Sliding member and method for manufacturing same

Abstract

A sliding member 1 is made of a metal material as a base material, has a sliding surface 10, and has, in the sliding surface 10, a diffusion penetration layer 11 containing at least one of a carbide or a boride. In a plan view, the sliding surface 10 has: a plurality of furrow parts 3 extending in a prescribed direction; a plurality of raised bed parts 2 positioned between two adjacent furrow parts 3 of the plurality of furrow parts 3; and a plurality of protrusion parts 4 that are arranged along the two edges of each of the plurality of furrow parts 3 and that are each positioned between a corresponding one of the furrow parts 3 and an adjacent one of the raised bed parts 2. In a cross-sectional view, the furrow parts 3 are each more recessed than the raised bed parts 2 adjacent thereto on both sides, and each of the plurality of protrusion parts 4 protrudes more than the raised bed parts 2 adjacent thereto on both sides.

Description

Sliding member and method for manufacturing the same

[0001] The present invention relates to a sliding member that slides against other components or materials, and to a method for manufacturing the same.

[0002] Currently, sliding members are widely used in various mechanical structures. For example, Patent Document 1 discloses a sliding mechanism comprising a sliding member housing having a pair of sliding surfaces, and a sliding member slidably positioned between the pair of sliding surfaces via a lubricant. Furthermore, at least one of the pair of sliding surfaces of the sliding member housing has a groove extending in a direction intersecting the sliding direction of the sliding member.

[0003] The groove portion of the sliding mechanism described in Patent Document 1 has the effect of suppressing solid contact and adhesive wear between the sliding member and the sliding member housing portion by collecting wear particles generated during the sliding process in the concave groove, thereby suppressing the jamming of wear particles, and by retaining lubricating oil.

[0004] Japanese Patent Publication No. 2023-165044

[0005] However, the sliding mechanism described in Patent Document 1 does not have an abrasion-resistant coating or the like on the sliding surface, and therefore the abrasion resistance of the sliding surface is low. As a result, when used in an environment where high pressure is applied to the sliding surface, that is, an environment where the sliding materials are in strong contact with each other, or when used in a so-called dry environment without lubricant, the abrasion resistance of the sliding surface is insufficient, causing the groove to disappear prematurely, and making it difficult to maintain the effect of suppressing the jamming of wear particles and the suppression of adhesive wear for a long period of time. The present invention has been made in view of these problems, and aims to provide a sliding member and a method for manufacturing the same that have excellent abrasion resistance and adhesion resistance even under harsh conditions.

[0006] The sliding member of the present invention is a sliding member having a sliding surface and a metal material as the base material, wherein the sliding surface is provided with a diffusion permeation layer containing at least one of carbide or boride, and the sliding surface further comprises, in plan view, a plurality of grooves extending in a predetermined direction, a plurality of ridges located between two adjacent grooves, and a plurality of protrusions located along both edges of each groove and between each groove and its adjacent ridge, and in cross-sectional view, each groove is recessed compared to the ridges on either side of it, and each of the multiple protrusions protrudes compared to the ridges on either side of it.

[0007] The diffusion permeation layer preferably contains at least one of vanadium carbide and chromium carbide as the carbide.

[0008] The thickness of the diffusion permeation layer is preferably 5 to 200 μm.

[0009] The average height of the multiple protrusions is preferably 1 to 7 μm.

[0010] The ratio of the average width of the multiple furrows to the average width of the multiple ridges is preferably 1.0 or less.

[0011] The present invention also provides a method for manufacturing a sliding member, the manufacturing method comprising: (a) irradiating a metal substrate with a laser beam to form, in plan view, a plurality of grooves extending in a predetermined direction, a plurality of ridges located between two adjacent grooves, and a plurality of protrusions along both edges of each groove and between each groove and its adjacent ridge; and (b) forming a diffusion penetration layer containing carbide or boride on the surface of the substrate on which step (a) has been performed, wherein in cross-sectional view, the grooves are recessed compared to the ridges, and the protrusions protrude compared to the ridges.

[0012] The present invention provides a sliding member having excellent wear resistance and adhesion resistance, and a method for manufacturing the same.

[0013] Figure 1 is a perspective view showing the structure of the sliding surface of the sliding member. Figure 2 is a cross-sectional view showing the structure of the sliding surface and its vicinity of the sliding member. Figure 3 is a diagram illustrating the manufacturing method of the sliding member. Figure 4 shows the results of the ball-on-disk test for Examples 1 to 8. Figure 5 shows the results of the ball-on-disk test for Comparative Examples 1 and 2.

[0014] <Sliding Member> An embodiment of the sliding member of the present invention will be described below. The present invention is not limited to the following embodiment.

[0015] Figure 1 is a perspective view showing the structure of the sliding surface 10 of the sliding member 1 according to this embodiment, and Figure 2 is a cross-sectional view showing the structure of the sliding surface 10 and its vicinity of the sliding member 1. In the figures, the x-axis, y-axis, and z-axis are perpendicular to each other.

[0016] The sliding member 1 according to this embodiment has a sliding surface 10 that is positioned to face the mating material.

[0017] Furthermore, the sliding surface 10, in plan view, has a plurality of grooves 3 extending in a predetermined direction (shown as the z-axis direction in Figures 1 and 2), a plurality of ridges 2 located between two adjacent grooves 3, and a plurality of projections 4 located along both edges of each groove 3 and between each groove 3 and its adjacent ridge 2. In cross-sectional view, each groove 3 is recessed compared to the ridges 2 on either side of it, and each projection 4 of the plurality of projections 4 protrudes compared to the ridges 2 on either side of it. That is, in cross-sectional view, the sliding member 1 according to this embodiment has the grooves 3 recessed below the reference plane A (towards the inside of the base material) and the projections 4 protruding above the reference plane A (towards the mating material). Furthermore, the sliding surface 10 has a surface shape in which ridges 2, protrusions 4, grooves 3, and protrusions 4 are repeatedly arranged in this order in the x-axis direction. It is also preferable that the predetermined direction (z-axis direction) in which the protrusions 4, grooves 3, etc. extend intersects with the sliding direction with respect to the mating material.

[0018] When the sliding member 1 is in use, only the projection 4 that protrudes beyond the ridge 2 contacts and slides against the mating material, thus keeping the contact area with the mating material low and suppressing adhesion. Furthermore, since the ridge 2 and groove 3, which are lower than the projection 4, are provided on both sides of the projection 4, foreign matter such as adhesive and wear particles generated during sliding between the projection 4 and the mating material can be collected by both the ridge 2 and groove 3. As a result, abrasive wear, which is likely to occur when foreign matter gets caught between the sliding surface 10 and the mating material, can also be suppressed.

[0019] Furthermore, because the sliding surface 10 has three levels of height due to the projection 4, the ridge 2 which is lower than the projection 4, and the groove 3 which is even lower than the ridge 2, even if the height of the projection 4 decreases due to wear, the ridge 2 which protrudes higher than the groove 3 will come into contact with the mating material, keeping the contact area small and maintaining the effect of suppressing adhesion, while the effect of collecting foreign matter by the groove 3 will also be maintained.

[0020] The average height H of the multiple protrusions 4 from the reference surface A is preferably 1 to 20 μm. An average height H of 1 μm or more allows each protrusion 4 to protrude from the reference surface A even if it is slightly worn, thus maintaining the effect of suppressing adhesion by reducing the contact area and collecting foreign matter using the ridges 2 and grooves 3. If the average height H is less than 1 μm, the mating material may come into contact with the ridges 2. Therefore, the contact area cannot be reduced, and the effect of reducing adhesion may not be sufficiently obtained. On the other hand, if the average height H is too large, wear of the protrusions 4 is more likely to occur. From the viewpoint of reducing wear of the protrusions 4 during sliding, an average height H of 7 μm or less is more preferable.

[0021] Furthermore, the average depth D of the multiple grooves 3 from the reference surface A is preferably 5 to 20 μm. An average depth D of 5 μm or more allows a large amount of foreign matter to be collected in the grooves 3. An average depth D of 20 μm or less makes it easier to remove the foreign matter collected in the grooves 3.

[0022] Furthermore, the ratio (G / R) of the average width G of the multiple grooves 3 to the average width R of the multiple ridges 2 is preferably 1.0 or less, and more preferably 0.5 or less. A larger average width R of the multiple ridges 2 means that the spacing between the protrusions 4 located on both edges of each ridge 2 is wider. In other words, the number of protrusions 4 per unit area decreases, and the contact area of ​​the protrusions 4 with the mating material decreases, thus further suppressing adhesion. The lower limit of the ratio G / R is not limited to a specific numerical value, but it is preferably 0.1 or more. The average width R of the multiple ridges 2 is, for example, 200 to 400 μm. The average width G of the multiple grooves 3 is, for example, 80 to 120 μm.

[0023] Each of the above average values ​​is the average of any two measured values.

[0024] Furthermore, for the sake of clarity in the drawings, the contours of the sliding surface 10 in cross-section, that is, the shapes of the ridges 2, grooves 3, and protrusions 4, are depicted as simple straight lines. However, the actual object has a complex shape that includes irregularities and undulations. The reference surface A in this invention can be derived from the undulation curve when the sliding surface 10 is viewed in cross-section.

[0025] The above waviness curve is obtained, for example, based on JIS B 0601 (2013) using the following method. First, a surface roughness measuring device is used to obtain a measured cross-sectional curve that spans multiple ridges 2, multiple grooves 3, and multiple protrusions 4. Next, a contour curve filter is applied to the measured cross-sectional curve with a cutoff value λs = 8 μm to obtain a cross-sectional curve. At this time, at least one end of the measured cross-sectional curve is positioned on the ridges 2. Then, a contour curve filter is applied to the measured cross-sectional curve with a cutoff value λc: 2.5 mm and λf: no upper limit to obtain a waviness curve. Finally, by superimposing the obtained cross-sectional curve and the waviness curve so that the ends located on the ridges 2 coincide, the waviness curve can be considered as the position of the reference plane.

[0026] Furthermore, a roughness curve can also be obtained from the measured cross-sectional curve by applying appropriate cutoff values ​​λs and λc. The values ​​of the cutoff values ​​λs, λc, and λf should be set appropriately based on JIS B 0633 (2013) and JIS B 0651 (2013).

[0027] The height of the projection 4 is the shortest distance from the reference plane A to the highest point of the projection 4. The depth of the groove 3 is the shortest distance from the reference plane A to the deepest point of the groove 3. The width of the groove 3 is the shortest distance between the intersections of the projections 4 adjacent to the groove 3 and the reference plane A. The width of the ridge 2 is the shortest distance between the intersections of the projections 4 adjacent to the ridge 2 and the reference plane A.

[0028] Examples of mating materials (not shown) include metals and alloys that contain components that are prone to adhesion during sliding. The mating material may be, for example, a part within a device, or a workpiece being molded.

[0029] As shown in Figure 2, the sliding member 1 has a metal material as its base material and has a diffusion penetration layer 11 on the surface of the sliding surface 10 that contains at least one of carbides or borides.

[0030] The base material is a metallic material that forms the base of the sliding member 1, and is preferably an iron alloy (steel) or a cemented carbide. Examples of cemented carbides include materials obtained by mixing and sintering tungsten carbide and cobalt.

[0031] The diffusion-penetrating layer 11 is harder than the base material made of metal and has excellent wear resistance, so the surface shape of the sliding surface 10, such as the protrusions 4, can be maintained for a long period of time. In addition, the diffusion-penetrating layer 11 has better adhesion resistance than the base material made of metal.

[0032] As the carbide contained in the diffusion penetration layer 11, carbides containing at least one metal selected from the group consisting of titanium (Ti), chromium (Cr), manganese (Mn), tantalum (Ta), hafnium (Hf), vanadium (V), niobium (Nb), molybdenum (Mo), and tungsten (W) can be mentioned. Among them, it is preferable that the diffusion penetration layer 11 contains at least one of vanadium carbide and chromium carbide as the carbide. By the diffusion penetration layer 11 containing vanadium carbide or chromium carbide, a film particularly excellent in wear resistance and seizure resistance can be obtained. Further, as the boride contained in the diffusion penetration layer 11, borides containing at least one metal selected from the group consisting of iron (Fe), titanium (Ti), vanadium (V), niobium (Nb), molybdenum (Mo), and tungsten (W) can be mentioned.

[0033] The diffusion penetration layer 11 is preferably provided over the entire sliding surface 10. That is, it is preferable that the ridge portion 2, the groove portion 3, and the protrusion portion 4 are covered with the diffusion penetration layer 11.

[0034] Further, the thickness of the diffusion penetration layer 11 is preferably 5 to 200 μm. By the thickness being 5 μm or more, it becomes possible to maintain the shape of the sliding surface 10 for a long period. Although the upper limit of the thickness is not particularly limited, if it is about 200 μm or less, it can be easily formed by the salt bath method described later.

[0035] <Manufacturing method of the sliding member> Along with FIG. 3, an embodiment of the manufacturing method of the sliding member 1 will be described. The manufacturing method of this embodiment includes (a) a laser processing step (upper and middle in FIG. 3) and (b) a diffusion penetration layer forming step (lower in FIG. 3).

[0036] In the laser processing step described in (a) above, a laser beam is repeatedly irradiated onto the surface of the metal substrate 12 in a predetermined direction, thereby forming ridges 2, grooves 3, and protrusions 4 on the surface. Specifically, the areas irradiated with the laser beam become grooves 3 that are recessed in a cross-sectional view compared to the ridges 2, which are the unirradiated areas. Furthermore, the metal molten by the laser beam irradiation rises onto both edges of the grooves 3, and after cooling and solidification, forms protrusions 4 that protrude beyond the ridges 2 in a cross-sectional view. In other words, the grooves 3 and the protrusions 4 located on both edges of the grooves 3 can be formed simultaneously by laser beam irradiation. By repeatedly performing this laser beam irradiation, a surface shape is formed in which ridges 2, protrusions 4, grooves 3, and protrusions 4 are repeatedly arranged in this order, as shown in Figures 1 and 2, thereby forming the sliding surface 10.

[0037] In the subsequent step (b), a diffusion-penetrating layer 11 containing carbides or borides is formed on the surface of the metal substrate 12 that has undergone step (a). The diffusion-penetrating layer 11 is formed by a diffusion-penetrating treatment. The diffusion-penetrating treatment is a treatment method that forms a modified layer on the substrate surface by penetrating elements such as metal elements or metalloid elements from the substrate surface into the substrate, and reacting these elements with components inside the substrate to form compounds. Common diffusion-penetrating treatments include TRD treatment, calorizing treatment, chromizing treatment, boronizing treatment, carburizing treatment, and nitriding treatment. By forming a diffusion-penetrating layer 11 containing carbides or borides on the surface of the metal substrate 12 by such a diffusion-penetrating treatment, it is possible to form a wear-resistant film while maintaining the surface shape of the metal substrate 12 after laser processing. Known methods for forming the diffusion-penetrating layer 11 include the salt bath method, the powder pack method, and the coating method.

[0038] Here, the salt bath method is preferably used as step (b). In the salt bath method, anhydrous borax (Na) is heated to a molten state. ２ B ４ O ７A method of forming a metal carbide film on the surface of a substrate by immersing a carbon-containing substrate in a molten salt bath having [compound name] as the main component and then cooling it. As an example of the salt bath for forming the diffusion penetration layer 11 containing vanadium carbide (VC), a salt bath using vanadium pentoxide (V ２ O ５ ) as a vanadium compound for carbide formation and metallic aluminum (Al) as a reducing agent can be mentioned. In this salt bath, both vanadium pentoxide (V ２ O ５ ) and metallic aluminum (Al) exist in a molten state, and fine particles of metallic vanadium (V) are precipitated in the salt bath by the reduction reaction of metallic aluminum (Al) as represented by the following formula (1). 3V ２ O ５ + 10Al → 6V + 5Al ２ O ３ (1) When a carbon-containing substrate is immersed in the salt bath in which such a reaction proceeds, a part of the fine vanadium (V) particles generated by the above formula (1) and the carbon contained in the substrate preferentially bond to form a diffusion penetration layer 11 containing vanadium carbide (VC) on the surface of the substrate. The salt bath preferably contains anhydrous borax (Na ２ B ４ O ７ ) as the main component, 30% or less of boron carbide (B ４ C) or metallic aluminum (Al) as a reducing agent, and 30% or less of vanadium pentoxide (V ２ O ５ ). The temperature of the salt bath is preferably 800 to 1150°C.

[0039] Hereinafter, examples and comparative examples to which the present invention is applied will be described. These examples illustrate the present invention and do not limit the scope of the invention.

[0040] <Preparation of Test Specimens> [Examples 1-8] Multiple SKD11 flat plates with dimensions of 50 mm x 25 mm x 5 mm were prepared as substrates. By irradiating the surface of each flat plate with a laser beam under different irradiation conditions, test specimens having ridges, grooves, and protrusions of the dimensions shown in Table 1 were prepared. A pulsed laser was used as the laser, and the output (W) and power density (W / cm²) were set according to the desired shape. ２ Irradiation conditions such as spot diameter (mm) and feed rate (m / s) were adjusted as appropriate.

[0041]

[0042] The height of the protrusions, the width of the ridges, and the width of the grooves shown in Table 1 were measured using a digital microscope VHX-X1 (manufactured by Keyence Corporation).

[0043] Subsequently, a salt bath method was performed under the following conditions to form a 10 μm thick diffusion and permeation layer of vanadium carbide (VC) on the substrate surface. • Salt bath composition: Anhydrous borax (Na ２ B ４ O ７ ) 85%, metallic aluminum (Al) 10%, vanadium pentoxide (V ２ O ５ ) 5% • Salt bath temperature: 1000℃ • Immersion time: 16 hours

[0044] [Comparative Example 1] The same flat plate as in the example was prepared, but instead of processing by laser beam irradiation, Al ２ O ３ Test specimens with an arithmetic mean roughness (Ra) of 0.4 μm were prepared by blast treatment using abrasive material. The arithmetic mean roughness (Ra) was measured using a digital microscope VHX-X1 (manufactured by Keyence Corporation). Subsequently, a salt bath method was performed under the same conditions as in the example to form a 10 μm thick diffusion and penetration layer of vanadium carbide (VC) on the substrate surface.

[0045] [Comparative Example 2] A flat plate identical to that in the example was prepared and polished using SiC abrasive paper (#400) and diamond gel (6 μm) to create a test specimen with an arithmetic mean roughness (Ra) of 0.1 μm. Subsequently, a salt bath method was performed under the same conditions as in the example to form a 10 μm thick diffusion and penetration layer of vanadium carbide (VC) on the substrate surface.

[0046] <Evaluation> A ball-on-disc test was performed on each specimen under the following conditions: Apparatus: Tribogear Type 35 Load: 200g Rotation speed: 600rpm Rotation diameter: 20mm Time: 5 minutes Counter material: φ10mm (SUS304) ball

[0047] After the ball-on-disk test, EDS (energy-dispersive X-ray spectroscopy) analysis was performed on the surface of the test specimen to detect the presence of Fe elements on the specimen surface. The results of the Fe element mapping are shown in Figures 4 and 5. In Figures 4 and 5, the bright areas represent regions where Fe elements are present.

[0048] <Results> In Comparative Examples 1 and 2 in Figure 5, Fe is attached to the entire area in contact with the mating material, the sphere. In contrast, in Examples 1 to 8 in Figure 4, the area where Fe is attached is limited compared to Comparative Examples 1 and 2, and it can be seen that the amount of Fe attached is less than in Comparative Examples 1 and 2. From these results, it was found that Examples 1 to 8 have superior adhesion resistance compared to Comparative Examples 1 and 2. One possible reason for this difference is that the contact area with the mating material in the Examples is smaller than the contact area with the mating material in the Comparative Examples. Furthermore, in Examples 1 to 8, almost no Fe was detected at the tip of the projection 4, and Fe was detected mostly near the boundary between the projection 4 and the ridge 2, and near the boundary between the projection 4 and the groove 3. In other words, no foreign matter is attached to the tip of the projection 4, which is the contact surface with the mating material, and it was found that abrasive wear caused by foreign matter getting caught between the projection 4 and the mating material can be suppressed.

[0049] Furthermore, among the examples, the Fe adhesion area was smaller in Examples 1 to 6, which had a G / R ratio of 1.0 or less, compared to Examples 7 and 8, which had a relatively large G / R ratio of 1.50. In Examples 1 to 4, which had a G / R ratio of 0.5 or less, the Fe adhesion area was particularly small. In other words, it was found that a smaller G / R ratio results in a smaller contact area and superior adhesion resistance.

[0050] The sliding member of the present invention is applicable to various devices used in the automotive industry, the steel industry, and other sectors, such as press dies, bearings, die casting machines, and wire drawing machines.

[0051] 1. Sliding member 10. Sliding surface 2. Ridge 3. Groove 4. Projection A. Reference surface H. Average height of projection D. Average depth of groove G. Average width of groove

Claims

1. A sliding member having a sliding surface and a metal material as the base material, wherein the sliding surface is provided with a diffusion penetration layer containing at least one of carbides or borides, and the sliding surface further comprises, in plan view, a plurality of grooves extending in a predetermined direction, a plurality of ridges located between two adjacent grooves, and a plurality of projections located along both edges of each groove and between each groove and its adjacent ridge, and in cross-sectional view, each groove is recessed compared to the ridges on either side of it, and each projection of the plurality of projections protrudes compared to the ridges on either side of it.

2. The sliding member according to claim 1, wherein the diffusion permeation layer contains at least one of vanadium carbide and chromium carbide as the carbide.

3. The sliding member according to claim 1, wherein the thickness of the diffusion permeation layer is 5 to 200 μm.

4. The sliding member according to claim 1, wherein the average height of the plurality of protrusions is 1 to 7 μm.

5. The sliding member according to claim 1, wherein the ratio of the average width of the plurality of grooves to the average width of the plurality of ridges is 1.0 or less.

6. A method for manufacturing a sliding member, comprising: (a) irradiating a metal substrate with a laser beam to form, in plan view, a plurality of grooves extending in a predetermined direction, a plurality of ridges located between two adjacent grooves, and a plurality of protrusions along both edges of each groove and between each groove and its adjacent ridge; and (b) forming a diffusion and penetration layer containing carbide or boride on the surface of the substrate from which step (a) has been performed, wherein in cross-sectional view, each groove is recessed compared to the adjacent ridges, and each of the multiple protrusions protrudes more than the adjacent ridges.

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