JP2000144280A - Sintered composite material and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a sintered composite material improved in wear resistance and also excellent in lubricity. SOLUTION: In this sintered composite material, amorphous carbon particles and graphite particles are dispersed into the continuous phases of pure aluminum or an aluminum alloy. As for the method for producing the sintered composite material, aluminum or aluminum alloy powder and a powdery mixture composed of amorphous carbon powder with 5 to 300 μm average particle size or graphite powder in which the particle size ratio with the pure aluminum or aluminum alloy powder is controlled to >=0.2 and aluminum borate powder with 2 to 300 μm average particle size are compacted, and the compacted body obtd. by the compacting is sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sintered composite material and a method for producing the same, and more particularly, to an aluminum-based sintered composite material having excellent wear resistance and a method for producing the same.

[0002]

2. Description of the Related Art There is a considerable demand for aluminum-based alloys having wear resistance in the field of sliding members such as cylinder liners, bearings, oil pump side blades and compressors.
Conventionally, a eutectic or hypereutectic Al-Si alloy, which is a wear-resistant aluminum-based alloy, exhibits excellent wear resistance because it has a structure in which primary and eutectic Si are dispersed in an Al matrix. It has been known.

Further, in order to further improve the wear resistance of an aluminum alloy, a sintered composite formed by adding hard particles such as ceramics and intermetallic compounds and / or lubricating particles such as a solid lubricant to a powder material. Materials are known. As hard particles, SiC, Al ₂ O ₃ , Si ₃ N ₄ , T
iC, Ti ₃ Al, Al borate and the like are known. As the lubricating particles, molybdenum disulfide (MoS ₂ ), graphite and the like are known.

[0004] However, when hard particles such as ceramics and intermetallic compounds are added to a powder material, although the wear resistance of the sintered composite material itself is improved, the sintered composite material cannot be used.
For example, if used as one of the sliding members, it will cause a violent attack on the counterpart metal and a large friction. as a result,
It is desirable that the coefficient of friction of the sintered composite be as low as possible in order to significantly reduce the life of the mating metal that makes up the part.

For example, JP-A-4-297534 describes a dispersion-strengthened metal matrix composite material using Al borate as hard particles. According to the invention described in this publication, a dispersion-strengthened metal composite material in which alumina particles are uniformly dispersed and which has excellent strength can be obtained. But,
The coefficient of friction of the composite material is still high, and no consideration is given to reducing the wear of the mating metal when the composite material is used as a sliding member.

Further, MoS _{2 is} used as lubricating particles in a powder material.
When added, the lubricating effect may not be exhibited due to the reaction with Al. In addition, oxidation by the air becomes a problem, and a special sintering method is required. Furthermore, when graphite is used as the lubricating particles for the powder material, the graphite has a layered crystal structure, which is easily broken (cleaved) by an external force, and thus hinders the sinterability of the composite material. That is, the graphite is destroyed during the mixing process with the Al powder, and the fine graphite powder generated thereby adheres to the surface of the Al powder and hinders the sinterability of the composite material. In addition, agglomeration of graphite is also included. This agglomeration leads to graphite falling off and a decrease in strength. In order to solve such problems, it has been known to coat a fine graphite powder with a metal in advance (JP-A-57-89404 and JP-A-59-110702). However, it is difficult to apply a uniform coating on graphite and to control the coating film thickness. Further, a wear-resistant composite material using pure aluminum, silicon and amorphous carbon (Japanese Patent Laid-Open No. 10-140265) is known. This wear-resistant composite material has excellent wear resistance when silicon is 10% by volume or more and amorphous carbon is 10% by volume or more. However, the invention described in this publication does not describe a wear-resistant composite material using a material other than amorphous carbon and silicon.

[0007] Therefore, an object of the present invention is to provide a sintered composite material having improved wear resistance and excellent lubricity as compared with the prior art.

[0008]

The sintered composite material of the present invention comprises a continuous phase of pure aluminum or an aluminum alloy,
Amorphous carbon particles or graphite particles and aluminum borate particles are dispersed. The method for producing a sintered composite material of the present invention is a method of mixing a mixture of pure aluminum or aluminum alloy powder, amorphous carbon powder having an average particle size of 5 to 300 μm, and aluminum borate powder having an average particle size of 2 to 300 μm. It is characterized in that the powder is compacted and the compact obtained by compacting is sintered. Further, the method for producing a sintered composite material of the present invention, pure aluminum or aluminum alloy powder, graphite powder having a particle size ratio of pure aluminum or aluminum alloy powder of 0.2 or more, the average particle size is 2 300 μm
And powder compaction of the mixed powder comprising the aluminum borate powder, and sintering the compact obtained by compacting.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy used for the sintered composite material of the present invention may be an alloy containing manganese, silicon, magnesium, copper, zinc or the like in order to improve the properties of aluminum as a material. it can. Specifically, Al-Cu-based, Al-Mg-based, Al-Si-
At least one alloy selected from the group consisting of Cu-based and Al-Si-Mg-based can be given.

The sintered composite material of the present invention has a structure in which amorphous carbon particles or graphite particles and aluminum borate particles are scattered in a continuous phase of pure aluminum or an aluminum alloy. Thus, when aluminum borate particles, which are hard particles having excellent load holding properties, and amorphous carbon particles or graphite particles, which have excellent lubricity, coexist in pure aluminum or an aluminum alloy,
The wear resistance of the sintered composite material can be improved by the so-called hybrid effect in which both properties are combined.

The wear resistance of the sintered composite material changes depending on the contents of aluminum borate particles and amorphous carbon particles or graphite particles. In the case of a sintered composite material containing amorphous carbon particles, when the total addition amount of the amorphous carbon particles and the aluminum borate particles is 20% by volume or more, the abrasion resistance tends to be significantly improved. In particular, when the content of aluminum borate particles is 10% by volume or more and the content of amorphous carbon particles or graphite particles is 10% by volume or more, high wear resistance is exhibited. Composites of the present invention having a content in this range exhibit higher wear resistance than conventional composites containing silicon and amorphous carbon particles. Further, even when the content of the aluminum borate particles is in the range of 5 to 10% by volume, if the content of the amorphous carbon particles or the graphite particles is 15% by volume or more, the composite material having the above content is provided. As in the case of, it shows excellent wear resistance. The upper limits of the contents of the aluminum borate particles and the amorphous carbon particles are, for example, about 50% by volume, respectively, and preferably about 20% by volume, respectively. Further, the content of the graphite particles can be determined in the same manner as the content of the amorphous carbon particles.

[0012] Amorphous carbon particles, higher strength than the other lubricant additives such as MoS _2, thereby improving the strength of the sintered composite material of the present invention. Further, amorphous carbon particles are also excellent in that there is almost no particle destruction during powder mixing.

The amorphous carbon particles contained in the composite material of the present invention may be in the form of a sphere, a lump or the like, but are preferably spherical. As described above, the amorphous carbon on the surface of the composite material is easy to fall off, and the oil accumulates in the cavities formed by the falling off, and serves as an oil pot, which is preferable because lubricity is improved. When the amorphous carbon is spherical, it is easier to fall off than when it is non-spherical,
The lubricity improving effect is high. Further, when the particle size is large, the particles are liable to fall off. Therefore, the average particle size is preferably in the range of 5 to 30 μm from the viewpoint of obtaining an appropriate lubricating property improving effect. The depression caused by dropping of the amorphous carbon particles having an average particle diameter in this range is suitable as an oil pot.

In the sintered composite material of the present invention, amorphous carbon having a surface coated with a metal element may be used. As described above, the oil pot improves lubricity, but when the sliding environment is dry, the oil pot is useless. Further, depending on the mating material, a material that does not fall off may have better wear resistance. By coating the surface of the amorphous carbon with a metal element, the adhesion between the amorphous carbon and the matrix interface can be improved, and the falling off can be reduced. By improving the adhesion, the wear resistance can be improved, and the strength characteristics of the composite material can be increased. In addition, as the metal element, those which do not form a brittle compound by reacting with Al as a base material, for example, Cu,
Fe, Ni, Ag and Al are used.

On the other hand, the graphite contained in the composite material of the present invention, which is also called graphite, graphite, etc., is one of the allotropes of carbon and can be either naturally produced or artificially produced. You can also. Further, the particle size of the graphite particles is suitably, for example, 20 to 180 μm. The particle size of the graphite particles is preferably 50 to 120 μm, more preferably 70 to 120 μm.
100 μm.

Further, the graphite particles are, for example, 5
The graphite particles having 0% or more can have a mass having an aspect ratio of 5 or less. Preferably, the aspect ratio of graphite particles of 70% or more, more preferably 80% or more, is 5 or less. The aspect ratio is preferably 3 or less. Furthermore, even when the composite material of the present invention is viewed three-dimensionally, the height / length ratio of graphite particles of 50% or more is suitably 5 or less. Preferably, the height / length ratio of the graphite particles of 70% or more, more preferably 80% or more, may be 5 or less.

Next, a method for producing the sintered composite material of the present invention will be described. The method for producing a sintered composite material according to the present invention includes mixing of pure aluminum or an aluminum alloy powder, amorphous carbon powder having an average particle size of 5 to 300 μm, and aluminum borate powder having an average particle size of 2 to 300 μm. Use powder. Further, in the method for producing a sintered composite material of the present invention, the particle size ratio of pure aluminum or aluminum alloy powder to the pure aluminum or aluminum alloy powder (graphite diameter / metal powder diameter) is 0.2 or more. A mixed powder composed of graphite powder and aluminum borate powder having an average particle diameter of 2 to 300 μm is used. The aluminum in the sintered composite material of the present invention includes not only high-purity aluminum but also aluminum containing a small amount of impurities such as Fe and Si. Furthermore, aluminum alloy metal powders include Al-Cu, Al-Mg, Al-S
At least one selected from the group consisting of i-Cu-based and Al-Si-Mg-based can be given.

As the amorphous carbon powder, it is suitable to use one having an average particle diameter in the range of 5 to 300 μm, and preferably in the range of 5 to 30 μm. This is because, when the composite material is subjected to secondary processing, if the particle size is too large, amorphous carbon will fall off the composite material surface, and as a result, the amount of amorphous carbon on the sliding surface will decrease, This is because there is a possibility that the desired wear resistance may not be obtained. or,
If the particle diameter of the amorphous carbon is too small, agglomeration of the amorphous carbon occurs, leading to a reduction in strength.

The aluminum borate powder has an average particle size of 2
It is appropriate to use those having a size in the range of 300 to 300 μm, preferably 5 to 200 μm, more preferably 8 to 200 μm.
Powder in the range of ３０30 μm. By using a powder having such a particle size range, it is possible to prevent agglomeration occurring in aluminum borate having a small particle size and a reduction in strength caused by the aggregation, and to reduce the aggressiveness of a counterpart material occurring in aluminum borate having a large particle size. Can be suppressed.

As for the graphite powder, it is appropriate to use one having a particle size ratio (diameter of graphite powder / diameter of metal powder) of 0.2 or more to pure aluminum or aluminum alloy powder. 0.2 to 1.8
And more preferably 0.5 to 1.2, and still more preferably 0.7 to 1.0. 0.2 particle size ratio
By setting the range to ~ 1.8, it is possible to prevent the graphite powder from adhering to the metal powder containing aluminum and hindering the sinterability of the composite material. Furthermore, by setting the particle size ratio to 0.2 or more, the wear resistance can be improved as compared with the existing composite material. Similarly, the graphite powder tends to adhere to the metal powder and hinder the sinterability of the sintered composite. On the other hand, if the particle size ratio exceeds 1.8 and the graphite powder particle size is too large, the strength of the sintered composite material is reduced. However, when the use of the composite material is mainly intended for wear resistance, the upper limit of the particle size ratio is not particularly limited. Here, the particle size ratio means the ratio of the average particle size.

The shape of the graphite powder is not particularly limited as long as the ratio of the particle diameter to the pure aluminum or aluminum alloy powder is 0.2 or more. For example, the shape may be a sphere, a flake, a lump, or the like. Preferably, a lump can be used. The use of the massive graphite powder has the advantage that the particle size destruction at the time of powder mixing is further reduced and the fine graphite adheres little to the surface of the Al powder.

The range of the average particle size of the graphite powder to be used can be appropriately changed according to the particle size of the base material aluminum or aluminum alloy powder. For example, when aluminum powder having a particle size of about 100 μm obtained by a general powder production method is used, graphite powder having an average particle size in the range of 20 to 180 μm can be used. Further, as the aluminum powder or the like as a base material, for example, when using a smaller particle size obtained by a rapid solidification method or the like,
Graphite having a smaller average particle size can be used accordingly. In this case, if the aluminum powder of the base material is also small and fine, it is advantageous in that the strength of the obtained composite material is also improved.

In a matrix powder (pure aluminum or aluminum alloy powder), an amorphous carbon powder or a graphite powder (particle diameter ratio of matrix powder to 0.2 or more)
And aluminum borate powder are uniformly dispersed to obtain a mixed powder. The content of aluminum borate powder and amorphous carbon powder or graphite powder contained in the mixed powder,
It can be set as appropriate according to the composition of the composite material as a product. In particular, as described in the above description of the composite material, when the content of the aluminum borate powder is 10% by volume or more and the content of the amorphous carbon powder or the graphite powder is 10% by volume or more, or Even if the content of the aluminum borate powder is 5 to 10% by volume,
Content of amorphous carbon powder or graphite powder is 1
When the content is 5% by volume or more, a composite material having excellent wear resistance can be obtained. Therefore, each component is adjusted so that the content of the aluminum borate powder and the amorphous carbon powder or the graphite powder in the composite material is within the above range. Can be set. As a general tendency, the greater the amount of amorphous carbon powder added, the better the wear resistance effect.

After mixing the matrix powder with the amorphous carbon powder or graphite powder and aluminum borate, the mixed powder of the matrix powder, the amorphous carbon powder or graphite powder and the aluminum borate powder is compacted. In the compacting, generally, after a mixed powder is filled in a molding die, pressure is applied by a compressor (press). To obtain a product with higher density and higher strength, the molding pressure may be increased or re-pressing may be performed.

Thereafter, the compact obtained by compacting is subjected to a degassing treatment as required. This degassing process is mainly performed to remove the moisture of the green compact.

The green compact thus obtained can be sintered to produce a sintered composite material. Examples of sintering methods include hot pressing, powder extrusion, powder forging, powder rolling, and isostatic pressing.

The hot pressing method is a method in which the mixed powder is subjected to compression molding or filling in a sealed can or the like, degassing is performed if necessary, and compression is performed during heating to perform sintering. Powder extrusion is a method in which a mixed powder is extruded by an extruder and solidified by molding. The powder forging method is a method in which forging is performed by heat. The powder rolling method refers to a powder rolling method in which a mixed powder is directly rolled and formed into a thin plate. Isostatic pressing is a method in which a mixed powder is filled in a container such as a sealed can, and the pressure is applied isotropically to the container through a liquid medium or the like to form the container. Hot isostatic pressing (HIP) ) And cold isostatic pressing (CI
P).

Generally, by performing the above-described sintering,
A sintered composite can be obtained, but depending on the product,
After sintering, secondary processing such as heat treatment may be performed. For example, if you want to increase the strength of the product,
Aging treatment or the like may be performed.

The present invention will be further described below with reference to examples. Example 1 A sintered composite material of the present invention was produced by a sintered metal production process of a hot press method. The production process is the same as the existing one, (1) prepare raw material powder, (2) mix powder, (3) produce green compact, (4) degas, (5) heat Hot pressing is performed to form (6) a sintered composite material.

As the sintered composite material according to the present invention,
Pure aluminum was used as the base material of (1). The particle size of the powder is-# 200 (about 78 µm or less). To this, 0 to 15% by volume of amorphous carbon powder (glassy carbon) and aluminum borate were added. These were mixed with the powder of the above (2) using a blender (mixer), and the green compact of the above (3) was formed by cold pressing. The obtained green compact is
As the degassing process (4), a vacuum heating degassing process was performed. Then, the hot press of (5) is performed at 500 ° C. for 4 hours.
The operation was performed at 5 tons / cm ² for 5 minutes to obtain the sintered composite material (6).

FIG. 1 shows the structure of a sintered composite material composed of pure aluminum, aluminum borate (10% by volume), and amorphous carbon (10% by volume) obtained by the hot pressing method described above. In FIG. 1, amorphous carbon is clearly shown in a black circle, and aluminum borate is shown in black as a large number of points or groups of points. The other part is pure aluminum of the base material. As is clear from FIG. 1, aluminum borate particles and amorphous carbon particles are scattered in the continuous phase of pure aluminum.

Example 2 A test was conducted to evaluate the wear characteristics of the sintered composite material.
As a test device, a ball-on-disk wear tester shown in FIG. 2 was used. The evaluation of the wear characteristics was carried out by rotating the sintered composite material with a ball-on-disk wear tester and sliding the ball against the material under a predetermined load. The test conditions are as follows. Ball: Bearing steel (SUJ-2, diameter 6 mm) Load: 1.0 Newton Circumferential speed: 60 mm / sec Sliding distance: 200 × 10 ³ mm Test atmosphere: Unlubricated atmosphere

As a sintered composite material, the result of a test in which amorphous carbon was contained at 10% by volume and aluminum borate powder at 0 to 15% by volume with respect to pure aluminum,
As shown in FIG. FIG. 3A shows the relationship between the content of aluminum borate and the wear volume. In FIG. 3A, the horizontal axis represents the content of aluminum borate, and the vertical axis represents the wear volume. FIG. 3B shows the relationship between the content of aluminum borate and the coefficient of friction. The horizontal axis of FIG. 3B indicates the content of aluminum borate, and the vertical axis indicates the coefficient of friction.

As is apparent from FIG. 3A, the wear resistance is improved as the content of aluminum borate is increased. FIG. 4 shows that among these sintered composite materials, amorphous aluminum was converted to pure aluminum by 10%.
% Of aluminum borate and 10 or 15% by volume of aluminum borate.
The comparison in the case of containing 5% by volume and 10% by volume of amorphous carbon is shown. In particular, FIG. 4 (a) shows the relationship with the wear volume of each sintered composite material, and FIG. 4 (b) shows the relationship with the friction coefficient of each sintered composite material. Prior art pure Al + Si (1
5% by volume) + Less amount of aluminum borate as hard particles compared to GC (amorphous carbon) (10% by volume)
(For example, pure Al + Al borate (10% by volume) + GC (amorphous carbon) (10% by volume)) also shows good wear resistance. Even if the hard particles are reduced, the wear characteristics are good,
The workability in the subsequent secondary processing and the cutability in the cutting work can be improved. Further, when the content of aluminum borate increases, more excellent wear resistance is exhibited.

Example 3 The abrasion resistance of the sintered composite material of the present invention comprising pure aluminum, aluminum borate and amorphous carbon was measured using pure aluminum, silicon and amorphous carbon described in JP-A-10-140265. Sintered composite material (comparative example)
Was compared with the abrasion resistance. The abrasion resistance test was performed in the same manner as the method described in Example 2. The content of amorphous carbon contained in the sintered composite material is 10% by volume (constant)
The content of aluminum borate (Example) or silicon (Comparative Example) was changed to 0, 5, 10, and 15% by volume, respectively. FIG. 5 shows the results. In the figure, the vertical axis indicates the wear volume, and the horizontal axis indicates the content of aluminum borate or silicon. From the results shown in FIG. 5, 5% by volume
It can be seen that when aluminum borate is added, the abrasion volume is reduced to less than half and the abrasion characteristics are improved as compared with the case of 0% by volume. Further, when 10% by volume or more of aluminum borate is added, the wear volume is half or less than that of the case where 10% by volume or more of silicon is added. In this range, the composite material of the present invention has It can be seen that the composite material has better wear characteristics than the composite material described in JP-A-10-140265.

[0035]

According to the present invention, in an aluminum or aluminum alloy which is a soft material having a high coefficient of friction and easy to wear, amorphous carbon particles and / or graphite particles are contained in a continuous phase of the aluminum or aluminum alloy. By interspersing the aluminum borate particles, a sintered composite material having improved wear resistance can be obtained without performing other processing.

According to the present invention, the aluminum-based metal has the advantage of being suitable for weight reduction, but is a material which is soft, has a high coefficient of friction, and is easily worn. However, the wear-resistant sintered composite material of the present invention does not require a separate surface treatment and has high wear resistance.

Further, according to the present invention, even when the sintered composite material of the present invention is used as one of the sliding members, the aggressiveness to the counterpart metal can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure state in which a hypereutectic Al—Si alloy contains amorphous carbon particles and aluminum borate.

FIG. 2 is a view showing a ball-on-disk wear tester.

FIG. 3 is a view showing a wear amount and a wear coefficient of the sintered composite material of the present invention.

FIG. 4 is a view showing a wear amount and a wear coefficient of the sintered composite material of the present invention and a comparative material.

FIG. 5 is a view showing wear volumes of the sintered composite material of the present invention and a comparative material.

Claims (11)

[Claims] 1. A sintered composite material comprising amorphous carbon particles or graphite particles and aluminum borate particles dispersed in a continuous phase of pure aluminum or an aluminum alloy. 2. The method according to claim 1, wherein the aluminum alloy is Al-Cu based,
The sintered composite material according to claim 1, wherein the sintered composite material is at least one alloy selected from the group consisting of l-Mg, Al-Si-Cu, and Al-Si-Mg. 3. The sintered composite material according to claim 1, wherein the amorphous carbon particles are spherical particles. 4. The sintered composite material according to claim 1, wherein the amorphous carbon particles are amorphous carbon particles coated with a metal element. 5. The content of aluminum borate particles is 5 to 5.
10 vol%, the content of amorphous carbon particles is 15 vol% or more, or the content of aluminum borate particles is 10 vol% or more, and the content of amorphous carbon particles is 1 vol.
The sintered composite material according to claim 1, wherein the content is 0% by volume or more. 6. The sintered composite material according to claim 1, wherein the shape of the graphite particles is a lump. 7. A powder compact comprising a mixed powder of pure aluminum or aluminum alloy powder, amorphous carbon powder having an average particle size of 5 to 300 μm, and aluminum borate powder having an average particle size of 2 to 300 μm, A method for producing a sintered composite material, comprising sintering a green compact obtained by compacting. 8. A pure aluminum or aluminum alloy powder, a graphite powder having a particle size ratio of the pure aluminum or aluminum alloy powder of 0.2 or more, and an aluminum borate powder having an average particle size of 2 to 300 μm. A method for producing a sintered composite material, comprising compacting a mixed powder and sintering a compact obtained by compacting. 9. The method according to claim 8, wherein the upper limit of the particle size ratio is 1.8 or less. 10. An aluminum alloy powder comprising Al-Cu
System, Al-Mg system, Al-Si-Cu system, Al-Si-
The method according to any one of claims 7 to 9, which is at least one alloy powder selected from the group consisting of Mg-based. 11. When the content of aluminum borate in the sintered composite material is 5 to 10% by volume and the content of amorphous carbon is 15% by volume or more, or when the content of aluminum borate is 10% by volume or more. The method according to claim 7, wherein the contents of the aluminum borate powder and the amorphous carbon powder in the mixed powder are selected so that the amorphous carbon content is 10% by volume or more.