Sliding member
The alternating DLC layer structure in the sliding member addresses shape conformity and seizure resistance issues by promoting fine separation and adhesion, enhancing wear resistance and seizure resistance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DAIDO METAL IND CO LTD
- Filing Date
- 2023-04-27
- Publication Date
- 2026-06-17
Smart Images
Figure 0007875154000001 
Figure 0007875154000002 
Figure 0007875154000003
Abstract
Description
Technical Field
[0001] This embodiment relates to a sliding member.
Background Art
[0002] Conventionally, as a sliding member used for a bearing, a member having a DLC (Diamond Like Carbon) layer formed on the outermost surface that slides against a mating member is known (Patent Document 1). A sliding member with a DLC layer formed thereon has a reduced coefficient of friction with the mating member. Therefore, the sliding member with a DLC layer formed thereon has the characteristic that the frequency of seizure occurrence decreases. On the other hand, since the DLC layer is very hard, it is difficult to cause wear and deformation. Therefore, there is a problem that it is difficult to expect to secure an oil clearance due to the shape conformity between the sliding member having a DLC layer and the mating member. Further, when peeling occurs due to the brittleness of the DLC layer, it causes a local increase in the coefficient of friction and a decrease in seizure resistance.
[0003] In the case of Patent Document 1, a cause portion that causes intentional separation is provided in the DLC layer. By separating the DLC layer starting from this cause portion, the DLC layer follows the base material and is deformed to improve the shape conformity. However, the required performance of the sliding member has increased, and the sliding conditions between the sliding member and the mating member have become even more severe. Therefore, further fine separation of the DLC layer is required.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] Therefore, the objective is to provide a sliding member that achieves further fine separation of the DLC layer, further improves shape conformability, and consequently further improves seizure resistance. [Means for solving the problem]
[0006] A sliding member according to one embodiment comprises a bearing alloy layer and a first DLC layer provided on the sliding side of the bearing alloy layer with respect to a mating material. The first DLC layer is formed of DLC containing a predetermined additive element, and high-concentration portions with a high concentration of the additive element and low-concentration portions with a lower concentration of the additive element than the high-concentration portions are alternately formed in a direction perpendicular to the thickness direction.
[0007] Thus, in the sliding member according to one embodiment, the first DLC layer has high-concentration and low-concentration areas formed in a direction perpendicular to the thickness direction due to variations in the concentration of the additive elements. In other words, the first DLC layer of the sliding member according to one embodiment has alternating high-concentration and low-concentration areas at the atomic level. Therefore, the first DLC layer is promoted to separate starting from the areas of strength variation caused by these variations in the concentration of the additive elements. Consequently, the first DLC layer is separated more finely, further improving its conformability to the shape and further improving its resistance to seizing. [Brief explanation of the drawing]
[0008] [Figure 1] Schematic diagram showing the cross-section along line II in Figure 2. [Figure 2] A schematic diagram of a sliding member according to one embodiment, viewed from the axial end. [Figure 3] A schematic diagram showing a cross-section of another embodiment of the sliding member according to one embodiment. [Figure 4] A schematic diagram showing the main part of a sliding member according to one embodiment. [Figure 5] A schematic diagram of the formed interface in a sliding member according to one embodiment, viewed from the direction of arrow V shown in Figure 4. [Figure 6] Schematic diagram illustrating the structure of the first DLC layer of a sliding member according to one embodiment. [Figure 7] A schematic diagram showing a cross-section of another embodiment of the sliding member according to one embodiment. [Figure 8] Schematic diagram showing the conditions for the baking test. [Figure 9] A schematic diagram showing the contact between the first DLC layer and the mating material in a sliding member according to one embodiment. [Figure 10] A schematic diagram showing the settling of the first DLC layer and the mating material in a sliding member according to one embodiment. [Figure 11] A schematic diagram showing the settling of the first DLC layer and the mating material in a sliding member according to one embodiment, as viewed from the axial end. [Figure 12] A schematic diagram showing an example of a sliding member according to one embodiment. [Modes for carrying out the invention]
[0009] The following describes embodiments of the sliding members based on the drawings. As shown in Figures 1 and 2, the sliding member 10 comprises a first DLC layer 11 and a bearing alloy layer 12. The first DLC layer 11 is provided on the side of the bearing alloy layer 12 that slides against the mating material. The first DLC layer 11 is laminated on the bearing alloy layer 12 and bonded to the bearing alloy layer 12. The bearing alloy layer 12 is formed of an alloy such as Cu-based or Al-based. The sliding member 10 may also have a backing layer 13 made of Fe or steel. The first DLC layer 11 forms a sliding surface 14 on the opposite side from the bearing alloy layer 12 that slides against the mating material. The first DLC layer 11 has a hardness of 250HV to 1500HV based on Vickers hardness (HV). This reduces the aggressiveness of the first DLC layer 11 towards the mating material.
[0010] The first DLC layer 11 contains pre-defined additive elements. The additive elements are one or more elements selected from elements that form carbides, such as W, Co, Zr, Ta, Nb, V, Ti, Cr, Si, Ni, and Mo. The first DLC layer 11 contains 1 vol% to 60 vol% of the additive elements as a whole. This makes the first DLC layer 11 more ergonomically conformable. In addition, the sliding member 10 may include an intermediate layer 15 in addition to the first DLC layer 11 and the bearing alloy layer 12, as shown in Figure 3. The intermediate layer 15 is provided between the first DLC layer 11 and the bearing alloy layer 12. The intermediate layer 15 is formed of one or more elements selected from W, Co, Zr, Ta, Nb, V, Ti, Cr, Si, Ni, and Mo, similar to the additive elements. As shown in Figure 1, the end of the first DLC layer 11 on the bearing alloy layer 12 side is the formation interface 16. Furthermore, in the case of a sliding member 10 having an intermediate layer 15 as shown in Figure 3, the end of the first DLC layer 11 on the intermediate layer 15 side is the forming interface 16. Hereinafter, when the term "forming interface 16" is used in this specification, it refers to the end face of the first DLC layer 11 on the bearing alloy layer 12 side and the end face of the first DLC layer 11 on the intermediate layer 15 side.
[0011] As shown in Figures 4 and 5, the first DLC layer 11 comprises a high-concentration section 21, a low-concentration section 22, and a core section 23. The high-concentration section 21 and the low-concentration section 22 differ in the concentration of the additive elements contained in the first DLC layer 11. These high-concentration section 21 and low-concentration section 22 are formed alternately in a direction perpendicular to the thickness direction, that is, in the planar direction of the formation interface 16, in other words, in the direction along the sliding surface 14.
[0012] The high-concentration section 21 has an additive element concentration of 1 vol% to 60 vol%, while the low-concentration section 22 has an additive element concentration of 0.5 vol% to 59 vol%. This allows the first DLC layer 11 to conform to its shape while reducing the impact on sliding performance. The high-concentration section 21 is a region where the additive element concentration is relatively higher than that of the low-concentration section 22. The concentration of the additive element does not clearly change at the boundary between the high-concentration section 21 and the low-concentration section 22. In other words, as schematically shown in Figure 4, the concentration of the additive element changes continuously at the boundary between the high-concentration section 21 and the low-concentration section 22. In Figure 4, for ease of understanding, the high-concentration section 21, where the additive element concentration is higher, is schematically shown in a dark color, and the low-concentration section 22 is shown in a light color. Furthermore, the high-concentration section 21 does not necessarily have to be formed in a clear columnar shape in the thickness direction of the first DLC layer 11. In other words, the high-concentration portion 21 may be formed in a three-dimensional hemispherical area centered on the core portion 23. Even when the high-concentration portion 21 is formed three-dimensionally in this way, a low-concentration portion 22 exists between adjacent high-concentration portions 21. In the first DLC layer 11, it is preferable that the concentration difference between the region with the highest concentration of the added element in the high-concentration portion 21 and the region with the lowest concentration of the added element in the low-concentration portion 22 is 1 vol% or more. By forming such a concentration difference, separation is promoted in the first DLC layer 11, and shape conformation becomes easier.
[0013] The core part 23 is provided on the bearing alloy layer 12 side of the first DLC layer 11. When the first DLC layer 11 and the bearing alloy layer 12 are directly laminated, the core part 23 is provided at the formation interface 16 which is the end on the bearing alloy layer 12 side of the first DLC layer 11. Also, when the intermediate layer 15 is provided, the core part 23 is provided at the formation interface 16 which is the end on the intermediate layer 15 side of the first DLC layer 11. The core part 23 is provided corresponding to the high-concentration part 21 of the first DLC layer 11. That is, the core parts 23 are respectively located at the ends on the bearing alloy layer 12 side in the high-concentration part 21 of the first DLC layer 11. The core part 23 is a region where the concentration of the additive element is high in the first DLC layer 11. In this case, it is preferable that the concentration of the additive element in the core part 23 is 60% or more. The region of the first DLC layer 11 excluding the additive element is composed of a-C:H. In FIG. 4, for easy understanding, the core part 23 is schematically shown in white. The concentration of the additive element also changes continuously between the high-concentration part 21 and the core part 23.
[0014] As shown in FIG. 6, the outer diameter a of the core part 23 is set to 1 nm ≤ a ≤ 125 nm. Based on the outer diameter a of this core part 23, the shortest distance Da between the core parts 23 is 2a ≤ Da ≤ 8a. The distance Da between the core parts 23 corresponds to the shortest distance to the centers of adjacent core parts 23 in the cross-section in the thickness direction of the first DLC layer 11 as shown in FIGS. 1, 4, and 6. From this, the shortest distance Da between the core parts 23 is set to be sufficiently small, about several nm to several hundred nm, as compared with the prior art. The structure of the first DLC layer 11 as shown in FIG. 4 is similarly formed in the cross-section in the direction of arrow X in FIG. 1.
[0015] The core parts 23 are arranged almost evenly at the formation interface 16 which is the end on the bearing alloy layer 12 side of the first DLC layer 11 as shown in FIG. 5. These core parts 23 are formed by the additive element at the formation interface 16 when only the additive element is sputtered prior to the formation of the first DLC layer 11 by sputtering. At this time, the additive element forming the core part 23 is arranged almost regularly while maintaining the interval Da correlated with the outer diameter a of the core part 23 based on its own interaction and sputtering conditions.
[0016] Preferably, with respect to the outer diameter a of the core part 23, for the high-concentration part 21, the distance Db to another adjacent high-concentration part 21 is about Db = 2a, as shown in FIG. 6. In this case, the distance Db may be in the range of about 2a ≤ Db ≤ 8a. Similarly, for the low-concentration part 22, with respect to the outer diameter a of the core part 23, the distance Dc to another adjacent low-concentration part 22 is preferably about Dc = 2a. Also in this case, the distance Dc may be in the range of about 2a ≤ Dc ≤ 8a. The high-concentration part 21 is formed by sputtering carbon (C) for forming the first DLC layer 11 together with the additive element, and grows from the formation interface 16 in the thickness direction of the first DLC layer 11 corresponding to the core part 23. That is, the high-concentration part 21 extends from the core part 23 to the side opposite to the bearing alloy layer 12. Also, a low-concentration part 22 having a lower concentration of the additive element than the high-concentration part 21 is formed between the high-concentration parts 21 formed corresponding to the core part 23.
[0017] As shown in FIG. 4, at the boundary between the high-concentration part 21 and the low-concentration part 22, the concentration of the additive element changes continuously, and the concentration of the additive element does not change clearly at the boundary between the high-concentration part 21 and the low-concentration part 21. Therefore, the distances Db and Dc are defined and calculated as follows. First, the center point of the core part 23 at the formation interface 16 is extracted. From this center point, a circular region is defined along the formation interface 16 with a radius of 1 / 4 of the distance Da. The width of this region, that is, the length of the portion corresponding to the diameter of the circular region centered on the center point is defined as the distance Dc. Then, the region sandwiched by the defined distance Dc is defined as the distance Db.
[0018] By providing an intermediate layer 15 between the first DLC layer 11 and the bearing alloy layer 12, the adhesion of the additive elements growing from the formation interface 16 to the intermediate layer 15 is enhanced. In other words, it is preferable that the intermediate layer 15 be formed of the same element as the additive elements or an element with high material commonality with the additive elements. By selecting elements in this way to form the intermediate layer 15, the core 23 is more easily formed in the intermediate layer 15, and the adhesion to the intermediate layer 15 is also improved. It is preferable that the intermediate layer 15 be formed with a thickness of about 0.1 μm to 1 μm. This ensures reliable adhesion between the first DLC layer 11 and the bearing alloy layer 12.
[0019] The sliding member 10 may further include a second DLC layer 30, as shown in Figure 7. The second DLC layer 30 is laminated on the sliding side of the first DLC layer 11, that is, on the side of the first DLC layer 11 opposite to the bearing alloy layer 12. The second DLC layer 30 is formed of DLC, similar to the first DLC layer 11. The concentration of additive elements in the second DLC layer 30 is set lower than the total concentration of additive elements contained in the first DLC layer 11. That is, the concentration of additive elements in the second DLC layer 30 is lower than that of the first DLC layer 11 to which it is laminated, and the concentration of additive elements is set to 0-20 vol%. By setting the concentration of additive elements in the second DLC layer 30 in this way, the aggressiveness of the second DLC layer 30 towards the mating material can be reduced, and the difference in hardness with the first DLC layer 11 can be easily adjusted. Also, when the thickness of the first DLC layer 11 is T1 and the thickness of the second DLC layer 30 is T2, T1 > T2. Thus, the second DLC layer 30 is formed thinner than the first DLC layer 11. The hardness of the second DLC layer 30 is preferably set to 250 HV to 1500 HV. In this case, it is more preferable that the difference in hardness between the first DLC layer 11 and the second DLC layer 30 is 100 HV or less. This reduces the aggressiveness of the second DLC layer 30 towards the mating material. The concentrations of the additive elements in the first DLC layer 11, the high-concentration section 21, the low-concentration section 22, and the second DLC layer 30 are measured from the cross-section of the sliding member 10 using an electron beam microanalyzer (EPMA). The overall concentration of the additive elements in the first DLC layer 11 is calculated by averaging the concentrations of the additive elements in the high-concentration section 21 and the low-concentration section 22.
[0020] Next, an example of a manufacturing method for the sliding member 10 will be described. The first DLC layer 11 is formed using a sputtering apparatus as described above. The material on which the bearing alloy layer 12 is formed is housed in a chamber. The chamber in which the material is housed has an interior area of, for example, 1.0 × 10 -3The pressure is reduced to below Pa. After the pressure reduction, the material is pre-treated, for example, with an inert gas. Once the pre-treatment is complete, cores 23 are formed on the surface of the bearing alloy layer 12, which will become the formation interface 16. Prior to the formation of these cores 23, an intermediate layer 15 may be formed on the surface of the bearing alloy layer 12. The intermediate layer 15 is formed by sputtering an additive element alone onto the surface of the bearing alloy layer 12. The cores 23 are formed on the formation interface 16 by sputtering for a short time, such as a few minutes. At this time, the cores 23 are formed on the formation interface 16 at intervals Da corresponding to the outer diameter a of the cores 23, as shown in Figure 6, due to the interaction of the additive elements. The outer diameter a and interval Da of these cores 23 are controlled by, for example, the required sputtering time, bias voltage, the target used, and the pressure inside the chamber. The outer diameter a and interval Da are controlled in particular by the pressure inside the chamber.
[0021] The material on which the core 23 is formed is then subjected to a first DLC layer 11. The first DLC layer 11 is formed by sputtering for a significantly longer period of time compared to the formation of the core 23. Furthermore, when forming the first DLC layer 11, the film thickness per unit time is set to be larger than that for the formation of the core 23. Once the first DLC layer 11 is formed, a second DLC layer 30 is formed as needed. When forming the second DLC layer 30, the film thickness per unit time is set to be smaller than that for the first DLC layer 11. The sliding member 10 is formed by the above procedure. Note that the above disclosure is just one example of a manufacturing method, and the manufacturing method for forming the high-concentration portion 21 and the low-concentration portion 22 in the first DLC layer 11 is not limited to the above disclosure.
[0022] The operation of the sliding member 10 of this embodiment will be described below based on verification of the examples and comparative examples. The examples and comparative examples were evaluated based on a seizure test. The seizure test was performed under the conditions shown in Figure 8. In the seizure test, the sliding member 10 of the examples and comparative examples, which were molded into a half-split shape, was used. In the seizure test, based on the conditions shown in Figure 8, the maximum surface pressure at which seizure did not occur was measured when the sliding member was slid with improper contact against a shaft-shaped mating material 40 made of S55C, as shown in Figures 9 and 10.
[0023] As shown in Figure 9, when the sliding member 10 and the mating material 40 are slid against each other with improper contact, the bearing alloy layer 12 of the sliding member 10 deforms as shown in Figure 10 due to the force applied from the mating material 40. At this time, the first DLC layer 11 of the sliding member 10 according to this embodiment is promoted to separate starting from areas of strength variation due to differences in the concentration of the additive elements. That is, since the first DLC layer 11 is formed with alternating high-concentration areas 21 and low-concentration areas 22 with different concentrations of additive elements, a difference in strength occurs at minute intervals. As a result, the first DLC layer 11 is promoted to separate finely starting from these areas of strength variation. Therefore, as in the sliding member 10 according to this embodiment, the finely fractured first DLC layer 11 deforms in accordance with the deformation of the bearing alloy layer 12, as shown in Figures 10 and 11. As a result, even when the sliding member 10 is in improper contact with the mating material 40, it can easily follow the deformation of the bearing alloy layer 12, thereby improving seizure resistance.
[0024] As shown in Figure 12, Examples 1 to 15 are examples in which the first DLC layer 11 is directly laminated to the bearing alloy layer 12 and no intermediate layer 15 is provided. Examples 16 to 24 are examples in which an intermediate layer 15 is provided between the first DLC layer 11 and the bearing alloy layer 12. Examples 18 to 24 are examples in which a second DLC layer 30 is provided in addition to the first DLC layer 11.
[0025] On the other hand, Comparative Examples 1 and 2 are examples in which a first DLC layer 11 containing additive elements is provided in the bearing alloy layer 12, but a concentration distribution of the additive elements is not formed in the first DLC layer 11. In other words, in Comparative Examples 1 and 2, high-concentration areas 21 and low-concentration areas 22 are not formed in the first DLC layer 11. Comparative Examples 3 and 4 are examples in which an intermediate layer 15 is provided between the first DLC layer 11 and the bearing alloy layer 12. The first DLC layer 11 in Comparative Examples 3 and 4 does not contain additive elements.
[0026] Examples 1 to 24 demonstrate improved seizure resistance compared to Comparative Examples 1 to 4. Specifically, in the first DLC layer 11, which is formed with alternating high-concentration sections 21 and low-concentration sections 22 as in Examples 1 to 24, fracture is promoted in the low-concentration sections 22 when stress is applied due to improper contact. As a result, the first DLC layer 11 improves its ability to follow the deformation of the bearing alloy layer 12. Consequently, the seizure resistance of the sliding member 10 is improved. Furthermore, Examples 1 to 13 show that the type and combination of additive elements contained in the first DLC layer 11 do not affect seizure resistance.
[0027] Examples 12 to 24 show that the seizure resistance improves as the spacing Da of the core portions 23 decreases. When the spacing Da of the core portions 23 decreases, the spacing Db of the high-concentration portions 21 and the spacing Dc of the low-concentration portions 22 naturally decrease as well. As a result, the first DLC layer 11 undergoes more fine fracture as the spacing Da of the core portions 23 decreases. Consequently, the first DLC layer 11 becomes more responsive to the deformation of the bearing alloy layer 12. As a result, the seizure resistance of the sliding member 10 is improved.
[0028] Examples 15 and 16 show that Example 16, in which the intermediate layer 15 is provided, exhibits improved seizure resistance. The intermediate layer 15 contributes to improving the adhesion of the core portion 23, which is the starting point for the growth of the high-concentration portion 21. That is, the intermediate layer 15 is formed of an element with the same or similar properties as the additive element added to the first DLC layer 11, and has high affinity with the core portion 23. Therefore, forming the intermediate layer 15 increases the adhesion between the first DLC layer 11 and the bearing alloy layer 12. As a result, the detachment of the first DLC layer 11 from the bearing alloy layer 12 is reduced, and the seizure resistance of the sliding member 10 is further improved.
[0029] Examples 17 to 24, in which the second DLC layer 30 is provided, show further improvement in seizure resistance. The second DLC layer 30 contributes to reducing the contact resistance between the sliding member 10 and the mating material 40, especially in the initial stages of sliding with the mating material 40. Therefore, by providing the second DLC layer 30, damage during sliding between the sliding member 10 and the mating material 40 is reduced, and the seizure resistance of the sliding member 10 is further improved. In this case, Examples 21 to 24, in which T1 > T2, show further improvement in seizure resistance. By making T1 > T2 in this way, the separation of the first DLC layer 11 that follows the deformation of the bearing alloy layer 12 is further promoted. As a result, further improvement in seizure resistance can be achieved. In addition, Example 24, in which the difference in hardness between the first DLC layer 11 and the second DLC layer 30 is 100 HV or less, shows further improvement in seizure resistance. In this way, by reducing the difference in hardness between the first DLC layer 11 and the second DLC layer 30, the adhesive strength between the first DLC layer 11 and the second DLC layer 30 is improved. As a result, further improvement in seizure resistance can be achieved.
[0030] The present invention described above is not limited to the embodiments described above, and can be applied to various embodiments without departing from the spirit of the invention. [Explanation of Symbols]
[0031] In the drawing, 10 is the sliding member, 11 is the first DLC layer, 12 is the bearing alloy layer, 15 is the intermediate layer, 21 is the high-concentration section, 22 is the low-concentration section, 23 is the core section, and 30 is the second DLC layer.
Claims
1. A sliding member comprising a bearing alloy layer and a first DLC layer provided on the sliding side of the bearing alloy layer with respect to the mating material, The first DLC layer is Formed from DLC containing pre-set additive elements, High-concentration sections with a high concentration of the additive element and low-concentration sections with a lower concentration of the additive element than the high-concentration sections are alternately formed in a direction perpendicular to the thickness direction. Sliding member.
2. The first DLC layer further comprises a core portion provided on the bearing alloy layer side corresponding to the high-concentration portion, wherein the concentration of the additive element is higher than that of the high-concentration portion. The sliding member according to claim 1.
3. The outer diameter a of the core is 1 nm ≤ a ≤ 125 nm. In a cross-section perpendicular to the thickness direction of the first DLC layer, the spacing Da between adjacent core portions is 2a ≤ Da ≤ 8a. The sliding member according to claim 2.
4. The aforementioned additive element is one or more of the elements that form carbides. A sliding member according to any one of claims 1 to 3.
5. The aforementioned additive element is one or more selected from W, Co, Zr, Ta, Nb, V, Ti, Cr, Si, Ni, and Mo. The sliding member according to claim 4.
6. The system further comprises an intermediate layer provided between the bearing alloy layer and the first DLC layer, formed of one or more elements selected from W, Co, Zr, Ta, Nb, V, Ti, Cr, Si, Ni, and Mo. The sliding member according to claim 1.
7. The first DLC layer is provided on the sliding side, and further comprises a second DLC layer made of DLC in which the concentration of the additive element is lower than the concentration of the additive element contained in the entire first DLC layer. The sliding member according to claim 6.
8. The thickness T1 of the first DLC layer and the thickness T2 of the second DLC layer are, T1 > T2 That is, The sliding member according to claim 7.
9. The difference in hardness between the first DLC layer and the second DLC layer is 100 HV or less. The sliding member according to claim 7.