Ceramic slide member and method for manufacturing the same

Abstract

To provide a ceramic slide member, and the like, capable of ensuring high mechanical strength and reducing a coefficient of friction at high temperatures.SOLUTION: A ceramic slide member comprises a ceramic base material containing Si, and an oxidizable non-oxide dispersed in the base material. The oxidizable non-oxide has the ability to react with oxygen upon contact with oxygen to form an oxide. The oxide functions as a lubricant, so it is desirable that a PB ratio be 1.0 or more, but it is more desirable that the PB ratio be 2.0 or more. In particular, it is preferable that the PB ratio be 2.5 or more, such as NbC, NbN, TaC, and TaN, in which the metal ions are Nb or Ta, and it is especially preferable that the PB ratio be 3.0 or more, such as VC and VN, in which the metal ions are V.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a ceramic sliding member and a method for manufacturing the same.

Background Art

[0002] Since ceramic materials are excellent in heat resistance, high-temperature strength, corrosion resistance, and high-temperature hardness, they are used as sliding members such as bearings in high-temperature environments such as gas turbines. In addition, they are lighter than metal bearing members and require less energy to drive, so it is highly expected that they will reduce the environmental load.

[0003] For example, in Patent Document 1, a ceramic rolling bearing material is disclosed in which cubic ZrO of 0.5% to 20.0% by volume is dispersed in a matrix mainly composed of alumina with an aggregated particle size of 10 μm or less to improve mechanical strength. 2

[0004] ​On the one hand, the strength of a member with ceramics as the base material is very sensitive to defects in the matrix surface layer. To improve the robustness of the product, it is required to reduce the surface layer defects of the parts generated during the manufacturing process as much as possible. On the other hand, so-called oxidation-induced self-healing ceramics have been proposed. Oxidation-induced self-healing ceramics are dispersed in the ceramic base material, and non-oxides that are highly active against oxidation in a high-temperature atmosphere oxidize at high temperature with oxygen in the atmosphere existing outside due to the generation of cracks on the base material, and the oxides generated thereby automatically fill and bond the cracks to completely recover the strength, that is, they have a so-called "self-healing function". Therefore, oxidation-induced self-healing ceramics are highly expected to be applied to next-generation high-temperature structural members that require high performance and high safety. In Patent Document 2, a ceramics containing aluminum oxide as the base material is disclosed, which contains an oxidation-active non-oxide and a healing accelerator, for example, magnesium oxide or manganese oxide, to accelerate the speed required for strength recovery in the self-healing process, and to lower the temperature required for crack healing, thereby realizing high functionality, for oxidation-induced self-healing ceramics.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, although such self-healing ceramics are said to be applicable to various applications used at high temperatures, in reality, they have rarely been applied as sliding members so far. Usually, lubrication is required for sliding members. Generally, when used in an air atmosphere at 500°C or higher, polymer-based lubricating oils will volatilize, and solid lubricants such as graphite will have their lubricating functions impaired due to oxidation. Therefore, sliding in an oil-free environment is often forced. As a result, the friction coefficient tends to be relatively large, and the high temperature of the members due to the increase in frictional heat generated will further promote the wear (scuffing and delamination) of the surface layer of the sliding member, and as a result, there is a problem of being easily short-lived.

[0007] In order to solve the above-mentioned problems, an object of the present invention is to provide a ceramic sliding member or the like that can ensure high mechanical strength and can reduce the friction coefficient at high temperatures.

Means for Solving the Problems

[0008] The ceramic sliding member of the present invention includes a non-oxide ceramic base material containing Si and a non-oxide having oxidation activity dispersed in the base material, and the PB ratio represented by the following (1) of the non-oxide having oxidation activity is 1.0 or more. PB ratio = volume of oxide per metal ion / volume per metal atom ··· (1) Further, the non-oxide having oxidation activity is preferably a V-based non-oxide.

[0009] Furthermore, the manufacturing method of the ceramic sliding member of the present invention includes a step of sintering a mixture of a non-oxide ceramic base material powder containing Si and a powder of a non-oxide having oxidation activity in a non-oxidizing atmosphere to obtain a sintered body, and a step of processing the sintered body into a predetermined shape to obtain a processed body. Further, the non-oxide having oxidation activity is preferably a V-based non-oxide. Furthermore, it is preferably further provided with a step of heat-treating the processed body in an air atmosphere at 650°C or higher and 1300°C or lower.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a ceramic sliding member or the like that can ensure high mechanical strength and reduce the friction coefficient at high temperatures.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments for carrying out the present invention will be described.

[0013] The ceramic sliding member of the present invention includes a non-oxide ceramic base material containing Si and a non-oxide having oxidation activity dispersed in the base material, and the PB ratio of the non-oxide having oxidation activity is 1.0 or more. Further, the oxidation-active non-oxide is preferably a V-based non-oxide.

[0014] Furthermore, the method for manufacturing the ceramic sliding member of the present invention includes a step of sintering a mixture of a non-oxide ceramic base material powder containing Si and a powder of a non-oxide having oxidation activity in a non-oxidizing atmosphere to obtain a sintered body, and a step of processing the sintered body into a predetermined shape to obtain a processed body. Further, the oxidation-active non-oxide is preferably a V-based non-oxide. Furthermore, it is preferable to further include a step of heat-treating the processed body in an air atmosphere at 650°C or higher and 1300°C or lower.

[0015] Next, the configuration according to the present invention will be described in detail. The ceramic sliding member of the present invention is a self-healing material. As a self-healing mechanism, with respect to cracks generated in the ceramic base material, the oxidation-active non-oxides dispersed inside the base material react with oxygen in the air under a high-temperature environment to generate oxides, which are filled into the cracks, thereby restoring the strength. For example, when the non-oxide is a vanadium (V)-based compound, the V-based non-oxide oxidizes to become a glass mainly composed of vanadium oxide under a high-temperature environment, fills the crack portion, and restores the strength. In the present invention, it is a non-oxide ceramic base material containing Si. For example, when it is made of a nitride, SiO 2 generated by high-temperature oxidation is filled into the crack portion as a healing substance. In addition, when the added non-oxide is a V-based compound, oxides formed by the V-based non-oxide are also precipitated at high temperatures. Among the oxides formed by this V-based non-oxide, V 2 O 5has a melting point of about 670 °C and is known to serve as an oxidation aid. Therefore, when vanadium non-oxide is used as an additive and heat-treated at 700 °C or higher, the precipitated V 2 O 5 spreads efficiently on the surface of the ceramic base material as a liquid phase, and at the same time, the surface oxidation of the ceramic base material (formation of SiO 2 ) is promoted, and as a result, it is expected to exhibit self-healing properties superior to those of ceramic-only materials. In addition, since the viscosity of V 2 O 5 at its melting point is about 60 Pa·S, which is equivalent to that of engine oil, it is expected not only to promote the oxidation of the ceramic base material but also to improve the self-lubricating properties of the member. Therefore, the ceramic sliding member of the present invention is particularly suitable for members that slide against each other in a high-temperature environment. That is, it is suitable for a ceramic sliding member that can be used in a high-temperature environment of 650 °C or higher. For example, as the sliding member, it can be applied to bearings used at 650 °C or higher, casting cores, brake materials, and the like.

[0016] [Ceramic base material] The ceramic base material is preferably one that can withstand high temperatures, such as alumina (Al 2 O 3 ), sialon (SiAlON), silicon nitride (Si 3 N 4 ), zirconia (ZrO 2 ), etc. In this embodiment, a non-oxide containing Si is used. Si can form a protective film with low oxygen permeability on the matrix surface layer and prevent unnecessary oxidation of the non-oxides dispersed inside the base material. For application to dynamic members such as bearings, it is preferable to use silicon nitride (Si 3 N 4 ), which has relatively excellent toughness among ceramics.

[0017] [Non-oxide] Oxidation-active non-oxides have the ability to undergo an oxidation reaction with oxygen upon contact with oxygen to form oxides. At this time, they may be combined with the aforementioned ceramic base material to form compounds such as glass. Examples of the oxidation-active non-oxides include nitrides, carbides, and carbonitrides. Further, since the formed oxides function as lubricants, it is desirable that the Pilling-Bedworth ratio (PB ratio) represented by the following formula (1) of the oxidation-active non-oxide is 1.0 or more, and those with a PB ratio exceeding 2.0 are more desirable. In particular, those with a PB ratio of 2.5 or more, such as NbC (niobium carbide), NbN (niobium nitride), TaC (tantalum carbide), and TaN (tantalum nitride) where the metal ions are Nb (PB ratio: 2.68) or Ta (PB ratio: 2.50), are more preferable. Furthermore, those showing a PB ratio of 3.0 or more, such as VC (vanadium carbide) and VN (vanadium nitride) where the metal ion is V (PB ratio: 3.19) (referred to as V-based non-oxides), are particularly preferable. When the PB ratio is large, the volume increase accompanying oxidation becomes large, so that a sliding layer made of an oxide that exhibits a friction reduction effect at high temperatures can be more reliably formed. Also, it is preferable that the material has a glass transition temperature on the lower temperature side than the use temperature range, and even if it crystallizes, it is preferable that the oxide takes a layered structure substance that does not hinder the lubricated state as a solid lubricant. PB ratio = volume of oxide per one metal ion / volume per one metal atom ···(1) (= molar volume of metal oxide / molar volume of metal)

[0018] [Composition ratio] Non-oxides with an oxidation activity and a PB ratio higher than 1.0, such as VC, VN, NbC, NbN, TaC, and TaN, increase the precipitation of oxides with lubricating performance as the addition amount increases. Therefore, it is preferable that the non-oxide with oxidation activity in the ceramic base material contains 1.0 vol% or more, and particularly preferably 3.0 vol% or more. On the other hand, if the addition amount becomes too large, there is a risk of causing deterioration of the surface roughness of the base material surface and malfunction of the member due to dimensional changes. For this reason, the addition amount of the non-oxide is preferably 20.0 vol% or less, and more preferably 10.0 vol% or less.

[0019] Next, a method for manufacturing a ceramic sliding member will be described. The method for manufacturing a ceramic sliding member includes a step of sintering a mixture of a non-oxide compound powder containing Si and a powder of a non-oxide with oxidation activity, such as a compound powder containing V, in a non-oxidizing atmosphere to obtain a sintered body, and a step of processing the sintered body into a predetermined shape to obtain a target processed body. Incidentally, if necessary, as a sintering aid, Y 2 O 3 is desirably mixed.

[0020] First, a step of sintering a mixture of a non-oxide compound powder containing Si and a powder of a non-oxide with oxidation activity in a non-oxidizing atmosphere to obtain a sintered body will be described. In the following description, an example in which a compound powder containing V is used as the non-oxide powder is shown, but the same applies to other metals. The non-oxide powder containing Si is a raw material that becomes the ceramic base material in the sintered body. For example, silicon nitride can be used, and any powder physical properties can be considered as long as they are suitable for dispersibility with non-oxides and densification during molding. Similarly, the compound powder containing V is a raw material that is an oxidation-active non-oxide. In order to achieve both the effect of reducing the friction coefficient of the sliding surface and the strength, for example, the non-oxide powder is preferably less than 10.0 times the average particle diameter of the base material particles obtained by measurement according to JIS Z8825:2013 "Particle Size Analysis - Laser Diffraction / Scattering Method". In sintering in a non-oxidizing atmosphere, for example, it can be sintered in an atmosphere of argon or nitrogen, and an argon atmosphere is particularly preferred. In order to enhance the reactivity upon contact with oxygen, it is preferable to have a uniform dispersion state during mixing. For this, it is preferable to use pulverization and mixing using media such as a ball mill. If it is wet mixing, in the subsequent drying process, in order to obtain a high density during sintering, a method considering the pulverized particle size and shape after drying is preferred. Also, in sintering, sintering with pressure applied such as hot pressing may be used to obtain a high density.

[0021] Next, the sintered body is processed into a predetermined shape to obtain a processed body such as a sliding member. The processing method for processing into a predetermined shape is not particularly limited, but high-speed processing using a grinding machine or the like is preferred.

[0022] Subsequently, it may have a step of heat-treating the processed body in an oxidizing atmosphere. By this heat treatment, the sliding characteristics when used as a ceramic sliding member can be further improved. As the heat treatment atmosphere, it is preferably carried out under conditions where the V-based non-oxide is oxidized to layered V 2 O 5 and the oxygen partial pressure is preferably 1.0×10 -4 Pa or more, and more preferably the atmospheric atmosphere of 1.0×10 4It is preferably Pa or more. By arranging so that oxygen contacts the sliding surface of the sliding member, it is preferable because it avoids the inclusion of impurities in the sliding surface and oxygen is easily supplied to the surface defects. The heat treatment temperature can be in the range of 650°C or more and 1300°C or less, and particularly preferably 700°C to 1000°C. The high-temperature holding time is preferably determined according to the degree of the heat treatment temperature. For example, when heat-treating at 700°C in an air atmosphere, the high-temperature holding time can be in the range of 1 second to 1 hour.

[0023] The mechanism of reducing the friction coefficient (improving lubrication characteristics) in the ceramic sliding member of the present invention will be described. For example, when heating a V-based non-oxide, V having a layered structure starts to precipitate from about 650°C. 2 O 5 Such a layered structure produces a friction coefficient reduction effect due to the effect of solid lubrication by sliding between the layered structures. When further heated, at about 700°C or higher, V 2 O 5 melts. That is, since the sliding surface can be uniformly covered with molten V 2 O 5 , it can function as fluid lubrication. And it can be used without problems at a normal use temperature of 1300°C or less, which is below the vaporization temperature of V 2 O 5 (1750°C).

[0024] Thus, when using a V-based non-oxide, theoretically, V of the layered structure substance 2 O 5 is used as a lubricant, and when the melting point is reached (approximately 700°C or higher in an air atmosphere), it behaves as fluid lubrication, and when the melting point is not reached (approximately less than 700°C in an air atmosphere), it is expected to show the behavior of a solid lubricant as a layered structure substance. This is expected to contribute to improving the lubrication characteristics even in an environment with a severe temperature cycle. Also, at a temperature above the layered crystallization of V 2 O 5 , and further at a temperature above the melting point of V 2 O 5By heat-treating at a temperature equal to or higher than the melting temperature, a lubricating layer can be formed on the sliding surface in advance, enabling high lubricating characteristics to be exhibited. That is, it is desirable that an oxide (more preferably a crystal having a layered structure) formed by oxidizing a non-oxide is formed on the surface layer of the sliding member.

[0025] At this time, if the PB ratio of the non-oxide with oxidation activity is less than 1.0, when an oxide is generated from the dispersed state of the non-oxide, a volume reduction occurs, making it difficult to uniformly form a lubricating layer on the sliding surface. However, if the PB ratio is 1.0 or more, at least a lubricating layer made of an oxide comparable to the dispersed state of the non-oxide can be formed. Furthermore, as the PB ratio increases, it becomes possible to more reliably cover the entire sliding surface with a lubricating layer. For example, when the PB ratio is 2.5 or more, and further 3.0 or more, most of the sliding surface can be covered with a lubricating layer, and the thickness of the lubricating layer can be increased, making it more effective.

[0026] In addition, even in non-oxides other than V-based ones, the same effect can be exhibited in the temperature range for generating layered oxides and the melting temperature range of the oxides. Therefore, it is desirable to select a non-oxide suitable for the use temperature range and having a high PB ratio.

Example

[0027] Si 3 N 4 / 4.0vol%Y 2 O 3 material was used as a comparative example, and Si 3 N 4 / 6.0vol%VN / 4.0vol%Y 2 O 3 material (PB ratio of V: 3.19) was used as Example 1, and self-healing characteristics were confirmed by a three-point bending strength test, and self-lubricating characteristics were confirmed by a high-temperature friction and wear test.

[0028] [Confirmation of self-healing characteristics by three-point bending strength test] First, for weighing the raw materials, in the comparative example, Si 3 N 4 was 90.0vol%, Y2 O 3 is 4.0 vol%, and in Example 1, Si 3 N 4 is 90.0 vol%, VN powder is 6.0 vol%, and Y 2 O 3 was weighed so as to be 4.0 vol%. As raw materials, Si 3 N 4 powder was SN-9FWS manufactured by Denka, vanadium nitride (VN) powder was manufactured by Nippon Shinku Metal, and Y 2 O 3 powder used was RUP manufactured by Shin-Etsu Chemical Co., Ltd. After weighing, these powders were wet-mixed for 24 hours using 2-propanol as a mixed solvent with silicon nitride balls and nylon mill pods. The mixed slurry was dried in a blowing air environment at 200 °C for at least 2 hours, and the obtained dried powder was hot press sintered under predetermined conditions (in the comparative example, atmosphere: N 2 gas, holding temperature: 1850 °C, load pressure: 40 MPa, holding time: 2 hours, heating rate: 10 °C / min, cooling rate: 5 °C / min, in Example 1, atmosphere: N 2 gas, holding temperature: 1800 °C, load pressure: 40 MPa, holding time: 2 hours, heating rate: 10 °C / min, cooling rate: 5 °C / min) to produce a sintered body of about 40 mm × 40 mm × t5 mm. The obtained sintered body was ground and polished to obtain a 3 mm × 4 mm × 40 mm bending test piece in accordance with JIS standard R1601 "Room Temperature Bending Strength Test of Fine Ceramics".

[0029] The test pieces were prepared by classifying them into three types [As material (base material), Damage material (pre-cracked material), Heal material (self-healing heat-treated material)]. Vickers marks (test load: 2 kgf, holding time: 10 sec) were introduced into the Damage material and Heal material using a microhardness tester manufactured by Future-Tech, and the Heal material was subjected to self-healing heat treatment at 700 °C for 10 minutes in an air atmosphere at a heating rate of 10 °C / min using a muffle furnace. Note that JEOL ARM-200F was used for TEM observation of the healed part.

[0030] In Fig. 1, Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) and Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 shows the three-point bending strength of the material (Example 1). In the figure, "As" is the strength of the base material, "Damage" is the strength of the pre-cracked material, and "Heal" is the strength of the self-healing heat-treated material. The strength of the comparative example is the average value of n = 2, and the strength of Example 1 is the average value of n = 4. The As material strength of the comparative example was about 930 MPa, the Damage material strength was about 525 MPa, and the Heal material strength was about 590 MPa. The As material strength of Example 1 was about 735 MPa, the Damage material strength was about 600 MPa, and the Heal material strength was about 750 MPa. From the above, Si in Example 1 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material is the Si in the comparative example 3 N 4 / 4.0 vol% Y 2 O 3 material was confirmed to have better self-healing characteristics (higher mechanical strength). This is because V 2 O 5 promoted the surface oxidation of the silicon nitride base material (formation of SiO 2 ) as an oxidation aid.

[0031] Figure 2 shows the STEM image of the healed part of the Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1) (acceleration voltage: 200 kV). From STEM-EDX observation, it was confirmed that the crack part 1 introduced by the Vickers mark was filled with the oxide 2 which is the healing substance, and these healing substances were confirmed to be the oxide 4 formed by the Si-based oxide 3 and the V-based non-oxide. In addition, regarding the oxide formed by the V-based non-oxide deposited by the heat treatment at 700 °C, it has been clarified from the results of the subsequent in-situ high-temperature bulk XRD (Figure 4) that it is V 2 O 5 . It has been clarified that it is V 2O 5 Since the material itself has a layered structure, it is easily exfoliated, and it is difficult to firmly bond the crack opening surfaces to each other. On the other hand, V 2 O 5 has the role of an oxidation aid and has the potential to promote the oxidation of the silicon nitride base material (precipitation of Si-based oxides) at high temperatures. In Figure 1, Si 3 N 4 / 6.0vol%VN / 4.0vol%Y 2 O 3 material (Example 1) shows better self-healing characteristics (higher mechanical strength) than the Si 3 N 4 / 4.0vol%Y 2 O 3 material (Comparative Example). Therefore, it is clear that V 2 O 5 promotes the oxidation of the silicon nitride base material. From the above considerations, in the Si 3 N 4 / 6.0vol%VN / 4.0vol%Y 2 O 3 material (Example 1), the silicon nitride base material and the additive agent VC are oxidized by heat treatment at 700 °C to generate the healing substances SiO 2 and V 2 O 5 . Moreover, V 2 O 5 enables the strength recovery to the As material strength by promoting the further precipitation of SiO 2 as an oxidation aid. Although the crack opening surfaces are firmly bonded by SiO 2 , V 2 O 2 which spreads more efficiently than SiO 5 between the sliding surfaces serves as a lubricant, enabling the combined use of member strength recovery and self-lubrication.

[0032] [Confirmation of Lubrication Effect by High-Temperature Friction and Wear Test] A sintered body was obtained in the same manner as the test specimens for the three-point bending test (comparative example, Example 1). A disk shape of φ50 mm × 5 mm t was obtained from the sintered body by grinding and polishing. As a result of measuring the surface roughness at three locations on the disk with a SurfCorder SE800 manufactured by Kosaka Laboratory Ltd., the arithmetic mean roughness Ra was 0.36 ± 0.1 μm, confirming that it was in a quasi-mirror finish state. The obtained pin and disk were manufactured by Bruker A pin-on-disk test (load: 5 N, sliding speed: 5.24 mm / sec, temperature: 100°C to 800°C) was conducted using a multi-functional testing machine UMT TriboLab. The friction coefficient adopted was the average value of the friction coefficient for 30 seconds between 15 and 45 seconds during a 60-second test time. For the Si 3 N 4 / 4.0 vol% Y 2 O 3 material, the same test was also conducted. Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 For the in-situ bulk XRD of the Si N / 4.0 vol% Y 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) and Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 O material (Example 1), for the in-situ high-temperature observation, a high-temperature heating stage manufactured by Linkam and an optical microscope SZX12 manufactured by OLYMPUS were used, and continuous optical microscope observations were carried out under the conditions of a heating temperature of 1000°C and a heating rate of 10°C / min.

[0033] In Fig. 3, for the Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) and Si 3N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 The relationship between temperature and friction coefficient in the pin-on-disk test with each specimen of the SiN / 6.0 vol% VN / 4.0 vol% Y material (Example 1) as the sliding counterparty is shown. Si 3 N 4 / 4.0 vol% Y 2 O 3 In the case of the SiN / 4.0 vol% Y material (Comparative Example), the friction coefficient changed from about 0.67 from 100°C to 650°C, and then decreased slightly to 0.64 at 700°C. However, from 700°C to 950°C, the friction coefficient tended to increase towards 0.70. On the other hand, Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 In the case of the SiN / 6.0 vol% VN / 4.0 vol% Y material (Example 1), the friction coefficient tended to decrease from 0.70 to 0.60 from 100°C to 600°C, decreased rapidly to about 0.35 at 650 and 700°C, increased to 0.55 at 750°C, and then tended to increase towards 0.70 up to 950°C. Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 The SiN / 6.0 vol% VN / 4.0 vol% Y material (Example 1) is Si 3 N 4 / 4.0 vol% Y 2 O 3 It was revealed that it showed excellent self-lubricating characteristics between 600°C and 850°C, especially a reduction in the friction coefficient of more than 40% between 650°C and 700°C, compared to the SiN / 4.0 vol% Y material (Comparative Example).

[0034] Figure 4 shows the relationship between temperature and friction coefficient in the pin-on-disk test with SUJ2 of the SiN / 4.0 vol% Y material (Comparative Example) and the SiN / 6.0 vol% VN / 4.0 vol% Y material (Example 1) as the sliding counterparty. Si 3 N 4 / 4.0 vol% Y 2 O 3 material (Comparative Example) and Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1). Si 3 N 4 / 4.0 vol% Y 2O 3 In the case of the O material (comparative example), the friction coefficient changed from about 0.65 from 100°C to 200°C, and then decreased linearly to 0.4 when heated to 500°C, and showed an increasing tendency of the friction coefficient after 600°C. On the other hand, for Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1), from 100°C to 600°C, Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) showed the same behavior, and after 600°C, it was confirmed that the friction coefficient changed from 0.29 to 0.43. Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) was found to exhibit better self-lubricating properties (a friction coefficient about 20% lower).

[0035] Figure 5 shows the in-situ high-temperature bulk XRD of the Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1). Figure 5 shows the XRD results from room temperature → heating to 1000°C → cooling to 500°C from bottom to top. At the start of heating, diffraction peaks of β-Si 3 N 4 and VN were confirmed. However, diffraction peaks of V 2 O 5 appeared around 650°C - 730°C during heating. Note that from 730°C and above during heating, the peak of V 2 O 5 disappeared, and the peak of V 2 O 5 appeared again from 620°C during cooling. Also, the peak of YVO 4 appeared from 750°C during heating. From the above, around 650°C during heating, precipitation of solid-phase V 2 O 5 accompanied by oxidation of VC, and from 730°C and above during heating, V 2 O 5It is presumed that liquefaction (disappearance of the periodic structure) occurs due to reaching the melting point. In addition, by comparing with the results of Fig. 3, solid phase V around 650 °C 2 O 5 precipitation, and above 700 °C, it became clear that the melting of V 2 O 5 reduced the friction coefficient. That is, it is possible to exhibit excellent self-lubricating properties at high temperatures.

[0036] Fig. 6 shows in-situ observations at high temperatures of Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example) and Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1). Fig. 6 shows the in-situ observation results of heating from room temperature to 1000 °C from bottom to top. In the Si 3 N 4 / 4.0 vol% Y 2 O 3 material (comparative example), no clear morphological change in the surface layer was confirmed during the heating process. On the other hand, in the Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 material (Example 1), at the start of heating, bright spot patterns derived from added VN could be confirmed in the Si 3 N 4 substrate, but the bright spot patterns disappeared around 500 °C during heating, and low-brightness spot patterns appeared around 650 °C during heating. After exceeding 700 °C during heating, liquid precipitate 6 was confirmed on the surface layer. By comparing the above surface oxidation behavior with Fig. 3 and Fig. 4, the precipitation of solid phase V 2 O 5 around 650 °C, and above 700 °C, it is presumed that V 2 O 5 is melting. Similar to the results of high-temperature in-situ powder XRD, this result, when compared with the results of Fig. 3 and Fig. 4, shows the precipitation of solid phase V 2 O 5 around 650 °C, and V 2O 5 It has been clarified that the melting of [substance] reduces the friction coefficient. That is, it is possible to exhibit excellent self-lubricating properties at high temperatures.

[0037] [Influence of heat treatment on the strength characteristics of the processed body] Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 The mechanical strength characteristics of the [material (Example 1)] were evaluated when heat treatment at 700 °C for 10 minutes in an air atmosphere was carried out on the As material and when it was not carried out. Fig. 7 is an optical microscope image of the surface of the member after heat treatment at 700 °C for 10 minutes. In the figure, "As" is the base material that has been ground and polished in accordance with JIS standard R1601, "Room Temperature Bending Strength Test of Fine Ceramics", and "As + healing heat treatment (700 °C × 10 minutes)" is the above base material that has been subjected to a healing heat treatment at 700 °C for 10 minutes in an air atmosphere. While there were scratches due to polishing on the surface of "As", in "As + healing heat treatment (700 °C × 10 minutes)", the polishing scratches were covered by shiny brownish deposits, and a checkerboard-patterned structure was formed. It is presumed that the brownish deposits are oxides formed by V-based non-oxides from SEM-EDX observations. Combining with the results shown in Figs. 5 and 6, it is considered that it is [substance]. 2 O 5 It is considered to be [substance].

[0038] Fig. 8 shows Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3The Weibull plots (relationship between three-point bending strength and cumulative failure probability) are shown for the As material (Example 1) with and without heat treatment at 700 °C for 10 minutes in an air atmosphere. In the figure, "As" is the base material that has been ground and polished in accordance with JIS standard R1601, "Room Temperature Bending Strength Test of Fine Ceramics", and "As + healing heat treatment (700 °C × 10 minutes)" is the base material that has been subjected to a healing heat treatment at 700 °C for 10 minutes in an air atmosphere. In both cases, the number of tests is n = 12. The Weibull coefficient of "As" is m = 11.54, and the average bending strength is 756.0 MPa. On the other hand, the Weibull coefficient of "As + healing heat treatment (700 °C × 10 minutes)" is m = 15.91, and the average bending strength is 820.1 MPa. From the above, it was confirmed that the robustness of the base material itself is improved by heat-treating the base material. This is presumably because microcracks including polishing scratches generated on the surface of the bulk body during the processing process were comprehensively healed. That is, the robustness of the mechanical strength can be improved by heat-treating the processed body.

[0039] From the above, Si 3 N 4 / 6.0 vol% VN / 4.0 vol% Y 2 O 3 The material (Example 1) showed strength recovery up to the base material strength by heat treatment at 700 °C for 10 minutes in an air atmosphere, and also confirmed a reduction in the friction coefficient due to vanadium-based oxides (V 2 O 5 ) precipitating at 650 °C or higher. That is, it was confirmed that high-temperature oxidation improves the mechanical strength by strength recovery (suppression of strength degradation) and reduces the friction coefficient (high slidability), and it was confirmed that both self-healing characteristics and self-lubricating characteristics are realized when applied to sliding members such as bearings.

Explanation of symbols

[0040] 1 ··· Crack introduced by Vickers 2 ··· Oxide 3 ··· Healing part (Si-based oxide) 4 ··· Healing part (oxide formed by V-based non-oxide) 5 ··· VN 6... Liquid precipitate 7... Grinding scratch 8... Ochreous precipitate (oxide formed by V series non-oxide)

Claims

1. The present invention includes a ceramic matrix of a non-oxide containing Si, and an oxidation-active non-oxide dispersed in the matrix, The ceramic sliding member is characterized in that the PB ratio of the oxidation-active non-oxide, represented by the following (1), is 1.0 or more. PB ratio = oxide volume per metal ion / volume per metal atom (1)

2. 2. The ceramic sliding member according to claim 1, wherein the oxidation-active non-oxide is a V-based non-oxide.

3. A method for producing a ceramic sliding member according to claim 1, comprising the steps of: A step of sintering a mixture of a non-oxide ceramic base powder containing a Si-containing powder and an oxidation-active non-oxide powder in a non-oxidizing atmosphere to obtain a sintered body; A step of processing the sintered body into a predetermined shape to obtain a processed body; 2. A method for producing a ceramic sliding member comprising the steps of:

4. 4. The method for producing a ceramic sliding member according to claim 3, wherein the oxidatively active non-oxide is a V-based non-oxide.

5. 5. The method for producing a ceramic sliding member according to claim 3, further comprising a step of heat treating the processed body in an air atmosphere at 650° C. or more and 1300° C. or less.

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