Preparation process of micro-arc oxidation composite film layer with high wear resistance and corrosion resistance

Abstract

The preparation process comprises the following steps: connecting an aluminum alloy with an anode of a micro-arc oxidation alternating current power supply, and immersing the aluminum alloy in an electrolytic solution in a stainless steel electrolytic bath; the stainless steel electrolytic bath is connected with a cathode of the micro-arc oxidation alternating current power supply; the surface of the aluminum alloy is subjected to micro-arc oxidation treatment, and an Al2O3 / MoS2 / CePO4 composite ceramic film layer is constructed on the surface of the aluminum alloy in situ; wherein the electrolytic solution comprises a solvent, which is deionized water; the solute comprises the following components in parts by mass in each liter of solvent: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na (Ethylene Diamine Tetraacetic Acid), 5 parts of sodium molybdate, 10 parts of sodium sulfide and 5-12.5 parts of cerium acetate. According to the preparation process of the high-wear-resistance and high-corrosion-resistance micro-arc oxidation composite film layer, the high-wear-resistance and high-corrosion-resistance composite ceramic film layer is constructed on the surface of the aluminum alloy in situ, and the wear resistance and the corrosion resistance of the surface of the aluminum alloy are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy surface treatment, and in particular relates to a preparation process of a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film layer. Background Art

[0002] Aluminum alloys are widely used in high-speed rail, automobiles, ships, aerospace and other fields due to their own advantages. However, due to defects such as low surface hardness, poor wear resistance and insufficient corrosion resistance of aluminum alloys, the application of aluminum alloys in some special occasions is limited. Therefore, surface treatment technologies that modify the surface of aluminum alloys through physical, chemical, metal heat and other reactions are of great significance. Surface treatment technologies applicable to aluminum alloys include: coating technology, conversion film technology and high-energy beam surface strengthening. Among them, although coating technology can improve surface properties, the process flow is complicated and the electrolytic solution of the coating is prone to cause serious pollution to the environment. The film layer prepared by conversion film technology is thin in thickness and low in hardness. The wear resistance and corrosion resistance are not enough to support the application of aluminum alloys in the field of strong friction and strong corrosion. In high-energy beam surface strengthening, the surface roughness of the film layer prepared by plasma implantation is high and microcracks are obvious. Laser strengthening technology has problems such as high cost, high energy consumption and low production efficiency. High-energy beam surface enhancement also includes micro-arc oxidation (MAO), also known as microplasma oxidation. This surface treatment technique involves the synergistic interaction of aluminum alloy, electrolyte solution, and electrical parameters to generate instantaneous high-temperature, high-pressure arc discharge on the aluminum alloy surface. This process repeatedly breaks through and solidifies the oxide film deposited on the surface, and in situ builds a ceramic film primarily composed of metal oxides on the aluminum alloy surface. Commonly used electrolytic solutions for MAO include sodium silicate, sodium phosphate, sodium aluminate, and sodium boride systems. However, existing electrolytic solution systems struggle to meet the demands for high wear and corrosion resistance in harsh environments. This has led to the emergence of deposition-based MAO and in-situ reaction-based MAO. Deposition-based MAO modifies the film by adding solid particles (such as molybdenum disulfide and graphite) to the electrolyte, but this approach carries challenges such as high preparation costs and the need to consider the distribution and adhesion of the deposited particles within the film. While in-situ reaction-based MAO can generate composite films in situ through chemical reactions in the electrolyte under high temperature and high pressure, relatively little research has focused on this approach due to the complex high-temperature and high-pressure reactions involved.

[0003] Patent CN201810847345.9 discloses a highly wear-resistant, self-lubricating micro-arc oxidation film on the surface of 2xxx aluminum and aluminum alloys, which includes a DC copper-rich passivation film preparation time of 10-30 minutes and a double-pulse AC self-lubricating dense layer preparation time of 180-400 minutes. By adding molybdenum disulfide and graphite particles to the double-pulse AC electrolytic solute in the second stage, a portion of molybdenum disulfide and graphite particles are doped during the film growth process, thereby forming a micro-arc oxidation film with a dual wear-resistant / friction-reducing mechanism, and the surface hardness can reach 1000HV. However, the dual process flow usually greatly reduces production efficiency in actual industrial production. Some of the molybdenum disulfide and graphite particles doped in the film layer will also have a greater risk of falling off between the particles and the film layer as the aluminum alloy is used and aged. Therefore, further research is still needed to achieve excellent surface modification of aluminum alloys. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation process for a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film layer, which can in situ construct an Al2O3 / MoS2 / CePO4 micro-arc oxidation composite ceramic film layer with high wear resistance and corrosion resistance on the surface of an aluminum alloy, thereby increasing the surface hardness of the aluminum alloy and improving the wear resistance and corrosion resistance of the aluminum alloy surface.

[0005] The technical solution provided by the present invention is:

[0006] A preparation process of a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film layer, comprising:

[0007] The aluminum alloy is connected to the anode of a micro-arc oxidation AC power supply and immersed in an electrolytic solution in a stainless steel electrolytic cell; the stainless steel electrolytic cell is connected to the cathode of the micro-arc oxidation AC power supply; after the micro-arc oxidation AC power supply is turned on, the surface of the aluminum alloy is micro-arc oxidized to form an Al2O3 / MoS2 / CePO4 composite ceramic film layer in situ on the surface of the aluminum alloy;

[0008] Wherein, the electrolytic solution comprises:

[0009] a solvent, which is deionized water;

[0010] The solute, its components and the mass fraction of each component in each liter of solvent are:

[0011] 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 5 to 12.5 parts of cerium acetate.

[0012] Preferably, the aluminum alloy is 6082-T6 aluminum alloy.

[0013] Preferably, the aluminum alloy needs to be pretreated before the micro-arc oxidation treatment is performed on the aluminum alloy surface:

[0014] Step 1: Polish the aluminum alloy to a mirror finish using 120#, 240#, 320#, 400#, 500#, and 600# sandpaper in sequence;

[0015] Step 2: Clean the polished aluminum alloy using ultrasonic waves;

[0016] Step 3: Use a hair dryer to dry the liquid stains on the surface of the cleaned aluminum alloy;

[0017] Step 4: immerse the dried aluminum alloy in 50 g / L NaOH solution, deionized water, 2% HF+20% HNO3 solution, and deionized water in sequence; wherein, the aluminum alloy is immersed in each solution for 10 seconds.

[0018] Preferably, the most preferred electrolytic solution is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 7.5 parts of cerium acetate.

[0019] Preferably, the setting parameters of the micro-arc oxidation AC power supply are: constant current mode, current density of 11A / dm 2 , the operating frequency is 500Hz, the positive and negative duty cycle is 30%, the number of pulses is 1, and the oxidation time is 20min.

[0020] Preferably, during the micro-arc oxidation treatment of the aluminum alloy surface, the temperature of the electrolytic solution in the stainless steel electrolytic tank is controlled below 30°C.

[0021] Preferably, after the aluminum alloy surface is subjected to micro-arc oxidation treatment, the aluminum alloy is cleaned with deionized water, and an in-situ constructed Al2O3 / MoS2 / CePO4 composite ceramic film layer is obtained on the aluminum alloy surface.

[0022] Preferably, the volume wear rate of the optimal Al2O3 / MoS2 / CePO4 composite ceramic film layer constructed in situ on the aluminum alloy surface using the most preferred electrolytic solution is 4.9×10 -7 mm 3 / N·mm, and the average friction coefficient is 0.56.

[0023] Preferably, the optimal self-corrosion ionization density of the Al2O3 / MoS2 / CePO4 composite ceramic film is 1.98×10 -7 A.cm -2 , the corrosion potential is -0.20V.

[0024] The beneficial effects of the present invention are:

[0025] (1) The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film provided by the present invention can in situ synthesize cerium phosphate on the basis of the Al2O3 / MoS2 composite ceramic film by adding cerium acetate of different concentrations into the electrolytic solution, effectively avoiding the in situ polymerization of sodium ions and phosphate ions in the electrolytic solution, making the surface of the Al2O3 / MoS2 composite ceramic film present a "scale" morphology, reducing the surface porosity of the Al2O3 / MoS2 composite ceramic film, reducing defects, improving the surface hardness of the aluminum alloy, and realizing wear-resistant and corrosion-resistant modification of the aluminum alloy surface.

[0026] (2) The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film provided by the present invention is based on the existing micro-arc oxidation surface modification. By utilizing various reactions during the film growth process, an Al2O3 / MoS2 / CePO4 micro-arc oxidation composite ceramic film layer with high wear and corrosion resistance is spontaneously and uniformly grown along with the film layer on the aluminum alloy surface, thereby improving the wear and corrosion resistance of the aluminum alloy surface. The volume wear rate of the optimal Al2O3 / MoS2 / CePO4 composite ceramic film layer is as low as 4.9×10 -7 mm 3 / N·mm, the average friction coefficient is 0.56, and the self-corrosion current density is 1.98×10 -7 A.cm -2 , the corrosion potential is -0.20V, and it has the characteristics of uniform phase distribution, high adhesion, low porosity and high hardness; at the same time, the preparation process of the high wear-resistant and corrosion-resistant micro-arc oxidation composite film layer provided by the present invention achieves high production efficiency, short oxidation time, low cost, convenient operation and non-toxic and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a phase composition diagram of the Al2O3 / MoS2 / CePO4 composite ceramic film layer described in the present invention.

[0028] Figure 2 This is a statistical diagram of the hardness of the Al2O3 / MoS2 / CePO4 composite ceramic film layer described in the present invention.

[0029] Figure 3 This is the surface morphology of the most preferred Al2O3 / MoS2 / CePO4 composite ceramic film layer described in the present invention.

[0030] Figure 4 This is the cross-sectional morphology and element distribution diagram of the most preferred Al2O3 / MoS2 / CePO4 composite ceramic membrane layer described in the present invention.

[0031] Figure 5 This is a statistical graph of the average friction coefficient and volume wear rate of the Al2O3 / MoS2 composite ceramic film layer described in the present invention and the most preferred Al2O3 / MoS2 / CePO4 composite ceramic film layer.

[0032] Figure 6 This is an electrochemical polarization curve diagram of the Al2O3 / MoS2 composite ceramic membrane layer described in the present invention and the most preferred Al2O3 / MoS2 / CePO4 composite ceramic membrane layer. DETAILED DESCRIPTION

[0033] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0034] like Figure 1-6 As shown, the present invention provides a preparation process for a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film layer. By using an in-situ synthesis method, an Al2O3 / MoS2 / CePO4 composite ceramic film layer is in situ constructed on the surface of a 6XXX aluminum alloy. The specific implementation process is as follows:

[0035] Step 1: Pre-treat the aluminum alloy:

[0036] Step 1: Polish the aluminum alloy to a mirror finish using 120#, 240#, 320#, 400#, 500#, and 600# sandpaper in sequence.

[0037] Step 2: Immerse the mirror-polished aluminum alloy in a beaker filled with anhydrous ethanol. Place the beaker containing the aluminum alloy in an ultrasonic cleaner filled with clean water at room temperature and clean the aluminum alloy with ultrasound for 5 minutes.

[0038] Step 3: Take out the cleaned aluminum alloy and use a hair dryer to dry the liquid stains on the surface of the aluminum alloy.

[0039] Step 4: Immerse the dried aluminum alloy in a beaker containing 50 g / L NaOH solution, a beaker containing deionized water solution, a beaker containing 2% HF + 20% HNO3 solution, and a beaker containing deionized water solution, respectively, to remove oil stains and oxide layers on the surface of the aluminum alloy; the aluminum alloy is immersed in each solution for 10 seconds.

[0040] Step 2: Preparation of composite ceramic film layer:

[0041] Step 1. Fix the stirring shaft and stirring blades of the mechanical stirrer in the middle position of the stainless steel electrolytic cell; connect the pretreated aluminum alloy to the fixed electrode anode of the micro-arc oxidation AC power supply and immerse it in the electrolytic solution in the stainless steel electrolytic cell, use the anode beam to fix the immersed aluminum alloy so that the immersed aluminum alloy is set in the middle position between the stirring shaft and the inner wall of the stainless steel electrolytic cell; connect the stainless steel electrolytic cell to the fixed electrode cathode of the micro-arc oxidation AC power supply; and achieve the connection of the high-voltage electric field closed loop through the above operations.

[0042] Wherein, the aluminum alloy is 6082-T6 aluminum alloy. The electrolytic solution includes: a solvent, which is deionized water; a solute, whose components and the mass fraction of each component in each liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 5 to 12.5 parts of cerium acetate; the concentrations of each component in the electrolytic solution are 15g / L of sodium hexametaphosphate, 10g / L of EDTA-2Na, 5g / L of sodium molybdate, 10g / L of sodium sulfide, and 5 to 12.5g / L of cerium acetate. The setting parameters for the micro-arc oxidation AC power supply are: constant current mode, current density of 11A / dm 2 , the operating frequency is 500Hz, the positive and negative duty cycle is 30%, the number of pulses is 1, and the oxidation time is 20min.

[0043] By adding different concentrations of cerium acetate to the electrolytic solution, composite ceramic membrane layers with different properties can be obtained; among them, the most preferred electrolytic solution is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 7.5 parts of cerium acetate; the concentrations of each component in the most preferred electrolytic solution are 15g / L of sodium hexametaphosphate, 10g / L of EDTA-2Na, 5g / L of sodium molybdate, 10g / L of sodium sulfide, and 7.5g / L of cerium acetate.

[0044] Step 2: After the micro-arc oxidation AC power supply is turned on, the surface of the aluminum alloy is subjected to micro-arc oxidation treatment. During the micro-arc oxidation treatment of the aluminum alloy, the temperature of the electrolytic solution in the stainless steel electrolytic cell is controlled below 30°C.

[0045] Step 3: After micro-arc oxidation treatment of the aluminum alloy surface, the aluminum alloy is washed with deionized water to obtain an in-situ constructed Al2O3 / MoS2 / CePO4 composite ceramic film on the aluminum alloy surface. The volume wear rate of the optimal Al2O3 / MoS2 / CePO4 composite ceramic film in-situ constructed on the aluminum alloy surface using the most preferred electrolytic solution is 4.9×10 - 7 mm 3 / N·mm, the average friction coefficient is 0.56; the self-corrosion ionization density is 1.98×10 -7 A.cm -2 , the corrosion potential is -0.20V.

[0046] The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film provided by the present invention is different from that of conventional ceramic layers in that EDTA-2Na, sodium molybdate, sodium sulfide and cerium acetate are added to the phosphate solute.

[0047] The purpose of adding EDTA-2Na to the electrolytic solution is to stabilize the metal ions and rare earth elements in the electrolytic cell and promote various reactions during the in-situ growth of the film layer.

[0048] The purpose of adding sodium molybdate and sodium sulfide to the electrolytic solution is to replace sodium thiomolybdate and alkaline sodium hydroxide through the reaction of water, sodium sulfide and sodium molybdate. Under the promotion of the complexing agent, the sodium thiomolybdate obtained by the reaction reacts with the ionized hydrogen ions to form thiomolybdic acid. Thiomolybdic acid decomposes under the action of a high electric field to obtain molybdenum trisulfide and hydrogen sulfide. Molybdenum trisulfide has relatively poor thermal stability and is easily transformed into stable molybdenum disulfide in high-temperature aqueous solution. Molybdenum disulfide with good thermal stability spontaneously and evenly accumulates with the accumulation of this film layer. When sodium molybdate and sodium sulfide are added to the electrolytic solution, the specific reaction that occurs is:

[0049] 4Na2S+Na2MoO4+4H2O=Na2MoS4+8NaOH;

[0050] 2H+Na2MoS4=H2MoS4+2Na;

[0051] H2MoS4=MoS3+H2S;

[0052] MoS3=MoS2+S.

[0053] The purpose of adding cerium acetate to the electrolytic solution is to allow the hydrolyzed main salt and the ionized trivalent cerium element to synthesize water-insoluble cerium phosphate in situ on the aluminum alloy surface under the action of the complexing agent and high temperature and high electric field. The cerium phosphate with good stability spontaneously and evenly accumulates along with the accumulation of this film layer. The specific reaction that occurs when cerium acetate is added to the electrolytic solution is:

[0054] (NaPO3)6+18H2O→6H3PO4+6Na + +3H + ;

[0055] H3PO4→H + +PO4 3- ;

[0056] (CH3CO3)3Ce·xH2O→Ce 3+ +CH3COO - +CO2↑+H2O;

[0057] Ce 3+ +PO4 3- →Ce(PO4).

[0058] When aluminum alloy is exposed to high temperature and high electric field, the trivalent aluminum ions spontaneously ionized on the surface of the aluminum alloy react with the hydrolyzed hydroxide ions to form hydrated alumina. This type of alumina easily loses water under high temperature and transforms into alumina. In addition, the active aluminum metal and the oxygen obtained by electrolysis are also prone to oxidation reaction to form alumina. When the surface temperature of the aluminum alloy is higher than 150°C, the in-situ synthesized alumina is prone to transform into γ-type alumina. When the temperature exceeds 1200°C, γ-type alumina will transform into α-type alumina. As a hard material, α-type alumina is an important material for micro-arc oxidation surface strengthening of aluminum alloys. The specific reaction is as follows:

[0059] Al 3+ +OH - →Al(OH)3→Al2O3+nH2O;

[0060] Al 3+ +H2O→Al2O3+H3O + ;

[0061] 2Al+3O2→2Al2O3;

[0062] AlOOH → transforms into γ-Al2O3 when the temperature exceeds 150℃ → transforms into α-Al2O3 when the temperature exceeds 1200℃.

[0063] like Figure 1-6 As shown in the figure, except for the 6082 aluminum alloy that has been subjected to T6 heat treatment, the other raw materials used in the examples are all commercially available conventional raw materials unless otherwise specified; the process methods used in the examples are all the preparation processes of the high wear-resistant and corrosion-resistant micro-arc oxidation composite film provided by the present invention unless otherwise specified; the setting parameters for the micro-arc oxidation AC power supply are all: constant current mode, current density 11A / dm 2 , operating frequency is 500Hz, positive and negative duty cycle is 30%, number of pulses is 1, and working time is 20min.

[0064] Comparative Example 1:

[0065] The electrolytic solution used is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, and 10 parts of sodium sulfide; the concentrations of each component in the electrolytic solution are 15 g / L of sodium hexametaphosphate, 10 g / L of EDTA-2Na, 5 g / L of sodium molybdate, and 10 g / L of sodium sulfide.

[0066] The conventional micro-arc oxidation surface treatment technology in the art was adopted, and the aluminum alloy surface was subjected to micro-arc oxidation treatment using Comparative Example 1. After the 6082-T6 aluminum alloy after micro-arc oxidation treatment was cleaned with deionized water, an in-situ constructed MoS2 / CePO4 composite ceramic film layer was obtained on the aluminum alloy surface.

[0067] Example 2:

[0068] The electrolytic solution used is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 5 parts of cerium acetate; the concentrations of each component in the electrolytic solution are 15 g / L of sodium hexametaphosphate, 10 g / L of EDTA-2Na, 5 g / L of sodium molybdate, 10 g / L of sodium sulfide, and 5 g / L of cerium acetate.

[0069] After the aluminum alloy surface was subjected to micro-arc oxidation treatment using Example 2, the 6082-T6 aluminum alloy after micro-arc oxidation treatment was cleaned with deionized water, and an Al2O3 / MoS2 / CePO4 composite ceramic film layer constructed in situ was obtained on the aluminum alloy surface.

[0070] Example 3:

[0071] The electrolytic solution used is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 7.5 parts of cerium acetate; the concentrations of each component in the electrolytic solution are 15 g / L of sodium hexametaphosphate, 10 g / L of EDTA-2Na, 5 g / L of sodium molybdate, 10 g / L of sodium sulfide, and 7.5 g / L of cerium acetate.

[0072] After the aluminum alloy surface was subjected to micro-arc oxidation treatment using Example 3, the 6082-T6 aluminum alloy after micro-arc oxidation treatment was cleaned with deionized water, and an optimal in-situ constructed Al2O3 / MoS2 / CePO4 composite ceramic film layer was obtained on the aluminum alloy surface.

[0073] Example 4:

[0074] The electrolytic solution used is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 10 parts of cerium acetate; the concentrations of each component in the electrolytic solution are 15 g / L of sodium hexametaphosphate, 10 g / L of EDTA-2Na, 5 g / L of sodium molybdate, 10 g / L of sodium sulfide, and 10 g / L of cerium acetate.

[0075] After the aluminum alloy surface was subjected to micro-arc oxidation treatment using Example 4, the 6082-T6 aluminum alloy after micro-arc oxidation treatment was cleaned with deionized water, and an Al2O3 / MoS2 / CePO4 composite ceramic film layer constructed in situ was obtained on the aluminum alloy surface.

[0076] Example 5:

[0077] The electrolytic solution used is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 12.5 parts of cerium acetate; the concentrations of each component in the electrolytic solution are 15 g / L of sodium hexametaphosphate, 10 g / L of EDTA-2Na, 5 g / L of sodium molybdate, 10 g / L of sodium sulfide, and 12.5 g / L of cerium acetate.

[0078] After the aluminum alloy surface was subjected to micro-arc oxidation treatment using Example 5, the 6082-T6 aluminum alloy after micro-arc oxidation treatment was cleaned with deionized water, and an Al2O3 / MoS2 / CePO4 composite ceramic film layer constructed in situ was obtained on the aluminum alloy surface.

[0079] The difference between Comparative Example 1, Example 2, Example 3, Example 4, and Example 5 is that: Comparative Example 1 does not add cerium acetate, and Examples 2, Example 3, Example 4, and Example 5 add cerium acetate at different concentrations of 5, 7.5, 10, and 12.5 g / L to 15 g / L sodium hexametaphosphate, 10 g / L EDTA-2Na, 5 g / L sodium molybdate, and 10 g / L sodium sulfide electrolytic solutes, respectively.

[0080] The performance of the composite ceramic film layer on the surface of the aluminum alloy prepared at different cerium acetate concentrations was characterized and tested, wherein: a D / max-2500 / pc diffractometer was used to detect the surface phase of the composite film layer; a DHV-1000AV digital microhardness tester was used with a test load of 1N and a holding time of 10s. The hardness test was performed on 10 points on each test surface, and the average value was taken after removing the maximum and minimum values, which was the microhardness value of the composite film layer; a Zeiss SIGMA 500 field emission scanning electron microscope was used to photograph the surface morphology of the composite film layer; Image J software was used to statistically analyze the surface pores of the composite film layer photographed by the scanning electron microscope; and an AZtec X-Max The element distribution of the composite film cross section was photographed by a 50-degree energy spectrometer. The tribological test of the composite film was carried out using an HT-1000 high-temperature friction and wear tester. The test temperature was room temperature, the coupling material was a silicon nitride sphere with a diameter of 6.35 mm, the external load was 5 N, the coupling speed was 535 rpm, the coupling wear radius was 4 mm, and the test time was 10 min. The electrochemical test of the composite film was carried out using a Shanghai Chenhua electrochemical workstation, a chi760e system three-electrode system, in which the working electrode was the sample to be tested, the auxiliary electrode was a platinum electrode, and the reference electrode was a calomel electrode filled with a saturated KCl solution. A 3.5% NaCl solution was used as the corrosion medium, and the test area was 1.5 cm. 2 .

[0081] The performance characterization and test results are as follows:

[0082] like Figure 1 As shown, a D / max-2500 / pc diffractometer was used to perform phase detection on the composite ceramic film layers obtained in Comparative Example 1, Example 2, Example 3, Example 4, and Example 5, and the phases contained on the surfaces of the composite ceramic film layers obtained in Comparative Example 1, Example 2, Example 3, Example 4, and Example 5 were observed. Figure 1 It can be seen that the composite ceramic membrane layer obtained in Comparative Example 1 contains aluminum, γ-type alumina, α-type alumina, and molybdenum disulfide; in addition to containing aluminum, γ-type alumina, α-type alumina, and molybdenum disulfide, the composite ceramic membrane layers obtained in Example 2, Example 3, Example 4, and Example 5 all have obvious cerium phosphate diffraction peaks at 2θ=27.0°, 28.8°, and 31.1°, thereby confirming the successful in-situ synthesis of cerium phosphate in the composite ceramic membrane layer, that is, the successful construction of the composite phase.

[0083] like Figure 2As shown, the surface hardness of the aluminum alloy and the composite ceramic film obtained in Comparative Example 1, Example 2, Example 3, Example 4, and Example 5 was tested using a DHV-1000AV digital microhardness tester to observe the effect of the concentration of cerium acetate added on the surface wear resistance of the composite ceramic film. The surface hardness of the aluminum alloy is one of the important conditions for evaluating the surface wear resistance of the aluminum alloy. Figure 2 It can be seen that with the increase of the added concentration of cerium acetate, the surface hardness of the obtained composite ceramic film layer shows a trend of first increasing and then decreasing. The hardness of Example 2, Example 3, Example 4, and Example 5 are all stronger than the prior art. Among them, the surface hardness of the composite ceramic film layer prepared in Example 3 can reach up to 961.79HV1, making the aluminum alloy surface more wear-resistant. It can be seen from the experimental data that the component selection of the electrolytic solution in Example 3 is the most preferred.

[0084] like Figure 3 As shown, a Zeiss SIGMA 500 field emission scanning electron microscope was used to magnify the surface morphology of the composite ceramic film layer on the aluminum alloy surface prepared in the most preferred embodiment 3 by 200 times and to observe the effect of the concentration of cerium acetate added on the surface morphology of the composite ceramic film layer. The Image J software was used to magnify the surface of the micro-arc oxidation composite ceramic film layer obtained in Comparative Example 1, Example 2, Example 3, Example 4, and Example 5 by 200 times to perform pore statistics. The porosities obtained were: 2.00%, 1.65%, 1.66%, 1.90%, and 2.03%, respectively. At the same magnification, the lower the porosity of the film surface, the more likely the composite layer has good corrosion resistance. Figure 3 It can be seen that the surface of the composite ceramic film prepared in the most preferred embodiment 3 is affected by the electrolytic solution and the micro-arc oxidation operating parameters, with some pores transforming into a closed "scale" morphology, and a small amount of "spherical" deposits appearing around the remaining pores. The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film provided by the present invention can reduce the surface porosity and defects of the Al2O3 / MoS2 composite ceramic film.

[0085] like Figure 4 As shown, the cross section of the composite ceramic film layer on the surface of the aluminum alloy prepared in the most preferred embodiment 3 was magnified 1500 times by using an AZtec X-Max 50 energy spectrometer to observe the cross section morphology and element distribution of the micro-arc oxidation composite layer obtained in the most preferred embodiment 3. Figure 4 It can be seen that the cross-section of the composite ceramic film layer obtained in the most preferred embodiment 3 is relatively evenly distributed with aluminum, oxygen, cerium, phosphorus, molybdenum, and sulfur elements. This also indirectly proves that part of the solutes in the electrolytic solution can be retained in the micro-arc oxidation film layer in some form during the micro-arc oxidation process, and can also be accumulated as the film layer grows in situ.

[0086] like Figure 5As shown, the composite ceramic film obtained in Comparative Example 1 and the most preferred embodiment 3 was subjected to tribological tests using an HT-1000 high temperature friction and wear tester. Figure 5 It can be seen that after the tribological test, the friction coefficient of the composite ceramic film layer obtained in the most preferred embodiment 3 is 0.56, which is 0.01 lower than that in the comparative embodiment 1. The volume wear rate calculation formula in tribology is used to obtain the volume wear rate of the composite ceramic film layers in the comparative embodiment 1 and the most preferred embodiment 3. Among them, the volume wear rate of the composite ceramic film layer obtained in the most preferred embodiment 3 is reduced by 4.0×10 -8 mm 3 / N·mm.

[0087] Among them, the calculation principle of volume wear rate after tribological testing is as follows:

[0088]

[0089] Where I is the volume wear rate, mm 3 / N·mm; 2ηrS is the wear volume of the composite ceramic film, mm 3 ; N is the applied load, N; L is the moving distance, mm.

[0090] like Figure 6 As shown, the composite ceramic film layer was electrochemically tested using the Shanghai Chenhua electrochemical workstation, chi760e system three-electrode system, and the results were as follows: Figure 6 and Table 1, thereby observing the electrochemical corrosion resistance of the composite ceramic film layer obtained in Example 1 and the most preferred embodiment 3. The polarization curves of the composite ceramic film layer obtained in Comparative Example 1, Example 2, Example 3, Example 4, and Example 5 were subjected to Tafel fitting calculation to obtain the corrosion potential E of the composite ceramic film layer as shown in Table 1. corr and self-corrosion current density I corr .

[0091] Table 1 Corrosion potential E of the composite ceramic film obtained in various embodiments corr and self-corrosion current density I corr

[0092] project <![CDATA[E corr (V)]]> <![CDATA[I corr (A / cm 2 )]]> Comparative Example 1 -1.06 <![CDATA[1.81×10 -6 ]]> Example 2 -1.06 <![CDATA[5.32×10 -7 ]]> Example 3 -0.20 <![CDATA[1.98×10 -7 ]]> Example 4 -1.19 <![CDATA[3.54×10 -6 ]]> Example 5 -0.47 <![CDATA[3.10×10 -7 ]]>

[0093] Among them, the Tafel fitting equation is:

[0094] η=a+b×log|i|

[0095] Where η is the corrosion potential, V; a and b are two constants, a is the overpotential value when the current density is unity; i is the self-corrosion current density A / cm 2 .

[0096] By comparing the corrosion potential and self-corrosion current density of the composite ceramic film layer, the corrosion resistance of the film layer was evaluated. The higher the corrosion potential and the lower the corrosion current density, the better the corrosion resistance of the film layer, among which the self-corrosion current density is dominant. It can be seen from Table 1 that Example 2, Example 3, and Example 5 are all superior to Comparative Example 1 to varying degrees, among which Example 3 is the best.

[0097] Depend on Figure 6 As can be seen from Table 1, the composite ceramic film layer obtained in the most preferred embodiment 3 relative to the comparative embodiment 1 has a significant positive shift in the corrosion potential on the ordinate, a decrease in the self-corrosion current density on the abscissa, an improved anode passivation ability, and an obstruction in the transfer of the corrosive medium, and the corrosion resistance of the composite ceramic film layer is significantly improved.

[0098] The preparation process of the high wear-resistant and corrosion-resistant micro-arc oxidation composite ceramic film provided by the present invention is to add appropriate concentrations of sodium hexametaphosphate, EDTA-2Na, sodium molybdate, sodium sulfide and cerium acetate solutes to the electrolyte, and to combine the constant current mode, 11A / dm 2 The micro-arc oxidation operating parameters are a current density of 1000 nm, an operating frequency of 500 Hz, a positive and negative duty cycle of 30%, and an oxidation time of 20 min. Combined with the pretreatment process of sandpaper polishing, ultrasonic cleaning, and acid-base solution activation, and utilizing the various reactions produced by the electrolytic solution under high temperature and high pressure environment, an Al2O3 / MoS2 / CePO4 composite ceramic film with high wear and corrosion resistance can be in situ constructed on the surface of 6082-T6 aluminum alloy, thereby improving the surface hardness of the aluminum alloy and enhancing the wear and corrosion resistance of the aluminum alloy surface. The volume wear rate of the optimal Al2O3 / MoS2 / CePO4 composite ceramic film is as low as 4.9×10 -7 mm 3 / N·mm, the average friction coefficient is 0.56, and the self-corrosion current density is 1.98×10 -7 A.cm -2 , the corrosion potential is -0.20V, and it has the characteristics of uniform phase distribution, high adhesion, low porosity and high hardness, while achieving the process advantages of high production efficiency, short oxidation time, low cost, convenient operation and non-toxic and pollution-free.

[0099] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film, characterized in that: include: The aluminum alloy was connected to the anode of a micro-arc oxidation AC power supply and immersed in the electrolytic solution in a stainless steel electrolytic cell; The stainless steel electrolytic cell is connected to the cathode of the micro-arc oxidation AC power supply; after the micro-arc oxidation AC power supply is turned on, the surface of the aluminum alloy is micro-arc oxidized to form an Al2O3 / MoS2 / CePO4 composite ceramic film layer in situ on the surface of the aluminum alloy; Wherein, the electrolytic solution comprises: a solvent, which is deionized water; The solute, its components and the mass fraction of each component in each liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 5 to 12.5 parts of cerium acetate.

2. The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 1, characterized in that: The aluminum alloy is 6082-T6 aluminum alloy.

3. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 2, characterized in that: Before micro-arc oxidation treatment of the aluminum alloy surface, the aluminum alloy needs to be pretreated: Step 1: Polish the aluminum alloy to a mirror finish using 120#, 240#, 320#, 400#, 500#, and 600# sandpaper in sequence; Step 2: Clean the polished aluminum alloy using ultrasonic waves; Step 3: Use a hair dryer to dry the liquid stains on the surface of the cleaned aluminum alloy; Step 4: immerse the dried aluminum alloy in 50 g / L NaOH solution, deionized water, 2% HF+20% HNO3 solution, and deionized water in sequence; wherein, the aluminum alloy is immersed in each solution for 10 seconds.

4. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 1, characterized in that: The most preferred electrolytic solution is: the solvent is deionized water; the solute components and the mass fractions of each component per liter of solvent are: 15 parts of sodium hexametaphosphate, 10 parts of EDTA-2Na, 5 parts of sodium molybdate, 10 parts of sodium sulfide, and 7.5 parts of cerium acetate.

5. The preparation process of the highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 1, characterized in that: The parameters of the micro-arc oxidation AC power supply are: constant current mode, current density of 11A / dm 2 , the operating frequency is 500Hz, the positive and negative duty cycle is 30%, the number of pulses is 1, and the oxidation time is 20min.

6. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 1, characterized in that: During the micro-arc oxidation treatment of the aluminum alloy surface, the temperature of the electrolytic solution in the stainless steel electrolytic tank is controlled below 30°C.

7. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 4, characterized in that: After the aluminum alloy surface was subjected to micro-arc oxidation treatment, the aluminum alloy was cleaned with deionized water, and an Al2O3 / MoS2 / CePO4 composite ceramic film layer was formed in situ on the aluminum alloy surface.

8. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 7, characterized in that: The volume wear rate of the optimal Al2O3 / MoS2 / CePO4 composite ceramic film layer constructed in situ on the aluminum alloy surface using the most preferred electrolytic solution is 4.9×10 -7 mm 3 / N·mm, and the average friction coefficient is 0.

56.

9. The process for preparing a highly wear-resistant and corrosion-resistant micro-arc oxidation composite film according to claim 8, characterized in that: The optimal self-corrosion ionization density of the Al2O3 / MoS2 / CePO4 composite ceramic film is 1.98×10 -7 A.cm -2 , the corrosion potential is -0.20V.

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