Plating material

Abstract

A plating material (10) comprises: a base material (11); an underplating layer (12) provided on the base material (11); and a main plating layer (13) provided above the underplating layer (12). The thickness of the underplating layer (12) is 10 μm or more. The ratio of the thickness of the underplating layer (12) to the thickness of the main plating layer (13) is 1 / 4 or more.

Description

Plated material

[0001] The present invention relates to a plated material.

[0002] In recent years, the demand for hybrid vehicles and electric vehicles has been increasing. However, since high-output motors are used, a large current flows through their wiring and terminals, resulting in a large amount of heat generation. Therefore, heat resistance performance is required for the terminals used in these vehicles. On the other hand, the tin plating commonly used in gasoline vehicles has a high electrical resistance, so it is likely to generate heat and does not have very high heat resistance. Therefore, there is a risk that the tin plating will be deteriorated by this heat. Therefore, it has been proposed to use silver plating with low electrical resistance instead of tin plating for the high-voltage connector terminals used in hybrid vehicles and electric vehicles.

[0003] On the other hand, since silver plating has low wear resistance, it is known to add antimony to silver plating to increase its hardness and improve its wear resistance. In Patent Document 1, a silver or silver alloy layer with an antimony concentration of 0.1% by mass or less is formed on at least a part of the surface of a copper or copper alloy member, and a silver alloy layer containing 0.5% by mass or more of antimony is formed as the outermost layer on this silver or silver alloy layer.

[0004] Japanese Patent Application Laid-Open No. 2009-79250

[0005] However, the prior art does not disclose improving the wear resistance by the apparent increase in Vickers hardness in a plated material having a copper or copper alloy member and two alloy layers, where the Vickers hardness in the outermost silver alloy layer is higher.

[0006] The present invention has been made in view of the problems of such prior art. The object of the present invention is to provide a plated material that exhibits good sliding characteristics in an environment with, for example, Arizona sand by improving the wear resistance by an apparent increase in hardness.

[0007] A plating material according to an embodiment of the present invention comprises a substrate, an under-plating layer provided on the substrate, and a main plating layer provided on the under-plating layer. The thickness of the under-plating layer is 10 μm or more. The ratio of the thickness of the under-plating layer to the thickness of the main plating layer is 1 / 4 or more.

[0008] According to the present invention, it is possible to provide a plating material that can improve wear resistance by increasing its apparent hardness.

[0009] Figure 1 is a cross-sectional view showing an example of a plated material according to one embodiment. Figure 2 is a schematic diagram illustrating the general outline of a pin-on-disk abrasion test. Figure 3 is a graph showing the particle size distribution of Arizona sand attached to a metal terminal. Figure 4 is a graph showing the relationship between the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer and the apparent hardness increase. Figure 5 is a graph showing the relationship between the thickness of the main plating layer and the apparent hardness increase. Figure 6 is a schematic diagram illustrating the Rabinowicz model. Figure 7 is another graph showing the relationship between the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer and the apparent hardness increase. Figure 8 is a graph showing the abrasion resistance results for Example 47 and Comparative Example 14. Figure 9 is a graph showing the abrasion resistance results for Example 48 and Comparative Example 15.

[0010] The plated material according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0011] As shown in Figure 1, the plating material 10 according to this embodiment comprises a base material 11, an undercoat plating layer 12, and a main plating layer 13. The undercoat plating layer 12 is provided on the base material 11. The main plating layer 13 is provided on the undercoat plating layer 12. In other words, the undercoat plating layer 12 is positioned between the base material 11 and the main plating layer 13. In the plating material 10 according to this embodiment, the undercoat plating layer 12 is in direct contact with the base material 11, and the entire surface of the base material 11 is covered by the undercoat plating layer 12. The main plating layer 13 is in direct contact with the undercoat plating layer 12, and the entire surface of the undercoat plating layer 12 is covered by the main plating layer 13. The main plating layer 13 is the outermost layer, and its surface is exposed.

[0012] (Base material 11) The base material 11 is the material to be plated on the undercoat plating layer 12 and the main plating layer 13. The base material 11 may be made of a conductive metal. The metal contained in the base material 11 may be copper, aluminum, magnesium, iron, and alloys containing these metals. Among these, copper and copper alloys are suitable when the plating material 10 is used as a terminal, etc., because of their high electrical conductivity. The copper alloy is preferably an alloy composed of Cu, at least one selected from the group consisting of Si, Fe, Mg, P, Ni, Sn, Co, Zn, Be, Pb, Te, Ag, Zr, Cr, Al, and Ti, and unavoidable impurities. The amount of copper in the copper alloy is preferably 85% by mass or more, more preferably 92% by mass or more. The amount of copper in the copper alloy is preferably 99.95% by mass or less. The total content of unavoidable impurities may be 0.5% by mass or less, or less than 0.05% by mass. The shape of the base material 11 is not particularly limited and can be shaped according to the application.

[0013] (Undercoat Plating Layer 12) The undercoat plating layer 12 is a plating film that serves as the base for the main plating layer 13. The undercoat plating layer 12 may be a nickel plating layer or a nickel alloy plating layer. When the undercoat plating layer 12 contains nickel or a nickel alloy, the undercoat plating layer 12 can suppress the diffusion of elements constituting the substrate 11 into the main plating layer 13, thereby improving contact reliability and heat resistance. The nickel alloy may contain Ni and at least one selected from the group consisting of W, P, Zn, and Sn. The undercoat plating layer 12 may contain nickel in amounts of, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. Alternatively, the undercoat plating layer 12 may contain nickel in amounts of, for example, 100% by mass or less, 95% by mass or less, or 90% by mass or less. The undercoat plating layer 12 may be a single layer or a combination of multiple layers, such as a nickel plating layer and a nickel alloy plating layer.

[0014] The thickness of the undercoat plating layer 12 is 10 μm or more. When the thickness of the undercoat plating layer 12 is 10 μm or more, it is possible to suppress Arizona sand from penetrating the undercoat plating layer 12 and reaching the substrate 11. The thickness of the undercoat plating layer 12 may be 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, or 35 μm or more. There is no particular upper limit to the thickness of the undercoat plating layer 12, but the thickness of the undercoat plating layer 12 may be 60 μm or less. The thickness of the undercoat plating layer 12 may be 50 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. The thicker the undercoat plating layer 12, the better the abrasion resistance, but exceeding 60 μm is not practical from the standpoint of cost or time.

[0015] The undercoat plating layer 12 may be a non-porous plating layer. A non-porous plating layer means a plating that is substantially free of pores. The porosity of the non-porous plating layer may be, for example, 5 volume% or less, 1 volume% or less, or 0.1 volume% or less, relative to the undercoat plating layer 12.

[0016] The Vickers hardness of the undercoat plating layer 12 may be higher than that of the main plating layer 13. Similarly, the Vickers hardness of the plating material 10 may be higher than that of the main plating layer 13. Such a plating material 10 can further improve wear resistance. Note that when the Vickers hardness of the plating material 10 is higher than that of the main plating layer 13, this is also referred to as an apparent hardness increase.

[0017] In this specification, Vickers hardness is measured in accordance with JIS Z2244-1:2020 and obtained in an environment of 25°C. In this specification, the Vickers hardness of the undercoat plating layer 12 is the Vickers hardness of the surface of the undercoat plating layer 12 measured from a direction perpendicular to the thickness direction. In this specification, the Vickers hardness of the main plating layer 13 is the Vickers hardness of the surface of the main plating layer 13 measured from a direction perpendicular to the thickness direction. These Vickers hardness values ​​can be obtained, for example, by measuring the cross-section of the undercoat plating layer 12 or the main plating layer 13 using a microhardness tester DUH-211 manufactured by Shimadzu Corporation. However, if the thickness of the main plating layer 13 is thin, such as 2.5 μm to 5 μm, the Vickers hardness of the surface (exposed surface) of the main plating layer 13 measured from a direction perpendicular to the thickness direction may be measured with a low load of 1 gf. Furthermore, in this specification, the Vickers hardness of the plating material 10 is the Vickers hardness measured from the surface of the main plating layer 13 of the plating material 10, which comprises a base material 11, an undercoat plating layer 12, and the main plating layer 13.

[0018] The Vickers hardness of the undercoat plating layer 12 may be 200 Hv or more and 1,000 Hv or less. When the Vickers hardness of the undercoat plating layer 12 is 200 Hv or more, wear resistance can be further improved. Also, when the Vickers hardness of the undercoat plating layer 12 is 1,000 Hv or less, the flexibility of the undercoat plating layer 12 can be improved, and cracking of the undercoat plating layer 12 can be suppressed. The Vickers hardness of the undercoat plating layer 12 may be 250 Hv or more. The Vickers hardness of the undercoat plating layer 12 may be 800 Hv or less, 600 Hv or less, 400 Hv or less, or 300 Hv or less.

[0019] The undercoat plating layer 12 can be plated by known plating methods. For example, the undercoat plating layer 12 may be formed by electroplating by immersing the substrate 11 in a plating bath. When forming a nickel plating layer, a nickel plating bath can be used, and when forming a nickel alloy plating layer, a nickel alloy plating bath can be used. When forming the undercoat plating layer 12 by electroplating, the electrolytic conditions such as current density and temperature should be set after considering various factors such as productivity, plating bath composition, ion concentration, and the shape of the object to be plated.

[0020] A nickel plating bath may contain, for example, a nickel salt, a pH buffer, a brightener, etc. The nickel salt may include at least one salt selected from the group consisting of, for example, nickel sulfate, nickel chloride, and nickel sulfamate. The pH buffer may include at least one selected from the group consisting of, for example, boric acid, citric acid, and nickel acetate. The brightener may include at least one selected from the group consisting of, for example, sulfamates, saccharin, sulfonamide, sulfinic acid, naphthalene, sodium naphthalene sulfonate, and nickel acetate. A nickel alloy plating bath may contain a metal salt containing a metal in addition to the nickel plating bath. A nickel alloy plating bath may contain a metal salt containing at least one element selected from the group consisting of W, P, Zn, and Sn that co-deposits in the plating film with nickel.

[0021] (Plating layer 13) The plating layer 13 may be a silver plating layer or a silver alloy plating layer. The silver alloy plating layer may contain at least one metal selected from the group consisting of tin (Sn), copper (Cu), nickel (Ni), cobalt (Co), palladium (Pd), bismuth (Bi), indium (In), zinc (Zn), titanium (Ti), antimony (Sb), selenium (Se), and tellurium (Te). Silver alloys having these metals can be expected to have improved Vickers hardness compared to pure silver, due to smaller crystal grains or the formation of intermetallic compounds between silver and the above metals. The plating layer 13 may contain silver in amounts of, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. Alternatively, the plating layer 13 may contain silver in amounts of, for example, 100% by mass or less, 95% by mass or less, or 90% by mass or less.

[0022] The silver alloy may be a binary alloy containing two metal components, a ternary alloy containing three metal components, or an alloy containing four or more metal components. Furthermore, the plating layer 13 may be a single layer, or it may be a multi-layer structure combining a silver plating layer and a silver alloy plating layer.

[0023] The plating layer 13 may contain additive particles. The additive particles may include, for example, carbon particles, and the carbon particles may be dispersed within the plating layer 13. By including carbon particles in the plating layer 13, the wear resistance of the plating material 10 may be further improved. The carbon particle content in the plating layer 13 may be 0.1% by mass or more and 50% by mass or less. By keeping the carbon particle content within the above range, the wear resistance can be further improved. The carbon particle content in the plating layer 13 may be 1% by mass or more, 5% by mass or more, or 10% by mass or more. In addition, the carbon particle content in the plating layer 13 may be 40% by mass or less, or 30% by mass or less.

[0024] The proportion (area ratio) of carbon particles on the surface of the plating layer 13 containing carbon particles serves as an indicator of wear resistance. From the viewpoint of balancing wear resistance and conductivity, the area ratio is preferably 1 to 80 area%, more preferably 1.5 to 80 area%, and even more preferably 2 to 80 area%. The area ratio can be measured by the method described in the examples.

[0025] The shape of the added particles is not particularly limited and may be needle-shaped, rod-shaped, spherical, prismatic, plate-shaped, disc-shaped, amorphous, or a mixture thereof. The average particle diameter of the added particles may be 0.1 nm or more and 10 μm or less. The average particle diameter of the added particles may be 1 nm or more, 100 nm or more, or 1 μm or more. In addition, the average particle diameter of the added particles may be 5 μm or less, or 1 μm or less. The average particle diameter of the added particles is the average value of the equivalent circle diameter measured by cross-sectional observation with an electron microscope such as a TEM (transmission electron microscope) or SEM (scanning electron microscope).

[0026] The plating layer 13 may not contain substantially any antimony. By substantially not containing antimony in the plating layer 13, the heat resistance of the plating material 10 can be improved. It should be noted that substantially not containing antimony in the plating layer 13 means that the plating layer 13 contains less than 1% by mass of antimony. The antimony content in the plating layer 13 may be less than 1.6% by mass, less than 1% by mass, less than 0.5% by mass, less than 0.1% by mass, less than 0.05% by mass, or less than 0.01% by mass.

[0027] The thickness of the main plating layer 13 may be 2.5 μm or more. The thickness of the main plating layer 13 may be less than 2.5 μm, for example, because even if the thickness of the main plating layer 13 is less than 2.5 μm and the ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 is greater than 4, the apparent increase in hardness will not be that significant. The thickness of the main plating layer 13 may be 10 μm or more. The thicker the main plating layer 13, the longer the sliding distance until the substrate 11 is exposed due to wear. The thickness of the main plating layer 13 may be 15 μm or more, 20 μm or more, or 30 μm or more.

[0028] The thickness of the main plating layer 13 may be 40 μm or less. The thickness of the main plating layer 13 may exceed 40 μm, but even if the thickness of the main plating layer 13 exceeds 40 μm, the rate of apparent hardness increase is small. The thickness of the main plating layer 13 may be 30 μm or less, 20 μm or less, or 15 μm or less.

[0029] The ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 is 1 / 4 or more. By doing so, an apparent increase in hardness can be achieved. The ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 may be 1.3 or more. This can further increase the apparent increase in hardness and further improve wear resistance. The ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 may be 1.5 or more, 2 or more, or 2.5 or more.

[0030] The ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 may be 4 or less. Although an apparent increase in hardness can be achieved even if the ratio is greater than 4, the apparent increase in hardness is not very large even if the ratio is greater than 4. The ratio of the thickness of the base plating layer 12 to the thickness of the main plating layer 13 may be 3 or less, 2.5 or less, 2 or less, or 1.5 or less.

[0031] The Vickers hardness of the plating layer 13 may be 60 Hv or more and less than 250 Hv. If the Vickers hardness of the plating layer 13 is 60 Hv or more, wear resistance can be further improved. Also, if the Vickers hardness of the plating layer 13 is less than 250 Hv, the flexibility of the plating layer 13 can be improved, and cracking of the plating layer 13 can be suppressed. The Vickers hardness of the plating layer 13 may be less than 250 Hv, less than 200 Hv, less than 100 Hv, or less than 80 Hv.

[0032] The plating layer 13 can be plated by known plating methods. For example, the plating layer 13 may be formed by electroplating by immersing a member plated with a base plating layer 12 (substrate 11) in a plating bath. When forming a silver plating layer, a silver plating bath can be used, and when forming a silver alloy plating layer, a silver alloy plating bath can be used. When forming the plating layer 13 by electroplating, the electrolytic conditions such as current density and temperature should be set after considering various factors such as productivity, plating bath composition, ion concentration, and the shape of the object to be plated.

[0033] The silver plating bath may contain, for example, silver salts, conductivity salts, brighteners, and additive particles. Examples of materials used for the silver salts include silver cyanide, silver iodide, silver oxide, silver sulfate, silver nitrate, silver methanesulfonate, and silver chloride. The conductivity salt may contain at least one salt selected from the group consisting of, for example, potassium cyanide, sodium cyanide, potassium pyrophosphate, silver methanesulfonate, potassium iodide, and sodium thiosulfate. Examples of brighteners include metallic brighteners such as antimony, selenium, and tellurium, and organic brighteners such as benzenesulfonic acid and mercaptan. Examples of additive particles include carbon particles such as graphite, graphene, and diamond. The silver ion concentration of the silver alloy plating bath may be, for example, 30 g / L to 50 g / L.

[0034] The silver alloy plating bath may, in addition to the silver plating bath, contain, for example, a salt of at least one metal selected from the group consisting of tin (Sn), copper (Cu), nickel (Ni), cobalt (Co), palladium (Pd), bismuth (Bi), indium (In), zinc (Zn), titanium (Ti), antimony (Sb), selenium (Se), and tellurium (Te).

[0035] As described above, the plating material 10 according to this embodiment comprises a base material 11, an undercoat plating layer 12 provided on the base material 11, and a main plating layer 13 provided on the undercoat plating layer 12. The thickness of the undercoat plating layer 12 is 10 μm or more. The ratio of the thickness of the undercoat plating layer 12 to the thickness of the main plating layer 13 is 1 / 4 or more.

[0036] Therefore, according to the plating material 10 of this embodiment, wear resistance can be improved by increasing the apparent hardness. In this embodiment, an example in which an undercoat plating layer 12 and a main plating layer 13 are provided on the entire surface of the substrate 11 has been described, but it is also possible to plate only the sliding parts and leave the other parts unplated. Furthermore, as shown in Figure 1, the plating material 10 may or may not have a silver strike plating layer 14 between the undercoat plating layer 12 and the main plating layer 13 in order to ensure adhesion.

[0037] The plating material 10 according to this embodiment can be used in electrical components having electrical contacts such as connectors, switches, and terminals. Since these electrical components are repeatedly inserted and removed and subjected to sliding, the plating material 10 according to this embodiment can improve wear resistance.

[0038] The embodiment will be described in more detail below with reference to examples and comparative examples, but the embodiment is not limited to these examples.

[0039] [Preparation of Plating Material] (Preparation of Substrate) First, the metal substrate, which was a C1020-H copper plate, was pretreated. Specifically, the metal substrate was washed with alkaline degreasing, then pickled by immersion in 10% methanesulfonic acid for 2 minutes, and finally rinsed with water.

[0040] (Undercoat Plating Layer) Next, a nickel plating layer was formed as an undercoat plating layer over the entire surface of the metal substrate. Specifically, the pre-treated metal substrate was immersed in a nickel plating bath and subjected to constant current electrolysis to achieve the thickness of the undercoat plating layer shown in Table 1. After the electrolysis was completed, the metal substrate was removed from the nickel plating bath and washed with water. The composition of the nickel plating bath was 229 g / L nickel sulfate, 42 g / L nickel chloride, and 37 g / L boric acid.

[0041] (This plating layer) Next, a silver plating layer was formed as this plating layer on the entire surface of the undercoat plating layer. Specifically, the metal substrate on which the nickel plating layer was formed was immersed in a silver plating bath and subjected to constant current electrolysis so as to have the thickness of this plating layer described in Table 1. The composition of the silver plating bath was 5.5 g / L of silver methanesulfonate and 60 g / L of free methanesulfonic acid. As a result, a plated material including the metal substrate, the undercoat plating layer, and this plating layer was obtained.

[0042] [Evaluation] The Vickers hardness of the plated material produced as described above was measured, and a pin-on-disk wear test was carried out.

[0043] (Vickers hardness) Using a microhardness tester DUH-211 manufactured by Shimadzu Corporation, the Vickers hardness of the plated material measured from the surface of this plating layer was measured at the load described in Table 1 in an environment of 25°C in accordance with JIS Z2244-1:2020. That is, the Vickers hardness of the plated material was measured for Example 1 and Example 2, and the Vickers hardness of this plating layer was measured for Comparative Example 1 and Comparative Example 2.

[0044] (Pin-on-disk wear test) Based on the mud and salt water insertion and extraction test according to UL2251, as shown in Figure 2, a pin-on-disk wear test was carried out. Specifically, first, the undercoat plating layer and this plating layer were formed on the surface of a cylindrical copper material (C1100-H) with a diameter of 4 mm to produce a cylindrical evaluation sample 21. Next, a water-resistant abrasive paper 23 was installed on the turntable 22 of an IS-POLISHER manufactured by Ikegami Seiki Co., Ltd. The water-resistant abrasive paper 23 having a particle size #2500 defined in JIS R6010 and adjusted so that the surface roughness Ra was 0.5 μm or less was used.

[0045] Then, the evaluation sample 21 was pressed against the polishing surface of the water-resistant abrasive paper 23 with a load of 200 gf, and while flowing a 5 mass% sodium chloride aqueous solution over the water-resistant abrasive paper 23, the turntable 22 was rotated at a speed of 1.65 rps to carry out the pin-on-disk wear test. The wear test was carried out until the sliding distance described in Table 1 was reached, and the wear depth of the sample was confirmed after the wear test.

[0046]

[0047] As shown in Table 1, it was found that Example 1 having an undercoat plating layer had a higher Vickers hardness and higher wear resistance than Comparative Example 1 without an undercoat plating layer. Similarly, it was found that Example 2 having an undercoat plating layer had a higher Vickers hardness and higher wear resistance than Comparative Example 2 without an undercoat plating layer. From these results, it was found that by providing an undercoat plating layer, an apparent increase in hardness occurs such that the Vickers hardness of the plating material becomes higher than the Vickers hardness of this plating layer.

[0048] Incidentally, the water-resistant abrasive paper 23 for the wear test was obtained by taking out a metal terminal immersed in a muddy brine containing 5% by mass of Arizona sand coarse, 5% by mass of sodium chloride, and 90% by mass of pure water as defined in ISO 12103-1, and selecting an abrasive paper having a particle size distribution close to that of the Arizona sand adhering to the metal terminal. The results of measuring the Arizona sand adhering to the metal terminal using a particle size measuring device LA-950V2 manufactured by Horiba, Ltd. are shown in FIG. 3. From the particle size distribution in FIG. 3, since the most frequent value of the particle size is 10 μm, it can be seen that by making the undercoat plating layer 10 μm or more, the Arizona sand can be suppressed from reaching the base material, and the wear resistance can be improved. Also, from the particle size distribution in FIG. 3, since almost all particles are less than 50 μm, it can be seen that by making the thickness of the undercoat plating layer 60 μm or less, the Arizona sand can be sufficiently suppressed from reaching the base material, and the wear resistance can be improved.

[0049] Next, as shown in Tables 2 to 7, multiple plating materials with different plating thicknesses for the undercoat and main plating layers were prepared using the same method as described above. The Vickers hardness of the plating materials measured from the surface of the main plating layer was then measured using the same method as described above. However, the composition of the silver plating bath in the examples and comparative examples described in Tables 2 to 6 was 5.5 g / L of silver methanesulfonate and 60 g / L of free methanesulfonic acid. In addition, the silver plating bath in the examples and comparative examples described in Table 7 was a silver cyanide bath. The antimony content in the main plating layer of the examples and comparative examples described in Table 7 was 0.5% by mass or more and less than 1.6% by mass. The measurement results at loads of 100 gf, 200 gf, 300 gf, 500 gf, and 1000 gf are shown in Tables 2 to 7, respectively. Note that the Vickers hardness of Examples 3 to 46 and Comparative Examples 4, 6, 8, 10, and 12 refers to the Vickers hardness of the plating material. Furthermore, the Vickers hardness values ​​for Comparative Examples 3, 5, 7, 9, 11, and 13 represent the Vickers hardness of the present plating layer.

[0050] Furthermore, in Tables 2 to 7, the apparent hardness increase is the difference in hardness between the Vickers hardness of the plating layer and the Vickers hardness of the plating material at the same load. Specifically, as shown in Table 2, at a load of 100 gf, the hardness difference is the hardness difference compared to each example based on Comparative Example 3. As shown in Table 3, at a load of 200 gf, the hardness difference is the hardness difference compared to each example based on Comparative Example 5. As shown in Table 4, at a load of 300 gf, the hardness difference is the hardness difference compared to each example based on Comparative Example 7. As shown in Table 5, at a load of 500 gf, the hardness difference is the hardness difference compared to each example based on Comparative Example 9. As shown in Table 6, at a load of 1000 gf, the hardness difference is the hardness difference compared to each example based on Comparative Example 11. As shown in Table 7, in the cases of Examples 40 to 46, the hardness difference is the hardness difference based on Comparative Example 13.

[0051] Furthermore, for the first reference plated material prepared by forming the above-mentioned undercoat plating layer with a thickness of 10 μm on the above-mentioned substrate, the Vickers hardness of the undercoat plating layer was measured at room temperature with a load of 100 gf and was found to be 250 Hv. In addition, for Examples 3 and 4, the Vickers hardness of the undercoat plating layer measured from a direction perpendicular to the thickness direction with a load of 0.5 gf was approximately the same as the Vickers hardness of the first reference plated material. Also, for Examples 3 and 4, the Vickers hardness of the exposed surface of the main plating layer measured from the thickness direction with a load of 0.5 gf was approximately the same as the Vickers hardness listed in Table 2 for the plated material of Comparative Example 3. Furthermore, the Vickers hardness of the main plating layer of Example 5 measured from a direction perpendicular to the thickness direction with a load of 0.5 gf was approximately the same as the Vickers hardness listed in Table 2 for the plated material of Comparative Example 3.

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058] As shown in Tables 2 to 7, it was confirmed that an apparent increase in hardness occurs when the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer (thickness ratio) is 1 / 4 or more. From the test results in Table 1, it can be seen that wear resistance improves when the Vickers hardness increases, and therefore wear resistance improves when the thickness ratio is 1 / 4 or more.

[0059] Furthermore, as shown in Figure 4, increasing the thickness ratio tends to increase the apparent hardness, but beyond a thickness ratio of 4, increasing the thickness ratio does not significantly change the apparent hardness. Therefore, it can be seen that the thickness ratio at which the effect of relatively increasing the apparent hardness with respect to the thickness ratio is obtained is 4 or less.

[0060] Furthermore, as shown in Figure 5, the relationship between the thickness of the plating layer and the apparent hardness increase shows that when the thickness of the plating layer is 40 μm or more, the apparent hardness increase is small. For example, as shown in Figure 5, when the thickness of the plating layer is 50 μm, the apparent hardness increase is +2 Hv. Therefore, it can be seen that a greater effect of apparent hardness increase is obtained when the thickness of the plating layer is 40 μm or less.

[0061] Furthermore, for abrasive wear in which hard particles such as Arizona sand are interposed in the plated portion that is the wear area, the Rabinowicz model is known, as shown in the following equation (1) and Figure 6.

[0062] V = 2kWL / πH tanθ (1) In the above formula (1), V is the wear volume, k is the coefficient, W is the load, L is the sliding distance, H is the hardness of the plating, and θ is the angle formed by the inclined portion of the tip of the hard particle protrusion and the perpendicular line passing through the tip of the protrusion.

[0063] From the above formula (1), since the wear volume is inversely proportional to the hardness of the plating material, doubling the hardness of the plating material can reduce the wear volume by 50%. Here, the Vickers hardness of the plating material in Comparative Example 3 is 69 Hv, so in order to halve the wear volume of the plating material in Comparative Example 3, the Vickers hardness should be 138 Hv. In other words, from Figure 7, it can be seen that if the thickness ratio is set to 1.3 or more so that the apparent hardness increase (hardness difference) is 69 Hv or more, it may be possible to halve the wear volume of the plating material in Comparative Example 3. The thicker the underplating layer, the better the wear resistance, but anything exceeding 60 μm is not practical from the standpoint of cost or time.

[0064] Next, the wear resistance of the main plating layer with added graphite particles was evaluated. First, the undercoat plating layer and the main plating layer were formed on the entire surface of the metal substrate, which had been pre-treated in the same manner as in the above example, so that the thickness of each layer was as shown in Table 8.

[0065]

[0066] However, the nickel plating bath used had a composition of 342 g / L nickel sulfamate (80 g / L Ni concentration) and 45 g / L boric acid. Furthermore, a sulfonic acid-based Ag strike plating solution (Dynesilver GPE-ST manufactured by Yamato Kasei Co., Ltd.) was used for this plating layer, with a current density of 5 A / dm². ２ After electroplating (Ag strike plating) for 90 seconds, silver-graphite composite plating was performed to achieve the plating thickness shown in Table 8. For the plating solution, a sulfonic acid-based silver plating solution containing 50 g / L of artificial graphite particles and 30 g / L of Ag was prepared by adding oxidized artificial graphite particles with an average particle size of 5 μm (PAG-3000 manufactured by Nippon Graphite Industry Co., Ltd.) to a sulfonic acid-based silver plating solution with an Ag concentration of 30 g / L (Dyne Silver GPE-PL manufactured by Yamato Kasei Co., Ltd.). For the oxidation treatment of the artificial graphite particles, first, 6% by weight of artificial graphite particles was added to 3 L of pure water, and this mixed solution was heated to 50°C while stirring. Next, 1.2 L of 0.1 mol / L potassium persulfate aqueous solution was gradually added dropwise to this mixed solution as an oxidizing agent, and the solution was stirred for 2 hours to perform the oxidation treatment. After that, the solution was filtered using filter paper and washed with water. The plating conditions were: stirring speed 250 rpm, current density 3 A / dm ２ The plated surface was then ultrasonically cleaned at 28 kHz for 4 minutes to remove the graphite.

[0067] Next, the carbon area ratio of the surface of the plated layer prepared as described above was measured. The carbon area ratio of the surface of the plated layer was measured as follows: Using a desktop microscope (TM4000 Plus manufactured by Hitachi High-Tech Corporation), the surface of the plated layer was observed at an acceleration voltage of 5 kV and magnified 1000 times. The backscattered electron composition (COMPO) image (1 field of view) was binarized using GIMP 2.10.10 (image analysis software), and the area ratio occupied by carbon on the surface of the plated layer was calculated. Specifically, assuming that the highest brightness of all pixels was 255 and the lowest brightness was 0, the gradation was binarized so that pixels with a brightness of 127 or less were black and pixels with a brightness greater than 127 were white. The image was then separated into silver parts (white parts) and carbon particle parts (black parts), and the ratio Y / X of the number of pixels in the carbon particle part to the total number of pixels X in the image was calculated as the carbon area ratio (%) of the surface. As a result, the carbon area ratio of the surface of the plated layer was 38%.

[0068] Furthermore, a pin-on-disk abrasion test was conducted on the plated material prepared as described above, except that water-resistant abrasive paper 23 with a grit size of #2500 was used, in the same manner as described above. The results are shown in Figures 8 and 9.

[0069] As shown in Figures 8 and 9, the plating materials of Examples 47 and 48 showed smaller wear depth values ​​compared to the plating materials of Comparative Examples 14 and 15. These results confirm that it is possible to improve wear resistance even when the plating layer contains carbon particles.

[0070] The entire contents of Japanese Patent Application No. 2024-167333 (filing date: September 26, 2024) and Japanese Patent Application No. 2025-148967 (filing date: September 9, 2025) are incorporated herein by reference.

[0071] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0072] 10 Plating material 11 Substrate 12 Undercoat plating layer 13 Main plating layer

Claims

1. A plating material comprising: a base material; an undercoat plating layer provided on the base material; and a main plating layer provided on the undercoat plating layer, wherein the thickness of the undercoat plating layer is 10 μm or more, and the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer is 1 / 4 or more.

2. The plating material according to claim 1, wherein the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer is 4 or less, and the thickness of the main plating layer is 2.5 μm or more.

3. The plating material according to claim 1 or 2, wherein the thickness of the main plating layer is 10 μm or more and 40 μm or less.

4. The plating material according to any one of claims 1 to 3, wherein the thickness of the undercoat plating layer is 60 μm or less.

5. The plating material according to any one of claims 1 to 4, wherein the ratio of the thickness of the undercoat plating layer to the thickness of the main plating layer is 1.3 or more.

6. The plating material according to any one of claims 1 to 5, wherein the Vickers hardness of the undercoat plating layer is higher than that of the main plating layer.

7. The plating material according to any one of claims 1 to 6, wherein the undercoat plating layer is a nickel plating layer or a nickel alloy plating layer, the Vickers hardness of the undercoat plating layer is 250 Hv or more and 1,000 Hv or less, and the main plating layer is a silver plating layer or a silver alloy plating layer, the Vickers hardness of the main plating layer is 60 Hv or more and less than 250 Hv.

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