阅读说明：本技术 单相置换固溶体氧化物陶瓷涂层及其制备方法 (Single-phase replacement solid solution oxide ceramic coating and preparation method thereof ) 是由 杨凯 张喆轶 庄寅 钟兴华 陶顺衍 倪金星 赵华玉 盛靖 丁传贤 于 2019-10-12 设计创作，主要内容包括：本发明涉及单相置换固溶体氧化物陶瓷涂层及其制备方法,所述单相置换固溶体氧化物陶瓷涂层的化学组成为Cr<Sub>2-δ</Sub>Al<Sub>δ</Sub>O<Sub>3</Sub>,0.29≤δ≤1.00；优选地,所述单相置换固溶体氧化物陶瓷涂层的厚度为100～700μm。(The invention relates to a single-phase replacement solid solution oxide ceramic coating and a preparation method thereof, wherein the chemical composition of the single-phase replacement solid solution oxide ceramic coating is Cr 2‑δ Al δ O 3 Delta is more than or equal to 0.29 and less than or equal to 1.00; preferably, the thickness of the single-phase replacement solid solution oxide ceramic coating is 100-700 mu m.)

1. A single-phase substitutional solid solution oxide ceramic coating with uniform composition and structure, wherein the chemical composition of the single-phase substitutional solid solution oxide ceramic coating is Cr_2-δAl_δO₃Delta is more than or equal to 0.29 and less than or equal to 1.00; preferably, the thickness of the single-phase replacement solid solution oxide ceramic coating is 100-700 mu m.

2. A method for preparing a single-phase substitutional solid solution oxide ceramic coating with uniform composition and structure according to claim 1, comprising:

(1) mixing Al₂O₃Powder and Cr₂O₃Mixing the powders, and performing heat treatment at 1700-1900 deg.CContinuously dissolving solid, and crushing to obtain sprayable single-phase continuous replacement solid solution powder;

(2) and performing plasma spheroidization on the obtained sprayable single-phase continuous replacement solid solution powder, and then coating the powder on the surface of a base material by thermal spraying to obtain the single-phase replacement solid solution oxide ceramic coating.

3. The method according to claim 2, wherein the Al is₂O₃The phase of the powder is alpha-Al₂O₃(ii) a The Al is₂O₃The particle size of the powder is nano-scale, submicron-scale or micron-scale; the Cr is₂O₃The phase of the powder is Cr₂O₃(ii) a The Cr is₂O₃The particle size of the powder is nano-scale, sub-micron scale, or micro-scale.

4. A method according to claim 2 or 3, characterized in that Al is used₂O₃Powder and Cr₂O₃The sum of the masses of the powders is 100wt%, and the Al₂O₃The mass fraction range of the powder is 10-40 percent, and the Cr content is₂O₃The mass fraction range of the powder is 60-90%.

5. The production method according to any one of claims 2 to 4, wherein the atmosphere of the heat treatment is an inert gas and oxygen; wherein the partial pressure of oxygen is above 0.02 MPa.

6. The preparation method according to any one of claims 2 to 5, wherein the particle size of the sprayable single-phase continuous replacement solid solution powder is between 10 and 60 μm.

7. The preparation method according to any one of claims 2 to 6, wherein the plasma spheroidizing process has the following process parameters: the plasma gas argon flow is 25-35 slpm, the plasma gas hydrogen flow is 3-5 slpm, the current is 350-450A, the power is 20-30 kW, the powder feeding carrier gas argon flow is 3-4 slpm, the powder feeding speed is 5-10 g/min, and the spraying distance is 200-300 mm; preferably, the sprayable single-phase continuous replacement solid solution powder after plasma spheroidizing is sieved, so that the particle size distribution of the sprayable single-phase continuous replacement solid solution powder is 10-45 mu m.

8. The production method according to any one of claims 2 to 7, wherein the thermal spraying is plasma spraying; the plasma spraying process parameters comprise: 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.

9. The production method according to any one of claims 2 to 8, wherein the substrate is a metal substrate, a ceramic substrate, or a graphite substrate.

10. The method for preparing according to any one of claims 2 to 9, wherein an actual deposition temperature is controlled to be 150 to 300 ℃ during the thermal spraying.

Technical Field

The invention relates to a single-phase replacement solid solution oxide ceramic coating with uniform components and structure and a preparation method thereof, belonging to the technical field of ceramic coatings.

Background

The ceramic coating technology is widely applied to the field of surface engineering and is an important way for improving the performances of wear resistance, high temperature resistance, oxidation resistance, corrosion resistance and the like of a substrate material. The frictional wear under the condition of high load (i.e. high PV value is load P × speed V, usually not less than 15MPa · m/s) is often accompanied by complex harsh working environments such as high temperature, oxygen enrichment, wide temperature range thermal shock, etc., and brings great challenges to the service reliability and service life of the ceramic coating. Foreign high-bearing wear-resistant ceramic coating parts are strictly forbidden to China, and the development of aerospace industry in China is greatly restricted.

In general, oxides, carbides, nitrides, borides, and the like are typical wear-resistant ceramic coating materials. For example, in common oxide wear resistant ceramic materials, Al₂O₃(in the form of. alpha. -Al)₂O₃For example, the thermal conductivity is 36 W.m^-1·K^-1) The heat conductivity of the alloy is superior to that of Cr₂O₃、ZrO₂And TiO₂。

Sintered Al₂O₃The advantages of the bulk ceramic are: high hardness, high strength, good thermal stability, oxidation resistance, high heat conductivity, alpha-Al₂O₃Is a main crystal phase and has the defects of low plastic toughness; plasma spraying of Al₂O₃The coating has the advantages that: high hardness, high strength, high temperature resistance and oxidation resistance, and has the defect of gamma-Al₂O₃The crystal phase is the main crystal phase, the heat conductivity is low, and the ductility and toughness are low. To suppress Al₂O₃The thermal conductivity coefficient of the coating is characterized by negative temperature coefficient, particularly the thermal conductivity of the coating shows attenuation trend at the temperature of more than 500 ℃, and Al is designed and prepared based on heterogeneous nucleation and partial solid solution₂O₃-Cr₂O₃Composite coating, strengthening phase interface, refining crystal grains, improving interfacial bonding between coating layers, and obtaining heatThe initial value of the conductivity is high, and the composite coating with the positive temperature coefficient characteristic is presented after the temperature is 400 ℃, so that the synchronous optimization of the heat conduction, the toughness and the wear resistance of the coating is realized.

However, it is necessary to point out the points ① Al₂O₃-Cr₂O₃The composite coating is a multiphase system coating (the coating contains gamma-Al) obtained by taking powder prepared by a mechanical mixing method as a raw material and spraying plasma₂O₃、α-Al₂O₃、Cr₂O₃) ② the characteristic of multiphase system can make the coating composition and structure appear micro-area differentiation, which brings certain problems to the reliability of long service life and quality consistency and stability under the harsh working condition of the coating, ③ the stability of long-term microstructure and performance of the coating under the working conditions of high temperature, high load, oxygen enrichment and thermal shock, which needs to be realized by the homogenization and stabilization of the coating composition, structure and performance.

Disclosure of Invention

Aiming at the defects of long service life and high reliability of the wear-resistant oxide ceramic coating in a harsh service environment, the prior art has some defects, and aiming at the problems, the invention aims to provide a single-phase replacement solid solution oxide ceramic coating with uniform components and structure and a preparation method thereof. The main purpose is to enable the sprayed coating to have single phase composition, uniform component distribution and fine control of crystal structure, and simultaneously realize synchronous optimization of heat conduction, toughness and wear resistance of the coating so as to meet the requirements of long service life and high reliability service of the wear-resistant oxide ceramic coating under the harsh working condition of high PV value.

In one aspect, the present invention provides a single phase substitutional solid solution oxide ceramic coating with uniform composition and structure, the chemical composition of which is Cr_2-δAl_δO₃Delta is more than or equal to 0.29 and less than or equal to 1.00; preferably, the thickness of the single-phase replacement solid solution oxide ceramic coating is 100-700 mu m.

In the present disclosure, single phase substitutional solid solution ceramic coatings are compositionally and structurally uniformHas the composition of Cr_2-δAl_δO₃(wherein δ is 0.29 to 1.00). In terms of crystal structure, single-phase replacement of Cr solid solution_2-δAl_δO₃Coating and single phase Cr₂O₃The coating has the same lattice framework structure. The phase in the coating presents a single-phase continuous solid solution mode, the components are uniform, the structural consistency is good, the consistency of the performance of the coating micro-area can be ensured, and the reliability and the quality stability of the long-service life of the coating under the harsh working condition can be greatly facilitated.

In another aspect, the present invention provides a method for preparing the single-phase substitutional solid solution oxide ceramic coating with uniform components and structure, comprising:

(1) mixing Al₂O₃Powder and Cr₂O₃After mixing the powder, carrying out heat treatment at 1700-1900 ℃ to realize continuous solid solution, and then crushing to obtain sprayable single-phase continuous replacement solid solution powder;

(2) and performing plasma spheroidization on the obtained sprayable single-phase continuous replacement solid solution powder, and then coating the powder on the surface of a base material by thermal spraying to obtain the single-phase replacement solid solution oxide ceramic coating.

Preferably, the Cr is₂O₃The phase of the powder is Cr₂O₃(ii) a The Cr is₂O₃The particle size of the powder is nano-scale, sub-micron scale, or micro-scale.

Preferably, the Al is₂O₃The phase of the powder is alpha-Al₂O₃(ii) a The Al is₂O₃The particle size of the powder is nano (20-100nm), submicron (150nm-1 μm), or micron (1-5 μm). Wherein, Al₂O₃The phase of the powder is alpha-Al₂O₃，Cr₂O₃The phase of the powder is Cr₂O₃With alpha-Al₂O₃The crystal structures of (A) and (B) are the same and belong to a trigonal system. alpha-Al₂O₃And Cr₂O₃Has good chemical stability and mechanical property, and the same crystal structure makes solid solution easily formed between them.

Preferably, Al is used₂O₃Powder and Cr₂O₃The sum of the masses of the powders is 100wt%, and the Al₂O₃The mass fraction range of the powder is 10-40 percent, and the Cr content is₂O₃The mass fraction range of the powder is 60-90%.

Preferably, the atmosphere of the heat treatment is inert body and oxygen; wherein the partial pressure of oxygen is above 0.02 MPa. In a specific mode of operation, Al is added before the heat treatment₂O₃Powder and Cr₂O₃Placing the mixed powder in a heating furnace, introducing inert gas (such as Ar gas) into the heating furnace to drive the original air in the furnace, and introducing pure oxygen to make O₂The partial pressure in the heating furnace reaches more than 0.02 MPa.

Preferably, the particle size of the sprayable single-phase continuous replacement solid solution powder is between 10 and 60 mu m. Specifically, cooling is performed after the completion of the heat treatment, and the solid solution Cr is continuously replaced for the single phase after cooling_2-δAl_δO₃(wherein. delta. is 0.29 to 1.00) and pulverizing (i.e., pulverizing) the resulting pulverized material to a particle size of 60 μm or less (which can be sprayed directly) or 5 μm or less (which is required to be further granulated).

Further, when granulation is required after the powder material is crushed, it is preferable to prepare a suspension-stabilized slurry and then spray-granulate the suspension-stabilized slurry. The invention adopts a spray granulation method to prepare Cr_2-δAl_δO₃The single-phase continuous solid solution powder has the advantages that: 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, the plasma spheroidizing process parameters are as follows: the plasma gas argon flow is 25-35 slpm, the plasma gas hydrogen flow is 3-5 slpm, the current is 350-450A, and the power is 2030kW, 3 ~ 4slpm of powder feeding carrier gas argon gas flow, 5 ~ 10g/min of powder feeding speed, spraying distance 200 ~ 300 mm. The purpose of plasma spheroidization is as follows: so that Cr is contained in_2-δAl_δO₃The surface layer of the single-phase continuous solid solution powder is fused and densified, the edge angle area on the surface of the powder is eliminated, better sphericity is obtained, the fluidity of the spraying powder is promoted, and the phase composition of the spraying powder is not changed. Preferably, the sprayable single-phase continuous replacement solid solution powder after plasma spheroidizing is sieved, so that the particle size distribution of the sprayable single-phase continuous replacement solid solution powder is 10-45 mu m.

Preferably, the thermal spraying is plasma spraying; the plasma spraying process parameters comprise: 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.

Preferably, the substrate is a metal substrate, a ceramic substrate, or a graphite substrate. Preferably, the substrate is cleaned and grit blasted prior to spraying.

Preferably, the actual deposition temperature is controlled to be between 150 and 300 ℃ in the thermal spraying process. If the temperature is too high, the coating is easy to generate more cracks in the spraying process, even cracks or peeling phenomena occur under the natural cooling condition, and the residual stress is too large. If the temperature is lower, the interface bonding between the single-sheet layers (splats) in the coating is not good, the porosity of the coating is increased, the hardness and the bonding strength are reduced, and the wear resistance is reduced.

The invention has the advantages and beneficial effects that:

(1) the invention obtains the single-phase continuous replacement solid solution Cr by preparing the single-phase continuous replacement solid solution powder and spraying plasma_2-δAl_δO₃Ceramic coating, which is different from Al prepared by powder spraying by the prior mechanical mixing method₂O₃-Cr₂O₃The former is a single phase continuous solid solution system, while the latter is a multiphase system. The single-phase replacement solid solution Cr obtained by the invention_2-δAl_δO₃Ceramic coatingThe micro-area differentiation of components and structures of a multi-phase coating system is effectively inhibited, so that the spray coating has single-phase composition, uniform component distribution and fine control of a crystal structure, and the reliability and quality consistency stability of long-service life under the harsh working condition of the coating are favorably improved;

(2) the invention provides a single-phase replacement solid solution oxide ceramic coating with uniform components and structure and a preparation method thereof, and simultaneously realizes synchronous optimization of heat conduction, toughness and wear resistance of the coating so as to meet the requirements of long service life and high reliability service of the wear-resistant oxide ceramic coating under the harsh working condition of high PV value.

Drawings

FIG. 1 shows high purity Al₂O₃XRD pattern of the powder;

FIG. 2 shows high purity Cr₂O₃XRD pattern of the powder;

FIG. 3 is Al₂O₃And Cr₂O₃A binary equilibrium phase diagram of (a);

FIG. 4 shows a single-phase continuous substitution solid solution of Cr_2-δAl_δO₃(wherein δ 1.00) SEM morphology of the powder after re-granulation agglomeration after crushing;

FIG. 5 is a single-phase continuous substitution solid solution of Cr_2-δAl_δO₃(wherein δ 1.00) EDS spectroscopy component analysis of the powder after re-granulation agglomeration after crushing;

FIG. 6 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ ═ 1.00) cross-sectional SEM morphology;

FIG. 7 shows a single-phase continuous substitution solid solution of Cr_2-δAl_δO₃(wherein δ is 0.77) SEM morphology of powder directly available for spray coating after crushing;

FIG. 8 shows a single-phase continuous substitution solid solution of Cr_2-δAl_δO₃(wherein delta is 0.29-1.00);

FIG. 9 is a comparison of XRD patterns of powder and coating: (a) cr (chromium) component₂O₃Coating; (b) single-phase continuous replacement of solid solution Cr_2-δAl_δO₃(wherein δ is 0.77) powder; (c) single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃，δ＝0.77)；

FIG. 10 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ ═ 0.77) and corresponding EDS spectral composition analysis (b);

FIG. 11 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ ═ 0.54) TEM structure observation;

FIG. 12 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ ═ 0.29) TEM structure observation;

FIG. 13 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ ═ 0.54) and corresponding EDS spectral composition analysis;

FIG. 14 is a photograph of an installation drawing of the resulting coated friction pair subjected to a frictional wear test;

FIG. 15a shows a single-phase-substitutional solid solution oxide ceramic coating (Cr) under 1.5Nm of initial setting conditions_2-δAl_δO₃δ ═ 0.29) friction torque curve of friction pair;

FIG. 15b shows a single-phase-replacement solid solution oxide ceramic coating (Cr) under the initial setting condition of 3.0Nm_2-δAl_δO₃δ ═ 0.29) friction torque curve of friction pair;

FIG. 15c shows a single-phase-substitutional solid solution oxide ceramic coating (Cr) under the initial setting condition of 8.0Nm_2-δAl_δO₃δ ═ 0.29) friction torque curve of friction pair;

FIG. 15d shows a single-phase-replacement solid solution oxide ceramic coating (Cr) under 10.0Nm in the initial setting condition_2-δAl_δO₃δ ═ 0.29) friction torque curve of friction pair;

FIG. 16 is a single phase replacement solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ 1.00) coefficient of friction curve (hour 1);

FIG. 17 is a drawing ofPhase-displaced solid solution oxide ceramic coating (Cr)_2-δAl_δO₃δ 1.00) coefficient of friction curve (10 th hour)

FIG. 18 shows Al prepared in comparative example 1₂O₃-Cr₂O₃XRD pattern (a) and cross-sectional SEM topography observation (b) of the composite coating, wherein Al₂O₃The mass fraction of the powder is 40%;

FIG. 19 is a single phase replacement solid solution oxide ceramic coating (Cr) under the same test conditions_2-δAl_δO₃δ 1.00) (a) friction pair and Al₂O₃-Cr₂O₃A comparison graph of friction coefficient curves of the coating (b) friction pair;

FIG. 20 is an XRD pattern of the coating obtained in comparative example 4;

FIG. 21 is an SEM topography observation of the coating obtained in comparative example 5.

Detailed Description

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

Aiming at the challenges of long service life and high reliability service of the wear-resistant oxide ceramic coating, the invention eliminates or inhibits the problems caused by the micro-area differentiation of the coating components and the structure to the reliability and consistent quality stability of the long service life under the harsh working condition of the coating.

In one embodiment of the present invention, the composition of the single-phase substitutional solid solution oxide ceramic coating is Cr_2-δAl_δO₃(abbreviated as Cr)_2-δAl_δO₃Ceramic coating), wherein delta is 0.29-1.00. The obtained coating has single phase composition, uniform component distribution and refined control of a crystal structure, and simultaneously realizes synchronous optimization of heat conduction, toughness and wear resistance of the coating so as to meet the requirements of long service life and high reliability service of the wear-resistant oxide ceramic coating under the harsh working condition of high PV value. Preferably, Cr_2-δAl_δO₃Ceramic coatingThe layer thickness can be 100 to 700 μm. The preparation method of the single-phase substitutional solid solution oxide ceramic coating with uniform components and structure provided by the invention is exemplarily described below.

Preparation of uniformly mixed Al₂O₃/Cr₂O₃Powder (mixed powder or mixed powder). Wherein Al is₂O₃The mass fraction of the powder can be 10-40%, and the Cr content can be₂O₃The mass fraction of the powder can be 60-90%, and the sum of the mass of the powder and the mass of the powder is 100 wt%. Al (Al)₂O₃Powder and Cr₂O₃The powder particle size can be nano (20-100nm), or submicron (150nm-1 μm), or micron (1-5 μm). Further, Al₂O₃The powder has many homogeneous crystals, and more than 10 kinds of variants are reported according to the research, namely alpha, beta, gamma, delta, zeta, theta, eta, NEN, chi, rho and the like. In these variants, α -Al₂O₃The powder has optimal chemical stability, highest heat conduction and mechanical properties. And, alpha-Al₂O₃And Cr₂O₃Has the same crystal structure and belongs to a trigonal system. Al (Al)³⁺Has an ionic radius of 0.0535nm and Cr³⁺Has an ionic radius of 0.0615nm, the charge numbers of the two are identical, for Al³⁺Substitution of Cr³⁺In other words, the ionic radius deviation ratio was 13%, and the above analysis showed that these factors are favorable for the formation of a continuous substitutional solid solution. In addition, Al is used to ensure the effect of forming single-phase continuous replacement solid solution in the subsequent steps₂O₃Powder and Cr₂O₃The purity of the powder should reach more than 99.9%.

In an alternative embodiment, Al₂O₃Powder and Cr₂O₃The mixing mode of the powder can be ultrasonic stirring and mixing, ball milling and mixing and the like. As an example, Al₂O₃And Cr₂O₃The powder is firstly put into ethanol or deionized water for ultrasonic stirring and dispersion, and then wet ball milling is carried out to ensure Al₂O₃Powder and Cr₂O₃The powders are mixed uniformly. As a detailed example of mixing, include: mixing Al₂O₃Powder and Cr₂O₃The powder is placed into ethanol or deionized water for ultrasonic stirring and dispersion, and the mass ratio of the two powders is as follows: al (Al)₂O₃The mass fraction range of the powder is 10-40 percent, and the Cr content is₂O₃The mass fraction range of the powder is 60-90%. The addition amount of the solvent can be 50-150% of the mass of the powder. By using ultrasonic dispersion 'cavitation effect' and combining mechanical stirring or magnetic stirring to Al₂O₃Powder and Cr₂O₃The powder is pre-dispersed in ethanol or deionized water solvent. The ultrasonic frequency is more than or equal to 20KHz, and the power density is more than or equal to 0.3W/cm²The stirring speed is more than or equal to 100rpm, and the ultrasonic stirring dispersion time is more than or equal to 2 h. More preferably, after the ultrasonic agitation and dispersion, Al is added₂O₃Powder and Cr₂O₃The mixed suspension of the powders was wet ball milled and mixed. Wherein, when wet ball milling is carried out, alumina grinding balls are adopted (so that pollution caused by grinding balls made of other materials can be avoided), and the preferred ball-to-material ratio 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. 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. Ball milling and mixing for 4-8 h to prepare suspension stable slurry, and sieving to remove grinding balls. Then filtering, drying and crushing to obtain uniformly mixed Al₂O₃/Cr₂O₃And (3) powder.

Preparation of single-phase continuous replacement solid solution Cr_2-δAl_δO₃(wherein δ is 0.29 to 1.00). Specifically, uniformly mixed Al₂O₃/Cr₂O₃The powder is put into an electric arc furnace for heating and solution treatment (namely heat treatment), and the chemical composition of the solid solution is ensured to form a single-phase continuous replacement solid solution Cr_2-δAl_δO₃. In thatUniformly mixed Al in electric arc furnace₂O₃/Cr₂O₃The powder is subjected to high-temperature heating solution treatment, and the purpose of the heat treatment is to enable Al to be subjected to solution treatment₂O₃And Cr₂O₃Fully solid-soluted, the process is Al³⁺And Cr³⁺Are substituted by each other. Based on alpha-Al₂O₃And Cr₂O₃Same crystal structure, Al³⁺And Cr³⁺The same valence, consistent electronegativity, ionic radius difference less than 15%, and the like, Al₂O₃And Cr₂O₃An infinitely substitutional solid solution can be formed. In this solid solution, Cr³⁺And Al³⁺Occupying O^2-The octahedral gaps formed. And let Al let³⁺And Cr³⁺Being able to displace one another, it is necessary to impart energy to them to move them away from the sites of the original oxide lattice. For this reason, it is important to select an appropriate temperature range for the heat treatment. Wherein the temperature of the heat treatment can be 1700-1900 ℃ for realizing Cr₂O₃With Al₂O₃Continuous solid solution of (2). Below 1700 ℃, it is not favorable for the formation of continuous substitution solid solution; above 1900 ℃, the cost is greatly increased, and the excessive temperature may cause Al₂O₃And Cr₂O₃It is noted that the heat treatment temperature is selected in consideration of two factors, ① Al₂O₃And Cr₂O₃② Al, the melting temperature of the raw material powder is reduced when the particle size is nano-scale or submicron-scale₂O₃And Cr₂O₃Tend to be below their respective melting point temperatures. The time of the heat treatment can be 12-48 hours, and the smooth completion of the solid solution process is ensured.

In an alternative embodiment, the choice of the atmosphere in which it is heat treated is also important during the heat treatment. An inert gas (e.g., Ar gas) is first introduced into the furnace to drive off the original air in the furnace. N in the air at the solid solution temperature of 1700-1900 DEG C₂Also participate in chemical reactions to form nitrides, and thus are required to be usedPerforming high-temperature protection on the inert gas; secondly, oxygen-deficient reaction is easy to occur in the process of forming the high-temperature solid solution, and oxygen deficiency can influence the chemical composition and the structural uniformity and stability of the solid solution, so that pure oxygen needs to be introduced, and the oxygen partial pressure is ensured to reach more than 0.02MPa, so that effective supplement can be achieved, and the negative influence of the high-temperature oxygen-deficient reaction on the chemical composition and the microstructure of the solid solution is avoided. After proper solution treatment temperature, solution treatment time, protective atmosphere and necessary oxygen partial pressure, single-phase continuous replacement solid solution Cr is formed_2-δAl_δO₃。

Preparing the sprayable single-phase continuous replacement solid solution powder. The single-phase continuous replacement solid solution is firstly cooled to room temperature and then is crushed into powder, and the particle size range of the crushed powder has two choices: firstly, the particle size range of the powder can be directly used for spraying a coating; secondly, the particle size range of the powder cannot be directly sprayed, and granulation and agglomeration treatment are needed, so that powder suitable for spraying is obtained. When the particle size of the crushed powder reaches dozens of microns, the requirement of common thermal spraying powder on the particle size distribution can be met. Aiming at the single-phase continuous replacement of solid solution Cr of the invention_2-δAl_δO₃The powder is suitable for thermal spraying when the particle size of the powder is below 60 mu m (when the particle size of the powder exceeds 60 mu m, insufficient melting and the phenomenon of powder inclusion can occur in the spraying process, thus influencing the compactness and bonding strength of the coating). However, the powder particle size should exceed 10 μm to ensure smooth powder feeding during the spraying process (too fine powder has poor flowability and is liable to block the nozzle of the spray gun). Similarly, the single phase can be continuously substituted for Cr solid solution_2-δAl_δO₃The particle size range of the crushed powder reaches below 5 mu m, even reaches submicron or nanometer, the powder can not be directly sprayed, and granulation and agglomeration treatment are needed, so that the powder suitable for spraying is obtained. At this time, granulation and agglomeration treatment is carried out, and the specific steps can be as follows: firstly, uniformly mixing by utilizing a wet ball mill (refer to the relevant description process in the step (1)), preparing suspension stable slurry, and sieving to remove grinding balls. Then mechanically stirring at the rotating speed of 40-100 rpm, and carrying out spray granulation to obtain a single phaseContinuous substitution of solid solution Cr_2-δAl_δO₃(wherein delta is 0.29 to 1.00). 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 ℃.

Plasma spheroidizing of the sprayable single-phase continuous replacement solid solution powder. The sprayable single-phase continuous replacement solid solution powder is subjected to plasma spheroidization to obtain the powder with certain particle size distribution, compact surface, good sphericity and good fluidity. Argon and hydrogen are used as plasma gas, and the specific process parameters of plasma spheroidization are as follows: the argon gas flow is 25-35 slpm, the hydrogen gas flow is 3-5 slpm, the current is 350-450A, the power is 20-30 kW, the powder conveying carrier gas argon gas flow is 3-4 slpm, the powder conveying speed is 5-10 g/min, and the spraying distance is 200-300 mm. Preferably, the obtained plasma-treated Cr is_2-δAl_δO₃The plasma spheroidizing method has the advantages that ① only melts the single-phase continuous replacement solid solution powder surface or subsurface obtained by heat treatment, the edge angle area of the powder surface is eliminated, better sphericity is obtained, the strength and the composition of the whole powder particle are not changed, the density of the powder particle surface layer is improved by ②, the flowability of the powder is promoted, ③ is favorable for improving the density of a deposited coating and the interface combination between single-sheet layers (splats).

Preparation of Cr by thermal spraying_2-δAl_δO₃And (3) coating the ceramic. Spheroidized Cr by using plasma obtained by thermal spraying_2-δAl_δO₃The powder is deposited on the surface of the base material to prepare single-phase continuous replacement solid solution Cr_2-δAl_δO₃And (4) coating. The substrate is not particularly limited, and includes but is not limited toLimited to metal or ceramic or graphite. Before deposition, the substrate may be cleaned and grit blasted to remove grease and adsorbates and increase the roughness of the substrate surface to improve the interfacial bonding between the coating and the substrate for deposition. The thermal spraying can be plasma spraying (the melting point of the ceramic powder is higher so as to ensure that the ceramic powder can be effectively melted in the spraying process, thereby obtaining better spreading and depositing characteristics of powder molten drops on the surface of a base material and reducing gaps and cracks between solidified sheet layers). It should be understood that other thermal spray methods such as supersonic flame spraying, detonation spraying, etc. may be used. Argon and hydrogen can be used as working gas for plasma spraying. In one example, the plasma spray parameters are: 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. Spray-coated Cr_2-δAl_δO₃The thickness of the ceramic coating is 100 to 700 μm.

The actual deposition temperature of the spraying is controlled to be 150-300 ℃, the actual deposition temperature of the coating is regulated and controlled mainly by setting the pressure and flow of cooling gas and Venturi cooling gas on a plasma spray gun, a spraying program control path, residence time, a spraying power value and the like, the main purposes are that ① controls the level of the compressive stress in the coating, the expansion of microcracks in the coating under a wide-temperature-range thermal shock condition under a high-PV-value abrasion working condition is effectively retarded, the long-term service reliability of the coating is improved, ② avoids that the interface combination between a single-chip layer (splat) and a base material and the single-chip layer is influenced by too low deposition temperature, and the proper deposition temperature of ③ is favorable for maintaining the uniformity of the coating structure.

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.