Sliding member

Abstract

Provided is a sliding member having excellent peeling resistance against a plating layer even when sliding under high surface pressure exceeding 1.5 GPa in terms of hertzian surface pressure. A sliding member (1) comprises: a substrate (2) including a sliding surface (20) that slides on other members; and a plating layer (3) disposed at least on the sliding surface (20). The plating layer (3) includes a matrix (30) and polytetrafluoroethylene (31). The matrix (30) is a Zn-Ni alloy containing 10.0-17.0 mass% of Ni, with the remainder comprising Zn and impurities. The content of polytetrafluoroethylene (31) in the plating layer (3) is 6.5-21.0 mass%.

Description

[Technical Field]

[0001] The present disclosure relates to a slide member. [Background technology]

[0002] A sliding member is a general term for a member that comes into contact with at least a portion of another member and slides over the contacting portion. Examples of sliding members include train wheels and rails, engine cylinders and pistons, crankshafts and connecting rods, tools used in drilling, saw blades, pulleys, gears, industrial screws, nuts, bearings, guide members, and dies. Sliding members repeatedly slide over other members.

[0003] A plating layer may be formed on the surface of a sliding member. The plating layer may be, for example, an alloy plating layer. For example, Japanese Patent Laid-Open No. 2014-228063 (Patent Document 1), Japanese Patent Laid-Open No. 05-279772 (Patent Document 2), and Japanese Patent Laid-Open No. 2013-032571 (Patent Document 3) propose sliding members having an alloy plating layer formed on the surface.

[0004] The sliding member described in Patent Document 1 has a tin-zinc alloy plating layer made of tin and zinc formed on the sliding surface. The sliding member described in Patent Document 1 has an alloy plating layer thickness of 10 to 25 μm. The alloy plating layer is characterized in that the weight ratio of zinc to the total tin and zinc is 20 to 80%. Patent Document 1 states that this sliding member can reduce the amount of wear even under severe sliding conditions in the sliding part, and can contribute to extending the life of various machines.

[0005] The sliding member described in Patent Document 2 has a plating layer formed thereon containing, by weight, 10 to 35% Zn, 2 to 20% Pb, 1 to 10% Ni, 0.1 to 1% B (boron), and the remainder Cu and impurities. Patent Document 2 states that this results in a sliding member with excellent seizure resistance, wear resistance, and corrosion resistance even under severe operating conditions of high speeds and high temperatures.

[0006] The sliding member described in Patent Document 3 is characterized by comprising a substrate having a metallic surface and a zinc alloy plating layer provided on the substrate. The zinc alloy plating layer has a chemical composition containing, by mass, 2 to 8% Ni and 0.1 to 3% Mo, with the balance being Zn and impurities. The zinc alloy plating layer has a hardness of 150 to 350 Hv and a thickness of 0.1 to 30 μm. Patent Document 3 states that this not only imparts excellent corrosion resistance to the substrate, but also results in a zinc alloy plated member that can be used as a sliding member. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-228063 [Patent Document 2] Japanese Patent Application Publication No. 05-279772 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-032571 Summary of the Invention [Problem to be solved by the invention]

[0008] Among sliding members, there are some that slide under high contact pressure exceeding 1.5 GPa in Hertzian contact pressure. Examples of such sliding members include train wheels and rails, and industrial screws. However, sliding under high contact pressure makes the plating layer formed on the sliding member more susceptible to peeling. Furthermore, if the plating layer peels, there is a concern that the seizure resistance and corrosion resistance of the sliding member may be reduced. Therefore, it is preferable that the plating layer has excellent peeling resistance even when sliding under high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0009] On the other hand, Patent Documents 1 to 3 do not consider at all the peeling resistance of the plating layer when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. For example, in paragraph 0029 of Patent Document 1, a sliding test was carried out at a contact pressure of 224 MPa. Furthermore, in paragraph 0009 of Patent Document 2, it is stated that a maximum load of 500 kgf / cm 2 The seizure resistance is evaluated using a pressure of 0.049 GPa, which can be converted to Pa units. In Patent Document 3, no sliding test is conducted. Therefore, even if the techniques disclosed in Patent Documents 1 to 3 are used, it may not be possible to improve the peeling resistance of the plating layer during sliding under a high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0010] An object of the present disclosure is to provide a slide member that exhibits excellent resistance to peeling of a plating layer even when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. [Means for solving the problem]

[0011] The sliding member according to the present disclosure comprises: a substrate including a sliding surface that slides against another member; a plating layer disposed on at least the sliding surface, The plating layer is comprising a matrix and polytetrafluoroethylene; the matrix phase is a Zn-Ni alloy containing 10.0 to 17.0 mass% Ni, the balance being Zn and impurities; The content of the polytetrafluoroethylene in the plating layer is 6.5 to 21.0 mass %. [Effects of the Invention]

[0012] The sliding member according to the present disclosure exhibits excellent resistance to peeling of the plating layer even when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of a sliding member according to the present embodiment. [Figure 2]FIG. 2 is a graph showing the relationship between the Ni content and polytetrafluoroethylene (PTFE) content of the Zn-Ni alloy plating layer and the peeling resistance of the Zn-Ni alloy plating layer when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. [Figure 3] FIG. 3 is a graph showing the relationship between the PTFE / Ni ratio and the peeling resistance of the Zn—Ni alloy plating layer during sliding under a high Hertzian contact pressure exceeding 1.5 GPa. [Figure 4] FIG. 4 is a photograph of the plating layer of test number 10 of this example. [Figure 5] FIG. 5 is a black and white binarized image of the photograph in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present embodiment will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0015] The present inventors have investigated slide members that have excellent resistance to peeling of the plating layer even when sliding under a high Hertzian contact pressure of more than 1.5 GPa, and have obtained the following findings.

[0016] If the plating layer is destroyed during sliding under a high Hertzian pressure exceeding 1.5 GPa, the plating layer will peel off from the surface of the substrate. On the other hand, if the plating layer has a high hardness, the plating layer is less likely to be damaged during sliding. Therefore, the inventors thought that if the hardness of the plating layer is increased, peeling of the plating layer may be suppressed even during sliding under a high Hertzian pressure exceeding 1.5 GPa.

[0017] Incidentally, if a zinc (Zn)-containing plating layer is formed among the plating layers, the corrosion resistance of the slide member is improved by sacrificial corrosion protection. For this reason, Zn-containing plating layers have been used for slide members up to now. However, Zn has a relatively low hardness. Therefore, the present inventors thought that even if a Zn plating layer is formed, it would not be possible to improve the peeling resistance of the plating layer during sliding under a high Hertzian contact pressure exceeding 1.5 GPa.

[0018] Among Zn-based alloys, Zn-Ni alloys consisting of nickel (Ni) and the balance Zn and impurities have high hardness. Therefore, the inventors believed that forming a plating layer from a Zn-Ni alloy consisting of Ni and the balance Zn and impurities would improve the peeling resistance of the plating layer even during sliding under a high Hertzian contact pressure of more than 1.5 GPa. In this specification, a plating layer consisting of Ni and the balance Zn and impurities is referred to as a Zn-Ni alloy plating layer or simply as a plating layer.

[0019] Zn-Ni alloys are known to have eta, gamma, and / or alpha phases depending on the Ni content. The eta phase is a Zn phase with Ni dissolved in it. The gamma phase is Ni5Zn 21 The alpha phase is an intermetallic compound phase. The alpha phase is a Ni phase containing Zn in solid solution. It is known that when the Ni content is 10.0 mass% or less, the Zn-Ni alloy becomes a mixed phase of eta and gamma phases. It is known that when the Ni content is 10.0 to 17.0 mass%, the Zn-Ni alloy mainly contains gamma phase. It is known that when the Ni content exceeds 17.0 mass%, the Zn-Ni alloy becomes a mixed phase of gamma and alpha phases. Of the eta, gamma, and alpha phases, the gamma phase has the highest hardness. Therefore, it is believed that when the Ni content in the matrix of the Zn-Ni alloy plating layer is 10.0 to 17.0 mass%, the hardness of the Zn-Ni alloy plating layer will be increased.

[0020] The present inventors have conducted further studies and have found that in the case of a Zn-Ni alloy plating layer containing 10.0 to 17.0 mass% of Ni, adding 6.5 to 21.0 mass% of polytetrafluoroethylene (PTFE) improves peel resistance even under high Hertzian contact pressures exceeding 1.5 GPa.

[0021] The inventors conducted the following experiment. A steel plate measuring 150 mm in length, 100 mm in width, and 0.8 mm in thickness was prepared. A Zn-Ni alloy plating layer was formed on the surface of the steel plate. The Zn-Ni alloy plating layer contained a matrix and polytetrafluoroethylene (PTFE). The matrix of the Zn-Ni alloy plating layer was a Zn-Ni alloy consisting of Ni, with the remainder being Zn and impurities. The Ni content and PTFE content of the Zn-Ni alloy plating layer were varied to test the peeling resistance of the Zn-Ni alloy plating layer. The peeling resistance evaluation test was conducted under the following conditions: Apparatus: Adhesion-Sliding Tester No. 7 manufactured by Shinko Engineering Co., Ltd.; Sliding indenter: SUJ2 steel ball with a diameter of 4.763 mm; Load: 3 kgf (Hertzian surface pressure (average surface pressure): 1.56 GPa); Sliding width: 10 mm; Sliding speed: 4 mm / s; Temperature: 1 to 30°C; No oil application. The sliding indenter was slid under the above conditions. If the Zn-Ni alloy plating layer does not peel off, the sliding resistance is low because the sliding indenter slides against the Zn-Ni alloy plating layer. If the Zn-Ni alloy plating layer peels off, the sliding indenter slides against the steel sheet, causing a sudden increase in sliding resistance. Therefore, the number of sliding cycles at which the sliding resistance increased to three times or more the sliding resistance of the previous sliding cycle was defined as the "number of sliding cycles at which the Zn-Ni alloy plating layer peeled off." The results of the peeling resistance evaluation test are shown in Figure 2.

[0022] Figure 2 shows the relationship between the Ni content of the Zn-Ni alloy plating layer, the polytetrafluoroethylene (PTFE) content, and the peeling resistance of the Zn-Ni alloy plating layer when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. The horizontal axis of Figure 2 represents the Ni content of the parent phase of the Zn-Ni alloy plating layer in mass %. The vertical axis of Figure 2 represents the PTFE content in the Zn-Ni alloy plating layer in mass %. In Figure 2, open circles indicate that the Zn-Ni alloy plating layer peeled after 600 or more sliding cycles. In Figure 2, filled circles indicate that the Zn-Ni alloy plating layer peeled after fewer than 600 sliding cycles.

[0023] 2, when the Ni content was within the range of 10.0 to 17.0 mass% and the PTFE content was within the range of 6.5 to 21.0 mass%, the Zn-Ni alloy plating layer did not peel off even after sliding 600 times under a high Hertzian contact pressure exceeding 1.5 GPa. In other words, it was revealed that when the Ni content was within the range of 10.0 to 17.0 mass% and the PTFE content was within the range of 6.5 to 21.0 mass%, the peeling resistance of the Zn-Ni alloy plating layer was improved during sliding under a high Hertzian contact pressure exceeding 1.5 GPa.

[0024] The present inventors investigated the Vickers hardness of the Zn—Ni alloy plating layer when PTFE was contained, and as a result, obtained the following findings.

[0025] [Table 1]

[0026] Table 1 shows an excerpt from the Examples described below. Referring to Table 1, the hardness of the PTFE-containing Zn-Ni alloy plating layers of Test Nos. 3 to 5 is lower than that of Test No. 15, which does not contain PTFE. Furthermore, comparing Test Nos. 4 and 5, which have similar Ni contents, the hardness of the Zn-Ni alloy plating layer decreases as the PTFE content increases. The PTFE-free Zn-Ni alloy plating layer of Test No. 15 peeled off after five sliding cycles. In contrast, the PTFE-containing Zn-Ni alloy plating layers of Test Nos. 3 to 5 peeled off after 600 or more sliding cycles. These results demonstrate a completely different finding from conventional findings: despite the hardness of the Zn-Ni alloy plating layer decreasing due to the inclusion of PTFE, its peel resistance increases.

[0027] Although the above-mentioned Ni content and PTFE content reduce the hardness of the Zn-Ni alloy plating layer, the reason for the increased peel resistance of the Zn-Ni alloy plating layer during sliding under a high Hertzian pressure exceeding 1.5 GPa is unclear. However, when PTFE is not contained, the peel resistance during sliding under a high Hertzian pressure exceeding 1.5 GPa is low. From this, it is believed that PTFE contributes to the improvement of peel resistance during sliding under a high Hertzian pressure exceeding 1.5 GPa. The present inventors believe as follows: When the Zn-Ni alloy plating layer is formed, internal stress is generated in the Zn-Ni alloy plating layer. If the internal stress is high, the Zn-Ni alloy plating layer is more likely to peel at the interface between the Zn-Ni alloy plating layer and the substrate when an external force is applied.

[0028] On the other hand, in the early stage of the formation of the Zn-Ni alloy plating layer, PTFE may affect the adsorption of Zn ions to the steel sheet surface, which may reduce the internal stress of the Zn-Ni alloy plating layer. As a result, the present inventors believe that if the Zn-Ni alloy plating layer contains PTFE, the internal stress generated during the formation of the Zn-Ni alloy plating layer will be reduced, and peeling of the Zn-Ni alloy plating layer will be suppressed.

[0029] The sliding member of this embodiment, which has been completed based on the above findings, has the following configuration.

[0030] [1] a substrate including a sliding surface that slides against another member; a plating layer disposed on at least the sliding surface, The plating layer is comprising a matrix and polytetrafluoroethylene; the matrix phase is a Zn-Ni alloy containing 10.0 to 17.0 mass% Ni, the balance being Zn and impurities; The content of the polytetrafluoroethylene in the plating layer is 6.5 to 21.0 mass%. Sliding member.

[0031] [2] The sliding member according to [1], The plating layer satisfies formula (1): Sliding member. 0.85≦[PTFE] / [Ni]≦1.05 (1) Here, in formula (1), the content of the polytetrafluoroethylene in the plating layer in mass % is substituted for [PTFE], and the content of Ni in the parent phase in mass % is substituted for [Ni].

[0032] [3] The sliding member according to [1] or [2], The blackened area ratio on the surface of the plating layer is 30% or less. Sliding member.

[0033] [Sliding member] 1 is a cross-sectional view of a slide member 1 according to this embodiment. Referring to FIG. 1, slide member 1 includes a substrate 2 and a plating layer 3.

[0034] [Base material] The substrate 2 includes a sliding surface 20 that slides against another member. The other member is another sliding member. The sliding member 1 slides against the other sliding member at the sliding surface 20. As will be described later, the sliding surface 20 is a surface formed on the substrate 2, and a plating layer 3 is disposed on the sliding surface 20. Therefore, when the sliding member 1 according to this embodiment slides against another member, the plating layer 3 is disposed between the sliding surface 20 and the other sliding member.

[0035] The substrate 2 is not particularly limited as long as it is used as the sliding member 1 and is a plateable member. Examples of the substrate 2 include train wheels and rails, engine cylinders and pistons, crankshafts and connecting rods, drilling tools, saw blades, pulleys, gears, industrial screws, nuts, bearings, guide members, and molds. The composition of the substrate 2 is not particularly limited. The substrate 2 may be made of a single metal or an alloy, and may have a plating layer formed on its surface. Examples of the substrate 2 include carbon steel, stainless steel, alloy steel, carbon steel with a plating layer formed thereon, stainless steel with a plating layer formed thereon, and alloy steel with a plating layer formed thereon.

[0036] [Plating layer] The plating layer 3 is disposed at least on the sliding surface 20. When the substrate 2 includes a surface other than the sliding surface 20, the plating layer 3 may be disposed only on the sliding surface 20, or may be disposed on the sliding surface 20 and other surfaces.

[0037] The plating layer 3 includes a matrix 30 and polytetrafluoroethylene (PTFE) 31 .

[0038] [Chemical composition of the parent phase] The matrix 30 of the plating layer 3 is a Zn-Ni alloy consisting of 10.0 to 17.0 mass% nickel (Ni), with the remainder being zinc (Zn) and impurities. In other words, the matrix 30 is a Zn-Ni alloy consisting of 10.0 to 17.0 mass% Ni, 83.0 to 90.0 mass% Zn, and impurities. Zn-Ni alloys with this composition are known to contain primarily gamma phases. In this case, the hardness of the Zn-Ni alloy plating layer is increased, and the peel resistance of the plating layer 3 is improved even during sliding under a high Hertzian contact pressure exceeding 1.5 GPa. The lower limit of the Ni content of the matrix 30 of the plating layer 3 is preferably 10.3 mass%, more preferably 10.5 mass%, even more preferably 10.8 mass%, and even more preferably 11.0 mass%. The upper limit of the Ni content in the matrix 30 of the plating layer 3 is preferably 16.5 mass%, more preferably 16.0 mass%, even more preferably 15.0 mass%, and even more preferably 14.0 mass%. Examples of impurities include hydrogen (H), oxygen (O), and iron (Fe). The matrix 30 of the plating layer 3 may contain impurities in a total amount of 1.0 mass% or less. The Ni content refers to the Ni content in the matrix 30.

[0039] [Polytetrafluoroethylene] Polytetrafluoroethylene (PTFE) 31 is (C2F4) n In this specification, PTFE 31 refers to particles primarily composed of polytetrafluoroethylene. Specifically, PTFE 31 refers to particles containing 98% by mass or more of polytetrafluoroethylene, with the remainder being impurities. In other words, the PTFE 31 contained in the plating layer 3 according to this embodiment corresponds to polytetrafluoroethylene particles. The PTFE 31 according to this embodiment is not particularly limited, and well-known polytetrafluoroethylene particles can be used. The size of the PTFE 31 is not particularly limited, and the particle size of the PTFE 31 may be, for example, 0.1 to 2.0 μm or 0.4 to 1.0 μm. The particle size of the PTFE 31 refers to the average particle size of the PTFE 31.

[0040] In this embodiment, the content of PTFE 31 in the plating layer 3 is 6.5 to 21.0 mass%. If the plating layer 3 contains a Zn-Ni alloy mother phase 30 consisting of 10.0 to 17.0 mass% Ni, with the remainder being Zn and impurities, and 6.5 to 21.0 mass% PTFE 31, peeling resistance is improved even during sliding under a high Hertzian contact pressure exceeding 1.5 GPa. The lower limit of the content of PTFE 31 is preferably 6.7 mass%, more preferably 6.9 mass%, even more preferably 7.0 mass%, even more preferably 7.5 mass%, and even more preferably 8.0 mass%. The upper limit of the content of PTFE 31 is preferably 20.5 mass%, more preferably 20.0 mass%, even more preferably 19.5 mass%, even more preferably 19.0 mass%, even more preferably 18.5 mass%, even more preferably 18.0 mass%, even more preferably 17.5 mass%, and even more preferably 17.0 mass%. The PTFE content refers to the PTFE content in the plating layer 3.

[0041] [Ratio of PTFE content to Ni content] There are no particular restrictions on the ratio of the PTFE content in the plating layer 3 to the Ni content in the matrix 30. However, it is preferable that the ratio satisfies formula (1). 0.85≦[PTFE] / [Ni]≦1.05 (1) Here, in formula (1), the content of PTFE 31 in the plating layer 3 in mass % is substituted for [PTFE], and the content of Ni in the parent phase 30 in mass % is substituted for [Ni].

[0042] Hereinafter, the ratio of the PTFE 31 content in mass% in the plating layer 3 to the Ni content in mass% in the matrix 30 is referred to as the "PTFE / Ni ratio." FIG. 3 is a graph showing the relationship between the PTFE / Ni ratio and the peel resistance of the Zn—Ni alloy plating layer 3 during sliding under a high Hertzian contact pressure exceeding 1.5 GPa. FIG. 3 was obtained from an example described below. The vertical axis of FIG. 3 represents the number of sliding cycles at which the plating layer 3 peeled in a peel resistance evaluation test. The horizontal axis of FIG. 3 represents the PTFE / Ni ratio of the plating layer 3. Referring to FIG. 3, a PTFE / Ni ratio of 0.85 or more and 1.05 or less further enhances the peel resistance of the plating layer 3 during sliding under a high Hertzian contact pressure exceeding 1.5 GPa. A more preferable lower limit of the PTFE / Ni ratio is 0.88, and even more preferably 0.90. A more preferable upper limit of the PTFE / Ni ratio is 1.03, and even more preferably 1.00.

[0043] [Method for measuring the composition of the plating layer] The composition of the plating layer 3 is measured by the following method. The surface of the plating layer 3 is analyzed by energy dispersive X-ray spectroscopy (EDX) using a field emission electron probe microanalyzer (FE-EPMA). Specifically, the measurement magnification is set to 1000x, and an electron beam is irradiated with an acceleration voltage of 15 kV and a maximum probe current of 1 nA to measure the Kα ray intensity, and the nickel (Ni) count, zinc (Zn) count, and fluorine (F) count within the field of view are measured. The obtained F count is converted to the F content in mass %. The F content in mass % is divided by the atomic weight of F to convert to the F molar amount. The CF2 content in mass % is calculated from the F molar amount, and this is taken as the PTFE 31 content in mass %. This determines the PTFE 31 content in the plating layer 3. The obtained Ni count is converted to the Ni content in mass %. The obtained Ni content is the Ni content relative to the entire plating layer 3. Therefore, this Ni content is converted into the Ni content relative to the parent phase 30 of the plating layer 3 that does not contain PTFE 31. In this way, the Ni content in the parent phase 30 of the plating layer 3 is determined.

[0044] The plating layer 3 may contain impurities. The impurities are selected from the group consisting of hydrogen (H), oxygen (O), and Fe, for example. The total amount of impurities contained in the plating layer 3 is, for example, less than 1.0 mass%, and more preferably less than 0.5 mass%. Therefore, the plating layer 3 may be a plating layer 3 made of a parent phase 30, PTFE 31, and one or more impurities selected from the group consisting of hydrogen (H), oxygen (O), and Fe. The content of impurities may be 0 mass%. Therefore, the plating layer 3 may be a plating layer 3 made of a parent phase 30 and PTFE 31.

[0045] [Crystal structure of Zn-Ni alloy] The matrix 30 of the coating layer 3 is a Zn-Ni alloy containing 10.0 to 17.0 mass% nickel (Ni) and the remainder zinc (Zn) and impurities. In this case, the matrix 30 of the coating layer 3 includes a gamma phase. The gamma phase has the chemical formula NiZn 21 The parent phase 30 of the plating layer 3 may include an eta phase. The eta phase is a phase with a hexagonal crystal structure, with the chemical formula Zn, lattice constants a = 0.267 nm and c = 0.495 nm. The parent phase 30 of the plating layer 3 may include an alpha phase. The alpha phase is a phase with a face-centered cubic crystal structure, with the chemical formula Ni, and lattice constant a = 0.352 nm. Of the eta phase, gamma phase, and alpha phase, the gamma phase has the highest hardness. Therefore, the parent phase 30 of the plating layer 3 is preferably a single gamma phase.

[0046] [Method for identifying the crystal structure of the parent phase of the plating layer] The crystal structure of the parent phase 30 of the plating layer 3 is identified by the following method. X-ray diffraction measurement is performed on the surface of the plating layer 3 under the following measurement conditions. The obtained measured profile is compared with the values ​​recorded on an ICDD (International Center for Diffraction Data) card to identify the phase. Equipment: X-ray diffraction equipment ·X-ray tube: Co-Kα ray Scan range: 2θ=10~110° Scan step: 0.02°

[0047] [Plating layer thickness] The thickness of the plating layer 3 is not particularly limited. When the thickness of the plating layer 3 is 1.0 μm or more, durability can be stably obtained. When the thickness of the plating layer 3 is 60.0 μm or less, excessive manufacturing costs can be suppressed. Therefore, the thickness of the plating layer 3 is preferably 1.0 to 60.0 μm. The lower limit of the thickness of the plating layer 3 is more preferably 2.0 μm, even more preferably 3.0 μm, even more preferably 5.0 μm, even more preferably 7.0 μm, and even more preferably 10.0 μm. The upper limit of the thickness of the plating layer 3 is more preferably 55.0 μm, even more preferably 50.0 μm, even more preferably 45.0 μm, even more preferably 40.0 μm, even more preferably 35.0 μm, even more preferably 30.0 μm, even more preferably 25.0 μm, and even more preferably 20.0 μm.

[0048] [Method for measuring plating layer thickness] The thickness of the plating layer 3 is measured by the following method. The thickness of the plating layer 3 is measured at any four points on the surface of the plating layer 3 using an eddy current phase-type film thickness meter. The measurement of the plating layer 3 is performed using a method that complies with ISO (International Organization for Standardization) 21968 (2005). The arithmetic average of the measurement results at the four points is taken as the thickness of the plating layer 3.

[0049] [Blackened area ratio of plating layer] As a result of investigations by the present inventors, it has become clear that when the Zn-Ni alloy plating layer 3 contains a large amount of PTFE 31, i.e., 6.5% by mass or more, black unevenness may occur on the surface of the plating layer 3. In this specification, "black unevenness" means that part or all of the surface of the plating layer 3 has turned black. The present inventors believed that suppressing black unevenness on the surface of the plating layer 3 would improve the appearance of the slide member 1. In the slide member 1 of this embodiment, the blackened area ratio on the surface of the plating layer 3 is preferably 30% or less. In this case, the slide member 1 has excellent appearance of the plating layer 3 even when the content of PTFE 31 in the plating layer 3 is as high as 6.5% by mass or more. The upper limit of the blackened area ratio on the surface of the plating layer 3 is more preferably 20%, and even more preferably 15%. The blackened area ratio on the surface of the plating layer 3 may be 0%.

[0050] In this embodiment, the blackened area ratio can be determined by the following method. Specifically, a photograph is taken of an area measuring 100 mm long x 100 mm wide from the surface of the plating layer 3 of the slide member 1. The blackened area is identified from the obtained photograph, and the area ratio of the blackened area is determined. Note that a person skilled in the art would naturally be able to identify the blackened area. Alternatively, the obtained photograph may be binarized by image processing to determine the area ratio.

[0051] [Other configurations] As described above, the slide member 1 according to this embodiment includes the substrate 2 and the plating layer 3 formed on the sliding surface 20 of the substrate 2. Here, the slide member 1 may include components other than the substrate 2 and the plating layer 3. For example, another plating layer may be formed as an upper layer on the plating layer 3 of the slide member 1, a chemical conversion treatment layer may be formed, or a lubricating coating layer may be formed.

[0052] The sliding member 1 of this embodiment can be suitably used when sliding under a high Hertzian pressure exceeding 1.5 GPa. However, the use of the sliding member 1 of this embodiment is not limited to sliding under a high Hertzian pressure exceeding 1.5 GPa. The sliding member 1 of this embodiment can also be suitably used when sliding under a Hertzian pressure of 1.5 GPa or less.

[0053] [Manufacturing method] The method for manufacturing the slide member 1 of this embodiment includes a preparation step and a plating layer formation step.

[0054] [Preparation process] In the preparation step, a substrate 2 and a plating solution are prepared. As described above, the substrate 2 is used as the slide member 1, and is not particularly limited as long as it is made of a material that can be plated. The plating solution contains zinc ions, nickel ions, PTFE3, and a solvent. The plating solution preferably contains 1 to 100 g / L of zinc ions, 1 to 100 g / L of nickel ions, and 1 to 50 g / L of PTFE3. The solvent is, for example, water. The plating solution may contain other components. The other components are, for example, selected from the group consisting of a conductive additive (supporting electrolyte) and a surfactant. The conductive additive is, for example, selected from the group consisting of sodium sulfate, ammonium sulfate, and ammonium chloride. The surfactant is, for example, selected from the group consisting of cationic, anionic, and nonionic surfactants.

[0055] [Plating layer formation process] In the plating layer forming step, the plating layer 3 is formed by plating treatment. In the plating layer forming step, at least the sliding surface 20 of the substrate 2 is brought into contact with a plating solution. As a result, the plating layer 3 is formed on at least the sliding surface 20 of the substrate 2. The plating layer 3 is preferably formed by electroplating. In electroplating, at least the sliding surface 20 of the substrate 2 is brought into contact with a plating solution and an electric current is applied. The electroplating conditions can be set appropriately. For example, the electroplating conditions are a plating solution pH of 1 to 10, a plating solution temperature of 10 to 70°C, and a current density of 1 to 100 A / dm 2 and processing time: 0.1 to 90 minutes.

[0056] To suppress black unevenness on the surface of plating layer 3, plating is carried out, for example, under the following conditions: In this case, the blackened area ratio on the surface of plating layer 3 can be reduced to 30% or less. Ni in plating solution 2+ / Zn 2+ Molar ratio≦1.5 Metal salt concentration in plating solution (Ni 2+ and Zn 2+ Total of (total)≦1.5M PTFE concentration in plating solution ≦25g / L Plating solution temperature: 57~65℃ Plating solution pH 2~4 Plating solution flow rate (linear flow rate): 0.1-0.4 m / sec. ·Current density≦3A / dm 2

[0057] [Surface preparation process] The above manufacturing method may optionally include a surface preparation step prior to the plating layer formation step. The surface preparation step may include, for example, pickling and alkaline degreasing. In the surface preparation step, oil and dirt adhering to the sliding surface 20 of the substrate 2 are removed. The surface preparation step may further include grinding processes such as sandblasting and mechanical grinding. Only one of these surface preparation steps may be performed, or multiple surface preparation steps may be performed in combination.

[0058] The sliding member 1 of this embodiment is manufactured through the above steps. However, the above-described manufacturing method of the sliding member 1 of this embodiment is only one example of the manufacturing method of the sliding member 1 of this embodiment, and the manufacturing method is not limited to this. The sliding member 1 of this embodiment may be manufactured by other methods. [Example]

[0059] The effects of the sliding member of this embodiment will be described in more detail below using examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the sliding member of this embodiment. Therefore, the sliding member of this embodiment is not limited to this one example of conditions.

[0060] In the examples, plating layers with different compositions were formed on steel sheets, and the peeling resistance of the plating layers was evaluated when sliding under a high Hertzian contact pressure exceeding 1.5 GPa. Specifically, the following was performed.

[0061] [Preparation process] In this example, a commercially available cold-rolled steel sheet was used as the substrate. The cold-rolled steel sheet was 150 mm long, 100 mm wide, and 0.8 mm thick. The steel type was SPCC (low carbon steel) as specified in Japanese Industrial Standards (JIS) G3141 (2021). A 100 mm long x 100 mm wide area of ​​the surface of the cold-rolled steel sheet was plated.

[0062] The plating solution was an aqueous solution containing zinc sulfate heptahydrate: 100 to 250 g / L, nickel sulfate hexahydrate: 150 to 350 g / L, sodium sulfate: 75 g / L, and polytetrafluoroethylene (PTFE): 0 to 25 g / L, with a pH of 2 to 4. The metal salt concentration of the plating solution (Ni 2+ and Zn 2+ The total amount of the plating solution (total amount of the above) was 1.5M or less. The composition of the plating solution was changed within the above range to form a plating layer on the steel sheet of each test number. This changed the composition of the plating layer for each test number. Note that in test numbers 16 to 18, the plating solution did not contain PTFE, but instead contained 3 to 10 g / L of graphite. The plating layer was formed by electroplating. The plating conditions were plating solution temperature: 50 to 60°C, current density: 1 to 10 A / dm 2 and plating anode (counter electrode): titanium plate coated with iridium oxide. In this example, the PTFE particles used had an average particle size of 0.4 to 1.0 μm, and were composed of 98 mass % or more of polytetrafluoroethylene, with the remainder being impurities.

[0063] In addition to the above conditions, test numbers 1 to 5 and 7 to 9 met the following conditions: Ni in plating solution 2+ / Zn 2+ Molar ratio≦1.5 Plating solution temperature: 57-60℃ Plating solution flow rate (linear flow rate): 0.1-0.4 m / sec. ·Current density≦3A / dm 2

[0064] Test No. 6 was plated under the following conditions. Ni in plating solution 2+ / Zn 2+ Molar ratio = 3.0 Plating solution temperature: 50℃ Plating solution flow rate (linear flow rate) 0 m / sec. ·Current density≦3A / dm 2

[0065] Test No. 10 was plated under the following conditions. Ni in plating solution 2+ / Zn 2+ Molar ratio = 3.0 Plating solution temperature: 57-60℃ Plating solution flow rate (linear velocity) 0.5m / sec. ·Current density 6A / dm 2

[0066] [Test for measuring the composition of the plating layer] The composition of the plating layer for each test number was measured using the following method. The surface of the plating layer for each test number was analyzed by energy dispersive X-ray spectroscopy (EDX) using a JEOL JXA-8530F field emission electron probe microanalyzer (FE-EPMA). Specifically, an electron beam was irradiated at a magnification of 1000x, an acceleration voltage of 15 kV, and a maximum irradiation current of 1 nA to measure the Kα ray intensity, and the nickel (Ni), zinc (Zn), and fluorine (F) counts within the field of view were measured. The resulting F counts were converted to the F content in mass %. The F content in mass % was then divided by the atomic weight of F to convert it to the molar amount of F. The CF2 content in mass % was calculated from the molar amount of F, and this was taken as the PTFE content in mass %. The PTFE content in the plating layer was calculated using this method. The results are shown in the "PTFE content (mass %)" column in Table 2.

[0067] The obtained Ni counts were converted to the Ni content in mass %. The obtained Ni content was the Ni content relative to the entire plating layer. Therefore, this Ni content was converted to the Ni content relative to the matrix of the plating layer that did not contain PTFE. This determined the Ni content in the matrix of the plating layer. The results are shown in the "Ni content (mass %)" column of Table 2. The matrix of the plating layer for each test number was a Zn-Ni alloy consisting of Ni as shown in Table 2, with the remainder consisting of Zn and impurities. In Table 2, the "[PTFE] / [Ni]" column shows the ratio of the PTFE content (mass %) in the plating layer to the Ni content (mass %) in the matrix. Note that in Test No. 15, the plating layer did not contain PTFE. In Test Nos. 16 to 18, the plating layer did not contain PTFE, but instead contained graphite. For Test Nos. 16 to 18, the graphite content is shown in the "PTFE content (mass %)" column of Table 2.

[0068] [Table 2]

[0069] [X-ray diffraction measurement test of the parent phase of the plating layer] The crystal structure of the parent phase of the plating layer for each test number was identified using the following method. X-ray diffraction measurements were performed on the surface of the plating layer under the following measurement conditions. The phase was identified by comparing the obtained measured profile with the value recorded on the ICDD card. As a result, in all examples, the parent phase of the plating layer contained a gamma phase. The parent phase of the plating layers for test numbers 1, 4 to 6, and 10 was a single gamma phase. Equipment: X-ray diffraction equipment Rigaku Corporation RINT-2500 ·X-ray tube: Co-Kα ray Scan range: 2θ=10~110° Scan step: 0.02°

[0070] [Plating layer thickness measurement test] The thickness of the plating layer for each test number was measured using the following method. The thickness of the plating layer was measured at four random locations on the surface of the plating layer using an eddy current phase-type film thickness meter PHASCOPE PM910 manufactured by Helmut Fischer GmbH. The plating layer was measured using a method in accordance with ISO 21968 (2005). The arithmetic mean of the measurement results at the four locations was taken as the thickness of the plating layer. The results are shown in the "Thickness of plating layer (μm)" column in Table 2.

[0071] [Peeling resistance evaluation test] A test to evaluate the peeling resistance of the plating layer was conducted on the steel sheets having the plating layer with each test number. The test to evaluate the peeling resistance of the plating layer was conducted under the following conditions: Apparatus: Adhesion-Sliding Tester No. 7 manufactured by Shinko Engineering Co., Ltd.; Sliding indenter: SUJ2 steel ball with a diameter of 4.763 mm; Load: 3 kgf (Hertzian surface pressure (average surface pressure): 1.56 GPa); Sliding width: 10 mm; Sliding speed: 4 mm / s; Temperature: 1 to 30°C; Oiling: None. The number of sliding cycles at which the sliding resistance increased to three times or more the sliding resistance of the previous sliding cycle was defined as the "number of sliding cycles at which the plating layer peeled." The results are shown in the "Number of sliding cycles at which the plating layer peeled" column in Table 3.

[0072] [Table 3]

[0073] [Blackened area ratio measurement test] The blackened area ratio of the plating layer surface of test numbers 1 to 15 was measured using the following method. A photograph was taken of the entire area of ​​100 mm length x 100 mm width where the plating layer was formed. Figure 4 is a photograph of the plating layer of test number 10. The obtained photograph was binarized into black and white by image processing. Figure 5 is a black and white image of the photograph of Figure 4. From the binarized black and white image, the area ratio of the black portion to the total area was calculated. The results are shown in the "Blackened area ratio (%)" column of Table 3.

[0074] [Plating layer hardness measurement test] The hardness of the plating layer was measured for test numbers 3 to 5 and 15. The plating layer hardness measurement test was carried out under the following conditions. The Vickers hardness (Hv) of the plating layer surface was measured using a microhardness tester FISCHERSCOPE (registered trademark) HM2000 manufactured by Helmut Fischer GmbH. The load was 10 to 50 mN. The load was adjusted so that six times the indentation depth (μm) was equal to or less than the plating layer thickness. The results are shown in the "Hardness (Hv) of plating layer" column in Table 3.

[0075] [Evaluation results] Referring to Tables 2 and 3, the plating layers of test numbers 1 to 10 contained a Zn-Ni alloy parent phase consisting of 10.0 to 17.0 mass% Ni, with the remainder being Zn and impurities, and PTFE contained in the plating layer at a content of 6.5 to 21.0 mass%. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled was 600 or more. It was found that the sliding members including the plating layers of test numbers 1 to 10 had excellent peeling resistance of the plating layer when sliding under a high Hertzian contact pressure of more than 1.5 GPa.

[0076] Furthermore, for test numbers 7 to 9, in which the PTFE / Ni ratio was 0.85 or more and 1.05 or less, the number of sliding cycles when the plating layer peeled in the peeling resistance evaluation test was 2000 or more. Compared with test numbers 1 to 6 and 10, it was found that the sliding members including the plating layers of test numbers 7 to 9 had even better peeling resistance of the plating layer when sliding under a high contact pressure of more than 1.5 GPa in Hertzian contact pressure.

[0077] The blackened area ratio of the plating layer surface of test numbers 1 to 5 and 7 to 9 was 30% or less. Compared with test number 6 and test number 10, the sliding members having the plating layers of test numbers 1 to 5 and 7 to 9 were found to have excellent peeling resistance of the plating layer during sliding under a high Hertzian contact pressure of more than 1.5 GPa, and further, to have excellent appearance of the plating layer even when the PTFE content in the plating layer was as high as 6.5% or more.

[0078] On the other hand, the plating layer of Test No. 11 had an excessively low PTFE content. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding member including the plating layer of Test No. 11 could not improve the peeling resistance of the plating layer when sliding under a high Hertzian contact pressure exceeding 1.5 GPa.

[0079] The plating layer of Test No. 12 had too low a Ni content and a PTFE content. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding member including the plating layer of Test No. 12 could not improve the peeling resistance of the plating layer when sliding under a high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0080] The plating layer of Test No. 13 had an excessively low Ni content. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding member including the plating layer of Test No. 13 could not improve the peeling resistance of the plating layer when sliding under a high Hertzian contact pressure exceeding 1.5 GPa.

[0081] The plating layer of Test No. 14 had an excessively high Ni content. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding member including the plating layer of Test No. 14 could not improve the peeling resistance of the plating layer when sliding under a high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0082] The plating layer of test number 15 did not contain PTFE. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding member including the plating layer of test number 15 could not improve the peeling resistance of the plating layer when sliding under a high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0083] The plating layers of test numbers 16 to 18 contained graphite instead of PTFE. As a result, in the peeling resistance evaluation test, the number of sliding cycles when the plating layer peeled off was less than 600. It was found that the sliding members including the plating layers of test numbers 16 to 18 could not improve the peeling resistance of the plating layer when sliding under a high contact pressure exceeding 1.5 GPa in Hertzian contact pressure.

[0084] The embodiments of the present invention have been described above. However, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be appropriately modified and carried out without departing from the spirit of the present invention. [Explanation of symbols]

[0085] 1. Sliding member 2 Base material 3 plating layer 20 sliding surface 30 Mother phase 31 Polytetrafluoroethylene (PTFE)

Claims

1. a substrate including a sliding surface that slides against another member; a plating layer disposed on at least the sliding surface, The plating layer is comprising a matrix and polytetrafluoroethylene; the matrix phase is a Zn-Ni alloy containing 10.0 to 17.0 mass% Ni, the balance being Zn and impurities; The content of the polytetrafluoroethylene in the plating layer is 6.5 to 21.0 mass%. Sliding member.

2. The sliding member according to claim 1, The plating layer satisfies formula (1): Sliding member. 0.85≦[PTFE] / [Ni]≦1.05 (1) Here, in formula (1), [PTFE] is substituted with the content of polytetrafluoroethylene in the plating layer in mass %, and [Ni] is substituted with the content of Ni in the parent phase in mass %.

3. The sliding member according to claim 1 or 2, the blackened area ratio on the surface of the plating layer is 30% or less; Sliding member.

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