High-performance ScYSZ thermal barrier coating with continuously-prepared double-gradient structure and preparation method of high-performance ScYSZ thermal barrier coating

Abstract

The invention discloses a continuously prepared high-performance ScYSZ thermal barrier coating with a double-gradient structure and a preparation method thereof, and the preparation method comprises the following steps: preparing an ScYSZ layered structure layer on a high-temperature alloy matrix by using agglomerated ScYSZ ceramic powder by adopting a supersonic plasma spraying process; carrying out ball milling on the nanocrystalline scandium-yttrium co-stable zirconia ceramic powder and absolute ethyl alcohol containing a dispersing agent to obtain suspension liquid; and preparing a vertical crack structure layer on the ScYSZ layered structure layer by using the suspension liquid through a supersonic speed suspension liquid plasma spraying process, so as to form the high-performance ScYSZ thermal barrier coating with a double-gradient structure. The nano structure in the ScYSZ coating containing the layered structure can greatly reduce the heat conductivity of the coating, so that the heat insulation effect of the coating is further enhanced; and the stress damage tolerance of the coating is increased through the ScYSZ coating with the vertical crack structure, thermal stress accumulation of the coating under the cold and hot alternating cycle service condition is reduced, and thermal stress is easy to release.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature protective coatings, and in particular relates to a high-performance ScYSZ thermal barrier coating with a continuously prepared double-gradient structure and a preparation method thereof. Background Art

[0002] Thermal barrier coatings are widely used in hot end components of aircraft engines and heavy-duty gas turbines due to their low thermal conductivity, good high temperature resistance and corrosion resistance. As aircraft engines and gas turbines develop towards high thermal efficiency, low emissions, high thrust-to-weight ratio, and high power, the gas inlet temperature at the front end of the turbine is getting higher and higher, and the maximum temperature is much higher than the temperature bearing capacity of nickel-based high-temperature alloys. The most widely used 8YSZ thermal barrier coating system is prone to sintering, phase change, corrosion, and reduced strain tolerance due to long-term service in a high temperature environment of 1200°C. However, the scandium-yttrium co-stabilized zirconia (ScYSZ) ceramic coating has lower thermal conductivity and excellent high-temperature tetragonal phase structure stability compared to traditional 8YSZ ceramic thermal insulation coatings.

[0003] In the coating structure system, the supersonic plasma spraying process can produce a coating with a typical layered structure, and the supersonic suspension plasma spraying process can produce a coating with a vertical crack structure. However, a large number of interlayer interfaces in the layered structure are often the nucleation points of cracks, which easily lead to interlayer cracking and premature failure of the coating during service. The vertical crack structure can greatly improve the service life of the thermal barrier coating under the service conditions of hot and cold alternating cycles due to its high strain tolerance, but the introduction of vertical cracks makes the thermal insulation effect of the coating far inferior to that of the plasma sprayed layered structure coating. Summary of the invention

[0004] In order to overcome the problem that 8YSZ ceramic thermal insulation coatings in the prior art are difficult to serve for a long time in a high-temperature thermochemical multi-field coupling environment above 1200°C, the purpose of the present invention is to provide a high-performance ScYSZ thermal barrier coating with a continuously prepared double gradient structure having low thermal conductivity, good strain tolerance and high thermal cycle life, and a preparation method thereof. The thermal barrier coating prepared by this method is suitable for high-temperature environments above 1200°C.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for continuously preparing a high-performance ScYSZ thermal barrier coating with a double gradient structure comprises the following steps:

[0007] The agglomerated ScYSZ ceramic powder is sprayed by supersonic plasma to prepare a ScYSZ layered structure layer on a high-temperature alloy substrate;

[0008] ball-milling nanocrystalline scandium-yttrium co-stabilized zirconia ceramic powder and anhydrous ethanol containing a dispersant to obtain a suspension;

[0009] The suspension is sprayed using a supersonic suspension plasma spraying process to prepare a vertical crack structure layer on the ScYSZ layered structure layer, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0010] A further improvement of the present invention is that the thickness of the ScYSZ layered structure layer is 100 μm.

[0011] A further improvement of the present invention is that the supersonic plasma spraying process parameters are: current of 430-450A, voltage of 125-140V, main gas argon flow rate of 110-120L / min, secondary gas hydrogen flow rate of 15-17L / min, spraying distance of 90-110mm and powder feeding amount of 14-18g / min.

[0012] A further improvement of the present invention is that the dispersant is polyethylene glycol.

[0013] A further improvement of the present invention is that the mass ratio of the nanocrystalline scandium-yttrium co-stabilized zirconia ceramic powder to the dispersant is 20-40:1-4.

[0014] A further improvement of the present invention is that the coating thickness of the vertical crack structure layer is 100 μm.

[0015] A further improvement of the present invention is that the process parameters of the supersonic suspension plasma spraying are: current of 380-420A, voltage of 110-150V, main gas argon flow rate of 60-70L / min, secondary gas hydrogen flow rate of 16-22L / min, spraying distance of 40mm, and suspension powder feeding rate of 15-25mL / min.

[0016] A further improvement of the present invention is that the high temperature alloy substrate is preheated to 180° C. before preparing the vertical crack structure layer on the ScYSZ layered structure layer by using the suspension using a supersonic suspension plasma spraying process.

[0017] A further improvement of the present invention is that the agglomerated ScYSZ ceramic powder is prepared by the following process: nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder, a binder and water are mixed to obtain a slurry, the slurry is ball-milled, and then the powder is agglomerated by centrifugal spray granulation to obtain an agglomerated ScYSZ ceramic powder.

[0018] A high-performance ScYSZ thermal barrier coating with a double gradient structure comprises a ScYSZ layered structure layer and a vertical crack structure layer arranged from bottom to top on a high-temperature alloy substrate.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention adopts supersonic plasma spraying technology to prepare a ScYSZ coating with a layered structure, and continuously prepares a ScYSZ coating with a vertical crack structure on the ScYSZ coating with a layered structure by supersonic suspension plasma spraying technology. The nanostructure in the ScYSZ coating with a layered structure can greatly reduce the thermal conductivity of the coating, so as to further enhance the thermal insulation effect of the coating; and the ScYSZ coating with a vertical crack structure increases the stress damage tolerance of the coating, reduces the thermal stress accumulation of the coating under the service conditions of hot and cold alternating cycles, and is easy to release thermal stress; the ScYSZ coating with a layered structure at the bottom can effectively improve the disadvantage of poor thermal insulation performance of the vertical crack structure layer, and the ScYSZ ceramic material has low thermal conductivity and excellent high-temperature tetragonal phase stability, which is generally beneficial to prolonging the service life of the hot end components under higher temperatures and more complex and harsh environments.

[0021] Furthermore, during the preparation process of the double-gradient structure ScYSZ coating, the concentration of the supersonic suspension slurry, the suspension powder feeding rate, the power and other preparation factors are adjusted to achieve the formation of a vertical crack structure of the coating, which ultimately affects the thermal stress release of the coating under hot and cold alternating cycle service conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the double gradient structure high performance ScYSZ thermal barrier coating of Example 1;

[0023] Figure 2 is a SEM image of the double gradient structure high performance ScYSZ thermal barrier coating of Example 1;

[0024] Figure 3 is the TEM morphology of the nanocrystalline ScYSZ powder of Example 1;

[0025] Figure 4 is the morphology of the agglomerated ScYSZ ceramic powder of Example 1;

[0026] Figure 5 This is the insulation temperature variation curve of the double gradient structure coating of Example 1 at 1200°C. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0028] A method for continuously preparing a high-performance ScYSZ thermal barrier coating with a double gradient structure according to the present invention comprises the following steps:

[0029] Step 1, dissolving scandium chloride hexahydrate, yttrium chloride hexahydrate, zirconium oxychloride octahydrate and citric acid in a molar ratio of 0.14:0.01:0.925:1.075 in deionized water to form a colorless transparent solution, then placing the prepared solution in a 60°C water bath and stirring for 24 hours to perform a sol-gel reaction to obtain a wet gel, and placing the gel product after the reaction in a 60°C oven for drying to finally obtain a dry gel precursor.

[0030] Step 2: The dry gel precursor is placed in a muffle furnace at 1100° C. for 4 hours to obtain nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder.

[0031] Nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder, a binder (polyvinyl alcohol PVA) and water are mixed to obtain a slurry, wherein the weight concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 50wt.%, the weight concentration of the binder polyvinyl alcohol PVA is 1wt.% and the weight concentration of deionized water is 49wt.%, the slurry is ball-milled by a planetary ball mill, the ball milling speed is 400r / min, and the ball milling time is 8h, and then the powder is agglomerated by a centrifugal spray granulation dryer to obtain an agglomerated ScYSZ ceramic powder, which is suitable for supersonic plasma spraying process requirements and has good fluidity, wherein the process parameters of the centrifugal spray granulation dryer are: an inlet air temperature of 220°C, a centrifugal frequency of 250Hz, and a feed rate of 20mL / min.

[0032] Step 3, placing the agglomerated ScYSZ ceramic powder obtained in step 2 in a supersonic plasma spraying powder feeding device, using a supersonic plasma spraying process, adjusting the supersonic plasma spraying process parameters to prepare a ScYSZ layered structure layer on a high-temperature alloy substrate, with a coating thickness of 100 μm. The supersonic plasma spraying process parameters are: current of 430-450A, voltage of 125-140V, main gas argon flow rate of 110-120L / min, secondary gas hydrogen flow rate of 15-17L / min, spraying distance of 90-110mm, and powder feeding amount of 14-18g / min.

[0033] Step 4, ball-milling and dispersing the nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder in step 2 with anhydrous ethanol containing dispersant polyethylene glycol (PEG) to obtain a suspension, wherein the mass concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 20-40wt.%, and the mass concentration of the dispersant is 1-4wt.%, and the suspension is transported to an atomizer by a peristaltic pump, and the suspension is atomized by the atomizer and then sent into the jet of a supersonic plasma spray gun, and a vertical crack structure layer is prepared on the ScYSZ layered structure layer by a supersonic suspension plasma spraying process, and the coating thickness is 100μm, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0034] Among them, the process parameters of supersonic suspension plasma spraying are: current of 380-420A, voltage of 110-150V, main gas argon flow rate of 60-70L / min, secondary gas hydrogen flow rate of 16-22L / min, spraying distance of 40mm, suspension powder feeding rate of 15-25mL / min, and the substrate is preheated to 180°C before spraying.

[0035] Example 1

[0036] The preparation method of the high-performance ScYSZ thermal barrier coating with a double gradient structure of the present invention is as follows:

[0037] Step 1, dissolving scandium chloride hexahydrate, yttrium chloride hexahydrate, zirconium oxychloride octahydrate and citric acid in a molar ratio of 0.14:0.01:0.925:1.075 in deionized water to form a colorless transparent solution, then placing the prepared solution in a 60°C water bath and stirring for 24 hours to perform a sol-gel reaction to obtain a wet gel, and placing the gel product after the reaction in a 60°C oven for drying to finally obtain a dry gel precursor.

[0038] Step 2, the dry gel precursor is placed in a muffle furnace at 1100°C for 4 hours to obtain nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder. The TEM morphology of the powder is as follows: Figure 3 As shown, it can be seen that the grain size of the powder is in the range of 10 to 40 nm, and the grain size distribution is uniform.

[0039] Nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder, binder polyvinyl alcohol and water are mixed to obtain a slurry, wherein the weight concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 50wt.%, the weight concentration of the binder polyvinyl alcohol PVA is 1wt.% and the weight concentration of deionized water is 49wt.%, the slurry is ball-milled by a planetary ball mill at a ball milling speed of 400r / min for 8h, and then the powder is agglomerated by a centrifugal spray granulation dryer to obtain an agglomerated ScYSZ ceramic powder, which is suitable for supersonic plasma spraying process requirements and has good fluidity, see Figure 4 It can be seen that the agglomerated ScYSZ ceramic powder has good sphericity and the particle size is in the range of 10-50 μm. The process parameters of the centrifugal spray granulation dryer are: inlet air temperature is 220 °C, centrifugal frequency is 250 Hz, and feed rate is 20 mL / min.

[0040] Step 3, placing the agglomerated ScYSZ ceramic powder obtained in step 2 in a supersonic plasma spraying powder feeding device, using a supersonic plasma spraying process, adjusting the supersonic plasma spraying process parameters to prepare a ScYSZ layered structure layer on a high-temperature alloy substrate, with a coating thickness of 100 μm. The supersonic plasma spraying process parameters are: current of 430A, voltage of 138V, main gas argon flow rate of 120L / min, secondary gas hydrogen flow rate of 16L / min, spraying distance of 100mm, and powder feeding amount of 16g / min.

[0041] Step 4, ball-milling and dispersing the nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder in step 2 with anhydrous ethanol containing dispersant polyethylene glycol (PEG) to obtain a suspension, wherein the mass concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 20wt.%, and the mass concentration of the dispersant is 1wt.%, and the suspension is transported to an atomizer by a peristaltic pump, and the suspension is atomized by the atomizer and then sent into the jet of a supersonic plasma spray gun, and a coating with a vertical crack structure is prepared on the ScYSZ layered structure layer by a supersonic suspension plasma spraying process, and the coating thickness is 100μm, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0042] Among them, the supersonic suspension plasma spraying process parameters are: current of 420A, voltage of 150V, main gas argon flow rate of 70L / min, secondary gas hydrogen flow rate of 22L / min, spraying distance of 40mm, suspension powder feeding rate of 25mL / min, and the substrate is preheated to 180°C before spraying.

[0043] The structure of the double gradient structure high performance ScYSZ thermal barrier coating provided by the present invention is as follows Figure 1 As shown, there are layered structure layers and vertical crack structure layers from bottom to top on the high-temperature alloy substrate.

[0044] The SEM image of the double gradient structure high performance ScYSZ thermal barrier coating provided in Example 1 of the present invention is as follows: Figure 2 As shown, it can be seen that the gray part in the figure is the high-temperature alloy matrix part, the middle is the layered structure ScYSZ ceramic layer, and the top layer is the vertical crack structure ScYSZ ceramic layer.

[0045] Refer to the device in the literature (Y. Wang, Y. Bai, GH Liu, et al., Wide-velocity range high-energy plasma sprayed yttria-stabilized zirconia thermal barrier coating—Part II: Structural defects and thermal-bonding properties, Surface and Coatings Technology, 476 (2024) 130203.) for thermal insulation effect testing. Figure 5 It can be seen from the thermal insulation effect curve of the double gradient structure coating that the T1 and T3 curves represent the surface temperature of the uncoated substrate and the surface temperature of the coated substrate respectively, and the T2 and T4 curves represent the back temperature of the uncoated substrate and the back temperature of the coated substrate respectively. The difference in the stable stage of the curve, i.e. (T3-T4)-(T1-T2), is the thermal insulation effect of the coating. The calculated thermal insulation temperature of the coating is about 96°C, indicating that the double gradient structure coating has a good thermal insulation effect of 1200°C.

[0046] Example 2

[0047] Step 1, same as in Example 1;

[0048] Step 2, same as in Example 1;

[0049] Step 3, same as in Example 1;

[0050] Step 4, ball-milling and dispersing nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder and anhydrous ethanol containing dispersant polyethylene glycol (PEG) to obtain a suspension, wherein the mass concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 20wt.%, and the mass concentration of the dispersant is 1wt.%, and the suspension is transported to an atomizer by a peristaltic pump, and the suspension is atomized by the atomizer and then sent into the jet of a supersonic plasma spray gun, and a coating with a vertical crack structure is prepared on the ScYSZ layered structure layer by a supersonic suspension plasma spraying process, and the coating thickness is 100μm, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0051] Among them, the supersonic suspension plasma spraying process parameters are: current is 380A, voltage is 110V, main gas argon flow rate is 60L / min, secondary gas hydrogen flow rate is 16L / min, spraying distance is 40mm, suspension powder feeding rate is 25mL / min, and the substrate is preheated to 180℃ before spraying.

[0052] Example 3

[0053] Step 1, same as in Example 1;

[0054] Step 2, same as in Example 1;

[0055] Step 3, same as in Example 1;

[0056] Step 4, ball-milling and dispersing nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder and anhydrous ethanol containing dispersant polyethylene glycol (PEG) to obtain a suspension, wherein the mass concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 20wt.%, and the mass concentration of the dispersant is 1wt.%, and the suspension is transported to an atomizer by a peristaltic pump, and the suspension is atomized by the atomizer and then sent into the jet of a supersonic plasma spray gun, and a coating with a vertical crack structure is prepared on the ScYSZ layered structure layer by a supersonic suspension plasma spraying process, and the coating thickness is 100μm, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0057] Among them, the process parameters of supersonic suspension plasma spraying are: current of 400A, voltage of 130V, main gas argon flow rate of 70L / min, secondary gas hydrogen flow rate of 22L / min, spraying distance of 40mm, suspension powder feeding rate of 20mL / min, and the substrate is preheated to 180°C before spraying.

[0058] Example 4

[0059] Step 1, same as in Example 1;

[0060] Step 2, same as in Example 1;

[0061] Step 3, same as in Example 1;

[0062] Step 4, ball-milling and dispersing nanocrystalline scandium yttrium co-stabilized zirconia (ScYSZ) ceramic powder and anhydrous ethanol containing dispersant polyethylene glycol (PEG) to obtain a suspension, wherein the mass concentration of the nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder is 20wt.%, and the mass concentration of the dispersant is 1wt.%, and the suspension is transported to an atomizer by a peristaltic pump, and the suspension is atomized by the atomizer and then sent into the jet of a supersonic plasma spray gun, and a coating with a vertical crack structure is prepared on the ScYSZ layered structure layer by a supersonic suspension plasma spraying process, and the coating thickness is 100μm, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

[0063] Among them, the supersonic suspension plasma spraying process parameters are: current is 390A, voltage is 110V, main gas argon flow rate is 70L / min, secondary gas hydrogen flow rate is 16L / min, spraying distance is 40mm, suspension powder feeding rate is 15mL / min, and the substrate is preheated to 180℃ before spraying.

[0064] The present invention provides a method for continuously preparing a dual-gradient structure thermal barrier coating. The obtained layered and vertical crack dual-structure ScYSZ coating has excellent structural stability, high-temperature thermal shock resistance and excellent thermal insulation performance. The thermal protective coating prepared by the present invention has broad application prospects in the use of high-end equipment metal hot end components of aircraft engines and heavy-duty gas turbines.

[0065] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for continuously preparing a high-performance ScYSZ thermal barrier coating with a double gradient structure, characterized in that: The following steps are involved: The agglomerated ScYSZ ceramic powder is sprayed by supersonic plasma to prepare a ScYSZ layered structure layer on a high-temperature alloy substrate; ball-milling nanocrystalline scandium-yttrium co-stabilized zirconia ceramic powder and anhydrous ethanol containing a dispersant to obtain a suspension; The suspension is sprayed using a supersonic suspension plasma spraying process to prepare a vertical crack structure layer on the ScYSZ layered structure layer, forming a high-performance ScYSZ thermal barrier coating with a double gradient structure.

2. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The thickness of the ScYSZ layer structure is 100 μm.

3. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The process parameters of supersonic plasma spraying are: current of 430-450A, voltage of 125-140V, main gas argon flow rate of 110-120L / min, secondary gas hydrogen flow rate of 15-17L / min, spraying distance of 90-110mm and powder feeding amount of 14-18g / min.

4. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The dispersant is polyethylene glycol.

5. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The mass ratio of the nanocrystalline scandium-yttrium co-stabilized zirconia ceramic powder to the dispersant is 20-40:1-4.

6. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The coating thickness of the vertical crack structure layer is 100 μm.

7. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The process parameters of supersonic suspension plasma spraying are: current 380-420A, voltage 110-150V, main gas argon flow rate 60-70L / min, secondary gas hydrogen flow rate 16-22L / min, spraying distance 40mm, suspension powder feeding rate 15-25mL / min.

8. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: Before preparing a vertical crack structure layer on the ScYSZ layered structure layer using a supersonic suspension plasma spraying process, the high-temperature alloy substrate is preheated to 180°C.

9. The method for preparing a high-performance ScYSZ thermal barrier coating with a continuous double gradient structure according to claim 1, characterized in that: The agglomerated ScYSZ ceramic powder is prepared by the following process: nanocrystalline scandium yttrium co-stabilized zirconia ceramic powder, a binder and water are mixed to obtain a slurry, the slurry is ball-milled, and then the powder is agglomerated by centrifugal spray granulation to obtain the agglomerated ScYSZ ceramic powder.

10. A high performance ScYSZ thermal barrier coating with a double gradient structure prepared according to the method of any one of claims 1 to 9, characterized in that: It comprises a ScYSZ layered structure layer and a vertical crack structure layer which are arranged from bottom to top on a high temperature alloy substrate.

Images