Why do Motor plain bearings need copper plating after turning and grinding and how to ensure the effect?

In actual operation, Motor plain bearings need to withstand a variety of complex working conditions, such as continuous friction, different degrees of load and possible corrosive media. The wear resistance and corrosion resistance of the bearing surface directly determine its service life and the overall operating stability of the motor. Although turning and grinding can shape the shape of the bearing and improve the surface accuracy, it is difficult to meet the stringent requirements under long-term complex working conditions with the basic material alone, which provides an application space for copper plating. ​

Copper plating is to form a layer of copper film on the surface of the bearing by electrochemical or chemical methods. This layer of copper film is not simply attached, but is closely integrated with the bearing matrix, giving the bearing new performance advantages. From a microscopic level, copper atoms can fill the tiny pores and uneven areas left on the bearing surface due to turning and grinding, making the surface smoother and denser, and reducing the surface roughness. This change in microstructure directly affects the friction characteristics of the bearing during operation, reduces the friction resistance between the bearing and the journal, and thus reduces energy loss. ​
The implementation of the copper plating process requires multiple delicate steps. The first is the preparation of the plating solution. The composition of the plating solution is one of the key factors that determine the quality of copper plating. Different types of plating solutions have different composition ratios and characteristics. In common plating solution systems, the main salt is copper salt, which provides a source of copper ions for the copper plating process; the complexing agent can form a stable complex with copper ions, control the release rate of copper ions, and make copper deposit evenly on the bearing surface; additives can improve the performance of the plating solution and the quality of the coating, such as brighteners can make the coating brighter and smoother, and leveling agents can enhance the flatness of the coating. These components work together to build a stable plating solution environment. ​
After the plating solution is prepared, the bearing must be strictly pretreated. The purpose of pretreatment is to remove impurities such as oil stains and oxide films on the bearing surface to ensure that the copper plating layer is well combined with the bearing matrix. Pretreatment generally includes steps such as degreasing and pickling. The degreasing process completely removes the grease on the bearing surface through the emulsification and saponification of chemical agents; pickling uses acidic solutions to dissolve the surface oxide film to expose a fresh and clean metal surface. The pretreatment effect directly affects the adhesion of the copper plating layer. If the pretreatment is not thorough, the copper plating layer is prone to peeling and other problems. ​
In the copper plating process, the control of temperature and current density is crucial. Temperature has a significant impact on the chemical reaction rate and stability of the plating solution during the copper plating process. If the temperature is too low, the copper plating speed is slow, the production efficiency is low, and it may cause the plating layer to be coarse and of poor quality; if the temperature is too high, some components in the plating solution may decompose and fail, affecting the performance of the plating solution, and may also cause defects such as scorching and brittleness in the plating layer. The current density is also critical, which determines the deposition speed and deposition method of copper ions on the bearing surface. If the current density is too small, the amount of copper ion deposition is small, and the copper plating layer grows slowly; if the current density is too large, the copper ions are excessively deposited in local areas, which will cause problems such as rough plating and burrs. In actual operation, it is necessary to accurately adjust the temperature and current density according to factors such as the composition of the plating solution and the material of the bearing to find the best combination of process parameters. ​
After the copper plating is completed, the detection of the quality of the copper plating layer is indispensable. The test content covers many aspects, such as uniformity of coating thickness, surface quality, bonding strength, etc. Through instruments such as metallographic microscopes, the microstructure of the copper plating layer can be observed to determine whether it is uniform and dense; the surface roughness can be measured using a surface roughness meter to evaluate the improvement effect of copper plating on surface quality; the bonding strength between the copper plating layer and the bearing matrix can be detected using methods such as peeling test and bending test. Only when all the test indicators meet the requirements can the copper plating treatment achieve the expected effect. ​
The performance improvement brought by copper plating to motor sliding bearings is very significant. In terms of wear resistance, the copper film has good hardness and wear resistance, and can effectively resist friction and wear during operation. When the bearing and the journal slide relative to each other, the copper plating layer can slow down the loss rate of the surface material and extend the service life of the bearing. In terms of corrosion resistance, copper itself has a certain corrosion resistance. The copper plating layer is like a protective barrier, isolating the bearing matrix from external corrosive media and reducing the risk of corrosion. Even in an environment containing corrosive components such as acids and alkalis, copper-plated bearings can maintain good stability and reduce performance degradation and failures caused by corrosion.​
Copper plating also has a positive effect on the lubrication performance of bearings. The smooth and dense copper-plated surface helps the lubricant to be evenly distributed on the bearing surface and form a stable oil film. The presence of the oil film further reduces the friction coefficient, reduces the heat generated by friction, and makes the bearing run more smoothly. At the same time, a good lubrication state can also reduce wear and corrosion, forming a virtuous cycle and ensuring the long-term stable operation of the bearing. ​
From the perspective of manufacturing process, although copper plating increases the production link, it has significant economic benefits in terms of long-term use and maintenance costs. The long life characteristics of copper-plated bearings reduce the replacement frequency, equipment downtime and maintenance costs. This advantage is particularly prominent in some key equipment that runs continuously, avoiding production interruptions and economic losses caused by bearing failures. ​
With the development of technology, the copper plating process of motor sliding bearings is also constantly improving and innovating. The research and development of new plating solution formulas and additives aims to further improve the quality and efficiency of copper plating; the application of automated and intelligent copper plating equipment makes the copper plating process parameter control more accurate, reduces the influence of human factors, and improves production stability and consistency. In the future, the copper plating process is expected to improve bearing performance while paying more attention to environmental protection and energy conservation, and promote the development of motor sliding bearing manufacturing to a higher level.