Preparation method of corrosion-resistant, wear-resistant and high-compatibility biomedical magnesium alloy protective coating

Abstract

The invention discloses a preparation method of a corrosion-resistant, wear-resistant and high-compatibility magnesium alloy biological protective coating, belongs to the field of biological coatings, and aims at solving the problem that an existing magnesium alloy coating material is degraded too fast. According to the preparation method, Mg-1. 5Zn-0. 5Ca alloy is selected as a matrix, firstly, a porous oxide layer is prepared on the surface of the magnesium alloy through a micro-arc oxidation process so as to improve the corrosion resistance of the coating, and then a hydroxyapatite coating is prepared on the surface of the oxide layer through a plasma spraying process so as to improve the biocompatibility and wear resistance of the coating. The prepared composite coating has good performance, the process is simple, and industrial production is easy.

Description

Technical Field

[0001] This invention belongs to the field of bio-coatings and relates to a method for preparing a corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating. Background Technology

[0002] The incidence of orthopedic diseases such as osteoporotic fractures, tumor bone resection, and artificial joint replacement is rising significantly, requiring more than 20 million bone repair materials globally each year. While traditional titanium-based or cobalt-chromium alloy implants are clinically mature, their permanent implantation characteristics fundamentally contradict the need for dynamic reconstruction of the body's own bone. There is an urgent need to develop a new generation of bone implant materials that combine biodegradability and functional biomimicry. Magnesium alloys, due to their elastic modulus similar to human bone (~30-40 GPa), controllable biodegradation rate (5-15 mmol / m² / day), and potential for promoting bone integration, have become the most promising candidate materials for biodegradable metal implants. However, current magnesium alloy systems generally suffer from excessively rapid degradation rates, leading to drastic changes in the local microenvironment: on the one hand, excessive hydrogen evolution may form gas cavities that interfere with tissue repair; on the other hand, an increase in local pH (reaching above 10) can induce an alkaline microenvironment, causing cell membrane damage and protein denaturation. Micro-arc oxidation, as a key technology for improving the corrosion resistance of magnesium alloy surfaces, provides a new strategy for solving the mechanical-biological compatibility problem of magnesium alloys in orthopedic applications, and its natural porosity facilitates osteoblast adsorption. However, the formation of micro-arc oxidation coatings somewhat restricts the biocompatibility of magnesium alloys. Therefore, to further improve its surface biocompatibility, a composite hydroxyapatite layer can effectively improve its survival in osteogenic environments. Plasma spraying, as a material surface strengthening and modification technology, has wide applications in the preparation of wear-resistant and corrosion-resistant coatings, and its industrial production is quite large-scale. Applying a hydroxyapatite layer using plasma spraying technology can effectively improve its protective performance and biocompatibility. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a method for preparing a corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating, which solves the problems of poor corrosion resistance and rapid degradation of magnesium alloys in the prior art, and improves the service life of magnesium alloys.

[0004] The technical solution of the present invention is as follows: A method for preparing a corrosion-resistant, highly compatible biomedical magnesium alloy protective coating includes the following steps: (1) Select Mg-Zn-Ca alloy as magnesium alloy substrate and perform surface treatment on magnesium alloy substrate; (2) Using the polished magnesium alloy substrate obtained in step (1) as the anode and the stainless steel plate as the cathode, the magnesium alloy substrate is subjected to micro-arc oxidation treatment in the electrolyte to obtain a magnesium alloy sample after micro-arc oxidation treatment; wherein, the composition of the electrolyte is: 10-15 g / L Na3PO4, 2-5 g / L NaOH and 10-30 ml / L ethylene glycol; the parameters of the micro-arc oxidation treatment are: frequency 400-600 kHz, duty cycle 10-30%, current density 1-3 A / dm², and treatment time 10-15 minutes; (3) Place the hydroxyapatite powder into the plasma spraying powder chamber and use a plasma spraying machine to spray the micro-arc oxidation magnesium alloy sample obtained in step (2) to obtain a magnesium alloy composite coating sample after micro-arc oxidation / plasma spraying. (4) The magnesium alloy sample obtained in step (3) is subjected to surface cleaning treatment.

[0005] Preferably, in step (1), the magnesium alloy substrate is a Mg-1.5Zn-0.5Ca alloy, specifically composed of: 1.42-1.69%Zn, 0.41-0.62%Ca, 0.003%Fe, 0.06%Si, 0.002%Ni, with Mg as the balance.

[0006] Preferably, in step (1), the specific method of surface treatment is as follows: the magnesium alloy is sanded with water sandpaper from 120 grit to 2000 grit, then cleaned with anhydrous ethanol and dried with cold air.

[0007] Preferably, in step (3), the hydroxyapatite particles are nano-sized hydroxyapatite particles with a particle size of 20-50 nm.

[0008] Preferably, in step (3), the protective gas used in the plasma spraying equipment is nitrogen, with an inlet rate of 30-50 L / min, and the combustion-supporting gas is helium, with an inlet rate of 10-20 L / min.

[0009] Preferably, in step (3), the process parameters used for plasma spraying are: power 10-30W, current 400-800A, spraying distance 40-80mm, and powder feeding rate 2-6 L / min.

[0010] The present invention also provides a biomedical magnesium alloy protective coating that is corrosion-resistant, wear-resistant, and highly compatible, prepared by the above method.

[0011] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: This invention is the first to combine micro-arc oxidation (MAO) with plasma spraying technology. The MAO layer, acting as an inner layer, enhances the corrosion resistance of magnesium alloys, while the porous nature of MAO serves as an anchor point for the hydroxyapatite layer, achieving a stable bond between the two. The plasma-sprayed hydroxyapatite layer, acting as an outer layer, both seals the micropores of the MAO layer and improves the biocompatibility of the magnesium alloy. This combination of technologies solves both the problems of poor corrosion resistance and rapid degradation in magnesium alloys, as well as the poor biocompatibility of single-coating systems. Furthermore, both MAO and plasma spraying technologies are mature and suitable for large-scale industrial production. Attached Figure Description

[0012] Figure 1 Surface and cross-sectional morphology and elemental distribution of the sample in Example 1.

[0013] Figure 2 Surface and cross-sectional morphology and elemental distribution of control group 1 sample Figure 3 Corrosion resistance test of Sample 1 and Control Group 1.

[0014] Figure 4 Abrasion resistance test of sample 1 in Example 1 and control group 1.

[0015] Figure 5 Example 1: XRD patterns after different degradation times.

[0016] Figure 6 XRD patterns of control group 1 after different degradation times. Detailed Implementation

[0017] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0018] Example 1 Step 1: Grind the magnesium alloy with water sandpaper from 120 grit to 2000 grit; clean with anhydrous ethanol and then air dry with cold air.

[0019] Step 2: Using the polished magnesium alloy substrate as the anode and the stainless steel plate as the cathode, the magnesium alloy substrate is subjected to micro-arc oxidation treatment in an electrolyte solution to obtain a magnesium alloy sample after micro-arc oxidation treatment. The electrolyte composition is: 15 g / L Na3PO4, 3 g / L NaOH, and 20 ml / L ethylene glycol. The electrical parameters used are: frequency 500 kHz, duty cycle 30%, current density 3 A / dm², and treatment time 15 minutes.

[0020] Step 3: Hydroxyapatite powder is placed in the plasma spraying powder chamber, and the micro-arc oxidation magnesium alloy sample obtained in Step 2 is sprayed using a plasma spraying machine to obtain a magnesium alloy composite coating sample after micro-arc oxidation / plasma spraying. The hydroxyapatite particle size is 20 nm. The protective gas nitrogen inlet rate of the plasma spraying equipment is 30 L / min, and the combustion gas inlet rate is 10 L / min. The process parameters used for plasma spraying are: power 30W, current 600A, spraying distance 60mm, and powder feed rate 3 L / min.

[0021] Step 4: Use a blower to remove any residual material from the surface of the composite coating sample. For example... Figure 1 The surface and cross-sectional morphology of the composite coating are shown. The pores of the micro-arc oxidation are covered and filled by the hydroxyapatite composite coating, which can effectively prevent the corrosive medium from corroding the magnesium alloy substrate, thereby improving the corrosion resistance.

[0022] Control group 1 The difference between Control Group 1 and Example 1 is that the Control Group did not undergo plasma spraying to prepare a hydroxyapatite coating. For example... Figure 2 The surface and cross-sectional morphology of a single micro-arc oxidation coating are shown. Open pores exist on the surface, reducing its corrosion resistance.

[0023] Performance testing 1. Corrosion resistance test like Figure 3 The results show the electrochemical test results for Example 1 and Control Group 1, with the test solution being a simulated body fluid. The corrosion current density in Example 1 decreased to the order of 10. -9 A / cm 2 The number of samples was approximately 4 units lower than that of the magnesium substrate and 1 order of magnitude lower than that of control group 1. Electrochemical impedance spectroscopy (EIS) tests showed that Example 1 had the largest impedance arc radius, and its corrosion resistance was significantly higher than that of control group 1 and the magnesium substrate. The composite coating effectively blocked the penetration of corrosive media and improved its corrosion resistance in simulated body fluids.

[0024] 2. Abrasion resistance test like Figure 4 The figure shows the friction coefficient curves for Example 1 and Control Group 1. The friction coefficient of Control Group 1 rises rapidly in a very short time, reaching approximately 0.25 before entering a stable upward phase, indicating significant wear degradation. After 20 minutes of wear testing, the friction coefficient almost reaches 0.5, with an average friction coefficient of approximately 0.35. In contrast, Example 1 exhibits superior frictional stability during the wear process, with its friction coefficient consistently remaining around 0.02 and showing minimal fluctuation.

[0025] 3. Surface phase analysis after different degradation times like Figure 5 and Figure 6 The X-ray diffraction (XRD) patterns of Example 1 and Control Group 1 at different times during simulated body fluid immersion are shown. A distinct Mg(OH)₂ peak was observed in Control Group 1, indicating severe corrosion. However, this characteristic peak was not found in Example 1, indicating that no corrosion occurred.

[0026] It should be understood that the application of the present invention is not limited to the above embodiments. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating, characterized in that, The method includes the following steps: (1) Select Mg-Zn-Ca alloy as magnesium alloy substrate and perform surface treatment on magnesium alloy substrate; (2) Using the polished magnesium alloy substrate obtained in step (1) as the anode and the stainless steel plate as the cathode, the magnesium alloy substrate is subjected to micro-arc oxidation treatment in the electrolyte to obtain a magnesium alloy sample after micro-arc oxidation treatment; wherein, the composition of the electrolyte is: 10-15 g / L Na3PO4, 2-5 g / L NaOH and 10-30 ml / L ethylene glycol; the parameters of the micro-arc oxidation treatment are: frequency 400-600 kHz, duty cycle 10-30%, current density 1-3 A / dm², and treatment time 10-15 minutes; (3) Place the hydroxyapatite powder into the plasma spraying powder chamber and use a plasma spraying machine to spray the micro-arc oxidation magnesium alloy sample obtained in step (2) to obtain a magnesium alloy composite coating sample after micro-arc oxidation / plasma spraying. (4) The magnesium alloy sample obtained in step (3) is subjected to surface cleaning treatment.

2. The method for preparing the corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating according to claim 1, characterized in that, In step (1), the magnesium alloy substrate is composed of Mg-1.5Zn-0.5Ca alloy, specifically: 1.42-1.69%Zn, 0.41-0.62%Ca, 0.003%Fe, 0.06%Si, 0.002%Ni, with Mg as the balance.

3. The method for preparing the corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating according to claim 1, characterized in that, In step (1), the specific method of surface treatment is as follows: the magnesium alloy is sanded with water sandpaper from 120 grit to 2000 grit, then cleaned with anhydrous ethanol and dried with cold air.

4. The method for preparing the corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating according to claim 1, characterized in that, In step (3), the hydroxyapatite particles are nano-sized hydroxyapatite particles with a particle size of 20-50 nm.

5. The method for preparing the corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating according to claim 1, characterized in that, In step (3), the protective gas used in the plasma spraying equipment is nitrogen, with an inlet rate of 30-50 L / min, and the combustion-supporting gas is helium, with an inlet rate of 10-20 L / min.

6. The method for preparing the corrosion-resistant, wear-resistant, and highly compatible biomedical magnesium alloy protective coating according to claim 1, characterized in that, In step (3), the process parameters used for plasma spraying are: power 10-30W, current 400-800A, spraying distance 40-80mm, and powder feeding rate 2-6 L / min.

7. A biomedical magnesium alloy protective coating that is corrosion-resistant, wear-resistant, and highly compatible, prepared according to any one of claims 1 to 6.

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