Micro-arc oxidation coating for artificial hip joint Ti6Al4V alloy and preparation method of micro-arc oxidation coating

Abstract

The invention discloses a micro-arc oxidation coating for an artificial hip joint Ti6Al4V alloy and a preparation method of the micro-arc oxidation coating. The preparation method comprises the following steps that S1, pretreatment is conducted; s2, preparing a micro-arc oxidation electrolyte; s3, preparing a micro-arc oxidation coating; s4, cleaning and drying treatment; a preparation method of the electrolyte comprises the steps that 6 g of sodium metaaluminate solid powder, 4 g of potassium hydroxide solid powder, 2 g of sodium hexametaphosphate solid powder, 4 g of sodium silicate solid powder and 4 g of yttrium oxide nanoparticles are sequentially weighed and added into a beaker, then 980 mL of ultrapure water at the temperature of 60 DEG C is added into the beaker, and stirring is conducted for 2 min while the temperature is kept; the yttrium oxide particles are approximately spherical or ellipsoidal, the particle size range is 20-50 nm, and the purity is 99.99%. The yttrium oxide nanoparticles are introduced into the electrolyte, the micro-arc oxidation coating containing the yttrium oxide is prepared on the surface of the Ti6Al4V alloy, and compared with a traditional micro-arc oxidation coating, the surface porosity of the micro-arc oxidation coating containing the yttrium oxide is remarkably reduced, and the compactness is remarkably improved.

Description

Technical Field

[0001] The invention relates to a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints and a preparation method thereof, belonging to the technical field of surface modification of artificial hip joints. Background Art

[0002] Total hip arthroplasty (THA), used to treat damaged or diseased hip joints, is one of the most successful treatments in orthopedics. Ti6Al4V alloy is widely used as the material for modular artificial hip stems. However, the disadvantages of Ti6Al4V alloy are its relatively low surface hardness and poor wear resistance. Clinical evaluations have found that during various human activities, relative movement occurs between the femoral head and the femoral stem (head-neck interface), resulting in micron-level wear, which evolves into fretting corrosion under the action of body fluids. After fretting corrosion, the service performance of Ti6Al4V alloy deteriorates, and metal ions and wear debris are released into body fluids, causing metal allergies or metal poisoning, and even causing osteolysis and prosthesis loosening. Therefore, reducing fretting corrosion damage in Ti6Al4V alloy is crucial to ensure the long-term and stable use of artificial hip joints.

[0003] Surface modification technologies offer effective and feasible solutions to these limitations. Micro-arc oxidation (MAO), a plasma electrolytic oxidation process, boasts simplicity, low cost, efficient processing, strong controllability, and environmental friendliness. It has attracted considerable attention for light alloy surface protection and has reached industrialization. By simply immersing a Ti6Al4V substrate in an electrolyte and initiating an electrochemical reaction, MAO forms a hard ceramic coating on the substrate surface. These ceramic coatings exhibit high surface hardness, excellent wear resistance, and corrosion resistance. Furthermore, unlike some physical vapor deposition (PVD) and chemical vapor deposition (CVD) coatings, MAO coatings grow through a substrate transformation process rather than external deposition. There is no artificial interface between the substrate and the coating. This ensures a close bond between the coating and the substrate, resulting in excellent adhesion and a long service life. These unique advantages of MAO have made it a popular choice for Ti6Al4V substrate surface protection, offering promising potential and promising prospects for improving fretting corrosion resistance.

[0004] Patent CN102199785A proposes a micro-arc oxidation solution for a titanium alloy wear-resistant coating and its application. Although the proposed micro-arc oxidation coating effectively improves the wear resistance of the substrate, the entire coating has a sparse structure and is composed of a large number of porous structures. This limits its application in artificial hip joints because body fluids can penetrate the coating and the substrate through the pores, making the coating's corrosion resistance difficult to guarantee. Patent CN119307996A discloses a biomedical titanium alloy with a micro-arc oxidation surface modification and its preparation method. The resulting micro-arc oxidation coating can simultaneously improve the wear resistance and corrosion resistance of the substrate. However, the coating has a large number of porous structures and large pores with a pore size of 0.5-4μm. The large number of surface pores in the micro-arc oxidation coating make it easier for energy to accumulate on the material surface during wear, triggering material stress concentration and thus initiating microcracks. This may lead to premature fatigue damage in the coating, thereby reducing the service performance and service life of the coating. Patent CN116479495A introduces diamond into the Ti6Al4V alloy micro-arc oxidation coating, but the surface roughness and porosity of the coating are very large, and the density and uniformity are poor, which also limits the long-term stable use of the coating. Therefore, in order to ensure the practicality of the micro-arc oxidation coating at the head-neck interface of the artificial hip joint, it is necessary to control the porosity and roughness of the coating. It is very important to propose a micro-arc oxidation coating on the Ti6Al4V alloy surface that has both excellent density and uniformity.

[0005] In response to the above problems, this application is filed. Summary of the Invention

[0006] In response to the fretting corrosion damage problem of Ti6Al4V alloy and to ensure the long-term stable use of artificial hip joints, the present invention proposes a micro-arc oxidation coating for Ti6Al4V alloy of artificial hip joints and a preparation method thereof by using micro-arc oxidation technology. A micro-arc oxidation coating with excellent density and uniformity is prepared on the surface of Ti6Al4V alloy, and fretting corrosion tests are carried out. Combined with the actual service status of artificial hip joints, its anti-fretting corrosion effect is examined.

[0007] The first object of the present invention is to provide a method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints, comprising the following steps: S1: Preprocessing A hole with a diameter of 2 mm was machined in the center of the Ti6Al4V alloy substrate specimen, and the specimen was ultrasonically cleaned in anhydrous ethanol; S2: Preparation of micro-arc oxidation electrolyte The micro-arc oxidation electrolyte is an alkaline system. The components of the electrolyte are sodium metaaluminate, sodium hexametaphosphate, sodium silicate, potassium hydroxide and yttrium oxide nanoparticles. The concentrations of the substances in the electrolyte are as follows: sodium metaaluminate 6g / L, potassium hydroxide 4g / L, sodium hexametaphosphate 4g / L, sodium silicate 4g / L, yttrium oxide 4g / L; S3: Preparation of micro-arc oxidation coating The Ti6Al4V substrate was used as the anode, the stainless steel container was used as the cathode, the electrode spacing was 25 mm, the micro-arc oxidation electrolyte obtained in step S2 was used as the electrolyte, and the constant voltage mode was adopted with an applied voltage of 300 V, a frequency of 400 Hz, a duty cycle of 50%, and an electrolysis time of 30 min; S4: Cleaning and drying The coated Ti6Al4V alloy sample obtained in step S3 is placed in anhydrous ethanol for ultrasonic cleaning, and then dried and stored in a sterile drying oven.

[0008] Using this technical solution, before micro-arc oxidation coating, a hole-machining tool was used to drill a 2mm diameter hole in the center of the titanium alloy substrate sample to connect the sample to the wire for electrical connection. The sample was then ultrasonically cleaned in anhydrous ethanol for 2 minutes to remove surface impurities and improve film quality.

[0009] Preferably, the electrolyte preparation method in step S2 is: weigh 6 g of sodium aluminate solid powder, 4 g of potassium hydroxide solid powder, 2 g of sodium hexametaphosphate solid powder, 4 g of sodium silicate solid powder, and 4 g of yttrium oxide nanoparticles in sequence, and add them to a beaker, then add 980 mL of ultrapure water at 60°C to the beaker, maintain the temperature and stir for 2 minutes.

[0010] Preferably, the yttrium oxide particles in step S2 are approximately spherical or ellipsoidal, with a particle size range of about 20-50 nm and a purity of 99.99%.

[0011] Using the above technical solution, an alkaline system is used as the micro-arc oxidation electrolyte. The electrolyte components are sodium metaaluminate (NaAlO2), sodium hexametaphosphate ((NaPO3)6), sodium silicate (Na2SiO3), potassium hydroxide (KOH), and yttrium oxide (Y2O3) nanoparticles. First, 6g of sodium metaaluminate solid powder, 4g of potassium hydroxide solid powder, 2g of sodium hexametaphosphate solid powder, 4g of sodium silicate solid powder, and 4g of yttrium oxide nanoparticles are weighed on an electronic balance and added to a beaker. The yttrium oxide particles are approximately spherical or ellipsoidal in shape, with a particle size range of approximately 20-50 nm and a purity of 99.99%. Next, add 980 mL of 60°C ultrapure water to the beaker. Maintain the temperature with a heater and stir with a stirring rod for 2 minutes to fully dissolve the various substances in the electrolyte. The concentrations of the electrolyte substances reach the following: 6 g / L sodium metaaluminate, 4 g / L potassium hydroxide, 4 g / L sodium hexametaphosphate, 4 g / L sodium silicate, and 4 g / L yttrium oxide. Then, add 500 mL of the prepared electrolyte to the electrolytic cell as the electrolyte.

[0012] Preferably, the Ti6Al4V alloy substrate sample in step S1 is prepared by the following method: processing the Ti6Al4V alloy into a rectangular sample block with a size of 10mm×10mm×3mm, and then grinding and polishing the surface of 10mm×10mm to obtain a Ti6Al4V alloy substrate sample with a surface roughness Ra<0.1μm.

[0013] Preferably, the chemical composition of the Ti6Al4V alloy is: Al 6.05wt%, V 3.95wt%, Fe 0.11wt%, C 0.014wt%, O 0.14wt%, N 0.006wt%, H 0.001wt%, and Ti 89.729 wt%.

[0014] Preferably, the Ti6Al4V alloy has a tensile strength of 860 MPa, a yield strength of 795 MPa, an elongation of 12%, an elastic modulus of 110 GPa, and a Poisson's ratio of 0.3.

[0015] Using the above technical solution, Ti6Al4V alloy was processed into a rectangular specimen with a size of 10mm×10mm×3mm using electric spark wire cutting technology. The surface of the 10mm×10mm piece was then polished on a polishing machine with 600#, 1000#, 1500#, and 2000# sandpaper for 10 minutes in sequence, and then precisely polished using W2.5 diamond grinding paste and a 3000# roughness cloth grinding disc, ultimately making the surface roughness of the Ti6Al4V alloy Ra <0.1μm.

[0016] Preferably, the electrolyte in step S3 is continuously stirred at a speed of 300 rpm and the temperature is 28-32°C.

[0017] Using the aforementioned technical solution, micro-arc oxidation coatings were produced using a WHD-30 micro-arc oxidation experimental apparatus. This apparatus primarily consists of a high-voltage power supply, an electrolytic cell, a temperature control system, a stirring and circulation system, an electrode fixture, and a parameter monitoring and operation panel. During the experiment, a Ti6Al4V substrate served as the anode, a stainless steel container served as the cathode, and the electrodes were kept 25 mm apart. The micro-arc oxidation process was conducted in constant voltage mode, with an applied voltage of 300 V, a frequency of 400 Hz, a duty cycle of 50%, and an electrolysis time of 30 minutes. During the process, the electrolyte was continuously stirred at 300 rpm by a stirrer to prevent uneven composition and temperature distribution. Simultaneously, a micro-circulation pump (flow rate approximately 1.0 L / min) continuously introduced the electrolyte into a condenser jacket for heat exchange. Constant-temperature cooling water (temperature control accuracy ±1°C) was introduced into the jacket. The electrolyte temperature was monitored in real time using an immersion digital thermometer, and the cooling water flow rate was adjusted to maintain the system temperature within the range of 28-32°C.

[0018] The second object of the present invention is to provide a micro-arc oxidation coating prepared by the above method, wherein the micro-arc oxidation coating contains yttrium oxide, and the micro-arc oxidation coating has a porosity of 2.8%, a surface roughness Ra=0.12μm, a thickness of 29μm, a microhardness of 782HV, and an elastic modulus of 89GPa.

[0019] Beneficial effects of the present invention: (1) The present invention introduces yttrium oxide nanoparticles into the electrolyte and prepares a yttrium oxide-micro-arc oxidation coating on the surface of Ti6Al4V alloy. Compared with the traditional micro-arc oxidation coating, the surface porosity of the micro-arc oxidation coating containing yttrium oxide is significantly reduced and the density is significantly improved.

[0020] (2) Compared with traditional micro-arc oxidation coatings, the micro-arc oxidation coating containing yttrium oxide proposed in the present invention has lower surface roughness and better uniformity, higher microhardness, elastic modulus, coating adhesion and other mechanical properties.

[0021] (3) The yttria-containing micro-arc oxidation coating proposed in the present invention significantly improves the fretting corrosion resistance of Ti6Al4V substrate and traditional micro-arc oxidation coating.

[0022] (4) The coating preparation process of the present invention is simple, safe, environmentally friendly and has good controllability, and can be used for actual industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the surface morphology of the micro-arc oxidation coating on the Ti6Al4V alloy surface in Comparative Example 1 (Control Group B).

[0024] Figure 2 Surface morphology of the micro-arc oxidation coating containing yttria on the surface of the Ti6Al4V alloy in Example 1 (experimental group A).

[0025] Figure 3 1 is a comparison chart of the surface porosity of the micro-arc oxidation coatings prepared in Example 1 and Comparative Example 1.

[0026] Figure 4 Surface roughness comparison of the micro-arc oxidation coatings obtained in Example 1 and Comparative Example 1.

[0027] Figure 5 This is the cross-sectional morphology of the micro-arc oxidation coating on the surface of the Ti6Al4V alloy in Comparative Example 1 (Control Group B).

[0028] Figure 6 This is the cross-sectional morphology of the micro-arc oxidation coating containing yttria on the surface of the Ti6Al4V alloy in Example 1 (experimental group A).

[0029] Figure 7 This is a comparison chart of the microhardness of the micro-arc oxidation coatings prepared by Ti6Al4V alloy, Example 1 and Comparative Example 1.

[0030] Figure 8 3 is a comparison chart of the elastic modulus of the micro-arc oxidation coatings prepared in Example 1 and Comparative Example 1.

[0031] Figure 9 This is a comparison chart of the fretting corrosion volume of the micro-arc oxidation coating prepared by Ti6Al4V alloy, Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0033] Example 1 A method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints comprises the following steps: S1: Preprocessing A hole with a diameter of 2 mm was machined in the center of the Ti6Al4V alloy substrate specimen, and the specimen was ultrasonically cleaned in anhydrous ethanol; S2: Preparation of micro-arc oxidation electrolyte The micro-arc oxidation electrolyte is an alkaline system. The components of the electrolyte are sodium metaaluminate, sodium hexametaphosphate, sodium silicate, potassium hydroxide and yttrium oxide nanoparticles. The concentrations of the substances in the electrolyte are as follows: sodium metaaluminate 6g / L, potassium hydroxide 4g / L, sodium hexametaphosphate 4g / L, sodium silicate 4g / L, yttrium oxide 4g / L; S3: Preparation of micro-arc oxidation coating The Ti6Al4V substrate was used as the anode, the stainless steel container was used as the cathode, the electrode spacing was 25 mm, the micro-arc oxidation electrolyte obtained in step S2 was used as the electrolyte, and the constant voltage mode was adopted with an applied voltage of 300 V, a frequency of 400 Hz, a duty cycle of 50%, and an electrolysis time of 30 min; S4: Cleaning and drying The coated Ti6Al4V alloy sample obtained in step S3 is placed in anhydrous ethanol for ultrasonic cleaning, and then dried and stored in a sterile drying oven.

[0034] In this embodiment, the electrolyte preparation method in step S2 is as follows: 6 g of sodium aluminate solid powder, 4 g of potassium hydroxide solid powder, 2 g of sodium hexametaphosphate solid powder, 4 g of sodium silicate solid powder, and 4 g of yttrium oxide nanoparticles are weighed in sequence and added to a beaker, and then 980 mL of ultrapure water at 60°C is added to the beaker, and the temperature is maintained while stirring for 2 minutes.

[0035] In this embodiment, the yttrium oxide particles in step S2 are approximately spherical or ellipsoidal, with a particle size range of about 20-50 nm and a purity of 99.99%.

[0036] In this embodiment, the Ti6Al4V alloy substrate sample in step S1 is prepared by the following method: the Ti6Al4V alloy is processed into a rectangular sample block with a size of 10 mm × 10 mm × 3 mm, and then the surface of the 10 mm × 10 mm is ground and polished to obtain a Ti6Al4V alloy substrate sample with a surface roughness Ra < 0.1 μm.

[0037] In this embodiment, the chemical composition of the Ti6Al4V alloy is: Al 6.05wt%, V 3.95wt%, Fe 0.11wt%, C 0.014wt%, O 0.14wt%, N 0.006wt%, H 0.001wt%, and Ti 89.729wt%.

[0038] In this embodiment, the Ti6Al4V alloy has a tensile strength of 860 MPa, a yield strength of 795 MPa, an elongation of 12%, an elastic modulus of 110 GPa, and a Poisson's ratio of 0.3.

[0039] In this embodiment, the electrolyte in step S3 is continuously stirred at a speed of 300 rpm and the temperature is 28-32°C.

[0040] Comparative Example 1 The difference from Example 1 is that yttrium oxide is not added to the electrolyte.

[0041] Test Example 1 Test groups: Example 1 (experimental group A) and comparative example 1 (control group B).

[0042] Test method: (1) SEM observation of the coating surfaces of Example 1 and Comparative Example 1; (2) Porosity: Analyze the coating porosity according to GB / T 11373-2008; (3) Surface roughness: Analyze the surface roughness of the coating using confocal 3D microscopy; (4) SEM observation of the coating cross-sections of Example 1 and Comparative Example 1; (5) Microhardness: Test the microhardness of the coating according to GB / T 4956-2017; (6) Elastic modulus: The elastic modulus of the coating is tested using the international standard ISO14577-1-2015.

[0043] Test results: (1) Figure 1 The surface morphology of a conventional micro-arc oxidation coating on a Ti6Al4V alloy (control group B) is shown. It can be seen that the micro-arc oxidation coating has large pores and uneven material distribution. Figure 2 The surface morphology of a yttria-containing micro-arc oxidation coating on a Ti6Al4V alloy is shown (experimental group A). Compared to the control group B, the surface pores of the yttria-containing micro-arc oxidation coating are much smaller, and many pores are even closed.

[0044] (2) Reference Figure 3 The surface porosity of the control group B is 9.2%, while the surface porosity of the experimental group A is only 2.8%, which is much smaller than that of the control group B. This shows that the addition of yttrium oxide can significantly reduce the surface porosity of the coating.

[0045] (3) Reference Figure 4 The surface roughness Ra of the traditional micro-arc oxidation coating (control group B) is 0.24μm, while the surface roughness Ra of the yttrium oxide-containing micro-arc oxidation coating (experimental group A) is 0.12μm, which is half that of the control group B.

[0046] (4) Reference Figure 5 and Figure 6 Compared with the traditional micro-arc oxidation coating (control group B), the micro-arc oxidation coating containing yttrium oxide (experimental group A) has smaller pores, better density, and the coating thickness is also higher than that of the control group B.

[0047] (5) Reference Figure 7Both experimental group A and control group B can effectively improve the microhardness of Ti6Al4V alloy. Among them, the micro-arc oxidation coating containing yttrium oxide (experimental group A) has higher microhardness. The microhardness of experimental group A is 2.27 times and 1.43 times that of Ti6Al4V alloy and control group B, respectively.

[0048] (6) Reference Figure 8 , the micro-arc oxidation coating containing yttrium oxide (experimental group A) has a higher elastic modulus.

[0049] Test Example 2 Test groups: Example 1 and Comparative Example 1.

[0050] Test method: (1) Preprocessing A copper wire with a length of about 10 cm was welded on the back of all Ti6Al4V alloy samples to connect the working electrode to study its electrochemical characteristics. The flat samples were encapsulated with epoxy resin, leaving only 10 mm 2 research surface.

[0051] (2) Experiment Fretting corrosion tests were conducted on a fretting corrosion testing machine (patent number CN108760618A). The counter-grinding material was zirconia-toughened alumina. Electrochemical testing was performed using a three-electrode system: a saturated Ag / AgCl reference electrode, a platinum counter electrode, and a Ti6Al4V working electrode. Fretting tests were performed in a mixture of newborn calf serum and phosphate-buffered saline (PBS) to simulate a body fluid environment. The composition and concentration of PBS were as follows: 4.05 mM / L Na2HPO4, 0.95 mM / L NaCl2PO4, and 72.5 mM / L NaCl. The initial protein concentration of the NCS solution was 80 g / L. NCS was diluted to 30 g / L using a 0.01 M PBS solution according to ISO 14242-1 and ASTM G71-81 standards.

[0052] (3) Cleaning and storage After the fretting corrosion experiment, in order to avoid the influence of residual corrosion solution and accurately evaluate the wear resistance and corrosion resistance, the test samples were cleaned in anhydrous ethanol for 2 minutes, dried and placed in a sterile drying oven.

[0053] Test results: Depend on Figure 9 It can be seen that both experimental group A and control group B can effectively reduce the fretting corrosion volume of Ti6Al4V alloy, but the yttria-containing micro-arc oxidation coating (experimental group A) has higher fretting corrosion resistance. The fretting corrosion resistance of experimental group A is 8.3 times and 4.17 times that of Ti6Al4V alloy and control group B, respectively.

[0054] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as illustrative and non-restrictive in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents of the claims are intended to be included therein.

[0055] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints, characterized in that: The steps include: S1: Preprocessing A hole with a diameter of 2 mm was machined in the center of the Ti6Al4V alloy substrate specimen, and the specimen was ultrasonically cleaned in anhydrous ethanol; S2: Preparation of micro-arc oxidation electrolyte The micro-arc oxidation electrolyte is an alkaline system. The components of the electrolyte are sodium metaaluminate, sodium hexametaphosphate, sodium silicate, potassium hydroxide and yttrium oxide nanoparticles. The concentrations of the substances in the electrolyte are as follows: sodium metaaluminate 6g / L, potassium hydroxide 4g / L, sodium hexametaphosphate 4g / L, sodium silicate 4g / L, yttrium oxide 4g / L; S3: Preparation of micro-arc oxidation coating The Ti6Al4V substrate was used as the anode, the stainless steel container was used as the cathode, the electrode spacing was 25 mm, the micro-arc oxidation electrolyte obtained in step S2 was used as the electrolyte, and the constant voltage mode was adopted with an applied voltage of 300 V, a frequency of 400 Hz, a duty cycle of 50%, and an electrolysis time of 30 min; S4: Cleaning and drying The coated Ti6Al4V alloy sample obtained in step S3 is placed in anhydrous ethanol for ultrasonic cleaning, and then dried and stored in a sterile drying oven.

2. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joint according to claim 1, characterized in that: The electrolyte preparation method in step S2 is as follows: 6 g of sodium aluminate solid powder, 4 g of potassium hydroxide solid powder, 2 g of sodium hexametaphosphate solid powder, 4 g of sodium silicate solid powder, and 4 g of yttrium oxide nanoparticles are weighed in sequence and added to a beaker, and then 980 mL of ultrapure water at 60°C is added to the beaker, and the temperature is maintained while stirring for 2 minutes.

3. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joint according to claim 1, characterized in that: The yttrium oxide particles in step S2 are approximately spherical or ellipsoidal, with a particle size range of 20-50 nm and a purity of 99.99%.

4. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joint according to claim 1, characterized in that: The Ti6Al4V alloy substrate sample in step S1 is prepared by the following method: the Ti6Al4V alloy is processed into a rectangular sample block with a size of 10 mm × 10 mm × 3 mm, and then the surface of the 10 mm × 10 mm is ground and polished to obtain a Ti6Al4V alloy substrate sample with a surface roughness Ra < 0.1 μm.

5. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints according to claim 4, characterized in that: The chemical composition of the Ti6Al4V alloy is: Al 6.05wt%, V 3.95wt%, Fe 0.11wt%, C 0.014wt%, O 0.14wt%, N 0.006wt%, H 0.001wt%, and Ti 89.729wt%.

6. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints according to claim 4, characterized in that: The Ti6Al4V alloy has a tensile strength of 860 MPa, a yield strength of 795 MPa, an elongation of 12%, an elastic modulus of 110 GPa, and a Poisson's ratio of 0.

3.

7. The method for preparing a micro-arc oxidation coating of Ti6Al4V alloy for artificial hip joints according to claim 1, characterized in that: The electrolyte in step S3 is continuously stirred at a speed of 300 rpm and the temperature is 28-32°C.

8. A micro-arc oxidation coating prepared by the method according to any one of claims 1 to 7, characterized in that: The micro-arc oxidation coating contains yttrium oxide, and has a porosity of 2.8%, a surface roughness Ra of 0.12 μm, a thickness of 29 μm, a microhardness of 782 HV, and an elastic modulus of 89 GPa.

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