A method for preparing a medical Ti-Sn-Mo alloy coating on a pure titanium surface

Abstract

The application discloses a preparation method of a medical Ti-Sn-Mo alloy coating on a pure titanium surface and relates to the technical field of titanium alloy industry. The Ti-Sn-Mo alloy coating is prepared by laser cladding technology, the wear resistance of the coating is improved, material wear and host reaction are reduced, the elastic modulus of the Ti-Sn-Mo alloy coating is reduced by introducing Mo elements, the Ti-Sn-Mo alloy coating is closer to human bones, and stress shielding is reduced. Different from traditional TC4 alloy, the Ti-Sn-Mo alloy coating does not contain toxic Al and V elements, the biocompatibility is improved, better metallurgical bonding is realized by laser cladding technology, porosity and inclusions are reduced, a fine microstructure is prepared by rapid heating and cooling, the wear resistance and hardness of the coating are improved, and the problems of the prior art, such as the large difference between the elastic modulus and human bones and the toxicity of Al and V elements to cells, are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of titanium alloy industry, in particular to a preparation method of a medical Ti-Sn-Mo alloy coating on a pure titanium surface. BACKGROUND

[0002] Titanium alloy is mainly applied to the parts with relatively frequent activities or friction in the human body implant material; however, long-term friction can cause material wear, thereby causing a series of host reactions such as inflammation, allergy and even cancer; in addition, due to the large elastic modulus difference between the titanium alloy and the human body bone, the "stress shielding" phenomenon can occur, thereby causing bone degradation and loss of function; therefore, it is of great significance to find a medical titanium alloy with good mechanical properties and low elastic modulus in the medical field, and the current medical level can be improved.

[0003] For example, the patent with the publication number CN111172532A discloses a method for preparing a middle-entropy alloy coating on the surface of a pure titanium plate, which comprises workpiece pretreatment; coating pretreatment: mixing metal powders with components of Fe, Ni or Cr, Ni into a paste in an equimolar ratio, coating the surface of the pretreated workpiece, and then drying the workpiece coated with the metal powder coating; performing pulse laser surface cladding treatment on the workpiece after the coating pretreatment; and obtaining a workpiece with a surface having a FeNiTix or CrNiTix middle-entropy alloy coating, wherein x=1-2; the method for preparing a middle-entropy alloy coating on the surface of a pure titanium plate provided by the application conforms to the performance change rule of the pure titanium plate, can effectively improve the mechanical properties such as the microhardness and strength of the pure titanium plate, makes the hardening layer depth reach 400-500 mu m, and the structure is more fine and uniform, and the method is convenient to operate, simple in equipment, economical and practical, reliable in technology, high in efficiency, stable in quality, and can achieve good economic benefits.

[0004] However, the traditional titanium alloy will face some problems in long-term use, such as inflammation, allergy and even cancer caused by wear; the "stress shielding" phenomenon caused by the large difference in elastic modulus between the titanium alloy and the human body bone, thereby causing bone degradation and loss of function; the most common medical titanium alloy on the market is TC4, but its elastic modulus exceeds 100 GPa, which is much higher than that of the human body bone, and the Al and V elements in the TC4 are toxic to cells; therefore, the development of a non-toxic and low-elasticity medical titanium alloy has been a research focus. SUMMARY

[0005] In view of the defects of the prior art, the present application provides a preparation method of a pure titanium surface medical Ti-Sn-Mo alloy coating, solves the "stress shielding" phenomenon caused by the large difference between the elastic modulus and the human bone, thereby causing bone degradation and loss of function; the most common medical titanium alloy on the market is TC4, but its elastic modulus exceeds 100GPa, which is much higher than that of human bone, and the Al and V elements in it are toxic to cells.

[0006] To achieve the above object, the present application is realized by the following technical scheme:

[0007] The present application provides a preparation method of a pure titanium surface medical Ti-Sn-Mo alloy coating, which adopts laser cladding technology to clad a Ti-10Sn-xMo (x=5, 10, 15, 20, wt%) alloy coating on the surface of pure titanium, and the specific steps include:

[0008] Step 1. Material preparation, spherical Ti powder, spherical Sn powder and spherical Mo powder are mixed according to the ratio of Ti-10Sn-xMo (x=5, 10, 15, 20, wt%);

[0009] Step 2. Substrate treatment, using a medium-strength TA1 pure titanium plate as the substrate, polishing and preheating treatment are performed on the substrate;

[0010] Step 3. Laser cladding, using a laser machine with a wavelength of 1080nm for cladding, using coaxial powder feeding to control the powder flow and coating thickness in real time, and using high-purity argon as the protective gas;

[0011] Step 4. Cooling and detection, the alloy coating is placed on a heating furnace for furnace cooling to avoid the difference in cooling speed between the substrate and the coating causing the coating to crack;

[0012] Step 5. Adjust the powder ratio according to the Ti-10Sn-xMo (x=5, 10, 15, 20, wt%) ratio, and repeat steps 1-4.

[0013] The present application is further provided that in step 1, after the powder is proportionally configured, it is mixed in a vertical planetary ball mill at a speed of 200-300r / min, and the ball milling time is 2-3h to uniformly mix the powder;

[0014] The application is further provided that the cladding layer powder used in the process of cladding Ti-10Sn-xMo alloy coating on the pure titanium surface is all elemental powder, including spherical Ti powder (purity > 99.4%, powder particle size 70-120 mu m), spherical Sn powder (purity > 99.6%, powder particle size 60-90 mu m) and spherical Mo powder (99.99%, powder particle size 60-80 mu m), and the powder also contains other impurities, and it is found by EDS energy spectrum scanning that the impurities are mainly C, O and Si and the like;

[0015] The application is further provided that a 4-inch silicon carbide louver is used to polish the pure titanium surface in the polishing stage, and the excess grinding dust is wiped off with ethanol until the metal luster is shown, so as to avoid the influence of impurities on the cladding layer properties;

[0016] The application is further provided that the preheating temperature in step 2 is 400 DEG C;

[0017] The application is further provided that the laser cladding step of step 3 comprises:

[0018] Firstly, the preheated substrate is taken out from the heating furnace and placed on the workbench;

[0019] The powder is loaded into the powder feeder, and the laser power is adjusted to 2000 W and the speed is 6 mm / s;

[0020] At the beginning, the protective Ar gas is started, and then the laser is started after the powder flows out, and the laser beam makes the powder rapidly heat up to a temperature higher than the melting point on the surface of the substrate;

[0021] The molten pool is formed by melting, and the liquid pool is expanded on the surface of the material through surface tension and capillary phenomenon, and gradually solidifies to form a uniform and dense cladding layer;

[0022] During this period, goggles can be used to observe the state of the laser molten pool, and bubbles are continuously generated on the molten pool, which is the gas discharged after the powder is melted, and a good molten pool state can avoid alloy porosity;

[0023] The application is further provided that the laser cladding process is carried out at a laser power of 2000 W and a scanning speed of 6 mm / s;

[0024] The application is further provided that the laser cladding process is carried out at a laser power of 2000 W and a scanning speed of 6 mm / s;

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] The present application is prepared by laser cladding technology of Ti-Sn-Mo alloy coating, improves the wear resistance of the coating, reduces material wear and host reaction, and reduces the elastic modulus of the Ti-Sn-Mo alloy coating by introducing Mo element, so that it is more close to human bone, and reduces the stress shielding phenomenon;

[0027] The present application is different from the traditional TC4 alloy, which contains Al and V elements which are toxic to cells; the present application uses Ti-Sn-Mo alloy coating, which does not contain toxic elements, improves biocompatibility; and realizes better metallurgical bonding by laser cladding technology, reduces porosity and inclusions, and prepares fine microstructure by rapid heating and cooling, improves the wear resistance and hardness of the coating;

[0028] The present application uses pure titanium substrate with similar thermal expansion coefficient and melting point of the coating, and performs preheating treatment, reduces the risk of cracking, and has low cost;

[0029] The present application solves the "stress shielding" phenomenon caused by the large difference between the elastic modulus and human bone, thereby causing bone degradation and loss of function; the most common medical titanium alloy on the market is TC4, but its elastic modulus exceeds 100GPa, which is much higher than that of human bone, and the Al and V elements in it are toxic to cells. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The present application is a preparation method flow chart of pure titanium surface medical Ti-Sn-Mo alloy coating;

[0031] Figure 2 The present application is an X-ray diffraction (XRD) diagram of Ti-10Sn-xMo alloy coating in the preparation process of pure titanium surface medical Ti-Sn-Mo alloy coating;

[0032] Figure 3 The present application is the wear surface morphology of Ti-10Sn-xMo alloy coating in the preparation process of pure titanium surface medical Ti-Sn-Mo alloy coating;

[0033] Figure 4 The present application is the microstructure of Ti-10Sn-xMo alloy coating in the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating;

[0034] Figure 5 The present application is the influence of Mo content on the friction coefficient and hardness of Ti-10Sn-xMo alloy coating in the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating;

[0035] Figure 6Potentiodynamic polarization curve of Ti-10Sn-xMo alloy coating for the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating of the present application;

[0036] Figure 7 Change of corrosion potential of Ti-10Sn-xMo alloy coating for the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating of the present application with time;

[0037] Figure 8 Electrochemical impedance spectroscopy (EIS) of Ti-10Sn-xMo alloy coating for the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating of the present application;

[0038] Figure 9 Effect of Mo content on hardness of Ti-10Sn-xMo alloy coating for the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating of the present application;

[0039] Figure 10 Change of friction coefficient of Ti-10Sn-xMo alloy coating for the preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating of the present application with time. DETAILED DESCRIPTION

[0040] In order to make the personnel in the art better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0042] The present application will be further described in detail below in combination with the drawings:

[0043] Example 1

[0044] The application provides a preparation method of a medical Ti-Sn-Mo alloy coating on a pure titanium surface, which comprises powder mixing and alloy preparation.

[0045] The powder mixing comprises the following steps:

[0046] The powder used in the application is elemental powder, which comprises spherical Ti powder (purity > 99.4 %, powder particle size 70 μm-120 μm), spherical Sn powder (purity > 99.6 %, powder particle size 60 μm-90 μm) and spherical Mo powder (99.99 %, powder particle size 60 μm-80 μm). The powder also contains some impurities, which are mainly C, O and Si, etc. as shown in Table 1.

[0047] When the alloy is prepared by laser cladding, uneven powder mixing will result in great difference in composition of the prepared alloy at different positions. After the elemental powder is proportioned, the powder is mixed in a vertical planetary ball mill (Changsha Tianchuang XQM-44) at a rotating speed of 200 r / min for 3 h, so that the powder is uniformly mixed.

[0048] Table 1 Chemical composition of impurities in elemental powder and mixed powder (mass fraction, %)

[0049]

[0050] The laser cladding technology is gradually mature, and the cracking of the cladding layer is one of the common problems in the laser cladding process. The main factors affecting it are the thermal expansion coefficient and the bonding strength between the coating and the substrate. In order to prevent the poor bonding between the cladding layer and the substrate material and the easy cracking, the thermal expansion coefficients and melting points of the substrate and the alloy are required to be as close as possible.

[0051] In the application, the substrate material is a medium-strength TA1 pure titanium plate purchased from Dongguan Changanyulian Metal Products Company, which has a size of 100 mm x 100 mm x 8 mm. Although the strength of the pure titanium is insufficient to meet the requirements of bone implants, it is still widely used in the field of bone plates and fixing screws due to its good biocompatibility and plasticity. In addition, the melting point of the pure titanium is close to that of the titanium alloy cladding layer, which avoids the cracking problem caused by the large difference in melting point. At the same time, the price of the pure titanium is low, so it is an excellent material for laser cladding preparation of medical titanium alloy substrate. The chemical composition of the pure titanium (TA1) is shown in Table 2, which contains some impurities such as C, N and O in addition to Ti.

[0052] Table 2 Chemical composition of pure titanium (TA1) (mass fraction, %)

[0053]

[0054] The alloy preparation comprises the following steps:

[0055] The application adopts laser cladding technology to cladding Ti-10Sn-5Mo alloy coating on the surface of pure titanium; a commercial laser machine (IPGYLS-10000, IPG company, USA) with a wavelength of 1080 nm and a spot diameter of 4.0 mm is used as a laser source to perform laser cladding on a pure Ti plate; before laser cladding, a far-infrared microcrystalline electric heating plate (DB-XWJ) is used to preheat the base material; during the laser cladding experiment, a double-cylinder double-control powder feeder (PF2-2LC) is used to feed powder, and high-purity argon (Ar) gas is used as the protective gas, and the steps include:

[0056] (1) Before cladding, the base material (pure titanium) is polished, the surface of the pure titanium is polished smooth by a 4-inch silicon carbide louvre, the excess grinding dust is wiped off with ethanol, and a metallic luster is shown to avoid impurities affecting the properties of the cladding layer;

[0057] (2) After polishing, the base material is placed in a heating furnace for preheating treatment, and the preheating temperature adopted is 400 DEG C. Preheating can avoid most cracks;

[0058] (3) The cladding powder feeding mode is coaxial powder feeding, which can control the flow rate in real time and regulate the coating thickness;

[0059] (4) The laser scanning speed v is 6 mm / s, the protective gas (Ar gas) flow rate is 10 (L / min), the powder feeding rate is 1.3 (r / min), the defocusing amount is 40 mm, and the overlap rate is 50%. In the experimental stage, the laser power (1000 w, 1500 w, 2000 w, 2500 w) is changed to prepare the alloy coating, and the results show that when the power is 2000 w, the coating quality is the best and the hardness is the highest, so the laser power is selected as 2000 w and the scanning speed is 6 mm / s;

[0060] (5) First, the preheated base material is taken out of the heating furnace and placed on a flat workbench, the powder is loaded into the powder feeder, the laser power (2000 w) and speed (6 mm / s) are adjusted, the protective Ar gas is turned on at the beginning, then the laser is turned on after the powder flows out, the laser beam makes the powder rapidly heat up to a temperature higher than the melting point on the surface of the base material, and a layer of liquid pool is formed by melting and melting, the liquid pool expands on the material surface through surface tension and capillary phenomenon, and gradually solidifies to form a uniform and dense cladding layer; During this period, goggles can be used to observe the state of the laser melt pool, and bubbles are constantly coming out on it, which is the gas discharged after the powder is melted. Good melt pool state can avoid alloy porosity; finally, a 25 mm*40 mm alloy block coating is prepared;

[0061] (6) The alloy coating is placed on the heating furnace for furnace cooling to avoid the difference in cooling speed between the base material and the coating leading to cracking of the coating.

[0062] Example 2

[0063] The difference from Example 1 is that the powder mixing ratio is different, and a Ti-10Sn-10Mo alloy coating is cladded on the surface of pure titanium by laser cladding technology.

[0064] Example 3

[0065] The difference from Example 1 is that the powder mixing ratio is different, and a Ti-10Sn-15Mo alloy coating is cladded on the surface of pure titanium by laser cladding technology.

[0066] Example 4

[0067] The difference from Example 1 is that the powder mixing ratio is different, and a Ti-10Sn-20Mo alloy coating is cladded on the surface of pure titanium by laser cladding technology.

[0068] Experimental Example

[0069] The hardness and friction and wear of the prepared alloy coating are detected, and the detection parameters of the coatings of Example 1-Example 4 are divided into Experimental Group 1, Experimental Group 2, Experimental Group 3 and Experimental Group 4, and the specific detection results are shown in Table 3 and Table 4;

[0070] Table 3 Average friction coefficient of Ti-Sn-Mo ternary alloy

[0071]

[0072] Table 4 Hardness detection of Ti-Sn alloy under different process parameters

[0073]

[0074]

[0075] Combined with Table 3 and Table 4 and Figures 2-10 It can be seen that the friction coefficient of Ti-Sn-Mo alloy presents a trend of decreasing and then increasing with the increase of Mo, and the smaller the friction coefficient, the better the wear resistance of the alloy, among which the friction coefficients of Ti-10Sn-10Mo and Ti-10Sn-15Mo alloys are relatively small and have little difference, and the friction coefficients are 0.637 and 0.641 respectively, indicating that the wear resistance is good;

[0076] With the change of Mo content, the microhardness of Ti-Sn-Mo alloy presents a rule of first increasing and then decreasing; with the increase of Mo content, the hardness of the alloy gradually increases, reaches a maximum value and then gradually decreases, and when the Mo content is 10% and 15%, the hardness of Ti-Sn-Mo alloy has little difference, being 661.38HV and 660.72HV respectively. The preparation method of pure titanium surface medical Ti-Sn-Mo alloy coating by laser cladding technology improves the wear resistance, hardness and biocompatibility of the coating, and has broad application prospect.

[0077] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application, on the basis of the technical scheme, falls within the protection scope of the present application.

Claims

1. A method for preparing a medical-grade Ti-Sn-Mo alloy coating on a pure titanium surface, characterized in that, A Ti-10Sn-xMo alloy coating is deposited on the surface of pure titanium using laser cladding technology, where x represents 5, 10, 15, or 20, indicating the mass percentage of Mo. The specific steps include: Step 1. Material preparation: Mix spherical Ti powder, near-spherical Sn powder, and near-spherical Mo powder according to the ratio of Ti-10Sn-xMo, where x is 5, 10, 15, or 20. Step 2. Substrate treatment: Using TA1 pure titanium sheet as the substrate, the substrate is ground, polished and preheated. Step 3. Laser cladding: A laser with a wavelength of 1080nm is used for cladding. The powder flow rate and coating thickness are controlled in real time using a coaxial powder feeding method. High-purity argon is used as the protective gas. Step 3, the laser cladding step, includes: First, remove the preheated substrate from the heating furnace and place it on the worktable; The powder is loaded into the powder feeder, and the laser power is adjusted to 2000w and the scanning speed to 6mm / s; At the beginning, the protective Ar gas is turned on first, and then the laser is turned on after the powder flows out. The laser beam causes the powder to heat up rapidly to a temperature higher than the melting point on the substrate surface. The melting process forms a liquid pool, which expands on the material surface through surface tension and capillary action, and gradually solidifies to form a uniform and dense cladding layer. During the laser cladding process, the Ar gas flow rate was 10 L / min, the powder feeding rate was 1.3 r / min, the defocusing amount was 40 mm, and the overlap rate was 50%. Step 4. Cooling and testing: Place the alloy coating on the heating furnace and cool it with the furnace. Step 5. Adjust the powder ratio according to the Ti-10Sn-xMo ratio, where x is 5, 10, 15 or 20, and repeat the operations of steps 1-4.

2. The method for preparing a medical-grade Ti-Sn-Mo alloy coating on a pure titanium surface according to claim 1, characterized in that, In step 1, after the powder is prepared according to the ratio, it is mixed in a vertical planetary ball mill at a speed of 200-300 r / min for 2-3 hours to mix the powder evenly.

3. The method for preparing a medical-grade Ti-Sn-Mo alloy coating on a pure titanium surface according to claim 2, characterized in that, The cladding powders used in the process of cladding Ti-10Sn-xMo alloy coating on pure titanium surfaces are all elemental powders, including: spherical Ti powder with a purity greater than 99.4% and a particle size of 70μm to 120μm; near-spherical Sn powder with a purity greater than 99.6% and a particle size of 60μm to 90μm; and near-spherical molybdenum powder with a purity of 99.99% and a particle size of 60μm to 80μm.

4. The method for preparing a medical-grade Ti-Sn-Mo alloy coating on a pure titanium surface according to claim 3, characterized in that, During the grinding and polishing stage, 4-inch silicon carbide louvers are used to grind the pure titanium surface, and ethanol is used to wipe away excess abrasive particles until a metallic luster is revealed.

5. The method for preparing a medical-grade Ti-Sn-Mo alloy coating on a pure titanium surface according to claim 4, characterized in that, The preheating temperature in step 2 is 400℃.

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