The electroplated abrasive method is a common method for manufacturing superabrasive tools. The quality of electroplating directly affects the life and performance of electroplated superabrasive tools, and the electroplating process is the main factor affecting the quality of electroplating. In the paper, the pre-plating treatment and the nickel-plating process in the original electroplating basic process were improved. The process of adding deburring, electrochemical degreasing, anodizing and the like in the pre-plating treatment and the charging in the nickel plating process were proposed. And a new set of electroplating process with inrush current, and carried out experimental research, the results show that: the new process enhances the bonding strength of the coating and improves the quality of electroplating; secondly, the plating solution formulation and current density, bath temperature, The influence of process parameters such as pH on the plating quality was obtained and optimized results were obtained.
Key words: electroplating process; superhard abrasive; electroplating solution; orthogonal test
1 Introduction
The electroplated abrasive method was a new method of manufacturing superabrasive tools developed in the 1960s. For superabrasives, such as diamond, due to its non-platability, the essence of the electroplating process is "electroforming", in which the metal ions in the electroplating solution are deposited on the substrate at the cathode and then deposited on the substrate. The diamond abrasive grains falling on the substrate are buried by the deposited bonding metal to form a tool. Electroplated metal bond single-layer superabrasive grinding wheels are widely used in electroplated abrasives, not only for grinding workpiece surfaces (especially forming rotary surfaces), but also for trimming ordinary grinding wheels (referred to as rollers). The quality of electroplating directly determines the performance and service life of the electroplated superabrasive tool. There is no bonding force between the diamond abrasive grains and the substrate, but only the interaction between the substrate and the bonding metal. Therefore, the process problem of solving the plating quality is essentially solving the problem of the metal plating process. Using traditional techniques, problems such as uneven plating and weak bonding strength often occur in the electroplating process. For this reason, domestic and foreign scholars are still working on electroplating processes.
2 Electroplating process analysis and improvement
2.1 Electroplating basic process analysis
Electroplated metal is a process in which a metal alloy is deposited on a surface of a workpiece by electrolysis to form a uniform, dense, and well-bonded metal. Electroplating must have an external DC power supply, as well as an electroplating device consisting of a specific plating solution and a specific metal anode.
With pure nickel as the metal anode and nickel salt as the plating solution, the electrode reaction of the electroplated bonding metal is as follows:
(1) Anode reaction: the metal nickel loses electrons and becomes divalent nickel ions into the plating solution, which ensures the normal replenishment of nickel ions in the plating solution;
(2) Cathodic reaction: Nickel ions are deposited from the nickel salt plating solution onto the working surface of the electroplated substrate.
The electroplating solution is mainly composed of five major components: main salt, conductive liquid, buffer, chloride and additives.
Any complete plating process generally involves three stages: pre-plating, electroplating, and post-plating. The single-plated abrasive tool is made by electroplating, and the process route is: pre-plating treatment of the substrate → nickel plating on the substrate → sanding (fixed sand) → plating nickel (thickening).
In the whole electroplating process, the factors affecting the plating quality are: (1) the bonding force between the bonding metal and the substrate; (2) the working surface of the electroplating substrate, the thickness of the plating layer is not uniform and there is no fine structure; (3) The coating fails to reach the specified thickness and has a certain amount of porosity;
The first factor influencing factors is related to pre-plating treatment, and pre-plating treatment is the most important factor. According to statistics from the Japanese electroplating industry, the plating layer is not well combined, and more than 90% of it is due to poor pre-plating treatment. Poor pre-plating treatment seriously affects the service life of the plated parts. Each process of pre-plating treatment directly affects the quality of the coating. Therefore, each step of the pre-plating treatment must be strictly performed. Only in this way can the coating with uniformity, good surface integrity and strong bonding be obtained, thereby improving the service life and processing precision of the electroplated grinding wheel.
In the pre-plating treatment, there are special acid and alkali treatment additives in foreign countries. Most of the degreasing and pickling use multiple electrolytic treatments. In addition, the low-temperature degreasing of 40 ° C ~ 46 ° C, and most of China in the 60 ° C ~ 90 ° C degreasing, has attracted attention to normal temperature and low temperature degreasing, but has not been fully promoted and applied. The use of mechanical grinding and mechanical cleaning for pre-plating products to improve product quality has not received much attention in China.
2.2 Improvement of the basic process of electroplating
In order to improve the quality of the coating, through the analysis and comparison of the domestic and international electroplating industry, the pre-plating process is improved, and the deburring, electrochemical degreasing, anodizing and other processes are added on the basis of the original electroplating process. The effect is shown in Table 1.
The original pre-plating treatment process: cleaning→chemical degreasing→acid washing; new pre-plating treatment process: deburring→cleaning→chemical degreasing→electrochemical degreasing→acid washing→anode treatment.
The pre-plating treatment process used here, such as mechanical deburring, honing the part to be plated, changing the surface condition of the substrate to be plated before plating; performing electrochemical degreasing and anodizing, greatly changing the surface of the substrate The state of the bath improves the dispersibility and coverage of the bath. Comparative experiments show that the new process improves the uniformity and surface integrity of the coating, enhances the bonding strength of the coating, and ensures the quality of the coating. The test results of the coating adhesion test are shown in Fig. 1.
In order to ensure good bonding between the plating layer and the substrate, in addition to carefully completing the various processes of the pre-plating treatment, attention should also be paid to the process of plating the underlayer. After the surface cleaning and activation of the substrate, in order to avoid re-generation of the oxide film before the start of electroplating, it is necessary to plate the plating as quickly as possible, and it is preferable to take a charging and sinking measure. The so-called charging into the tank means that the pre-treated substrate is connected to the negative electrode of the electroplating power source, and the nickel anode in the plating tank is connected to the positive electrode of the power source. When the power is turned on, the cathode is quickly moved into the groove to start electroplating. The charging into the groove can avoid the phenomenon of the double electrode, which causes the surface of the plated part close to the cathode to react with the anode before the energization to form an oxide film.
For substrates made of materials such as high carbon steel alloy steel, and substrates with complex shapes, cavities and rough surfaces, inrush current is required at the beginning of electroplating, that is, when plating is started, the plating is applied under normal conditions. The current density is 2 to 3 times higher, so that the surface of the plated part is quickly deposited with a thin layer of fine plating and then quickly restored to a normal current density. This allows the coating on the surface of the part to be evenly distributed and firmly bonded.
3 plating solution formula and process parameter optimization
3.1 Optimization of plating solution formulation
The plating solution is mainly composed of a nickel salt, and the components thereof are nickel sulfate, cobalt sulfate, sodium chloride, boric acid, saccharin, butynediol, and sodium lauryl sulfate. 1.4 In order to study the influence of plating composition on the plating quality, the L9 (34) orthogonal table design experiment was used. The horizontal values ​​of each factor are shown in Table 2. The bonding strength of the coating was used as the evaluation index, and the main in the plating solution. The composition of nickel sulfate, cobalt sulfate, boric acid, process parameters optimization.
The orthogonal experimental arrangement and results are shown in Table 3. Through the visual analysis of the experimental results, it can be seen that when the contents of nickel sulfate, cobalt sulfate and boric acid in the composition of the plating solution are: 240G/L and 8G/L40G/L, respectively, Achieve greater plating strength. Comprehensive consideration, optimize the plating solution formula: nickel sulfate 240G / L, cobalt sulfate 8G / L, boric acid 40G / L, sodium chloride 15G / L, saccharin 1G / L, butyne II 1.4 alcohol 0.8G / L, twelve Sodium alkyl sulfate 0.8 G / L. Further experiments have shown that this set of formulations can achieve the desired bond strength.
3.2 Optimization of process parameters
After the bath formulation is preferred, the main process parameters that affect the bond strength of the bond to the substrate are: current density, bath temperature, and pH. According to the three factors and three levels of orthogonal design, the horizontal values ​​of each factor are shown in Table 4. The bonding strength of the coating is also used as the evaluation index to optimize the process parameters. The experimental results and analysis are shown in Table 5.
It can be seen from Table 5 that the most influential factor on the bonding strength of the coating is the current density. The maximum difference of this factor is 7.334, followed by the bath temperature and finally the pH of the bath. The process conditions for obtaining the maximum plating bond strength in the experiment were: current density = 0.10 kA/m2, bath temperature = 70 ° C, pH = 4.0. According to the mean value of the experimental results of the same level in each factor in Table 5, the three levels of each factor are the abscissa, and the mean value of the experimental results corresponding to each level value is the ordinate, and a visual map is shown in Fig. 2.
It can be seen from Fig. 2 that the current density = 0.1 kA/m2, the plating bath temperature = 70 ° C, and the pH value = 4.0 are all ideal levels, and the bonding strength of the plating layer is the largest, which is consistent with the conclusions analyzed above.
4 Conclusion
In this paper, through the improvement of the original electroplating basic process, the deburring, electrochemical degreasing, anode treatment and other processes have been added. The test shows that the process enhances the bonding strength of the coating and improves the plating quality.
Through the experimental study on the formulation and process parameters of the electroplating solution, it is found that the content of nickel sulfate, cobalt sulfate and boric acid in the composition of the electroplating solution has an influence on the plating quality, and the main electroplating solution formula which can obtain the maximum plating bonding strength is: nickel sulfate 240G / L, cobalt sulfate 8G / L, boric acid 40G / L. In the process parameters (current density, bath temperature, pH value) affecting the bonding strength between the nickel plating layer and the substrate, the influence of current density is obvious, and the influence trend curve is extremely variable, when the current density is 0.1 kA/m2. The bonding strength between the plating layer and the substrate is maximized, and the effects of the plating solution temperature and the pH value of the plating solution are monotonously changed. The plating process parameters for obtaining a large plating bonding strength are: current density 0.1 kA/m 2 , plating solution temperature 70 °C, pH 4.0.
Key words: electroplating process; superhard abrasive; electroplating solution; orthogonal test
1 Introduction
The electroplated abrasive method was a new method of manufacturing superabrasive tools developed in the 1960s. For superabrasives, such as diamond, due to its non-platability, the essence of the electroplating process is "electroforming", in which the metal ions in the electroplating solution are deposited on the substrate at the cathode and then deposited on the substrate. The diamond abrasive grains falling on the substrate are buried by the deposited bonding metal to form a tool. Electroplated metal bond single-layer superabrasive grinding wheels are widely used in electroplated abrasives, not only for grinding workpiece surfaces (especially forming rotary surfaces), but also for trimming ordinary grinding wheels (referred to as rollers). The quality of electroplating directly determines the performance and service life of the electroplated superabrasive tool. There is no bonding force between the diamond abrasive grains and the substrate, but only the interaction between the substrate and the bonding metal. Therefore, the process problem of solving the plating quality is essentially solving the problem of the metal plating process. Using traditional techniques, problems such as uneven plating and weak bonding strength often occur in the electroplating process. For this reason, domestic and foreign scholars are still working on electroplating processes.
2 Electroplating process analysis and improvement
2.1 Electroplating basic process analysis
Electroplated metal is a process in which a metal alloy is deposited on a surface of a workpiece by electrolysis to form a uniform, dense, and well-bonded metal. Electroplating must have an external DC power supply, as well as an electroplating device consisting of a specific plating solution and a specific metal anode.
With pure nickel as the metal anode and nickel salt as the plating solution, the electrode reaction of the electroplated bonding metal is as follows:
(1) Anode reaction: the metal nickel loses electrons and becomes divalent nickel ions into the plating solution, which ensures the normal replenishment of nickel ions in the plating solution;
(2) Cathodic reaction: Nickel ions are deposited from the nickel salt plating solution onto the working surface of the electroplated substrate.
The electroplating solution is mainly composed of five major components: main salt, conductive liquid, buffer, chloride and additives.
Any complete plating process generally involves three stages: pre-plating, electroplating, and post-plating. The single-plated abrasive tool is made by electroplating, and the process route is: pre-plating treatment of the substrate → nickel plating on the substrate → sanding (fixed sand) → plating nickel (thickening).
In the whole electroplating process, the factors affecting the plating quality are: (1) the bonding force between the bonding metal and the substrate; (2) the working surface of the electroplating substrate, the thickness of the plating layer is not uniform and there is no fine structure; (3) The coating fails to reach the specified thickness and has a certain amount of porosity;
The first factor influencing factors is related to pre-plating treatment, and pre-plating treatment is the most important factor. According to statistics from the Japanese electroplating industry, the plating layer is not well combined, and more than 90% of it is due to poor pre-plating treatment. Poor pre-plating treatment seriously affects the service life of the plated parts. Each process of pre-plating treatment directly affects the quality of the coating. Therefore, each step of the pre-plating treatment must be strictly performed. Only in this way can the coating with uniformity, good surface integrity and strong bonding be obtained, thereby improving the service life and processing precision of the electroplated grinding wheel.
In the pre-plating treatment, there are special acid and alkali treatment additives in foreign countries. Most of the degreasing and pickling use multiple electrolytic treatments. In addition, the low-temperature degreasing of 40 ° C ~ 46 ° C, and most of China in the 60 ° C ~ 90 ° C degreasing, has attracted attention to normal temperature and low temperature degreasing, but has not been fully promoted and applied. The use of mechanical grinding and mechanical cleaning for pre-plating products to improve product quality has not received much attention in China.
2.2 Improvement of the basic process of electroplating
In order to improve the quality of the coating, through the analysis and comparison of the domestic and international electroplating industry, the pre-plating process is improved, and the deburring, electrochemical degreasing, anodizing and other processes are added on the basis of the original electroplating process. The effect is shown in Table 1.
The original pre-plating treatment process: cleaning→chemical degreasing→acid washing; new pre-plating treatment process: deburring→cleaning→chemical degreasing→electrochemical degreasing→acid washing→anode treatment.
The pre-plating treatment process used here, such as mechanical deburring, honing the part to be plated, changing the surface condition of the substrate to be plated before plating; performing electrochemical degreasing and anodizing, greatly changing the surface of the substrate The state of the bath improves the dispersibility and coverage of the bath. Comparative experiments show that the new process improves the uniformity and surface integrity of the coating, enhances the bonding strength of the coating, and ensures the quality of the coating. The test results of the coating adhesion test are shown in Fig. 1.
In order to ensure good bonding between the plating layer and the substrate, in addition to carefully completing the various processes of the pre-plating treatment, attention should also be paid to the process of plating the underlayer. After the surface cleaning and activation of the substrate, in order to avoid re-generation of the oxide film before the start of electroplating, it is necessary to plate the plating as quickly as possible, and it is preferable to take a charging and sinking measure. The so-called charging into the tank means that the pre-treated substrate is connected to the negative electrode of the electroplating power source, and the nickel anode in the plating tank is connected to the positive electrode of the power source. When the power is turned on, the cathode is quickly moved into the groove to start electroplating. The charging into the groove can avoid the phenomenon of the double electrode, which causes the surface of the plated part close to the cathode to react with the anode before the energization to form an oxide film.
For substrates made of materials such as high carbon steel alloy steel, and substrates with complex shapes, cavities and rough surfaces, inrush current is required at the beginning of electroplating, that is, when plating is started, the plating is applied under normal conditions. The current density is 2 to 3 times higher, so that the surface of the plated part is quickly deposited with a thin layer of fine plating and then quickly restored to a normal current density. This allows the coating on the surface of the part to be evenly distributed and firmly bonded.
3 plating solution formula and process parameter optimization
3.1 Optimization of plating solution formulation
The plating solution is mainly composed of a nickel salt, and the components thereof are nickel sulfate, cobalt sulfate, sodium chloride, boric acid, saccharin, butynediol, and sodium lauryl sulfate. 1.4 In order to study the influence of plating composition on the plating quality, the L9 (34) orthogonal table design experiment was used. The horizontal values ​​of each factor are shown in Table 2. The bonding strength of the coating was used as the evaluation index, and the main in the plating solution. The composition of nickel sulfate, cobalt sulfate, boric acid, process parameters optimization.
The orthogonal experimental arrangement and results are shown in Table 3. Through the visual analysis of the experimental results, it can be seen that when the contents of nickel sulfate, cobalt sulfate and boric acid in the composition of the plating solution are: 240G/L and 8G/L40G/L, respectively, Achieve greater plating strength. Comprehensive consideration, optimize the plating solution formula: nickel sulfate 240G / L, cobalt sulfate 8G / L, boric acid 40G / L, sodium chloride 15G / L, saccharin 1G / L, butyne II 1.4 alcohol 0.8G / L, twelve Sodium alkyl sulfate 0.8 G / L. Further experiments have shown that this set of formulations can achieve the desired bond strength.
3.2 Optimization of process parameters
After the bath formulation is preferred, the main process parameters that affect the bond strength of the bond to the substrate are: current density, bath temperature, and pH. According to the three factors and three levels of orthogonal design, the horizontal values ​​of each factor are shown in Table 4. The bonding strength of the coating is also used as the evaluation index to optimize the process parameters. The experimental results and analysis are shown in Table 5.
It can be seen from Table 5 that the most influential factor on the bonding strength of the coating is the current density. The maximum difference of this factor is 7.334, followed by the bath temperature and finally the pH of the bath. The process conditions for obtaining the maximum plating bond strength in the experiment were: current density = 0.10 kA/m2, bath temperature = 70 ° C, pH = 4.0. According to the mean value of the experimental results of the same level in each factor in Table 5, the three levels of each factor are the abscissa, and the mean value of the experimental results corresponding to each level value is the ordinate, and a visual map is shown in Fig. 2.
It can be seen from Fig. 2 that the current density = 0.1 kA/m2, the plating bath temperature = 70 ° C, and the pH value = 4.0 are all ideal levels, and the bonding strength of the plating layer is the largest, which is consistent with the conclusions analyzed above.
4 Conclusion
In this paper, through the improvement of the original electroplating basic process, the deburring, electrochemical degreasing, anode treatment and other processes have been added. The test shows that the process enhances the bonding strength of the coating and improves the plating quality.
Through the experimental study on the formulation and process parameters of the electroplating solution, it is found that the content of nickel sulfate, cobalt sulfate and boric acid in the composition of the electroplating solution has an influence on the plating quality, and the main electroplating solution formula which can obtain the maximum plating bonding strength is: nickel sulfate 240G / L, cobalt sulfate 8G / L, boric acid 40G / L. In the process parameters (current density, bath temperature, pH value) affecting the bonding strength between the nickel plating layer and the substrate, the influence of current density is obvious, and the influence trend curve is extremely variable, when the current density is 0.1 kA/m2. The bonding strength between the plating layer and the substrate is maximized, and the effects of the plating solution temperature and the pH value of the plating solution are monotonously changed. The plating process parameters for obtaining a large plating bonding strength are: current density 0.1 kA/m 2 , plating solution temperature 70 °C, pH 4.0.
Led Pixel Light,Smart Pixel Light,Full Color Rgb Led Pixel Light,Waterproof Smart Pixel Light
Shen zhen SH LED Technology Co.,Ltd , https://www.pixellightsolutions.com