A silicon carbide whisker-reinforced alumina ceramic material having a directional array of whiskers and a method of making the same

Abstract

The application relates to the technical field of ceramic materials, and provides a SiC-whisker-reinforced alumina ceramic material with whisker directional arrangement and a preparation method thereof. SiC whiskers are magnetically modified by being coated with cobalt, then the magnetically modified SiC whisker powder is mixed with Al2O3 ceramic slurry which has been ball milled, and sodium polystyrene sulfonate is added to the mixture for sufficient mixing in a dispersing machine. Then, an electric field and a magnetic field are simultaneously applied to the mixed solution, so that the SiC whiskers are turned under the action of the electric field and the magnetic field, and directional arrangement of the SiC whiskers in a certain direction is realized. The solution is immediately transferred into a freeze-drying machine to freeze and fix the directional arrangement, and then vacuum sublimation drying is carried out at low temperature, so that the Al2O3-Y2O3-SiC ceramic material with SiC whisker directional arrangement is prepared. w The mixed powder is subjected to hot-pressing sintering to prepare the SiC-whisker-reinforced alumina ceramic material with obvious whisker directional arrangement. The ceramic material can be used for preparing a ceramic cutting tool, and is used for high-efficiency cutting of a nickel-based high-temperature alloy.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement and its preparation method. Background Technology

[0002] Alumina ceramics are widely studied and applied due to their high hardness, high wear resistance, good high-temperature resistance, and excellent oxidation resistance. They are mainly used in extreme environments such as high temperature, corrosion, and high wear, as well as in some electronic components, such as grinding balls, corrosion-resistant parts, cutting tools, and electronic substrates. However, the high brittleness, low strength, and poor impact resistance of alumina ceramics significantly limit their widespread application.

[0003] SiC whiskers are high-strength single-crystal fibers with diameters ranging from nanometers to micrometers. They contain few chemical impurities and have few structural defects, exhibiting characteristics such as high melting point, low density, high strength, high modulus, low thermal expansion coefficient, and strong resistance to wear, corrosion, and high-temperature oxidation. Adding a certain amount of SiC whiskers to an Al2O3 ceramic matrix can significantly improve the toughness of Al2O3 ceramics. However, if SiC whiskers are randomly distributed in the Al2O3 matrix, their reinforcing effect cannot be fully realized. High orientation and directional distribution of SiC whiskers are necessary to maximize their reinforcing effect. Existing technology discloses a whisker-reinforced alumina composite ceramic and its preparation method and application. This method uses hot-press flow sintering to flow the sample in a one-dimensional or two-dimensional direction within a mold, preparing whisker-reinforced alumina ceramics with oriented whisker arrangement. However, because the orientation of whiskers is achieved solely through hot-press sintering to allow powder particles to flow, the degree of orientation is not high, and the sintering temperature is relatively high, resulting in high energy consumption. Existing technology discloses a highly oriented, functional composite material of calcium sulfate whiskers and its preparation method. This involves adding an aqueous solution of sodium polyacrylate electrolyte, applying an electric field to the solution, and using a filter to orient the calcium sulfate whiskers. Then, by introducing a crosslinking agent (N,N-methylenebisacrylamide) and an initiator (ammonium persulfate), a crosslinking reaction occurs, solidifying the solution with the oriented calcium sulfate whiskers. Finally, organic matter is removed at high temperature to obtain a dense inorganic oriented calcium sulfate whisker composite material. While this method can achieve oriented whisker alignment, it is relatively complex, limiting its industrial production. Furthermore, N,N-methylenebisacrylamide itself is toxic; inhalation or ingestion can damage the central nervous system. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention aims to propose a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement and its preparation method.

[0005] According to a first aspect of the present invention, the present invention provides the following technical solution:

[0006] A method for preparing a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement includes the following steps:

[0007] S1. Magnetization treatment of SiC whiskers: SiC whiskers are dispersed in ethanol, cobalt nitrate hexahydrate and citric acid are added, the pH is adjusted to acidic, ball milling is performed in a ball mill for 2-3 hours and then dried. After drying, SiC whisker powder with magnetic Co coating is obtained by reduction in H2 at a temperature of 400-600℃.

[0008] S2. Slurry preparation: Weigh a certain amount of Al2O3 powder and Y2O3 powder, add anhydrous ethanol, and ball mill and mix them for 2-4 hours to obtain Al2O3-Y2O3 ceramic slurry;

[0009] S3. Mixing: The Al2O3-Y2O3 ceramic slurry obtained in step S2, the Co-coated SiC whisker powder obtained in step S1, and the sodium polystyrene sulfonate powder are thoroughly mixed in a disperser to obtain Al2O3-Y2O3-SiC. w Mixed solutions;

[0010] S4, Electric-Magnetic Field Assisted Oriented Alignment: Al2O3-Y2O3-SiC obtained in step S3 w An electric field and a magnetic field are applied to the mixed solution for 3 to 5 minutes, with the angle between the electric field direction and the magnetic field direction being 80 to 100°. The alignment direction of SiC whiskers in the EB plane is controlled by adjusting the ratio of electric field strength E to magnetic field strength B, E / B.

[0011] S5. Freeze-drying: The solution after step S4 is promptly transferred to a freeze dryer for freeze-drying to obtain Al2O3-Y2O3-SiC with oriented SiC whiskers. w powder;

[0012] S6. Sintering: The Al2O3-Y2O3-SiC obtained in step S5 is sintered. w The powder is placed in a graphite mold and hot-pressed and sintered to obtain a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement.

[0013] As a preferred embodiment of the preparation method of the SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, wherein: Al2O3-Y2O3-SiC with oriented SiC whiskers w The content of Al2O3 powder in the powder is 68~84.5wt%, and the content of SiC is... wThe content of the powder is 15~30wt%; the content of the Y2O3 powder is 0.5~2wt%.

[0014] As a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S1, the mass ratio of cobalt nitrate hexahydrate to SiC whiskers is 1:3~5; the pH value is 3~5; the diameter of SiC whiskers is 0.2~1μm and the aspect ratio is 20~100.

[0015] As a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S2, the particle size of Al2O3 powder is <1μm; the particle size of Y2O3 powder is <2μm.

[0016] As a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S3, the mass ratio of sodium polystyrene sulfonate powder to Co-coated SiC whisker powder is 1:(80~150), the speed of the disperser is 600~1000 rpm, and the mixing time is 2~4 h.

[0017] In a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S4, the electric field strength E is 0.5~2.0V / cm and the magnetic field strength B is 0.1~3.0T.

[0018] As a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S5, the freeze-drying includes two stages: the first stage is freeze-drying, wherein the freezing temperature of freeze-drying is -40~-50℃ and the freezing time is 1~3h; the second stage is sublimation drying, wherein the vacuum degree of sublimation drying is 5~20Pa, the temperature is -40~-50℃ and the time is 20~30h.

[0019] As a preferred embodiment of the preparation method of SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to the present invention, in step S6, the hot pressing sintering temperature is 1750~1850℃, the holding time is 1~2h, and the pressure is 25~40MPa.

[0020] According to a second aspect of the present invention, the present invention provides the following technical solution:

[0021] A SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement is prepared by the above-described method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement.

[0022] As a preferred embodiment of the SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement described in this invention, the SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement has a relative density ≥98%, a hardness HV3 ≥2050, a flexural strength ≥700MPa, and a fracture toughness Kic ≥6.5MPa·m. 1 / 2 .

[0023] The beneficial effects of this invention are as follows:

[0024] This invention provides a SiC whisker-reinforced alumina ceramic material with oriented whisker alignment and its preparation method. The SiC whiskers are magnetized by coating them with cobalt. The magnetized SiC whisker powder is then mixed with ball-milled Al2O3 ceramic slurry, and sodium polystyrene sulfonate is added, followed by thorough mixing in a disperser. An electric field and a magnetic field are simultaneously applied to the mixed solution, causing the SiC whiskers to orient themselves under the influence of the electric and magnetic fields, achieving oriented alignment in a specific direction. This solution is then promptly transferred to a freeze dryer to freeze-fix this oriented alignment, followed by vacuum sublimation drying at low temperature to prepare Al2O3-Y2O3-SiC with oriented SiC whisker alignment. w By mixing powders and hot-pressing and sintering these powders, SiC whisker-reinforced alumina ceramic materials with significant whisker orientation can be prepared. These ceramic materials can be used to prepare ceramic cutting tools for efficient cutting of nickel-based superalloys. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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 the structures shown in these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of applying electric and magnetic fields to a solution.

[0027] Figure 2 Al2O3-Y2O3-SiC prepared in Example 1 w SEM image of the mixed powder.

[0028] Figure 3 Al2O3-Y2O3-SiC prepared for Comparative Example 5 w SEM image of the mixed powder.

[0029] Figure 4The image shows the fracture surface SEM image of the SiC whisker-reinforced Al2O3 ceramic material prepared in Example 1.

[0030] Figure 5 The fracture surface SEM image is shown for the SiC whisker-reinforced Al2O3 ceramic material prepared in Example 5.

[0031] Figure 6 SEM image of the fracture surface of the SiC whisker-reinforced Al2O3 ceramic material prepared for Comparative Example 1.

[0032] Figure 7 SEM image of the fracture surface of the SiC whisker-reinforced Al2O3 ceramic material prepared for Comparative Example 5.

[0033] In the diagram, 1 is the electrode and 2 is the container.

[0034] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides a SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement and its preparation method, which has the following advantages:

[0037] (1) By adding cobalt nitrate and ball milling SiC whiskers, the cobalt nitrate is reduced to cobalt in a hydrogen atmosphere, and the SiC whiskers are coated with cobalt, thus achieving magnetic modification of SiC whiskers. At the same time, the presence of cobalt can form a liquid phase at high temperature, which improves the wettability of SiC whiskers and Al2O3 and enhances the interfacial bonding force between SiC whiskers and Al2O3.

[0038] (2) After fully dispersing and mixing the magnetically modified SiC whiskers with Al2O3-Y2O3 ceramic slurry and adding sodium polystyrene sulfonate, the SO3 provided by the sodium polystyrene sulfonate... 2- It will be adsorbed on the surface of SiC whiskers, facilitating the binding of SiC whiskers with positively charged ions and increasing the bonding strength between SiC whiskers and cobalt. Meanwhile, sodium polystyrene sulfonate is an organic electrolyte solution, and under the influence of electric and magnetic fields (see schematic diagram of applying electric and magnetic fields to the solution...), Figure 1As shown (where 1 is the electrode and 2 is the container), SiC whisker particles can be oriented, achieving their directional alignment in a certain direction. The solution is transferred to a freeze dryer for immediate freeze-drying. Because drying occurs in a frozen state, the volume remains almost unchanged, preserving the Al2O3-Y2O3-SiC structure. w The original orientation of SiC whiskers in the mixed powder.

[0039] (3) Al2O3-Y2O3-SiC w After hot pressing and sintering, mixed powders can be used to prepare SiC whisker-reinforced alumina ceramic materials with a microstructure of significant SiC whisker orientation, high fracture toughness and bending strength. This material can be used to make ceramic cutting tools for efficient cutting of nickel-based high-temperature alloys.

[0040] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0041] The specific preparation parameters for the SiC whisker-reinforced alumina ceramic materials in Examples 1-5 are shown in Table 1 below.

[0042] Table 1. Preparation parameters and conditions of SiC whisker-reinforced alumina ceramic materials in Examples 1-5

[0043]

[0044]

[0045] Examples 1-5 were prepared according to the process parameters in Table 1. Weighed SiC whiskers, cobalt nitrate hexahydrate, and citric acid were first ball-milled in a ball mill, then dried. The dried powder was then reduced in a hydrogen atmosphere to obtain cobalt-coated magnetically modified SiC whisker powder. Al2O3 powder and Y2O3 powder were weighed and poured into a ball mill jar. φ5mm Al2O3 grinding balls were added at a ball-to-powder ratio of 6:1, and anhydrous ethanol was added. The Al2O3 and Y2O3 powders were ball-milled and mixed to prepare an Al2O3-Y2O3 ceramic slurry. The ball-milled Al2O3-Y2O3 ceramic slurry was then thoroughly dispersed and mixed with cobalt-coated SiC whisker powder and sodium polystyrene sulfonate powder in a disperser. Under the influence of an external electric and magnetic field, the SiC whiskers were oriented. After 3-5 minutes, the Al2O3-Y2O3-SiC slurry was promptly dispersed and mixed. w The container of the mixed solution was transferred to a freeze dryer for freeze drying. The freeze-dried powder was then placed into a graphite mold and hot-pressed for sintering to prepare a SiC whisker-reinforced alumina ceramic material sample. This ceramic sample was then subjected to laser cutting, surface grinding, and sharpening to obtain ceramic cutting tools of the desired shape.

[0046] The specific preparation parameters for SiC whisker-reinforced alumina ceramic materials in Comparative Examples 1-5 are shown in Table 2 below.

[0047] Table 2. Preparation parameters and conditions for SiC whisker-reinforced alumina ceramic materials in Comparative Examples 1-5

[0048]

[0049]

[0050] The difference between Comparative Example 1 and Example 1 is that, in the SiC whisker magnetization treatment stage, the mass ratio of cobalt nitrate to SiC whiskers is 1:2, and the pH value is 6.

[0051] The difference between Comparative Example 2 and Example 2 is that the mass ratio of sodium polystyrene sulfonate to SiC whiskers is 1:70, and the electric field strength E is 0.4V / cm.

[0052] The difference between Comparative Example 3 and Example 3 is that the particle size of Al2O3 powder is 1.2 μm, the mass ratio of sodium polystyrene sulfonate to SiC whiskers is 1:160, and the hot pressing sintering temperature is 1700℃.

[0053] The difference between Comparative Example 4 and Example 4 is that the pH value was 2 and the electric field strength was 2.5 V / cm during the SiC whisker magnetization treatment stage.

[0054] The difference between Comparative Example 5 and Example 5 is that the mass ratio of cobalt nitrate to SiC whiskers is 1:6, and the magnetic field strength is 3.5T.

[0055] Al2O3-Y2O3-SiC prepared in Example 1 w SEM images of the mixed powder are shown below. Figure 2 As shown. Al₂O₃-Y₂O₃-SiC prepared in Comparative Example 5. w SEM images of the mixed powder are shown below. Figure 3 As shown. By Figure 2 and Figure 3 It can be seen that, Figure 2 The SiC whiskers have a distinct directional alignment along a certain direction, while Figure 3 The SiC whiskers do not exhibit any orientation. This indicates that when the mass ratio of cobalt nitrate to SiC whiskers exceeds 1:5, that is, when the cobalt content is low, even increasing the magnetic field strength cannot achieve the directional alignment of the SiC whiskers.

[0056] The fracture surface SEM image of the SiC whisker-reinforced Al2O3 ceramic material prepared in Example 1 is shown below. Figure 4 As shown in the figure. The fracture surface SEM image of the SiC whisker-reinforced Al2O3 ceramic material prepared in Example 5 is shown in the figure. Figure 5 As shown in the figure. The fracture surface SEM image of the SiC whisker-reinforced Al2O3 ceramic material prepared in Comparative Example 1 is shown in the figure. Figure 6 As shown in the figure. The fracture surface SEM image of the SiC whisker-reinforced Al2O3 ceramic material prepared in Comparative Example 5 is shown in the figure. Figure 7 As shown. By Figure 4-7 It can be seen that the SiC whiskers are clearly oriented in a certain direction in the fracture surface SEM of Examples 1 and 5, while the SiC whiskers of Comparative Examples 1 and 5 are randomly distributed in the Al2O3 matrix and their distribution has no orientation.

[0057] The flexural strength, hardness, and density of the SiC whisker-reinforced alumina ceramic materials prepared in each embodiment and comparative example were tested, and the results are shown in Table 3. It can be seen that the SiC whisker-reinforced alumina ceramic material prepared in this invention has a relative density ≥98%, a hardness HV3 ≥2050, a flexural strength ≥700MPa, and a fracture toughness Kic ≥6.5MPa·m. 1 / 2 .

[0058] The testing of bending strength, hardness, and fracture toughness was performed according to "JB / T 12613-2016 Test Methods for the Properties of Ceramic Cutting Tool Materials". The specimen size for bending strength was 4mm × 3mm × 46mm, with a span of 30mm and a loading rate of 0.5mm / min. Density was tested using the Archimedes' displacement method, while hardness and fracture toughness were tested using the indentation method with a loading pressure of 3kg.

[0059] Table 3. Properties of SiC whisker-reinforced alumina ceramics prepared in each example and comparative example.

[0060]

[0061] The ceramic samples from Examples 1, 5, Comparative Example 1, and 5 were used to prepare ceramic turning inserts (RNGN120700T01020). Turning tests were conducted on the prepared ceramic inserts using a nickel-based superalloy GH4169 (HRC 35~45). Dry turning was performed with the following cutting parameters: cutting speed Vc = 300 m / min, feed rate f = 0.18 mm / rev, depth of cut Ap = 0.5 mm. Tool failure was defined as a wear VB reaching 0.2 mm. The tool life results are shown in Table 4. It is evident that the SiC whisker-reinforced alumina ceramic tool prepared using the method of this invention has a significantly better cutting life than the comparative example.

[0062] Table 4 Tool Cutting Life

[0063]

[0064] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement, characterized in that, Includes the following steps: S1. Magnetization treatment of SiC whiskers: SiC whiskers are dispersed in ethanol, cobalt nitrate hexahydrate and citric acid are added, the pH is adjusted to acidic, ball milled in a ball mill and then dried, and then reduced in H2 to obtain SiC whisker powder with magnetic Co coating; the mass ratio of cobalt nitrate hexahydrate to SiC whiskers is 1:3~5; the pH value is 3~5. S2. Slurry preparation: Weigh a certain amount of Al2O3 powder and Y2O3 powder, add anhydrous ethanol, and ball mill to mix them to obtain Al2O3-Y2O3 ceramic slurry; the particle size of Al2O3 powder is <1μm; S3. Mixing: The Al2O3-Y2O3 ceramic slurry obtained in step S2, the Co-coated SiC whisker powder obtained in step S1, and the sodium polystyrene sulfonate powder are thoroughly mixed in a disperser to obtain Al2O3-Y2O3-SiC. w Mixed solution; the mass ratio of sodium polystyrene sulfonate powder to Co-coated SiC whisker powder is 1:(80~150); S4, Electric-Magnetic Field Assisted Oriented Alignment: Al2O3-Y2O3-SiC obtained in step S3 w An electric field and a magnetic field are applied to the mixed solution, and the alignment direction of SiC whiskers in the EB plane is controlled by adjusting the ratio of electric field strength E to magnetic field strength B, E / B; the electric field strength E is 0.5~2.0V / cm, and the magnetic field strength B is 0.1~3.0T. S5. Freeze-drying: The solution after step S4 is promptly transferred to a freeze dryer for freeze-drying to obtain Al2O3-Y2O3-SiC with oriented SiC whiskers. w powder; S6. Sintering: The Al2O3-Y2O3-SiC obtained in step S5 is sintered. w The powder is placed in a graphite mold and hot-pressed and sintered at a temperature of 1750~1850℃ to obtain SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement.

2. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, Al2O3-Y2O3-SiC with oriented SiC whiskers w The content of Al2O3 powder in the powder is 68~84.5wt%, and the content of SiC is... w The content of the powder is 15~30wt%; the content of the Y2O3 powder is 0.5~2wt%.

3. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, In step S1, the diameter of the SiC whiskers is 0.2~1μm and the aspect ratio is 20~100.

4. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, In step S2, the particle size of the Y2O3 powder is <2μm.

5. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, In step S3, the speed of the disperser is 600~1000 rpm, and the mixing time is 2~4 hours.

6. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, In step S5, freeze drying includes two stages: the first stage is freeze drying, wherein the freezing temperature is -40~-50℃ and the freezing time is 1~3h; the second stage is sublimation drying, wherein the vacuum degree of sublimation drying is 5~20Pa, the temperature is -40~-50℃, and the time is 20~30h.

7. The method for preparing SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 1, characterized in that, In step S6, the holding time for hot pressing sintering is 1~2 hours, and the pressure is 25~40 MPa.

8. A SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement, characterized in that, The SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement as described in any one of claims 1-7 was prepared.

9. The SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement according to claim 8, characterized in that, The SiC whisker-reinforced alumina ceramic material with oriented whisker arrangement has a relative density ≥98%, a hardness HV3 ≥2050, a flexural strength ≥700MPa, and a fracture toughness Kic ≥6.5MPa·m. 1 / 2 .

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