A method for preparing a deformable zirconia-based ceramic dynamic seal material

Abstract

The application discloses a preparation method of a deformable zirconia-based ceramic dynamic sealing material, and is based on the structure / function integrated design principle of advanced ceramic materials, combines the high wear resistance of a three-dimensional continuous structure zirconia-based self-lubricating composite material and the pseudo-elasticity of a zirconia-based shape memory ceramic, and constructs the zirconia-based ceramic dynamic sealing material with a layered structure through a layer-by-layer dry pressing and hot pressing sintering method. The surface lubricating wear-resistant layer is a graphite / zirconia self-lubricating composite material with a three-dimensional continuous structure, and the internal deformation mark layer is a cerium oxide / zirconia composite material with pseudo-elasticity.

Description

Technical Field

[0001] This invention belongs to the field of ceramic dynamic sealing material preparation technology, and relates to a method for preparing ceramic dynamic sealing materials, particularly a method for preparing deformable zirconia-based ceramic dynamic sealing materials. Background Technology

[0002] Carbon graphite materials and their composites are widely used as dynamic sealing materials in aerospace power and transmission systems. Their tribological and mechanical properties directly affect the reliability, stability, and durability of sealing devices under harsh operating conditions. However, traditional carbon graphite materials suffer from low strength, poor oxidation resistance, and poor wear resistance, making it difficult to meet the sealing requirements under high-temperature conditions (≥400 ℃). Zirconia-based ceramic self-lubricating composites are a novel type of self-lubricating composite material, mainly composed of a lubricating phase and a zirconia ceramic matrix. The zirconia ceramic matrix framework structure ensures that the material possesses advantages such as high strength, wear resistance, and pseudo-elasticity, thus potentially meeting the sealing application requirements of harsh environments that conventional carbon graphite materials cannot handle. To improve the comprehensive performance of zirconia-based self-lubricating composites, this invention is based on the structural / functional integrated design principle of advanced ceramic materials. Combining the high wear resistance of the three-dimensional continuous structure of zirconia-based self-lubricating composites with the pseudo-elasticity of zirconia-based shape memory ceramics, the two are respectively constructed as a layered surface wear-resistant layer and an internal deformation-imprinted layer, thereby preparing a zirconia-based ceramic dynamic sealing material with both excellent wear resistance and pseudo-elasticity. Summary of the Invention

[0003] The purpose of this invention is to disclose a method for preparing a deformable zirconia-based ceramic dynamic sealing material, so as to improve the wear resistance, airtightness and deformation imprinting function of the dynamic sealing material, broaden the research ideas of controlling the structure of ceramic dynamic sealing materials, and provide technical support for exploring aerospace ceramic sealing materials.

[0004] I. Preparation of Zirconia-based Ceramic Dynamic Sealing Materials

[0005] The method for preparing the zirconia-based ceramic dynamic sealing material of the present invention includes the following steps:

[0006] (1) First, select ZrO2(3Y) powder and graphite particles as raw materials for the surface lubrication and wear-resistant layer at a mass ratio of 3~5:2. Then, select ZrO2 powder and CeO2 powder as raw materials for the internal deformation imprint layer at a molar ratio of 4~6.5:1. Finally, mix the two raw materials separately in a planetary ball mill.

[0007] The purity of the raw materials ZrO2(3Y) powder, graphite particles, ZrO2 powder and CeO2 powder is ≥99%, and the particle size of the raw materials is 0.5 ~250μm.

[0008] During grinding, the mass ratio of grinding balls to raw materials is 1:1 to 3:1, the rotation speed of the ball mill is 100 to 200 r / min, and the grinding time is 3 to 20 h.

[0009] (2) The obtained mixed surface lubrication wear-resistant layer material and internal deformation imprint layer material are dry pressed layer by layer and then pressed into a green blank by a hydraulic press at 20 ~ 45 MPa. The green blank is then hot-pressed and sintered, and naturally cooled to room temperature to obtain zirconia-based ceramic dynamic sealing material.

[0010] The sintering process has a significant impact on the structure and properties of zirconia-based ceramic dynamic sealing materials. Lower sintering temperatures, shorter holding times, and lower pressures fail to adequately densify the zirconia-based ceramic dynamic sealing materials. Conversely, higher sintering temperatures, longer holding times, and higher pressures result in excessive internal stress in the ceramic, leading to higher brittleness. Therefore, the hot-pressing sintering process in this invention is as follows: heating rate of 10-15 °C / min, sintering temperature of 1500-1700 °C, holding time of 1.5-4.5 h, pressure of 1.0-3.0 MPa, and vacuum degree <10. 1 Pa.

[0011] Synthesis mechanism of the present invention: Spark plasma sintering is a novel rapid sintering technology that introduces DC pulse current into the sintering process. The pressure head applies pressure to the material while also acting as a carrier for the current to pass through.

[0012] Unlike traditional sintering techniques that typically utilize radiative heating from a heating element, spark plasma sintering heats materials using the thermal effect generated by a large current passing through a mold or conductive sample. Under high-temperature sintering conditions, zirconia-based ceramic dynamic sealing materials exhibit a connected tetragonal zirconia structure at the interface between the surface lubricating and wear-resistant layer and the internal deformation-imprinted layer. This enhances the interfacial bonding strength between the two layers, ensuring the reliability of the composite material in harsh application environments.

[0013] II. Structural Characterization of Zirconia-based Ceramic Dynamic Sealing Materials

[0014] This invention ingeniously constructs a deformable zirconia-based ceramic dynamic sealing material with a layered structure through layer-by-layer dry pressing and hot pressing sintering. The surface layer is a lubricating and wear-resistant layer, and the middle layer is a deformation-imprinted layer. XRD and SEM characterization are as follows:

[0015] Figure 1 The image shows the XRD pattern of the zirconia-based ceramic dynamic sealing material prepared according to this invention. The XRD pattern indicates that the prepared zirconia-based ceramic dynamic sealing material mainly consists of… t -ZrO2 phase (JCPDS No. 50-1059) mIt consists of the ZrO2 phase (JCPDS No. 86-1451) and the graphite phase (JCPDS No. 41-1487). It is important to note that ZrO2 is primarily in the tetragonal phase. t It exists in the form of -ZrO2, with only a small amount of monoclinic phase. m -ZrO2. In addition, trace amounts of ZrC phase were detected in both composite materials (JCPDS No. 35-0784), indicating that ZrO2 reacted with C to form ZrC after sintering in a hot-pressing furnace.

[0016] Figure 2 This image shows a SEM image of the longitudinal section of the zirconia-based ceramic dynamic sealing material prepared according to the present invention. The large spherical particles in the lubrication and wear-resistant layer are graphite phase, while other areas are ZrO2(Y2O3) phase. This is beneficial for the formation of a three-dimensional continuous ZrO2 matrix. The gray areas in the deformation-imprinted layer are ZrO2(CeO2) phase. As can be seen from the image, the thickness of the lubrication and wear-resistant layer is approximately 420 μm. The graphite phase in the zirconia-based dynamic sealing material is distributed in a relatively aggregated spherical morphology within the ZrO2(Y2O3) matrix, and no pores or gaps were observed at the interface between the graphite phase and the ZrO2(Y2O3) matrix.

[0017] III. Performance Evaluation of Zirconia-based Ceramic Dynamic Sealing Materials

[0018] 1. Tribological properties

[0019] Test Method: First, the sintered samples were cut into blocks measuring 12.5 mm × 12.5 mm × 3.5 mm for friction testing. Before the friction test, the samples were polished to a smooth surface with a roughness of less than 0.3 μm, and then ultrasonically cleaned with acetone. Subsequently, the tribological properties of the zirconia-based ceramic dynamic sealing material at 600 °C under atmospheric conditions were studied using a high-temperature tribological testing machine. The load, frequency, reciprocating stroke, and temperature for the friction experiment were 28.26 N (corresponding to a contact pressure of 1.0 MPa), 10 Hz, 5 mm, and 600 °C, respectively. During the experiment, the friction coefficient was recorded in real time using data acquisition software.

[0020] Figure 3 Typical friction coefficient curves and corresponding two-dimensional profile curves of the worn surface are shown for zirconia-based ceramic dynamic sealing materials under different times (1h, 2h, 3h, and 4h) and different loads (1.0MPa, 1.5MPa, 2.0MPa, and 2.5MPa). Figure 3As can be seen from a and 3b, the friction coefficient curves of the zirconia-based ceramic dynamic sealing material at different times consistently show a highly similar trend; that is, after the break-in period, the curves enter a relatively stable stage and exhibit similar friction coefficients (0.27 ~ 0.28). Furthermore, under loads of 1.0 MPa to 2.5 MPa, the friction coefficient curves of the zirconia-based ceramic dynamic sealing material become smooth and remain stable after a short break-in period. Figure 3 In samples c and 3d, it can be observed that the wear depth of the zirconia-based ceramic dynamic sealing material gradually increases with time and load, but its wear rate remains essentially at the same level. The wear rate of the zirconia-based ceramic dynamic sealing material after 1 hour is 5.8 × 10⁻⁶. -5 mm 3 / N·m, its wear rate increases slightly to 6.9×10 at 4 h. -5 mm 3 / N·m; The wear rate of the zirconia-based ceramic dynamic sealing material at 1.0 MPa is 5.8 × 10⁻⁶ N·m. -5 mm 3 / N·m, its wear rate at 2.5 MPa is 5.49×10 -5 mm 3 / N·m. Therefore, zirconia-based ceramic dynamic sealing materials can still maintain excellent friction reduction and wear resistance even after long-term and high-load conditions at 600°C.

[0021] 2. Pseudoelastic properties

[0022] Test method: First, the sintered sample was machined into a rectangle of 7.5 mm × 3 mm × 3 mm. Before the test, the sample was carefully polished to a surface roughness of less than 0.5 μm, a parallelism error of less than 0.01 mm between the upper and lower surfaces, and an axial perpendicularity error of less than 0.01 mm. The uniaxial compression load range was 2000 N ~ 12000 N, and the indenter descent rate was 0.05 mm / min.

[0023] Figure 4 The figure shows the displacement-load curve of the zirconia-based ceramic dynamic seal material. As can be seen from the figure, the zirconia-based ceramic dynamic seal material did not exhibit brittle fracture during the loading and unloading process with a maximum load of 2000 N. A distinct inverse strain plateau was formed during unloading, which is likely due to martensitic transformation. Subsequently, compression cycle tests were conducted on the zirconia-based ceramic dynamic seal material with maximum loads of 4000 N, 6000 N, 8000 N, 10000 N, and 12000 N. The results show that the zirconia-based ceramic dynamic seal material can still maintain excellent pseudoelasticity during the subsequent compression cycle tests, and can basically recover the macroscopic shape change of the composite material during loading after unloading.

[0024] In summary, this invention, based on the principle of structural / functional integration of three-dimensional continuous graphite / zirconia composite material friction-reducing and wear-resistant design and tetragonal zirconia optimized control with deformation imprinting function, prepares zirconia-based ceramic dynamic sealing materials with both excellent wear resistance and pseudo-elasticity to meet the sealing application requirements of long-cycle and high-load conditions in the aerospace field. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the zirconia-based ceramic dynamic sealing material of this invention.

[0026] Figure 2 This is a SEM image of the longitudinal section of the zirconia-based ceramic dynamic sealing material of the present invention.

[0027] Figure 3 The curves showing the variation of the friction coefficient and wear rate of the zirconia-based ceramic dynamic sealing material of the present invention with experimental time and contact pressure are shown; where a and b are the friction coefficient variation curves, and c and d are the wear rate variation curves.

[0028] Figure 4 This is a displacement-load curve of the zirconia-based ceramic dynamic sealing material of the present invention under uniaxial compression at room temperature; where a-2000N load, b-4000 N load, c-6000 N load, d-8000 N load, e-10000N load, and f-12000N load. Detailed Implementation

[0029] The present invention will be further explained and described below with reference to specific embodiments.

[0030] Example 1

[0031] (1) ZrO2(3Y) powder, graphite particles, ZrO2 powder and CeO2 powder were taken as raw materials. ZrO2(3Y) powder and graphite particles were selected as raw materials for the surface lubrication and wear-resistant layer (the volume ratio of the two is 3:2), and ZrO2 powder and CeO2 powder were selected as raw materials for the internal deformation imprint layer (the molar ratio of the two is 5.7:1). They were then placed in a polytetrafluoroethylene ball mill jar (zirconia balls: mixed powder = 2:1); the ball mill jar was placed in a planetary ball mill and ball milled at a speed of 100 r / min for 8 h to obtain mixed powder.

[0032] (2) The mixed surface lubrication wear-resistant layer material and the internal deformation imprint layer material obtained in step (1) are dry-pressed layer by layer (the layer thickness can be flexibly selected according to the actual application situation). That is, first, a layer of surface lubrication layer material is dry-pressed in a steel mold, then a layer of internal deformation imprint layer material is dry-pressed on top of it, and finally a layer of surface lubrication wear-resistant layer material is dry-pressed. In this embodiment, the thickness ratio of surface lubrication wear-resistant layer: internal deformation imprint layer: surface lubrication wear-resistant layer is 1:2:1. Then, a green blank is formed by pressing it with a hydraulic press at 30MPa, and then the green blank is hot-pressed and sintered. Hot-pressing sintering process conditions: the atmosphere furnace is evacuated to make the vacuum reading value <10 1 Pa, then the furnace temperature was increased from room temperature to 1500 ℃ at a heating rate of 10 ℃ / min and held for 3 h; then the power was turned off and the furnace was allowed to cool naturally to room temperature to obtain zirconia-based ceramic dynamic sealing material.

[0033] XRD patterns ( Figure 1 This indicates that the prepared zirconia-based ceramic dynamic sealing material is mainly composed of... t -ZrO2 phase, m Composed of ZrO2 and graphite phases, without other impurity phases; SEM image ( Figure 2 The elemental distribution diagram shows that the lubricating and wear-resistant layer in the prepared zirconia-based ceramic dynamic sealing material has a three-dimensional continuous ZrO2 matrix with a thickness of 420 μm, and the deformation imprinted layer is a ZrO2 (CeO2) phase.

[0034] (3) Tribological properties of zirconia-based ceramic dynamic sealing material: coefficient of friction is 0.27, and wear rate is 5.8 × 10⁻⁶. -5 mm. Pseudoelastic properties of zirconia-based ceramic dynamic sealing materials: Excellent pseudoelasticity can be achieved in the load range of 2000 N ~ 12000 N.

[0035] Example 2

[0036] (1) ZrO2(3Y) powder, graphite particles, ZrO2 powder and CeO2 powder were taken as raw materials. ZrO2(3Y) powder and graphite particles were selected as raw materials for the surface lubrication and wear-resistant layer (the volume ratio of the two is 3:2), and ZrO2 powder and CeO2 powder were selected as raw materials for the internal deformation imprint layer (the molar ratio of the two is 5.7:1). Then they were placed in a polytetrafluoroethylene ball mill jar (zirconia balls: mixed powder = 2:1); the ball mill jar was placed in a planetary ball mill and ball milled at a speed of 100 r / min for 16 h to obtain mixed powder;

[0037] (2) The mixed surface lubrication and wear-resistant layer material and the internal deformation imprint layer material obtained in step (1) are dry-pressed layer by layer and then pressed into a green blank by a hydraulic press at 30 MPa. The green blank is then hot-pressed and sintered. Hot-pressing and sintering process conditions: The atmosphere furnace is evacuated to make the vacuum reading <10. 1 Pa was applied, and then the furnace temperature was increased from room temperature to 1600 ℃ at a heating rate of 10 ℃ / min and held for 3 h. The power was then turned off and the material was allowed to cool naturally to room temperature to obtain a zirconia-based ceramic dynamic sealing material. XRD patterns showed that the prepared zirconia-based ceramic dynamic sealing material mainly consisted of... t -ZrO2 phase, m - Composed of ZrO2 and graphite phases, without other impurity phases; SEM images and elemental distribution diagrams show that the lubricating and wear-resistant layer in the prepared zirconia-based ceramic dynamic sealing material has a three-dimensional continuous ZrO2 matrix with a thickness of 420 μm, and the deformation imprinted layer is a ZrO2 (CeO2) phase.

[0038] (3) Tribological properties of zirconia-based ceramic dynamic sealing material: friction coefficient is 0.28, wear rate is 5.49 × 10 -5 mm. Pseudoelastic properties of zirconia-based ceramic dynamic sealing materials: Excellent pseudoelasticity can be achieved in the load range of 2000 N ~ 12000 N.

[0039] Example 3

[0040] (1) ZrO2(3Y) powder, graphite particles, ZrO2 powder and CeO2 powder were taken as raw materials. ZrO2(3Y) powder and graphite particles were selected as raw materials for the surface lubrication and wear-resistant layer (the volume ratio of the two is 3:2), and ZrO2 powder and CeO2 powder were selected as raw materials for the internal deformation imprint layer (the molar ratio of the two is 5.7:1). Then they were placed in a polytetrafluoroethylene ball mill jar (zirconia balls: mixed powder = 2:1); the ball mill jar was placed in a planetary ball mill and ball milled at a speed of 100 r / min for 24 h to obtain mixed powder;

[0041] (2) The mixed surface lubrication and wear-resistant layer material and the internal deformation imprint layer material obtained in step (1) are dry-pressed layer by layer and then pressed into a green blank by a hydraulic press at 30 MPa. The green blank is then hot-pressed and sintered. Hot-pressing and sintering process conditions: The atmosphere furnace is evacuated to make the vacuum reading <10. 1 Pa, then the furnace temperature was increased from room temperature to 1700 ℃ at a heating rate of 10 ℃ / min and held for 3 h; subsequently, the power was turned off and the material was allowed to cool naturally to room temperature to obtain a zirconia-based ceramic dynamic sealing material. XRD pattern ( Figure 1 This indicates that the prepared zirconia-based ceramic dynamic sealing material is mainly composed of... t -ZrO2 phase,m - Composed of ZrO2 and graphite phases, without other impurity phases; SEM images and elemental distribution diagrams show that the lubricating and wear-resistant layer in the prepared zirconia-based ceramic dynamic sealing material has a three-dimensional continuous ZrO2 matrix with a thickness of 420 μm, and the deformation imprinted layer is a ZrO2 (CeO2) phase.

[0042] (3) Tribological properties of zirconia-based ceramic dynamic sealing material: coefficient of friction is 0.26, and wear rate is 5.3 × 10⁻⁶. -5 mm. Pseudoelastic properties of zirconia-based ceramic dynamic sealing materials: Excellent pseudoelasticity can be achieved in the load range of 2000 N~12000 N.

[0043] In the above embodiments, the purity of the raw materials ZrO2(3Y) powder, graphite particles, ZrO2 powder and CeO2 powder used is ≥99%, and the particle size of the raw materials is 0.5~250μm.

Claims

1. A method for preparing a deformable zirconia-based ceramic dynamic sealing material, characterized in that, Includes the following steps: (1) First, select 3Y-ZrO2 powder and graphite particles as raw materials for the surface lubrication and wear-resistant layer at a mass ratio of 3~5:

2. Then, select ZrO2 powder and CeO2 powder as raw materials for the internal deformation imprint layer at a molar ratio of 4~6.5:

1. The purity of the raw materials 3Y-ZrO2 powder, graphite particles, ZrO2 powder and CeO2 powder is ≥99%, and the particle size of the raw materials is 0.5~250μm. Finally, mix the two raw materials in a planetary ball mill. The mass ratio of grinding balls to raw materials is 1:1~3:

1. The rotation speed of the ball mill is 100~200 r / min, and the ball milling time is 3~20 h. (2) The mixed surface lubricating wear-resistant layer material and the internal deformation imprint layer material obtained in step (1) are dry-pressed layer by layer. That is, the surface lubricating layer material is first dry-pressed in a steel mold, then the internal deformation imprint layer material is dry-pressed on top of it, and finally the surface lubricating wear-resistant layer material is dry-pressed again. Then, the green blank is formed by pressing it with a hydraulic press at 20~45MPa. The green blank is hot-pressed and sintered, and then naturally cooled to room temperature to obtain the zirconia-based ceramic dynamic sealing material. The hot-pressing sintering process conditions are: heating rate of 10~15 ℃ / min, sintering temperature of 1500~1700 ℃, holding time of 1.5~4.5h, pressure of 1.0~3.0MPa, and vacuum degree <10 1 Pa.

2. A deformable zirconia-based ceramic dynamic sealing material as described in claim 1, for sealing applications under long-cycle and high-load conditions in the aerospace field.

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