Method for preparing alumina-based eutectic ceramic coating via laser cladding

Abstract

A method for preparing an alumina-based eutectic ceramic coating via laser cladding uses rare earth oxide, zirconium oxide and alumina as raw materials, and prepares an alumina-based eutectic ceramic powder by a sintering reaction method or a solvent-precipitation method, the alumina-based eutectic ceramic powder is mixed with a binder, a dispersant and a defoamer to prepare a slurry, and then spheroidized and granulated to prepare an eutectic ceramic spherical feed, the colloid is removed from the spherical feed, and then laser cladding is performed on a sandblasted alumina substrate by synchronous powder feeding to prepare the alumina-based eutectic ceramic coating with few grain boundaries and strong CMAS corrosion resistance. The coating prepared by the invention has the advantages of high temperature resistance, good oxidation resistance, and excellent corrosion resistance.

Description

Method for Preparing Alumina-Based Eutectic Ceramic Coating via Laser Cladding

[0001] FIELD OF INVENTION

[0002] The present invention relates to the field of environmental barrier coating or integrated thermal / environmental barrier protective coating, and more particularly to a method for preparing an alumina-based eutectic ceramic coating via laser cladding.

[0003] DESCRIPTION OF RELATED ARTS

[0004] Advanced aviation power systems are known as the crown jewel of modern industry". They not only reflect a country's scientific and technological level and industrial foundation, but also reflect its economic and national defense strength. With the continuous development of aircraft engines, more stringent requirements have been placed on their efficiency and thrust-to-weight ratio. Increasing the temperature of the turbine front air inlet is a key technical approach to achieve a high thrust-to-weight ratio and improve efficiency. Currently, typical high-temperature structural materials widely used in aircraft engines include single crystal high-temperature alloys, SiCf / SiC ceramic-based composites, and oxide ceramic-based composites such as  . When these high-temperature structural materials are used as aircraft engine structural components, molten oxide particles (such as dust, volcanic ash, and desert sand ) are inhaled into the engine in a high temperature environment at about 1200°C, a eutectic reaction will occur to generate a low melting point glass phase CMAS (  low melting point environmental deposits). These deposits will adhere to the surface of the engine structural parts and react chemically with the high temperature structural materials, thus shortening the service life of the engine. Therefore, in order to ensure the effective service of these high temperature structural materials when used as aircraft engine structural parts, it is necessary to coat their surface with an environmental barrier coating or an integrated thermal / environmental barrier protective coating with excellent high temperature resistance, wear resistance, high temperature mechanical properties, and excellent water vapor and CMAS corrosion resistance.

[0005] Eutectic ceramics made of alumina and aluminate by directional solidification technology are regarded as new structural materials with great application potential because of their high melting point, excellent wear resistance, excellent high-temperature mechanical properties, and excellent resistance to high-temperature water vapor and CMAS corrosion. For example, the bending strength of Y3Al5O12 / Al2O3eutectic ceramics prepared by directional solidification did not decrease significantly after being kept in a 1700°C water vapor environment for 100 to 200 hours, thus demonstrating its excellent high-temperature mechanical properties and resistance to water vapor corrosion. The research of SUN et al. showed that after the eutectic ceramics prepared by directional solidification reacted in a CMAS molten salt corrosion environment at a high temperature of 1500°C for 50 hours, there was no CMAS penetration along the grain boundary, and the excellent CMAS corrosion resistance was still maintained. Current studies have revealed that the reason why the above-mentioned Y3Al5O12 / Al2O3eutectic ceramic materials have such excellent performance is mainly attributed to the strong chemical bonds between atoms in the eutectic aluminate materials and the unique eutectic microstructure:   phases are continuously distributed and intertwined along the solidification direction, and the number of high-temperature unstable defects such as grain boundaries is greatly reduced, thereby significantly improving its mechanical properties and corrosion resistance. Although Y3Al5O12 / Al2O3eutectic ceramics have excellent performance, they still face challenges when applied to ceramic protective coatings for aircraft engines. The current commonly used preparation methods, such as atmospheric plasma spraying, electron beam physical vapor deposition and supersonic flame spraying, are difficult to obtain eutectic structures with intertwined and continuous distribution.

[0006] Laser cladding is an advanced surface modification technology. Its characteristics are that by adding cladding materials to the surface of the substrate and using the extremely concentrated energy of the high-energy laser beam, the surface of the workpiece is instantly micro-melted, and the powder material preset on the surface of the workpiece or automatically transported synchronously with the laser beam is completely melted. After the laser beam scans, the substrate solidifies rapidly by self-cooling, thereby forming a dense coating chemically bonded to the substrate. By finely adjusting the power of the laser beam, the scanning speed, and the composition of the cladding material, a temperature gradient in a specific direction can be established inside the molten pool. This temperature gradient is designed to ensure that the molten material can achieve directional growth in the opposite direction of the heat flow during the solidification process. In addition, the solidification rate is one of the key factors affecting the effect of directional solidification. Therefore, by precisely controlling the scanning path and speed of the laser beam, the solidification rate of the molten pool can be adjusted to match the temperature gradient, thereby achieving the goal of directional solidification.

[0007] Based on this, this study successfully prepared an alumina-based eutectic ceramic coating with strong CMAS corrosion resistance using laser cladding technology, and further studied the CMAS corrosion resistance of the coating at a higher temperature (1500°C). The research results show that the alumina-based eutectic ceramic coating prepared in this study has a dense structure and still maintains excellent CMAS corrosion resistance at 1500°C. This achievement not only expands the application temperature range of alumina-based eutectic ceramic materials to 1500°C, but also provides strong support for the increase of the air inlet temperature of aircraft engines and the further improvement of work efficiency.

[0008] SUMMARY OF THE PRESENT INVENTION

[0009] The present invention aims to provide a method for preparing an alumina-based eutectic ceramic coating via laser cladding, wherein a ceramic coating with a dense structure and two-phase directional arrangement is prepared via laser cladding, so as to achieve the goal of protecting hot end components from CMAS corrosion at ultra-high temperatures and extend the service life of the engine.

[0010] The present invention provides a method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, the method comprises the following steps:

[0011] (1) preparing an alumina-based eutectic ceramic powder by a sintering reaction method or a solvent-precipitation method using rare earth oxide, zirconium oxide and aluminum oxide as raw materials;

[0012] (2) mixing the alumina-based eutectic ceramic powder with a binder, a dispersant, and a defoamer to prepare a slurry, and then spheroidizing and granulating to obtain  an eutectic ceramic spherical feed with tight internal bonding, good fluidity, and high sphericity;

[0013] (3) After the spherical feed obtained in the step (2) is decolloided, performing laser cladding on a sandblasted alumina substrate by synchronous powder feeding to prepare an alumina-based eutectic ceramic coating with few grain boundaries and strong CMAS corrosion resistance.

[0014] The present invention provides a method for preparing an alumina-based eutectic ceramic coating via laser cladding, wherein the eutectic component of the raw materials in the step (1) is selected from a binary eutectic of aluminum oxide Al2O3and rare earth oxide RE2O3, or a binary eutectic of aluminum oxide Al2O3and zirconium oxide ZrO2, or a ternary eutectic of aluminum oxide Al2O3, rare earth oxide RE2O3and zirconium oxide ZrO2, wherein RE is one or more of Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The raw material powder of rare earth oxide can be selected from a single powder or mixed powder of rare earth oxide, rare earth fluoride, rare earth fluoride oxide, rare earth hydroxide, rare earth carbonate and rare earth nitrate, as long as it can be finally converted into oxide; the raw material powder of aluminum oxide can be selected from a single powder or mixed powder of aluminum oxide, aluminum sulfate, aluminum carbonate and aluminum alcohol; the raw material powder of zirconium oxide can be selected from a single powder or mixed powder of zirconium oxide, zirconium oxychloride, zirconium sulfate and zirconium oxychloride; similarly, the selection of raw materials of aluminum oxide and zirconium oxide is not limited to a single powder source, as long as it can be finally converted into aluminum oxide or zirconium oxide (and its eutectic ceramic phase, for aluminum oxide). The mass fraction of Al2O3powder ranges from 10 to 90 wt%, the mass fraction of RE2O3powder ranges from 10 to 90 wt%, and the mass fraction of ZrO2powder ranges from 10 to 90 wt%, and the sum of the mass percentages is 100 wt%.

[0015] The present invention provides a method for preparing an alumina-based eutectic ceramic coating via laser cladding, wherein in the step (1), the alumina-based eutectic ceramic powder raw material can be prepared by a sintering reaction method. The raw materials are mechanically mixed and reacted with a solid phase, and the mechanical mixing can be solid phase mixing, liquid phase mixing, or a combination of other methods. Then, the raw material powder after uniform mixing is sintered. Normal pressure sintering, gas sintering, hot pressing sintering, hot isostatic pressing sintering, or a combination of these methods can be selected. The reaction temperature is 1200-1600 °C, and the holding time is 2-24 h. It can also be prepared by a solvent-precipitation method, in which alumina or aluminate is dispersed in an aqueous solution of a rare earth salt to form a slurry, and a precipitant is added to the slurry to crystallize a precursor containing rare earth and aluminum into a precipitate; the precipitate is collected by solid-liquid separation to obtain the alumina-based eutectic ceramic powder.

[0016] For preparing the alumina-based eutectic ceramic coating via laser cladding provided by the present invention, the solid content of the slurry in the step (2) is 30-70 wt%; the binder is selected from one or more of polyvinyl alcohol, paraffin, sodium lignin sulfonate and glycerol, and any binder that can enhance the molding of raw material powder in the slurry can be used, and the amount added is 0.05-5.00 wt %; the dispersant is selected from one or more of polyacrylamide, polymethacrylic acid, polyethyleneimine, sodium silicate, and polyethylene glycol, and any dispersant that can effectively prevent particle aggregation can be used, and the amount added is 0.05-5.00 wt%; the defoamer is selected from one or more of n-butanol, n-octanol, and dimethyl silicone oil, and any defoamer that can remove bubbles contained in the slurry can be used, and the amount added is 0.1-5.0 wt %.

[0017] The present invention provides a method for preparing an alumina-based eutectic ceramic coating via laser cladding, wherein the process parameters of the spheroidization granulation in the step (2) are as follows: an air inlet temperature of 100-300°C, an air outlet temperature of 100-200°C, a peristaltic pump speed of 10-30 rpm, an atomizer speed of 9000-14000 rpm, a nozzle pressure of 0.05-1.00 MPa, and an air inlet volume of 1.5-3.0 m3 / min. The selection of the above spheroidization granulation parameters can be improved and optimized according to the selection of actual components, as long as the sphericity and density of the spherical feed meet its melting and deposition in the subsequent spraying process.

[0018] For preparing the alumina-based eutectic ceramic coating via laser cladding provided by the present invention, the sintering temperature for removing the colloid from the spherical feed in the step (3) is 1000-1500°C, and the holding time is 3-10 h.

[0019] For preparing the alumina-based eutectic ceramic coating via laser cladding provided by the present invention, the alumina substrate in the step (3) is pretreated by sandblasting, and quartz sand, corundum or a combination of the two are selected as the sandblasting medium, as long as the surface roughness of the substrate after pretreatment is 2-5 μm. The laser cladding process steps in the step (3) are as follows: preheating the substrate or not, the preheating can be done by ordinary heating of the substrate or laser heating, the substrate preheating temperature is 100-1500°C, the purpose is to achieve good bonding between the spherical feed and the substrate; selecting a suitable laser power in the range of 500-12000 W to achieve melting of the spherical feed; selecting a suitable laser scanning speed in the range of 3-100 mm / s, selecting a suitable laser spot diameter in the range of 5-50 mm; selecting a suitable defocusing amount in the range of 5-50 mm; selecting a suitable powder feeding speed in the range of 0.5-10.0 r / min; and selecting a suitable overlap rate in the range of 10-90%. The above laser cladding parameters, including the laser scanning speed, laser spot diameter, defocusing amount, powder feeding speed and overlap rate, can be improved and optimized according to the actual coating thickness and morphology structure, as long as a good bonding between the coating and the substrate can be achieved.

[0020] The advantages and beneficial effects of the present invention are as follows.

[0021] (1) The present invention uses oxides or aluminates as raw materials to sequentially realize the preparation of alumina-based eutectic ceramic powder raw materials, the preparation of eutectic ceramic spherical feeds, and the laser cladding preparation of alumina-based eutectic ceramic coatings, thereby obtaining a dense ceramic coating with eutectic structure characteristics.

[0022] (2) The process of the present invention is simple and the molding speed is fast. The present invention selects to deliver the obtained spherical feed material to the vicinity of the substrate by synchronous powder feeding, and uses a high-energy laser beam to melt the feed material and clad it on the surface of the substrate. Synchronous powder feeding makes the cladding layer uniform and the work efficiency high, which is convenient for automatic control. Since the loose powder has high laser absorption rate and high thermal efficiency, a high-quality coating can be obtained.

[0023] (3) The coating prepared by the present invention has a strong interface bond with the substrate. Compared with atmospheric plasma spraying, electron beam physical vapor deposition and supersonic flame spraying, which are commonly used to prepare protective coatings, laser cladding can melt both the coating and the upper surface of the substrate, and local mutual diffusion will occur in the molten state, resulting in chemical bonding between the coating and the substrate, and a strong interface bond.

[0024] (4) In the reaction between the alumina-based eutectic ceramic coating prepared by the present invention and CMAS at 1500°C, no obvious CMAS infiltration along the grain boundaries is observed, thereby avoiding the generation of internal swelling cracks. The present invention increases the coating application temperature of alumina-based eutectic ceramic materials to 1500°C, providing material support and coating technology reserves for improving the air inlet temperature and engine efficiency of aircraft engines.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG.1 is a surface morphology of the Y3Al5O12 / Al2O3eutectic ceramic coating in Example 1;

[0027] FIG.2 is an XRD spectrum of the reaction product of the Y3Al5O12 / Al2O3eutectic ceramic coating in Example 1 after reacting with CMAS at 1500°C for 50 h;

[0028] FIG.3 is a cross-sectional morphology of the Y3Al5O12 / Al2O3eutectic ceramic coating in Example 2;

[0029] FIG.4 is a surface scanning distribution diagram of the elements of the  eutectic ceramic coating after reacting with CMAS at 1500 °C for 50 h in Example 2; wherein (a) local cross-sectional morphology, (b) Al, (c) Yb, (d) Mg, (e) Si, (f) Ca;

[0030] FIG.5 is a cross-sectional morphology of the Y3Al5O12 / Al2O3eutectic ceramic coating in Example 3;

[0031] FIG.6 is a cross-sectional morphology of the Y3Al5O12 / Al2O3eutectic ceramic coating in Example 3 after reacting with CMAS at 1500°C for 50 h;

[0032] FIG.7 is a surface scanning distribution diagram of the elements of the   eutectic ceramic coating in Comparative Example 1 after reacting with CMAS at 1500 °C for 50 h; wherein (a) local cross-sectional morphology, (b) Al, (c) Y, (d) Mg, (e) Si, (f) Ca;

[0033] FIG.8 is a cross-sectional morphology of the Y3Al5O12 / Al2O3eutectic ceramic coating in Comparative Example 2 after reacting with CMAS at 1500°C for 50 h;

[0034] FIG. 9 is a surface scanning distribution diagram of the elements of the   eutectic ceramic coating in Comparative Example 3 after reacting with CMAS at 1500 °C for 50 h; wherein (a) local cross-sectional morphology, (b) Al, (c) Yb, (d) Mg, (e) Si, and (f) Ca.

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0036] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0037] The performance test information in the following embodiments is obtained by a field emission scanning electron microscopy ( SUPRA 5 5, Zeiss, Germany) which is used to observe the surface, cross section and morphology of the prepared samples after reaction with CMAS;

[0038] X-ray diffraction analysis is made to the product after the reaction of the sample and CMAS by X-ray diffractometer (D / max-2400, Rigaku, Japan).

[0039] Example 1

[0040] Rare earth oxide Y2O3powder and Al2O3powder were used as raw materials, and Y3Al5O12 / Al2O3eutectic ceramic powder raw material was obtained by mechanical mixing and sintering reaction of the raw materials. Mechanical mixing was carried out in a planetary ball mill, and the medium was anhydrous ethanol, wherein the mass ratio of the mixed powder to anhydrous ethanol was 1:1, the ball-to-material ratio was 1:2, the ball milling speed was 160 rpm, and the mixing ball milling time was 24 h. The mixed slurry was dried at 80 °C and then sieved to obtain a uniformly mixed oxide raw material. The oxide raw material powder was subjected to a pressureless solid phase reaction at 1400 °C for 3 h to obtain Y3Al5O12(YAG) / Al2O3eutectic ceramic powder raw material.

[0041] Y3Al5O12 / Al2O3eutectic ceramic powder after solid phase reaction was prepared into the slurry and the spherical feed. The solid content of the slurry was 50 wt%; the binder was polyvinyl alcohol, and the addition amount was 0.8 wt%; the dispersant was polyethylene glycol, and the addition amount was 0.2 wt%; the defoamer was n-octanol, and the addition amount was 0.1 wt%; the ball-to-material mass ratio was 1: 1, the ball mill speed was 160 rpm, and the mixing ball milling time was 24 h. The spray granulation parameters were as follows: the inlet temperature was 250°C, the outlet temperature was 120°C, the peristaltic pump speed was 12 rpm, the atomizer speed was 9000 rpm, the nozzle pressure was 0.2 MPa, and the air inlet volume was 2.0 m3 / min. Then the high-density spherical feedstock was sintered at high temperature, the temperature was selected as 1100 °C, and the holding time was 10 h.

[0042] First, the alumina substrate was pretreated by sandblasting, and quartz sand was selected as the sandblasting medium. The surface roughness of the substrate after pretreatment was 3.0 μm. The laser cladding parameters were as follows: the substrate preheating temperature was 900 °C, the laser power was 600 W, the laser scanning speed was 9 mm / s, the laser spot diameter was 5 mm, the defocus was 17 mm, the powder feeding speed was 1.5 r / min, and the overlap rate was 40%.

[0043] The prepared alumina-based eutectic ceramic coating was tested as follows.

[0044] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 33mol% CaO-6.5mol% Al2O3-9mol%MgO-45mol%SiO2, the reaction temperature was 1500℃, the reaction time was 50h, and the CMAS coating amount was 30 mg / cm2.

[0045] As shown in FIG.1, in order to characterize the crystal structure of the alumina-based eutectic ceramic coating, the surface morphology of the obtained sample was analyzed in this embodiment. The results showed that the YAG and Al2O3phases of the coating obtained in this embodiment were evenly distributed, showing the characteristics of dendrite growth.

[0046] Referring to FIG. 2, in order to test the CMAS corrosion resistance of the sample prepared in this example, the crystal structure of the reaction product of the sample and CMAS was analyzed using an X-ray diffractometer. The results showed that a large amount of CMAS crystalline phase existed on the surface of the sample after reacting with CMAS at 1500 °C for 50 h, showing excellent high-temperature CMAS corrosion resistance.

[0047] Example 2

[0048] Using rare earth oxide Yb2O3powder and Al2O3powder as raw materials, the  eutectic ceramic powder raw material was obtained by mechanical mixing and sintering reaction of the raw materials. Mechanical mixing was carried out in a planetary ball mill, the medium was anhydrous ethanol, the mass ratio of the mixed powder to anhydrous ethanol was 1:1, the ball-to-material ratio was 1:1, the ball milling speed was 160 rpm, and the mixing ball milling time was 24 h. The mixed slurry is dried at 80 °C and then sieved to obtain a uniformly mixed oxide raw material. The oxide raw material powder was subjected to a pressureless solid phase reaction at 1500 °C for 3 h to obtain the Yb3Al5O12 / Al2O3eutectic ceramic powder raw material.

[0049] Yb3Al5O12 / Al2O3eutectic ceramic powder after solid phase reaction was prepared into the slurry and the spherical feed. The solid content of the slurry was 60 wt%; paraffin was selected as the binder, and its addition amount was 1.0 wt%; polyacrylamide was selected as the dispersant, and its addition amount was 0.5 wt%; dimethyl silicone oil was selected as the defoamer, and its addition amount was 0.5 wt%; the ball-to-material mass ratio was 1:2, the ball mill speed was 160 rpm, and the mixing ball milling time was 24 h. The spray granulation parameters were as follows: the inlet temperature was 250 °C, the outlet temperature was 120 °C, the peristaltic pump speed was 12 rpm, the atomizer speed was 10000 rpm, the nozzle pressure was 0.5 MPa, and the air intake volume was 1.5 m3 / min. Subsequently, the prepared high-density spherical feed was sintered at high temperature, the temperature was selected to be 1300 °C, and the insulation time was 3 h.

[0050] First, the alumina substrate was pretreated by sandblasting, and corundum was selected as the sandblasting medium. After pretreatment, the surface roughness of the substrate was 2.5 μm. The laser cladding parameters were as follows: the substrate preheating temperature was 400 °C, the laser power was 500 W, the laser scanning speed was 5 mm / s, the laser spot diameter was 8 mm, the defocus was 20 mm, the powder feeding speed was 3.0 r / min, and the overlap rate was 50%.

[0051] The prepared alumina-based eutectic ceramic coating was tested as follows.

[0052] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 33mol%CaO-6.5mol%Al2O3-9mol%MgO-45mol%SiO2, the reaction temperature was 1500 ℃, the reaction time was 50 h, and the CMAS coating amount was 30 mg / cm2.

[0053] A shown in FIG.3, in order to characterize the coating structure of the alumina-based eutectic ceramic coating, the cross-sectional morphology of the obtained sample was analyzed in this embodiment. The results showed that the YbAG and Al2O3phases of the coating obtained in this embodiment were evenly distributed, showing the characteristics of dendrite growth.

[0054] Referring to FIG.4, in order to test the CMAS corrosion resistance of the sample prepared in this example, the element distribution of the cross section of the sample after corrosion was observed and analyzed using a scanning electron microscope. The results showed that after the sample reacted with CMAS at 1500 °C for 50 h, there was no CMAS penetration along the grain boundary, showing excellent high-temperature CMAS corrosion resistance.

[0055] Example 3

[0056] Yttrium nitrate (Y(NO3)3) and aluminum oxide (Al2O3) are used as raw material powders, and a Y3Al5O12 / Al2O3eutectic ceramic powder raw material was prepared by a solvent-precipitation method. Aluminum oxide (Al2O3)) powder with an average particle size D50 of 5 μm was dispersed in a 0.01 mol / L yttrium nitrate aqueous solution to prepare a slurry. Next, urea was added to the slurry in an amount corresponding to 10 mol of urea per 1 mol of yttrium nitrate, and the solution was stirred to crystallize the precipitate. Then, the obtained precipitate as a precursor containing rare earth yttrium and aluminum was collected by solid-liquid separation.

[0057] Y3Al5O12 / Al2O3eutectic ceramic precipitate prepared by solvent-precipitation method was used to prepare the slurry and the spherical feed. The solid content of the slurry was 70 wt%; glycerol was selected as the binder, and its addition amount was 2.0 wt%; polyethyleneimine was selected as the dispersant, and its addition amount was 2.0 wt%; n-butanol was selected as the defoamer, and its addition amount was 1.0 wt%; the ball-to-material mass ratio was 1: 1, the ball mill speed was 160 rpm, and the mixing ball milling time was 24 h. The spray granulation parameters were as follows: the inlet temperature was 200 °C, the outlet temperature was 100 °C, the peristaltic pump speed was 10 rpm, the atomizer speed was 14000 rpm, the nozzle pressure was 0.2 MPa, and the air intake volume was 2.0 m3 / min. Then, the high-density spherical feedstock was sintered at a high temperature of 1500 °C and the holding time was 5 h.

[0058] First, the alumina substrate was pretreated by sandblasting, and quartz sand was selected as the sandblasting medium. The surface roughness of the substrate after pretreatment was 3.0 μm. The laser cladding parameters were as follows: the substrate preheating temperature was 600 °C, the laser power was 2000 W, the laser scanning speed was 30 mm / s, the laser spot diameter was 10 mm, the defocus was 30 mm, the powder feeding speed was 5 r / min, and the overlap rate was 30%.

[0059] The prepared alumina-based eutectic ceramic coating was tested as follows.

[0060] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 33mol%CaO-6.5mol%Al2O3-9mol%MgO-45mol%SiO2, the reaction temperature was 1500 ℃, the reaction time was 50h, and the CMAS coating amount was 30 mg / cm2.

[0061] As shown in FIG.5, in order to characterize the coating structure of the alumina-based eutectic ceramic coating, the cross-sectional morphology of the obtained sample was analyzed in this embodiment. The results showed that the YAG and Al2O3phases of the coating obtained in this embodiment were evenly distributed, showing the characteristics of dendrite growth.

[0062] Referring to FIG. 6, in order to test the CMAS corrosion resistance of the sample prepared in this example, the cross section of the sample after corrosion was observed using a scanning electron microscope. The results showed that after the sample reacted with CMAS at 1500 °C for 50 h, there was no CMAS penetration along the grain boundary, showing excellent high-temperature CMAS corrosion resistance.

[0063] Comparative Example 1

[0064] YAG / Al2O3eutectic ceramic spherical feed was obtained by the same method and parameters as in Example 1.

[0065] The coating was prepared by atmospheric plasma spraying on the alumina substrate after sandblasting. The parameters of atmospheric plasma spraying were as follows: the electric current was 650 A, the gas composition as 40Ar / 10H2slpm, the feed rate was 30%, and the spray distance was 110 mm.

[0066] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 3mol%CaO-6.5mol%Al2O3-9mol%MgO- , the reaction temperature was 1500 ℃, the reaction time was 50h, and the CMAS coating amount was 30 mg / cm2.

[0067] As shown in FIG.7, in order to test the CMAS corrosion resistance of the sample prepared in this embodiment, the element distribution of the cross section of the sample after corrosion was observed and analyzed using a scanning electron microscope. The results showed that after the sample reacted with CMAS at 1500 °C for 50 h, CMAS was detected to be penetrated along the grain boundary and the coating was completely penetrated, proving that the coating prepared by atmospheric plasma spraying had poor CMAS corrosion resistance.

[0068] Comparative Example 2

[0069] YAG / Al2O3eutectic ceramic spherical feed was obtained by the same method and parameters as in Example 1.

[0070] The coating was prepared by atmospheric plasma spraying on the alumina substrate after sandblasting. The parameters of atmospheric plasma spraying were as follows: the electric current was 600 A, the gas composition was 40Ar / 10H2slpm, the feed rate was 40%, and the spray distance was 90 mm.

[0071] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 3mol%CaO-6.5mol%Al2O3-9mol%MgO- , the reaction temperature was 1500 ℃, the reaction time was 50h, and the CMAS coating amount was 30 mg / cm2.

[0072] As shown in FIG. 8, in order to test the CMAS corrosion resistance of the sample prepared in this embodiment, the cross section of the sample after corrosion was observed using a scanning electron microscope. The results showed that after the sample reacted with CMAS at 1500 °C for 50 h, CMAS was detected to be penetrated along the grain boundary and the coating was completely penetrated, proving that the coating prepared by atmospheric plasma spraying had poor CMAS corrosion resistance.

[0073] Comparative Example 3

[0074] YbAG / Al2O3eutectic ceramic spherical feed was obtained by the same method and parameters as in Example 2.

[0075] The coating was prepared by atmospheric plasma spraying on the alumina substrate after sandblasting. The parameters of atmospheric plasma spraying were as follows: the electric current was 650 A, the gas composition was 40Ar / 10H2slpm, the feed rate was 30%, and the spraying distance was 110 mm.

[0076] A CMAS corrosion test was carried out on the surface of the prepared alumina-based eutectic ceramic coating. The parameters of the CMAS corrosion test were as follows: the composition of CMAS was 3mol%CaO-6.5mol%Al2O3-9mol%MgO- , the reaction temperature was 1500 ℃, the reaction time was 50h, and the CMAS coating amount was 30 mg / cm2.

[0077] As shown in FIG. 9, in order to test the CMAS corrosion resistance of the sample prepared in this embodiment, the element distribution of the cross section of the sample after corrosion was observed and analyzed using a scanning electron microscope. The results showed that after the sample reacted with CMAS at 1500 °C for 50 h, CMAS was detected to be penetrated along the grain boundary and the coating was completely penetrated, proving that the coating prepared by atmospheric plasma spraying had poor CMAS corrosion resistance.

[0078] Although the present invention has been disclosed as above with some embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the main purpose and scope of the present invention. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, comprising the following steps:(1) preparing an alumina-based eutectic ceramic powder by a sintering reaction method or a solvent-precipitation method using rare earth oxide, zirconium oxide and aluminum oxide as raw materials;(2) mixing the alumina-based eutectic ceramic powder with a binder, a dispersant, and a defoamer to prepare a slurry, and then spheroidizing and granulating to obtain an eutectic ceramic spherical feed; and(3) After the eutectic ceramic spherical feed obtained in the step (2) is decolloided, performing laser cladding on a sandblasted alumina substrate by synchronous powder feeding to prepare an alumina-based eutectic ceramic coating.

2. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein an eutectic component of the raw materials in the step (1) is selected from a binary eutectic of aluminum oxide Al2O3and rare earth oxide RE2O3, or a binary eutectic of aluminum oxide Al2O3and zirconium oxide ZrO2, or a ternary eutectic of aluminum oxide Al2O3, rare earth oxide  and zirconium oxide ZrO2, wherein RE is one or more of Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, wherein a raw material powder of rare earth oxide is selected from a single powder or mixed powder of rare earth oxide, rare earth fluoride, rare earth fluoride oxide, rare earth hydroxide, rare earth carbonate and rare earth nitrate; wherein a raw material powder of aluminum oxide is selected from a single powder or mixed powder of aluminum oxide, aluminum sulfate, aluminum carbonate and aluminum alcohol; wherein a raw material powder of zirconium oxide is selected from a single powder or mixed powder of zirconium oxide, zirconium oxychloride, zirconium sulfate and zirconium oxychloride.

3. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 2, wherein a mass fraction of Al2O3powder ranges from 10 to 90 wt%, a mass fraction of RE2O3powder ranges from 10 to 90 wt%, and a mass fraction of ZrO2powder ranges from 10 to 90 wt%, and a sum of the mass percentages is 100 wt%.

4. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein in the sintering reaction method, a reaction temperature is 1200-1600 °C, and a holding time is 2-24 h.

5. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein in the solvent-precipitation method, alumina or aluminate is dispersed in an aqueous solution of a rare earth salt to form a slurry, and a precipitant is added to the slurry to crystallize a precursor containing rare earth and aluminum into a precipitate, the precipitate is collected by solid-liquid separation to obtain the alumina-based eutectic ceramic powder.

6. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein a solid content of the slurry in the step (2) is 30-70 wt%;  the binder is selected from one or more of polyvinyl alcohol, paraffin, sodium lignin sulfonate an glycerol, and an amount added is 0.05-5.00 wt %;  the dispersant is selected from one or more of polyacrylamide, polymethacrylic acid, polyethyleneimine, sodium silicate, and polyethylene glycol, and an amount added is 0.05-5.00 wt%;  the defoamer is selected from one or more of n-butanol, n-octanol, and dimethyl silicone oil, and an amount added is 0.1-5.0 wt %.

7. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein process parameters of the spheroidizing and granulating step in the step (2) are as follows: an air inlet temperature ranges from 100-300 °C, an air outlet temperature ranges from 100-200 °C, a peristaltic pump speed ranges from 10-30 rpm, an atomizer speed ranges from 9000-14000 rpm, a nozzle pressure ranges from 0.05-1.00 MPa, and an air inlet volume ranges from 1.5-3.0 m3 / min.

8. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein a sintering temperature for removing a colloid from the eutectic ceramic spherical feed in the step (3) is 1000-1500°C, and the holding time is 3-10 h.

9. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein quartz sand, corundum or a combination of the two are selected as a sandblasting medium in the step (3).

10. The method for preparing an aluminum oxide-based eutectic ceramic coating via laser cladding, as recited in claim 1, wherein process parameters of the laser cladding in the step (3) are as follows:  a substrate preheating temperature ranges from 100-1500°C, a laser power ranges from 500-12000 W, a laser scanning speed ranges from 3-100 mm / s, a laser spot diameter ranges from 5-50 mm; a defocusing amount ranges from 5-50 mm, a powder feeding speed ranges from 0.5-10.0 r / min, and an overlap rate ranges from 10-90%.

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