Method for improving surface roughness by combining different alloys on the surface of a mirror

Abstract

The present invention relates to the field of mirror processing. A method for improving the surface roughness by combining different alloys on the surface of a mirror includes the following steps: Step 1, rough machining; Step 2, cleaning the surface of the reflector and storing it; Step 3, cleaning the vacuum coating machine; Step 4, putting nickel with a purity greater than 99.99% and phosphorus with a purity greater than 99.99% into two different crucibles respectively; Step 5, hanging the mirror in the vacuum coating machine and placing the crucibles on the electron beam evaporator; evacuating the air and heating the crucibles with the electron beam evaporator. The current of the electron beam evaporator under the crucible containing nickel is 400 mA, and the current of the electron beam evaporator under the crucible containing phosphorus is 200 mA; and the working time ratio of the electron beam evaporator under the crucible containing nickel to the electron beam evaporator under the crucible containing phosphorus is 9:1; Step 6, magnetorheological polishing. The final roughness Ra is less than or equal to 2 nm.

Description

Technical Field

[0001] The present invention relates to the technical field of mirror processing, and specifically relates to a method for improving surface roughness and surface shape. Background Art

[0002] At present, all-aluminum cameras are being used as space cameras in the space field. The mirrors in the cameras generally use mirrors made of aluminum alloy 6061-T6. These mirrors are all turned by single-point diamond turning, and the roughness can only reach Ra5-7nm, far from meeting the growing technical requirements. Also, due to the influence of various factors such as fixture error, tool error, and ambient error during the single-point diamond turning process, it is very difficult to make the surface shape RMS of mirrors with a diameter above 200mm better than 1 / 15λ (λ = 632.8nm). Using magnetorheological technology can improve the surface shape, but the roughness will decrease sharply while improving the surface shape. How to correct the surface shape of the aluminum alloy 6061-T6 mirror while maintaining a relatively high roughness is an urgent problem to be overcome in the research and development of mirrors. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention provides a method for improving the surface roughness by combining different alloys on the surface of a mirror to solve at least one of the above technical problems.

[0004] The technical solution of the present invention is: a method for improving the surface roughness by combining different alloys on the surface of a mirror, which is characterized by including the following steps:

[0005] Step 1, the PV value of the overall surface shape of the rough machining of the reflecting surface of the mirror is less than or equal to 1 micron, and the surface roughness Ra is less than or equal to 10nm;

[0006] Step 2, clean the surface of the reflector and store it;

[0007] Step 3, clean the vacuum coating machine;

[0008] Step 4, put nickel with a purity greater than 99.99% and phosphorus with a purity greater than 99.99% into two different crucibles respectively;

[0009] Step 5, hang the mirror in the vacuum coating machine, and place the crucibles on the electron beam evaporator;

[0010] Vacuumize and heat the crucibles with the electron beam evaporator. The current of the electron beam evaporator under the crucible with nickel placed is 400 mA, and the current of the electron beam evaporator under the crucible with phosphorus placed is 200 mA;

[0011] The electron beam evaporator below the crucible containing nickel and the electron beam evaporator below the crucible containing phosphorus work alternately, and the working time ratio of the electron beam evaporator below the crucible containing nickel to the electron beam evaporator below the crucible containing phosphorus is 9:1;

[0012] The thickness of the coating is controlled within 1-2 microns;

[0013] Step six, magnetorheological polishing, and the final roughness is less than or equal to 2 nm.

[0014] Further preferably, in step two, in a laminar flow hood, wear clean gloves and a mask, carefully observe the surface dust or oil stains under a 100w lamp during the process, then first use a handheld airbag to clean the surface of the part to make the particulate dust break away from the surface, and then rinse the surface layer with acetone.

[0015] Further preferably, in step two, store the cleaned mirror in a constant temperature cabinet or a nitrogen cabinet.

[0016] Further preferably, in step three, the tooling fixtures required inside the coating machine are treated with a sandblaster to ensure that there are no obvious burrs on the surface. After sandblasting, use ultrasonic cleaning. Before installing, clean the surface again with a dust-free cloth and alcohol, and stick tinfoil inside the coating machine for anti-pollution protection.

[0017] Further preferably, in step five, the mirror is placed on the umbrella rack at the top of the vacuum coating machine, and the rotation speed of the umbrella rack is 3-5 revolutions per minute.

[0018] Further preferably, the material of the mirror surface of the mirror is 6061-T6.

[0019] Further preferably, in step one, the surface appearance is not lower than the US military standard 80 / 50.

[0020] Further preferably, the mirror is placed above the position between the two crucibles, and the rotation center line direction of the mirror is the center line direction of the mirror.

[0021] Further preferably, the total heating time in step five is 16 hours, and the number of alternating coating times is at least 30 times.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) Effectively control the proportion of the alloy in the gold surface coating of the aluminum mirror.

[0024] 2) Avoid uneven melting of different alloys in the same crucible, which may cause spray points on the surface of the aluminum mirror and affect the final polishing of the part.

[0025] 3) Compared with traditional electroless nickel - phosphorus plating, the coating can be thinner and can fully maintain the original surface shape of the parts. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the internal structure of the vacuum coating machine of the present invention;

[0027] Figure 2 It is a surface test result diagram of the product after coating of the present invention. Detailed Embodiments

[0028] The present invention will be further described below with reference to the drawings.

[0029] See Figures 1 to 2 , Specific Embodiment 1, a method for improving the surface roughness by combining different alloys on the surface of a reflector, including the following steps:

[0030] Step 1, the PV value of the rough - machined surface of the reflecting surface of the reflector is less than or equal to 1 micron, and the surface roughness Ra is less than or equal to 10 nm; the surface appearance is not lower than the US military standard 80 / 50.

[0031] Step 2, clean the surface of the reflector and store it;

[0032] In a laminar flow hood, wear clean gloves and a mask. During the process, place it under a 100 - w light to carefully observe the surface dust or oil stains. Then, first use a handheld airbag to clean the surface of the part to make large - particle dust break away from the surface, and then use acetone to flush the surface layer.

[0033] Place the cleaned reflector in a constant - temperature cabinet or a nitrogen cabinet for storage.

[0034] Step 3, clean the vacuum coating machine;

[0035] Treat the tooling fixtures required inside the coating machine with a sandblaster to ensure that there are no obvious burrs on the surface. After sandblasting, clean it with ultrasonic waves. Before installing, clean the surface again with a lint - free cloth and alcohol, and paste tinfoil inside the coating machine for anti - pollution protection.

[0036] Step 4, put nickel with a purity greater than 99.99% and phosphorus with a purity greater than 99.99% into two different crucibles respectively;

[0037] Step 5, hang the reflector in the vacuum coating machine, and place the crucibles on the electron beam evaporator;

[0038] The crucible is evacuated and heated by an electron beam evaporator. The current of the electron beam evaporator under the crucible containing nickel is 400 mA, and the current of the electron beam evaporator under the crucible containing phosphorus is 200 mA. Nickel changes from solid state to liquid state and finally to gaseous state under continuous heating with a current of 400 mA. Phosphorus directly changes from solid state to gaseous state under continuous power supply and heating with a current of 200 mA. Two current controllers are used to control different electron beam evaporators respectively to ensure that the temperatures of different crucible materials are at the optimal vaporization temperature. The heating temperature of the electron beam evaporator under the crucible containing nickel is controlled at 1600 °C (+ / -50 °C) to achieve the optimal vaporization temperature of nickel. The heating temperature of the electron beam evaporator under the crucible containing phosphorus is controlled at 1400 °C (+ / -50 °C) to achieve the optimal vaporization temperature of phosphorus.

[0039] The electron beam evaporator under the crucible containing nickel and the electron beam evaporator under the crucible containing phosphorus work alternately, and the working time ratio of the electron beam evaporator under the crucible containing nickel to the electron beam evaporator under the crucible containing phosphorus is 9:1;

[0040] The thickness of the coating is controlled within 1 - 2 microns;

[0041] Step six, magnetorheological polishing, the final roughness is less than or equal to 2 nm, and the surface shape PV value is less than or equal to 30 nm. See Figure 2 。

[0042] Figure 2 In it, the roughness is 1.672 nm, and the surface shape PV value is 25.6 nm.

[0043] In step five, the mirror is placed on the umbrella rack at the top of the vacuum coating machine, and the rotation speed of the umbrella rack is 3 - 5 revolutions per minute. The mirror is placed above the position between the two crucibles, and the direction of the rotation center line of the mirror is the center line direction of the mirror.

[0044] The material of the mirror surface of the mirror is 6061 - T6.

[0045] The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and retouches can still be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the surface roughness by combining different alloys on the surface of a mirror, characterized in that, It includes the following steps: Step 1: The PV value of the rough machined surface of the reflecting surface of the mirror is less than or equal to 1 μm, and the surface roughness Ra is less than or equal to 10 nm; Step 2: Clean the surface of the reflector and store it; Step 3: Clean the vacuum coating machine; Step 4: Put nickel with a purity greater than 99.99% and phosphorus with a purity greater than 99.99% into two different crucibles respectively; Step 5: Hang the mirror in the vacuum coating machine, and place the crucibles on the electron beam evaporator; Vacuumize and heat the crucibles with the electron beam evaporator. The current of the electron beam evaporator under the crucible with nickel is 400 mA, and the current of the electron beam evaporator under the crucible with phosphorus is 200 mA; The electron beam evaporator under the crucible with nickel and the electron beam evaporator under the crucible with phosphorus work alternately, and the working time ratio of the electron beam evaporator under the crucible with nickel to the electron beam evaporator under the crucible with phosphorus is 9:1; The thickness of the coating is controlled at 1-2 μm; Step 6: Magnetorheological polishing, and the final roughness Ra is less than or equal to 2 nm.

2. The method for improving surface roughness by combining different alloys on the surface of a mirror according to claim 1, characterized in that: In Step 2, in a laminar flow bench, wear clean gloves and a mask, carefully observe the surface dust or oil stains under a 100w light during the process, then first use a handheld airbag to clean the surface of the part to make the particulate dust break away from the surface, and then flush the surface with acetone.

3. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: In Step 2, store the cleaned mirror in a constant temperature cabinet or a nitrogen cabinet.

4. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: In Step 3, treat the tooling fixtures required inside the coating machine with a sandblaster to ensure that there are no obvious burrs on the surface. After sandblasting, clean it with ultrasonic waves. Before installing, clean the surface again with a dust-free cloth and alcohol, and paste tinfoil inside the coating machine for anti-pollution protection.

5. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: In Step 5, place the mirror on the umbrella stand at the top of the vacuum coating machine, and the rotation speed of the umbrella stand is 3-5 revolutions per minute.

6. The method for improving the surface roughness by combining different alloys on the surface of a mirror according to claim 1, characterized in that: The material of the mirror surface of the said mirror is 6061-T6.

7. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: In Step 1, the surface appearance is not lower than the US military standard 80 / 50.

8. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: The mirror is placed above the position between the two crucibles, and the rotation center line direction of the mirror is the center line direction of the mirror.

9. The method for improving the surface roughness by combining different alloys on the surface of the mirror according to claim 1, characterized in that: The total heating time in Step 5 is 16 hours, and the number of alternating coating times is at least 30 times.

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