Vacuum pump rotor surface treatment method

Abstract

The invention relates to the technical field of vacuum pumps, and particularly discloses a vacuum pump rotor surface treatment method which is characterized by comprising the following steps: substrate pretreatment including ultrasonic cleaning, micro-arc oxidation treatment and low-temperature plasma treatment; modification treatment is conducted, specifically, the PTFE nano particles are modified; chemical nickel plating treatment: putting the rotor substrate subjected to substrate pretreatment into a chemical nickel plating solution, and adding modified PTFE (Polytetrafluoroethylene) nanoparticles to form a composite coating on the surface of the rotor substrate; curing: heating and curing the rotor substrate subjected to the chemical nickel plating treatment; and polishing: carrying out polishing treatment on the heated and cured rotor base body. The binding force of the coating and the metal matrix can be improved, and the problem of peeling during high-speed operation is solved.

Description

Technical Field

[0001] This invention relates to the field of vacuum pump technology, specifically to a method for surface treatment of a vacuum pump rotor. Background Technology

[0002] Vacuum pumps used in the semiconductor industry require rotors with both high surface hardness and corrosion resistance. Current rotor surface protection primarily involves directly spraying a pure PTFE (Teflon) coating onto the rotor surface. While this provides corrosion resistance (resistant to media such as sulfurous acid), it has significant drawbacks, mainly three major problems: 1. Low bonding strength: The bonding strength between the coating and the metal substrate is <10MPa, and it is easy to peel off under high-speed operation; 2. Weak resistance to particle erosion: Solid particles (such as metal shavings) or carbonized colloids (such as butadiene polymers) in the feed medium can scratch the coating, causing corrosive media to penetrate into the substrate; 3. Insufficient temperature resistance: Long-term operating temperature ≤260℃, PTFE decomposes and fails after exceeding the temperature. Summary of the Invention

[0003] The purpose of this invention is to provide a surface treatment method for a vacuum pump rotor to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: a method for surface treatment of a vacuum pump rotor, characterized by comprising the following steps: S10, Matrix pretreatment, the matrix pretreatment includes: S11, Ultrasonic cleaning: The rotor substrate is placed in the cleaning solution and cleaned by ultrasonic waves. S12, Micro-arc oxidation treatment: The cleaned rotor substrate is placed in an electrolyte for treatment; S13, Low-temperature plasma treatment: The rotor substrate that has undergone oxidation treatment is subjected to plasma treatment in a vacuum environment, thereby forming active groups on the surface of the rotor substrate. S20, Modification treatment: Modification of PTFE nanoparticles; S30, electroless nickel plating: The rotor substrate that has undergone substrate pretreatment is placed into an electroless nickel plating solution, and modified PTFE nanoparticles are added to form a composite coating on the surface of the rotor substrate. S40, Curing: Curing the rotor substrate that has undergone chemical nickel plating by heating; S50, Polishing: Polishing the rotor substrate after it has been heated and cured.

[0005] Further, in step S11, the cleaning solution comprises the following components in the following volume ratio: 80% deionized water, 5% sodium dodecylbenzenesulfonate, 3% disodium ethylenediaminetetraacetate, 2% benzotriazole, and 10% additives.

[0006] Further, in step S11, the cleaning step includes: placing the rotor substrate to be treated into a cleaning basket, then completely immersing it in the cleaning solution, and then placing the cleaning basket into an ultrasonic cleaner, setting the frequency of the ultrasonic cleaner to 40kHz, the power to 200W, the cleaning time to 15 minutes, and the cleaning temperature to 35℃.

[0007] Further, in step S12, the electrolyte includes sodium silicate, sodium hydroxide, and glycerol.

[0008] Furthermore, in step S12, during electrolysis, a voltage of 320V is applied, and the current density is controlled at 12A / dm³. 2 The oxidation time was set to 12 minutes, and the solution temperature was maintained at 25°C.

[0009] Furthermore, in step S13, argon and oxygen with a volume ratio of 8:2 are used, radio frequency power of 120W is applied, and the processing time is 8 minutes.

[0010] Further, in step S20, PTFE nanoparticles with a particle size of 50-200 nm are added to a KH-550-ethanol solution, stirred in a constant temperature water bath at 50°C for 1 hour, and then filtered and dried for later use.

[0011] Further, in step S30, the electroless nickel plating solution contains 25 g / L nickel sulfate, 30 g / L sodium hypophosphite, 15 g / L sodium acetate, 0.3 g / L sodium citrate, and 0.1 g / L sodium dodecylbenzenesulfonate.

[0012] Further, in step S30, the temperature of the plating solution is controlled at 86-90℃, the pH value at 4.6-5.0℃, and the stirring rate at 200rpm. The modified PTFE nanoparticles are added to the plating solution in three batches, with an interval of 20min between each batch, and the deposition time is 90min.

[0013] The present invention has the following beneficial effects: This invention can improve the adhesion between the composite coating and the metal substrate, solving the problem of peeling off at high speeds; the long-term operating temperature is increased to 350°C, meeting the requirements of high-temperature semiconductor processes; the resistance to particle erosion is improved, and the wear is reduced to 1.1μm in a medium containing 5μm metal debris; the coefficient of friction μ is less than 0.09, combining lubricity and hardness. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1 The surface treatment method for the vacuum pump rotor in this embodiment mainly includes substrate pretreatment, ultrasonic cleaning, micro-arc oxidation treatment, low-temperature plasma treatment, modification treatment, electroless nickel plating treatment, curing treatment and polishing treatment performed sequentially or simultaneously. The rotor substrate is a nickel-phosphorus alloy material.

[0016] Specifically, ultrasonic cleaning involves immersing the rotor substrate in a cleaning solution and cleaning it using ultrasound. The cleaning solution comprises the following components in the following volume ratios: 80% deionized water, 5% surfactant (sodium dodecylbenzenesulfonate), 3% chelating agent (disodium ethylenediaminetetraacetate), 2% corrosion inhibitor (benzotriazole), and 10% additives. The cleaning steps include: placing the rotor substrate to be treated in a cleaning basket, then completely immersing it in the cleaning solution, and then placing the cleaning basket into an ultrasonic cleaner. The ultrasonic cleaner is set to a frequency of 40kHz, a power of 200W, a cleaning time of 15 minutes, and a cleaning temperature controlled at 35℃. During the cleaning process, the cavitation effect of ultrasound generates microbubbles in the cleaning solution. When these bubbles burst on the substrate surface, they generate a strong impact force, peeling off surface oil, dust, and other impurities. At the same time, the surfactant in the cleaning solution reduces the adhesion between oil and the substrate, the chelating agent removes the oxide film on the metal surface, and the corrosion inhibitor prevents the substrate from being corroded during the cleaning process.

[0017] Micro-arc oxidation involves immersing a cleaned rotor substrate in an electrolyte solution comprising 15 g / L sodium silicate, 5 g / L sodium hydroxide, and 3 g / L glycerol. The cleaned rotor substrate serves as the anode, and a stainless steel plate as the cathode. The substrate is then placed in the electrolyte, and a power supply is applied at 320V, with a current density controlled at 12A / dm². The oxidation time is set to 12 minutes, and the solution temperature is maintained at 25°C. During micro-arc oxidation, as the voltage increases, micro-arc discharge occurs on the substrate surface. The instantaneous high temperature and pressure cause a chemical reaction between the aluminum and the electrolyte, forming a porous ceramic oxide film on the substrate surface. These pores increase the surface roughness of the substrate, providing more anchoring points for the subsequent coating adhesion.

[0018] Low-temperature plasma treatment involves subjecting the oxidized rotor substrate to plasma treatment in a vacuum environment using an argon-oxygen mixture with a volume ratio of 8:2. The micro-arc oxidized substrate is placed in the vacuum chamber of the plasma treatment equipment, and a vacuum pump is activated to create a vacuum. The mixed gas is then introduced through the gas inlet at a flow rate of 60 sccm. The radio frequency power supply is turned on, applying 120W of power for 8 minutes. In the plasma environment, high-energy particles continuously bombard the substrate surface, breaking the chemical bonds of surface atoms and forming numerous active groups. This alters the surface microstructure, further enhancing surface activity and wettability, which is beneficial for the formation of strong chemical bonds between the coating and the substrate.

[0019] The modification of PTFE nanoparticles includes adding PTFE nanoparticles with a particle size of 50-200 nm to a 5% (w / w) KH-550-ethanol solution, wherein the volume ratio of ethanol to water in the ethanol solution is 9:1. After stirring in a constant temperature water bath at 50°C for 1 hour, the mixture is filtered, dried, and ready for use. The amino groups in the KH-550 molecule can form coordination bonds with nickel ions in the nickel-phosphorus alloy, and its hydrophobic ends can combine with the surface of the PTFE particles, improving the hydrophobicity of the particles and preventing agglomeration in the plating solution. After modification, the particles are filtered, dried, and then filtered through a 100-mesh filter to remove a small amount of agglomerated particles, ensuring particle dispersion.

[0020] Furthermore, during the electroless nickel plating co-deposition process, the electroless nickel plating solution contains 25 g / L nickel sulfate, 30 g / L sodium hypophosphite, 15 g / L sodium acetate, 0.3 g / L sodium citrate, and 0.1 g / L sodium dodecylbenzene sulfonate. The rotor substrate is placed in the electroless nickel plating solution, and the temperature of the plating solution is controlled at 86-90℃, the pH value at 4.6-5.0℃, and the stirring speed at 200 rpm. The modified PTFE nanoparticles are added to the plating solution in three batches, with an interval of 20 min between each batch, and the deposition time is 90 min. This avoids local enrichment of particles and achieves uniform co-deposition, thereby forming a composite coating on the rotor surface. Finally, the mass fraction of PTFE nanoparticles in the coating is stabilized at 12%-15%.

[0021] Furthermore, during the curing process, a segmented heating method is adopted. First, the temperature is kept at 180℃ for 1 hour to remove residual moisture and plating solution impurities in the coating and avoid the generation of bubbles in subsequent high-temperature treatment. Then, the temperature is kept at 280℃ for 2 hours to promote the crystallization of nickel-phosphorus alloy and improve the hardness and wear resistance of the coating. Finally, the temperature is kept at 320℃ for 1 hour to stabilize the interfacial bonding between PTFE nanoparticles and nickel-phosphorus matrix and prevent decomposition.

[0022] Furthermore, after polishing, the surface roughness Ra is reduced to ≤0.2μm, thus lowering operating resistance, while ensuring a total coating thickness of 20-25μm.

[0023] Performance tests were conducted on the treated samples. The coating could be continuously operated at 300℃ for 1000 hours without decomposition or peeling. After being washed for 800 hours in a medium containing 5μm metal debris (flow rate of 10m / s), the wear amount was only 1.1μm, improving the erosion resistance. After being immersed in sulfurous acid at 200℃ for 1000 hours, the corrosion rate was only 0.0018mm / a, showing strong corrosion resistance. At the same time, the friction system temperature was around 0.085 at 350℃, breaking through the temperature limit of grease lubrication.

[0024] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for surface treatment of a vacuum pump rotor, characterized in that, Includes the following steps: S10, Matrix pretreatment, the matrix pretreatment includes: S11, Ultrasonic cleaning: The rotor substrate is placed in the cleaning solution and cleaned by ultrasonic waves. S12, Micro-arc oxidation treatment: The cleaned rotor substrate is placed in an electrolyte for treatment; S13, Low-temperature plasma treatment: The rotor substrate that has undergone oxidation treatment is subjected to plasma treatment in a vacuum environment, thereby forming active groups on the surface of the rotor substrate. S20, Modification treatment: Modification of PTFE nanoparticles; S30, electroless nickel plating: The rotor substrate that has undergone substrate pretreatment is placed into an electroless nickel plating solution, and modified PTFE nanoparticles are added to form a composite coating on the surface of the rotor substrate. S40, Curing: Curing the rotor substrate that has undergone chemical nickel plating by heating; S50, Polishing: Polishing the rotor substrate after it has been heated and cured.

2. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S11, the cleaning solution comprises the following components in the following volume ratio: 80% deionized water, 5% sodium dodecylbenzenesulfonate, 3% disodium ethylenediaminetetraacetate, 2% benzotriazole, and 10% additives.

3. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S11, the cleaning step includes: placing the rotor substrate to be treated into a cleaning basket, then completely immersing it in the cleaning solution, and then placing the cleaning basket into an ultrasonic cleaner. The ultrasonic cleaner is set to a frequency of 40kHz, a power of 200W, a cleaning time of 15 minutes, and a cleaning temperature of 35℃.

4. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S12, the electrolyte includes sodium silicate, sodium hydroxide, and glycerol.

5. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S12, during electrolysis, a voltage of 320V is applied and the current density is controlled at 12A / dm³. 2 The oxidation time was set to 12 minutes, and the solution temperature was maintained at 25°C.

6. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S13, argon and oxygen with a volume ratio of 8:2 are used, radio frequency power of 120W is applied, and the processing time is 8 minutes.

7. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S20, PTFE nanoparticles with a particle size of 50-200 nm are added to a KH-550-ethanol solution, stirred in a constant temperature water bath at 50°C for 1 hour, and then filtered and dried for later use.

8. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S30, the electroless nickel plating solution contains 25 g / L nickel sulfate, 30 g / L sodium hypophosphite, 15 g / L sodium acetate, 0.3 g / L sodium citrate, and 0.1 g / L sodium dodecylbenzenesulfonate.

9. The surface treatment method for a vacuum pump rotor according to claim 1, characterized in that: In step S30, the temperature of the plating solution is controlled at 86-90℃, the pH value at 4.6-5.0℃, and the stirring rate at 200rpm. The modified PTFE nanoparticles are added to the plating solution in three batches, with an interval of 20min between each batch, and the deposition time is 90min.