Sliding members and methods for manufacturing sliding members

Abstract

This invention provides a sliding member and a method for manufacturing the sliding member, controlling the addition of Bi to the alloy layer to further improve sintering resistance without reducing fatigue resistance. One embodiment of the sliding member (10) includes: a substrate (11); and an alloy layer (12) having Cu as the main component and containing Bi, forming a sliding surface (14) on the side opposite to the substrate (11). The alloy layer (12) has a first region and a second region. The first region is defined as a region with a thickness of 30% from the interface (13) on the substrate (11) side to the sliding surface (14) side. The second region is defined as a region with a thickness of 10% from the sliding surface (14) to the substrate (11) side. Compared to the Bi phase contained in the first region, the Bi phase contained in the second region has a plurality of Bi phases with large cross-sectional areas in any observation section.

Description

Technical Field

[0001] This invention relates to sliding members and methods for manufacturing sliding members. Background Technology

[0002] It is known that in sliding components with Cu-based alloy layers, Bi is added to the alloy layer. The Bi added to the alloy layer forms a soft phase that is softer than the matrix. As a result, sliding components with Cu-based alloy layers achieve improved running-in performance and improved resistance to sintering.

[0003] In recent years, due to the increase in engine power and the reduction in bearing area associated with engine miniaturization, the load applied to sliding components has increased. Therefore, it is required that sliding components have higher resistance to sintering. To improve the resistance to sintering of sliding components, it is preferable to increase the amount of Bi added to the alloy layer (Patent Documents 1, 2).

[0004] However, as the amount of Bi in the alloy layer increases, fatigue resistance decreases. Therefore, simply increasing the amount of Bi added to the alloy layer is insufficient to further improve the sintering resistance of the sliding component.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-53349;

[0008] Patent Document 2: Japanese Patent Application Publication No. 2018-145505. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Therefore, the object of the present invention is to provide a sliding member and a method for manufacturing the sliding member, wherein the Bi added to the alloy layer is controlled to further improve the sintering resistance without causing a decrease in fatigue resistance.

[0011] Solution for solving the problem

[0012] One embodiment of the sliding member includes: a substrate; and an alloy layer, primarily composed of Cu and containing Bi, forming a sliding surface on the side opposite to the substrate. The alloy layer has a first region and a second region. The first region is defined as a region with a thickness of 30% from the interface on the substrate side to the sliding surface side. The second region is defined as a region with a thickness of 10% from the sliding surface to the substrate side. Compared to the Bi phase contained in the first region, the Bi phase contained in the second region has a greater distribution of Bi phases with larger cross-sectional areas in any observation section.

[0013] In this way, compared to the Bi phase contained in the first region near the substrate, the Bi phase contained in the second region near the sliding surface has a greater distribution of Bi phases with larger cross-sectional areas. When the temperature of the alloy layer rises due to sliding between the sliding member and the opposing member, the Bi phase contained in the alloy layer dissolves from the matrix of the alloy layer. In particular, the Bi phase distributed in the second region near the sliding surface dissolves from the matrix of the alloy layer and spreads in layers between the sliding member and the opposing member. Since Bi is a soft metal, the layered Bi present between the alloy layer and the opposing member mitigates the local contact between the alloy layer and the opposing member. As a result, sintering between the sliding member and the opposing member during sliding is reduced. On the other hand, in the first region of the alloy layer, the Bi phase is mainly a finely refined Bi phase. The finer the Bi phase distributed in the matrix of the alloy layer, the more it hinders the development of internal cracks in the alloy layer. Therefore, the alloy layer suppresses crack development in the first region near the substrate. As a result, the delamination of the alloy layer and the substrate associated with crack development is reduced, and fatigue resistance is improved. Therefore, it is possible to further improve the sintering resistance without reducing the fatigue resistance by controlling the Bi added to the alloy layer.

[0014] In one embodiment of the sliding member, preferably, the cross-sectional area of ​​any observed section in the Bi phase dispersed in the first region is 250 μm. 2 The Bi phases mentioned above constitute less than 6% of the total number of phases. The cross-sectional area of ​​any observed section in the Bi phase dispersed in the second region is 250 μm². 2 The above-mentioned Bi phase accounts for more than 10% by number.

[0015] Furthermore, one embodiment of the manufacturing method for the sliding member includes a casting process and a cooling process. The casting process casts an alloy layer, primarily composed of Cu and containing Bi, on one side of a substrate. The cooling process, in the casting process, cools the substrate from the other side using a cooling material, causing the alloy layer to solidify in one direction. In the cooling process, as a predetermined set time elapses from the start, the size and quantity of the Bi phase contained in the alloy layer are controlled in the thickness direction by reducing the supply of the cooling material.

[0016] Therefore, in the manufacturing method of the sliding member according to one embodiment, the size and quantity of the Bi phase in the first region near the substrate and the second region near the sliding surface of the alloy layer are controlled. Thus, the Bi added to the alloy layer can be controlled, enabling further improvement in sintering resistance without reducing fatigue resistance.

[0017] In one embodiment of the manufacturing method of the sliding member, preferably, a heat treatment step is further included after the cooling step: the sliding member on which the alloy layer is formed on the substrate is held at 650 to 800°C for more than 1 hour.

[0018] Furthermore, in one embodiment of the manufacturing method of the sliding member, preferably, the casting process is centrifugal casting: while rotating the cylindrical substrate around an axis, the alloy layer is formed on the inner circumferential surface of the substrate. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the structure of a sliding member according to one embodiment;

[0020] Figure 2 This is a schematic diagram illustrating the structure of a sliding member according to one embodiment;

[0021] Figure 3 This is a schematic cross-sectional view showing the structure of the alloy layer in an observation section of a sliding member according to one embodiment;

[0022] Figure 4 This is a schematic diagram showing the state of a sliding member relative to an opposing member in one embodiment;

[0023] Figure 5 This is a schematic diagram showing the development of cracks in the alloy layer of the sliding member in the comparative example;

[0024] Figure 6 This is a schematic diagram illustrating a method for manufacturing a sliding member according to one embodiment;

[0025] Figure 7 This is a schematic diagram illustrating the verification results of an embodiment and a comparative example of a sliding member according to one implementation.

[0026] Figure 8 This is a schematic diagram illustrating the verification results of an embodiment of the sliding member.

[0027] Figure 9 This is a schematic diagram showing the verification results of an embodiment and a comparative example of a sliding member according to one implementation. Detailed Implementation

[0028] Hereinafter, a sliding member according to one embodiment will be described based on the accompanying drawings.

[0029] like Figure 1As shown, the sliding member 10 has a substrate 11 and an alloy layer 12. The alloy layer 12 is disposed on the substrate 11 by casting it onto one side of the substrate 11, namely the interface 13. In the sliding member 10, the surface of the alloy layer 12 is the sliding surface 14. In this case, the alloy layer 12 is preferably cast directly onto the interface 13 of the substrate 11.

[0030] The substrate 11 is a so-called backing layer, formed of an Fe-based or Cu-based material. In the case of an Fe-based substrate 11, for example, hypoeutectoid steel, eutectoid steel, hypereutectoid steel, cast iron, high-speed steel, tool steel, austenitic stainless steel, ferrite stainless steel, etc., can be used. Furthermore, in the case of a Cu-based substrate 11, for example, pure copper, phosphor bronze, brass, chromium copper, beryllium copper, Cosene alloy, etc., can be used. The thickness of the substrate 11 is preferably set to approximately 1.0 to 25.0 mm.

[0031] Alloy layer 12 is primarily composed of Cu and also contains Bi. Furthermore, alloy layer 12 may contain approximately 5 to 15% by mass of Sn. The inclusion of Sn in alloy layer 12 improves fatigue resistance. When the proportion of Sn in alloy layer 12 is less than 5% by mass, its contribution to improving fatigue resistance decreases. On the other hand, when the proportion of Sn in alloy layer 12 exceeds 15% by mass, the Cu-Sn compound formed by the main components of alloy layer 12, Cu and Sn, is prone to precipitate. Therefore, when Sn is excessively high, it leads to a decrease in the adhesion between the substrate 11 and alloy layer 12.

[0032] The alloy layer 12 may also contain one or more of Al, Zn, Mn, Si, Ni, Fe, P, Zr, Ti, and Mg as additive elements. These additive elements are preferably present in the alloy layer 12 at a content of 5% by mass or less. Al, Zn, Mn, Si, Ni, P, Zr, Ti, and Mg contribute to solid solution strengthening. Mn, Si, Ni, Fe, P, Zr, Ti, and Mg contribute to the precipitation of compounds. Furthermore, in addition to the above-mentioned additive elements, the alloy layer 12 may also contain any one or both of Mo2C or graphite. Mo2C or graphite is preferably present in the alloy layer 12 at a total proportion of 10% by volume or less.

[0033] like Figure 2 As shown, in addition to the substrate 11 and alloy layer 12, the sliding member 10 may also have a cover layer 15. The cover layer 15 is formed overlapping the alloy layer 12 on the surface of the alloy layer 12, i.e., the surface opposite to the substrate 11. The cover layer 15 is preferably made of a soft metal such as Sn or Bi. Furthermore, the cover layer 15 may be made of a resin in which a solid lubricant has been dispersed. When the sliding member 10 has the cover layer 15, the outermost surface of the cover layer 15 is the sliding surface 14 that slides relative to the other member.

[0034] like Figure 3 As shown, the alloy layer 12 has a first region A1 and a second region A2 in the thickness direction. Figure 3 In the illustrated embodiment, the first region A1 is defined as 30% of the thickness of the alloy layer 12 in the thickness direction from the interface 13 with the substrate 11 towards the sliding surface 14. The second region A2 is defined as 10% of the thickness of the alloy layer 12 in the thickness direction from the sliding surface 14 towards the substrate 11. The alloy layer 12 has a Bi phase 22 dispersed in the matrix 21. The cross-sectional area of ​​the Bi phase 22 in any observation section D of the first region A1 and the second region A2 is different. Specifically, the second region A2 contains more large Bi phases than the Bi phase contained in the first region A1. Furthermore, as... Figure 1 As shown, the observation section D is an arbitrary region defined on any cross section cut in the thickness direction of the alloy layer 12. In addition, when an intermediate layer is provided between the substrate 11 and the alloy layer 12, the first region A1 is defined as a region with a thickness of 30% from the interface of the alloy layer 12 on the substrate 11 side, that is, the interface between the alloy layer 12 and the intermediate layer, towards the sliding surface 14 side.

[0035] like Figure 3 As shown, alloy layer 12 contains Bi phase 22 with various cross-sectional areas in any observation section D. Here, the cross-sectional area in any observation section D is 250 μm. 2 The Bi phase 22 described above is referred to as a "specific Bi phase". In this embodiment, the "specific Bi phase" dispersed in the first region A1 near the substrate 11 accounts for 6% or less of the number of phases in the observation section D. On the other hand, the "specific Bi phase" dispersed in the second region A2 near the sliding surface 14 accounts for 10% or more of the number of phases in the observation section D. Thus, compared to the first region A1 near the substrate 11, the "specific Bi phase" with a larger cross-sectional area is mostly contained in the second region A2 near the sliding surface 14. In other words, in this embodiment, among the Bi phase 22 contained in the alloy layer 12, the Bi phase with a smaller cross-sectional area is mostly distributed on the side near the substrate 11, and the Bi phase with a larger cross-sectional area is mostly distributed on the side near the sliding surface 14. Furthermore, the Bi phase 22 contained in the alloy layer 12 is preferably provided to have an upper limit of 10000 μm in cross-sectional area. 2 Approximately. That is, the cross-sectional area of ​​the "specific Bi phase" is preferably 250–10000 μm. 2 Furthermore, the average area of ​​Bi phase 22 contained in the first region A1 is preferably between 10 and 80 μm. 2 Within this range. On the other hand, the average area of ​​Bi phase 22 contained in the second region A2 is preferably between 120 and 450 μm. 2Within the range. Furthermore, the average area of ​​Bi phase 22 in the second region A2 is preferably more than twice the average area of ​​Bi phase 22 in the first region A1. In this way, the average area of ​​Bi phase 22 contained in the first region A1 near the sliding surface 14 is larger than that of Bi phase 22 contained in the second region A2 near the interface 13 with the substrate 11.

[0036] The alloy layer 12 has a Cu-based alloy microstructure, i.e., a structure in which Bi phase 22 is dispersed in the matrix 21. The Bi phase 22 contained in this alloy layer 12 is as follows: Figure 4 As shown, when the sliding member 10 slides relative to the opposing member 31, it helps to reduce sintering. Specifically, when the sliding member 10 slides relative to the opposing member 31, the temperature of the alloy layer 12 in contact with the opposing member 31, especially the sliding surface 14, rises. As the temperature of the alloy layer 12 rises due to the sliding, the Bi phase 22 contained in the alloy layer 12 dissolves from the substrate 21 of the alloy layer 12. In particular, the Bi phase 22 facing the sliding surface 14 dissolves from the substrate 21 of the alloy layer 12. The dissolved Bi spreads in layers on the sliding surface 14 where the sliding member 10 slides with the opposing member 31. Since Bi is a soft metal, its presence between the alloy layer 12 and the opposing member 31 mitigates their local contact. As a result, sintering during the sliding of the sliding member 10 relative to the opposing member 31 is reduced due to the dissolved Bi.

[0037] In this way, the Bi phase 22 contained in the alloy layer 12 helps to reduce sintering. Here, the Bi that helps reduce sintering is predominantly present in the Bi phase 22 dispersed in the alloy layer 12 near the sliding surface 14. Therefore, by increasing the amount of Bi phase 22 dispersed in the region near the sliding surface 14, the sliding member 10 can achieve improved sintering resistance. In this embodiment, the alloy layer 12 contains a plurality of phases with a cross-sectional area of ​​250 μm in the second region A2 near the sliding surface 14. 2 The above refers to the "specific Bi phase". Therefore, by using the large "specific Bi phase" contained in the substrate 21 as a supply source, sufficient Bi is supplied to the sliding surface 14 where the sliding member 10 contacts the opposing member 31. In particular, by setting 10% of the sliding surface 14 in the thickness direction as the second region A2, the "specific Bi phase" contained in the second region A2 can be reliably and rapidly supplied to the sliding surface 14.

[0038] On the other hand, the Bi phase 22 formed from the soft metal Bi is softer and has lower strength than the matrix 21 of the Cu-based alloy. Therefore, when a crack 33 forms near the sliding surface 14, such as Figure 5As shown, crack 33 tends to propagate along the boundary between the matrix 21 and the Bi phase 22. When crack 33, generated near the sliding surface 14, propagates through the alloy layer 12 and reaches the interface 13 between the substrate 11 and the alloy layer 12, the alloy layer 12 may peel off from the substrate 11, leading to fatigue failure. This peeling of the alloy layer 12 reduces the fatigue resistance of the sliding member 10.

[0039] The larger the Bi phase 22, the longer the boundary between the matrix 21 and the Bi phase 22, and the easier it is for this boundary to be continuous. Therefore, cracks 33 originating in the matrix 21 tend to propagate deeper into the substrate 11 via the boundary between the matrix 21 and the Bi phase 22. Consequently, cracks 33 originating near the sliding surface 14 tend to propagate towards the substrate 11. For this reason, it is important to refine the Bi phase 22 to suppress crack 33 propagation in order to improve fatigue resistance. Therefore, as... Figure 3 As shown, in this embodiment, the first region A1 of the alloy layer 12 near the interface 13 with the substrate 11 contains a relatively small cross-sectional area of ​​250 μm. 2 The above-mentioned "specific Bi phase" is specifically defined as follows: In particular, 30% of the portion of the alloy layer 12 extending from the interface 13 with the substrate 11 towards the sliding surface 14 in the thickness direction is designated as a first region A1, which contains a smaller amount of the "specific Bi phase". Therefore, the Bi phase 22 contained in the first region A1 is primarily a finely refined Bi phase. Consequently, the propagation of crack 33 is suppressed within the alloy layer 12, particularly in the first region A1 near the substrate 11. As a result, peeling of the alloy layer 12 is reduced, and the fatigue resistance of the sliding member 10 is improved.

[0040] As described above, in this embodiment, the size and quantity of the Bi phase 22 contained in the alloy layer 12 vary along the thickness direction of the alloy layer 12. That is, in this embodiment, compared to the first region A1, the alloy layer 12 contains a large number of "specific Bi phases" with large cross-sectional areas in the second region A2. Therefore, sufficient Bi is supplied to the sliding surface 14 from these "specific Bi phases," reducing sintering during sliding relative to the opposing member 31. On the other hand, compared to the second region A2, the alloy layer 12 contains fewer "specific Bi phases" with large cross-sectional areas in the first region A1, achieving miniaturization of the Bi phase 22 in the first region A1. Therefore, the crack 33 generated near the sliding surface 14 of the alloy layer 12 is suppressed from developing in the first region A1. As a result, the alloy layer 12 reduces peeling from the substrate 11, improving the fatigue resistance of the sliding member 10. Therefore, by controlling the size and quantity of the Bi phase contained in the alloy layer 12, it is possible to further improve the sintering resistance without reducing the fatigue resistance.

[0041] In this embodiment, the content of Bi in the alloy layer 12 is preferably 5 to 25% by mass. If the Bi content in the alloy layer 12 is 5% by mass or more, it helps to improve sintering resistance. On the other hand, since Bi is soft, an excessively high Bi content in the alloy layer 12 can negatively impact fatigue resistance. Therefore, the Bi content in the alloy layer 12 is preferably 25% by mass or less. Furthermore, the thickness of the alloy layer 12 is preferably set to approximately 0.1 to 5.0 mm.

[0042] Furthermore, the proportion of the "specific Bi phase" contained in the first region A1 of alloy layer 12 in the observation section D is preferably 1% to 6%. When the proportion of the "specific Bi phase" in the first region A1 is less than 1%, the overall Bi content of alloy layer 12 is likely to be less than 5% by mass, which does not help improve the sintering resistance of alloy layer 12. On the other hand, when the proportion of the "specific Bi phase" in the first region A1 is greater than 6%, the Bi content in alloy layer 12 is likely to be greater than 30% by mass, increasing the amount of expensive Bi used. Furthermore, the proportion of the "specific Bi phase" contained in the second region A2 of alloy layer 12 is preferably 10% to 30% in the observation section D. When the proportion of the "specific Bi phase" in the second region A2 is less than 10%, the Bi supplied to the sliding surface 14 is insufficient, which does not help improve the sintering resistance of alloy layer 12. On the other hand, when the proportion of the "specific Bi phase" in the second region A2 is greater than 30%, the overall Bi content of alloy layer 12 is greater than 30% by mass, increasing the amount of expensive Bi used.

[0043] Next, the manufacturing method of the sliding member 10 having the above structure will be described.

[0044] First, prepare substrate 11. For example... Figure 6 As shown, in this embodiment, the substrate 11 is formed into a cylindrical shape. A casting process is performed on the prepared substrate 11 to cast an alloy that becomes the alloy layer 12. The Cu-based alloy containing Bi, which becomes the alloy layer 12, is supplied in a molten state and cast onto the substrate 11 in an overlapping manner. When a cylindrical substrate 11 is used as in this embodiment, the alloy that becomes the alloy layer 12 is cast onto the inner circumferential surface of the cylindrical substrate 11 by centrifugal casting. Furthermore, it is preferable that the oxide film formed on the surface of the substrate 11 is removed using, for example, an oxide film remover before casting the alloy into the alloy layer 12. In this case, the oxide film is removed from the substrate 11 by immersion in, for example, an oxide film remover. During the formation of the alloy layer 12, the remover, along with the removed oxide film, floats to the outermost surface of the alloy layer 12 and solidifies together with the oxide film. By removing the solidified material, the oxide film on the surface of the substrate 11 can be easily removed after the formation of the alloy layer 12.

[0045] Simultaneously with the casting process, a cooling process is performed on the substrate 11 by cooling with a cooling material 41. Specifically, the substrate 11 is cooled from the side opposite to the interface 13 where the alloy layer 12 is formed by the cooling material 41. When a cylindrical substrate 11 is used as in this embodiment, cooling is performed by providing the cooling material 41 to the outer peripheral surface 42 of the cylindrical substrate 11. The cooling material 41 is, for example, a liquid such as water or oil, or a gas such as air. The cooling material 41 can also be a solid such as dry ice. For example, by blowing or impacting the cooling material 41, the substrate 11 can be cooled from the outer peripheral surface 42 opposite to where the alloy layer 12 is formed. As a result, the alloy layer 12 formed on the substrate 11 solidifies in one direction from the outer peripheral surface 42 side of the substrate 11.

[0046] In this cooling process, the supply of cooling material 41 is reduced after a predetermined set time has elapsed since the start of the process. Specifically, the cooling process includes a first cooling stage and a second cooling stage. In the first cooling stage, the supply of cooling material 41 is large, and the formed alloy layer 12 cools rapidly. In the second cooling stage, the supply of cooling material 41 is small, and the formed alloy layer 12 cools gradually. The cooling process is performed simultaneously and in parallel with the continuous casting process, transitioning continuously from the first cooling stage to the second cooling stage by the difference in the supply of cooling material 41. That is, in the cooling process, the first cooling stage begins together with the casting process, and after a predetermined time has elapsed, the supply of cooling material 41 is reduced to transition to the second cooling stage. As an example, in the first cooling stage, for example, the supply of cooling material 41 is reduced to approximately 1 cm³. 3 The amount of water supplied to the substrate 11 is set to 0.05–0.5 liters / min, and the cooling process lasts for 5–40 seconds. Then, in the second cooling stage implemented after the first cooling stage, for example, water is supplied to each 1 cm... 3 The amount of water supplied to the substrate 11 is set to less than 0.05 liters / min, and the cooling process is carried out for more than 10 seconds. The specific values ​​of the first and second cooling stages are just examples and can be arbitrarily changed according to the size of the substrate 11 used, the type of alloy layer 12, etc.

[0047] By rapidly cooling the cast alloy in the first cooling stage, the alloy cast in the first region A1 of the alloy layer 12 near the substrate 11 solidifies rapidly. Therefore, the growth of the Bi phase 22 contained in the first region A1 of the alloy layer 12 is hindered, and the Bi phase 22 contained in the alloy layer 12 is refined. On the other hand, by changing the supply amount of cooling material 41 during the alloy casting process and transitioning to the second cooling stage, the alloy cast in the second region A2 of the alloy layer 12 away from the substrate 11 solidifies more slowly. Therefore, the growth of the Bi phase 22 contained in the second region A2 of the alloy layer 12 is promoted, and the Bi phase 22 contained in the alloy layer 12 becomes larger.

[0048] In this way, in the manufacturing method of this embodiment, by changing the cooling of the alloy layer 12 formed in the cooling process, a first region A1 containing fine Bi phase 22 is formed on the side near the substrate 11, and a second region A2 containing large Bi phase 22 is formed on the side near the sliding surface 14.

[0049] Furthermore, in this embodiment, a heat treatment process is included after the cooling process. The heat treatment process is performed after the alloy layer 12 is formed by casting the substrate 11. The sliding member 10 on which the alloy layer 12 is formed is heat-treated at 650–800°C. In this heat treatment process, further growth of the Bi phase 22 contained in the alloy layer 12 is promoted. In particular, the large Bi phase contained in the second region A2 further grows through heat treatment, resulting in an increase in cross-sectional area. Setting the temperature in this heat treatment to 650°C or higher promotes the growth of the Bi phase 22, and setting it to 800°C or lower reduces the energy input. Therefore, the heat treatment is preferably performed at 650–800°C.

[0050] Through the above steps, a sliding member 10 that controls the cross-sectional area of ​​the Bi phase 22 in the thickness direction of the alloy layer 12 can be manufactured. Furthermore, in the above embodiment, an example of forming the alloy layer 12 on a cylindrical substrate 11 by centrifugal casting was described. However, it is also possible to use an alloy, for example, cast into an arc-shaped or flat substrate 11 to form the alloy layer 12. In this case, similar to the above embodiment, the alloy layer 12 can be formed on one interface 13 side of the substrate 11, and the other end face can be cooled by the cooling material 41. Alternatively, if an intermediate layer is provided between the substrate 11 and the alloy layer 12, the alloy layer 12 is cast onto the substrate 11 on which the intermediate layer has been pre-formed.

[0051] (Example)

[0052] Next, use Figures 7-9 The embodiments of this implementation are compared with comparative examples and verified.

[0053] In the embodiments and comparative examples, the substrate 11 is a cylindrical shape with an inner diameter of 80 mm, an axial length of 120 mm, and a thickness of 5 mm. The alloy layer 12 is formed by centrifugally casting a Cu-based alloy on the inner circumferential side of the substrate 11. The thickness of the alloy layer 12 is 5 mm. Water is used as the cooling material 41 in the cooling process. The actual flow rate and supply time of the water that becomes the cooling material 41 are as follows: Figures 7-9 As shown. The water flow rate is converted to per 1cm. 3The amount of substrate 11 supplied is as follows: 0.034 L / min for 5 L / min, 0.050 L / min for 7.5 L / min, 0.168 L / min for 25 L / min, 0.202 L / min for 30 L / min, 0.336 L / min for 50 L / min, 0.470 L / min for 70 L / min, and 0.672 L / min for 100 L / min.

[0054] The cross-sectional area and number ratio of the "specific Bi phase" contained in the alloy layer 12 were measured by image analysis. Specifically, a cross-sectional image of the observed section in the alloy layer 12 was acquired under a microscope, and the acquired cross-sectional image was binarized into the matrix 21 and Bi phase 22 of the alloy layer 12. The cross-sectional area of ​​the Bi phase 22 contained in the cross-sectional image was measured using image analysis software. The number ratio of the "specific Bi phase" contained in the first region A1 and the second region A2 was calculated based on the measured cross-sectional area of ​​the Bi phase 22. The cross-sectional area and number ratio of the "specific Bi phase" in the embodiment were observed at three locations near the two ends and the center of the obtained sliding member 10 along the axial direction, and their average value was used.

[0055] The sintering resistance and fatigue resistance of the sliding member 10 were evaluated. Sintering resistance was evaluated by measuring the surface pressure of the specimen during sintering, while a load was applied to the specimen made from the sliding member 10 and it rotated to become the axis of the opposing member 31. A test bushing with an axial length of 20 mm was cut from the sliding member 10 formed under the above conditions was used for the specimen. Fatigue resistance was evaluated by measuring the maximum surface pressure without fatigue, as the fatigue strength, while a load was applied to the specimen and it rotated to become the axis of the opposing member 31. A test bushing with an axial length of 30 mm was cut from the sliding member 10 formed under the above conditions was used for the specimen.

[0056] exist Figure 7 In Examples 2, 4-8 and Comparative Examples 1-7, the alloy layer 12 contains the same content of Bi and Sn. In these Examples 2, 4-8 and Comparative Examples 1-7, the conditions of the first and second cooling stages in the cooling process and the conditions of the heat treatment process were changed. Furthermore, in Examples 1 and 3, the Bi content in the alloy layer 12 was changed. Examples 1-8 satisfy the conditions of the cooling and heat treatment processes of this embodiment, while Comparative Examples 1-7 do not satisfy the conditions of the cooling and heat treatment processes of this embodiment.

[0057] According to Comparative Examples 1 and 2, it was shown that when the cooling water volume was too large, the proportion of the "specific Bi phase" in the second region was equal to that in the first region A1. That is, when the cooling water volume was too large, the Bi phase 22 was refined throughout the alloy layer 12. Therefore, it can be seen that the Bi supplied to the sliding surface 14 decreased, and the sintering resistance decreased. Furthermore, Comparative Example 3 showed that when the cooling water volume was insufficient, the proportion of the "specific Bi phase" in the first region A1 was equal to that in the second region A2. That is, when the cooling water volume was insufficient, the Bi phase in the alloy layer 12 became larger. Therefore, it can be seen that the development of cracks 33 in the alloy layer 12 was not suppressed, and the fatigue resistance decreased. Comparative Example 4 without heat treatment, Comparative Example 5 with insufficient heat treatment temperature, and Comparative Example 6 with insufficient heat treatment time all showed that the formation of the "specific Bi phase" was hindered, and the sintering resistance decreased. Comparative Example 7 did not satisfy any of the conditions of the cooling process and the heat treatment process of this embodiment. In this comparative example 7, it is shown that the "specific Bi phase" in both the first region A1 and the second region A2 does not meet the requirements of this embodiment, and both sintering resistance and fatigue resistance are reduced.

[0058] Figure 8 Examples 2, 9-19 illustrate the effects of various additive elements in alloy layer 12. In Example 9, Sn is not included in the alloy layer. Therefore, Example 2, which includes Sn in alloy layer 12, exhibits excellent fatigue resistance. In Examples 12-17, alloy layer 12 contains one or more of Al, Zn, Mn, Si, Ni, Fe, P, Zr, Ti, and Mg at a mass percentage of 5% or less. These additive elements contribute to improved fatigue resistance by enhancing solid solutions or precipitation of compounds in the matrix 21 of alloy layer 12. Example 18 includes Mo2C as a solid lubricant in alloy layer 12, and Example 19 includes graphite as a solid lubricant in alloy layer 12. Improved sintering resistance was observed in Examples 18 and 19, where alloy layer 12 includes solid lubricants.

[0059] Figure 9Based on Example 2, the effect of the cooling process is shown. In Comparative Example 8, compared to Example 2, the cooling in the first cooling stage of the cooling process was slightly excessive. Therefore, in Comparative Example 8, the "specific Bi phase" only exists in the range of about 5% of the thickness direction of the alloy layer 12 from the sliding surface 14. Consequently, the "specific Bi phase" contained in the second region A2 is reduced, and the supply of Bi to the sliding surface 14 is insufficient. As a result, the sintering resistance of Comparative Example 8 is reduced compared to Example 2. Furthermore, in Comparative Example 9, compared to Example 2, the cooling in the first cooling stage of the cooling process is slightly insufficient. Therefore, in Comparative Example 9, the fine Bi phase only exists in the range of about 14% of the thickness direction of the alloy layer 12 from the interface 13 on the substrate 11 side. Therefore, the fine Bi phase contained in the first region A1 is insufficient, and the reduction in the development of cracks 33 in the alloy layer 12 is inadequate. As a result, the fatigue resistance of Comparative Example 9 is reduced compared to Example 2.

[0060] The present invention described above is not limited to the above embodiments, and can be applied to various embodiments without departing from its spirit.

[0061] Explanation of reference numerals in the attached figures

[0062] In the attached figures, 10 represents a sliding member; 11 represents a substrate; 12 represents an alloy layer; 13 represents an interface; 14 represents a sliding surface; 22 represents the Bi phase; A1 represents the first region; and A2 represents the second region.

Claims

1. A sliding member having: Substrate; and An alloy layer, primarily composed of Cu and containing Bi, forms a sliding surface on the side opposite to the substrate. The alloy layer has: The first region is defined as a region with a thickness of 30% from the interface on the substrate side to the sliding surface side. The second region is defined as a region extending 10% of the thickness from the sliding surface to the substrate side. Compared to the Bi phase contained in the first region, the Bi phase contained in the second region contains many Bi phases with large cross-sectional areas in any observation section. In the Bi phase dispersed in the first region, the cross-sectional area of ​​any observed section is 250 μm. 2 The Bi phases mentioned above account for less than 6% of the total. In the Bi phase dispersed in the second region, the cross-sectional area of ​​any observed section is 250 μm. 2 The Bi phase accounts for more than 10% of the total number of phases.

2. A method for manufacturing a sliding member, wherein the sliding member is the sliding member according to claim 1, the manufacturing method comprising: The casting process involves casting an alloy layer, primarily composed of Cu and containing Bi, onto one side of the substrate; and In the cooling process, simultaneously and in parallel with the casting of the alloy layer, the substrate is cooled from another side using a cooling material, causing the alloy layer to solidify in one direction. In the cooling process, When a preset time has elapsed since the start, the size and quantity of the Bi phase contained in the alloy layer are controlled in the thickness direction of the alloy layer by reducing the supply of the cooling material. Furthermore, a heat treatment process is included after the cooling process: the sliding member on which the alloy layer is formed on the substrate is kept at 650~800°C for more than 1 hour.

3. The method for manufacturing a sliding member according to claim 2, wherein, The casting process is centrifugal casting: while rotating the cylindrical substrate around an axis, the alloy layer is formed on the inner circumferential surface of the substrate.

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