JP2942830B1 - Self-lubricating ceramics - Google Patents

Abstract

The present invention provides a self-lubricating ceramic which exhibits a low friction coefficient and high wear resistance stably even in an oxidizing atmosphere from a low temperature range to a high temperature range. SOLUTION: This self-lubricating ceramic is made of BaC
of a self-lubricating oxide such as rO ₄ , BaCr ₂ O ₄
It is made of a sintered ceramic containing 80 vol% and 85 to 20 vol% of a hard ceramic material such as Al ₂ O ₃ or partially stabilized zirconia. The structure of the ceramic layer on the friction surface side includes at least 15 vol% or more of coarse particles composed of self-lubricating oxide particles having a particle diameter of 0.02 to 3.0 mm, which is given as an average value of the minor axis and the major axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-lubricating ceramic which can be mainly applied to sliding parts of various machines and has a low friction coefficient and excellent wear resistance in a wide range from room temperature to high temperature. is there.

[0002]

2. Description of the Related Art For sliding parts of high-efficiency engines and gas turbines, materials having a low friction coefficient and excellent wear resistance from room temperature to high temperature are required. At present, the demand for such materials is increasing. Similar problems also exist in continuous casting machines, heat treatment furnaces, and the like, and there is potentially a considerable need for sliding materials that have low friction and low wear from room temperature to high temperatures. However, a material that exhibits a low friction coefficient and high wear resistance stably even in an oxidizing atmosphere from room temperature to a high temperature of about 1000 ° C. has not yet been developed.

For example, graphite, MoS ₂ , WS _{2 and the} like exhibit a low friction coefficient of about 0.1 at low temperatures,
In the above oxidizing atmosphere, the friction coefficient sharply increases due to oxidation. CaF ₂ , BaF ₂ , CeF _3, etc. are expected as low-friction-coefficient materials for high temperatures, but have high friction coefficients at low temperatures, and are degraded by oxidation in an oxidizing atmosphere at about 1000 ° C. Even for ceramics such as BaCrO ₄ (used in the present invention), a sintered body of fine powder (about several μm) uniformly mixed by a ball mill or the like has a friction coefficient of about 0.3 in a high temperature region of about 400 ° C. or more. However, in a low temperature range below that, the friction coefficient increases to 0.5 to 0.7.

[0004] In order to address such a problem and develop a self-lubricating material having excellent friction characteristics that does not vary with temperature conditions, the present inventors have been conducting research on oxide ceramics for many years. However, among them, when friction between aluminas is performed while supplying powder such as BaCrO ₄ onto an alumina substrate, 0.3 to 0.3 ° C. from room temperature to around 1000 ° C.
It has been found that a friction coefficient of 0.4 can be obtained (Patent No. 2
590444).

Further, based on the above findings, BaCrO ₄
In the center of the -Al ₂ O ₃ system has been developing research of self-lubricating ceramics. However, when various ceramics produced by uniformly mixing and sintering fine powder (about several μm) were prepared and their friction characteristics were evaluated, the friction coefficient was about 400 ° C.
In the above high temperature region, it is around 0.3, but in the low temperature region below it, it becomes a high value of 0.5 to 0.7 (Kazutoku Umeda, Akihiro Tanaka, Takaaki Musha, "Self-lubricating composite materials Prototype by Spark Plasma Sintering Method ", Proceedings of the Japan Society of Lubrication Tribology Conference, Tokyo, spring 1996), which cannot be used as a stable self-lubricating material over a wide temperature range from room temperature to high temperature.

Therefore, in order to reduce the friction coefficient in the low temperature region, a study was conducted focusing on the particle size of each single phase. As a result, it was found that a single coarse particle (including a particle aggregate) having a certain size or more on the friction surface. The same applies to the following.)
It has been found that the friction coefficient in the low-temperature region is remarkably reduced, the friction coefficient in the high-temperature region is further improved, and various conditions for further improving the improvement effect have also been found.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made based on such findings, and the technical problem thereof is that a low coefficient of friction and a high resistance to high and low temperatures are ensured even in an oxidizing atmosphere. An object of the present invention is to provide a novel self-lubricating ceramic exhibiting wear properties.

[0008]

Means for Solving the Problems The self-lubricating ceramic of the present invention for solving the above-mentioned problems is basically composed of B
aCrO ₄ , BaCr ₂ O ₄ , BaZrO ₃ , BaTi
O ₃ , Cr ₂ O ₃ , BaO, CaZrO ₃ and CaC
An oxide system containing 15 to 80 vol% of one or more self-lubricating oxides selected from the group A of rO ₄ , Al ₂ O ₃ , partially stabilized zirconia, Cr ₂ O ₃ , Si ₃
Nitride containing N _4, a sintered ceramic containing 85～20Vol% of one or more hard ceramic material selected from carbide and sialon group B including SiC, ceramic layer of the friction surface Has a particle diameter of 0.02 to 3.0 mm as an average value of the minor axis and the major axis in a plane parallel to the friction surface, or
The cross-sectional area given as the average of the minimum and maximum is 400
coarse particles of single-phase particles of [mu] m ² ～9Mm of the group A where a ² self-lubricating oxide, at least 15
vol% or more.

In the above self-lubricating ceramic,
It is more effective that the self-lubricating oxide of Group A is 20 to 60% by volume and the hard ceramic material of Group B is 80 to 40% by volume. Further, the self-lubricating oxidation of Group A on the friction surface side is more effective. The particle size of the coarse particles of the product is 0.5 to
It is more effective that the amount is 20 vol% or more at 2.0 mm. In the structure of the ceramic layer on the friction surface side, as the remainder of the coarse particles of the self-lubricating oxide of the group A, use the same or less group B particles or mixed particles of the group A and the group B as the coarse particles. Can be.

Further, the ceramic layer on the friction surface side is simultaneously sintered with a substrate made of one or more hard ceramic materials selected from the group B to form a two-layer structure, or to form the ceramic layer. A stress relaxation layer having an intermediate composition between the two may be interposed between the substrate and the substrate, and these may be simultaneously sintered. Further, the self-lubricating ceramic, by heat treatment of the sintered body in the air, recovers the oxygen amount reduced during sintering to substantially the level near the stoichiometric value, lower the friction coefficient, and Can be stabilized.

According to the self-lubricating ceramic of the present invention having the above structure, when rubbing against alumina in an oxidizing atmosphere (atmosphere), the total temperature from room temperature to a high temperature of about 1000 ° C. Within this range, the coefficient of friction in the steady state at each temperature is at least 0.4 or less, and can be 0.3 or less by setting preferable conditions. In addition, it exhibits excellent wear resistance (for example, 10 ^-6 to 10 ^-7 mm ³ / Nm in specific wear amount), and does not cause deterioration or deterioration in characteristics due to oxidation at high temperatures. This excellent frictional property is not obtained simply by selecting the composition or the like, but is due to the texture structure in which single-phase coarse particles are present.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically. As described above, the self-lubricating ceramic of the present invention basically comprises BaCrO ₄ , BaCr ₂ O ₄ ,
BaZrO ₃ , BaTiO ₃ , Cr ₂ O ₃ , BaO, C
15~80vol of AZrO ₃ and one or more self-lubricating oxide selected from the group A of CaCrO ₄
%, Al ₂ O ₃ , partially stabilized zirconia (ZrO ₂ )
Oxide containing Cr and Cr ₂ O ₃ , nitride containing Si ₃ N ₄ , carbide containing SiC, and B of Sialon
It is composed of a sintered ceramic containing 85 to 20 vol% of one or more hard ceramic materials selected from the group. In this self-lubricating ceramic, what is particularly important is that the structure of the ceramic layer on the friction surface side has a grain size of 0. 0 in a plane parallel to the friction surface.
The cross-sectional area given in the range of 02 to 3.0 mm or as an average of the minimum and maximum is 400 μm ^{2 to} 9 mm ²
At least 15 vol% or more of coarse particles composed of single-phase particles of the self-lubricating oxide of Group A in the range of (a). Here, the particle diameter of the coarse particles is defined as an average value of the minor axis and the major axis. The above 0.02 to 3.
Range of cross-sectional area of the particle size range and 400μm ² ~9mm ² is called 0 mm, a range of particle size and cross-sectional area of parallel cross-section on the friction surface, is within the range within a cross section perpendicular to the friction surface No need.

When the above ceramics has a fine uniform structure prepared from a uniform fine mixed powder (about several μm), the coefficient of friction against alumina in the atmosphere is about 4
In a high temperature region of 00 ° C. or higher, the value is about 0.3 to 0.4, but in a low temperature region below that, only a high value of 0.5 to 0.7 can be obtained. On the other hand, in the ceramic of the present invention, the friction surface has a microscopic heterogeneous structure in which single-phase coarse particles of the self-lubricating oxide of Group A are dispersed. The drawback is that the high coefficient of friction in the low temperature region is remarkably low, and the coefficient of friction in the high temperature region is also improved, so that it is 0.4 or less in the entire temperature region in an oxidizing atmosphere from room temperature to around 1000 ° C. With the improved one, a substantially uniform low coefficient of friction of 0.3 or less can be obtained.

[0014] When the group A coarse particles are present in a certain amount or more, the remaining particles of the group A phase, the group B phase, and the mixed phase thereof have the same particle size as the group A coarse particles. Even if it is fine, the above low coefficient of friction can be obtained. The wear resistance of the sintered body is not inferior to that of the uniform sintered body.

The reason why the coefficient of friction is low in a microscopically nonuniform structure in which coarse particles are dispersed has not been sufficiently elucidated at present, but is considered to be due to the following reasons. That is, the lubricating component in the sintered ceramics is a self-lubricating oxide of Group A, and the coefficient of friction is reduced by forming a film rich in the lubricating component on the friction surface. However, if the particles of both the groups A and B are too finely mixed, the friction coefficient around the particles of the group A is high.
While the lubricating performance of the self-lubricating oxide of Group A cannot be sufficiently exhibited, such as being difficult to form a low friction film because of being inhibited by the particles of the group, the lubricating component is distributed with a certain size or more, It is considered that the distribution of the hard material of the group B in an appropriate size around the periphery has a favorable effect on the friction coefficient and its temperature dependency. Further, when the sintered body of the self-lubricating ceramic according to the present invention is sufficiently heat-treated in the atmosphere, the above-mentioned coefficient of friction is further reduced and becomes more stable. This is probably because the heat treatment and the crystal structure return to a normal state.

[0016] The ceramics of the present invention can be basically produced by ordinary ceramics manufacturing techniques. The method of distributing the coarse particles of group A on the friction surface side is not particularly limited, but it is a simple and easy method to use a powder having a particle size corresponding to the method. Usually, the powders of both groups A and B are used after adjusting the particle size, but the powders of group B may be fine powders whose particle size is not adjusted. In addition, A without particle size adjustment
Even when the group B fine powder and the particle size adjusted B group powder are used, a sintered structure in which the group A coarse particles are dispersed can be obtained.

The particle size of the powder can be adjusted by various methods. As one method, the fine powder may be granulated to a desired particle size range using an appropriate granulator. As another method, the bulk material can be appropriately pulverized and sieved to adjust the particle size. The lump can be prepared by various methods such as a cake obtained by drying and solidifying a powder made into a paste with a liquid such as water, a semi-sintered body such as a green compact, and a normal sintered body.

It is important that the mixing of the powders is carried out in such a way that the initial particle size is substantially maintained, avoiding the grinding of the size-controlling particles. For example, the powder can be mixed while gently mixing with an appropriate spatula or the like, or the powder is put in a bag and shaken gently to substantially maintain the powder particle size. Also,
It is also possible to put only the powder in a V mixer and slowly rotate to mix.

The molding and sintering of the powder can be performed by a method generally used in ceramics and powder metallurgy. For example, die molding, pressure molding by CIP or the like, pressureless sintering, hot pressing, HIP, spark plasma sintering (SP
S) or the like can be performed. Among these, SPS does not require powder compaction, a compact sintered body can be obtained in a short time at a low temperature, there is no deformation at the time of sintering, and it is easy to prepare a multilayer body. It is a suitable method. The appropriate sintering temperature differs depending on the composition and the sintering method, and is not specifically limited. However, in the case of SPS, it is approximately 1100 to 1400 ° C.

The particle size of the coarse single phase particles or particle aggregate is
If it is too small, the effect on the temperature dependence of the friction coefficient will be small. If it is too large, the distribution of the friction coefficient and the wear amount on the material surface will be non-uniform, which is not suitable for practical use. The range of the particle size in which a material having a small coefficient of friction and a small amount of wear and showing practically uniform performance is 0.02 to 0.02 in the average value of the minor axis and the major axis.
It is 3.0 mm, more preferably 0.5 to 2.0 mm. The particle size of the coarse particles can be controlled by the particle size of the raw material powder. In a sintered body obtained by unidirectional pressure sintering such as SPS, the particle size of coarse particles in a plane perpendicular to the pressing direction is substantially the same as the particle size of the granular powder of the raw material. This is because the radial direction is constrained by the inner wall of the graphite mold, so that shrinkage and densification proceed preferentially in the pressure direction, and the bulky coarse powder densifies into a plate shape, and the in-plane in the direction perpendicular to the pressure It is explained that the particle size in the sample hardly changes. Therefore, 0.02-3.0
If the raw material powder whose particle size is adjusted to the range of the particle size selected from mm is used, a sintered body having substantially the same particle size can be obtained. By using the surface of the sintered body perpendicular to the pressing direction as the friction surface, an expected low coefficient of friction can be obtained.

The particle size of these coarse particles is not limited to one range, and two or more types of particles having different particle size ranges are mixed in various ratios according to the target tribological characteristics. Can be used. Room temperature to 100
In order to obtain a friction coefficient of 0.4 or less in the entire temperature range around 0 ° C., the content of the coarse particles in Group A is 1% of the entire ceramics.
It is at least 5 vol%, more preferably at least 20 vol%. As long as the particle size and content of the coarse particles in Group A satisfy the above conditions, there is no limitation except that the particle size of the remaining phase is equal to or less than this. Therefore, for the remaining phase, any of the powder of Group B, the fine powder of Group B, the non-milled mixed powder, and the homogeneous mixed powder whose particle size has been adjusted can be used alone or in combination.

When the amount of the self-lubricating oxide in Group A is too small, the coefficient of friction increases, whereas when the amount of the hard material in Group B is too small, wear increases. Then,
The composition range where a low coefficient of friction and sufficient wear resistance are obtained is
As described above, the amount of the self-lubricating oxide in Group A is 15 to 8
0 vol, more preferably 20 to 60 vol%.

Although the sintered body can be used as it is as a self-lubricating material for various sliding parts, the tribological properties, particularly the friction coefficient, are further reduced and stabilized by heat treatment in the air. . This is considered to be because the amount of oxygen that deviated from the stoichiometric value due to the influence of temperature and atmosphere during sintering is restored to the original value by firing, and the crystal structure becomes a normal state. For example, BaCrO ₄ is yellow and has an oxygen stoichiometry of 25.3%, but 1300%.
When SPS sintering is performed at ℃, the color becomes green and the amount of oxygen is reduced by about 2%, and the state of the X-ray diffraction peak is considerably different from that of the raw material powder. It was confirmed that when this was subjected to a heat treatment at 1000 ° C. for 6 hours in the air, the color became yellow again, and the amount of oxygen and the X-ray diffraction pattern returned to almost the same state as the raw material powder.

The problem of the sintered body of the present invention is that the strength is inferior to ordinary engineering ceramics such as alumina and zirconia, and the strength decreases as the content of group A increases. As a countermeasure, it is effective to adopt a two-layer structure using alumina or zirconia having high strength as a substrate. It is not necessary to adjust the particle size of the powder for the substrate. This two-layer structure improves the strength and further reduces the coefficient of friction of the self-lubricating layer on a hard substrate. On the other hand, in the two-layer structure, cracks and peeling may occur due to residual stress due to the difference in the coefficient of thermal expansion between the substrate and the self-lubricating layer. When the content of the group A of the self-lubricating layer is high,
This tendency becomes stronger. Cracks and peeling can be prevented by appropriately inserting an intermediate layer whose composition is changed stepwise between the self-lubricating layer and the substrate to relax the stress. With proper design of the intermediate layer, the tribological properties of the self-lubricating layer are not substantially impaired. It is not necessary to adjust the particle size of the powder used for the intermediate layer, but a powder whose sphere diameter has been adjusted may be used.

[0025]

[Example 1] BaCrO ₄ powder as a reagent was filled under pressure into an alumina crucible and fired at 700 ° C for 1 hour in the atmosphere to obtain a semi-sintered body. In addition, A having an average particle size of 0.2 μm
Water was added to l ₂ O ₃ powder to make a paste, which was dried and solidified on a hot plate at about 300 ° C. Next, these lumps were pulverized and sieved in a mortar to give a particle size of 0.43 to 0.4.
The powder was made into a 71 mm granular powder, and both powders were mixed in a polyethylene bag so as not to break the granules. This mixed powder was filled in a graphite mold, pressurized to 70 MPa with an SPS device, and pressurized to 130 MPa.
5. Perform sintering at 0 ° C. for 5 minutes, diameter 20 mm, thickness 6.
A dense sintered body of 5 mm BaCrO ₄ -50 vol% Al ₂ O ₃ was produced. The particle diameters of the BaCrO ₄ particles and Al ₂ O ₃ particles in a plane perpendicular to the pressing direction in the sintered body were in the range of 0.4 to 0.7 mm, which was substantially equal to the particle diameter of the granular powder. .

The above sintered body was polished with a 200-mesh diamond grindstone and then cut to obtain a 17 × 10 × 6 mm
A ball-on-block reciprocating friction test was conducted at a load of 9.8 N and a friction speed of 1.2 m / min from the room temperature to 1000 ° C. in the air at 200 ° C. intervals, using an alumina ball as a mating material. While heating
Friction was performed at each temperature for 10 minutes, and the friction coefficient was measured.
As shown in Table 1, the steady-state friction coefficient of Example 1 was 0.37 or less in the entire temperature range from room temperature to 1000 ° C.

On the other hand, both powders crushed in the mortar were crushed again in a mortar until the particle size became several μm, mixed uniformly, and sintered uniformly under the same conditions as in Example 1 with the same composition. In the comparative example of the structure, the coefficient of friction was about 0.3 at 600 ° C or higher, but was 0.45 to 400 ° C or lower.
This is a high value of 0.58, which is clearly different from Example 1. In Example 1, the specific wear amount at 800 ° C. was 2.3 × 10 ⁻⁵ mm ³ / Nm, showing excellent wear resistance.

[0028]

[Table 1] Temperature (℃) Room temperature 200 400 600 800 1000 Example 1 0.37 0.35 0.32 0.28 0.26 0.27 Comparative example 0.55 0.58 0.45 0.31 0.29 0.30

Example 2 Alumina powder and a mixed powder similar to that of Example 1 were filled in a graphite mold in a laminated state, and sintered at 1300 ° C.-70 MPa-5 min by an SPS apparatus.
After polishing, the alumina layer forming the substrate has a thickness of about 5.5.
mm, BaCrO ₄ -50 vol% Al ₂ O ₃ is about 0.3 mm.
Two-layer test pieces having a thickness of 5 mm were prepared. The coefficient of friction shown in Table 2 was lower than that of the single-layer sintered body of Example 1 at each temperature, and the effect of the hard substrate was recognized. The effect of the substrate was also observed in the comparative example of the two-layer sintered body having the same composition prepared from the uniform fine mixed powder, but the coefficient of friction at 400 ° C. or less was 0.4.
Above is clearly inferior to Example 2. Also,
The specific wear amount at 800 ° C. of Example 2 was 5.2 × 10
^{At −6} mm ³ / Nm, the wear resistance is also improved due to the effect of the hard substrate.

[0030]

[Table 2] Temperature (° C) Room temperature 200 400 600 800 1000 Example 2 0.35 0.33 0.30 0.27 0.26 0.26 Comparative example 0.52 0.55 0.41 0.30 0.28 0.29

Example 3 The same test piece as in Example 2 was heat-treated at 1000 ° C. in the air for 6 hours, and then subjected to a friction test. As shown in Table 3, the friction coefficient was smaller at each temperature than when the heat treatment in Table 2 was not performed.
When the temperature is 0.3 or less in the entire temperature range, the effect of the heat treatment is remarkably recognized. Although the comparative example in which the fine powder was uniformly mixed also had an effect of heat treatment, the friction coefficient was not as high as that of Example 3 in general, and a large difference was observed particularly in a low temperature region of 400 ° C. or lower. The specific wear of the heat-treated sample was at the same level as that of the sample without heat treatment.

[0032]

[Table 3] Temperature (℃) 25 200 400 600 800 1000 Example 3 0.28 0.28 0.26 0.25 0.21 0.22 Comparative Example 0.48 0.47 0.38 0.28 0.27 0.27

Example 4 BaCrO ₄ -50 vol%
The same two-layer sintered body as in Example 2 in which the particle diameter of the raw material powder of Al ₂ O ₃ was changed was subjected to a heat treatment at 1000 ° C. for 6 hours in the air. Table 4 shows the particle size of the coarse particles in the sintered body and the friction coefficient at each temperature. All the samples had a coefficient of friction of 0.4 or less over the entire temperature range, but the coefficient of friction when using coarse particles in the range of 0.49 to 2.13 μm was 0.3 or less, which was particularly excellent. Was.

[0034]

[Table 4] Raw material particle size Coarse particle size Friction coefficient (mm) (mm) Room temperature 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ 0.03-0.06 0.02-0.06 0.38 0.40 0.36 0.32 0.27 0.27 0.10-0.20 0.08-0.21 0.35 0.37 0.30 0.28 0.25 0.26 0.50-0.60 0.49-0.62 0.30 0.30 0.28 0.26 0.24 0.25 0.71-0.85 0.66-0.87 0.28 0.28 0.27 0.25 0.21 0.23 1.18-1.40 1.04-1.44 0.25 0.25 0.24 0.23 0.20 0.22 1.70-2.00 1.58-2.13 0.28 0.25 0.25 0.20 0.18 0.17 2.36-2.80 2.10-2.95 0.31 0.33 0.29 0.27 0.25 0.24

Example 5 The same BaCrO ₄ -50v as in Example 2 was obtained by using two or more kinds of raw material powders having different particle diameters.
ol% Al ₂ O _{3, and} a two-layer sintered body
Heat treatment was performed at 0 ° C. for 6 hours. The powder of each particle size was made equal. The raw material particle diameter and the coarse particle diameter corresponded in the same manner as in Example 4. Table 5 shows the friction coefficients of various samples. It was found that even when two or more powders having different particle size ranges were mixed, a low friction coefficient was obtained in all temperature regions.

[0036]

[Table 5] Raw material particle size (mm) 25 ℃ 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ 0.01-0.25, 0.43-0.60 0.34 0.32 0.30 0.27 0.26 0.27 0.71-0.85, 0.43-0.60 0.32 0.32 0.29 0.26 0.24 0.26 0.85 -1.00,0.60-0.71 0.28 0.28 0.26 0.23 0.20 0.22 1.18-1.40,0.71-0.85 0.25 0.21 0.20 0.20 0.18 0.19 1.70-2.00,0.85-1.00,0.25-0.43 0.30 0.28 0.26 0.24 0.22 0.24

[Embodiment 6] In Embodiment 5, the particle diameters of BaCrO ₄ and Al ₂ O ₃ are the same.
Then, samples were prepared in the case where the particle diameters of both powders were changed, and in the case where fine powder having a particle diameter of 0.03 mm or less was used as one of the powders. The sample configuration was a two-layer sintered body similar to that of Example 2, and heat treatment was performed in the air at 1000 ° C. for 6 hours. The particle size of the coarse particles corresponded to the particle size of the raw material powder as in Example 4. Table 6 shows the friction coefficient of each sample. BaC
Even if the particle sizes of rO ₄ and Al ₂ O ₃ are different,
When a fine BaCrO ₄ powder of 2 mm or less is used,
When this is mixed with coarse-grained Al ₂ O ₃ powder, 0.1% is added to the sintered body.
A fine BaCrO ₄ aggregate of at least 02 mm is generated,
It has been found that a low coefficient of friction can be obtained.

[0038]

[Table 6] Raw material particle size (mm) Friction coefficient BaCrO ₄ Al ₂ O ₃ 25 ° C 200 ° C 400 ° C 600 ° C 800 ° C 1000 ° C 0.43-0.71 0.25-0.43 0.30 0.29 0.27 0.24 0.22 0.22 1.00-1.70 0.71-1.00 0.32 0.30 0.28 0.26 0.22 0.20 1.00-1.18 <0.02 0.33 0.31 0.28 0.27 0.26 0.28 <0.02 1.00-1.18 0.30 0.31 0.25 0.21 0.22 0.24

Example 7 0.85-1.0 mm Ba
BaCrO ₄ -AlO uniformly mixed with coarse powder of CrO _{4
3 The} powder is mixed so that coarse powder is not crushed,
A sintered body of O ₄ -50 vol% Al ₂ O ₃ was produced. The sample had a two-layer structure, and after polishing, was heat-treated at 1000 ° C. for 6 hours in the air. Table 7 shows the friction coefficient of the sample in which the ratio of the coarse powder was changed. In BaCrO ₄ coarse powder 10 vol%, but the friction coefficient of below 400 ℃ exceeds 0.4, equal to or greater than 20 vol%, the remainder be used homogeneous powder mixture to around 1000 ° C. from room It was confirmed that the coefficient of friction was 0.4 or less in the entire temperature range.

[0040]

[Table 7] Amount of coarse powder Friction coefficient (vol%) Room temperature 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ 10 0.43 0.44 0.42 0.38 0.30 0.27 20 0.38 0.37 0.31 0.28 0.27 0.27 30 0.36 0.35 0.30 0.27 0.25 0.26

Example 8 A two-layer sintered body similar to that of Example 2 in which the composition of BaCrO ₄ —Al ₂ O ₃ was changed using a raw material powder of 0.71 to 0.85 mm, 1000
Heat treatment was performed at -6 ° C for 6 hours. Table 8 shows the friction coefficients of various samples. When BaCrO ₄ was 10 vol%, the coefficient of friction exceeded 0.4 at many temperatures, but at 15 vol% or more, it was 0.4 or less in the entire temperature range. In addition, BaC
When the amount of rO ₄ exceeds 70% by volume, the friction coefficient increases and the friction increases. As a result, the friction coefficient tends to be unstable.

[0042]

[Table 8] BaCrO ₄ coefficient of friction (vol%) 25 ° C 200 ° C 400 ° C 600 ° C 800 ° C 1000 ° C 10 0.55 0.55 0.51 0.48 0.40 0.38 15 0.40 0.38 0.36 0.30 0.25 0.24 20 0.31 0.32 0.27 0.24 0.24 0.22 30 0.29 0.27 0.25 0.24 0.22 0.21 60 0.28 0.26 0.24 0.24 0.21 0.21 70 0.30 0.30 0.28 0.28 0.26 0.26 80 0.36 0.34 0.32 0.30 0.28 0.27

Example 9 The same BaCrO ₄ -50 vo as in Example 2 was obtained using a raw material powder of 0.85 to 0.1 mm.
A two-layer sintered body of 1% Al ₂ O ₃ was prepared and heat-treated in the air under various conditions. Table 9 shows the friction coefficients of various samples. In the heat treatment for 3 hours, the color of the sample and the coefficient of friction hardly changed at 400 ° C. as compared with the untreated product.
At 600 ° C. or higher, the color changed from green to yellow, and a remarkable decrease in the coefficient of friction was observed. The higher the heat treatment temperature, the greater the effect. The heat treatment at 1000 ° C. had a remarkable effect even for one hour, but the longer the heat treatment time, the more the friction coefficient in the low temperature region was further improved.

[0044]

[Table 9] Heat treatment conditions Friction coefficient Room temperature 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ No heat treatment 0.36 0.35 0.30 0.26 0.24 0.26 400 ℃ -3 hours 0.35 0.34 0.30 0.26 0.25 0.25 600 ℃ -3 hours 0.31 0.30 0.30 0.26 0.24 0.23 800 ° C-3 hours 0.28 0.27 0.27 0.25 0.22 0.23 1000 ° C-3 hours 0.26 0.27 0.26 0.25 0.22 0.22 1200 ° C-3 hours 0.25 0.26 0.25 0.23 0.20 0.20 1000 ° C-1 hour 0.28 0.28 0.27 0.24 0.21 0.22 1000 ° C-6 hours 0.25 0.25 0.25 0.25 0.22 0.21 1000 ° C-9 hours 0.25 0.25 0.24 0.23 0.20 0.21

Example 10 The self-lubricating layer contained 0.71
Various kinds of A to G in Table 10 were used using 1.00 mm powder.
Layer samples were prepared. The thickness after polishing is about 0.5 mm for the self-lubricating layer and about 5.5 mm for the substrate. Table 11 shows the friction coefficient and the specific wear rate at 800 ° C. of these samples.

[0046]

TABLE 10 Symbol self-lubricating layer (vol%) substrate _{A 50BaCr 2 O 4 -50Al 2 O} 3 Al 2 O 3 B 50Cr 2 O 3 -50Al 2 O 3 Al 2 O 3 C 25BaCrO 4 -25BaCr 2 O 4 - _{50Al 2 O 3 Al 2 O 3} D 25BaCrO 4 -25Cr 2 O 3 -50Al 2 O 3 Al 2 O 3 E 50BaTiO 3 -50Al 2 O 3 Al 2 O 3 F 50BaZrO 3 -50Al 2 O 3 Al 2 O 3 G 50 (50 mol% Cr ₂ O ₃ -50 mol% BaO) -50 AlO ₃ Al ₂ O ₃

[0047]

[Table 11] Friction coefficient Symbol 25 ℃ 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ A 0.38 0.31 0.25 0.25 0.26 0.26 B 0.39 0.40 0.38 0.35 0.36 0.36 C 0.33 0.29 0.28 0.29 0.27 0.20 D 0.33 0.25 0.26 0.26 0.27 0.30 E 0.40 0.37 0.35 0.36 0.28 0.30 F 0.38 0.38 0.36 0.34 0.32 0.28 G 0.35 0.32 0.28 0.28 0.27 0.26

[Example 11] For a two-layer sample, a multilayer sample as shown in Table 12 was prepared for a sample in which cracks were generated or a self-lubricating layer was peeled off. ZrO ₂ is 3 mol% Y ₂ O ₃
Of partially stabilized zirconia was used. Powder having a particle size of 0.85 to 1.00 mm was used for the self-lubricating layer on the surface. In these multilayer sintered bodies, cracks and peeling were prevented as a result of the stress being alleviated by the intermediate layer. Table 13 shows the friction coefficient of each sample.

[0049]

[Table 12] Symbol Sample composition (composition is vol%) A (BaCrO ₄ -50ZrO ₂ ) /0.5mm- (BaCr ₂ O ₄ -75ZrO ₂ ) /0.2mm-
ZrO ₂ /5.5mm B (BaCrO ₄ -30ZrO ₂ ) /0.5mm- (BaCrO ₄ -50ZrO ₂ ) /0.2mm-
(BaCrO ₄ -75ZrO ₂ ) /0.2mm-ZrO ₂ C (BaZrO ₃ -50ZrO ₂ ) /0.5mm- (BaZrO ₃ -75ZrO ₂ ) /0.2mm-Z
rO ₂ /5.5mm

[0050]

[Table 13] Symbol Friction coefficient Room temperature 200 ℃ 400 ℃ 600 ℃ 800 ℃ 1000 ℃ A 0.35 0.35 0.32 0.31 0.30 0.30 B 0.30 0.28 0.27 0.26 0.07 0.28 C 0.37 0.35 0.30 0.28 0.29 0.30

[0051]

According to the self-lubricating ceramics of the present invention described in detail above, a novel self-lubricating property exhibiting a low friction coefficient and high wear resistance stably even in an oxidizing atmosphere from a low temperature range to a high temperature range. Ceramics can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-11559 (JP, A) JP-A-62-21755 (JP, A) JP-A-61-36173 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C04B 35/00-35/22 C04B 35/42 C04B 35/46-35/493

Claims (9)

(57) [Claims] 1. A method according to claim 1, wherein BaCrO ₄ , BaCr ₂ O ₄ , BaZr
O ₃ , BaTiO ₃ , Cr ₂ O ₃ , BaO, CaZrO
One or two selected from group A of ₃ and CaCrO ₄
15 to 80 vol% of at least one kind of self-lubricating oxide;
one or two selected from the group B of l ₂ O ₃ , partially stabilized zirconia, oxides containing Cr ₂ O ₃ , nitrides containing Si ₃ N ₄ , carbides containing SiC, and sialon
It is composed of sintered ceramics containing 85% to 20% by volume of at least one kind of hard ceramic material. It contains at least 15 vol% or more of coarse particles composed of single-phase particles or aggregates of single-phase particles of the self-lubricating oxide of the above-mentioned A group, which is 0.02 to 3.0 mm.
Self-lubricating ceramics characterized by the following. 2. BaCrO ₄ , BaCr ₂ O ₄ , BaZr
O ₃ , BaTiO ₃ , Cr ₂ O ₃ , BaO, CaZrO
One or two selected from group A of ₃ and CaCrO ₄
15 to 80 vol% of at least one kind of self-lubricating oxide;
one or two selected from the group B of l ₂ O ₃ , partially stabilized zirconia, oxides containing Cr ₂ O ₃ , nitrides containing Si ₃ N ₄ , carbides containing SiC, and sialon
It is made of sintered ceramics containing 85 to 20 vol% of at least one kind of hard ceramic material, and has a cross section of 400 μm in which the structure in the ceramic layer on the friction surface side is given as a minimum and maximum average value in a plane parallel to the friction surface coarse particles comprising an aggregate of single-phase particles or single-phase particles of self-lubricating oxide of the group a is where the ^{2 ~9mm 2,} comprising at least 15 vol% or more, self-lubricating ceramic, characterized in that. 3. The self-lubricating oxide of Group A contains 20 to 60 vol.
1%, and the hard ceramic material of group B is 80 to 40 v
3. The self-lubricating ceramic according to claim 1, wherein the content is ol%. 4. The coarse particles of the self-lubricating oxide of Group A on the friction surface side have a particle size of 0.5 to 2.0 mm and an amount of 2 to 2.
The self-lubricating ceramic according to claim 1, wherein the content is 0 vol% or more. 5. The self-lubricating ceramic according to claim 1, wherein the structure of the ceramic layer on the friction surface side is such that the coarse particles of the self-lubricating oxide of Group A are the remainder. A self-lubricating ceramic, comprising: the same or less than B group particles or mixed particles of A group and B group. 6. The self-lubricating ceramic according to claim 1, wherein the ceramic layer on the friction surface side comprises a substrate made of one or more hard ceramic materials selected from Group B. A self-lubricating ceramic formed by simultaneous sintering to form a two-layer structure. 7. The self-lubricating ceramic according to claim 6, wherein a stress relaxation layer having an intermediate composition between the two is interposed between the ceramic layer and the substrate, and these are simultaneously sintered. Self-lubricating ceramics. 8. The method according to claim 1, wherein the amount of oxygen reduced during sintering is restored to a level substantially near the stoichiometric value by heat-treating the sintered body of self-lubricating ceramics in the air. Self-lubricating ceramics according to any of the above. 9. The self-lubricating oxide is BaCrO ₄ , BaC
1 or 2, self-lubricating ceramic according to any one of claims 1 to 8 hard ceramic material is Al ₂ O ₃ is selected from the r ₂ O _4.