Multi-element rare earth doped HfO2 thermal barrier coating material and preparation method thereof

Abstract

The invention relates to a multi-element rare earth doped HfO2 thermal barrier coating material and a preparation method thereof, and belongs to the technical field of thermal protection coatings. The thermal barrier coating material is prepared from Gd2O3, Yb2O3, Y2O3 and HfO2, wherein the Gd2O3, the Yb2O3, the Y2O3 and the HfO2 are The thermal barrier coating material is of a single c-phase structure. The raw material powder is ground to obtain mixed powder, the mixed powder is sintered after being ground and compacted, and finally the coating material is obtained through grinding and screening. The rare earth elements Gd < 3 + >, Yb < 3 + > and Y < 3 + > with large ion radiuses are doped to replace tetravalent Hf4 < + > crystal lattice positions, a large number of point defects are formed in crystal lattices, and a large number of oxygen vacancies are generated due to the charge balance effect, so that phonon scattering heat transfer is remarkably enhanced, and the multi-element rare earth doped HfO2 thermal barrier coating material has low thermal conductivity.

Description

Technical Field

[0001] The present invention relates to a multi-element rare earth doped HfO2 thermal barrier coating material and a preparation method thereof, belonging to the technical field of thermal protective coatings. Background Art

[0002] The continuous development of jet propulsion systems toward higher thrust-to-weight ratios means that the engine's hot-end components will be subjected to higher operating temperatures. While the front inlet temperature of a current turbine engine with a thrust-to-weight ratio of 10 is approximately 2000K, the operating temperature of the hot-end components of engines with higher thrust-to-weight ratios may reach 2500K-3000K. Under these operating conditions, conventional 6-8wt% Y2O3-stabilized ZrO2 (YSZ) thermal barrier coatings no longer meet the thermal protection requirements. Prolonged service at operating temperatures exceeding 1200°C can cause sintering and phase transformation of the YSZ coating. Therefore, researchers have developed rare earth oxide (RE2O3)-stabilized ZrO2 materials, which offer even higher temperature resistance. Furthermore, the use of multiple RE2O3 co-doped ZrO2 materials can further improve sintering resistance and reduce thermal conductivity (e.g., Chinese patent application CN 115536386 A). However, materials co-doped with ZrO2 and containing multiple RE2O3 are prone to failure when used at temperatures above 1600°C. Furthermore, the higher the service temperature, the more pronounced the failure behavior becomes, manifested primarily by increasingly intense sintering. This sintering causes grain growth, structural densification, and decreased porosity. This increases the thermal conductivity and elastic modulus of the coating, reducing its thermal insulation and mechanical properties, ultimately impacting its service life. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a multi-element rare earth doped HfO2 thermal barrier coating material and a preparation method thereof.

[0004] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0005] A multi-element rare earth doped HfO2 thermal barrier coating material, wherein the thermal barrier coating material is recorded as xGd2O3-yYb2O3-zY2O3-75HfO2 in molar percentage, wherein x, y, and z are all greater than 0, x+y+z=25, x is 1-5, and y:z=1:3; the thermal barrier coating material has a single c-phase structure.

[0006] A method for preparing the multi-element rare earth doped HfO2 thermal barrier coating material of the present invention comprises the following steps:

[0007] (1) Pure La2O3, Gd2O3, Yb2O3, Y2O3 and HfO2 powder raw materials are charged into a ball mill according to the molar ratio, and anhydrous ethanol and zirconia grinding balls are added for ball milling to obtain a mixed powder;

[0008] (2) grinding and compacting the mixed powder, sintering the mixed powder at 1000-1200°C for 2-4 hours, then sintering the mixed powder at 1300-1400°C for 2-6 hours, and finally sintering the mixed powder at 1500-1600°C for 2-10 hours, and cooling the mixed powder to obtain a sintered powder;

[0009] (3) The sintered powder is ground and sieved, anhydrous ethanol and zirconium oxide grinding balls are added for ball milling, and sieved to obtain a multi-element rare earth doped HfO2 thermal barrier coating material.

[0010] Preferably, in step (1), the particle size of the powder raw materials is 0.1 μm to 3 μm.

[0011] Preferably, in step (1), the pure powder raw material is obtained by the following method: calcining the powder raw material at 800-1000° C. for 1-1.5 h, and cooling to obtain a pure powder raw material.

[0012] Preferably, in step (1), during ball milling, the mass ratio of zirconia grinding balls, powder raw material and anhydrous ethanol is 3:1:2 to 5:1:2.

[0013] Preferably, in step (1), during ball milling, the ball milling speed is 300-400 rpm, and the ball milling time is 3-6 h.

[0014] Preferably, in step (3), the product is ground and passed through a 10-mesh sieve.

[0015] Preferably, in step (3), during ball milling, the mass ratio of zirconia grinding balls, sintered powder and anhydrous ethanol is 3:1:2 to 5:1:2.

[0016] Preferably, in step (3), during ball milling, the zirconia grinding balls are composed of zirconia grinding balls with diameters of 1 mm, 3 mm and 5 mm in a mass ratio of 1:3:1.

[0017] Preferably, in step (3), sieving is performed to obtain a powder having a particle size of 0.2 to 2 μm.

[0018] Preferably, in step (1) and step (3), after the ball milling is completed, the anhydrous ethanol is removed by rotary evaporation and the mixture is dried to obtain a mixed powder; more preferably, the rotary evaporation temperature is 70-80°C, the rotation speed is 30-50 r / min; the drying temperature is 80-120°C, and the drying time is 10-12 h.

[0019] Beneficial effects

[0020] The present invention provides a multi-element rare earth doped HfO2 thermal barrier coating material, wherein the raw materials of the thermal barrier coating material are composed of Gd2O3, Yb2O3, Y2O3 and HfO2; by strictly controlling the selection and dosage of the doping substances, the material has a single c-phase stable structure, and the Gd with a larger ion radius is 3+ 、Yb 3+ and Y 3+ Rare earth element doping to replace tetravalent Hf 4+ The lattice position forms a large number of point defects in the lattice, and a large number of oxygen vacancies are generated due to the charge balance effect, which significantly enhances the phonon scattering heat transfer and makes the multi-element rare earth doped HfO2 thermal barrier coating material have a lower thermal conductivity. The doping elements can replace Hf 4+ Entering the HfO2 lattice, due to Gd 3+ 、Yb 3+ 、Y 3+ The ionic radius of Hf 4+ , thus generating lattice distortion in the HfO2 lattice, which in turn enhances phonon scattering, reduces thermal conductivity, and also reduces the driving force for phase transitions, inhibiting element diffusion, thereby improving high-temperature stability and sintering resistance. Small amounts of Gd2O3 doping can improve sintering resistance; Yb2O3 can form defect clusters at grain boundaries, inhibiting grain boundary movement, further increasing sintering resistance; and Y2O3 can achieve overall performance improvements. Through co-doping modification of multiple rare earth oxides, the advantages of each doping component can be combined to achieve excellent thermal insulation performance, improving the high-temperature sintering resistance and phase stability of traditional thermal barrier coatings.

[0021] The present invention provides a method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material, wherein each raw material powder is ground to obtain a mixed powder, the mixed powder is ground, vibrated and then sintered, and finally ground and sieved to obtain the coating material. The initial grain size of the material prepared by the multi-step sintering method is smaller than that of the material prepared by the single-step sintering method, which can increase the intrinsic sintering resistance of the material; and because the total amount of rare earth oxide doping is high and the ion radius is large, the concentration of crystal defects inside the material increases, effectively reducing the diffusion rate between the lattices during the sintering process. In addition, due to the high melting point characteristics of HfO2 itself, the difficulty of densification of coatings and ceramics increases. Under these combined effects, the HfO2 thermal barrier coating material has better resistance to high-temperature sintering. The method is simple to operate, low in cost, and highly reliable. In particular, by adopting a multi-step sintering method to prepare the coating material, the intrinsic sintering resistance of the material is increased and the process time is shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The XRD patterns of the initial state of the materials of the examples and comparative examples are shown in FIG.

[0023] Figure 2The XRD patterns of the examples and comparative examples after heat treatment at 1400°C are shown.

[0024] Figure 3 This is a comparison chart of the sintering resistance of the materials of Example 1 and Comparative Example 1 after heat treatment at 1400°C.

[0025] Figure 4 is the thermal conductivity of the materials of Examples and Comparative Examples.

[0026] Figure 5 The microstructures of the materials prepared in Example 1 and Comparative Example 1.

[0027] Figure 6 Schematic diagram of the multi-step sintering of multi-rare earth doped HfO2 thermal barrier coating material. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] (1) Gd2O3, Yb2O3, Y2O3, and HfO2 powders with a particle size of 0.1 μm to 3 μm were loaded into different corundum crucibles, and calcined at 1000°C for 1.5 h in a box-type resistance furnace. The crucibles were then cooled to room temperature to remove moisture and impurities adsorbed in the powders.

[0031] (2) Pure Gd2O3, Yb2O3, Y2O3 and HfO2 powder raw materials are loaded into a polyurethane ball mill according to a molar ratio of 1:6:18:75, and anhydrous ethanol and zirconia balls are added. The mass ratio of zirconia balls, powder raw materials and anhydrous ethanol is 4:1:2 to obtain a mixture 1# of original powder and ball material.

[0032] (3) The polyurethane ball mill jar containing the mixture 1# was transferred to a planetary ball mill and mechanically ball-milled for 4 h at a ball-milling speed of 300 r / min; the ball-milled suspension 1# was poured into an eggplant-shaped bottle and dried on a rotary evaporator at a water bath temperature of 70°C and a speed of 50 r / min; the mixed powder after rotary evaporation was dried in a drying oven at a drying temperature of 100°C for 12 h to obtain a dry mixed powder.

[0033] (4) The dried mixed powder is preliminarily ground until no obvious lumps are left. The resulting powder is placed in a corundum crucible and sintered in an air atmosphere through a multi-step sintering method, including low-temperature preheating at 1200°C for 2 hours, preliminary sintering at 1400°C for 4 hours, and high-temperature sintering at 1600°C for 6 hours. The powder is then cooled in the furnace to obtain a ternary doped hafnium oxide-based sintered powder.

[0034] (5) The sintered powder is preliminarily ground until no obvious lumps are left and the particle size reaches less than 2 mm, and then transferred to a polyurethane ball mill, and anhydrous ethanol and zirconia balls are added. The mass ratio of zirconia balls, powder raw materials and anhydrous ethanol is 4:1:2 to obtain a mixture 2# of sintered powder and ball materials.

[0035] (6) The polyurethane ball mill jar containing the mixture 2# was transferred to a planetary ball mill and mechanically ball-milled for 4 h at a ball-milling speed of 300 r / min; the zirconia grinding balls were composed of zirconia grinding balls with diameters of 1 mm, 3 mm, and 5 mm at a mass ratio of 1:3:1; the milled suspension 2# was poured into an eggplant-shaped bottle and dried on a rotary evaporator at a water bath temperature of 70°C and a speed of 50 r / min; the sintered powder after rotary evaporation was dried in a drying oven at a drying temperature of 100°C for 12 h to obtain a dry sintered powder.

[0036] (7) The dried sintered powder is sieved with a standard test sieve to obtain a powder with a particle size of 0.2 to 2 μm, i.e., a multi-element rare earth doped HfO2 thermal barrier coating material; denoted as 1GdYbYSH.

[0037] Example 2

[0038] The specific process is the same as that of Example 1, with only the components changed. The molar ratio of Gd2O3, Yb2O3, Y2O3 and HfO2 is 3:5.5:16.5:75; denoted as 3GdYbYSH.

[0039] Example 3

[0040] The specific process is the same as that of Example 1, with only the components changed. The molar ratio of Gd2O3, Yb2O3, Y2O3 and HfO2 is 5:5:15:75; denoted as 5GdYbYSH.

[0041] Comparative Example

[0042] The YSZ used is commercial powder with a composition of Y2O3 and ZrO2 in a molar ratio of 4:96; it is denoted as YSZ.

[0043] like Figure 1 and 2 The XRD patterns of the embodiment and the comparative example are shown. The initial state of the conventional YSZ material is t phase, which decomposes into m+c phase after high temperature heat treatment, and has poor phase stability. However, the multi-element rare earth doped HfO2 thermal barrier coating material has a high total doping content, and its doping elements are closely related to Hf 4+ Due to the large radius difference, both the initial state and after high-temperature heat treatment are single c-phase structures with excellent phase stability.

[0044] like Figure 3The figure shows a comparison of the microstructures of the embodiment and the comparative example after the same heat treatment time. After sintering at 1400°C / 32h, the grain size of the HfO2 thermal barrier coating material is approximately 2.95μm, which is smaller than the 4.35μm of the ZrO2 thermal barrier coating material. After sintering at 1400°C / 32h, the porosities of the ZrO2 and HfO2 thermal barrier coating materials are 1.82% and 3.53%, respectively. The porosity of the HfO2 material is approximately twice that of the ZrO2 thermal barrier coating material. The smaller the grain size and the higher the porosity after sintering, the better the sintering resistance of the material.

[0045] like Figure 4 The thermal conductivity data of the embodiments and comparative examples are shown. In the range of 1000-1400°C, the thermal conductivity of the multi-element rare earth doped HfO2 thermal barrier coating material is lower than that of the YSZ material. The lowest thermal conductivity is 0.85W (m·K) at 1000°C, while the thermal conductivity of the YSZ material at 1000°C is 1.42W (m·K).

[0046] like Figure 5 The figure shows the grain comparison between multi-step sintering and single-step sintering. The initial grain size after multi-step sintering is small and the intrinsic anti-sintering ability is strong. Figure 6 The figure shows a schematic diagram of multi-step sintering and single-step sintering. In the low-temperature stage, the heating power of the material is relatively low, and the various materials used for the reaction are gradually activated. The temperature is increased when key sintering reactions or microstructure adjustments are required, which reduces energy waste and meets the requirements of energy conservation and emission reduction. In addition, the high-temperature sintering time of the process is shortened, and production efficiency is improved.

[0047] In summary, the invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention shall be deemed to be within the scope of protection of the present invention.

Claims

1. A multi-element rare earth doped HfO2 thermal barrier coating material, characterized by: The thermal barrier coating material is recorded as xGd2O3-yYb2O3-zY2O3-75HfO2 in molar percentage, where x, y, and z are all greater than 0, x+y+z=25, x is 1-5, and y:z=1:3; the thermal barrier coating material has a single c-phase structure.

2. A method for preparing the multi-element rare earth doped HfO2 thermal barrier coating material according to claim 1, characterized in that: The method steps include: (1) Pure La2O3, Gd2O3, Yb2O3, Y2O3 and HfO2 powder raw materials are charged into a ball mill according to the molar ratio, and anhydrous ethanol and zirconia grinding balls are added for ball milling to obtain a mixed powder; (2) grinding and compacting the mixed powder, sintering the mixed powder at 1000-1200°C for 2-4 hours, then sintering the mixed powder at 1300-1400°C for 2-6 hours, and finally sintering the mixed powder at 1500-1600°C for 2-10 hours, and cooling the mixed powder to obtain a sintered powder; (3) The sintered powder is ground and sieved, anhydrous ethanol and zirconium oxide grinding balls are added for ball milling, and sieved to obtain a multi-element rare earth doped HfO2 thermal barrier coating material.

3. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (1), the particle size of the powder raw materials is 0.1 μm to 3 μm.

4. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (1), the pure powder raw material is obtained by the following method: calcining the powder raw material at 800-1000° C. for 1-1.5 hours, and cooling to obtain a pure powder raw material.

5. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (1), during ball milling, the mass ratio of zirconia grinding balls, powder raw materials and anhydrous ethanol is 3:1:2 to 5:1:2; the ball milling speed is 300 to 400 rpm, and the ball milling time is 3 to 6 hours.

6. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (3), the product is ground and passed through a 10-mesh sieve.

7. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (3), during ball milling, the mass ratio of zirconia grinding balls, sintered powder and anhydrous ethanol is 3:1:2 to 5:1:

2.

8. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (3), during ball milling, the zirconia grinding balls are composed of zirconia grinding balls with diameters of 1 mm, 3 mm and 5 mm in a mass ratio of 1:3:

1.

9. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (3), the powder is sieved to obtain a particle size of 0.2 to 2 μm.

10. The method for preparing a multi-element rare earth doped HfO2 thermal barrier coating material according to claim 2, characterized in that: In step (1) and step (3), after the ball milling is completed, the anhydrous ethanol is removed by rotary evaporation and the mixture is dried to obtain a mixed powder; more preferably, the rotary evaporation temperature is 70-80° C., the rotation speed is 30-50 r / min; the drying temperature is 80-120° C., and the drying time is 10-12 h.

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