A nickel-titanium composite coating and its preparation method and application

Abstract

The present invention discloses a nickel-titanium composite coating, its preparation method, and application. The preparation method comprises: pretreating a substrate; and, using ultrahigh-speed laser cladding technology, cladding a cladding material onto the surface of the substrate, followed by solution treatment, thereby obtaining the nickel-titanium composite coating. The laser power used in the ultrahigh-speed laser cladding technology is 2200 to 3800W; the cladding material comprises 60wt% nickel and 40wt% titanium. The present invention utilizes ultrahigh-speed laser cladding technology and solution treatment to produce a pore-free and crack-free nickel-titanium composite coating. It also facilitates the formation of a titanium oxide structure on the surface of the nickel-titanium composite coating, significantly improving the coating's corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the field of surface protection and relates to a nickel-titanium composite coating and a preparation method and application thereof, and in particular to a nickel-titanium composite coating prepared based on ultra-high-speed laser cladding in-situ synthesis and solution treatment. Background Art

[0002] The unique characteristics of the marine environment mean that engineering structural materials that have performed well in conventional environments will be subjected to greater challenges in terms of corrosion resistance and mechanical properties in marine environments. Failures have been common in past marine exposure tests. Equipment maintenance costs in marine environments are quite high. Therefore, developing a coating to improve the corrosion resistance of the substrate of marine engineering equipment is of great significance to the long-term operational stability, safety and reliability of marine engineering facilities. Nickel-based alloys offer superior plasticity, toughness, oxidation resistance, and corrosion resistance to iron-based alloys and are widely used in marine engineering equipment. However, due to the high price, poor machinability, and mechanical properties of NiTi alloys, they are not suitable for machining large structures, which greatly limits their application in the fields of machinery and engineering materials. The poor machinability of NiTi alloys currently stems from their high work hardening capacity and high sensitivity to temperature and phase transformations. During machining, defects such as cracks, chip layers, surface spalling, feed marks, microchip debris, and slip zones can be observed on the surface of NiTi alloys. Therefore, providing a new processing method for NiTi alloys is an urgent problem to be solved. Summary of the Invention

[0003] The main purpose of the present invention is to provide a nickel-titanium composite coating and its preparation method and application, so as to overcome the shortcomings of the prior art.

[0004] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0005] An embodiment of the present invention provides a method for preparing a nickel-titanium composite coating, which comprises:

[0006] Pre-treating the substrate;

[0007] and, using ultra-high-speed laser cladding technology to clad the cladding material on the surface of the obtained substrate, followed by solution treatment, thereby obtaining a nickel-titanium composite coating;

[0008] The laser power used in the ultra-high-speed laser cladding technology is 2200-3800W; the cladding material includes: 60wt% nickel and 40wt% titanium.

[0009] An embodiment of the present invention further provides a nickel-titanium composite coating prepared by the aforementioned preparation method, wherein the nickel-titanium composite coating comprises a NiTi solid solution and a TiO2 oxide film formed on the surface of the NiTi solid solution.

[0010] The embodiment of the present invention also provides the application of the aforementioned nickel-titanium composite coating in the corrosion resistance of key components of marine engineering equipment.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The present invention is obtained through reasonable component design, which reduces production costs and significantly improves the hardness and corrosion resistance of the substrate surface. This experiment adopts a coaxial powder feeding laser cladding process. By utilizing ultra-high-speed laser cladding process technology, it can achieve good metallurgical bonding between the cladding layer and the substrate, and the coating has good density;

[0013] (2) This application adopts a laser cladding and solution treatment scheme. Based on the characteristics of laser cladding in a high-temperature oxidizing environment, which is conducive to the formation of a continuous, dense and stable oxide film on the surface of titanium alloy, the nickel-titanium alloy is prepared by in-situ synthesis through ultra-high-speed laser cladding technology. The TiO2 oxide film formed on the surface can make the cladding layer exhibit excellent corrosion resistance and high hardness. After solution treatment, the passive film on the coating surface further grows, and the corrosion resistance of the coating is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 is a cross-sectional SEM image of a coating prepared by laser cladding in Example 2 of the present invention;

[0016] Figure 2 is a cross-sectional EDS image of a coating prepared by laser cladding in Example 2 of the present invention;

[0017] Figure 3 is an XPS graph of the coating prepared by laser cladding treatment in Example 2 of the present invention;

[0018] Figure 4 is a potentiodynamic polarization diagram of a coating obtained by laser cladding in Example 2 of the present invention;

[0019] Figure 5 is a cross-sectional SEM image of a coating prepared by laser cladding and solution treatment in Example 2 of the present invention;

[0020] Figure 6 is a cross-sectional EDS image of a coating prepared by laser cladding and solution treatment in Example 2 of the present invention;

[0021] Figure 7 3 is the Nyquist diagram of the coating prepared by laser cladding and solution treatment in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The technical solution of the present invention will be clearly and completely described below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making any creative effort shall fall within the scope of protection of the present invention.

[0023] Specifically, as one aspect of the technical solution of the present invention, a method for preparing a nickel-titanium composite coating includes:

[0024] Pre-treating the substrate;

[0025] and, using ultra-high-speed laser cladding technology to clad the cladding material on the surface of the obtained substrate, followed by solution treatment, thereby obtaining a nickel-titanium composite coating;

[0026] The laser power used in the ultra-high-speed laser cladding technology is 2200-3800W; the cladding material includes: 60wt% nickel and 40wt% titanium.

[0027] The present invention utilizes ultra-high-speed laser cladding technology and solution treatment to make the prepared nickel-titanium composite coating free of pores and cracks, while also facilitating the formation of titanium oxide structure on the surface of the nickel-titanium composite coating, thereby greatly improving the corrosion resistance of the coating.

[0028] In some preferred embodiments, the preparation method includes: using coaxial powder feeding technology to transport the cladding material to the surface of the substrate, and then using ultra-high-speed laser cladding technology to clad the cladding material on the surface of the substrate; wherein the laser line scanning speed is 40m / min and the defocus amount is 11mm.

[0029] In some preferred embodiments, the laser power is selected from any one of 2200W, 2600W, 3000W, 3400W, and 3800W.

[0030] Furthermore, the laser power is 2600W.

[0031] In some preferred embodiments, the laser beam spot diameter is 2 mm.

[0032] In some preferred embodiments, the solution treatment temperature is 1000-1100° C., and the time is 2 h; the working atmosphere used in the solution treatment is a protective gas atmosphere.

[0033] Furthermore, the protective gas atmosphere includes an argon atmosphere.

[0034] In some preferred embodiments, the preparation method further comprises: mechanically mixing spherical nickel powder and spherical titanium powder using a planetary gravity stirring device to obtain the cladding material; wherein the mechanical mixing is performed at a rotation speed of 1000-2000 rpm and for a time of 240-480 s.

[0035] Furthermore, the purity of nickel and titanium in the cladding material is above 99 wt%.

[0036] In some preferred embodiments, the pretreatment includes: ultrasonically cleaning the surface of the substrate with anhydrous ethanol for 30-60 minutes.

[0037] In some preferred embodiments, the copper alloy coating has a thickness of 100-200 μm.

[0038] In some preferred embodiments, the material of the substrate includes Q355 steel.

[0039] In some more specific embodiments, the method for preparing the nickel-titanium composite coating specifically includes:

[0040] (1) Ni and Ti are mechanically mixed by a planetary gravity mixer to obtain NiTi alloy powder (i.e., the aforementioned "cladding material");

[0041] (2) pre-treating the substrate;

[0042] (3) subjecting the cladding material obtained in step (1) to ultra-high-speed laser cladding at different power gradients to obtain a cladding coating combined with the base material;

[0043] (4) The cladding coatings prepared at different powers are subjected to solution treatment to form a nickel-titanium composite coating on the substrate surface.

[0044] Furthermore, 60% of the spherical Ni powder and 40% of the spherical Ti powder were mechanically mixed using a VM300SA3 planetary gravity mixer at a rotation speed of 2000 rpm and a setting time of 240 s.

[0045] Furthermore, the pretreatment process is: before laser cladding, the substrate is ultrasonically cleaned with anhydrous ethanol, and the setting time is 30 minutes.

[0046] Furthermore, uniformly mixed NiTi alloy powder is delivered to the substrate surface by coaxial powder feeding technology for laser cladding, the defocus amount is 11 mm, the laser power is selected from any one of 2200 W, 2600 W, 3000 W, 3400 W, and 3800 W, the laser beam spot diameter is 2 mm, and the laser line scanning speed is 40 m / min.

[0047] Furthermore, the sample was subjected to solution treatment at 1050°C for 2 hours in a SGL-1700C high-temperature vacuum tube furnace.

[0048] Another aspect of the embodiments of the present invention further provides a nickel-titanium composite coating prepared by the aforementioned preparation method, wherein the nickel-titanium composite coating includes a NiTi solid solution and a TiO2 oxide film formed on the surface of the NiTi solid solution.

[0049] Furthermore, the corrosion potential of the nickel-titanium composite coating in a 3.5% NaCl solution is -0.448 V, and the corrosion current density is 6.665E -06 A / cm 2 .

[0050] Another aspect of the embodiments of the present invention further provides the application of the aforementioned nickel-titanium composite coating in corrosion resistance of key components of marine engineering equipment.

[0051] 60NiTi alloy is a new generation of wear-resistant and corrosion-resistant lightweight friction pair materials. Its typical characteristics are low density, high specific strength, high hardness, non-magneticity, good dimensional stability and strong corrosion resistance. It is an ideal surface modification material. NiTi alloy can take into account both good wear resistance and excellent corrosion resistance, which is a characteristic that existing marine engineering materials are difficult to possess. Since NiTi alloy is relatively expensive, has poor machinability, and its mechanical properties are lower than those of ordinary stainless steel materials, it is not suitable for processing large structures, which greatly limits its application in the fields of machinery and engineering materials. Therefore, this application forms a nickel-titanium composite coating on the surface of the Q355 steel substrate through a technology that combines ultra-high-speed laser cladding technology and solution treatment, and further improves the wear resistance and corrosion resistance through the titanium oxide structure on the surface of the nickel-titanium composite coating. At the same time, the prepared nickel-titanium composite coating is free of cracks and pores.

[0052] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0053] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0054] In the following examples of the present invention, an electrochemical workstation was used to test the corrosion resistance. The parameters during the test were set as follows: initial potential -0.7 V, end potential 0.1 V, scan rate 0.0002 V / s; high frequency 100000 Hz, low frequency 0.01 Hz, and amplitude 0.005 V.

[0055] Comparative Example 1

[0056] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0057] The preparation steps and experimental operations are as follows:

[0058] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min and a stirring time of 240s.

[0059] Step 2: The powder in step 1 is mixed evenly with terpineol and then pre-placed on the surface of the substrate, and a high-temperature box-type muffle furnace is used for solution treatment at 1050° C. for 2 hours.

[0060] Experiments have shown that after solution treatment alone, the coating has a very poor bond with the specimen, with extensive cracking and peeling off from the substrate. It is impossible to obtain a complete, high-quality coating through solution treatment alone.

[0061] Example 1

[0062] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0063] The preparation steps and experimental operations are as follows:

[0064] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min and a stirring time of 240s.

[0065] In step 2, an LDF 4000-40 laser was used for laser cladding, with a cladding power of 2200 W and a laser scanning linear speed of 40 m / min.

[0066] Step 3: subject the sample to solution treatment at 1050°C.

[0067] Step 4: Use scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to perform element and microstructural analysis on the sample after solution treatment.

[0068] Step 5: Electrochemical testing was performed on the solution treated sample in a 3.5% NaCl solution, and the electrochemical data were analyzed using CHI660E and ZSimpWin software.

[0069] Experiments have shown that, after solution treatment, the oxide film on the coating surface of this embodiment further grows, the electrochemical impedance value further increases, and the corrosion resistance of the coating is significantly improved.

[0070] Comparative Example 1

[0071] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0072] The preparation steps and experimental operations are as follows:

[0073] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min and a stirring time of 240s.

[0074] Step 2: The powder in step 1 is mixed evenly with terpineol and then pre-placed on the surface of the substrate, and a high-temperature box-type muffle furnace is used for solution treatment at 1050° C. for 2 hours.

[0075] The experiments revealed that the coating had very poor adhesion to the specimen after solution treatment alone, with extensive cracking and peeling off from the substrate. It was impossible to obtain a complete, high-quality coating through solution treatment alone.

[0076] Example 2

[0077] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0078] The preparation steps and experimental operations are as follows:

[0079] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min for 240s.

[0080] In step 2, an LDF 4000-40 laser was used for laser cladding, with a cladding power of 2600 W and a laser scanning linear speed of 40 m / min.

[0081] Step 3: subject the sample to solution treatment at 1050°C.

[0082] Step 4: Use scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to perform element and microstructural analysis on the sample after solution treatment.

[0083] Step 5: Electrochemical testing of the solution-treated sample was performed in a 3.5% NaCl solution, and electrochemical data were analyzed using CHI660E and ZSimpWin software.

[0084] The experiment found that after the solution treatment, the corrosion resistance of the coating of this embodiment was significantly improved. Figure 5It can be seen that the oxide layer structure is clearly observed on the coating surface. The coating surface prepared with a power of 2600W forms a continuous, uniform and dense oxide film, and the surface is also relatively smooth. Figure 6 The EDS spectrum shows that there is enrichment of Ti and O elements on the coating surface, and it is speculated that the oxide layer structure is mainly composed of titanium oxide. Figure 5 Nyquist plot of the coating after solution treatment prepared for 2600W power.

[0085] Figure 7 The results show that after solution treatment, the capacitance arc radius of the coating sample increased significantly, and the corrosion resistance of the coating was significantly improved. It can be inferred that the further growth of the oxide film structure after solution treatment is conducive to the coating to obtain better corrosion resistance. After solution treatment, the resistance at the junction of the coating and the substrate increased from 302.1Ω·cm to 1. 2 Increased to 2143Ω·cm 2 , the capacitance at the junction of the coating and the substrate is 3.416×10 -2 Ω -1 cm -2 ·s n Reduced to 1.429×10 -3 Ω -1 cm -2 ·s n , the passivation film capacitance value is also increased by 7.725×10 -3 Ω -1 cm -2 ·s n Reduced to 5.397×10 -4 Ω -1 cm -2 ·s n .

[0086] Figure 4 This is a potentiodynamic polarization curve of the coating prepared in Example 2 of the present invention. As shown in the figure, the detection curves all have the characteristics of passivation phenomenon, and the passivation range is obvious, which also indicates that a passivation film structure exists on the surface of the ultra-high-speed laser cladding NiTi coating. The corrosion current density of the prepared coating is 20.06μA / cm 2 After solution treatment, the corrosion current is reduced to 6.665μA / cm 2， This indicates that solution treatment slows corrosion and improves corrosion resistance. Corrosion potential is a thermodynamic concept of the potential for reactive corrosion and is closely related to the dynamic properties of a material. The corrosion potential of the coatings prepared was -0.513 V, which decreased to -0.410 V after solution treatment, significantly enhancing corrosion resistance. The coating prepared at 2600 W of solution treatment exhibited the lowest corrosion current density and corrosion potential, indicating the best corrosion resistance.

[0087] Example 3

[0088] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0089] The preparation steps and experimental operations are as follows:

[0090] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min for 240s.

[0091] In step 2, an LDF 4000-40 laser was used for laser cladding, with a cladding power of 3000 W and a laser scanning linear speed of 40 m / min.

[0092] Step 3: subject the sample to solution treatment at 1050°C.

[0093] Step 4: Use scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to perform element and microstructural analysis on the sample after solution treatment.

[0094] Step 5: Electrochemical testing was performed on the solution treated sample in a 3.5% NaCl solution, and the electrochemical data were analyzed using CHI660E and ZSimpWin software.

[0095] Experiments have shown that, after solution treatment, the oxide film on the coating surface of this embodiment further grows, the electrochemical impedance value further increases, and the corrosion resistance of the coating is significantly improved.

[0096] Example 4

[0097] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0098] The preparation steps and experimental operations are as follows:

[0099] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min for 240s.

[0100] In step 2, an LDF 4000-40 laser was used for laser cladding, with a cladding power of 3400 W and a laser scanning linear speed of 40 m / min.

[0101] Step 3: subject the sample to solution treatment at 1050°C.

[0102] Step 4: Use scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to perform element and microstructural analysis on the sample after solution treatment.

[0103] Step 5: Electrochemical testing of the solution-treated sample was performed in a 3.5% NaCl solution, and electrochemical data were analyzed using CHI660E and ZSimpWin software.

[0104] Experiments have shown that, after solution treatment, the oxide film on the coating surface of this embodiment further grows, the electrochemical impedance value further increases, and the corrosion resistance of the coating is significantly improved.

[0105] Example 5

[0106] The powder raw material composition is 60% spherical Ni powder and 40% spherical Ti powder.

[0107] The preparation steps and experimental operations are as follows:

[0108] Step 1: Use a planetary gravity mixer to mechanically mix 200g of this ratio at a stirring speed of 2000r / min for 240s.

[0109] In step 2, an LDF 4000-40 laser was used for laser cladding, with a cladding power of 3800 W and a laser scanning linear speed of 40 m / min.

[0110] Step 3: subject the sample to solution treatment at 1050°C.

[0111] Step 4: Use scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) to perform element and microstructural analysis on the sample after solution treatment.

[0112] Step 5: Electrochemical testing of the solution-treated sample was performed in a 3.5% NaCl solution, and electrochemical data were analyzed using CHI660E and ZSimpWin software.

[0113] Experiments have shown that, after solution treatment, the oxide film on the coating surface of this embodiment further grows, the electrochemical impedance value further increases, and the corrosion resistance of the coating is significantly improved.

[0114] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0115] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-titanium composite coating, characterized in that include: Pre-treating the substrate; and, using ultra-high-speed laser cladding technology to clad the cladding material on the surface of the obtained substrate, followed by solution treatment, thereby obtaining a nickel-titanium composite coating; The nickel-titanium composite coating includes a NiTi solid solution and a TiO2 oxide film formed on the surface of the NiTi solid solution; the nickel-titanium composite coating has a corrosion potential of -0.410 V and a corrosion current density of 6.665 μA / cm in a 3.5% NaCl solution. 2 ; Among them, the laser power used in the ultra-high-speed laser cladding technology is 2600W; the cladding material includes: 60wt% nickel and 40wt% titanium; the solution treatment temperature is 1050°C and the time is 2h.

2. The preparation method according to claim 1, wherein include: Coaxial powder feeding technology is used to transport the cladding material to the surface of the substrate, and then ultra-high-speed laser cladding technology is used to clad the cladding material on the surface of the substrate; wherein the laser line scanning speed is 40m / min and the defocus amount is 11mm.

3. The preparation method according to claim 1, wherein: The working atmosphere adopted in the solution treatment is a protective gas atmosphere.

4. The preparation method according to claim 1, characterized in that The process further comprises: mechanically mixing spherical nickel powder and spherical titanium powder using a planetary gravity stirring device to obtain the cladding material; wherein the mechanical mixing is performed at a rotation speed of 1000-2000 rpm and for a time of 240-480 seconds; The purity of nickel and titanium in the cladding material is above 99wt%.

5. The preparation method according to claim 1, characterized in that The pretreatment includes: using anhydrous ethanol to perform ultrasonic cleaning on the surface of the substrate for 30-60 minutes.

6. The preparation method according to claim 1, wherein: The thickness of the nickel-titanium composite coating is 100-200 μm.

7. The preparation method according to claim 1, wherein: The material of the substrate includes Q355 steel.

8. A nickel-titanium composite coating prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the nickel-titanium composite coating according to claim 8 in corrosion resistance of key components of marine engineering equipment.

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