JPH06234564A - Low friction ceramics, sliding parts and wear resistant parts made of the same and their production - Google Patents

Abstract

PURPOSE:To produce low friction ceramics having a low coefft. of friction and high strength. CONSTITUTION:An Fe-O compd. is dispersed in Si-contg. nonoxide ceramics as a matrix phase. When the resulting ceramics is fired in a nitrogen atmosphere, a reduction reaction takes place and the Fe-O compd. turns into an Fe-Si compd. The fired ceramics is heated in the air to convert the Fe-Si compd. in at least a part near the surface into the Fe-O compd. and a low friction and high strength structure is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to low-friction ceramics, sliding parts and wear-resistant parts made of the same, and methods for manufacturing them.

[0002]

2. Description of the Related Art Conventionally, silicon carbide SiC, boron nitride BN
Those that reduce the coefficient of friction is dispersed in a silicon nitride Si ₃ N _4, for example, disclosed in JP-A-59-30769. Further, silicon nitride Si ₃ N ₄ to which an oxide of iron Fe such as Fe ₃ O ₄ is added as a sintering aid is
For example, JP-A-58-64268 and JP-A-59-
It is disclosed in JP-A-88374 and JP-A-61-72685.

Further, among engine parts, iron-based metallic materials have been conventionally used for sliding parts such as cylinder liners and piston rings. Further, in order to improve the wear resistance of these sliding parts, there is also one manufactured using silicon nitride Si ₃ N ₄ .

Further, among engine parts, as rocker arms, rocker arm seats, tappets, cams, push rod cams and other wear resistant parts used in rocker arm type valve trains, they are superior in wear resistance to metals. As a material, partially stabilized zirconia, Al ₂ O ₃ , Y ₂ O
Si ₃ N ₄ added with a metal oxide such as ₃ as a sintering aid
It has been developed to use ceramic materials such as.

[0005]

By the way, ceramics made of silicon nitride are desired to have a low coefficient of friction. Generally, in Si ₃ N ₄ , silicon carbide,
When particles of boron nitride or oxide are dispersed,
Poor reactivity at the bond interface reduces the strength of the material itself. Further, in a material containing boron nitride, that portion may be oxidized at a high temperature to change the crystal structure and increase the friction coefficient. As disclosed in the above publication, when a metal oxide such as Fe ₃ O ₄ is added as a sintering aid, the addition amount is small and low friction characteristics cannot be obtained.

Further, ceramics do not necessarily have low frictional properties in the boundary lubrication region, and a material containing boron nitride forms boron oxide at 600 ° C. or higher, which causes a change in crystal structure. There is a problem that the coefficient increases.

Further, in a composite of Si ₃ N ₄ and an oxide of iron Fe, a reduction reaction occurs during firing, and FeO, Fe ₂ O
Even if added in the form of ₃ , ₃ Fe ₃ O ₄ in the mixing stage, it changes into a Fe—Si-based compound after firing. Such compounds are also excellent in the adsorptivity with the lubricating oil, but in order to further improve the adsorptivity and lower the friction, it is desirable to leave them in the oxide state.

By the way, the iron-based metallic material is much worn and inferior in durability as compared with ceramics. Further, as sliding parts, phenomena such as adhesion and seizure occur in metal materials under high temperature and low lubricating oil viscosity lubrication conditions. Therefore, it has been attempted to use ceramics such as Si ₃ N ₄ in place of the metal material in the production of sliding parts. Although ceramics such as Si ₃ N ₄ have excellent wear resistance, Materials with lower friction are desired.

When a wear-resistant part is made of partially stabilized zirconia, the wear amount of the wear-resistant part itself is reduced, but the wear of the part made of the mating metal material in combination with the wear-resistant part is reduced. Occurs. In addition, when a wear resistant part made of a ceramic material such as Si ₃ N ₄ to which a metal oxide such as Al ₂ O ₃ or Y ₂ O ₃ is added as a sintering aid is used in a high temperature range, The friction coefficient and the amount of wear of the wear parts increase, and the characteristics of the wear parts deteriorate significantly.

Therefore, an object of the present invention is to solve the above-mentioned problems, and FeO, Fe ₂ O ₃ , Fe ₃ O _4, etc. are contained in a matrix phase containing Si ₃ N ₄ or SiC as a main component. Fe oxide which was present as a compound was dispersed by oxidizing the Fe oxide of
Fe- which is excellent in adsorbing an e-Si compound with oil
It is an object of the present invention to provide a low-friction ceramic that reduces friction by changing to an O-based oxide and a method for producing the same.

Another object of the present invention is that a ceramic containing Si as a main component is used as a mother phase, Fe compounds are dispersed in the mother phase, and pores are filled with a solid lubricant. It is an object of the present invention to provide a low-friction ceramic which is excellent in the adsorptivity of the above, and has a low friction in the boundary lubrication region by the action of the solid lubricant, and a method for producing the same.

Still another object of the present invention is to use a ZrO ₂ or Al ₂ O ₃ oxide ceramics as a mother phase, in which a compound consisting of Fe—O is dispersed at least on the surface of the mother phase. Accordingly, it is an object of the present invention to provide a low-friction ceramic that reduces friction and a method for producing the same.

Another object of the present invention is FeO, Fe ₂ O.
_A predetermined amount of Fe oxide such as ₃ , Fe ₃ O ₄ is added and dispersed in the Si ₃ N ₄ mother phase, and the sintering conditions and the particle size of the added oxide should be optimized. By Si ₃
It is an object of the present invention to provide a low-friction ceramic having a small amount of meshing with a mating agent at the time of sliding because the N ₄ crystal grains are fine and uniform, and having low friction and high strength, and a method for producing the same.

Still another object of the present invention is to use conventional Si ₃
Provided is a low-friction ceramic having a lower friction coefficient and excellent wear resistance as compared with N ₄ ceramics, and by using the low-friction ceramic, sliding parts such as a cylinder liner and a piston ring used even under severe sliding conditions can be provided. It is an object of the present invention to provide a sliding part made of low friction ceramics which is manufactured and improves engine performance, and a manufacturing method thereof.

Another object of the present invention is the conventional Si ₃ N ₄
We provide low-friction ceramics that have a lower coefficient of friction and superior wear resistance compared to ceramics, and use these low-friction ceramics to manufacture engine valve train parts such as rocker arms, rocker arm seats, tappets, cams, etc. Wear-resistant parts made of low-friction ceramics that can improve durability and exhibit preferable performance when lubricating oil such as an engine has a high temperature or when the viscosity of lubricating oil is reduced to reduce friction, It is to provide a manufacturing method.

[0016]

In order to achieve the above object, the present invention is configured as follows. That is,
In the present invention, a ceramic different from a compound composed of Fe-O is used as a mother phase, and Fe- is formed on at least the surface of the mother phase.
The present invention relates to a low-friction ceramic having a compound of O dispersed therein.

In this low friction ceramic,
The mother phase of the ceramic is an oxide ceramic,
In particular, it is ZrO ₂ or Al ₂ O ₃ . And the F
The size of the compound of e is 10 μm or less,
The above compound is contained in an amount of 5 wt% or more in terms of FeO, Fe ₂ O ₃ , and Fe ₃ O ₄ .

Alternatively, in this low-friction ceramic, the mother phase of the ceramic is a ceramic containing Si as a main component, and particularly any one of Si ₃ N ₄ , SiC and a composite thereof. The size of the Fe compound is 10 μm or less, and the Fe compound is 5 wt% when converted to FeO, Fe ₂ O ₃ , and Fe ₃ O _4.
The above is included.

Further, in this low friction ceramic,
A Fe compound is dispersed in a matrix of a non-oxide ceramic containing Si, and pores are filled with a solid lubricant,
In particular, the solid lubricant is graphite or a composite based on it. Non-oxide ceramics containing Si include SiC, Si ₃ N ₄ , SiC and Si ₃ N _4.
And composite materials, Si-Al-O-N (sialon), Si
There is -ON.

Alternatively, the present invention relates to a low friction ceramic which is characterized in that a Si ₃ N ₄ ceramic is used as a mother phase and an Fe-Si compound is dispersed therein. In addition, in this low friction ceramic, the Si ₃ N ₄
Has a maximum crystal grain size of 20 μm or less,
The size of the compound is 10 μm or less.

Further, according to the present invention, an oxide of Fe is added to a non-oxide ceramic containing Si, mixed with distilled water and a binder, and the mixture is granulated to form a raw material, thereby forming a compact. Production of a low-friction ceramics characterized by producing, firing the molded body in a nitrogen atmosphere to produce a fired body, and then heating the fired body in the atmosphere to oxidize a portion of the Fe compound. Regarding the method. Further, in this method for producing low-friction ceramics, the heating temperature of the fired body in the atmosphere is 800 ° C. or higher.

Alternatively, according to the present invention, an oxide of Fe is added to Si ₃ N ₄ ceramics and mixed with methanol and a binder, and the mixture is granulated to form a raw material to prepare a compact, The present invention relates to a method for producing a low-friction ceramic, which comprises degreasing and then firing in a nitrogen atmosphere at a one-stage holding temperature and then at a maximum holding temperature to produce a Si ₃ N ₄ fired body. Moreover, in this method for producing low-friction ceramics, the particle size of the Fe oxide is 10 μm or less, and the firing temperature is 1400 ° C.
2100 ° C., in particular, the first stage holding temperature of the firing temperature is 1450 ° C. to 1750 ° C., and the maximum holding temperature is 1750 ° C. to 2000 ° C.

Alternatively, the present invention relates to a sliding component made of low-friction ceramics in which Fe-Si compound is dispersed with silicon nitride ceramics as a mother phase.

In addition, a cylinder liner is produced in the sliding component made of this low friction ceramics.

In the sliding parts made of this low friction ceramic, particularly in the case of the cylinder liner, the Fe--Si compound is FeO, Fe ₂ O ₃ , Fe ₃ O ₄
It is contained in an amount of 5 to 40 wt%.

A piston ring is produced in the sliding component made of the low friction ceramics.

In the sliding component made of this low friction ceramic, particularly in the case of a piston ring, the Fe--Si compound is FeO, Fe ₂ O ₃ , Fe ₃ O ₄
It is contained in an amount of 5 to 20 wt%.

Alternatively, according to the present invention, an oxide of Fe is added to a raw material powder containing silicon nitride ceramics as a main component, and the mixture is mixed with methanol and a binder, and the mixture is granulated to form a raw material, which is then formed into a compact. Is manufactured, and the molded body is degreased and then heated and fired at a maximum temperature of 1850 ° C. in a nitrogen gas atmosphere to form a dense sintered body.

Alternatively, the present invention is characterized in that a non-oxide ceramic containing Si is used as a mother phase, in which at least one kind of Fe or its oxide or silicide compound is dispersed. The present invention relates to wear-resistant parts made of low friction ceramics.

Further, in the wear resistant component made of this low friction ceramic, the non-oxide ceramic containing Si is either Si ₃ N ₄ or SiC.

Further, in the wear resistant component made of this low friction ceramic, the size of Fe or its compound contained in the ceramic is 10 μm or less.

Further, in the wear resistant component made of this low friction ceramic, Fe or its compound contained in the above ceramic is contained in an amount of 5 to 25 wt% in terms of oxide.

Further, in the wear resistant component made of this low friction ceramic, the four-point bending strength of the ceramic is 750 MPa or more.

In addition, in this wear resistant part made of low friction ceramics, engine valve system parts such as rocker arm seats, cams and tappets are manufactured.

Alternatively, according to the present invention, an oxide of Fe is added to a raw material powder containing silicon nitride ceramics as a main component, and the mixture is mixed with methanol and a binder, and the mixture is granulated to preform a raw material, which is then subjected to intermediate molding. A molded body is manufactured, the intermediate molded body is molded by CIP to form a molded body, and the molded body is degreased at 2000 ° C. in a nitrogen gas atmosphere.
The present invention relates to a method for manufacturing wear-resistant parts made of low-friction ceramics, which comprises heating and firing to form a dense sintered body.

[0036]

The low friction ceramics and the method for producing the same according to the present invention are configured as described above and operate as follows. That is, in the low-friction ceramics, the compound consisting of Fe-O is dispersed at least on the surface of the ceramics, which is different from this, as the mother phase, so that Fe-
The compound consisting of O and the interface between it and the mother phase serve as active points and have excellent adsorptivity with oil, so that the composite ceramic has low friction, and grain growth is suppressed, resulting in high strength. Like Further, when the mother phase of the ceramic is made of oxide ceramics such as ZrO ₂ , it is possible to perform firing in normal air, but the mother phase of the ceramic is non-oxidized such as Si ₃ N ₄ and SiC. In the case of physical ceramics, a reduction reaction occurs during firing in a nitrogen N ₂ atmosphere, so that it changes to a Fe—Si compound. Therefore, by performing heat treatment in an atmosphere containing oxygen after firing, that is, in the atmosphere, at least Fe near the surface is heated.
The compound of -Si is converted into a Fe-O oxide having a good adsorption property to oil, thereby forming a structure having low friction and high strength.

Further, this low friction ceramic is Fe
Fe oxide such as O, Fe ₂ O ₃ and Fe ₃ O ₄ is added as a raw material in a predetermined amount in the mother phase of the ceramic, that is, 5 wt.
% To 40 wt% makes it possible to obtain a composite ceramic material of a ceramic and an iron compound, which has good adsorbability with oil and has a low friction coefficient and high strength.

Further, the sliding parts made of the low friction ceramics according to the present invention have a low friction coefficient even when the lubricating oil viscosity is low because the Fe-Si compound is dispersed with the silicon nitride ceramics as the mother phase. And has excellent wear resistance. In particular, the Si ₃ N ₄ sliding parts containing 5 to 40 wt% of iron oxide are excellent in the above characteristics. Therefore, when the sliding parts of the engine such as the cylinder liner and the piston ring are manufactured, the engine performance can be improved.

The wear-resistant component made of the low-friction ceramic according to the present invention has a non-oxide ceramic containing Si as a mother phase, in which at least one of Fe, or an oxide or a silicide thereof is contained. Since the above is dispersed, compared to conventional Si ₃ N ₄ ceramics,
Even in a high temperature range of 150 ° C. or higher, the friction property and the wear property can be improved, and moreover, the mechanical property is equivalent to that of the conventional Si ₃ N ₄ ceramics.

[0040]

Embodiments of the low friction ceramics and the manufacturing method thereof according to the present invention will be described below with reference to the drawings.
First, an embodiment of the low friction ceramics and the method for producing the same according to the present invention will be described as a first embodiment. In the manufacturing method of Example 1 The low-friction ceramic, firstly, the _{Si 3 N 4, Al 2 O} 3 and Y ₂ O ₃ is incorporated in the following ratios. Si ₃ N ₄ : Al ₂ O ₃ : Y ₂ O ₃ =
It is mixed in a ratio of 90: 5: 5. With respect to this total amount, three types of Fe oxides, namely FeO, Fe ₂ O ₃ , Fe ₃ O ₄
Was mixed with distilled water and a binder in a ball mill for about 24 hours to prepare a mixture, and the mixture was granulated by a spray dryer to prepare granules.

Then, these granulated granules are
After preforming in a mold with internal dimensions of 25 × 20 × 100 mm, the preform is approximately 2000 kgf by CIP.
Various rectangular parallelepiped molded bodies were obtained by the pressure of / cm ² .
After degreasing these shaped bodies, these degreased shaped bodies were heated and fired to a maximum temperature of 1850 ° C. in a N ₂ atmosphere of 9.3 MPa to obtain many dense sintered bodies. The sintered body in this state is used as a comparative test piece.

Next, these sintered bodies were subjected to 40
Oxidation was carried out by holding each temperature of 0 ° C., 800 ° C., 1000 ° C. and 1200 ° C. for 6 hours. These sintered bodies produced through the above steps were ground and polished to perform a sliding test, and various rectangular parallelepiped sliding test pieces were produced as sliding test pieces of 16 × 10 × 70 mm. . A silicon nitride Si ₃ N ₄ sintered body having a relative density of 99% or more was prepared as a mating member, that is, a mating sliding test piece for performing a sliding test on these sintered bodies. A pin was produced in which the end surface of the test piece was a spherical surface having a curvature radius of 45 mm.

Then, on one surface of the rectangular parallelepiped sliding test piece,
Set the pins of the mating sliding test piece so that they are almost vertical, load 3.0 kgf, temperature 150 ° C, sliding speed 1.0
The friction coefficient was measured under the sliding test condition of m / s. At the time of this sliding test, a synthetic oil having excellent heat resistance was used as a lubricating oil. FIG. 1 shows changes in the friction coefficient when the oxidation temperature in the atmosphere was changed as described above.
FIG. 1 is a graph showing the relationship between the friction coefficient and the processing temperature in the atmosphere in the manufacturing process of this low-friction ceramic. As can be seen from FIG. 1, it was confirmed that the oxidation temperature in the atmosphere tended to decrease the friction coefficient from around 800 ° C.

Further, the oxidation temperature in the atmosphere is 1000
When a rectangular parallelepiped sliding test piece at ℃ was identified by X-ray microanalysis method, the phase existing therein was found to be changed from the original Fe-Si to a compound composed of Fe-O. Further, after heating the rectangular parallelepiped sliding test piece and the comparative test piece before oxidation to 150 ° C.,
When one drop of lubricating oil was dripped on their surface and the spread, that is, the contact angle was observed, the sample after oxidation had a larger spread, that is, a smaller contact angle, than the original material. Is superior to the original compound in the adsorptivity with the lubricating oil.

Further, a rectangular parallelepiped sliding test piece having an oxidation temperature of 1000 ° C. in the atmosphere produced by the above-mentioned manufacturing method was cut to prepare a large number of 4-point bending strength test pieces, and the strength was measured according to JIS standard. On average, 4-point bending strength 896
It was found that the sample had sufficient strength such as MPa and Weibull coefficient of 18.3 (the number of test pieces was 30). Further, FIG. 2 shows the results of measuring the friction coefficient under each condition, with the horizontal axis representing the parameters summarizing the load, speed, and viscosity of the lubricating oil of the sliding test piece. FIG. 2 is a graph showing the relationship of the friction coefficient with respect to the parameters of load, speed and lubricating oil viscosity with respect to the amount of iron oxide added to this low friction ceramic. In FIG. 2, when the load is F, the speed is V, and the viscosity of the lubricating oil is η, the parameter P is as follows. P = log (η × V / F). The unit of P is as follows. The unit of P is [× 10 ^-6 · (m ² /
S) · (m / S) / kgf]. As can be seen from FIG. 2, the oxidation-treated rectangular parallelepiped sliding test piece is more effective in reducing friction in the mixed to boundary lubrication region than the as-nitrided test piece.

Another embodiment of the low friction ceramics and the manufacturing method thereof according to the present invention will be described as a second embodiment. Example 2 In this method for producing low-friction ceramics, silicon carbide powder, boron as a sintering aid, and Fe
10 wt% of ₃ O ₄ is blended. Double the amount of distilled water was added thereto, and the mixture was mixed in the same manner as in Example 1 to prepare a mixture.
The mixture was granulated with a spray dryer to form granules. Then, a sintered body was prepared under the same conditions as in Example 1 to prepare a test piece. In this manufacturing process, the load was 3.0 kgf and the oxidizing condition was 1000 ° C. in the air for 6 hours. When the sliding characteristics and strength of these test pieces were measured, the following results were obtained. That is, the test piece of the oxidized sintered body had a friction coefficient of 0.016 and a four-point bending strength of 482 MPa. On the other hand, the test piece of the sintered body which was not subjected to the oxidation treatment had a friction coefficient of 0.021 and a 4-point bending strength of 47.
It was 8 MPa. The silicon carbide-based sintered body is slightly inferior to the silicon nitride-based sintered body in terms of strength, but even when silicon carbide is used as the matrix, that is, the matrix phase, the effect of oxidizing the sintered body is high. confirmed.

Next, another embodiment of the low friction ceramics according to the present invention will be described as a third embodiment. In the manufacturing method of Example 3 This low friction ceramics, _{Si 3 N 4, Al 2 O} 3 and Y ₂ O ₃ is incorporated in the following ratios. _{Si 3 N 4: Al 2 O} 3: Y 2 O 3 = 90:
Blend at a ratio of 5: 5. 3 types of F for this total amount
The oxide of e, namely FeO, Fe ₂ O ₃ , Fe ₃ O ₄ is 25
wt% was added, and the mixture was mixed with distilled water and a binder in a ball mill for about 24 hours to prepare a mixture, and then the mixture was granulated by a spray dryer to prepare granules.

Then, the granulated particles are
First, after preforming in a mold with an inner size of 25 × 20 × 100 mm, the preform is approximately 1000 by CIP.
Various rectangular parallelepiped compacts were obtained by the pressure of kgf / cm ² . After degreasing these molded bodies, the degreased molded bodies were subjected to a maximum temperature of 180 in a N ₂ atmosphere of 9.3 MPa.
A large number of sintered bodies were obtained by heating and firing to 0 ° C. The sintered body in this state has pores with a size of several tens of microns scattered on its surface.

These sintered bodies produced through the above steps were ground and polished to produce a rectangular parallelepiped sliding test piece as a 16 × 10 × 70 mm sliding test piece.
A graphite powder surface coated with calcium phosphate, a solid lubricant, was placed on top. Then, in order to rub the graphite powder into the pores of the sintered body, an edge-shaped plate having the same width as the plate of the sintered body and a radius of curvature of 10 mm was set to be substantially vertical, and 50
After heating to 0 ° C., it was reciprocated at a speed of 0.5 m / s. By this treatment, the graphite could be rubbed into the pores of the sintered body. It was also confirmed that the graphite solid lubricant used here was stable even at 500 ° C.

As the test piece and the mating material produced in the above steps, a Si ₃ N ₄ sintered body having a relative density of 99% or more and a pin whose end face was a spherical surface having a radius of curvature of 45 mm was produced. The result of the sliding test using the pin is shown in FIG.
FIG. 3 is a graph showing the relationship of the friction coefficient with respect to the load, speed, and parameters of the lubricating oil viscosity with respect to the amount of iron oxide added to this low-friction ceramic. In FIG. 3, the load,
The horizontal axis is a parameter summarizing the speed and the viscosity of the lubricating oil, and the vertical axis is the measured value of the friction coefficient under each condition. FIG. 3 is a graph similar to FIG. As shown in FIG. 3, Si ₃ N ₄ containing iron oxide according to the present invention is added.
The sintered body of is Si ₃ N without addition of iron oxide.
Compared to ₄ , it is effective in lowering friction in the mixed to boundary lubrication region, and compared to materials that do not contain solid lubricant,
It was confirmed that it is advantageous for lowering friction in the boundary lubrication region.

Further, a 4-point bending strength test piece was prepared by cutting out from the test piece used in Example 3 above. The strength of the four-point bending strength test piece was measured and found to be 483 MPa.

Next, another embodiment of the low friction ceramics according to the present invention will be described as a fourth embodiment. [Example 4] In this method for producing low-friction ceramics, silicon carbide powder, boron as a sintering aid, and Fe
25 wt% of ₃ O ₄ is blended. After adding twice the amount of distilled water thereto and mixing in the same manner as in Example 3 to prepare a mixture,
The mixture was granulated with a spray dryer to form granules. Then, a sintered body was prepared under the same conditions as in Example 3 to prepare a test piece. When the sliding characteristics and strength of these test pieces were measured, the following results were obtained. That is, the test piece of the sintered body in which the solid lubricant was rubbed had a boundary lubrication region friction coefficient of 0.18 and a four-point bending strength of 362 MPa. On the other hand, in the test piece of the sintered body in which the solid lubricant was not rubbed in, the friction coefficient in the boundary lubrication region was 0.28, and the four-point bending strength was 345 MPa. It was confirmed that the silicon carbide-based sintered body had a composite effect of containing iron oxide and rubbing the solid lubricant, although it was slightly inferior in strength to the silicon nitride-based sintered body. [Hereafter, this page margin]

Further, still another embodiment of the low friction ceramics and the method for manufacturing the same according to the present invention will be explained as a fifth embodiment. [Example 5] In this method for producing low-friction ceramics, in the production process in Example 3, a sintered body test piece that was oxidized in the atmosphere at 1000 ° C after the above-described degreased molded body was sintered was used. Similarly, a solid lubricant was rubbed into the pores of the sintered body to prepare a sliding test piece. When a sliding test was conducted on the sliding test piece, a reduction in the friction coefficient in the mixed lubrication range was confirmed.

Next, another embodiment of the low friction ceramics and the method for producing the same according to the present invention will be described as a sixth embodiment. [Embodiment 6] In this method for producing low-friction ceramics, as the oxide ceramics, three kinds of iron oxides, that is, FeO and Fe ₂ O ₃ are added to Y ₂ O ₃ and partially stabilized zirconia ZrO ₂ powder. , Fe ₃ O ₄ were added in a predetermined amount and mixed with distilled water and a binder in a ball mill for about 24 hours to prepare a mixture, and then the mixture was granulated by a spray dryer to prepare granules. At this time, the amount of the Fe oxide added was changed variously to form various particles.

Next, these granulated materials were subjected to
After preforming in a mold with internal dimensions of 25 × 20 × 100 mm, the preform is approximately 2000 kgf by CIP.
Various rectangular parallelepiped molded bodies were obtained by the pressure of / cm ² .
The maximum temperature of these molded products is 1650 ° C in the atmosphere.
The mixture was heated and fired to obtain various compact sintered bodies. Then
To perform a sliding test, these sintered bodies were ground and polished to prepare various rectangular parallelepiped sliding test pieces as sliding test pieces of 16 × 10 × 70 mm. As a counterpart member for performing a sliding test of these sintered bodies, that is, a counterpart sliding test piece, a counterpart sliding test piece was made of chill cast iron, and the end surface of the counterpart sliding test piece was curved. Radius 45 mm
A spherical pin was prepared.

Then, on one surface of the rectangular parallelepiped sliding test piece,
Set the pins of the mating sliding test piece so that they are almost vertical, load 1.0 kgf, temperature 150 ° C, sliding speed 1.0
The friction coefficient was measured under the sliding test condition of m / s. At the time of this sliding test, a synthetic oil having excellent heat resistance was used as a lubricating oil. Various iron oxides (Fe _m O _n
That is, FIG. 4 shows the measurement results of the change in the friction coefficient when the oxidation temperature in the atmosphere of oxide ceramics in which the amounts of FeO, Fe ₂ O ₃ and Fe ₃ O ₄ ) added were changed. FIG. 4 is a graph showing the measurement results of the friction coefficient with respect to the addition amount of Fe _m O _n in this low friction ceramic. As can be seen from FIG. 4, it can be confirmed that the friction coefficient of the material in which iron oxide is mixed with ZrO ₂ is lowered by the addition of iron oxide. Addition amount of iron oxide is 10wt% ~
In the range of 30 wt%, the friction coefficient μ is about 0.02
It was as low as 0.01, and it was confirmed that the friction coefficient μ tends to slightly increase when the amount of iron oxide added is more than that. In a composite material containing a large amount of iron oxide added (30 wt% or more), the microstructure observation shows that the additive phase aggregates, and pores remain with it, and these pores are mated when sliding. It is presumed that the friction resistance increased due to the meshing with the material. Further, in FIG. 4, the point _where the addition amount of the iron oxide Fe _m O _n is 0 is a comparative example showing conventional ZrO ₂ .

Next, the ZrO ₂ sliding test piece was subjected to X-ray microanalysis to identify the phases present therein, and it was found that a compound consisting of Fe—O was present. It is presumed that this compound has excellent adsorptivity with the lubricating oil.

Further, the above ZrO ₂ sliding test piece was heated to 150 ° C., one drop of lubricating oil was dropped on the surface of the sliding test piece, and its spread, that is, the contact angle was observed. Compared with the ZrO ₂ material without addition, the sliding test piece of ZrO ₂ compounded with oxide has a larger spread of lubricating oil, that is, a smaller contact angle. Is considered to have improved. Therefore, it is presumed that the decrease in the friction coefficient due to the combination of the iron oxide with the ZrO ₂ ceramics obtained in Example 6 is due to the improvement in the adsorptivity with the lubricating oil.

Next, the ZrO ₂ sliding test piece was cut to prepare a four-point bending test piece, and its strength was measured according to JIS standards. The results shown in FIG. 5 were obtained. . FIG. 5 is a graph showing the average of four-point bending strength with respect to the amount of iron oxide added to this low-friction ceramic. As can be seen from FIG. 5, the strength decreases as the amount of Fe _m O _n added increases. And the addition amount of Fe _m O _n is 3
It was found that up to 0 wt%, the four-point bending strength had sufficient strength, and the strength was equivalent to or higher than that of ZrO ₂ without addition. In addition, in FIG.
amount of _m O _n is is a comparative example showing a conventional ZrO ₂ points 0.

Next, another embodiment of the low friction ceramics and the method for producing the same according to the present invention will be described as a seventh embodiment. [Example 7] In this method for producing low-friction ceramics, aluminum oxide Al was used as the oxide ceramics.
₂ O ₃ as a mother phase, in which iron oxides, namely FeO,
Fe ₂ O ₃ and Fe ₃ O ₄ were added in predetermined amounts, a composite ceramic was produced by the same manufacturing process as in Example 6, and the sliding characteristics and 4-point bending strength of the composite ceramic were measured. Got That is, the one in which iron oxide was not added to Al ₂ O ₃ had a friction coefficient of 0.06 and a four-point bending strength of 420 MPa. On the other hand, Al ₂
Regarding the composite ceramic in which iron oxide is added to O ₃ , the friction coefficient is 0.035 when the iron oxide content is 10 wt%, the four-point bending strength is 396 MPa, and the friction coefficient is 0 when the iron oxide content is 20 wt%. 0.022, the 4-point bending strength is 401 MPa, the friction coefficient is 0.029 when the iron oxide is 30 wt%, and the 4-point bending strength is 356M.
Further, when the iron oxide content was 40 wt%, the friction coefficient was 0.021, and the four-point bending strength was 322 MPa. That is, by adding iron oxide to Al ₂ O ₃ , it was possible to secure high strength and obtain a low friction coefficient.

Next, another embodiment of the low friction ceramics and the method for producing the same according to the present invention will be described as an eighth embodiment. [Embodiment 8] In this low-friction ceramic, the non-oxide ceramic containing Si is Si ₃ N ₄ , and this low-friction ceramic can be produced as follows. In this method for producing low friction ceramics, Si ₃ N ₄ , Al ₂ O ₃ and Y ₂ O ₃ are mixed in the following ratios. Si ₃ N ₄ : Al ₂ O ₃ : Y ₂ O ₃ = 9
It is mixed in a ratio of 0: 5: 5. Particle size 3 for this total amount
Three types of Fe oxides of less than μm, namely FeO and Fe ₂ O
_A predetermined amount of ₃ , Fe ₃ O ₄ was added, and the mixture was mixed with methanol and a binder in a ball mill for about 24 hours to prepare a mixture, and then the mixture was granulated by a spray dryer to prepare granules. At this time, the types of iron oxides were changed to make three types of granules.

Then, these granulated granules were
First, after preforming in a mold having an inner size of 25 × 20 × 100 mm, the preforming body is approximately 2000 by CIP.
Various rectangular parallelepiped compacts were obtained by the pressure of kgf / cm ² . After degreasing these molded bodies, these degreased molded bodies were held at a single stage holding temperature in a N ₂ atmosphere of 9.3 MPa,
Sintered bodies of Si ₃ N ₄ with different firing conditions such as the maximum holding temperature were fired. As a result of observing the structure of these fired bodies, it was found that the size of the crystal grains of Si ₃ N ₄ was different by changing the firing temperature.

These Si ₃ produced through the above steps
In order to perform a sliding test, the N ₄ sintered body was ground and polished to prepare various rectangular parallelepiped sliding test pieces as 16 × 10 × 70 mm test pieces for sliding test. So Si ₃
In order to investigate the relationship between the maximum crystal grain size in the crystal structure of N ₄ and the friction coefficient, as a mating member, that is, a mating sliding test piece,
A Si ₃ N ₄ sintered body having a relative density of 99% or more was produced, and a φ8 × 23 mm pin was produced in which the end surface of the mating sliding test piece was a spherical surface having a radius of curvature of 45 mm.

Then, on one surface of the rectangular parallelepiped sliding test piece,
Set the pins of the mating sliding test piece so that they are almost vertical, load 1.0 kgf, temperature 150 ° C, sliding speed 1.0
The friction coefficient was measured under the sliding test condition of m / s. At the time of this sliding test, a synthetic oil having excellent heat resistance was used as a lubricating oil. Fig. 6 shows the test results of Si ₃ N ₄ .
Shown in. FIG. 6 is a graph showing the relationship between the friction coefficient and the maximum crystal grain size of this low friction ceramic. As can be seen from FIG. 6, it was found that the friction coefficient increases when the maximum crystal grain size exceeds 20 μm. Judging from the fact that the frictional morphology of Si ₃ N ₄ is due to the loss of crystal grains, in the case of Si ₃ N ₄ having a large crystal grain size, the part where the loss of crystal grains occurs becomes a large hole, and these holes are the counterparts. It could be estimated that the friction coefficient would be increased because of meshing with the material. In addition, as a result of observing the structure of the composite ceramics of Si ₃ N ₄ and iron oxide, the first holding temperature is 1500 ° C. to 1750 ° C. under the firing condition that the maximum grain size is 20 μm or less.
And the maximum holding temperature is 1750 ° C to 2000 ° C.
It turned out that Furthermore, when the firing temperature of Si ₃ N ₄ was set to 1400 ° C. or lower or 2100 ° C. or higher, a dense sintered body could not be obtained.

Further, a rectangular parallelepiped sliding test piece manufactured by the manufacturing method of the above-mentioned Example 8 was cut to manufacture a 3 × 4 × 40 four-point bending strength test piece, and its strength was measured. The results shown are obtained. FIG. 7 is a graph showing the relationship between the addition amount of Fe _m O _{n and} the 4-point bending strength of this low friction ceramic. As can be seen from FIG. 7, Fe _m
According to increase the amount of O _n, strength decreases.
Then, Fe _m amount of O _n is 10 wt% 20 wt%
S The 4-point flexural strength test pieces, without the addition of Fe _m O _n
It was found that the strength was equal to or higher than that of i ₃ N ₄ . Further, Fe _m O _n in FIG. 7
The point where the addition amount of is 0 is a comparative example showing conventional Si ₃ N ₄ .

Further, the structure of the sliding test piece in which the amount of Fe _m O _n added was 10 wt% was changed to SEM (Scanning Electron Micr
oscopy) showed that the addition amount of Fe _m O _n was 10
In the wt% sliding test piece, the iron-containing portion had a size of 10 μm or less, did not form a solid solution, and existed in a state in which iron was uniformly dispersed in the Si ₃ N ₄ grain boundaries. It could be confirmed. In addition, the results of analysis using X-ray microanalysis for this phase are shown in FIG. As can be seen from FIG. 8, it was found that the above phase was a Fe—Si compound. Si
Almost no pores were observed in the structure of the composite ceramic of ₃ N ₄ and iron oxide, and the growth of Si ₃ N ₄ crystal particles was suppressed by the presence of iron oxide, resulting in fine and uniform crystal particles. It was speculated that Such a structure is considered to be advantageous for increasing the strength in view of the Griffith relational expression.

As to the sliding test piece in which the amount of Fe _m O _n added was further increased, as shown in FIG. 7, the strength was lowered.
Aggregation of Fe _m O _n was observed, and pores were present at the aggregation. That is, it is considered that as a result of the pores remaining in the sliding test piece, these pores serve as the starting points of the fracture, and the strength of the sliding test piece is reduced.

Then, by the same manufacturing method as in Example 8, 10 w of Fe ₃ O ₄ having a particle size of 5, 7, 10, 15 and 20 μm was used instead of Fe ₃ O _{4 having} a particle size of 3 μm or less.
The t% calcined by adding a Si ₃ N _4, to produce a sintered body test piece of the composite ceramic the top of the Si ₃ N ₄ and the iron oxide.
When the coefficient of friction and the four-point bending strength of these sintered test pieces were measured by the same method as in Example 8, the following results were obtained. That is, the friction coefficient of the sintered body of Fe ₃ O _{4 having} a particle size of 5 μm was 0.0080, and the four-point bending strength was 990 MPa. The friction coefficient of the sintered body of Fe ₃ O _{4 having} a particle size of 7 μm was 0.0085, and the four-point bending strength was 977 MPa. The friction coefficient of the sintered body of Fe ₃ O _{4 having} a particle size of 10 μm was 0.0092, and the four-point bending strength was 921 MPa. The friction coefficient of the sintered body of Fe ₃ O _{4 having} a particle size of 15 μm was 0.016, and the four-point bending strength was 657 MPa. The friction coefficient of the sintered body of Fe ₃ O _{4 having} a particle size of 20 μm was 0.027, and the four-point bending strength was 421 MPa. From this, it was found that Si ₃ N ₄ to which an iron oxide having a particle size of Fe ₃ O ₄ of more than 10 μm was added has a large friction coefficient and a reduced strength. Particle size is 10 μm
When observing the structure of the sintered body containing iron oxides exceeding 1.0, aggregates of oxides are observed in these, and pores remain in them, increasing the friction coefficient due to meshing with the mating material. It is speculated that these pores became the starting point of fracture and caused the strength to decrease.

[Embodiment 9] Next, an embodiment of a sliding component made of low-friction ceramics and a method of manufacturing the same according to the present invention will be described.
As described below. [Example 9] Si ₃ N ₄ , Al ₂ O ₃ , and Y ₂ O ₃ were used as 9
The oxides of iron FeO, Fe ₂ O ₃ , and Fe ₃ O having a particle diameter of 3 μm or less are mixed with the compounding ratio of 0: 5: 5.
₄ was added in a predetermined amount and mixed with methanol and a binder in a ball mill for about 24 hours to prepare a mixture, and then the mixture was granulated by a spray dryer to prepare granules. 25 × 20 × 10 using the granular material as a raw material
After preforming in a mold having 0 mm as the inner size to prepare a preforming body, the preforming body is subjected to CIP to about 2000 k.
A rectangular parallelepiped compact was obtained with a pressing pressure of gf / cm ² . After degreasing the compact, it was heated and fired up to 1850 ° C. in a nitrogen gas N ₂ atmosphere of 9.3 MPa to obtain a dense sintered compact. This sintered body was processed into a slide test plate of 16 × 10 × 65 mm.

On the other hand, a Si ₃ N ₄ sintered body having a relative density of 99% or more was produced as a counterpart material for the sliding test of the sliding test plate. A φ8 × 23 mm pin was used in which the tip surface of the mating material Si ₃ N ₄ sintered body was a spherical surface having a curvature radius of 9 mm. A pin is set on one surface of a rectangular parallelepiped test piece so as to be almost vertical, and a test is performed under a sliding test condition of a load of 1 kgf, a temperature of 150 ° C. and a sliding speed of 0.1 m / s, and a sliding test plate. The friction coefficient μ of was measured. At this time, as the lubricating oil, a synthetic oil with various heat-resistant additives added with various lubricating oil additives was used. FIG. 9 shows the sliding test results of Si ₃ N ₄ containing the added amount of iron oxide. In the comparative example, the amount of iron oxide added is zero. As can be seen from FIG. 9, the amount of iron oxide added to Si ₃ N ₄ is 10 to 20 wt.
When it was%, the friction coefficient μ was the lowest, and when it was more than that, it slightly increased, but the effect of addition, that is, the effect of reducing the friction coefficient μ was confirmed over the entire addition amount range.

Example 10 A silicon nitride Si ₃ N _{4 obtained} by adding 20 wt% of Fe ₃ O ₄ and firing by the same method for producing a sintered body as in Example 9 had the same dimensions as in Example 9. Plates and pins were made. Further, for silicon nitride Si ₃ N ₄ to which iron oxide was not added, and an iron-based metal material, plates and pins were similarly prepared. A sliding test was conducted by combining various materials of the above three types. At that time, load 1
The lubricating oil used was 0 kgf, the sliding speed was 0.1 m / s, the temperature was 200 ° C., and the sliding time was 2 hours. The same lubricating oil as in Example 9 and a lubricating oil having a lower viscosity were used. The results are shown in Table 1. In the table, the silicon nitride obtained by adding 20 wt% of Fe ₃ O ₄ to the present invention is the product of the present invention, the silicon nitride containing no iron oxide is the conventional product, the iron-based metal material is iron, and the same viscosity as that of Example 9 is used. Of the lubricating oil of higher viscosity and lower viscosity of the lubricating oil of lower viscosity.

[Table 1]

The sliding test condition in Table 1 is a condition called boundary lubrication in which solids frequently come into contact with each other. It can be seen from Table 1 that silicon nitride added with an oxide of iron has a low friction coefficient μ and excellent wear resistance in the boundary lubrication state as compared with the iron-based metal material and the conventional silicon nitride material. I can say. Further, since the product of the present invention has a low oil viscosity,
It did not cause seizure even in the case where an iron-based metal material causes seizure, and exhibited a low coefficient of friction and low wear compared to conventional silicon nitride. Therefore, it was confirmed that the low-viscosity oil can be used by using the product of the present invention in a portion where the low-viscosity oil could not be used, because the lubrication state becomes severe in the conventional product.

[Embodiment 11] In the same manner as in Embodiment 9, F
A cylinder liner and a piston ring, which are engine parts, of silicon nitride (hereinafter, referred to as a developed product, which is a product of the present invention) added with 10 wt% of e ₃ O ₄ were manufactured. In addition, silicon nitride without adding iron oxide (hereinafter referred to as conventional product)
The same thing was also manufactured. In order to know the frictional force between the piston ring and the cylinder liner by incorporating these parts into the engine, the motor driving force when the engine was rotated by the motor was measured. As a result, with the combination of the present invention, about 25
% Driving force has decreased. Further, the driving force was reduced by about 15% both in the combination of the conventional piston ring and the cylinder liner of the present invention, and in the combination of the piston ring of the present invention and the conventional cylinder liner. Further, when the motor driving force was measured using low viscosity oil in the engine of the combination of the present invention, it was reduced by about 40%.

The lubrication state between the piston ring and the cylinder liner in the engine is boundary lubrication at the top dead center and the bottom dead center, there is no fixed contact in other regions, and the frictional force is dominated by the viscosity of the lubricating oil. It is in a lubricated state. Therefore, by using the product of the present invention, the frictional force between the top dead center and the bottom dead center is reduced, and by using the low-viscosity oil, the frictional force of other parts is reduced, so that the performance is improved. It seems that it has appeared.

Example 12 From the test piece used in Example 9, a 3 × 4 × 40 test piece for 4-point bending strength test was cut out, and the strength was measured. The results of the 4-point bending average strength are shown in FIG. As can be seen from FIG. 10, the product of the present invention to which 10 to 20 wt% of iron oxide is added has the same strength as or higher than the normal Si ₃ N ₄ without addition. It was confirmed. The structure of the product of the present invention to which 10 wt% of iron oxide was added was observed by SEM. From this, the size of the part containing iron is 1
It can be seen that when it is 0 μm or less, it does not form a solid solution and exists in a state of being uniformly dispersed in the silicon nitride crystal grain boundaries. Figure 1 shows the results of an analysis of this phase using the X-ray microscopic analysis method.
As shown in Fig. 1, this analysis revealed that this phase was a Fe-Si compound. Porosity was hardly observed in the structure, and it was speculated that the growth of silicon nitride crystal grains was suppressed by the presence of iron oxide, resulting in fine and uniform crystal grains. In such a structure, the relation strength of Griffith decreases, but when the structure was observed, aggregation of iron oxide was observed,
It was speculated that this was the starting point of the destruction as a result of the remaining pores.

The number of cylinder liners constituting the engine is 5
Since a strength of 00 MPa or more is required, it is difficult to obtain the strength shown in FIGS.
From 0, the addition amount of iron oxide is 5 wt% to 500 MPa or more, in which the effect of reducing the friction coefficient μ appears, and it is considered that 40 wt% or less is particularly preferable. Also, the piston ring installed in the ring groove of the piston is 80
Since a strength of 0 MPa or more is required, the results shown in FIGS.
The amount of iron oxide added is from 5 wt% at which the effect of reducing the friction coefficient μ appears to a strength of 800 MPa or more.
It is considered that 20 wt% or less is preferable.

Next, an embodiment of a wear resistant part made of low friction ceramics and a method of manufacturing the same according to the present invention will be explained as a thirteenth embodiment. [Example 13] Si ₃ N ₄ , Al ₂ O ₃ , and Y ₂ O ₃ were used as 9 parts.
It was blended at a blending ratio of 0: 5: 5, and a predetermined amount of iron oxide having a particle diameter of 1 μm or less was added to this total weight, and methanol,
After mixing with a binder in a ball mill for about 24 hours to prepare a mixture, the mixture was granulated by a spray dryer to prepare granules. The granular material is used as a raw material to preform in a mold having an internal size of 25 × 20 × 100 mm to prepare a preformed body, and then the preformed body is subjected to C
A rectangular parallelepiped molded body was obtained by IP with a pressing pressure of about 2000 kgf / cm ² . After degreasing the molded body, 9.3 MPa
In N ₂ atmosphere, the material was heated and fired up to 2000 ° C. to produce a dense sintered body. This sintered body is processed into 16 × 1
A sliding test piece of 0 × 70 mm was prepared.

On the other hand, a Si ₃ N ₄ sintered body having a relative density of 99% or more was prepared as a counterpart material for the sliding test of the sliding test piece. The tip surface of the mating member was a spherical surface having a radius of curvature of 9 mm, and a pin of φ8 × 23 mm was used as the mating member. A pin is set on one surface of a rectangular parallelepiped test piece so as to be almost vertical, a load of 1 kgf, a temperature of 150 ° C., and a sliding speed of 1 m / s.
The friction coefficient μ of the sliding test piece was measured under the above sliding conditions. At this time, as the lubricating oil, a synthetic oil with various heat-resistant additives added with various lubricating oil additives was used. FIG. 12 shows the sliding test results of Si ₃ N ₄ with the addition amount of iron oxide. 12
As can be seen, the amount of iron oxide added is 10 to 20 wt.
%, The friction coefficient μ becomes the lowest, and when it is more than that, it slightly increases, but the effect of addition is observed in the entire area where iron oxide is added. At this time, the point where the added amount of iron oxide is zero is a conventional product and is a comparative example. When observing the structure of the test piece containing a large amount of iron oxide added, it is inferred that pores remained and the friction resistance increased due to meshing with the mating material during sliding.

[Example 14] Next, a sliding test similar to that of Example 13 was conducted by changing the temperature of the lubricating oil. The results are shown in Table 2. As a result, the measured friction coefficient μ of Si ₃ N ₄ added with 10 wt% of iron oxide at 25 ° C. to 200 ° C. (invention product) is lower than that of Si ₃ N ₄ not added (conventional product). became. Also, at this time, as a result of measuring the amount of wear of both, as shown in Table 3, Si ₃ N ₄ with 10 wt% addition of iron oxide in each temperature range was compared to Si ₃ N ₄ without addition, And the amount of pin wear was small.

[Table 2]

[Table 3]

[Example 15] Next, a sliding test similar to that of Example 13 was conducted by changing the viscosity of the lubricating oil. As a result, as shown in Table 4, irrespective of the viscosity of the lubricating oil, Si ₃ N ₄ containing 10 wt% of iron oxide has a higher friction coefficient than Si ₃ N ₄ containing no iron oxide. μ became a low value. Further, as the viscosity of the lubricating oil decreased, the difference in the friction coefficient μ between the two tended to increase. Here, the lubricating oil viscosity is 10 cst (centistokes) and 4 cst
Tested in the case of (centistokes).

[Table 4]

Example 16 From the test piece used in Example 13, 3 × 4 × 40 test pieces for 4-point bending strength test were cut out and their strengths were measured. The results of the 4-point bending average strength MPa are shown in FIG. The four-point bending average strength tends to decrease as the amount of Fe oxide added to Si ₃ N ₄ increases. However, it was confirmed that the strength was equal to or higher than that of Si ₃ N ₄ (conventional product) added with 0 wt% up to the addition amount of Fe oxide of 10 wt%. The amount of Fe oxide added to Si ₃ N ₄ is 1
When the structure of the 0 wt% product of the present invention is observed, it is found that the portion containing Fe does not form a solid solution but exists in a dispersed state. Almost no pores were observed in the structure of the product of the present invention, and the growth of crystal particles was suppressed by the oxide of Fe.
It was found to be fine and uniform. Such a structure is considered to be advantageous for high strength in view of the Griffith relational expression. On the other hand, when the amount of Fe oxide added to Si ₃ N ₄ is further increased, the strength decreases, but the SEM (Scanning Electron Microscopy) observation of those structures revealed that agglomeration of oxide was observed. It is considered that the pores remained in the steel, which acted as the starting point of the fracture and reduced the strength.

Example 17 By the same manufacturing method as in Example 13, Si ₃ N ₄ containing 10 wt% of iron oxide was added.
A rocker arm sheet and a tappet were produced using (the product of the present invention) and Si ₃ N ₄ (conventional product) to which iron oxide was not added as a comparative material. These parts were incorporated into a rig tester with an improved cylinder head and a diesel engine, respectively, and the amounts of wear were compared.

First, the oil temperature was set in the rig device at 80 ° C., and 1
Table 5 shows the wear amounts of the rocker arm seat and the cam, which were subjected to a wear test for 100 hours at a rotation speed of 500 rpm.
The amount of wear of the rocker arm seat and the cam of the present invention was 40% less than that of the conventional product. Further, as a result of conducting a similar test by raising the oil temperature to 150 ° C., the wear amount of the conventional product was about 3.5 times that of the product of the present invention.

[Table 5]

Next, a tappet was installed in a diesel engine, a durability test was conducted for 500 hours at a rotation speed of 3000 rpm, and the amount of wear at that time was measured. The results are shown in Table 6.
As shown in FIG. 4, the wear amount of the tappet of the product of the present invention was reduced by 40% as compared with the conventional product. The wear of the push rod cam was below the measurement limit.

[Table 6] Further, as a material of the rocker arm sheet and the tappet, as a result of studying the addition amount of iron oxide between 5 and 40 wt%, when the addition amount of iron oxide exceeds 25 wt%,
The friction coefficient μ and wear amount of each part tended to increase. Further, when the addition amount of iron oxide exceeds 30 wt%,
Cracks and cracks were noticeable in each part, and some parts were damaged. It is considered that this is because the hardness and strength decrease as the amount of iron oxide added increases. Therefore,
The rocker arm seat has high surface pressure (50 kgf
/ When used in cm ² or more), the amount of iron oxide is less 25 wt% (4-point bending strength: If it is 750MPa or higher), 4-point bending strength: be 750MPa or more, it has been found that desirable.

[0085]

The low-friction ceramics and the method for producing the same according to the present invention are configured as described above and have the following effects. That is, according to the present invention, since the compound consisting of Fe-O is dispersed in at least the surface of the ceramic, which is different from this, as the mother phase, Fe-O
Since the compound consisting of is excellent in the adsorptivity with oil, the composite ceramic has low friction and high strength. Further, when the mother phase of the ceramic is made of an oxide ceramic such as ZrO ₂ , the above constitution can be obtained even by firing in the usual atmosphere. Also,
When the mother phase of the ceramic is a non-oxide ceramic such as Si ₃ N ₄ or SiC, a reduction reaction occurs during firing in a nitrogen N ₂ atmosphere, so that the Fe-Si compound is converted to oxygen. By heating in an atmosphere containing Fe, the Fe—Si compound is converted to Fe—O at least in the vicinity of the surface, and the above-mentioned structure having low friction and high strength is formed. Therefore, this low friction ceramic
Compared with conventional ceramics, it has a low friction coefficient, and has a low friction coefficient and a strength equal to or higher than that of the additive-free one.

That is, this low-friction ceramic has a non-oxide ceramic containing Si as a mother phase, in which F
Since the compound composed of e-O is dispersed, it has high friction and low strength due to its excellent adsorptivity with the lubricating oil.

Further, in this low friction ceramic, since the Fe compound is dispersed in the matrix of the non-oxide ceramic containing Si and the solid lubricant is filled in the pores, the low friction ceramic is low especially in the boundary lubrication region. It is friction and has high strength.

Further, since the low-friction ceramic has an oxide ceramic as a mother phase and a compound consisting of Fe-O dispersed therein, it has a low friction because it is excellent in adsorbability with a lubricating oil. Moreover, it has high strength.

Further, since the Si ₃ N ₄ ceramics is used as the mother phase and the Fe--Si compound is dispersed therein,
Since the Si ₃ N ₄ crystal particles are fine and uniform, they show little friction with the mating material during sliding and show low friction and high strength.

Therefore, the present invention has a low friction coefficient as compared with the conventional ceramics such as silicon nitride, has almost no pores, and has a low friction coefficient and a strength equal to that of the additive-free one. Alternatively, it becomes a composite material of ceramics having higher strength, and sufficient strength that can be used for engine parts and the like can be secured. In addition, this low-friction ceramic has a predetermined amount of Fe oxide such as FeO, Fe ₂ O ₃ , and Fe ₃ O ₄ in the mother phase, that is, 5 wt% to 40%.
By adding wt% and dispersing it, it is possible to obtain a composite material of ceramics and iron oxide which has good adsorbability with oil and has a low friction coefficient and high strength.

Further, the sliding parts made of the low friction ceramics according to the present invention have a low friction coefficient even when the lubricating oil viscosity is low because the Fe-Si compound is dispersed with the silicon nitride ceramics as the mother phase. And has excellent wear resistance. Therefore, even engine parts are suitable for making cylinder liners or piston rings,
In particular, Si ₃ N ₄ containing 5 to 40 wt% of iron oxide
In addition to the above characteristics, sliding parts can also secure the strength required for a cylinder liner or piston ring.
Even under severe sliding conditions such as a heat shield engine, it can be sufficiently used and engine performance can be improved.

The wear-resistant component made of the low-friction ceramics according to the present invention has a non-oxide ceramic containing Si as a mother phase, in which at least one compound of Fe or its oxide or silicide is contained. Since the above is dispersed, compared to conventional Si ₃ N ₄ ceramics,
Even in a high temperature range of 150 ° C. or higher, the friction characteristics and the wear characteristics can be improved, and moreover, the mechanical characteristics, that is, the strength, are the same as those of the conventional Si ₃ N ₄ ceramics. Therefore, this wear-resistant component is preferably applied to a rocker arm seat, a cam, a tappet, a push rod cam, etc. as a valve operating system component for an engine, and in particular, a valve operating system for a heat-shielding engine under severe operating conditions. It is suitable for use in parts, and when the lubricating oil becomes hot, or when the viscosity of the lubricating oil is lowered to reduce friction, this wear resistant part exhibits favorable characteristics and improves engine performance. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the friction coefficient and the processing temperature in the atmosphere in the manufacturing process of this low-friction ceramics.

FIG. 2 is a graph showing the relationship of the friction coefficient with respect to the parameters of load, speed and lubricating oil viscosity with respect to the amount of iron oxide added to this low friction ceramic.

FIG. 3 is a graph showing a relationship of a friction coefficient with respect to parameters of load, speed and lubricating oil viscosity with respect to the amount of iron oxide added to the low friction ceramic.

FIG. 4 is a graph showing the measurement results of the friction coefficient with respect to the addition amount of Fe _m O _n in this low friction ceramic.

FIG. 5 is a graph showing the average of four-point bending strength with respect to the amount of iron oxide added to this low-friction ceramic.

FIG. 6 is a graph showing the relationship between the friction coefficient and the maximum crystal grain size of this low-friction ceramic.

FIG. 7 is a graph showing the relationship of 4-point bending strength with respect to the amount of Fe _m O _n added for this low-friction ceramic.

FIG. 8 is a graph showing the results of analysis of this low-friction ceramic using an X-ray microanalysis method.

FIG. 9 is a graph showing the measurement results of the friction coefficient with respect to the addition amount of Fe _m O _n in the low-friction ceramics that make up this sliding component.

FIG. 10 is a graph showing the four-point bending average strength with respect to the amount of iron oxide added in the low-friction ceramics for producing this sliding component.

FIG. 11 is a graph showing the results of analysis of the low-friction ceramics used to manufacture this sliding component using an X-ray microanalysis method.

FIG. 12 is a graph showing the measurement results of the friction coefficient with respect to the amount of Fe _m O _n added in the low-friction ceramics for producing this wear-resistant component.

FIG. 13 is a graph showing the 4-point bending average strength with respect to the amount of iron oxide added in the low-friction ceramics from which this wear resistant component is manufactured.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Sakaguchi 8 Tsutana, Fujisawa City, Kanagawa Prefecture Isuzu Ceramics Laboratory Co., Ltd.

Claims (33)

[Claims] 1. A low-friction ceramic in which a compound of Fe—O is dispersed in at least the surface of the mother phase with a ceramic different from the compound as the mother phase. 2. The low-friction ceramic according to claim 1, wherein a matrix phase of the ceramic is an oxide. 3. The oxide ceramic is ZrO ₂ or Al.
The low-friction ceramic according to claim 2, which is ₂ O ₃ . 4. The size of the Fe compound is 10 μm.
The low-friction ceramic according to claim 1, wherein: 5. The Fe compound is FeO, Fe
The low-friction ceramic according to claim 1, which is contained in an amount of 5 wt% or more in terms of ₂ O ₃ and Fe ₃ O ₄ . 6. The low-friction ceramic according to claim 1, wherein the mother phase of the ceramic is a ceramic containing Si as a main component. 7. The low-friction ceramic according to claim 6, wherein the ceramic containing Si as a main component is any one of Si ₃ N ₄ , SiC and a composite thereof. 8. The size of the Fe compound is 10 μm.
The low friction ceramics according to claim 6, wherein: 9. The Fe compound is FeO, Fe
The low friction ceramics according to claim 6, wherein the content is 5 wt% or more in terms of ₂ O ₃ and Fe ₃ O ₄ . 10. The low-friction ceramic according to claim 6, wherein the Fe compound is dispersed in the matrix of the non-oxide ceramic containing Si and the pores are filled with a solid lubricant. 11. The low-friction ceramic according to claim 10, wherein the solid lubricant is graphite or a composite material based on it. 12. A matrix of Si ₃ N ₄ ceramics,
Fe-Si compound is dispersed in the low friction ceramics. 13. The maximum crystal grain of Si ₃ N ₄ is 20.
The low-friction ceramic according to claim 12, which has a thickness of not more than μm. 14. The size of the Fe—Si compound is 10
The low-friction ceramic according to claim 12, which has a thickness of not more than μm. 15. A non-oxide ceramic containing Si is added with an oxide of Fe and mixed with distilled water and a binder, and the mixture is granulated to form a raw material, thereby producing a compact. A method for producing a low-friction ceramic, which comprises firing a molded body in a nitrogen atmosphere to produce a fired body, and then heating the fired body in the atmosphere to oxidize a portion of a Fe compound. 16. The heating temperature of the fired body in the atmosphere is 8
The method for producing a low-friction ceramic according to claim 15, wherein the method is performed at a temperature of 00 ° C or higher. 17. An oxide of Fe is added to Si ₃ N ₄ ceramics, which is mixed with methanol and a binder, and the mixture is granulated to form a raw material to produce a green body. After degreasing, the product is baked in a nitrogen atmosphere under a single-stage holding temperature and then under the maximum holding temperature firing conditions to produce Si ₃ N 2.
_{4. A} method for producing low-friction ceramics, which comprises producing a fired body. 18. The method for producing a low-friction ceramic according to claim 17, wherein the particle diameter of the Fe oxide is 10 μm or less. 19. The firing temperature is 1400 ° C. to 2100.
18. The method for producing a low-friction ceramic according to claim 17, wherein the temperature is 0 ° C. 20. The first stage holding temperature of the firing temperature is 1
450 ° C to 1750 ° C, and the maximum holding temperature is 17
The temperature range is from 50 ° C to 2000 ° C.
The method for producing a low-friction ceramic according to 1. 21. A sliding component made of low-friction ceramics, wherein Fe-Si compound is dispersed with silicon nitride ceramics as a mother phase. 22. The sliding component made of low friction ceramics according to claim 21, which is a cylinder liner. 23. The Fe—Si compound is FeO, Fe.
_The sliding component made of low friction ceramics according to claim 21 or 22, wherein the sliding component is contained in an amount of 5 to 40 wt% in terms of ₂ O ₃ and Fe ₃ O ₄ . 24. The sliding component made of low friction ceramics according to claim 21, which is a piston ring. 25. The Fe—Si compound is FeO, Fe.
_The sliding component made of low friction ceramics according to claim 21 or 24, wherein the sliding component is contained in an amount of 5 to 20 wt% in terms of ₂ O ₃ and Fe ₃ O ₄ . 26. An oxide of Fe is added to a raw material powder containing silicon nitride ceramics as a main component, mixed with methanol and a binder, and the mixture is granulated to form a raw material to produce a compact, A method for producing a sliding component made of low-friction ceramics, characterized in that the compact is degreased and then heated and fired in a nitrogen gas atmosphere to a maximum temperature of 1850 ° C. to form a dense sintered body. 27. Low friction, characterized in that a non-oxide ceramic containing Si is used as a matrix phase, and at least one kind of Fe or its oxide or silicide compound is dispersed therein. Wear resistant parts made of ceramics. 28. The wear resistant component made of low friction ceramics according to claim 27, wherein the non-oxide ceramic containing Si is any one of Si ₃ N ₄ and SiC. 29. The wear resistant component made of low friction ceramics according to claim 27, wherein the size of Fe or its compound contained in said ceramics is 10 μm or less. 30. The wear resistant component made of low friction ceramics according to claim 27, wherein Fe or its compound contained in said ceramics is contained in an amount of 5 to 25 wt% in terms of oxide. 31. The 4-point bending strength of the ceramic is 7
The wear-resistant component made of the low-friction ceramic according to claim 27, which has a pressure of 50 MPa or more. 32. The low friction ceramics according to any one of claims 27, 28, 29, 30 and 31, which are engine valve system parts such as rocker arm seats, cams and tappets. Wear resistant parts. 33. An intermediate compact is produced by adding an oxide of Fe to a raw material powder containing silicon nitride ceramics as a main component, mixing the mixture with methanol and a binder, and preforming the raw material obtained by granulating the mixture. Then, the intermediate compact is molded by CIP to prepare a compact, and after degreasing, the compact is heated and fired to 2000 ° C. in a nitrogen gas atmosphere to form a dense sintered compact. A method of manufacturing wear-resistant parts made of ceramics.