Method for preparing high wear-resistant aluminum alloy micro-arc oxidation composite coating by laser cladding

Abstract

The application discloses a method for preparing a high-wear-resistance aluminum alloy micro-arc oxidation composite coating by laser cladding, which comprises the following steps: immersing an aluminum alloy with a surface ceramic film layer prepared by a micro-arc oxidation process into a palygorskite suspension liquid, taking out and drying after standing, and then performing laser cladding treatment to prepare the high-wear-resistance aluminum alloy micro-arc oxidation composite coating. The composite coating prepared by the method has a significantly reduced friction coefficient, and the average friction coefficient is smaller than that of a single micro-arc oxidation ceramic film coating. The wear rate of the composite coating sample is significantly reduced, and the wear resistance of the aluminum alloy is improved.

Description

Technical Field

[0001] This invention belongs to the field of material surface coating technology, specifically relating to a method for preparing a high wear-resistant aluminum alloy micro-arc oxidation composite coating by laser cladding. Background Technology

[0002] Aluminum and its alloys are excellent conductors of heat, with a thermal conductivity three times that of iron, and are widely used in various radiators and heat exchangers in industry. However, the insufficient wear resistance, corrosion resistance, and fatigue resistance of aluminum alloys limit their application range. Although hard anodized aluminum alloys offer moderate improvements in surface hardness, wear resistance, and corrosion resistance, the widespread use of acids in electrochemical plating solutions makes the anodizing process environmentally unfriendly. Therefore, improving the wear resistance of aluminum surfaces is an essential improvement method.

[0003] Existing technologies have proposed numerous surface treatment techniques, including anodizing, micro-arc oxidation, vapor deposition, conversion coating, and electroplating, to improve the corrosion resistance and wear resistance of aluminum. Among these, micro-arc oxidation stands out. Micro-arc oxidation is a surface modification technology developed based on anodizing. It uses instantaneous high-temperature sintering in a micro-arc discharge zone to produce an oxide film layer on the metal surface with high hardness, high strength, insulation, wear resistance, corrosion resistance, high-temperature resistance, and other excellent properties. However, due to the presence of micro-arc oxidation discharge channels, a porous, volcano-like morphology is formed on the micro-arc oxidation surface, increasing the contact area of ​​the friction surface, thereby increasing friction and the coefficient of friction. Furthermore, the porous film layer may also accommodate more lubricant, leading to poor lubrication and further increasing friction.

[0004] Therefore, the porous volcanic oxide ceramic film on the surface of aluminum alloy micro-arc oxidation significantly increases the wear of frictional components and leads to a high coefficient of friction. This may negatively impact the material's performance, such as reducing its wear resistance and service life. Further improvements to the ceramic film of micro-arc oxidation are necessary to reduce the coefficient of friction and enhance its wear resistance.

[0005] CN 103014706 A discloses a method for preparing a ceramic film on a metal surface, comprising the following steps: pre-positioned laser cladding or simultaneous laser cladding of a ceramic film obtained by micro-arc oxidation and ceramic powder. This method can increase the thickness of the micro-arc oxidized ceramic film, thereby achieving greater wear resistance and corrosion resistance. However, the main purpose of this method is to increase the thickness of the micro-arc oxidized ceramic film, without improving the coefficient of friction. Moreover, the ceramic powder has poor adhesion, and laser melting on the micro-arc oxidized layer easily leads to problems such as coating peeling, unevenness, and high surface roughness, which still cannot solve the problem of high friction coefficient caused by high roughness of the micro-arc oxidized film proposed in this application. In addition, excessive laser power can cause deformation of the substrate, further affecting the quality of the surface coating. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for preparing a high-wear-resistant aluminum alloy composite coating that is low-energy-consumption, simple to operate, and pollution-free.

[0007] The principle of this invention lies in the following: Attapulgite clay is prepared into a suspension, and after heating and drying, the dried attapulgite clay is evenly distributed on the surface of the micro-arc oxidation film. After cladding with a laser marking machine, a dense coating is formed and tightly bonded to the oxide film. This composite coating enhances the wear resistance of the micro-arc oxidation surface.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a high wear-resistant aluminum alloy micro-arc oxidation composite coating by laser cladding, wherein the method is as follows:

[0010] An aluminum alloy with a ceramic film layer on its surface, prepared by micro-arc oxidation process, is immersed in an attapulgite suspension, left to stand, dried, and then subjected to laser cladding to obtain a high wear-resistant aluminum alloy micro-arc oxidation composite coating.

[0011] The attapulgite suspension contains 0.2-0.6% attapulgite by mass, preferably 0.4%. Generally, attapulgite is added to deionized water according to a specific mass ratio, and then ultrasonically vibrated to form a homogeneous suspension. The ultrasonication time is generally 3-4 hours.

[0012] The settling time is generally 3 to 4 hours.

[0013] The drying process typically involves drying at 70-75°C for 20-30 minutes.

[0014] The laser parameters for the laser cladding process are: power of 50 W, scanning speed of 1000 mm / s, frequency of 20 kHz, height of 134 mm, spot size of 30 × 30 mm, and 3 scans in one direction.

[0015] The preferred method for the micro-arc oxidation process is to use a bipolar micro-arc oxidation power supply. The aluminum alloy is subjected to micro-arc oxidation treatment in an electrolyte, which grows a dense ceramic film on the surface of the aluminum alloy.

[0016] The electrolyte formulation includes sodium hexametaphosphate, sodium silicate, polyethylene glycol, and sodium hydroxide.

[0017] Furthermore, the electrolyte comprises the following components at mass concentrations: 33-37 g / L sodium hexametaphosphate, 2-6 g / L sodium silicate, 1-2 g / L polyethylene glycol, and 1-2 g / L sodium hydroxide, preferably including 35 g / L sodium hexametaphosphate, 4 g / L sodium silicate, 2 g / L polyethylene glycol, and 1 g / L sodium hydroxide.

[0018] Furthermore, the preferred electrical parameters of the bipolar micro-arc oxidation power supply are: constant current control mode, and forward current setpoint of 0.8~1.2 A / dm. 2 The negative current setting is 0.2~0.4 A / dm. 2 The pulse frequency is 400~700 Hz, the positive duty cycle is 20%, the negative duty cycle is 20%, and the micro-arc oxidation duration is set to 13~17 min.

[0019] Preferably, the forward current setting is 1.0 A / dm. 2 The negative current setting is 0.4 A / dm. 2 The pulse frequency was 600 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation duration was set to 15 min.

[0020] The present invention also provides a high wear-resistant aluminum alloy micro-arc oxidation composite coating prepared by the above method.

[0021] This invention involves attaching attapulgite clay to the micro-arc oxide layer of aluminum metal through suspension impregnation, and then obtaining a composite coating through laser cladding.

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

[0023] 1. The preparation method is simple, the preparation conditions involved are safe, and the cost is low.

[0024] 2. The preparation process produces no pollutants, making it environmentally friendly and suitable for large-scale production.

[0025] 3. The friction coefficient of the prepared composite coating is significantly reduced. Tribological experiments were conducted with zirconia balls (10 mm in diameter) under a load of 5 N, a sliding speed of 60 mm / s, and water lubrication conditions. The average friction coefficient was lower than that of the single micro-arc oxidation ceramic film coating. The wear rate of the composite coating sample was significantly reduced, which improved the wear resistance of the aluminum alloy. Attached Figure Description

[0026] Figure 1 The graph shows the friction coefficient curves of the aluminum substrate, single coating, and composite coating under water lubrication conditions in Example 3.

[0027] Figure 2 The images show the surface wear morphology of the aluminum substrate, single coating, and composite coating under water lubrication conditions in Example 3. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] Example 1: Adjust the electrical parameters of the bipolar micro-arc oxidation power supply, setting the forward current to 0.8 A / dm. 2 The negative current setting is 0.2 A / dm. 2 The pulse frequency was 400 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation time was set to 13 min. An electrolyte was prepared by dissolving 33 g of sodium hexametaphosphate, 2 g of sodium silicate, 1 g of polyethylene glycol, and 1 g of sodium hydroxide in 1 L of deionized water at room temperature. A dense ceramic layer was grown on the surface of 6061 aluminum alloy in the electrolyte. 0.2 g of attapulgite powder was added to 99.8 mL of deionized water and ultrasonically vibrated to form a uniform suspension. The micro-arc-oxidized aluminum alloy was immersed in the suspension and allowed to stand for 3 hours. After removal, it was dried in an oven at 70 ℃ for 30 min, resulting in a uniform distribution of the dried attapulgite on the surface of the micro-arc-oxidized ceramic film. The sample was then clad using a laser marking machine to obtain a composite coating based on micro-arc oxidation and laser cladding.

[0030] The laser parameters for the laser cladding process are: power of 50 W, scanning speed of 1000 mm / s, frequency of 20 kHz, height of 134 mm, spot size of 30 × 30 mm, and 3 scans in one direction.

[0031] Example 2: Adjust the electrical parameters of the bipolar micro-arc oxidation power supply, setting the forward current to 0.9 A / dm. 2 The negative current setting is 0.3 A / dm. 2The pulse frequency was 500 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation time was set to 14 min. An electrolyte was prepared by dissolving 34 g of sodium hexametaphosphate, 3 g of sodium silicate, 2 g of polyethylene glycol, and 1 g of sodium hydroxide in 1 L of deionized water at room temperature. A dense ceramic layer was grown on the surface of 6061 aluminum alloy in the electrolyte. 0.3 g of attapulgite powder was added to 99.7 mL of deionized water and ultrasonically vibrated to form a uniform suspension. The micro-arc-oxidized aluminum alloy was immersed in the suspension and allowed to stand for 3 hours. After removal, it was dried in an oven at 70 ℃ for 30 min, resulting in a uniform distribution of the dried attapulgite on the surface of the micro-arc-oxidized ceramic film. The sample was then laser-clad using a laser marking machine to obtain a composite coating based on micro-arc oxidation and laser cladding. The laser parameters were the same as in Example 1.

[0032] Example 3: Adjust the electrical parameters of the bipolar micro-arc oxidation power supply, setting the forward current to 1.0 A / dm. 2 The negative current setting is 0.4 A / dm. 2 The pulse frequency was 600 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation time was set to 15 min. An electrolyte was prepared by dissolving 35 g of sodium hexametaphosphate, 4 g of sodium silicate, 2 g of polyethylene glycol, and 1 g of sodium hydroxide in 1 L of deionized water at room temperature. A dense ceramic layer was grown on the surface of 6061 aluminum alloy in the electrolyte. 0.4 g of attapulgite powder was added to 99.6 mL of deionized water and ultrasonically vibrated to form a uniform suspension. The micro-arc-oxidized aluminum alloy was immersed in the suspension and allowed to stand for 3 hours. After removal, it was dried in an oven at 70 ℃ for 30 min, resulting in a uniform distribution of the dried attapulgite on the surface of the micro-arc-oxidized ceramic film. The sample was then laser-marked for cladding treatment, ultimately obtaining a composite coating based on micro-arc oxidation and laser cladding. The laser parameters were the same as in Example 1.

[0033] A steel wool abrasion resistance testing machine (model 339-GSR Ⅱ) was used to conduct sliding wear tests using the ball-disc contact method. The friction pair material was zirconia balls (the density of the zirconia balls was 6.01 g / cm³). 3 The diameter of the ball was 10 mm. The coefficient of friction under water lubrication conditions was determined during sliding wear under a fixed load (5 N) and a fixed sliding speed (60 mm / s). The friction time was fixed at 10 min, and the displacement amplitude was set to 10 mm. Experiments were conducted using the composite coating sample from Example 3 and a micro-arc oxidation film sample without laser cladding treatment. Figure 1The friction coefficient curve is shown. After the sliding wear test, the sample and zirconia balls were removed, and the sample was ultrasonically cleaned in anhydrous ethanol to remove friction debris. It was then dried with a hair dryer, and the wear morphology of the sample and mating parts was observed using a metallographic microscope (AOSVI, M330-HK830). Finally, the results were obtained... Figure 2 The wear morphology of the sample shown. Figure 2 In the figure, (a) shows the wear surface of the aluminum substrate, (b) shows the wear surface of the micro-arc oxide film sample, and (c) shows the wear surface of the composite coating sample.

[0034] Figure 1 The results show that the friction coefficient of the composite coating sample under water lubrication conditions is lower than that of the aluminum substrate and the micro-arc oxide film. Figure 1 In the initial stage of the friction experiment, the friction coefficients of the three samples under water lubrication conditions showed a stable upward trend with increasing friction time. The friction coefficient of the micro-arc oxide film layer was generally lower than that of the aluminum substrate, and the friction coefficient of the composite coating sample was generally lower than that of the micro-arc oxide film layer. The composite coating sample had the lowest friction coefficient because the attapulgite cladding on the surface is a clay mineral with a high specific surface area and strong water adsorption properties. It can absorb water and expand, which weakens the contact and adhesion between clay particles, reduces the surface adhesion force, and thus lowers the friction coefficient.

[0035] Figure 2 The results show that under water lubrication conditions, the aluminum substrate exhibits the most wear debris on its friction surface, with the micro-arc oxide film layer producing more wear debris than the composite coating. The aluminum substrate surface, in direct contact with the mating pair, experiences the greatest wear. The micro-arc oxide film layer isolates the aluminum substrate from the mating pair, resulting in primarily abrasive and adhesive wear during friction. The composite coating produces the fewest debris because the attapulgite cladding forms a more wear-resistant structure on the surface of the micro-arc oxide film. Furthermore, the wear tracks on the composite coating are finer than those on the aluminum substrate, indicating that the composite coating surface has fewer protrusions and lower roughness than the aluminum substrate surface.

[0036] Example 4: Adjust the electrical parameters of the bipolar micro-arc oxidation power supply, setting the forward current to 1.1 A / dm. 2 The negative current setting is 0.4 A / dm. 2The pulse frequency was 700 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation time was set to 16 min. An electrolyte was prepared by dissolving 36 g of sodium hexametaphosphate, 5 g of sodium silicate, 2 g of polyethylene glycol, and 1 g of sodium hydroxide in 1 L of deionized water at room temperature. A dense ceramic layer was grown on the surface of 6061 aluminum alloy in the electrolyte. 0.5 g of attapulgite powder was added to 99.5 mL of deionized water and ultrasonically vibrated to form a uniform suspension. The micro-arc-oxidized aluminum alloy was immersed in the suspension and allowed to stand for 3 hours. After removal, it was dried in an oven at 70 ℃ for 30 min, resulting in a uniform distribution of the dried attapulgite on the surface of the micro-arc-oxidized ceramic film. The sample was then laser-clad using a laser marking machine to obtain a composite coating based on micro-arc oxidation and laser cladding. The laser parameters were the same as in Example 1.

[0037] Example 5: Adjust the electrical parameters of the bipolar micro-arc oxidation power supply, setting the forward current to 1.2 A / dm. 2 The negative current setting is 0.4 A / dm. 2 The pulse frequency was 700 Hz, the positive duty cycle was 20%, the negative duty cycle was 20%, and the micro-arc oxidation time was set to 17 min. An electrolyte was prepared by dissolving 37 g of sodium hexametaphosphate, 6 g of sodium silicate, 2 g of polyethylene glycol, and 2 g of sodium hydroxide in 1 L of deionized water at room temperature. A dense ceramic layer was grown on the surface of 6061 aluminum alloy in the electrolyte. 0.6 g of attapulgite powder was added to 99.4 mL of deionized water and ultrasonically vibrated to form a uniform suspension. The micro-arc-oxidized aluminum alloy was immersed in the suspension and allowed to stand for 3 hours. After removal, it was dried in an oven at 70 ℃ for 30 min, resulting in a uniform distribution of the dried attapulgite on the surface of the micro-arc-oxidized ceramic film. The sample was then clad using a laser marking machine to obtain a composite coating based on micro-arc oxidation and laser cladding. The laser parameters were the same as in Example 1.

[0038] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for preparing a high-wear-resistant aluminum alloy micro-arc oxidation composite coating by laser cladding, characterized in that The method is: The aluminum alloy with a ceramic film layer prepared by a micro-arc oxidation process is immersed in a palygorskite suspension, and after standing, it is taken out and dried, and then laser cladding treatment is performed to prepare a high-wear-resistant aluminum alloy micro-arc oxidation composite coating; the laser parameters of the laser cladding treatment are: power is 50 W, frequency is 20 kHz, height is 134 mm, spot size is 30*30 mm, and scanning times are single-direction scanning 3 times.

2. The method of claim 1, wherein In the palygorskite suspension, the mass percentage content of palygorskite is 0.2-0.6 %.

3. The method of claim 2, wherein The palygorskite suspension is formed by adding palygorskite to deionized water in a mass ratio and ultrasonic oscillation.

4. The method of claim 1, wherein The standing time is 3-4 hours.

5. The method of claim 1, wherein The micro-arc oxidation process uses a bipolar micro-arc oxidation power supply, and the aluminum alloy is subjected to micro-arc oxidation treatment in an electrolyte, and a dense ceramic film layer grows on the surface of the aluminum alloy.

6. The method of claim 5, wherein The formula of the electrolyte includes sodium hexametaphosphate, sodium silicate, polyethylene glycol, and sodium hydroxide.

7. The method of claim 6, wherein The electrolyte includes the following mass concentrations of components: 33-37 g / L sodium hexametaphosphate, 2-6 g / L sodium silicate, 1-2 g / L polyethylene glycol, and 1-2 g / L sodium hydroxide.

8. The method of claim 6, wherein The electrical parameters of the bipolar micro-arc oxidation power supply are as follows: the control mode is constant current, the forward current setting value is 0.8-1.2 A / dm 2 , the negative current setting value is 0.2-0.4 A / dm 2 , the pulse frequency is 400-700 Hz, the positive duty ratio is 20%, the negative duty ratio is 20%, and the micro-arc oxidation duration is 13-17 min.

9. The high-wear-resistant aluminum alloy micro-arc oxidation composite coating prepared by the method of any one of claims 1-8.

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