JP7391356B2 - Multilayer material and its manufacturing method, multilayer material plating method - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Publication date: September 5, 2018 Publication: Japan Institute of Metals 2018 Autumn Lecture (163rd) Conference Program, Venue B, J31 [Publications] Held Date: September 19, 2018 Meeting name: Japan Institute of Metals 2018 Autumn Lecture (163rd) Conference Venue: Tohoku University Kawauchi Kita Campus (41 Kawauchi, Aoba-ku, Sendai City)

The present invention relates to a multilayer material that is a composite material with improved mechanical strength by alternately laminating Ni--W layers or Ni--P layers and Ni layers, and a method for manufacturing the same. The present invention also relates to a plating method for plating a base material with a multilayer material in which Ni--W layers or Ni--P layers and Ni layers are alternately laminated.

Fine holes or thin tubes used as metal nozzles or transfer pipes that inject various fluids and control the form of the fluids are made of various materials such as stainless steel and high-strength alloy steel. Although the fluid has high mechanical strength, if the fluid is a molten resin, it has high reactivity with the member and is subject to severe wear due to corrosion. The same applies when injecting acidic fluid. Additionally, fluids such as muddy water cause severe mechanical wear.

In order to improve these drawbacks, there is a need to form a metal or alloy coating having excellent properties such as high abrasion resistance, high corrosion resistance, and high heat resistance on the inner wall surface of the nozzle. Such coating materials are also required to have high adhesion. In electroless plating, there is no metal with high wear resistance and high adhesion. Fortunately, several years ago, the present inventor developed an ideal nanocrystalline nickel-tungsten (Ni-W) alloy coating material that satisfies all of the above characteristics using an electrolytic deposition method.

Nanocrystalline single-phase materials and amorphous single-phase materials are generally extremely hard and are known to be destroyed brittlely without work hardening during plastic deformation (Non-patent Document 1). ). The present inventors have developed a Ni-W alloy that exhibits a tensile strength of approximately 2 to 3 GPa using an electrolytic deposition method, and have found that the structure can be changed by controlling the W content of this alloy. It is known (Non-patent Documents 2 and 3). Nanocrystalline single-phase Ni-W alloys and amorphous single-phase Ni-W alloys produced by the methods of Non-Patent Documents 2 and 3 show brittle fracture as before.

On the other hand, the present inventors found that a Ni-W alloy prepared with a W content of approximately 14 to 20 at% has a nanocrystalline/amorphous composite structure and has a plastic elongation exceeding 5%. It has also been confirmed that

Japanese Patent Application Publication No. 2001-342591

J. R. Trelewicz, C. A. Schuh: Acta Materialia, 55 (2007), 5948-5958 I. Matsui, Y. Takigawa, T. Uesugi, K. Higashi: Materials Letters, 99 (2013), 65-67 Toru Yamazaki: Surface Technology, Vol.55 No.4 (2004), 242-247

The electrolytically deposited Ni-W alloy has a nanocrystalline/amorphous composite structure and exhibits high tensile strength of approximately 2 to 3 GPa and high plastic elongation of over 5%. However, the nanocrystalline single phase and the amorphous single phase are extremely hard and are brittlely destroyed without undergoing work hardening during plastic deformation. It has also been confirmed that Ni-W alloys having a nanocrystalline/amorphous composite structure also exhibit volume reduction (shrinkage) during storage at room temperature, resulting in a decrease in ductility and progression of embrittlement.

Figure 1 shows the results of measuring the relationship between the nominal strain and nominal stress of a Ni-W alloy sample immediately after fabrication and after storage at room temperature for 2 years. The Ni-W alloy sample is the same as the tensile test piece of the Ni-W single layer material described below, and the measurement method of the nominal strain and stress is the same as the tensile test described below. Immediately after fabrication (immediately after manufacture), the Ni-W alloy sample fractured at a nominal strain exceeding 6%, but after being stored at room temperature for 2 years after fabrication, the Ni-W alloy sample reached a nominal strain of 3%. It broke before I could do it. That is, the Ni-W alloy sample after being stored at room temperature for two years has significantly lower ductility than the Ni-W alloy sample immediately after fabrication.

FIG. 2 shows a conceptual diagram explaining the principle of embrittlement of Ni-W alloy. Ni-W alloy has a nanocrystalline/amorphous composite structure. Immediately after fabrication, the Ni-W alloy has a large free volume in the amorphous portion, but after aging, the free volume in the amorphous portion decreases, making it difficult for metal atoms to move. As a result, crystal growth does not occur at the nanocrystal/amorphous interface, resulting in shrinkage and embrittlement.

The present inventors have conducted extensive studies on means to suppress the embrittlement that occurs over time in Ni-W alloys. As a result, by alternately laminating multiple electrolytically deposited Ni layers with a smaller amount of shrinkage than the Ni-W alloy and electrolytically deposited Ni-W alloy layers at a specific thickness, the Ni-W It has been found that shrinkage of the layer can be suppressed. In addition, the present inventors also developed a Ni-P alloy at the interface by stacking multiple layers alternately with electrolytically deposited Ni at a specific thickness for a Ni-P alloy that has physical properties similar to the Ni-W alloy. The present inventors have discovered that the shrinkage of can be suppressed, and have completed the present invention.

Specifically, the present invention includes:
Ni layers and Ni-W layers or Ni-P layers are stacked alternately,
The thickness of each layer of the Ni layer and the Ni-W layer or the Ni-P layer is 0.75 μm or more and 2 μm or less,
Regarding multilayer materials.

Although Ni-W alloy has high strength, it shrinks and becomes brittle over time even at room temperature. On the other hand, Ni has low shrinkage and high ductility. By adjusting the thickness of each Ni layer and Ni-W layer to 0.75 μm or more and 2 μm or less, and stacking multiple layers alternately, shrinkage of the Ni-W layer over time is suppressed, resulting in high strength and Can function as a highly ductile multilayer material. In addition, the Ni-P alloy has similar physical properties to the Ni-W alloy, and the thickness of each Ni layer and Ni-W layer is adjusted to 0.75 μm or more and 2 μm or less, and multiple layers are alternately layered. By stacking, the shrinkage of the Ni-W layer over time is suppressed, allowing it to function as a high-strength, high-ductility multilayer material.

The proportion of W in the Ni-W layer or the proportion of P in the Ni-P layer is preferably 15 atomic % or more and 20 atomic % or less.

The present invention also provides
a step (a) of depositing a Ni layer on the base material by electrolytic deposition;
A step (b1) of depositing a Ni-W layer or a step (b2) of depositing a Ni-P layer on the base material by electrolytic deposition,
(c) dissolving the base material;
Alternately repeating the step (a) and the step (b1) or the step (b2),
The thickness of the Ni layer formed in the step (a) is 0.75 μm or more and 2 μm or less,
The thickness of the Ni-W layer formed in the step (b1) or the Ni-P layer formed in the step (b2) is 0.75 μm or more and 2 μm or less, respectively.
The present invention relates to a method for manufacturing a multilayer material, characterized in that:

The present invention further includes:
a step (a) of depositing a Ni layer on the base material by electrolytic deposition;
A step (b1) of depositing a Ni-W layer on a base material by an electrolytic deposition method or a step (b2) of depositing a Ni-P layer,
Alternately repeating the step (a) and the step (b1) or the step (b2),
The thickness of the Ni layer formed in the step (a) is 0.75 μm or more and 2 μm or less,
The thickness of the Ni-W layer formed in the step (b1) or the Ni-P layer formed in the step (b2) is 0.75 μm or more and 2 μm or less, respectively.
The present invention relates to a multilayer material plating method characterized by the following.

The multilayer material manufacturing method and multilayer material plating method of the present invention include:
The proportion of W in the Ni-W layer formed in the step (b1) or the proportion of P in the Ni-P layer formed in the step (b2) may be 15 atomic % or more and 20 atomic % or less. preferable.

According to the present invention, shrinkage over time that occurs in Ni-W alloys or Ni-P alloys can be suppressed, and multilayer materials and multilayer material plating with high strength and high ductility can be obtained.

The results of measuring the relationship between the nominal strain and nominal stress of Ni-W alloy samples immediately after fabrication and after storage at room temperature for 2 years are shown. A conceptual diagram explaining the principle of embrittlement of Ni-W alloy is shown. (a) shows the pattern of the photomask used, and (b) shows the shape of the tensile test piece. This is a scanning electron micrograph of a cross section of a tensile test piece in which 24 Ni layers and 24 Ni-W layers were laminated. The stress-strain curve of the tensile test piece immediately after fabrication is shown. An electron micrograph of the fracture surface of the tensile test piece after the completion of the fracture test is shown. The stress-strain curves of the Ni-W single layer material and Ni single layer material tensile test specimens are shown after being stored at room temperature for 1 week and 1 month. It is an electron micrograph showing the change in the fracture surface of a tensile test piece (single layer material) after completion of the fracture test. It is a graph showing changes in the stress-strain curve of a tensile test piece that is a multilayer material. It is an electron micrograph showing the change in the fracture surface of a tensile test piece (multilayer material) after the completion of the fracture test. A conceptual diagram illustrating the peak separation of Ni-W and Ni in the Ni/Ni-W multilayer material is shown. A schematic diagram of the measurement section of the TMA measurement device is shown. The measurement results of thermomechanical analysis are shown. The amount of thermal shrinkage of Ni single-layer material (coarse-grained Ni) and Ni-W single-layer material during isothermal holding period at 317 °C for 110 minutes is shown. The amount of thermal shrinkage of three types of single-layer materials and three types of laminated materials in the isothermal holding period at 317 °C for 110 minutes is shown. A graph plotting the relationship between the thickness per layer and plastic strain of a Ni/Ni-W multilayer material is shown. A conceptual diagram of embrittlement suppression in Ni/Ni-W multilayer materials is shown.

Embodiments of the present invention will be described below with reference to the drawings as appropriate. The present invention is not limited to the following description.

[Example of fabrication of Ni/Ni-W multilayer material]
A test sample in the form of a tensile test piece was prepared using photolithography technology according to the following procedure. The Ni-W alloy was fabricated under conditions such that it had a nanocrystalline/amorphous two-phase mixed structure, and the alloy composition was found to be Ni-16.9 at% by EPMA analysis. Ni plating was made using Watt bath Ni, which allows for the preparation of high-strength samples. Table 1 shows the bath composition and electrodeposition conditions for Ni-W alloy plating, and Table 2 shows the bath composition and electrodeposition conditions for Watt bath Ni plating.

Using photolithography technology, a Ni-W alloy layer and a pure Ni layer are formed by electrolytic deposition into the shape of a tensile test piece on a Cu substrate. A chromium (VI) saturated solution + concentrated sulfuric acid) was used to dissolve the material, and a laminate of Ni layer/Ni-W layer, which was an electrolytic deposit, was obtained. FIG. 3 shows the pattern of the photomask used and the shape of the tensile test piece.

FIG. 4 shows a scanning electron micrograph of a cross section of a tensile test piece in which 24 Ni layers and 24 Ni-W layers were laminated (48 layers in total, each layer having a thickness of 0.33 μm). In FIG. 4, the layer that appears bright is the Ni layer. As shown in FIG. 4, there were no defects in the tensile test piece, and no peeling occurred at the interface between the Ni layer and the Ni-W layer.

Two types of single layer materials and three types of multilayer materials (laminated materials) shown in Table 3 were prepared as tensile test pieces. The Ni single layer material is a Ni single layer material having a nanocrystalline structure.

[Tensile test]
A tensile test was conducted at room temperature to measure the tensile strength and ductility of the five types of tensile test specimens prepared. A Shimadzu micro auto (MST-I Type HS/HR) was used for the test. The shape of the parallel part of the tensile test piece was as shown in FIG. 3(b), and the initial strain rate was 4.2×10 ⁻⁴ /sec. The plastic elongation was calculated by drawing a straight line with an inclination in the elastic deformation region from the breaking point of the stress-strain curve, and taking the intersection with the horizontal axis as the plastic elongation.

FIG. 5 shows the stress-strain curve of the tensile test piece immediately after fabrication. The tensile strength was approximately 3 GPa for the Ni-W single layer material and approximately 2 GPa for the Ni single layer material. Next, looking at the plastic elongation, the 8-layer material and the 16-layer material showed larger plastic elongation than the Ni single-layer material and the Ni-W single-layer material. On the other hand, the 48-layer material showed an intermediate elongation between the Ni-W single-layer material and the Ni single-layer material.

FIG. 6 shows an electron micrograph of the fracture surface of the tensile test piece after the fracture test. Looking at the fractured surface of the Ni-W layer, it was confirmed that the dimple pattern was finer in the multilayer material compared to the single layer material, and the ductility was improved due to the effect of multilayering. It was also confirmed that the fracture in the multilayer material was not caused by interfacial peeling of the layers. This is consistent with the stress-strain curve results shown in FIG.

FIG. 7 shows the stress-strain curves of the Ni-W single layer material and Ni single layer material tensile test specimens after storage for one week and one month at room temperature. It was confirmed that the tensile test piece after storage at room temperature had lower ductility and became brittle compared to the tensile test piece immediately after preparation.

FIG. 8 is an electron micrograph showing changes in the fracture surfaces of the tensile test pieces (Ni-W single layer material and Ni single layer material) after the completion of the fracture test. No significant difference was observed in the fracture surface of the Ni single-layer material. On the other hand, after one month of storage at room temperature, the Ni-W single-layer material was confirmed to have become brittle, with the number and depth of dimples decreasing compared to immediately after fabrication.

FIG. 9 is a graph showing changes in the stress-strain curve of a tensile test piece that is a multilayer material. The 8-layer material and the 16-layer material maintained approximately 2% plastic elongation even after being stored at room temperature for one month. Regarding the 48-layer material, there was little plastic elongation and no significant change over time was observed.

FIG. 10 is an electron micrograph showing changes in the fracture surface of the tensile test piece (multilayer material) after the fracture test. From FIG. 10, little change was observed immediately after fabrication and after one month of storage at room temperature.

[Measurement of crystal size]
In-situ XRD measurements were performed on six types of tensile test specimens, including single-layered Ni materials deposited by electrolytic deposition in a sulfamic acid bath, and the crystallite size was calculated from the X-ray profile shapes. In-situ XRD measurements were performed simultaneously with the tensile tests. The crystallite size was calculated from the (111) diffraction peak of Ni and the (111) diffraction peak of Ni-W using the Scherrer equation (Equation 1). However, since Ni-W has a nanocrystalline/amorphous composite structure, it is not accurate to express only the crystalline phase, such as (111), but this is used here for convenience.

Here, D is the crystallite size (nm), λ is the wavelength (nm), B is the half width (rad.), and θ _B is the diffraction angle (deg.). The measurements were performed at BL46XU in the large synchrotron radiation facility SPring-8, with a measurement angle of 7.7027° to 38.3841° and a beam energy of 30 keV (wavelength 0.04133 nm).

XRD measurements were performed by continuously irradiating the parallel part of the specimen with a beam in an area of 0.4 × 0.4 mm ² under the conditions of a time resolution of 2.0 sec, a measurement angle of 7.7027° to 38.3841°, and a beam energy of 30 keV (wavelength 0.04133 nm). Ta. The diffraction lines obtained at this time can be measured simultaneously over a wide range in a short time using six one-dimensional detectors, MYTHEN.

As a result of the obtained XRD measurement and tensile test, the amount of peak shift and change in half-width of the X-ray diffraction profile due to stress application were determined. Regarding the amount of peak shift, generally when tensile stress is applied to a sample, the X-ray diffraction peak shifts to the lower angle side. Then, the (hkl) lattice spacing d _hkl (nm) obtained from Bragg's equation (Equations 2 and 3) increases.

Here, the lattice strain ε _hkl was determined from Equation 4, with the lattice spacing at the time of the stress being 0 MPa as d ⁰ _hkl .

The lattice strain ε _hkl and the applied true stress were plotted. Analysis of this measurement result was performed on the (111) peaks of Ni-W and the (111) and (200) peaks of Ni. However, for the Ni/Ni-W laminate, the diffraction peaks are located close to each other and require separation, so peak separation was performed as shown in FIG. 11. That is, since the diffraction peak of the (111) plane has the highest intensity for both Ni and Ni-W, these two peaks were separated and the peak position and half-value width were determined. At this time, since Ni-W contains an amorphous phase, the expression (111) plane is originally not accurate, but for convenience, it is referred to as (111) plane.

The crystallite size of Ni and Ni-W in the single-layer material and the multi-layer material was calculated from the diffraction peak position and half-value width obtained from the XRD measurement results using the Scherrer equation (Equation 1). Table 4 shows the measurement results of crystallite size of five types of tensile test specimens. From Table 4, it was confirmed that the Ni-W layer and the Ni layer have similar structures regardless of whether the material is a single-layer material or a multi-layer material.

[Thermomechanical analysis]
In order to investigate the amount of shrinkage due to free volume reduction of Ni-W single-layer materials, Ni single-layer materials, and Ni/Ni-W multilayer materials, we used a thermomechanical analyzer (TMA analyzer/Rigaku TMA8310) to Displacement (deformation of the sample) during high temperature holding under stress was measured. FIG. 12 shows a schematic diagram of the measurement section of the TMA measurement device. Here, a tensile test piece was attached as a sample, and the tensile load was 1.96 MPa. The temperature was set at a heating rate of 10 K/min to approximately 300 °C, held for 2 hours, and then air cooled to room temperature. However, when the set temperature was set to 300 °C, the temperature during isothermal holding was 317 °C.

FIG. 13 shows the measurement results of TMA analysis. As a reference sample, a coarse-grained Ni single-layer material prepared from a sulfamic acid bath was also measured. Normal materials expand as the temperature rises, expand slightly during isothermal maintenance, and return to a value slightly larger than 0 when cooled. The fine-grained Ni single-layer material prepared by the Watt bath showed a shrinkage of about 20 μm, and the Ni-W single-layer material showed a large shrinkage of about 30 μm. Additionally, three types of multilayer materials also experienced shrinkage.

For easier comparison, the measurement results of this TMA analysis were compared using data from 10 minutes after the temperature reached 300°C to 110 minutes. In this way, it is possible to correct slight deviations in expansion and contraction caused by the timing of temperature rise and cooling, and it is expected that high-speed test results with simulated changes over time will be obtained. Figure 14 shows the amount of thermal shrinkage of the Ni single layer material (coarse grained Ni, sulfamic acid bath) and the Ni-W single layer material in the isothermal holding period at 317°C for 110 minutes. In the case of common metal materials such as coarse-grained Ni single-layer materials, there was almost no displacement during the isothermal holding period of TMA. On the other hand, the Ni-W single layer material immediately after fabrication showed a large shrinkage of about 0.05%. Furthermore, after 4 months had elapsed, the amount of shrinkage in the Ni-W single layer material was smaller than that immediately after fabrication. This confirmed that the Ni-W single-layer material contracts even at room temperature.

Figure 15 shows the amount of thermal shrinkage of three types of single-layer materials and three types of laminated materials in the isothermal holding period at 317°C for 110 minutes. During isothermal holding, the fine-grained Ni single-layer material showed a shrinkage of about 0.02%, but the Ni-W single-layer material showed a large shrinkage of about 0.05%. On the other hand, the Ni/Ni-W multilayer material exhibits a shrinkage amount intermediate to that of the single-layer material, with the 8-layer material showing approximately 0.045%, the 16-layer material approximately 0.035%, and the 48-layer material approximately 0.03%. The amount of shrinkage decreased as the thickness around the area became thinner. From this, the single-layer fine-grained Ni material and the single-layer Ni-W material exhibit shrinkage when used alone, but since the amount of shrinkage of the fine-grained Ni material is smaller than that of Ni-W, the Ni/Ni-W multilayer material exhibits shrinkage. In the material, it was considered that the shrinkage of the Ni-W layer was suppressed by the Ni layer. In addition, it was suggested that in Ni/Ni-W multilayer materials, the shrinkage suppression effect increases as the number of layers increases (decreases the thickness per layer).

FIG. 16 shows a graph plotting the relationship between the thickness per layer of the Ni/Ni-W multilayer material and the plastic elongation and TMA shrinkage. TMA analysis shows that in multilayer materials, shrinkage due to aging can be suppressed by decreasing the thickness of each layer, but in tensile tests, the largest plastic elongation was observed when the thickness of each layer was 1 μm. It was done. Therefore, in order to suppress embrittlement due to aging and exhibit good plastic elongation, the thickness of the multilayer material is preferably 0.75 μm or more and 2 μm or less per layer, and 0.85 μm or more and 1.3 μm or less. It was determined that the following is more preferable.

The multilayer material of the present invention has two or more stacked Ni layers and Ni-W layers or Ni-P layers. In the case of a cylindrical member that can be balanced even if residual stress occurs, it is sufficient to laminate two or more layers in total for the entire multilayer material, but in the case of a planar member, a total of three or more layers may be laminated. It is preferable that From the viewpoint of the generation of residual stress during electrodeposition, it is practical that the number of laminated layers in the entire multilayer material is 50 or less.

When three or more Ni-W layers or Ni-P layers are laminated as a whole, the outermost layer (surface layer) may be the Ni-W layer or the Ni-P layer.

In the present invention, the Ni layer is not limited to a Ni layer composed only of Ni, but may be a Ni layer hardened by adding a trace amount of B.P. Such a hardened Ni layer, if it maintains a face-centered cubic close-packed atomic structure, will not react well in a heated atmosphere, as in the case of a Ni layer composed only of Ni. Since there is no volumetric shrinkage, it has the same effect as a Ni layer made of only Ni.

FIG. 17 shows a conceptual diagram of embrittlement suppression in Ni/Ni-W multilayer materials. The Ni-W layer shrinks over time due to the decrease in free volume in the amorphous phase over time. Since the Ni layer is a fine-grained material produced by electrolytic deposition, the grain boundaries are non-equilibrium grain boundaries, which tend to become balanced over time. At that time, it is thought that the free volume in the non-equilibrium grain boundaries is lost and shrinkage occurs. Both the Ni layer and the Ni-W layer shrink over time at room temperature, but since the amount of shrinkage of the Ni layer is small, less than half of the amount of shrinkage of the Ni-W layer, Ni/Ni-W multilayer materials It is thought that the Ni layer suppresses the shrinkage of the Ni-W layer. In this case, it is predicted that tensile residual stress is applied to the Ni-W layer and compressive residual stress is applied to the Ni layer.

In this specification, a Ni-W alloy layer and a pure Ni layer are formed by electrolytic deposition into the shape of a tensile test piece on a Cu substrate using photolithography technology, and then the substrate (base material) is formed. Cu was dissolved by acid. However, if the base material is not removed, it can be used as a plated product plated with a multilayer material.

In this specification, an example of the production of a Ni/Ni-W multilayer material has been described, but like the Ni-W alloy, the Ni-P alloy has an amorphous single-layer structure, a nanocrystalline single-layer structure, or an amorphous and nanocrystalline structure. It is assumed that the same experimental results as the Ni/Ni-W laminate will be obtained for the Ni/Ni-P laminate.

The multilayer material, its manufacturing method, and the multilayer material plating method of the present invention are applicable to the field of metals, metallurgy, and the formation of high-strength and highly durable surface coatings, high-strength nanometal molds, and microstructure members that take advantage of excellent spring properties. It is useful in technical fields such as development.

Claims (8)

Ni layers and Ni-W layers or only Ni-P layers are stacked alternately,
The thickness of each layer of the Ni layer and the Ni-W layer or the Ni-P layer is 0.75 μm or more and 2 μm or less,
The number of laminated Ni layers and Ni-W layers or Ni-P layers is 3 or more and 50 or less,
Multilayer material. The proportion of W in the Ni-W layer or the proportion of P in the Ni-P layer is 15 atomic % or more and 20 atomic % or less,
Multilayer material according to claim 1. The outermost layer is a Ni-W layer or a Ni-P layer,
The multilayer material according to claim 1 or 2. a step (a) of depositing a Ni layer on the base material by electrolytic deposition;
A step (b1) of depositing a Ni-W layer or a step (b2) of depositing a Ni-P layer on the base material by electrolytic deposition,
(c) dissolving the base material;
Alternately repeating the step (a) and the step (b1) or the step (b2),
The thickness of the Ni layer formed in the step (a) is 0.75 μm or more and 2 μm or less,
The thickness of the Ni-W layer formed in the step (b1) or the Ni-P layer formed in the step (b2) is 0.75 μm or more and 2 μm or less, respectively.
A method for manufacturing a multilayer material, characterized by: The proportion of W in the Ni-W layer formed in the step (b1) or the proportion of P in the Ni-P layer formed in the step (b2) is 15 atomic % or more and 20 atomic % or less,
A method for manufacturing a multilayer material according to claim 4 . a step (a) of depositing a Ni layer on the base material by electrolytic deposition;
A step (b1) of depositing a Ni-W layer on a base material by an electrolytic deposition method or a step (b2) of depositing a Ni-P layer,
Alternately repeating the step (a) and the step (b1) or only the step (b2),
The thickness of the Ni layer formed in the step (a) is 0.75 μm or more and 2 μm or less,
The thickness of the Ni-W layer formed in the step (b1) or the Ni-P layer formed in the step (b2) is 0.75 μm or more and 2 μm or less, respectively,
A multilayer material plating method characterized in that the number of stacked Ni layers and Ni-W layers or Ni-P layers is 3 or more and 50 or less . The proportion of W in the Ni-W layer formed in the step (b1) or the proportion of P in the Ni-P layer formed in the step (b2) is 15 atomic % or more and 20 atomic % or less,
The multilayer material plating method according to claim 6 . The outermost layer is a Ni-W layer or a Ni-P layer,
The multilayer material plating method according to claim 6 or 7.

Images