阅读说明：本技术 一种适用于热喷涂的Al2O3-YAG复合粉体及其制备方法和应用 (Al suitable for thermal spraying2O3-YAG composite powder and preparation method and application thereof ) 是由 杨凯 张喆轶 荣建 庄寅 钟兴华 盛靖 陶顺衍 邵芳 丁传贤 于 2020-04-26 设计创作，主要内容包括：本发明涉及一种适用于热喷涂的Al<Sub>2</Sub>O<Sub>3</Sub>-YAG复合粉体及其制备方法和应用,所述Al<Sub>2</Sub>O<Sub>3</Sub>-YAG复合粉体的制备方法包括：(1)将Al<Sub>2</Sub>O<Sub>3</Sub>粉末和Y<Sub>2</Sub>O<Sub>3</Sub>粉末混合,得到Al<Sub>2</Sub>O<Sub>3</Sub>/Y<Sub>2</Sub>O<Sub>3</Sub>混合粉体；(2)将所得Al<Sub>2</Sub>O<Sub>3</Sub>/Y<Sub>2</Sub>O<Sub>3</Sub>混合粉体在T<Sub>1</Sub>下进行煅烧处理,得到煅烧粉体,其中900℃≤T<Sub>1</Sub>≤1000℃；(3)将所得煅烧粉体重复步骤(2)至少N-1次,设置第N次煅烧处理的煅烧温度为T<Sub>N</Sub>,且T<Sub>N</Sub>＞T<Sub>N-1</Sub>,直至T<Sub>N</Sub>为1500℃,得到所述Al<Sub>2</Sub>O<Sub>3</Sub>-YAG复合粉体,其中N≥2。(The invention relates to Al suitable for thermal spraying 2 O 3 -YAG composite powder, preparation method and application thereof, and Al 2 O 3 The preparation method of the YAG composite powder comprises the following steps: (1) mixing Al 2 O 3 Powder and Y 2 O 3 Mixing the powders to obtain Al 2 O 3 /Y 2 O 3 Mixing the powder; (2) mixing the obtained Al 2 O 3 /Y 2 O 3 Mixing the powder at T 1 Then calcining to obtain calcined powder, wherein900℃≤T 1 Less than or equal to 1000 ℃; (3) repeating the step (2) for at least N-1 times, and setting the calcination temperature of the Nth calcination treatment as T N And T is N ＞T N‑1 Up to T N At 1500 ℃ to obtain the Al 2 O 3 -YAG composite powder, wherein N is more than or equal to 2.)

1. Al (aluminum)₂O₃The preparation method of the YAG composite powder is characterized by comprising the following steps:

(1) mixing Al₂O₃Powder and Y₂O₃Mixing the powders to obtain Al₂O₃/Y₂O₃Mixing the powder;

(2) mixing the obtained Al₂O₃/Y₂O₃Mixing the powder at T₁Calcining to obtain calcined powder with temperature not lower than 900 deg.c₁≤1000℃；

(3) Repeating the step (2) for at least N-1 times, and setting the calcination temperature of the Nth calcination treatment as T_NAnd T is_N＞T_N-1Up to T_NAt 1500 ℃ to obtain the Al₂O₃-YAG composite powder, wherein N is more than or equal to 2.

2. The method according to claim 1, wherein the Al is₂O₃The main crystal phase of the powder was α -Al₂O₃Said Y is₂O₃The main crystal phase of the powder is c-Y₂O₃(ii) a The Al is₂O₃The mass fraction of the powder is 45-75 wt%, and Y₂O₃The mass fraction range of the powder is 25 wt% -55 wt%, and the sum of the mass percentages is 100 wt%.

3. The method according to claim 1 or 2, wherein Y is₂O₃The granularity of the powder is nano-scale or submicron-scale, and is preferably 20-500 nm; the Al is₂O₃Granules of powderThe degree is nano-scale or submicron scale, preferably 20-500 nm.

4. The process according to any one of claims 1 to 3, wherein T is 50 ℃ or more_N-T_N-1200 ℃ or less, preferably 50 ℃ or less T_N-T_N-1≤100℃。

5. The method according to claim 4, wherein the temperature is raised from room temperature to T for each calcination treatment when N is 2 or more₁Keeping the temperature for 1 to 4 hours under the temperature, and then heating to T DEG C_NAnd carrying out calcination treatment.

6. The method according to any one of claims 1 to 5, wherein the time for each calcination treatment is 1 to 4 hours, preferably 1.5 to 3 hours, and more preferably 2 to 3 hours.

7. The method according to any one of claims 1 to 6, wherein Al is added₂O₃/Y₂O₃Adding a binder or/and a dispersant into the mixed powder while performing wet ball milling treatment, and performing spray granulation to obtain Al₂O₃/Y₂O₃Granulating powder; preferably, the Al obtained is subjected to a first calcination treatment₂O₃/Y₂O₃Pretreating the granulated powder at 350-400 ℃ for 4-6 hours; more preferably, the binder is selected from at least one of polyvinyl alcohol, paraffin, glycerin and sodium lignosulfonate, and the dispersant is selected from at least one of sodium silicate, sodium metasilicate, sodium citrate, sodium humate, polyacrylamide, hydroxymethyl cellulose and hydroxymethyl cellulose sodium.

8. The production method according to any one of claims 1 to 7, wherein the temperature is lowered to room temperature after each calcination treatment, and the obtained calcined powder is ground; preferably, the grinding process is performed by hand grinding.

9. Al prepared by the preparation method according to any one of claims 1 to 8₂O₃-YAG composite powder.

10. Al according to claim 9₂O₃Al prepared from YAG composite powder₂O₃-YAG amorphous ceramic coating.

Technical Field

The invention relates to Al₂O₃-YAG composite powder, in particular Al suitable for thermal spraying₂O₃-YAG composite powder and a preparation method and application thereof, in particular to Al suitable for thermal spraying deposition₂O₃A preparation method of oxide powder of YAG amorphous ceramic coating, belonging to the technical field of ceramic coating.

Background

The material friction and wear (often accompanied by complex harsh working environments such as high temperature, oxygen enrichment, wide temperature range thermal shock and the like) under the condition of high PV value (load P multiplied by velocity V, usually more than or equal to 15 MPa.m/s) are key factors determining the service reliability and service life of mechanical systems such as aerospace and aeroengines, space vehicles, high-end pump valves and the like. In surface engineering, the ceramic coating is deposited on the substrate by using a thermal spraying technology, so that the performances of abrasion resistance, high temperature resistance, oxidation resistance, corrosion resistance and the like of the substrate can be obviously improved, and further, the abrasion resistance, the service reliability and the service life of related mechanical key parts are improved.

The atmospheric plasma spraying is the main process for preparing high-melting-point wear-resistant ceramic coating by thermal spraying at present, in the spraying process, powder raw materials are carried into plasma jet flow by argon/hydrogen flow in a powder feeder to be heated and accelerated, then the powder raw materials impact the surface of a base material or a coating deposited firstly at high speed in a molten or semi-molten state, and the coating with a certain thickness is formed by stacking layer by layer. The preparation process has the characteristics of high enthalpy, steep temperature gradient, high cooling rate and the like, and can deposit an amorphous coating besides a high-melting-point crystalline coating.

Under the condition of high PV value abrasion, the ceramic coating needs to bear large pressure, high friction rate and high friction heat (the highest temperature of a friction contact surface is close to or even exceeds 1000 ℃) and severe thermal shock generated by the high friction rate, so the ceramic coating applied to service under the working condition of high-bearing friction abrasion generally has the following characteristics: high fracture toughness. The coating needs to have good toughness and interface bonding to resist crack initiation and propagation caused by large stress applied under large load and high friction rate; ② good heat-conducting property. Under the condition of a high PV value, frictional heat suddenly increases, and the thermal stress between the coating and the metal substrate caused by the difference of thermal expansion coefficients is obviously increased, so that the coating needs to have good heat-conducting property to dissipate the frictional heat, reduce the thermal stress and improve the wear-resisting property of the coating; good high-temperature mechanical property and microstructure adjustable adaptability. Under the long-term high-temperature and high-stress service environment, the stability of the microstructure of the coating is difficult to maintain due to factors such as grain boundary creep, grain growth, desolvation effect, diffusible phase change and the like, and the heat conduction, mechanics and wear resistance of the coating are influenced.

In response to this harsh condition, high temperature and oxidation resistant oxides, such as Al, are typically used to prepare the coating₂O₃、Cr₂O₃、ZrO₂And TiO₂α -Al is generally selected in consideration of the requirements of heat conduction and mechanical properties₂O₃Powder (α -Al)₂O₃Has a thermal conductivity of 36 W.m^-1·K^-1Is superior to Cr₂O₃、ZrO₂And TiO₂) The wear-resistant ceramic coating is prepared from the raw materials and applied to the harsh working condition (the alumina has 8 phase forms, namely rho-Al₂O₃、χ-Al₂O₃、κ-Al₂O₃、η-Al₂O₃、γ-Al₂O₃、- Al₂O₃、θ-Al₂O₃、α-Al₂O₃Wherein, α -Al₂O₃The highest of the 8 phases of alumina) but it has been found that stable α -Al is used₂O₃The powder is used as raw material, and the main crystal phase of the coating obtained in the plasma spraying process is changed into gamma-Al₂O₃Phase (coating with small amount of α -Al₂O₃Phase). This is due to the fact that the process of depositing the powder particles on the surface of the substrate or previously deposited coating after melting is a rapid solidification process with cooling rates as high as 10⁶K/s, easily forms metastable phase, and during rapid solidification, the nucleation order of each phase in the melt is determined by the critical nucleation free energy of the solid phase, but the size of the non-solid phase free energy, so that the gamma-Al with lower critical nucleation free energy is firstly nucleated₂O₃Phase, but γ -Al₂O₃Both the mechanical property and the heat-conducting property of the alloy are far lower than α -Al₂O₃(γ-Al₂O₃The thermal conductivity is 1.6 W.m^-1·K^-1)。

Preparation of Al by thermal spraying₂O₃α -Al lifting in wear-resistant ceramic coating₂O₃The methods of phase content are mainly as follows, ① increasing the deposition temperature of the substrate, and increasing the deposition temperature can improve Al₂O₃Interface bonding of monolithic layer (splat) to substrate and monolithic layer, resulting in improved Al₂O₃The compactness, microhardness, toughness and thermal conductivity of the coating are improved, but α -Al is improved₂O₃The phase content is very limited, the deposition temperature is raised from 140 ℃ to 660 ℃, α -Al₂O₃Increasing the phase content from 20% to 26%, the improvement effect of the coating strength and toughness and thermal conductivity is limited, and the continuous increase of the deposition temperature is not suitable for preparing the coating on the surface of most metal substrates, ② laser remelting post-treatment, plasma spraying of Al₂O₃α -Al in the coating can be increased by laser remelting on the surface of the coating₂O₃The phase content is adopted, so that a cladding layer with fine tissue, low porosity and high hardness is obtained, but the consistency of the hardness, microstructure and mechanical property of the coating along the thickness direction is poor, the fracture toughness is reduced, the residual internal stress is large, the cracking failure of the coating is easily caused in the severe abrasion process, ③ raw material is nanocrystallized, and the nano α -Al is adopted₂O₃Powder prepared Al₂O₃The coating generally has higher hardness and toughness, better sliding resistance and erosion and abrasion resistance, and α -Al in the coating₂O₃The phase content can reach more than 50 percent. However, nanostructured Al under high PV abrasion conditions₂O₃④ is compounded with other oxides, utilizing Cr to enhance the stability of the coating, increasing the phonon scattering and difficult to ensure good thermal conductivity due to more crystal boundaries of the nano coating₂O₃The heat conductivity of the alloy shows positive temperature coefficient characteristics, crystal structure and solid solution characteristics along with temperature rise, composite powder is prepared by a mechanical mixing method, and Al is prepared by plasma spraying₂O₃-Cr₂O₃α -Al in the coating by using partial solid solution and heterogeneous nucleation₂O₃The phase content is increased, and the composite coating has more than single Al₂O₃Or Cr₂O₃High toughness, heat conductivity and antiwear performance of coating ⑤ amorphous Al₂O₃And (3) base composite coating. With Al₂O₃For example, the YAG amorphous coating is prepared by in-situ spraying by utilizing the characteristics of high enthalpy, steep temperature gradient and quick solidification of plasma spraying. The coating has compact structure, low porosity and good interlayer interface bonding, and the amorphous phase main body part contains more free volume and can effectively form a shear band during deformation so as to ensure that the shear band has high fracture toughness; the main body part of the amorphous structure can improve the corrosion resistance of the amorphous composite ceramic coating; meanwhile, a small amount of nano-crystalline grains dispersed in the coating can improve the mechanical property and the wear resistance of the coating. However, the preparation process requires the powder particles to be fully melted, so that the nano powder is generally selected and storedIn the problem of obtaining Al in situ₂O₃The proportion change range of an amorphous phase in the YAG amorphous coating is large, the component distribution is uneven, the content of dispersed crystal grains is high, and the stability and quality consistency of a microstructure are difficult to control.

In conclusion, the method for preparing the amorphous ceramic coating by using the nano powder is a relatively effective method, on one hand, the influence of more crystal boundaries of the nano coating on heat conduction is avoided, and on the other hand, α -Al is improved₂O₃The content of the coating ensures certain mechanical property and heat-conducting property of the coating. Such as amorphous Al₂O₃-a YAG composite coating. Amorphous Al₂O₃The YAG composite coating is a ceramic coating which can integrate toughness, heat conduction and high-temperature microstructure stability, and has excellent application prospect under the harsh working conditions of high PV value, high temperature, oxygen enrichment and wide temperature range (the phases of alumina in the coating are α -Al₂O₃YAG phase is the best oxide for high temperature creep resistance), but in the preparation of amorphous Al₂O₃The YAG composite coating has the problems that the nano-powder is too light in weight, and the mobility of the nano-powder directly transmitted by adopting gas-solid two-phase flow is poor in the atmospheric plasma spraying process, so that the gun is easily blocked and the spraying is not facilitated. The powder fluidity can be effectively improved by adopting spray granulation, but the bonding strength among powder particles is limited, agglomerated particles are easy to crack under strong powder conveying airflow, the effective deposition of a coating is influenced, and further treatment needs to be carried out on granulated powder. The problem of poor fluidity can be solved by adopting the liquid-solid two-phase transmission nano powder. However, the amorphous Al is directly prepared by the nano powder transmitted by both gas-solid two-phase and liquid-solid two-phase₂O₃YAG composite coatings all have the following drawbacks: (1) during thermal spraying, Al₂O₃/Y₂O₃The powder particles will experience different thermal histories and α -Al cannot be guaranteed₂O₃And c-Y₂O₃Can fully react in a short time to generate enough YAG phase; (2) if a YAG phase is formed in situ in the spraying process, the forms and the contents of the YAG phase are different in different powder particle molten drops, so that the uniformity of components in the final deposited coating cannot be ensured; (3) in the spraying processIn the process, α -Al₂O₃And c-Y₂O₃During the reaction to generate YAG, more heat energy is consumed, so that the practical deposition supercooling degree is reduced, the amorphous phase content in the coating is reduced, the variation amplitude is large, and the glass transition temperature is reduced.

Disclosure of Invention

In view of the above-mentioned disadvantages of the prior art, it is an object of the present invention to provide a method for thermal spraying Al₂O₃Method for preparing oxide powder of YAG amorphous ceramic coating to ensure Al₂O₃The YAG amorphous ceramic coating is effectively deposited, has high amorphous content and uniform components, thereby realizing the stable integration of toughness, heat conduction and high-temperature microstructure of the coating, and ensuring that the coating can obtain long service life and high reliability service under severe service environments such as high PV value, high temperature, strong oxidation, wide temperature range thermal shock, corrosion and the like.

In one aspect, the present invention provides an Al₂O₃The preparation method of the YAG composite powder comprises the following steps:

(1) mixing Al₂O₃Powder and Y₂O₃Mixing the powders to obtain Al₂O₃/Y₂O₃Mixing the powder;

(2) mixing the obtained Al₂O₃/Y₂O₃Mixing the powder at T₁Calcining to obtain calcined powder with temperature not lower than 900 deg.c₁≤1000℃；

(3) Repeating the step (2) for at least N-1 times, and setting the calcination temperature of the Nth calcination treatment as T_NAnd T is_N＞T_N-1Up to T_NAt 1500 ℃ to obtain the Al₂O₃YAG composite powder, wherein N is more than or equal to 2.

In the present disclosure, the Al obtained by granulation is subjected to effective solid-phase reaction diffusion control by a successive stepwise temperature rise cyclic calcination treatment₂O₃/Y₂O₃The composite powder can fully generate a series of solid phase reactions to finally generate Al₂O₃a/YAG composite powder. At the same time, regulation and control are carried out in the course of the reactionYAG phase growth form, and a uniform network structure is formed in the composite powder. By adopting the method, Al is greatly improved₂O₃The yield of YAG in the/YAG composite powder is improved while Al is avoided₂O₃Hard agglomeration of/YAG composite powder. In the above preparation process, the total number of times of calcination treatment was set to N, including: at T₁Next, the calcination treatment was performed as the first + N-1 times of repeating the step (2).

Preferably, the Al is₂O₃The main crystal phase of the powder was α -Al₂O₃Said Y is₂O₃The main crystal phase of the powder is c-Y₂O₃Wherein, α -Al₂O₃And c-Y₂O₃The phase forms of the alumina and the yttria with the most stable chemical property and better mechanical and heat-conducting properties are respectively adopted.

Preferably, the Al is₂O₃The mass fraction of the powder is 45-75 wt%, and Y₂O₃The mass fraction range of the powder is 25 wt% -55 wt%, and the sum of the mass percentages is 100 wt%.

Preferably, said Y is₂O₃The granularity of the powder is nano-scale or submicron scale, and is preferably 20-500 nm; the Al is₂O₃The particle size of the powder is nano-scale or submicron scale, and preferably 20-500 nm.

Preferably, T is not less than 50 DEG C_N-T_N-1200 ℃ or less, preferably 50 ℃ or less T_N-T_N-1Is less than or equal to 100 ℃. In the above preparation process, the temperature of each calcination treatment is increased (T)_N-T_N-1) The temperature can be the same or different, and the temperature increase distribution of each time is between 50 ℃ and 200 ℃, and the temperature of the calcination treatment in the Nth time reaches 1500 ℃.

Preferably, when N is more than or equal to 2, the temperature is increased from room temperature to T for each calcination treatment₁Keeping the temperature for 1 to 4 hours under the temperature, and then heating to T DEG C_NAnd carrying out calcination treatment.

Preferably, the time of each calcination treatment is 1 to 4 hours, preferably 1.5 to 3 hours, and more preferably 2 to 3 hours.

Preferably, Al is added₂O₃/Y₂O₃Adding a binder or/and a dispersant into the mixed powder while performing wet ball milling treatment, and performing spray granulation to obtain Al₂O₃/Y₂O₃Granulating powder;

preferably, the Al obtained is subjected to a first calcination treatment₂O₃/Y₂O₃Pretreating the granulated powder at 350-400 ℃ for 4-6 hours (aiming at fully eliminating the binder in the granulated powder);

more preferably, the binder is selected from at least one of polyvinyl alcohol, paraffin, glycerin and sodium lignosulfonate, and the dispersant is selected from at least one of sodium silicate, sodium metasilicate, sodium citrate, sodium humate, polyacrylamide, hydroxymethyl cellulose and hydroxymethyl cellulose sodium. The invention adopts a spray granulation method to prepare Al₂O₃/Y₂O₃The method has the advantages of: the spray drying operation is continuous and controllable, is suitable for drying heat-sensitive and non-heat-sensitive materials, and is suitable for drying aqueous solution and organic solvent materials, the raw material liquid can be solution, slurry, emulsion, paste and the like, the flexibility is very high, the powder quality stability is good, the powder making efficiency is high, and the prepared powder has uniform components, good physical and chemical properties and good sphericity.

Preferably, after each calcination treatment, the temperature is reduced to room temperature, and then the obtained calcined powder is ground; preferably, the grinding process is manual grinding (or manual grinding).

In another aspect, the invention also provides Al prepared by the preparation method₂O₃-YAG composite powder.

In still another aspect, the present invention also provides an Al alloy made from the above Al₂O₃Al prepared from YAG composite powder₂O₃-YAG amorphous ceramic coating.

Has the advantages that:

the invention provides Al suitable for thermal spraying deposition₂O₃The preparation method of oxide powder of YAG amorphous ceramic coating is characterized by that firstly, the nano-grade or submicron-grade powder raw material is undergone the processes of spray granulation and agglomeration to obtain micron-grade granules, then utilizing high-temp. solid-phase reaction diffusion control and successively-stepped temp. -raising circulation calcination to prepare spray-coated powder so as to obtain the Al powder suitable for hot-spray gas-solid two-phase flow transmission₂O₃YAG powder for depositing amorphous Al₂O₃YAG coating the obtained sprayable powder consists of α -Al₂O₃And the aluminum-doped Yttrium Aluminum Garnet (YAG) phase is uniformly distributed, so that the direct spraying of Al is avoided₂O₃/Y₂O₃Powder mixture of α -Al could not be obtained₂O₃And c-Y₂O₃Can fully react in a short time to generate enough YAG phase and YAG phase morphology and content which have the problem of difference in different powder particle molten drops, and simultaneously, ensures that α -Al is not caused in the spraying process₂O₃And c-Y₂O₃The reaction generates YAG while consuming more heat energy, ensuring the necessary actual deposition subcooling to achieve efficient deposition of the amorphous coating. The successive stepwise heating circulation calcining method effectively utilizes diffusion control of high-temperature stepwise solid-phase reaction, fully considers factors such as reaction temperature, diffusion rate, critical nucleation rate, crystal growth rate and the like, regulates and controls the growth form of YAG phase to form a uniform network structure in the composite powder, is favorable for promoting the uniform distribution of the phase in the composite powder and furthest forms an amorphous phase in situ, thereby effectively improving the content of the amorphous phase, improving the strength, the density and the stability of the composite powder and further improving the component uniformity and the performance consistency of the sprayed and deposited composite coating.

Drawings

FIG. 1 shows Al obtained by spray granulation₂O₃/Y₂O₃DTA curve (heating rate 5K/min) of the composite powder;

FIG. 2 is a photograph of the obtained macroscopic powder, wherein a-spray granulation powder, b-900 ℃ calcination treatment, c-1000 ℃ calcination treatment, d-1100 ℃ calcination treatment, e-1200 ℃ calcination treatment, f-1300 ℃ calcination treatment, g-1400 ℃ calcination treatment, h-1500 ℃ calcination treatment;

FIG. 3 shows the morphology of the obtained micro powder, wherein a, b-spray granulation powder, c, d-900 ℃ calcination treatment, e, f-1000 ℃ calcination treatment, g, h-1100 ℃ calcination treatment;

FIG. 4 shows the morphology of the obtained micro powder, wherein i, j-1200 ℃ calcination treatment, k, l-1300 ℃ calcination treatment, m, n-1400 ℃ calcination treatment, o, p-1500 ℃ calcination treatment;

FIG. 5 is an XRD spectrum of an original spray granulated powder and a successively stepwise temperature rise cycle calcination-treated powder (from 900 ℃ C. and gradually rising to 1500 ℃ C.);

FIG. 6 is an X-ray photoelectron spectrum (1200 deg.C, 1300 deg.C, 1500 deg.C) of a successively stepwise temperature rise cycle calcination-treated powder;

FIG. 7 shows Al as sprayed₂O₃-a (a) cross-sectional morphology and (b) surface morphology of YAG amorphous ceramic coating;

FIG. 8 shows Al as sprayed₂O₃-XRD pattern of YAG amorphous ceramic coating.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the present disclosure, Al is selected₂O₃Powder and Y₂O₃The powder is used as a raw material, high-temperature solid-phase reaction diffusion control is utilized, and Al is prepared by successive stepwise heating and cyclic calcination₂O₃-YAG composite powder to obtain composite powder suitable for thermal spraying gas-solid two-phase flow transmission for depositing amorphous Al₂O₃YAG coating, ensuring Al₂O₃YAG amorphous ceramic coating (i.e. amorphous Al)₂O₃YAG coating) and the resulting amorphous Al₂O₃The YAG coating has high amorphous content and uniform composition. Al is exemplarily described below₂O₃A preparation method of YAG composite powder.

Al₂O₃/Y₂O₃And (4) preparing mixed powder. Mixing a certain proportion of nano-grade or submicron-grade Al₂O₃And Y₂O₃Ball milling and mixing the powder by a wet method and drying to obtain Al₂O₃/Y₂O₃Mixing the powder.

Al₂O₃/Y₂O₃And (4) preparing the granulation powder. Mixing a certain proportion of nano-grade or submicron-grade Al₂O₃And Y₂O₃The powders were wet ball milled to form a uniformly mixed suspension. Then spray granulation is carried out to obtain Al₂O₃/Y₂O₃And (4) granulating powder. The nano-scale or submicron-scale raw materials can be fully retained in the agglomerated particles by adopting a spray granulation method. Wherein, a binder and a dispersant are added in suspension.

The adopted raw material is Al₂O₃Powder and Y₂O₃The powder has nanometer or submicron particle size and α -Al as the component₂O₃And c-Y₂O₃。

Al₂O₃Powder and Y₂O₃The mass percent of the powder can be 45-75% and 25-55% respectively, the main reason for adopting the two raw material powders is that ① refers to Al₂O₃-Y₂O₃The method comprises the steps of determining a composition distribution ratio corresponding to a eutectic point through an equilibrium phase diagram of a system, ② generating a pseudo-eutectic phenomenon through a large supercooling degree of plasma spraying, namely expanding a composition range of a eutectic area, ③ changing enthalpy and temperature gradient caused by the change of plasma spraying process parameters, enabling composite powder to be subjected to different thermal histories and having a certain influence on the formation of an amorphous phase, and ④ constructing a deep eutectic phenomenon through the large supercooling degree of the plasma spraying, greatly reducing the actual deposition temperature and being lower than the glass transition temperature, generating a solute trapping phenomenon, and stopping the growth of the eutectic phase, thereby greatly forming the amorphous phase.

In a single Al₂O₃/Y₂O₃In the preparation of the granulated powder, in the case of wet ball milling, the two powders are placed in a ball mill, and the raw materials are mixed by using alumina or zirconia balls, preferablyThe ball-to-material ratio of (A) is 2: 1-4: 1. In addition, a dispersant, a binder, and the like may be added. The addition amount of the dispersing agent can be 0.2-1.0% of the mass of the powder, and the addition amount of the binding agent can be 0.5-2.0% of the mass of the powder. In addition, the addition amount of the solvent can be 50-150% of the mass of the powder. The dispersant includes, but is not limited to, one or a combination of sodium silicate, sodium metasilicate, sodium citrate, sodium humate, polyacrylamide, hydroxymethyl cellulose and hydroxymethyl cellulose sodium. The binder includes, but is not limited to, one or a combination of polyvinyl alcohol, paraffin, glycerol and sodium lignosulfonate. As the solvent, one or a combination of two of water (preferably deionized water) and ethanol is included, but not limited thereto. Ball milling and mixing are carried out uniformly, suspension stable slurry is prepared, and grinding balls are removed through sieving. Then mechanically stirring at the rotating speed of 40-100 rpm, and carrying out spray granulation to obtain Al₂O₃/Y₂O₃And (3) composite powder. Preferably, centrifugal spray granulation is used. Centrifugal spray granulation can select the atomizer rotational speed to be 10000 ~ 15000rpm, and the charge pump rotational speed is 15 ~ 40rpm, and the temperature of air inlet is 200 ~ 300 ℃, and the air-out temperature is 90 ~ 120 ℃.

For Al₂O₃YAG mixed powder or Al₂O₃The YAG granulated powder is respectively subjected to successive stepwise heating and cyclic calcination treatment. Effective solid-phase reaction diffusion control is carried out by utilizing successive stepwise temperature rise cyclic calcination treatment to obtain Al by granulation₂O₃/Y₂O₃The composite powder can fully generate a series of solid phase reactions to finally generate Al₂O₃YAG composite powder; meanwhile, the growth form of YAG phase is regulated and controlled in the reaction process, and a uniform network structure is formed in the composite powder.

Preferably, the obtained granulated powder is preheated and then is subjected to successive stepwise heating and cyclic calcination treatments. The preheating temperature is 350-400 ℃, and the preheating time is 4-6 hours. The purpose of the preheating treatment is as follows: the binder in the granulated powder is heated and volatilized to remove the binder, so that impurities are prevented from being introduced into the subsequent powder during calcination treatment. The preheating treatment is carried out first, which is a further preferable operation. If the high-temperature calcination treatment is directly carried out, the binder in the granulated powder can be directly carbonized, and then impurities are introduced into the composite powder, so that certain negative effects can be generated on the structure and the performance of a subsequent coating.

The high temperature calcination process is divided into several sub-stages (e.g., N (N.gtoreq.2, preferably 3. ltoreq. N.ltoreq.9)), each sub-stage including: heating up, heat preservation and cooling down. In each cycle of heating-heat preservation-cooling stage, after the temperature is raised to the set highest temperature, the temperature is preserved for 2-4 hours, and then the temperature is cooled to the room temperature. The maximum temperature of the cyclic calcination treatment can be increased from 900 ℃ to 1000 ℃ to 1500 ℃ gradually. Preferably, every 50-150 ℃ is determined as a cyclic calcination treatment stage, and within the interval temperature range, the YAM, YAP and YAG can be ensured to be fully subjected to solid phase reaction in the respective reaction stages. Al (Al)₂O₃And Y₂O₃The solid-phase reaction process of (1) firstly generates YAM, then generates YAP and finally generates YAG. Preferably, the three compounds are initially formed at temperatures within 100 ℃. For nanoscale or submicron powders, Al³⁺The diffusion reaction distance is shorter, and the solid-phase reaction is more favorably carried out. If the temperature interval is too large, the ion diffusion reaction time is insufficient, and the yield of the intermediate compound is influenced, which affects the amount of the subsequent product. If the calcination treatment is carried out in one step, a lot of hard agglomerates are accumulated in the powder, the accumulation at high temperature is more serious, the solid-phase reaction process is influenced, and the hard agglomerates in the powder are difficult to eliminate, so that the yield of YAG is reduced finally. The benefits of the stepwise calcination are: because the powder agglomerate is crushed (i.e. ground) again after each calcination, smooth solid-phase reaction can be ensured, and hard agglomeration is effectively eliminated. In-situ high-temperature stepwise solid-phase reaction: al (Al)₂O₃+2Y₂O₃→Y₄Al₂O₉(YAM)、Al₂O₃+Y₄Al₂O₉→4YAlO₃(YAP)、 Al₂O₃+3YAlO₃→Y₃Al₅O₁₂(YAG) to obtain Al₂O₃a/YAG composite powder. Here, Al₂O₃And Y₂O₃The solid-phase reaction process of the YAG generated by the reaction is controlled by the factors such as reaction temperature, diffusion rate, critical nucleation rate, crystal growth rate and the like, wherein the temperature and the diffusion rate play the main factors. In the solid phase reaction process, for Al with different grain diameters₂O₃And Y₂O₃As for particles, the difference of effective contact areas among the particles causes the difference of the thickness of a diffusion medium required to penetrate for reaction diffusion and the diffusion rate of diffusion ions in different diffusion media at a specific temperature, so that the specific new phase forming temperature of a reaction product and an intermediate product is not a fixed value, wherein the forming temperature of a YAM phase is 900-1200 ℃, the forming temperature of a YAP phase is 1100-1300 ℃, the forming temperature of a YAG phase is 1300-1600 ℃, the phase starting reaction temperature is lower, and a reaction latent temperature difference exists between the two, but for the powder preparation link of a required phase, the temperature of a reactant is only ensured to be kept for enough time within the phase forming temperature range, the specific temperature rising system can carry out sectional temperature rise to specific temperature heat preservation treatment according to the appropriate temperature rise speed of a furnace in different temperature ranges, the growth form of the YAG phase is regulated and controlled by controlling the heat treatment temperature and the heat preservation time, so that the YAG phase forms a network structure in the composite powder₂O₃② is beneficial to improving the strength, density and stability of the composite powder, thus the composite powder can not be blown away by powder-feeding carrier gas in the transportation and spraying processes, stable molten liquid drops can be formed in plasma flame flow, and ③ promotes the uniformity of components in the sprayed and deposited composite coating.

In an alternative embodiment, in order to obtain an ideal networked composite powder structure, the granulated particles are subjected to successive stepwise heating cycle calcination treatments, and each calcination treatment is finished by manually crushing the granulated particles. The temperature range of successive stepwise temperature rise and cyclic calcination is 900-1500 ℃, and the temperature range required by new phase formation is met. The aim of multiple calcination treatments and manual crushing is to avoid the formation of strong chemical bonds between adjacent granulated particles due to solid-phase reaction, so that the particles are coarse and poor in spraying effect, and to ensure that the granulated particles are in a proper spraying particle size range while keeping the internal networking structure of the granulated particles as far as possible. In addition, the other purpose of the multiple calcination is to avoid the direct one-time heating calcination treatment to cause the reaction (more than or equal to 1400 ℃) between the granulated particles and the inner wall of the corundum crucible, and the powder forms large sintered blocks to influence the actual deposition effect of the coating.

Finally, Al generated by high-temperature solid-phase reaction₂O₃The YAG composite powder is sieved by 300 meshes and 500 meshes, and the powder with the grain diameter of 500 meshes to 300 meshes is taken as the proper spraying powder, because the grain diameter of the powder has great influence on the actual deposition effect of a spraying coating, the specific points are that when ① powder particles are too small, the flowability of the powder is weakened, the consistency and the smoothness of the powder fed into a thermal spraying flame flow in the spraying process are influenced, and the uniformity of the coating is influenced, in addition, when the too fine powder is overheated in the thermal spraying process, the flying speed of liquid drops and the spreading deposition appearance are influenced, the splashing phenomenon can be caused, the porosity of the coating is increased, the interface bonding strength between the coating layers is reduced, and the residual tensile stress is easily presented in the coating, if the spraying granulation is carried out, the granules are easy to break due to insufficient strength in a stronger powder feeding airflow, when ② powder particles are large, the melting point of the ceramic powder is higher, the retention time in the thermal spraying flame flow is in millisecond level, if the melting degree of the ceramic powder is weakened, the degree of the granules is limited, the compression stress is likely to exceed the critical stress, the cracking of the coating is easy to be larger, the interface bonding of the coating is not easy to cause, the intermediate layer cracking, the influence is caused, and the mechanical bonding of the intermediate layer is not easy to be reduced, and the intermediate layer.

In the present invention, Al is obtained₂O₃the/YAG composite powder is prepared from α -Al₂O₃And the aluminum-doped Yttrium Aluminum Garnet (YAG) phase is uniformly distributed, so that the direct spraying of Al is avoided₂O₃/Y₂O₃Powder of α -Al could not be obtained₂O₃And c-Y₂O₃Can fully react in a short time to generate enough YAG phase and YAG phase morphology and content which have difference in different powder particle molten drops, and simultaneously, ensures that α -Al is not caused in the thermal spraying process₂O₃And c-Y₂O₃The reaction generates YAG while consuming more heat energy, ensuring the necessary actual deposition subcooling to achieve efficient deposition of the amorphous coating. The successive stepwise heating circulation calcining method effectively utilizes diffusion control of high-temperature stepwise solid-phase reaction, fully considers factors such as reaction temperature, diffusion rate, critical nucleation rate, crystal growth rate and the like, regulates and controls the growth form of YAG phase to form a uniform network structure in the composite powder, is favorable for promoting the uniform phase distribution in the composite powder and furthest forms an amorphous phase in situ, thereby effectively improving the content of the amorphous phase, improving the strength, the density and the stability of the composite powder and further improving the deposition efficiency, the component uniformity and the performance consistency of the spray-deposited composite coating.

In an alternative embodiment, the Al obtained₂O₃The YAG composite powder is suitable for thermal spraying gas-solid two-phase flow transmission and is used for depositing amorphous Al₂O₃-a YAG coating. Specifically, the Al can be prepared by thermal spraying technique₂O₃-YAG amorphous ceramic coating. Wherein the thermal spraying can be plasma spraying; the parameters of the plasma spraying include: plasma gas argon gas flow 45 ~ 55slpm, plasma gas hydrogen gas flow 7 ~ 10slpm, current 600 ~ 700A, power 45 ~ 50kW, powder feeding carrier gas argon gas flow 3 ~ 4slpm, powder feeding rate 30 ~ 40g/min, spraying distance 100 ~ 120 mm.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.