A wet particle electrolyte electrochemical mechanical polishing method for complex metal structures

Abstract

The present invention provides a wet particle electrolyte electrochemical mechanical polishing method for metal complex structural parts. The method comprises the following steps: fixing the metal sample on a rotating spindle with a special clamp, rotating axially with the rotating spindle, and immersing the metal sample in a reaction tank filled with wet particle electrolyte. Driven by the rotating spindle, the metal sample and the wet particle electrolyte generate relative motion; the contact area between the single wet particle electrolyte and the metal sample is smaller than the area of ​​the metal sample; during the polishing process, the metal sample is connected to the positive pole of a DC power supply, the negative pole of the power supply is connected to the cathode of the reaction tank wall, and the anode and cathode are connected through the wet particle electrolyte. The present invention has the advantages of using wet particles as electrolytes and no additional liquid electrolyte is added. The wet particle electrolyte can selectively remove rough peaks on the surface of the metal sample, has a fast polishing rate, significantly improves the roughness before and after polishing, is simple to operate, and has flexible and adjustable process parameters.

Description

Technical Field

[0001] The invention relates to the technical field of polishing processing, in particular to a wet particle electrolyte electrochemical mechanical polishing method for metal complex structural parts. Background Art

[0002] Complex structural parts are widely used in aerospace, shipbuilding, military, automotive and other fields due to their excellent mechanical properties such as high strength and light weight. Their application in high-end equipment is gradually increasing. With the increasing complexity of part structures, surface polishing technology for complex structural parts has become an urgent problem that needs to be solved. The polishing process of complex structural parts can remove the processing damage layer and internal residual stress of the previous process, and improve the overall mechanical properties of the parts. Due to the complex surface shape, internal cavity and thin wall characteristics of complex structural parts, traditional polishing technology cannot efficiently polish complex structural parts.

[0003] Traditional mechanical polishing methods for complex structural parts not only have high equipment development costs, but also have low polishing efficiency, which cannot meet the needs of efficient polishing of parts. Abrasive flow polishing is suitable for polishing small complex structural parts with internal cavities, but cannot meet the polishing needs of large-sized parts. Electrochemical polishing is widely used for polishing complex structural parts due to its advantages such as high polishing efficiency, simple equipment, and the ability to polish large-sized parts. However, most electrolytes used in electrochemical polishing are prepared with harmful ingredients, causing certain damage to the environment. In addition, the tip discharge principle of electrochemical polishing will destroy the sharp structure of complex structural parts, limiting the application of electrochemical polishing in engineering. During the electrochemical polishing process, a passivation film will be enriched at the rough peaks on the workpiece surface, hindering the further progress of the reaction. The removal rate is limited by the dissolution rate of the oxide, and the material removal rate cannot be further improved. In the existing technology, (Millet, PS. (2020). Method for smoothing and polishing metals via ion transport free solid bodies and solid bodies for performing the method. US10683583B2.) the use of porous resin particles to adsorb electrolyte can initially achieve a polishing effect. However, this method still uses traditional electrolyte, which causes certain harm to the environment and personnel. Summary of the Invention

[0004] In response to the above technical problems, a method for electrochemical mechanical polishing of complex metal structures using a wet granular electrolyte is provided. The technical means employed by the present invention are as follows:

[0005] A method for electrochemical mechanical polishing of a complex metal structure using a wet granular electrolyte comprises the following steps:

[0006] Step 1: Fix the metal sample on a rotating spindle with a special fixture so that it can rotate axially along the rotating spindle;

[0007] Step 2: Fill the reaction cell with wet granular electrolyte and completely immerse the metal sample in the wet granular electrolyte;

[0008] Step 3: Under the drive of the rotating spindle, the metal sample and the wet granular electrolyte generate relative motion; the contact area between the wet granular electrolyte and the metal sample is smaller than the area of ​​the metal sample;

[0009] Step 4: During the polishing process, the metal sample is connected to the positive electrode of the DC power supply as the anode; the cathode set on the wall of the reaction cell is connected to the negative electrode of the DC power supply; the wet granular electrolyte connects the anode and the cathode;

[0010] The wet granular electrolyte is a cation exchange resin with a porous structure, and acidic groups can be fixed on the cross-linked skeleton of the electrolyte particles.

[0011] The electrochemical mechanical polishing based on moist granular electrolyte described in the present invention is a processing method in which the original electrolyte is replaced by moist granular electrolyte and the material removal rate is increased through the mechanical action of the moist granular electrolyte.

[0012] Driven by the rotating spindle, the metal sample and the wet granular electrolyte produce relative motion, which can cause the wet granular electrolyte and the surface of the metal sample to rub, collide and plow against each other.

[0013] Preferably, the special fixture is a disc-type fixture made of materials such as nylon, PEEK, acrylic, etc., which can polish 4 metal samples at the same time, and the fixture is not conductive.

[0014] The fixable acidic groups include sulfonic acid groups -SO3H, carboxylic acid groups -COOH and other acidic groups, and no additional electrolyte needs to be added. The water content of the conductive particle medium needs to be reasonably controlled.

[0015] The water content of the granular electrolyte affects the degree of ionization of the acidic groups and thus affects the conductivity of the wet granular electrolyte.

[0016] The reaction pool is a cylindrical reaction pool made of non-conductive materials such as acrylic. The size of the reaction pool must be appropriate to ensure that the metal sample is completely immersed.

[0017] The cathode is made of inert materials such as stainless steel or graphite rings. The cathode material is attached to the inner wall of the reaction tank and is distributed in a ring shape.

[0018] Preferably, the polishing spindle can be accompanied by translational movement during rotational movement, thereby ensuring the surface polishing uniformity of the metal sample.

[0019] Preferably, the pressure control during the polishing process can be controlled by the speed of the rotating spindle.

[0020] The contact area between the wet granular electrolyte and the metal sample is much smaller than the area of ​​the metal sample; the electrolyte particles selectively remove the rough peaks on the surface of the material without adding additional mechanical scratches.

[0021] Furthermore, the wet granular electrolyte has a particle size of 0.5-0.8 mm.

[0022] As a preferred solution, the moisture content of the wet granular electrolyte is controlled by the following process:

[0023] a) Immerse the wet granular electrolyte in deionized water for 30 min;

[0024] b) heating the wet granular electrolyte in a hot oven for 10-30 minutes; measuring the moisture content of the wet granular electrolyte every 5 minutes during this period;

[0025] As a preferred solution, the instrument used to measure the moisture content of the wet granular electrolyte is a soil parameter rapid tester.

[0026] Furthermore, the voltage applied to the surface of complex metal structures should not be too large and should be controlled within 0 to 3V.

[0027] Furthermore, the motor speed needs to be controlled within 50 to 300 rpm, and the polishing time needs to be reasonably controlled within 0.5 h to 1.5 h.

[0028] Compared with the prior art, the method for electrochemical mechanical polishing of complex metal structures using a moist granular electrolyte provided by the present invention has the following advantages:

[0029] 1. High polishing removal efficiency. This method directly removes rough peaks on the sample surface through the electrochemical-mechanical coupling removal action of a moist granular electrolyte. Electrochemical oxidation forms an oxide film on the sample's rough peaks, which is then removed by the mechanical action of the moist granular electrolyte, exposing a new surface and thereby improving the removal rate throughout the polishing process.

[0030] 2. The wet granular electrolyte contains acidic groups, and no additional electrolyte is required. Under electrochemical action, it can promote the oxidation of rough peaks on the sample surface and improve the removal rate during the entire electrochemical mechanical polishing process.

[0031] 3. The polishing spindle can simultaneously rotate and translate, ensuring uniform polishing of complex curved surfaces on metal parts. In particular, the pressure during polishing can be controlled by the speed of the rotating spindle.

[0032] Compared with the prior art, the method for electrochemical mechanical polishing of complex metal structures using a moist granular electrolyte provided by the present invention has the following advantages:

[0033] 1. High polishing removal efficiency. This method directly removes rough peaks on the sample surface through the electrochemical-mechanical coupling removal action of a moist granular electrolyte. Electrochemical oxidation forms an oxide film on the sample's rough peaks, which is then removed by the mechanical action of the moist granular electrolyte, exposing a new surface and thereby improving the removal rate throughout the polishing process.

[0034] 2. The wet granular electrolyte contains acidic groups, and no additional electrolyte is required. Under electrochemical action, it can promote the oxidation of rough peaks on the sample surface and improve the removal rate during the entire electrochemical mechanical polishing process.

[0035] 3. The polishing spindle can simultaneously rotate and translate, ensuring uniform polishing of complex curved surfaces on metal parts. In particular, the pressure during polishing can be controlled by the speed of the rotating spindle. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0037] Figure 1 Schematic diagram of the electrochemical mechanical polishing device for wet granular electrolyte of metal complex structures according to the present invention.

[0038] Figure 2 The surface morphology of pure copper before polishing in an embodiment of the present invention is shown in FIG. 1 , where (a) is a field emission scanning electron microscope surface morphology image, and (b) is a ZYGO white light interferometer surface morphology image.

[0039] Figure 3 The surface morphology of pure copper after polishing in an embodiment of the present invention is shown in FIG. 1 , where (a) is a field emission scanning electron microscope surface morphology image, and (b) is a ZYGO white light interferometer surface morphology image.

[0040] In the figure: 1. Reaction cell; 2. Stainless steel cathode; 3. Wet granular electrolyte; 4. DC power supply; 5. Fixture; 6. Metal sample; 7. Rotating spindle. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0042] like Figure 1 As shown, an embodiment of the present invention discloses a method for electrochemical mechanical polishing of complex metal components using a moist granular electrolyte. The polishing apparatus employed in this method includes a reaction cell 1, a stainless steel cathode 2, a moist granular electrolyte 3, a DC power supply 4, a fixture 5, a metal sample 6, and a rotating spindle 7. The fixture 5 is threadedly connected to the rotating spindle 7 and fixed to the bottom end of the rotating spindle 7. The metal sample 6 is secured to the fixture 5, and the annular stainless steel cathode 2 is embedded in the inner wall of the reaction cell 1. The moist granular electrolyte 3 is added to the reaction cell 1, and the metal sample 6 is completely immersed in the moist granular electrolyte 3. The positive electrode of the DC power supply 4 is connected to the metal sample 6, and the negative electrode of the DC power supply 4 is connected to the stainless steel cathode 2. The polishing method is as follows: the DC power supply is adjusted to an appropriate voltage to induce an electrochemical reaction on the surface of the metal sample. The metal sample is then driven axially by the rotating spindle, which is driven by a motor. The moist granular electrolyte experiences acceleration upon contact with the metal sample, continuously colliding with the metal sample and mechanically removing surface roughness peaks.

[0043] The following is a specific example to illustrate the technical effect of the present invention. In this embodiment, a cation exchange resin is used as a wet particle electrolyte. The metal sample is pure copper. Before polishing, the surface of the pure copper is polished with 600# sandpaper to deteriorate the surface. Scanning electron microscopy of the pure copper sample before polishing shows that there are obvious scratches on its surface and the surface is relatively rough. The surface morphology measurement results are as follows: Figure 2 shown.

[0044] The specific process steps for electrochemical mechanical polishing of a complex metal structure using a wet granular electrolyte are as follows:

[0045] (1) Before polishing, the pure copper surface was polished with 600# sandpaper to deteriorate the surface. The sample was then ultrasonically cleaned with ethanol and deionized water. The original morphology before polishing was measured using a field emission scanning electron microscope and a ZYGO white light interferometer. Figure 2 As shown in (a) and (b), it can be seen that there are obvious scratches on the surface, and the surface is relatively rough, with a surface roughness of 433.507nm.

[0046] (2) The wet granular electrolyte uses a polystyrene-based cation exchange resin and adjusts the moisture content of the wet granular electrolyte to control the moisture content to be between 35% and 55%.

[0047] (3) Fix the pure copper sample on a fixture and immerse it in a moist granular electrolyte.

[0048] (4) Apply a DC voltage of 0 to 3 V between the anode and cathode. Start the motor and control the spindle speed to 50 to 300 rpm. Polishing time is 0.5 to 1.5 hours.

[0049] Preferably, the polishing voltage should be controlled within a reasonable range, with 1V being optimal, and the voltage and rotation speed should be reasonably matched to achieve controllable removal.

[0050] (5) After polishing, remove the metal sample and ultrasonically clean the sample with ethanol and deionized water in turn, and measure the surface roughness after polishing.

[0051] In step (4), the polishing effects under different parameters are shown in Table 1

[0052] Table 1

[0053] name Moisture content Motor speed Polishing time surface roughness Example 1 50.2％ 160 r / min 1h 98.178nm Example 2 50.2％ 300r / min 1 h 36.709nm Example 3 40％ 160r / min 1 h 64.283nm Example 4 40％ 300r / min 1 h 22.434nm

[0054] After the pure copper sample is polished, its surface quality is obviously better. Figure 2 The scratches in the surface disappear, the surface becomes flat, and the roughness value is reduced to about 22.434nm. The surface morphology measurement results after polishing are as follows Figure 3 The present invention has the advantages of fast polishing removal rate, obvious improvement of roughness before and after polishing, simple operation and flexible and adjustable process parameters.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for electrochemical mechanical polishing of complex metal structures using a moist granular electrolyte, characterized in that: The following steps are involved: Step 1: Fix the metal sample on a rotating spindle with a special fixture so that it can rotate axially along the rotating spindle; Step 2: Fill the reaction cell with wet granular electrolyte and completely immerse the metal sample in the wet granular electrolyte; Step 3: Under the drive of the rotating spindle, the metal sample and the wet granular electrolyte generate relative motion; the contact area between the wet granular electrolyte and the metal sample is smaller than the area of ​​the metal sample; Step 4: During the polishing process, the metal sample is connected to the positive electrode of the DC power supply as the anode; the cathode set on the wall of the reaction cell is connected to the negative electrode of the DC power supply; the wet granular electrolyte connects the anode and the cathode; The wet granular electrolyte is a cation exchange resin with a porous structure. Acidic groups can be fixed on the cross-linked skeleton of the electrolyte particles. The fixed acidic groups include sulfonic acid groups (SO3H) and carboxylic acid groups (COOH). No additional electrolyte is required, and the moisture content of the conductive granular medium can be adjusted according to preset requirements. The cathode is made of an inert material and is attached to the inner wall of the reaction tank in a ring shape; The material of the metal complex structure is pure copper, the voltage applied to the surface of the metal complex structure is controlled at 0-3V; the motor speed is controlled at 50-300rpm, and the polishing time is controlled at 0.5-1.5h; the water content of the wet granular electrolyte is between 35% and 55%; during the polishing process, the polishing spindle can be accompanied by translational movement while rotating.

2. The method for electrochemical mechanical polishing of metal complex structures using a wet granular electrolyte according to claim 1, characterized in that: The special fixture is not conductive, and the reaction pool is made of non-conductive material.

3. The method for electrochemical mechanical polishing of metal complex structures using a wet granular electrolyte according to claim 1, characterized in that: The particle size of the wet granular electrolyte is 0.5-0.8 mm.

4. The method for electrochemical mechanical polishing of metal complex structures using a wet granular electrolyte according to claim 1, characterized in that: The pressure during polishing can be controlled by the speed of the rotating spindle.

5. The method for electrochemical mechanical polishing of metal complex structures using a wet granular electrolyte according to claim 1, characterized in that: The moisture content of the wet granular electrolyte is controlled by the following process: a) Immerse the wet granular electrolyte in deionized water for 30 min; b) The wet granular electrolyte is then heated in a hot oven for 10-30 minutes; during this period, the moisture content of the wet granular electrolyte is measured every 5 minutes.

6. The method for electrochemical mechanical polishing of a complex metal structure using a wet granular electrolyte according to claim 5, characterized in that: The instruments used to measure the moisture content of moist granular electrolytes include soil parameter rapid testers.

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