High-entropy zirconate coating with sintering resistance and low heat conduction capacity and preparation method of high-entropy zirconate coating

Abstract

The invention belongs to the technical field of high-entropy ceramic materials, and particularly relates to a high-entropy zirconate coating with sintering resistance and low heat conduction capacity and a preparation method of the high-entropy zirconate coating. The prepared zirconate (La0. 2Sm0. 2Eu0. 2Yb0. 2Y0. 2) 2 (Zr0. 7Nb0. 3) 2O7 is used as a raw material, and the coating is prepared through an atmospheric plasma spraying technology. The prepared coating shows a layered structure, pores exist in the surface and the interior of the coating, and the crystal structure is a pyrochlore phase structure. The high-entropy ceramic coating has the characteristics of low thermal conductivity, high-temperature resistance, sintering resistance and high-temperature phase stability, and has important significance in promoting research of thermal barrier coating materials and application of a thermal barrier coating technology.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal barrier coating materials and preparation thereof, and in particular relates to a high-entropy zirconate coating with sintering resistance and low thermal conductivity and a preparation method thereof. Background Art

[0002] Thermal barrier coatings (TBCs) are primarily used in aerospace engines and gas turbine hot-end components to provide thermal insulation. Their core function is to enhance the long-term serviceability of hot-end components in high-temperature environments, strengthen their thermal insulation, and enhance their ability to withstand extreme environments, thereby extending component life. Ideal TBC materials require low thermal conductivity, a thermal expansion coefficient that matches that of the substrate, excellent high-temperature phase stability, and good sintering resistance. However, YSZ, a commonly used TBC material, undergoes phase transformations when subjected to long-term operation above 1200°C. This phase transformation can lead to performance degradation and coating shedding, particularly severe material damage. Therefore, research into new TBC materials is essential. In recent years, high-entropy ceramics, developed by drawing on the concept of high-entropy alloys, have been shown to manipulate performance by modifying the chemical bonding and band structure of the material. Among these, high-entropy zirconates exhibit superior thermal properties to traditional YSZ (yttria-stabilized zirconia) and are considered promising candidates for next-generation engine TBCs.

[0003] Atmospheric plasma spraying (APS) technology utilizes a high-temperature plasma flame (approximately 15,000°C) to feed powdered material into a nozzle through a powder feeder. The material is heated to a molten state and then accelerated by an airflow to form a coating on the workpiece surface. Key process parameters include power, gas flow rate, powder feed rate, and spray distance. When thermal barrier coatings operate under ultra-high temperature conditions, prolonged operation can cause material deformation and shedding, shortening their service life or even leading to failure.

[0004] In response to the problems existing in the above-mentioned thermal barrier coating material YSZ, the development of high-entropy rare earth zirconate ceramic coatings with low thermal conductivity and high-temperature resistance and sintering resistance and their preparation methods are of great significance to promoting the development of thermal barrier coating technology. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of existing materials and provide a high-entropy zirconate ceramic coating with low thermal conductivity and sintering resistance and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention provides a high entropy zirconate coating with sintering resistance and low thermal conductivity. The high entropy ceramic coating structure is a pyrochlore structure, and the chemical composition of the coating is (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr0.7 Nb 0.3 )2O7.

[0007] Furthermore, the preparation method of the high-entropy zirconate coating with sintering resistance and low thermal conductivity comprises the following steps: step A, weighing rare earth oxide powder and calcining (900°C, 2h) to remove moisture and impurities, cooling and weighing powders according to the molar ratio of La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, and Nb2O5 of 1:1:1:1:1:3.5:1.5, placing the powders in a ball mill for mixing; drying and sieving the powders after ball milling, placing them in a muffle furnace, and reacting them by a high-temperature solid-phase method to obtain (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 powder;

[0008] Furthermore, the solution medium used in the ball mill is anhydrous ethanol, the ball milling beads are made of zirconia material, the mass ratio of ball milling beads to powder is 1.5:1, the ball milling time is 8 to 12 hours, and the rotation speed is 320 to 400 r / min.

[0009] Furthermore, the drying temperature is 70-100° C., and the drying time is 12-24 hours.

[0010] Furthermore, the solid phase reaction temperature in air atmosphere is 1400-1500° C., the holding time is 2-8 hours, and the heating rate is 5° C. / min.

[0011] In step B, PVA is added to the powder, the powder is bonded and granulated, and the powder is sieved to obtain powder particles between 80 and 200 meshes. The substrate is sandblasted to remove the oxide layer and other contaminants on the substrate surface; the powder is sprayed on the substrate surface by atmospheric plasma spraying to form a ceramic coating.

[0012] Furthermore, the PVA is a 4 wt% polyvinyl alcohol solution prepared by mixing polyvinyl alcohol and deionized water.

[0013] Furthermore, the sand used for the substrate sand blasting is white corundum sand with a mesh size of 30 to 60.

[0014] Furthermore, the spraying power of the atmospheric plasma spraying is 35-45 kW, the argon gas flow rate is 30-50 L / min, the powder feeding rate is 30-50 g / min, and the spraying distance is 80-120 mm.

[0015] Through the above technical solution, it can be seen that the beneficial effects of the present invention are:

[0016] 1. The powder used to prepare this high-entropy ceramic coating is obtained by applying an AB high-entropy design to La2Zr2O7. Due to the porosity of the material and the high-entropy design of the AB co-doping, the material exhibits low thermal conductivity.

[0017] 2. The present invention is to (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 ceramic coating was calcined at high temperature for 100 hours, and XRD diffraction analysis was performed on the calcined sample. The phase structure did not change, and the shape of the coating did not change, indicating that the sample is stable in the actual working environment and has good high-temperature resistance and sintering resistance.

[0018] 3. The powder of the present invention is prepared by a high-temperature solid-phase reaction method, in which multiple substances react chemically in a high-temperature environment to generate new substances. This method has low cost, high yield, and a simple preparation process. The present invention uses atmospheric plasma spraying to prepare a high-entropy zirconate ceramic coating. This thermal barrier coating preparation technology has a high deposition rate and does not require many spraying materials. It is relatively low in cost, simple to operate, and the process is relatively mature and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 XRD patterns of the coatings prepared in Examples 1-6 and Comparative Examples 1 and 3;

[0020] Figure 2 The SEM images of the surfaces (a, b) and cross-sections (c, d) of the coatings prepared in Example 1 and Example 2 are shown; images a and c are from Example 1, and images b and d are from Example 2.

[0021] Figure 3 XRD patterns of the coatings prepared in Examples 2, 4, 6 and Comparative Example 5 before and after calcination at 1250° C. for 100 hours;

[0022] Figure 4 TG and DSC curves of the coatings prepared in Examples 3 and 6; Figure a is for Example 3, and Figure b is for Example 6;

[0023] Figure 5 Thermal diffusivity diagrams of the coatings prepared in Examples 3, 6 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to specific embodiments.

[0025] The substrates described in the following examples and comparative examples are made of 304 stainless steel.

[0026] Example 1:

[0027] The present embodiment has a high entropy zirconate coating with sintering resistance and low thermal conductivity and its preparation method, the specific steps are as follows: Step A, La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, Nb2O5 powders are calcined at 900℃ for 2h to remove moisture and impurities, and then cooled in the furnace. After cooling, the given chemical formula (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 molar ratio is weighed and mixed. The mixed powder is packed into a can according to the mass ratio of powder and zirconium oxide ball milling beads of 1 to 1.5. The medium is anhydrous ethanol, and the medium and powder are mixed at a mass ratio of 2 to 1. Place it in a ball mill and ball mill at a speed of 350r / min for 8h. The ball-milled slurry is placed in an oven and dried at 80℃ for 12h. After drying, it is heated to 1500℃ in a muffle furnace at a heating rate of 5℃ / min and kept warm for 6h to obtain (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 powder.

[0028] Step B: The cooled powder is ground through an 80-mesh sieve to obtain ceramic powder. 27 ml of a 4 wt% polyvinyl alcohol solution is added to every 100 g of powder for bonding and granulation, and powder particles of 80 to 200 mesh are screened. The substrate is sandblasted with 40-mesh white corundum sand by a sandblaster to remove pollutants on the substrate surface and make the substrate surface uniform. The powder particles are sprayed on the substrate surface by atmospheric plasma spraying to form a ceramic coating (thickness of 271.29 ± 40.51 μm). The spraying parameters are: spraying power 35 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feeding rate 40 g / min.

[0029] Example 2:

[0030] The difference between this embodiment and embodiment 1 is that the thickness of the ceramic coating formed in step B is 345.62±18.27 μm, and the spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feeding rate 40 g / min.

[0031] Example 3:

[0032] The present embodiment has a high entropy zirconate coating with sintering resistance and low thermal conductivity and its preparation method, the specific steps are as follows: Step A, La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, Nb2O5 powders are calcined at 900℃ for 2h to remove moisture and impurities, and then cooled in the furnace. After cooling, the given chemical formula (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 molar ratio is weighed and mixed. The mixed powder is packed into a can according to the mass ratio of powder and zirconium oxide ball milling beads of 1 to 1.5. The medium is anhydrous ethanol, and the medium and powder are mixed at a mass ratio of 2 to 1. The mixture is placed in a ball mill and ball milled at a speed of 380r / min for 10 hours. The ball-milled slurry is placed in an oven and dried at 80℃ for 16 hours. After drying, it is heated to 1450℃ in a muffle furnace at a heating rate of 5℃ / min and kept warm for 6 hours to obtain (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 powder.

[0033] Step B: The cooled powder is ground through an 80-mesh sieve to obtain ceramic powder. 27 ml of a 4 wt% polyvinyl alcohol solution is added to every 100 g of powder for bonding and granulation, and powder particles of 80 to 200 mesh are screened. The substrate is sandblasted with 50-mesh white corundum sand by a sandblaster to remove pollutants on the substrate surface and make the substrate surface uniform. The powder particles are sprayed on the substrate surface by atmospheric plasma spraying to form a ceramic coating (thickness of 244.51 ± 12.49 μm). The spraying parameters are: spraying power 40 kW, argon gas flow rate 50 L / min, spraying distance 100 mm, and powder feeding rate 40 g / min.

[0034] Example 4:

[0035] The difference between this embodiment and embodiment 3 is that the thickness of the ceramic coating formed in step B is 345.68±24.54 μm, and the spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 120 mm, and powder feeding rate 40 g / min.

[0036] Example 5:

[0037] The present embodiment has a high entropy zirconate coating with sintering resistance and low thermal conductivity and its preparation method, the specific steps are as follows: Step A, La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, Nb2O5 powders are calcined at 900℃ for 2h to remove moisture and impurities, and then cooled in the furnace. After cooling, the given chemical formula (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 molar ratio is weighed and mixed. The mixed powder is packed into a can according to the mass ratio of powder to zirconium oxide ball milling beads of 1 to 1.5. The medium is anhydrous ethanol, and the medium and powder are mixed at a mass ratio of 2 to 1. The mixture is placed in a ball mill and ball milled at a speed of 400r / min for 12h. The ball-milled slurry is placed in an oven and dried at 80℃ for 24h. After drying, it is heated to 1450℃ in a muffle furnace at a heating rate of 5℃ / min and kept warm for 8h to obtain (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 powder.

[0038] Step B: The cooled powder is ground through an 80-mesh sieve to obtain ceramic powder. 27 ml of a 4 wt% polyvinyl alcohol solution is added to every 100 g of powder for bonding and granulation, and powder particles of 80 to 200 mesh are screened. A sandblaster is used to sandblast the substrate with 60-mesh white corundum sand to remove pollutants on the substrate surface and make the substrate surface uniform. Atmospheric plasma spraying is used to spray the powder particles on the substrate surface to form a ceramic coating (thickness of 398.95 ± 28.20 μm). The spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feeding rate 30 g / min.

[0039] Example 6:

[0040] The difference between this embodiment and embodiment 5 is that the thickness of the ceramic coating formed in step B is 345.69±13.83 μm, and the spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feeding rate 50 g / min.

[0041] Comparative Example 1:

[0042] The difference between this embodiment and embodiment 1 is that the thickness of the ceramic coating formed in step B is 387.73±21.24 μm, and the spraying parameters are: spraying power 45 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feeding 40 g / min.

[0043] Comparative Example 2:

[0044] The difference between this embodiment and embodiment 3 is that the thickness of the ceramic coating formed in step B is 408.09±19.20 μm, and the spraying parameters are: spraying power 40 kW, argon gas flow rate 30 L / min, spraying distance 100 mm, and powder feeding 40 g / min.

[0045] Comparative Example 3:

[0046] The difference between this embodiment and embodiment 3 is that the thickness of the ceramic coating formed in step B is 312.67±23.59 μm, and the spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 80 mm, and powder feeding 40 g / min.

[0047] Comparative Example 4:

[0048] This comparative example provides a Gd2Zr2O7 thermal barrier coating and a preparation method thereof, wherein the preparation method is:

[0049] Step A: Gd2O3 and ZrO2 are heated at 850°C for 2 hours to remove moisture and impurities. After cooling, the powders are weighed and mixed according to the molar ratio of the chemical formula Gd2Zr2O7. The mixed powders are canned in a ratio of 1:1.5 by weight of powder to zirconia ball milling beads. The mixed medium is anhydrous ethanol, and the medium and powder are mixed in a ratio of 2:1 by weight. The mixture is then ball milled at 350 rpm for 8 hours. The milled slurry is dried in an oven at 80°C for 12 hours. After drying, it is heated in a muffle furnace at a heating rate of 5°C / min to 1500°C and held at this temperature for 6 hours to prepare Gd2Zr2O7 powder.

[0050] Step B: The cooled powder is ground through an 80-mesh sieve to obtain ceramic powder. 27 ml of a 4 wt% polyvinyl alcohol solution is added to every 100 g of the powder for bonding and granulation, and the powder particles are screened to 80 to 200 mesh. The substrate is sandblasted with 40-mesh white corundum sand by a sandblaster to remove contaminants on the substrate surface and make the substrate surface uniform. The powder particles are sprayed onto the substrate surface by atmospheric plasma spraying to form a ceramic coating (thickness of 223.45 ± 20.53 μm). The spraying parameters are: spraying power 40 kW, argon gas flow rate 50 L / min, spraying distance 100 mm, and powder feed rate 30 g / min.

[0051] Comparative Example 5:

[0052] This comparative example provides a La2Zr2O7 thermal barrier coating and a preparation method thereof, wherein the preparation method is:

[0053] Step A: La2O3 and ZrO2 are heated at 900°C for 2 hours to remove moisture and impurities. After cooling, powders are weighed and mixed according to the molar ratio of the chemical formula La2Zr2O7. The mixed powders are canned in a ratio of 1:1.5 by weight of powder and zirconium oxide ball milling beads. The medium is anhydrous ethanol, and the medium and powder are mixed in a ratio of 2:1 by weight. The mixture is placed in a ball mill and ball milled at 400 rpm for 12 hours. The ball-milled slurry is placed in an oven at 80°C for 24 hours. After drying, it is heated in a muffle furnace at a heating rate of 5°C / min to 1450°C and held at this temperature for 8 hours to prepare La2Zr2O7 powder.

[0054] Step B: The cooled powder is ground through an 80-mesh sieve to obtain ceramic powder. 27 ml of a 4 wt% polyvinyl alcohol solution is added to every 100 g of the powder for bonding and granulation, and the powder particles are screened to 80 to 200 mesh. The substrate is sandblasted with 60-mesh white corundum sand by a sandblasting machine to remove contaminants on the substrate surface and make the substrate surface uniform. The powder particles are sprayed onto the substrate surface by atmospheric plasma spraying to form a ceramic coating (thickness of 278.42 ± 23.41 μm). The spraying parameters are: spraying power 40 kW, argon gas flow rate 40 L / min, spraying distance 100 mm, and powder feed rate 30 g / min.

[0055] Figure 1 (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3)2O7 coating XRD pattern; It can be seen from the spectrum that the high entropy zirconate ceramic coatings prepared in Examples 1-6 and Comparative Examples 1 and 3 are all pyrochlore structures without obvious miscellaneous peaks.

[0056] Figure 2 (La prepared in Example 1 and Example 2 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )Surface SEM images and cross-sectional SEM images of 2O7 coating; Figure 2 It can be seen that both Examples 1 and 2 have typical layered coating structures. Example 1 has pores and microcracks on its surface, and unmelted particles can also be seen. Compared with Example 1, the coating prepared in Example 2 has fewer pores and a smoother surface, with essentially no unmelted particles.

[0057] Figure 3 The XRD patterns of the coatings prepared in Examples 2, 4, 6, and Comparative Example 5 before and after sintering at 1250°C for 100 hours show that the coatings prepared in Examples 2, 4, and 6 retain a well-developed pyrochlore phase after sintering at 1250°C for 100 hours. The peak positions and intensities remain essentially unchanged, and no peak separation occurs. This demonstrates that the materials maintain good performance even under high-load conditions in practical applications, exhibiting excellent sintering resistance and high-temperature resistance. However, in Comparative Example 5, a peak separation appears after sintering at 1250°C for 100 hours, and the peak intensity increases, demonstrating that the sintering resistance of Comparative Example 5 is not very good, and that changes in the material structure may lead to material failure in practical applications.

[0058] Figure 4 TG and DSC curves of the ceramic coatings prepared in Examples 3 and 6 show that the high entropy ceramic coatings prepared in Examples 3 and 6 have good thermal stability between room temperature and 1250°C, and the thermal weight loss is less than 1%.

[0059] Figure 5 The thermal diffusivity curves for the ceramic coatings prepared in Examples 3 and 6 and Comparative Examples 1-3 show changes in temperature. Within the same test temperature range, the thermal diffusivity values ​​for Example 6 are significantly lower than those for Comparative Examples 1-3. This low thermal diffusivity is crucial for thermal barrier coatings, significantly improving insulation efficiency and lowering the service temperature of the base metal, thereby extending the service life of hot-end components in ultra-high temperature environments.

[0060] In summary, the present invention prepares (La 0.2 Sm 0.2 Eu0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 The 2O7 high-entropy ceramic coating has good high-temperature phase stability, low thermal conductivity, and sintering resistance. The high-entropy zirconate ceramic coating and its preparation method provide a new approach to preparing high-entropy ceramic coatings for other systems and have broad application prospects in the field of thermal barrier coatings for aircraft engines.

[0061] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A high entropy zirconate coating with sintering resistance and low thermal conductivity, characterized in that: The high entropy zirconate ceramic coating is a pyrochlore structure, and its chemical composition is (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7.

2. A method for preparing a high entropy zirconate coating having sintering resistance and low thermal conductivity according to claim 1, characterized in that: The following steps are involved: To (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 ceramic powder is added with PVA to bond and granulate. After granulation, it is sieved and powder particles between 80 and 200 mesh are taken and sprayed on the substrate surface by atmospheric plasma to form a ceramic coating.

3. The method for preparing a high entropy zirconate coating having sintering resistance and low thermal conductivity according to claim 2, characterized in that: The (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 ceramic powder is prepared by mechanical ball milling and high temperature solid phase method. The specific steps are as follows: The raw materials La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, and Nb2O5 powders were calcined to remove moisture and impurities, weighed according to the chemical molar ratio, ball-milled, mixed, dried, sieved, placed in a muffle furnace, and reacted by a high-temperature solid-phase method to prepare (La 0.2 Sm 0.2 Eu 0.2 Yb 0.2 Y 0.2 )2(Zr 0.7 Nb 0.3 )2O7 ceramic powder.

4. The method for preparing a high entropy zirconate coating having sintering resistance and low thermal conductivity according to claim 3, characterized in that: The calcination temperature is 900° C. and the calcination time is 2 h.

5. The method for preparing a high entropy zirconate ceramic coating according to claim 3, wherein: The ball milling mixing medium is anhydrous ethanol, zirconia beads are used as ball milling beads, the mass ratio of ball milling beads to the total mass of La2O3, Sm2O3, Y2O3, Yb2O3, Eu2O3, ZrO2, and Nb2O5 powders is 1.5:1, the ball milling time is 8 to 12 hours, and the rotation speed is 320 to 400 r / min.

6. The method for preparing a high entropy zirconate coating with sintering resistance and low thermal conductivity according to claim 3, characterized in that: The drying temperature is 70-100° C., and the drying time is 12-24 hours.

7. The method for preparing a high entropy zirconate coating with sintering resistance and low thermal conductivity according to claim 3, characterized in that: The high-temperature solid-phase method has a heating rate of 5°C / min, a temperature of 1400-1500°C, and a reaction time of 2-8h.

8. The method for preparing a high entropy zirconate coating with sintering resistance and low thermal conductivity according to claim 2, characterized in that: The PVA is a 4 wt% polyvinyl alcohol solution prepared by mixing polyvinyl alcohol and deionized water.

9. The method for preparing a high entropy zirconate coating with sintering resistance and low thermal conductivity according to claim 2, characterized in that: The spraying parameters of atmospheric plasma spraying are: spraying power 35-45kW, argon gas flow rate 30-50L / min, powder feeding rate 30-50g / min, and spraying distance 80-120mm.

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