Sliding member

Abstract

The present invention provides a sliding member that promotes the adhesion of a solid lubricant to the mating material, thereby maintaining long-term resistance to seizing. [Solution] The sliding member 10 comprises a base material 11 mainly composed of Al with a surface hardness of HV110 or less, and a lubricating surface layer 14 provided on the sliding side of the base material 11 and containing a solid lubricant 16. The lubricating surface layer 14 has the base material surface 17, which is the surface of the base material 11, and the solid lubricant 16 exposed. In the sliding member 10, when the coefficient of variation B = D / A is calculated by dividing the observation area 21 set on the sliding surface 15 into nine unit areas 22 and determining the standard deviation in the observation area 21 from the ratio of the area occupied by the solid lubricant 16 in each of the nine unit areas, 10 ≤ A ≤ 40 and 0.1 ≤ B ≤ 0.3.

Description

Technical Field

[0001] This embodiment relates to a sliding member including a base material mainly composed of Al.

Background Art

[0002] Conventionally, a bearing including a base material mainly composed of Al has been used as a sliding member used in an internal combustion engine of a vehicle or the like. Such a sliding member includes a lubricating surface layer portion containing a solid lubricant on the surface side that slides with a mating member in order to improve seizure resistance (see Patent Document 1). That is, the friction coefficient is reduced by the solid lubricant contained in the lubricating surface layer portion, and the seizure resistance is improved.

[0003] However, the solid lubricant is distributed almost uniformly throughout the lubricating surface layer portion. Therefore, the solid lubricant contained in the lubricating surface layer portion quickly moves to the mating member at the start of sliding with the mating member. That is, the solid lubricant contained in the lubricating surface layer portion adheres to the mating member at the start of sliding. Then, the solid lubricant that has moved to the mating member disappears as the sliding continues without being fixed to the mating member. Therefore, the lubricating surface layer portion is worn out early at the start of sliding, making it difficult to maintain for a long period of time, and there is a problem of causing a decrease in seizure resistance in a short period of time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, an object is to provide a sliding member that promotes the fixing of the solid lubricant to the mating member and enables the maintenance of seizure resistance for a long period of time.

Means for Solving the Problems

[0006] The sliding member of this disclosure comprises a base material mainly composed of Al and having a surface hardness of HV110 or less, and a lubricating surface layer portion provided on the side of the base material that slides with a mating material and containing a solid lubricant. The lubricating surface layer portion has a sliding surface on the mating material side, and the base material surface, which is the surface of the base material, and the solid lubricant are exposed on the sliding surface. In the sliding member of this disclosure, the area S of the sliding surface is 30 μm × 30 μm, and S = 900 μm 2 When an arbitrary observation area is set, and within the observation area, the area occupied by the exposed solid lubricant is denoted as Sp, and the area ratio A (%) is set as area ratio A = Sp / S × 100, and the observation area is divided into nine 10 μm × 10 μm unit areas, and the standard deviation in the observation area obtained from the ratio of the area occupied by the solid lubricant in each of the nine unit areas is denoted as D, and the coefficient of variation B is set as coefficient of variation B = D / A, 10 ≤ A ≤ 40 0.1 ≤ B ≤ 0.3 That is the case.

[0007] Thus, in the sliding member of this disclosure, the sliding surface that slides against the mating material has an exposed substrate surface, which is the surface of the Al-based substrate, and a solid lubricant. In a pre-set observation area on this sliding surface, the area percentage (%) occupied by the solid lubricant and the coefficient of variation B, based on the standard deviation D of the unit area into which the observation area is divided, fall within the set range. This indicates that the substrate surface and solid lubricant exposed on the sliding surface are not uniformly distributed, but rather unevenly distributed. In other words, the sliding surface irregularly contains areas where the substrate surface is mainly exposed and areas where the solid lubricant is mainly exposed. Therefore, during sliding against the mating material, the solid lubricant moves to the mating material early in the areas where the solid lubricant is mainly exposed. At the same time, in the areas where the substrate surface is mainly exposed, the substrate forming the substrate surface adheres to the mating material. As a result, the mating material not only has solid lubricant moved and adhered to it, but the substrate also adheres to it. Furthermore, the solid lubricant contained in the substrate is retained by the mating material together with the substrate. Furthermore, the substrate that adheres to the mating material will have solid lubricant that has moved from the lubricating surface layer attached to it. In other words, the solid lubricant is retained on the surface of the substrate that adheres to the mating material, and is also contained within the adhered substrate. Therefore, the solid lubricant is retained on the mating material side for a long period of time. As a result, the solid lubricant is retained between the lubricating surface layer and the mating material for a long period of time. Therefore, it is possible to promote the adhesion of the solid lubricant to the mating material and maintain long-term seizure resistance. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing a sliding member according to one embodiment. [Figure 2] A schematic diagram showing the sliding surface of a sliding member according to one embodiment, viewed from the direction of arrow II in Figure 1. [Figure 3] Figure 2 shows a schematic diagram illustrating the observation area and unit area. [Figure 4] A schematic diagram showing a sliding member and a mating material according to one embodiment. [Figure 5] A schematic diagram showing a bearing to which a sliding member according to one embodiment is applied. [Figure 6] A schematic diagram showing the conditions for a seizure resistance test of a sliding member according to one embodiment. [Figure 7] A schematic diagram showing the relationship between time and the load applied to the sample in a seizure resistance test of a sliding member according to one embodiment. [Figure 8] A schematic diagram showing a test apparatus used for testing the seizure resistance of a sliding member according to one embodiment. [Figure 9] A schematic diagram showing the change in the back surface temperature of a bearing in response to a change in load during a seizure resistance test of a sliding member according to one embodiment. [Figure 10] A schematic diagram showing the results of seizure resistance tests in examples and comparative examples of sliding members according to one embodiment. [Figure 11] A schematic diagram showing the results of seizure resistance tests in examples and comparative examples of sliding members according to one embodiment. [Figure 12] A schematic diagram showing the results of seizure resistance tests in examples and comparative examples of sliding members according to one embodiment. [Figure 13] A schematic diagram showing the results of seizure resistance tests in examples and comparative examples of sliding members according to one embodiment. [Modes for carrying out the invention]

[0009] A sliding member according to one embodiment will be described below with reference to the drawings. As shown in Figure 1, the sliding member 10 according to one embodiment includes a base material 11. The base material 11 is an Al-based alloy with Al as the main component. The surface hardness of the base material 11 is set to HV110 or less. The Al-based alloy forming the base material 11 contains less than 30% by mass of additive elements other than Al. In other words, the base material 11 has an Al concentration C of 70% by mass or more. The additive elements added to the base material 11 are one or more selected from Sn, Zn, Si, Cu, V, Mn, Ti, Mg, Ni, and Zr. The sliding member 10 may also include a backing layer 12. The backing layer 12 can be, for example, an Fe alloy such as hypoeutectoid steel or stainless steel, Cu, or a Cu alloy. Note that the Al-based alloy that forms the base material 11 contains unavoidable impurities in addition to the additive elements.

[0010] The sliding member 10 is provided with a lubricating surface layer 14 on the surface side of the base material 11, that is, on the side that slides against the mating material 13. The lubricating surface layer 14 is provided on the outermost surface of the base material 11 that is in contact with the mating material 13, and forms a sliding surface 15 on the surface facing the mating material 13. In other words, the sliding member 10 slides against the mating material 13 on the sliding surface 15. The lubricating surface layer 14 contains a solid lubricant 16 together with the base material 11. The solid lubricant 16 can be molybdenum disulfide (MoS2), graphite, boron nitride (BN), tungsten disulfide (WS2), graphite fluoride (CF), melamine cyanurate (MCA), etc. The solid lubricant 16 may be one type or a mixture of two or more types.

[0011] The lubricating surface layer 14 contains a solid lubricant 16 in an Al-based alloy that forms the base material 11. Therefore, the sliding surface 15, which is the end face of the lubricating surface layer 14, has the base material surface 17, which is the surface of the base material 11, and the solid lubricant 16 exposed, as shown in Figure 2. On this sliding surface 15, the solid lubricant 16 and the base material surface 17 are in an irregular state with uneven distribution. Figure 2 is a schematic diagram showing the sliding surface 15 of the sliding member 10. The sliding surface 15 of the sliding member 10 is in a state where numerous island-like solid lubricants 16 are exposed on the base material surface 17. The shaded area in Figure 2 shows the base material surface 17. Note that Figure 1 shows the state in which the solid lubricant 16 adheres to the base material surface 17 while forming steps, for the sake of simplicity of explanation. However, the solid lubricant 16 becomes embedded in the base material 11 through processing of the sliding surface 15, forming a generally uniform surface with the base material surface 17.

[0012] The sliding surface 15 shown in Figure 2 is within the range set by the area ratio A and coefficient of variation B. The area ratio A and coefficient of variation B will be explained in detail below. An arbitrary observation area 21 measuring 30 μm × 30 μm is set on the sliding surface 15, as shown in Figure 3. The area enclosed by the thick solid line in Figure 3 is the observation area 21. The observation area 21 can be set at any position on the sliding surface 15 formed on the lubricating surface layer 14 of the sliding member 10. The area S of the observation area 21 with the above dimensions is S = 900 μm². 2That is. In the observation region 21 set in the lubricating surface layer portion 14, the solid lubricant 16 and the base material surface 17 are exposed as described above. In this observation region 21, the area occupied by the exposed solid lubricant 16 is defined as the area Sp. At this time, the area ratio A (%) is calculated as A = Sp / S×100.

[0013] In this case, in the observation region 21, a region containing an element constituting 7 mass% or more of the solid lubricant 16 is determined to have the solid lubricant 16 present. The element constituting the solid lubricant 16 means, for example, the element itself, that is, carbon (C) when the solid lubricant 16 is composed of a single element such as graphite. Also, when the solid lubricant 16 is composed of a compound of two or more elements, it means the element with the largest atomic weight. For example, in the case of MoS2, the element with the largest atomic weight is Mo. Also, for example, in the case of WS2, the element with the largest atomic weight is W, and for example, in the case of CF, the element with the largest atomic weight is F. Hereinafter, the element constituting the solid lubricant 16 is referred to as the "constituent element".

[0014] In the region determined to have the solid lubricant 16 present in the lubricating surface layer portion 14, the thickness of the solid lubricant 16 is 0.005 μm to 5 μm. Note that even in the region determined not to have the solid lubricant 16 present, that is, determined to be the base material surface 17, if it is less than 7 mass%, it may contain the constituent element of the solid lubricant 16. The analysis of the constituent element in the observation region 21 is carried out using an electron probe microanalyzer (EPMA: JXA-8530F manufactured by JEOL Ltd.).

[0015] Next, the coefficient of variation B will be described. The coefficient of variation B is calculated based on the standard deviation D of the ratio of the area of the solid lubricant 16 in the observation region 21 when the observation region 21 is divided into unit regions 22 as shown by the thick dashed line in FIG. 3. Specifically, the observation region 21 is divided into nine unit regions of 10 μm × 10 μm. For each of these nine unit regions 22, the ratio ri (i = 1 to 9) of the area occupied by the solid lubricant 16 is calculated. Then, based on the calculated ratio ri of the area for each unit region, the standard deviation D of the ratio of the area occupied by the solid lubricant 16 in the entire observation region 21 is calculated. The coefficient of variation B is calculated by dividing this standard deviation D by the above-described area ratio A (%), that is, B = D / A.

[0016] At this time, the area ratio A (%) and the coefficient of variation B in the sliding member 10 according to the present embodiment are 10 ≦ A ≦ 40 0.1 ≦ B ≦ 0.3 are satisfied.

[0017] When the area ratio A is less than 10%, the effect of improving seizure resistance cannot be obtained. On the other hand, when the area ratio A exceeds 40%, it becomes difficult to adjust the coefficient of variation B. In this case, from the viewpoint of adjusting the coefficient of variation B for improving seizure resistance, the area ratio A is more preferably 30% or less.

[0018] In this way, by setting the area ratio A and coefficient of variation B of the sliding member 10, the sliding member 10 of this embodiment can achieve improved long-term seizure resistance. Area ratio A represents the ratio of the area of ​​the solid lubricant 16 exposed on the sliding surface 15 to the area of ​​the base material surface 17. In other words, when area ratio A is large, the proportion of the area of ​​the solid lubricant 16 exposed on the sliding surface 15 is relatively large, and the proportion of the area of ​​the base material surface 17 is small. On the other hand, when area ratio A is small, the proportion of the area of ​​the solid lubricant 16 exposed on the sliding surface 15 is relatively small, and the proportion of the area of ​​the base material surface 17 is large. Furthermore, the coefficient of variation B represents the degree of dispersion of the solid lubricant 16 exposed on the sliding surface 15. In other words, the smaller the coefficient of variation B, the more uniformly the solid lubricant 16 is dispersed on the sliding surface 15, and the larger the coefficient of variation B, the more unevenly the solid lubricant 16 is dispersed. Therefore, when the coefficient of variation B is within the range of 0.1 ≤ B ≤ 0.3, it indicates that the solid lubricant 16 is distributed on the sliding surface 15 with an appropriate uneven distribution of density.

[0019] As described above, in this embodiment, the solid lubricant 16 and the base material surface 17 exposed on the sliding surface 15 are not uniformly distributed, but rather unevenly distributed. In other words, in this embodiment, the end face of the sliding member 10 on the mating material 13 side irregularly consists of a first region 31 where the solid lubricant 16 is mainly exposed, and a second region 32 where the base material surface 17 is mainly exposed, as shown in Figure 4. Therefore, when the sliding member 10 and the mating material 13 slide against each other, in the first region 31 of the sliding surface 15 where the solid lubricant 16 is mainly exposed, the solid lubricant 16 comes into contact with the mating material 13, and the solid lubricant 16 contained in the lubricating surface layer 14 moves to the mating material 13. At the same time, in the second region 32 where the base material surface 17 is mainly exposed, the base material 11 forming the base material surface 17 comes into contact with the mating material 13, and the Al-based alloy, which is the base material 11 forming the lubricating surface layer 14, moves to the mating material 13. Therefore, the mating material 13 has a base material region 33 to which the base material 11 transferred from the sliding member 10 adheres. In other words, the mating material 13 not only has the solid lubricant 16 moved from the lubricating surface layer 14 and adhered, but the base material 11 also adheres to it. As a result, the mating material 13 has a base material region 33 formed where not only the solid lubricant 16 but also a portion of the base material 11 adheres. The solid lubricant 16 that moved from the lubricating surface layer 14 also adheres to this base material region 33. Furthermore, the base material region 33 encompasses the solid lubricant 16 contained in the base material 11 that moved from the lubricating surface layer 14. Therefore, the base material region 33 to which the base material 11 adheres stably retains the solid lubricant 16 on the mating material 13 side for a long period of time. In this case, by appropriately setting the area ratio A and the coefficient of variation B, the solid lubricant 16 is retained for a long period of time in the sliding portion between the mating material 13 and the sliding member 10.

[0020] The solid lubricant 16 is preferably a metal sulfide, and more preferably MoS2 or WS2. The solid lubricant 16 made of a metal sulfide has the properties of high adhesion to the substrate 11 and is difficult to peel off from the substrate 11. The substrate 11 is transferred from the sliding member 10 to the mating material 13 by sliding between the sliding member 10 and the mating material 13. At this time, the solid lubricant 16 adheres to the substrate region 33 formed on the mating material 13. By using a metal sulfide as the solid lubricant 16, the solid lubricant 16 adheres more firmly to the substrate region 33. As a result, the solid lubricant 16 made of a metal sulfide can be retained between the sliding member 10 and the mating material 13 for a longer period of time.

[0021] Next, a method for manufacturing the sliding member 10 according to the above embodiment will be described. The sliding member 10 is manufactured by applying a solid lubricant 16 to an Al-based substrate 11. In this case, the solid lubricant 16 is applied by spraying, for example, fine powder of the solid lubricant 16 onto the surface of the substrate 11. In particular, the powder of the solid lubricant 16 is applied by impacting the surface of the substrate 11 at high speed, for example, by shot peening. By impacting the surface of the substrate 11 with the solid lubricant 16, the solid lubricant 16 penetrates the substrate 11. As a result, the solid lubricant 16 is fixed to the substrate 11 of the lubricating surface layer 14. At this time, a medium formed from, for example, nylon resin or melamine resin may be added to the solid lubricant 16. These nylon resin and melamine resin mediums have the property of not easily adhering to the substrate 11. Therefore, by adding a medium to the powder of the solid lubricant 16, the amount and distribution of the solid lubricant 16 adhering to the surface of the substrate 11 can be controlled. As a result, the medium functions as a modifier for adjusting the coefficient of variation B.

[0022] The surface hardness of the base material 11 was measured after applying the solid lubricant 16. The surface hardness was measured using a micro-Vickers hardness tester (Mitutoyo Corporation: HM-200). The test load was set to a relatively small load of 10 gf (0.098 N). In this embodiment, the surface hardness of the base material 11 is set to HV110 or less. If the surface hardness of the base material 11 is greater than HV110, excessive heat will be generated due to friction during sliding between the sliding member 10 and the mating material 13, making seizing more likely before the base material 11 adheres to the mating material 13. Therefore, adhesion of the base material 13 from the sliding member 10 to the mating material 13 is hindered. The surface hardness of the base material 11 was measured at multiple locations on the lubricated surface layer 14, and the average value was used.

[0023] The following describes an embodiment of the sliding member 10 of this embodiment. (Samples of the examples and comparative examples) As shown in Figure 5, the samples used for the examples and comparative examples are formed by processing the sliding member 10 into a halved bearing 40. Specifically, the base material 11 is joined to a plate-shaped backing layer 12. The joining of the base material 11 and the backing layer 12 can be done using well-known manufacturing methods, such as sintering or pressure welding by rolling. The joined base material 11 and backing layer 12 were formed into halved samples by mechanical processing such as pressing or cutting. The base material 11 is an Al-based alloy with a thickness of 0.3 mm. The backing layer 12 is made of cold-rolled steel sheet with a thickness of 1.2 mm. The solid lubricant 16 is applied to the surface of the base material 11 joined to the backing layer 12. Prior to the application of the solid lubricant 16, the surface of the base material 11 was degreased. Well-known general methods can be used to degrease the surface of the base material 11. The solid lubricant 16 is sprayed onto the degreased surface of the base material 11 along with compressed high-pressure air. As a result, the solid lubricant 16 is adhered to the surface of the base material 11 of the sliding member 10.

[0024] (Seizure resistance test) The seizure resistance of the samples used for the examples and comparative examples was verified under the conditions shown in Figure 6. The seizure resistance test was performed after a break-in period, as shown in Figure 7, while increasing the test surface pressure. The break-in period was performed with sufficient lubricating oil supplied between the sliding member 10 and the mating material 13. Subsequently, the seizure resistance test was performed while keeping the oil supply rate constant at 150 ml / min, and increasing the test surface pressure by 5 MPa every 10 minutes until seizure occurred. For the sample, seizure was determined to have occurred when the back surface temperature of the backing metal layer 12, that is, the temperature of the side of the backing metal layer 12 opposite to the mating material 13, reached 230°C. The back surface temperature was measured using a thermocouple (not shown).

[0025] The seizure resistance test was performed by assembling bearings 40 to form an annular shape, as shown in Figure 8, fixing them to a housing 41, and sliding them against a mating material 13. In this test, shims 42 were installed between the bearing 40 and the housing 41 at both axial ends of the sample bearing 40. The shims 42 were semi-cylindrical and installed on the lower side of the bearing 40 where the load was applied. The load was applied to the bearing 40 from top to bottom in Figure 8. The shims 42 were installed to apply a larger load to the samples of the examples and comparative examples earlier. That is, by installing the shims 42, the oil film breakdown of the lubricating oil was made more likely, and an environment in which the solid lubricant 16 was easily worn down was reproduced earlier. The shims 42 used in the verification had a thickness of 5 μm and an axial length of 2 mm.

[0026] In the seizure resistance test, the maximum surface pressure at which seizure does not occur in the reference comparative example sample was set to "1," and the evaluation was based on the degree to which the maximum surface pressure at which seizure does not occur improved in each sample of the example and comparative example using the same solid lubricant 16. For example, if the seizure resistance evaluation of the example is "1.1," and the maximum surface pressure at which seizure does not occur in the comparative example is "100 MPa," then the maximum surface pressure at which seizure does not occur in the example is "110 MPa."

[0027] As shown in Figure 9, when the applied load is changed in stages during a sliding test between the sliding member 10 and the mating material 13, the temperature T on the back side of the sliding member 10 rises sharply immediately after the load increases, reaching the peak temperature Tp. After that, the temperature T decreases from the peak temperature Tp, and then rises slightly for a certain period of time as the applied load remains constant, reaching the pre-occurring temperature Tb. This is because, in the seizure resistance test, as described above, by interposing the shim 42 between the sliding member 10 and the housing 41, temporary oil film breakdown is more likely to occur when the load increases, resulting in localized contact with the mating material 13. Then, as the lubricating oil film is formed, the temperature becomes generally stable up to the pre-occurring temperature Tb. Thus, each time the test load is changed, the temperature T reaches the peak temperature Tp and then the pre-occurring temperature Tb. The temperature difference dT is calculated based on these peak temperatures Tp and pre-occurring temperature Tb as dT = Tp - Tb. The average of the temperature difference dT detected for each increase in load is defined as the average temperature difference Ta. Thus, the average temperature difference Ta is calculated based on the temperature difference dT. Note that the temperature difference dT between the temperature Tb immediately before the final load that caused seizure due to the gradual increase in load was applied and the peak temperature Tp is not included in the calculation of this average temperature difference Ta.

[0028] (Verification results) As shown in Figure 10, Examples 1 to 7 and Comparative Examples 1 to 9 all use MoS2 as the solid lubricant 16 to verify the effects of area ratio A and coefficient of variation B. Of these, Comparative Example 2, which has the highest seizure resistance among Comparative Examples 1 to 9, is used as the standard for evaluation. Examples 1 to 7 all satisfy the area ratio A and coefficient of variation B of this embodiment. Furthermore, the base material 11 of Examples 1 to 4 is an Al-Sn-Si alloy, the base material 11 of Example 5 is an Al-Zn-Si alloy, the base material 11 of Example 6 is an Al-Zn-Si-Cu alloy, and the base material 11 of Example 7 is an Al-Sn-Cu alloy. In all of Examples 1 to 7, the Al concentration C of the alloy is 70 mass% or more, and the surface hardness is HV110 or less. In contrast, the coefficient of variation B of Comparative Examples 1, 3, 6, and 7 are all smaller than the lower limit. Furthermore, the coefficient of variation B of Comparative Example 2 is larger than the upper limit, and the area ratio A of Comparative Example 4 is smaller than the lower limit. Comparative Example 5 has a Cu-based alloy as the base material 11. Comparative Example 8 has a surface hardness greater than the upper limit, and Comparative Example 9 has an Al concentration C of the base material 11 less than the lower limit. Thus, Examples 1 to 7, which satisfy the area ratio A, coefficient of variation B, and surface hardness of this embodiment and have Al as the main component of the base material 11, all exhibit improved seizure resistance.

[0029] Examples 8 and Comparative Example 10, shown in Figure 11, use WS2 as the solid lubricant 16. Example 8 shows improved seizure resistance compared to Comparative Example 10, where the coefficient of variation B is smaller than the lower limit. Similarly, Examples 9 and Comparative Example 11, shown in Figure 12, use CF as the solid lubricant 16. Example 8 also shows improved seizure resistance compared to Comparative Example 11, where the coefficient of variation B is smaller than the lower limit. Thus, even when using different solid lubricants 16, Examples 8 to 9, which satisfy the area ratio A, coefficient of variation B, and surface hardness of this embodiment and whose base material 11 is mainly composed of Al, all show improved seizure resistance compared to the comparative examples.

[0030] Examples 10 to 12 shown in Figure 13 examine in detail the effect of the back surface temperature of the bearing 40 using the sliding member 10 of this embodiment. In this embodiment, heat generation is evaluated by the temperature difference dT between the peak temperature Tp and the immediate preceding temperature Tb.

[0031] When the solid lubricant 16 is smoothly transferred from the sliding member 10 to the mating material 13 through sliding between the sliding member 10 and the mating material 13, the average temperature difference Ta, that is, the average value of the difference between the peak temperature Tp and the immediate temperature Tb, becomes smaller. This is because the transfer of the solid lubricant 16 reduces the friction between the sliding member 10 and the mating material 13 from the beginning of sliding and maintains a stable reduction over a long period of time. In other words, the transfer of the solid lubricant 16 reduces heat generation due to friction and improves seizure resistance, even when sudden load fluctuations are applied from the beginning of sliding over a long period of time.

[0032] Comparing Example 10 with Examples 11 and 12, Examples 11 and 12 have a smaller average temperature difference Ta compared to Example 10. Examples 11 and 12, with their smaller average temperature difference Ta, have a larger average elemental concentration Cx in the observation area 21 compared to Example 10. The average elemental concentration Cx is the average value of the concentrations of the constituent elements of the solid lubricant 16 present in the lubricating surface layer 14 within the observation area 21. In other words, the average elemental concentration Cx is a value indicating the extent to which constituent elements are present in the observation area 21 set in the lubricating surface layer 14. Specifically, the 30 μm × 30 μm observation area 21 is divided into p pixels. For each divided pixel, the concentration of a constituent element, such as Mo, W, or F, is measured. The measured concentrations of constituent elements for each pixel are then accumulated. The accumulated concentrations of constituent elements are divided by the number of pixels p in the observation area 21. This allows for the calculation of the average elemental concentration Cx in the observation area 21. In other words, the average elemental concentration Cx is calculated as Cx = (sum of concentrations of constituent elements per pixel / number of pixels in the observation area). In this case, it is preferable that the distance between each pixel is 1 μm or less, and that the number of pixels p is 900 or more. In this embodiment, the number of pixels p in the observation area 21 was set to p = 200 × 200 = 40000.

[0033] In this embodiment, the elemental average concentration Cx is set to 2.0 mass% ≤ Cx ≤ 12 mass%. This indicates that when the elemental average concentration Cx is 2.0 mass% or higher, the solid lubricant 16 is abundant in the thickness direction in the lubricating surface layer 14. Therefore, even if the solid lubricant 16 is repeatedly transferred from the sliding member 10 to the mating material 13 due to sliding, the solid lubricant 16 is supplied from the sliding member 10 to the mating material 13 over a long period of time. As a result, the heat generated during sliding between the sliding member 10 and the mating material 13 is reduced from the initial stage of sliding to the long term. However, if the elemental average concentration Cx is excessive, the manufacturing of the sliding member 10 will be hindered. For this reason, the upper limit of the elemental average concentration Cx is set to 12 mass%.

[0034] 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]

[0035] In the drawing, 10 is the sliding member, 11 is the base material, 14 is the lubricating surface layer, 16 is the solid lubricant, 17 is the base material surface, and 21 is the observation area.

Claims

1. A substrate whose main component is Al and whose surface hardness is HV110 or less, The substrate is provided on the side that slides against the mating material and comprises a lubricating surface layer containing a solid lubricant, The Al concentration C of the aforementioned substrate is 70% by mass or more. The aforementioned lubricating surface layer is The mating material side has a sliding surface, A sliding member in which the base material surface, which is the surface of the base material, and the solid lubricant are exposed on the sliding surface, In the aforementioned sliding surface, the area S of a 30 μm × 30 μm area is S = 900 μm ２ Set an arbitrary observation area, In the observation area, let Sp be the area occupied by the exposed solid lubricant, and the area ratio A (%) be defined as area ratio A = Sp / S × 100. When the observation area is divided into nine 10 μm × 10 μm unit areas, and the standard deviation in the observation area is determined from the ratio of the area occupied by the solid lubricant in each of the nine unit areas, and the coefficient of variation B is set to B = D / A, 10 ≤ A ≤ 40 0.1 ≤ B ≤ 0.3 That is, Sliding member.

2. The aforementioned area ratio A is, 10 ≤ A ≤ 30 That is, The sliding member according to claim 1.

3. The solid lubricant is a sulfide. The sliding member according to claim 1.

4. The solid lubricant is MoS ２ or WS ２ That is, The sliding member according to claim 3.

5. In the observation region, the average concentration Cx of the constituent element with the largest atomic weight among the elements constituting the solid lubricant present in the lubricating surface layer is: 2.0 mass% ≤ Cx ≤ 12 mass% The sliding member according to claim 1.

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