JPH092877A - Silicon nitride based sintered body for sliding member and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a silicon nitride-based sintered body for a sliding member, which has excellent slidability with a mating member. [Structure] 1 wt% or more and 20 wt% or less of boron and an appropriate amount of a sintering aid are kneaded together with a silicon nitride powder to produce a compact, and the compact is then subjected to the highest density when boron is not added. Sintering is performed at a high temperature in the range of less than 150 ° C. as compared with the temperature reaching As a result, the Young's modulus (E) is
A silicon nitride-based sintered body for a sliding member having a viscosity of 100 GPa or more and 295 GPa or less is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride-based sintered body having excellent thermal conductivity and sliding characteristics, and a method for producing the same. Specifically, the Young's modulus (E) is reduced to improve the contact with the mating member, reduce the concentration of contact stress, further increase the wettability with the lubricating oil, and improve the wear resistance and seizure resistance. And a method of manufacturing the same.

[0002]

_2. Description of the Related Art A silicon nitride sintered body such as sialon in which Al element and O ₂ are dissolved in Si ₃ N ₄ or Si ₃ N ₄ is superior in strength, hardness and corrosion resistance at a high temperature compared to a metal material. Therefore, they are used for rolling elements and races of rolling bearings, sliding bearings, rocker arms of internal combustion engines, rolling rollers, cutting tools, dies, and the like.

In order to improve the sliding characteristics of a silicon nitride based sintered body, Japanese Patent Application Laid-Open Nos. 6-122555, 6-183841, 6-234564 include Si. Using non-oxide ceramics as a matrix,
A transition metal or a transition metal compound is dispersed therein to realize a high strength with a low friction coefficient.

Further, since a silicon nitride-based sintered body is difficult to be sintered, a dense sintered body is obtained by using a sintering aid. As the sintering aid, boron (B) is used. The prior art used is disclosed in JP-A-59-217675 and JP-B-62-1.
No. 4506 discloses this. However, in these prior arts, although the bending strength and the sinterability are improved by adding boron, they do not focus on the characteristics as a sliding member.

On the other hand, as a proposal for improving the characteristics of a silicon nitride-based sintered body as a sliding member, Japanese Patent Application Laid-Open No. 2-217380 has been proposed.
There is an official gazette. This publication discloses a silicon nitride-based sintered body for a sliding member, which is composed of inorganic compound particles such as carbide and a silicon nitride reaction sintered body having a smaller diameter than the inorganic compound particles. According to this publication, the characteristics required for the sliding member include high hardness, good compatibility with a sliding partner material, excellent corrosion resistance, high toughness and high thermal shock resistance. In addition, the Young's modulus (E) is high.

[0006]

If the surface in contact with the mating member is ground with extremely high precision, stress concentration can be avoided, but not only the processing cost is increased but also the swash plate type hydraulic As shown in Fig. 1 (a), the plunger of the equipment is in point contact, and the rolling roller is in linear contact as shown in Fig. 1 (b). Can not. In addition, even in the case of surface contact with the mating member, it can be considered that the contact is microscopically one-sided.

If the Young's modulus (E) is high when the sliding contact surface with the mating member is one-sided, it cannot be elastically deformed following the shape of the sliding contact surface of the mating member. As the pressure increases and the amount of wear increases, the rate of breakage and chipping increases.

The present invention is based on the background of the prior art described above, and has a low Young's modulus (E), excellent slidability with a mating member, and a wetting angle when a liquid lubricating oil is used. It is an object of the present invention to provide a silicon nitride-based sintered body for a sliding member having a small size and a high seizure limit, and a method for manufacturing the same.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a silicon nitride sintered body for a sliding member according to the present invention is obtained by kneading a silicon nitride powder, a sintering aid, and boron, followed by firing. Thus, the silicon nitride as the main component contains 1 wt% to 20 wt% of boron, 1 wt% to 15 wt% of the sintering aid, and the Young's modulus (E) is 100 GPa to 295 GPa. I made it. When the Young's modulus (E) is less than 100 GPa, there is a problem that abrasion tends to progress,
When the Young's modulus (E) exceeds 295 GPa, disadvantages per piece become significant. Here, the Young's modulus (E) is preferably larger than that of the other sliding member. 210 GPa or more when the mating sliding member is a steel material;
It is 0 GPa or more, 130 or more for a copper-based material, 110 or more for a titanium-based material, and 70 GPa or more for an aluminum-based material.

Further, another silicon nitride-based sintered body for a sliding member according to the present invention is obtained by kneading a silicon nitride-based powder, a sintering aid, and boron, forming the mixture into a predetermined shape, and firing. A silicon nitride-based sintered body for a sliding member obtained as described above, wherein boron is contained at 1 wt% or more and 20 wt% or less, and a sintering aid is contained at 1 wt% or more and 15 wt% or less, based on silicon nitride as a main component. A metal compound having a smaller wetting angle than the silicon nitride of the parent phase was deposited on at least the surface. Further, it is considered that the added boron forms some compound and contributes to improvement of wettability.
These compounds need only be present at least on the surface of the silicon nitride sintered body of the present invention in order to contribute to the improvement of the sliding characteristics.

In order to manufacture the silicon nitride sintered body for a sliding member, 1 wt% or more and 20 wt% or less of boron and 1 wt%
% To 15 wt% of a sintering aid is kneaded with a silicon nitride-based powder to produce a compact, and the compact is compared with the temperature at which the maximum density is reached when boron is not added.
Sinter at a high temperature below 50 ° C.

Silicon nitride powders include Si ₃ N ₄ and Si ₃
Sialon in which Al element and O ₂ are dissolved in N ₄ (Si-Al-O-
N) and the like, and any of α-type and β-type can be used as Si ₃ N _4. Examples of the production method include a direct nitridation method of Si, a reduction / nitridation method of silica, a thermal decomposition method of silicon diimide, There is a gas phase reaction method of SiH ₄ + NH ₃ + N ₂ , and Si ₃ N ₄
The average particle size of the powder is about 0.01 to 3.0 μm.

Examples of the sintering aid include cerium oxide, neodymium oxide, lanthanum oxide, ytterbium oxide, strontium oxide, titanium oxide and the like in addition to yttria, alumina and magnesia. The reason why the addition ratio of the sintering aid is 1 wt% or more and 15 wt% is that if it is less than 1 wt%, it becomes difficult to sinter silicon nitride having poor sinterability.
If it exceeds 5 wt%, the mechanical strength is reduced.

The reason why the addition ratio of boron is 1% by weight or more and 20% by weight is that if it is less than 1% by weight, the Young's modulus (E) cannot be sufficiently reduced, and the wetting angle cannot be reduced. When it exceeds, the mechanical strength is significantly reduced.

The method for producing a green body before firing of the silicon nitride sintered body for a sliding member according to the present invention includes casting,
Injection molding, extrusion molding, press molding and the like can be applied, and HIP or the like is used as a firing method.

The firing temperature is set higher than the temperature at which the maximum density is reached when boron is not added, in the range of less than 150 ° C. As shown in FIG. 4, the firing temperature when boron is not added is usually 10 to 50 ° lower than the temperature at which the maximum density is reached, which is optimum for obtaining a sintered body having high strength. The temperature at which the maximum density is reached depends on the type and amount of the sintering aid, and when the amount of the sintering aid is increased, the temperature at which the maximum density is reached decreases. Since boron has a high melting point, when boron is added to improve its sinterability, it must be fired at a high temperature depending on the amount of boron added. However, if the sintering temperature is too high, the pores will increase due to the decomposition of Si ₃ N ₄ , and the thermal conductivity will decrease, so that heat will not be diffused on the sliding surface and the seizure limit will decrease. As described above, it is suitable that the temperature is higher than the temperature at which the maximum density is reached when boron is not added in the range of less than 150 ° C.

[0017]

The silicon nitride sintered body for a sliding member of the present invention has a Young's modulus (E) of not less than 210 GPa and not more than 295 GPa. Therefore, the silicon nitride-based sintered body is easily elastically deformed, so that the contact surface pressure is reduced, the amount of wear due to sliding is small, and breakage is hardly generated.

Since the added boron is present in the form of some compound, the wetting angle when a liquid lubricant is used is reduced,
It is considered that the retention of the lubricant on the sliding portion is improved. Therefore, the silicon nitride sintered body for a sliding member of the present invention is effectively used as a plunger, a rolling roller, a bearing, a rocker arm of an internal combustion engine, a turbine rotor, etc. of a swash plate type hydraulic device.

[0019]

EXAMPLES Specific examples and comparative examples will be described below. Example 1 5 wt% of yttrium oxide (produced by Nippon Yttrium) and 3 wt.
% Of boron (manufactured by Kojundo Chemical Co., Ltd.) was added, and these powders were mixed and ground in ethanol using a ball mill. The obtained slurry was dried using a rotary evaporator, and then press-formed using a 35 × 55 mm mold (200).
kg / cm ² ) and CIP (pressure 3 t / cm ² ) to obtain a molded body. This compact was fired under the conditions of 1900 ° C., a nitrogen atmosphere, and 9 atmospheres, using silicon nitride and boron nitride powder as packing powder. Thereafter, a JIS piece of 3 × 4 × 40 mm was cut out, lap-finished using diamond paste, and the surface roughness was set to 0.8S.

The Young's modulus was measured by a resonance method.
The thermal conductivity was measured at room temperature by a laser flash method. To measure the wetting angle, a lubricating oil (10W30) with a viscosity of 0.0146 P · S (170 cst) was dropped on the test piece in a thermostatic chamber at 20 ° C, and the state of spreading the wetting angle immediately after dropping was photographed with a CCD camera. did. In order to ignore the effect of the waving phenomenon caused by the drop, the wetting angle one second after the drop was determined by image analysis.

(Example 2) A test piece was produced in the same manner as in (Example 1) except that the firing temperature was 1800 ° C.

Example 3 The firing temperature was 1600 ° C.
The amount of boron added was 1 wt%, the sintering aid was 7 wt% of Y ₂ O ₃ , Al ₂
A test piece was produced in the same manner as in the above (Example 1) except that O ₃ was 1 wt% and MgO was 2 wt%.

Example 4 The firing temperature was 1550 ° C.
The amount of boron added was 1 wt%, the sintering aid was 7 wt% of Y ₂ O ₃ , Al ₂
A test piece was produced in the same manner as in the above (Example 1) except that O ₃ was 1 wt% and MgO was 2 wt%.

Comparative Example 1 The firing temperature was 1800 ° C.
A test piece was produced by the same method as in the above (Example 1) except that boron was not added.

(Comparative Example 2) The firing temperature was 1550 ° C.
A test piece was produced by the same method as in the above (Example 1) except that boron was not added.

The following Table 1 compares the characteristic values of the test pieces of each of the examples and the comparative examples obtained as described above. It can be seen from Table 1 that the Young's modulus of the silicon nitride-based sintered body for a sliding member according to the present invention is significantly smaller than that of the comparative example. Also, as compared with Examples 1 and 2 and Examples 3 and 4, the bending strength, density and thermal conductivity can be improved by increasing the sintering temperature by 50 to 100 ° C. as compared with the case where boron is not added. Was confirmed.

FIG. 4 shows the relationship between the sintering temperature and the density of the sintered body of Comparative Example 1. Since this sintered body reaches the maximum density at around 1850 ° C., when boron is added, 1850 to 2050 is obtained.
It is appropriate to perform sintering in a temperature range of 00 ° C.

[0028]

[Table 1]

Further, the following (Table 2) and FIG. 2 show the experimental results of the load and the sliding speed, and FIG. 3 is a schematic diagram of the experimental apparatus. Here, the materials used in Examples 1 and 2 of this experiment are the same as the materials used in Examples 1 and 3 in (Table 1), and the materials used in Comparative Examples 1 and 2 are those in (Table 1). The materials used in Comparative Examples 1 and 2 are the same. From FIG. 2, it was confirmed that the addition of boron increases the seizure limit. In the experiment, the metal roller (SKD11: hardness HRC65) was used on the fixed side, and the cylindrical test pieces obtained in the above Examples and Comparative Examples were brought into contact with the metal roller under a load, and the test pieces were rolled. The burn-in speed was gradually increased, and the time of burning was plotted. In addition, 10W-30 as a lubricant
Mineral oil was used at a supply rate of 465 ml / min.

[0030]

[Table 2]

[0031]

As described above, the silicon nitride sintered body for a sliding member according to the present invention has a Young's modulus (E) of 100.
Since it is GPa or more and 295 GPa or less, the silicon nitride-based sintered body is easily elastically deformed in accordance with the shape of the mating member even in the state of point contact or line contact with the mating member. Therefore, the amount of wear due to sliding is small, and breakage is unlikely to occur. Further, since the added boron forms some compound and exists on the surface of the sintered body, the wetting angle when a liquid lubricant is used is reduced without reducing the strength, and the lubricant in the sliding portion is reduced. Is improved. Therefore, it is effective when used as a plunger, a rolling roller, a bearing of a swash plate type hydraulic device, a rocker arm of an internal combustion engine, a turbine rotor, and the like.

[Brief description of drawings]

FIG. 1A is a diagram showing a point contact portion of a swash plate type hydraulic device, and FIG. 1B is a diagram showing a line contact portion of a rolling roller.

FIG. 2 is a graph showing the result of a burn-in limit test.

FIG. 3 is a schematic diagram of an experimental device for load and slip velocity.

FIG. 4 is a graph showing the relationship between firing temperature and density.

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[Procedure amendment]

[Submission date] July 5, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction contents]

(Comparative Example 2) The firing temperature was 1550 ° C.
A test piece was manufactured by the same manufacturing method as in the above ( Example 3 ) except that boron was not added.

Front Page Continuation (72) Inventor Yasunobu Kawakami 1-4-1 Chuo, Wako City, Saitama Stock Company Honda R & D Co., Ltd.

Claims (3)

[Claims] 1. A silicon nitride-based sintered body for a sliding member obtained by kneading a silicon nitride-based powder, a sintering aid, and boron, forming the mixture into a predetermined shape, and firing the mixture. It is characterized by containing 1 wt% or more and 20 wt% or less of boron, 1 wt% or more and 15 wt% or less of a sintering aid, and having a Young's modulus (E) of 100 GPa or more and 295 GPa or less based on silicon nitride as a main component. Silicon nitride sintered body for sliding members. 2. A silicon nitride-based sintered body for a sliding member, which is obtained by kneading silicon nitride-based powder, a sintering aid, and boron, molding the mixture into a predetermined shape, and then firing the mixture. Boron is contained in an amount of 1 wt% or more and 20 wt% or less and a sintering aid is contained in an amount of 1 wt% or more and 15 wt% or less with respect to silicon nitride as a main component, and a metal compound having a wetting angle smaller than that of silicon nitride of the parent phase is present on at least the surface. A silicon nitride-based sintered body for a sliding member, which is characterized by being deposited. 3. The method according to claim 1, wherein 1 wt% or more and 20 wt% or less of boron and 1 wt%
A sintering aid of at least 15 wt% or less is kneaded with a silicon nitride-based powder to produce a compact, and then the compact is compared with a temperature at which the maximum density is reached when boron is not added by 1%.
A method for producing a silicon nitride-based sintered body for a sliding member, wherein the sintered body is sintered at a high temperature within a range of less than 50 ° C.