Flowable ceramic powder as well as preparation method and application thereof

Abstract

According to the flowable ceramic powder, the preparation method and the application of the flowable ceramic powder, the oxide or the composite oxide serves as the raw material powder, the ignition substance is added into the raw material powder to form the first powder, the first powder is placed in an induction melting furnace to be subjected to induction heating and melting at the heating power of 60-150 kW, and after the first powder is completely melted, the first powder is cooled to the room temperature to obtain the flowable ceramic powder. An induction coil is moved at the speed of 30-100 mm / h to carry out pulling crystallization on the melt so that the melt can be homogenized, ceramic crystals are obtained, target ceramic powder with fluidity is obtained through crushing and powdering treatment, the obtained target ceramic powder is high in density and close to the theoretical density, the target ceramic powder serves as a spraying raw material, and spraying is carried out on the target ceramic powder. The thermal barrier coating with vertical longitudinal cracks can be prepared by a thermal spraying method, and the CMAS corrosion resistance of the coating is excellent.

Description

Technical Field

[0001] The present application relates to the technical field of the preparation of thermal barrier coating materials, and particularly relates to a flowable ceramic powder, a preparation method thereof, and an application thereof. Background Art

[0002] The service performance of the hot-end components of an aeroengine in a high-temperature gas environment directly determines its thrust-to-weight ratio and reliability. With the gas inlet temperature breaking through 1600 °C, traditional superalloy materials are difficult to meet the temperature resistance requirements. As a core protection technology, thermal barrier coatings (TBCs) can reduce the substrate temperature by 150 - 300 °C through the low thermal conductivity characteristics of the ceramic layer (such as ZrO2 - Y2O3), significantly improving the component life. However, the deposition problem of silicate dust (CMAS) in the atmospheric environment has become increasingly prominent: factors such as volcanic eruptions, coal combustion emissions, and sandstorms have led to an increase in the CMAS concentration. Its molten state (1200 - 1400 °C) will penetrate along the pores and cracks of the coating and react chemically with the ceramic layer (such as Y2O3 dissolution, ZrO2 phase transformation), resulting in coating sintering densification, insulation performance failure, and interfacial stress concentration, ultimately leading to spalling.

[0003] Currently, thermal barrier coatings are mainly prepared by plasma spraying and electron beam physical vapor deposition. Due to its low cost and high deposition efficiency, plasma spraying technology has become the industrial mainstream. However, the spherical powders used in it (such as those prepared by spray granulation, high-temperature sintering, and plasma spheroidization processes) have significant defects such as insufficient powder density and coating crack morphology. Although electron beam physical vapor deposition can prepare a pore-free columnar crystal coating, the equipment is expensive, the deposition rate is low, and the bonding strength between columnar crystals is insufficient, making it difficult to withstand the thermal stress caused by CMAS corrosion.

[0004] Related technologies have defects in the anti-CMAS corrosion performance: the mismatch between the powder density and the coating structure leads to a high coating porosity and transverse crack dominance, and the CMAS melt can quickly penetrate along the transverse cracks to the coating - substrate interface. Vertical longitudinal cracks can mechanically hinder the penetration of CMAS, but the existing powder processes cannot achieve this structure. In summary, related technologies cannot balance the coating density, crack morphology, and anti-CMAS corrosion performance. Summary of the Invention

[0005] In view of the problems existing in the background art, the present application provides a flowable ceramic powder, a preparation method thereof and an application. By using an oxide or a composite oxide as a raw material powder, placing the raw material powder in an induction melting furnace for induction heating and melting to obtain ceramic crystals, and performing crushing and pulverization treatment on the ceramic crystals to obtain a target ceramic powder with fluidity. The target ceramic powder has a high density, close to the theoretical density. Using the flowable target ceramic powder as a spraying raw material, a thermal barrier coating with vertical longitudinal cracks can be prepared, and the coating has excellent resistance to CMAS corrosion.

[0006] The specific invention content is as follows:

[0007] According to the first aspect of the present application, a preparation method of a flowable ceramic powder is provided. The preparation method specifically includes the following steps:

[0008] S1. Using an oxide or a composite oxide as a raw material powder, adding an igniter into the raw material powder according to a mass ratio of 1% - 20% to form a first powder; placing the first powder in an induction melting furnace with a power of 60 - 150 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 30 - 100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals;

[0009] S2. Performing crushing and pulverization treatment on the ceramic crystals to obtain a target ceramic powder with a particle size of 10 - 100 μm;

[0010] The oxide is selected from one or more of zirconia, yttria, gadolinia, hafnium oxide, tantalum oxide, ytterbium oxide, alumina, calcium oxide, magnesium oxide, scandium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide;

[0011] The composite oxide includes a single compound formed by at least two metal elements corresponding to the oxides and oxygen elements.

[0012] Optionally, the igniter is graphite or the metal corresponding to the raw material powder.

[0013] Optionally, when the raw material powder is zirconia, yttria, or gadolinia, step S1 includes:

[0014] Adding an igniter into the raw material powder according to a mass ratio of 5% - 10% to form a first powder; placing the first powder in an induction melting furnace with a power of 100 - 120 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 60 - 80 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals.

[0015] Optionally, when the raw material powder is hafnium oxide, tantalum oxide, or ytterbium oxide, step S1 includes:

[0016] Add an igniter to the interior of the raw material powder according to a mass ratio of 8-15% to form a first powder; place the first powder in an induction melting furnace with a power of 60-80 kW for induction heating and melting. After the first powder is completely melted, move the induction coil at a rate of 90-100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals.

[0017] Optionally, the flow rate of the target ceramic powder is 5 s / 50 g to 40 s / 50 g.

[0018] Optionally, the target ceramic powder is a solid irregular ceramic powder with a bulk density greater than 5.5 g / cm 3 。

[0019] Optionally, the crushing and pulverizing treatment of the ceramic crystals includes:

[0020] Use a hammer crusher, jaw crusher, and roll crusher to crush the ceramic crystals into particles; use air jet milling and ball milling to pulverize the particles to obtain a second powder; screen the second powder to obtain the target ceramic powder.

[0021] According to a second aspect of the present application, there is provided a flowable ceramic powder obtained according to the above preparation method.

[0022] According to a third aspect of the present application, there is provided an application of a flowable ceramic powder, where the flowable ceramic powder is used as a spraying raw material for the preparation of a thermal barrier coating.

[0023] Optionally, a thermal barrier coating with vertical longitudinal cracks is prepared from the flowable ceramic powder by thermal spraying.

[0024] Compared with the prior art, the present application has the following advantages:

[0025] The present application provides a flowable ceramic powder, a preparation method thereof, and an application thereof. The preparation method includes the following steps: using an oxide or a composite oxide as a raw material powder, adding an igniter into the raw material powder according to a mass ratio of 1% to 20% to form a first powder; placing the first powder in an induction melting furnace with a power of 60 to 150 kW for induction heating and melting, and after the first powder is completely melted, moving the induction coil at a rate of 30 to 100 mm / h to perform drawing crystallization on the melt to obtain ceramic crystals; performing crushing and pulverization treatment on the ceramic crystals to obtain a target ceramic powder with a particle size of 10 to 100 μm; the oxide is selected from one or more of zirconia, yttria, gadolinia, hafnium oxide, tantalum oxide, ytterbium oxide, alumina, calcium oxide, magnesium oxide, scandium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide; the composite oxide includes a single compound formed by at least two metal elements corresponding to the oxides and oxygen elements. Using the flowable ceramic powder as a spraying raw material, a thermal barrier coating with vertical longitudinal cracks is prepared.

[0026] The present application provides a preparation method for a flowable ceramic powder. By using an oxide or a composite oxide as a raw material powder, adding an igniter into the raw material powder to form a first powder, placing the first powder in an induction melting furnace for induction heating and melting at a heating power of 60 to 150 kW, and after the first powder is completely melted, moving the induction coil at a rate of 30 to 100 mm / h to perform drawing crystallization on the melt to homogenize the melt, obtaining ceramic crystals, and obtaining a target ceramic powder with fluidity through crushing and pulverization treatment. The obtained target ceramic powder has a high density and is close to the theoretical density. Using the target ceramic powder as a spraying raw material, a thermal barrier coating with vertical longitudinal cracks can be prepared by thermal spraying, and the coating has excellent CMAS corrosion resistance. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 Shows the flow chart of the preparation method of the flowable ceramic powder provided by the embodiment of the present application;

[0029] Figure 2 Shows the SEM image of the thermal barrier coating with vertical longitudinal cracks provided by the embodiment of the present application. Detailed Embodiments

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation on the present application and its application or use. Based on the embodiments in the present application, any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with the features of other existing technologies falls within the protection scope of the present application. In addition, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0031] In the embodiments, if the specific experimental steps or conditions are not specified, the operations or conditions of the conventional experimental steps described in the existing technologies in the field can be followed. For the reagents and other instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchase. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus the repeated description thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0032] For technologies, methods, and devices known to those of ordinary skill in the relevant fields, detailed discussions may not be made, but in appropriate cases, the said technologies, methods, and devices should be regarded as part of the specification of the present application.

[0033] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0034] Corrosion of yttria-stabilized zirconia (YSZ) thermal barrier coatings in the atmospheric environment by silicate dust (CMAS, mainly composed of CaO-MgO-Al2O3-SiO2) can cause the porosity of the coating to drop suddenly from 25% to 5%, and the thermal diffusivity to increase by 133%, significantly shortening the coating life.

[0035] Currently, thermal barrier coatings are mainly prepared by air plasma spraying (APS) and electron beam physical vapor deposition (EB-PVD). The air plasma spraying technology has the following deficiencies:

[0036] Insufficient powder density: There are hollow structures inside the spray granulated powder (for example, the density of alumina powder is only 1.4 - 1.6 g / cm 3 ), and the density of the high-temperature sintered powder is less than 85% of the theoretical value due to particle agglomeration. Although the plasma spheroidized powder can improve the sphericity, there are still micropores inside (for example, the density of zirconia powder is about 2.8 - 3.2 g / cm 3 ).

[0037] Coating crack morphology is limited: Powders with low density are prone to form a layered stacking structure during spraying, resulting in the coating mainly having transverse cracks (crack density > 50 cracks / mm), while the proportion of vertical longitudinal cracks (crack density < 10 cracks / mm) is less than 10%.

[0038] Process defects: The high-temperature jet (15000 - 20000 °C) in plasma spraying will cause excessive oxidation of the powder (such as the oxidation rate of aluminum powder > 15%), and the porosity of the coating is as high as 10 - 20%, providing a channel for CMAS penetration.

[0039] Although electron beam physical vapor deposition can prepare a pore-free columnar crystal coating, the equipment is expensive, the deposition rate is low (< 100 μm / h), and the bonding strength between columnar crystals is insufficient, making it difficult to withstand the thermal stress caused by CMAS corrosion.

[0040] There are significant defects in the anti-CMAS corrosion performance of related technologies:

[0041] Mismatch between powder density and coating structure: Powders with low density (such as spray granulated Al2O3 powder with a density of 1.75 g / cm 3 ) result in a high porosity and transverse crack-dominated coating. The CMAS melt can quickly penetrate along the transverse cracks to the coating-substrate interface, shortening the corrosion cycle by more than 50%.

[0042] Lack of vertical crack control technology: Vertical longitudinal cracks (width < 1 μm, depth > 100 μm) can hinder CMAS penetration through the "crack bridging" mechanism, but the existing powder processes cannot achieve this structure. For example, the proportion of vertical cracks in traditional plasma spraying coatings is less than 10%. Although the rare earth zirconate coating can form a dense barrier layer by reacting to generate an apatite phase, its fracture toughness is insufficient, and the thermal cycle life is only 50% of that of the YSZ coating.

[0043] Insufficient coordination between material system and process: Existing powders (such as YSZ) react with CMAS to form a low melting point phase (such as perovskite), and the preparation of solid high-density powders (such as Gd2Zr2O7) relies on high-temperature sintering (> 1800 °C), resulting in high costs and difficulty in large-scale production.

[0044] In summary, related technologies cannot balance the coating density, crack morphology, and anti-CMAS corrosion performance. There is an urgent need to develop solid high-density powders and their supporting preparation processes to achieve a thermal barrier coating dominated by vertical longitudinal cracks and fundamentally solve the CMAS erosion problem.

[0045] In view of the problems of coating density, crack morphology, and anti-CMAS corrosion performance existing in related technologies, on the one hand, the present application provides a method for preparing a flowable ceramic powder. Figure 1The flowchart of the preparation method of the flowable ceramic powder provided by the embodiment of the present application is shown. As Figure 1 shown, the preparation method specifically includes the following steps:

[0046] S1. Using an oxide or a composite oxide as a raw material powder, adding an igniter into the raw material powder according to a mass ratio of 1% to 20% to form a first powder; placing the first powder in an induction melting furnace with a power of 60 to 150 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 30 to 100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals;

[0047] S2. Performing crushing and pulverization treatment on the ceramic crystals to obtain target ceramic powder with a particle size of 10 to 100 μm;

[0048] The oxide is selected from one or more of zirconia, yttria, gadolinia, hafnium oxide, tantalum oxide, ytterbium oxide, alumina, calcium oxide, magnesium oxide, scandium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide;

[0049] The composite oxide includes a single compound formed by at least two metal elements corresponding to the oxides and oxygen elements.

[0050] It should be noted that the oxide is selected from one or more of zirconia, yttria, gadolinia, hafnium oxide, tantalum oxide, ytterbium oxide, alumina, calcium oxide, magnesium oxide, scandium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide. When the oxide is one kind, for example, the oxide is a single powder of zirconia or yttria, adding an igniter into the single powder to form a first powder, placing the first powder in an induction melting furnace for heating and melting, and performing pulling crystallization on the melt to obtain ceramic crystals. When the oxide is two kinds, for example, the oxides are zirconia and yttria, mixing zirconia and yttria evenly according to a certain mass ratio such as 92:8, adding an igniter inside to form a first powder, placing the first powder in an induction melting furnace for heating and melting, and performing pulling crystallization on the melt to obtain ceramic crystals. When the oxide is three kinds or more, mixing multiple oxides evenly according to a certain mass ratio, and the mass fraction of one oxide is 1% to 99%. Similarly, adding an igniter inside the multiple oxides to form a first powder, placing the first powder in an induction melting furnace for heating and melting, and performing pulling crystallization on the melt to obtain ceramic crystals.

[0051] It should also be noted that the composite oxide includes at least two single compounds formed by the metal elements corresponding to the oxides and oxygen elements. For example, yttrium zirconate powder that has been pre-synthesized and reacted well using zirconia and yttrium oxide, or gadolinium zirconate that has been pre-synthesized and reacted well using zirconia and gadolinium oxide, is used as the raw material.

[0052] It should also be noted that the types of oxides or composite oxides listed herein are the oxides and composite oxides used in the preparation of the embodiments of the present application and common ones. However, other oxides or composite oxides that can be used to prepare the materials of the thermal barrier coating system can also be used as the raw material powders of the present application and are within the protection scope of the present application. They are not listed one by one herein.

[0053] It should be noted that the first powder is placed in an induction melting furnace with a power of 60 - 150 kW for induction heating and melting. The power of induction heating is 60 - 150 kW, specifically it can be 60 kW, 70 kW, 80 kW... 150 kW. During the induction melting process, the heating power is one of the core process parameters. The heating power directly affects the melting efficiency, the state of the molten pool, and the material quality. The heating power directly controls the energy input intensity through the eddy current effect generated by electromagnetic induction, and thus determines the heating rate of the melt. High power can quickly increase the temperature of the furnace charge, shorten the melting time, and improve production efficiency. However, when the heating power is greater than 150 kW, it will cause the temperature to be too high. On the one hand, it will increase energy consumption and cause waste. On the other hand, the violent melting of the raw materials may cause the bubbles to be released violently, resulting in the molten material spraying out. When the heating power is less than 60 kW, it may lead to insufficient temperature of the molten pool, which is not enough to completely melt the oxide, increasing the melting cycle and reducing the crystal density. In addition, the heating power needs to be matched with the size of the melting crucible. The diameter of the equipment crucible in the embodiments of the present application is 30 cm. If the crucible size is increased or decreased, the required heating power should be increased or decreased accordingly. The present application will not further limit this.

[0054] It should also be noted that after the first powder is completely melted, the induction coil is moved at a rate of 30 - 100 mm / h to perform pulling crystallization on the melt. It is necessary to wait until the first powder is completely melted before starting to move the induction coil. If the coil is moved before the powder is completely melted, it will cause the powder to stop melting. The width of the coil is about 5 cm, and the rate of moving the induction coil is 30 - 100 mm / h, specifically it can be 30 mm / h, 40 mm / h, 50 mm / h... 100 mm / h. In induction melting, moving the induction coil effectively suppresses the temperature gradient and local overheating by dynamically adjusting the electromagnetic field distribution. At the same time, moving the coil ensures that the materials at different positions in the height direction of the crucible can be melted and crystallized.

[0055] In specific implementation, an igniter is added to the raw material powder body in a mass ratio of 1% to 20% to form a first powder body. The first powder body is placed in an induction melting furnace of a water-cooled copper crucible. The water-cooled copper crucible can avoid the pollution of the internal crystal by the crucible material. Copper has good processing performance, good thermal conductivity and low cost. Then, the heating power supply is turned on to start heating up. The heating power is 60 - 150 kW. The powder body is subjected to induction heating and melting, and kept warm for 5 - 30 minutes to ensure that the powder body is completely melted. After the powder body is completely melted, the induction coil is moved at a rate of 30 - 100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals. The ceramic crystals are taken out and subjected to crushing and pulverization treatment to obtain target ceramic powder with a particle size of 10 - 100 μm. This method uses a water-cooled copper crucible. Since induction heating is the eddy current effect generated by electromagnetic induction, that is, induction heating starts from the inside of the powder body. At this time, due to the eddy current effect, there is a temperature difference between the edge temperature and the internal center temperature. The edge temperature is lower, and the part of the powder body in contact with the water-cooled copper crucible will not melt during the heating process. That is, the powder body's own cold shell is used as the crucible to prevent the pollution of the outside crucible material.

[0056] In this embodiment, an oxide or a composite oxide is used as the raw material powder body. An igniter is added to the inside of the raw material powder body to form a first powder body. The first powder body is placed in an induction melting furnace and subjected to induction heating and melting at a heating power of 60 - 150 kW. After the first powder body is completely melted, the induction coil is moved at a rate of 30 - 100 mm / h to perform pulling crystallization on the melt to make the melt uniform, and ceramic crystals are obtained. After being subjected to crushing and pulverization treatment, target ceramic powder with fluidity is obtained. Different from the commonly used preparation method of fused zirconia in industry (industrial fused zirconia is obtained through one-step arc furnace melting. The fused stabilized zirconia process can be divided into two types according to the raw materials: one is to use zircon sand as the raw material, and in the arc furnace, two processes of desilication and stabilization are completed through one-time melting, which is called the one-time melting method; the other is to use fused desilicated zircon as the raw material, and after mixing with a stabilizer, it is melted in an electric furnace to form stabilized zirconia, which is called the two-time melting method), the target ceramic powder obtained by the preparation method of this application has high purity, high density, is close to the theoretical density, and the composition is easier to control. At the same time, a water-cooled crucible is used, and the powder body's own cold shell is used as the crucible, and there is no problem of crucible pollution.

[0057] In some embodiments, the igniter is graphite or the metal corresponding to the raw material powder body.

[0058] It should be noted that the igniter is graphite or the metal corresponding to the raw material powder. When the raw material powder is an oxide, for example, when zirconia is used as the raw material, the igniter can be selected as zirconium metal; when the raw material powder is two oxides, for example, zirconia and yttrium oxide with a mass ratio of 92:8, the igniter is selected as the metal corresponding to the oxide with a larger mass fraction. At this time, zirconium metal is selected as the igniter; when the raw material powder is three or more kinds, the three oxides are mixed in a certain mass fraction, and the igniter is selected as the metal corresponding to the oxide with a larger mass fraction; select a metal with good compatibility with the melt to avoid introducing heterogeneous phases. When the cost of the metal is relatively high, graphite can be selected as the igniter, and later treatment is required to remove the graphite to avoid impurities.

[0059] In this embodiment, induction melting relies on the alternating magnetic field to generate eddy current heat in the conductor. When the conductivity of the raw material powder is poor or the size is large, the direct heating efficiency is low. Graphite or metal igniter, as a high-conductive body, preferentially absorbs the energy of the induction coil, generates high temperature on the surface through the skin effect, quickly melts itself and conducts heat to the surrounding raw material powder. That is, graphite or metal as the igniter can quickly establish the initial conditions of electromagnetic induction heating through its own conductive characteristics, and at the same time assist in optimizing the melt uniformity and environmental control.

[0060] In some embodiments, when the raw material powder is zirconia, yttrium oxide, and gadolinium oxide, step S1 includes:

[0061] Add an igniter to the inside of the raw material powder according to a mass ratio of 5% - 10% to form a first powder; place the first powder in an induction melting furnace with a power of 100 - 120 kW for induction heating and melting. After the first powder is completely melted, move the induction coil at a rate of 60 - 80 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals.

[0062] It should be noted that most of the raw material powders in this application are oxides with stable chemical properties and not easily oxidized. Therefore, the induction melting process is carried out in an atmospheric atmosphere. The air convection in the atmosphere can enhance the heat exchange between the melt and the coil, eliminating complex equipment such as vacuum pumps and gas supply devices, and reducing equipment investment and maintenance costs. However, if the raw material powder is an easily oxidized compound, the induction melting process can be carried out under vacuum conditions.

[0063] In some embodiments, when the raw material powder is hafnium oxide, tantalum oxide, and ytterbium oxide, step S1 includes:

[0064] Add an igniter to the inside of the raw material powder according to a mass ratio of 8-15% to form a first powder; place the first powder in an induction melting furnace with a power of 60-80 kW for induction heating and melting. After the first powder is completely melted, move the induction coil at a rate of 90-100 mm / h to draw and crystallize the melt to obtain ceramic crystals.

[0065] In some embodiments, the flow rate of the target ceramic powder is 5 s / 50 g to 40 s / 50 g.

[0066] It should be noted that the target ceramic powder obtained by the preparation method of this application is a fluid powder, and the flow rate of the target ceramic powder is 5 s / 50 g to 40 s / 50 g. Specifically, it can be 5 s / 50 g, 10 s / 50 g, 15 s / 50 g... 40 s / 50 g. The obtained fluid powder can be used as a spraying raw material to prepare a thermal barrier coating. Using fluid powder can ensure the stability of the spraying process, the uniformity of the coating structure and the reliability of the performance. When the flow rate is between 5 s / 50 g and 40 s / 50 g, it is preferably 10 s / 50 g to 20 s / 50 g. Powders with suitable fluidity can be evenly dispersed in the powder feeder, avoiding fluctuations in the powder feeding amount caused by powder agglomeration, bridging or blockage. When the flow rate is greater than 40 s / 50 g, powders with poor fluidity will cause uneven flow rate due to increased frictional resistance, resulting in uneven coating thickness or defects.

[0067] It should be noted that the particle size of the target ceramic powder obtained by the preparation method of this application is 10-100 μm, preferably 10-60 μm. Controlling the powder particle size within a certain range can facilitate the regulation of the melting state, deposition behavior and internal stress distribution of the particles during the preparation of the thermal barrier coating, prompting cracks to be generated directionally along the coating thickness direction (vertical direction), thereby improving the CMAS resistance of the coating. When the particle size is appropriately 10-100 μm, the particles melt moderately in the flame flow, the surface is molten while part of the solid core is retained inside (or completely melted), and after hitting the substrate, they spread into thin sheets. When cooling, uniform shrinkage stress is generated along the coating thickness direction (longitudinal). When the particle size is less than 10 μm, the particles are completely melted, and the "thin sheet" after spreading shrinks laterally during cooling, easily forming lateral cracks or reticulated microcracks; when the particle size is greater than 100 μm, the particle core is not melted, and the internal residual stress is concentrated after deposition, and the crack initiation is irregular, making it difficult to form vertical longitudinal cracks.

[0068] In some embodiments, the target ceramic powder is a solid irregular ceramic powder with a bulk density greater than 5.5 g / cm 3 .

[0069] It should be noted that the relative density of different materials varies. The theoretical density described in this application is calculated by multiplying the theoretical density of each oxide by the sum of their respective proportions. For example, when the ceramic powder is yttrium zirconate, where zirconia accounts for 92% and yttria accounts for 8%, the theoretical density is = 92% × the theoretical density of tetragonal zirconia (6.10 g / cm 3 ) + 8% × the theoretical density of yttria (5.01 g / cm 3 ) = 6.01 g / cm 3 .

[0070] It should be noted that the edges and corners of the solid irregular powder form a micro-anchoring structure in the coating, enhancing the mechanical interlocking between the lamellae. At the same time, longitudinal cracks can release the thermal stress generated by thermal cycling, preventing the coating from peeling due to stress accumulation. Meanwhile, the solid irregular powder reduces the porosity of the coating, effectively blocking the intrusion of high-temperature combustion gas (above 1600 °C) and CMAS molten salt.

[0071] It should be noted that the coatings prepared from low-density powders (such as spray granulated powders, with a density ≤ 4.0 g / cm 3 ) mainly have transverse cracks, while high-density solid powders (with a density ≥ 5.5 g / cm 3 ) require good fluidity to ensure the high-speed impact of particles during spraying, promoting the formation of longitudinal cracks perpendicular to the substrate. Such cracks can block the transverse penetration path of CMAS and maintain the integrity of the coating through the crack closure effect.

[0072] In this embodiment, by preparing solid irregular ceramic powders with a bulk density greater than 5.5 g / cm 3 , and using them as spraying raw materials, a thermal barrier coating with vertical longitudinal cracks can be prepared, and the coating has excellent resistance to CMAS corrosion.

[0073] In some embodiments, the crushing and pulverizing treatment of the ceramic crystal includes: using a hammer crusher, jaw crusher, or roller press to crush the ceramic crystal into particles; using air jet milling or ball milling to pulverize the particles to obtain a second powder; and screening the second powder to obtain the target ceramic powder.

[0074] In this embodiment, through the multi-stage crushing - pulverizing - screening process, through the synergistic effects of coarse crushing for pre-forming, fine crushing for controlling particle size, and screening for impurity removal, the particle size of the ceramic powder is made precise, the morphology is made irregular, and the composition is made uniform, providing a key raw material guarantee for the preparation of thermal barrier coatings.

[0075] In a second aspect, the present application provides a flowable ceramic powder, which is obtained according to the above preparation method.

[0076] In a third aspect, the present application provides an application of a flowable ceramic powder, and the flowable ceramic powder is used as a spraying raw material for preparing a thermal barrier coating.

[0077] In some embodiments, a thermal spraying method is adopted to prepare a thermal barrier coating with vertical longitudinal cracks from the flowable ceramic powder.

[0078] It should be noted that the edges and corners of the irregular powder form "stress concentration sources" during impact, preferentially inducing microcracks at the contact points of the edges and corners. Subsequently, the impact stress of the subsequent powder expands in the vertical direction to form coherent longitudinal cracks.

[0079] Specifically, taking the plasma spraying technology as an example, the specific implementation process of preparing a vertical longitudinal crack-dominated thermal barrier coating with a flowable solid irregular ceramic powder as the raw material is as follows:

[0080] First, the surface of the substrate is roughened by sandblasting to form a rough surface, increasing the mechanical bite area, and ultrasonic cleaning is used to remove oil stains and sandblasting residual particles; then, the surface of the substrate is preheated so that the temperature of the substrate is 200-300 °C, reducing the temperature difference between the coating and the substrate, reducing the transverse thermal stress, and making the cracks tend to expand along the spraying direction (vertical direction); an atmospheric plasma spraying system is adopted, the surface of the substrate is perpendicular to the plasma jet, equipped with a high-frequency induction plasma gun with a power of 30-100 kW, a frequency of 20-40 kHz, and the amplitude of the vibratory powder feeder is 5-10 μm; the plasma gas is argon and hydrogen with a volume ratio of 8:2, and the hydrogen increases the heat enthalpy of the flame flow to ensure that the solid powder is fully melted. When impacting the substrate, the kinetic energy is converted into vertical stress to induce the initiation of longitudinal cracks; the carrier gas powder feeding rate is 40-60 g / min, and the spraying distance is 100-150 mm. Spraying at a short distance (<150 mm) makes the particle velocity ≥600 m / s, and the instantaneous stress generated during impact exceeds the fracture strength of the coating, inducing through-thickness cracks perpendicular to the substrate; the moving speed of the spray gun is 100-200 mm / s, and the uniform movement ensures uniform deposition of the coating, avoiding chaotic cracks caused by local overheating. In addition, "thin layer and multi-pass" spraying needs to be adopted, with the thickness of each coating being 5-10 μm and the total thickness being 200-300 μm. After depositing 5-10 layers, pause for 10 seconds, and use the natural cooling of the coating to form interlayer shrinkage stress, promoting the extension of cracks in the vertical direction.

[0081] In this embodiment, the preparation process of the thermal barrier coating realizes the transition of the thermal barrier coating from "dominated by transverse cracks" to "penetrated by longitudinal cracks" through the full-process control of solid irregular powder design - high-energy plasma spraying - crack orientation regulation - post-treatment strengthening. The high kinetic energy impact of solid powder is utilized to induce vertical cracks, the spraying parameters are optimized to ensure the orderly growth of cracks, and the crack stability is improved through post-treatment, ultimately significantly enhancing the CMAS corrosion resistance and service life of the coating, providing an engineering path for the next-generation high-temperature thermal barrier coating technology.

[0082] To enable those skilled in the art to understand this application more clearly, the following examples are now used to elaborate in detail on a flowable ceramic powder, its preparation method, and its application described in this application.

[0083] Example 1

[0084] Mix zirconia and ignition metal zirconium with a mass ratio of 95:5 to form the first powder; add the above first powder to a water-cooled copper crucible and place it in an induction melting furnace to start induction heating with a heating power of 100 kW. After observing that the powder is completely melted, start moving the induction coil at a moving rate of 80 mm / h to perform pulling crystallization on the melt. After 6 hours of melting and crystallization, zirconia ceramic crystals are obtained, crushed into particles using a jaw crusher, and the above particles are ball-milled and pulverized to form the second powder. The second powder is sieved through vibration to obtain zirconia target ceramic powder with a particle size of 30 - 50 μm. The flow rate of the powder is 10 s / 50 g, and the bulk density of the powder is 5.6 g / cm 3 (monoclinic phase).

[0085] Example 2

[0086] Zirconia and yttrium oxide are used as raw material powders and mixed with ignition metal zirconium to form the first powder; among them, the mass ratio of zirconia to yttrium oxide is 92:8, and the mass ratio of the raw material powder to ignition metal zirconium is 95:5; add the above first powder to a water-cooled copper crucible and place it in an induction melting furnace to start induction heating with a heating power of 100 kW. After observing that the powder is completely melted, start moving the induction coil at a moving rate of 80 mm / h to perform pulling crystallization on the melt. After 6 hours of melting and crystallization, zirconia yttrium ceramic crystals are obtained, crushed into particles using a hammer crusher, and the above particles are ball-milled and pulverized to form the second powder. The second powder is sieved through vibration to obtain zirconia yttrium target ceramic powder with a particle size of 30 - 60 μm. The flow rate of the powder is 15 s / 50 g, and the bulk density of the powder is 5.89 g / cm 3 .

[0087] Example 3

[0088] Zirconia and gadolinium oxide are used as raw material powders, which are mixed with the igniter zircon metal to form a first powder; among them, the mass ratio of zirconia to gadolinium oxide is 1:1, and the mass ratio of the raw material powder to the igniter zircon metal is 92:8; the above-mentioned first powder is added to a water-cooled copper crucible and then placed in an induction melting furnace to start induction heating with a heating power of 120 kW. After observing that the powder is completely melted, the induction coil is started to move, and the moving speed of the induction coil is 60 mm / h. The melt is subjected to pulling crystallization. Through 5 hours of melting and crystallization, zirconium gadolinium oxide ceramic crystals are obtained. They are crushed by a jaw crusher to form particles, and the above particles are ball-milled and pulverized to form a second powder. The second powder is sieved by vibration to obtain zirconium gadolinium oxide target ceramic powder with a particle size of 30 - 60 μm. The flow rate of the powder is 12 s / 50 g, and the bulk density of the powder is 6.77 g / cm 3 。

[0089] Example 4

[0090] Hafnium oxide and ytterbium oxide are used as raw material powders, which are mixed with the igniter graphite to form a first powder; among them, the mass ratio of hafnium oxide to ytterbium oxide is 1:2, and the mass ratio of the raw material powder to the igniter graphite is 90:10; the above-mentioned first powder is added to a water-cooled copper crucible and then placed in an induction melting furnace to start induction heating with a heating power of 80 kW. After observing that the powder is completely melted, the induction coil is started to move, and the moving speed of the induction coil is 100 mm / h. The melt is subjected to pulling crystallization. Through 4 hours of melting and crystallization, hafnium ytterbium oxide ceramic crystals are obtained. They are crushed by a jaw crusher to form particles, and the above particles are ball-milled and pulverized to form a second powder. The second powder is sieved by vibration to obtain hafnium ytterbium oxide target ceramic powder with a particle size of 10 - 40 μm. The flow rate of the powder is 20 s / 50 g, and the bulk density of the powder is 9.75 g / cm 3 。

[0091] Example 5

[0092] Zirconium yttrium oxide is used as the raw material powder, which is mixed with the igniter zircon metal to form a first powder; among them, the mass ratio of the raw material powder to the igniter zircon metal is 95:5; the above-mentioned first powder is added to a water-cooled copper crucible and then placed in an induction melting furnace to start induction heating with a heating power of 100 kW. After observing that the powder is completely melted, the induction coil is started to move, and the moving speed of the induction coil is 80 mm / h. The melt is subjected to pulling crystallization. Through 6 hours of melting and crystallization, zirconium yttrium oxide ceramic crystals are obtained. They are crushed by a jaw crusher to form particles, and the above particles are ball-milled and pulverized to form a second powder. The second powder is sieved by vibration to obtain zirconium yttrium oxide target ceramic powder with a particle size of 20 - 50 μm. The flow rate of the powder is 15 s / 50 g, and the bulk density of the powder is 5.62 g / cm 3 。

[0093] Preparation of Thermal Barrier Coating with Vertical Longitudinal Cracks

[0094] The surface of the titanium alloy substrate was subjected to sandblasting for roughening treatment, and the surface of the titanium alloy substrate was preheated to 200 °C. The surface of the titanium alloy substrate was perpendicular to the plasma jet. The yttria-stabilized zirconia target ceramic powder prepared in Example 2 was taken, and an atmospheric plasma spraying system was used with a power of 60 kW, a frequency of 25 kHz, and the amplitude of the vibratory powder feeder was 8 μm; the plasma gas was argon and hydrogen with a volume ratio of 8:2, the carrier gas powder feeding rate was 40 g / min, the spraying distance was 120 mm, and the gun moving speed was 150 mm / s. The first layer was sprayed with a coating thickness of 10 μm. The above spraying steps were continued to be repeated, and it was paused for 10 seconds after every 5 - 10 layers were deposited. The total coating thickness was 200 μm to obtain a thermal barrier coating, and its SEM image is as Figure 2 shown, and the formed thermal barrier coating has vertical longitudinal cracks.

[0095] The preparation process of the thermal barrier coating with vertical longitudinal cracks in other examples is the same as the above process, and the obtained SEM images are similar to Figure 2 those, and will not be repeated here for illustration.

[0096] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0097] For method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily essential to the present application.

[0098] The above has introduced in detail a flowable ceramic powder, its preparation method and its application provided by the present application. Specific examples are used herein to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for preparing a flowable ceramic powder, characterized in that, The preparation method includes the following steps: S1. Using an oxide or a composite oxide as the raw material powder, adding an igniter into the raw material powder according to a mass ratio of 1% to 20% to form a first powder; placing the first powder in an induction melting furnace with a power of 60 - 150 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 30 - 100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals; S2. Crushing and pulverizing the ceramic crystals to obtain target ceramic powder with a particle size of 10 - 100 μm; The oxide is selected from one or more of zirconia, yttria, gadolinia, hafnium oxide, tantalum oxide, ytterbium oxide, alumina, calcium oxide, magnesium oxide, scandium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, and samarium oxide; The composite oxide includes a single compound formed by at least two metal elements corresponding to the oxides and oxygen elements.

2. The preparation method according to claim 1, characterized in that, The igniter is graphite or the metal corresponding to the raw material powder.

3. The preparation method according to claim 2, characterized in that, When the raw material powder is zirconia, yttria, or gadolinia, step S1 includes: Adding an igniter into the raw material powder according to a mass ratio of 5% to 10% to form a first powder; placing the first powder in an induction melting furnace with a power of 100 - 120 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 60 - 80 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals.

4. The preparation method according to claim 2, characterized in that, When the raw material powder is hafnium oxide, tantalum oxide, or ytterbium oxide, step S1 includes: Adding an igniter into the raw material powder according to a mass ratio of 8 - 15% to form a first powder; placing the first powder in an induction melting furnace with a power of 60 - 80 kW for induction heating and melting. After the first powder is completely melted, moving the induction coil at a rate of 90 - 100 mm / h to perform pulling crystallization on the melt to obtain ceramic crystals.

5. The preparation method according to claim 1, characterized in that, The flow rate of the target ceramic powder is 5 s / 50 g - 40 s / 50 g.

6. According to the preparation method described in any one of claims 1-5, it is characterized in that The target ceramic powder is a solid irregular ceramic powder with a bulk density greater than 5.5 g / cm 3 .

7. The preparation method according to claim 1, characterized in that, The crushing and pulverizing treatment of the ceramic crystals includes: Using a hammer crusher, jaw crusher, or roll crusher to crush the ceramic crystals into particles; using air jet milling or ball milling to pulverize the particles to obtain a second powder; screening the second powder to obtain the target ceramic powder.

8. A flowable ceramic powder, characterized in that, The flowable ceramic powder is obtained according to the preparation method described in any one of claims 1 - 7.

9. The application of the flowable ceramic powder according to claim 8, characterized in that, The flowable ceramic powder is used as a spraying raw material for the preparation of a thermal barrier coating.

10. The application according to claim 9, characterized in that, Using a thermal spraying method, the flowable ceramic powder is prepared into a thermal barrier coating with vertical longitudinal cracks.

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