Ceramic composition and ceramic component

Abstract

This ceramic composition contains alumina (Al2O3) and tungsten carbide (WC). In this ceramic composition, an atomic layer comprising hafnium (Hf) is present in the grain boundary between crystal grains of alumina (Al2O3) and crystal grains of tungsten carbide (WC). The atomic layer includes two or more layers of atomic arrangements of hafnium.

Description

Ceramic composition and ceramic part

[0001] The present invention relates to ceramic compositions and ceramic parts containing same.

[0002] Alumina (Al ２ O ３ In order to improve the properties of ceramic compositions containing alumina (Al ２ O ３ ) and a technique of including tungsten carbide (WC) in the alloy.

[0003] For example, Patent Document 1 discloses alumina (Al ２ O ３ and tungsten carbide (WC); wherein the atomic layer formed by at least one element selected from transition metals belonging to groups 4 to 6 of the periodic table, yttrium (Y), scandium (Sc) and lanthanoids is alumina (Al ２ O ３ A ceramic composition is disclosed that is characterized by the presence of tungsten carbide (WC) crystal grains at the grain boundaries between WC crystal grains.

[0004] Patent No. 6491363

[0005] As mentioned above, alumina (Al ２ O ３ Various approaches have been proposed to improve the properties of ceramic compositions containing tungsten carbide (WC).

[0006] One aspect of the present invention is to further improve the environmental performance of ceramic compositions containing alumina and tungsten carbide.

[0007] [1] The ceramic composition according to one aspect of the present invention is alumina (Al ２ O ３ ) and tungsten carbide (WC), wherein the alumina (Al ２ O ３At the grain boundaries between the crystal grains of the tungsten carbide (WC) and the crystal grains of the tungsten carbide (WC), there are atomic layers formed by hafnium (Hf), and the atomic layers include atomic arrangements of two or more layers of hafnium.

[0008] [2] In the ceramic composition according to one aspect of the present invention described in [1], the ratio of pores in any one cross section of the ceramic composition may be 0.1% or less.

[0009] [3] In the ceramic composition according to one aspect of the present invention described in [1] or [2], the atomic layer may be formed of a metal crystalline phase of hafnium (Hf) at the grain boundary.

[0010] [4] In the ceramic composition according to one aspect of the present invention described in [3], the atomic layer may be formed on a (210) plane of the hafnium (Hf) metal crystalline phase at the grain boundary.

[0011] [5] In the ceramic composition according to one aspect of the present invention described in [4], the metal crystalline phase of the hafnium (Hf) may be a hexagonal crystal, and the atomic layer may be formed to a thickness equivalent to three layers of a (210) plane of the hexagonal crystal.

[0012] [6] A ceramic part according to another aspect of the present invention includes the ceramic composition according to any one of [1] to [5].

[0013] [7] The ceramic part according to one aspect of the present invention described in [6] may be used in any one of a gas turbine component, a jet nozzle for an artificial satellite, a mold for a lens, a sealing material, an aircraft engine component, and a cutting tool.

[0014] According to one aspect of the present invention, a ceramic composition having improved ductility and bending strength properties in a high-temperature environment can be obtained.

[0015] FIG. 1 is a perspective view showing the appearance of a ceramic composition according to one embodiment. FIG. 2 is a view showing a TEM image of the A-A cross section of a ceramic composition according to one example. FIG. 3 is a view showing a HAADF-STEM image of the vicinity of a grain boundary of a ceramic composition according to one example. FIG. 4 is a view showing a HAADF-STEM image of the vicinity of a grain boundary of a ceramic composition according to one example and a simulated image. FIG. 5 is a view showing a HAADF-STEM image of the vicinity of a grain boundary of a ceramic composition according to one example. FIG. 6 is a view showing an SEM image of a cross section of a ceramic composition according to one example, with each component color-coded. FIG. 7 is a view showing a TEM image of a cross section of a ceramic composition after stress has been applied. FIG. 8 is a view showing an SEM image of a cross section of a ceramic composition after stress has been applied, with each component color-coded. FIG. 9 is a flowchart showing the flow of a method for producing a ceramic composition according to one embodiment.

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a ceramic composition 10, which is an example of a ceramic composition, will be described as an example. The ceramic composition 10 is suitable for use as a material for ceramic parts included in devices used in high-temperature environments of 1400°C or higher. Specifically, the ceramic composition 10 is used as a material for ceramic parts such as gas turbine components, satellite jet nozzles, lens molds, sealing materials, aircraft engine components, and cutting tools.

[0017] (Configuration of ceramic composition) Fig. 1 is a perspective view showing the appearance of a ceramic composition 10. The ceramic composition 10 is made of alumina (Al ２ O ３ ) and tungsten carbide (WC). In this ceramic composition 10, alumina (Al ２ O ３ At the grain boundaries between crystal grains of tungsten carbide (WC) and tungsten carbide (WC), there are atomic layers formed by hafnium (Hf). This atomic layer includes an atomic arrangement of two or more layers.

[0018] The atomic layer formed by hafnium (Hf) is, for example, hafnia (HfO ２) as a raw material when producing the ceramic composition 10.

[0019] Figure 2 shows an example of a TEM image of the A-A cross section of the ceramic composition 10 shown in Figure 1. The TEM image shown in Figure 2 can be obtained by observing a sample prepared by the following procedure with a transmission electron microscope.

[0020] First, the ceramic composition was cut into a φ3 mm disk plate in a predetermined position and direction using a diamond cutter and an ultrasonic disk cutter, and then the thickness was adjusted to less than 100 μm using 30 μm diamond polishing paper and thinned. Next, a dimple was applied to the center of the disk using a dimpler, and the disk was then processed using a precision ion polishing system (PIPS). The TEM image shown in Figure 2 was obtained by observing a sample obtained by ion polishing under the following conditions: Ar ions, accelerating voltage 4.0 kV, beam irradiation angle ±4°, and then performing a damaged layer removal process at 1.0 kV for 2 minutes after penetration of the sample.

[0021] FIG. 3 shows an example of a HAADF-STEM image of the vicinity of a grain boundary of the ceramic composition 10 shown in FIG. 1. HAADF-STEM (High-Angle Annular Dark Field Scanning Transmission Electron Microscopy) is a high-angle scattering annular dark field scanning transmission microscope. In the HAADF-STEM image, heavy elements appear bright. When compared with a structural model, it can be seen that the bright white dots correspond to tungsten (W) atomic columns.

[0022] Image A of Fig. 3 is an HAADF-STEM image of the vicinity of the grain boundary between the alumina crystal grains and the tungsten carbide crystal grains in Image B. In Image A of Fig. 3, the atomic layer of the alumina crystal grains is the alumina layer 20, the atomic layer of the tungsten carbide crystal grains is the WC layer 30, and the atomic layer derived from the hafnium compound is the Hf layer 40.

[0023] As shown in FIG. 3, in the ceramic composition 10, the Hf layer 40 exists between the alumina layer 20 and the WC layer 30. In other words, the ceramic composition 10 is made of alumina (Al ２ O ３ An atomic layer formed by hafnium (Hf) exists at the grain boundary between the crystal grains of silicon dioxide (SiO2) and the crystal grains of tungsten carbide (WC). The Hf layer 40 includes an atomic arrangement of two or more layers. For example, in image A shown in FIG. 3, the Hf layer 40 is formed by an arrangement of two layers of Hf atoms.

[0024] The Hf layer 40 includes two or more layers of atomic arrangement, which allows the Hf layer 40 to form a hafnium (Hf) metal crystalline phase. Hafnium (Hf) is an element classified as a transition metal, and has a metal crystalline phase with a hexagonal close-packed structure at room temperature and normal pressure. That is, the metal crystalline phase of hafnium (Hf) is hexagonal.

[0025] As shown in FIG. 4, the Hf layer 40 is preferably formed from the (210) plane of the metal crystalline phase of hafnium (Hf).

[0026] Furthermore, as shown in FIG. 5, it is more preferable that the Hf layer 40 be formed to a thickness equivalent to three layers of the (210) plane of the hexagonal crystal.

[0027] As described above, the presence of Hf layer 40 containing two or more layers of atomic arrangement at the grain boundaries between alumina crystal grains and tungsten carbide crystal grains can improve the adhesion strength between the alumina crystal grains and tungsten carbide crystal grains.

[0028] Furthermore, since the Hf layer 40 is formed from a metal crystalline phase of hafnium, it is possible to obtain a ceramic composition that is excellent in ductility in a high-temperature environment (for example, 1400° C. or higher).

[0029] (Regarding Pores in Ceramic Composition) Next, the pores contained in the ceramic composition 10 will be described. Here, pores refer to voids contained within the solid ceramic composition 10. The pores contained in the ceramic part obtained after molding and processing the ceramic composition 10 are also called cavities.

[0030] For example, when a ceramic composition is placed in a high-temperature environment of 1400° C. or higher and subjected to stress, the proportion of pores or cavities contained in the composition tends to increase. This proportion tends to increase over time.

[0031] It is known that fracture of ceramic components in high-temperature environments is caused by the formation, growth, and connection of pores or cavities in the ceramic composition. Furthermore, when a ceramic composition is processed into a ceramic component of a predetermined shape, the proportion of pores or cavities tends to increase when stress such as bending is applied to the ceramic composition.

[0032] Therefore, by keeping the ratio of pores contained in the ceramic composition as low as possible, it is expected that a ceramic composition with higher performance (specifically, a ceramic composition with excellent high-temperature ductility) can be obtained.

[0033] In the ceramic composition 10 according to this embodiment, the pore ratio in any one cross section is preferably 0.1% or less. This allows for a ceramic composition with excellent high-temperature ductility to be obtained. The ceramic composition 10 having such properties can be produced by the method described below.

[0034] The pore ratio can be determined by taking multiple samples from the target ceramic composition or ceramic part and calculating the pores of each sample based on the pore measurement method described below. If the pore ratio of the sample with the largest pore ratio among the multiple samples is 0.1% or less, the pore ratio can be determined to be 0.1% or less.

[0035] In the ceramic composition 10 according to this embodiment, the lower limit of the pore ratio is not particularly limited. In a typical ceramic composition containing alumina and tungsten carbide, it is difficult to achieve zero pores (no pores). Therefore, the pore ratio in the ceramic composition 10 according to this embodiment is greater than 0%.

[0036] In the ceramic composition 10 according to this embodiment, an increase in the pore ratio can be suppressed even after stress application (for example, bending) (see FIGS. 7 and 8). FIG. 7 and FIG. 8 show the results of observing a cross section of the ceramic composition 10 after stress application (after a bending test) in this example.

[0037] (Method for Measuring Pore Ratio) Here, an example of a method for measuring the pore ratio contained in the ceramic composition 10 will be described.

[0038] First, the solid ceramic composition 10 is broken into small pieces, and any cross section is polished to the order of several microns. Next, a cross-section perpendicular to the cross section is processed using a shielding plate in a depth direction of 50 μm or more from the polished surface to form an ion-milled cross section with polishing damage removed, which serves as the observation surface. For example, an Ar ion milling device with an acceleration voltage of 5 to 6 kV is used as the processing device. An area of ​​300 μm x 300 μm or more is secured as the observation surface.

[0039] Next, an SEM image of the observation surface is taken. For example, an electron microscope with a voltage variable between 0.1 kV and 20 kV is used to photograph the observation surface and obtain image data. The resolution and magnification of the obtained image data are adjusted so that the resolution (number of pixels) is at least 10 times that of the smallest grain in the ceramic structure, and the image data is saved in a data format that does not require irreversible processing (for example, tiff or bmp).

[0040] The obtained image data is then subjected to image analysis. Specifically, the obtained image data is quantized into four values ​​using a region-classifying function of image analysis software (for example, Avizo software for materials research (Thermo Fisher Scientific Inc.)). Specifically, the image data is quantized into four regions as follows: A: alumina (Al ２ O ３ A: Region formed by tungsten carbide (WC); C: Region formed by hafnium (Hf); D: Pore region.

[0041] When converting to four values, the grain boundary layer is not taken into consideration, regardless of whether the material is the same or different from the other material. In the case of the same material, it is extracted as a continuous region. Note that SEM images contain overlapping information in the depth direction, so regions are divided based on the observed top surface information. The area and occupancy rate of each region are calculated using pixel spacing and the software's 2D calculation function for digitization.

[0042] An example of an image obtained by performing quaternary processing on an SEM image of an arbitrary cross section of the ceramic composition 10 using the above method is shown in Fig. 6. In Fig. 6, the results of calculating the occupancy ratio of each of the above regions A to D are also shown below the image.

[0043] As shown in FIG. 6, it was confirmed that the ceramic composition 10 according to this embodiment had a pore ratio of 0.1% or less in any one cross section.

[0044] 8 shows an example of an image obtained by subjecting an SEM image of an arbitrary cross section of the ceramic composition 10 after stress application to a quaternary processing. Below the image, Fig. 8 also shows the results of calculating the occupancy ratio of each of the above regions A to D.

[0045] 8, it was confirmed that the pore ratio in any one cross section of the ceramic composition 10 after stress application was 0.1% or less. This confirmed that the ceramic composition 10 according to this embodiment can suppress an increase in the pore ratio even after stress application (for example, bending).

[0046] The above-described method for measuring the pore ratio can also be used to calculate the proportion (volume %) of each component contained in the ceramic composition 10 .

[0047] Specifically, the area of ​​each region is calculated for the image data that has been quaternized for each of the four regions A to D. Then, A / (A+B+C+D), B / (A+B+C+D), and C / (A+B+C+D) are calculated based on the calculated values.

[0048] This gives the proportion (vol %) of each component in the ceramic composition 10. FIGS. 6 and 8 show the ratio (vol %) of alumina (Al２ O ３ ) component, tungsten carbide (WC) component, and hafnium (Hf) component.

[0049] (Method for Manufacturing Ceramic Composition) Next, a method for manufacturing the ceramic composition 10 will be described. Fig. 9 shows an example of a method for manufacturing the ceramic composition 10.

[0050] First, alumina, tungsten carbide, and a hafnium compound, which are raw materials for the ceramic composition, are prepared (step S11). Each raw material is prepared in the form of powder. Specifically, alumina (Al ２ O ３ ) powder, tungsten carbide (WC) powder with an average particle size of about 0.7 μm, hafnia (HfO ２ ) powder is used.

[0051] The average particle size of the hafnia powder described here is an example. In order to more uniformly disperse the hafnia powder at the interfaces between the alumina crystal particles and the tungsten carbide crystal particles, it is preferable that the hafnia powder be a finer powder. The average particle size of the powder can be measured using a laser diffraction particle size distribution analyzer.

[0052] Next, the prepared raw materials are weighed and mixed in a predetermined ratio (step S12). The mixing ratio of the raw materials here can be determined based on the desired ratio (e.g., volume %) of each component in the resulting ceramic composition 10. For example, when the raw material powders are mixed and then fired to produce the ceramic composition 10, the raw material powders can be mixed so that the mixing ratio of each raw material powder is the desired volume %. The volume % of each raw material powder can be determined based on the mass of each raw material powder used in the mixture and the specific gravity of each raw material.

[0053] Since the raw materials hardly react with each other during the manufacturing process, by adjusting the volume percentage of each raw material used for mixing, it is possible to set the volume percentage of each component in the ceramic composition 10 to a desired value. The proportion (volume percentage) of each component in the manufactured ceramic composition 10 can be determined by the method described above.

[0054] Then, pre-mixing and pulverization is carried out (step S13). At this time, it is preferable to carry out a dispersion and mixing process in which only the hafnia powder is pulverized first. Specifically, the hafnia powder is pre-pulverized for about 40 hours using a solvent and a ball mill. Alternatively, the hafnia powder particles may be pulverized using a technique such as bead mill pulverization.

[0055] In the pre-mixing and grinding step, the alumina powder and the tungsten carbide powder are mixed together with a solvent (e.g., ethanol) using a ball mill, while the particles of each powder are ground. The processing time here may be shorter than 20 hours or longer than 20 hours.

[0056] Next, a slurry is obtained by mixing and pulverizing (step S14). Specifically, the pre-pulverized hafnia powder and a solvent (e.g., ethanol) are added to the mixture of alumina powder and tungsten carbide powder in the ball mill, and further mixing and pulverization are carried out.

[0057] This results in a slurry in which alumina, tungsten carbide, and hafnia particles are dispersed. In this embodiment, the time for adding hafnia to the mixture of alumina and tungsten carbide and further mixing and grinding can be approximately 20 hours. However, this is not limiting, and in other embodiments, the time may be less than 20 hours or greater than 20 hours.

[0058] Next, the slurry is dried to produce a mixed powder (step S15). For example, a method for obtaining the mixed powder from the slurry includes drying the slurry in a hot water bath to remove the solvent from the slurry, and then passing the obtained powder through a sieve.

[0059] Finally, the mixed powder is sintered by hot pressing to obtain a ceramic composition from the mixed powder (step S16). In this embodiment, the mixed powder is filled into a carbon mold and heated while being uniaxially pressed. This results in a ceramic composition 10, which is a sintered body of the mixed powder.

[0060] The hot pressing conditions in this embodiment are, for example, as follows: the firing temperature is 1700°C or higher and 1900°C or lower (preferably 1800°C or higher and 1900°C or lower, more preferably 1880°C), the firing time is 1 hour or higher and 3 hours or lower (preferably 2 hours), the pressure is 25 MPa or higher and 35 MPa or lower (preferably 30 MPa), and the atmospheric gas is argon (Ar). The firing temperature during firing is preferably set near the liquid phase formation temperature of alumina and hafnia. This can promote the movement (diffusion) of specific elements.

[0061] By the above-described manufacturing method, a solid ceramic composition 10 is obtained. In the ceramic composition 10 manufactured by this manufacturing method, alumina (Al ２ O ３ A hafnium segregation layer (i.e., Hf layer 40) is formed at the grain boundary (i.e., interface) between the crystal grains of aluminum (i.e., alumina layer 20) and the crystal grains of tungsten carbide (WC) (i.e., WC layer 30) (see FIG. 3, etc.). This is thought to strengthen the adhesion at the interface and allow the ceramic composition 10 to exhibit high-temperature ductility.

[0062] That is, it is possible to obtain a ceramic composition 10 that maintains high ductility even in a high-temperature environment of about 1400° C. and has a bending strength exceeding 400 MPa. Furthermore, the ceramic composition 10 according to this embodiment can keep the pore ratio in the composition low (for example, 0.1% or less) even after stress is applied.

[0063] (Ceramic Part) The ceramic part according to this embodiment includes a ceramic composition 10. The ceramic part can be produced, for example, by deforming (e.g., cutting, grinding, polishing, etc.) a rectangular parallelepiped ceramic composition 10 as shown in Fig. 1 into a predetermined shape.

[0064] Such a ceramic part can maintain its performance even in a high-temperature environment of, for example, 1400°C or higher. Therefore, the ceramic part according to this embodiment is suitable for use as a ceramic part for devices used in high-temperature environments. Specific examples of such ceramic parts include gas turbine components, spray nozzles for artificial satellites, molds for lenses, sealing materials, aircraft engine components, and cutting tools.

[0065] Summary of the embodiment The ceramic composition 10 according to the present embodiment has improved heat resistance compared to conventional heat-resistant alloy members used in high-temperature environments. Furthermore, the ceramic composition 10 according to the present embodiment has a reduced risk of brittle fracture compared to conventional ceramic parts used in high-temperature environments, improving reliability. These characteristics make the ceramic composition 10 according to the present embodiment applicable to components of devices and systems used in high-temperature environments, such as those in aerospace and power generation.

[0066] Furthermore, the ceramic composition 10 according to the present embodiment can maintain its strength during deformation processing, making it possible to perform superplastic deformation processing and joining, and improving the moldability and sealing properties of complex shapes. These characteristics enable its use as a curved lens mold or sealing material.

[0067] As described above, the ceramic composition 10 according to this embodiment is excellent in strength and ductility in high-temperature environments, and is expected to exhibit a wide range of effects, such as improved life and workability.

[0068] Examples The present invention will be described below with reference to examples, but the present invention is not limited to the examples below.

[0069] In this example, the ceramic composition 10 was manufactured based on the above-described manufacturing method, and the high-temperature ductility of the ceramic composition was evaluated. As a comparative example, a ceramic composition not including the Hf layer 40 was manufactured, and the high-temperature ductility of the ceramic composition was similarly evaluated.

[0070] (Raw Materials for Ceramic Composition) The raw materials for the ceramic composition according to the examples and comparative examples and their blending ratios (volume %) were as follows.

[0071] <Example> 1. Alumina (Al) with an average particle size of 0.5 μm ２ O ３ ) powder: 55% 2. Tungsten carbide (WC) powder with an average particle size of 0.7 μm: 45% 3. Hafnia (HfO ２ ) Powder: 1% (blending ratio (volume %) when the total of the main components 1 and 2 above is taken as 100%)

[0072] <Comparative Example> 1. Alumina (Al) with an average particle size of 0.5 μm ２ O ３ 1. ) powder: 55% 2. Tungsten carbide (WC) powder with an average particle size of 0.7 μm: 45%

[0073] (Hot Press Conditions) In both the Examples and Comparative Examples, the hot press conditions during production were as follows: Firing temperature: 1880° C. Firing time: 2 hours Pressure: 30 MPa Atmospheric gas: argon (Ar)

[0074] (Evaluation of High-Temperature Ductility) The ceramic compositions according to the Examples and Comparative Examples were subjected to a bending strength test under the following method and conditions to evaluate high-temperature ductility.

[0075] <Testing method for bending strength> Bending strength was measured using a test piece having a total length of 35 mm, a width of 4 mm, and a thickness of 3 mm. The tester determined the three-point bending strength of each sample of the examples and comparative examples in accordance with Japanese Industrial Standard JIS R1601 under the following conditions: Temperature: 1400°C Atmospheric gas: Argon (Ar) Deflection rate: 0.5 mm / min Bending span distance: 30 mm Testing machine: MST808 type ultra-high temperature material testing machine Jig material: SiC

[0076] <Results> It was confirmed that the ceramic compositions according to the examples had a bending strength of more than 400 MPa at a temperature of 1400° C. In contrast, it was confirmed that the ceramic compositions according to the comparative examples broke when a bending stress of about 300 MPa was applied at a temperature of 1400° C.

[0077] (HAADF-STEM Image of Ceramic Composition) A HAADF-STEM image of a cross section of the ceramic composition according to this example before the bending test is shown in FIG. 3. As shown in FIG. 3, alumina (Al ２ O ３ It was confirmed that an atomic layer formed by hafnium (Hf) exists at the grain boundary between crystal grains of tungsten carbide (WC) and crystal grains of tungsten carbide (WC). It was also confirmed that the atomic layer formed by hafnium includes an atomic arrangement of two or more layers, forming a metal crystalline phase of hafnium (Hf).

[0078] It was confirmed that in the ceramic composition according to the comparative example, no hafnium atomic layer was formed at the grain boundaries.

[0079] (TEM Image of Ceramic Composition) A TEM image of a cross section of the ceramic composition according to this example before the bending test is shown in Fig. 2. A TEM image of a cross section of the ceramic composition according to this example after the bending test is shown in Fig. 7. The TEM image shown in Fig. 7 was obtained by observing a sample prepared in the same manner as the TEM image shown in Fig. 2.

[0080] As shown in Figure 2, it was confirmed that there were almost no pores in the structure of the ceramic composition before the bending test. Furthermore, as shown in Figure 7, it was confirmed that there were almost no pores (cavities) in the structure of the ceramic composition after the bending test.

[0081] (Pore Ratio of Ceramic Composition) The measurement results of the pore ratio of one cross section of the ceramic composition according to this example before the bending test are shown in Fig. 6. Moreover, the measurement results of the pore ratio of one cross section of the ceramic composition according to this example after the bending test are shown in Fig. 8.

[0082] As shown in FIGS. 6 and 8, it was confirmed that the pore ratio of the ceramic composition according to this example did not change before and after the bending test.

[0083] (Summary of Examples) From the above results, it was confirmed that the ceramic composition according to the present examples has ductility (the property of not breaking due to brittleness) even in an ultra-high temperature environment of 1400°C or more, and can maintain a high bending strength of 400 MPa or more.

[0084] It was also confirmed that the ceramic composition of this example can suppress the generation of pores when stress is applied in a high-temperature environment, which is likely to occur in conventional ceramic compositions. This is thought to be due to the hafnium metal layer contained in the ceramic composition of this example improving the sliding performance at the interfaces between the alumina crystal grains and the tungsten carbide crystal grains.

[0085] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, configurations obtained by combining the configurations of different embodiments described in this specification are also included in the scope of the present invention.

[0086] 10: Ceramic composition 20: Alumina layer (alumina crystal grains) 30: WC layer (tungsten carbide crystal grains) 40: Hf layer (atomic layer formed by hafnium)

Claims

1. Alumina (Al ２ O ３ A ceramic composition containing alumina (Al) and tungsten carbide (WC), ２ O ３ A ceramic composition comprising: an atomic layer formed by hafnium (Hf) present at a grain boundary between a crystal grain of tungsten carbide (WC) and a crystal grain of tungsten carbide (WC), and the atomic layer includes an atomic arrangement of two or more layers of hafnium.

2. The ceramic composition according to claim 1, wherein the pore ratio in any one cross section of said ceramic composition is 0.1% or less.

3. The ceramic composition according to claim 1 or 2, wherein the atomic layers are formed at the grain boundaries by a metal crystalline phase of hafnium (Hf).

4. The ceramic composition according to claim 3, wherein the atomic layers are formed on the (210) plane of the hafnium (Hf) metal crystalline phase at the grain boundaries.

5. The ceramic composition according to claim 4, wherein the hafnium (Hf) metal crystalline phase is a hexagonal crystal, and the atomic layer is formed to a thickness equivalent to three layers of the (210) plane of the hexagonal crystal.

6. A ceramic part comprising the ceramic composition of claim 1 or 2.

7. The ceramic part according to claim 6, which is used in any one of a gas turbine component, a jet nozzle for an artificial satellite, a mold for a lens, a sealing material, an aircraft engine component, and a cutting tool.

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