Corrosion-resistant high-superelasticity additive manufacturing nickel-titanium alloy and preparation method and application thereof

Abstract

The invention discloses a corrosion-resistant high-superelasticity additive manufacturing nickel-titanium alloy and a preparation method and application thereof. The preparation method comprises the three steps of additive manufacturing forming, pretreatment and surface treatment. According to the method, a nanosecond pulse laser remelting method is adopted, the surface quality of the additive manufacturing nickel-titanium alloy is optimized through parameters within a specific range, fine and uniform equiaxed grain structures are formed on a remelting layer through accurate thermophysical regulation and control of the nanosecond pulse laser remelting process, columnar grains are reserved on a base layer, and the overall hyperelastic effect is improved; and a stable passive film is formed in the corrosion process, so that the release of matrix nickel is effectively inhibited, and the corrosion resistance is improved. The preparation method disclosed by the invention has the advantages of accuracy and controllability, high processing efficiency and wide applicability, and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification, and in particular relates to a corrosion-resistant, superelastic additively manufactured nickel-titanium alloy and a preparation method and application thereof. Background Art

[0002] Nickel-titanium alloys have excellent biocompatibility, superelasticity, and shape memory effects, making them widely used in the biomedical field. At the same time, the widespread use of nickel-titanium alloys in the biomedical field places higher demands on the complexity and precision of the manufacturing process. To meet these challenges, additive manufacturing technology, with its superior free-forming capabilities and precision machining advantages, provides a new solution for the efficient production and personalized customization of nickel-titanium alloys.

[0003] However, due to the rapid melting and solidification characteristics of the additive manufacturing process, as well as the influence of powder material properties and process parameters, the prepared nickel-titanium alloy surface generally has defects, such as high surface roughness, large porosity, and unfused defects. Severe surface defects may directly lead to the dissolution and release of nickel in the human body environment. Although nickel is firmly bound in the form of intermetallic compounds, nickel release caused by corrosion is inevitable in the biological environment. Excessive nickel exposure may lead to a variety of health problems, including asthma, allergic reactions, cellular hypersensitivity, cytotoxicity, and genotoxicity. Although existing surface modification methods for additively manufactured nickel-titanium alloys improve their corrosion resistance, they do not focus on nickel release (CN118204513A). In addition, the superelastic effect is also an important performance indicator for additively manufactured nickel-titanium alloys, because it indicates the ability of nickel-titanium alloys to achieve elastic recovery within a large strain range under external force. This property is crucial for the application of biomedical devices in complex mechanical environments. According to literature research, the superelastic recovery rate of additively manufactured nickel-titanium alloy after spray surface modification is usually 38.8% to 47.7% (CN117144273A).

[0004] At present, there are no research reports on the laser remelting process to modify additively manufactured nickel-titanium alloys, nor is there a method that can simultaneously improve the corrosion resistance and superelasticity of additively manufactured nickel-titanium alloys. In addition, the existing methods to improve its corrosion resistance do not pay attention to the risk of surface nickel release. Therefore, it is necessary to propose a comprehensive performance optimization method for additively manufactured nickel-titanium alloys, which can improve the surface to inhibit nickel release while taking into account the superelasticity of the material, thereby meeting its dual needs for safety and functionality in the biomedical field. Summary of the Invention

[0005] To address the aforementioned issues, the primary objective of the present invention is to provide a method for preparing a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. This method utilizes a nanosecond pulsed laser remelting process to convert the surface metallic nickel into stable nickel oxide, effectively inhibiting the release of nickel into the human body. By improving the stability of the surface passivation film, the risk of direct contact between the substrate and the corrosive medium during corrosion is reduced, thereby enhancing corrosion resistance.

[0006] The second object of the present invention is to provide a corrosion-resistant, superelastic additively manufactured nickel-titanium alloy prepared by the above preparation method.

[0007] The third object of the present invention is to provide an application of the above-mentioned corrosion-resistant and superelastic nickel-titanium alloy in additive manufacturing.

[0008] The primary purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a corrosion-resistant, superelastic nickel-titanium alloy by additive manufacturing comprises the following steps:

[0010] Step 1: Additive Manufacturing

[0011] According to the pre-designed nickel-titanium-based shape memory alloy formula, alloy rods are produced by vacuum melting. Under a protective gas atmosphere, nickel-titanium alloy spherical powder is produced by electrode induction atomization method. The powder is then printed and formed by selective laser melting process to obtain nickel-titanium alloy parts.

[0012] Step 2: Pre-treatment

[0013] Separating the nickel-titanium alloy part from the substrate in step 1 by wire cutting, cleaning and drying the surface, and rough grinding to obtain a nickel-titanium alloy primary product;

[0014] Step 3: Surface treatment

[0015] Nanosecond pulse laser is used to perform surface remelting treatment on the primary product of nickel-titanium alloy in step 2 to obtain corrosion-resistant and highly elastic additively manufactured nickel-titanium alloy.

[0016] Preferably, the nickel-titanium alloy spherical powder in step 1 is a nickel-titanium nearly equiatomic ratio alloy or a nickel-rich alloy powder, with a composition of Ni 50+x Ti 50-x (x=0~0.8).

[0017] Preferably, the preparation parameters of the electrode induction atomization method in step 1 are as follows: the electrode induction heating temperature is 1300-1800°C, the melting power is 15-25KW, the atomization pressure is 1-4MPa, the atomization gas temperature is 20-40°C, and the protective gas is any one of nitrogen, helium, and argon.

[0018] Preferably, the selective laser melting process parameters in step 1 are as follows: laser power P = 80 ~ 200W, scanning speed V = 800 ~ 1800mm / s, powder layer thickness t = 0.02 ~ 0.04mm, scanning path is interlayer rotation 90 ° or 67 °, scanning spacing is 50 ~ 120μm.

[0019] Preferably, the surface cleaning solution in step 2 is anhydrous ethanol.

[0020] Preferably, the rough grinding step in step 2 is specifically performed by using a grinding and polishing machine in combination with sandpaper; the rotation speed of the grinding and polishing machine is 500-900 rpm, and the specification of the sandpaper is 80-180 mesh.

[0021] Preferably, the processing chamber is vacuumed before the nanosecond pulse laser remelting in step 3, and the remelting is performed when the oxygen content is 100-1000 ppm.

[0022] Preferably, the nanosecond pulse laser remelting process parameters in step three include: pulse width τ = 2 ~ 20ns, laser power P = 20 ~ 100W, laser focal length f = 165 ~ 185mm, laser scanning rate V = 1000 ~ 2000mm / s, spot diameter d = 0.05 ~ 0.25mm, laser frequency v = 250 ~ 500MHz.

[0023] Preferably, the nanosecond pulse laser remelting scanning strategy in step three adopts zigzag cross scanning, with a scanning spacing of h=20-60 μm, and a scanning angle of 90° with the selective laser melting process in step one to release the accumulated residual stress.

[0024] The second object of the present invention is achieved through the following technical solutions:

[0025] A corrosion-resistant, superelastic additively manufactured nickel-titanium alloy is prepared by the above-mentioned preparation method.

[0026] Preferably, the surface of the corrosion-resistant superelastic additively manufactured nickel-titanium alloy forms a surface fine-grained zone with a thickness of 58 to 126 μm and a grain size of 4 to 7 μm. The interior is columnar crystal with a grain size of 8 to 27 μm in width and 59 to 127 μm in length. Both the surface and the interior are austenite phase at room temperature.

[0027] Preferably, in the corrosion-resistant superelastic additively manufactured nickel-titanium alloy, the metallic nickel signal peak completely disappears in the surface XPS analysis.

[0028] The third object of the present invention is achieved through the following technical solutions:

[0029] A corrosion-resistant, superelastic additively manufactured nickel-titanium alloy has applications in medical devices and medical implants.

[0030] Specifically, the medical implants are cardiovascular stents, orthopedic implants and dental braces.

[0031] The preparation principle of the present invention is:

[0032] This invention uses a nanosecond pulsed laser remelting process to rapidly melt and solidify the surface of additively manufactured nickel-titanium alloys using a high-energy-density laser beam, significantly optimizing their microstructure and surface chemistry. Rapid cooling refines the grains, reducing defects and residual stresses while guiding the grains to grow preferentially in specific directions, enhancing superelastic properties. Furthermore, nanosecond pulsed laser remelting converts the surface metallic nickel into stable nickel oxide, improving the alloy's corrosion resistance and inhibiting nickel ion precipitation, thereby enhancing the material's long-term service stability and safety in biomedical applications.

[0033] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0034] (1) The nanosecond pulse laser remelting process used in the present invention is highly controllable. By adjusting parameters such as laser power, scanning speed, and scanning path, precise optimization of local areas can be achieved, effectively addressing the surface treatment requirements of complex geometric structures in additive manufacturing. In addition, nanosecond pulse laser remelting completes the processing in a non-contact manner, avoiding surface damage or contamination that may be introduced by traditional mechanical methods, further improving the processing quality.

[0035] (2) The nanosecond pulse laser remelting adopted by the present invention uses a high energy density laser beam to rapidly melt and solidify the material surface, refine the grain structure, optimize the microstructure, and improve the uniformity of the structure;

[0036] (3) The nanosecond pulse laser remelting process used in the present invention forms a strong temperature gradient and directional heat flow during the rapid heating and cooling process, which promotes grain refinement, enhances the superelasticity of nickel-titanium alloy, and improves the functional stability of the alloy under complex loading conditions;

[0037] (4) The present invention adopts a nanosecond pulse laser remelting process to effectively inhibit the release of nickel into the human body environment by converting the surface metallic nickel into stable nickel oxide. By improving the stability of the surface passivation film, the risk of direct contact between the substrate and the corrosive medium during the corrosion process of additively manufactured nickel-titanium alloy is reduced, thereby enhancing the corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Ni obtained in Example 1 49.3 Ti 50.7 SEM images of alloy powder;

[0039] Figure 2(a) and (b) are the columnar crystal EBSD images of the additively manufactured nickel-titanium alloy cross section before and after remelting obtained in Example 1;

[0040] Figure 3 (a) and (b) are the superelastic stress-strain curves of the additively manufactured nickel-titanium alloy obtained in Example 1 before and after remelting after 10 tensile cycles;

[0041] Figure 4 The potentiodynamic polarization curves of the additively manufactured nickel-titanium alloy in the initial state and the remelted state obtained in Example 1;

[0042] Figure 5 (a) and (b) are the XPS elemental energy spectra of the initial and remelted states of the additively manufactured nickel-titanium alloy obtained in Example 1, respectively. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0044] Example 1

[0045] Step 1: Additive Manufacturing

[0046] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.1 Ti 49.9 (at%) as the basic material, after obtaining alloy rods through vacuum melting, spherical alloy powders (such as Figure 1 ), and printed it through a selective laser melting process to obtain a nickel-titanium alloy part; the preparation parameters of the electrode induction atomization method are as follows: electrode induction heating temperature of 1500°C, melting power of 15KW, atomization pressure of 3.5MPa, atomization gas temperature of 20°C, and shielding gas of argon. The obtained powder is placed in a powder bin for additive manufacturing; the additive manufacturing (selective laser melting) process parameters are: laser power P = 140W, scanning speed V = 800mm / s, powder layer thickness t = 0.04mm, scanning path with 90° inter-layer rotation, and scanning spacing of 50μm;

[0047] Step 2: Pre-treatment

[0048] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 100-mesh sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 600 RPM to obtain a nickel-titanium alloy primary product;

[0049] Step 3: Surface treatment

[0050] The nickel-titanium alloy primary product obtained in step 2 is placed in a working chamber, evacuated to an oxygen content of 800 ppm, and the surface of the nickel-titanium alloy primary product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 3 ns, laser power P = 60 W, laser focal length f = 175 mm, laser scanning rate V = 1800 mm / s, spot diameter d = 0.10 m, laser frequency v = 250 MHz, and the nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 30 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0051] The additive manufacturing nickel-titanium alloy prepared in step 1 of this embodiment has no obvious defects on the surface, and the cross-sectional grain morphology is columnar grains (such as Figure 2 (a)), the average grain width is 12.45 μm, the average grain length is 78.36 μm, and the strain recovery rate in the 10-cycle superelastic test is 51.9% (e.g. Figure 3 (a)) Potentiodynamic polarization curve test was conducted with Hank's solution as the medium at 37°C. The corrosion current density was 3.58×10 -6 A.cm -2 (like Figure 4 After nanosecond pulse laser remelting, corrosion-resistant and highly elastic nickel-titanium alloy was obtained, and a large number of equiaxed grains appeared in the cross section of the remelted layer (such as Figure 2 (b)), the thickness of the surface fine grain zone is 69.0 μm, the average grain size is 6.12 μm, and the strain recovery rate in the 10-cycle superelastic test is 70.3% (e.g. Figure 3 (b)) At 37°C, the potentiodynamic polarization curve test was performed using Hank's solution as the medium. The corrosion current density was 2.22×10 -7 A.cm -2 (like Figure 4 ); In the surface XPS analysis, the metal Ni signal peaks 852.3eV and 869.5eV were observed in the sample before remelting (such as Figure 5 (a)), the Ni signal peak of the sample metal disappears completely after remelting (e.g. Figure 5 (b)).

[0052] Example 2

[0053] Step 1: Additive Manufacturing

[0054] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.3 Ti 49.7(at%) is used as the base material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1700°C, the melting power is 20KW, the atomization pressure is 2MPa, the atomization gas temperature is 40°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing molding, wherein the additive manufacturing (selective laser melting) process parameters are: laser power P = 160W, scanning speed V = 1500mm / s, powder layer thickness t = 0.02mm, the scanning path is 67° interlayer rotation, and the scanning spacing is 60μm;

[0055] Step 2: Pre-treatment

[0056] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 90-grit sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 500 RPM to obtain a nickel-titanium alloy primary product;

[0057] Step 3: Surface treatment

[0058] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 800 ppm. The surface of the initial nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 5 ns, laser power P = 50 W, laser focal length f = 165 mm, laser scanning rate V = 1900 mm / s, spot diameter d = 0.10 mm, laser frequency v = 350 MHz, and the nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 20 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0059] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 23.89 μm, an average grain length of 101.74 μm, a strain recovery rate of 49.7% in a superelastic test after 10 tensile cycles, and a corrosion current density of 4.38×10 -6 A.cm -2 After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross-section of the remelted layer. The thickness of the surface fine-grained zone was 64.3 μm, and the average grain size was 6.73 μm. The strain recovery rate in the superelastic test after 10 tensile cycles was 67.9%. The potentiodynamic polarization curve test using Hank's solution at 37°C showed a corrosion current density of 2.74×10-7 A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0060] Example 3

[0061] Step 1: Additive Manufacturing

[0062] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.5 Ti 49.5 (at%) is used as the basic material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1500°C, the melting power is 25KW, the atomization pressure is 4MPa, the atomization gas temperature is 35°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing molding, wherein the additive manufacturing (selective laser melting) process parameters are: laser power P = 180W, scanning speed V = 1200mm / s, powder layer thickness t = 0.03mm, the scanning path is a 90° rotation between layers, and the scanning spacing is 70μm;

[0063] Step 2: Pre-treatment

[0064] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 120-grit sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 700 RPM to obtain a nickel-titanium alloy primary product;

[0065] Step 3: Surface treatment

[0066] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 1000 ppm. The surface of the initial nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 6 ns, laser power P = 30 W, laser focal length f = 175 mm, laser scanning rate V = 2000 mm / s, spot diameter d = 0.20 mm, laser frequency v = 400 MHz. The nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 35 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0067] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 17.32 μm, an average grain length of 85.67 μm, a strain recovery rate of 51.34% in a superelastic test after 10 tensile cycles, and a potential polarization curve test using Hank's solution at 37°C, with a corrosion current density of 6.25×10 -6 A.cm -2 After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross-section of the remelted layer. The thickness of the surface fine-grained zone was 58.5 μm, and the average grain size was 5.09 μm. The strain recovery rate in the superelastic test after 10 tensile cycles was 71.23%. The potentiodynamic polarization curve test using Hank's solution at 37°C showed a corrosion current density of 1.32×10 -7 A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0068] Example 4

[0069] Step 1: Additive Manufacturing

[0070] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.4 Ti 49.6 (at%) is used as the basic material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1600°C, the melting power is 25KW, the atomization pressure is 3MPa, the atomization gas temperature is 40°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing molding, wherein the additive manufacturing (selective laser melting) process parameters are: laser power P = 180W, scanning speed V = 1800mm / s, powder layer thickness t = 0.03mm, the scanning path is an interlayer rotation of 67°, and the scanning spacing is 90μm;

[0071] Step 2: Pre-treatment

[0072] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 140-mesh sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 500 RPM to obtain a nickel-titanium alloy primary product;

[0073] Step 3: Surface treatment

[0074] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 1000 ppm. The surface of the primary nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 8 ns, laser power P = 20 W, laser focal length f = 180 mm, laser scanning rate V = 1500 mm / s, spot diameter d = 0.25 mm, laser frequency v = 350 MHz, and the nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 25 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0075] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 9.56 μm, an average grain length of 63.42 μm, a strain recovery rate of 50.32% in a superelastic test after 10 tensile cycles, and a corrosion current density of 5.38×10 -6 A.cm -2 After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross-section of the remelted layer. The thickness of the surface fine-grained zone was 55.1 μm, and the average grain size was 5.35 μm. The strain recovery rate in the superelastic test after 10 tensile cycles was 72.63%. The potentiodynamic polarization curve test using Hank's solution at 37°C showed a corrosion current density of 3.72×10 -7 A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0076] Example 5

[0077] Step 1: Additive Manufacturing

[0078] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.2 Ti 49.7(at%) is used as the base material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1600°C, the melting power is 20KW, the atomization pressure is 3.5MPa, the atomization gas temperature is 35°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing, wherein the additive manufacturing process parameters are: laser power P = 200W, scanning speed V = 1700mm / s, powder layer thickness t = 0.04mm, the scanning path is a 90° rotation between layers, and the scanning spacing is 100μm;

[0079] Step 2: Pre-treatment

[0080] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 140-mesh sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 600 RPM to obtain a nickel-titanium alloy primary product;

[0081] Step 3: Surface treatment

[0082] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 700 ppm. The surface of the initial nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 12 ns, laser power P = 80 W, laser focal length f = 170 mm, laser scanning rate V = 1400 mm / s, spot diameter d = 0.15 mm, laser frequency v = 300 MHz, and the nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 45 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0083] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 26.48 μm, an average grain length of 119.83 μm, a strain recovery rate of 49.37% in a superelastic test after 10 tensile cycles, and a corrosion current density of 4.39×10 -6 A·cm. After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross section of the remelted layer. The thickness of the surface fine-grained zone was 115.1μm, and the average grain size was 6.23μm. The strain recovery rate in the superelastic test after 10 tensile cycles was 69.25%. The potentiodynamic polarization curve test was performed at 37°C using Hank's solution as the medium, and the corrosion current density was 4.73×10 -7A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0084] Example 6

[0085] Step 1: Additive Manufacturing

[0086] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.2 Ti 49.7 (at%) is used as the base material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1750°C, the melting power is 15KW, the atomization pressure is 2MPa, the atomization gas temperature is 25°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing, wherein the additive manufacturing process parameters are: laser power P = 150W, scanning speed V = 1000mm / s, powder layer thickness t = 0.03mm, scanning path is 67° interlayer rotation, and scanning spacing is 80μm;

[0087] Step 2: Pre-treatment

[0088] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 180-grit sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 700 RPM to obtain a nickel-titanium alloy primary product;

[0089] Step 3: Surface treatment

[0090] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 600 ppm. The surface of the primary nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 15 ns, laser power P = 100 W, laser focal length f = 165 mm, laser scanning rate V = 1900 mm / s, spot diameter d = 0.20 mm, laser frequency v = 500 MHz, and the nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 45 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0091] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 14.72 μm, an average grain length of 92.15 μm, a strain recovery rate of 52.87% in a superelastic test after 10 tensile cycles, and a corrosion current density of 3.72×10 -6 A.cm -2 After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross-section of the remelted layer. The thickness of the surface fine-grained zone was 93.4 μm, and the average grain size was 5.69 μm. The strain recovery rate in the 10-cycle tensile superelastic test was 72.42%. The potentiodynamic polarization curve test was performed at 37°C using Hank's solution as the medium, and the corrosion current density was 3.84×10 -6 A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0092] Example 7

[0093] Step 1: Additive Manufacturing

[0094] In this embodiment, according to the pre-designed nickel-titanium-based shape memory alloy formula, Ni 50.7 Ti 49.3 (at%) is used as the base material, and after obtaining the alloy rod by vacuum melting, the spherical alloy powder is prepared by electrode induction atomization, and the spherical alloy powder is printed and formed by the selective laser melting process to obtain nickel-titanium alloy parts; wherein the preparation parameters of the electrode induction atomization method are as follows: the electrode induction heating temperature is 1550°C, the melting power is 20KW, the atomization pressure is 3.8MPa, the atomization gas temperature is 30°C, and the protective gas is argon. The obtained powder is placed in a powder bin for additive manufacturing, wherein the additive manufacturing process parameters are: laser power P = 120W, scanning speed V = 900mm / s, powder layer thickness t = 0.02mm, the scanning path is a 90° rotation between layers, and the scanning spacing is 100μm;

[0095] Step 2: Pre-treatment

[0096] The nickel-titanium alloy component in step 1 was separated from the substrate by wire cutting, cleaned with anhydrous ethanol and dried, and 160-grit sandpaper was fixed to a grinding and polishing machine using Velcro, and the speed was adjusted to 900 RPM to obtain a nickel-titanium alloy primary product;

[0097] Step 3: Surface treatment

[0098] The component obtained in step 2 is placed in a work chamber and evacuated to an oxygen content of 700 ppm. The surface of the initial nickel-titanium alloy product is remelted using a nanosecond pulse laser to obtain a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy. The nanosecond pulse laser remelting process parameters in this embodiment are: pulse width τ = 18 ns, laser power P = 70 W, laser focal length f = 180 mm, laser scanning rate V = 1700 mm / s, spot diameter d = 0.20 mm, laser frequency v = 450 MHz. The nanosecond pulse laser remelting scanning strategy adopts a zigzag cross scan with a scanning pitch of 35 μm. The scanning angle forms a 90° angle with the selective laser melting process in step 1.

[0099] The additively manufactured nickel-titanium alloy prepared in step 1 of this embodiment has no obvious surface defects, columnar grains in cross section, an average grain width of 20.38 μm, an average grain length of 110.29 μm, a strain recovery rate of 51.83% in a superelastic test after 10 tensile cycles, and a potential polarization curve test using Hank's solution at 37°C, with a corrosion current density of 6.38×10 -6 A.cm -2 After nanosecond pulse laser remelting, a corrosion-resistant, highly elastic additively manufactured nickel-titanium alloy was obtained. A large number of equiaxed grains appeared in the cross-section of the remelted layer. The thickness of the surface fine-grained zone was 74.5 μm, and the average grain size was 5.98 μm. The strain recovery rate in the 10-cycle superelastic test was 73.83%. The potentiodynamic polarization curve test using Hank's solution at 37°C showed a corrosion current density of 7.24×10 -7 A.cm -2 ; In the surface XPS analysis, metal Ni signal peaks of 852.3eV and 869.5eV were observed in the sample before remelting, and the metal Ni signal peaks of the sample completely disappeared after remelting.

[0100] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principles of the present invention shall be considered equivalent replacements and shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing, characterized in that: The steps include: Step 1: Additive Manufacturing According to the pre-designed nickel-titanium-based shape memory alloy formula, alloy rods are produced by vacuum melting. Under a protective gas atmosphere, nickel-titanium alloy spherical powder is produced by electrode induction atomization method. The powder is then printed and formed by selective laser melting process to obtain nickel-titanium alloy parts. Step 2: Pre-treatment Separating the nickel-titanium alloy part from the substrate in step 1 by wire cutting, cleaning and drying the surface, and coarse grinding to obtain a nickel-titanium alloy primary product; Step 3: Surface treatment Nanosecond pulse laser is used to perform surface remelting treatment on the primary product of nickel-titanium alloy in step 2 to obtain corrosion-resistant and highly elastic additively manufactured nickel-titanium alloy.

2. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: The preparation parameters of the electrode induction atomization method in step 1 are as follows: the electrode induction heating temperature is 1300-1800°C, the melting power is 15-25KW, the atomization pressure is 1-4MPa, the atomization gas temperature is 20-40°C, and the protective gas is any one of nitrogen, helium, and argon.

3. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: The process parameters of the selective laser melting in step 1 are as follows: laser power P = 80 ~ 200 W, scanning speed V = 800 ~ 1800 mm / s, powder layer thickness t = 0.02 ~ 0.04 mm, scanning path is an interlayer rotation of 90 ° or 67 °, and a scanning spacing of 50 ~ 120 μm.

4. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: The rough grinding step in step 2 is specifically performed by using a grinding and polishing machine in combination with sandpaper; the rotation speed of the grinding and polishing machine is 500-900 rpm, and the specification of the sandpaper is 80-180 mesh.

5. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: Before the nanosecond pulse laser remelting in step 3, the processing chamber is first vacuumed, and the remelting is performed when the oxygen content is 100-1000 ppm.

6. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: The nanosecond pulse laser remelting process parameters described in step three include: pulse width τ = 2 ~ 20ns, laser power P = 20 ~ 100W, laser focal length f = 165 ~ 185mm, laser scanning rate V = 1000 ~ 2000mm / s, spot diameter d = 0.05 ~ 0.25mm, laser frequency v = 250 ~ 500MHz.

7. The method for preparing corrosion-resistant superelastic nickel-titanium alloy by additive manufacturing according to claim 1, characterized in that: The nanosecond pulse laser remelting scanning strategy in step three adopts zigzag cross scanning, with a scanning spacing of h=20-60 μm, and a scanning angle of 90° with the selective laser melting process in step one.

8. A corrosion-resistant, superelastic additively manufactured nickel-titanium alloy, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.

9. The corrosion-resistant superelastic additively manufactured nickel-titanium alloy according to claim 8, characterized in that: The surface of the corrosion-resistant superelastic additively manufactured nickel-titanium alloy forms a surface fine-grained zone with a thickness of 58 to 126 μm and a grain size of 4 to 7 μm. The interior is columnar crystal with a grain size of 8 to 27 μm in width and 59 to 127 μm in length. Both the surface and the interior are in the austenite phase at room temperature.

10. Use of the corrosion-resistant, superelastic additively manufactured nickel-titanium alloy according to any one of claims 8 or 9 in medical devices and medical implants.

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