Ceramic sintered body

Abstract

Disclosed is a ceramic sintered body which can give consideration to both toughness and wear resistance. This ceramic sintered body contains a first compound and a second compound. The first compound is silicon carbide, and the second compound is a diboride of a Group 4 element. The proportion of the second compound in the ceramic sintered body is 50% by mass to 70% by mass. When a 300 [mu] m * 300 [mu] m region of the polished surface of the ceramic sintered body is divided into 400 sections of 15 [mu] m * 15 [mu] m, and the area ratio of the first compound is determined for each of the sections, the coefficient of variation CV of the area ratio of the first compound is greater than 0.14 and less than 0.23.

Description

Technical Field

[0001] This application discloses a ceramic sintered body. Background Technology

[0002] Ceramic sintered bodies can be used as various structural materials. High toughness is often required for ceramic sintered bodies. One method to improve the toughness of ceramic sintered bodies is to generate residual stress by mixing two phases with different thermal expansion differences, thereby suppressing crack propagation (e.g., Patent Documents 1 and 2).

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2016-132607 Patent Document 2: Japanese Patent Application Publication No. 2005-035803 Summary of the Invention

[0004] The problem that the invention aims to solve There is room for improvement in balancing toughness and wear resistance in traditional ceramic sintered bodies.

[0005] Methods for solving problems This application discloses several methods as means to solve the above-mentioned problems.

[0006] <Method 1> A ceramic sintered body comprising a first compound and a second compound, wherein, The first compound is silicon carbide. The second compound is a diboride of a group 4 element. The second compound constitutes 50% to 70% by mass in the ceramic sintered body. When the 300μm×300μm region of the polished surface of the ceramic sintered body is divided into 400 15μm×15μm partitions, and the area ratio of the first compound is determined for each partition, the coefficient of variation (CV) of the area ratio of the first compound is greater than 0.14 and less than 0.23.

[0007] <Method 2> According to the ceramic sintered body of method 1, wherein the second compound is made of Ti 1－x Zr x B2 (0≤x≤0.05) is used to represent this.

[0008] <Method 3> The ceramic sintered body according to method 1 or method 2, wherein the coefficient of variation (CV) is 0.15 to 0.20.

[0009] <Method 4> The ceramic sintered body according to any one of methods 1 to 3, wherein the ceramic has a strength of 5.0 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 480 MPa.

[0010] <Method 5> The ceramic sintered body according to any one of methods 1 to 3, wherein the ceramic has a strength of 5.5 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 500 MPa.

[0011] <Method 6> According to any one of methods 1 to 5, in the case of an abrasive wear test on the ceramic sintered body, the wear amount of the ceramic sintered body per unit amount of particles is 0.5 mm. 3 / kg or less.

[0012] <Method 7> A ceramic sintered body comprising a first compound and a second compound, wherein, The first compound is silicon carbide. The second compound is made with Ti 1－x Zr x B2 (0≤x≤0.05) represents the diborides of group 4 elements. The second compound constitutes 50% to 70% by mass in the ceramic sintered body. With 5.0 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 500 MPa. In the case of abrasive wear test on the ceramic sintered body, the wear amount of the ceramic sintered body per unit amount of particles was 0.5 mm. 3 / kg or less.

[0013] Invention Effects In the ceramic sintered body disclosed herein, both high toughness and wear resistance can be achieved. Attached Figure Description

[0014] Figure 1 This is a schematic diagram representing an example of a sintered ceramic body.

[0015] Figure 2AThis is a schematic diagram used to illustrate crack propagation in ceramic sintered bodies with a small coefficient of variation (CV).

[0016] Figure 2B This is a schematic diagram used to illustrate crack propagation in ceramic sintered bodies with a coefficient of variation (CV) within a specified range.

[0017] Figure 2C This is a schematic diagram used to illustrate crack propagation in ceramic sintered bodies with a large coefficient of variation (CV).

[0018] Figure 3 This is a schematic diagram illustrating the abrasive testing apparatus. Detailed Implementation

[0019] The ceramic sintered body according to the embodiments will now be described with reference to the accompanying drawings. However, the ceramic sintered body of this disclosure is not limited to the following embodiments.

[0020] 1. Sintered ceramic body The ceramic sintered body disclosed herein comprises a first compound and a second compound. The first compound is silicon carbide. The second compound is a diboride of a Group IV element. The second compound constitutes 50% to 70% by mass of the ceramic sintered body. When a 300 μm × 300 μm region of the polished surface of the ceramic sintered body is divided into 400 15 μm × 15 μm partitions, and the area ratio of the first compound is determined for each partition, the coefficient of variation (CV) of the area ratio of the first compound is greater than 0.14 and less than 0.23.

[0021] 1.1 Compound 1 The ceramic sintered body disclosed herein contains silicon carbide as a first compound. The proportion of the first compound in the ceramic sintered body depends on the proportion of the second compound described later. The proportion of the first compound in the ceramic sintered body can be, for example, 30% to 50% by mass, 32% to 48% by mass, or 34% to 46% by mass. These lower and upper limits can also be combined arbitrarily.

[0022] In the ceramic sintered body disclosed herein, the morphology of the first compound is not particularly limited. For example, as... Figure 1As shown, the ceramic sintered body 10 has a first phase 10a composed of a first compound. The size and shape of this first phase 10a are not particularly limited. The first phase 10a may also be composed of grains of the first compound. When the first phase 10a is composed of a single grain, the diameter of that grain (the equivalent circle diameter in the cross-section) may, for example, be 1 μm to 10 μm or 2 μm to 5 μm. These lower and upper limits can be arbitrarily combined. A "grain" may consist of a single microcrystal or multiple microcrystals aggregated into one grain. Furthermore, it is considered that even when the grains of the first compound and the second compound (described later) are grains composed of multiple microcrystals aggregated into one grain, cracks propagate between the grains of the first compound and the grains of the second compound.

[0023] In the ceramic sintered body disclosed herein, the first compound exists somewhat non-uniformly in such a way that the coefficient of variation (CV) with respect to its area ratio is within a specified range. Details regarding the coefficient of variation (CV) will be explained later.

[0024] 1.2 Compound 2 The ceramic sintered body disclosed herein contains a diboride of a Group IV element as a second compound. The Group IV element (titanium group elements) is at least one of titanium, zirconium, and hafnium. That is, the second compound can also be a diboride of titanium, a diboride of zirconium, a diboride of hafnium, a composite diboride of titanium and zirconium, a composite diboride of titanium and hafnium, a composite diboride of zirconium and hafnium, or a composite diboride of titanium, zirconium, and hafnium. According to the inventors, when the second compound is a diboride containing titanium, the ceramic sintered body tends to be a sintered body with superior toughness and wear resistance. In particular, when the second compound is a diboride containing Ti... 1－x Zr x In the case of compounds represented by B2 (0≤x≤0.05), a significant improvement in toughness and wear resistance can be expected.

[0025] The proportion of the second compound in the ceramic sintered body is 50% to 70% by mass. If the proportion of the second compound in the ceramic sintered body is too low, both the toughness and wear resistance of the ceramic sintered body tend to deteriorate. On the other hand, if the proportion of the second compound in the ceramic sintered body is too high, the wear resistance of the ceramic sintered body tends to deteriorate. In addition, the proportion of the second compound in the ceramic sintered body also affects other mechanical properties such as flexural strength. According to the inventors' view, when the proportion of the second compound in the ceramic sintered body is 50% to 70% by mass, the ceramic sintered body can achieve a balance between high toughness and wear resistance, and the ceramic sintered body becomes more likely to have excellent flexural strength, etc. The proportion of the second compound in the ceramic sintered body can be 52% to 68% by mass, or 54% to 66% by mass. These lower and upper limits can also be arbitrarily combined.

[0026] In the ceramic sintered body disclosed herein, the morphology of the second compound is not particularly limited. For example, as... Figure 1 As shown, the ceramic sintered body 10 has a second phase 10b composed of a second compound. The size and shape of this second phase 10b are not particularly limited. The second phase 10b can also be composed of grains of the second compound. When the second phase 10b is composed of a single grain, the diameter of that grain (the equivalent circle diameter in the cross-section) can be, for example, 1 μm to 10 μm or 2 μm to 5 μm. These lower and upper limits can be arbitrarily combined. A "grain" can consist of a single microcrystal or multiple microcrystals aggregated into one grain.

[0027] 1.3 Other ingredients In addition to the first and second compounds described above, the ceramic sintered body disclosed herein may also contain other components. Examples of other components include components derived from impurities present in the raw materials, components derived from impurities introduced during the manufacturing process, and components that are major constituents of the grain boundary phase, such as carbides other than the first compound and borates other than the second compound. Specifically, other components may include at least one selected from carbides of Group IV elements and boron carbide. It is preferable that other components are few in number. For example, the combined percentage of the first and second compounds in the ceramic sintered body may be 90% to 100% by mass, 95% to 100% by mass, or 99% to 100% by mass. These lower and upper limits can be combined arbitrarily.

[0028] 1.4 Coefficient of Variation (CV) It can be considered that the higher the fracture toughness value of a ceramic sintered body, which represents the ease of crack propagation, the more suppressed the fracture during wear, thereby improving wear resistance. As a method to improve the fracture toughness value of a ceramic sintered body, there are (1) developing columnar particles, (2) imparting a stress field that makes crack propagation difficult by combining two or more materials, or bending the propagation path, etc. Regarding (1), it is a method used in specific materials that undergo dissolution and reprecipitation during sintering, mainly used in Si3N4-based materials. In the ceramic sintered body disclosed in this invention, the fracture toughness value is improved by the method of (2). That is, by utilizing the thermal expansion difference between the two materials, the residual stress generated when returning from the high temperature during sintering to room temperature is used to suppress crack propagation, thereby achieving high toughness.

[0029] As shown in Patent Document 1, by increasing the segregation of the mixed dissimilar materials, a larger residual stress field is generated, which can further improve the fracture toughness of the ceramic sintered body. However, according to the inventors, such a large non-uniformity may become the initiation point of fracture, thus becoming a significant defect. For example, initial cracks may exist between dissimilar materials due to large residual stress. The smaller the initial defect and the larger the fracture toughness of a brittle material like ceramic, the higher the strength. However, the fracture toughness is only an indicator of the difficulty of crack propagation; even a relatively small stress can lead to fracture when the initial defect is large. According to the inventors, if the non-uniform distribution of the two materials is excessively increased in the ceramic sintered body, even with a high fracture toughness, the defect that becomes the initiation point of fracture increases, resulting in poor wear resistance.

[0030] As described above, by allowing the two components (phases) to exist unevenly in the sintered ceramic body, crack propagation caused by residual stress can be suppressed in a relatively large area, thus achieving high toughness. When the unevenness of the two components (phases) is small (i.e., when the two components (phases) are uniformly dispersed), cracks tend to propagate linearly in the sintered ceramic body, resulting in decreased toughness. Figure 2A On the other hand, if the two components (phases) are excessively uneven, the area of ​​peeling and the wear volume will increase during the wear of the ceramic sintered body, thus making the wear resistance more susceptible to deterioration. Figure 2C In other words, it can be said that in ceramic sintered bodies, by achieving an appropriate degree of non-uniformity in the distribution of these two components (phases), it is possible to balance high toughness and wear resistance. Figure 2B ).

[0031] Based on the above viewpoints, for the ceramic sintered body of this disclosure, by dividing the 300μm×300μm region of the grinding surface of the ceramic sintered body into 400 15μm×15μm partitions, and determining the area ratio of the first compound for each partition, by ensuring that the coefficient of variation (CV) of the area ratio of the first compound is greater than 0.14 and less than 0.23, both high toughness and wear resistance can be achieved. Figure 2B If the coefficient of variation (CV) is too small, the crack will easily propagate in a linear fashion. Figure 2A Furthermore, if the coefficient of variation (CV) is too large, the wear volume is likely to increase. Figure 2C In particular, when the coefficient of variation (CV) is between 0.15 and 0.20, the high toughness and wear resistance are even better.

[0032] Furthermore, the coefficient of variation (CV) for the area ratio of the first compound can be obtained by using SEM-EDS, EPMA, or similar methods to obtain the elemental distribution in the polished surface of the ceramic sintered body. For example, a mapping image of the elemental distribution in the polished surface can be determined by SEM-EDS, and its area fraction can be determined using image analysis software. The 300 μm × 300 μm region of the obtained observation image is divided into 400 (20 × 20) 15 μm × 15 μm partitions, and the area fraction of silicon carbide as the first compound is calculated for each partition. Based on the area fraction calculated for each partition, the standard deviation and mean (arithmetic mean) of the area fraction are calculated. The standard deviation is divided by the mean to obtain the coefficient of variation (CV). Furthermore, for polished surfaces of sintered bodies with an area less than 10 mm², the coefficient of variation is determined by... 2 In this case, it is sufficient to calculate the coefficient of variation (CV) for just one region of the polished surface, confirming whether the CV for that region exceeds 0.14 and is below 0.23. On the other hand, in a polished surface that serves as a sintered body, a 10mm thickness can be ensured. 2 Given the above area, for the 10 regions where the distance between the center points is 1 mm or more, the coefficient of variation (CV) was calculated to confirm whether the CV of each region exceeded 0.14 and was less than 0.23. In the ceramic sintered body of this disclosure, the CV of all 10 regions exceeded 0.14 and was less than 0.23.

[0033] 1.5 Other As described above, the ceramic sintered body of this disclosure, by comprising the first compound and a specified amount of the second compound, and satisfying the coefficient of variation (CV) described above, can achieve both high toughness and wear resistance. The ceramic sintered body of this disclosure may, for example, possess the following mechanical properties.

[0034] 1.5.1 Fracture toughness value (KIC) The ceramic sintered body disclosed herein may, for example, have a strength of 5.0 mPa·m. 1 / 2 The above fracture toughness values ​​are preferred, with 5.5 mPa·m being the ideal value. 1 / 2 The above fracture toughness values ​​are not specifically limited in terms of upper limit; higher values ​​are preferred. The ceramic sintered body disclosed herein may, for example, have a fracture toughness of 6.0 mPa·m. 1 / 2 The following are the fracture toughness values. Furthermore, the fracture toughness values ​​were determined according to the SEPB method of JIS-R1607.

[0035] 1.5.2 Bending strength The ceramic sintered body disclosed herein may, for example, have a flexural strength of 480 MPa or higher. Preferably, it has a flexural strength of 500 MPa or higher. There is no particular upper limit to the flexural strength; a higher value is preferred. The ceramic sintered body disclosed herein may, for example, have a flexural strength of 550 MPa or lower. Furthermore, the flexural strength is determined by a three-point bending test according to JIS-R1601.

[0036] One embodiment of the ceramic sintered body may also have a strength of 5.0 mPa·m. 1 / 2 It has the above fracture toughness value and a flexural strength of over 480 MPa, and can also have a flexural strength of 5.5 mPa·m. 1 / 2 The above fracture toughness values, and a flexural strength of over 500 MPa, can also be 5.0 mPa·m. 1 / 2 ~6.0 mPa·m 1 / 2 It exhibits high fracture toughness and a flexural strength of 480 MPa to 550 MPa, and can also achieve 5.5 mPa·m. 1 / 2 ~6.0 mPa·m 1 / 2 It has a fracture toughness value and a bending strength of 500MPa to 550MPa.

[0037] 1.5.3 Abrasion resistance For example, when the ceramic sintered body disclosed herein is subjected to an abrasive wear test, the wear amount of the ceramic sintered body per unit amount of particles can also be 0.5 mm. 3 / kg or less. Furthermore, the "abrasive wear test" mentioned in this application refers to the use of... Figure 3 The experiment was conducted using the apparatus shown. Specifically, a 55mm × 20mm × 20mm test piece 1 was cut from the ceramic sintered body, and the entire 55mm × 20mm test surface was ground using a #2000 diamond grinding wheel before being used for the experiment. Figure 3In the apparatus shown, a grinding wheel 3 with a diameter of 224 mm and a width of 12 mm, bonded with nitrile rubber, is used. The grinding wheel 3 rotates at 200 rpm, the pressing load on the test piece 1 is 130 N, and silica sand No. 6, serving as abrasive particles 4, is fed from the projection nozzle 2 between the test piece 1 and the grinding wheel 3 at a feeding rate of 350 g / min. The test is conducted until the total amount of abrasive particles 4 fed reaches 21 kg. The weight of the test piece 1 before and after the test is measured, and the wear volume is calculated from its weight change and the density obtained by Archimedes' method. This volume is then divided by the total weight of the fed abrasive particles 4 to calculate the wear amount (mm) of the ceramic sintered body per unit of fed particles (1 kg of fed particles). 3 / kg). In addition, prior to the weight determination, test piece 1 was ultrasonically cleaned in acetone to remove particles and debris remaining on its surface before weight determination. For conditions other than those described above, ASTM G65 shall be followed.

[0038] 1.5.4 Vickers Hardness The ceramic sintered body disclosed herein may, for example, have a Vickers hardness of 2000 to 2500. Furthermore, the Vickers hardness is measured using a mirror-polished ceramic sintered body, according to JIS-R1610, with the indentation load set to 98 N.

[0039] 1.5.5 Density The ceramic sintered body disclosed herein may, for example, have a density of 3.5 g / cm³. 3 ~5.0g / cm 3 The density of the ceramic sintered body can vary depending on the type of the second compound, etc. Furthermore, the ceramic sintered body disclosed herein can, for example, have a relative density of 97% or higher. Moreover, the density is determined using the Archimedes method.

[0040] 2. Manufacturing method of ceramic sintered body The ceramic sintered body disclosed herein can be manufactured, for example, by the method described below. That is, a method for manufacturing a ceramic sintered body according to one embodiment includes: mixing powder of a first compound, powder of a second compound, any sintering aid (auxiliary raw material), and any other raw materials to obtain a granulated body; and shaping the granulated body and degreasing and firing it.

[0041] 2.1 Powder of Compound 1 and Powder of Compound 2 The powders of the first compound and the second compound can be manufactured using known methods. Their respective particle sizes are not particularly limited and can be appropriately selected based on target performance, etc. The average particle size of the powder of the first compound can, for example, be 10 nm to 5 μm. Similarly, the average particle size of the powder of the second compound can, for example, be 500 nm to 5 μm. The powders of the first and second compounds can be used individually or in combination of two or more. Furthermore, the average particle size refers to the particle size (D50, median particle size) calculated as the cumulative 50% of the particle size distribution based on volume using laser diffraction and scattering. The average particle size is measured using a laser diffraction particle size distribution measuring device LA-960 manufactured by Horiba Corporation, with the result obtained by adding sodium hexametaphosphate as a dispersant in a pure water solvent.

[0042] 2.2 Auxiliary raw materials The powders described above are sometimes difficult to sinter. Therefore, in one embodiment of the manufacturing method, a sintering aid, which serves as an auxiliary material, may be mixed together with the powders. The type of sintering aid used as an auxiliary material is not particularly limited. For example, it may be at least one of carbon, such as carbon black, or carbides, such as boron carbide.

[0043] 2.3 Other raw materials In one embodiment of the manufacturing method, other raw materials that can become the first compound and the second compound after firing may also be mixed together with the powder described above. For example, by including a carbide of a Group 4 element (e.g., a carbide of a Group 4 element different from the Group 4 element constituting the second compound) with the powder described above, the powder of the second compound can react with the carbide of the Group 4 element during firing. Thus, for example, a complex diboride containing multiple Group 4 elements can be obtained as the second compound.

[0044] 2.4 Powder mixing and granulation Granulated bodies can be obtained by mixing the aforementioned powders, auxiliary materials, and other raw materials. The mixing ratio of the powders, auxiliary materials, and other raw materials can be appropriately determined according to the properties of the target ceramic sintered body. That is, the mixture is mixed at a ratio where the content of the second compound in the final ceramic sintered body is 50% to 70% by mass. Furthermore, the method for mixing and granulating the powders, auxiliary materials, and other raw materials is not particularly limited. For example, the powders, auxiliary materials, and other raw materials can be mechanically mixed with a binder, dispersant, and solvent to obtain a slurry, and then the slurry can be dried by spray drying or the like to obtain the desired granulated body. The types of binders, dispersants, and solvents are not particularly limited in this case. Furthermore, the size of the granulated body is not particularly limited.

[0045] Here, when the amount of dispersant added is small, the same type of raw material powder agglomerates with each other, and the aforementioned coefficient of variation (CV) increases. When the amount of dispersant added is large, the raw material powder is uniformly dispersed, and the aforementioned coefficient of variation (CV) decreases. Furthermore, the effect on the dispersion state of the raw material powder varies depending on the type of dispersant. It is preferable to determine the type and amount of dispersant in a way that ultimately yields the desired coefficient of variation (CV). Additionally, when the mixing time is extended during the mechanical mixing (kneading) of the raw material powder and auxiliary materials, the raw material powder breaks down, agglomerates, and the aforementioned coefficient of variation (CV) decreases. When the mixing time is shortened, the raw material powder does not break down, resulting in a state where the same type of raw material powder agglomerates with each other, and the aforementioned coefficient of variation (CV) tends to increase. It is preferable to determine the mixing method and mixing time in a way that ultimately yields the desired coefficient of variation (CV). As described above, by adjusting the type, amount, and mixing conditions of the dispersant, the non-uniformity of the raw material powder can be controlled, thereby controlling the aforementioned coefficient of variation (CV) within a desired range.

[0046] 2.5 Forming and sintering of granules The aforementioned granules are shaped before firing. The granules can be shaped using known forming methods. The forming method can be selected appropriately based on the shape of the target ceramic sinter. For example, the granules can be pressure-formed by filling a mold, pressure-forming can be performed using CIP (Ceramic In-Place) or similar methods, or a combination of these methods can be used.

[0047] As described above, the content of the second compound, a key requirement of the ceramic sintered body of this disclosure, and the coefficient of variation (CV) of the area ratio of the first compound can be achieved by controlling the mixing conditions of the raw material powders, etc. In other words, regardless of the firing conditions, the requirements of the ceramic sintered body of this disclosure are met. Regarding this, the firing conditions only need to be conditions that allow for the appropriate sintering of the aforementioned raw material powders and auxiliary materials. The heating rate, maximum temperature, holding time at the maximum temperature, cooling rate, etc., during firing can be optimized based on the types of the aforementioned powders, auxiliary materials, and other raw materials, and the optimal conditions can be selected based on the mechanical properties of the final obtained ceramic sintered body. Firing can be performed multiple times; alternatively, HIP (High-Intensity Interval) firing can also be performed.

[0048] 3. Applications As described above, in the ceramic sintered body of this disclosure, by including a predetermined amount of a second compound together with the first compound, and keeping the coefficient of variation (CV) of the first compound within a predetermined range, both high toughness and wear resistance can be achieved. For example, when the ceramic sintered body of this disclosure is used as a component exposed to sliding wear, such as a positioning guide roller for steel plate passage or a chute liner in the top hopper of a blast furnace, the wear rate can be suppressed and the repair cycle of the component can be extended.

[0049] 4. Supplement The ceramic sintered body disclosed herein may also have the following composition. In this case, both high toughness and wear resistance can be achieved. That is, the ceramic sintered body of one embodiment may also include a first compound and a second compound, wherein the first compound is silicon carbide and the second compound is made of Ti. 1－x Zr x The second compound, represented by B2 (0≤x≤0.05), is a diboride of a Group 4 element, and constitutes 50%–70% by mass of the sintered ceramic body, having a strength of 5.0 mPa·m. 1 / 2 The above fracture toughness values ​​indicate a flexural strength of over 500 MPa. Under abrasive wear testing of the ceramic sintered body, the wear amount per unit particle input is 0.5 mm. 3 / kg or less. Details of each component are as described above.

[0050] Example The following embodiments are shown and the invention is further described, but the invention is not limited to the following embodiments. The invention can be employed under various conditions as long as it does not depart from its spirit and purpose.

[0051] 1. Evaluation of the fabrication of sintered ceramic bodies 1.1 Examples 1-8, Comparative Examples 1-2 SiC powder (α-type, average particle size 0.7 μm), TiB2 powder (average particle size 2 μm), ZrB2 powder (average particle size 2 μm), and ZrC powder (average particle size 2 μm) were mixed with sintering aids, distilled water, dispersants, and binders in the manner shown in Table 1 below, and then mixed in a rotary ball mill for 10 hours to obtain a slurry. The obtained slurry was then subjected to air-jet drying by spray drying to obtain granules.

[0052] Here, a polyacrylic acid-based dispersant is used as the dispersant, and the amount of dispersant added is set to 1% by mass relative to the total mass of the raw material powder. In addition, the amount of distilled water added is set to 80% by mass relative to the total mass of the raw material powder. Furthermore, as sintering aids, carbon powder (carbon black, average particle size 0.05 μm) and boron carbide powder (average particle size 0.8 μm) are added at 1% by mass relative to the total mass of the raw material powder.

[0053] The obtained granules were shaped under uniaxial pressure of 10 MPa, placed in a rubber container, and CIP-formed at 140 MPa to obtain a shaped body. The shaped body was then degreased in an Ar atmosphere and sintered at atmospheric pressure at 2150°C for 8 hours in an Ar atmosphere to obtain an intermediate sintered body. The intermediate sintered body was then subjected to HIP treatment at 2000°C and 198 MPa Ar pressure for 3 hours to obtain an evaluation ceramic sintered body.

[0054] 1.2 Comparative Examples 3-6 The same raw material powders as those in Examples 1-8 and Comparative Examples 1-2 were mixed with sintering aids, distilled water, dispersants, and binders in the manner shown in Table 1 below, and then mixed in a rotary ball mill for 10 hours to obtain a slurry. The obtained slurry was then subjected to air-jet drying by spray drying to obtain granules.

[0055] Here, a polyacrylic acid-based dispersant was used as the dispersant. The amount of dispersant added relative to the total mass of the raw material powders was set to 0.5% by mass in Comparative Examples 3 and 4, and 0.2% by mass in Comparative Examples 5 and 6. The amount of distilled water added, the type of sintering aid, and the amount added were the same as above. When the amount of dispersant is small, the same type of raw material powder agglomerates with each other, and the non-uniform distribution of the phases in the ceramic sintered body increases. That is, the smaller the amount of dispersant, the larger the coefficient of variation (CV) described later.

[0056] The obtained granules were subjected to forming, degreasing, firing, and HIP treatment in the same manner as Examples 1-8 and Comparative Examples 1-2, thereby obtaining ceramic sintered bodies for evaluation.

[0057] 1.3 Example 9 and Comparative Example 7 200g of the raw material powder in the proportions shown in Table 1 below was mixed with 300ml of organic solvent using a planetary ball mill. The mixture was then dried in a fume hood to evaporate the organic solvent, thereby obtaining a mixed powder. The obtained mixed powder was subjected to forming, firing, and HIP treatment in the same manner as in Examples 1-8 and Comparative Examples 1-2 to obtain a ceramic sintered body for evaluation. In Examples 9 and Comparative Example 7, carbon powder (carbon black, average particle size 0.05μm) and boron carbide powder (average particle size 0.8μm) were added as sintering aids during mixing using a planetary ball mill, at a mass percentage relative to the total mass of the above raw material powder.

[0058] Here, the mixing time based on the planetary ball mill was set to 6 hours in Example 9 and 12 hours in Comparative Example 7. With a longer mixing time, the raw material powder is broken down, resulting in a sintered body with uniformly dispersed phases. In other words, the longer the mixing time, the smaller the coefficient of variation (CV) described later.

[0059] 2. Evaluation of Ceramic Sintered Bodies The density, relative density, flexural strength, fracture toughness (KIC), and Vickers hardness of the ceramic sintered body were measured. Additionally, abrasive tests were performed on the ceramic sintered body to determine the wear amount per unit particle input (1 kg). The 300 μm × 300 μm area of ​​the abrasive surface of the ceramic sintered body was divided into 400 15 μm × 15 μm zones. For each zone, the area ratio of silicon carbide was determined by SEM-EDS, thereby measuring the coefficient of variation (CV) of the silicon carbide area ratio. Details of each measurement method are described in the embodiments. The respective measurement results are shown in Table 1 below.

[0060] The following can be seen from the results shown in Table 1.

[0061] In the ceramic sintered body of Comparative Example 1, the content of compound 2 (diboride of group 4 element) was relatively low. Therefore, both toughness and wear resistance were insufficient.

[0062] In the ceramic sintered body of Comparative Example 2, the content of compound 2 (diboride of a group 4 element) is relatively high. Therefore, although toughness is ensured, the area of ​​delamination increases when the ceramic sintered body is worn, resulting in insufficient wear resistance.

[0063] In the ceramic sintered bodies of Comparative Examples 3-6, the coefficient of variation (CV) for the area ratio of the first compound (silicon carbide) was relatively large, indicating that the first compound was in a state of excessive inhomogeneity. Therefore, under the residual stress generated by the inhomogeneity of the two materials, crack propagation suppression can be achieved, and toughness is ensured. However, when the ceramic sintered body experiences wear, the area of ​​peeling increases, resulting in insufficient wear resistance (see [reference]). Figure 2C ).

[0064] In the ceramic sintered body of Comparative Example 7, the coefficient of variation (CV) for the area ratio of the first compound (silicon carbide) was small, indicating that the first compound was in a uniformly dispersed state. Therefore, the crack propagation suppression effect due to residual stress could not be obtained, and both toughness and wear resistance became insufficient (see [reference]). Figure 2A ).

[0065] In contrast, in the ceramic sintered bodies of Examples 1-9, by keeping the content of the second compound (diboride of a group IV element) within a specified range and the coefficient of variation (CV) of the area ratio of the first compound (silicon carbide) within a specified range, high toughness is achieved through the crack propagation suppression effect caused by residual stress. Furthermore, when the ceramic sintered body experiences wear, the area of ​​delamination is reduced, resulting in excellent wear resistance (see [reference]). Figure 2B ).

[0066] Furthermore, as shown in Examples 1-9, the same effect was achieved when the second compound was either TiB2 or ZrB2. It can be assumed that, in the periodic table, the same effect can also be achieved for diborides of Hf (hafnium), which belong to the same group as Ti and Zr. In other words, as long as the second compound is a diboride of a Group 4 element, it can be said that the desired effect can be achieved.

[0067] Furthermore, it can be considered that ZrC, as one of the other components in Table 1, constitutes Ti as the second compound in the ceramic sintered body. 1－x Zr x B2. In other words, based on the results shown in Examples 1-9, it can be said that using Ti... 1－x Zr x When B2 (0≤x≤0.05) is used as the second compound, excellent results can be achieved.

[0068] As described above, ceramic sintered bodies containing the first compound and the second compound and satisfying the following conditions A to D can be said to be able to achieve both high toughness and wear resistance.

[0069] Requirement A: The first compound is silicon carbide.

[0070] Requirement B: The second compound is a diboride of a group IV element.

[0071] Requirement C: The proportion of the second compound in the sintered ceramic body is 50% to 70% by mass.

[0072] Requirement D: When the 300μm×300μm region of the polished surface of the ceramic sintered body is divided into 400 15μm×15μm partitions, and the area ratio of the first compound is determined for each partition, the coefficient of variation (CV) of the area ratio of the first compound is greater than 0.14 and less than 0.23.

[0073] Furthermore, the results above indicate that: in the first compound, silicon carbide, and in the second compound, Ti... 1－x Zr x Under the condition that the diborides of Group 4 elements represented by B2 (0≤x≤0.05) and the above-mentioned second compound account for 50% to 70% by mass in the ceramic sintered body, by setting the CV value to 0.15 to 0.20, a ceramic with a strength of 5.0 mPa·m is obtained. 1 / 2 For sintered bodies with fracture toughness values ​​above and flexural strength of 500 MPa or higher, the wear amount per unit particle input during abrasive wear testing is 0.5 mm. 3 / kg or less.

[0074] Symbol explanation: 1 Test piece 2. Projection nozzle 3 Grinding wheel 4. Wear particles 10 Ceramic sintered body 10a Phase 1 (Silicon Carbide) 10b Phase 2 (Diborides of Group 4 elements)

Claims

1. A ceramic sintered body comprising a first compound and a second compound, wherein, The first compound is silicon carbide. The second compound is a diboride of a group 4 element. The second compound constitutes 50% to 70% by mass in the ceramic sintered body. When the 300μm×300μm region of the polished surface of the ceramic sintered body is divided into 400 15μm×15μm partitions, and the area ratio of the first compound is determined for each partition, the coefficient of variation (CV) of the area ratio of the first compound is greater than 0.14 and less than 0.

23.

2. The ceramic sintered body according to claim 1, wherein, The second compound uses Ti 1－x Zr x B2 (0≤x≤0.05) is used to represent this.

3. The ceramic sintered body according to claim 1 or 2, wherein, The coefficient of variation (CV) is 0.15 to 0.

20.

4. The ceramic sintered body according to any one of claims 1 to 3, wherein, With 5.0 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 480 MPa.

5. The ceramic sintered body according to any one of claims 1 to 3, wherein, It has 5.5 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 500 MPa.

6. The ceramic sintered body according to any one of claims 1 to 5, wherein, In the case of abrasive wear test on the ceramic sintered body, the wear amount of the ceramic sintered body per unit amount of particles was 0.5 mm. 3 / kg or less.

7. A ceramic sintered body comprising a first compound and a second compound, wherein, The first compound is silicon carbide. The second compound is made with Ti 1－x Zr x B2 (0≤x≤0.05) represents the diborides of group 4 elements. The second compound constitutes 50% to 70% by mass in the ceramic sintered body. With 5.0 mPa·m 1 / 2 The above fracture toughness values, and It has a bending strength of over 500 MPa. In the case of abrasive wear test on the ceramic sintered body, the wear amount of the ceramic sintered body per unit amount of particles was 0.5 mm. 3 / kg or less.

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