CN114606550B - Electrolyte of biomedical magnesium alloy product and surface layer preparation method - Google Patents
Electrolyte of biomedical magnesium alloy product and surface layer preparation method Download PDFInfo
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Abstract
The invention discloses an electrolyte of a biomedical magnesium alloy product and a surface layer preparation method, belongs to the technical field of alloy coating preparation, and aims to solve the problem of low surface temperature of a biomedical magnesium alloy productThe technical problem of how to reduce the corrosion rate of the magnesium alloy and improve the corrosion resistance and wear resistance of the surface layer of the magnesium alloy is that the adopted technical scheme is as follows: an electrolyte of a biomedical magnesium alloy product is composed of the following raw materials in parts by weight: na (Na) 2 SiO 3 ·9H 2 0.5 to 1.5 percent of O; na (Na) 2 B 4 O 7 ·10H 2 0.3 to 0.8 percent of O; pullulan is 0.05% -0.5%; naOH is 0.05 to 0.3 percent; the others are water. An electrolyte and a surface layer preparation method of a biomedical magnesium alloy product are disclosed, wherein the preparation method comprises the following steps: s1, pretreating a substrate sample of AZ31B magnesium alloy; s2, performing MAO treatment on a substrate sample of the AZ31B magnesium alloy by using the electrolyte of the biomedical magnesium alloy product of any one of claims 1 or 2 to obtain a micro-arc oxidation film layer sample.
Description
Technical Field
The invention relates to the technical field of alloy coating preparation, in particular to an electrolyte of a biomedical magnesium alloy product and a surface layer preparation method.
Background
The biomedical metal material is an application material which can be used for clinical medical repair and has a good supporting effect in a human body, such as stainless steel, titanium alloy, cobalt-chromium alloy and the like. However, these medical grade metallic materials also have their own disadvantages. The stainless steel applied clinically contains a large amount of nickel elements, and after the stainless steel is implanted into a human body, nickel ions are separated out due to the corrosion effect, so that serious pathological changes occur around human tissues, and the health of the human body is affected. The medical titanium and the titanium alloy are nontoxic, can be applied in a high-temperature environment or a low-temperature environment, and can generate good physical bonding and chemical bonding with human tissues, so that the medical titanium and the titanium alloy are widely applied. However, the elastic modulus of human skeleton is 20-30GPa, and the elastic modulus of titanium alloy is 50-110GPa, and the large difference between the two is easy to cause the stress shielding effect, thereby causing the phenomena of implant falling off and skeleton dysplasia. The cobalt-chromium alloy has good wear resistance and mechanical property, is suitable for being used as a long-term implant, but is expensive and has a relatively serious stress shielding effect. Compared with traditional biomedical metal materials such as stainless steel, titanium alloy and the like, the density and the elastic modulus of the magnesium alloy are closer to those of natural bones, so that the stress shielding effect at the interface of human bones and implants can be effectively reduced, and the magnesium alloy is more suitable for repairing bones and promoting the growth of bones. The magnesium alloy also has good biocompatibility. The magnesium ions generated by degradation can participate in various metabolic reactions of human bodies and are also accessory factors of various enzymes of the human bodies. Therefore, the application of magnesium alloy as biodegradable material in human skeleton and other human implant materials has been the focus of research. Magnesium is a relatively active metal with high corrosion and degradation rates in the human environment. Therefore, it is not possible to maintain the mechanical integrity of the bone before it heals. Corrosion of magnesium alloys also significantly increases the pH in the vicinity of the tissue and generates large amounts of hydrogen gas, which delays healing of the damaged tissue and even leads to tissue necrosis. These disadvantages are the most important problems limiting the application of magnesium alloys as human implant materials. Therefore, how to reduce the corrosion rate of the magnesium alloy and improve the corrosion resistance and wear resistance of the surface layer of the magnesium alloy is a technical problem to be solved urgently at present.
Disclosure of Invention
The technical task of the invention is to provide an electrolyte of a biomedical magnesium alloy product and a surface layer preparation method, so as to solve the problems of reducing the corrosion rate of magnesium alloy and improving the corrosion resistance and wear resistance of the surface layer of the magnesium alloy.
The technical task of the invention is realized in the following way, and the electrolyte of the biomedical magnesium alloy product consists of the following raw materials in parts by weight:
Na 2 SiO 3 ·9H 2 0.5 to 1.5 percent of O;
Na 2 B 4 O 7 ·10H 2 0.3 to 0.8 percent of O;
pullulan is 0.05% -0.5%;
NaOH is 0.05 to 0.3 percent;
the others are water.
Preferably, pullulan is 0.1% to 0.3%.
An electrolyte and a surface layer preparation method of a biomedical magnesium alloy product are disclosed, wherein the preparation method comprises the following steps:
s1, pretreating a substrate sample of AZ31B magnesium alloy;
s2, MAO treatment is carried out on the substrate sample of the AZ31B magnesium alloy by using the electrolyte of the biomedical magnesium alloy product to obtain a micro-arc oxidation film layer sample.
Preferably, the pretreatment of the substrate sample of the AZ31B magnesium alloy in the step S1 is specifically as follows:
s101, sequentially polishing the test piece by using 800#, 1000# and 1200# water sandpaper until the surface roughness Ra is 0.1 mu m;
s102, ultrasonically cleaning a substrate sample of the AZ31B magnesium alloy by respectively using petroleum ether, absolute ethyl alcohol and deionized water, wherein the treatment time is 30min each time;
and S103, blow-drying the surface of the substrate sample of the AZ31B magnesium alloy by using nitrogen, and immediately sealing for later use.
Preferably, the MAO treatment in step S2 is specifically as follows:
s201, using an AZ31B magnesium alloy rod as a substrate sample fixing piece of an AZ31B magnesium alloy;
s202, clamping a substrate sample of AZ31B magnesium alloy at the tail end of an AZ31B magnesium alloy rod and fixing the substrate sample at the central position of an electrolytic cell;
s203, connecting the upper end of the AZ31B magnesium alloy rod with an anode of a micro-arc oxidation power supply, and tightly winding the naked AZ31B magnesium alloy rod by the raw material tape to prevent the naked AZ31B magnesium alloy rod from reacting with the electrolyte;
s204, connecting a cathode of the micro-arc oxidation power supply by adopting a stainless steel annular tube;
s205, opening the magnetic stirrer to enable the magnetic rotor to rotate rapidly and stably;
s206, starting a circulating water cooling system to keep the working temperature of the electrolyte below 30 ℃;
s207, closing a micro-arc oxidation power supply;
s208, manually adjusting a current knob to enable the working current of the micro-arc oxidation power supply to reach a set value within 3min, and recording the working voltage in the whole operation period in detail;
s209, after finishing, manually zeroing the current, disconnecting the main power supply, and taking out a substrate sample of the AZ31B magnesium alloy;
s210, washing the surface of the substrate sample of the AZ31B magnesium alloy by using deionized water, and drying at room temperature to obtain the micro-arc oxidation film layer sample.
Preferably, the working parameters of the micro-arc oxidation power supply in step S207 are as follows:
current density 70mA/cm 2 ；
Duty cycle 25%;
the frequency is 300Hz;
the deposition time was 20min.
Preferably, the size of the substrate sample of the AZ31B magnesium alloy is 35mm multiplied by 2mm, which facilitates micro-arc oxidation treatment.
More preferably, the diameter of the AZ31B magnesium alloy rod is 3mm.
The electrolyte and the surface layer preparation method of the biomedical magnesium alloy product have the following advantages:
the pullulan is added into the electrolyte to improve the corrosion resistance and the corrosion and abrasion resistance of the MAO ceramic film layer, and meanwhile, the surface layer preparation production process has high production efficiency, low cost and simple operation;
the pullulan is used as an electrolyte additive, the influence of the concentration on the microstructure, chemical components, corrosion resistance and corrosion and abrasion resistance of the micro-arc oxidation ceramic layer is researched, and the action mechanism of the pullulan in the micro-arc oxidation process is analyzed;
and thirdly, the medical micro-arc oxidation ceramic composite coating prepared by the invention does not contain toxic substances, has excellent corrosion resistance, and has the advantages of convenience, high efficiency, environmental protection, high production efficiency and low cost.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic structural diagram of a micro-arc oxidation apparatus;
FIG. 2 is a schematic view of the micro-topography of the surface of the micro-arc oxidation film layer of the MAO-0.0 sample;
FIG. 3 is a schematic view of the micro-topography of the surface of the micro-arc oxidation film layer of the MAO-0.5 sample;
FIG. 4 is a schematic view of the micro-topography of the surface of the micro-arc oxidation film layer of the MAO-1.0 sample;
FIG. 5 is a schematic view of the micro-topography of the surface of the micro-arc oxidation film layer of the MAO-1.5 sample;
FIG. 6 is a surface Image of MAO-0.0 sample micro-arc oxidation film layer processed by Image-J software;
FIG. 7 is a surface Image of MAO-0.5 sample micro-arc oxidation film layer processed by Image-J software;
FIG. 8 is a surface Image of the MAO-1.0 sample micro-arc oxidation film layer after being processed by Image-J software;
FIG. 9 is a surface Image of the MAO-1.5 sample micro-arc oxidation film layer after being processed by Image-J software;
FIG. 10 is a schematic view showing the cross-sectional morphology of the micro-arc oxidation film of the MAO-0.0 sample;
FIG. 11 is a schematic view showing the cross-sectional morphology of the micro-arc oxidation film of the MAO-0.5 sample;
FIG. 12 is a schematic view showing the cross-sectional morphology of the micro-arc oxidation film of the MAO-1.0 sample;
FIG. 13 is a schematic view showing the cross-sectional morphology of the micro-arc oxidation film of the MAO-1.5 sample;
FIG. 14 is an XRD pattern of the micro-arc oxidation film layer;
FIG. 15 is a graph of substrate and membrane zeta potential polarization;
FIG. 16 is a schematic graph of the open circuit potential of the substrate and MAO membrane as a function of time;
FIG. 17 is a graph showing the coefficient of friction of the substrate and MAO membrane as a function of time;
FIG. 18 is a graph of the average friction coefficient and wear rate of the substrate and MAO membrane over time;
FIG. 19 is a schematic diagram of a mill mark SEM topography of a magnesium alloy substrate sample;
FIG. 20 is a schematic view of the SEM topography of the wear scar of the MAO-0.0 micro-arc oxidation film sample;
FIG. 21 is a schematic view of the SEM topography of the wear scar of the MAO-0.5 micro-arc oxidation film sample;
FIG. 22 is a schematic view of the SEM topography of the wear scar of the MAO-1.0 micro-arc oxidation film sample;
FIG. 23 is a SEM image of the wear scar of MAO-1.5 micro-arc oxidation film sample.
Detailed Description
The electrolyte and the surface layer preparation method of the biomedical magnesium alloy product of the invention are described in detail below with reference to the attached drawings and specific examples.
Example 1:
the invention provides an electrolyte of a biomedical magnesium alloy product, which is shown in the following table 1:
TABLE 1 micro-arc Oxidation electrolyte composition
Example 2:
the invention provides a surface layer preparation method of a biomedical magnesium alloy product, which comprises the following steps:
s1, pretreating a substrate sample of an AZ31B magnesium alloy;
s2, MAO treatment is carried out on the substrate sample of the AZ31B magnesium alloy by using the electrolyte of the biomedical magnesium alloy product to obtain the micro-arc oxidation film layer sample. The electrolyte formula is as follows:
in the present embodiment, the pretreatment of the substrate sample of the AZ31B magnesium alloy in step S1 is specifically as follows:
s101, sequentially polishing the test piece by using 800#, 1000# and 1200# water sandpaper until the surface roughness Ra is 0.1 mu m;
s102, ultrasonically cleaning a substrate sample of the AZ31B magnesium alloy by respectively using petroleum ether, absolute ethyl alcohol and deionized water, wherein the treatment time is 30min each time;
and S103, blow-drying the surface of the substrate sample of the AZ31B magnesium alloy by using nitrogen, and immediately sealing for later use.
The MAO treatment in step S2 in this example is specifically as follows:
s201, using an AZ31B magnesium alloy rod as a substrate sample fixing piece of an AZ31B magnesium alloy;
s202, clamping a substrate sample of AZ31B magnesium alloy at the tail end of the AZ31B magnesium alloy rod and fixing the substrate sample at the central position of an electrolytic cell;
s203, connecting the upper end of the AZ31B magnesium alloy rod with an anode of a micro-arc oxidation power supply, and tightly winding the naked AZ31B magnesium alloy rod by the raw material tape to prevent the naked AZ31B magnesium alloy rod from reacting with the electrolyte; as shown in figure 1, the micro-arc oxidation equipment consists of a micro-arc oxidation power supply 1, a numerical control operation system 2, an electrolytic tank 3, a cooling tank 4, an automatic stirrer 5 and a cooling system 6.
S204, connecting a cathode of the micro-arc oxidation power supply by adopting a stainless steel annular tube;
s205, opening the magnetic stirrer to enable the magnetic rotor to rotate rapidly and stably;
s206, starting a circulating water cooling system to keep the working temperature of the electrolyte below 30 ℃;
s207, closing a micro-arc oxidation power supply;
s208, manually adjusting a current knob to enable the working current of the micro-arc oxidation power supply to reach a set value within 3min, and recording the working voltage in the whole operation period in detail;
s209, after finishing, manually zeroing the current, disconnecting the main power supply, and taking out a substrate sample of the AZ31B magnesium alloy;
s210, washing the surface of the substrate sample of the AZ31B magnesium alloy by using deionized water, and drying at room temperature to obtain the micro-arc oxidation film layer sample.
In this embodiment, the working parameters of the micro arc oxidation power supply in step S207 are specifically as follows:
current density 70mA/cm 2 ；
Duty cycle 25%;
the frequency is 300Hz;
the deposition time was 20min.
The substrate sample of the AZ31B magnesium alloy in this example has a size of 35mm × 35mm × 2mm, which facilitates micro-arc oxidation treatment.
The diameter of the AZ31B magnesium alloy rod in this example is 3mm.
[ surface and Cross-sectional morphology of micro-arc Oxidation film ]
As shown in fig. 2-5, low-power and high-power SEM topography of ceramic membrane layers after 20min MAO treatment of substrate samples that are AZ31B magnesium alloys. From the low-power SEM image, the surfaces of the four micro-arc oxidation film layers are distributed with a plurality of micro-pores which have different sizes and are in a crater shape. In the MAO treatment process, a substrate sample of the AZ31B magnesium alloy and electrolyte undergo a complex electrochemical reaction, a large amount of oxygen and molten substances are separated out from the surface of an oxide film layer, and a pore channel is formed. From the high power SEM image, the surface was coated with micro-cracks and penetrated micro-pores.
After pullulan is added into the electrolyte, because the MAO treatment process is similar to the oxidation process without adding polysaccharide, the surface microstructures of the micro-arc oxidation film layers are very similar, and the structural difference of the surfaces of the four micro-arc oxidation film layers cannot be clearly distinguished by naked eyes. And analyzing the surface SEM Image of the micro-arc oxidation film layer by adopting Image-J Image analysis software so as to obtain surface pore information. The software processing area is 566X 391 mu m 2 And only the statistical area is larger than 10 mu m 2 The micropore information of (2). As shown in fig. 6-9, which are images of the surface after Image-J processing, the porosity information is shown in table 2:
TABLE 2 film layer surface porosity information
As can be seen from table 2, as the concentration of pullulan in the electrolyte increases, the surface porosity of the micro-arc oxidation film layer tends to decrease first and then increase. Among them, the MAO-1.5 micro-arc oxidation film sample had the highest surface porosity of 1.63%, while the MAO-1.0 micro-arc oxidation film sample had the lowest surface porosity of only 0.96%.
Table 3 EDS analysis (wt.%) of MAO membrane surface
As can be seen from Table 3, the elemental compositions and contents of the four micro-arc oxide film layers are not significantly different, and all the micro-arc oxide film layers mainly contain O, mg, si and B, which indicates that SiO in the electrolyte 3 2- And B 4 O 7 2- And also directly participate in the formation of the micro-arc oxidation film layer. After pullulan is added into the electrolyte, a small amount of C element is detected in the formed micro-arc oxidation film layer and is increased along with the increase of the concentration of the polysaccharide, which indicates that the organic polysaccharide also participates in the deposition of the micro-arc oxidation film layer. In addition, the micro-arc oxidation film layer also contains a small amount of Al and Zn elements which are all from the base sample material of the AZ31B magnesium alloy.
As shown in FIGS. 10-13, the thickness of the micro-arc oxide film layer formed in the base electrolyte was about 38 μm. Specifically, after pullulan is added into the electrolyte, the thickness of the micro-arc oxidation film layer is increased and then decreased along with the increase of the concentration of the pullulan. The thickness of the MAO-1.0 micro-arc oxide film sample was the largest and about 50 μm. When the concentration of polysaccharide was increased to 1.5g/L, the thickness of the film layer was slightly decreased, and the thickness was about 44 μm. In addition, all the micro-arc oxidation film layers are well combined with the substrate sample of the AZ31B magnesium alloy, and no discontinuous or fault area appears at the film-substrate combination position.
The roughness of the surfaces of the four micro-arc oxidation film layers is measured by using a portable roughness meter. The roughness of the base sample of the AZ31B magnesium alloy after grinding and polishing is 0.12 mu m, and the roughness of the base sample is obviously improved after MAO treatment. The roughness of the micro-arc oxidation film generated in the basic electrolyte is 1.66 mu m, and the surface roughness is obviously reduced after pullulan is added, wherein the surface roughness of a MAO-0.5 micro-arc oxidation film sample and the surface roughness of a MAO-1.0 micro-arc oxidation film sample are 1.43 mu m and 1.25 mu m respectively. When the concentration of the polysaccharide is increased to 1.5g/L, the surface roughness of the micro-arc oxidation film layer is increased again, and the value is 1.68 mu m. From this, it is known that the surface roughness of the micro-arc oxidation film layer is in positive correlation with the surface porosity of the micro-arc oxidation film layer, that is, the higher the surface porosity of the micro-arc oxidation film layer is, the greater the surface roughness is, and the pore information of the surface of the micro-arc oxidation film layer is shown in table 2.
[ chemical composition of micro-arc oxidation coating ]
As shown in the attached figure 14, the XRD patterns of all the micro-arc oxidation film layers show strong diffraction peaks of Mg, which are caused by the penetration of X-rays through the film layers. The addition of the pullulan in the electrolyte does not change the phase components of the micro-arc oxidation film layers, and the four micro-arc oxidation film layers have MgO and Al except the Mg strong diffraction peak 2 O 3 、Mg 2 SiO 4 、Mg(AlH 4 ) 2 、Mg 2 B 2 O 5 And Mg 3 (BO 3 ) 2 Six phases, which are the result of the electrochemical reaction that takes place between the base sample of AZ31B magnesium alloy and the electrolyte. In addition, the EDS analysis results show that, when pullulan is added to the electrolyte, the micro-arc oxide film layer contains a small amount of C element, but no C-related crystal phase exists in the XRD pattern, which may be because the C element-containing crystal product is too small or the C element-containing crystal product exists in the micro-arc oxide film layer in the form of an amorphous phase, and thus no C element-related diffraction peak is detected.
[ zeta potential polarization curve test ]
TABLE 4 potentiodynamic polarization curve test results
As shown in FIG. 15, the self-etching potential (E) was obtained by Tafel extrapolation corr ) Corrosion current density (I) corr ) And anode/cathode Tafel slope (. Beta.) a /β c ) The experimental data are shown in Table 4. As can be seen from Table 4, E for the four MAO samples corr Compared with untreated AZ31B magnesium alloy substrate samples, the samples are respectively moved forward by 0.18, 0.22, 0.33 and 0.27V vs. Ag/AgCl, which shows that the samples are subjected to micro-arc oxidationThe sample of (a) has a lower tendency to corrode in simulated body fluids. From the corrosion current perspective, I of four micro-arc oxidation film layers corr Compared with the substrate, the corrosion speed of the sample after micro-arc oxidation in simulated body fluid is remarkably reduced by 3-4 orders of magnitude. In particular, the MAO-1.0 sample had the highest E corr (-1.05Vvs. Ag/AgCl) and lowest I corr (1.24×10 -9 A/cm 2 ) From this, it was found that 1.0g/L is the concentration of pullulan for preparing the micro-arc oxidation film layer having the best corrosion resistance.
[ corrosive wear properties ]
Before formal loading abrasion, the samples were soaked in simulated body fluid for 10min to reach a more stable electrochemical state. As shown in FIG. 16, the relatively stable OCP values obtained after soaking untreated AZ31B magnesium alloy substrate samples, MAO-0.0 micro-arc oxidation film layer samples, MAO-0.5 micro-arc oxidation film layer samples, MAO-1.0 micro-arc oxidation film layer samples, and MAO-1.5 micro-arc oxidation film layer samples in SBF for 10min were-1.46, -1.41, -1.37, -1.30, and-1.35Vvs. Ag/AgCl, respectively. The stable OCP value can reflect the corrosion tendency of the micro-arc oxidation film layer, and the result is also quite consistent with the analysis result of the corrosion potential of the micro-arc oxidation film layer PDP.
For the substrate sample of the AZ31B magnesium alloy, once the substrate sample is loaded and slid, the OCP value is rapidly reduced to-1.75Vvs. As rubbing progresses, the OCP value fluctuates dramatically around-1.75vvs. Ag/AgCl because the wear scar region in SBF will generate new passivation film after rubbing, and the new passivation film is removed by dual ball rubbing, and this passivation-depassivation dynamic balance process results in smooth fluctuation of OCP value. After the sliding is finished, the OCP value is gradually and slowly recovered, which shows that a new passive film is continuously generated on the surface of the grinding mark.
After the loading friction, the open circuit potentials of different micro-arc oxidation film layers show different change rules. For the MAO-0.0 micro-arc oxidation film sample and the MAO-0.5 micro-arc oxidation film sample, the OCP value also sharply decreases once the sample is loaded and slides, which indicates that the surface of the micro-arc oxidation film is abraded. For the MAO-0.0 sample, the OCP initially dropped to about-1.48Vvs. Ag/AgCl and then fluctuated sharply to about-1.45Vvs. Ag/AgCl until the end of the glide. The OCP value of the MAO-0.5 micro-arc oxidation film layer sample is reduced to about-1.44Vvs. Ag/AgCl after being loaded, the OCP value is gradually restored to-1.42Vvs. Ag/AgCl at the later stage along with the friction, and then the operation is stable until the end. The OCP value of the MAO-0.5 micro-arc oxidation film sample was higher and more stable during the entire abrasion period compared to the MAO-0.0 micro-arc oxidation film sample, indicating that the film of the MAO-0.5 micro-arc oxidation film sample has more excellent abrasion resistance.
The MAO-1.0 micro-arc oxidation film samples and the MAO-1.5 micro-arc oxidation film samples showed very different abrasion behavior than the other micro-arc oxidation film samples. After loading and rubbing, the OCP values of the two micro-arc oxidation film layers are kept stable and do not have a descending trend. The OCP value of the MAO-1.0 micro-arc oxidation film layer sample is continuously stabilized at-1.30Vvs. During the entire sliding period, the OCP value of the MAO-1.5 micro-arc oxidation film sample was always fluctuated dramatically around-1.35Vvs. From the above analysis, the MAO-1.0 micro-arc oxidation film layer has the best performance of corrosion and abrasion resistance compared with the other three micro-arc oxidation film layers.
As shown in fig. 17 and 18, the friction coefficient of the base sample of AZ31B magnesium alloy was maintained at about 0.22 after the friction was applied, and the friction coefficient gradually increased to about 0.26 after sliding for 10 min. This is probably because oxidation products generated during the preliminary immersion are present in the wear scar region at the initial stage of the rubbing and can play a certain lubricating role, and as the rubbing proceeds, the oxidation products are completely pushed out of the wear scar region, thereby causing an increase in COF.
All micro-arc oxide film layers had higher COF than the substrate samples of AZ31B magnesium alloy, which was caused by their higher surface roughness. Specifically, as the rubbing proceeds, the COF of the ceramic film layer gradually increases and becomes stable. Of these, the MAO-1.5 micro-arc oxidation film samples had the most pronounced fluctuations in coefficient of friction, which resulted from the highest surface roughness and porosity of the film. As can be seen from FIG. 18, the average coefficient of friction of the ceramic membrane layer showed a tendency to decrease first and then increase as the concentration of pullulan increased, wherein the MAO-1.0 micro-arc oxidation membrane layer sample had the lowest average COF, which was 0.26. The average COF of MAO-1.5 micro-arc oxidation film samples was highest, up to 0.31.
FIG. 19 also compares the wear rates of the magnesium alloy substrate and the micro-arc oxide film layer, with the untreated AZ31B magnesium alloy substrate sample having the highest wear rate (4.9X 10) among all the test samples -4 mm 3 N -1 m -1 ). After MAO treatment, due to the high hardness characteristic of the micro-arc oxidation film layer, the micro-arc oxidation wear rate is obviously reduced, and the rule is consistent with the COF rule, namely, the micro-arc oxidation wear rate shows a trend of firstly reducing and then increasing along with the increase of the concentration of the pullulan. The MAO-1.0 micro-arc oxidation film sample had the lowest wear rate (5.03X 10) -5 mm 3 N -1 m -1 ) The wear rate of MAO-1.5 micro-arc oxidation film sample is the highest and is as high as 9.67 multiplied by 10 -5 mm 3 N -1 m -1 。
To further explore the erosion mechanism of the samples, as shown in fig. 19-23, the surface of the base sample of AZ31B magnesium alloy was scratched with a large number of scratches and furrows in the sliding direction, which is a typical abrasive wear mechanism. When the micro-arc oxidation film layer is mixed with Al 2 O 3 When the dual ball is rubbed, the film layer protrusion structure with high brittleness is easy to have brittle fracture in the rubbing process, and the generated abrasive grains and chips can be filled into micropores along with the rubbing sliding, so that a smoother grinding mark appearance is formed.
In the later 10min recovery period of the abrasion test, the grinding mark area of the substrate sample of the AZ31B magnesium alloy is passivated again to generate a new passivation film, so that a large amount of O element is detected in the grinding mark area. In the grinding mark area of the micro-arc oxidation film layer, a large amount of Si and B elements can be detected, and the fact that the micro-arc oxidation film layer does not fall off from a substrate sample of AZ31B magnesium alloy after the abrasion test is proved.
Table 5 EDS analysis (wt.%) of wear scar on the sample
From table 5 it can be seen that: in the abrasion stage, the stable OCP values of the micro-arc oxidation film layer sample are sequenced as follows: MAO-1.0 > MAO-1.5 > MAO-0.5 > MAO-0.0. In addition, wear rate detection shows that the MAO-1.0 micro-arc oxidation film layer sample has the lowest wear rate, so that the MAO-1.0 micro-arc oxidation film layer sample has the best anti-corrosion wear performance in terms of the comprehensive open circuit potential and wear rate. Although the stable OCP value of MAO-1.5 micro-arc oxidation film sample is inferior to that of MAO-1.0 micro-arc oxidation film sample, it showed the highest wear rate, which is related to its higher porosity and lower film hardness. It is known that the anti-abrasion performance of the film depends on the structure and hardness of the film. After pullulan is added into the electrolyte, the corrosion and abrasion resistance of the film layer is obviously improved, the abrasion resistance can be obtained, and the optimal polysaccharide concentration is 1.0 g/L.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. The electrolyte of the biomedical magnesium alloy product is characterized by comprising the following raw materials in parts by weight:
Na 2 SiO 3 ·9H 2 0.5 to 1.5 percent of O;
Na 2 B 4 O 7 ·10H 2 0.3 to 0.8 percent of O;
pullulan is 0.05% -0.5%;
NaOH is 0.05 to 0.3 percent;
the others are water.
2. The electrolyte for biomedical magnesium alloy products according to claim 1, wherein Pullulan is 0.1-0.3%.
3. A surface layer preparation method of a biomedical magnesium alloy product is characterized by comprising the following steps:
s1, pretreating a substrate sample of AZ31B magnesium alloy;
s2, performing MAO treatment on a substrate sample of the AZ31B magnesium alloy by using the electrolyte of the biomedical magnesium alloy product of any one of claims 1 or 2 to obtain a micro-arc oxidation film layer sample.
4. The surface layer preparation method of a biomedical magnesium alloy product according to claim 3, wherein the pretreatment of the substrate sample of the AZ31B magnesium alloy in the step S1 is as follows:
s101, sequentially using 800#, 1000# and 1200# waterproof abrasive paper to polish the test piece until the surface roughness Ra of the test piece is 0.1 mu m;
s102, ultrasonically cleaning a substrate sample of the AZ31B magnesium alloy by respectively using petroleum ether, absolute ethyl alcohol and deionized water, wherein the treatment time is 30min each time;
s103, blow-drying the surface of the substrate sample of the AZ31B magnesium alloy by nitrogen, and immediately sealing for later use.
5. The method for preparing a surface layer of a biomedical magnesium alloy product according to claim 3, wherein the MAO treatment in the step S2 is as follows:
s201, using an AZ31B magnesium alloy rod as a substrate sample fixing piece of an AZ31B magnesium alloy;
s202, clamping a substrate sample of AZ31B magnesium alloy at the tail end of the AZ31B magnesium alloy rod and fixing the substrate sample at the central position of an electrolytic cell;
s203, connecting the upper end of the AZ31B magnesium alloy rod with an anode of a micro-arc oxidation power supply, and tightly winding the naked AZ31B magnesium alloy rod by the raw material belt;
s204, connecting a cathode of the micro-arc oxidation power supply by adopting a stainless steel annular tube;
s205, opening the magnetic stirrer to enable the magnetic rotor to rotate rapidly and stably;
s206, starting a circulating water cooling system to keep the working temperature of the electrolyte below 30 ℃;
s207, closing a micro-arc oxidation power supply;
s208, manually adjusting a current knob to enable the working current of the micro-arc oxidation power supply to reach a set value within 3min, and recording the working voltage in the whole operation period in detail;
s209, after finishing, manually zeroing the current, disconnecting the main power supply, and taking out a substrate sample of the AZ31B magnesium alloy;
s210, washing the surface of the substrate sample of the AZ31B magnesium alloy by using deionized water, and drying at room temperature to obtain the micro-arc oxidation film layer sample.
6. The surface layer preparation method of the biomedical magnesium alloy product as claimed in claim 5, wherein the working parameters of the micro-arc oxidation power supply in the step S207 are as follows:
current density 70mA/cm 2 ；
Duty cycle 25%;
the frequency is 300Hz;
the deposition time was 20min.
7. The method for preparing a skin layer of a biomedical magnesium alloy product according to claim 3, wherein the size of the base sample of the AZ31B magnesium alloy is 35mm x 2mm.
8. The method for producing a skin layer of a biomedical magnesium alloy product according to claim 5, wherein the diameter of the AZ31B magnesium alloy rod is 3mm.
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| CN108950651A (en) * | 2018-07-16 | 2018-12-07 | 江苏科技大学 | A kind of preparation method of the magnesium alloy surface micro-arc electrophoresis layer of biological composite membrane containing HA |
| CN113638026A (en) * | 2021-07-30 | 2021-11-12 | 江苏科技大学 | Magnesium alloy surface MAO-LDH biological composite membrane layer and preparation method and application thereof |
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| CN108950651A (en) * | 2018-07-16 | 2018-12-07 | 江苏科技大学 | A kind of preparation method of the magnesium alloy surface micro-arc electrophoresis layer of biological composite membrane containing HA |
| CN113638026A (en) * | 2021-07-30 | 2021-11-12 | 江苏科技大学 | Magnesium alloy surface MAO-LDH biological composite membrane layer and preparation method and application thereof |
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