A method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy

Abstract

The present invention provides a method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy. The method uses tantalum metal powder and performs selective laser cladding on the surface of the titanium alloy under the condition of remelting. The laser power of the laser is 175-185 W, and the thickness of each layer of tantalum metal powder on the surface of the titanium alloy is 10 μm, so as to obtain a titanium alloy with a dense tantalum coating on the surface. The titanium alloy with a dense tantalum coating on the surface is subjected to surface mechanical grinding treatment with steel balls for 25-35 min to form a dense nanocrystalline tantalum coating with compressive stress on the surface of the titanium alloy. The dense nanocrystalline tantalum coating of the present invention has high bonding strength, excellent bioactivity and good mechanical properties, and can significantly improve the corrosion resistance of the titanium alloy in simulated body fluid.

Description

Technical Field

[0001] The present invention belongs to the field of biomedical materials, and particularly relates to a method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy. Technical Background

[0002] Titanium and its alloys, as traditional orthopedic implant materials, are the most widely used bio-metallic materials today. They are widely used in the biomedical field due to their light weight, low density, corrosion resistance, low temperature resistance, strong stability, and excellent material properties. However, the general low hardness and poor wear resistance of titanium alloy materials, and the easy occurrence of wear during use, to a certain extent limit their development.

[0003] Since titanium alloy is a bio-inert material, when the material is implanted into the body, it does not react or only has a weak chemical reaction with the surrounding tissues. Compared with bioactive materials, it cannot promote cell growth, etc. Therefore, there are many reports on improving the properties of magnesium alloys at present, such as alloying, increasing purity, surface modification, etc.; among them, surface modification is a method with less cost, simple and easy to implement, and can improve the comprehensive properties of titanium alloy while enhancing the bioactivity of titanium alloy. Metal tantalum has attracted much attention in the field of biomedical materials due to its unique advantages such as extremely high corrosion resistance, good biocompatibility, and high osteogenicity, especially having great development potential as a bone metal implant. Titanium alloy can meet various properties of a biomedical implant material to a certain extent. Compared with titanium alloy, the bone activity and biocompatibility of metal tantalum are higher. Therefore, preparing a tantalum coating on the surface of a titanium alloy implant can have stronger stability, and at the same time solve the problem that the low biocompatibility between the titanium alloy implant and human bone due to interosseous wear of the titanium alloy implant leads to a slow bone growth and healing rate, and can better accelerate bone bonding, promote the bone growth rate, and enhance stability.

[0004] The methods for tantalum modification on the surface of titanium alloy mainly include chemical vapor deposition, physical vapor deposition, selective laser melting, micro-arc oxidation and other processes. The bonding strength of the tantalum coating prepared by chemical vapor deposition and physical vapor deposition with the substrate is generally 40-70 MPa, and the bonding strength is not as good as that of the tantalum coating prepared by the selective laser melting process. However, due to the high melting point of tantalum in the tantalum coating prepared by the selective laser melting process, there are a large number of unmelted tantalum particles inside the coating. For high-melting-point metals, some scholars have proposed using a remelting process, but it will cause the mechanical properties of the material to decrease. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy, which has high bonding strength, excellent bioactivity and good mechanical properties, and can significantly improve the corrosion resistance of titanium alloy in simulated body fluid.

[0006] The present invention is realized through the following technical solutions:

[0007] A method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy, comprising the following steps:

[0008] S1. Using tantalum metal powder, selective laser cladding is carried out on the surface of the titanium alloy under the condition of remelting. The laser power of the laser is 175-185 W, and the thickness of each layer of tantalum metal powder on the surface of the titanium alloy is 10 μm, obtaining a titanium alloy with a dense tantalum coating on the surface;

[0009] S2. The titanium alloy with a dense tantalum coating on the surface is subjected to surface mechanical grinding treatment with steel balls for 25-35 min, and a dense nanocrystalline tantalum coating with compressive stress is formed on the surface of the titanium alloy.

[0010] Preferably, the titanium alloy described in S1 is polished smoothly first, then ultrasonically cleaned, and then selective laser cladding is carried out.

[0011] Preferably, the selective laser cladding in S1 is carried out in a laser melting rapid prototyping machine.

[0012] Preferably, the scanning rate of the laser in S1 is 700-900 mm / s, and the scanning pitch is 0.03-0.05 mm.

[0013] Preferably, the particle size of the tantalum metal powder in S1 is 10 μm.

[0014] Preferably, the total thickness of the tantalum metal powder on the surface of the titanium alloy in S1 is 150 μm.

[0015] Preferably, the surface mechanical grinding treatment in S2 is carried out in a nanocrystallization testing machine for metal materials.

[0016] Preferably, there are 50 steel balls in S2, and the diameter is 3-8 mm.

[0017] Preferably, the steel balls in S2 are GCr15 steel balls.

[0018] A dense nanocrystalline tantalum coating with compressive stress obtained by the method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy according to any one of the above, characterized in that from the substrate to the outer surface are successively a titanium alloy, a titanium-tantalum solid solution, and a dense nanocrystalline tantalum coating with compressive stress.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] A method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy. First, the selective laser melting technology is adopted, and a dense tantalum coating is prepared on the surface of the titanium alloy by means of remelting. The tantalum-titanium solid solution is adjacent to the matrix titanium alloy. Then, the surface of the titanium alloy is nanostructured by the method of SMAT. The obtained tantalum coating is nanocrystalline tantalum and has compressive stress. The tantalum-titanium solid solution and the tantalum coating are melt-bonded to the matrix, having high bonding strength, excellent bioactivity and good mechanical properties, and can significantly improve the corrosion resistance of the titanium alloy in simulated body fluid. The present invention selects metallic tantalum powder, and the raw material composition is simple. The SMAT process can improve the mechanical properties of the material to a certain extent. The selective laser melting and SMAT operations are simple, easy to control, and the process is stable. The present invention only prepares a tantalum coating on the surface of the titanium alloy, reducing the consumption of tantalum and effectively controlling the cost.

[0021] The dense nanocrystalline tantalum coating with compressive stress prepared by the present invention is melt-bonded to the matrix through the tantalum-titanium solid solution, having high bonding strength and not being prone to peeling during the process of implanting into the body. For the coating prepared by the present invention, since the matrix is a titanium alloy, it can meet various properties of a biomedical implant material to a certain extent. The surface is pure tantalum, having bioactivity, which can better accelerate bone bonding, promote the bone growth rate, and enhance the stability. Since the surface tantalum is nanocrystalline, the biological performance is further improved. Since the surface has compressive stress, the fatigue performance of the material is significantly improved, increasing the service life of the material. Description of the Drawings

[0022] Figure 1a It is a cross-sectional morphology diagram of the tantalum-titanium solid solution layer prepared by the selective laser melting process (a) in the present invention;

[0023] Figure 1b It is a cross-sectional morphology diagram of the tantalum-titanium solid solution layer prepared by the selective laser melting process (b) in the present invention;

[0024] Figure 1c It is a cross-sectional morphology diagram of the tantalum-titanium solid solution layer prepared by the selective laser melting process (c) in the present invention;

[0025] Figure 1d It is a cross-sectional morphology diagram of the tantalum-titanium solid solution layer prepared by the selective laser melting process (d) in the present invention;

[0026] Figure 2a It is a SEM diagram of the surface morphology of the tantalum coating (coating of Example 1) prepared by the selective laser melting using the present invention;

[0027] Figure 2b It is Figure 2a The enlarged view of the part within the dashed box in

[0028] Figure 2cEnergy spectrum diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention;

[0029] Figure 3a SEM cross-sectional morphology diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention;

[0030] Figure 3b For Figure 3a Enlarged view of the part within the dashed box in;

[0031] Figure 3c Cross-sectional mapping diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention;

[0032] Figure 4a Low-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-10;

[0033] Figure 4b High-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-10;

[0034] Figure 5a Low-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-20;

[0035] Figure 5b High-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-20;

[0036] Figure 6a Low-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-30;

[0037] Figure 6b High-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-30;

[0038] Figure 7a Low-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-40;

[0039] Figure 7b High-magnification surface morphology SEM diagram of the tantalum coating (Example 1 coating) prepared by selective laser melting using the present invention after being treated by the SMAT process, numbered S-3-40;

[0040] Figure 8a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered S-3-50 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0041] Figure 8b SEM micrograph of the high-magnification surface morphology of tantalum coating numbered S-3-50 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0042] Figure 9a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered M-5-10 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0043] Figure 9b SEM micrograph of the high-magnification surface morphology of tantalum coating numbered M-5-10 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0044] Figure 10a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered M-5-20 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0045] Figure 10b SEM micrograph of the high-magnification surface morphology of tantalum coating numbered M-5-20 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0046] Figure 11a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered M-5-30 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0047] Figure 11b SEM micrograph of the high-magnification surface morphology of tantalum coating numbered M-5-30 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0048] Figure 12a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered M-5-40 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0049] Figure 12b SEM micrograph of the high-magnification surface morphology of tantalum coating numbered M-5-40 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0050] Figure 13a SEM micrograph of the low-magnification surface morphology of tantalum coating numbered M-5-50 prepared by selective laser melting according to the present invention and treated by SMAT process;

[0051] Figure 13bSEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for M-5-50;

[0052] Figure 14a SEM micrograph of the low-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-10;

[0053] Figure 14b SEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-10;

[0054] Figure 15a SEM micrograph of the low-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-20;

[0055] Figure 15b SEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-20;

[0056] Figure 16a SEM micrograph of the low-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-30;

[0057] Figure 16b SEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-30;

[0058] Figure 17a SEM micrograph of the low-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-40;

[0059] Figure 17b SEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-40;

[0060] Figure 18a SEM micrograph of the low-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-50;

[0061] Figure 18b SEM micrograph of the high-magnification surface morphology of the tantalum coating prepared by selective laser melting using the present invention after being treated by the SMAT process for L-8-50;

[0062] Figure 19aThe optical micrograph of the cross-section of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT process with GCr15 steel balls of 3 mm in diameter;

[0063] Figure 19b The optical micrograph of the cross-section of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT process with GCr15 steel balls of 5 mm in diameter;

[0064] Figure 19c The optical micrograph of the cross-section of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT process with GCr15 steel balls of 8 mm in diameter;

[0065] Figure 20 The surface residual stress map of the tantalum coating prepared by selective laser melting after being treated by different SMAT processes;

[0066] Figure 21 The XRD pattern of the surface of the tantalum coating after SMAT before and after selective laser melting in Example 3 of the present invention;

[0067] Figure 22a The low-resolution bright-field image of TEM of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT;

[0068] Figure 22b The TEM diffraction ring pattern of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT;

[0069] Figure 22c The dark-field image of TEM of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT;

[0070] Figure 22d The high-resolution bright-field image of TEM of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT;

[0071] Figure 23 The high-resolution inverse Fourier transform pattern of the tantalum coating prepared by selective laser melting of the present invention after being treated by SMAT. Detailed implementation manners

[0072] The following further describes the present invention in detail with specific embodiments, which are explanations rather than limitations of the present invention.

[0073] A method for preparing a nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy according to the present invention includes the following steps:

[0074] Step 1, selective laser melting of the titanium alloy substrate;

[0075] The surface of the titanium alloy was polished smoothly with sandpaper, then ultrasonically cleaned, and then placed in a 3D printing device, the HRPM-IIB type laser melting rapid prototyping machine;

[0076] The tantalum metal powder was sieved through a 10 μm sieve and then placed in the HRPM-IIB type laser melting rapid prototyping machine; a laser was used, with the laser power of the laser being 175 - 185 W, the scanning rate being 700 - 900 mm / s, the scanning spacing being 0.03 - 0.05 mm, the powder layer thickness per layer being 10 μm, and each layer being scanned twice. That is, under the condition of remelting, a 150 μm coating was selectively laser cladded (SLC) on the surface of the titanium alloy substrate to obtain a titanium alloy with a dense tantalum coating on its surface.

[0077] Step 2, SMAT treatment of the dense tantalum coating on the titanium alloy surface;

[0078] The titanium alloy with a dense tantalum coating on its surface was placed in a surface mechanical attrition treatment (SMAT) device, the SNC-2 type metal material surface nanocrystallization testing machine, and 50 GCr15 steel balls with a diameter of 5 mm were added therein, and it was treated for 25 - 35 min, such that the surface underwent severe plastic deformation, the tantalum coating on the surface formed nanocrystals, and compressive stress was generated to obtain a nanocrystalline tantalum coating with compressive stress.

[0079] The nanocrystalline tantalum coating with compressive stress obtained by the above method has a three-layer structure from the substrate to the outer surface, namely titanium alloy, titanium-tantalum solid solution, and pure tantalum, and is in a dense form. The surface layer is a nanocrystalline tantalum coating with compressive stress, and this coating is melt-bonded to the substrate through the titanium-tantalum solid solution, having a high bonding strength.

[0080] Example 1:

[0081] The surface of the titanium alloy Ti-6Al-7Nb was polished smoothly with sandpaper, then ultrasonically cleaned, and then placed in the HRPM-IIB type laser melting rapid prototyping machine.

[0082] The tantalum coating was selectively laser cladded on the surface of Ti-6Al-7Nb using the following different processes. Since the unmelted tantalum particles exist in the titanium-tantalum solid solution layer and do not exist in the pure tantalum layer, and tantalum is expensive, the total powder layer thickness was 60 μm. The parameters used were as follows, the scanning rate was 800 mm / s, and the scanning spacing was 0.04 mm:

[0083] (a) The laser power was 180 W, the powder layer thickness per layer was 20 μm, the powder particle size was 50 μm (there were gaps between the powders, and drum powder spreading would make the spread powder not dense, and the melted thickness was 20 microns), and the number of cladding times per layer was 1 time;

[0084] (b) The laser power was 180 W, the powder layer thickness per layer was 20 μm, the powder particle size was 10 μm, and the number of cladding times per layer was 1 time;

[0085] (c) The laser power is 180 W, the powder laying thickness per layer is 10 μm, the powder particle size is 10 μm, and the number of cladding times per layer is 1 time;

[0086] (d) The laser power is 180 W, the powder laying thickness per layer is 10 μm, the powder particle size is 10 μm, and the number of cladding times per layer is 2 times.

[0087] The coating on the titanium alloy surface obtained is a titanium-tantalum solid solution layer, and the cross-sectional morphology diagrams are successively Figure 1a 、 Figure 1b 、 Figure 1c and Figure 1d , and it can be concluded that Figure 1a 、 Figure 1b 、 Figure 1c and Figure 1d all have unmolten tantalum particles in the titanium-tantalum solid solution layer, but by reducing the powder laying thickness per layer and the powder particle size, and increasing the number of cladding times per layer, (d) can greatly reduce the generation of unmolten tantalum particles. Among them, Figure 1d has the fewest and smallest unmolten tantalum particles under the corresponding process, so the (d) process is selected and its process is used for subsequent experiments.

[0088] Using the above (d) process, a tantalum coating is selectively laser cladded on the titanium alloy surface, and the total powder laying thickness is 150 μm, and a dense tantalum coating can be prepared on the titanium alloy surface.

[0089] Its surface morphology is as shown in Figure 2a and Figure 2b , and the energy spectrum diagram is as shown in Figure 2c . From Figure 2a and Figure 2b , it can be concluded that its surface morphology is similar to fish scale pattern after selective laser cladding, and the horizontal traces are the path traces of laser scanning; according to the energy spectrum display, its characteristic peaks all show tantalum, so the surface is pure tantalum. The cross-sectional morphology is as shown in Figure 3a and Figure 3b , and the mapping diagram is as shown in Figure 3c . From Figure 3a , it can be seen that there is an obvious three-layer structure of titanium alloy matrix layer - titanium-tantalum solid solution layer - pure tantalum layer, and there are only sporadic unmolten tantalum particles in the titanium-tantalum solid solution layer. It is difficult to see the unmolten tantalum particles under the low magnification of Figure 3a , and the unmolten particles can be seen only under the high magnification of Figure 3b (shown within the dotted line frame); from the Figure 3c mapping diagram, the element distribution of its three-layer structure can be clearly seen, and the thickness of the pure tantalum layer can be seen to be about 30 μm. And its bonding strength is detected to be 149 ± 0.7 MPa.

[0090] Example 2:

[0091] Selective laser melting of tantalum coating on the surface of titanium alloy was carried out by the process (d) of Example 1, with the total powder laying thickness of 150 μm.

[0092] The titanium alloy with a dense tantalum coating on the surface was placed in an SNC-2 type surface nanocrystallization testing machine for metal materials and treated by different SMAT processes. The specific process parameters are as follows:

[0093] (a) 90 GCr15 steel balls with a diameter of 3 mm were treated for 10, 20, 30, 40, and 50 minutes respectively, and numbered as S-3-10, S-3-20, S-3-30, S-3-40, and S-3-50 respectively;

[0094] (b) 50 GCr15 steel balls with a diameter of 5 mm were treated for 10, 20, 30, 40, and 50 minutes respectively, and numbered as M-5-10, M-5-20, M-5-30, M-5-40, and M-5-50 respectively;

[0095] (c) 18 GCr15 steel balls with a diameter of 8 mm were treated for 10, 20, 30, 40, and 50 minutes respectively, and numbered as L-8-10, L-8-20, L-8-30, L-8-40, and L-8-50 respectively. The surface morphologies of the treatments (a), (b), and (c) are as shown in Figure 4a 、 Figure 4b 、 Figure 5a 、 Figure 5b 、 Figure 6a 、 Figure 6b 、 Figure 7a 、 Figure 7b 、 Figure 8a 、 Figure 8b 、 Figure 9a 、 Figure 9b 、 Figure 10a 、 Figure 10a 、 Figure 11a 、 Figure 11b 、 Figure 12a 、 Figure 12b 、 Figure 13a 、 Figure 13b 、 Figure 14a 、 Figure 14b 、 Figure 15a 、 Figure 15b 、 Figure 16a 、 Figure 16b 、 Figure 17a 、 Figure 17b 、 Figure 18a and Figure 18bAs shown in the figure, it can be seen that the height of the tantalum layer on the surface under different processes has a certain degree of fluctuation. The longer the SMAT time, the greater the fluctuation. However, when the SMAT time exceeds 30 minutes, cracks will occur on the surface regardless of whether 3, 5, and 8 mm GCr15 steel balls are used at high magnification. Therefore, 30 minutes is selected as the SMAT process of the present invention.

[0096] The cross-sectional optical microscope images under different SMAT processes are as Figure 19a , Figure 19b and Figure 19c shown. It can be seen that the thicknesses of the deformed layers after SMAT treatment for 30 minutes with 3, 5, and 8 mm GCr15 steel balls can reach 669, 812, and 752 μm respectively. The thickness of the deformed layer is the largest when using 5 mm steel balls for SMAT treatment for 30 minutes.

[0097] The residual stress diagrams under different SMAT processes are as Figure 20 shown. It can be obtained that the surface of the tantalum coating without SMAT treatment is in tensile stress, and the magnitude of the tensile stress reaches 156.27 ± 45.57. While the surface of the tantalum coating after SMAT treatment is in compressive stress, and the maximum compressive stress will occur after SMAT treatment for 30 minutes with 5 mm steel balls, and the magnitude of the compressive stress is 301.32 ± 46.32. Therefore, SMAT treatment for 30 minutes with 5 mm steel balls is adopted.

[0098] Example 3:

[0099] The tantalum coating is selectively laser melted on the surface of the titanium alloy by using the process (d) of Example 1, and the total powder laying thickness is 150 μm respectively.

[0100] The titanium alloy with a total powder laying thickness of 150 μm and a dense tantalum coating on the surface is placed in an SNC-2 type metal material surface nanocrystallization testing machine, and SMAT treatment is carried out for 30 minutes by using 5 mm GCr15 steel balls.

[0101] The XRD diagrams of the surface of the tantalum coating under the two processes are as Figure 21 shown. According to the XRD characteristic peaks, the surface is all tantalum, but the peaks of tantalum become wider to a certain extent after SMAT. Combining Figure 20 , the reason is that the existence of compressive stress makes the characteristic peaks broaden.

[0102] The TEM images of the tantalum coating prepared by selective laser melting after SMAT treatment are as Figure 22a , Figure 22b , Figure 22c , Figure 22d and Figure 23 shown. Figure 22b It shows that the surface is tantalum. Figure 22a , Figure 22d andFigure 22c The grain size of tantalum can be obtained to be approximately 20 nm, Figure 23 and a large number of dislocations can be seen in the tantalum on the surface.

Claims

1. A method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy, characterized in that, It includes the following steps: S1. Using tantalum metal powder with a particle size of 10 μm, selective laser cladding is carried out on the surface of titanium alloy Ti-6Al-7Nb in a laser melting rapid prototyping machine under remelting conditions. The laser power of the laser is 175 - 185 W, the scanning speed is 700 - 900 mm / s, the scanning spacing is 0.03 - 0.05 mm, the thickness of each layer of tantalum metal powder on the surface of titanium alloy Ti-6Al-7Nb is 10 μm, the number of cladding times for each layer is 2 times, and the total thickness is 150 μm, obtaining a titanium alloy with a dense tantalum coating on the surface; S2. The titanium alloy with a dense tantalum coating on the surface is subjected to surface mechanical grinding treatment with steel balls in a metal material surface nanocrystallization testing machine for 25 - 35 min, and a dense nanocrystalline tantalum coating with compressive stress is formed on the surface of titanium alloy Ti-6Al-7Nb.

2. The method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy according to claim 1, characterized in that, The titanium alloy Ti-6Al-7Nb described in S1 is first polished smoothly, then ultrasonically cleaned, and then selective laser cladding is carried out.

3. The method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy according to claim 1, characterized in that There are 50 steel balls in S2, and the diameter is 3 - 8 mm.

4. The method for preparing a dense nanocrystalline tantalum coating with compressive stress on the surface of a titanium alloy according to claim 1, characterized in that, The steel balls in S2 are GCr15 steel balls.

5. A compressive stress-containing dense nanocrystalline tantalum coating obtained by a method for preparing a compressive stress-containing dense nanocrystalline tantalum coating on the surface of a titanium alloy according to any one of claims 1 to 4, characterized in that, From the substrate to the outer surface are titanium alloy, titanium-tantalum solid solution, and a dense nanocrystalline tantalum coating with compressive stress.

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