Method for improving mechanical property and corrosion resistance of aluminum alloy surface

Abstract

The invention discloses a method for improving the mechanical property and corrosion resistance of an aluminum alloy surface. The method comprises the steps that firstly, oil stains, oxides and impurities on the surface of an aluminum alloy matrix are removed through ultrasonic cleaning; then the aluminum alloy matrix is subjected to micro-arc oxidation treatment, so that an oxidation film is formed on the surface of the aluminum alloy matrix; depositing a SiCOx coating or a SiOx coating on the surface of the oxide film through a plasma enhanced chemical vapor deposition process, namely a PECVD (Plasma Enhanced Chemical Vapor Deposition) process; and finally, optimizing the performance of the oxide film surface deposition coating by controlling PECVD process parameters. The mechanical property, the wear resistance and the corrosion resistance of the aluminum alloy are remarkably improved through the composite coating, the problems of surface micropores and insufficient durability existing in a traditional aluminum alloy treatment method are solved, and the method has wide industrial application prospects and can be used for aluminum alloy parts requiring high wear resistance and high corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and in particular to a method for improving the mechanical properties and corrosion resistance of an aluminum alloy surface. Background Art

[0002] Aluminum alloys have been widely used in aerospace, automobile manufacturing, construction engineering, and electronic equipment due to their excellent specific strength, good electrical and thermal conductivity, and easy processing and forming. However, the surface of aluminum alloys is easily affected by corrosion and wear during actual use, especially in harsh environments such as marine atmosphere, high humidity or acidic environment, where the surface of aluminum alloys is prone to oxidative corrosion. In addition, the surface hardness and wear resistance of aluminum alloys are low, which limits their application in high friction and high wear environments. Therefore, how to effectively improve the mechanical properties, tribological properties, and corrosion resistance of the aluminum alloy surface has become an urgent problem to be solved.

[0003] To solve the above problems, other surface treatments are usually performed after MAO treatment, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). However, these methods still have defects such as poor coating adhesion and complex processes to a certain extent. Therefore, it is necessary to develop a new composite surface treatment technology to further improve the comprehensive performance of aluminum alloy surfaces. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for improving the mechanical properties and corrosion resistance of the surface of aluminum alloy in view of the defects involved in the background technology. Through the combined application of micro-arc oxidation and plasma enhanced chemical vapor deposition (PECVD), a multi-layer composite coating is formed on the surface of the aluminum alloy, thereby significantly improving its mechanical properties, wear resistance and corrosion resistance.

[0005] The present invention adopts the following technical solutions to solve the above technical problems: A method for improving the mechanical properties and corrosion resistance of aluminum alloy surface, comprising the following steps: Step 1), removing oil stains, oxides and impurities on the surface of the aluminum alloy substrate by ultrasonic cleaning; Step 2), performing micro-arc oxidation treatment on the aluminum alloy substrate to form an oxide film on the surface thereof; Step 3), depositing a SiCOx coating or a SiOx coating on the surface of the oxide film by a plasma enhanced chemical vapor deposition process, i.e., a PECVD process; Step 4) Optimize the performance of the deposited coating on the oxide film surface by controlling the PECVD process parameters.

[0006] As a further optimization scheme of the method for improving the mechanical properties and corrosion resistance of the aluminum alloy surface of the present invention, when ultrasonic cleaning is performed in step 1), a 5-10% concentration of sodium hydroxide solution is used, the temperature is maintained at 50° C. at an ultrasonic frequency of 40 kHz, and the cleaning treatment is performed for 10 minutes.

[0007] As a further optimization scheme of the method for improving the surface mechanical properties and corrosion resistance of aluminum alloy of the present invention, when the aluminum alloy substrate is subjected to micro-arc oxidation treatment in the step 2), a mixed electrolyte of phosphate, silicate and borate is used, the voltage range is set to 450-500 V, the current density is controlled at 10-20 A / dm², the pulse power frequency is set to 500-1000 Hz, the oxidation time is 15-30 minutes, and the electrolyte temperature is maintained at 20-30°C.

[0008] As a further optimization scheme of the method of improving the mechanical properties and corrosion resistance of the aluminum alloy surface of the present invention, when depositing the SiCOx coating on the surface of the oxide film in step 3), hexamethyldisilane is selected as the precursor and oxygen is used as the reaction gas.

[0009] As a further optimization scheme of the method for improving the mechanical properties and corrosion resistance of the aluminum alloy surface of the present invention, when depositing the SiOx coating on the surface of the oxide film in step 3), silane is used as a precursor and oxygen is used as a reaction gas.

[0010] As a further optimization scheme of the method for improving the surface mechanical properties and corrosion resistance of aluminum alloy of the present invention, in the step 4), the HMDSO gas flow rate is controlled at 10-20 sccm, the SiH4 flow rate is 5-10 sccm, the oxygen flow rate is 20-50 sccm, the RF power is set to 100-200W, the deposition pressure is maintained at 100-300 mTorr, the deposition time is 30-60 minutes, and the substrate temperature is controlled at 100-150°C.

[0011] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: 1. The present invention effectively fills the micropores and cracks of the MAO coating, and enhances the density and hardness of the coating; the composite coating has excellent gap filling performance and higher scratch resistance, which greatly reduces the wear rate of the aluminum alloy surface and prolongs its service life in high friction and high wear environments; 2. The present invention deposits a composite coating on the MAO coating by PECVD, which significantly enhances the corrosion resistance of the aluminum alloy surface; the corrosion potential of the composite coating is significantly higher than that of the MAO coating, and can more effectively resist oxidation reactions in corrosive environments, thereby providing more lasting protection, allowing the aluminum alloy to exhibit superior corrosion resistance in harsh environments such as acidic and marine environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart was prepared for the present invention. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings: The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete, and will fully express the scope of the present invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0014] like Figure 1 As shown, the present invention discloses a method for improving the mechanical properties and corrosion resistance of the aluminum alloy surface, comprising the following steps: Step 1), removing oil stains, oxides and impurities on the surface of the aluminum alloy substrate by ultrasonic cleaning; Step 2), performing micro-arc oxidation treatment on the aluminum alloy substrate to form an oxide film on the surface thereof; Step 3), depositing a SiCOx coating or a SiOx coating on the surface of the oxide film by a plasma enhanced chemical vapor deposition process, i.e., a PECVD process; Step 4) Optimize the performance of the deposited coating on the oxide film surface by controlling the PECVD process parameters.

[0015] When ultrasonic cleaning is performed in step 1), a sodium hydroxide solution with a concentration of 5-10% is used, and the cleaning process is performed at an ultrasonic frequency of 40 kHz and a temperature maintained at 50° C. for 10 minutes.

[0016] When the aluminum alloy substrate is subjected to micro-arc oxidation treatment in the step 2), a mixed electrolyte of phosphate, silicate and borate is used, the voltage range is set to 450-500 V, the current density is controlled at 10-20 A / dm², the pulse power frequency is set to 500-1000 Hz, the oxidation time is 15-30 minutes, and the electrolyte temperature is maintained at 20-30°C.

[0017] In the step 3), when depositing the SiCOx coating on the surface of the oxide film, hexamethyldisilane is selected as a precursor and oxygen is used as a reaction gas; when depositing the SiOx coating on the surface of the oxide film, silane is used as a precursor and oxygen is used as a reaction gas.

[0018] In the step 4), the HMDSO gas flow rate is controlled at 10-20 sccm, the SiH4 flow rate is 5-10 sccm, the oxygen flow rate is 20-50 sccm, the RF power is set to 100-200 W, the deposition pressure is maintained at 100-300 mTorr, the deposition time is 30-60 minutes, and the substrate temperature is controlled at 100-150°C. Example

[0019] First, the aluminum alloy surface was ultrasonically cleaned to remove surface dirt and oxides. Subsequently, an oxide layer was generated by micro-arc oxidation (MAO) treatment with an oxidation voltage of 450 V and a current density of 20 A / dm 2 , the treatment time is 20 minutes. Then, the PECVD process is used to deposit the SiCOx coating. The process parameters are: the flow rate of hexamethyldisilane is 60 sccm, the reaction chamber pressure is 40 Pa, the temperature is 250℃, the RF power is 200 W, and the deposition time is 30 minutes. Finally, the SiCOx / MAO composite coating is obtained. Its roughness Ra is 1.1 μm, the hardness is 385 Hv, the friction coefficient is 0.369, and the wear rate is 0.8x10 -6 mm 3 / Nm, corrosion voltage -0.0212 V, corrosion current 5.92x10 -6 A / cm 2 . Example

[0020] After the same ultrasonic cleaning on the aluminum alloy surface, the micro-arc oxidation treatment parameters were adjusted to an oxidation voltage of 500 V, a current density of 25 A / dm², and a treatment time of 25 minutes to obtain a denser oxide layer. Then, the SiOx coating was deposited by the PECVD process, with the flow rate of hexamethyldisilane set to 50 sccm, the reaction chamber pressure of 30 Pa, the temperature set to 220°C, the RF power of 150 W, and the deposition time of 25 minutes. Finally, the SiOx / MAO composite coating was obtained. Its roughness Ra1.2 μm, hardness 350 Hv, friction coefficient 0.173, wear rate 0.8x10 -6 mm 3 / Nm, corrosion voltage -0.0245 V, corrosion current 11.31x10 - 6 A / cm 2 . Example

[0021] After ultrasonic cleaning of the aluminum alloy surface, micro-arc oxidation treatment with a voltage of 450 V and a current density of 20 A / dm² was used for 15 minutes to generate a preliminary oxide layer. Then, a multilayer composite coating was deposited by PECVD process, firstly SiCOx coating deposition and then SiOx coating deposition. The parameters of SiCOx coating are: hexamethyldisilane flow rate 55sccm, chamber pressure 35 Pa, temperature 240℃, RF power 180 W, deposition time 20 minutes. Then, SiOx coating deposition was carried out with the following parameters: hexamethyldisilane flow rate 45sccm, chamber pressure 28 Pa, temperature 210℃, RF power 130 W, deposition time 20 minutes. Finally, SiOx / MAO composite coating was obtained. Its roughness Ra0.7 μm, hardness 425 Hv, friction coefficient 0.164, wear rate 0.3x10 -6 mm 3 / Nm, corrosion voltage -0.0098 V, corrosion current 3.42x10 -6 A / cm 2 .

[0022] The composite coating of the present invention has a porosity lower than that of the micro-arc oxidation coating alone, a hardness higher than that of the micro-arc oxidation coating alone, a corrosion potential significantly higher than that of the untreated micro-arc oxidation coating, has better wear resistance and adhesion, and exhibits stronger corrosion resistance, and is suitable for industrial applications with high performance requirements.

[0023] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0024] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for improving the mechanical properties and corrosion resistance of aluminum alloy surface, characterized in that: The following steps are involved: Step 1), removing oil stains, oxides and impurities on the surface of the aluminum alloy substrate by ultrasonic cleaning; Step 2), performing micro-arc oxidation treatment on the aluminum alloy substrate to form an oxide film on the surface thereof; Step 3), depositing a SiCOx coating or a SiOx coating on the surface of the oxide film by a plasma enhanced chemical vapor deposition process, i.e., a PECVD process; Step 4) Optimize the performance of the deposited coating on the oxide film surface by controlling the PECVD process parameters.

2. The method for improving the surface mechanical properties and corrosion resistance of aluminum alloy according to claim 1, characterized in that: When ultrasonic cleaning is performed in step 1), a sodium hydroxide solution with a concentration of 5-10% is used, and the cleaning process is performed at an ultrasonic frequency of 40 kHz and a temperature maintained at 50° C. for 10 minutes.

3. The method for improving the surface mechanical properties and corrosion resistance of aluminum alloy according to claim 1, characterized in that: When the aluminum alloy substrate is subjected to micro-arc oxidation treatment in the step 2), a mixed electrolyte of phosphate, silicate and borate is used, the voltage range is set to 450-500 V, the current density is controlled at 10-20 A / dm², the pulse power frequency is set to 500-1000 Hz, the oxidation time is 15-30 minutes, and the electrolyte temperature is maintained at 20-30°C.

4. The method for improving the mechanical properties and corrosion resistance of the aluminum alloy surface according to claim 1, characterized in that: When depositing the SiCOx coating on the surface of the oxide film in step 3), hexamethyldisilane is selected as a precursor and oxygen is used as a reaction gas.

5. The method for improving the surface mechanical properties and corrosion resistance of aluminum alloy according to claim 1, characterized in that: When depositing the SiOx coating on the surface of the oxide film in step 3), silane is used as a precursor and oxygen is used as a reaction gas.

6. The method for improving the surface mechanical properties and corrosion resistance of aluminum alloy according to claim 1, characterized in that: In the step 4), the HMDSO gas flow rate is controlled at 10-20 sccm, the SiH4 flow rate is 5-10 sccm, the oxygen flow rate is 20-50 sccm, the RF power is set to 100-200 W, the deposition pressure is maintained at 100-300 mTorr, the deposition time is 30-60 minutes, and the substrate temperature is controlled at 100-150°C.

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