Method for wear and corrosion resistance composite modification of medical magnesium alloy

Abstract

The application provides a wear-resistant and corrosion-resistant composite modification method of a magnesium alloy. The method comprises the following steps: laser texturing is performed on the surface of the magnesium alloy, and high-current pulsed ion beams are used to irradiate and strengthen the textured surface of the magnesium alloy. The textured surface of the magnesium alloy is processed and the ion beam irradiation strengthening treatment is performed on the textured surface, so that a textured modified surface with uniform composition and refined structure can be obtained.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and more particularly to a method for wear-resistant and corrosion-resistant composite modification of medical magnesium alloys. Background Technology

[0002] Compared to implantable materials such as stainless steel and titanium alloys, magnesium alloys possess properties similar to human bone in density and elastic modulus, as well as biodegradability, making them a potential candidate for novel biodegradable medical implants. On one hand, magnesium alloys can naturally degrade under physiological conditions through electro-corrosion, producing magnesium ions, an essential metallic element for the human body. This natural degradation after recovery avoids the pain associated with secondary surgery and saves on medical costs. On the other hand, the elastic modulus of magnesium alloys is closer to that of natural bone, providing support and protection to the injured area during recovery. Furthermore, in the later stages of recovery, it provides sufficient mechanical stimulation to the bone tissue at the injured site, preventing osteoporosis and other symptoms caused by the stress-shielding effect of permanent implants such as stainless steel and titanium-based alloys due to their excessively high elastic modulus. However, the high chemical reactivity and extremely low chemical potential of magnesium alloys, leading to poor corrosion resistance, and their weak surface mechanical properties resulting in poor wear resistance, limit their widespread application.

[0003] To improve the wear and corrosion resistance of magnesium alloys, many researchers have employed surface modification techniques to treat the surface of magnesium alloys, significantly enhancing their corrosion resistance. Surface alloying is an effective measure to reduce the corrosion rate of magnesium alloys in human body fluids; however, during the degradation process of magnesium alloys, alloying elements also dissolve into the body fluids, and many heavy metal elements cannot be used due to their toxicity to humans. For example, aluminum is considered a significant contributing factor to Alzheimer's disease. Surface coating technology is considered another feasible method to improve the corrosion resistance of magnesium alloys. By preparing a corrosion-resistant coating on the magnesium alloy, contact between the corrosive liquid and the magnesium alloy substrate can be prevented, thereby improving the corrosion resistance of the magnesium alloy. Among them, magnesium alloys treated with micro-arc oxidation technology can reduce the corrosion rate by about 10-40% compared with other surface treatment methods, and their lifespan in an in vitro simulated body fluid environment can reach 7 weeks. However, due to the presence of porosity on the oxide film surface, its lifespan as an implant still cannot meet the requirements of human rehabilitation.

[0004] Currently, there is no perfect process for improving the wear resistance and corrosion resistance of magnesium alloys. Summary of the Invention

[0005] In response to the aforementioned technical problems, a wear-resistant and corrosion-resistant composite modification technology for magnesium alloys is provided, which can be used for magnesium alloy surface treatment to obtain a textured modified surface with uniform composition and refined microstructure.

[0006] This invention employs a combined laser texturing and high-current pulsed ion beam irradiation technique to modify magnesium alloys for wear resistance and corrosion resistance. The technique involves laser processing to create microtextures on the surface of the magnesium alloy substrate and high-current pulsed ion beam irradiation to refine the surface composition and microstructure. The specific steps are as follows:

[0007] First, a laser is used to texture the surface of the magnesium alloy.

[0008] The first step is to determine the size and area occupancy of the micro-texture pits on the magnesium alloy surface based on the size and quantity of wear debris in the human body, and then select appropriate laser processing parameters with an energy density of 50-250 J / cm². 2 The number of pulses is 5-30.

[0009] The second step involves placing the magnesium alloy substrate at the laser focal point and pre-processing the magnesium alloy with micro-pits using different energy densities and pulse number parameters to determine the relationship between the micro-pit geometry and the laser parameters.

[0010] The third step involves fixing the prepared magnesium alloy device at the laser focal point based on the microtexture parameters selected in the first step and the relationship between the laser parameters and the micro-pit geometry in the second step. Then, appropriate laser parameters are selected to perform microtexture processing on the magnesium alloy surface.

[0011] The fourth step is to remove the magnesium alloy device, use high-grit sandpaper to remove the micro-flanges generated by laser processing on the surface of the device, clean the device with acetone solution in an ultrasonic bath, and then place it in a desiccator for drying.

[0012] Then, the textured magnesium alloy devices were subjected to ion beam irradiation modification treatment.

[0013] Fifth, based on the wear resistance and corrosion resistance requirements of magnesium alloys, select an appropriate irradiation intensity of 100-250 A / cm. 2 The number of irradiations is 2-10 times;

[0014] Step 6: Vacuum evacuation to determine the relationship between irradiation intensity and distance from the anode surface.

[0015] The Faraday cup of the irradiation intensity measuring device is placed directly opposite the anode of the ion source. The distance between the Faraday cup and the anode surface is continuously changed to obtain the corresponding relationship between the ion beam intensity and the distance to the anode surface.

[0016] Step 7: Based on the irradiation parameters selected in Step 5 and the positional relationship between the irradiation intensity and the anode surface in Step 7, the textured magnesium alloy sample is placed on the sample stage of the high-current pulsed ion beam device. The sample stage is placed in the vacuum chamber of the high-current pulsed ion beam device so that the magnesium alloy is fully exposed to the irradiation area of ​​the high-current pulsed ion beam.

[0017] The fourth step is to close the vacuum chamber and subject the textured magnesium alloy to irradiation modification treatment.

[0018] Close the vacuum chamber and use a vacuum pump to maintain the vacuum level within the chamber at 0.8-1.1 × 10⁻⁶. -2 Pa. Under room temperature vacuum conditions, the oxide film was irradiated with a high-current pulsed ion beam with a pulse width of 70 ns. The rapid remelting effect of the ion beam resulted in a more uniform surface composition and refined grains in the textured magnesium alloy.

[0019] In this invention, laser texturing and high-current pulsed ion beam technology are used to perform composite modification treatment on magnesium alloys. This process maintains the chemical composition of the magnesium alloy surface while making the surface composition more uniform and the grains finer, thereby improving the corrosion resistance of the magnesium alloy.

[0020] Laser texturing is used to create microtextures on the surface of magnesium alloys, which can collect wear debris during the wear process of magnesium alloys, transforming the wear mechanism of magnesium alloys from adhesive wear and abrasive wear to a single adhesive wear; thus improving the tribological properties of magnesium alloys.

[0021] This invention employs a combined modification treatment of laser texturing and high-current pulsed ion beam, which on the one hand changes the surface structure of magnesium alloy; on the other hand, makes the surface composition more uniform and the grains more refined; the internal stress is reduced by secondary irradiation treatment with high-current pulsed ion beam around the micro-pits.

[0022] Processing microtextures on the surface of magnesium alloys alters the wear mechanism, transforming it from abrasive wear + adhesive wear to a single adhesive wear mode.

[0023] High-current pulsed ion beam irradiation improves the mechanical properties of magnesium alloy surfaces, and in conjunction with laser texturing technology to capture wear debris, it improves the wear resistance of magnesium alloys. At the same time, ion beam irradiation homogenizes the surface composition and refines the grains of magnesium alloys, thus improving their corrosion resistance.

[0024] The present invention has the following advantages:

[0025] 1. This invention alters the wear mechanism of magnesium alloy surfaces by processing microtextures on the surface, transforming the wear mechanism from abrasive wear + adhesive wear to a single adhesive wear mode.

[0026] 2. High-current pulsed ion beam irradiation improves the mechanical properties of magnesium alloy surfaces, and in conjunction with laser texturing technology to capture wear debris, it improves the wear resistance of magnesium alloys. At the same time, ion beam irradiation homogenizes the surface composition and refines the grains of magnesium alloys, thus improving their corrosion resistance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the original magnesium alloy surface;

[0029] Figure 2 A schematic diagram of laser-textured magnesium alloy surface;

[0030] Figure 3 A schematic diagram of the surface modification of a magnesium alloy by laser texturing and ion beam irradiation;

[0031] Figure 4 This is a diagram showing the grain changes on the surface of a composite modified magnesium alloy.

[0032] Figure 5 The polarization curves of the composite modified magnesium alloy are shown.

[0033] Figure 6 The friction and wear properties of composite modified magnesium alloys. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0038] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0039] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0040] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0041] Example 1

[0042] A method for wear-resistant and corrosion-resistant composite modification of magnesium alloys includes the following steps:

[0043] 1) The requirements are a 5% increase in the surface strength of the magnesium alloy after irradiation, a wear grain size of 10 μm, and a 1-level improvement in the microcrystalline grain size grade. The study used micropits with a diameter and depth of φ50×40μm. 2 The area occupancy rate is 5%; the irradiation intensity of the high-current ion beam is 100 A / cm. 2 The number of irradiation sessions was 3.

[0044] 2) Place the magnesium alloy device at the focal point of the laser, start the laser, set the laser energy density and number of irradiations, perform laser etching on the magnesium alloy surface to process textured micropits, and measure the depth and diameter of the micropits; adjust the energy density and number of irradiations to continue etching, and repeat the measurement of the depth and diameter of the micropits to obtain the corresponding relationship between the depth and diameter of the micropits and the energy density and number of irradiations.

[0045] 3) Based on the relationship between the laser parameters and the micro-pit shape obtained in step 2), a laser energy density of 100 J / cm² is selected. 2 The irradiation was performed three times to create micro-pits on the magnesium alloy surface, and the micro-texture was prepared by evenly distributing the pits on the magnesium alloy surface with an area coverage of 5%.

[0046] 4) Use 2000# silicon carbide sandpaper to remove the micro-protrusions around the textured magnesium alloy micro-pits, then immerse the device in propanol solution for ultrasonic cleaning for 10 minutes, and blow dry for later use.

[0047] 5) Evacuate the vacuum chamber using a combination of mechanical and molecular pumps to achieve a vacuum level of 0.8-1.1 × 10⁻⁶. -2 Pa, the irradiance was measured and determined to be 100 A / cm² using a Faraday cup. 2 The position is 16cm from the anode surface;

[0048] 6) Fix the textured magnesium alloy device on the cage so that the magnesium alloy surface is 16cm away from the anode surface;

[0049] 7) Start the ion source for irradiation treatment;

[0050] 8) Repeat step 7) 3 times to end the irradiation experiment.

[0051] 9) Open the vacuum chamber, remove the composite-modified magnesium alloy device, and test the surface hardness, surface density, and surface porosity of the irradiated device. The hardness of the irradiated device increased from 560 HV of the original magnesium alloy to 720 HV, an increase of approximately 28.6%, the average grain size increased by one level, and the composition became more uniform.

[0052] 10) The electrochemical corrosion resistance of the composite modified magnesium alloy obtained in this embodiment was tested. Figure 5 The polarization curves of the original magnesium alloy and the composite-modified magnesium alloy are shown under the same test conditions. A three-electrode system was used (the low-porosity micro-arc oxidation film sample on the magnesium alloy surface was used as the research electrode, a platinum electrode as the auxiliary electrode, and a saturated calomel electrode as the reference electrode), and a 0.01 mol / L NaCl solution was used as the electrolyte. Compared with the original magnesium alloy, the corrosion potential and pitting breakdown potential of the composite-modified magnesium alloy increased from -1586 mV and -1482 mV to -1328 mV and -827 mV, respectively, significantly improving the corrosion resistance of the magnesium alloy.

[0053] 12) The wear resistance of the composite modified magnesium alloy obtained in this embodiment was tested. Figure 6 The bar chart shows the tribological properties of the original magnesium alloy and the composite-modified magnesium alloy under the same test conditions. Using a ball-and-disc tribological testing machine, under dry friction conditions of 0.1 N load, 0.1 m / s sliding speed, and 30 m sliding distance, compared to the original magnesium alloy, the coefficient of friction of the composite-modified magnesium alloy decreased from 0.38 to 0.32, and the wear amount decreased from 26 mg to 3.5 mg. The composite modification treatment significantly improved the tribological properties of the magnesium alloy.

[0054] Example 2

[0055] A method for wear-resistant and corrosion-resistant composite modification of magnesium alloys includes the following steps:

[0056] 1) The requirement is that the surface strength of the magnesium alloy will increase by 10% after irradiation, the abrasive grain size will be 15 μm, and the microcrystalline grain size grade will be improved by one level. The study uses micropit diameter and depth of... The area occupancy rate is 8%; the irradiation intensity of the high-current pulse ion beam is 150 A / cm. 2 The number of irradiation sessions was 5.

[0057] 2) Place the magnesium alloy device at the focal point of the laser, turn on the laser, set the output power and number of irradiations, and perform laser etching on the surface of the magnesium alloy to process textured micropits. Measure the depth and diameter of the micropits. Adjust the output power and number of irradiations to perform etching, and repeat the measurement of the depth and diameter of the micropits to obtain the corresponding relationship between the depth and diameter of the micropits and the output power and number of irradiations.

[0058] 3) Based on the relationship between the laser parameters and the micro-pit shape obtained in step 2), a laser energy density of 150 J / cm² is selected. 2 The irradiation was repeated 6 times to process micro-pits on the magnesium alloy surface, and the micro-texture was prepared by evenly distributing the pits on the magnesium alloy surface with an area coverage of 8%.

[0059] 4) Use 2000# silicon carbide sandpaper to remove the micro-protrusions around the textured magnesium alloy micro-pits, then immerse the device in propanol solution for ultrasonic cleaning for 10 minutes, and blow dry for later use.

[0060] 5) Evacuation was performed using a combination of mechanical and molecular pumps to achieve a vacuum level of 0.8-1.1 × 10⁻² Pa in the vacuum chamber. The irradiation intensity was measured and determined to be 150 A / cm² using a Faraday cup. 2 The position is 15.5cm from the anode surface;

[0061] 6) Fix the textured magnesium alloy device on the cage so that the magnesium alloy surface is 15.5 cm away from the anode surface;

[0062] 7) Start the ion source for irradiation treatment;

[0063] 8) Repeat step 7) 5 times to end the irradiation experiment.

[0064] 9) Open the vacuum chamber, remove the composite-modified magnesium alloy device, and test the surface hardness, surface density, and surface porosity of the irradiated device. The hardness of the irradiated device increased by 800 HV from the original magnesium alloy's 560 HV, an increase of approximately 42.8%. The average grain size improved by two levels, and the composition became more uniform.

[0065] 10) The electrochemical corrosion resistance of the composite modified magnesium alloy obtained in this embodiment was tested. A three-electrode system was used (the low-porosity micro-arc oxidation film sample on the magnesium alloy surface was used as the research electrode, a platinum electrode as the auxiliary electrode, and a saturated calomel electrode as the reference electrode), and a 0.01 mol / L NaCl solution was used as the electrolyte. Compared with the original magnesium alloy, the corrosion potential and pitting breakdown potential of the composite modified magnesium alloy increased from -1530 mV and -1280 mV to -980 mV and -650 mV, respectively, significantly improving the corrosion resistance of the magnesium alloy.

[0066] 12) The wear resistance of the composite modified magnesium alloy obtained in this embodiment was tested. Using a ball-and-disc friction and wear testing machine, under dry friction conditions of a load of 0.2 N, a sliding speed of 0.1 m / s, and a sliding distance of 30 m, compared with the original magnesium alloy, the coefficient of friction of the composite modified magnesium alloy decreased from 0.41 to 0.30, and the wear amount decreased from 32 mg to 4 mg. The composite modification treatment greatly improved the friction and wear performance of the magnesium alloy.

[0067] The above micro-pit texture processing technology is illustrated as follows: Figure 1 and Figure 2 As shown, the irradiation process using an ion source and the surface finish of the irradiated specimen are as follows: Figure 3 and Figure 4 As shown; Figure 5The polarization curves of the composite modified magnesium alloy are shown. Figure 6 This is a diagram showing the tribological properties of a composite modified magnesium alloy.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of wear and corrosion resistance composite modification of medical magnesium alloys, Characterized in that, It comprises the following steps: Step one, using laser to pre-process the micro-pit texture on the surface of magnesium alloy sample at the intersection of laser; Pre-processing parameter selection: Estimating the size and quantity of wear debris 10-100 μm in the wear process in the organism; The diameter of the textured micro-pit is 50-200 μm and the depth is 100 μm, and the area occupancy is 2%-10%; Energy density 50-250 J / cm 2 ; The irradiation times are 2-10 times; Step two, place the magnesium alloy sample at the focal point of the laser, adjust the laser energy density and irradiation times, measure the diameter and depth of the micro-pit using 3D confocal laser scanning microscope, and determine the relationship between laser energy density and irradiation times and micro-pit diameter and depth; Step three, according to the selected textured micro-pit diameter and depth in step one and the relationship between laser energy density and irradiation times and micro-pit diameter and depth in step two, place the magnesium alloy device at the focal point of the laser, and use the laser to process the micro-pit texture on the surface of the magnesium alloy under the selected area occupancy; Step four, after the micro-pit texture processing, the magnesium alloy is irradiated by the strong current pulsed ion beam at room temperature and vacuum degree of 0.8-1.1×10 -2 Under the direct irradiation mode at room temperature and under the condition of 0.8-1.1×10-4 Pa, the irradiation intensity and irradiation times are selected according to the surface hardness and grain uniformity requirements of the magnesium alloy. Step five, determine the relationship between irradiation intensity and the distance from the anode surface; place the irradiation intensity measuring device Faraday cup opposite the anode of the ion source; close the vacuum chamber and control the vacuum degree in the vacuum chamber to 0.8-1.1x10 -2 Pa by the vacuum pump; continuously change the distance between the Faraday cup and the anode surface to obtain the corresponding relationship between the ion beam intensity and the distance from the anode surface; Step six, according to the selected irradiation intensity in step four and the relationship between irradiation intensity and the position of the anode surface in step five, place the textured magnesium alloy device on the sample table of the strong current pulsed ion beam device, and place the sample table in the vacuum chamber of the strong current pulsed ion beam device to fully expose the surface of the magnesium alloy to the irradiation area of the strong current pulsed ion beam; Step seven, close the vacuum chamber, the vacuum degree in the vacuum chamber is controlled at 0.8-1.1*10 -2 Pa, irradiation modification treatment is carried out on the textured magnesium alloy surface; under the condition of room temperature, the magnesium alloy surface is refined by the rapid heating and cooling of the ion beam, and the hardness is improved.

2. The wear-resistant and corrosion-resistant composite modification method of medical magnesium alloy according to claim 1, characterized in that: In step one, the diameter and depth of the textured micro-pit are determined according to the size of the wear debris, when the wear debris is 10 μm, the diameter of the textured micro-pit is determined to be 50 μm, and when the wear debris is 100 μm, the diameter of the textured micro-pit is determined to be 200 μm; the area occupancy of the micro-texture is related to the quantity of wear debris, and the area occupancy gradually increases from 2% to 10% with the increase of the quantity of wear debris.

3. The wear-resistant and corrosion-resistant composite modification method of medical magnesium alloy according to claim 2, characterized in that: According to the surface grain refinement and chemical composition homogenization degree of the magnesium alloy, the beam current density and irradiation times of the high current pulsed ion beam in the irradiation process are determined; when the surface grain size of the magnesium alloy is required to be increased by 1 level, the lower limit value of 50 A / cm 2 is adopted for the beam current density of the high current pulsed ion beam in the irradiation process, and the lower limit value of 1 time is adopted for the irradiation times; when the surface grain size of the magnesium alloy is required to be increased by 5 levels, the upper limit value of 100 A / cm 2 is adopted for the beam current density of the high current pulsed ion beam in the irradiation process, and the upper limit value of 5 times is adopted for the irradiation times.

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