Surface modified titanium alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of alloy materials, and particularly relates to a surface modified titanium alloy and a preparation method and application thereof. The surface modified titanium alloy comprises a base body, a first transition layer, a second transition layer and a functional layer, wherein the first transition layer, the second transition layer and the functional layer are sequentially stacked on the surface of the base body. The base body is made of titanium alloy; the material for forming the first transition layer is a mixture of vanadium and first silicon; the material for forming the second transition layer is a mixture of chromium and second silicon; and the functional layer is made of an Inconel 718 alloy. The two transition layers are formed by the vanadium silicon and the chromium silicon, so that the titanium element in the matrix can be prevented from diffusing into the functional layer to generate a brittle and hard intermetallic compound, and the surface coating of the matrix is prevented from cracking; and meanwhile, the Inconel 718 functional layer has excellent high-temperature mechanical property, and the high-temperature tribological property of the titanium alloy base material is improved by means of the excellent high-temperature mechanical property of the Inconel 718 functional layer.

Description

Technical Field

[0001] This invention belongs to the field of alloy materials technology, specifically relating to a surface-modified titanium alloy, its preparation method, and its application. Background Technology

[0002] Titanium alloys possess excellent properties and the following advantages: (1) high strength, capable of withstanding significant mechanical stress; (2) strong corrosion resistance, resistant to corrosion and oxidation; (3) lightweight yet high strength, achieving both low self-weight and excellent structural performance; and (4) good biocompatibility, being non-toxic and harmless to human tissues without causing rejection reactions. Therefore, titanium alloys are frequently used as one of the main lightweight structural materials, capable of manufacturing aircraft landing gear and various casings for engines and compressors, and are widely applied in high-end fields such as aviation, aerospace, and marine engineering, as well as in fields such as biomedical devices. However, the poor wear resistance and susceptibility to oxidation at high temperatures severely limit their application environment. Especially under high-temperature (above 600℃) and high-speed friction conditions, high temperatures can cause titanium alloys to oxidize and peel off, while friction exacerbates the shedding of the oxide film on the surface of the titanium alloy, leading to premature failure. Summary of the Invention

[0003] In view of this, the present invention provides a surface-modified titanium alloy, its preparation method and application. The surface-modified titanium alloy improved by the present invention has good high-temperature resistance and wear resistance, thus expanding its application range.

[0004] To solve the above-mentioned technical problems, the present invention provides a surface-modified titanium alloy, comprising a substrate and a first transition layer, a second transition layer and a functional layer sequentially stacked on the surface of the substrate;

[0005] The substrate is a titanium alloy;

[0006] The material forming the first transition layer is a mixture of vanadium and silicon.

[0007] The material forming the second transition layer is a mixture of chromium and silicon;

[0008] The functional layer is Inconel 718;

[0009] Preferably, the thickness of the first transition layer is 1 to 1.2 mm;

[0010] The thickness of the second transition layer is 1–1.2 mm;

[0011] The thickness of the functional layer is 1.2 to 1.5 mm.

[0012] Preferably, the mass percentage of the first silicon in the mixture of vanadium and first silicon is 0.5% to 1%;

[0013] The mixture of vanadium and first silicon is a mixture of vanadium powder and first silicon powder, wherein the particle size of the vanadium powder is 10-90 μm and the purity of the vanadium powder is greater than or equal to 90%.

[0014] The particle size of the first silicon powder is 50-90 μm, and the purity of the first silicon powder is greater than or equal to 99.5%.

[0015] Preferably, the mass percentage of the second silicon in the mixture of chromium and the second silicon is 0.5% to 1%;

[0016] The mixture of chromium and silicon is a mixture of chromium powder and silicon powder, wherein the particle size of the chromium powder is 10-90 μm and the purity of the chromium powder is greater than or equal to 90%.

[0017] The particle size of the second silicon powder is 50-90 μm, and the purity of the second silicon powder is greater than or equal to 99.5%.

[0018] Preferably, the titanium alloy comprises Ti-6Al-4V;

[0019] The titanium alloy is a sheet material with a thickness of ≥5mm.

[0020] This invention also provides a method for preparing the surface-modified titanium alloy described above, comprising the following steps:

[0021] A first laser cladding is performed on the surface of a titanium alloy using a mixture of vanadium and silicon as raw materials to form a first transition layer;

[0022] A second laser cladding is performed on the surface of the first transition layer using a mixture of chromium and silicon as raw materials to form a second transition layer;

[0023] A third laser cladding is performed on the surface of the second transition layer using Inconel 718 alloy as the raw material to form a functional layer;

[0024] The alloy after forming the functional layer is annealed to obtain the surface-modified titanium alloy.

[0025] Preferably, before the first laser cladding, the process further includes: subjecting the mixture of vanadium and silicon to a first drying process; and washing the titanium alloy after sandblasting.

[0026] The process before the second laser cladding also includes: subjecting the mixture of the chromium and the second silicon to a second drying process;

[0027] The third laser cladding Inconel 718 alloy is Inconel 718 alloy powder, and the particle size of the Inconel 718 alloy powder is 50-120 μm;

[0028] The process before the third laser cladding also includes: subjecting the Inconel 718 alloy powder to a third drying process.

[0029] Preferably, the first laser cladding and the second laser cladding are respectively performed using the pre-powder method, with a pre-thickness of 1.2 to 1.4 mm and independent laser processing parameters including: laser power of 1350 to 1500 W, scanning speed of 320 to 400 mm / min, spot diameter of 3 to 5 mm, and overlap rate of 40 to 60%.

[0030] The third laser cladding is performed using a coaxial powder feeding method. The laser processing parameters include: laser power of 1650-1900W, scanning speed of 680-800mm / min, spot diameter of 3-5mm, overlap rate of 40-60%, and powder feeding rate of 0.7-0.9r / min.

[0031] The first, second, and third laser cladding processes were carried out in a protective atmosphere.

[0032] Preferably, the annealing temperature is 500–650°C, and the annealing holding time is 2–4 hours.

[0033] The present invention also provides the application of the surface-modified titanium alloy described in the above technical solution or the surface-modified titanium alloy prepared by the preparation method described in the above technical solution in aerospace.

[0034] This invention provides a surface-modified titanium alloy, comprising a substrate and a first transition layer, a second transition layer, and a functional layer sequentially stacked on the surface of the substrate; the substrate is a titanium alloy; the material forming the first transition layer is a mixture of vanadium and silicon; the material forming the second transition layer is a mixture of chromium and silicon; and the functional layer is an Inconel 718 alloy. This invention uses vanadium-silicon and chromium-silicon to form two transition layers, which prevents titanium elements in the substrate from diffusing into the functional layer and forming brittle intermetallic compounds, thereby preventing cracking of the coating on the substrate surface. The doping of silicon into the first and second transition layers improves the formability of the transition layers, enhances their metallurgical quality, reduces the probability of porosity, and improves the interfacial bonding performance of the coating. In this invention, the strengthening phase and solid solution strengthening effect in the Inconel 718 alloy microstructure result in a significantly higher microhardness of the Inconel 718 functional layer than the titanium alloy substrate; simultaneously, the Inconel 718 functional layer possesses excellent high-temperature mechanical properties, which improve the high-temperature tribological properties of the titanium alloy substrate.

[0035] This invention also provides a method for preparing the surface-modified titanium alloy described in the above technical solution, comprising the following steps: performing a first laser cladding on the surface of a titanium alloy using a mixture of vanadium and silicon as raw materials to form a first transition layer; performing a second laser cladding on the surface of the first transition layer using a mixture of chromium and silicon as raw materials to form a second transition layer; performing a third laser cladding on the surface of the second transition layer using Inconel 718 alloy as raw materials to form a functional layer; and annealing the alloy after forming the functional layer to obtain the surface-modified titanium alloy. The coating prepared on the surface of the titanium alloy by the laser cladding method of this invention has a dense structure, no cracks or pore defects on the surface, and a metallurgical bond between the substrate, the transition layer, and the functional layer. The coating exhibits high bonding strength, high hardness, and low friction coefficient and wear rate under high-temperature conditions, demonstrating excellent high-temperature wear resistance. This effectively meets the requirements for use in high-temperature and severely worn environments in aerospace, shipbuilding, and chemical industries. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the surface-modified titanium alloy prepared in Example 1;

[0037] Figure 2 Microstructure of the cladding layer of the surface-modified titanium alloy prepared in Example 1;

[0038] Figure 3 This is a bar chart comparing the friction coefficients of the Inconel 718 functional layer and the titanium alloy substrate in Examples 1 and 2 at 600°C and 800°C.

[0039] Figure 4 The bar chart shows the wear rate of the Inconel 718 functional layer and the titanium alloy substrate in Examples 1 and 2 at 600°C and 800°C. Detailed Implementation

[0040] This invention provides a surface-modified titanium alloy, comprising a substrate and a first transition layer, a second transition layer, and a functional layer sequentially stacked on the surface of the substrate;

[0041] The substrate is a titanium alloy;

[0042] The material forming the first transition layer is a mixture of vanadium and silicon.

[0043] The material forming the second transition layer is a mixture of chromium and silicon;

[0044] The functional layer is made of Inconel 718 alloy.

[0045] In one specific embodiment of the present invention, the titanium alloy can be Ti-6Al-4V; the titanium alloy can be a sheet, and the thickness of the sheet can be ≥5mm, or 5-10mm; the Ti-6Al-4V is an α+β type two-phase titanium alloy with good comprehensive performance. When the first transition layer is prepared on the substrate surface, β-Ti and V elements in the titanium alloy form a continuous solid solution, and α-Ti and V elements form a limited solid solution. Furthermore, the thermal expansion coefficients of V and Ti are close, improving the compatibility between the titanium alloy and the V layer and reducing the residual thermal stress caused by the large difference in thermophysical parameters. When the second transition layer is prepared on the first transition layer, on the one hand, Cr and V elements are infinitely miscible; on the other hand, Cr elements can form a stable solid solution with most elements in the functional layer (Ni, Fe, Mo, etc.), and Cr elements are one of the main elements in the Inconel 718 alloy. This invention improves the compatibility between the titanium alloy substrate and Inconel 718 by setting a first transition layer and a second transition layer, increases the interfacial bonding strength in the gradient transition zone, alleviates coating interface cracking caused by the large difference in thermophysical parameters between the two alloys (titanium alloy and Inconel 718), and reduces the occurrence of brittle intermetallic compounds, thereby improving the bonding force between the substrate and the functional layer and thus improving the high-temperature friction resistance of the surface-modified titanium alloy.

[0046] In one specific embodiment of the present invention, the thickness of the first transition layer can be 1-1.2 mm, specifically 1 mm, 1.1 mm, or 1.2 mm; the mass percentage content of the first silicon in the mixture of vanadium and first silicon can be 0.5-1%, specifically 0.5%, 0.8%, or 1%; the mixture of vanadium and first silicon can be a mixture of vanadium powder and first silicon powder, wherein the particle size of the vanadium powder can be 10-90 μm; the purity of the vanadium powder can be greater than or equal to 90%, and can also be greater than or equal to 99%; the particle size of the first silicon powder can be 50-90 μm; the purity of the first silicon powder can be greater than or equal to 99.5%, and can also be greater than or equal to 99.7%.

[0047] In one specific embodiment of the present invention, the thickness of the second transition layer can be 1-1.2 mm, specifically 1 mm, 1.1 mm, or 1.2 mm; the mass percentage of the second silicon in the mixture of chromium and the second silicon can be 0.5-1%, specifically 0.5%, 0.8%, or 1%; the mixture of chromium and the second silicon can be a mixture of chromium powder and silicon powder, the particle size of the chromium powder can be 10-90 μm; the purity of the chromium powder can be greater than or equal to 90%, and can also be greater than or equal to 99%; the particle size of the second silicon powder can be 50-90 μm; the purity of the second silicon powder can be greater than or equal to 99.5%, and can also be greater than or equal to 99.7%.

[0048] In one specific embodiment of the present invention, the thickness of the functional layer can be 1.2–1.5 mm, specifically 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm. In this invention, Inconel 718 alloy is a precipitation-hardening nickel-chromium-iron alloy containing niobium and molybdenum. Due to the addition of a large number of strengthening elements, such as W, Mo, and Nb, which are high-melting-point metals, it possesses excellent mechanical properties, oxidation resistance, and corrosion resistance at high temperatures, and can serve for extended periods at temperatures above 650°C. Therefore, using laser cladding technology to prepare a Ni-based coating on the surface of titanium alloys can significantly improve the hardness and high-temperature wear resistance of titanium alloys, meeting their requirements for use under high-temperature and severe wear conditions. During high-temperature friction, the Ni, Cr, and Mo alloying elements in Inconel 718 alloy undergo tribochemical reactions to form oxides and bimetallic composite salts such as NiO, MoO2, MoO3, Cr2O3, and NiMoO4. These substances cover the wear surface, providing good friction reduction and wear resistance, thereby reducing further wear of the coating.

[0049] This invention also provides a method for preparing the surface-modified titanium alloy described above, comprising the following steps:

[0050] A first laser cladding is performed on the surface of a titanium alloy using a mixture of vanadium and silicon as raw materials to form a first transition layer;

[0051] A second laser cladding is performed on the surface of the first transition layer using a mixture of chromium and silicon as raw materials to form a second transition layer;

[0052] A third laser cladding is performed on the surface of the second transition layer using Inconel 718 alloy as the raw material to form a functional layer;

[0053] The alloy after forming the functional layer is annealed to obtain the surface-modified titanium alloy.

[0054] This invention uses a mixture of vanadium and silicon as raw materials to perform a first laser cladding on the surface of a titanium alloy to form a first transition layer. As a specific embodiment of this invention, before the first laser cladding, the process may further include: first drying the mixture of vanadium and silicon; and washing the titanium alloy after sandblasting. As another specific embodiment of this invention, the mixture of vanadium and silicon can be obtained by first ball milling vanadium powder and silicon powder; the rotation speed of the first ball mill can be 80–120 r / min, specifically 80 r / min, 90 r / min, 100 r / min, 110 r / min, or 120 r / min; the first ball milling time can be 8–12 h, specifically 8 h, 9 h, 10 h, 11 h, or 12 h. In one specific embodiment of the present invention, the first drying can be vacuum drying, and the temperature of the first drying can be 60-90°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C; the first drying time can be 1-2 hours, specifically 1 hour, 1.5 hours or 2 hours; the present invention does not have a special limitation on the porosity of the vacuum drying, as long as it is under vacuum conditions.

[0055] This invention does not have special requirements for the sandblasting treatment; conventional methods in the art can be used. In one specific embodiment of this invention, the washing may include sequential alcohol washing and acetone washing; the solvent for the alcohol washing can be ethanol. This invention, through sandblasting and washing, can effectively clean oil stains and other impurities from the surface of titanium alloys, thereby improving the absorption rate of the titanium alloy substrate to laser beams and reducing reflection.

[0056] In one specific embodiment of the present invention, the first laser cladding can be performed using a pre-powder method, with a pre-powder thickness of 1.2–1.4 mm, specifically 1.2 mm, 1.3 mm, or 1.4 mm. Laser processing parameters may include: laser power of 1350–1500 W, scanning speed of 320–400 mm / min, spot diameter of 3–5 mm, and overlap rate of 40–60%. Alternatively, the parameters may include: laser power of 1400–1450 W, scanning speed of 350–380 mm / min, spot diameter of 3–4 mm, and overlap rate of 40–50%.

[0057] In one specific embodiment of the present invention, the first laser cladding can be carried out in a protective atmosphere, which can be argon gas, and the oxygen content in the protective atmosphere is less than 50 ppmm.

[0058] As a specific embodiment of the present invention, the first laser cladding may further include: removing the oxide film on the surface of the product after the first laser cladding; the present invention has no special requirements for the removal method, and conventional methods in the art can be used.

[0059] After forming the first transition layer, the present invention uses a mixture of chromium and silicon as raw material to perform a second laser cladding on the surface of the first transition layer to form a second transition layer. In one specific embodiment of the present invention, the process may further include a second drying of the mixture of chromium and silicon before the second laser cladding. In another specific embodiment of the present invention, the mixture of chromium and silicon can be obtained by second ball milling of chromium powder and silicon powder; the rotation speed of the second ball mill can be 80–120 r / min, specifically 80 r / min, 90 r / min, 100 r / min, 110 r / min, or 120 r / min; the ball milling time can be 8–12 h, specifically 8 h, 9 h, 10 h, 11 h, or 12 h. In another specific embodiment of the present invention, the second drying can be vacuum drying; the second drying temperature can be 60–90 °C, specifically 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, or 90 °C; the second drying time can be 1–2 h, specifically 1 h, 1.5 h, or 2 h.

[0060] In one specific embodiment of the present invention, the second laser cladding can be performed using a pre-powder method, with a pre-powder thickness of 1.2–1.4 mm, specifically 1.2 mm, 1.3 mm, or 1.4 mm. Laser processing parameters may include: laser power of 1350–1500 W, scanning speed of 320–400 mm / min, spot diameter of 3–5 mm, and overlap rate of 40–60%. Alternatively, the parameters may include: laser power of 1400–1450 W, scanning speed of 350–380 mm / min, spot diameter of 3–4 mm, and overlap rate of 40–50%.

[0061] In one specific embodiment of the present invention, the second laser cladding can be performed in a protective atmosphere, which can be argon gas, and the oxygen content in the protective atmosphere is less than 50 ppmm.

[0062] As a specific embodiment of the present invention, the second laser cladding may further include: removing the oxide film on the surface of the product after the second laser cladding; the present invention has no special requirements for the removal method, and conventional methods in the art can be used.

[0063] After forming the second transition layer, the present invention uses Inconel 718 alloy as raw material to perform a third laser cladding on the surface of the second transition layer to form a functional layer. In one specific embodiment of the present invention, the Inconel 718 alloy used for the third laser cladding can be Inconel 718 alloy powder, and the particle size of the Inconel 718 alloy powder can be 50–120 μm; the Inconel 718 alloy powder can be prepared by argon atomization; the use of argon atomization in the preparation of Inconel 718 alloy powder in the present invention can avoid severe oxidation and reduce the oxygen content in the Inconel 718 alloy powder. As a specific embodiment of the present invention, the process before the third laser cladding may further include: subjecting the Inconel 718 alloy powder to a third drying process; the third drying process may be vacuum drying, and the temperature of the third drying process may be 60-90°C, specifically 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C; the time of the third drying process may be 1-2 hours, specifically 1 hour, 1.5 hours, or 2 hours; the present invention does not have a special limitation on the vacuum degree of the vacuum drying process, as long as it is under vacuum conditions. In one specific embodiment of the present invention, the third laser cladding can be performed using a coaxial powder feeding method. The laser processing parameters may include: laser power of 1650-1900W, scanning speed of 680-800mm / min, spot diameter of 3-5mm, overlap rate of 40-60%, and powder feeding rate of 0.7-0.9r / min; or: laser power of 1750-1800W, scanning speed of 750-800mm / min, spot diameter of 3-4mm, overlap rate of 40-50%, and powder feeding rate of 0.7-0.8r / min.

[0064] In one specific embodiment of the present invention, the third laser cladding can be performed in a protective atmosphere, which can be argon gas, and the oxygen content in the protective atmosphere is less than 50 ppmm.

[0065] As a specific embodiment of the present invention, the third laser cladding may further include: removing the oxide film on the surface of the product after the third laser cladding; the present invention has no special requirements for the removal method, and conventional methods in the art can be used.

[0066] In this invention, the laser cladding method has outstanding advantages such as concentrated energy, metallurgical bonding between the prepared cladding layer and the substrate, low heat input, uniform and fine microstructure of the cladding layer, and high solid solubility of alloying elements. The cladding layer obtained by the laser cladding method of this invention has fewer pores and cracks inside, which can significantly improve the surface properties of metal materials.

[0067] After forming the functional layer, the present invention anneales the alloy after forming the functional layer to obtain the surface-modified titanium alloy. In one specific embodiment of the present invention, the annealing temperature can be 500–650°C, specifically 500°C, 550°C, 580°C, 600°C, or 650°C; the holding time of the annealing treatment can be 2–4 hours, specifically 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours; the annealing treatment can be carried out in a vacuum heat treatment furnace. The present invention, through annealing, can reduce the internal stress generated during the preparation of the cladding layers (first transition layer, second transition layer, and functional layer) and the stress release deformation during subsequent use of the product.

[0068] In one specific embodiment of the present invention, the annealing process may further include: cooling the annealed product to room temperature; the room temperature may be 20–35°C, or 25–30°C. In another specific embodiment of the present invention, the cooling method may be furnace cooling.

[0069] This invention employs laser cladding to prepare an Inconel 718 high-temperature wear-resistant coating on a titanium alloy surface by adding two transition layers, V and Cr, to address the problems of low hardness and poor high-temperature wear resistance in titanium alloys. The first and second transition layers improve the compatibility between the titanium alloy and Inconel 718, increase the interfacial bonding strength in the gradient transition zone, alleviate interfacial cracking caused by significant differences in thermophysical parameters between the two alloys, and reduce the formation of brittle intermetallic compounds. The prepared Inconel 718 functional layer exhibits no obvious cracks or porosity, demonstrating high hardness and good high-temperature wear resistance. The main phase in the Ni-based alloy of this invention is γ-Ni, which contains dissolved alloying elements such as Cr and Fe, providing excellent solid solution strengthening. The rapid heating and cooling of laser cladding prevents grain growth, thus refining the grain size in the coating and achieving grain refinement strengthening. The Ni, Ti, Al, and Nb elements in the coating undergo metallurgical reactions to form Ni4Nb and Ni3(Al,Ti) intermetallic compounds. The hardness of the coating is improved by utilizing solid solution strengthening, grain refinement strengthening, and the strengthening effect of intermetallic compounds, thereby ultimately improving the wear resistance of titanium alloys.

[0070] This invention also provides applications of the surface-modified titanium alloys described in the above-described technical solutions or prepared by the methods described in the above-described technical solutions in the aerospace field. As a specific embodiment of this invention, the application can be for manufacturing ball-and-socket nozzles for aerospace engine vector control mechanisms, titanium alloy blades, compressor rotors, and splined shafts for mechanical transmission systems.

[0071] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0072] Example 1

[0073] After sandblasting the surface of a 5mm thick titanium alloy Ti-6Al-4V plate, it was first cleaned with ethanol and then washed with acetone to obtain pretreated titanium alloy Ti-6Al-4V.

[0074] Vanadium powder with a purity ≥90% and a particle size of 10–90 μm and silicon powder with a purity ≥99.5% and a particle size of 50–90 μm were placed in a ball mill and ball-milled for 10 hours at a speed of 100 r / min to obtain a mixture of vanadium powder and silicon powder, wherein the mass percentage of silicon powder in the mixture was 0.5%; the mixture of vanadium powder and silicon powder was then vacuum-dried at 80℃ for 2 hours to obtain a dried mixture of vanadium powder and silicon powder.

[0075] Chromium powder with a purity ≥90% and a particle size of 10–90 μm and silicon powder with a purity ≥99.5% and a particle size of 50–90 μm were placed in a ball mill and ball-milled for 10 hours at a speed of 100 r / min to obtain a mixture of chromium powder and silicon powder, wherein the mass percentage of silicon powder in the mixture was 0.5%; the mixture of chromium powder and silicon powder was then vacuum-dried at 80℃ for 2 hours to obtain a dried mixture of chromium powder and silicon powder.

[0076] Inconel 718 alloy powder with a particle size of 50-120 μm was prepared by argon atomization and then vacuum dried at 80 °C for 2 h to obtain dried Inconel 718 alloy powder.

[0077] A 1.2 mm thick mixture of dried vanadium and silicon powder was pre-placed on the surface of a pretreated titanium alloy Ti-6Al-4V. The sample underwent a first laser cladding process using a continuous-flow fiber laser in a pure argon atmosphere, with argon continuously introduced to maintain an oxygen content below 50 ppm. After the first laser cladding, the sample was removed, and the surface oxide film was cleaned to obtain a 1 mm thick first transition layer (vanadium-silicon layer). The processing parameters for the first laser cladding were: laser power 1500 W, scanning speed 400 mm / min, spot diameter 3 mm, and overlap rate 50%.

[0078] A mixture of dried chromium powder and silicon powder with a thickness of 1.4 mm was pre-placed on the surface of the first transition layer using a pre-powder method. The sample was then subjected to a second laser cladding using a continuous-flow fiber laser in a pure argon atmosphere. Argon gas was continuously introduced during the cladding process to ensure that the oxygen content was below 50 ppm. After the second laser cladding was completed, the sample was removed and the oxide film on the surface was cleaned to obtain a second transition layer (chromium-silicon layer) with a thickness of 1.2 mm. The processing parameters for the second laser cladding were: laser power 1350 W, scanning speed 400 mm / min, spot diameter 3 mm, and overlap rate 50%.

[0079] Using dried Inconel 718 alloy powder as raw material, a third laser cladding was performed on the surface of the second transition layer using a coaxial powder feeding method. The cladding environment was a pure argon atmosphere. After the cladding was completed, the sample was removed and the oxide film on the surface was cleaned to obtain an Inconel 718 functional layer with a thickness of 1.2 mm. The processing parameters for the third laser cladding were: laser power 1800 W, scanning speed 800 mm / min, spot diameter 3 mm, overlap rate 50%, and powder feeding rate 0.8 r / min.

[0080] The material forming the Inconel 718 functional layer was placed in a vacuum heat treatment furnace and annealed at 600°C for 4 hours. It was then cooled to room temperature (25°C) with the furnace to obtain a surface-modified titanium alloy.

[0081] Example 2

[0082] The surface-modified titanium alloy was prepared according to the method of Example 1, except that the mass percentage of silicon powder in the mixture of vanadium powder and silicon powder was 1%, and the mass percentage of silicon powder in the mixture of chromium powder and silicon powder was 1%; the ball milling time in the preparation of the mixture of vanadium powder and silicon powder and the mixture of chromium powder and silicon powder was 12 h; the thickness of the first transition layer (vanadium-silicon layer) was 1.2 mm, the thickness of the second transition layer (chromium-silicon layer) was 1.2 mm; the laser power of the first laser cladding was 1350 W; the laser power of the third laser cladding was 1750 W, and the annealing temperature was 550 °C.

[0083] Figure 1 This is a schematic diagram of the structure of the surface-modified titanium alloy prepared in Example 1.

[0084] The microstructure of the cladding layer of the surface-modified titanium alloy prepared in Example 1 was observed under a microscope, and the microstructure image is shown below. Figure 2 As shown. By Figure 2 It can be seen that the cladding layer has a distinct four-layer structure. The coating structure is uniform and the microstructure is fine. Neither the transition layer nor the functional layer has obvious defects such as pores or cracks. The cladding quality is good, and there is a good metallurgical bond between adjacent layers.

[0085] The high-temperature wear resistance of the cladding layer on the surface of the surface-modified titanium alloys prepared in Examples 1 and 2 was tested according to the following method:

[0086] (1) Microhardness: The microhardness of the cladding layer was tested using an MH-5-VM type microhardness tester. The load was 200g and the holding time was 10s. The microhardness was measured every 0.1 or 0.2mm from the surface of the cladding layer to the titanium alloy substrate. The same point was measured three times, and the average hardness value was taken. Six values ​​were randomly selected from the test results and listed in Table 1.

[0087] (2) High-temperature reciprocating wear test: The test sample was processed into a friction specimen with dimensions of 31mm×10mm×4mm. After polishing the surface of the specimen, it was cleaned with anhydrous ethanol. Dry friction and wear tests were conducted on the cladding layer (Inconel 718 functional layer) and titanium alloy substrate of the specimen using an MFT-3000 high-temperature friction testing machine. The test temperatures were 600℃ and 800℃. The corresponding friction pair was a Si3N4 ball with a diameter of 6.35mm (hardness: 1700±20Hv). The test conditions were: load 20N, stroke 5mm, frequency 5Hz, and time 60min. To ensure the authenticity and repeatability of the test data, three tests were conducted at each temperature point under the same conditions, and the average value was taken. The results are listed in Table 2.

[0088] Table 1. Hardness of the surface-modified titanium alloys prepared in Examples 1-2

[0089]

[0090] Combining Table 1 and Figure 3 It can be seen that the microhardness of the Inconel 718 functional layer is significantly higher than that of the titanium alloy substrate. From the cladding layer to the titanium alloy substrate, the microhardness shows a smooth gradient trend without any obvious abrupt change. This gradient trend indicates that no brittle and hard intermetallic compound is formed at the interface between the cladding layer and the substrate, which is conducive to the effective transfer of load during friction.

[0091] Table 2. Wear resistance properties of the surface-modified titanium alloys prepared in Examples 1-2 at different temperatures.

[0092]

[0093] Based on Table 2, a bar chart comparing the friction coefficients of the Inconel 718 functional layer and the titanium alloy substrate in Examples 1 and 2 at 600°C and 800°C was plotted. Figure 3 As shown in Table 2, a bar chart comparing the wear rates of the Inconel 718 functional layer and the titanium alloy substrate in Examples 1 and 2 at 600°C and 800°C is plotted. Figure 4 As shown. (Combined with Table 2 and...) Figure 3 , 4 It can be seen that the Inconel 718 functional layer in the surface-modified titanium alloy prepared by the present invention has excellent high-temperature wear resistance. At 600℃ and 800℃, its friction coefficient and wear rate are significantly lower than those of the titanium alloy matrix.

[0094] The modified coating on the titanium alloy surface provided by this invention has high hardness and good high-temperature mechanical properties, thus exhibiting excellent resistance to plastic deformation. The modified coating provided by this invention has good formation and is metallurgically bonded to the substrate, without obvious cracks and pores. It has high microhardness and excellent high-temperature wear resistance, and can provide long-term and effective high-temperature wear protection for titanium alloys.

[0095] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A surface-modified titanium alloy, characterized in that, It includes a substrate and a first transition layer, a second transition layer, and a functional layer sequentially stacked on the surface of the substrate; The substrate is a titanium alloy; The material forming the first transition layer is a mixture of vanadium and silicon. The material forming the second transition layer is a mixture of chromium and silicon; The functional layer is Inconel 718.

2. The surface-modified titanium alloy according to claim 1, characterized in that, The thickness of the first transition layer is 1 to 1.2 mm; The thickness of the second transition layer is 1–1.2 mm; The thickness of the functional layer is 1.2 to 1.5 mm.

3. The surface-modified titanium alloy according to claim 1 or 2, characterized in that, The mass percentage of the first silicon in the mixture of vanadium and first silicon is 0.5% to 1%. The mixture of vanadium and first silicon is a mixture of vanadium powder and first silicon powder, wherein the particle size of the vanadium powder is 10-90 μm and the purity of the vanadium powder is greater than or equal to 90%. The particle size of the first silicon powder is 50-90 μm, and the purity of the first silicon powder is greater than or equal to 99.5%.

4. The surface-modified titanium alloy according to claim 1 or 2, characterized in that, The mass percentage of the second silicon in the mixture of chromium and second silicon is 0.5% to 1%. The mixture of chromium and silicon is a mixture of chromium powder and silicon powder, wherein the particle size of the chromium powder is 10-90 μm and the purity of the chromium powder is greater than or equal to 90%. The particle size of the second silicon powder is 50-90 μm, and the purity of the second silicon powder is greater than or equal to 99.5%.

5. The surface-modified titanium alloy according to claim 1, characterized in that, The titanium alloy comprises Ti-6Al-4V; The titanium alloy is a sheet material with a thickness of ≥5mm.

6. The method for preparing the surface-modified titanium alloy according to any one of claims 1 to 5, characterized in that, Includes the following steps: A first laser cladding is performed on the surface of a titanium alloy using a mixture of vanadium and silicon as raw materials to form a first transition layer; A second laser cladding is performed on the surface of the first transition layer using a mixture of chromium and silicon as raw materials to form a second transition layer; A third laser cladding is performed on the surface of the second transition layer using Inconel 718 alloy as the raw material to form a functional layer; The alloy after forming the functional layer is annealed to obtain the surface-modified titanium alloy.

7. The preparation method according to claim 6, characterized in that, The process before the first laser cladding includes: subjecting the mixture of vanadium and silicon to a first drying process; and washing the titanium alloy after sandblasting. The process before the second laser cladding also includes: subjecting the mixture of the chromium and the second silicon to a second drying process; The third laser cladding Inconel 718 alloy is Inconel 718 alloy powder, and the particle size of the Inconel 718 alloy powder is 50-120 μm; The process before the third laser cladding also includes: subjecting the Inconel 718 alloy powder to a third drying process.

8. The preparation method according to claim 6 or 7, characterized in that, The first laser cladding and the second laser cladding are respectively performed using the pre-powder method. The pre-powder thickness is 1.2 to 1.4 mm. The independent laser processing parameters include: laser power of 1350 to 1500 W, scanning speed of 320 to 400 mm / min, spot diameter of 3 to 5 mm, and overlap rate of 40 to 60%. The third laser cladding is performed using a coaxial powder feeding method. The laser processing parameters include: laser power of 1650-1900W, scanning speed of 680-800mm / min, spot diameter of 3-5mm, overlap rate of 40-60%, and powder feeding rate of 0.7-0.9r / min. The first, second, and third laser cladding processes were carried out in a protective atmosphere.

9. The preparation method according to claim 6, characterized in that, The annealing temperature is 500–650°C, and the annealing holding time is 2–4 hours.

10. The application of the surface-modified titanium alloy according to any one of claims 1 to 5 or the surface-modified titanium alloy prepared by the preparation method according to any one of claims 6 to 9 in aerospace.

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