Vacuum technology plays a crucial role in modern science and industry, and the surface treatment quality of the vacuum chamber, as the core component of the vacuum system, directly affects the performance and reliability of the vacuum system. The surface treatment of vacuum chambers should not only ensure good airtightness and corrosion resistance, but also minimize phenomena such as gas release and adsorption to maintain a high vacuum environment.
Common surface treatment methods for vacuum chambers
(1) Cleaning
1. Solvent cleaning
Use appropriate organic solvents such as acetone, ethanol, etc. to remove contaminants such as grease and dirt from the surface of the vacuum chamber. This method is simple and easy to implement, but its effectiveness is limited for some stubborn stains.
2. Acid washing
Use acidic solutions such as hydrochloric acid, sulfuric acid, etc. to remove oxides and rust from metal surfaces. Attention should be paid to controlling the concentration of acid solution and treatment time to avoid excessive corrosion.
3. Alkali washing
For some oil pollutants, alkaline washing can have a good removal effect. Meanwhile, alkaline washing also helps to improve the microstructure of metal surfaces.
,Principles and characteristics of cleaning methods
Solvent cleaning mainly relies on the dissolution effect of organic solvents to remove pollutants; Acid washing and alkali washing use chemical reactions to remove specific pollutants. The cleaning method is simple to operate, but there may be cases of incomplete cleaning.
Shot peening
Shot peening is a cold working process that uses pellets to bombard the surface of a workpiece and implant residual compressive stress to enhance its fatigue strength.
After shot blasting treatment, the dirt on the surface of the workpiece is removed, the surface of the workpiece is not damaged, and the surface area is increased. Due to the fact that the surface of the workpiece is not damaged during the processing, the excess energy generated during processing can cause surface strengthening of the workpiece substrate. By using a high-speed rotating impeller to throw small steel balls or iron balls out and impact the surface of the parts at high speed, the oxide layer on the surface of the parts can be removed.
Sandblasting
Sandblasting is the process of cleaning and roughening the surface of a substrate using the impact of a high-speed sand flow. Compressed air is used as the driving force to form a high-speed jet beam that sprays materials (copper ore, quartz sand, diamond sand, iron sand, Hainan sand) onto the surface of the workpiece to be treated, causing changes in the appearance or shape of the outer surface of the workpiece.
1. Package the sealing surface and cutting edge of the chamber to prevent sand spraying;
2. Sandblasting the chamber according to user requirements (using 120 molybdenum sand and 80 molybdenum bowl in a ratio of 2:1)
3. After spraying the sand, rinse the chamber with clean water, dry it with an air gun, and then wipe it with alcohol. Let it air dry naturally for half a day.
mechanical polishing
Mechanical polishing is a polishing method to obtain a smooth surface by cutting and plastic deformation of the material surface to remove the convex parts after polishing. Generally, petroleum stick, wool wheel, sandpaper, etc. are used, and manual operation is the main method. Special parts such as rotary surface can use auxiliary tools such as rotary table, and ultra precision polishing can be used for those with high surface quality requirements. Ultra precision polishing is the use of specially designed grinding tools, which are pressed tightly onto the surface of the workpiece being processed in a polishing solution containing abrasives, and undergo high-speed rotational motion. This technology can achieve a surface roughness of Ra0.008 μ m, which is the highest among various polishing methods. This method is commonly used for optical lens molds.
chemical polishing
Chemical polishing is the process of allowing the micro protruding and concave parts of a material to dissolve preferentially in a chemical medium, resulting in a smooth surface. The main advantage of this method is that it does not require complex equipment, can polish workpieces with complex shapes, can polish many workpieces at the same time, and has high efficiency. The core issue of chemical polishing is the configuration of polishing solution. The surface roughness obtained by chemical polishing is generally around 10 μ m.
Electrolytic polishing
The basic principle of electrolytic polishing is the same as chemical polishing, which relies on selective dissolution of small protrusions on the surface of the material to make the surface smooth. Compared with chemical polishing, it can eliminate the influence of cathodic reactions and achieve better results. The electrochemical polishing process is divided into two steps: (1) macroscopic leveling, dissolution products diffuse into the electrolyte, and the geometric roughness of the material surface decreases, with Ra>1 μ m. (2) micro level leveling, anodic polarization, and surface brightness increase, with Ra<1 μ m.
(1) Greatly improve surface corrosion resistance. Due to the selective dissolution of elements by electrolytic polishing, a dense and strong chromium rich solid transparent film is formed on the surface, and an equipotential surface is formed, thereby eliminating and reducing micro battery corrosion.
(2) The micro surface after electrolytic polishing is smoother and has a higher reflectivity compared to mechanical polishing.
(3) Electrolytic polishing is not limited by the size and shape of the workpiece. Electrolytic polishing can be applied to workpieces that are not suitable for mechanical polishing, such as the inner walls of slender tubes, bends, bolts, nuts, and the inner and outer walls of containers.
Millimeter energy mirror processing equipment
As a new polishing process, it has unique advantages in the processing of many types of metal components. Can replace traditional metal surface finishing equipment and processes such as grinding machines, rolling machines, boring and rolling machines, honing machines, polishing machines, sand belt machines, etc; Making high smoothness machining of metal workpieces a breeze. Haoke can not only polish, but also bring many additional benefits: it can improve the surface smoothness of the processed workpiece by more than 3 levels (the roughness Ra value can easily reach below 0.2); And the surface microhardness of the workpiece is increased by more than 20%; And greatly improved the surface wear resistance and corrosion resistance of the workpiece. Hooke can be used to process various stainless steel and other metal workpieces.
Ultrasonic polishing
Place the workpiece in an abrasive suspension and place it together in an ultrasonic field, relying on the oscillation of ultrasonic waves to grind and polish the abrasive on the surface of the workpiece. Ultrasonic machining has low macroscopic force and will not cause deformation of the workpiece, but it is difficult to manufacture and install the fixture. Ultrasonic processing can be combined with chemical or electrochemical methods. On the basis of solution corrosion and electrolysis, ultrasonic vibration is applied to stir the solution, causing the dissolved products on the surface of the workpiece to detach and the corrosion or electrolyte near the surface to be uniform; The cavitation effect of ultrasound in liquid can also suppress the corrosion process and promote surface brightening.
Fluid polishing
Fluid polishing relies on the high-speed flow of liquid and the abrasive particles carried by it to wash the surface of the workpiece to achieve the purpose of polishing. Common methods include abrasive jet machining, liquid jet machining, fluid dynamic grinding, etc. Fluid dynamic grinding is driven by hydraulic pressure, which causes the liquid medium carrying abrasive particles to flow back and forth at high speed over the surface of the workpiece. The medium is mainly made of special compounds (polymer like substances) with good flowability at lower pressures and mixed with abrasives, which can be made of silicon carbide powder.
Magnetic grinding and polishing
Magnetic grinding and polishing is the process of using magnetic abrasives to form abrasive brushes under the action of a magnetic field for grinding and processing workpieces. This method has high processing efficiency, good quality, easy control of processing conditions, and good working conditions. By using appropriate abrasives, the surface roughness can reach Ra0.1 μ m. The polishing in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of molds should be called mirror processing. It not only has high requirements for polishing itself, but also has high standards for surface flatness, smoothness, and geometric accuracy. Surface polishing generally only requires obtaining a shiny surface. The standard for mirror processing is divided into four levels: AO=Ra0.008 μ m, A1=Ra0.016μm,A3=Ra0.032μm,A4=Ra0.063μm, Due to the difficulty in accurately controlling the geometric accuracy of parts using methods such as electrolytic polishing and fluid polishing, and the inadequate surface quality of methods such as chemical polishing, ultrasonic polishing, and magnetic abrasive polishing, mechanical polishing is still the main method for mirror processing of precision molds.
Chemical conversion treatment
1. Phosphating treatment
Form a phosphating film on the metal surface to enhance corrosion resistance and coating adhesion.
2. Chromate treatment
Forming a chromate conversion film can improve the corrosion resistance of metals, but its application is limited due to environmental issues.
Phosphating treatment and chromate treatment form a protective film on the surface through chemical reactions, enhancing corrosion resistance. Relatively simple and easy to implement,
anodic oxidation
Mainly used for metals such as aluminum alloys to form a dense oxide film on the metal surface, improving corrosion resistance and hardness.
The use of electrochemical principles to generate oxide films on metal surfaces has good performance, but is only applicable to specific metals.
The selection and application of surface treatment methods for vacuum chambers are crucial for the performance of vacuum systems. By selecting appropriate methods such as cleaning, sandblasting, polishing, coating, and chemical conversion treatment, the surface performance of vacuum chambers can be effectively improved to meet the needs of different fields and application scenarios.
In practical applications, it is necessary to comprehensively consider various factors, select the most suitable surface treatment method, and strengthen quality control and testing to ensure the reliability and stability of the vacuum chamber.
