A low-friction wear-resistant antibacterial composite coating based on micro-arc oxidation and a preparation method and application thereof

Abstract

The application discloses a low-friction wear-resistant antibacterial composite coating based on micro-arc oxidation and a preparation method and application thereof, and the preparation method comprises the following steps: step 1, oil removal, polishing, polishing, cleaning pretreatment are performed on a titanium alloy; step 2, the titanium alloy after the pretreatment is immersed into prepared electrolyte, micro-arc oxidation treatment is performed, and a micro-arc oxidation coating is obtained, and the electrolyte comprises sodium metasilicate, sodium hydroxide and gallium oxide; and step 3, the micro-arc oxidation coating is cleaned and dried, and the low-friction wear-resistant antibacterial composite coating is obtained. The composite coating has good antibacterial performance, mechanical properties, tribological properties and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and in particular to a low-friction, wear-resistant, and antibacterial composite coating based on micro-arc oxidation, its preparation method, and its application. Background Technology

[0002] Metallic materials have a wide range of applications in the biomedical field, including dental materials, orthopedic materials, soft tissue repair materials, and auxiliary therapeutic materials. Currently, commonly used metallic materials in orthodontic clinical treatment include titanium alloys, nickel-titanium alloys, and austenitic stainless steel. Materials used in orthodontic treatment must meet the requirements of being biomaterials, meaning they must possess excellent mechanical properties, tribological properties, antibacterial properties, and corrosion resistance, in addition to good biocompatibility. Titanium and titanium alloys have gradually become one of the preferred materials in clinical orthodontic treatment due to their good biocompatibility. However, titanium alloys themselves have poor mechanical and tribological properties. During clinical use, their surfaces are easily damaged by friction, leading to the generation of abrasive debris and triggering a series of inflammatory reactions, causing significant pain for patients. Furthermore, titanium alloys lack antibacterial capabilities, making them prone to bacterial infection during clinical use. Infection is a common problem faced by biomaterials in clinical use and a major challenge for clinicians. This is related to both improper operation during treatment and changes in the local environment of the biomaterial, affecting microbial growth and increasing the likelihood of bacterial infection. Titanium alloys are used long-term in the oral cavity as medical materials, and it is also necessary to ensure that they do not corrode and fail under the long-term oral environment. Therefore, improving the mechanical, tribological, antibacterial, and corrosion-resistant properties of titanium alloys is particularly important. Micro-arc oxidation technology is one of the effective methods to solve these problems. This technology can grow a micro-arc oxidation coating mainly composed of oxides on the surface of titanium alloys in situ. As a typical hard ceramic coating, this coating is dense and has a high bonding force with the titanium alloy, which can effectively improve the mechanical and tribological properties of the titanium alloy surface. In corrosive media, the micro-arc oxidation coating can also protect the titanium alloy from corrosion. Considering the application of titanium alloys in the biomedical field, how to further realize the multi-functional integration of mechanical, tribological, antibacterial, and corrosion-resistant properties of micro-arc oxidation coatings on titanium alloy surfaces has become a new problem. The composition of the electrolyte in micro-arc oxidation technology is an important parameter affecting the coating performance. By introducing antibacterial additives into the electrolyte and optimizing process parameters, it is possible to achieve the integrated functions of low friction, wear resistance, antibacterial, and corrosion resistance of the micro-arc oxidation coating without weakening its original performance, which is expected to solve the above problems.

[0003] Studies have found that gallium oxide can effectively inhibit the formation of bacterial biofilms, suppress bacterial growth, and possess bactericidal activity. The antibacterial mechanism of gallium oxide differs from that of antibiotics; its antibacterial mechanism relies on chemical mimicry, primarily related to its "ferrolike" properties. 3+ with Fe3+ Their chemical properties are very similar, therefore Ga 3+ It can replace Fe 3+ Ga participates in physiological metabolism 3+ After replacing Fe, which serves as the redox active center of the protein. 3+ Subsequently, it can inhibit the physiological activity of related proteins, thereby acting as Fe. 3+ It functions through competitive inhibitors. And Fe... 3+ Fe plays an important role in the formation of biofilms within organisms. 3+ As a coenzyme, Ga participates in many redox-related enzymes in cells. 3+ In replacing Fe 3+ Subsequently, it could not achieve the same effect, thus hindering biofilm formation and inhibiting bacterial invasion. Gallium oxide is an inorganic antibacterial agent. Foreign literature reports that gallium oxide has good antibacterial activity against Acinetobacter baumannii, etc., while domestic literature is relatively scarce, mainly focusing on its effects on biofilm formation by Staphylococcus epidermidis and Escherichia coli. Furthermore, gallium oxide has also shown considerable effectiveness in two different animal infection models: acute pneumonia and respiratory biofilm infection. Current research on gallium oxide mainly focuses on its preparation and optical properties, with relatively little research on its antibacterial properties. Gallium oxide is a solid powder that can be uniformly dispersed in electrolytes and can be coated with antibacterial properties through micro-arc oxidation technology, showing broad application prospects.

[0004] Therefore, this invention mainly uses micro-arc oxidation technology to treat titanium alloys. The resulting micro-arc oxidation coating effectively improves the mechanical, tribological and corrosion resistance properties of titanium alloys. On this basis, gallium oxide is added to the electrolyte as an antibacterial agent to obtain a low-friction, wear-resistant and antibacterial composite coating. Summary of the Invention

[0005] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a method for preparing a low-friction, wear-resistant, and antibacterial composite coating based on micro-arc oxidation.

[0006] Another objective of this invention is to provide the application of the composite coating on titanium alloy surfaces.

[0007] The technical solution adopted to achieve the purpose of this invention is:

[0008] A method for preparing a low-friction, wear-resistant, and antibacterial composite coating based on micro-arc oxidation includes the following steps:

[0009] Step 1: Pre-treatment of titanium alloy by degreasing, grinding, polishing and cleaning;

[0010] Step 2: Immerse the pretreated titanium alloy in the prepared electrolyte for micro-arc oxidation treatment to obtain a micro-arc oxidation coating. The electrolyte includes sodium metasilicate, sodium hydroxide, and gallium oxide.

[0011] Step 3: Clean and dry the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0012] In the above technical solution, step 1, the degreasing specifically includes: cleaning the titanium alloy after wire cutting with alkaline solution; immersing the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes and then rinsing it with deionized water to remove residual sodium hydroxide solution from the surface.

[0013] In the above technical solution, step 1, the polishing specifically includes: polishing the titanium alloy after surface degreasing with sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0014] In the above technical solution, in step 1, after polishing, the surface finish Ra of the titanium alloy is less than 0.8.

[0015] In the above technical solution, step 1, the cleaning specifically includes: the polished titanium alloy is first placed in acetone for ultrasonic cleaning for 25-30 minutes, then placed in anhydrous ethanol for ultrasonic cleaning for 25-30 minutes, and finally ultrasonically cleaned with deionized water for 3-5 minutes, and dried at 60°C to obtain the pretreated titanium alloy.

[0016] In the above technical solution, in step 2, the concentration of sodium metasilicate in the electrolyte is 10-20 g / L, the concentration of sodium hydroxide is 1.5-2 g / L, and the concentration of gallium oxide is 2-20 g / L. Preferably, the concentration of gallium oxide is 10-20 g / L.

[0017] In the above technical solution, in step 2, during the micro-arc oxidation treatment, the pretreated titanium alloy is used as the anode. A hole is drilled in the pretreated titanium alloy, and an aluminum wire passes through the hole to immerse the pretreated titanium alloy in the prepared electrolyte. A stainless steel plate is used as the cathode, and a pulse voltage is used as the voltage for micro-arc oxidation. During the micro-arc oxidation process, the electrolyte is stirred by a stirrer, and the temperature of the electrolyte is controlled by a circulating water system. Preferably, the electrolyte temperature is below 25°C, the positive voltage is 300-400V, the negative voltage is 50-70V, and the current density is 4-6A / dm³. 2 The duty cycle is 10-20%, the frequency is 300-500Hz, the oxidation time is 3-5min, and the distance between the anode and cathode is 50-60mm.

[0018] Another aspect of the present invention includes a low-friction, wear-resistant, and antibacterial composite coating prepared by the method described above.

[0019] Another aspect of the present invention includes the application of the low-friction, wear-resistant, and antibacterial composite coating in biomedical materials.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention prepares a low-friction, wear-resistant, and antibacterial composite coating on the surface of medical titanium alloy using micro-arc oxidation technology, which improves the mechanical and tribological properties of the titanium alloy surface. The presence of the surface oxide film also enhances its corrosion resistance. By adding gallium oxide antibacterial agent to the electrolyte, a micro-arc oxidation coating containing antibacterial elements is formed. This not only endows the micro-arc oxidation coating with antibacterial properties, but also the synergistic effect of gallium oxide and the micro-arc oxidation coating improves the overall mechanical, tribological, and corrosion resistance properties of the coating.

[0022] 2. The choice of substrate determines the composition of the micro-arc oxidation coating. In this invention, titanium alloy is used as the substrate, and gallium oxide is composited into the micro-arc oxidation coating through micro-arc oxidation technology. The resulting coating effectively overcomes the shortcomings of titanium alloy as a biomedical material, such as high friction coefficient and poor wear resistance.

[0023] 3. The raw materials used in this invention are green and environmentally friendly, non-toxic and pollution-free; the preparation process is simple and easy to operate; the production efficiency is high and it is suitable for industrial production. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a micro-arc oxidation device;

[0025] Figure 2 The surface morphology of the ordinary micro-arc oxidation coating in Comparative Example 1 is shown.

[0026] Figure 3 The surface morphology of the low-friction, wear-resistant, and antibacterial composite coating in Example 4;

[0027] Figure 4 The cross-sectional morphology of the ordinary micro-arc oxidation coating in Comparative Example 1 is shown.

[0028] Figure 5 This is the cross-sectional morphology of the low-friction, wear-resistant, and antibacterial composite coating in Example 4;

[0029] Figure 6 The mechanical properties of low-friction, wear-resistant, and antibacterial composite coatings with different gallium oxide contents;

[0030] Figure 7 The coefficient of friction of low-friction, wear-resistant, and antibacterial composite coatings with different gallium oxide contents;

[0031] Figure 8The self-corrosion current and potential of untreated titanium alloy with low-friction, wear-resistant and antibacterial composite coatings with different gallium oxide contents;

[0032] Figure 9 This is a scanning electron microscope image of the adhesion of Streptococcus mutans to untreated titanium alloy;

[0033] Figure 10 The image shows the scanning electron microscope image of the adhesion of Streptococcus mutans to the ordinary micro-arc oxidation coating in Comparative Example 1.

[0034] Figure 11 The image shows a scanning electron microscope image of the adhesion of Streptococcus mutans to the low-friction, wear-resistant, and antibacterial composite coating of Example 4.

[0035] In the diagram: 1-Cooling tank, 3-Electrolyte, 4-Stirring system, 5-Coolant return pipe, 6-Coolant inlet pipe Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0037] Example 1

[0038] A method for preparing a low-friction, wear-resistant, and antibacterial composite coating on the surface of medical titanium alloy using micro-arc oxidation technology includes the following steps:

[0039] Step 1, Pre-treatment of the titanium alloy: including degreasing, grinding, polishing, and cleaning; specific steps are as follows:

[0040] Degreasing: Immerse the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes, then remove it and rinse it with deionized water to remove the residual sodium hydroxide solution on the surface.

[0041] Grinding: After degreasing the surface, the titanium alloy is ground using sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0042] Polishing: The titanium alloy after surface grinding is polished to achieve a surface finish of Ra less than 0.8;

[0043] Cleaning: The polished titanium alloy is first placed in a beaker containing acetone and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Then it is placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Finally, it is ultrasonically cleaned with deionized water for 5 minutes at a temperature of 60-70℃ and a frequency of 75-85KHz. Then it is dried in a 60℃ oven to obtain the pretreated titanium alloy.

[0044] Step 2: Immerse the pretreated titanium alloy in the prepared electrolyte solution for micro-arc oxidation treatment to obtain a micro-arc oxidation coating; the specific steps are as follows:

[0045] like Figure 1 As shown, the pretreated titanium alloy obtained in step 1 is immersed in an electrolyte 3 containing 20 g / L sodium metasilicate, 2 g / L sodium hydroxide, and 2 g / L gallium oxide through an aluminum wire. The electrolyte 3 is located in a cooling tank 1. The electrolyte is mixed evenly by a stirring system 4. The cooling tank 1 is equipped with a cold water jacket and the temperature of the electrolyte is controlled by a circulating water system. The cold water jacket is equipped with a coolant return pipe 5 and a coolant inlet pipe 6. Then, the pretreated titanium alloy (micro-arc oxidation sample 2) and the stainless steel electrolytic cell are connected to the anode and cathode of the micro-arc oxidation pulse DC power supply through wires to obtain a connected micro-arc oxidation device. The following examples and comparative examples all use this micro-arc oxidation device.

[0046] Turn on the connected micro-arc oxidation device's pulsed DC power supply. The operating mode is constant voltage mode, i.e., positive pulse voltage 300V, negative pulse voltage 50V, positive pulse duty cycle 10%, negative pulse duty cycle 10%, and current density 6A / dm³. 2 Micro-arc oxidation was performed for 5 minutes at a frequency of 500Hz to obtain a micro-arc oxidation coating.

[0047] Step 3: Post-process the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0048] The micro-arc oxidation coating obtained in step 2 was ultrasonically cleaned with deionized water to remove residual electrolyte on the surface, and then dried with a hair dryer to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0049] Example 2

[0050] A method for preparing a low-friction, wear-resistant, and antibacterial composite coating on the surface of medical titanium alloy using micro-arc oxidation technology includes the following steps:

[0051] Step 1, Pre-treatment of the titanium alloy: including degreasing, grinding, polishing, and cleaning; specific steps are as follows:

[0052] Degreasing: Immerse the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes, then remove it and rinse it with deionized water to remove the residual sodium hydroxide solution on the surface.

[0053] Grinding: After degreasing the surface, the titanium alloy is ground using sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0054] Polishing: The titanium alloy after surface grinding is polished to achieve a surface finish of Ra less than 0.8;

[0055] Cleaning: The polished titanium alloy is first placed in a beaker containing acetone and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Then it is placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Finally, it is ultrasonically cleaned with deionized water for 5 minutes at a temperature of 60-70℃ and a frequency of 75-85KHz. Then it is dried in a 60℃ oven to obtain the pretreated titanium alloy.

[0056] Step 2: Immerse the pretreated titanium alloy in the prepared electrolyte solution for micro-arc oxidation treatment to obtain a micro-arc oxidation coating. The specific steps are as follows:

[0057] The pretreated titanium alloy obtained in step 1 is immersed in an electrolyte containing 20 g / L sodium metasilicate, 2 g / L sodium hydroxide, and 4 g / L gallium oxide through an aluminum wire. At the same time, the electrolyte is mixed evenly through a stirring system 4. Then, the pretreated titanium alloy and the stainless steel electrolytic cell are connected to the anode and cathode of the micro-arc oxidation pulsed DC power supply through wires to obtain a connected micro-arc oxidation device.

[0058] Turn on the connected micro-arc oxidation device pulse DC power supply. The operating mode is constant voltage mode, i.e., positive pulse voltage 300V, negative pulse voltage 50V, positive pulse duty cycle 10%, negative pulse duty cycle 10%, and current density 6A / dm³. 2 Micro-arc oxidation was performed for 5 minutes at a frequency of 500Hz to obtain a micro-arc oxidation coating.

[0059] Step 3: Post-process the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0060] The micro-arc oxidation coating obtained in step 2 was ultrasonically cleaned with deionized water to remove residual electrolyte on the surface, and then dried with a hair dryer to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0061] Example 3

[0062] A method for preparing a low-friction, wear-resistant, and antibacterial composite coating on the surface of medical titanium alloy using micro-arc oxidation technology includes the following steps:

[0063] Step 1, Pre-treatment of the titanium alloy: including degreasing, grinding, polishing, and cleaning; specific steps are as follows:

[0064] Degreasing: Immerse the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes, then remove it and rinse it with deionized water to remove the residual sodium hydroxide solution on the surface.

[0065] Grinding: After degreasing the surface, the titanium alloy is ground using sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0066] Polishing: The titanium alloy after surface grinding is polished to achieve a surface finish of Ra less than 0.8;

[0067] Cleaning: The polished titanium alloy is first placed in a beaker containing acetone and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Then it is placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Finally, it is ultrasonically cleaned with deionized water for 5 minutes at a temperature of 60-70℃ and a frequency of 75-85KHz. Then it is dried in a 60℃ oven to obtain the pretreated titanium alloy.

[0068] Step 2: Immerse the pretreated titanium alloy in the prepared electrolyte solution for micro-arc oxidation treatment to obtain a micro-arc oxidation coating. The specific steps are as follows:

[0069] The pretreated titanium alloy obtained in step 1 is immersed in an electrolyte containing 20 g / L sodium metasilicate, 2 g / L sodium hydroxide, and 10 g / L gallium oxide through an aluminum wire. At the same time, the electrolyte is mixed evenly through a stirring system 4. Then, the pretreated titanium alloy and the stainless steel electrolytic cell are connected to the anode and cathode of the micro-arc oxidation pulsed DC power supply through wires to obtain a connected micro-arc oxidation device.

[0070] Turn on the connected micro-arc oxidation device's pulsed DC power supply. The operating mode is constant voltage mode, i.e., positive pulse voltage 300V, negative pulse voltage 50V, positive pulse duty cycle 10%, negative pulse duty cycle 10%, and current density 6A / dm³. 2 Micro-arc oxidation was performed for 5 minutes at a frequency of 500Hz to obtain a micro-arc oxidation coating.

[0071] Step 3: Post-process the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0072] The micro-arc oxidation coating obtained in step 2 was ultrasonically cleaned with deionized water to remove residual electrolyte on the surface, and then dried with a hair dryer to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0073] Example 4

[0074] A method for preparing a low-friction, wear-resistant, and antibacterial composite coating on the surface of medical titanium alloy using micro-arc oxidation technology includes the following steps:

[0075] Step 1, Pre-treatment of the titanium alloy: including degreasing, grinding, polishing, and cleaning; specific steps are as follows:

[0076] Degreasing: Immerse the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes, then remove it and rinse it with deionized water to remove the residual sodium hydroxide solution on the surface.

[0077] Grinding: After degreasing the surface, the titanium alloy is ground using sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0078] Polishing: The titanium alloy after surface grinding is polished to achieve a surface finish of Ra less than 0.8;

[0079] Cleaning: The polished titanium alloy is first placed in a beaker containing acetone and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Then it is placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Finally, it is ultrasonically cleaned with deionized water for 5 minutes at a temperature of 60-70℃ and a frequency of 75-85KHz. Then it is dried in a 60℃ oven to obtain the pretreated titanium alloy.

[0080] Step 2 involves immersing the pretreated titanium alloy in a prepared electrolyte solution for micro-arc oxidation treatment to obtain a micro-arc oxidation coating. This process includes the following steps:

[0081] The pretreated titanium alloy obtained in step 1 was immersed in an electrolyte containing 20 g / L sodium metasilicate, 2 g / L sodium hydroxide, and 20 g / L gallium oxide via an aluminum wire. Simultaneously, the electrolyte was mixed uniformly using a stirring system 4. Then, the pretreated titanium alloy and the stainless steel electrolytic cell were connected to the anode and cathode of a micro-arc oxidation pulsed DC power supply via wires, respectively. A schematic diagram of the connected micro-arc oxidation device is shown below. Figure 1 As shown;

[0082] Turn on the connected micro-arc oxidation device's pulsed DC power supply. The operating mode is constant voltage mode, i.e., positive pulse voltage 300V, negative pulse voltage 50V, positive pulse duty cycle 10%, negative pulse duty cycle 10%, and current density 6A / dm³. 2 Micro-arc oxidation was performed for 5 minutes at a frequency of 500Hz to obtain a micro-arc oxidation coating.

[0083] Step 3: Post-process the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0084] The micro-arc oxidation coating obtained in step 2 was ultrasonically cleaned with deionized water to remove residual electrolyte on the surface, and then dried with a hair dryer to obtain a low-friction, wear-resistant, and antibacterial composite coating.

[0085] Comparative Example 1

[0086] A method for preparing a conventional micro-arc oxidation coating on the surface of a medical titanium alloy using micro-arc oxidation technology includes the following steps:

[0087] Step 1, Pre-treatment of the titanium alloy: including degreasing, grinding, polishing, and cleaning; specific steps are as follows:

[0088] Degreasing: Immerse the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes, then remove it and rinse it with deionized water to remove the residual sodium hydroxide solution on the surface.

[0089] Grinding: After degreasing the surface, the titanium alloy is ground using sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

[0090] Polishing: The titanium alloy after surface grinding is polished to achieve a surface finish of Ra less than 0.8;

[0091] Cleaning: The polished titanium alloy is first placed in a beaker containing acetone and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Then it is placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes at a temperature of 60-70℃ and a frequency of 35-45KHz. Finally, it is ultrasonically cleaned with deionized water for 5 minutes at a temperature of 60-70℃ and a frequency of 75-85KHz. Then it is dried in a 60℃ oven to obtain the pretreated titanium alloy.

[0092] Step 2: Immerse the pretreated titanium alloy in the prepared electrolyte solution for micro-arc oxidation treatment to obtain a micro-arc oxidation coating; the specific steps are as follows:

[0093] The pretreated titanium alloy is immersed in an electrolyte containing 20 g / L sodium metasilicate and 2 g / L sodium hydroxide through an aluminum wire. At the same time, the electrolyte is mixed evenly by a stirring system 4. Then, the pretreated titanium alloy and the stainless steel electrolytic cell are connected to the anode and cathode of the micro-arc oxidation pulse DC power supply through wires to obtain a connected micro-arc oxidation device.

[0094] Turn on the connected micro-arc oxidation device's pulsed DC power supply. The operating mode is constant voltage mode, i.e., positive pulse voltage 300V, negative pulse voltage 50V, positive pulse duty cycle 10%, negative pulse duty cycle 10%, and current density 6A / dm³. 2Micro-arc oxidation was performed for 5 minutes at a frequency of 500Hz to obtain a micro-arc oxidation coating.

[0095] Step 3: Post-process the micro-arc oxidation coating to obtain a composite coating.

[0096] The micro-arc oxidation coating obtained in step 2 was ultrasonically cleaned with deionized water to remove residual electrolyte on the surface, and then dried with a hair dryer to obtain a regular micro-arc oxidation coating.

[0097] Analysis of results from Examples 1-4 and Comparative Example 1:

[0098] The surfaces of the ordinary micro-arc oxidation coating obtained in Comparative Example 1 and the low-friction, wear-resistant, and antibacterial composite coating obtained in Example 4 are as follows: Figures 2-3 As shown, the cross-sectional scanning electron microscope (SEM) images of the ordinary micro-arc oxidation coating obtained in Comparative Example 1 and the low-friction, wear-resistant, and antibacterial composite coating obtained in Example 4 are as follows: Figures 4-5 As shown in the figure. By comparing the surface morphology of ordinary micro-arc oxidation coating and low-friction wear-resistant antibacterial composite coating, it can be found that the porosity and pore size of low-friction wear-resistant antibacterial composite coating are reduced. At the same time, the cross-sectional images show that the dense layer of low-friction wear-resistant antibacterial composite coating is thicker and more uniform, and its loose layer has fewer pores compared with ordinary micro-arc oxidation coating. The thickness of low-friction wear-resistant antibacterial composite coating is about 4μm. These results indicate that low-friction wear-resistant antibacterial composite coating has a better mechanical structure.

[0099] The coatings obtained in Comparative Example 1 and Examples 1 to 4 were subjected to mechanical property testing using a nanoindenter. The test results are as follows: Figure 6 As shown, compared with Comparative Example 1, the hardness and elastic modulus of the low-friction wear-resistant antibacterial composite coatings obtained in Examples 1 to 4 are improved. In particular, the low-friction wear-resistant antibacterial composite coating obtained under the highest gallium oxide concentration condition in Example 4 has a hardness of 13.5 GPa and an elastic modulus of 113 GPa, exhibiting the best mechanical properties.

[0100] We then used a ball-and-disc friction tester (TRB) to test the coatings obtained in Comparative Example 1 and Examples 1 to 4. 3 Friction tests were conducted on a circular track with a diameter of 1 mm on the upper edge of a CSM (Anton Paar) friction pair, using stainless steel balls (6 mm, Shanghai Panlian Technology). The results are as follows: Figure 7 As shown, the friction coefficient of Comparative Example 1 is 0.22. Although the friction coefficient shows an increasing trend with the increase of gallium oxide concentration, we quickly found that the friction coefficient gradually decreases with further increase of gallium oxide concentration, reaching a minimum of 0.14 in Example 4, which shows better low friction performance.

[0101] In addition, the scanning electron microscope images also showed that the porosity and pore size of the low-friction wear-resistant antibacterial composite coating were reduced. At the same time, the cross-sectional images showed that the dense layer of the low-friction wear-resistant antibacterial composite coating was thicker and more uniform, and its loose layer had fewer pores compared with ordinary micro-arc oxidation coatings. The overall film thickness was about 4μm.

[0102] The samples obtained in Comparative Example 1 and Examples 1-4 were placed in an artificial saliva environment using an electrochemical workstation to test their corrosion resistance. Figure 8 As shown, the self-corrosion current of the low-friction, wear-resistant, and antibacterial composite coatings of gallium oxide with different concentrations (i.e., Examples 1 to 4) decreases with increasing potential, indicating that passivation has occurred. The dense oxide film on the coating surface hinders ion diffusion, and the self-corrosion potential E corr Both are an order of magnitude higher than pure titanium, resulting in better corrosion resistance.

[0103] Bacterial adhesion tests were conducted using *Streptococcus mutans* (model S. mutans, ATCC 25175) on untreated titanium alloy, ordinary micro-arc oxidation coating, and low-friction wear-resistant antibacterial composite coating. The results are as follows: Figure 9-11 As shown, the low-friction, wear-resistant, and antibacterial composite coating exhibits the best antibacterial adhesion, while the surface of the ordinary micro-arc oxidation coating has more bacterial adhesion, and the untreated titanium alloy surface even shows a cluster of Streptococcus mutans, indicating that the presence of gallium oxide gives the low-friction, wear-resistant, and antibacterial composite coating excellent antibacterial adhesion.

[0104] In summary, when the concentration of gallium oxide in the electrolyte is 10–20 g / L, the overall performance is superior compared to that at 2–4 g / L. When the concentration of gallium oxide in the electrolyte is higher than 20 g / L, biocompatibility is relatively compromised. Therefore, the optimal performance corresponds to a gallium oxide concentration of 10–20 g / L.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-friction, wear-resistant, and antibacterial composite coating based on micro-arc oxidation, characterized in that, Includes the following steps: Step 1: Pre-treatment of titanium alloy by degreasing, grinding, polishing and cleaning; Step 2: Immerse the pretreated titanium alloy in an electrolyte containing sodium metasilicate, sodium hydroxide and gallium oxide for micro-arc oxidation treatment to obtain a micro-arc oxidation coating. Step 3: Clean and dry the micro-arc oxidation coating to obtain a low-friction, wear-resistant, and antibacterial composite coating. The electrolyte contains sodium metasilicate at a concentration of 10–20 g / L, sodium hydroxide at a concentration of 1.5–2 g / L, and gallium oxide at a concentration of 10–20 g / L. During micro-arc oxidation, the electrolyte temperature is below 25°C, the positive voltage is 300-400V, the negative voltage is 50-70V, and the current density is 4-6A / dm³. 2 The duty cycle is 10-20%, the frequency is 300-500Hz, the oxidation time is 3-5min, and the distance between the anode and cathode is 50-60mm.

2. The preparation method according to claim 1, characterized in that, In step 1, the degreasing specifically includes: cleaning the titanium alloy after wire cutting with an alkaline solution; immersing the titanium alloy in a 5-10% sodium hydroxide solution for 15-20 minutes and then rinsing it with deionized water to remove residual sodium hydroxide solution from the surface.

3. The preparation method according to claim 1, characterized in that, In step 1, the polishing specifically includes: polishing the titanium alloy after surface degreasing with sandpaper of 200#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence.

4. The preparation method according to claim 1, characterized in that, In step 1, after polishing, the surface finish Ra of the titanium alloy is less than 0.

8.

5. The preparation method according to claim 1, characterized in that, In step 1, the cleaning process specifically includes: the polished titanium alloy is first placed in acetone for ultrasonic cleaning for 25-30 minutes, then placed in anhydrous ethanol for ultrasonic cleaning for 25-30 minutes, and finally ultrasonically cleaned with deionized water for 3-5 minutes, and then dried at 60°C to obtain the pretreated titanium alloy.

6. The preparation method according to claim 1, characterized in that, In step 2, during the micro-arc oxidation process, the pretreated titanium alloy is used as the anode. A hole is drilled in the pretreated titanium alloy, and an aluminum wire passes through the hole to immerse the pretreated titanium alloy in the prepared electrolyte. The stainless steel plate is used as the cathode, and the pulse voltage is used as the voltage for micro-arc oxidation. During the micro-arc oxidation process, the electrolyte is stirred by a stirrer, and the temperature of the electrolyte is controlled by a circulating water system.

7. The low-friction, wear-resistant, and antibacterial composite coating obtained by the preparation method according to any one of claims 1-6.

8. The application of the low-friction, wear-resistant, and antibacterial composite coating as described in claim 7 in biomedical materials.

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