Method for producing electroless nickel-plated component assembly and electroless nickel-plated component assembly produced thereby

Abstract

Provided is a method for producing an electroless nickel-plated component. An electroless nickel-plated layer formed on the surface of components, according to the present invention, can prevent elements in the alloy of various components exposed to high temperature environments of 600°C or higher from becoming volatile, and, due to the plated layer stably maintaining adhesiveness for an extended period of time and having high hardness and being resistant to abrasion and corrosion, can also protect the component surface in various physical and chemical environments, and thus the electroless nickel-plated layer can be widely applied to a variety of components, such as SOFCs, that are subject to high temperature conditions.

Description

Method for manufacturing an electroless nickel-plated part joint and an electroless nickel-plated part joint manufactured thereby

[0001] The present invention relates to a method for manufacturing an electroless nickel-plated part joint, and more specifically, to a method for manufacturing an electroless nickel-plated part joint and an electroless nickel-plated part joint manufactured thereby.

[0002] Electroless plating is a method in which a metal plating layer is formed on a target object through a metal oxidation-reduction reaction. Since plating is possible regardless of the shape of the product, it is used in various industrial fields.

[0003] Meanwhile, with growing concerns about the depletion of existing energy resources like oil and natural gas, and increasing demand for environmentally friendly resources, research into fuel cells is actively underway as a new alternative energy source. Fuel cells are known as an environmentally friendly energy source that utilizes the reverse reaction of water electrolysis. Various types of fuel cells are currently being developed, including phosphate fuel cells, molten carbonate fuel cells, and solid oxide fuel cells (SOFCs).

[0004] Among these, the solid oxide fuel cell (SOFC) is a fuel cell that uses a solid oxide that can transmit oxygen or hydrogen ions as an electrolyte, and operates at the highest temperature (600 to 1000℃) of the existing fuel cells. Since all components are made of solids, it has a simpler structure than other fuel cells, and there are no problems with electrolyte loss, replenishment, or corrosion. In addition, since it operates at high temperatures, it does not require a precious metal catalyst, and it is easy to supply fuel through direct internal reforming. Since it emits high-temperature gas, it is possible to generate combined heat and power using waste heat. Therefore, research and development is actively being conducted in advanced countries such as the United States and Japan.

[0005] Because solid oxide fuel cells operate at high temperatures, various components that make up the fuel cell are made of heat-resistant metals. In addition, some components are being replaced with corrosion-resistant stainless steel to prevent corrosion from the high-temperature steam generated during fuel cell operation.

[0006] Meanwhile, stainless steel contains alloying elements such as chromium to prevent surface corrosion. At high SOFC operating temperatures, chromium migrates to the surface of components and forms a chromium oxide film, thereby protecting the stainless steel surface. However, the chromium oxide film reacts with oxygen and water vapor in the high-temperature SOFC operating temperature range to form a chromium gas phase. The volatilized chromium gas phase migrates into the cathode due to the partial pressure difference that occurs during operation, ultimately poisoning the cathode and causing serious degradation of SOFC performance.

[0007] To solve these problems, research is being conducted to form an electroless nickel plating layer on the stainless steel surface to prevent poisoning by chromium volatilization on the stainless steel surface. However, the formed electroless nickel plating layer has good adhesion and bonding with the surface of the part at room temperature or relatively low temperature, but there is a problem that the adhesion and bonding rapidly decrease at the high operating temperature at which SOFC operates.

[0008] In addition, when forming an electroless nickel plating layer to prevent poisoning by chromium volatilization on a stainless steel surface, the formed plating layer may melt or peel off during a joining operation such as welding or brazing performed at a temperature of about 1000°C or higher, thereby failing to completely prevent chromium volatilization, and there is a problem in that the molten film material acts as an impurity at the joining interface, thereby hindering the joining characteristics.

[0009] Accordingly, there is an urgent need for research on an electroless nickel plating method that can prevent the elements in the alloy forming the components of various devices used under high-temperature conditions, such as SOFC, from volatilizing under high-temperature conditions, while the formed plating layer maintains excellent adhesion for a long time and has high hardness, thereby protecting the surface of the components under various physical / chemical environments, and also has excellent bonding characteristics and can ensure bonding reliability even when components requiring electroless nickel plating perform bonding operations such as welding and brazing.

[0010] The present invention has been devised in consideration of the above points, and the purpose of the present invention is to provide a method for manufacturing an electroless nickel-plated part joint, which can prevent elements in an alloy forming parts of various devices operating under high-temperature conditions, such as SOFCs, from volatilizing under high-temperature conditions, while allowing the formed plating layer to maintain stable adhesion for a long time and have high hardness, corrosion resistance, and wear resistance, thereby protecting the surface of the parts under various physical / chemical environments, and an electroless nickel-plated part joint manufactured thereby.

[0011] In addition, the present invention has another purpose of providing a method for manufacturing an electroless nickel-plated part joint, which can ensure a smooth process for assembling and joining various parts to be plated, has excellent joint properties between parts, and thus secures joint reliability that prevents gas leakage, and improves hardness, corrosion resistance, wear resistance, adhesion, etc., and an electroless nickel-plated part joint manufactured thereby.

[0012] In order to solve the above-described problem, the present invention provides a method for manufacturing an electroless nickel-plated part joint for at least two plated parts to be joined together, the method comprising the steps of: (1) performing a pretreatment process including a sandblasting process and a nickel strike plating process on each of the plated parts to be joined together; (2) forming an electrolytic nickel plating layer on the surface of each of the plated parts; (3) manufacturing a plated part joint by joining the plated parts together; (4) forming an electroless nickel plating layer on the plated part joint; and (5) performing a high-temperature heat treatment on the electroless nickel-plated part joint at a temperature of 550°C or higher.

[0013] According to one embodiment of the present invention, the pretreatment process may further include a degreasing process performed between the sandblasting process and the nickel strike plating process by immersing in a 10 to 15 wt% degreasing solution at 40 to 60°C for 1 to 10 minutes and then electrolytic degreasing for 1 to 5 minutes under a current density of 1 to 2 A / d㎡, an acid etching process performed by immersing in an etching solution mixed with a 1 to 7 wt% nitric acid solution, a 1 to 6 wt% hydrofluoric acid solution, and a 1 to 15 wt% hydrochloric acid solution for 1 to 10 minutes, and an activation process performed by immersing in a 15 to 25 wt% hydrochloric acid solution for 2 to 15 minutes.

[0014] In addition, the sandblasting process can be performed so that the center line average roughness (Ra) of the plating area is 0.8 ㎛ or more, and more preferably 0.8 to 5.0 ㎛.

[0015] In addition, the nickel strike plating process can be performed for 5 to 10 minutes at a current density of 1.5 to 5.0 A / d㎡ after immersing the plated part in a nickel strike plating solution.

[0016] In addition, step (4) is performed under an electrolytic plating solution at a temperature of 50 to 60°C and a current density of 3 to 7 A / dm. 2 (4) can be performed by immersing the plated part in an electroless nickel plating solution having a pH of 4 to 5 at a temperature of 80 to 90°C for 20 to 120 minutes.

[0017] Additionally, the joining of step (5) can be performed by one or more of welding, soldering, brazing, and diffusion bonding methods.

[0018] In addition, step (5) can perform high-temperature heat treatment at 550°C or higher for 3 to 7 hours on a cooled part after low-temperature heat treatment performed at 190 to 410°C for 1 to 9 hours.

[0019] Additionally, high-temperature heat treatment can be performed at a temperature of 600 to 700°C for 4 to 5 hours under a vacuum atmosphere.

[0020]

[0021] In addition, the present invention provides an electroless nickel plated part joint manufactured according to the present invention.

[0022] The method for manufacturing an electroless nickel-plated component joint according to the present invention prevents the elements in the alloy constituting various components from volatilizing in a high-temperature environment of 600°C or higher by forming an electroless nickel-plated layer on the surface of the component, and the formed plating layer stably maintains adhesion for a long period of time and has high hardness, wear resistance, and corrosion resistance, thereby protecting the surface of the component under various physical / chemical environments. In addition, the electrolytic nickel-plated layer formed prior to the formation of the electroless nickel-plated layer prevents the melting of the electroless nickel-plated layer during a joining process such as welding or brazing between components due to the electroless nickel-plated layer provided to prevent volatilization of elements in the alloy, and thereby prevents the interference of the joining process due to corrosion of the crystal boundaries of nickel particles, deformation, and formation of a nickel-phosphorus alloy, as well as the failure of the joining between components, so that the component joint thus realized can have excellent joining characteristics and excellent joining durability. Furthermore, the electrolytic nickel plating layer acts as an electroless plating precursor layer that facilitates the formation of an electroless nickel plating layer on the surface of a part after bonding between parts and forms it at the desired thickness level, thereby forming an electroless nickel plating layer with a uniform thickness on the surface of a part even for a part with a complex shape, thereby preventing the occurrence of dimensional differences depending on the location, and thereby being very suitable for various parts requiring airtightness and precision, and can be widely applied to parts in various devices used under high-temperature conditions such as SOFC.

[0023] Figure 1 is a cross-sectional view of an electroless nickel plated part joint according to one embodiment of the present invention.

[0024] FIG. 2 and FIG. 3 are graphs showing a photograph of the surface of a plated part and the measured surface roughness, respectively, after completing the sandblasting process as a pretreatment process of step (1) in a method for manufacturing an electroless nickel plated part joint according to one embodiment of the present invention.

[0025] FIG. 4 is a photograph of a component on which an electrolytic nickel plating layer is formed during a process for manufacturing an electroless nickel plating component joint according to one embodiment of the present invention.

[0026] FIG. 5 is a photograph after the bonding process of a component on which an electrolytic nickel plating layer is formed by a method for manufacturing an electroless nickel plating component bond according to one embodiment of the present invention.

[0027] FIGS. 6A and 6B are views of a component joint after forming an electroless nickel plating layer by a method for manufacturing an electroless nickel plating component joint according to one embodiment of the present invention. FIG. 6A is a photograph of the component joint, and FIG. 6B is a SEM-EDS analysis result for a cross-section of the component joint.

[0028] FIGS. 7a and 7b are photographs of a part after forming an electroless nickel plating layer and performing high-temperature heat treatment by a method for manufacturing an electroless nickel plating part joint according to an embodiment of the present invention. FIG. 7a is a photograph of the surface of an electroless nickel plating part subjected to high-temperature heat treatment, and FIG. 7b is a photograph after cross-cut evaluation of the surface of an electroless nickel plating part subjected to high-temperature heat treatment.

[0029] FIG. 8 is a SEM-EDS analysis result of a cross-section of a non-bonded area in a high-temperature heat-treated electroless nickel plated part joint according to one embodiment of the present invention.

[0030] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0031]

[0032] A method for manufacturing an electroless nickel-plated part joint according to one embodiment of the present invention is a method for manufacturing an electroless nickel-plated part joint for at least two plated parts to be joined together, comprising: (1) performing a pretreatment process including a sandblasting process and a nickel strike plating process on each of the plated parts to be joined together; (2) forming an electrolytic nickel plating layer on the surface of each of the plated parts; (3) manufacturing a plated part joint by joining the plated parts together; (4) forming an electroless nickel plating layer on the plated part joint; and (5) performing a high-temperature heat treatment on the electroless nickel-plated part joint at a temperature of 550°C or higher.

[0033]

[0034] First, as step (1) according to the present invention, a step of preprocessing each plated part to be mutually joined is performed.

[0035] Each of the plated parts to be mutually bonded may be a component within a known device in which electroless nickel plating and bonding between components are planned, and the present invention is not particularly limited thereto. For example, the plated parts may be various components such as various pipes, pins, plates, covers, etc. In addition, the device on which the plated parts are mounted may be, for example, a device that is exposed to a high temperature environment, for example, an environment of 600°C or higher, or an operating temperature of 600°C or higher. As a specific example, the device may be a solid oxide fuel cell, and the plated parts may be various components constituting a heat exchanger provided in the solid oxide fuel cell, and there is no limitation in size, type, shape, etc.

[0036] In addition, the material of the plated part may be a known material that can be bonded to each other and electroless nickel plated, and for example, may be a stainless steel alloy. The present invention is not particularly limited with respect to the detailed composition thereof, and for example, there is no limitation on SS310, SS304, STS304L, etc. The following description of the various steps is based on the case where the material of the plated part is stainless steel, but is not limited thereto.

[0037]

[0038] The pretreatment process for the plated part includes a sandblasting process and a nickel strike plating process, and may further include known pretreatment sub-processes performed before electroless nickel plating, such as a degreasing process, an acid etching process, and an activation process, between the sandblasting process and the nickel strike plating process.

[0039]

[0040] The sandblasting process and the nickel strike plating process performed as pretreatment processes can be combined with the high-temperature heat treatment of step (5) described below to enable the electroless nickel plating layer to maintain excellent adhesion at high temperatures. The electroless nickel plating layer formed in step (4) described below can have its hardness reduced when heat treated at a high temperature exceeding 400°C, so the heat treatment is not usually performed at a high temperature of 500 to 600°C or higher. Although the reduced hardness does not directly cause a reduction in adhesion, the reduced hardness may be undesirable as it increases the probability of causing a reduction in adhesion. However, the present invention performs electroless nickel plating on the surface on which the sandblasting process and the nickel strike plating process performed as pretreatment processes have been performed even when the high-temperature heat treatment of step (5) is performed, so that the electroless nickel plating layer formed under high-temperature usage conditions can maintain excellent adhesion for a long time. If either the sandblasting process or the nickel strike plating process is not performed during the pretreatment process, or if both the sandblasting process and the nickel strike plating process are performed as pretreatment processes but step (5) described below is not performed, or if the heat treatment is performed but the heat treatment is performed at a temperature lower than 550°C, there is a concern that partial peeling may occur after the high-temperature heat treatment in step (5), or even if there is no abnormality in appearance after the high-temperature heat treatment, the time for maintaining adhesion during use in a high-temperature environment may be shortened.

[0041]

[0042] The above sandblasting process can be performed using conventional equipment, methods, and conditions in the art. Preferably, the surface of the plated part that has undergone the sandblasting process may have a centerline average roughness (Ra) of 0.8 ㎛ or more, more preferably 0.8 to 5.0 ㎛, and even more preferably 0.8 to 2.2 ㎛. If the centerline average roughness is less than 0.8 ㎛, it may be difficult to achieve the desired level of high-temperature adhesion, etc. In addition, if the centerline average roughness exceeds 5.0 ㎛, uniform treatment may not be applied to the entire surface area during the nickel strike plating process pretreatment, and as a result, there is a concern that the adhesion may deteriorate after the high-temperature heat treatment in step (5) or the time for stably maintaining adhesion during use at high temperatures may be shortened.

[0043]

[0044] In addition, as a pretreatment process, the plated part is formed on the surface later to enhance the formability, adhesion, and durability of the electrolytic nickel plating layer, and at the same time, the electrolytic nickel plating layer formed to have these characteristics further enhances the adhesion of the electroless nickel plating layer, and by combining with the sandblasting process performed previously, the electrolytic nickel plating layer and the electroless nickel plating layer formed can have excellent adhesion even in the high-temperature heat treatment in step (5) described below and in a high-temperature usage environment. The nickel strike plating process can be performed through methods and conditions known in the art. However, it is preferable that the plated part is immersed in the nickel strike plating solution for 10 to 20 minutes and then performed at a current density of 1.5 to 5.0 A / d㎡ for 5 to 10 minutes, and through this, it can be advantageous to achieve the purpose of the present invention, and if the current density and / or performing time are exceeded during the nickel strike plating, it may be difficult to ensure high-temperature adhesion. The above nickel strike solution can be used without limitation as long as it is a nickel strike solution known to be suitable for the material of the plated part, for example, stainless steel, and specifically, it can be a mixed solution of a 120 to 240 g / l nickel chloride aqueous solution and a 65 to 125 g / l hydrochloric acid aqueous solution, or a mixed solution of 110 to 120 g / l nickel sulfate, 110 to 120 g / l nickel chloride, 10 to 20 g / l boric acid, and 10% hydrochloric acid, but is not limited thereto.

[0045]

[0046] Meanwhile, the above-described nickel strike plating process can be more preferably performed on a surface-activated plated part, and for this purpose, an activation process can be further performed between the above-described sandblasting process and the nickel strike plating process, through which nickel strike plating and electrolytic nickel plating can be smoothly performed on the surface of the plated part.

[0047] In addition, before performing the activation process, a degreasing process and an acid etching process can be further performed to remove foreign substances such as surface contamination and rust from the plated parts that have undergone the sandblasting process.

[0048] The above degreasing process is a process for removing foreign substances and oil components present on the surface of a plated part, and can be carried out in a conventional manner. The degreasing process can be carried out, for example, by immersing the plated part in a degreasing solution or by an electrolytic degreasing method in which a voltage is applied after immersion. At this time, the degreasing solution used for immersion degreasing or electrolytic degreasing is preferably to contain at least one selected from sodium carbonate, sodium hydroxide (NaOH), and a surfactant. In addition, the degreasing solution is preferably a solution containing an anionic surfactant such as ethoxylated nonylphenol. Anionic surfactants are effective in removing oil components. For example, the degreasing solution can be composed of an aqueous solution containing 80 to 150 g / L of sodium carbonate (Na2CO3), 80 to 150 g / L of sulfuric acid (H2SO4), and 2 to 7 ml / L of an anionic surfactant based on 1 liter (L) of the total degreasing solution.

[0049] In addition, during electrolytic degreasing, the plated part may be immersed in a 10 to 15 wt% degreasing solution at 40 to 60°C for 1 to 10 minutes and then electrolytic degreasing may be performed for 1 to 5 minutes under a current density of 1 to 2 A / d㎡, more preferably, immersed in a 12 to 15 wt% degreasing solution at 50 to 55°C for 3 to 5 minutes and then electrolytic degreasing may be performed for 1 to 3 minutes under a current density of 1 to 2 A / d㎡, and additionally, washing may be performed after electrolytic degreasing.

[0050]

[0051]

[0052] *Next, the acid etching process is a process for removing oxide films or smut, which is a reducing metal, formed on the surface of the plated part, and this can be performed using a conventional acid etching method. For example, the acid etching process can be performed through cleaning with an etching solution, which is an acid solution. Specifically, the etching solution may be a 1 to 7 wt% nitric acid aqueous solution, a 1 to 6 wt% hydrofluoric acid aqueous solution, a 1 to 15 wt% hydrochloric acid aqueous solution, and more preferably a 3 to 7 wt% nitric acid aqueous solution, a 3 to 6 wt% hydrofluoric acid aqueous solution, and a 10 to 15 wt% hydrochloric acid mixed in a volume ratio of 1: 0.1 to 3: 0.1 to 3.

[0053] Additionally, the acid etching process can be performed by immersing the plated part in such an etching solution for 1 to 10 minutes, more preferably 5 to 10 minutes, and, if necessary, a further washing process can be performed after immersion.

[0054] Additionally, the acid etching process can be performed at room temperature, for example, at a temperature of 20 to 25°C, but is not limited thereto.

[0055]

[0056] Next, the activation process activates the surface so that the nickel strike plating process formed on the surface of the plated part and the electrolytic nickel plating described later can be smoothly performed. An activation method known to be suitable for a specific plated part and type of plating can be used. For example, the activation process can be performed by immersing in a 15 to 30 wt% hydrochloric acid aqueous solution for 2 to 15 minutes, more preferably in a 15 to 25 wt% hydrochloric acid aqueous solution for 2 to 15 minutes, and this can advantageously achieve the purpose of the present invention. In addition, a washing process can be further performed after surface activation, if necessary. In addition, the activation process can be performed at room temperature, for example, 20 to 25°C.

[0057]

[0058] Next, as step (2) according to the present invention, a step of forming an electrolytic nickel plating layer is performed.

[0059] (2) The electrolytic nickel plating layer formed through step (3) acts as a bonding auxiliary layer that facilitates the bonding process between parts performed in step (3) and minimizes tissue damage and impurity generation in the bonded area of ​​the parts and the adjacent non-bonded area due to the bonding process, and acts as a precursor layer that facilitates and uniformly forms the electroless nickel plating layer formed in step (4) described below.

[0060] Specifically, when the joining process of step (3) described below is performed while an electrolytic nickel plating layer is formed on the surface of the part, it can prevent problems of contamination due to structural transformation, damage, and impurity generation of the alloy part caused by high heat concentrated on a certain area, and it facilitates the joining process and improves the joining quality, thereby helping to maintain excellent airtightness for a long time.

[0061] In addition, when an electroless nickel plating layer is formed directly on the surface of an alloy part and then the joining process of step (3) described later is performed, the melting phenomenon of the electroless nickel plating layer and the resulting corrosion at the grain boundaries of nickel particles, deformation, and formation of a nickel-phosphorus alloy may cause the joining process to be hindered, and the problem of poor joining between parts may occur, and the resulting poor joining of the joint of the part joint may cause fluid, for example, high-pressure flowing gas leakage and reduced joining durability. The electrolytic nickel plating layer can prevent such problems.

[0062]

[0063] For example, step (2) is a plating solution at a temperature of 50 to 60°C and a current density of 3 to 7 A / dm. 2 It can be performed for 2 to 3 minutes under the conditions of .

[0064] The electrolytic plating solution may be used without limitation in the case of a known electrolytic nickel plating solution, and preferably may contain 450 to 500 g / l of nickel sulfate, 30 to 40 g / l of nickel chloride, and 40 to 50 g / l of boric acid, and the pH of the electrolytic plating solution may be 3.9 to 4.3, thereby being advantageous in forming an electrolytic nickel plating layer having a desired thickness, excellent adhesion, and durability.

[0065] In addition, the electrolytic nickel plating process is not limited to the conventional electrolytic nickel plating process, as it can be performed by appropriately adopting the equipment, method, and conditions, for example, a temperature of 50 to 60°C and a current density of 3 to 7 A / dm. 2 It can be performed for 2 to 3 minutes under the condition of , and through this, it can be advantageous to form an electrolytic nickel plating layer having the desired thickness, excellent adhesion, and durability.

[0066] Meanwhile, even if the nickel strike plating process is performed as a pretreatment process in step (1) described above when step (2) is omitted, the electroless nickel plating layer in step (4) described below may not be formed, or even if formed, it may be difficult to form it with the desired thickness.

[0067]

[0068] Next, as step (3) according to the present invention, a step of joining parts is performed.

[0069] (3) The bonding performed in step may be a conventional bonding process performed using an appropriate temperature, method, and device considering the specific material type of the component. For example, the bonding may be performed through one or more of welding, brazing, soldering, and diffusion bonding, and a detailed description thereof is omitted in the present invention.

[0070] Meanwhile, step (3) may be performed before the formation of the electroless nickel plating layer, which is step (4) described later. This is because, as described above, when the electroless nickel plating layer is present, the phosphorus (P) component contained in the electroless nickel plating layer may be completely or partially melted by the high temperature applied in the bonding process during the bonding process, which may cause a bonding failure at the interface between parts during the bonding process and leakage of gas, etc. through the bonded portion. In addition, the electroless nickel plating layer may be damaged by the bonding process, making it difficult to prevent volatilization of elements such as chromium that form the alloy at high temperatures.

[0071] Accordingly, performing step (4) after step (3), which is the bonding process between parts, is advantageous in ensuring the confidentiality of the bonding and in fully maintaining the quality of the electroless nickel plating layer implemented through step (4).

[0072]

[0073] Next, as step (4) according to the present invention, a step of forming an electroless nickel plating layer is performed. The electroless nickel plating layer can prevent volatilization of components (e.g., chromium, etc.) that can volatilize at high temperatures among the elements forming the plated part, and can improve the corrosion resistance, wear resistance, etc. of the plated part.

[0074] (4) Electroless nickel plating in step 4 can be performed by immersing the plated part joint in a nickel-phosphorus containing plating solution having a pH of 4 to 5 and then performing the process at a temperature of 80 to 90°C for 20 to 120 minutes, thereby advantageously forming an electroless nickel plating layer having a uniform thickness and excellent surface quality to the desired thickness.

[0075] The electroless nickel plating solution may be a plating solution used in conventional electroless nickel plating containing a nickel precursor, and the present invention is not particularly limited thereto. For example, the electroless nickel plating solution includes a solvent, a nickel metal salt as a nickel precursor, and a reducing agent, and may further include other known complexing agents, stabilizers, metal stabilizers, and pH adjusters.

[0076] The above solvent is a common one used in electroless nickel plating solutions, and may be water, for example.

[0077] In addition, the nickel metal salt, which is a nickel precursor, may include, for example, nickel hydrochloride, and as a specific example, may include at least one of nickel sulfamate, nickel sulfate, nickel chloride, nickel nitrate, nickel oxide, and nickel carbonate. In addition, the nickel metal salt may be included in an amount ranging from 4 g to 7 g per 1 liter of the electroless nickel plating solution.

[0078] In addition, the reducing agent can reduce nickel ions dissociated from the nickel metal salt. The reducing agent may include, for example, at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine, and preferably, hypophosphite, and may include at least one of sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite as the hypophosphite. In addition, the electroless nickel plating layer formed due to the inclusion of such a phosphorus reducing agent may contain a phosphorus component.

[0079] Additionally, the reducing agent may be included in an amount ranging from 20 g to 50 g per 1 liter of the electroless nickel plating solution, but is not limited thereto.

[0080] In addition, since known additives can be used in the electroless nickel plating solution, a detailed description thereof is omitted in the present invention.

[0081]

[0082] Meanwhile, a step of activating the surface of the component joint may be further performed before forming the electroless nickel plating layer in step (4).

[0083] The process of activating the surface of the component joint is to activate the surface so that electroless nickel plating can be smoothly performed. Depending on the material of the specific component, an activation method known to be suitable may be utilized. For example, the surface activation method may be based on the surface activation process performed in step (1) described above, and a detailed description thereof will be omitted.

[0084]

[0085] Referring to FIG. 1, a component joint (100) implemented through the above-described method may include an electrolytic nickel plating layer (20) formed with a thickness of 2 to 4.5 μm from the surface of an alloy (10) in a non-joined area where a joint is not formed, and an electroless nickel plating layer (30) formed with a thickness of 6.5 to 20 μm on the electrolytic nickel plating layer (20). In addition, a joint material used in a welding or brazing process may be interposed between the electrolytic nickel plating layer (20) and the electroless nickel plating layer (30) in the area where a joint is formed.

[0086] Meanwhile, the thickness of the electrolytic nickel plating layer (20) formed as described above may be 2 to 4.5 ㎛, the thickness of the electroless nickel plating layer (30) may be 6.5 to 20 ㎛, and the thickness of the total nickel plating layer formed may be 10 ㎛ or more, which may be advantageous in maximizing the ease of the bonding process, the airtightness of the bonding portion, and the volatilization prevention of at least some elements constituting the component. If the thickness of the electrolytic nickel plating layer is less than 2 ㎛, the effect due to the electrolytic nickel plating layer may be minimal, and the volatilization prevention synergy effect for the elements constituting the component through the electrolytic nickel plating layer may be minimal. In addition, if the thickness of the electrolytic nickel plating layer exceeds 4.5 ㎛, the deposition unevenness of the electroless nickel plating layer may occur, there is a concern that the adhesion with the electroless nickel plating layer may decrease, and there is a concern that the electroless nickel plating layer may peel off or lift off during long-term use, which is not economically sound. Furthermore, if the thickness of the electroless nickel plating layer is less than 6.5㎛, the effect of preventing the volatilization of the elements constituting the component may not be significant, or its long-term durability may be weakened. Furthermore, if the thickness of the electroless nickel plating layer exceeds 20㎛, the density of the electroless nickel plating layer decreases, which may result in poor long-term durability and may be economically unfavorable.

[0087]

[0088] Next, as step (5) according to the present invention, a step of high-temperature heat treatment of the electroless nickel-plated component joint at a temperature of 550°C or higher is performed.

[0089] (5) The high-temperature heat treatment in step (5) is performed to prevent the deterioration of the adhesion of the electroless nickel plating layer that occurs when the joint body on which the electroless nickel plating layer is formed is placed in a high-temperature environment. The high-temperature heat treatment can be performed at a temperature of 550°C or higher for 3 to 7 hours, and preferably, can be performed at a temperature of 600 to 700°C for 3 to 5 hours. If the high-temperature heat treatment is performed at a temperature of less than 550°C, even though the heat treatment is performed, for example, peeling of the electroless nickel plating layer may occur on the surface of the electroless nickel plating part joint body during use in a high-temperature environment. In addition, when the heat treatment is performed at a temperature exceeding 700°C, the level of improvement in high-temperature adhesion may be minimal, and there is a concern that the electroless nickel plating layer may melt.

[0090] In addition, the high-temperature heat treatment can preferably be performed under a vacuum atmosphere, which can be advantageous in further improving high-temperature adhesion while eliminating concerns about hardness reduction due to high-temperature heat treatment.

[0091] In addition, the high-temperature heat treatment may be conducted at a rate of 10 to 16°C / min until the desired heat treatment temperature is reached, which may be advantageous in achieving the purpose of the present invention. If the rate of heating is less than 10°C / min, there is a risk that the process time may be delayed, and if it exceeds 16°C / min, it may be difficult to maintain continuous adhesion when exposed to a high-temperature environment during use.

[0092]

[0093] Meanwhile, according to a preferred embodiment of the present invention, step (5) may further perform a low-temperature heat treatment at 190 to 410°C for 1 to 9 hours prior to the high-temperature heat treatment, thereby further improving the adhesion and hardness of the electroless nickel plating layer under a high-temperature environment. In addition, the low-temperature heat treatment may additionally eliminate hydrogen embrittlement occurring during the activation process performed prior to the formation of the electroless nickel plating layer, or the acid etching or activation process in step (1).

[0094] In addition, the high-temperature heat treatment after the low-temperature heat treatment can preferably be performed through different heat treatment processes, and in particular, a cooling process can be performed between the low-temperature heat treatment and the high-temperature heat treatment, which can be more advantageous in maintaining the adhesion of the electroless nickel plating layer and improving the hardness under high-temperature environments. If the high-temperature heat treatment is performed continuously without cooling after the low-temperature heat treatment, the high-temperature adhesion of the electroless nickel plating layer may actually deteriorate.

[0095]

[0096] The present invention will be described in more detail through the following examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0097]

[0098] <Example 1>

[0099] Two stainless steel (STS304L) parts, a 0.5 mm thick chromium-containing alloy, were prepared as plated parts and then subjected to a pretreatment process. First, a sandblasting process was performed on the surface, and the average centerline roughness of the surface after the sandblasting process was 0.839 μm. Afterwards, the parts were immersed in a 12.5 wt% degreasing solution (Clean-L20) at 55°C for 5 minutes, and then electrolytic degreasing was performed for 2 minutes at a current density of 2 A / d㎡. Afterwards, an etching process was performed at 23°C for 5 minutes in an etching solution containing a mixture of 5 wt% nitric acid solution, 4 wt% hydrofluoric acid solution, and 12.5 wt% hydrochloric acid solution. Afterwards, the surface was activated by immersing in a 22 wt% hydrochloric acid solution at 23°C for 2 minutes, and then washed with water. Afterwards, the sample was immersed in a nickel strike solution containing 250 g / L of nickel chloride and 100 ml / L of hydrochloric acid solution at 23°C for 15 minutes, and nickel strike plating was performed for 10 minutes under a current density of 2 A / d㎡, and then washed with water.

[0100] Afterwards, an electrolytic nickel plating solution containing 480 g / l of nickel sulfate, 34 g / l of nickel chloride, and 45 g / l of boric acid with a pH of 4.0 was used at a temperature of 55°C and a current density of 5 A / dm. 2 Electrolytic nickel plating was performed for 2.5 minutes under the conditions of .

[0101] Two stainless steel parts were then welded using conventional conditions and methods to produce a stainless steel part joint. The part joint was then immersed in a 22 wt% hydrochloric acid solution at 23°C for 2 minutes to activate the surface.

[0102] Afterwards, the surface-activated stainless steel part joint was electroplated with an electroless nickel plating solution (Atotech) at pH 4.7 and 83°C. TM ) was immersed for 30 minutes to form an electroless nickel plating layer.

[0103] Afterwards, the component joint having an electroless nickel plating layer formed thereon was mounted on a furnace, heated at a heating rate of 15°C / min in an air atmosphere, and subjected to low-temperature heat treatment at 350°C for 1.5 hours followed by natural cooling. Afterwards, the low-temperature heat-treated component was remounted on the furnace, heated at a heating rate of 15°C / min in a vacuum atmosphere, and subjected to high-temperature heat treatment at 620°C for 4 hours followed by natural cooling to manufacture a component having an electroless nickel plating layer formed thereon.

[0104]

[0105] <Examples 2 to 4>

[0106] A part was manufactured in the same manner as Example 1, but the surface roughness was changed after the sandblasting process as shown in Table 1 below, or the temperature was changed during high-temperature heat treatment to manufacture a part having an electroless nickel plating layer as shown in Table 1 below.

[0107]

[0108] Comparative Examples 1 to 5

[0109] A part was manufactured in the same manner as in Example 1, but the sandblasting process or the nickel strike plating process was omitted as a pretreatment process as in Table 1 below, or the high-temperature heat treatment or the low-temperature heat treatment and the high-temperature heat treatment were omitted to manufacture a part having an electroless nickel plating layer formed as in Table 1 below.

[0110]

[0111] Experimental Example 1

[0112] The following physical properties were evaluated for parts formed with an electroless nickel plating layer manufactured through examples and comparative examples, and the results are shown in Table 1 below.

[0113]

[0114] 1. Surface roughness measurement

[0115] In Examples 1 and 2, the surface roughness of the plated part surface after the sandblasting process was measured using a confocal microscope, and the related photographs are shown in FIGS. 1 and 2, respectively.

[0116]

[0117] 2. Analysis of plating condition before high-temperature heat treatment (SEM-EDX)

[0118] During the manufacturing process of the component joint of Example 1, SEM photographs were taken of the component joint before high-temperature heat treatment, and SEM-EDS analysis was performed on the photographed portion, and the results are shown in Figs. 6a and 6b.

[0119] As can be seen in Figure 6b,

[0120] It can be seen that an electroless nickel plating layer is formed on an electrolytic nickel plating layer, and the thickness of the electrolytic nickel plating layer formed at this time is about 4㎛, and the thickness of the electroless nickel plating layer is about 8㎛.

[0121]

[0122] 3. Evaluation of abnormal appearance of part joints after high-temperature heat treatment

[0123] For each example and comparative example, 10 specimens were evaluated for appearance abnormality, and the number of specimens in which plating layers such as electroless nickel plating layers were peeled was counted. If the number of specimens in which peeling occurred was 0, it was evaluated as ×, if peeling occurred in 1 to 3 specimens, it was evaluated as △, and if peeling occurred in 4 or more specimens, it was evaluated as ○.

[0124]

[0125] 4. Evaluation of the adhesion of the electroless nickel plating layer after exposure to a high-temperature environment

[0126] For the part joints with no appearance abnormalities, they were exposed to a temperature of 650℃ for 50 hours.

[0127] Afterwards, mandrel bending tests were performed at 90° and 180°, respectively, and the presence or absence of poor plating adhesion was visually evaluated. The evaluation results were indicated as ○ if lifting or peeling occurred, △ if cracks occurred, and × if there were no abnormalities.

[0128] In addition, after performing a 10×10 cross-cut evaluation at 1 cm intervals, the number of cells with even a small amount of peeling out of a total of 100 cells was counted. At this time, the cross-cut evaluation was evaluated according to the ASTM D3359 Standard Test Method for Rating Adgesion by Tape Test.

[0129]

[0130] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Pretreatment process Sandblasting presence / Surface roughness (Ra, ㎛) ○ / 0.839 ○ / 0.775 ○ / 0.839 ○ / 0.839 Not performed ○ / 0.839 ○ / 0.839 ○ / 0.839 ○ / 0.839 Nickel strike plating ○○○○○ Not performed ○○○ Low temperature heat treatment Temperature (℃) / Time / Atmosphere 350 / 1.5h / Standby 350 / 1.5h / Standby Not performed 350 / 1.5h / Standby 350 / 1.5h / Standby 400 / 1h / Standby 350 / 1.5h / Standby Not performed High temperature Heat treatment temperature (℃) / time / atmosphere 620 / 4h / vacuum 620 / 4h / vacuum 620 / 4h / vacuum 560 / 6h / vacuum 620 / 4h / vacuum 620 / 4h / vacuum not performed 500 / 8h / vacuum not performed Appearance evaluation of plating layer × × × × ○ △ × × × Adhesion evaluation after high temperature exposure 90 ° bending / 180 ° bending / Number of peeled sections after crosscut evaluation × / × / 0 × / ○ / 2 2 ○ / ○ / 16 × / × / 10 Not evaluated ○ / ○ / 45 ○ / ○ / 100 ○ / ○ / 58 ○ / ○ / 100

[0131] As can be seen from Table 1, in Comparative Examples 1 and 2, in which neither the sandblasting process nor the nickel strike plating process was performed as a pretreatment process, it can be seen that the frequency of appearance abnormalities occurring after high-temperature heat treatment is higher compared to the examples.

[0132] In addition, it can be seen that in Comparative Examples 3 and 5, which did not perform high-temperature heat treatment, or Comparative Example 4, in which the high-temperature heat treatment temperature was outside the range of the present invention, the adhesion of the electroless nickel plating layer was significantly reduced or lost after the parts were exposed to high temperatures for a long period of time, compared to the examples.

[0133]

[0134] Comparative Example 6

[0135] A component assembly was manufactured in the same manner as in Example 1, but the nickel strike plating process and the electrolytic nickel plating process were omitted as pretreatment processes, and an electroless nickel plating layer was formed.

[0136]

[0137] <Comparative Example 7>

[0138] A component joint was manufactured in the same manner as in Example 1, but the nickel strike plating process was omitted as a pretreatment process, thereby forming an electroless nickel plating layer.

[0139]

[0140] Experimental Example 2

[0141] The ease and quality of the welding process were evaluated for Example 1 and Comparative Examples 6 to 7, and the results are shown in Table 2 below.

[0142] Specifically, 10 welding experts evaluated the ease of the welding process and the quality of the joint after welding, and gave relative scores from 0 to 10 based on the evaluation results, with 10 points for very good and 0 points for poor, and calculated the average value.

[0143] Example 1 Comparative Example 6 Comparative Example 7 Ease of welding process and welding quality 9.86.27.2

[0144] As can be seen from Table 2, Example 1, which had both an electrolytic nickel plating layer and an electroless nickel plating layer formed after performing a nickel strike plating process, was superior in terms of ease of welding process and quality compared to Comparative Example 6, in which neither the nickel strike plating process nor the electrolytic nickel plating process was performed, and Comparative Example 7, in which the nickel strike plating process was omitted before the electrolytic nickel plating process.

[0145]

[0146] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. A method for manufacturing an electroless nickel plated part joint for at least two mutually bonded plated parts, (1) A step of performing a pretreatment process including a sandblasting process and a nickel strike plating process for each plated part to be mutually joined; (2) A step of forming an electrolytic nickel plating layer on the surface of each plated part; (3) A step of manufacturing a plated part joint by joining plated parts together; (4) A step of forming an electroless nickel plating layer on the plated part joint; and (5) A method for manufacturing an electroless nickel-plated part joint, comprising the step of performing high-temperature heat treatment on an electroless nickel-plated part joint at a temperature of 550°C or higher.

2. In paragraph 1, The above pretreatment process is between the sandblasting process and the nickel strike plating process. A degreasing process performed by immersing in a 10 to 15 wt% degreasing solution at 40 to 60°C for 1 to 10 minutes and then electrolytic degreasing for 1 to 5 minutes under a current density of 1 to 2 A / d㎡. An acid etching process performed by immersing in an etching solution containing a mixture of 1 to 7 wt% nitric acid aqueous solution, 1 to 6 wt% hydrofluoric acid aqueous solution, and 1 to 15 wt% hydrochloric acid aqueous solution for 1 to 10 minutes, and A method for manufacturing an electroless nickel plated part joint, further comprising an activation process performed by immersing in a 15 to 25 wt% hydrochloric acid aqueous solution for 2 to 15 minutes.

3. In paragraph 1, A method for manufacturing an electroless nickel plated part joint, wherein the above sandblasting process is performed so that the center line average roughness (Ra) of the plated area is 0.8 ㎛ or more.

4. In paragraph 1, The above nickel strike plating process is a method for manufacturing an electroless nickel plated part joint, which is performed by immersing the plated part in a nickel strike plating solution and then applying a current density of 1.5 to 5.0 A / d㎡ for 5 to 10 minutes.

5. In paragraph 3, A method for manufacturing an electroless nickel plated part joint, wherein the center line surface roughness is performed to be 0.8 to 5.0 ㎛.

6. In paragraph 1, (4) Step 4: Temperature of 50 to 60 ℃ and current density of 3 to 7 A / dm under electrolytic plating solution. 2 It is performed for 2 to 3 minutes under the condition of (4) A method for manufacturing an electroless nickel plated part joint, which is performed by immersing the plated part in an electroless nickel plating solution having a pH of 4 to 5 at a temperature of 80 to 90°C for 20 to 120 minutes.

7. In paragraph 1, (5) A method for manufacturing an electroless nickel plated part joint, wherein the step of joining is performed by one or more of welding, soldering, brazing, and diffusion bonding.

8. In paragraph 1, (5) A method for manufacturing an electroless nickel plated part joint, characterized in that the step comprises performing a high-temperature heat treatment at 550°C or higher for 3 to 7 hours on a cooled part after a low-temperature heat treatment performed at 190 to 410°C for 1 to 9 hours.

9. In paragraph 8, A method for manufacturing an electroless nickel plated part joint, wherein high-temperature heat treatment is performed at a temperature of 600 to 700°C for 4 to 5 hours in a vacuum atmosphere.

10. An electroless nickel plated part joint manufactured according to any one of claims 1 to 9.

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