Aero-Engine Blades
Stringent Surface Requirements
The surface roughness requirements for aero-engine blades are extremely high. The surface roughness Ra of the blade profile usually needs to be controlled below 0.4μm, and in critical areas such as the blade tip and leading edge, it even has to reach below 0.2μm. This is because when the engine operates at high speed, there is intense relative motion between the blade and the air. If the surface roughness does not meet the standard, problems such as airflow separation and intensified turbulence will occur, leading to a significant drop in the engine's aerodynamic efficiency and a sharp increase in fuel consumption, severely affecting the engine's performance and flight safety. For example, on the fan blades of a high-bypass turbofan engine, to ensure smooth airflow passage and reduce energy loss, the blade surface must be as smooth as a mirror to meet strict aerodynamic performance requirements.
In terms of surface hardness, since the blades need to withstand high temperature, high pressure, and the huge centrifugal force brought by high-speed rotation, as well as resist the impact of foreign objects, extremely high surface hardness is required. Advanced materials such as titanium alloys and nickel-based superalloys are usually adopted, and through multiple strengthening processes such as carburizing, nitriding, and thermal spraying, the surface hardness of the blades can reach above 60HRC. Taking titanium alloy blades as an example, after nitriding treatment, a titanium nitride layer with extremely high hardness is formed on the surface, which not only significantly improves the wear resistance of the blades but also enhances their corrosion resistance, ensuring that the blades can operate stably for a long time in a harsh working environment.
Surface finish is also one of the key indicators for aero-engine blades. High surface finish helps to improve the aerodynamic performance of the blades, reduce air resistance, and lower the probability of surface crack initiation, thus increasing the fatigue life of the blades. During the blade processing, multiple fine polishing and grinding processes are required to ensure that there are no any scratches, pits, or other defects on the surface, presenting an almost perfect smooth appearance.
Processing and Treatment Difficulties and Solutions
The processing and surface treatment of aero-engine blades face numerous challenges. The blade shape is complex, usually a thin-walled special-shaped structure, which is extremely prone to deformation during processing. For example, during CNC milling, due to the cutting force, the blade may experience twisting, warping, and other deformations. To solve this problem, special clamping fixtures such as vacuum adsorption fixtures and multi-point flexible fixtures are used, which can evenly distribute the clamping force and reduce blade deformation. At the same time, optimizing cutting parameters, such as reducing the cutting speed, decreasing the feed rate, choosing an appropriate cutting depth, and adopting high-speed cutting technology, can also effectively reduce the cutting force and the risk of blade deformation. In addition, the application of real-time monitoring and compensation technology is crucial. By measuring the deformation amount of the blade in real time during processing and using the CNC system to adjust the tool path in a timely manner to compensate for the deformation, the processing accuracy is ensured.
Most blade materials are difficult-to-machine alloys. For example, titanium alloys have poor thermal conductivity and high cutting temperatures, and superalloys have severe work hardening, which causes rapid tool wear and low processing efficiency. To address this issue, new tool materials have been developed, such as ultra-fine-grained cemented carbide, coated cemented carbide, ceramic tools, and cubic boron nitride tools. These tool materials have higher hardness, wear resistance, and thermal stability, and can effectively resist the high-temperature and high-pressure impacts during cutting, reducing tool wear. At the same time, advanced cutting processing methods such as laser-assisted machining and cryogenic cooling machining are adopted. Laser-assisted machining can use lasers to preheat the workpiece before cutting to reduce the material's hardness and improve its cutting performance; cryogenic cooling machining sprays cryogenic media such as liquid nitrogen and liquid carbon dioxide into the cutting zone to reduce the cutting temperature, reduce tool wear, and improve processing efficiency and blade quality.
Automobile Engine Pistons
Special Surface Requirements
Automobile engine pistons bear complex working conditions of high temperature, high pressure, and high-speed reciprocating motion during operation, so they have strict requirements for surface quality. In terms of surface hardness, the piston top directly bears the impact of high-temperature and high-pressure gases in the combustion chamber, and the working temperature can be as high as 300 - 400 °C, and the pressure can reach several megapascals. This requires the piston top to have relatively high hardness, and the general heat treatment hardness is 207 - 240HB to prevent surface plastic deformation, cracks, and other defects. The piston ring groove area is equally critical and needs to bear the reciprocating friction and lateral pressure of the piston ring. Its surface hardness requirements are even higher. Through nitriding, hard chromium plating, and other treatments, the hardness can be increased to 600 - 800HV, effectively enhancing the wear resistance and ensuring good sealing performance between the piston ring and the ring groove, reducing gas leakage and improving engine power.
Wear resistance is crucial for pistons because pistons move at high speed in the cylinder and frequently rub against the cylinder wall. If the wear resistance is insufficient, severe wear will occur in a short time, resulting in a decrease in engine power, an increase in fuel consumption, and excessive emissions. To improve wear resistance, the piston skirt usually adopts surface coating technologies, such as spraying graphite, molybdenum disulfide, and other solid lubricant coatings, which can not only reduce the friction coefficient but also repair the worn surface to a certain extent; the piston ring adopts processes such as chromium plating and nitriding to form a hard and wear-resistant plating layer or diffusion layer on its surface, greatly extending the service life of the piston assembly.
In terms of surface finish, a smooth piston surface helps to reduce the friction resistance between the piston and the cylinder wall, improve mechanical efficiency, and reduce fuel consumption. The surface roughness Ra of the piston outer cylindrical surface is generally required to be controlled between 0.8 - 1.6μm. Through fine grinding, honing, and other processing technologies, the surface is ensured to be flat and smooth, avoiding serious faults such as cylinder scoring and piston seizure caused by rough surfaces.
Process Measures to Achieve Surface Requirements
In the casting process, lightweight and thermally conductive materials such as aluminum alloys are selected, and precision casting processes such as low-pressure casting and lost foam casting are used to ensure the dimensional accuracy and internal quality of the piston blank. Low-pressure casting can precisely control the filling speed and pressure to make the molten metal fill the mold smoothly, reducing defects such as pores and shrinkage porosity; lost foam casting can produce piston blanks with complex shapes and relatively high precision. In the mechanical processing stage, a CNC machining center is used to precisely control the dimensional tolerances of various parts of the piston, such as the cylindricity of the piston pin hole and the ellipticity of the piston skirt. The errors are controlled within a very small range. For example, the cylindricity error of the piston pin hole is required to be controlled within ±0.005mm. By adopting high-precision boring and reaming processes and combining online measurement and compensation technology, the dimensional accuracy and shape accuracy of the pin hole are ensured. During surface treatment, the process parameters are strictly controlled, such as the nitriding temperature, time, gas flow rate, and the current density and plating solution composition during chromium plating. When performing nitriding treatment, appropriate nitriding temperatures (such as 500 - 550 °C) and times (such as 20 - 50 hours) can make a uniform and dense nitride layer form on the surface of the piston ring groove, improving hardness and wear resistance; when chromium plating, precisely controlling the current density (such as 30 - 50A/dm²) and plating solution composition ensures the quality and thickness of the chromium plating layer to meet the high hardness and wear resistance requirements of the piston ring groove.
Summary and Outlook
In the field of mechanical processing, the importance of the surface quality of metal parts is self-evident. It permeates all aspects of product performance, service life, and market competitiveness. Through in-depth discussions on surface roughness, surface hardness, surface finish, surface integrity, and various surface treatment processes, we clearly recognize that each link is closely connected and jointly determines the quality of metal parts.
Surface roughness affects the friction, wear, fatigue, and fitting accuracy characteristics of parts from a microscopic level. Precise control of its value is the basis for achieving excellent performance of parts; surface hardness is like a solid fortress, effectively resisting wear and compression, and multiple strengthening methods provide powerful protection for metal parts under different working conditions; surface finish is unique in presenting aesthetics and quality. Polishing, grinding, electrolytic polishing, and other processes make products complement each other in appearance and practicality; surface integrity covers multi-dimensional characteristics such as micro-geometry, physical mechanics, and metallurgical chemistry, and is a key element to ensure the stable comprehensive performance of metal parts, which needs to be carefully maintained during processing; electroplating, anodizing, blackening treatment, spraying, and other surface treatment processes are like magic brushes, customized according to requirements, endowing metal parts with diverse excellent properties such as corrosion resistance, decoration, and wear resistance.
Looking ahead, mechanical processing and metal part surface treatment technologies will continue to develop in multiple directions. With the continuous enhancement of environmental awareness, green and environmentally friendly surface treatment processes will become the mainstream trend. For example, developing new chromium-free electroplating technologies to reduce heavy metal pollution; developing spraying materials and processes with low volatile organic compound (VOC) content to reduce the impact on the atmospheric environment and achieve sustainable development. The application of digital and intelligent technologies will become increasingly widespread. With the help of big data, artificial intelligence, and automated control technologies, real-time optimization of processing parameters, accurate prediction of surface quality, and intelligent monitoring will be realized, significantly improving production efficiency and product quality stability. In an increasingly growing market environment with personalized customization requirements, surface treatment processes will become more flexible and diverse, able to quickly respond to customers' special requirements for different performances and appearances, providing customized metal part solutions for various fields. The continuous emergence of new materials and new technologies, such as the in-depth application of nanotechnology and bionic technology in surface treatment, is expected to break through existing performance bottlenecks, providing metal materials with extraordinary performance for frontier fields such as aerospace and high-end equipment manufacturing, and opening a new chapter in mechanical processing and surface treatment technologies. In short, continuously paying attention to and closely following these development trends is of profound significance for mechanical processing enterprises to maintain their competitiveness and promote the progress of the industry. Let us jointly look forward to a more brilliant future in the metal processing field.
EATHU's Outstanding Contributions in the Field of Mechanical Processing
EATHU, as a leading enterprise in the field of mechanical processing, plays an important role in controlling the surface quality of metal parts.
In terms of processing technology research and development, EATHU invests a large amount of resources in innovative research. Regarding the precise control of surface roughness, EATHU's scientific research team conducts in-depth research on cutting mechanisms and tool wear laws and develops an advanced intelligent processing system. This system can dynamically adjust cutting parameters in real time according to the characteristics of workpiece materials, tool states, and processing requirements, ensuring that the surface roughness is stabilized at an extremely low level. For example, when processing high-precision molds, through the optimization of this system, the surface roughness of the molds can reach below Ra0.1μm, greatly improving the molding accuracy and service life of the molds.
For improving surface hardness, EATHU cooperates with material research institutions to jointly develop new surface strengthening processes. By adopting a unique multi-element co-diffusion technology, multiple alloy elements are simultaneously infiltrated into the metal surface to form a composite strengthening layer with ultra-high hardness and good toughness. In the processing of high-strength bolts, after applying this process, the surface hardness of the bolts is increased to above 65HRC while maintaining good toughness, effectively improving the fatigue performance and fastening reliability of the bolts.
In terms of improving surface finish, EATHU has introduced advanced ultra-precision polishing equipment and processes. Combined with the independently developed polishing fluid formula, it can achieve atomic-level polishing of the metal part surface. In the processing of optical lenses, EATHU's polishing process makes the surface roughness of the lenses reach below Ra0.01μm, and the surface flatness reaches λ/20 (λ is the wavelength of light), ensuring the high optical performance of the lenses.
EATHU pays attention to the comprehensive guarantee of surface integrity. During the processing, advanced online monitoring technologies are adopted to monitor parameters such as the temperature, stress, and deformation of the workpiece in real time. Through closed-loop control with the processing equipment, the processing strategy is adjusted in a timely manner to avoid surface integrity damage caused by improper processing parameters. For example, when processing aerospace components, EATHU's online monitoring and control technology ensures that the residual stress on the part surface is in an optimal state, improving the fatigue performance and reliability of the part.
In terms of surface treatment process innovation, EATHU actively explores environmentally friendly and efficient alternative solutions. It has developed a new water-based electroplating process. Compared with traditional electroplating processes, this process reduces heavy metal emissions by more than 90% while improving the uniformity and adhesion of the plating layer. In the electroplating production of automobile parts, adopting this water-based electroplating process not only reduces environmental pollution but also improves the quality and market competitiveness of the products.
EATHU is also committed to providing customized solutions for customers. According to the special requirements of customers in different industries for the surface performance of metal parts, from material selection, processing process design to surface treatment scheme formulation, it provides one-stop services. In the field of medical device manufacturing, EATHU has customized a set of solutions including high-precision processing and special surface treatment for customers, making the parts of medical devices meet strict hygiene standards while having excellent wear resistance and corrosion resistance, extending the service life of medical devices, and improving the safety and reliability of medical equipment.
EATHU, by virtue of its advantages in technological innovation, process optimization, and customized services, continuously promotes the mechanical processing industry to move towards higher quality, more environmental protection, and more intelligent directions, providing high-quality metal part processing solutions for the global manufacturing industry and setting an outstanding benchmark in the field of mechanical processing.