9. The method for preparing an ultra-high temperature thermal protective coating according to claim 8, characterized in that: The process parameters of high-energy plasma spraying are: 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.

10. An ultra-high temperature thermal protective coating, characterized in that: The ultra-high temperature thermal protective coating is prepared by the method described in claim 8 or 9.

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