Sliding element

Abstract

Sliding element (1) comprising a steel back sheet (10) as the outermost layer, a sintered lining (11) consisting of Cu, Bi and Sn, and an electroplated cover layer (12) as the sliding surface, which consists of Bi and Sb, wherein the Sb concentration in the cover layer (12) increases with height from the surface of the cover layer (12) such that the Sb concentration is at its maximum at the interface (X) on the lining (11), wherein the increase in the Sb concentration in a first region, where the distance from the interface (X) to the lining (11) is 4 µm or less, at a first height from the surface of the cover layer (12) is greater than the increase in the Sb concentration in a second region at a height from the surface of the cover layer (12) that is less than the first height.

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a sliding element with a cover layer made of a plating film of a Bi and Sb alloy. Description of the state of the art

[0002] A sliding element with a top layer containing a bi-coating and an silver interlayer is known (see JP2006-266445 A). In JP2006-266445 A, the size of the silver crystal grains in the interlayer is adjusted to improve the layer adhesion of the top layer. Similarly, the size of the bi-crystal grains in the coating is adjusted to improve the adhesion and fatigue resistance of the top layer.

[0003] However, even if layer adhesion is improved by adjusting the crystal grain size as in JP2006-266445 A, the problem remains that layer delamination is unavoidable in the case of a two-layer surface layer structure. Furthermore, sudden changes in the surface properties during wear are unavoidable if the surface layer has a two-layer structure. SUMMARY OF THE INVENTION

[0004] The present invention was developed in view of these problems, and the object of the present invention is to provide a sliding element with a top layer that prevents the layers from separating while achieving favorable fatigue resistance.

[0005] To fulfill the task, the sliding element comprises a cover layer formed with a plating film made of a Bi and Sb alloy, wherein the Sb concentration in the cover layer increases with height from the surface of the cover layer.

[0006] In the aforementioned configuration, the top layer contains not only Bi, which is soft, but also Sb, which is hard, and the hard Sb improves fatigue resistance. Because the Sb concentration increases with height above the surface, favorable uniformity is achieved during the initial wear period, and high wear resistance is achieved in the advanced wear stage. Because the Sb concentration increases with height above the surface, layer separation is prevented.

[0007] The concentration gradient of Sb in a first region at a first height above the surface of the cover layer can be higher than the concentration gradient of Sb in a second region at a height above the surface of the cover layer that is lower than the first height. With such a configuration, the hardness of the cover layer can increase abruptly with progressive wear.

[0008] It has been confirmed that both uniformity and fatigue resistance were achieved when the average concentration of Sb in the surface layer was adjusted to between 1.3 wt% and 3.0 wt%. The term "average concentration of Sb in the surface layer" refers to the average concentration of Sb over the entire height from the surface of the surface layer. List of characters Fig.Figure 1 is a perspective view of the sliding element according to the embodiments of the present invention; Fig. 2 is a diagram of Sb concentrations in cover layers; Fig. 3 is a photo of the cross-section of a top layer; Fig. Figure 4 is an explanatory view of a fatigue test; and Fig. Figure 5 is a diagram showing the relationship between the Sb concentration and the proportion of the fatigue zone. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0009] Some embodiments of the present invention are described in the following order. (1) First embodiment: (1-1) Configuration of the sliding element: (1-2) Method for manufacturing the sliding element: (2) Other embodiments: First embodiment: Configuration of the sliding element:

[0010] Fig.Figure 1 is a perspective view of a sliding element according to an embodiment of the present invention. The sliding element 1 has a rear panel 10 , a lining 11 and a top layer 12 on. The sliding element 1 is a semi-expanding metal element, formed by splitting a hollow tube in the radial direction and with a semi-circular cross-section. A sliding bearing. A is achieved by inserting two sliding elements 1 formed into a tubular shape. The plain bearing A It carries a cylindrical countershaft in a hollow area inside. 2 (Engine crankshaft). The outer diameter of the countershaft 2 is slightly smaller than the inner diameter of the plain bearing A Lubricating oil (engine oil) is provided in a slot located between the outer circumferential surface of the countershaft. 2 and the inner circumferential surface of the sliding bearing Ais designed. The outer circumferential surface of the counter shaft slides with the lubricating oil thus provided. 2 on the inner circumferential surface of the sliding bearing A .

[0011] The sliding element 1 is achieved by laminating the back panel 10 , the lining 11 and the top layer 12 , manufactured in this order towards the center of curvature. Accordingly, the back panel sheet forms 10 the outermost layer of the sliding body 1 , and the sliding layer 12 forms the innermost layer of the sliding element 1 The rear panel 10 , the lining 11 and the top layer 12 They each have a uniform thickness in the circumferential direction. The thickness of the back panel sheet. 10 The lining thickness is 1.8 mm. 11 is 0.2 mm, and the thickness of the top layer 12is 20 µm. This is twice the radius of the surface of the top layer. 12 on the side of the center of curvature (inner diameter of the sliding element) 1 ) is 55 mm. The width of the plain bearing A is 19 mm. In the following, the term "inside" refers to the side of the center of curvature of the sliding element. 1 , and the term "outside" refers to the side opposite the center of curvature of the sliding element. 1 The inside of the top layer 12 forms the sliding surface of the counter shaft 2 .

[0012] The rear panel 10 It consists of steel containing 0.15 wt% C, 0.06 wt% Mn, and the remainder Fe. The back panel sheet 10 It doesn't need to be made of steel, as long as the back panel is 10 consists of a material that transfers the load from the counter shaft 2 through the lining 11 and the top layer 12 can wear.

[0013] The lining 11 is a layer applied to the inside of the rear panel 10 is laminated and represents the base layer according to the invention. The lining 11 Contains 10 wt% Sn, 8 wt% Bi, and the remainder is Cu and unavoidable impurities. Examples of unavoidable impurities in the lining. 11 These include Mg, Ti, B, Pb, and Cr, which are introduced during refining or scrapping. The content of unavoidable impurities in the lining. 11 The total mass percentage is 0.5% or less.

[0014] The top layer 12 is a feature on the inner surface of the lining 11 laminated layer. The top layer 12 is a plating film made of a bi- and sb alloy. The top layer 12 Contains Bi, Sb, and unavoidable impurities. The content of unavoidable impurities in the surface layer 12The total mass percentage is 0.5% or less. [Table 1] Distance from interface (µm) First area Second area average concentration overall First area / Second area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Sb concentration of example A Concentration (mass %) 13,12 9,30 4,19 2,39 2,53 2,14 2,56 1,99 2,31 2,18 1,94 2,67 1,98 2,18 2,12 2,14 1,76 2,05 2,36 1,73 3,05 - Increase (mass % / µm) 3,82 5,11 1,80 0,14 0,39 0,42 0,57 0,32 0,13 0,24 0,73 0,69 0,20 0,06 0,02 0,38 0,29 0,31 0,63 - - - average increase (mass % / µm) 2,72 0,36 - 7,6 Standard deviation (mass %) 4,89 0,27 - 18,1 Sb concentration of example B Concentration (mass %) 4,37 2,78 1,57 1,66 0,90 1,42 0,96 0,83 0,94 1,07 1,11 1,11 1,05 1,26 0,53 0,63 0,95 0,55 - - 1,31 - Increase (mass % / µm) 1,59 1,21 0,09 0,76 0,52 0,46 0,13 0,11 0,13 0,04 0,00 0,06 0,21 0,73 0,10 0,32 0,40 - - - - - average increase (mass % / µm) 0,91 0,25 - - - 3,7 Standard deviation (mass %) 1,31 0,40 - - - 3,2 Sb concentration of example C Concentration (mass %) 1,83 0,92 1,34 1,62 0,38 1,22 1,71 1,78 2,28 2,44 2,26 2,72 1,42 1,69 2,90 1,88 2,39 3,26 - - 1,89 - Increase (mass % / µm) 0,91 0,42 0,28 1,24 0,84 0,49 0,07 0,50 0,16 0,18 0,46 1,30 0,27 1,21 1,02 0,51 0,87 - - - - - average increase (mass % / µm) 0,71 0,61 - - - 1,2 Standard deviation (mass %) 0,39 0,98 - - - 0,4 Table 1 lists the concentrations (mass concentrations) of Sb in the surface layer 12 on. Fig. Figure 2 is a diagram and shows concentrations (mass concentrations) of Sb in the top layer. 12 In Fig. 2 gives the horizontal axis the distance from the interface to the lining. 11 The vertical axis indicates the Sb concentration. Table 1 and Fig. Figure 2 shows the concentrations (triangles) of Sb in example A, which approach each other at about 2 mass-%, the concentrations (circles) of Sb in example B, which approach each other at about 1 mass-%, and the concentrations (quadrilaterals) of example C, which shows no increase in concentration. As in Fig. As shown in Figure 2, in examples A and B the Sb concentration is at its maximum at the interface on the lining. 11The Sb concentration decreases continuously in examples A and B, while the distance from the interface to the lining increases. 11 rises (where the height is measured from the surface of the top layer). 12 decreases). The average concentration of Sb in the surface layer 12 The total was 3.05% by mass.

[0015] In examples A and B, when the distance from the interface to the lining 11 As the temperature rises, the increase in Sb concentration (absolute value) decreases, and the Sb concentration approaches a nearly constant level in the range where the distance from the interface to the lining increases. 11 at least 4 µm. In examples A and B, the rise and standard deviation of the Sb concentration in a first region (region where the distance from an interface is X to the lining 11 4 µm or less) where the height is measured from the surface of the top layer 12a first height is greater than the rise and standard deviation of the Sb concentration in a second area (area where the distance from the interface X to the lining 11 greater than 4 µm), where the height from the surface of the top layer is greater than the first height.

[0016] In Example A, the increase in Sb concentration in the first area was 7.6 times the increase in Sb concentration in the second area. In Example A, the standard deviation of the Sb concentration in the first area was 18.1 times the standard deviation of the Sb concentration in the second area. In Example B, the increase in Sb concentration in the first area was 3.7 times the increase in Sb concentration in the second area. In Example B, the standard deviation of the Sb concentration in the first area was 3.2 times the standard deviation of the Sb concentration in the second area.

[0017] The top layer12 The present embodiment was formed using a manufacturing process similar to that in Example A, and the Sb concentration in the surface of the cover layer 12 With a thickness of 20 µm, the Sb concentration was 1.8% by mass. Accordingly, it can be stated that in the present embodiment, an increase in Sb concentration similar to that in Example A occurred. Fig. 2 is present. The Sb concentration in the top layer 12 is achieved by varying the Sb concentration in the electroplating bath of the top layer 12 Adjustable, as described below.

[0018] Fig. Figure 3 is a photo of the cross-section of the top layer 12 The cross-sectional photo of the Fig. Figure 3 shows the completed image, so that areas with higher Sb concentrations appear darker. As in Fig. As shown in Figure 3, the Sb concentration decreases continuously as the height decreases from the surface of the top layer. 12decreases. That is, the Sb concentration increases continuously as the height decreases from the surface of the top layer. 12 increases. Because the remainder, apart from Sb, can be assumed to be Bi, the Bi concentration decreases continuously as the height from the surface of the cover layer increases. 12 increases. This means that the bi concentration rises continuously as the height increases from the surface of the top layer. 12 decreases. Fig. Figure 3 is a photo of the cross-section of the top layer 12 with a thickness of approximately 10 µm.

[0019] The Sb concentration in the top layer 12 was measured by energy-dispersive X-ray spectroscopy using an electron beam microanalyser (JMS-6610A, manufactured by JEOL). In particular, a multitude of rectangular regions E at a distance from the interface X between the cover layer were measured. 12 and the lining 11Rectangular areas E were formed at 1 µm intervals from the top edge (edge ​​of the surface), and the average mass concentration of Sb in each rectangular area E was measured as the Sb mass concentration at the respective distance. A total area EA consisting of all rectangular areas E was formed, and the average mass concentration of Sb in the total area EA was measured as the average total Sb concentration in the top layer.

[0020] If a long-term test sample (connecting rod R) with a cover layer 12 similar to the sliding element described above 1 After manufacturing and measuring the proportion of the fatigue zone in the endurance test specimen, a fatigue zone proportion of 30% was found, which is favorable. The fatigue zone proportion was measured as follows. Fig. Figure 4 is an explanatory view of the fatigue test. As in Fig.As shown in 4, the connecting rod R designed with cylindrical through holes at both ends in the longitudinal direction, and a test shaft H (hatched) was held at one end through the through hole.

[0021] A top layer 12 (black) was applied in the same way as the sliding element. 1 in the inner circumferential surface of the through hole of the connecting rod R , which the test wave H holds, trained. The test wave H was outside the connecting rod R on both sides in the axial direction of the test shaft H held, which rotated at a sliding speed of 6.6 m / s. The term sliding speed is the relative speed between the surface of the cover layer. 12 and the test wave H The end of the connecting rod R on the side opposite the test shaft H was with a movable body Fconnected, which extends in the longitudinal direction of the connecting rod R moved back and forth, and the oscillating load of the movable body F It was set to 80 MPa. Engine oil at approximately 140°C was circulated between the connecting rod. R and fed to the test shaft H.

[0022] This condition was maintained for 50 hours as a continuous test on the top layer. 12 After the endurance test, the inner surface (sliding surface) of the top layer was 12 The photograph was taken from a position on a line perpendicular to the surface, with the line serving as the principal optical axis, and the photographed image was used as the evaluation image. The evaluation image showed damaged areas of the surface of the top layer. 12The images were viewed using a binocular microscope (magnifying glass), and the damaged surface area, i.e., the surface area of ​​the damaged areas, was calculated. Specifically, the damaged surface area was defined as the entire surface area of ​​the top layer appearing in the evaluation image. 12 The area was divided, and the result, the proportion of the fatigue zone, was determined, expressed as a percentage.

[0023] Since in the top layer 12In the embodiment described above, where both hard Sb and soft Bi are used, the fatigue resistance is improved by the hard Sb. Because the Sb concentration increases with height above the surface, favorable uniformity is achieved in the initial wear period, and high wear resistance is achieved in the advanced wear stage. Since the Sb concentration increases with height above the surface, layer separation can be prevented. Cu has the property of dispersing more readily in Sb than Bi. However, adjusting the average overall concentration of Sb in the surface layer is possible. 12 of less than 3.1% by mass the amount of Cu that is removed from the lining 11 into the top layer 12 dispersed into it, suppressing and preventing the phenomenon that the otherwise dispersed Cu would lower the fatigue resistance.

[0024] The increase in Sb concentration in the first area (area where the distance from the interface X to the lining 11 4 µm or less), where the height is measured from the surface of the top layer 12 The first height is greater than the increase in Sb concentration in the second area (area where the distance from the interface X to the lining 11 (greater greater than 4 µm), where the height from the surface of the top layer is greater than the first height. Such a configuration rapidly increases the hardness of the top layer. 12 with increasing wear and tear. Method for manufacturing the sliding element:

[0025] A flat plate made of low-carbon steel with the same thickness as the back panel sheet. 10 was prepared.

[0026] Powder from the material that forms the lining 11The resulting mixture was distributed on the flat plate made of low-carbon steel. Specifically, copper powder, bi-powder, and tin powder were distributed on the flat plate made of low-carbon steel, such that the mass ratio of the components in the lining described above was achieved. 11 was obtained. Alloy powder of Cu-Bi, Cu-Sn or the like can be spread on the flat plate of low-carbon steel, as long as the mass ratio of each component in the lining is correct. 11 The particle size of the powder was adjusted to a maximum of 150 µm using a test sieve (JIS Z8801).

[0027] Then the flat plate made of low-carbon steel and the powder distributed on it were sintered. The sintering temperature was regulated to between 700°C and 1000°C, and the sintering was carried out in an inert atmosphere. After sintering, the result was cooled. The lining 11It does not have to be formed by sintering and can be formed, for example, by casting.

[0028] After cooling, a copper alloy layer formed on the flat plate of low-carbon steel. The copper alloy layer contained soft bi-particles that precipitated during cooling.

[0029] The low-carbon steel, coated with a copper alloy layer, was then pressed into a mold formed by uniformly splitting a hollow tube radially into two parts. The pressing was carried out such that the outer diameter of the low-carbon steel matched the outer diameter of the sliding element. 1 corresponded.

[0030] Then the surface of the rear panel was 10 The formed copper alloy layer was trimmed. The extent of the cutting was controlled so that the thickness of the layer on the back panel was reduced. 10formed copper alloy layer with the thickness of the lining 11 was identical. This made the lining 11 formed after cutting from the copper alloy layer. The cutting was carried out, for example, using a lathe with a cutting tool made of sintered diamond. The surface of the lining 11 After cutting, the interface of the lining formed 11 to the top layer 12 .

[0031] Then the top layer was applied 12 by laminating bismuth onto the surface of the lining 11 The coating was formed by electroplating to a thickness of up to 10 µm. The electroplating process was as follows: First, the surface of the lining was 11 It was rinsed with water. Furthermore, the surface of the lining was cleaned. 11 washed with acid to remove unwanted oxides from the surface of the lining 11to remove. Then the surface of the lining was 11 Rinsed again with water.

[0032] After completion of the aforementioned pretreatment, an electric current was applied to the lining. 11 A sample was set up and immersed in an electroplating bath for electroplating. The electroplating bath consisted of 150 g / L methanesulfonic acid, 20 g / L dimethanesulfonic acid, and 25 g / L organic surfactant. 0.18 g / L of pure Sb was dissolved in the electroplating bath by electrolysis. The temperature of the electroplating bath was set to 30°C. A direct current with a current density of 2.0 A / dm² was applied. 2 was attached to the lining 11 created.

[0033] In the electroplating bath, the methanesulfonic acid can be adjusted to 50 to 250 g / L, the dimethanesulfonic acid to 5 to 40 g / L, the Sb to 0.1 to 3 g / L, and the organic surfactant to 0.5 to 50 g / L. The temperature of the electroplating bath can be adjusted to 20°C to 50°C, and the current density applied to the lining can be adjusted. 11 The applied current can range from 0.5 to 7.5 A / dm² 2 The Sb concentration in the top layer will be adjusted. 12 can be increased by increasing the Sb ion concentration in the electroplating bath.

[0034] For example, by adjusting the Sb concentration in the electroplating bath to 0.2 g / L, Sb concentrations (triangles) were obtained that were approximately 2 wt% in Fig. There were 2. By adjusting the Sb concentration in the electroplating bath to 0.1 g / L, Sb concentrations (circles) were obtained that approximate 1 wt% in Fig.There were 2. It was understood that the increases in Sb concentration were achieved by using methanesulfonic acid in the electroplating bath. When the top layer 12 A top layer was formed in an electroplating bath using ethylenediaminetetraacetic acid (EDTA) instead of methanesulfonic acid. 12 formed without an increase in concentration, as in example C. Fig. 2.

[0035] Therefore, electroplating was carried out, followed by rinsing and drying. This completed the process for the sliding element. 1 Completed. By mounting two sliding elements. 1 The plain bearing A was formed inside a pipe, and then the plain bearing A was attached to a motor. Other versions:

[0036] Table 2 lists the results from measuring the proportion of the fatigue zone of a variety of examples 1 to 8, where the thickness of the cover layer 12and the Sb concentration on the surface was different. The first embodiment corresponds to Example 7. Fig. Figure 5 is a diagram showing the proportions of the fatigue zones in examples 1 to 8. Fig. 5 The vertical axis represents the proportion of the fatigue zone, and the horizontal axis represents the Sb concentration in the surface. [Table 2] Sample No. Top layer thickness (µm) Sb concentration (mass %) in surface area Percentage of the fatigue zone (%) 1 11 0 9,9 2 11 1,7 0,2 3 11 2,6 0,8 4 14 0 31,5 5 14 1,8 2,4 6 20 0 41,1 7 (first embodiment) 20 1,8 29,6 8 20 2,4 21,8

[0037] The greater the thickness of the top layer 12 The larger the area of ​​fatigue, the greater the proportion of the area affected by fatigue. This result likely arose because the internal stresses on the surface layer... 12 increase when the thickness of the top layer 12 increases, regardless of the Sb concentration. However, it has been confirmed that the use of Sb in the top layer 12 successfully reduced the proportion of the fatigue zone in all thicknesses. Accordingly, the sliding element can 1They can also be formed with favorable fatigue resistance even if the thickness of the top layer is 12 as in the first embodiment, 20 µm.

[0038] When comparing the proportion of the fatigue zone with identical thicknesses, the proportion of the fatigue zone with a higher Sb concentration in the surface can be suppressed. The proportion of the fatigue zone can be suppressed by adjusting the Sb concentration in the surface to 1.0% to 3.0% by mass (ideally 1.7% to 2.6% by mass).

[0039] In the first embodiment, the sliding element was used as an example. 1 explains which is the plain bearing A for bearing the crankshaft of an engine, however, the sliding element according to the invention can 1 for forming the plain bearing Acan be used for other purposes. For example, a gearbox bushing or a radial bearing, such as a piston bushing or piston eye, can be fitted with the sliding element according to the invention. 1 to be formed. The sliding element according to the invention can also be an axial bearing, any type of ring disc or a swashplate for a motor vehicle air compressor. The lining matrix 11 is not limited to a copper alloy and can be made from matrix materials according to the hardness of the counter shaft 2 be selected. The back panel 10 is not essential and can be omitted. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2006266445 A [0002, 0003]

Claims

[1] Sliding element with a cover layer formed with a plating film of a Bi and Sb alloy, wherein the Sb concentration in the cover layer increases with height from the surface of the cover layer. [2] Sliding element according to claim 1, wherein the increase in Sb concentration in a first area at a first height from the surface of the cover layer is greater than the increase in Sb concentration in a second area at a height from the surface of the cover layer which is less than the first height.