A method for controlling a dendritic structure of a multi-principal-element rare earth-doped zirconia thermal barrier coating

Abstract

The application discloses a control method of a multi-principal-element rare earth doped zirconium oxide thermal barrier coating dendritic structure, and belongs to the field of thermal barrier coatings. The control method comprises the following steps: placing a high-temperature alloy sample with a bonding layer into a first electrolyte, taking the high-temperature alloy sample as a negative electrode, taking a graphite plate as a positive electrode, connecting a micro-arc oxidation power supply, performing first electrolysis, depositing an oxidation-resistant ceramic barrier layer on the surface of the high-temperature alloy sample, then placing the high-temperature alloy sample with the oxidation-resistant ceramic barrier layer into a second electrolyte, taking the high-temperature alloy sample as a negative electrode, taking the graphite plate as a positive electrode, connecting the micro-arc oxidation power supply, and performing second electrolysis. The first electrolyte comprises aluminum nitrate and a rare earth element metal salt, and the second electrolyte comprises zirconium nitrate and a rare earth element metal salt. The process parameter of the application is convenient to adjust, the doping of the rare earth element and the introduction of the oxidation-resistant barrier layer effectively improve the compactness of the dendritic structure coating, and the heat insulation temperature and the thermal shock performance of the dendritic structure coating are improved.

Description

Technical Field

[0001] This invention belongs to the field of thermal barrier coating technology, specifically relating to a method for preparing thermal barrier coatings, and more specifically to a method for controlling the dendritic structure of a multi-principal rare earth-doped zirconium oxide thermal barrier coating. Background Technology

[0002] Thermal barrier coatings are commonly used on the surfaces of high-temperature hot-end components. They are coating systems with surface protection functions, offering excellent thermal insulation. Their primary purpose is to reduce the operating temperature of the substrate, protecting it from corrosion, wear, and high-temperature oxidation. Applying thermal barrier coatings to high-temperature engine hot-end components not only reduces fuel consumption, improves efficiency, and extends the service life of hot-end components, but also enhances the substrate's resistance to high-temperature corrosion and increases the engine's operating temperature.

[0003] Currently, the main methods for preparing thermal barrier coatings include plasma spraying and electron beam physical vapor deposition (EBPD). Plasma spraying uses a plasma gun to generate a plasma flame, heating and melting the coating material. This flame is then atomized by a high-speed gas stream and sprayed onto the substrate surface at high velocity to form a coating. Its composition can be controlled artificially, and it has high production efficiency. However, the resulting coating has a layered structure with pores and voids, limiting its thermal shock resistance. EBPD involves emitting an electron beam from an electron gun after the vacuum chamber reaches a certain vacuum level. This beam directly irradiates the pre-evaporated material, heating and vaporizing it. The material vapor is deposited onto the substrate in atomic or molecular form to form a coating. This technology has expensive equipment and high manufacturing costs, and it requires a vacuum environment, making it difficult to deposit large-area samples. Furthermore, both methods struggle to prepare thermal barrier coatings on the surfaces and internal cavities of workpieces with complex shapes.

[0004] Liquid phase plasma electrolysis is a novel technology developed from anodic oxidation to grow thermal barrier coatings on metal surfaces. Based on the polarity of the power supply connected to the sample, it is mainly divided into anodic liquid phase plasma electrolysis and cathodic liquid phase plasma electrolysis. A significant advantage of this technology is its ability to prepare coatings on complex surfaces and cavities. Anodic liquid phase plasma electrolysis oxidation, also commonly known as "micro-arc oxidation," uses valve metals such as Al, Mg, and Ti and their alloys as the anode. However, it is only applicable to valve metals and cannot be used for non-valve metal high-temperature alloys.

[0005] Existing technologies suffer from problems such as complex processes for preparing thermal barrier coatings on the surface of aero-engines, expensive equipment, limited thermal shock resistance, and difficulty in preparing long-life thermal barrier coatings on the inner surface of complex parts. Summary of the Invention

[0006] The purpose of this invention is twofold: firstly, to address the challenge of fabricating long-life, high-reliability thermal barrier coatings on the surfaces of complex aero-engine components using existing technologies; and secondly, to overcome the limitations of traditional layered and columnar crystal thermal barrier coatings in terms of thermal shock resistance, the susceptibility of YSZ materials to phase transformation at 1200℃, and poor thermal insulation performance. This invention utilizes liquid-phase plasma electrolysis technology to control the dendritic structure of multi-principal rare-earth-doped zirconia thermal barrier coatings, thereby improving the high reliability of thermal barrier coatings on complex component surfaces. Specifically, the high-entropy strategy of multi-principal rare-earth doping reduces phonon scattering, increasing the thermal insulation temperature of the coating, while the appropriately sized and shaped dendritic structure significantly enhances the coating's strain tolerance, thus improving its thermal cycling life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for controlling the dendritic structure of a multi-principal-element rare-earth-doped zirconium oxide thermal barrier coating includes the following steps:

[0009] A high-temperature alloy sample with a bonding layer is placed in a first electrolyte. Using the high-temperature alloy sample as the negative electrode and the graphite plate as the positive electrode, a micro-arc oxidation power supply is connected to perform a first electrolysis, depositing an oxidation-resistant ceramic barrier layer on the surface of the high-temperature alloy sample. Then, the high-temperature alloy sample with the oxidation-resistant ceramic barrier layer is placed in a second electrolyte. Using the high-temperature alloy sample as the negative electrode and the graphite plate as the positive electrode, a micro-arc oxidation power supply is connected to perform a second electrolysis, obtaining a dendritic multi-principal rare-earth-doped zirconium oxide thermal barrier coating. The first electrolyte includes aluminum nitrate and rare-earth element metal salts, and the second electrolyte includes zirconium nitrate and rare-earth element metal salts.

[0010] Furthermore, in the first electrolyte, the concentration of aluminum nitrate is 0.1–1 mol / L, and the concentration of rare earth element metal salt is 0.01–0.5 mol / L. The rare earth element metal salt is one of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

[0011] Furthermore, in the second electrolyte, the concentration of zirconium nitrate is 0.1–1 mol / L, the concentration of rare earth element metal salt is 0.01–0.5 mol / L, and two or more of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate are present.

[0012] Furthermore, the solvent used in both the first and second electrolysis processes is a mixture of ethanol and water.

[0013] Furthermore, the rare earth element metal salts in the first electrolyte and the second electrolyte are two or more of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

[0014] Furthermore, the conditions for the first and second electrolysis are as follows: pulse voltage of 200–500V, operating frequency of 100–1000Hz, duty cycle of 5–30%, electrolysis temperature of 0–50℃, and time of 10–120min.

[0015] Furthermore, the high-temperature alloy sample with the binder layer was prepared by the following process:

[0016] The surface of the high-temperature alloy sample is sandblasted, and then a wide-velocity high-energy plasma spraying method is used to spray the surface of the high-temperature alloy sample to form an adhesive layer, thus obtaining a high-temperature alloy sample with an adhesive layer.

[0017] Furthermore, the thickness of the adhesive layer is 50–150 μm.

[0018] Furthermore, the adhesive layer material is NiCrAlY, NiCoCrAlY, or CoNiCrAlY.

[0019] Furthermore, the high-temperature alloy samples are iron-based high-temperature alloys, nickel-based high-temperature alloys, or cobalt-based high-temperature alloys.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention prepares a rare-earth-doped zirconia thermal barrier coating using cathodic liquid-phase plasma electrolytic deposition technology. The porous, cross-linked dendritic structure of the coating significantly improves its thermal cycling life, making it applicable to the field of surface thermal protection technology. Specifically, it exhibits the following advantages:

[0022] 1) The entire process is carried out in the liquid phase environment of the electrolyte, which can form a thermal barrier coating of a certain thickness on the inner and outer surfaces of any complex-shaped workpiece, especially the inner and outer surfaces of irregular-shaped parts.

[0023] 2) This invention only requires the matrix material to be conductive, so it is applicable to all metals and has a wide range of matrix material applicability.

[0024] 3) The equipment required by this invention is simple and low in cost. By adjusting power parameters such as voltage, frequency, and duty cycle, as well as the composition of the electrolyte, the composition of the thermal barrier coating can be controlled, and the coating structure such as pore size and thickness can be adjusted. The process is simple and does not require harsh conditions such as atmosphere protection and high temperature.

[0025] 4) The generation and participation of plasma on the workpiece surface during processing, with its high energy density, causes the deposits on the workpiece surface to undergo discharge sintering, forming a thermal barrier coating. During discharge, plasma breakdown occurs at weak points in the coating, and the high temperature causes the coating at those points to melt and sputter outwards. Under the quenching effect of the electrolyte, it rapidly solidifies to form a porous, cross-linked dendritic structure. The abundant pores and defects in this porous, cross-linked dendritic structure can effectively reduce phonon thermal conductivity, which is beneficial to reducing the thermal conductivity of the thermal barrier coating, thereby increasing the coating's insulation temperature. Furthermore, the vertical crack-like defects within the structure can, to some extent, improve the coating's strain tolerance under thermal loads, effectively enhancing the coating's thermal cycle life.

[0026] 5) The multi-principal rare earth doped zirconium oxide coating material system forms a mesoscale defect structure, in which the lattice atoms are highly disordered, resulting in intense phonon-grain boundary scattering, which is conducive to reducing the thermal conductivity of the thermal barrier coating and improving the thermal insulation temperature of the coating at the mesoscale level.

[0027] 6) Pre-depositing a rare-earth-doped antioxidant ceramic layer can effectively induce uniform plasma discharge, thereby improving the uniformity and density of ceramic coating deposition in the thermal barrier coating system. Furthermore, the rare-earth-doped antioxidant layer can effectively alleviate the thermal expansion mismatch between the binder layer and the ceramic layer, thus enhancing the coating's protective performance. Attached Figure Description

[0028] Figure 1 The images show cross-sectional SEM images of the thermal barrier coatings prepared in Example 1 of this invention, where (a) is a ZrO2 coating with a duty cycle of 10%; (b) is a ZrO2 coating with a duty cycle of 20%; (c) is a YSZ coating; (d) is a 5% Ce-doped YSZ thermal barrier coating; (e) is a 10% Ce-doped YSZ thermal barrier coating; (f) is a 20% Ce-doped YSZ thermal barrier coating; (g) is an alumina layer combined with a 10% Ce-doped YSZ thermal barrier coating; (h) is an alumina layer combined with a 20% Ce-doped YSZ thermal barrier coating; (i) is a rare earth-doped ZrCeGdYO2 thermal barrier coating; and (j) is a rare earth-doped ZrCeGdYO2 thermal barrier coating after adding a barrier layer.

[0029] Figure 2 XRD phase analysis results of the rare earth element Ce-doped YSZ thermal barrier coating prepared in Example 1 of this invention;

[0030] Figure 3 The thermal insulation temperature per 100 μm thickness of the thermal barrier coating prepared in Example 1 of the present invention, wherein (a) is a CeYSZ coating; and (b) is a Ce-doped YSZ thermal barrier coating after adding an antioxidant barrier layer.

[0031] Figure 4The images show the surface of the thermal barrier coating prepared in Example 1 of this invention after different thermal shock cycles. (a) is the YSZ coating, with 20, 40 and 58 cycles from left to right; (b) is the Ce-doped YSZ thermal barrier coating, with 50, 98 and 105 cycles from left to right; and (c) is the Ce-doped YSZ thermal barrier coating after adding an antioxidant barrier layer, with 270, 350 and 450 cycles from left to right. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] This invention discloses a method for controlling the dendritic structure of a multi-principal rare-earth-doped zirconia thermal barrier coating, comprising two control strategies: one is to directly deposit a multi-principal rare-earth-doped ceramic layer on a sprayed adhesive layer, and the other is to pre-fabricate an anti-oxidation barrier layer on the sprayed adhesive layer before depositing the ceramic layer. Specifically, for the first strategy, a bonding layer is sprayed onto the surface of a high-temperature alloy sample using a wide-velocity high-energy plasma spraying technique; subsequently, the high-temperature alloy sample with the bonding layer is immersed in an electrolyte to deposit the multi-principal rare-earth-doped ceramic layer. The process involves connecting a pulsed power supply, using the high-temperature alloy sample as the negative electrode and a graphite plate as the positive electrode, and electrolyzing in an electrolyte at 0–50°C for 10–120 minutes under conditions of a pulse voltage of 200–500V, a working frequency of 100–1000Hz, and a duty cycle of 5–30%. For the second strategy, an anti-oxidation ceramic barrier layer is first deposited on the surface of the high-temperature alloy sample using the above technique, and then the multi-principal rare-earth-doped coating is deposited. The equipment used in this invention is simple and the process parameters are easy to adjust. The doping of rare earth elements and the introduction of an antioxidant barrier layer effectively improve the density of the dendritic structure coating, resulting in an improvement in its thermal insulation temperature and thermal shock performance.

[0034] The control method of the present invention specifically includes the following steps:

[0035] (1) Surface pretreatment of high temperature alloy sample: The surface of the high temperature alloy sample is sandblasted and a NiCrAlY, NiCoCrAlY or CoNiCrAlY bonding layer with a thickness of 50 to 150 μm is sprayed on its surface by wide velocity range high energy plasma spraying to obtain a high temperature alloy sample with bonding layer; wherein, the high temperature alloy sample is an iron-based high temperature alloy, a nickel-based high temperature alloy or a cobalt-based high temperature alloy.

[0036] (2) Preparation of electrolyte: Use an ethanol solution with a water volume percentage of 10-50% as the solvent;

[0037] Aluminum nitrate and a rare earth metal salt are added to a solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate is 0.1–1 mol / L, and the concentration of the rare earth metal salt is 0.01–0.5 mol / L. The concentration of the rare earth metal salt is determined based on the concentration of zirconium nitrate. The rare earth metal salt is one of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

[0038] A second electrolyte is prepared by adding zirconium nitrate and rare earth metal salts to a solvent. The concentration of zirconium nitrate in the second electrolyte is 0.1–1 mol / L, and the concentration of the rare earth metal salts is determined based on the concentration of zirconium nitrate. The rare earth metal salts are two or more selected from yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate. The concentration of each rare earth metal salt is 0.01–0.5 mol / L.

[0039] (3) Preparation of rare earth element doped zirconia thermal barrier coating: The high-temperature alloy sample with adhesive layer prepared in step (1) is placed in the first electrolyte. The high-temperature alloy sample is used as the negative electrode and the graphite plate is used as the positive electrode. A micro-arc oxidation power supply is connected. Under the conditions of pulse voltage of 200-500V, working frequency of 100-1000Hz and duty cycle of 5-30%, it is electrolyzed in the electrolyte at 0-50℃ for 10-120min to deposit an anti-oxidation ceramic barrier layer. After the deposition is completed, it is placed in the second electrolyte. The high-temperature alloy sample is used as the negative electrode and the graphite plate is used as the positive electrode. A micro-arc oxidation power supply is connected. Under the conditions of pulse voltage of 200-500V, working frequency of 100-1000Hz and duty cycle of 5-30%, it is electrolyzed in the electrolyte at 0-50℃ for 10-120min. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to obtain a dendritic structure of multi-principal rare earth-doped zirconium oxide thermal barrier coating, in which ZrO2 is a t' tetragonal phase.

[0040] The rare-earth-doped zirconia thermal barrier coating prepared by this invention has a porous, cross-linked dendritic structure. With increasing rare-earth element content, the structure near the substrate becomes relatively denser; with the introduction of an antioxidant barrier layer, the size of the dendritic structure decreases, and the coating density increases. Furthermore, the thermal insulation temperature of a 100 μm thick rare-earth-doped zirconia thermal barrier coating is 40-80℃.

[0041] Under thermal shock conditions of rapid heating to 1300℃ in 10-30s, holding at that temperature for 5-8min, and then rapid air cooling to room temperature in 10-30s, the rare earth-doped zirconia thermal barrier coating undergoes 300-800 thermal cycles.

[0042] Example 1

[0043] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0044] (2) Preparation of electrolyte: Two solutions were prepared using an ethanol solution with a water volume fraction of 30% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 0.5 mol / L and the concentration of yttrium nitrate was 0.10 mol / L.

[0045] Zirconium nitrate, yttrium nitrate, and cerium nitrate were added to a solvent to prepare a second electrolyte. In the second electrolyte, the concentrations of zirconium nitrate, cerium nitrate, and yttrium nitrate were 0.5 mol / L, 0.10 mol / L, and 0.10 mol / L, respectively.

[0046] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the sample was placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0047] The coating underwent thermal insulation temperature testing at 1200℃ and thermal shock testing at 1300℃. Figure 2 It can be seen that the thermal insulation temperature of the coating is 52℃ for every 100μm thickness.

[0048] The coating surface after different number of cycles is as follows Figure 4 As shown in (c), the thermal shock life of the coating reaches 450 cycles, which is nearly eight times higher than the thermal shock life of the YSZ thermal barrier coating of 58 cycles, indicating that the addition of the antioxidant barrier layer significantly improves the thermal shock performance of the coating.

[0049] Example 2

[0050] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0051] (2) Preparation of electrolyte: Two solutions were prepared using an ethanol solution with a water volume fraction of 30% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 0.5 mol / L and the concentration of yttrium nitrate was 0.20 mol / L.

[0052] Zirconium nitrate, yttrium nitrate, and cerium nitrate were added to a solvent to prepare a second electrolyte. In the second electrolyte, the concentrations of zirconium nitrate, cerium nitrate, and yttrium nitrate were all 0.5 mol / L.

[0053] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 30°C for 60 minutes under the conditions of pulse voltage of 200V, working frequency of 500Hz and duty cycle of 10%. After deposition, the sample was placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 30°C for 60 minutes under the conditions of pulse voltage of 200V, working frequency of 500Hz and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0054] from Figure 1 As can be seen in (h), compared with Example 1, with the continuous increase of rare earth element content, the number of electrolyte cations increases, the content of formed hydroxides increases, and thus the coating thickness increases. The density of the coating near the substrate is further improved, exhibiting a dendritic structure with circular pore cross-linking.

[0055] Example 3

[0056] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 150μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0057] (2) Preparation of electrolytes: Two solutions were prepared using an ethanol solution with a water volume fraction of 30% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 0.5 mol / L and the concentration of yttrium nitrate was 0.20 mol / L. Zirconium nitrate, yttrium nitrate, cerium nitrate, and gadolinium nitrate were added to the solvent to prepare the second electrolyte. In the second electrolyte, the concentration of zirconium nitrate was 1 mol / L, the concentration of cerium nitrate was 0.10 mol / L, the concentration of yttrium nitrate was 0.10 mol / L, and the concentration of gadolinium nitrate was 0.10 mol / L.

[0058] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 50°C for 10 min under the conditions of pulse voltage of 500V, working frequency of 1000Hz, and duty cycle of 30%. After deposition, a ceramic barrier layer was formed. The sample was then placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped YSZ thermal barrier coating on the sample surface.

[0059] from Figure 1 As can be seen from (j), after adding the barrier layer, the dendritic size of the multi-principal rare earth doped coating cross section decreases and the longitudinal crack defects increase, which is a dendritic structure with longitudinal crack cross-linking.

[0060] Example 4

[0061] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCoCrAlY bonding layer with a thickness of 150μm was sprayed on its surface by wide velocity range high energy plasma spraying.

[0062] (2) Preparation of electrolytes: Two solutions were prepared using an ethanol solution with a water volume fraction of 30% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 0.5 mol / L and the concentration of yttrium nitrate was 0.20 mol / L. Zirconium nitrate, yttrium nitrate, cerium nitrate, and gadolinium nitrate were added to the solvent to prepare the second electrolyte. In the second electrolyte, the concentration of zirconium nitrate was 1 mol / L, the concentration of cerium nitrate was 0.10 mol / L, the concentration of yttrium nitrate was 0.10 mol / L, and the concentration of gadolinium nitrate was 0.10 mol / L.

[0063] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 30°C for 120 min under the conditions of pulse voltage of 300V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the sample was placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped YSZ thermal barrier coating on the sample surface.

[0064] Example 5

[0065] (1) Surface pretreatment of high temperature alloy samples: The surface of iron-based high temperature alloy samples was sandblasted and a CoNiCrAlY adhesive layer with a thickness of 100μm was sprayed on the surface using a wide velocity range high energy plasma spraying method.

[0066] (2) Preparation of electrolytes: Two solutions were prepared using an ethanol solution with a water volume fraction of 10% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 0.1 mol / L and the concentration of yttrium nitrate was 0.01 mol / L. Zirconium nitrate, scandium nitrate, and lanthanum nitrate were added to the solvent to prepare the second electrolyte. In the second electrolyte, the concentration of zirconium nitrate was 1 mol / L, the concentration of scandium nitrate was 0.01 mol / L, and the concentration of lanthanum nitrate was 0.5 mol / L.

[0067] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 0℃ for 60 min under the conditions of pulse voltage of 200V, working frequency of 100Hz, and duty cycle of 5%. After deposition, the sample was placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40℃ for 30 min under the conditions of pulse voltage of 100V, working frequency of 700Hz, and duty cycle of 20%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0068] Example 6

[0069] (1) Surface pretreatment of high temperature alloy samples: The surface of cobalt-based high temperature alloy samples was sandblasted and a NiCoCrAlY bonding layer with a thickness of 50μm was sprayed on the surface by plasma spraying.

[0070] (2) Preparation of electrolytes: Two solutions were prepared using an ethanol solution with a water volume fraction of 50% as the solvent. Aluminum nitrate and yttrium nitrate were added to the solvent to prepare the first electrolyte. In the first electrolyte, the concentration of aluminum nitrate was 1 mol / L and the concentration of yttrium nitrate was 0.50 mol / L. Zirconium nitrate, yttrium nitrate, cerium nitrate, and gadolinium nitrate were added to the solvent to prepare the second electrolyte. In the second electrolyte, the concentration of zirconium nitrate was 0.1 mol / L, the concentration of cerium nitrate was 0.20 mol / L, the concentration of yttrium nitrate was 0.30 mol / L, and the concentration of gadolinium nitrate was 0.50 mol / L.

[0071] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the first electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 30℃ for 30 min under the conditions of pulse voltage of 400V, working frequency of 1000Hz, and duty cycle of 20%. After deposition, the sample was placed in the second electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 40℃ for 100 min under the conditions of pulse voltage of 400V, working frequency of 500Hz, and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped YSZ thermal barrier coating on the sample surface.

[0072] Comparative Example 1

[0073] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0074] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 30% as the solvent, zirconium nitrate is added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 0.5 mol / L.

[0075] (3) Preparation of zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a zirconia thermal barrier coating on the sample surface.

[0076] from Figure 1 As can be seen in (a), the coating exhibits a more dispersed dendritic porous structure.

[0077] from Figure 1 As can be seen in (g), compared with Comparative Example 1, the dendritic structure of the coating after the prefabricated barrier layer is smaller, the coating density is increased, the cross-sectional thickness is uniform, and there are no vertical pores penetrating the coating. It is a dendritic structure with circular pore cross-linking.

[0078] Comparative Example 2

[0079] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0080] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 30% as the solvent, zirconium nitrate is added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 0.5 mol / L.

[0081] (3) Preparation of zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 40°C for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz and duty cycle of 20%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0082] from Figure 1 As can be seen in (b), compared to Comparative Example 1, as the duty cycle increases, the duration of the voltage difference between the anode and cathode is increased, resulting in Zr 4+ The extended time for ions to move toward the cathode and the increased duty cycle also enhance the duration of plasma discharge, leading to the sintering transformation of Zr(OH)4 into ZrO2 coating. As a result, the coating formation rate is faster and the coating thickness is increased.

[0083] Comparative Example 3

[0084] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0085] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 30% as the solvent, zirconium nitrate, yttrium nitrate and cerium nitrate are added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 0.5 mol / L, the concentration of cerium nitrate is 0.05 mol / L, and the concentration of yttrium nitrate is 0.05 mol / L.

[0086] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40℃ for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0087] from Figure 1 As can be seen from (c) and (d), compared with the zirconium oxide coating structure, the YSZ coating has increased thickness and longer dendrites; further comparison reveals that the CeYSZ coating has uniform cross-sectional thickness and no pores penetrating the coating, and the coating structure near the substrate is dense, which is a porous cross-linked dendritic structure.

[0088] from Figure 2 As can be seen, the coating is entirely composed of the t'-ZrO2 phase. Although yttrium and cerium nitrates were added to the electrolyte, no corresponding oxide components were detected in the coating, indicating that yttrium and cerium were successfully doped into the ZrO2 lattice. Furthermore, no binder layer phase was observed in the XRD pattern, indicating that the coating is relatively thick and X-rays cannot penetrate it, resulting in a metallurgical bond between the coating and the binder layer with better bonding strength.

[0089] The coating underwent thermal insulation temperature testing at 1200℃ and thermal shock testing at 1300℃. Figure 3 It can be seen that the thermal insulation temperature of the coating is 40℃ per 100μm thickness. The coating surface after different cycles is as follows: Figure 4 As shown in (a), (b) and (c), the thermal shock lifetime of the coating reaches 105 cycles, which is nearly twice that of the 58 cycles of the YSZ thermal barrier coating, indicating that the doping of Ce element significantly improves the performance of the coating.

[0090] Comparative Example 4

[0091] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 100μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0092] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 30% as the solvent, zirconium nitrate, yttrium nitrate and cerium nitrate are added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 0.5 mol / L, the concentration of cerium nitrate is 0.10 mol / L, and the concentration of yttrium nitrate is 0.10 mol / L.

[0093] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate was used as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 30°C for 60 min under the conditions of pulse voltage of 200V, working frequency of 500Hz and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0094] from Figure 1 As can be seen in (e), compared with Comparative Example 3, as the voltage during the coating preparation process is reduced, the compactness of the coating near the substrate is further improved, and no cracks are observed between the coating and the adhesive layer.

[0095] Comparative Example 5

[0096] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 150μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0097] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 30% as the solvent, zirconium nitrate, yttrium nitrate and cerium nitrate are added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 0.5 mol / L, the concentration of cerium nitrate is 0.20 mol / L, and the concentration of yttrium nitrate is 0.20 mol / L.

[0098] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was performed in the electrolyte at 40℃ for 30 min under the conditions of pulse voltage of 300V, working frequency of 500Hz and duty cycle of 10%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped zirconia thermal barrier coating on the sample surface.

[0099] from Figure 1 As can be seen in (f), the coating cross-section has a uniform thickness, a dense overall structure, and no longitudinal defects, and is a porous cross-linked dendritic structure.

[0100] Comparative Example 6

[0101] (1) Surface pretreatment of high temperature alloy sample: The surface of GH4169 high temperature alloy sample was sandblasted and a NiCrAlY bonding layer with a thickness of 150μm was sprayed on its surface using wide velocity range high energy plasma spraying technology.

[0102] (2) Preparation of electrolyte: Using an ethanol solution with a water volume fraction of 50% as the solvent, zirconium nitrate, yttrium nitrate, cerium nitrate and gadolinium nitrate are added to the solvent to prepare the electrolyte. The concentration of zirconium nitrate in the electrolyte is 1 mol / L, the concentration of cerium nitrate is 0.10 mol / L, the concentration of yttrium nitrate is 0.10 mol / L, and the concentration of gadolinium nitrate is 0.10 mol / L.

[0103] (3) Preparation of rare earth element-doped zirconia thermal barrier coating: The GH4169 high-temperature alloy sample with the adhesive layer prepared in step (1) was placed in the electrolyte. The high-temperature alloy sample was used as the negative electrode and the graphite plate as the positive electrode. A micro-arc oxidation power supply was connected, and electrolysis was carried out in the electrolyte at 20℃ for 60 min under the conditions of pulse voltage of 200V, working frequency of 500Hz and duty cycle of 20%. After deposition, the high-temperature alloy sample was rinsed with deionized water and dried in an oven to form a rare earth element-doped YSZ thermal barrier coating on the sample surface.

[0104] from Figure 1 As can be seen in (i), the longitudinal defects of the coating section are reduced, indicating that it is a porous cross-linked structure.

[0105] A comparison of Comparative Examples 1-6 and Examples 1-6 shows that, in this invention, the cathode liquid-phase plasma electrolysis technology uses the metal being processed as the cathode. The generation of plasma and its participation on the workpiece surface during the processing result in a high energy density that causes the deposits on the workpiece surface to discharge and sinter, forming a thermal barrier coating. Therefore, it can overcome the limitations of the substrate material and still obtain metal or ceramic coatings on non-valve metals. Because plasma participates in the formation of the thermal barrier coating, plasma breakdown occurs at the weak points of the coating during discharge. The high temperature causes the coating at that point to melt and sputter outwards. Under the quenching action of the electrolyte, it rapidly solidifies to form a porous cross-linked dendritic structure, giving the coating excellent properties.

[0106] This invention provides a method for preparing rare-earth-doped YSZ thermal barrier coatings using cathodic liquid-phase plasma electrolytic deposition technology. The entire process is carried out in a liquid-phase environment of the electrolyte, allowing coatings to be formed on the inner and outer surfaces of workpieces with any complex shape. Since only the substrate material needs to be conductive, it is applicable to all metals, offering broad substrate material suitability. The equipment requires only a common micro-arc oxidation power supply, resulting in low equipment cost. The coating composition and structure can be controlled by adjusting power supply parameters such as voltage, frequency, and duty cycle, as well as the electrolyte composition. The process is simple and does not require harsh conditions such as atmospheric protection or high temperatures. During the process, plasma is generated and participates on the workpiece surface. The high energy density of the plasma causes the deposits on the workpiece surface to sinter, forming a ceramic coating and imparting excellent properties to the coating. The equipment used in this invention is simple, process parameters are easy to adjust, and the coating structure and thickness can be flexibly controlled.

[0107] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0108] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for controlling the dendritic structure of a multi-principal rare-earth-doped zirconium oxide thermal barrier coating, characterized in that, Includes the following steps: A high-temperature alloy sample with a bonding layer is placed in a first electrolyte. Using the high-temperature alloy sample as the negative electrode and the graphite plate as the positive electrode, a micro-arc oxidation power supply is connected to perform a first electrolysis, depositing an oxidation-resistant ceramic barrier layer on the surface of the high-temperature alloy sample. Then, the high-temperature alloy sample with the oxidation-resistant ceramic barrier layer is placed in a second electrolyte. Using the high-temperature alloy sample as the negative electrode and the graphite plate as the positive electrode, a micro-arc oxidation power supply is connected to perform a second electrolysis, obtaining a dendritic multi-principal rare-earth-doped zirconium oxide thermal barrier coating. The first electrolyte includes aluminum nitrate and rare-earth element metal salts, and the second electrolyte includes zirconium nitrate and rare-earth element metal salts.

2. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, In the first electrolyte, the concentration of aluminum nitrate is 0.1–1 mol / L, and the concentration of rare earth element metal salt is 0.01–0.5 mol / L. The rare earth element metal salt is one of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

3. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, In the second electrolyte, the concentration of zirconium nitrate is 0.1–1 mol / L, and the concentration of rare earth element metal salt is 0.01–0.5 mol / L. The rare earth element metal salt is two or more of yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

4. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The solvent used in the first and second electrolysis processes is a mixture of ethanol and water.

5. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The rare earth element metal salts in the first and second electrolytes are two or more of the following: yttrium nitrate, cerium nitrate, scandium nitrate, ytterbium nitrate, gadolinium nitrate, and lanthanum nitrate.

6. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The conditions for the first and second electrolysis are as follows: pulse voltage of 200–500V, operating frequency of 100–1000Hz, duty cycle of 5–30%, electrolysis temperature of 0–50℃, and time of 10–120min.

7. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, High-temperature alloy specimens with a binder layer are prepared by the following process: The surface of the high-temperature alloy sample is sandblasted, and then a wide-velocity high-energy plasma spraying method is used to spray the surface of the high-temperature alloy sample to form an adhesive layer, thus obtaining a high-temperature alloy sample with an adhesive layer.

8. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The thickness of the adhesive layer is 50–150 μm.

9. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The adhesive layer material is NiCrAlY, NiCoCrAlY, or CoNiCrAlY.

10. The method for controlling the dendritic structure of the multi-principal rare-earth-doped zirconium oxide thermal barrier coating according to claim 1, characterized in that, The high-temperature alloy samples are iron-based, nickel-based, or cobalt-based high-temperature alloys.

Images