A high-strength wear-resistant ceramic material and its preparation method

Abstract

This invention relates to the field of high-performance ceramics, and discloses a high-strength wear-resistant ceramic material and its preparation method. This invention achieves a balance between high surface wear resistance and structural toughness through a synergistic strategy of multiphase composite toughening and stepped temperature-controlled sintering. Using alumina as the wear-resistant matrix, silicon carbide nanowires are interwoven internally to form a framework to hinder microcrack propagation. Zirconia induces a phase transformation in the stress zone to absorb destructive energy, and trace amounts of cerium dioxide are used to improve high-temperature structural stability. A two-stage stepped heating process stabilizes the cerium ion state and inhibits grain coarsening; combined with molding and constant-pressure densification processes, it promotes the formation of a physical anchoring and stress dissipation network in the matrix. This effectively reduces the risk of fracture under stress and meets the service requirements of heavy-load conditions.

Description

Technical Field

[0001] This invention relates to the field of high-performance ceramics, and more specifically, to a high-strength, wear-resistant ceramic material and its preparation method. Background Technology

[0002] With the rapid iteration of high-end precision machinery manufacturing and modern biomedical devices (such as artificial joint replacement prostheses and precision orthopedic implants), extremely stringent requirements are placed on the long-term service stability of core load-bearing components under complex working conditions. Traditional metal-based materials often gradually fail due to long-term stress fatigue, chemical corrosion in complex environments, or the release of metal ions caused by continuous friction. Special structural ceramic materials, with their advantages of chemical inertness, biocompatibility, and surface hardness, are gradually replacing traditional metals and becoming key candidate materials for these core load-bearing components. In environments that cope with high-frequency, long-term continuous physical friction and complex multi-directional mechanical loads, ceramic components can theoretically maintain an extremely smooth surface finish and stable geometry for a long time, which is particularly important for maintaining the long-term operation of the overall mechanical transmission system or biomechanical system.

[0003] Existing special ceramic material systems generally face irreconcilable physical contradictions when dealing with the aforementioned extremely complex composite stress conditions. In order to prevent the formation of spalling or wear particles on the material surface under long-term high-frequency friction, it is usually necessary to induce an extremely dense microcrystalline structure inside the material to obtain extremely high surface rigidity. However, this inevitably leads to the material exhibiting extreme brittleness. When the component encounters unexpected mechanical impact or heavy alternating stress, this tightly locked brittle structure is prone to catastrophic fracture or fragmentation. If the physical toughness of the material against external heavy loads and impacts is improved by changing the internal microphase structure, it will severely damage the original dense surface network of the ceramic, causing the material to rapidly chip or peel off during continuous contact friction, significantly shortening the actual service life of the component. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a high-strength wear-resistant ceramic material and its preparation method, solving the problem that existing ceramics cannot simultaneously achieve high strength and wear resistance.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a high-strength, wear-resistant ceramic material includes the following steps: S1: Weigh 70-85 parts by weight of alumina, 15-30 parts by weight of zirconium oxide and 2.5-4.5 parts by weight of cerium oxide dry powder raw materials and put them into a planetary ball mill. After adding dispersion medium and dispersant, coarse mixing is carried out. After coarse mixing, add 2-6 parts by weight of silicon carbide nanowires and ball mill at low speed. Spray dry the mixed slurry to obtain composite granulated powder. S2 The composite granulated powder is filled into a mold and sealed. After being compressed by a cold isostatic press, the pressure is gradually released to obtain a ceramic blank. S3 The ceramic blank is transferred to a vacuum hot pressing sintering furnace for low-temperature volatilization and impurity removal. The temperature was raised to 1050℃~1300℃ for 1~5 hours to carry out the cerium ion reduction transformation. The material is heated to 1500~1600℃ for densification sintering, and then cooled to obtain the high-strength wear-resistant ceramic material.

[0007] In a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S1, the alumina is 82 parts, the zirconium oxide is 18 parts, the cerium oxide is 3.5 parts, and the silicon carbide nanowires are 4 parts.

[0008] In a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S3, the parameters of the reduction transformation are constant temperature at 1200℃ for 2.5h; and the temperature of the densification sintering is 1550℃.

[0009] In a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S1, the dispersion medium is one of deionized water, anhydrous ethanol, and isopropanol, and the dispersant is one of polyethylene glycol, polyvinyl alcohol, and sodium polyacrylate; the operating parameters of the coarse mixing process are continuous ball milling at 200-300 rpm for 4-8 hours; and the operating parameters of the low-speed ball milling process are mixing at 100-150 rpm for 1-2 hours.

[0010] As a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S1, the spray drying process involves setting the inlet air temperature of the spray drying tower to 200~240℃ and the outlet air temperature to 90~110℃ for granulation, and after granulation and screening, the composite granulated powder is obtained.

[0011] In a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S2, the mold is made of polyurethane, silicone, or natural rubber; the compression process parameters are set as follows: main pressure 200-300 MPa, holding pressure for 1-3 minutes.

[0012] In a preferred embodiment of the method for preparing the high-strength wear-resistant ceramic material according to the present invention, step S2 specifically includes: First, depressurize to 50 MPa at a depressurization rate of 15~25 MPa / s; then depressurize to standard atmospheric pressure at a low depressurization rate of 0.5~1 MPa / s.

[0013] As a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S3, the low-temperature volatilization and impurity removal process specifically includes: slowly heating to 700-900°C at a heating rate of 3-5°C / min and holding at that temperature for 1-3 hours to volatilize and remove the residual organic components inside the initial blank.

[0014] As a preferred embodiment of the method for preparing high-strength wear-resistant ceramic materials according to the present invention, in step S3, the densification sintering process further includes applying a physical pressure of 25~35MPa in the axial direction and maintaining it for 1~2h.

[0015] This invention also provides a high-strength wear-resistant ceramic material prepared by the above method, wherein: the ceramic material consists of a composite fine-grained matrix composed of alumina and zirconium oxide, with trivalent cerium ions enriched and strongly pinned at the grain boundaries of the composite fine-grained matrix; silicon carbide nanowires are uniformly interwoven and densely wrapped by the composite fine-grained matrix, and the silicon carbide nanowires are constructed inside the matrix into a one-dimensional mechanical interlocking network that consumes energy during bridging and pull-out.

[0016] The beneficial effects of this invention are as follows: Through a synergistic strategy of multiphase composite toughening and stepped temperature-controlled sintering, a balance between high surface wear resistance and structural toughness is achieved in special ceramic materials. Alumina is used to construct the wear-resistant matrix, and zirconium oxide and silicon carbide nanowires are introduced to form a multidimensional structural reinforcement. The silicon carbide nanowires intertwine within the ceramic matrix to form a framework, which can hinder the propagation of microcracks when the material is under stress; zirconium oxide induces a phase transition in the micro-stressed region to absorb destructive energy, thereby improving the material's ability to resist transient mechanical loads. The addition of trace amounts of cerium dioxide improves the structural stability of the multiphase composite system at high temperatures.

[0017] By employing a two-stage stepped heating process, the state of trivalent cerium ions is first stabilized to ensure the stability of the grain boundary energy state before sintering, thereby suppressing abnormal growth and coarsening of alumina grains at high temperatures and ensuring the microscopic uniformity of the overall structure.

[0018] During the molding and densification stages, the pretreatment of cold isostatic pressing combined with the constant pressure process of vacuum hot pressing promotes the formation of a physical anchoring network between silicon carbide nanowires and the ultrafine-grained ceramic matrix. The final ceramic product maintains a high-density, wear-resistant microcrystalline lattice on the surface while constructing a stress dissipation network inside, effectively reducing the risk of traditional ceramics breaking under stress and meeting the service requirements of precision load-bearing components under heavy load conditions. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The figure shows the experimental results of optimizing the alumina-zirconium ceramic substrate composition.

[0021] Figure 2 The figure shows the experimental results of optimizing the phase change stabilizer ratio.

[0022] Figure 3 Figure showing the experimental results of optimizing the phase ratio for toughening silicon carbide nanowires.

[0023] Figure 4 Figure showing the experimental results for optimizing densification sintering parameters. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "example" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The appearance of an embodiment in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0027] Example 1 This embodiment aims to screen a special ceramic material system that combines extremely high surface wear resistance with overall structural toughness. This is intended to overcome the problem of physical brittleness often associated with traditional structural ceramic materials when pursuing surface rigidity to resist continuous friction.

[0028] 1.1 Screening of ceramic substrates The base material determines the theoretical upper limit of the finished product's hardness and basic wear resistance. It needs to possess intrinsic hardness and chemical stability to withstand continuous physical friction, as well as good lattice compatibility and thermodynamic stability to adapt to various modified materials.

[0029] The experiments were divided into four categories: A1 alumina-silicon carbide composite ceramics, A2 alumina-titanium carbide composite ceramics, A3 silicon nitride-silicon carbide composite ceramics, A4 alumina-zirconia composite ceramics, A5 zirconia-tungsten carbide composite ceramics, A6 Sialon composite ceramics, A7 boron carbide-silicon carbide composite ceramics, A8 mullite-zirconia composite ceramics, A9 alumina-titanium nitride composite ceramics, and A10 magnesium oxide-partially stabilized zirconia composite ceramics.

[0030] After sintering, ceramic samples from each group were taken and their Vickers hardness was tested using a Vickers hardness tester. Quantifying the surface rigidity of the substrate material reflects the material's ability to resist localized plastic deformation and determines the theoretical upper limit of the hardness of the ceramic component when subjected to continuous physical friction.

[0031] Each set of samples was cut and processed into long strip test beams of standard dimensions, with a single-sided V-notch pre-fabricated at the mid-span of the test beam. The pre-notched test beam was placed on a universal testing machine, and a three-point bending test was performed using the single-sided notched beam method (SENB) until the specimen fractured to test its fracture toughness. This assesses the fundamental ability of the substrate structure to prevent the initiation and propagation of microcracks through its internal native network when subjected to transient mechanical impacts.

[0032] Each group of samples was processed into standard, unnotched rectangular test strips, and the edges of the strips were chamfered to eliminate stress concentration caused by processing defects. Three-point bending tests were performed using a universal testing machine, and the maximum critical load at which the specimen fractured was recorded. This load was then converted into bending strength using the stress formula. This quantifies the ultimate fracture threshold of the material at the macroscopic level under heavy alternating stress and mechanical bending loads, reflecting the overall load-bearing capacity of the material's framework.

[0033] A ball-and-disc tribological testing machine was used, with standard pure alumina ceramic balls as the grinding media, to test the polished surfaces of each group of samples under dry sliding friction conditions at room temperature. After the test, the wear track profile was scanned and extracted using a white light interferometer to calculate the wear volume, and then the specific wear rate was calculated. By simulating real continuous mechanical friction conditions, the actual volume loss level of the material was quantified to characterize the long-term service life and surface dynamic stability of ceramic components in a frictional environment.

[0034] The test results are as follows: A7 has good surface rigidity, but its fracture toughness is low. Its brittle nature makes it prone to shattering under transient impact, rendering it unsuitable for load-bearing structural components. A3 has high bending strength, but its Vickers hardness is too low, making it unable to withstand long-term micro-friction and wear. A5 has good fracture toughness and extremely strong impact resistance, but under continuous friction conditions, wear and detachment of the two-phase grain boundaries leads to a high specific wear rate, resulting in a lower expected long-term service life. A1 has a good specific wear rate, indicating low surface friction, but its low bending strength suggests internal bonding defects, making it prone to macroscopic fracture.

[0035] Group A4 (alumina-zirconia composite ceramics) exhibits excellent overall performance. It lies in a balance zone between high rigidity and brittleness and high toughness and wear, and is easy to modify and process, thus making it suitable as a ceramic substrate.

[0036] 1.2 Screening of toughening materials While alumina-zirconia composite substrates have achieved a preliminary balance between surface rigidity and structural toughness, there is still room for improvement in their overall mechanical properties. The introduction of toughening materials aims to further enhance the substrate's impact resistance and surface wear resistance by utilizing the skeletal structure formed by their interwoven structure within the matrix.

[0037] The selected toughening materials and their addition ratios were all based on relevant academic literature and mature industrial formulations. To ensure that each component could exhibit its intrinsic optimal mechanical properties in the comparative tests, the test ratios all adopted their theoretically optimal doping amounts. The addition amounts of each component below are all based on 100 parts by mass of the total mass of the alumina-zirconia composite substrate.

[0038] Experimental groups: B1 with 1.0 part by mass of carbon nanotubes, B2 with 15.0 parts by mass of continuous alumina fibers, B3 with 3.0 parts by mass of silicon carbide nanowires, B4 with 0.5 parts by mass of graphene, B5 with 2.0 parts by mass of hexagonal boron nitride nanosheets, B6 with 1.5 parts by mass of MXenes nanosheets, B7 with 8.0 parts by mass of nano-titanium carbide particles, B8 with 10.0 parts by mass of nano-tungsten carbide particles, B9 with 5.0 parts by mass of nano-silicon nitride particles, B10 with 4.0 parts by mass of yttrium oxide (Y2O3), B11 with 2.0 parts by mass of magnesium oxide (MgO), and B12 with 3.5 parts by mass of lanthanum oxide (La2O3).

[0039] The performance of toughening agents is evaluated by testing fracture toughness, Vickers hardness, flexural strength, and specific wear rate.

[0040] The test results are as follows: Among them, graphene significantly reduced the specific wear rate because the two-dimensional shear layered structure easily forms a self-lubricating film during friction. However, the bending strength showed a significant decrease because the extremely large specific surface area easily caused severe micro-agglomeration in the ceramic slurry, forming a large number of heterogeneous micropores inside after sintering, which became stress concentration points when subjected to macroscopic bending.

[0041] Nanoscale titanium carbide particles significantly improve surface rigidity, mainly due to the efficient pinning effect of ultrahard dispersed particles on the matrix grain boundaries. However, the fracture toughness decreases significantly because zero-dimensional particles cannot provide stress bridging or pull-out energy dissipation mechanisms for one-dimensional configurations. High concentration doping makes the grain boundaries extremely rigid, exhibiting typical transgranular cleavage fracture when encountering transient impacts.

[0042] The significant improvement in bending strength of continuous alumina fibers indicates that a through-type load-bearing skeleton has been constructed on a macroscopic scale, and the ultimate threshold for resisting mechanical bending loads has increased significantly. However, the high volume effect of macroscopic long fibers disrupts the microscopic continuity of the original matrix rigid network, resulting in a significant decrease in the macroscopic surface rigidity of the finished product.

[0043] Yttrium oxide has good fracture toughness. It can stimulate and stabilize zirconium oxide through stress-induced phase transformation and close the initial microcracks by volume expansion. However, due to the lack of a macroscopic framework of physically hard phase in the matrix, the phase transformation layer is prone to micro-stress fatigue and large-area dynamic spalling under continuous high-pressure sliding friction conditions, resulting in a significantly higher wear rate.

[0044] While silicon carbide nanowires cause a slight decrease in the Vickers hardness and flexural strength of the finished product compared to the substrate, this is because during sintering, the one-dimensional nanowires interpenetrate between the matrix grains, inhibiting grain rearrangement and densification. Furthermore, the difference in thermal expansion coefficients between the nanowires and the substrate leads to localized microscopic residual stress at the interface during cooling. However, the crack deflection, grain boundary bridging, and fracture pull-out effects provided by the one-dimensional framework at the microscale significantly improve fracture toughness while maintaining a low specific wear rate. This combination successfully achieves considerable impact toughness and stable wear resistance through a controllable, slight loss in hardness and strength. Therefore, silicon carbide nanowires were ultimately selected as the toughening component of the material.

[0045] 1.3 Screening of Phase Change Stabilizers During the cooling process after high-temperature sintering, the zirconia grains in the alumina-zirconia composite system spontaneously undergo a martensitic phase transformation from tetragonal to monoclinic (tm). This microscopic crystal plane reconstruction process is accompanied by a volume expansion of approximately 3% to 5%, which easily induces localized microscopic tensile stresses that are difficult to release at grain boundaries and nanowire intersections. This stress concentration leads to the initiation of a spontaneous microcrack network within the substrate, compromising the initial structural strength and macroscopic compactness of the material after molding.

[0046] The introduction of phase transformation stabilizers aims to alter the lattice constant and surface free energy by replacing metal cations at the zirconia lattice nodes, forming a substitutional solid solution, and introducing oxygen vacancies. This retains the high-temperature tetragonal phase in a metastable state at room temperature, suppressing spontaneous volume expansion and microcrack defects during the sintering cooling stage. Simultaneously, it imparts stress-induced phase transformation activity to the material, ensuring that upon exposure to external mechanical impact, localized phase transformation expansion is triggered only under the high stress field at the crack tip, using the compressive stress generated by the expansion to forcibly close the propagating microcracks.

[0047] Experimental groups (based on 100 parts by mass of ceramic substrate): C1 with 5.0 parts yttrium oxide (Y2O3), C2 with 4.0 parts calcium oxide (CaO), C3 with 2.5 parts magnesium oxide (MgO), C4 with 4.0 parts cerium oxide (CeO2), C5 with 4.5 parts scandium oxide (Sc2O3), C6 with 7.0 parts neodymium oxide (Nd2O3), C7 with 6.5 parts samarium oxide (Sm2O3), C8 with 5.5 parts ytterbium oxide (Yb2O3), C9 with 7.5 parts gadolinium oxide (Gd2O3), and C10 with 6.0 parts lanthanum oxide (La2O3).

[0048] The performance of toughening agents is evaluated by testing fracture toughness, Vickers hardness, flexural strength, and specific wear rate.

[0049] The test results are as follows: Among them, yttrium oxide significantly improved the bending strength, indicating that its doping can form a relatively dense microstructure, suppress spontaneous cracking during the cooling stage, and avoid macroscopic defects; however, the wear rate was significantly higher because under continuous mechanical friction and shearing, the surface layer of this system is prone to micro-stress fatigue caused by phase transformation, which leads to cleavage and spalling of the surface grains.

[0050] Magnesium oxide significantly improves fracture toughness because it precipitates tetragonal phase within the matrix grains, and the compressive stress field generated by phase transformation expansion dissipates impact energy. However, the bending strength decreases significantly because it promotes grain boundary migration during high-temperature sintering, leading to abnormal growth of zirconia grains. The coarse grains increase the critical defect size inside the material.

[0051] Scandium oxide retains a high Vickers hardness, indicating that the ionic radius matching degree of the solid solution formed with zirconium oxide is relatively high, and the damage to intrinsic chemical bonds is relatively small; however, the fracture toughness is significantly lower because its stabilizing ability is too strong, which leads to the original metastable tetragonal phase being excessively locked. The material loses the energy-consuming mechanism of stress-induced phase transformation and exhibits pure physical brittleness.

[0052] The low wear rate of ytterbium oxide indicates that the small radius of Yb³⁺ ions results in a high local density in the solid solution formed with zirconium oxide on the surface, effectively resisting mechanical micro-cutting during continuous friction. However, its fracture toughness is significantly lower than the optimal level because its strong solid solution stability tendency increases the critical stress threshold for phase transformation triggering. This makes it difficult for some metastable tetragonal phases to be activated when encountering conventional transient impacts, thus limiting the ability of stress-induced phase transformation to dissipate impact energy.

[0053] Although cerium oxide causes a slight decrease in the Vickers hardness of the finished product compared to the ideal dense state, this is because the introduction of metal cations and oxygen vacancies alters the periodic arrangement of the original lattice chemical bonds; however, its fracture toughness, flexural strength, and specific wear rate remain at high levels, indicating that Ce... 4 ⁺ and Zr 4 The ionic radius difference of ⁺ is moderate, resulting in less lattice distortion caused by solid solution. This successfully preserved the tetragonal phase in a metastable state at room temperature and endowed it with high stress-induced activity. Therefore, cerium oxide was selected as the phase transformation stabilizer.

[0054] Example 2 Reference Figures 1 to 3 This is the second embodiment of the present invention. After determining the raw materials of the composite ceramic, it is necessary to further optimize the proportions of each component and explore the optimal microscopic physical and thermodynamic equilibrium critical point between the multiphase material systems in order to maximize the theoretical synergistic performance of the composite system.

[0055] 2.1 Optimization of Aluminum-Zirconium Ceramic Substrate Composition When a zirconia dispersed phase is introduced into an alumina matrix, if the zirconia doping amount is too low, the particle spacing of the dispersed phase will be too large, making it impossible to form an effective stress-induced phase transformation superposition stress field within the matrix, leading to the failure of the toughening mechanism. If the doping amount is too high, it will cause a significant decrease in macroscopic surface rigidity, triggering micro-agglomeration of zirconia particles. This will cause particles exceeding the critical size to undergo spontaneous phase transformation expansion prematurely during the cooling stage, inducing a microcrack network within the matrix. Based on 100 parts by mass of ceramic substrate, with other components remaining constant, experimental groups were set up with zirconia addition amounts ranging from 10 to 30 parts, in increments of 2 parts.

[0056] In addition to testing the fracture toughness and Vickers hardness of the sintered samples, the surfaces of each group of sintered samples need to be polished, followed by hot etching or chemical etching to clearly expose the grain boundaries. Microscopic morphology images are acquired using scanning electron microscopy (SEM), and the average grain size of the matrix is ​​statistically measured using the truncation method. The Zener pinning effect generated by zirconia dispersed particles at the matrix grain boundaries during high-temperature sintering is evaluated to assess the microscopic continuity and intrinsic mechanical strength of the matrix's underlying structure.

[0057] Polished ceramic samples from each group were used, with fully annealed and stress-relieved homogeneous powder standards as a reference. Grazing incidence X-ray diffraction (XRD) was performed on the sample surfaces, and the diffraction peak shifts of specific crystal planes were determined using the sin²ψ method. The macroscopic residual compressive stress of the test samples was calculated. The magnitude of the microscopic stress field spontaneously accumulated after sintering and cooling due to the inherent difference in the thermal expansion coefficients of the two phases was quantified, reflecting the degree of overlap of thermodynamic potential energy within the material, and assessing the upper limit of the energy barrier possessed by the material to resist the initiation and propagation of microcracks.

[0058] Test results are as follows Figure 1 As shown, the Vickers hardness decreases continuously with increasing zirconium oxide content. Through fitting calculations, the minimum addition amount for the average grain size of the matrix is ​​15.65 parts; the maximum addition amount for the macroscopic residual compressive stress is 21.41 parts; and the maximum addition amount for the fracture toughness is 18.28 parts. Averaging these values, the theoretical optimal proportion of the composite ceramic system under the multiple thermodynamic game of grain refinement strengthening, stress overlap, and phase transformation energy consumption is found to be 18.44 parts. Considering the control precision of the actual industrial powder proportioning and weighing system, the error tolerance of large-scale feeding, and the uniformity of powder mixing, the actual feeding proportion of zirconium oxide is set to 18 parts by mass.

[0059] 2.2 Optimization of Phase Change Stabilizer Ratio When cerium oxide is introduced into a composite ceramic substrate as a phase transformation stabilizer, if the doping amount is too low, the tetragonal phase cannot be retained to room temperature, causing spontaneous phase transformation expansion of zirconia during the sintering and cooling stage and the initiation of microcracks in the matrix. If the doping amount is too high, the tetragonal phase will become over-stabilized and locally transform into the cubic phase, losing its toughening activity of stress-induced phase transformation. Based on 100 parts by mass of ceramic substrate, the cerium oxide addition amount ranged from 1.0 to 5.0 parts, with an experimental group set up in increments of 0.5 parts.

[0060] In addition to testing fracture toughness, it is necessary to grind and press each group of samples into target materials, scan the sample surface using X-ray photoelectron spectroscopy (XPS), and calculate Ce³⁺ / Ce by finely fitting the characteristic peaks of Ce3d and O1s. 4 ⁺ Atomic ratio and relative oxygen vacancy content in the lattice. Quantify the concentration of microscopic lattice defects associated with valence reduction during high-temperature sintering of cerium oxide, and determine the level of chemical modification of the original lattice constant and distortion energy by the substitutional solid solution.

[0061] Standard-sized test beam samples from each group were placed in a high-pressure reactor and subjected to continuous aging treatment for a standard period at 134℃ and 0.2MPa water vapor. The aged samples were then removed and subjected to three-point bending tests using a universal testing machine. The residual flexural strength was recorded and compared with the initial flexural strength of the unaged samples in the same group to calculate the strength retention rate. This quantifies the degree of macrostructural degradation of the composite material under extreme hydrothermal coupled stress conditions and assesses the long-term inhibitory effect of the stabilizer on environmentally induced phase transitions and surface cleavage spalling.

[0062] Test results are as follows Figure 2 As shown, through curve fitting calculations, the addition amount at the critical point of marginal benefit decay of oxygen vacancy concentration (slope abrupt change point) is 3.92 parts; the addition amount at the maximum fracture toughness is 3.32 parts; the addition amount at the abrupt change in the S-shaped curve of flexural strength retention rate after aging is 2.78 parts; and the addition amount at the saturation extreme point is 3.48 parts. The theoretical optimal proportion is calculated to be 3.57 parts. Considering the control precision of the actual industrial powder proportioning and weighing system, the error tolerance of large-scale feeding, and the uniformity of powder mixing, the actual feeding proportion of cerium oxide is set at 3.5 parts.

[0063] 2.3 Optimization of toughening phase ratio for silicon carbide nanowires When silicon carbide nanowires are introduced as a toughening phase into composite ceramic substrates, if the amount of silicon carbide nanowires added is too low, an effective bridging and nanowire pull-out network cannot be constructed within the matrix, resulting in limited resistance to crack deflection and an insignificant toughening effect. If the amount added is too high, the nanowires are prone to micro-aggregation and the introduction of a large number of native pores, leading to a severe decrease in the density and overall flexural strength of the material. Experimental groups were set up with silicon carbide nanowire additions ranging from 1 to 10 parts per 100 parts by mass of ceramic substrate, using a step size of 1 part.

[0064] The performance of the finished product is evaluated by testing its fracture toughness and flexural strength.

[0065] Test results are as follows Figure 3 As shown, the maximum fracture toughness is 3.84 parts, which is not in the region of significant decrease in bending strength. Considering the actual industrial precision, the final feed ratio of silicon carbide nanowires is 4 parts by mass.

[0066] Example 3 Reference Figure 4 This is the third embodiment of the present invention. After determining the optimal ratio of each core component of the composite ceramic system, in order to ensure the physical stability and preparation feasibility of the benchmark formulation in a large-scale production environment, further adaptation and verification of the industrial scale-up process are required.

[0067] 3.1 Stepwise mixing of composite powders 82 parts of alumina, 18 parts of zirconium oxide, and 3.5 parts of cerium oxide dry powder were weighed and added to a planetary ball mill. An appropriate amount of deionized water was added as a dispersion medium (anhydrous ethanol or isopropanol can also be used), and polyethylene glycol was added dropwise as a dispersant (polyvinyl alcohol or sodium polyacrylate can also be used). The mixture was continuously ball-milled at 200-300 rpm for 4-8 hours. This allowed the inorganic particle phases to achieve thorough deagglomeration and uniform mixing at the microscopic level under mechanical shear force, resulting in a homogeneous substrate suspension slurry.

[0068] Four parts of silicon carbide nanowires were added to the above-mentioned substrate slurry and mixed at 100-150 rpm for 1-2 hours. A low-energy shear force field was used to uniformly disperse the one-dimensional nanomaterials among the substrate particle network, avoiding physical damage to the aspect ratio of the nanowires caused by prolonged mechanical impact.

[0069] After the mixing process is completed, the slurry is taken out and dried in a spray drying tower (inlet air temperature is 200~240℃, outlet air temperature is 90~110℃), and then granulated and screened to obtain composite granulated powder with uniform micro-component distribution and meeting the requirements of pressing flowability.

[0070] 3.2 Optimization of Cold Isostatic Pressing and Depressurization Process Parameters The composite granulated powder is uniformly filled into a flexible polyurethane mold (silicone or natural rubber can also be used) and sealed, then placed in a cold isostatic press. The main pressure is set to 200~300MPa and held for 1~3 minutes, causing the powder particles to shift and rearrange under omnidirectional fluid pressure, and the internal gas is extremely compressed, forming a high-density ceramic green body.

[0071] In the high-pressure zone (>50MPa), the gas is extremely compressed, resulting in minimal gas volume expansion due to pressure drop. A fixed depressurization rate of 15~25MPa / s is used to maximize the compression of the single-furnace operating cycle. In the low-pressure zone (<50MPa), according to Boyle's law, the gas volume will expand rapidly. Inappropriate depressurization can easily induce cracking of the green body. To ensure the quality of the finished product, depressurization is carried out at a low depressurization rate of 0.5~1MPa / s. The originally loose powder is compressed into a high-density ceramic green body with a certain initial strength.

[0072] 3.3 Gradient firing molding The formed ceramic blank is transferred to a vacuum hot pressing sintering furnace. It is first slowly heated to 700-900℃ at a heating rate of 3-5℃ / min and held for 1-3 hours to volatilize and remove the residual organic components such as polyethylene glycol inside the blank.

[0073] A review of numerous literatures on phase transformation toughened ceramics reveals that trivalent cerium ions (Ce³⁺) are the primary agents responsible for pinning grain boundaries and inducing oxygen vacancies in the system. Tetravalent cerium ions (Ce³⁺) are the secondary agents. 4The ionic radius of ⁺ is very close to that of zirconium ions in the matrix, and they have the same charge. After being incorporated into the crystal lattice, it cannot produce significant lattice distortion, nor can it generate oxygen vacancies to balance the charge. Therefore, it has almost no grain boundary dragging and phase transition stabilization performance.

[0074] If the temperature is rapidly increased to the final sintering temperature without a isothermal buffer, the matrix ceramic will undergo rapid and drastic densification shrinkage and grain growth, forming a rigid, closed lattice network. Ce2 then occurs within this dense, hard structure. 4 The reduction transformation from ⁺ to Ce³⁺ is caused by densification leading to premature closure of internal venting channels. This prevents the lattice oxygen released during the reduction reaction from escaping, resulting in severe thermodynamic inhibition of the reduction reaction and making it extremely difficult for the target valence state transition to occur completely. Furthermore, the ionic radius of Ce³⁺ is significantly larger than that of Ce. 4 ⁺ This delayed reduction phase transformation will forcibly induce microscopic volume expansion within the rigid matrix. The accumulated huge internal stress will directly induce intergranular microcracks, leading to the collapse of the ceramic's mechanical properties.

[0075] Existing literature thermal analysis data indicate that, under a vacuum-reducing atmosphere, the active thermodynamic window for cerium oxide to release oxygen on a large scale and transform into trivalent oxygen is usually above 1050℃, and the reaction time to complete is usually 1~5h, depending on the reaction temperature; while the critical temperature at which the alumina-zirconia composite matrix undergoes drastic densification shrinkage and abnormal grain growth is generally around 1300℃.

[0076] Based on the aforementioned physicochemical boundaries, 1200℃ was selected as the isothermal plateau. This temperature provides sufficient thermal driving force to ensure that cerium ions completely complete their valence transformation to Ce³⁺ within this time span; it is also below the critical line for the rigid closure of the matrix lattice. This provides unimpeded space for the oxygen atoms released during reduction and, before the ceramic shrinks drastically, constructs a Ce³⁺-dominated grain boundary segregation resistance network in advance, fundamentally suppressing abnormal grain growth in the subsequent high-temperature stage.

[0077] The conventional densification temperature for pure alumina / zirconia substrates is typically between 1450 and 1500 °C. However, silicon carbide nanowires form a rigid support network within the matrix, and their spatial obstruction effect severely hinders the shrinkage and rearrangement of matrix particles. It is necessary to screen for a temperature window (around 1700 °C) that allows the matrix to soften and flow sufficiently to encapsulate the nanowires, but without causing chemical degradation of the nanowires.

[0078] Experimental groups were set at 1400~1700℃ in 50℃ increments. After holding at 1200℃ for 2.5h, the temperature was increased to the experimental temperature at a rate of 10℃ / min. A physical pressure of 25~35MPa was applied axially and maintained for 1~2h for densification sintering. After sintering, the heating system was turned off, and the furnace was allowed to cool naturally to room temperature under vacuum before the samples were removed.

[0079] In addition to testing flexural strength and fracture toughness, the relative density needs to be determined using Archimedes' displacement method. After sintering and demolding, the sample surface is cleaned and dried at a constant temperature. Its dry weight in air is then measured using a high-precision analytical balance. Subsequently, the sample is completely immersed in deionized water and a vacuum is applied to ensure complete water penetration into the pores, and its buoyant weight in water is measured. Finally, the sample is removed and the surface free moisture is quickly wiped dry with damp filter paper, and its saturated wet weight is obtained. The actual bulk density of the sample is calculated and divided by the theoretical density of the formulation to obtain the relative density percentage. Relative density directly reflects the effect of the hot-pressing process on eliminating internal pores.

[0080] Test results are as follows Figure 4 As shown in the figure. Nonlinear curve fitting analysis of the data from each test group revealed that the relative density remained at 98.5% within the temperature range of 1482℃ to 1618℃, indicating an effective densification plateau. This demonstrates that within this temperature range, the softening and fluidity of the matrix effectively overcomes the spatial constraints imposed by the nanowire network.

[0081] Polynomial extreme value fitting was performed within the densification plateau region. The theoretical temperature coordinate corresponding to the maximum bending strength is 1538℃; the theoretical temperature coordinate corresponding to the maximum fracture toughness is 1568℃. This indicates that within the same densification plateau, there is a significant physical misalignment between the peak strength and toughness values ​​based on different defect evolution mechanisms.

[0082] Theoretically, the optimal sintering temperature for achieving a balance of comprehensive mechanical properties is 1553℃. However, considering the temperature control accuracy, ease of operation, and tolerance for errors in mass production of large-scale industrial vacuum hot presses, the actual densification sintering temperature is set at 1550℃.

[0083] Example 4 The fourth embodiment of the present invention provides a method for preparing a high-strength, wear-resistant ceramic material. The specific preparation steps are as follows: S1. Preparation and Stepwise Mixing of Composite Powder: Accurately weigh 82 parts by weight of alumina, 18 parts by weight of zirconium oxide, and 3.5 parts by weight of cerium oxide dry powder raw materials, and put them into a planetary ball mill. Add an appropriate amount of deionized water as a dispersion medium and add polyethylene glycol dropwise as a dispersant. Set the ball mill speed to 250 rpm and continuously ball mill for 6 hours for coarse mixing to obtain a homogeneous base suspension slurry.

[0084] Subsequently, four parts of silicon carbide nanowires were added to the slurry, and the ball mill speed was reduced to 120 rpm for low-speed, gentle mixing for 1.5 hours. After mixing, the slurry was pumped into a spray drying tower, and granulation was performed with the inlet air temperature set at 220℃ and the outlet air temperature at 100℃. After granulation and screening through a standard sieve, a composite granulated powder with good flowability was obtained.

[0085] S2. Cold Isostatic Pressing and Gradient Pressure Relief: The above-mentioned composite granulated powder is uniformly filled into a flexible polyurethane mold and completely sealed, then placed in the cavity of a cold isostatic press. The main pressure is set to 250 MPa, and high-pressure densification is performed by holding the pressure for 2 minutes.

[0086] After the pressure holding period, a gradient depressurization procedure is initiated: first, the cavity pressure is rapidly reduced to 50 MPa at a relatively high depressurization rate of 20 MPa / s; then, it automatically switches to a low depressurization rate of 0.8 MPa / s, slowly reducing to standard atmospheric pressure. Upon demolding, a high-density ceramic preform with no internal cracks and an intact surface is obtained. S3. Gradient hot pressing sintering: The ceramic blank is transferred to a vacuum hot pressing sintering furnace, and the following gradient temperature control program is executed: Low-temperature debinding: Slowly heat to 800℃ at a heating rate of 4℃ / min and maintain the temperature for 2 hours to completely volatilize and remove the residual organic components inside the blank.

[0087] Valence state transformation: Continue heating to 1200℃ and maintain the temperature at this temperature for 2.5h to promote the cerium ions in the system to fully and stably complete the reduction transformation to trivalent (Ce³⁺) and segregate towards the grain boundary.

[0088] Densification sintering: After the plateau period, the furnace temperature is increased to the final densification temperature of 1550℃ at a rate of 10℃ / min. At the same time, a constant physical pressure of 30MPa is applied along the mold axis and maintained at this temperature and pressure for 1 hour.

[0089] After the sintering process is completed, the heating and pressurization systems are turned off, and the furnace body is allowed to cool naturally to room temperature in a vacuum environment. The furnace is then opened and the sample is taken out, thus obtaining a high-strength, wear-resistant composite ceramic material with a uniform microstructure.

[0090] The prepared product has the following characteristics: relative density of 99.4% (measured by Archimedes' displacement method), flexural strength of 898 MPa (measured by three-point bending method), and fracture toughness of 19.35 MPa. (Measured using the single-sided V-beam method), Vickers hardness is 18.2 GPa, specific wear rate: (Tested using a ball-and-disc friction and wear tester), average grain size 0.42 μm (statistical analysis using SEM cross section method), flexural strength Weber modulus 21.8, flexural strength 915 MPa.

[0091] In summary, this invention achieves a balance between high surface wear resistance and structural toughness in special ceramic materials through a synergistic strategy of multiphase composite toughening and stepped temperature-controlled sintering. Alumina is used to construct the wear-resistant matrix, and zirconium oxide and silicon carbide nanowires are introduced to form a multidimensional structural reinforcement. The silicon carbide nanowires intertwine within the ceramic matrix to form a framework, which can hinder the propagation of microcracks when the material is under stress. Zirconia induces phase transitions in the microscopic stress regions to absorb destructive energy, thereby improving the material's resistance to transient mechanical loads. The addition of trace amounts of cerium dioxide improves the structural stability of the multiphase composite system at high temperatures.

[0092] By employing a two-stage stepped heating process, the state of trivalent cerium ions is first stabilized to ensure the stability of the grain boundary energy state before sintering, thereby suppressing abnormal growth and coarsening of alumina grains at high temperatures and ensuring the microscopic uniformity of the overall structure.

[0093] During the molding and densification stages, the pretreatment of cold isostatic pressing combined with the constant pressure process of vacuum hot pressing promotes the formation of a physical anchoring network between silicon carbide nanowires and the ultrafine-grained ceramic matrix. The final ceramic product maintains a high-density, wear-resistant microcrystalline lattice on the surface while constructing a stress dissipation network inside, effectively reducing the risk of traditional ceramics breaking under stress and meeting the service requirements of precision load-bearing components under heavy load conditions.

[0094] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-strength, wear-resistant ceramic material, characterized in that, Includes the following steps: S1: Weigh 70-85 parts by weight of alumina, 15-30 parts by weight of zirconium oxide and 2.5-4.5 parts by weight of cerium oxide dry powder raw materials and put them into a planetary ball mill. After adding dispersion medium and dispersant, coarse mixing is carried out. After coarse mixing, add 2-6 parts by weight of silicon carbide nanowires and ball mill at low speed. Spray dry the mixed slurry to obtain composite granulated powder. S2 The composite granulated powder is filled into a mold and sealed. After being compressed by a cold isostatic press, the pressure is gradually released to obtain a ceramic blank. S3 The ceramic blank is transferred to a vacuum hot pressing sintering furnace for low-temperature volatilization and impurity removal. The temperature was raised to 1050℃~1300℃ for 1~5 hours to carry out the cerium ion reduction transformation. The material is heated to 1500~1600℃ for densification sintering, and then cooled to obtain the high-strength wear-resistant ceramic material.

2. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S1, the alumina is 82 parts, the zirconium oxide is 18 parts, the cerium oxide is 3.5 parts, and the silicon carbide nanowires are 4 parts.

3. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S3, the parameters for the reduction transformation are constant temperature at 1200℃ for 2.5h; and the temperature for densification sintering is 1550℃.

4. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S1, the dispersion medium is one of deionized water, anhydrous ethanol, and isopropanol, and the dispersant is one of polyethylene glycol, polyvinyl alcohol, and sodium polyacrylate; the operating parameters of the coarse mixing process are continuous ball milling at 200-300 rpm for 4-8 hours; and the operating parameters of the low-speed ball milling process are mixing at 100-150 rpm for 1-2 hours.

5. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S1, the spray drying process involves setting the inlet air temperature of the spray drying tower to 200~240℃ and the outlet air temperature to 90~110℃ for granulation. After granulation and screening, the composite granulated powder is obtained.

6. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S2, the mold is made of polyurethane, silicone, or natural rubber; the compression process parameters are set as follows: main pressure 200-300 MPa, pressure holding 1-3 min.

7. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S2, the gradient decompression specifically includes: First, depressurize to 50 MPa at a depressurization rate of 15~25 MPa / s; then depressurize to standard atmospheric pressure at a low depressurization rate of 0.5~1 MPa / s.

8. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S3, the low-temperature volatilization and impurity removal process specifically includes: slowly heating to 700-900°C at a heating rate of 3-5°C / min and holding at that temperature for 1-3 hours to volatilize and remove the residual organic components inside the blank.

9. The method for preparing high-strength wear-resistant ceramic material according to claim 1, characterized in that, In step S3, the densification sintering process further includes: applying a physical pressure of 25-35 MPa in the axial direction and maintaining it for 1-2 hours.

10. A high-strength, wear-resistant ceramic material, prepared by any one of claims 1 to 9, characterized in that, The ceramic material consists of a composite fine-grained matrix composed of alumina and zirconium oxide, with trivalent cerium ions enriched and strongly pinned at the grain boundaries of the composite fine-grained matrix; silicon carbide nanowires are uniformly interwoven and densely wrapped by the composite fine-grained matrix, and the silicon carbide nanowires are constructed inside the matrix to form a one-dimensional mechanical interlocking network that consumes energy during bridging and pulling out.

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