Ceramic composition and ceramic component

Abstract

To further improve the characteristics in a high environment, of a ceramic composition containing alumina and tungsten carbide.SOLUTION: A ceramic composition contains alumina (Al2O3) and tungsten carbide (WC). In the ceramic composition, an atomic layer made from hafnium (Hf) exists in a crystal particle boundary between the crystal particles of the alumina (Al2O3) and the crystal particles of the tungsten carbide (WC). The atomic layer includes an atomic arrangement of hafnium of two or more layers.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A technique has been disclosed in which tungsten carbide (WC) is added to alumina (Al2O3) in order to improve the properties of a ceramic composition mainly composed of alumina (Al2O3).

[0003] For example, Patent Document 1 discloses a ceramic composition containing alumina (Al2O3) and tungsten carbide (WC), characterized in that an 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 present at the grain boundaries between alumina (Al2O3) crystal grains and tungsten carbide (WC) crystal grains. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6491363 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, various methods have been proposed to improve the properties of ceramic compositions containing alumina (Al2O3) and 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. [Means for solving the problem]

[0007] [1] A ceramic composition according to one aspect of the present invention is a ceramic composition containing alumina (Al2O3) and tungsten carbide (WC), wherein an atomic layer formed by hafnium (Hf) is present at the grain boundaries between crystal grains of the alumina (Al2O3) and crystal grains of the tungsten carbide (WC), and the atomic layer includes an atomic arrangement 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 boundaries.

[0010] [4] In the ceramic composition according to one aspect of the present invention described in [3], the atomic layer may be formed on the (210) plane of the hafnium (Hf) metal crystal 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 the (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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

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

[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, seal 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 contains alumina (Al2O3) and tungsten carbide (WC). In this ceramic composition 10, an atomic layer formed by hafnium (Hf) exists at the grain boundaries between alumina (Al2O3) crystal grains and tungsten carbide (WC) crystal grains. This atomic layer includes an atomic arrangement of two or more layers.

[0018] The atomic layer formed by hafnium (Hf) can be obtained by adding a hafnium compound such as hafnia (HfO 2 ) as a raw material when the ceramic composition 10 is manufactured.

[0019] Fig. 2 shows an example of a TEM image of the AA cross section of the ceramic composition 10 shown in Fig. 1. The TEM image shown in Fig. 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 3mm diameter disk in the desired position and direction using a diamond cutter and an ultrasonic disk cutter. Then, the thickness was adjusted to less than 100µm using 30µm diamond polishing paper and thinned. Next, a dimple was created in the center of the disk using a dimpler, and the disk was then polished using a precision ion polishing system (PIPS). The TEM image shown in Figure 2 was obtained by ion polishing using Ar ions, an acceleration voltage of 4.0kV, and a beam irradiation angle of ±4°. After penetration of the sample, the damaged layer was removed at 1.0kV for 2 minutes.

[0021] FIG. 3 shows an example of a HAADF-STEM image near 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 in 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 in 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 Figure 3, in the ceramic composition 10, an Hf layer 40 exists between an alumina layer 20 and a WC layer 30. In other words, in the ceramic composition 10, an atomic layer formed by hafnium (Hf) exists at the grain boundaries between alumina (Al2O3) crystal grains and tungsten carbide (WC) crystal grains. The Hf layer 40 includes an atomic arrangement of two or more layers. For example, in image A shown in Figure 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, so that the Hf layer 40 can form a metal crystalline phase of hafnium (Hf). 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 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 is 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] (Pores in ceramic compositions) Next, we will explain the pores contained in the ceramic composition 10. 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 the ceramic composition to have excellent high-temperature ductility. 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 general 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). FIGS. 7 and 8 show the results of observing a cross section of the ceramic composition 10 in this example after stress application (after a bending test).

[0037] (Method for measuring pore ratio) Here, an example of a method for measuring the ratio of pores 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 vertical ion milling method using a shielding plate is used to process the polished surface in a depth direction of 50 μm or more, forming an ion milled cross section from which polishing damage has been removed, and this is used 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 particle in the ceramic structure, and the 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 converted into four values ​​using the region division function of image analysis software (e.g., Avizo software for materials research (Thermo Fisher Scientific Inc.)). Specifically, the image data is converted into four values ​​for each of the following four regions: A: Area formed by alumina (Al2O3) B: Area formed by tungsten carbide (WC) C: Area formed by hafnium (Hf) D: Pore area

[0041] When converting to four values ​​as described above, grain boundary layers are 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 surface information. Numerical conversion uses pixel spacing and the software's 2D calculation function to calculate the area and occupancy rate of each region.

[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] Fig. 8 shows an example of an image obtained by quaternizing an SEM image of an arbitrary cross section of the ceramic composition 10 after stress application. Fig. 8 also shows the results of calculating the occupancy ratio of each of the above regions A to D below the image.

[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-mentioned 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, based on the calculated values, A / (A+B+C+D), B / (A+B+C+D), and C / (A+B+C+D) are calculated.

[0048] This provides the proportion (vol %) of each component in the ceramic composition 10. Figures 6 and 8 show the proportions of the alumina (Al2O3) component, the tungsten carbide (WC) component, and the hafnium (Hf) component contained in the ceramic composition 10.

[0049] (Method of manufacturing ceramic composition) Next, a description will be given of a method for producing the ceramic composition 10. Fig. 9 shows an example of a method for producing the ceramic composition 10.

[0050] First, the raw materials for the ceramic composition, alumina, tungsten carbide, and a hafnium compound, are prepared (Step S11). Each raw material is prepared in powder form. Specifically, alumina (Al2O3) powder with an average particle size of approximately 0.5 μm, tungsten carbide (WC) powder with an average particle size of approximately 0.7 μm, and hafnia (HfO2) powder with an average particle size of approximately 0.4 μm are 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 less than 20 hours or may be 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 a ball mill, and further mixing and pulverization are carried out.

[0057] This results in a slurry containing dispersed alumina, tungsten carbide, and hafnia particles. In this embodiment, the time for adding hafnia to the alumina and tungsten carbide mixture 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 to obtain a powder, 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 in the hot pressing, and the mixed powder is 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 the specific elements.

[0061] The above manufacturing method produces a solid ceramic composition 10. In the ceramic composition 10 manufactured by this manufacturing method, a hafnium segregation layer (i.e., Hf layer 40) is formed at the grain boundary (i.e., interface) between alumina (Al2O3) crystal grains (i.e., alumina layer 20) and tungsten carbide (WC) crystal grains (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 parts) The ceramic part according to this embodiment includes a ceramic composition 10. The ceramic part can be manufactured, 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 ceramic parts can maintain their performance even in high-temperature environments, for example, at 1400°C or higher. Therefore, the ceramic parts according to this embodiment are suitable for use as ceramic parts for devices used in high-temperature environments. Specific examples of such ceramic parts include gas turbine parts, spray nozzles for artificial satellites, molds for lenses, sealing materials, aircraft engine parts, and cutting tools.

[0065] (Summary of the embodiment) The ceramic composition 10 according to this embodiment has improved heat resistance compared to conventional heat-resistant alloy members used in high-temperature environments. Furthermore, the ceramic composition 10 according to this 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 this 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 formability 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] [Example] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[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 compositions) The raw materials and their blending ratios (vol %) of the ceramic compositions according to the examples and comparative examples were as follows:

[0071] <Example> 1. Alumina (Al2O3) powder with an average particle size of 0.5 μm: 55% 2. Tungsten carbide (WC) powder with an average particle size of 0.7 μm: 45% 3. Hafnia (HfO2) powder with an average particle size of approximately 0.4 μm: 1% (volume %) when the total of the main components 1 and 2 above is taken as 100%)

[0072] <Comparative Example> 1. Alumina (Al2O3) powder with an average particle size of 0.5 μm: 55% 2. Tungsten carbide (WC) powder with an average particle size of 0.7 μm: 45%

[0073] (Hot pressing conditions) In both the examples and comparative examples, the hot pressing conditions during production were as follows. Firing temperature: 1880℃ Baking 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 the high-temperature ductility.

[0075] <Bending strength test method> The 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℃ Atmospheric gas: Argon (Ar) Deflection speed: 0.5mm / min Bending span distance: 30mm Testing machine: MST808 type ultra-high temperature material testing machine Jig material: SiC

[0076] <Result> 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) An HAADF-STEM image of a cross section of the ceramic composition according to this example before bending test is shown in Figure 3. As shown in Figure 3, it was confirmed that an atomic layer formed by hafnium (Hf) was present at the grain boundary between alumina (Al2O3) crystal grains and tungsten carbide (WC) crystal grains. It was also confirmed that the atomic layer formed by hafnium contained two or more layers of atomic arrangements, 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 in one cross section of the ceramic composition according to this example before the bending test are shown in Fig. 6. The measurement results of the pore ratio in 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 of this example 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. [Explanation of symbols]

[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 ) and tungsten carbide (WC), The alumina (Al ２ O ３ an atomic layer formed by hafnium (Hf) is present at the grain boundary between a crystal grain of the tungsten carbide (WC) and a crystal grain of the tungsten carbide (WC), The atomic layer includes two or more layers of hafnium atomic arrangements. Ceramic composition.

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

3. The atomic layer is formed of a metal crystalline phase of the hafnium (Hf) at the grain boundary. The ceramic composition according to claim 1 or 2.

4. The atomic layer is formed on the (210) plane of the hafnium (Hf) metal crystalline phase at the grain boundary. The ceramic composition of claim 3.

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

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

7. It is used in any of gas turbine components, satellite jet nozzles, lens molds, seal materials, aircraft engine components, and cutting tools. The ceramic part according to claim 6.

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