Sliding bearing and method for manufacturing the same

Abstract

To provide a slide bearing excellent in non-seizure property.SOLUTION: The slide bearing comprises a base layer and a coating layer. The coating layer comprises at least two overlay layers and an intermetallic compound-containing layer each of which is located between adjacent overlay layers. The intermetallic compound-containing layer comprises a layered metal portion in an intermetallic compound matrix. An area of the layered metal portion is 60% to 95% of an area of the intermetallic compound-containing layer. The invention also relates to a method of producing the slide bearing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention particularly relates to a coating structure of a sliding bearing used in an internal combustion engine, a piston compressor, etc. In particular, it relates to a sliding bearing having a coating structure excellent in non-seizure property under abnormal load. The present invention also relates to a method for manufacturing this sliding bearing.

Background Art

[0002] Sliding members such as plain bearings of internal combustion engines often include a lining alloy of copper or aluminum joined to a steel backing. A tough surface that can withstand the load received by the sliding member during use can be obtained with a copper alloy or an aluminum alloy. Such a sliding member must have not only good conformability and compatibility but also appropriate non-seizure property. For this purpose, usually, a soft coating layer may be provided on the lining layer (bearing alloy layer).

[0003] For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2002-310158) describes a multi-layer sliding material in which a tin-copper-based tin-based overlay layer is provided on a bearing alloy layer via an intermediate layer for preventing copper diffusion. In this document, in order to be able to prevent a decrease in copper in the surface layer portion of the overlay layer made of a tin-based alloy over a long period without increasing the thickness of the intermediate layer, a plurality of layers with different copper contents are provided, thereby maintaining non-seizure property.

[0004] On the other hand, in order to improve wear resistance and non-seizure property, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 11-182549) discloses a sliding bearing in which hard particles having an average particle diameter of 15 μm or less are dispersed in a main load portion of an overlay in an amount of 0.3 to 25% by volume to enhance wear resistance and make seizure less likely to occur.

[0005] In the operating environment of a sliding bearing, there is a potential possibility that an abnormal load exceeding the design assumption may occur due to the operating conditions of the mounted application or disturbance factors. For example, when a vehicle or the like equipped with a sliding bearing fails, an abnormal load is applied to the sliding bearing, such as when the vehicle suddenly stops. Assuming such a case, the bearing is required to have particularly excellent seizure resistance improvement. In the method of embedding hard particles as in Patent Document 2, mixing into the overlay material in advance is necessary, which may impose restrictions on its composition and manufacturing method. Furthermore, in order to appropriately mix substances such as hard particles into the overlay material for improving seizure resistance assuming abnormal loads or failures, manufacturing restrictions occur due to the properties of the base material and additive materials. Also, restrictions may occur on the performance during normal use.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a coating structure for a sliding bearing having excellent seizure resistance. Another object of the present invention is to provide a coating structure for a sliding bearing and a manufacturing method thereof that are easy to manufacture and advantageous in manufacturing cost.

Means for Solving the Problems

[0008] According to one aspect of the present invention, there is provided a sliding bearing including a base layer and a coating layer. The coating layer of this sliding bearing is composed of at least two overlay layers in the thickness direction and intermetallic compound-containing layers respectively located between adjacent overlay layers. The intermetallic compound-containing layer includes a layered metal part in an intermetallic compound matrix, and the area of the layered metal part is 60% to 95% of the area of the intermetallic compound-containing layer.

[0009] According to one specific example, the coating layer consists of two overlay layers and an intermetallic compound-containing layer located between the two overlay layers.

[0010] According to one specific example, the overlay layer contains an SnCu alloy, the intermetallic compound layer contains SnNi intermetallic compound and SnNiCu intermetallic compound, and the metal part contains metal Ni. Preferably, the SnNi intermetallic compound is Ni3Sn4 and the SnNiCu intermetallic compound is Sn5(CuNi)6.

[0011] According to one specific example, the thickness of the intermetallic compound-containing layer is 1 to 10 μm, preferably 2 to 5 μm.

[0012] According to one specific example, the thickness of the overlay layer is 1 to 30 μm, preferably 5 to 20 μm.

[0013] According to one specific example, the base layer is a backing layer adhered with a lining layer, and the coating layer is provided on the lining layer. The lining layer preferably consists of a copper-based alloy or an aluminum-based alloy.

[0014] According to one specific example, the sliding bearing further includes a dam layer provided between the lining layer and the coating layer. The dam layer preferably contains at least one of the group consisting of nickel, cobalt, iron, copper, chromium, zinc, aluminum, and their alloys.

[0015] According to one specific example, the thickness of the dam layer is 0.5 to 10 μm, preferably 1 to 6 μm.

[0016] According to one specific example, the total thickness of the coating layer is 5 μm to 50 μm.

[0017] According to another aspect of the present invention, there is provided a method for manufacturing the above-described sliding bearing. This manufacturing method includes a step of preparing a base layer, a step of depositing a layer of a first metal or alloy on the base layer, a step of depositing a layer of a second metal or alloy on the first layer, a step of depositing another layer of the first metal or alloy on the second layer, and optionally, a step of depositing at least one set of layers of the second and first metals or alloys thereon, and a heat treatment step. The heat treatment step heats the deposited layers to a temperature that enables the diffusion of metal atoms of the layer of the first metal or alloy, and the metal atoms of the layer of the first metal or alloy diffuse into and react with the layer of the second metal or alloy to form an intermetallic compound within the second metal or alloy while leaving the second metal or alloy remaining.

[0018] According to one specific example, the base layer is a backing layer adhered with a lining layer. According to one specific example, this manufacturing method further includes a step of depositing a dam layer on the bearing lining layer.

[0019] The present invention and many of its advantages will be described in more detail below with reference to the accompanying schematic drawings. The drawings are for illustrative purposes only and show several non-limiting examples.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0021] Fig. 1 shows a schematic cross-sectional structure of an example of the sliding bearing 1 of the present invention. The sliding bearing 1 includes a base layer composed of a back metal 2 and a lining layer (bearing alloy layer) 3 joined to the back metal, an optional dam layer (diffusion shielding layer) 4 on the lining layer, and a coating layer 5 on the dam layer. It has a structure in which a first overlay layer 61, an intermetallic compound-containing layer 7, and a second overlay layer 62 are laminated. The surface of the first overlay layer 61 constitutes a sliding surface 10. In the intermetallic compound-containing layer 7, metallic parts 9 made of metal exist in an intermetallic compound matrix 8 made of an intermetallic compound. The metallic parts 9 extend in a layer shape substantially parallel to the sliding surface 10 but are segmented by the intermetallic compound matrix 8. The area of the layered metallic parts 9 is 60% to 95% of the area of the intermetallic compound-containing layer 7. Preferably, the area of the layered metallic parts 9 is 70% to 90% of the area of the intermetallic compound-containing layer 7.

[0022] The back metal 2 is not particularly defined in the present invention and can be made of any suitable material such as steel, bronze, or an aluminum alloy.

[0023] The lining layer 3 can be made of any suitable material, but in practice, either a copper alloy or an aluminum alloy is used.

[0024] When the sliding bearing 1 is used at a high temperature for a long time, diffusion occurs between the lining layer 3 and the coating layer 5 due to thermal effects. Therefore, it is preferable to provide a dam layer 4 to prevent this diffusion. The dam layer 4 contains at least one of the group consisting of nickel, cobalt, iron, copper, chromium, zinc, aluminum, and their alloys and is adhered by any conventional coating method. When the lining layer is a copper alloy, it is preferable to use nickel for the dam layer. Note that the dam layer may contain or consist of an intermetallic compound in addition to a metal or an alloy. An intermetallic compound may be formed by heat treatment described later, and it may have a multilayer structure such as a two-layer structure of a metal or alloy layer and an intermetallic compound layer. The thickness of the dam layer 4 is usually in the range of 0.5 to 10 μm, preferably in the range of 1 μm to 6 μm. The thickness of the dam layer 4 is selected according to the purpose. For example, increasing the thickness of the dam layer 4 can provide an excellent bearing alloy function. On the contrary, reducing the thickness of the dam layer 4 can provide excellent conformability even when the coating layer 5 wears.

[0025] The coating layer 5 has a structure in which a first overlay layer 61, an intermetallic compound-containing layer 7, and a second overlay layer 62 are laminated. The present invention is not limited to the above example. In the present invention, specific examples having three or more overlay layers and an intermetallic compound-containing layer between the overlay layers are also possible. FIG. 2 shows a schematic cross-sectional structure of another example of the sliding bearing 1 in which the coating layer has three overlay layers 61', 62', 63' and two intermetallic compound-containing layers 71, 72. In this example, except for the coating layer 5, the backing metal 2, the lining layer 3, the dam layer 4, and the coating layer 5' have the configuration as described above. Although not shown, it goes without saying that a configuration having four or more overlay layers is also within the scope of the present invention.

[0026] The plurality of overlay layers 6 in the coating layer 5 may have the same composition or different compositions. The overlay layer 6 can contain at least one of tin, bismuth, lead, silver, indium, gold, antimony, aluminum, and alloys thereof. The overlay layer 6 can be attached by any conventional coating method.

[0027] The overlay layer 6 can also contain one or more types of soft particles selected from the group consisting of PTFE, fluorinated polymers, metal sulfides, metal fluorides, metal sulfates, graphite and other soft carbonaceous particles, hexagonal boron nitride, layered silicates, titanium oxide, zinc oxide and lead oxide, and other particles showing a hexagonal crystal structure. Further, the overlay layer 6 can contain one or more types of hard particles selected from the group consisting of metal oxides, borides, carbides, nitrides, sulfates and silicides, diamond, carbon nanotubes, graphene and other hard carbonaceous particles, and other particles showing a cubic crystal structure.

[0028] When there are multiple layers of the intermetallic compound-containing layer 7 in the coating layer 5, the intermetallic compound matrix 8 can have the same composition or different compositions, and the metal part 9 can also have the same composition or different compositions. The intermetallic compound matrix 8 can be formed by depositing a metal layer using any conventional coating method and then performing a heat treatment, and requires at least two types of elements. One of them is selected from the group consisting of tin, bismuth, lead, silver, indium, gold, antimony, and aluminum, and the other one or more types of elements can be selected from the group including nickel, cobalt, zinc, silver, iron, copper, chromium, cadmium, and aluminum.

[0029] The intermetallic compound matrix 8 and / or the metal part 9 can also include one or more types of soft particles selected from the group consisting of PTFE, fluorinated polymers, metal sulfides, metal fluorides, metal sulfates, graphite and other soft carbonaceous particles, hexagonal boron nitride, layered silicates, titanium oxide, zinc oxide and lead oxide, and other particles showing a hexagonal crystal structure. Also, the intermetallic compound matrix 8 and / or the metal part 9 can include one or more types of hard particles selected from the group consisting of metal oxides, borides, carbides, nitrides, sulfates and silicides, diamond, carbon nanotubes, graphene and other hard carbonaceous particles, and other particles showing a cubic crystal structure.

[0030] The metal part 9 in the intermetallic compound-containing layer 7 in the coating layer 5 can be selected from nickel, cobalt, zinc, silver, iron, copper, chromium, cadmium, aluminum, etc. The metal part may consist of a pure metal or an alloy. The metal part 9 extends substantially parallel to the sliding surface 10 in a layered or flaky form, but is segmented by an intermetallic compound. FIG. 3 is a schematic view showing the extension of the metal part 9 in a direction parallel to the sliding surface 10. The layered metal part 9 does not substantially overlap in a direction perpendicular to the sliding surface 10. The area of the layered metal part 9 is 60% - 95%, preferably 70% - 90% of the area of the intermetallic compound-containing layer 7. Here, the area of the layered metal part 9 refers to the area of the projected metal part 9 on the sliding surface 10 when the metal part 9 is projected onto the sliding surface 10, and the area of the intermetallic compound-containing layer 7 is equal to the area of the sliding surface (however, the measurement of the area ratio is performed by cross-sectional observation as follows).

[0031] The measurement of the area ratio of the layered metal part is performed by observing the cross-section of the sliding bearing with an optical microscope or a scanning electron microscope (SEM), measuring the length of the metal part in a direction parallel to the sliding surface 10, and obtaining the ratio to the length of the intermetallic compound-containing layer 7. This ratio is equal to the area ratio.

[0032] The sliding bearing of the present invention has a multilayer structure of the coating layer 5, and the non-seizure property is improved by the intermetallic compound-containing layer 7 being dispersed by the load during abnormal load. Even when the uppermost overlay layer is worn, the subsequent lower layer portion is protected from wear and seizure by the intermetallic compound. At that time, it is considered that cracks occur at the locations of the intermetallic compound that segments the metal part 9. Thereby, even when a large frictional force is applied to the intermetallic compound-containing layer, the entire intermetallic compound-containing layer does not peel off simultaneously, but only local peeling occurs. The locations of the intermetallic compound that segments the metal part 9 can be adjusted by adjusting the product heat treatment time, and as a result, the segmentation size of the intermetallic compound can be controlled. It is possible to control to an appropriate segmentation size according to the film thickness, material, number of layers, etc. of the overlay layer 6. The appropriate segmentation size is preferably 0.1 μm to 30 μm, more preferably 1 μm to 20 μm. The segmentation size of the metal part 9 is controlled according to the film thickness, material, number of layers, etc. required depending on the bearing usage application, but in any case, by making the metal part 9 in a discontinuous state, it is possible to arrange the intermetallic compound matrix 8 and the metal part 9 relative to each other, and it is possible to exhibit excellent non-seizure property during abnormal load.

[0033] According to the present invention, a laminated multilayer coating structure is formed, which consists of an intermetallic compound-containing layer 7 and a thin overlay layer 6, and further consists of an intermetallic compound matrix 8 and a metal part 9 in the intermetallic compound-containing layer 7. By adopting such a laminated coating structure, the thickness of each layer can be set to be thin while maintaining the total thickness equivalent to that of a single layer, and the accumulation of plastic deformation under an external load can be significantly reduced, thereby improving the fatigue performance of the coating.

[0034] The thickness of the intermetallic compound-containing layer 7 ranges from 1 to 10 μm, preferably from 2 to 5 μm. Such a structure can form the best metal part 9 and improve the seizure resistance of the bearing. Although the thickness of the metal part 9 is not particularly defined, in order to achieve the above effects, it is preferably from 0.1 μm to 0.5 μm. If the thickness of the metal part 9 is too large, the amount of intermetallic compound will decrease and it will be difficult to obtain the above effects. Therefore, it is preferably 30% or less of the thickness of the intermetallic compound-containing layer 7.

[0035] The thickness of each overlay layer 6 ranges from 1 to 30 μm, preferably from 5 to 20 μm. The thickness of each overlay layer 6 is selected according to the purpose. For example, by increasing the thickness of the overlay layer 6, excellent conformability and foreign matter embedding property on the sliding surface can be obtained. On the contrary, by reducing the thickness of the overlay layer 6, excellent fatigue resistance on the sliding surface can be achieved. By increasing the thickness of all the overlay layers 6 together, very excellent conformability and foreign matter embedding property can be obtained. By reducing the thickness of all the overlay layers 6 together, very excellent fatigue resistance can be achieved. By ensuring the layer thickness of the entire coating layer 5 through lamination, excellent conformability and foreign matter embedding property can be continuously obtained.

[0036] Next, a method for manufacturing the sliding bearing of the present invention will be described. First, a base layer (preferably a backing layer with a lining layer adhered thereto) is prepared, then optionally a dam layer is attached, then a layer of a first metal or alloy is attached, a layer of a second metal or alloy is attached on the first layer, and another layer of the first metal or alloy is attached on the second layer. Further, optionally, one or more sets of layers of the second and first metals or alloys are attached thereon. The attachment method may be a conventionally used method such as plating or PVD. Next, heat treatment is performed on this member. The above-mentioned intermetallic compound is formed by heat treatment. By heat treatment, metal atoms in the layer of the first metal or alloy diffuse and react with the layer of the second metal or alloy to form a metal compound. However, the second metal or alloy is not completely converted into an intermetallic compound, and the second metal or alloy remains in a layered form, and the heat treatment temperature and time are adjusted so that the area ratio (as defined above) is 60% to 95%.

[0037] It is advantageous to perform the heat treatment at a temperature of 100°C to 250°C, preferably 150°C to 180°C. At a higher temperature, there is a risk that the crystal structure of the overlay layer will change and affect its tribological performance. Also, at a lower heat diffusion temperature, the treatment time will be longer and the manufacturing cost will increase. The time of the heat diffusion process is adjusted according to the composition of the coating, but it is advantageous to set it to 2 hours to 60 hours, preferably 12 hours to 36 hours.

[0038] According to the present invention, by the manufacturing method by heat diffusion, the management of complicated chemical processes is avoided, and furthermore, harmful internal stresses are reduced, and quality control and product performance can be improved.

Example

[0039] Suitable specific examples will be described only by way of illustration. CuPb22Sn (22 mass% Pb, 1.5 mass% Sn, balance Cu), Ni, SnCu3 (3 mass% Cu, balance Sn), Ni, and SnCu3 were sequentially deposited by plating to the indicated thicknesses in Table 1 on a 1.2 mm steel backing. Next, this member was heat-treated at 165 °C for 8 hours twice (for a total of 16 hours) to produce a sample of a sliding bearing having the structure shown in FIG. 1. Intermetallic compounds Sn5(CuNi)6 and Ni3Sn4 were formed by the reaction of SnCu3 and Ni during the heat treatment, but Ni remained in a layered form with a maximum thickness of about 0.5 μm while being segmented. The area ratio of the Ni layer was about 80%. Table 2 shows the thicknesses of the respective layers after the heat treatment.

[0040] JPEG0007693498000001.jpg47149

[0041] JPEG0007693498000002.jpg43165

[0042] Baking test The sample of the example of the present invention described in Table 2 above was subjected to a seizure test to examine non-seizure properties. As a comparative material, a sample was prepared by sequentially depositing CuPb22Sn (lining layer): 0.3 mm, Ni (dam layer): 2 μm, and SnCu3 (coating layer): 20 μm by plating or the like on a 0.7 mm steel backing. The configuration of the comparative material is different from that of the sample of the present invention in that the coating layer is a single layer of an Sn-Cu alloy.

[0043] The seizure performance test was conducted under oil cut conditions using a ring-on-disk tester. Table 3 shows the test conditions. The test method is as follows. A flat test specimen having a test portion with an outer diameter of φ27 mm and an inner diameter of φ22 mm was prepared and placed under a rotating annular mating member. The test specimen is configured to be able to supply lubricating oil from a lubricating oil supply port provided at the back. A hydraulic device is provided on the lower surface of the test specimen, and it can be pressurized against the mating member by hydraulic pressure, and the frictional torque applied to the test specimen and the temperature of the back surface of the test specimen can be measured. First, rotate the mating material without applying pressure and gradually increase the rotational speed. When the peripheral speed of the mating material reaches 2 m / s and the back surface temperature reaches 130 °C, increase the load to a test load of 10 MPa at a pace of 2 MPa every 2 minutes. When the load from the mating material to the test specimen reaches 10 MPa, stop supplying lubricating oil and start the test. It was determined that seizure occurred when the frictional torque exceeded 5 Nm or the back surface temperature exceeded 200 °C.

[0044] The results of the seizure test are shown in Fig. 4. The comparative material seized in about 40 to 75 minutes, while the sliding bearing of the present invention seized in 103 to 140 minutes.

[0045] JPEG0007693498000003.jpg74139

Explanation of Reference Signs

[0046] 1: Sliding bearing 2: Backing metal 3: Lining layer 4: Dam layer 5, 5’: Coating layer 6, 61, 62, 61’, 62’, 63’: Overlay layer 7, 71, 72: Intermetallic compound-containing layer 8: Intermetallic compound matrix 9: Metal part 10: Sliding surface

Claims

1. A sliding bearing comprising a base layer and a coating layer, wherein the coating layer consists of at least two overlay layers and intermetallic compound-containing layers respectively located between adjacent overlay layers, and the intermetallic compound-containing layer contains a layered metal part in an intermetallic compound matrix, and the area of the layered metal part is 60% to 95% of the area of the intermetallic compound-containing layer. A sliding bearing characterized by this.

2. The sliding bearing according to claim 1, wherein the coating layer consists of two overlay layers and an intermetallic compound-containing layer located between the two overlay layers.

3. The sliding bearing according to claim 1 or claim 2, wherein the overlay layer contains an SnCu alloy, the intermetallic compound matrix contains an SnNi intermetallic compound and an SnNiCu intermetallic compound, and the metal part contains metal Ni.

4. The SnNi intermetallic compound is Ni ３ Sn ４ and the SnNiCu intermetallic compound is Sn ５ (CuNi) ６ The sliding bearing according to claim 3.

5. The sliding bearing according to any one of claims 1 to 4, wherein the thickness of the intermetallic compound-containing layer is 1 to 10 μm.

6. The sliding bearing according to claim 5, wherein the thickness of the intermetallic compound-containing layer is 2 to 5 μm.

7. The sliding bearing according to any one of claims 1 to 6, wherein the thickness of the overlay layer is 1 to 30 μm.

8. The sliding bearing according to claim 7, wherein the thickness of the overlay layer is 5 to 20 μm.

9. The base layer is a back metal layer to which a lining layer is adhered, and the coating layer is provided on the lining layer. The sliding bearing according to any one of claims 1 to 8.

10. The sliding bearing according to claim 9, wherein the lining layer is made of a copper-based alloy or an aluminum-based alloy.

11. The sliding bearing according to claim 9 or claim 10, further comprising a dam layer provided between the lining layer and the coating layer, wherein the dam layer contains at least one of the group consisting of nickel, cobalt, iron, copper, chromium, zinc, aluminum, and alloys thereof.

12. The sliding bearing according to claim 11, wherein the thickness of the dam layer is 0.5 to 10 μm.

13. The sliding bearing according to claim 12, wherein the thickness of the dam layer is 1 to 6 μm.

14. The sliding bearing according to any one of claims 1 to 13, wherein the total thickness of the coating layer is 5 μm to 50 μm.

15. A method for manufacturing a sliding bearing according to any one of claims 1 to 14, comprising: preparing the base layer; depositing a first metal or alloy layer; depositing a second metal or alloy layer on the first layer; depositing another layer of the first metal or alloy on the second layer; heat-treating the deposited layers to a temperature that allows diffusion of metal atoms of the first metal or alloy layer, such that the metal atoms diffuse and react with the second metal or alloy layer, and forming an intermetallic compound within the position of the second metal or alloy layer while leaving the second metal or alloy remaining; and a method for manufacturing a sliding bearing.

16. The manufacturing method of the sliding bearing according to claim 15, wherein the base layer is a back metal layer to which a lining layer is adhered.

17. The manufacturing method of the sliding bearing according to claim 16, further comprising the step of attaching a dam layer onto the bearing lining layer.

18. The manufacturing method of the sliding bearing according to any one of claims 15 to 17, further comprising the step of attaching at least one set of layers of the second and first metals or alloys onto another layer of the first metal or alloy attached onto the second layer before the heat treatment.

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