In the field of mechanical engineering, the durability of mechanical parts is a key factor in ensuring the long-term stable operation of mechanical equipment. Surface treatment technology, as a method that can significantly improve the surface performance of mechanical parts, plays a crucial role in enhancing the durability of parts. This article will deeply explore the multi-faceted influences of surface treatment technology on the durability of mechanical parts.
Overview of Surface Treatment Technology
Surface treatment technology refers to the modification of the surface of mechanical parts through physical, chemical or mechanical methods to obtain the desired surface properties. Common surface treatment techniques include electroplating, painting, thermal spraying, surface hardening, chemical heat treatment, etc. These technologies can endow the surface of parts with excellent properties such as corrosion resistance, wear resistance, hardness and oxidation resistance without changing the base material of the parts.
The influence mechanism of surface treatment technology on the durability of mechanical parts
Improve corrosion resistance
Corrosion is one of the main reasons for the failure of mechanical parts. Many surface treatment techniques can form a dense protective film on the surface of parts, preventing corrosive media from coming into contact with the part base, thereby effectively enhancing the corrosion resistance of the parts. For example, electroplating is the process of depositing a metal on the surface of a part through an electrochemical method to form a metal coating. Galvanized coating is often used for steel parts and can provide good protection for the parts in the atmospheric environment.
When the zinc coating forms a primary cell with the steel substrate, zinc acts as the anode and corrodes preferentially, thereby protecting the steel substrate at the cathode. Coating is the process of applying organic paint on the surface of parts to form a continuous paint film. This layer of paint film can isolate oxygen, moisture and other corrosive substances. Anti-rust paint, which is widely used on large steel structures such as ships and Bridges, greatly extends the service life of the steel structures. Thermal spraying is a process where molten spray materials are atomized by high-speed gas flow and then sprayed onto the surface of parts to form a spray coating. For instance, in petrochemical equipment, the method of thermal spraying corrosion-resistant alloy coatings is often adopted to enhance the service life of the equipment in harsh corrosive environments.
Enhance wear resistance
During the operation of mechanical parts, they are often subject to the effects of friction and wear, which leads to the gradual loss of surface materials of the parts, affects the dimensional accuracy and performance of the parts, and thereby reduces the durability of the parts. Surface treatment technology can enhance the wear resistance of parts in various ways. Surface hardening can endow the surface of parts with a high-hardness martensitic structure, thereby enhancing surface hardness and wear resistance. The application of surface hardening technology on machine tool guide rails, crankshafts and other parts can significantly improve their wear resistance. Chemical heat treatments such as carburizing and nitriding can form a carburized layer with high hardness and good wear resistance on the surface of parts.
Take carburizing as an example. Low-carbon steel parts are heated in a carbon-rich medium to allow carbon atoms to penetrate the surface of the parts. Then, after quenching and tempering treatment, a high-carbon martensitic structure is formed on the surface, while the core still maintains good toughness. This microstructure state of a hard surface and a tough core enables the parts to not only have good wear resistance but also be able to withstand certain impact loads. Thermal spraying of wear-resistant coatings is also an effective means to improve the wear resistance of parts. For instance, when tungsten carbide coatings are sprayed on the surfaces of the buckets of excavators and the hammer heads of crushers, due to the extremely high hardness and wear resistance of tungsten carbide, the service life of these parts under high-wear conditions can be significantly prolonged.
Improve surface roughness
Surface roughness also has an important influence on the durability of mechanical parts. Appropriate surface treatment can improve the roughness of the part surface and reduce the microscopic unevenness of the surface. A smoother surface can reduce frictional resistance and lower the wear rate. For instance, polishing treatment can significantly reduce the surface roughness value of parts. In some precision mechanical parts with high surface quality requirements, such as the mirror surfaces of optical instruments and the cavity surfaces of precision molds, polishing technology is often adopted to enhance surface smoothness, reduce friction and wear, and increase the service life of parts. Meanwhile, an appropriate surface roughness can also improve the fatigue performance of the parts. Parts with small surface roughness have a lower possibility of stress concentration on the surface when subjected to alternating loads, thereby reducing the probability of fatigue crack initiation and increasing the fatigue life of the parts.
Improve the fatigue strength of the parts
Fatigue failure is a common failure form of mechanical parts under alternating loads. Surface treatment technology can enhance the fatigue strength of parts through multiple approaches. Shot peening is a commonly used surface strengthening method. It utilizes high-speed shot to impact the surface of parts, causing plastic deformation on the surface and forming a residual compressive stress layer. Residual compressive stress can counteract part of the tensile stress generated by the working load, delay the initiation and propagation of fatigue cracks, and thereby enhance the fatigue strength of the parts. Shot peening treatment has been widely applied to parts such as connecting rods and springs in automotive engines that bear alternating loads. In addition, some surface treatment techniques such as nitriding can not only enhance the surface hardness and wear resistance of parts, but also create compressive stress on the surface, improving the fatigue performance of parts.
Case Analysis of the Influence of Different Surface Treatment Technologies on the Durability of Mechanical Parts
- The application of electroplating in automotive parts
In the automotive industry, many components adopt electroplating surface treatment technology to enhance their durability. For instance, the wheels of a car are usually made of aluminum alloy. To enhance their corrosion resistance and decorative effect, electroplating treatment is carried out on the surface of the wheels. Common ones include chromium plating, nickel plating, etc. The chromium plating layer has excellent hardness and corrosion resistance, which can keep the wheel hub looking good in complex usage environments and prevent it from rusting and corroding easily. The nickel plating layer can enhance the wear resistance and anti-discoloration ability of the wheel hub. The service life of car wheels that have undergone electroplating treatment is significantly longer than that of untreated wheels, generally extending by 2 to 3 times.
- The application of coating in construction machinery
The working environment of construction machinery is harsh. It is exposed outdoors for a long time and is subject to the erosion of wind, sun, rain and various corrosive media. Therefore, coating has become an important means to improve the durability of construction machinery. Take excavators as an example. Their bodies, working devices and other parts are all coated with high-performance anti-corrosion paint. These coatings have excellent adhesion, weather resistance and corrosion resistance, and can effectively protect the body from erosion by the external environment. Excavators that have undergone coating treatment will have a significantly reduced corrosion rate of their bodies under normal usage conditions, and their service life can be extended by 5 to 10 years. Meanwhile, coating can also play a certain decorative role and enhance the appearance quality of construction machinery.
- The application of Thermal Spraying in Aero Engine Parts
Aero engines operate under harsh working conditions of high temperature, high pressure and high speed, and the performance requirements for parts are extremely high. Thermal spraying technology is widely applied in the parts of aero engines. For instance, when a ceramic coating is thermally sprayed on the surface of the blades of an aero engine, the ceramic coating has excellent high-temperature resistance, oxidation resistance and wear resistance, which can effectively protect the blades from corrosion and wear under the scouring of high-temperature gas. According to relevant research, the service life of aero engine blades coated with thermal spray ceramic can be increased by 3 to 5 times, significantly enhancing the reliability and durability of aero engines and reducing maintenance costs.
Selection and application precautions of surface treatment technologies
- Select the appropriate surface treatment technology based on the usage environment and working conditions of the parts
Different mechanical parts are exposed to various environmental and working conditions in actual use, such as temperature, humidity, corrosive media, and load types. Therefore, when choosing surface treatment technologies, these factors need to be fully considered. For parts that operate in a humid environment, surface treatment technologies with good corrosion resistance, such as electroplating and coating, should be given priority. For parts operating under high-wear conditions, surface treatment technologies that can enhance wear resistance should be selected, such as surface quenching and thermal spraying of wear-resistant coatings, etc. For parts subjected to alternating loads, it is important to pay attention to choosing surface treatment technologies that can enhance fatigue strength, such as shot peening and nitriding.
- Consider the influence of surface treatment technology on the size and accuracy of parts
Some surface treatment processes may have a certain impact on the size and accuracy of parts. For instance, the electroplating layer will increase the size of the part. Although the increase is usually small, on some parts with extremely high requirements for dimensional accuracy, this factor needs to be taken into account and an appropriate allowance should be reserved during the processing. The thickness of the thermal spray coating is relatively large, which may also affect the assembly dimensions of the parts. Therefore, before conducting thermal spray treatment, it is necessary to make reasonable adjustments to the design dimensions of the parts.
In addition, some operations such as heating and cooling during surface treatment processes may cause deformation of the parts, affecting their accuracy. These operations need to be controlled and corrected in the process design and subsequent processing.
- Ensure the stability and consistency of surface treatment quality
The stability and consistency of surface treatment quality are crucial for ensuring the durability of mechanical parts. In actual production, it is necessary to strictly control the surface treatment process parameters, such as the current density and time of electroplating, the thickness of the coating, curing temperature and time of painting, and the spraying materials and process parameters of thermal spraying. At the same time, it is necessary to strengthen the quality inspection of the surface treatment process, adopt appropriate inspection methods and standards, and conduct inspections on the appearance, coating thickness, hardness, adhesion and other aspects of the treated parts to ensure that the surface treatment quality of each part meets the requirements. Only by ensuring the stability and consistency of surface treatment quality can mechanical parts have reliable durability in practical use.
Conclusion
Surface treatment technology has a positive and significant impact on the durability of mechanical parts through multiple mechanisms such as enhancing their corrosion resistance, wear resistance, improving surface roughness and fatigue strength. Different surface treatment technologies have demonstrated excellent results in various application scenarios. For instance, electroplating is applied to automotive parts to enhance corrosion resistance and decorative properties, coating is used on construction machinery to resist the erosion of harsh environments, and thermal spraying is applied to parts of aero engines to meet the requirements of special working conditions such as high temperatures and high wear.
In practical applications, it is necessary to rationally select surface treatment technologies based on factors such as the usage environment of parts, working conditions, and requirements for dimensional accuracy, and strictly control the treatment quality. This is to fully leverage the advantages of surface treatment technologies in enhancing the durability of mechanical parts, ensure the long-term stable operation of mechanical equipment, reduce maintenance costs, and improve production efficiency and economic benefits. With the continuous advancement of technology, surface treatment technology is also constantly developing and innovating. In the future, it is expected to provide more and more effective solutions for improving the durability of mechanical parts.