JP3753981B2 - Aluminum alloy sprayed layer and sliding material with excellent sliding properties - Google Patents

Description

【００２４】
この表に見られるように、本発明法によりマトリックスの硬さを所定値以下にすることにより耐摩耗性が著しく向上する。
実施例3の粉末及び溶射層の金属顕微鏡組織をそれぞれ図2、3に示す。比較例3の粉末及び溶射層の金属顕微鏡組織をそれぞれ図4、5に示す。図2、3を図4、5と比較すると熱処理により粉末中のSi粒子層は粗大化し、またこれと対応して溶射層中のSi粒子も粗大化していることが分かる。
【００２５】
次に、溶射層の耐焼付試験を下記条件で行い、その結果を組成とともに図6（表2）に示す。
試験機：3ピン／ディスク摩擦摩耗試験機
荷重：40kgf／cm²より20kgf／cm²づつ漸増（最大150kgf／cm²）
回転数：7200rpm
時間：15分ずつステップアップ（計150分）
表2より、本発明の溶射層及び軟質皮膜を固着した溶射摺動材料はマトリックスが硬い比較例よりも耐焼付性が優れていることが分かる。
【００２６】
【発明の効果】
以上説明したように、本発明によると従来本出願人が提案した溶射Al合金よりも一層良好な耐摩耗性及び耐焼付性を達成することができる。
このために、本発明の溶射層は各種摺動材料として好ましく使用することができる。
【図面の簡単な説明】
【図１】 本発明のアルミニウム合金マトリックス表面硬さとSi量の関係を示すグラフである。
【図２】 実施例3のアトマイズ粉末の組織を示す金属顕微鏡写真である。
【図３】 実施例3の溶射層の組織を示す金属顕微鏡写真である。
【図４】 比較例3のアトマイズ粉末の組織を示す金属顕微鏡写真である。
【図５】 比較例3の溶射層の組織を示す金属顆微鏡写真である。
【図６】 焼付試験に供した供試材の性状と試験結果を示す図表（表2）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-Si-Al alloy sprayed layer and a sliding material excellent in sliding characteristics.
[0002]
[Prior art]
First, the prior art of an abrasion resistant aluminum alloy will be described.
Eutectic or hypereutectic Al-Si aluminum alloys produced by casting or forging have good wear resistance. However, if the Si content exceeds 15%, production becomes difficult. It will be constrained by the amount of Si.
In recent years, many powder metallurgy products using rapidly solidified aluminum alloy powders have been proposed (for example, Japanese Patent No. 2535789), and the Si content is very high, for example, 14 to 30%, so the wear resistance is remarkably improved. . However, since this alloy needs to be processed by hot extrusion followed by hot extrusion, it is necessary to invest in a very large capacity press and extruder to produce large parts. It must be said that cost competitiveness is extremely low.
[0003]
As a method of thermal spraying Al alloy with high Si content of 35-45% by weight that can exhibit excellent wear resistance, Si-Al alloy with Si content that does not crystallize primary Si and Si particles are prepared separately Thus, it is known to produce a high Si—Al alloy in which primary Si does not crystallize by spraying simultaneously (Japanese Patent No. 2792130). Since this publication does not show a specific method of spraying and a spray gun, it is considered to be a general flame spraying method. It is understood that it is necessary to use two kinds of powders as described above because crystallization of primary crystal Si cannot be avoided if one kind of powder is used in a general thermal spraying method.
Furthermore, it is known to add graphite as a solid lubricant to an aluminum alloy (Japanese Patent No. 2584488). However, the method of this publication employs a sintering method in a vacuum or an inert atmosphere, and graphite is mixed with aluminum alloy powder in a powder form.
[0004]
Tribologist Vol. 41, no. As described on pages 19 to 24 of No. 11, thermal spraying technology is widely adopted as a sliding layer forming technology. The thermal spray materials listed here are Zn, Al, white soluble alloys, heat resistant alloys, oxide ceramics, cermets, and the like. Incidentally, graphite, is not mentioned in that spraying known Tribo materials such as MoS _2.
[0005]
In Japanese Patent Application No. 10-68951, the present applicant has proposed a method of making the Si morphology granular by spraying a Si-containing aluminum alloy.
Subsequent research shows that the matrix of the sprayed Si-Al alloy is brittle because of the solid solution of Si, and there is room for improvement in terms of sliding properties.
[0006]
[Problems to be solved by the invention]
The development of conventional aluminum-based thermal spray materials is moving toward the refinement or suppression of primary Si, the increase in Si content, and the contrivance of the types of added metal components. However, there is a limit to the improvement of sliding characteristics by development in this direction. Furthermore, thermal spraying of an Al—Si alloy causes embrittlement.
It is an object of the present invention to provide an aluminum alloy sprayed layer that solves these problems of the prior art.
[0007]
[Means for Solving the Problems]
According to the usual spraying method for spraying ordinary Al-Si atomized powders, the present inventors cannot avoid the Al-Si alloy matrix being hardened by solid solution of Si. keeping the temperature to precipitate a solid solution of Si in the matrix; HVOF thermal spraying method to adopt; a part of the atomized powder comprises coarse particles of 75～200Myuemu, average particle size using the above powder 75 mu m Thus, the present invention was completed by finding an appropriate hardness range of the matrix. Coarse-grained powder uses the fact that the amount of dissolved Si is small because of the slow cooling rate during atomized powder production.
That is, the present invention includes an aluminum alloy containing 12 to 60% by weight of Si and 0.1 to 30% by weight of Sn and having Si particles dispersed therein, and the average surface hardness (Hv) of the aluminum alloy matrix is 50. It is an object to provide an aluminum alloy sprayed layer excellent in sliding characteristics, characterized in that ≦ Hv ≦ (5/2) Si (wt%) + 75.
The present invention will be described in detail below. Percentages are by weight unless otherwise specified.
[0008]
In the sprayed Al-Si alloy of the present invention, Si is finely dispersed in a large amount in an aluminum matrix to increase the hardness of the alloy and improve the wear resistance. Furthermore, the granular Si dispersed in a large amount makes it difficult for seizure due to the adhesion of the aluminum matrix to the counterpart material. If the Si content is less than 12%, this effect is small, whereas if it exceeds 60%, the alloy becomes brittle. In addition, preferable Si content is 15 to 60%, More preferably, it is 20 to 45%.
In the present invention, the Si particles are not granular, that is, a particle shape in which one direction in the material is clearly long, as seen in the Si particles of a rolled alloy. It is preferable to disperse in a lump shape, a polygonal shape, an island shape having a concavo-convex contour, and other irregular shapes not classified into these. More specifically, the ratio of the maximum diameter to the minimum diameter is 3 times or less on average.
[0009]
Subsequently, the range of the hardness (Hv) of the matrix of the aluminum alloy is as shown in FIG. Here, if the hardness is less than Hv50, the seizure resistance is poor, which is not preferable. By the way, Hv50 almost corresponds to the T6 tempered state of A2024 alloy. Next, when Hv> (5/2) Si (wt%) + 75, since the matrix is hard and brittle, the wear resistance is poor. Here, the gradient (5/2) of the linear equation means that the upper limit of the allowable matrix hardness increases as the Si amount increases. This means that if the amount of dispersed Si particles increases corresponding to the increase in Si amount, seizure can be prevented by the wear resistance action of the Si particles even if the matrix is somewhat hard. If this gradient is greater than (5/2), the abrasive wear will be severe in Al alloys with high Si composition, the amount of wear will increase and seizure will be easier, while if it is smaller than (5/2), seizure resistance will be increased. A good composition is excluded from the present invention in the high Si region. Similarly, the linear expression 75, together with the above gradient, defines an upper limit for acceptable matrix hardness.
The above primary equation defines a lower surface hardness (Hv) than a sliding layer made of ordinary sprayed atomized powder. By determining the hardness in this way, abrasive wear of the matrix occurs and wear resistance is improved. Preventing it from becoming defective.
[0010]
The hardness of the matrix of the aluminum alloy is measured by measuring a sample obtained by etching the structure of the polished sample with a micro Vickers hardness meter (load = 25 to 300 g). The average value of hardness is set so that a value representative of the hardness of the entire area in contact with the counterpart material is obtained.
[0011]
In addition, the solid solution Si in a matrix can be deposited by heat-processing the whole quantity or one part of atomized powder to 400-650 degreeC. Even if the hardness of the entire alloy is increased by precipitation, the hardness of the matrix may be decreased.
[0012]
In the present invention, Sn is added, and an Al—Si—Sn alloy having excellent wear resistance and seizure resistance is used as a matrix. Sn is a component that uniformly disperses in aluminum and imparts lubricity and conformability. Also, Sn adheres preferentially to the mating material and adheres to the mating material between the same material of Al and the bearing Al. This prevents the occurrence of sliding and improves seizure resistance.
If the Sn content is less than 0.1%, the effect of improving lubricity is small, and if it exceeds 30%, the strength of the alloy decreases. A preferable Sn content is 5 to 25%. The Sn phase exhibits a flake shape in the layer, and this shape is considered preferable in terms of lubricity.
[0014]
Furthermore, the present inventors formed an eutectic and hypereutectic region Al-Si aluminum alloy sliding material as a sliding layer on the surface of the swash plate by a simple method, and various conventional sliding layers. We conducted research to demonstrate better sliding characteristics.
Conventionally, no examination has been made to combine a thermal spraying technique with a tribo material such as graphite or MoS ₂ . By the way, the spraying temperature of the aluminum alloy needs to be 700 ° C. or higher, while the reaction between graphite and oxygen occurs actively at 500 ° C. or higher. Therefore, if even a small amount of oxygen is present in the spray flame, the graphite is in the sprayed layer. May not be included. Therefore, the present inventors were concerned that graphite may burn and disappear due to oxygen present in the spraying atmosphere, and that MoS ₂ may also decompose and disappear in the same manner. It has been found that these tribo materials can be dispersed in an Al material.
That is, the present invention includes an aluminum alloy containing 12 to 60% by weight of Si and 0.1 to 30% by weight of Sn, in which granular Si is dispersed, and a graphite type or an amorphous material dispersed in a matrix made of the aluminum alloy. It is intended to provide a sprayed layer excellent in sliding characteristics, characterized by comprising at least one dispersed phase of the group consisting of carbon and MoS _{2 in} the middle of both carbon and crystallized levels.
[0015]
In the present invention, the tribologist Vol. 41, no. 11, High-speed gas flame spraying method (HVOF) described in FIG. 2 is adopted. Since this method has the features described in the same page, page 20, right column, lines 4 to 13, it is considered that a characteristic Si phase form can be obtained.
As the thermal spraying powder, an atomized powder such as an Al—Si alloy or an Al—Si—Sn alloy can be used. These atomized powders may be completely melted on the substrate and then solidified, or a part thereof may be deposited on the substrate in an unmelted state to leave a powder structure.
As the thermal spraying conditions, an oxygen pressure of 0.9 to 1.2 MPa, a fuel pressure of 0.6 to 0.9 MPa, and a spraying distance of 50 to 250 mm are preferable.
The thickness of the sprayed layer is preferably 10 to 500 μm, more preferably 10 to 300 μm.
The hardness of the aluminum alloy after thermal spraying is in the range of Hv 100 to 400. Since the hardness of the conventional 12% Si-containing aluminum alloy is in the range of Hv 50-100, it can be said that the thermal sprayed layer of the present invention is very hard.
[0016]
Next, the phase dispersed in the aluminum alloy matrix by thermal spraying will be described. The material of the dispersed phase is sprayed together with the aluminum alloy or its raw material powder. According to the above-described high-speed gas flame spraying method, these tribo materials are relatively less likely to undergo combustion decomposition during spraying and are taken into the sprayed layer.
As the carbonaceous material, amorphous carbon, graphite, carbon having a middle degree of crystallization, or the like is used. Graphite can be either natural graphite and artificial graphite. Since graphite has a strong cleaving property, this property can be used to improve the sliding characteristics. A carbonaceous material with a remarkable graphite structure exerts the effect of cleavage, while the two-dimensional structure becomes obscured and exhibits wear resistance and improves sliding characteristics. Further, since these carbonaceous materials are not melted during the thermal spraying, they are dispersed as they are in the thermal spraying layer while keeping the raw material powder shape relatively.
Although MoS ₂ is another dispersed phase is a well known Tribo material, the effect of the sliding property improving the thermal sprayed layer under severe conditions less, but not more graphite than was mild conditions improve sliding characteristics There is an effect to do.
The amount of the tribo material is preferably 2 to 40% by weight, more preferably 5 to 25% by weight with respect to the sprayed layer. Moreover, it is preferable that the average particle diameter before thermal spraying of a tribo material is 10-50 micrometers, More preferably, it is 20-40 micrometers.
[0017]
Hard materials such as FeB, Fe ₃ P, A1 ₂ O ₃ , SiO ₂ , SiC, Si ₃ N ₄ are added to improve wear resistance in addition to the above-mentioned aluminum alloy and carbonaceous material and / or MoS ₂ You can also These materials are not dissolved during spraying but are dispersed in the alloy. These hard materials are preferably 20% by weight or less based on the entire sprayed layer.
[0018]
Various substrates such as iron, copper, and aluminum can be used as the substrate on which the sprayed layer is formed. If the surface of the substrate is roughened to a surface roughness of preferably Rz 10 to 60 μm by shot blasting or the like, the adhesion strength of the film is increased. When specifically to measure the adhesion strength by shear failure test method, while the adhesion strength of the sprayed Ni film to steel substrate (Shoddo blanking last) was 30～50MPa, adhesion strength of the present invention coating 40 It was 60 MPa. Therefore, it is possible to obtain the same adhesiveness as that of the Ni sprayed coating, which is conventionally said to have good adhesiveness .
[0019]
When the sprayed layer is used without an overlay, the surface of the sprayed layer is preferably finished to Rz3.2 μm or less.
When carrying out the present invention as a sliding material using overlay, a soft metal such as Sn-based or Pb-Sn, a solid lubricant such as MoS ₂ , graphite, MoS ₂ + graphite, or these resins are mixed with a resin. Various soft coatings with excellent conformability can be used by adhering to the sprayed layer. Combining the above-mentioned soft coating and sprayed layer dramatically improves the seizure resistance and provides performance that surpasses bronze-based sliding materials.
As described above, MoS ₂ present in the sprayed layer has little improvement effect on sliding characteristics under severe conditions where there is no refrigerating machine oil, but MoS ₂ as an overlay exhibits an excellent effect.
[0020]
[Action]
Generally, hardening / strengthening the matrix of aluminum alloy is effective for sliding properties, but in the case of a sprayed aluminum alloy, the hardening becomes excessive, resulting in abrasive wear and counterproductive effects. It has been proposed to precipitate solid solution elements from the matrix. On the other hand, the Al alloy in which the solute elements in the matrix are almost depleted as in the present invention usually tends to wear due to adhesion with the counterpart material, but in the case of a thermal spray material, a large amount of Si is preferable. Since it is contained in a granular form, no harmful effects are caused.
[0021]
【Example】
Example 1
Prepare aluminum alloy atomized powder (average particle size -75μm) whose composition and preparation method are shown in Table 1 below, and apply shot blasting with a steel grid (dimension 0.7mm) to a commercially pure aluminum rolled plate to roughen the surface. Thermal spraying was performed using a substrate roughened to Rz 45 μm.
Thermal spraying was performed using an HVOF type thermal spraying machine (DJ made by Sulzer Metco) under the following conditions.
Oxygen pressure: 1.0 Mpa
Fuel pressure: 0.7 MPa
Thermal spray distance: 180mm
Thermal spray layer thickness: 200 μm
[0022]
The abrasion resistance test of the sprayed layer was conducted under the following conditions, and the results are shown in Table 1 together with the composition.
Testing machine: 3-pin / disk friction and abrasion testing machine Load: 40 kgf / cm ²
Rotation speed: 700rpm
Time: 2Hr
[0023]
[Table 1]

[0024]
As can be seen from this table, the wear resistance is remarkably improved by reducing the hardness of the matrix to a predetermined value or less by the method of the present invention.
The metal microstructures of the powder and sprayed layer of Example 3 are shown in FIGS. 2 and 3, respectively. FIGS. 4 and 5 show metal microstructures of the powder and the sprayed layer of Comparative Example 3, respectively. Comparing FIGS. 2 and 3 with FIGS. 4 and 5, it can be seen that the Si particle layer in the powder is coarsened by the heat treatment, and the Si particles in the sprayed layer are also coarsened correspondingly.
[0025]
Next, a seizure resistance test of the sprayed layer was performed under the following conditions, and the results are shown in FIG. 6 (Table 2) together with the composition.
Tester: three-pin / disc friction wear testing machine Load: than 40kgf / cm ² 20kgf / cm ² increments increasing (up to 150 kgf / cm ²⁾
Rotation speed: 7200rpm
Time: Step up by 15 minutes (total 150 minutes)
From Table 2, it can be seen that the thermal spray sliding material to which the thermal spray layer and the soft coating of the present invention are fixed has better seizure resistance than the comparative example having a hard matrix.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to achieve better wear resistance and seizure resistance than the conventional sprayed Al alloy proposed by the present applicant.
For this reason, the sprayed layer of the present invention can be preferably used as various sliding materials.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the surface hardness of an aluminum alloy matrix of the present invention and the amount of Si.
2 is a metal micrograph showing the structure of atomized powder of Example 3. FIG.
3 is a metallographic micrograph showing the structure of the thermal sprayed layer of Example 3. FIG.
4 is a metallographic micrograph showing the structure of an atomized powder of Comparative Example 3. FIG.
5 is a metal condylar micrograph showing the structure of a sprayed layer of Comparative Example 3. FIG.
FIG. 6 is a table (Table 2) showing properties and test results of test materials subjected to a seizure test.

Claims (4)

An aluminum alloy produced by atomization containing 12 to 60% by weight of Si, 0.1 to 30% by weight of Sn, and the balance consisting of Al and inevitable impurities , partly containing 75 to 200 μm coarse grains , average particle size and high-speed gas flame spraying the above aluminum alloy powder 75 micron m, then 400 by heat treatment to 650 ° C., an average surface hardness of the aluminum alloy matrix (Hv) of 50 ≦ Hv ≦ (5/2) Si (wt%) was adjusted to + 75, the Si particles are dispersed, an aluminum alloy sprayed layer excellent in sliding characteristics.   The aluminum alloy sprayed layer having excellent sliding characteristics according to claim 1, wherein the Si particles are granular. The sliding according to claim 1 or 2, comprising the aluminum alloy and at least one dispersed phase of the group consisting of carbon and MoS _{2 in} which the balance is graphite-type or amorphous carbon, or the degree of crystallization is between them. Aluminum alloy sprayed layer with excellent properties. A slide in which an Sn or Pb-Sn metal coating or a solid lubricant coating in which MoS ₂ , graphite or MoS ₂ and graphite are mixed with a resin is fixed to the sprayed layer according to any one of claims 1 to 3. Moving material.

Images