TWI887636B - Copper sliding components - Google Patents

Abstract

The sliding component of the present invention comprises a bearing alloy composed of a Cu-Sn alloy, wherein the Cu-Sn alloy is composed of 1.5 to 10.0 mass % Sn and the remainder Cu and impurities, and high tin concentration regions are dispersed when observed from a cross section perpendicular to the sliding surface. The high tin concentration region has a Sn concentration of more than 1.1 times the average Sn concentration of the Cu-Sn alloy and has an area of more than 500 μm ^2. The number of high tin concentration regions is 5 to 93 per 1 mm ² .

Description

Copper sliding components

The present invention generally relates to a copper-based sliding member, and more particularly to a sliding member comprising a bearing alloy containing a Cu-Sn alloy.

Cu-Sn alloys are widely used as bearing alloys due to their high strength and excellent wear resistance. In recent years, with the increase in bearing loads caused by the reduction in bearing area due to the increase in engine power and engine miniaturization, there is a demand for further improvement in the wear resistance of sliding materials. As a countermeasure for improving wear resistance in the past, for example, there are those described in Patent Documents 1 and 2.

The copper alloy disclosed in Patent Document 1 allows Ag, Sn, Sb, In, Mn, Fe, Bi, Zn, Ni and/or Cr to be dissolved in the Cu matrix, and the secondary phase of these elements is not substantially formed. These additive elements dissolved in the Cu matrix move to the lining surface in parallel with the generation of friction heat and the change of the lining surface structure, forming a concentrated layer of the additive elements locally. The concentrated layer further reacts with the sulfur additive in the lubricating oil to form a sulfur compound, and the oxygen in the lubricating oil reacts with the additive elements to form an oxygen compound. The solid lubrication effect of the concentrated layer and the sulfur compound is excellent, and its sliding characteristics are still excellent even under high surface pressure, and it has the effect of reducing wear.

The bearing alloy of the sliding bearing of Patent Document 2 is characterized in that the concentration of the dispersed fine components (such as Sn) decreases continuously from the top range of the bearing metal of the sliding bearing toward the dividing surface range. The high load-bearing capacity of the sliding element is ensured by utilizing the range with a large tin ratio.

However, in Patent Document 1, since wear has progressed before the concentration layer of solid solution strengthening elements is formed, its wear resistance is insufficient for applications with large wear. In Patent Document 2, if only the top range that mainly bears the load is considered, the top range that mainly bears the load has only the same wear resistance as other previous technologies. In addition, the part with low Sn concentration cannot be used as the main load-bearing part, and is not suitable for applications where the load direction changes or where the bearing becomes a flat plate shape.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 9-249924

[Patent Document 2] Japanese Patent Publication No. 2000-27866

The purpose of the present invention is to provide a sliding component comprising a bearing alloy containing a Cu-Sn alloy, which has a new structure that can improve wear resistance.

According to one viewpoint of the present invention, a sliding component is provided, which is a sliding component having a sliding surface and includes a bearing alloy containing a Cu-Sn alloy, wherein the Cu-Sn alloy is composed of 1.5 to 10.0 mass % Sn and the remainder Cu and impurities, and high tin concentration regions are dispersed when observed from a cross section perpendicular to the sliding surface. The high tin concentration region has a tin concentration of more than 1.1 times the average Sn concentration of the Cu-Sn alloy (hereinafter also referred to as "Sn component") and has an area of more than 500 ^μm2 . The number of high tin concentration regions is 5 to 93 per 1 ^mm2 .

The Sn content of the Cu-Sn alloy is preferably 8.0 mass % or less. The Sn content of the Cu-Sn alloy is preferably 2.0 mass % or more.

The Cu-Sn alloy may further contain either or both of Ni: 0~5.0 mass % and P: 0~1.0 mass %.

According to one embodiment of the present invention, when observing from a cross section perpendicular to the sliding surface, the area occupied by the high tin concentration region is 5-47%.

According to a specific embodiment of the present invention, the bearing alloy may further contain either or both of solid lubricant particles and hard particles. The solid lubricant particles preferably include graphite particles, or are graphite. The hard particles preferably include SiC particles, or are SiC particles.

According to another aspect of the present invention, a sliding member is provided, which has a backing layer and a bearing alloy layer on the backing layer, and the bearing alloy layer includes the above-mentioned bearing alloy.

According to one embodiment of the present invention, the sliding component is a sliding bearing.

According to another aspect of the present invention, a bearing device including the above-mentioned sliding member is provided.

The present invention and its many advantages are described in detail below with reference to the attached schematic drawings. The drawings, for illustrative purposes, show several non-limiting embodiments.

1: Sliding member

2: Bearing alloy layer

3: Sliding surface

4: Backing layer

6: High tin concentration area

8: Matrix

[Figure 1] shows an example of the structure of a sliding member of a specific embodiment of the present invention.

[Figure 2] is a cross-sectional view perpendicular to the sliding surface of a Cu-Sn alloy sliding component of a specific embodiment of the present invention.

The sliding member of the present invention is a sliding member having a Cu-Sn alloy as a bearing alloy. The sliding member is applied to sliding bearings such as neck bearings and thrust bearings used in bearing parts of internal combustion engines and automatic transmissions for passenger cars. For example, the sliding member can be made into a sliding bearing formed into a cylindrical shape, or a cylindrical sliding bearing formed by combining a pair of members formed into a semi-cylindrical shape. Also, the thrust bearing can be made into a sliding bearing formed into a ring shape, or a ring-shaped bearing can be combined by combining a pair of members formed into a semi-circular ring shape. However, the sliding member can also be in other shapes and can be used as a sliding member other than a sliding bearing. For example, it can also be used as a flat sliding plate in the reciprocating sliding part of an industrial machine in a grease lubricated environment. A bearing device including such a sliding member is also the subject of the present invention.

Next, a configuration example of a sliding member 1 of a specific embodiment of the present invention is described. Referring to FIG1 , a bearing alloy layer 2 is provided on a backing layer 4. However, the backing layer 4 is an arbitrary element, and it is also possible to have only the bearing alloy layer 2 without the backing layer 4. The surface of the bearing alloy layer 2 becomes the sliding surface 3. As an arbitrary choice, a coating layer (overlay) can be provided on the bearing alloy layer 2. Including this case, the surface of the bearing alloy layer 2 is referred to as the sliding surface 3 in this specification.

The backing layer 4 is provided to improve the strength of the sliding member 1. Although there is no particular limitation, the backing layer 4 can use a metal plate of steel, Fe alloy, Cu, Cu alloy, etc. As the iron-based material, it is preferably a plate of a predetermined size of Fe alloy such as hypoeutectoid steel, austenitic stainless steel, ferrous stainless steel, etc.

As an optional option, a coating layer can be provided on the bearing alloy layer 2. The coating layer can be made of metals such as Bi, Sn, Pb, Ag, or alloys based on these metals or synthetic resins, etc., which are used to improve the running-in properties of the surface of the sliding layer. It can be a known coating layer, and its formation method can also use a known method.

As an optional option, an intermediate layer may be provided between the backing layer 4 and the bearing alloy layer 2. For example, a porous metal layer or an intermediate layer may be provided on the surface of the backing layer, that is, on the side of the backing layer that becomes the interface with the bearing alloy layer, thereby improving the bonding strength between the sliding layer and the backing layer.

The bearing alloy layer includes a bearing alloy composed of a Cu-Sn alloy. FIG2 shows a cross-sectional view of a sliding component 1 of a specific example of the present invention. The cross-sectional view is a cross-sectional view cut from a plane perpendicular to the sliding surface. As shown in FIG2, in the matrix 8 of the Cu-Sn alloy, high tin concentration regions 6 with relatively high Sn concentration are dispersed. The high tin concentration region 6 can be defined as: a region having a Sn concentration of 1.1 times or more relative to the average Sn concentration of the Cu-Sn alloy, and having an area of ^500μm2 or more. Even if it is a region having a Sn concentration of 1.1 times or more, if its area is less than ^500μm2 , it is not included in the high tin concentration region 6. In the Cu-Sn alloy of the present invention, the number of the high tin concentration regions 6 is 5 to 93 per 1 mm ² .

The term "average Sn concentration of Cu-Sn alloy" is used to represent the average Sn concentration in Cu-Sn alloy because there is a high Sn concentration region 6 and the Sn concentration in Cu-Sn alloy is uneven. In the present invention, its value is considered to be equal to the Sn component of Cu-Sn alloy.

The high Sn concentration region 6 with a high Sn concentration is relatively hard and has high wear resistance. When Sn is uniformly dissolved in the Cu-Sn alloy, the load is borne by the entire Cu-Sn alloy. However, even if it is a Cu-Sn alloy with the same composition, by dispersing the harder high Sn concentration region 6 in the softer matrix 8, the high Sn concentration region 6 mainly supports the opposite surface, thereby making it difficult to be worn as a whole. As a result, even if the average Sn concentration is the same, the wear resistance can be improved compared to the case where Sn is uniformly dissolved. Moreover, regardless of the depth, the cross section perpendicular to the sliding surface will become the above-mentioned structure, that is, the high tin concentration area 6 still exists in the depth direction, and high wear resistance can be maintained even if wear progresses.

The Cu-Sn alloy of the sliding component of the present invention is preferably such that Sn is solid-dissolved in Cu without substantially forming a secondary phase (intermetallic compound). The Cu-Sn secondary phase (intermetallic compound) is hard and brittle (brittle), and is easily broken and falls off. The fragments of the secondary phase after falling off will enter between the sliding surface and the opposing surface, causing damage to the sliding surface and accelerating wear. Therefore, it is possible to hinder the improvement of wear resistance. Regarding the substantial absence of a secondary phase in the Cu-Sn alloy, as long as there is no secondary phase with an area of more than ^3μm2 , it is considered to be "substantially absent". Whether the secondary phase with an area of more than ^3μm2 exists is confirmed using an electron microscope set to a magnification of 100 times or more.

Cu-Sn alloy contains Sn: 1.5~10.0 mass%, and the rest is Cu and impurities. When the Sn content is less than 1.5 mass%, the hardness cannot be increased to the extent that wear resistance can be obtained. In order to have a hardness that can obtain wear resistance, the minimum value of the Sn content is preferably 2.0 mass%. The minimum value of the Sn content is more preferably 3.0 mass%. If the Sn content exceeds 10.0 mass%, the possibility of forming a Cu-Sn secondary phase is high. In order to effectively reduce the possibility of forming a secondary phase, the maximum value of the Sn content is preferably 8.0 mass%. The maximum value of the Sn content is more preferably 6.5 mass%.

Cu-Sn alloys may further contain either or both of Ni: 0~5.0 mass% and P: 0~1.0 mass%. If these elements are contained within the above range, corrosion resistance can be improved and sintering can be easily improved. If 0~5.0 mass% Ni is added, strength will increase and wear resistance can be improved. However, if more than 5.0 mass% Ni is added, the sintering temperature will increase, resulting in increased costs. By adding 0~1.0 mass% P, sintering will be improved, so strength increases and wear resistance can be improved. However, if more than 1.0 mass% P is added, sintering will progress too much and become difficult to control.

In the Cu-Sn alloy, the area ratio of the high tin concentration region 6 is preferably 5-47% when observed from the cross section perpendicular to the sliding surface 3. When the area ratio of the high tin concentration region 6 is 5% or more, the above effect can be effectively exerted. If the area ratio is 47% or less, the stability of the sintering process can be ensured without reducing the strength of the bearing alloy layer, and it is easy to obtain a bearing alloy layer with the desired wear resistance.

The area of the high tin concentration region 6 is 500 μm ² or more. Even if the region has a Sn content that is 1.1 times or more of the Sn content of the Cu-Sn alloy, if the area is less than 500 μm ² , it is not included in the high tin concentration region 6. This is because if the area is small, the load bearing effect is poor and it does not contribute to the improvement of wear resistance.

In the Cu-Sn alloy of the present invention, the number of high tin concentration regions 6 is 5 to 93 per 1 mm ^2. When the number of high tin concentration regions 6 is less than 5 per 1 mm ² , the above effect cannot be exerted. When the number exceeds 93, the tin concentration tends to become uniform, and it may not be possible to obtain a high tin concentration region with an area of more than 500 μm ² and a tin concentration of more than 1.1 times that of the other side, which is mainly used to support the other side. In order to manufacture a bearing alloy layer with more than 93 high tin concentration regions, the particle size of the copper-tin alloy powder must be further reduced during manufacturing. In this case, if the particle size of the copper-tin alloy powder is too small, Sn becomes easy to diffuse during the sintering process. Therefore, the degree of Sn diffusion cannot be stably controlled during the sintering process, and the high Sn concentration region 6 cannot be stably formed.

As a more preferred specific example, the area ratio of the region where the Sn concentration is 1.2 times the Sn content of the Cu-Sn alloy (hereinafter referred to as the "threshold 1.2 times region") is 5-42%. More preferably, the area ratio of the region where the threshold is 1.3 times is 5-35%. Particularly preferably, the area ratio of the region where the threshold is 1.4 times is 5-26%. With such a structure, it is easier to obtain the above effect.

As a preferred specific example, the number of regions with a value 1.2 times the threshold is 5 to 84/mm ² . More preferably, the number of regions with a value 1.3 times the threshold is 5 to 61/mm ² . Particularly preferably, the number of regions with a value 1.4 times the threshold is 5 to 54/mm ² . With such a configuration, the above-mentioned effect can be more easily obtained.

As an arbitrary choice, the bearing alloy layer 2 may further contain: 0.1 to 12.0 mass % of solid lubricant particles selected from, for example, MoS ₂ , WS ₂ , graphite, and h-BN (hexagonal boron nitride). The solid lubricant preferably contains graphite. More preferably, the solid lubricant is graphite. 0.1 to 12.0 mass % of the solid lubricant can be dispersed in the base material of the Cu-Sn alloy to improve the lubricity and further improve the wear resistance. However, if the solid lubricant exceeds 12.0 mass %, it may hinder sintering.

As an arbitrary choice, the bearing alloy layer 2 may further contain: 0.1 to 5.0 mass % of hard particles selected from one or more of SiC, _Al2O3 , _SiO2 , _AlN , _Mo2C , WC, _Fe2P , _Fe3P . The hard particles preferably contain SiC. More preferably, the hard particles are SiC. 0.1 to 5.0 mass % of hard particles can be dispersed in the substrate to further improve the wear resistance. However, if the hard particles exceed 5.0 mass %, sintering may be hindered.

Next, the manufacturing method of the bearing alloy layer (Cu-Sn alloy) of the sliding component of the present invention is described. The manufacturing method includes the following steps.

1. Prepare copper-tin alloy powder and pure copper powder containing a predetermined amount of Sn. When either or both of Ni and P are contained as an optional element, copper powder containing these elements is used instead of copper-tin alloy powder (also in this case, hereinafter referred to as "copper-tin alloy powder").

2. Weigh the copper-tin alloy powder and pure copper powder so that the Sn content becomes a predetermined value (Sn is 1.5 to 10.0 mass%) (if Ni and P are contained as an optional option, it is below the predetermined limit).

3. Mix the weighed copper-tin alloy powder and pure copper powder. At this time, if either or both of solid lubricant particles and hard particles are further contained as an optional option, such particles are also added.

4. Spread the mixed powder on the substrate. For example, in the case of forming a bearing alloy layer on a backing pad, the substrate is the backing pad.

5. Sinter the spread powder at 800℃~900℃ for 10~31 minutes.

6. Roll the sintered body to a predetermined thickness.

7. The sintered body with a predetermined thickness is further sintered at 800℃~900℃ for 10~31 minutes.

Under the above sintering conditions, Sn in the copper-tin alloy powder will diffuse into the pure copper powder, but the sintering is not carried out to the extent that Sn diffuses uniformly throughout the alloy, and a region with a higher Sn concentration is formed centered on the original copper-tin alloy powder region. The area ratio of the high Sn concentration region and the number per unit area can be adjusted by adjusting the particle size of the copper-tin alloy powder, Sn concentration, and sintering conditions within the above range.

The Sn content of the copper-tin alloy powder used as the raw material is preferably 3-15 mass %, and the average particle size is preferably 10-75 μm. For example, although a portion with a higher Sn concentration can be formed by replacing the copper-tin alloy powder with pure tin powder, a brittle secondary phase will be formed, and thus the wear resistance may not be improved.

Next, the determination method for high tin concentration areas will be explained.

The high tin concentration region 6 is determined by performing surface analysis on the cross section of the bearing alloy layer 2 perpendicular to the sliding surface 3 using SEM-EPMA, and determining a high tin concentration region having a tin concentration of 1.1 times or more of the average Sn concentration of the Cu-Sn alloy. Examples of measurement conditions are shown in Table 1. The map obtained by the surface analysis is expressed in concentration using a calibration curve (standard condition), filtered with a median filter, and binarized. Furthermore, a Sn-concentrated region with an area of more than ^500μm2 is determined as a high tin concentration region. The threshold and analysis of the high tin concentration region must be performed in an area of more than ^0.5mm2 .

[Implementation example]

The samples shown in Tables 4 to 6 were prepared by the manufacturing method described above. Copper-tin alloy powder with a Sn content of 3 to 15 mass% and pure copper powder were mixed in the form of the composition shown in the table and then spread on the substrate. However, for samples 24 and 25, Cu-12Sn-15Ni-3P alloy powder was used instead of copper-tin alloy powder. For samples 27 to 29, 31, and 32, a predetermined amount of graphite powder and SiC powder were also mixed. The substrate used was a steel plate with a thickness of 2.2 mm.

The dispersed powder was subjected to the first sintering, rolling, and second sintering to obtain a bearing alloy layer with a thickness of 0.9 mm. The sintering conditions of each sample are shown in Table 2.

Furthermore, the number and area ratio of high Sn concentration regions (threshold 1.1 times, i.e. regions with Sn concentrations 1.1 times or more of the average Sn concentration) in the bearing alloy layer are measured by the measurement method described above.

The wear test of each sample was carried out according to the conditions shown in Table 3, and the wear amount of the sample after the test was measured. The results are shown in Tables 4 to 6.

According to the results shown in Table 4, it can be seen that the samples 1 to 23 of the embodiments of the present invention (the Cu-Sn alloy contains Sn: 1.5~10.0 mass%, and the number of high tin concentration regions with a threshold of 1.1 times is 5~93 per ^1mm2 ) have reduced wear based on the wear test when compared with the comparative examples of samples 41 to 47 that do not have high tin concentration regions if the Sn concentration is the same.

In the examples of the present invention, the Cu-Sn alloys of samples 24 and 25 contain 5.0% by mass of Ni and 1.0% by mass of P in addition to 4.0% by mass of Sn. Table 5 shows the wear of these samples based on the wear test. Table 5 also shows the test results of samples 13 and 20. The number and area ratio of Sn concentration and high concentration regions of samples 13 and 20 are the same as those of samples 24 and 25, respectively, but do not contain Ni and P. According to the results shown in Table 5, if the number and area ratio of Sn concentration and high concentration regions are the same, the wear can be reduced by adding Ni and P.

Table 6 shows a comparison between Samples 26 to 29, Sample 31 and Sample 32 (the bearing alloy contains graphite and SiC in addition to the Cu-Sn alloy containing 3.0 mass % Sn) of the embodiment of the present invention and Samples 26 and 30 that do not contain graphite and SiC. According to the results shown in Table 6, it can be seen that the wear amount based on the wear test can be reduced by containing graphite and SiC.

Table 7 shows the comparison of the wear amount of the sample of the present invention and the comparative example (no high concentration region) with the same average Sn concentration of the Cu-Sn alloy. According to Table 7, the sample with 40 high concentration regions/ ^mm2 shows better improvement in wear resistance than the sample with 5 high concentration regions/ ^mm2 . For any number of high concentration regions, the improvement in wear resistance is better in the range of average Sn concentration of 2.0 mass% to 8.0 mass%.

1: Sliding member 2: Bearing alloy layer 6: High tin concentration area 8: Matrix

Claims (11)

A sliding component is a sliding component having a sliding surface, and includes a bearing alloy containing a Cu-Sn alloy. The Cu-Sn alloy is composed of 1.5-10.0 mass % Sn and the remainder Cu and impurities. High Sn concentration regions are dispersed when observed from a cross section perpendicular to the sliding surface. The high Sn concentration regions have a Sn concentration of more than 1.1 times the average mass % of Sn contained in the Cu-Sn alloy and have an area of more than 500 μm ^2. The number of the high Sn concentration regions is 5-93 per 1 mm ² . The sliding member of claim 1, wherein, when observed from a cross section perpendicular to the sliding surface, the area ratio of the high tin concentration region is 5-47%. A sliding member as claimed in claim 1 or 2, wherein the Sn content of the aforementioned Cu-Sn alloy is 8.0 mass % or less. A sliding member as claimed in claim 1 or 2, wherein the Sn content of the aforementioned Cu-Sn alloy is 2.0 mass % or more. A sliding member as claimed in claim 1 or 2, wherein the Cu-Sn alloy further contains either or both of Ni: 5.0% by mass or less and P: 1.0% by mass or less. The sliding member of claim 1 or 2, wherein the bearing alloy further contains one or both of solid lubricant particles selected from one or more _{of MoS2, WS2 ,} graphite, and h-BN and hard particles selected from one or more _of SiC, _Al2O3 , _SiO2 , AlN, _Mo2C , WC, _Fe2P , and _Fe3P . As in claim 6, the sliding member, wherein the aforementioned solid lubricant particles are graphite particles. A sliding member as claimed in claim 6, wherein the aforementioned hard particles are SiC particles. A sliding member as claimed in claim 1 or 2, wherein the sliding member comprises a backing layer and a bearing alloy layer on the backing layer, and the bearing alloy layer comprises the bearing alloy. A sliding member as claimed in claim 9, wherein the sliding member is a sliding bearing. A bearing device includes a sliding member as claimed in claim 10.

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