WO2020173151A1 - Method for preparing amorphous oxide ceramic composite coating simultaneously having toughness, thermal conductivity and high-temperature structural stability - Google Patents

Abstract

Disclosed is a method for preparing an amorphous oxide ceramic composite coating simultaneously having toughness, thermal conductivity and high-temperature structural stability, wherein the amorphous oxide ceramic composite coating is an Al ₂O ₃-YAG amorphous ceramic coating. The preparation method comprises: (1) mixing an Al ₂O ₃ powder with a Y ₂O ₃ powder to obtain an Al ₂O ₃/Y ₂O ₃ mixed powder; (2) subjecting the obtained Al ₂O ₃/Y ₂O ₃ mixed powder to heat treatment at 1400°C to 1600°C to obtain an Al ₂O ₃/YAG composite powder; and (3) spray coating the obtained Al ₂O ₃/YAG composite powder onto a surface of a substrate by means of thermal spraying to obtain the Al ₂O ₃-YAG amorphous ceramic coating.

Description

Preparation method of amorphous oxide ceramic composite coating with strong, tough, thermally conductive and stable integration of high-temperature microstructure Technical field

The invention relates to a method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable and integrated with a high-temperature microstructure, and belongs to the technical field of ceramic coatings.

Background technique

Material friction and wear (often accompanied by high temperature, strong oxidation, and large thermal shock) under high PV value (P is contact pressure, V is friction rate) determines the reliability of mechanical systems such as aerospace and aviation engines, space vehicles and high-end pump valves The key factor of sex and longevity. The harsh engineering application conditions require that the friction material should have high hardness, high strength and toughness, high temperature resistance, oxidation resistance, wear resistance and good thermal shock resistance to ensure high reliability and long service life. However, the existing single structural materials cannot meet the requirements of the above special working conditions. Studies have shown that preparing ceramic coatings on the surface of high-strength heat-resistant metals is an important way to improve the properties of substrate materials such as wear resistance, high temperature resistance, thermal shock resistance and oxidation resistance.

Under high PV wear conditions, the ceramic coating needs to withstand high pressure, high friction rate and the resulting high friction heat (the highest temperature of the friction contact surface is close to or even more than 1000 ℃), and severe thermal shock. Facing the above-mentioned service conditions, traditional carbide and nitride ceramic materials are not suitable. Although WC/Co coating shows excellent wear resistance and corrosion resistance, its reliable service temperature is lower than 500℃; SiC and Si ₃ N ₄ ceramics cannot be coated by thermal spraying process; ceramics such as ZrC, B ₄ C and BN The coefficient of thermal expansion is low, the matching with the metal substrate is poor, and the coating is difficult to withstand high and low temperature impacts. Oxide ceramics (such as Al ₂ O ₃ , Cr ₂ O ₃ , ZrO ₂ and TiO ₂ ) have the characteristics of wear resistance, high temperature resistance, oxidation resistance and high thermal expansion coefficient. They are used as thermal spray coatings for high PV values and harsh Wear conditions have good potential. However, oxide ceramics have low toughness and strong crack sensitivity, which restricts their expanded application. Under the condition of high PV value, wear causes a sudden increase in heat generated by friction, and the thermal stress caused by the difference in thermal expansion coefficient between the coating and the metal substrate increases significantly, which requires the coating to have good high temperature microstructure stability and fracture toughness; Higher coating thermal conductivity is beneficial to dissipate frictional heat, reduce thermal stress, and improve its wear resistance. The thermal conductivity of the coating will become an important factor affecting its wear resistance.

Among the common oxide wear-resistant ceramic materials, Al ₂ O ₃ (the thermal conductivity of α-Al ₂ O ₃ is 36W·m ^-1 ·K ^-1 ) has better thermal conductivity than Cr ₂ O ₃ , ZrO ₂ and TiO ₂ . Thermal spray oxide wear-resistant ceramic coatings are mostly studied and applied to Al ₂ O ₃ and its composite coatings. Representative methods to improve Al ₂ O ₃ coating are the following: (1) Increase the deposition temperature of the substrate. Increasing the deposition temperature can improve the bonding between the Al ₂ O ₃ monolithic layer (splat) and the substrate and the monolithic layer, thereby improving the density, microhardness, toughness, and thermal conductivity of the Al ₂ O ₃ coating. However, the γ-Al ₂ O ₃ phase (thermal conductivity of 1.6W·m ^-1 ·K ^-1 ) in the coating is still the main crystalline phase, and the deposition temperature increases from 140°C to 660°C. The α-Al ₂ O _The content of the _three phases only increased from 20% to 26%, and the improvement effect of coating strength and toughness and thermal conductivity is limited (α-Al ₂ O ₃ has better thermal stability, mechanical and thermal conductivity compared to γ-Al ₂ O ₃ Performance); higher deposition temperature is not suitable for preparing ceramic coatings on most metal substrate surfaces. (2) Dry ice assisted deposition. Using dry ice on-line spraying technology to increase the bonding strength of plasma sprayed Al ₂ O ₃ coatings by 30% (the value exceeds 60 MPa), the porosity is reduced from 9.3% to 6.8%, and the residual compressive stress inside the coating is nearly doubled. Conducive to inhibit crack propagation and improve fracture toughness. However, the assisted deposition of dry ice will greatly reduce the deposition temperature and increase the cooling rate, which not only reduces the effective interfacial bonding between monolithic layers, but also increases the introduction of amorphous phases, resulting in a decrease in the high-temperature mechanical properties of the coating. (3) Post-treatment after laser remelting. Plasma sprayed Al ₂ O ₃ coating surface for laser remelting can increase the content of α-Al ₂ O ₃ phase in the coating, and obtain a cladding layer with fine structure, low porosity and high hardness, but the hardness of the cladding layer is along the thickness The direction changes are obvious, the microstructure and mechanical properties are poor, the fracture toughness is reduced, the residual internal stress is large, and the coating is easy to crack and fail during the harsh wear process. (4) Nanoization of coating microstructure. The nano-scale Al ₂ O ₃ coating with fine-grained strengthening and toughening effect shows higher hardness and toughness, better anti-sliding and erosion resistance performance, and the content of α-Al ₂ O ₃ phase in the coating can reach More than 50% (the new method of liquid-phase plasma spraying can prepare a nano-structured pure α-Al ₂ O ₃ phase coating). However, the existing problems are: ①Under the high friction and heat service environment generated by high PV value and harsh wear conditions, the long-term stability of the nano-coating microstructure is poor, and the coating strength and toughness change greatly under high temperature and strong thermal shock conditions. ②The nano-coating has many grain boundaries and enhanced phonon scattering, making it difficult to obtain good thermal conductivity. (5) Add metal phase to the coating. The addition of metal phase (such as Al) to the Al ₂ O ₃ coating improves the strength and toughness and thermal conductivity of the coating. In order to further improve the toughness and thermal conductivity of the coating to meet the harsh wear conditions with high PV values, it is necessary to continue to increase the content of metal Al. However, it is difficult to control the interface bonding performance of excessive metal phase and ceramic phase matrix, the number of interface defects increases greatly, and the hardness and strength of the coating decrease greatly, which is not conducive to its service under severe wear conditions. (6) Compound with other oxides. ① The low thermal conductivity of ZrO ₂ (or Y ₂ O ₃ partially stabilized ZrO ₂ (YSZ)) will significantly reduce the thermal conductivity of Al ₂ O ₃ -ZrO ₂ or Al ₂ O ₃ -YSZ composite coatings, and wear at high PV values. Under conditions, a large amount of heat will accumulate, causing rapid stress concentration, and causing rapid expansion of coating micro-cracks, reducing the wear-resistant life of the coating. ②TiO ₂ has good thermal conductivity, and can form a vacant solid solution with Al ₂ O ₃ to improve the bonding performance, compactness and toughness of the coating phase interface. However, the problem is that the addition of TiO ₂ reduces the high temperature creep resistance of the coating, and the high temperature mechanical properties of the coating will decrease, resulting in a decrease in its wear resistance and service life under high PV wear conditions. ③Using the thermal conductivity of Cr ₂ O ₃ to present positive temperature coefficient characteristics, crystal structure and solid solution characteristics with increasing temperature, the composite powder is prepared by mechanical mixing method, and Al ₂ O ₃ -Cr ₂ O ₃ composite coating is prepared by plasma spraying. Floor. Using partial solid solution and heterogeneous nucleation to increase the content of α-Al ₂ O ₃ phase in the coating, the composite coating has better toughness, thermal conductivity and resistance than a single Al ₂ O ₃ or Cr ₂ O ₃ coating. Grinding performance. In order to further enhance the solid solution effect and retain more α-Al ₂ O ₃ phase in the coating, nano-agglomerated powders are required. However, this will face the same problems: First, the grain boundaries of nanostructured coatings increase significantly, phonon scattering is significantly enhanced, and the high thermal conductivity of the coating is difficult to ensure; second, high PV value harsh wear produces high frictional heat and causes coating The nanocrystalline grains in the layer grow up, and the microstructure and mechanical properties of the coating are unstable. (7) Amorphous Al ₂ O ₃ based composite coating. Taking the Al ₂ O ₃ -YAG amorphous coating as an example, the amorphous composite ceramic coating is prepared by in-situ spraying with the characteristics of high enthalpy, steep temperature gradient and rapid solidification by thermal spraying. The coating structure is dense, the porosity is low, the interlayer interface is better, and the main part of the amorphous phase contains more free volume, which can effectively form a shear band during deformation, making it have higher fracture toughness; The main part of the state structure can improve the corrosion resistance of the amorphous composite ceramic coating; at the same time, a small amount of nanocrystalline particles dispersed in the coating can improve the mechanical properties and wear resistance of the coating. However, the above-mentioned amorphous ceramic coating uses nano Al ₂ O ₃ and Y ₂ O ₃ powder as raw materials, spray granulation to obtain sprayable Al ₂ O ₃ /Y ₂ O ₃ composite powder, and in-situ spray to prepare amorphous The coating has the following two problems: ①In the plasma spraying process, the proportion of the amorphous phase in the Al ₂ O ₃ -YAG amorphous coating obtained in situ varies greatly, the composition distribution is not uniform, and the dispersed grain content More, it is difficult to control microstructure stability and quality consistency; ②The glass transition temperature of the amorphous phase component is lower and close to 500℃, and the coating is served at high temperature, its microstructure stability is difficult to maintain, and the crystallization process The accompanying volume change in the coating will induce the initiation and propagation of microcracks in the coating and reduce the service life of the coating. (8) Eutectic Al ₂ O ₃ based composite coating. After the amorphous Al ₂ O ₃ composite coating is heat-treated, a eutectic ceramic coating (such as Al ₂ O ₃ -YAG, Al ₂ O ₃ -ZrO ₂ and other systems) can be obtained. The eutectic phase forms a three-dimensional interpenetrating network. Lock structure, the phase size is difficult to grow, and it has good high temperature microstructure stability; at the same time, the mechanical properties and thermal conductivity of the eutectic composite ceramic coating are greatly improved, and it is under high specific pressure, high temperature, oxygen enrichment, strong corrosion, etc. It has good application prospects under severe working conditions. However, there are two main problems: ① To obtain a eutectic Al ₂ O ₃ based composite coating, the heat treatment temperature required exceeds 1000 ℃. Except for high temperature alloys, most metal substrates are not capable of such high Heat treatment temperature, therefore, the actual range of use is greatly restricted; ②Amorphous ceramic coating is heat-treated to obtain a eutectic ceramic coating process, with the volume change, there is a large difference between the high thermal expansion coefficient and the superalloy substrate. Thermal stress can easily cause the coating to crack and peel off.

technical problem

The main problems in the previous research on Al ₂ O ₃ and its composite coatings are: First, traditional research aimed at relatively mild wear conditions, limited to the mechanical properties of the coating, ignoring a large amount of frictional heat accumulation and strong thermal shock stress. Impact; Second, facing the high friction heat service environment of high PV value and harsh working conditions, the high-temperature mechanical properties and thermal conductivity of the coating can be effectively improved at the same time, which is difficult to take into account; third, long-term high temperature, high stress and harsh service environment , Due to grain boundary creep, desolvation effect, diffusive phase change and other factors, it is difficult to maintain the stability of the coating microstructure, which will inevitably affect its thermal conductivity, mechanical and wear resistance; fourth, the amorphous ceramic coating The phase content varies greatly, the glass transition temperature is low, and the microstructure stability of the coating in service at high temperature is poor; fifth, the eutectic ceramic coating requires a high heat treatment temperature during the preparation process, and the coating is Cracking and peeling are easy to occur during heat treatment.

Technical solutions

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing an amorphous oxide ceramic composite coating that is strong, tough, thermally conductive, and stable at a high temperature. , Strong oxidation, wide temperature range thermal shock, corrosion and other harsh service environments to obtain long life and high reliability service, taking into account the high-temperature mechanical properties and thermal conductivity of the coating, and improve the coating's amorphous phase content, uniformity of composition distribution, Glass transition temperature, high temperature microstructure stability, interlayer interface bonding, etc. In the present invention, the coating is obtained by in-situ spray deposition for the first time, and no subsequent heat treatment is required, thereby avoiding the adverse effects of high-temperature heat treatment on the metal substrate and high thermal mismatch stress that easily cause coating cracking or peeling failure.

To this end, the present invention provides a method for preparing an amorphous oxide ceramic composite coating that is strong, tough, thermally conductive, and stable and integrated with high-temperature microstructure. The amorphous oxide ceramic composite coating is Al ₂ O ₃ -YAG Amorphous ceramic coating, the preparation method includes:

(1) Mixing Al ₂ O ₃ powder and Y ₂ O ₃ powder to obtain Al ₂ O ₃ /Y ₂ O ₃ mixed powder, and the Al ₂ O ₃ /Y ₂ O ₃ mixed powder contains Al ₂ O ₃ The mass fraction of powder ranges from 50% to 67%, and the mass fraction of Y ₂ O ₃ powder ranges from 33% to 50% (the sum of mass fractions is 100%);

(2) After heat treatment of the obtained Al ₂ O ₃ /Y ₂ O ₃ mixed powder at 1400-1600° C., an Al ₂ O ₃ /YAG composite powder is obtained;

(3) Spraying the obtained Al ₂ O ₃ /YAG composite powder on the surface of the substrate by thermal spraying to obtain the Al ₂ O ₃ -YAG amorphous ceramic coating.

In this disclosure, after mixing Al ₂ O ₃ powder (with a mass fraction of 50% to 67%) and Y ₂ O ₃ powder (with a mass fraction of 33% to 50%), heat treatment (1400 to 1600°C) The Al ₂ O ₃ /Y ₂ O ₃ composite powder undergoes a solid phase reaction (the chemical reaction is 5Al ₂ O ₃ +3Y ₂ O ₃ → 2Y ₃ Al ₅ O ₁₂ (YAG)) to form Al ₂ O ₃ /YAG Composite powder. At this time, the YAG phase forms a network structure in the Al ₂ O ₃ /YAG composite powder at the same time (solid phase reaction generates α-Al ₂ O ₃ and YAG phase, so that the YAG phase can be connected together, which is beneficial to Al ₂ O ₃ / High temperature microstructure stability of YAG composite powder).

Preferably, in step (1), the main crystal phase of the Al ₂ O ₃ powder is α-Al ₂ O ₃ , and the main crystal phase of the Y ₂ O ₃ powder is cY ₂ O ₃ . Among them, α-Al ₂ O ₃ and cY ₂ O ₃ are the phase forms with the most stable chemical properties and better mechanical and thermal conductivity in the components of alumina and yttria, respectively.

Preferably, in step (1), the Al ₂ O ₃ and Y ₂ O ₃ powders are wet-milled and mixed uniformly, and the powders are configured into a suspension stable slurry and then sprayed and granulated to obtain Al ₂ O ₃ /Y ₂ O ₃ Composite powder. The invention adopts the spray granulation method to prepare Al ₂ O ₃ /Y ₂ O ₃ composite powder. The advantages of this method are: the spray drying operation is continuous and controllable, suitable for the drying of heat-sensitive and non-heat-sensitive materials, For the drying of aqueous and organic solvent materials, the raw material liquid can be solution, slurry, emulsion, paste, etc., with great flexibility, good powder quality stability and high powdering efficiency. The prepared powder has uniform composition, good physical and chemical properties and better sphericity.

Preferably, in step (1), the particle size of the Al ₂ O ₃ powder is 2 nm to 2 μm, and the particle size of the Y ₂ O ₃ powder is 2 nm to 2 μm.

Preferably, in step (2), the heat treatment time is 2 to 4 hours.

Preferably, before thermal spraying, the obtained Al ₂ O ₃ /YAG composite powder is subjected to plasma spheroidization. Preferably, the parameters of the plasma spheroidization treatment include: argon and hydrogen are used as plasma gases, and the specific process parameters are: argon flow rate 30-40 slpm, hydrogen flow rate 3-7 slpm, current 350-500A, power 20- 35kW, powder feeding carrier gas argon flow rate 3 ~ 4slpm, powder feeding rate 5 ~ 15g/min, spraying distance 200 ~ 300mm. More preferably, the particle size of the Al ₂ O ₃ /YAG composite powder after plasma spheroidization is 20-40 μm. The purpose of plasma spheroidization is to melt and densify the surface layer of the Al ₂ O ₃ /YAG composite powder, eliminate the angular areas on the powder surface, obtain better sphericity, and promote the fluidity of the composite powder without changing it. The phase composition of the composite powder. The Al ₂ O ₃ /YAG composite powder treated by plasma spheroidization needs to be sieved after filtration and drying to obtain a sprayable composite with a certain particle size distribution, compact surface, good sphericity and good fluidity Powder (preferably, the particle size distribution range of the obtained composite powder is 20-40 μm, which is suitable for subsequent thermal spraying).

Preferably, in step (3), the thermal spraying is plasma spraying; the parameters of the plasma spraying include: plasma gas argon flow rate 45-55 slpm, plasma gas hydrogen flow rate 7-10 slpm, current 600-700A, power 45～50kW, powder feed carrier gas argon flow rate 3～4slpm, powder feed rate 30～40g/min, spray distance 100～120mm.

Preferably, during the thermal spraying process, the deposition temperature is kept below the glass transition temperature of the Al ₂ O ₃ -YAG system. Preferably, cooling is used to control the deposition temperature to be lower than the glass transition temperature of the Al ₂ O ₃ -YAG system. More preferably, the cooling method includes compressed air, circulating water or liquid nitrogen cooling.

Also, preferably, the deposition temperature is 100-250°C. In one solution, the actual deposition temperature of spraying can be controlled at 100-250°C through the combined cooling of compressed air, circulating water or liquid nitrogen.

After the obtained Al ₂ O ₃ /YAG composite powder is subjected to thermal spraying, the Al ₂ O ₃ -YAG deep eutectic system is constructed by using the larger undercooling degree of thermal spraying to make the actual deposition temperature of the composite coating (the deposition temperature here is Refers to the powder being heated and accelerated by the plasma flame, forming droplets and flying to the substrate or first depositing the coating surface, then impacting, spreading, cooling and solidifying. During the process, the substrate itself, compressed air, circulating water or liquid nitrogen is cooled Later, the temperature of the solid/liquid interface front of the liquid droplet during solidification is defined as the actual deposition temperature) lower than the glass transition temperature of the Al ₂ O ₃ -YAG system (generally 500-900°C), so that Al ₂ The O ₃ /YAG eutectic phase stops growing, and the Al ₂ O ₃ -YAG amorphous ceramic coating is obtained in situ. In the thermal spraying process, a large degree of undercooling is built, so that the actual spraying deposition temperature is much lower than the glass transition temperature of the coating, so that the amorphous ceramic coating is obtained in situ. And effectively control the internal compressive stress level of the coating, retard the expansion of microcracks in the coating under the wide temperature range thermal shock conditions of high PV value wear conditions, and improve the long-term service reliability of the coating. In addition, it is possible to prevent the excessively low deposition temperature from affecting the interface bonding between the splat and the substrate and the splat.

Preferably, the substrate is a metal substrate, a ceramic substrate, or a graphite substrate; preferably, the substrate is cleaned and sandblasted before spraying. Preferably, the thickness of the obtained amorphous oxide ceramic composite coating is 50-800 μm.

Beneficial effect

The preparation method of the present invention can be used to obtain the Al ₂ O ₃ -YAG amorphous ceramic composite coating that is strong and tough, thermally conductive and stable and integrated with high temperature microstructure. Among them, the amorphous phase content in the coating exceeds 90%, the composition is evenly distributed, and it has a high glass transition temperature and high-temperature microstructure stability, as well as interlayer interface bonding, density, etc., so that the coating can work at high PV values. , High temperature, strong oxidation, wide temperature range thermal shock, corrosion and other harsh service environments to obtain long life and high reliability service, taking into account the high temperature mechanical properties and thermal conductivity of the coating. In addition, in-situ spray deposition is used to obtain an amorphous ceramic coating with excellent high-temperature properties, and no subsequent heat treatment is required, thereby avoiding the harsh requirements of high-temperature heat treatment on the metal substrate and the high thermal mismatch stress that may cause the coating to crack or peel off The adverse effects of failure.

Description of the drawings

Figure 1 is the morphology and element distribution of the spray granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder prepared in Example 1: (a) SEM photo of the powder; (b) morphology of a single powder particle ; (C)-(f) EDS spectrum analysis diagram of a single powder particle;

Figure 2 shows the morphology of Al ₂ O ₃ /YAG composite powder after heat treatment at different heat treatment temperatures in Example 1 (the gray phase is α-Al ₂ O ₃ and the white phase is YAG): (a, b) 1400°C ; (C, d) 1550℃;

3 is an XRD pattern of the spray granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder prepared in Example 1;

4 is an XRD pattern of Al ₂ O ₃ /YAG composite powder obtained after heat treatment in Example 1;

Figure 5 is a schematic diagram of the principle of using plasma spraying to construct an Al ₂ O ₃ -YAG deep eutectic system and obtaining an Al ₂ O ₃ -YAG amorphous oxide ceramic coating in situ;

Figure 6 is the XRD pattern of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 1 (the amorphous phase content reaches more than 90%);

7 is a TEM structure analysis of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 2;

Figure 8 is the DSC curve of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 3 (heating rate 30K/min);

9 is a cross-sectional morphology and energy spectrum analysis of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 2;

10 is a diagram of the element distribution of the Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 2. It can be seen from the figure that the distribution of the elements in the coating amorphous matrix is uniform;

Figure 11 is the DSC curve (5K/min, 10K/min, 20K/min, 30K/min) of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating obtained at different heating rates in Example 3;

Figure 12 shows the sensitivity of the characteristic temperature with the heating rate in the DSC curve, where the change of the characteristic temperature with the heating rate reflects the sensitivity of the characteristic temperature to the heating rate, which also reflects the thermal stability of the crystallization process corresponding to the characteristic temperature . It can be seen from the figure that the linear relationship between the characteristic temperature T and ln(b) is consistent with Losocka’s empirical formula (ie T=A+B ln(b), where A and B are constants, and T is the corresponding characteristic Temperature (T _g , T _c1 , T _p1 , T _c2 , T _p2 ). A represents the characteristic temperature when the heating rate is 1K/min, and B represents the sensitivity of material structure changes at different heating rates), the nucleation of YAG phase The process is more sensitive to the heating rate, and the nucleation of a-Al ₂ O ₃ is relatively slow (T _c corresponds to the nucleation process, T _p corresponds to the growth process). In terms of the sensitivity of heating rate, the nucleation process of YAG phase is more sensitive than its growth process, while a-Al ₂ O ₃ is just the opposite. Its crystal growth process is more sensitive than its nucleation process (T _c1 and T _p1 correspond to It is YAG phase, T _c2 and T _p2 correspond to a-Al ₂ O ₃ phase);

Figure 13 shows three methods for calculating the activation energy of each stage corresponding to the characteristic temperature of the coating under non-isothermal conditions (Kissinger method, Augis-Bennett method and Ozawa method). From the figure, we can see: Kissinger, Augis-Bennett and Ozawa equations at different heating rates The graphs of, respectively take ln(T ² /b), ln(T/b) and ln(b) as the Y axis, and 1000/T as the X axis. Through linear fitting, the corresponding activation can be obtained from the slope Can (E _g , E _c1 , E _p1 , E _c2 , _Ep2 ). The activation energies calculated by these three methods are similar, indicating that these three methods are suitable for analyzing the crystallization behavior of amorphous coatings. In addition, E _{c2 is} much higher than E _c1 , indicating that the nucleation of a-Al ₂ O ₃ is much more difficult than that of YAG phase. This is consistent with the higher temperature required for the crystallization of a-Al ₂ O ₃ , that is, greater activation energy. At the same time, E _{c2 is} greater than _Ep2 , indicating that the nucleation process of a-Al ₂ O ₃ is more difficult than the grain growth process. In contrast, the nucleation of YAG phase is easier than its growth process;

Figure 14 is the local activation energy E _c (x) of the α-Al ₂ O ₃ and YAG phases of the amorphous ceramic coating during the crystallization process;

Figure 15 is the brittleness index F of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating under different heating rate conditions (the present invention uses the non-isothermal DSC thermal analysis method to test the brittleness index F of the coating (for amorphous materials, which Dynamic properties, such as viscosity, change greatly during the glass transition process. This temperature-dependent dynamic behavior is often called dynamic brittleness, which is considered to be related to many characteristics at the glass transition temperature, such as ratio Heat, elasticity and configuration entropy, etc. When the kinetic behavior of glass forming liquid follows the temperature dependence law of Arrhenius equation in a wide temperature range, then the glass forming liquid is considered "strong", similar to chemical reaction rate and crystal The glass-forming liquid is considered to be more brittle when its dynamic behavior greatly deviates from the Arrhenius law. The strong glass-forming liquid is more stable during the glass transition process than the brittle one, and The configuration change is smaller, such as specific heat. Therefore, the brittleness index is often used to evaluate the microstructure stability of amorphous materials during the glass transition process. The brittleness index F can be expressed as follows: F=E _g /RT _g ln(b ));

16 is the variation of the thermal diffusion coefficient with temperature of the Al ₂ O ₃ -YAG amorphous ceramic composite coating, Al ₂ O ₃ -Cr ₂ O ₃ coating, and Al ₂ O ₃ coating prepared in Example 4;

Figure 17 is the fracture toughness of the Al ₂ O ₃ -YAG amorphous ceramic composite coating, Al ₂ O ₃ -Cr ₂ O ₃ coating, and Al ₂ O ₃ coating prepared in Example 4 (the present invention uses the indentation method to roughly To evaluate the fracture toughness of the coating, the test load is 5kgf, and the dwell time is 10s. The simplified calculation formula for fracture toughness is adopted: K _IC =0.0752P (1/C) ^3/2 , where K _IC is the coating fracture toughness and P is Indenter load, C is 1/2 of the longitudinal crack length of Vickers indentation. The fracture toughness of the coating is the average of 5 measured data);

Figure 18 is the wear test photos and tribological properties of the Al ₂ O ₃ -YAG amorphous ceramic composite coating, Al ₂ O ₃ -Cr ₂ O ₃ coating, and Al ₂ O ₃ coating prepared in Example 5: (a )-(B) Coating wear test photos; (c) Coefficient of friction of coating; (d) Wear surface temperature of coating;

Figure 19 is the photo of the coated grinding ring after the wear test and the observation of the worn surface morphology: (a)-(b) Al ₂ O ₃ coating; (c)-(d) Al ₂ O ₃ -Cr ₂ O ₃ coating (E)-(f) Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 5;

20 shows the plastic deformation bands and dimples on the wear surface of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Example 5;

Figure 21 is a photo of Al ₂ O ₃ coating, Y ₂ O ₃ coating, Al ₂ O ₃ -Cr ₂ O ₃ coating after 1000h salt spray corrosion test;

Figure 22 is a photo of Al ₂ O ₃ -YAG amorphous ceramic composite coating, Al ₂ O ₃ -Y ₂ O ₃ coating, and Al ₂ O ₃ coating after thermal shock test (first peeling): (a) Al ₂ O ₃ ; (b) Al ₂ O ₃ -Y ₂ O ₃ ; (c) Al ₂ O ₃ -YAG;

Figure 23 is the photos before and after the wear test of Al ₂ O ₃ -YAG amorphous ceramic composite coating, Al ₂ O ₃ -Y ₂ O ₃ coating, and Al ₂ O ₃ coating grinding ring (2000N and 500rpm): (a) -(B) Al ₂ O ₃ ; (c)-(d) Al ₂ O ₃ -Y ₂ O ₃ ; (e)-(f) Al ₂ O ₃ -YAG;

Figure 24 is the cross-sectional morphology observation of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Comparative Example 2 after heat treatment at 1200°C for different times: (a) 24h; (b) 96h; (c) 240h; (d) 600h; (e) 800h; (f) 1000h;

Figure 25 is the XRD pattern of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Comparative Example 3 (the Al ₂ O ₃ /Y ₂ O ₃ composite powder is directly sprayed and deposited to obtain the coating);

Figure 26 is the DSC curve of the sprayed Al ₂ O ₃ -YAG amorphous ceramic composite coating prepared in Comparative Example 3 (the Al ₂ O ₃ /Y ₂ O ₃ composite powder is directly sprayed and deposited to obtain the coating);

Table 1 in FIG. 27 shows the comparison of the crystallization kinetics data of the Al ₂ O ₃ -YAG amorphous coating prepared by the present invention and 30 kinds of amorphous materials (ceramics, alloys, polymers, etc.) publicly reported in the literature.

Embodiments of the invention

The present invention will be further described below through the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, not to limit the present invention.

In the present disclosure, heat treatment is used to cause the Al ₂ O ₃ /Y ₂ O ₃ mixed powder to undergo a solid-phase reaction to form an Al ₂ O ₃ /YAG composite powder. At this time, the YAG phase forms a network structure in the Al ₂ O ₃ /YAG composite powder at the same time (solid phase reaction generates α-Al ₂ O ₃ and YAG phase, so that the YAG phase can be connected together, which is beneficial to Al ₂ O ₃ / High temperature microstructure stability of YAG composite powder). In addition, the present disclosure uses thermal spraying for the first time to construct an Al ₂ O ₃ -YAG deep eutectic system, so that the actual deposition temperature is lower than the glass transition temperature, so as to obtain in-situ toughness, thermal conductivity, and high-temperature microstructure stability Integrated Al ₂ O ₃ -YAG amorphous ceramic coating. The preparation method of the present invention also takes into account the high-temperature mechanical properties, thermal conductivity, and corrosion resistance of the coating, realizes the stable integration of the toughness, thermal conductivity, and high-temperature microstructure of the coating, so that the coating can work at high PV value, high temperature, and strong Long life and highly reliable service can be obtained under severe service environments such as oxidation, wide temperature range thermal shock, and corrosion. The following exemplarily describes the preparation method of the amorphous oxide ceramic composite coating provided by the present invention.

Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder (Al ₂ O ₃ /Y ₂ O ₃ mixed powder). The raw materials used are Al ₂ O ₃ and Y ₂ O ₃ powder. The particle size of the two powders can be nanometer or submicron, and the powder components can be α-Al ₂ O ₃ and cY ₂ O _{3 respectively} . The mass percentages of the Al ₂ O ₃ powder and Y ₂ O ₃ powder are 50% to 67% and 33% to 50%, respectively. The main reasons for using the above two raw material powder mass percentages are: ① Refer to the equilibrium phase diagram of the Al ₂ O ₃ -Y ₂ O ₃ system to determine the composition ratio corresponding to the eutectic point; ② The plasma spraying process is larger The degree of cooling will produce a "pseudo-eutectic" phenomenon, that is, expand the composition range of the eutectic region; ③ Plasma spraying process parameter changes cause changes in enthalpy and temperature gradient, the composite powder will experience different thermal history, The formation of phases will have a certain impact; ④ Use plasma spraying to build a "deep eutectic" phenomenon with a large degree of undercooling, which greatly reduces the actual deposition temperature, and is lower than the glass transition temperature, resulting in solute trapping (trapping) , The eutectic phase will stop growing, thus forming an amorphous phase.

In an alternative embodiment, the Al ₂ O ₃ and Y ₂ O ₃ powders are wet-milled and mixed uniformly, and the Al ₂ O ₃ /Y ₂ O ₃ composite powder (Al ₂ O ₃ /Y ₂ O ₃ mixed Powder) preparation. In one example, during wet ball milling, the above two powders are placed in a ball milling tank, and alumina or zirconia grinding balls are used to mix the raw materials. The preferred ball-to-battery ratio is 2:1 to 4:1. In addition, a dispersant, a binder, etc. can also be added. The amount of dispersant added can be 0.2% to 1.0% of the powder mass, and the amount of binder added can be 0.5% to 2.0% of the powder mass. In addition, the amount of solvent added can be 50% to 150% of the powder mass. As a dispersant, it includes, but is not limited to, one or a combination of sodium silicate, sodium metasilicate, sodium citrate, sodium humate, polyacrylamide, hydroxymethyl cellulose, and sodium hydroxymethyl cellulose. The binder includes, but is not limited to, one or a combination of polyvinyl alcohol, paraffin, glycerin, and sodium lignosulfonate. The solvent includes, but is not limited to, one or a combination of water (preferably deionized water) and ethanol. Then the ball mill is mixed uniformly to prepare a suspension stable slurry, and the ball is removed by sieving. Then, mechanical stirring is performed at a speed of 40-100 rpm, and spray granulation is performed to obtain Al ₂ O ₃ /Y ₂ O ₃ composite powder. Preferably, centrifugal spray granulation is used. Centrifugal spray granulation can choose atomizer rotation speed of 10000～15000rpm, feed pump rotation speed of 15～40rpm, inlet air temperature of 200～300℃, and outlet air temperature of 90～120℃.

Heat treatment in situ solid state reaction to obtain Al ₂ O ₃ /YAG composite powder. For Al ₂ O ₃ /YAG composite powder (preferably Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained by spray granulation), necessary heat treatment is required. Put the Al ₂ O ₃ /Y ₂ O ₃ composite powder into a corundum crucible, and then place it in a muffle furnace for heat treatment. The furnace has an atmospheric atmosphere. Start heating from room temperature at a heating rate of 5°C/min, heat up to 1400-1600°C, keep it for 2 to 4 hours, and then cool down with the furnace. Stepwise solid-phase reaction using in-situ high temperature: Al ₂ O ₃ +2Y ₂ O ₃ →Y ₄ Al ₂ O ₉ (YAM), Al ₂ O ₃ +Y ₄ Al ₂ O ₉ → 4YAlO ₃ (YAP), Al ₂ O ₃ +3YAlO ₃ →Y ₃ Al ₅ O ₁₂ (YAG) to obtain Al ₂ O ₃ /YAG composite powder. By controlling the heat treatment temperature and holding time, the YAG phase growth morphology is adjusted to form a network structure in the composite powder. The advantages of the network structure are: ① For a single powder particle, the α-Al ₂ O ₃ and YAG phases are uniformly distributed, which can effectively achieve "deep eutectic" during the spraying process, and form an amorphous phase in situ to the greatest extent , So as to effectively increase the content of amorphous phase; ② help to improve the strength, density and stability of the composite powder; ③ promote the uniformity of the composition in the spray deposited composite coating.

Thermal spraying obtains Al ₂ O ₃ -YAG amorphous ceramic coating in situ. The prepared Al ₂ O ₃ /YAG composite powder is deposited on the surface of the substrate by thermal spraying to prepare the Al ₂ O ₃ -YAG amorphous ceramic coating. The substrate is not particularly limited, including but not limited to metal or ceramic or graphite. Before deposition, the substrate can be cleaned and sandblasted to remove grease and adsorbents and increase the roughness of the substrate surface to improve the interface between the coating and the substrate, which is suitable for deposition.

Preferably, the thermal spraying is plasma spraying (the ceramic powder has a higher melting point to ensure that the ceramic powder can be effectively melted during the spraying process, so as to obtain better spread and deposition characteristics of the powder droplets on the surface of the substrate, and reduce solidified flakes. Gaps and cracks between layers). However, it should be understood that other thermal spraying methods such as supersonic flame spraying, explosive spraying, etc. can also be used. The working gas for plasma spraying can be argon and hydrogen. In an example, the plasma spraying parameters are: plasma gas argon flow rate 45～55slpm, plasma gas hydrogen flow rate 7～10slpm, current 600～700A, power 45～50kW, powder feeding carrier gas argon flow rate 3～4slpm, delivery The powder rate is 30-40g/min, and the spraying distance is 100-120mm. The thickness of the sprayed amorphous ceramic coating is 50-800μm.

During the spray deposition process, the substrate and the coating surface are cooled with compressed air, including the cooling gas and venturi cooling gas on the side of the spray gun, and the back of the substrate is cooled with circulating water or liquid nitrogen. The actual deposition temperature of spraying is controlled at 100～ 250°C. In order to increase the content of the amorphous phase in the sprayed Al ₂ O ₃ -YAG coating, it is necessary to effectively construct a "deep eutectic" system, so that the actual spray deposition temperature is much lower than the glass transition temperature, and the eutectic phase stops growing and is in situ An amorphous phase is formed. Thermal spraying has the characteristics of high enthalpy, steep temperature gradient and rapid cooling and solidification. For the Al ₂ O ₃ -YAG eutectic system, there will be no solid solution between α-Al ₂ O ₃ and YAG, so the equilibrium distribution coefficient k is low, which means a large degree of subcooling at the front of the solid-liquid interface. The use of compressed air, circulating water or liquid nitrogen during the spraying process will further increase the degree of subcooling during the deposition process. In addition, the formation of α-Al ₂ O ₃ /YAG eutectic phase requires alternating nucleation and growth of α-Al ₂ O ₃ phase and YAG phase, which consumes more time than single-phase crystallization. Under the above-mentioned deep undercooling conditions, the eutectic phase is more difficult to nucleate and grow, thereby effectively forming the amorphous phase and promoting the deposition of the amorphous ceramic coating. Through the implementation of active and passive cooling in the spray deposition process, the compressive stress level inside the coating is controlled, and the expansion of the microcracks in the coating under the wide temperature range thermal shock condition of the high PV value wear condition is effectively blocked, and the coating is improved Long-term service reliability. Moreover, the actual deposition temperature cannot be too low, and it is necessary to avoid that too low deposition temperature affects the interface bonding between the splat and the substrate and the monolith. The reason why the Al ₂ O ₃ /YAG composite powder after the heat treatment solid-phase reaction is used for spray deposition instead of directly using Al ₂ O ₃ /Y ₂ O ₃ composite powder for spraying is mainly because: ① Thermal spraying process Among them, the Al ₂ O ₃ /Y ₂ O ₃ composite powder particles will experience different thermal history, which cannot ensure that α-Al ₂ O ₃ and cY ₂ O ₃ can fully react in a short time to form sufficient YAG phase; ② In the process, the YAG phase is formed in situ, so the morphology and content of the YAG phase are also different in the droplets of different powder particles, which cannot ensure the uniformity of the composition in the final deposited coating; ③ If the Al ₂ O ₃ /Y ₂ O is sprayed directly ₃ composite _{powder, α-Al 2 O 3 cY} 2 O 3 reacts with the YAG process will consume more energy, resulting in deposition of the actual supercooling degree is reduced, the amorphous phase content of the coating decreases and the variation width than Large, the glass transition temperature decreases. In view of this, the Al ₂ O ₃ /YAG composite powder is selected for spray deposition. The coating obtained in this way has an amorphous phase content of more than 90%, a uniform composition distribution, a high glass transition temperature and high temperature microstructure stability. Sex.

Before thermal spraying, the Al ₂ O ₃ /YAG composite powder can be plasma spheroidized. The parameters include: Argon and hydrogen are used as plasma gases. The specific process parameters are: Argon flow rate 30-40slpm, hydrogen flow rate 3-7slpm, current 350-500A, power 20-35kW, powder carrier gas argon flow rate 3 ～4slpm, powder feeding rate 5～15g/min, spraying distance 200～300mm. The Al ₂ O ₃ /YAG composite powder is sent into the center of the plasma flame stream and sprayed into room temperature deionized water. Then the composite powder in deionized water is filtered, dried, and sieved to obtain a particle size distribution range of 20-40 μm, which is suitable for thermal spraying.

The advantages of plasma spheroidization are: ① Only the surface or sub-surface of the Al ₂ O ₃ /YAG composite powder obtained by the heat treatment is melted, and the angular areas on the powder surface are eliminated to obtain better sphericity without changing the entire powder The strength and phase composition of the bulk particles; ② Improve the density of the surface layer of the powder particles, and promote the fluidity of the composite powder; ③ Help improve the density of the deposited coating and the interface bonding between the splats .

In a detailed example of the preparation method of the amorphous oxide ceramic composite coating, the following steps may be included: (1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder (spray granulation is preferred), where Al The mass fraction of ₂ O ₃ powder ranges from 50% to 67%, the mass fraction of Y ₂ O ₃ powder ranges from 33% to 50%, and the particle sizes of Al ₂ O ₃ powder and Y ₂ O ₃ powder are nanometer or submicron level. (2) The Al ₂ O ₃ /YAG composite powder is obtained by in-situ solid-phase reaction by heat treatment, and the YAG phase forms a network structure in the composite powder. (3) Plasma spheroidization of the composite powder can obtain a sprayable composite powder with a certain particle size distribution, compact surface, good sphericity and good fluidity. (4) The Al ₂ O ₃ -YAG amorphous ceramic coating is obtained in situ by thermal spraying. The amorphous phase content in the coating exceeds 90%, the composition is evenly distributed, and it has a high glass transition temperature and high temperature microstructure stability.

The advantages and beneficial effects of the present invention:

(1) The present invention designs and prepares Al ₂ O ₃ /YAG composite powder, and uses the greater undercooling of plasma spraying to construct an Al ₂ O ₃ -YAG deep eutectic system, so that the actual deposition temperature is much lower than the vitrification Transition temperature to obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ. The amorphous ceramic coating has higher amorphous phase content, uniformity of composition distribution, glass transition temperature, better high-temperature microstructure stability, interlayer interface bonding, compactness and the like. The preparation method of the present invention also takes into account the high-temperature mechanical properties, thermal conductivity, and corrosion resistance of the coating, realizes the stable integration of the toughness, thermal conductivity, and high-temperature microstructure of the coating, so that the coating can work at high PV value, high temperature, and strong Long-life and high-reliability service under severe service environments such as oxidation, wide temperature range thermal shock, and corrosion;

(2) The use of in-situ spray deposition to obtain high-performance amorphous ceramic coatings without subsequent heat treatment can have good high-temperature performance and microstructure stability, thereby avoiding the harsh requirements of high-temperature heat treatment on metal substrates And the high thermal mismatch stress can easily lead to the adverse effects of coating cracking or peeling failure.

The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and cannot be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the present invention. The scope of protection. The specific process parameters in the following examples are only an example in the appropriate range, that is, those skilled in the art can make selections within the appropriate range through the description herein, and are not limited to the specific values illustrated below.

Example 1

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

Weigh Al ₂ O ₃ and Y ₂ O ₃ powders (the main crystal phases are α-Al ₂ O ₃ and cY ₂ O _{3 respectively} ). The particle size distribution ranges of the two powders are 30～150nm and 50～200nm respectively. _The mass fraction of ₂ O ₃ powder is 67%, and the mass fraction of Y ₂ O ₃ powder is 33%. Put Al ₂ O ₃ and Y ₂ O ₃ powder in a ball milling tank, using alumina grinding balls (3mm in diameter), the ball-to-battery ratio is 4:1, and the hydroxymethyl cellulose dispersant is 0.8 of the powder mass. %, the addition amount of polyvinyl alcohol binder is 1.5% of the powder mass, and the addition amount of deionized water is 120% of the powder mass. The above various raw materials are mixed by ball milling for 48 hours and then configured into a suspension stable slurry, sieved to remove the grinding balls, and then mechanically stirred at a speed of 60 rpm, and centrifuged for spray granulation. The spray granulation parameters are: the atomizer rotation speed is 12000rpm, the feed pump rotation speed is 25rpm, the inlet air temperature is 230°C, and the outlet air temperature is 120°C to obtain the original spray granulation composite powder (see Figure 1), and the element The distribution is uniform, the particle size is 10-60μm, and the granulated powder is composed of α-Al ₂ O ₃ and cY ₂ O ₃ (see Figure 3).

(2) Heat treatment in situ solid phase reaction to obtain Al ₂ O ₃ /YAG composite powder

The Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained by spray granulation is heat-treated to promote the in-situ solid phase reaction. Put the granulated powder into the corundum crucible, the powder accounts for 1/2 to 2/3 of the total volume of the crucible, and then put it in the muffle furnace for heating. The furnace has an atmospheric atmosphere. Start heating from room temperature at a heating rate of 5°C/min, heat up to 1500°C, keep it warm for 3 hours, then turn off the heating power and cool to room temperature along with the furnace. After heat treatment, Al ₂ O ₃ /YAG composite powder is obtained, and the powder morphology is shown in Figure 2. The YAG phase (white) forms a network structure in the composite powder. The composite powder obtained by the heat treatment solid-phase reaction is composed of α-Al ₂ O ₃ and Y ₃ Al ₅ O ₁₂ (YAG) (see Figure 4);

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidizing is performed on the Al ₂ O ₃ /YAG composite powder obtained by the heat treatment. Using argon and hydrogen as plasma gas, the specific process parameters are: argon flow 35slpm, hydrogen flow 5slpm, current 450A, power 30kW, powder carrier gas argon flow 4slpm, powder feeding rate 10g/min, spraying distance 270mm. The Al ₂ O ₃ /YAG composite powder is sent into the center of the plasma flame stream and sprayed into room temperature deionized water. The composite powder in deionized water is filtered out with a filter, and then put into an oven for drying treatment at a temperature of 120°C. After drying, the composite powder is sieved through 400 mesh and 700 mesh screens respectively to obtain a particle size distribution range of 20-40 μm, which is suitable for thermal spraying.

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

Plasma spraying is used to deposit the Al ₂ O ₃ /YAG composite powder prepared in step (3) on the surface of the cleaned and sandblasted high-strength graphite substrate. The spraying process parameters are: plasma gas argon flow rate 49slpm, plasma The gas hydrogen flow rate is 9slpm, the current is 660A, the power is 48kW, the powder feeding carrier gas argon flow rate is 4slpm, the powder feeding rate is 35g/min, and the spraying distance is 110mm. The substrate and the front of the coating are cooled by compressed air, including spray gun cooling air (0.2MPa) and Venturi cooling air (0.4MPa), the back of the substrate is cooled by circulating water, the flow rate is 0.1L/s, and the actual deposition temperature of spraying Control at 200±20℃. The thickness of the sprayed amorphous ceramic coating is 760μm. The Al ₂ O ₃ -YAG deep eutectic system is constructed by plasma spraying with a greater degree of subcooling, so that the actual deposition temperature is lower than the glass transition temperature, the eutectic phase stops growing, and Al ₂ O ₃ -YAG amorphous is obtained in situ The schematic diagram of the oxide ceramic coating is shown in Figure 5. The XRD analysis shows (see Figure 6): The actual sprayed Al ₂ O ₃ -YAG composite ceramic coating is mainly composed of an amorphous phase, of which the content of the amorphous phase is 94% and contains a very small amount of α-Al ₂ O ₃ and YAG grains.

Example 2

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

The spray granulation Al ₂ O ₃ /Y ₂ O ₃ composite powder preparation method is the same as in Example 1, except that the mass fraction of Al ₂ O ₃ powder is 50%, and the mass fraction of Y ₂ O ₃ powder is 50%. ；

(2) Heat treatment in situ solid phase reaction to obtain Al ₂ O ₃ /YAG composite powder

The granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained in step (1) is heat-treated, and the heat-treatment method is the same as that in Example 1, except that the heat-treatment temperature is 1600° C. and the heat preservation is 2 hours;

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidization is performed on the Al ₂ O ₃ /YAG composite powder obtained in step (2). Using argon and hydrogen as plasma gas, the specific process parameters are: argon flow 37slpm, hydrogen flow 7slpm, current 500A, power 35kW, powder carrier gas argon flow 4slpm, powder feeding rate 10g/min, spraying distance 230mm. The Al ₂ O ₃ /YAG composite powder is sent into the center of the plasma flame stream and sprayed into room temperature deionized water. The composite powder in deionized water is filtered, dried and sieved in the same way as in Example 1, and the particle size distribution range is 20-40 μm, which is suitable for thermal spraying.

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

Plasma spraying is used to deposit the Al ₂ O ₃ /YAG composite powder prepared in step (3) on the surface of the cleaned and sandblasted high-strength graphite substrate. The spraying process parameters are: plasma gas argon flow rate 49slpm, plasma The gas hydrogen flow rate is 10slpm, the current is 640A, the power is 47kW, the powder feeding carrier gas argon flow rate is 4slpm, the powder feeding rate is 35g/min, and the spraying distance is 110mm. The front of the substrate and the coating are cooled by compressed air, including spray gun cooling air (0.3MPa) and Venturi cooling air (0.35MPa), the back of the substrate is cooled by circulating water, the flow rate is 0.2L/s, and the actual deposition temperature of spraying Control at 180±20℃. The thickness of the sprayed amorphous ceramic coating is 420μm. The TEM analysis shows that the selected area electron diffraction of most areas of the sprayed coating shows obvious amorphous halo characteristics (see Figure 7). Therefore, the sprayed Al ₂ O ₃ -YAG coating is mainly composed of an amorphous phase. The cross-sectional morphology of the coating shows: high density, low porosity, and good interface bonding (see Figure 9). The Al, Y, and O elements in the coated amorphous matrix are evenly distributed (see Figure 10).

Example 3

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

The spray granulation Al ₂ O ₃ /Y ₂ O ₃ composite powder preparation method is the same as that in Example 1, except that the mass fraction of Al ₂ O ₃ powder is 60%, and the mass fraction of Y ₂ O ₃ powder is 40%. ；

(2) Heat treatment in situ solid phase reaction to obtain Al ₂ O ₃ /YAG composite powder

The granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained in step (1) is heat-treated, and the heat-treatment method is the same as that in Example 1, except that the heat-treatment temperature is 1400° C. and the heat preservation is 4 hours;

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidization is performed on the Al ₂ O ₃ /YAG composite powder obtained in step (2). Using argon and hydrogen as plasma gas, the specific process parameters are: argon flow 40slpm, hydrogen flow 6slpm, current 400A, power 28kW, powder carrier gas argon flow 4slpm, powder feed rate 15g/min, spray distance 300mm. The Al ₂ O ₃ /YAG composite powder is sent into the center of the plasma flame stream and sprayed into room temperature deionized water. The composite powder in deionized water is filtered, dried and sieved in the same way as in Example 1, and the particle size distribution range is 20-40 μm, which is suitable for thermal spraying.

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

Plasma spraying is used to deposit the Al ₂ O ₃ /YAG composite powder prepared in step (3) on the surface of the cleaned and sandblasted high-strength graphite substrate. The spraying process parameters are: plasma gas argon flow rate 49slpm, plasma Gas hydrogen flow rate is 8slpm, current is 680A, power is 49kW, powder feeding carrier gas argon flow rate is 4slpm, powder feeding rate is 32g/min, spraying distance is 120mm. The substrate and the front of the coating are cooled by compressed air, including spray gun cooling air (0.2MPa) and Venturi cooling air (0.4MPa), the back of the substrate is cooled by circulating water, the flow rate is 0.15L/s, and the actual deposition temperature of spraying Control at 220±20℃. The obtained sprayed Al ₂ O ₃ -YAG coating is mainly composed of amorphous phase and has a thickness of 510 μm.

The DSC differential thermal analysis of the sprayed Al ₂ O ₃ -YAG coating (see Figure 8) shows that there are two obvious exothermic peaks (T _p1 and T _p2 ), corresponding to YAG and α-Al ₂ O _{3 respectively} Phase crystallization process. Under different heating rates (5K/min, 10K/min, 20K/min, 30K/min), non-isothermal crystallization kinetics is used to study the characteristic temperature (T _g : glass transition temperature of the amorphous coating; T _c1 : YAG phase crystallization initial temperature; T _p1: YAG phase crystallization peak temperature; T _c2: crystallization initiation temperature α-Al ₂ O _{3 phase; T p2: α-Al 2} O 3 phase crystallization peak The relationship between temperature) and heating rate β (see Figure 11-13), the function relationship diagram between the crystallization activation energy E(x) and the crystallization volume fraction x of YAG and α-Al ₂ O ₃ phases is obtained . The function diagram of E(x)-x shows (see Figure 14): YAG phase growth process is difficult, α-Al ₂ O ₃ phase nucleation process is the most difficult, these factors are conducive to promoting Al ₂ O ₃ -YAG amorphous High temperature microstructure stability of the coating. Compared with the crystallization kinetics data of 30 amorphous materials (ceramics, alloys, polymers, etc.) publicly reported in the literature, the Al ₂ O ₃ -YAG amorphous coating prepared by the present invention has a higher glass transition temperature (T _g ), crystallization initial temperature (T _c ), peak temperature (T _p ), crystallization activation energy (E _c ) and nucleation resistance (E _c /RT _g ), see Table 1 in Figure 27 (using Kissinger method). In summary, the comparison of crystallization kinetics data shows that the Al ₂ O ₃ -YAG amorphous ceramic coating prepared by the present invention has excellent high temperature microstructure stability, and has good performance under high temperature and high PV wear conditions. Application potential.

Example 4

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

The spray granulation Al ₂ O ₃ /Y ₂ O ₃ composite powder preparation method is the same as in Example 1, except that the mass fraction of Al ₂ O ₃ powder is 55%, and the mass fraction of Y ₂ O ₃ powder is 45%. ；

(2) Heat treatment in situ solid phase reaction to obtain Al ₂ O ₃ /YAG composite powder

The granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained in step (1) is heat-treated, and the heat-treatment method is the same as that in Example 1, except that the heat-treatment temperature is 1550° C. and the heat preservation is 2 hours;

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidization is performed on the Al ₂ O ₃ /YAG composite powder obtained in step (2). Using argon and hydrogen as plasma gas, the specific process parameters are: argon flow 32slpm, hydrogen flow 4slpm, current 380A, power 23kW, powder carrier gas argon flow 3.5slpm, powder feed rate 8g/min, spray distance 250mm . The Al ₂ O ₃ /YAG composite powder is sent into the center of the plasma flame stream and sprayed into room temperature deionized water. The composite powder in deionized water is filtered, dried, and sieved. The method is the same as that of Example 1, and the particle size distribution range is 20-40 μm, which is suitable for thermal spraying;

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

Plasma spraying is used to deposit the Al ₂ O ₃ /YAG composite powder prepared in step (3) on the surface of the cleaned and sandblasted high-strength graphite substrate. The spraying process parameters are: plasma gas argon flow rate 46slpm, plasma Gas hydrogen flow is 7slpm, current is 670A, power is 46kW, powder-feeding carrier gas argon flow is 3.5slpm, powder-feeding rate is 37g/min, and spraying distance is 110mm. The substrate and the front of the coating are cooled by compressed air, including spray gun cooling air (0.3MPa) and Venturi cooling air (0.4MPa), the back of the substrate is cooled by circulating water, the flow rate is 0.2L/s, and the actual deposition temperature of spraying Control at 160±20℃. The obtained sprayed Al ₂ O ₃ -YAG coating is mainly composed of amorphous phase and has a thickness of 350 μm.

The non-isothermal crystallization kinetics of the coating prepared above is studied. The crystallization activation energy (E _c ) of the YAG and α-Al ₂ O ₃ phases are 820.7 kJ/mol and 1849.5 kJ/mol, respectively, which are much larger than the current ones. Publicly reported crystallization activation energy values of other amorphous materials. The calculation result of the brittleness index F shows (see Figure 15): The average value of the brittleness index F of the prepared Al ₂ O ₃ -YAG amorphous ceramic coating is 41, indicating that the amorphous ceramic coating is near the glass transition temperature. The configuration change is small, therefore, it has good high-temperature microstructure stability and toughness (F>100, brittle material; 30<F<100, material with good toughness; 16<F<30, excellent toughness material).

Compare the Al ₂ O ₃ -YAG amorphous ceramic coating prepared in Example 4 of the present invention with the Al ₂ O ₃ coating and the Al ₂ O ₃ -Cr ₂ O ₃ coating, and measure the thermal diffusion coefficient of each coating Changes with temperature. The results show that the thermal diffusivity of the sprayed Al ₂ O ₃ -YAG amorphous ceramic coating is higher (see Figure 16), which means it has better thermal conductivity.

The fracture toughness of Al ₂ O ₃ -YAG amorphous ceramic coating, Al ₂ O ₃ -Cr ₂ O ₃ coating and Al ₂ O ₃ coating are 4.3±0.5MPa·m ^1/2 and 2.7±0.4MPa· m ^1/2 and 1.6±0.2MPa·m ^1/2 (see Figure 17). It can be seen that the prepared Al ₂ O ₃ -YAG amorphous ceramic coating has higher fracture toughness.

Example 5

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

The preparation method of the spray granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder is the same as that in Example 1, except that: polyacrylamide is used as the dispersant;

(2) Heat treatment in situ solid phase reaction to obtain Al ₂ O ₃ /YAG composite powder

The granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained in step (1) is heat-treated, and the heat treatment method is the same as in Example 1. The obtained composite powder is composed of α-Al ₂ O ₃ and YAG, The YAG phase forms a network structure in the composite powder;

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidization is performed on the Al ₂ O ₃ /YAG composite powder obtained in step (2). The method of plasma spheroidization is the same as that of Example 1, and then filtered, dried, and sieved, the method is the same as that of Example 1. Similarly, the particle size distribution range is 20-40μm, which is suitable for thermal spraying;

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

The Al ₂ O ₃ /YAG composite powder prepared in step (3) is deposited on the surface of the cleaned and sandblasted stainless steel substrate by plasma spraying. The spraying process parameters are: plasma gas argon flow rate 53slpm, plasma gas hydrogen The flow rate is 7slpm, the current is 610A, the power is 46kW, the powder feeding carrier gas argon flow rate is 4slpm, the powder feeding rate is 36g/min, and the spraying distance is 120mm. The front of the substrate and the coating are cooled by compressed air, including spray gun cooling air (0.1MPa) and Venturi cooling air (0.3MPa), the back of the substrate is cooled by liquid nitrogen, and the actual deposition temperature of spraying is controlled at 120±20℃. The obtained sprayed Al ₂ O ₃ -YAG coating is mainly composed of amorphous phase and has a thickness of 300 μm.

The non-isothermal crystallization kinetics of the coating prepared above is studied. The crystallization activation energy (E _c ) of the YAG and α-Al ₂ O ₃ phases are 830.6 kJ/mol and 1860.3 kJ/mol, respectively, which are much larger than the current ones. Publicly reported crystallization activation energy values of other amorphous materials. This means that the Al ₂ O ₃ -YAG amorphous ceramic coating has excellent high temperature microstructure stability.

Compare the Al ₂ O ₃ -YAG amorphous ceramic coating prepared by the present invention with the Al ₂ O ₃ coating and Al ₂ O ₃ -Cr ₂ O ₃ coating to measure the friction and wear of the coating under high PV value performance. Under the conditions of a load of 2000N and a speed of 500rpm, the Al ₂ O ₃ -YAG amorphous ceramic coating shows a more stable friction coefficient and a lower wear surface temperature (see Figure 18). After abrasion, only the surface of the Al ₂ O ₃ -YAG amorphous ceramic coating is intact and smooth, without peeling, cracking, and bubbling. However, the surface of the Al ₂ O ₃ coating and the Al ₂ O ₃ -Cr ₂ O ₃ coating cracked, and obvious grid-like cracks appeared, indicating that the coating has failed (see Figure 19). Further analysis showed that some plastic deformation bands or dimples appeared on the wear surface of the Al ₂ O ₃ -YAG amorphous ceramic coating (see Figure 20). This indicates that the Al ₂ O ₃ -YAG amorphous ceramic coating has high strength and toughness, and can relieve the stress concentration during the wear process through a certain surface plastic deformation, and release a part of the stress, thereby ensuring the surface integrity and wear resistance. Reliability and longevity.

Example 6

A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable with high-temperature microstructures. The method includes the following steps:

(1) Preparation of Al ₂ O ₃ /Y ₂ O ₃ composite powder

The preparation method of spray granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder is the same as that in Example 1. The obtained granulated powder is composed of α-Al ₂ O ₃ and cY ₂ O ₃ ;

(2) Heat treatment in situ solid state reaction to obtain Al ₂ O ₃ /YAG composite powder

The granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder obtained in step (1) is heat-treated, and the heat treatment method is the same as in Example 1. The obtained composite powder is composed of α-Al ₂ O ₃ and YAG, The YAG phase forms a network structure in the composite powder;

(3) Plasma spheroidizing treatment of composite powder

Plasma spheroidization is performed on the Al ₂ O ₃ /YAG composite powder obtained in step (2). The method of plasma spheroidization is the same as that of Example 1, and then filtered, dried, and sieved, the method is the same as that of Example 1. Similarly, the particle size distribution range is 20-40μm, which is suitable for thermal spraying;

(4) Obtain Al ₂ O ₃ -YAG amorphous ceramic coating in situ by thermal spraying

Plasma spraying is used to deposit the Al ₂ O ₃ /YAG composite powder prepared in step (3) on the surface of the stainless steel substrate that has been cleaned and sandblasted. The spraying process parameters are: plasma gas argon flow rate 48slpm, plasma gas hydrogen Flow rate 10slpm, current 700A, power 50kW, powder feeding carrier gas argon flow rate 4slpm, powder feeding rate 35g/min, spraying distance 110mm. The substrate and the front of the coating are cooled by compressed air, including spray gun cooling air (0.1MPa) and Venturi cooling air (0.2MPa), the back of the substrate is cooled by liquid nitrogen, and the actual deposition temperature of spraying is controlled at 140±20℃. The obtained sprayed Al ₂ O ₃ -YAG coating is mainly composed of amorphous phase and has a thickness of 270 μm.

The non-isothermal crystallization kinetics of the coating prepared above is studied. The crystallization activation energy (E _c ) of the YAG and α-Al ₂ O ₃ phases are 807.6 kJ/mol and 1836.0 kJ/mol, respectively, which are much larger than the current ones. Publicly reported crystallization activation energy values of other amorphous materials. This means that the Al ₂ O ₃ -YAG amorphous ceramic coating has excellent high temperature microstructure stability.

The Al ₂ O ₃ -YAG amorphous ceramic coating prepared by the invention has excellent salt spray corrosion resistance, which benefits from the coating's amorphous phase matrix, high density and strong interface bonding. After 1000 hours of neutral salt spray corrosion test, the surface of Al ₂ O ₃ -YAG amorphous ceramic coating is almost intact, while Al ₂ O ₃ coating, Y ₂ O ₃ coating, Al ₂ O ₃ -Cr ₂ O ₃ Large areas of rust spots appeared on the coating surface (see Figure 21).

Comparison 1

In order to fully illustrate the superiority of the preparation method of the amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable at high temperature, an Al ₂ O ₃ -Y ₂ O ₃ coating was also prepared as a comparative example. Using micron-sized Al ₂ O ₃ powder (15～45μm) and Y ₂ O ₃ powder (15～45μm) as raw materials, direct mechanical mixing is used to prepare composite powder, in which the mass fraction of Al ₂ O ₃ powder is 67 %, the mass fraction of Y ₂ O ₃ powder is 33%, and the composition ratio is the same as in Example 1. The Al ₂ O ₃ -Y ₂ O ₃ composite coating was prepared by plasma spraying, and the preparation process parameters were the same as in Example 1. The phase composition of the sprayed coating is: α-Al ₂ O ₃ , γ-Al ₂ O ₃ , cY ₂ O ₃ , mY ₂ O ₃ and a small amount of YAM, YAP, YAG. In addition, the coating is not an amorphous coating, but a crystalline phase coating, and the composition is uneven.

The performance of Al ₂ O ₃ coating, Al ₂ O ₃ -Y ₂ O ₃ coating and Al ₂ O ₃ -YAG amorphous ceramic coating prepared by the present invention (Example 1 and Example 6) were compared: ① After 1000 hours of salt spray corrosion test, the surface of Al ₂ O ₃ -Y ₂ O ₃ coating has a large area of rust, while the surface of Al ₂ O ₃ -YAG amorphous ceramic coating is almost intact (see Figure 21); Repeated thermal shock assessment from room temperature cold water to 500℃, the number of thermal shocks when the Al ₂ O ₃ coating, Al ₂ O ₃ -Y ₂ O ₃ coating, and Al ₂ O ₃ -YAG amorphous ceramic coating first peeled off respectively It is: 29 times, 41 times, 67 times (see Figure 22). Therefore, the thermal shock resistance of Al ₂ O ₃ -Y ₂ O ₃ coating is not as good as that of Al ₂ O ₃ -YAG amorphous ceramic coating; ③ Under the conditions of 2000N and 500rpm, the surface of the Al ₂ O ₃ -YAG amorphous ceramic coating is intact, without peeling, cracking, and bubbling. However, the surface of the Al ₂ O ₃ coating and the Al ₂ O ₃ -Y ₂ O ₃ coating cracked, and obvious grid-like cracks appeared, indicating that the coating has failed (see Figure 23).

Comparison 2

The Al ₂ O ₃ -YAG amorphous ceramic coating was obtained according to the preparation method of Example 1, except that the substrate was a high-temperature alloy (GH3128). Heat treatment at 1200°C for different times, the purpose is to crystallize the coating completely, thereby obtaining a eutectic coating. However, with the volume change, there is a large thermal stress between the superalloy substrate with high thermal expansion coefficient, which causes the coating to crack and peel (see Figure 24), and it is impossible to carry out subsequent wear and service under severe conditions.

Comparison 3

First follow the step (1) in Example 1 to obtain granulated Al ₂ O ₃ /Y ₂ O ₃ composite powder. The difference is that the Al ₂ O ₃ /YAG composite is obtained by in-situ solid phase reaction without heat treatment in step (2) The powder and the step (3) plasma spheroidization treatment of the composite powder, and directly follow the step (4) in Example 1 to obtain the sprayed Al ₂ O ₃ -YAG amorphous ceramic coating.

The XRD and DSC analysis of the above-mentioned sprayed Al ₂ O ₃ -YAG amorphous ceramic coating show that: ① The amorphous phase content of the coating is 54% (see Figure 25), which is significantly lower than that of the coating prepared in Example 1. The content of amorphous phase contained; ② The glass transition temperature of the coating is 508°C (see Figure 26), which is also significantly lower than the glass transition temperature of the coating prepared in Example 3 (T _g =893°C).

Comparison 4

Preparation of Al ₂ O ₃ coating: direct use of micron-sized fused crushed Al ₂ O ₃ powder for plasma spraying, Al ₂ O ₃ powder median particle size D ₅₀ = 17.5μm, plasma spray parameters embodiment In Example 4, the process parameters for preparing Al ₂ O ₃ -YAG amorphous ceramic coating are the same.

Comparison 5

Preparation of Y ₂ O ₃ coating: directly use micron agglomerated and granulated Y ₂ O ₃ powder for plasma spraying. The median diameter of Y ₂ O ₃ powder is D ₅₀ =28 μm. Plasma spraying parameters and implementation In Example 4, the process parameters for preparing Al ₂ O ₃ -YAG amorphous ceramic coating are the same.

Comparison 6

Preparation of Al ₂ O ₃ -Cr ₂ O ₃ coating: Direct mechanical mixing of Al ₂ O ₃ and Cr ₂ O ₃ powders that are melted and crushed in micrometers, the mass fraction of Cr ₂ O ₃ is 70wt.%, and Al The mass fraction of ₂ O ₃ is 30wt.%. The median diameters of Al ₂ O ₃ and Cr ₂ O ₃ powders are D ₅₀ =17.5 μm and D ₅₀ =16.7 μm, respectively. The plasma spraying parameters are the same as those of Al ₂ O ₃ -YAG amorphous ceramic coating prepared in Example 4. The layer process parameters are the same.

Although the present invention has been disclosed as above in preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can use the methods and technical content disclosed above to improve the present invention without departing from the spirit and scope of the present invention. Possible changes and modifications to the technical plan. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solutions of the present invention belong to the protection scope of the technical solutions of the present invention.

Claims (10)

1. A method for preparing an amorphous oxide ceramic composite coating that is tough, thermally conductive, and stable at high temperature, and is characterized in that the amorphous oxide ceramic composite coating is Al ₂ O ₃ -YAG amorphous ceramic Coating, the preparation method includes:

   (1) Mix Al ₂ O ₃ powder and Y ₂ O ₃ powder to obtain Al ₂ O ₃ /Y ₂ O ₃ mixed powder;

   (2) After heat treatment of the obtained Al ₂ O ₃ /Y ₂ O ₃ mixed powder at 1400-1600° C., an Al ₂ O ₃ /YAG composite powder is obtained;

   (3) Spraying the obtained Al ₂ O ₃ /YAG composite powder on the surface of the substrate by thermal spraying to obtain the Al ₂ O ₃ -YAG amorphous ceramic coating.
2. The preparation method according to claim 1, wherein in step (1), the mass fraction of Al ₂ O ₃ powder in the Al ₂ O ₃ /Y ₂ O ₃ mixed powder ranges from 50% to 67% , The mass fraction of Y ₂ O ₃ powder ranges from 33% to 50%; preferably, the main crystal phase of the Al ₂ O ₃ powder is α-Al ₂ O ₃ , and the main crystal phase of the Y ₂ O ₃ powder It is cY ₂ O ₃ .
3. The preparation method according to claim 1 or 2, characterized in that, in step (1), the Al ₂ O ₃ and Y ₂ O ₃ powders are wet-milled and mixed uniformly, and are prepared into a suspension stable slurry and then sprayed. To obtain Al ₂ O ₃ /Y ₂ O ₃ composite powder.
4. The preparation method according to any one of claims 1 to 3, wherein in step (1), the particle size of the Al ₂ O ₃ powder is 2 nm to 2 μm, and the particle size of the Y ₂ O ₃ powder is 2nm～2μm.
5. The preparation method according to any one of claims 1-4, wherein in step (2), the heat treatment time is 2 to 4 hours.
6. The preparation method according to any one of claims 1-5, characterized in that, before the thermal spraying, the obtained Al ₂ O ₃ /YAG composite powder is subjected to plasma spheroidizing treatment; preferably, the plasma The parameters of spheroidization treatment include: Argon and hydrogen are used as plasma gas. The specific process parameters are: Argon flow rate 30-40slpm, hydrogen flow rate 3-7slpm, current 350-500A, power 20-35kW, powder carrier gas argon The air flow rate is 3 to 4 slpm, the powder feeding rate is 5 to 15 g/min, and the spraying distance is 200 to 300 mm; more preferably, the particle size of the Al ₂ O ₃ /YAG composite powder after plasma spheroidization is 20 to 40 μm.
7. The preparation method according to any one of claims 1-6, wherein the thermal spraying is plasma spraying; the parameters of the plasma spraying include: plasma gas argon flow rate 45-55 slpm, plasma gas hydrogen flow rate 7～10slpm, current 600～700A, power 45～50kW, powder feeding carrier gas argon flow 3～4slpm, powder feeding rate 30～40g/min, spraying distance 100～120mm.
8. The preparation method according to any one of claims 1-7, wherein the deposition temperature is kept lower than the glass transition temperature of the Al ₂ O ₃ -YAG system during the thermal spraying process; preferably, a cooling form is adopted The deposition temperature of the composite coating is controlled to be lower than the glass transition temperature of the Al ₂ O ₃ -YAG system; more preferably, the cooling method includes compressed air, circulating water or liquid nitrogen cooling.
9. The preparation method according to claim 8, wherein the deposition temperature is 100-250°C.
10. The preparation method according to any one of claims 1-9, wherein the substrate is a metal substrate, a ceramic substrate, or a graphite substrate; preferably, the substrate is cleaned before spraying And sandblasting.