Preparation method of nano-structure zirconium oxide-aluminum oxide ceramic composite coating

Abstract

The invention relates to a preparation method of a nano-structure zirconium oxide-aluminum oxide ceramic composite coating. According to the method, aluminum microspheres are introduced into a novel spherical reactive feed of a main body YSZ powder, and triggering of an in-situ thermit reaction in a thermal spraying process is utilized, so that the novel zirconium oxide-aluminum oxide thermal protection coating which takes a doped stable zirconium oxide-based solid solution with excellent heat insulation performance as a main phase and contains a uniformly dispersed CMAS corrosion-resistant aluminum oxide component is prepared. The raw materials for feeding are low in cost, and the coating preparation process is simple. And the obtained coating has excellent comprehensive performance.

Description

Technical Field

[0001] The technical solution of the invention relates to coating of materials using doped stable zirconium oxide and aluminum oxide, specifically a method for preparing a zirconium oxide-aluminum oxide nano-ceramic composite coating. Background Art

[0002] In the aviation industry, yttria-stabilized zirconia (YSZ) coatings prepared by thermal spraying have the advantages of high melting point, low thermal conductivity, excellent mechanical properties and a thermal expansion coefficient matching that of high-temperature alloys. They have been widely used in the surface protection of hot end components such as aircraft engine turbine blades, heat shields and flame tubes.

[0003] At present, the service stability of new thermal barrier coating materials needs to be verified for a long time. The challenges faced by traditional in-service yttria-stabilized zirconia coatings mainly include higher service temperatures (above 1200°C) and more severe molten salt corrosion. In response to the above challenges, technicians in the field of thermal barrier coatings have carried out a lot of work to reduce the thermal conductivity of coatings and improve the coating's resistance to molten salt corrosion, mainly including the use of multi-element doping to reduce thermal conductivity and the preparation of an anti-CMAS protective layer on the surface of the thermal barrier coating. Yang Jing et al. (reference: CN 118420358 A) obtained spherical (Ce 0.2 Dy 0.2 Sm 0.2 Eu 0.2 Yb 0.2 )2Zr2O7 high entropy rare earth zirconate powder. Lü Bowen et al. (reference: CN 116377372 A) prepared spherical (Y 0.2 Sm 0.2 Eu 0.2 G 0.2 Yb 0.2 )2Zr2O7 high entropy rare earth zirconate powder was used in plasma physical vapor deposition process to prepare high entropy rare earth zirconate coating. Guo Hongbo et al. (reference: CN 104988455 B) prepared a CMAS-resistant LaPO4 protective surface layer on the surface of YSZ thermal barrier coating by plasma spraying. Guo Lei et al. (reference: CN 111005024A) prepared a MAX phase CMAS-resistant protective surface layer on the surface of YSZ thermal barrier coating by slurry method. Wang Weize et al. (reference: CN 114752881 A) prepared a YbYSZ CMAS-resistant protective surface layer on the surface of YSZ thermal barrier coating by solution precursor plasma spraying method.

[0004] The implementation of the above technical methods has achieved certain results, but there are still the following three problems: first, the multi-doped zirconia-based powder needs to go through many preparation steps before it is finally granulated into spray powder; second, the compatibility between the anti-CMAS layer and the YSZ coating and the matching stability under long-term and high cycle times still need to be evaluated; finally, more importantly, the current modification methods for the YSZ coating are difficult to take into account multiple properties.

[0005] Therefore, it is urgent to propose an integrated modification method to achieve a technical method for the stable and efficient preparation of a multifunctional YSZ protective coating that combines high temperature resistance and CMAS corrosion resistance. Summary of the invention

[0006] The present invention is oriented to the actual needs in the aviation industry and the shortcomings of the prior art, and proposes a method for preparing a nanostructured zirconia-alumina ceramic composite coating. The method introduces aluminum microspheres into a new spherical reactive feed of the main YSZ powder, and uses the triggering of the in-situ aluminothermic reaction during the thermal spraying process to prepare a new zirconia-alumina thermal protective coating with a doped stable zirconia-based solid solution with excellent thermal insulation performance as the main phase and a uniformly dispersed alumina component that resists CMAS corrosion.

[0007] The technical solution of the present invention is:

[0008] A method for preparing a nanostructured zirconium oxide-aluminum oxide ceramic composite coating, the method comprising the following steps:

[0009] The first step is to prepare the yttria zirconia / alumina spherical reactive feedstock for the thermal spray process:

[0010] Mixing yttria-stabilized zirconia powder and micro-spherical aluminum powder to obtain a mixed powder; adding a binder to the mixed powder to obtain a composite powder with yttria-stabilized zirconia particles encapsulating an aluminum micro-spherical structure;

[0011] The mass fraction of yttria-stabilized zirconia powder in the mixed powder is 70-80%, and the mass ratio of the mixed powder to the binder is 100:0.1-2;

[0012] The particle size of the yttria-stabilized zirconium oxide powder used is 0.01-1 μm, the doping ratio of yttria in the powder is 3-8 wt.%, and the particle size of the aluminum powder used is 0.1-10 μm;

[0013] The binder used is polyvinyl alcohol or carboxymethyl cellulose.

[0014] The second step is to prepare the nanostructured zirconia-alumina ceramic composite coating:

[0015] The reactive yttria-stabilized zirconia / aluminum spherical composite powder prepared in the first step is sprayed on the surface of the substrate material pretreated in the second step by a thermal spraying method, and a nanostructured zirconia-aluminum oxide ceramic composite coating is prepared by in-situ thermal spraying synthesis;

[0016] Among them, the process parameters of the thermal spraying method are: the powder feeding gas is argon gas, and the powder feeding gas flow rate is 0.3-0.6m 3 / h, the spraying power is 28-35kW, the distance between the spray gun and the surface of the pretreated substrate material is 100-200mm, and the thickness of the prepared coating is 50-1000μm.

[0017] Before the second step, the surface of the substrate material to be coated may be pre-treated by any of the following two methods:

[0018] Method 1: When the base material is a metal material, sandblasting is first performed, and then a bonding layer is sprayed on the surface of the metal base material after sandblasting.

[0019] Alternatively, method 2: when the substrate material is an inorganic non-metallic material, sandblasting or sandpaper polishing is performed, and then a bonding layer is sprayed on the treated surface of the inorganic non-metallic substrate;

[0020] The metal matrix material is: titanium alloy, nickel-based high-temperature alloy, cobalt-based high-temperature alloy, steel, cast iron, aluminum alloy, nickel-chromium alloy, tungsten-based alloy or intermetallic compound; the bonding bottom material involved is: NiAl, NiCrAl, FeAl, NiCrAlY, CoCrAlY, CoNiCrAlY, NiCoCrAlYTa or NiCrBSi;

[0021] The non-metallic matrix material is: graphite, Cf / C composite material, Cf / SiC composite material, SiCf / SiC composite material, Al2O3f / Al2O3 composite material, zirconia or alumina-zirconia composite material; the bonding bottom material involved is: SiC, Si or HfO2, or no bonding bottom material is involved;

[0022] The nanostructured zirconium oxide-aluminum oxide ceramic composite coating prepared by the method has a heat-resistant temperature of 1100-1300° C. and can withstand 1-50h continuous penetration corrosion of CMAS molten salt at 1100-1250° C.

[0023] The raw materials involved in the preparation method of the nanostructured zirconia-alumina ceramic composite coating can all be obtained commercially, and the sandblasting process, sandpaper polishing process and bonding layer spraying process are all existing processes in the art.

[0024] The essential features of the present invention are:

[0025] From the perspective of the process route, the nanostructured zirconium oxide-aluminum oxide composite coating is prepared by using the thermal spray in-situ synthesis technology and the reactive composite feed composed of micron / submicron yttria-stabilized zirconium oxide and aluminum. From the perspective of performance effect, the nano-composite coating contains in-situ self-generated high-doping level solid solution components and aluminum oxide-zirconia eutectic components, so that the sprayed coating has good thermal insulation, chemical corrosion resistance and high temperature resistance.

[0026] The beneficial effects of the present invention are:

[0027] 1) The cost of the raw materials used for feeding is low, and the coating preparation process is simple. The present invention uses commercial yttria-stabilized zirconia and aluminum powder, which are low-cost, mature in preparation process and easily available, as raw materials, and can prepare spray powder with good sphericity through one-step spray granulation. This spherical powder is fully suitable for the atmospheric plasma spraying process, and has high powder deposition efficiency, and can achieve efficient deposition and repair of zirconia-alumina composite coatings of different thicknesses. There is no need for cumbersome processing of the feeding, but the in-situ introduction of component stable doping (reducing thermal conductivity) and alumina (anti-CMAS corrosion component) is achieved by triggering the in-situ reaction during the plasma spraying process and solidifying the melt deposition.

[0028] 2) The overall performance of the coating is better. First, the expected operating temperature of the coating can exceed 1250°C, which is higher than the ordinary 8YSZ thermal barrier coating in service. This is due to the fact that the main phase of the coating is YSZ, which has a more stable high-temperature phase structure and lower thermal conductivity. 3+ -Al 3+ Co-doped zirconia-based solid solution; secondly, the coating has stronger resistance to CMAS corrosion, thanks to the uniformly distributed hexagonal alumina phase introduced by the in-situ reaction system in the coating, which can form a high-melting-point crystalline phase with the molten salt, blocking the further corrosion of the molten salt into the coating; finally, the coating has better high-temperature mechanical properties. This is due to the inclusion of nanostructured alumina-zirconia nanoeutectics in the coating, which still has good mechanical properties at a level close to the eutectic temperature (1500°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the implementation scheme of the present invention will be described in detail below with reference to the accompanying drawings and specific examples.

[0030] Figure 1 This is a SEM morphology image of the yttria-stabilized zirconia / aluminum composite powder prepared in Example 1.

[0031] Figure 2This is a SEM image of the polished cross section of the zirconia-alumina composite coating prepared in Example 1.

[0032] Figure 3 This is the X-ray diffraction pattern of the surface of the zirconium oxide-aluminum oxide composite coating prepared in Example 1.

[0033] Figure 4 This is a morphology of the nano-alumina-zirconia eutectic in the zirconia-alumina composite coating prepared in Example 1.

[0034] Figure 5 This is a SEM image of the polished cross section of the zirconia-alumina composite coating prepared in Example 2.

[0035] Figure 6 This is a SEM morphology of the polished cross-section of the zirconia-alumina composite coating prepared in Example 3 after withstanding molten salt corrosion at 1250°C for 10 hours. DETAILED DESCRIPTION

[0036] Embodiment 1:

[0037] In this embodiment, a zirconia-alumina composite protective coating system is provided, which includes an alloy bonding layer and a ceramic surface layer from the inside to the outside. The alloy bonding layer is a NiCrAlY layer, and the ceramic surface layer is a zirconia-alumina layer synthesized in situ by atmospheric plasma spraying yttria-stabilized zirconia / aluminum feedstock. The specific steps include:

[0038] The first step is to prepare yttria-stabilized zirconia / aluminum spherical composite powder by spray granulation.

[0039] Select yttria-stabilized zirconia (purity: 99.9%, yttria content of 3wt.%) powder with a particle size range of 0.2-0.5μm and microspherical aluminum powder (purity: 99.9%) with a particle size range of 6-9μm. Among them, the mass ratio between yttria-stabilized zirconia powder and aluminum powder is 77:23. Add the two powders to deionized water and mix them evenly by centrifugal stirring, then add a binder (sodium carboxymethyl cellulose), and finally prepare a spherical composite feed by spray drying. The mass ratio between the above-mentioned yttria-stabilized zirconia-aluminum mixed powder and the binder is 100:0.2, the heating zone temperature of the spray drying equipment is 230°C, and the outlet temperature is 120°C. Figure 1 The above method can realize the encapsulation of aluminum microspheres by yttria-stabilized zirconia powder, and at the same time, the spray feed has good sphericity and dense structure.

[0040] The second step is the pretreatment of the substrate material.

[0041] The selected base material is GH3044 high temperature alloy (nickel-based high temperature alloy), and the pretreatment method is sandblasting. The sandblasting medium is corundum sand, the sandblasting angle is 40-60°, and the surface roughness of the base after sandblasting is 8-10μm. Then, a NiCrAlY bonding primer with a thickness of about 50μm is sprayed on the surface of the nickel-based high temperature alloy base material after sandblasting;

[0042] The third step is the preparation of zirconia-alumina composite coating.

[0043] The atmospheric plasma spraying method was adopted, and the process parameters were: spraying power was 32kW, spraying distance was 200mm, powder carrier gas was argon, and powder carrier gas flow rate was 0.8m 3 / h. The yttria-stabilized zirconia / aluminum composite powder prepared in the first step is sprayed on the surface of the nickel-based high-temperature alloy substrate material pretreated in the second step. Figure 2 and Figure 3 The characterization results show that the main phase of the prepared coating is doped and stabilized zirconium oxide and aluminum oxide, and the zirconium oxide is retained as a tetragonal phase. The thickness of the coating can reach more than 200μm, and the structure is dense and the layers are well bonded. From the high-magnification SEM characterization ( Figure 4 ) it can be seen that the coating also contains an alumina-zirconia eutectic structure with doped stabilized zirconia as the primary phase and a nanostructure.

[0044] Embodiment 2:

[0045] In this embodiment, a zirconia-alumina composite protective coating system is provided, which includes an alloy bonding layer and a ceramic surface layer from the inside to the outside. The alloy bonding layer is a NiCrAlY layer, and the ceramic surface layer is a zirconia-alumina layer synthesized by plasma spraying yttria-stabilized zirconia / aluminum feed reaction. The specific steps include:

[0046] The first step is to prepare yttria-stabilized zirconia / alumina spherical agglomerated powder by spray granulation.

[0047] Select yttria stabilized zirconia (yttria content of 3wt.%) powder with a particle size range of 0.2-0.5μm and micro-spherical aluminum powder with a particle size range of 6-9μm. The mass ratio between yttria stabilized zirconia powder and aluminum powder is 70:30. Add the two powders to a binder (sodium carboxymethyl cellulose)-deionized water solution and mix them evenly by centrifugal stirring, and then prepare a spherical composite feed by spray drying. The mass ratio between the above composite powder and the binder is 100:0.2, the temperature of the heating zone of the spray drying equipment is 230°C, and the outlet temperature is 120°C.

[0048] The second step is the pretreatment of the base material.

[0049] The selected base material is GH3044 high temperature alloy (nickel-based high temperature alloy), and the pretreatment method is sandblasting. The sandblasting medium is corundum sand, the sandblasting angle is 40-60°, and the surface roughness of the base after sandblasting is 8-10μm. Then, a NiCrAlY bonding primer with a thickness of 50μm is sprayed on the surface of the nickel-based high temperature alloy base material after sandblasting;

[0050] The third step is the preparation of zirconia-alumina composite coating.

[0051] The atmospheric plasma spraying method was adopted, and the process parameters were: plasma arc current 500A, voltage 64V, spraying distance 100mm, powder carrier gas argon, powder carrier gas flow rate 0.8m 3 The yttria-stabilized zirconia / aluminum composite powder prepared in the first step is sprayed on the surface of the nickel-based high-temperature alloy substrate material pretreated in the second step, thereby forming a zirconia-aluminum composite coating with a thickness of 200 μm and a dense structure ( Figure 5 ), that is, within the range of the powder preparation method and coating preparation process parameters described in the claims, stable deposition of the zirconium oxide-aluminum oxide composite coating can be achieved.

[0052] Embodiment 3:

[0053] In this embodiment, a zirconia-alumina composite protective coating system on the surface of a yttria-stabilized zirconia substrate is provided, wherein the ceramic surface layer is a zirconia-alumina layer synthesized by plasma spraying yttria-stabilized zirconia / aluminum feed reaction, and the specific steps include the following:

[0054] The first step is to prepare yttria-stabilized zirconia / aluminum spherical composite powder by spray granulation.

[0055] Select yttria stabilized zirconia (yttria content of 8wt.%) powder with a particle size range of 0.2-0.5μm and micro-spherical aluminum powder with a particle size range of 6-9μm. The mass ratio between yttria stabilized zirconia powder and aluminum powder is 72:28. Add the two powders to a binder (sodium carboxymethyl cellulose)-deionized water solution and mix them evenly by centrifugal stirring, and then prepare a spherical composite feed by spray drying. The mass ratio between the above composite powder and the binder is 100:0.1, the heating zone temperature of the spray drying equipment is 230°C, and the outlet temperature is 120°C.

[0056] The second step is the preparation of zirconia-alumina composite coating.

[0057] The atmospheric plasma spraying method was adopted, and the process parameters were: plasma arc current 500A, voltage 70V, spraying distance 100mm, powder carrier gas argon, powder carrier gas flow rate 0.3m 3The yttria-stabilized zirconia / aluminum composite powder prepared in the first step was sprayed onto the surface of the yttria-stabilized zirconia substrate material (with a yttria content of 8 wt.%), thereby forming a zirconia-aluminum composite coating with a thickness of 200 μm.

[0058] The third step is to test the CMAS corrosion resistance of the zirconia-alumina composite coating.

[0059] The four oxide powders constituting the corrosion molten salt were weighed and mixed in a molar ratio of 33CaO:9MgO:13Al2O3:45SiO2. After ball milling for 6 hours, the powder was dried at a constant temperature of 120°C for 24 hours, then ground with a mortar and sieved through a 300-mesh sieve. The CMAS corrosion test was carried out in a high-temperature box furnace. First, the CMAS powder was cold-pressed into a small cylinder (Φ3×3mm) with a mold and placed on the surface of the coating prepared in the second step. The heating rate was set to 10°C / min, and a corrosion test was carried out at 1250°C for 10 hours, and then cooled to room temperature with the furnace.

[0060] like Figure 6 The test results show that the zirconia-alumina composite coating prepared in this embodiment has good resistance to high-temperature CMAS molten salt corrosion, and there is no dissolution and cracking in the YSZ substrate under the coating due to CMAS corrosion, that is, the zirconia-alumina composite coating effectively blocks the corrosive medium above and inside the coating, while the coating itself still maintains a complete and dense structure, and has a good barrier effect.

[0061] The foregoing embodiments of the present invention are described for the purpose of explanation and illustration, but those skilled in the art will understand that the following embodiments are only used to illustrate the present application, and are not intended to limit the present invention to the precise forms in the embodiments. Those skilled in the art can achieve this by referring to the contents of this article and appropriately changing the conditions, routes, etc., but it should be noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

[0062] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a nanostructured zirconium oxide-aluminum oxide ceramic composite coating, characterized in that the method comprises the following steps: The first step is to prepare the yttria zirconia / alumina spherical reactive feedstock for the thermal spray process: Mixing yttria-stabilized zirconia powder and micro-spherical aluminum powder to obtain a mixed powder; adding a binder to the mixed powder to obtain a composite powder with yttria-stabilized zirconia particles encapsulating an aluminum micro-spherical structure; in, The mass fraction of the yttria-stabilized zirconia powder as a mixed powder is 70-80%, and the mass ratio of the composite powder to the binder is 100:0.1-2; The second step is to prepare the nanostructured zirconia-alumina ceramic composite coating: The reactive yttria-stabilized zirconia / aluminum spherical composite powder prepared in the first step is sprayed on the surface of the substrate material pretreated in the second step by a thermal spraying method, and a nanostructured zirconia-aluminum oxide ceramic composite coating is prepared by in-situ thermal spraying synthesis; Among them, the process parameters of the thermal spraying method are: the powder feeding gas is argon gas, and the powder feeding gas flow rate is 0.3-0.6m 3 / h, the spraying power is 28-35kW, the distance between the spray gun and the surface of the pretreated substrate material is 100-200mm, and the thickness of the prepared coating is 50-1000μm.

2. The method for preparing the nanostructured zirconium oxide-aluminum oxide ceramic composite coating according to claim 1, characterized in that Before the second step, the surface of the substrate material to be coated is pretreated by either of the following two methods: Method 1: When the base material is a metal material, sandblasting is first performed, and then a bonding layer is sprayed on the surface of the metal base material after sandblasting. Alternatively, method 2: when the base material is an inorganic non-metallic material, sandblasting or sandpaper polishing is performed, and then a bonding layer is sprayed on the treated surface of the inorganic non-metallic base.

3. The method for preparing the nanostructured zirconium oxide-aluminum oxide ceramic composite coating according to claim 2, characterized in that: The metal matrix material is: titanium alloy, nickel-based high-temperature alloy, cobalt-based high-temperature alloy, steel, cast iron, aluminum alloy, nickel-chromium alloy, tungsten-based alloy or intermetallic compound; the bonding bottom material involved is: NiAl, NiCrAl, FeAl, NiCrAlY, CoCrAlY, CoNiCrAlY, NiCoCrAlYTa or NiCrBSi; The non-metallic matrix material is graphite, Cf / C composite material, Cf / SiC composite material, SiCf / SiC composite material, Al2O3f / Al2O3 composite material, zirconia or alumina-zirconia composite material; the bonding bottom layer material involved is SiC, Si or HfO2, or no bonding bottom layer material is involved.

4. The method for preparing the nanostructured zirconia-alumina ceramic composite coating according to claim 2, characterized in that: The thickness of the bonding layer is 50-100 μm.

5. The method for preparing the nanostructured zirconia-alumina ceramic composite coating according to claim 1, characterized in that: The particle size of the yttria-stabilized zirconium oxide powder used is 0.01-1 μm, the doping ratio of yttria in the powder is 3-8 wt.%, and the particle size of the aluminum powder used is 0.1-10 μm.

6. The method for preparing the nanostructured zirconia-alumina ceramic composite coating according to claim 1, characterized in that: The binder used is polyvinyl alcohol or carboxymethyl cellulose.

7. The nanostructured zirconia-alumina ceramic composite coating prepared by the method of claim 1, wherein the coating The heat-resistant temperature is 1100-1300℃; at the same time, it can withstand 1-50h continuous penetration corrosion of CMAS molten salt at 1100-1250℃.

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