Screw anti-corrosion treatment method and anti-corrosion screw

Abstract

The invention discloses a screw anti-corrosion treatment method and an anti-corrosion screw. The method comprises the following steps: (1) nickel plating treatment; (2) aluminum spraying treatment; (3) high-temperature aluminizing; and (4) magnetic polishing. Through PVD nickel plating, high-temperature aluminum spraying, aluminizing and magnetic polishing treatment, a compact Al-Ni alloy layer is formed on the surface of the screw, no corrosion can be achieved for 1200 hours in a salt spray test, the surface roughness Ra is smaller than or equal to 0.2 micron, the corrosion resistance, the surface cleanliness and the binding force of the screw are remarkably improved, and the high-reliability requirement of semiconductor equipment is met.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a method for anti-corrosion treatment of screws and anti-corrosion screws, which is especially suitable for high-performance anti-corrosion treatment of screws in vacuum equipment in the semiconductor industry. Background Technology

[0002] In semiconductor vacuum equipment, fasteners such as screws play a crucial role in the normal operation of the equipment. Therefore, screws and other fasteners are required to have excellent corrosion resistance, low outgassing rate, and surface cleanliness.

[0003] In the prior art, the anti-corrosion treatment of fasteners such as screws mostly adopts a single coating, such as hot-dip galvanizing, as shown in the disclosure of Chinese Patent 202010793446.X.

[0004] Therefore, even after existing anti-corrosion treatment, screws still suffer from problems such as easy peeling of the anti-corrosion layer, poor anti-corrosion durability, and easy re-corrosion in actual use. Summary of the Invention

[0005] This invention provides a method for preventing screw corrosion and an anti-corrosion screw, which can solve the above-mentioned shortcomings of existing anti-corrosion technologies.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preventing corrosion of screws, comprising the following steps: (1) Nickel plating: A nickel layer is formed on the screw surface by physical vapor deposition; (2) Aluminum spraying treatment: Aluminum coating is sprayed onto the nickel layer using a high-temperature aluminum wire spraying process; (3) High-temperature aluminizing: Place the screws with nickel and aluminum coatings from step (2) into a high-temperature aluminizing furnace, and heat them under a vacuum of ≤1.0×10⁻⁶. -3 Under the condition of Pa, the temperature is raised to 850-950℃, and aluminizing is carried out at a constant temperature for 2-3 hours. After aluminizing, the furnace is cooled to below 30℃. (4) Magnetic polishing: Place the screws that have been aluminized in step (3) into a magnetic polishing machine, use zirconia ceramic beads as the polishing medium to polish the oxide layer and residue on the surface of the screws, dry them, and complete the anti-corrosion treatment.

[0007] In a preferred embodiment of the present invention, in step (1), the nickel plating process conditions are: vacuum degree ≤ 1.0 × 10⁻⁶. -3 Pa, temperature 220-230℃, time 20-25min.

[0008] In a preferred embodiment of the present invention, the thickness of the nickel layer is 10-18 μm.

[0009] In a preferred embodiment of the present invention, in step (2), the conditions of the high-temperature aluminum wire spraying process are: aluminum wire melting temperature 700-1000℃, spraying distance 100-200mm, atomizing gas is nitrogen, and pressure 0.4-0.8MPa.

[0010] In a preferred embodiment of the present invention, the diameter of the aluminum wire is 1.6-3.0 mm.

[0011] In a preferred embodiment of the present invention, in step (3), the heating rate is 10-15℃ / min.

[0012] In a preferred embodiment of the present invention, in step (4), the polishing process conditions are: rotation speed 2000-3000 rpm, polishing time 15-20 min, and the mass ratio of polishing medium to screw is 1:1 to 1:3.

[0013] In a preferred embodiment of the present invention, the zirconia ceramic beads have a particle size of 1.0-1.5 mm.

[0014] To solve the above-mentioned technical problems, the present invention also provides an anti-corrosion screw, which is prepared by the above method. The screw surface has a nickel layer and an aluminum layer, and the nickel layer and the aluminum layer form an alloy interface through high-temperature aluminizing.

[0015] In a preferred embodiment of the present invention, the thickness of the alloy interface is 2-5 μm.

[0016] The beneficial effects of this invention are as follows: This invention provides a screw anti-corrosion treatment method, which forms a dense Al-Ni alloy layer on the screw surface through PVD nickel plating, high-temperature aluminum spraying, aluminum diffusion, and magnetic polishing. This enhances the bonding force between the aluminum layer and the substrate, and improves corrosion resistance. The anti-corrosion screw prepared by this invention can withstand 1200 hours of salt spray testing without corrosion, and has a surface roughness Ra≤0.2μm. This significantly improves the screw's corrosion resistance, surface cleanliness, and bonding force, making it suitable for the high reliability requirements of semiconductor equipment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow of a screw anti-corrosion treatment method according to the present invention. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] Example 1 This invention discloses a method for preventing corrosion of screws, which specifically includes the following steps: (1) Nickel plating treatment: After the screws to be treated are cleaned by ultrasonic cleaning, they are placed in a physical vapor deposition (PVD) equipment with a vacuum degree ≤1.0×10 -3 Pa, nickel target material is deposited on the screw surface by high-temperature sputtering, the coating temperature is 230±5℃, the coating time is 20 minutes, and it is naturally cooled to the ambient temperature.

[0020] Nickel plating, with the nickel layer as an intermediate transition layer, enhances the bonding force between the aluminum layer and the substrate, and improves the adhesion between the aluminum layer and the screw body, thereby improving corrosion resistance.

[0021] (2) Aluminum spraying: The nickel-plated screws are fixed in the aluminum spraying fixture and the aluminum wire high-temperature melting process is adopted. Specifically, the diameter of the aluminum wire used is 1.5 mm, the aluminum wire melting temperature is 850℃ (plasma melting), the particle size of the aluminum powder after melting is 15±5 μm, the spraying distance is 150 mm, the atomizing gas is nitrogen, the pressure is 0.5 MPa, and a uniform aluminum coating is formed.

[0022] (3) High-temperature aluminizing: Place the aluminum-sprayed screws in a vacuum aluminizing furnace with a vacuum degree ≤1.0×10 -3 Pa, heat to 900±10℃ at a rate of 10℃ / min, aluminize at a constant temperature for 2.5 hours, cool with the furnace to below 30℃, open the vacuum valve, and remove the screws.

[0023] (4) Magnetic polishing: The aluminum-coated screws are placed in a magnetic polishing machine. Zirconia ceramic beads with a particle size of 1.0-1.5mm are used as the polishing medium. The mass ratio of polishing medium to screws is 1:2. The polishing speed is 2500 rpm, and the polishing time is 20 minutes to remove the surface oxide layer and unbonded particles, improve the density of the aluminum layer, and reduce the risk of subsequent corrosion. The surface roughness Ra after magnetic polishing is ≤0.2μm, which meets the requirements of semiconductor vacuum environment.

[0024] After polishing, place the screws in an oven at 60±5℃ and dry for 30 minutes. After inspection, package them.

[0025] The anti-corrosion screws prepared by the above method have a nickel layer and an aluminum layer on their surface, and the nickel layer and aluminum layer form an alloy interface with a thickness of 3μm by high-temperature aluminizing.

[0026] Example 2 This invention discloses a method for preventing corrosion of screws, which specifically includes the following steps: (1) Nickel plating treatment: After the screws to be treated are cleaned by ultrasonic cleaning, they are placed in a physical vapor deposition (PVD) equipment with a vacuum degree ≤1.0×10 -3 Pa, nickel target material is deposited on the screw surface by high-temperature sputtering, the coating temperature is 230±5℃, the coating time is 25 minutes, and it is naturally cooled to the ambient temperature.

[0027] (2) Aluminum spraying: The nickel-plated screws are fixed in the aluminum spraying fixture and the aluminum wire high-temperature melting process is adopted. Specifically, the diameter of the aluminum wire used is 1.5 mm, the aluminum wire melting temperature is 1000℃ (plasma melting), the particle size of the aluminum powder after melting is 15±5 μm, the spraying distance is 120 mm, the atomizing gas is nitrogen, the pressure is 0.5 MPa, and a uniform aluminum coating is formed.

[0028] (3) High-temperature aluminizing: Place the aluminum-sprayed screws in a vacuum aluminizing furnace with a vacuum degree ≤1.0×10 -3 Pa, heat to 900±10℃ at a rate of 10℃ / min, aluminize at a constant temperature for 2.5 hours, cool with the furnace to below 30℃, open the vacuum valve, and remove the screws.

[0029] (4) Magnetic polishing: The aluminum-coated screws are placed in a magnetic polishing machine. Zirconia ceramic beads with a particle size of 1.0-1.5mm are used as the polishing medium. The mass ratio of polishing medium to screws is 1:3. The polishing speed is 2500 rpm, and the polishing time is 20 minutes to remove the surface oxide layer and unbonded particles, improve the density of the aluminum layer, and reduce the risk of subsequent corrosion. The surface roughness Ra after magnetic polishing is ≤0.2μm, which meets the requirements of semiconductor vacuum environment.

[0030] After polishing, place the screws in an oven at 60±5℃ and dry for 30 minutes. After inspection, package them.

[0031] The anti-corrosion screws prepared by the above method have a nickel layer and an aluminum layer on their surface, and the nickel layer and aluminum layer form an alloy interface with a thickness of 5μm by high-temperature aluminizing.

[0032] Comparative Example 1 Compared with the example, the screw surface that has been ultrasonically cleaned is directly subjected to aluminum spraying, high-temperature aluminum diffusion and magnetic polishing, and the process conditions are the same as in Example 1.

[0033] Comparative Example 2 Compared with Example 1, magnetic polishing was performed directly after nickel plating, and the process conditions were the same as in Example 1.

[0034] Comparative Example 3 Compared to Example 1, no magnetic polishing was performed.

[0035] The performance of the anti-corrosion screws obtained in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 was tested, and the test results are shown in Table 1 below.

[0036] Table 1 Note: Adhesion testing was conducted according to ASTM D4541 standard; salt resistance testing was conducted according to ASTM B117 standard using a neutral salt spray test, with test conditions of 5% NaCl solution, temperature 35±2℃, and corrosion area <0.5%.

[0037] The test results above show that the present invention significantly improves the corrosion resistance, surface cleanliness and bonding strength of screws through the synergistic process of PVD nickel plating, high-temperature aluminum spraying, aluminum diffusion, magnetic polishing and drying. The screws can withstand 1200 hours of salt spray test without corrosion and have a surface roughness Ra≤0.2μm, making them suitable for the high reliability requirements of semiconductor equipment.

[0038] The present invention has the following advantages: 1. Combining PVD nickel plating with high-temperature aluminum spraying and aluminizing, using the nickel layer as an intermediate transition layer, enhances the adhesion between the aluminum layer and the substrate, avoiding the insufficient adhesion problem caused by direct aluminum spraying. This results in anti-corrosion screws with significantly better high-temperature oxidation resistance and chemical corrosion resistance than single plating.

[0039] 2. After aluminizing, magnetic polishing is introduced to effectively remove the surface oxide layer and residues, improve the density of the aluminum layer, reduce the risk of subsequent corrosion, and reduce the surface roughness (Ra≤0.2μm) after magnetic polishing, which meets the stringent requirements of semiconductor equipment for cleanliness and precision.

[0040] 3. High-temperature aluminizing (900℃) is carried out under ultra-high vacuum (1.0×10⁻³Pa), which avoids oxidation and promotes deep diffusion of aluminum atoms to form a uniform alloy layer.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preventing corrosion of screws, characterized in that, Includes the following steps: (1) Nickel plating: A nickel layer is formed on the screw surface by physical vapor deposition; (2) Aluminum spraying treatment: Aluminum coating is sprayed onto the nickel layer using a high-temperature aluminum wire spraying process; (3) High-temperature aluminizing: Place the screws with nickel and aluminum coatings from step (2) into a high-temperature aluminizing furnace, and heat them under a vacuum of ≤1.0×10⁻⁶. -3 Under the condition of Pa, the temperature is raised to 850-950℃, and aluminizing is carried out at a constant temperature for 2-3 hours. After aluminizing, the furnace is cooled to below 30℃. (4) Magnetic polishing: Place the screws that have been aluminized in step (3) into a magnetic polishing machine, use zirconia ceramic beads as the polishing medium to polish the oxide layer and residue on the surface of the screws, dry them, and complete the anti-corrosion treatment.

2. The method according to claim 1, characterized in that, In step (1), the nickel plating process conditions are: vacuum degree ≤ 1.0 × 10⁻⁶. -3 Pa, temperature 220-230℃, time 20-25min.

3. The method according to claim 2, characterized in that, The thickness of the nickel layer is 10-18 μm.

4. The method according to claim 1, characterized in that, In step (2), the conditions for the high-temperature aluminum wire spraying process are: aluminum wire melting temperature 700-1000℃, spraying distance 100-200mm, atomizing gas is nitrogen, and pressure 0.4-0.8MPa.

5. The method according to claim 4, characterized in that, The diameter of the aluminum wire is 1.6-3.0 mm.

6. The method according to claim 1, characterized in that, In step (3), the heating rate is 10-15℃ / min.

7. The method according to claim 1, characterized in that, In step (4), the polishing process conditions are: rotation speed 2000-3000 rpm, polishing time 15-20 min, and the mass ratio of polishing medium to screw is 1:1 to 1:

3.

8. The method according to claim 7, characterized in that, The zirconium oxide ceramic beads have a particle size of 1.0-1.5 mm.

9. A corrosion-resistant screw, characterized in that, The screw is prepared by any one of the methods described in claims 1-6, and the screw surface has a nickel layer and an aluminum layer, and the nickel layer and the aluminum layer form an alloy interface by high-temperature aluminizing.

10. The anti-corrosion screw according to claim 9, characterized in that, The thickness of the alloy interface is 2-5 μm.

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