Ceramic composition and ceramic component

Abstract

The ceramic composition contains aluminum oxide (Al2O3) and tungsten carbide (WC). In this ceramic composition, an atomic layer formed of hafnium (Hf) is present at the grain boundary between the grains of alumina (Al2O3) and the grains of tungsten carbide (WC). The atomic layer comprises an atomic arrangement of two or more layers of hafnium.

Description

TECHNICAL FIELD

[0001] The present application relates to a ceramic composition and a ceramic member containing the same. BACKGROUND

[0002] In order to improve the properties of a ceramic composition containing alumina (AI2O3) as a main component, a technique containing tungsten carbide (WC) in addition to alumina (AI2O3) has been disclosed.

[0003] For example, in Patent Literature 1, a ceramic composition containing alumina (AI2O3) and tungsten carbide (WC) is disclosed, which is characterized in that an atomic layer formed of at least one element selected from transition metals belonging to Groups 4 to 6 of the periodic table, yttrium (Y), scandium (Sc), and lanthanoid elements is present at the grain boundaries between alumina (AI2O3) grains and tungsten carbide (WC) grains.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent No. 6491363 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] As described above, in order to improve the properties of a ceramic composition containing alumina (AI2O3) and tungsten carbide (WC), various methods have been proposed.

[0009] In one aspect of the present application, the object is to further improve the properties of a ceramic composition containing alumina and tungsten carbide in a high-temperature environment.

[0010] METHOD FOR SOLVING THE PROBLEM [1]

[0012] The ceramic composition of one aspect of the present application is a ceramic composition containing alumina (AI2O3) and tungsten carbide (WC), in which an atomic layer formed of hafnium (Hf) is present at the grain boundaries between the grains of the above-mentioned alumina (AI2O3) and the above-mentioned tungsten carbide (WC), and the above-mentioned atomic layer contains two or more layers of atomic arrangement of hafnium. [2]

[0014] In the ceramic composition of one aspect of the present application described in [1], the ratio of pores in any one cross section of the above-mentioned ceramic composition can be 0.1% or less. [3]

[0016] In the ceramic composition of one aspect of the present invention described in [1] or [2], the atomic layer can be formed of the metal crystal phase of hafnium (Hf) at the grain boundary. [4]

[0018] In the ceramic composition of one aspect of the present invention described in [3], the atomic layer can be formed on the (210) plane of the metal crystal phase of hafnium (Hf) at the grain boundary. [5]

[0020] In the ceramic composition of one aspect of the present invention described in [4], the metal crystal phase of hafnium (Hf) is hexagonal, and the atomic layer can be formed with a thickness of three layers of the (210) plane of the hexagonal crystal. [6]

[0022] The ceramic member of another aspect of the present invention contains the ceramic composition described in any one of [1] to [5]. [7]

[0024] The ceramic member of one aspect of the present invention described in [6] can be used for any one of a member for a gas turbine, an ejection nozzle for an artificial satellite, a mold for a lens, a sealing material, a member for an engine of an aircraft, and a cutting tool.

[0025] Effects of the Invention

[0026] According to one aspect of the present invention, a ceramic composition having improved ductility and bending strength characteristics under a high temperature environment can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a perspective view showing the appearance of a ceramic composition of one embodiment.

[0028] Figure 2 is a graph showing a TEM image of a ceramic composition of one embodiment at A-A cross section.

[0029] Figure 3 is a graph showing a HAADF-STEM image of a ceramic composition of one embodiment near a grain boundary.

[0030] Figure 4 is a graph showing a HAADF-STEM image and a simulated image of a ceramic composition of one embodiment near a grain boundary.

[0031] Figure 5 is a graph showing a HAADF-STEM image of a ceramic composition of one embodiment near a grain boundary.

[0032] Figure 6is a diagram in which components are color-distinguished in a SEM image of a cross section of the ceramic composition of one embodiment.

[0033] Figure 7 is a diagram showing a TEM image of a cross section of the ceramic composition after stress application.

[0034] Figure 8 is a diagram in which components are color-distinguished in a SEM image of a cross section of the ceramic composition after stress application.

[0035] Figure 9 is a flowchart showing a flow of a manufacturing method of the ceramic composition of one embodiment. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the present application will be described with reference to the drawings. In this embodiment, a ceramic composition 10 as an example of a ceramic composition is described. The ceramic composition 10 is suitable as a material of a ceramic member contained in an apparatus used in a high-temperature environment of 1400 °C or higher. Specifically, the ceramic composition 10 is used as a material of a ceramic member such as a member for a gas turbine, an ejection nozzle for an artificial satellite, a mold for a lens, a sealing material, a member for an aircraft engine, and a cutting tool, for example.

[0037] (Configuration of Ceramic Composition)

[0038] Figure 1 is a perspective view showing the appearance of the ceramic composition 10. The ceramic composition 10 contains alumina (AI2O3) and tungsten carbide (WC). In the ceramic composition 10, an atomic layer formed of hafnium (Hf) is present at the grain boundary between the crystal grains of the alumina (AI2O3) and the crystal grains of the tungsten carbide (WC). Further, the atomic layer contains two or more atomic arrangements.

[0039] The atomic layer formed of hafnium (Hf) is obtained by adding a hafnium compound such as hafnium oxide (Hf02) as a raw material at the time of manufacturing the ceramic composition 10, for example.

[0040] Figure 2 is shown in Figure 1 The ceramic composition 10 shown in is an example of a TEM image of a cross section of A-A. Figure 2 The TEM image shown in can be obtained by observing a sample prepared by the following steps with a transmission electron microscope (TEM).

[0041] First, the ceramic composition was processed into a φ3 mm disc plate of a prescribed position and direction using a diamond cutter and an ultrasonic disc cutter, and the thickness was adjusted to less than 100 μm using 30 μm diamond polishing paper, and thinning was performed. Next, a pit was processed in the center of the disc using a pit gauge, and processing was performed using a precision ion polishing system (PIPS). Figure 2 The TEM image shown is an image obtained by observing a sample obtained by performing damage layer removal processing at 1.0 kV for 2 minutes after performing sample penetration under ion milling conditions of Ar ions, an acceleration voltage of 4.0 kV, and a beam irradiation angle of ±4°.

[0042] Figure 3 An example of a HAADF-STEM image of the vicinity of a grain boundary of the ceramic composition 10 is shown. Figure 1 The HAADF-STEM (High-Angle Annular Dark Field Scanning Transmission Electron Microscopy) is a high-angle scattering annular dark field scanning transmission electron microscope method. In the HAADF-STEM image, heavy elements are shown brightly. As compared with the structural model, it is known that the white points of high brightness correspond to atomic columns of tungsten (W).

[0043] Figure 3 Image A of FIG. 10 is a HAADF-STEM image of the vicinity of a grain boundary of an alumina grain and a tungsten carbide grain in Image B. In Image A of FIG. 10, Figure 3 In Image A of FIG. 10, the atomic layer of the alumina grain is set as an alumina layer 20, the atomic layer of the tungsten carbide grain is set as a WC layer 30, and the atomic layer derived from the hafnium compound is set as a Hf layer 40.

[0044] As shown in FIG. 11, Figure 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 has an atomic layer formed of hafnium (Hf) at the grain boundary of the alumina (AI2O3) grain and the tungsten carbide (WC) grain. Moreover, the Hf layer 40 includes two or more atomic arrangements. For example, in Image A shown in FIG. 12, Figure 3 In Image A shown in FIG. 12, the Hf layer 40 is formed in two layers of Hf atoms.

[0045] Since the Hf layer 40 includes two or more atomic arrangements, the Hf layer 40 is able to form a metallic crystal phase of hafnium (Hf). Hafnium (Hf) is an element classified as a transition metal, and has a metallic crystal phase of a hexagonal closest packing structure at normal temperature and normal pressure. That is, the metallic crystal phase of hafnium (Hf) is hexagonal.

[0046] In addition, asFigure 4 As shown, the Hf layer 40 is preferably formed in the (210) plane of the metal crystal phase of hafnium (Hf).

[0047] Further, as shown, the Hf layer 40 is more preferably formed in the (210) plane of the hexagonal crystal phase to a thickness of three layers. Figure 5

[0048] As described above, by providing the Hf layer 40 including two or more atomic arrangements at the grain boundary between the alumina grains and the tungsten carbide grains, the adhesion strength between the alumina grains and the tungsten carbide grains can be improved.

[0049] Further, by forming the Hf layer 40 in the metal crystal phase of hafnium, a ceramic composition having excellent ductility at high temperatures (e.g., 1400°C or higher) can be obtained.

[0050] (Regarding Pores in the Ceramic Composition)

[0051] Next, the pores contained in the ceramic composition 10 will be described. Here, the pores refer to voids contained in the solid ceramic composition 10. In addition, the pores contained in the ceramic member obtained after the ceramic composition 10 is shaped and processed are also referred to as cavities.

[0052] For example, if the ceramic composition is placed in a high-temperature environment of 1400°C or higher and a stress is applied, the ratio of the pores or cavities contained in the composition tends to increase. The ratio tends to increase over time.

[0053] It is known that the fracture of the ceramic member at high temperatures is caused by the generation, growth, and connection of the pores or cavities in the ceramic composition. In addition, when the ceramic composition is processed into a ceramic member of a prescribed shape, the ratio of the pores or cavities tends to increase due to the application of stress such as bending processing to the ceramic composition.

[0054] Therefore, by suppressing the ratio of the pores contained in the ceramic composition as low as possible, a ceramic composition having higher performance (specifically, a ceramic composition having excellent high-temperature ductility) can be expected.

[0055] In the ceramic composition 10 of the present embodiment, the ratio of the pores in any one cross section is preferably 0.1% or lower. Thereby, a ceramic composition having excellent high-temperature ductility can be obtained. Note that the ceramic composition 10 having such properties can be manufactured by the method described later.

[0056] ​The determination of the ratio of pores can be performed by cutting a plurality of samples from the subject ceramic composition or ceramic member and calculating the pores of each sample based on the pore measurement method described later. Also, regarding the sample having the largest ratio of pores among the plurality of samples, in the case where the ratio of pores is 0.1% or less, it can be determined that the ratio of pores is 0.1% or less.

[0057] In the ceramic composition 10 of the present embodiment, the lower limit value of the ratio of pores is not particularly limited. In a general ceramic composition containing alumina and tungsten carbide, it is difficult to make the pores zero (absence of pores). Therefore, the ratio of pores in the ceramic composition 10 of the present embodiment is greater than 0%.

[0058] For the ceramic composition 10 of the present embodiment, the increase in the ratio of pores after the application of stress (for example, bending processing or the like) can also be suppressed (refer to Figure 7 and Figure 8 ). Figure 7 and Figure 8 The results of observing one cross section of the ceramic composition 10 after the application of stress (after the bending test) in the present example are shown in

[0059] (Measurement method of the ratio of pores)

[0060] Here, one example of a measurement method of the ratio of pores contained in the ceramic composition 10 will be described.

[0061] First, the solid ceramic composition 10 is miniaturized, and then an arbitrary one of the cut surfaces is polished to the order of several micrometers. Next, by using a cross-sectional vertical ion milling method using a shadow mask, 50 μm or more is processed in the depth direction from the polished surface, and an ion-milled cross section from which polishing damage is removed is formed, which is used as an observation surface. As the processing device, for example, an Ar ion milling device accelerated at 5 to 6 kV is used. As the observation surface, an area of 300 μm x 300 μm or more is ensured.

[0062] Next, an SEM image of the observation surface is taken. For example, using an electron microscope capable of being variable at 0.1 kV to 20 kV, the observation surface is imaged, and image data is obtained. For the obtained image data, the resolution and magnification are adjusted so as to be 10 times or more of the smallest particle in the ceramic structure (number of pixels), and saved in a data format (for example, tiff or bmp) without irreversible processing.

[0063] Then, image analysis is performed on the obtained image data. Specifically, using the region division function of the image analysis software (for example, Avizo software for material research (Thermo Fisher Scientific Inc.) or the like), the obtained image data is four-valued. Specifically, four-valued according to the following four regions.

[0064] A: Region formed of aluminum oxide (AI2O3)

[0065] B: Region formed of tungsten carbide (WC)

[0066] C: Region formed of hafnium (Hf)

[0067] D: Region of pores

[0068] In the above four-valued, the grain boundary layer is not considered regardless of the same system or the different system. In the case of the same system, the regions are extracted as connected together. Note that the SEM image has overlapping information in the depth direction, and the regions are divided by observing the information of the top surface. The numerical values are calculated using the pixel interval and the two-dimensional calculation function of the software, and the area and the proportion of each region are calculated.

[0069] An example of the image after the four-valued processing of the SEM image of any one cross section of the ceramic composition 10 using the above method is shown in Figure 6 In addition, Figure 6 In

[0070] As shown in Figure 6 , in the ceramic composition 10 of the present embodiment, it is confirmed that the ratio of the pores in any one cross section is 0.1% or less.

[0071] In addition, Figure 8 An example of the image after the four-valued processing of the SEM image of any one cross section of the ceramic composition 10 after the application of stress is shown in Figure 8 In addition,

[0072] As shown in Figure 8 , in the ceramic composition 10 after the application of stress, it is also confirmed that the ratio of the pores in any one cross section is 0.1% or less. It is thus confirmed that the ceramic composition 10 of the present embodiment can suppress the increase in the ratio of the pores even after the application of stress (for example, bending processing, etc.).

[0073] Note that the above method of measuring the ratio of the pores can also be used for the calculation of the proportion (volume %) of each component contained in the ceramic composition 10.

[0074] Specifically, in the image data four-valued in four regions of A to D, the area of each region is calculated. Then, based on the calculated values, A / (A+B+C+D), B / (A+B+C+D), and C / (A+B+C+D) are calculated.

[0075] Thus, the proportions (volume %) of the respective components in the ceramic composition 10 are obtained. Figure 6 and Figure 8 The proportions of the aluminum oxide (AI2O3) component, the tungsten carbide (WC) component, and the hafnium (Hf) component contained in the ceramic composition 10 are shown in Table 1.

[0076] (Method for manufacturing ceramic composition)

[0077] Next, a method for manufacturing the ceramic composition 10 will be described. Figure 8 An example of the method for manufacturing the ceramic composition 10 is shown in Table 2.

[0078] First, an aluminum oxide, a tungsten carbide, and a hafnium compound, which are raw materials of the ceramic composition, are prepared (step Sll). Each of the raw materials is prepared in a powder state. Specifically, an aluminum oxide (AI2O3) powder having an average particle diameter of about 0.5 μm, a tungsten carbide (WC) powder having an average particle diameter of about 0.7 μm, and a hafnium dioxide (HfO2) powder having an average particle diameter of about 0.4 μm are used.

[0079] The average particle diameter of the hafnium dioxide powder described herein is an example. In order to more uniformly disperse the hafnium dioxide powder at the interface between the aluminum oxide crystal grains and the tungsten carbide crystal grains, the hafnium dioxide powder is preferably a finer powder. Note that the average particle diameter of the powder can be measured using a laser diffraction particle size distribution measuring device.

[0080] Next, each of the prepared raw materials is weighed and mixed at a predetermined proportion (step S12). The mixing proportion of each of the raw materials here can be determined based on the proportions (for example, volume %) of each of the components desired in the ceramic composition 10 to be obtained. For example, in a case where the ceramic composition 10 is manufactured by performing sintering after mixing each of the raw material powders, each of the raw material powders can be mixed in a manner such that the mixing proportion of each of the raw material powders is the desired volume %. The volume % of each of the raw material powders can be calculated based on the mass of each of the raw material powders used in the mixing and the specific gravity of each of the raw materials.

[0081] Each of the raw materials hardly reacts with each other in the manufacturing process, and thus, by adjusting the volume % of each of the raw materials used in the mixing, the volume % of each of the components in the ceramic composition 10 can be made to be a desired value. Note that the proportions (volume %) of each of the components in the manufactured ceramic composition 10 can be calculated by the above-described method.

[0082] Then, pre-mixing pulverization is performed (step S13). At this time, it is preferable to perform a dispersion mixing process in which only the hafnium dioxide powder is first pulverized. Specifically, the hafnium dioxide powder is pre-pulverized for about 40 hours using a solvent and a ball mill. Alternatively, as another method, the particles of the hafnium dioxide powder can be pulverized using a bead mill or the like.

[0083] Further, in the pre-mixing pulverization process, the alumina powder and the tungsten carbide powder are mixed with a solvent (for example, ethanol or the like) using a ball mill, while the particles of each powder are pulverized. The processing time here can be less than 20 hours or more than 20 hours.

[0084] Next, a slurry is obtained by mixing and pulverizing (step S14). Specifically, in the mixture in the ball mill to which the alumina powder and the tungsten carbide powder are added, a pre-pulverized hafnium dioxide powder and a solvent (for example, ethanol or the like) are added, and mixing and pulverization are further performed.

[0085] Thus, a slurry in which particles of each of the alumina, the tungsten carbide, and the hafnium dioxide are dispersed is obtained. In the present embodiment, the time for further performing mixing and pulverization after adding the hafnium dioxide to the mixture of the alumina and the tungsten carbide can be set to about 20 hours. However, this is not limiting, and in other embodiments, the time can be less than 20 hours or more than 20 hours.

[0086] Next, the slurry is dried to produce a mixed powder (step S15). As a method for obtaining a mixed powder from a slurry, for example, a method in which the slurry is dried while being heated in an airtight state, whereby the solvent is removed from the slurry to obtain a powder, and the obtained powder is sieved can be cited.

[0087] Finally, the mixed powder is sintered by hot pressing, and a ceramic composition is obtained from the mixed powder (step S16). In the present embodiment, in the hot pressing, the mixed powder is filled in a carbon mold, and heating is performed while the mixed powder is uniaxially pressed. Thus, a ceramic composition 10 that is a sintered body obtained by sintering the mixed powder is obtained.

[0088] The conditions for the hot pressing in the present embodiment are, for example, as described below. The sintering temperature is 1700°C or higher and 1900°C or lower (preferably, 1800°C or higher and 1900°C or lower, further preferably 1880°C), the sintering time is 1 hour or more and 3 hours or less (preferably, 2 hours), the pressure is 25 MPa or more and 35 MPa or less (preferably, 30 MPa), and the atmosphere gas is argon (Ar). The sintering temperature at the time of sintering is preferably set to be around the liquidus temperature of the alumina and the hafnium dioxide. Thus, the movement (diffusion) of specific elements can be promoted.

[0089] By the above manufacturing method, a ceramic composition 10 in a solid state can be obtained. In the ceramic composition 10 manufactured by the manufacturing method, at the grain boundary (that is, the interface) of the crystal grains of the alumina (Al2O3) (that is, the alumina layer 20) and the crystal grains of the tungsten carbide (WC) (that is, the WC layer 30), a segregation layer of hafnium (that is, the Hf layer 40) is formed (see FIG. 1). Figure 9 It is considered that by this, the adhesion of the interface can be strengthened, and the ceramic composition 10 can exhibit a high-temperature ductility function.

[0090] That is, it is possible to obtain the ceramic composition 10 which 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 of the present embodiment is able to suppress the ratio of pores within the composition to be low (for example, 0.1% or less) even after application of stress.

[0091] (Ceramic member)

[0092] The ceramic member of the present embodiment contains the ceramic composition 10. The ceramic member can be manufactured, for example, by deforming the rectangular parallelepiped-shaped ceramic composition 10 shown in FIG. 1 into a prescribed shape (for example, cutting, grinding, polishing, or the like). Figure 3

[0093] Such a ceramic member is able to maintain performance even in a high-temperature environment of 1400°C or higher, for example. Therefore, the ceramic member of the present embodiment is suitable as a ceramic member of a device used in a high-temperature environment. As such a ceramic member, specifically, for example, a gas turbine member, a satellite ejection nozzle, a lens mold, a sealing material, an aircraft engine member, a cutting tool, or the like can be cited.

[0094] (Summary of the present embodiment)

[0095] The ceramic composition 10 of the present embodiment has improved heat resistance compared to conventional heat-resistant alloy members used in a high-temperature environment. In addition, the ceramic composition 10 of the present embodiment has reduced likelihood of brittle fracture compared to conventional ceramic members used in a high-temperature environment, and thus has improved reliability. According to such characteristics, the ceramic composition 10 of the present embodiment is able to be applied to members of devices and systems and the like used in a high-temperature environment such as aerospace, power generation, and the like.

[0096] In addition, the ceramic composition 10 of the present embodiment is able to maintain strength at the time of deformation processing, and thus is able to realize superplastic deformation processing, joining, improved moldability of a complex shape, and improved sealing properties. According to such characteristics, it is also possible to realize use as a curved lens mold, a sealing material.

[0097] As described above, the ceramic composition 10 of the present embodiment has excellent strength and ductility in a high-temperature environment, and is able to be expected to exert effects of improving life, improving processability, and the like in various aspects.

[0098] [Example]

[0099] Hereinafter, an example of the present application will be described. Note that the present application is not limited to the following example.

[0100] ​In the present embodiment, the ceramic composition 10 was manufactured based on the above manufacturing method, and evaluation of high-temperature ductility was performed. In addition, as a comparative example, a ceramic composition not containing the Hf layer 40 was manufactured, and evaluation of high-temperature ductility was similarly performed.

[0101] (Raw materials of the ceramic composition)

[0102] The raw materials of the ceramic compositions of the examples and the comparative example and their blending ratios (vol%) are described below.

[0103] <Example>

[0104] 1. Alumina (Al2O3) powder having an average particle diameter of 0.5 μm: 55%

[0105] 2. Tungsten carbide (WC) powder having an average particle diameter of 0.7 μm: 45%

[0106] 3. Hafnium dioxide (HfO2) powder having an average particle diameter of about 0.4 μm: 1% (blending ratio (vol%) when the total of the components of the above 1. and 2. as the main components is taken as 100%)

[0107] <Comparative Example>

[0108] 1. Alumina (Al2O3) powder having an average particle diameter of 0.5 μm: 55%

[0109] 2. Tungsten carbide (WC) powder having an average particle diameter of 0.7 μm: 45%

[0110] (Conditions of hot pressing)

[0111] The conditions of hot pressing at the time of manufacturing of the examples and the comparative example were as described below.

[0112] Firing temperature: 1880°C

[0113] Firing time: 2 hours

[0114] Pressure: 30 MPa

[0115] Atmosphere gas: argon (Ar)

[0116] (Evaluation of high-temperature ductility)

[0117] For the ceramic compositions of the examples and the comparative example, a bending strength test was performed using the following method and conditions, and evaluation of high-temperature ductility was performed.

[0118] <Method of bending strength test>

[0119] The flexural strength was measured using test pieces having a total length of 35 mm, a width of 4 mm, and a thickness of 3 mm. The tester obtained the three-point flexural strength of each sample of the examples and comparative examples according to Japanese Industrial Standard JIS R 1601 under the following conditions.

[0120] • Temperature: 1400°C

[0121] • Atmosphere gas: Argon (Ar)

[0122] • Flexure speed: 0.5 mm / minute

[0123] • Bending span: 30 mm

[0124] • Tester: Ultra-high temperature material tester of MST808 type

[0125] • Gripper material: SiC

[0126] <Results>

[0127] It was confirmed that the ceramic composition of the example had a flexural strength exceeding 400 MPa under temperature conditions of 1400°C. In contrast, it was confirmed that the ceramic composition of the comparative example fractured when a flexural stress of about 300 MPa was applied under temperature conditions of 1400°C.

[0128] (HAADF-STEM image of the ceramic composition)

[0129] An HAADF-STEM image of one cross section of the ceramic composition of the present example before the flexural test is shown in Figure 1 As shown in Figure 3 , it was confirmed that an atomic layer formed of hafnium (Hf) exists at the grain boundary between the grains of aluminum oxide (AI2O3) and tungsten carbide (WC). Furthermore, it was confirmed that the atomic layer formed of hafnium contains two or more atomic arrangements, forming a metal crystal phase of hafnium (Hf).

[0130] Note that it was confirmed that the ceramic composition of the comparative example did not form an atomic layer of hafnium at the grain boundary.

[0131] (TEM image of the ceramic composition)

[0132] A TEM image of one cross section of the ceramic composition of the present example before the flexural test is shown in Figure 3 In addition, a TEM image of one cross section of the ceramic composition of the present example after the flexural test is shown in Figure 2 Figure 7 The TEM image shown in Figure 7 was obtained by preparing a sample in the same manner as the TEM image shown in

[0133] As shown in Figure 2 ​As shown in FIG. 6, it was confirmed that there were almost no pores in the structure of the ceramic composition before the bending test. In addition, as shown in FIG. 7, it was confirmed that there were also almost no pores (cavities) in the structure of the ceramic composition after the bending test. Figure 2

[0134] (Porosity ratio of ceramic composition)

[0135] The measurement results of the porosity ratio of one cross section of the ceramic composition of the present embodiment before the bending test are shown in FIG. 6. In addition, the measurement results of the porosity ratio of one cross section of the ceramic composition of the present embodiment after the bending test are shown in FIG. 7. Figure 7 Figure 6

[0136] As shown in FIG. 6 and FIG. 7, it was confirmed that the porosity ratio of the ceramic composition of the present embodiment did not change before and after the bending test. Figure 8 Figure 6 Figure 8

[0137] (Summary of the present embodiment)

[0138] According to the above results, it was confirmed that the ceramic composition of the present embodiment also has ductility (a property of not breaking in a brittle manner) in an ultrahigh temperature environment of 1400°C or higher, and is able to maintain a high bending strength of 400 MPa or more.

[0139] In addition, it was confirmed that the ceramic composition of the present embodiment is able to suppress the generation of pores when stress is applied in a high temperature environment, which easily occurs with conventional ceramic compositions. It is thought that this is because the hafnium metal layer contained in the ceramic composition of the present embodiment improves the slip properties of the interface between the alumina grains and the tungsten carbide grains.

[0140] It should be understood that the embodiments disclosed herein are illustrative only and not restrictive in all aspects. The scope of the present application is represented by the claims, not by the above description, and is intended to include all modifications within the meaning and range equivalent to the claims. In addition, a configuration obtained by combining the configurations of different embodiments described in the present specification is also included in the scope of the present application.

[0141] Explanation of symbols

[0142] 10: Ceramic composition

[0143] 20: Alumina layer (grains of alumina)

[0144] 30: WC layer (grains of tungsten carbide)

[0145] 40: Hf layer (atomic layer formed of hafnium)​​​​​

Claims

1. A ceramic composition which is a ceramic composition containing alumina (AI2O3) and tungsten carbide (WC), wherein, at a grain boundary of a crystal grain of the alumina (AI2O3) and a crystal grain of the tungsten carbide (WC), an atomic layer formed of hafnium (Hf) is present, the atomic layer contains two or more atomic arrangements of hafnium.

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

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

4. The ceramic composition of claim 3, wherein, the atomic layer is formed of a (210) plane of the metallic crystal phase of the hafnium (Hf) at the grain boundary.

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

6. A ceramic member containing the ceramic composition according to claim 1 or 2.

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

Images