High-entropy alloy coating for rail transit repair and preparation method of high-entropy alloy coating

Abstract

The invention relates to the technical field of novel material research and development and coatings, and discloses a high-entropy alloy coating for rail transit repair and a preparation method of the high-entropy alloy coating. The high-entropy alloy coating is formed by mixing iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder and forming the mixture on the rail transit base material through laser cladding. Wherein the high-entropy alloy coating is a solid solution with a face-centered cubic structure, the cluster formula of a cluster model of the high-entropy alloy coating is [Al < 0.6 > Mo < 0.4 >-Fe < 11-x > Ni < x > Cr < 1 >] Cr < 3 >, and x is 1, 1.5, 2, 2.5 or 3. The high-entropy alloy coating is superior to a traditional metal material in the aspects of strength, hardness, thermal stability, strong acid corrosion resistance and the like, a new direction is opened up for research on the corrosion resistance of the high-entropy alloy in a complex corrosion environment, and the functional application of the iron-rich high-entropy alloy is expanded.

Description

Technical Field

[0001] The present invention relates to the fields of new material research and development and coating technology, and particularly to a high-entropy alloy coating for rail transit repair, and also relates to a preparation method of the coating. Background Art

[0002] With the rapid development of urban rail transit, the problems of wear and corrosion of rail steel are becoming increasingly serious, significantly affecting the service life of the rail steel and becoming a key factor restricting the development of the industry. At present, the corrosion resistance and wear resistance of the existing rail steel materials are still insufficient in humid tunnel environments, industrial pollution areas, and marine climates. In tunnels, high humidity, groundwater containing chloride ions and sulfates, concrete materials used in the construction process, and corrosion caused by stray currents are the main reasons for accelerating the corrosion of rail steel. In humid and salt-rich environments such as tunnels, industrial pollution areas, and marine climate areas, the corrosion of rail steel is particularly serious.

[0003] The direct current traction system in the urban rail transit system may generate stray currents, which leak through the rail to the surrounding environment, further accelerating the corrosion process of the rail steel. The corrosion products may accumulate between the rail and the fasteners, leading to corrosion of the connection parts and thus affecting the integrity of the rail structure. In a humid environment, a water film is easily formed on the surface of the rail steel. After contacting with oxygen, the electrochemical corrosion is accelerated, ultimately resulting in the loss of materials. Therefore, there is an urgent need to develop new special materials with high efficiency, corrosion resistance, and wear resistance, as well as their preparation and repair technologies, to meet the needs of the rail transit industry. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a high-entropy alloy coating for rail transit repair and a preparation method thereof, so as to design a coating that is superior to traditional metal materials in terms of strength, hardness, thermal stability, and strong acid corrosion resistance.

[0005] A high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder, and aluminum powder are mixed and formed into the high-entropy alloy coating on a rail transit substrate by laser cladding.

[0006] Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 11-x Ni x Cr 1 Cr 3 , where x is 1, 1.5, 2, 2.5, or 3.

[0007] As a further improvement of the above solution, the aluminum powder used is nickel-coated aluminum powder with a ratio of 1:1. In the present invention, when using nickel-coated aluminum powder with a ratio of 1:1 to provide Al element, the amount of nickel powder can be reduced, and the cost can be lowered.

[0008] As a further improvement of the above solution, in the cluster model, the cluster center is occupied by Al and Mo, the 12 nearest neighbor atoms around the center are respectively occupied by 11-x Fe atoms, x Ni atoms, and 1 Cr atom, and the connection gaps between isolated clusters are filled by 3 Cr atoms. In the present invention, based on the cluster model to reflect the atomic occupancy in the alloy solid solution structure, it provides a basis for the optimization of the solid solution composition, making the alloy design efficient, significantly saving time and labor costs. Through composition regulation, the high-entropy alloy can simultaneously possess wear resistance and corrosion resistance, and has the potential to become a substitute material for steel used in rail transit.

[0009] As a further improvement of the above solution, the atomic content composition of the high-entropy alloy coating is as follows: Fe 50% - 70%, Ni 6% - 20%, Cr 25%, Mo 2.5%, Al 3.75%, totaling 100%.

[0010] As a further improvement of the above solution, the cluster formula of the high-entropy alloy coating cluster model is [Al 0.6 Mo 0.4 -Fe 10 Ni 1 Cr 1 Cr 3 .

[0011] A preparation method of a high-entropy alloy coating, which comprises the following steps:

[0012] S1 Based on the above-mentioned cluster model, weigh iron powder, chromium powder, nickel powder, molybdenum powder, and aluminum powder in sequence according to the mass ratio;

[0013] S2 After mixing the weighed metal powders, perform ball milling treatment to obtain mixed powder for standby;

[0014] S3 Perform surface treatment on the rail transit substrate;

[0015] S4 Pre-lay a layer of mixed powder on the surface of the rail transit substrate and compact it, and then use a broadband laser cladding device to process it, so that the mixed powder is cladded and formed on the rail transit substrate to obtain a high-entropy alloy coating.

[0016] As a further improvement of the above solution, the purity of the iron powder, chromium powder, nickel powder, and molybdenum powder is greater than 99.6%, and the powder particle sizes of the iron powder, chromium powder, nickel powder, molybdenum powder, and aluminum powder are not greater than 0.075 mm. In the present invention, a sieve with a mesh size of not less than 200 meshes is used for sieving to obtain metal powder with a particle size not greater than 0.075 mm.

[0017] As a further improvement of the above solution, based on the atomic content in the cluster formula of the cluster model, the mass content is converted to weigh the corresponding weight of the metal powder. The conversion formula for the mass content is as follows:

[0018] ;

[0019] In the above formula, A represents the relative atomic mass, N represents the atomic percentage, and m represents the metal element to be calculated.

[0020] As a further improvement of the above solution, the rail transit base material is made of 904L stainless steel. In the present invention, 904L stainless steel contains alloy elements such as Fe, Cr, Ni, and Mo, which are similar to the composition of the high-entropy alloy coating, helping to improve the wettability between the coating material and the base material, thereby promoting the successful preparation of the coating on the surface of the base material.

[0021] As a further improvement of the above solution, a grinding wheel and coarse sandpaper are used to polish the surface of the rail transit base material to remove the oxide scale until the surface of the base material shows metallic luster. Then, it is cleaned with alcohol to remove the stains on the surface of the base material. After drying with a hair dryer, it is stored in a vacuum drying oven for later use.

[0022] As a further improvement of the above solution, during the laser cladding process, argon gas is introduced for protection; the process parameters of the broadband laser cladding equipment are: laser wavelength 1064 nm, cladding power 2.5 kW, scanning speed 5 mm / s, rectangular spot size 20 mm × 2 mm, defocus amount 300 mm, and argon gas flow rate 25 L / min.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The high-entropy alloy coating of the present invention is superior to traditional metal materials in terms of strength, hardness, thermal stability, and strong acid corrosion resistance, opening up a new direction for the corrosion resistance research of high-entropy alloys in complex corrosion environments and expanding the functional applications of iron-rich high-entropy alloys.

[0025] In the present invention, based on the cluster model to reflect the atomic occupancy in the alloy solid solution structure, it provides a basis for the optimization of the solid solution composition, making the alloy design efficient, significantly saving time and labor costs. Through composition regulation, the high-entropy alloy can simultaneously possess wear resistance and corrosion resistance and has the potential to become a substitute material for rail transit steel.

[0026] The present invention uses laser cladding technology to form a high-entropy alloy coating. Compared with the preparation method of bulk high-entropy alloys, the coating obtained in this embodiment is in the form of a thin film, with a small amount of precious metal elements used, significantly reducing the cost. Moreover, the obtained coating has advantages such as a uniform organizational structure and small compositional segregation, demonstrating unique properties that cannot be compared with bulk materials. Description of the Drawings

[0027] Figure 1 The XRD patterns of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown.

[0028] Figure 2 The TEM images of the high-entropy alloy coatings of Examples 1, 2, and 5 of the present invention are shown.

[0029] Figure 3 The hardness diagrams of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown. In the figure, a is the hardness distribution curve and b is the average hardness diagram.

[0030] Figure 4 The wear curve diagrams and wear mass loss diagrams of the high-entropy alloy coatings of Examples 1-5 of the present invention.

[0031] Figure 5 The wear scar morphology diagrams and three-dimensional wear diagrams of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown.

[0032] Figure 6 The electrochemical polarization curves and impedance spectra of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown. In the figure, a is the polarization curve and b is the impedance curve.

[0033] Figure 7 The erosion mass loss curves and histograms of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown.

[0034] Figure 8 The erosion morphology diagrams of the high-entropy alloy coatings of Examples 1-5 of the present invention are shown. Detailed Embodiments

[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following will further describe the present invention in detail in combination with embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not used to limit the present invention.

[0036] The following will describe the specific embodiments of the present invention in detail.

[0037] Example 1

[0038] This embodiment provides a high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed and formed on the rail transit substrate by laser cladding to obtain the high-entropy alloy coating. The aluminum powder is nickel-coated aluminum powder with a ratio of 1:1. Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 10 Ni 1 Cr 1 Cr 3 , and the atomic content composition in the high-entropy alloy coating is as follows: Fe 62.5%, Ni 6.25%, Cr 25%, Mo 2.5%, Al 3.75%.

[0039] In the cluster model of the high-entropy alloy coating of this embodiment, the cluster center is occupied by Al and Mo, and the 12 nearest neighbor atoms around the center are occupied by 10 Fe atoms, 1 Ni atom and 1 Cr atom respectively. The connection gaps between isolated clusters are filled by 3 Cr atoms.

[0040] Example 2

[0041] This embodiment provides a high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed and formed on the rail transit substrate by laser cladding to obtain the high-entropy alloy coating. The aluminum powder is nickel-coated aluminum powder with a ratio of 1:1. Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 9.5 Ni 1.5 Cr 1 Cr 3 , and the atomic content composition in the high-entropy alloy coating is as follows: Fe 59.38%, Ni 9.38%, Cr 25%, Mo 2.5%, Al 3.75%.

[0042] In the cluster model of the high-entropy alloy coating of this embodiment, the cluster center is occupied by Al and Mo, and the 12 nearest neighbor atoms around the center are occupied by 9.5 Fe atoms, 1.5 Ni atoms and 1 Cr atom respectively. The connection gaps between isolated clusters are filled by 3 Cr atoms.

[0043] Example 3

[0044] This embodiment provides a high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed and formed on the rail transit substrate by laser cladding to obtain the high-entropy alloy coating. The aluminum powder is nickel-coated aluminum powder with a ratio of 1:1. Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 9 Ni 2 Cr 1 Cr 3 , and the atomic content composition in the high-entropy alloy coating is as follows: Fe 56.25%, Ni 12.5%, Cr 25%, Mo 2.5%, Al 3.75%.

[0045] In the cluster model of the high-entropy alloy coating of this embodiment, the cluster center is occupied by Al and Mo, and the 12 nearest neighbor atoms around the center are occupied by 9 Fe atoms, 2 Ni atoms, and 1 Cr atom respectively. The connection gaps between isolated clusters are filled by 3 Cr atoms.

[0046] Example 4

[0047] This embodiment provides a high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed and formed on the rail transit substrate by laser cladding to obtain the high-entropy alloy coating. The aluminum powder is nickel-coated aluminum powder with a ratio of 1:1. Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 8.5 Ni 2.5 Cr 1 Cr 3 , and the atomic content composition in the high-entropy alloy coating is as follows: Fe 53.13%, Ni 15.63%, Cr 25%, Mo 2.5%, Al 3.75%.

[0048] In the cluster model of the high-entropy alloy coating of this embodiment, the cluster center is occupied by Al and Mo, and the 12 nearest neighbor atoms around the center are occupied by 8.5 Fe atoms, 2.5 Ni atoms, and 1 Cr atom respectively. The connection gaps between isolated clusters are filled by 3 Cr atoms.

[0049] Example 5

[0050] This embodiment provides a high-entropy alloy coating for rail transit repair, which has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed and formed on the rail transit substrate by laser cladding to obtain the high-entropy alloy coating. The aluminum powder used is nickel-coated aluminum powder with a ratio of 1:1. Among them, the high-entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 8 Ni 3 Cr 1 Cr 3 , and the atomic content composition in the high-entropy alloy coating is as follows: Fe 50%, Ni 18.75%, Cr 25%, Mo 2.5%, Al 3.75%.

[0051] In the cluster model of the high-entropy alloy coating of this embodiment, the cluster center is occupied by Al and Mo, and the 12 nearest neighbor atoms around the center are occupied by 8 Fe atoms, 3 Ni atoms and 1 Cr atom respectively. The connection gaps between isolated clusters are filled by 3 Cr atoms.

[0052] Example 6

[0053] This embodiment provides a preparation method of a high-entropy alloy coating, which is used to fabricate any one of the high-entropy alloy coatings for rail transit repair as described in Examples 1 to 5. The preparation method includes the following steps:

[0054] S1 Based on the designed cluster model, iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are weighed in sequence according to the mass ratio.

[0055] The purities of the iron powder, chromium powder, nickel powder and molybdenum powder are all greater than 99.6%, and the powder particle sizes of the iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are all not greater than 0.075 mm. In this embodiment, a Sartorius electronic analytical balance with an accuracy of 0.1 mg is used for weighing, and a sieve with a mesh size of not less than 200 meshes is used for sieving, so as to obtain metal powders with a particle size not greater than 0.075 mm.

[0056] Based on the atomic content in the cluster formula of the cluster model, the mass content is converted to weigh the corresponding weight of metal powder. The conversion formula of the mass content is as follows:

[0057] ;

[0058] In the above formula, A represents the relative atomic mass, N represents the atomic percentage, and m represents the metal element to be calculated.

[0059] S2 After mixing the weighed metal powders, ball milling treatment is carried out to obtain mixed powders for standby.

[0060] Put the weighed metal powder into a 500 mL stainless steel ball milling tank, set the rotation speed of the ball mill to 180 r / min, and the ball milling time to 2 h. After screening through a 120-mesh stainless steel standard sieve, store the mixed powder in a vacuum drying oven for later use. The stainless steel ball milling tank contains stainless steel balls with a particle size of 3 - 10 mm, and the ratio of stainless steel balls to the mixed powder is 5:1.

[0061] S3 Perform surface treatment on the rail transit substrate.

[0062] The rail transit substrate is made of 904L stainless steel. Use a grinding wheel and coarse sandpaper to polish off the oxide scale on the surface of the rail transit substrate until the surface of the substrate shows metallic luster. Then, clean the surface of the substrate with alcohol to remove stains, dry it with a hair dryer, and store it in a vacuum drying oven for later use.

[0063] S4 Use a stainless steel hollow mold to evenly pre-lay the ball-milled alloy powder on the surface of the substrate to form a powder layer with a thickness of 1.2 mm, and compact it with a stainless steel cutter. Then, use a broadband laser cladding device to process it, so that the mixed powder is cladded and formed on the rail transit substrate to obtain a high-entropy alloy coating.

[0064] During the laser cladding process, argon gas is introduced for protection. The process parameters of the broadband laser cladding device are: laser wavelength 1064 nm, cladding power 2.5 kW, scanning speed 5 mm / s, rectangular spot size 20 mm × 2 mm, defocus amount 300 mm, and argon gas flow rate 25 L / min. In this embodiment, a fiber laser with the model RC-LMS-6000R is used for laser cladding treatment.

[0065] In this embodiment, the laser cladding technology adds a cladding powder material to the surface of the substrate, and uses a high-power and high-density laser beam to heat the cladding material and the surface of the substrate, so that they achieve metallurgical bonding and quickly cool and solidify to form a coating with excellent comprehensive performance. Laser cladding has the advantages of high material utilization rate, dense structure, controllable cladding layer thickness, and strong bonding between the coating and the substrate when preparing high-entropy alloy coatings. Broadband laser cladding, with the characteristics of ultra-fast heating and cooling (cooling rate up to 104 - 106 °C / s), can refine the solidification structure and achieve supersaturation, promoting the in-situ precipitation of uniform solid solutions and micro-nano dispersion phases, thereby significantly improving the strength, hardness, and corrosion resistance of the alloy. The coating prepared by this method has a uniform structure, controllable thickness, and can reach the millimeter level. In addition, as a surface modification technology, laser cladding can repair the substrate with less material, effectively saving precious metal elements and reducing costs.

[0066] The preparation method of this embodiment uses laser cladding technology to form a high-entropy alloy coating. Compared with the preparation method of bulk high-entropy alloys, the coating obtained in this embodiment is in the form of a thin film, with a small amount of precious metal elements used, significantly reducing the cost. Moreover, the obtained coating has advantages such as a uniform microstructure and small composition segregation, showing unique properties that cannot be compared with bulk materials.

[0067] A solid solution is composed of a solvent and solutes. Among them, the atoms of the element with a higher content are called solvent atoms, and the atoms of the element with a lower content are called solute atoms. In the high-entropy alloy coating of this embodiment, Fe is the solvent atom, and the other elements are solute atoms. The mixing enthalpy between each element is △H Fe-Ni =-2 kJ / mol, △H Fe-Cr =-1 kJ / mol, △H Fe-Mo =-2 kJ / mol, △H Fe-Al =-11 kJ / mol. The more negative the mixing enthalpy between the solute and solvent atoms, the more inclined the solute atoms are to occupy the cluster center, and vice versa, they occupy the position of the connecting atoms. Based on this, the present invention constructs a cluster type of [Al 0.6 Mo 0.4 -Fe 8 Ni 3 Cr 1 Cr 3 , and by adjusting the ratio of Fe and Ni, further constructs an [Al 0.6 Mo 0.4 -Fe 11-x Ni x Cr 1 Cr 3 high-entropy alloy system where x is 1, 1.5, 2, 2.5, or 3 to improve the hardness and corrosion resistance of the alloy.

[0068] Based on the cluster model, the present invention reflects the atomic occupancy in the solid solution structure of the alloy, provides a basis for optimizing the solid solution composition, makes the alloy design efficient, and can significantly save time and labor costs. Through composition regulation, the high-entropy alloy can simultaneously possess wear resistance and corrosion resistance, and has the potential to become a substitute material for steel used in rail transit.

[0069] The high-entropy alloy coating of the present invention is formed by five metals, namely Al, Mo, Fe, Ni, and Cr. Mo plays a role in enhancing the corrosion resistance of the alloy, Fe plays a role in enhancing the strength and hardness of the alloy, and Al has a strong affinity for oxygen and nitrogen, which can limit the expansion of the austenite phase region. Introducing aluminum into the high-entropy alloy can not only achieve solid solution strengthening, fine grain strengthening, and second-phase strengthening, but also improve corrosion resistance, reduce the weight of the alloy, and promote the precipitation of the second phase. In addition, Al has a relatively large atomic radius, and adding it to the alloy can significantly enhance the lattice distortion effect, improve the alloy strength, while achieving lightweight and reducing costs.

[0070] Next, the performance of the high-entropy alloy coatings in Examples 1 to 5 was tested. The performance tests included XRD phase characterization, TEM analysis, microhardness testing, friction and wear performance testing, electrochemical corrosion performance testing, and erosion corrosion experiments.

[0071] An X-ray diffractometer of model X'Pert PRO MPD was used for XRD phase characterization. The high-entropy alloy coating was cut into cubes of 10 mm × 10 mm × 10 mm to prepare XRD test samples. The surface of the coating was polished with sandpaper until smooth, then placed in alcohol and cleaned with an ultrasonic cleaner. The XRD test parameters were set as follows: anode Cu target, wavelength of 1.5406 Å, voltage of 45 kV, current of 40 mA, scanning range of 10° to 90°, scanning speed of 10° / min, and step size of 0.02°. After the test was completed, the Highscore Plus software was used to analyze and process the results, and Origin was used for plotting to obtain Figure 1 .

[0072] Analysis Figure 1 It can be seen that when x is 2.5 to 3, the coating is mainly composed of an FCC solid solution rich in the FeNi phase. As the content of Fe element in the coating increases, Fe 9 Ni 2 and Fe 9.5 Ni 1.5 In the coating, a weak BCC phase peak appears, while in the Fe 10 Ni 1 coating, the intensity of the BCC phase peak is significantly enhanced, indicating that the coating is composed of a duplex of FCC and BCC. From Figure 1 (b)'s partial enlarged view, it can be seen that as the Fe element increases, the intensities of the main peaks of the FCC phase (111) and (200) slightly decrease, and the peak positions remain unchanged, while the intensity of the main peak of the BCC precipitated phase (110) gradually increases and shows a slightly right-shifted trend. The XRD pattern proves that as the Fe content in the high-entropy alloy coating increases, the lattice distortion degree of the alloy decreases, and the mechanical and physical properties of the coating are improved.

[0073] The TEM analysis was carried out using a transmission electron microscope with the model of Tecnai G2 F20 S TWIN. The specific operation process will not be elaborated here. The TEM images are as shown in Figure 2 Figure Figure 2 . In 8 Fe 3 Ni 8 coating dendritic morphology, a1 is 3 Fe 9.5 Ni 1.5 coating dendritic diffraction spots, b is 9.5 Fe 1.5 Ni 10 coating dendritic morphology, b1 is 1 Fe 10 Ni 1 coating diffraction spots, c is 10 Fe 1 Ni

[0074] Detailed analysis Figure 2 shows that the 8 Fe 3 Ni 9.5 coating presents an obvious black dendritic morphology, and a large number of polygonal dendrites appear in the 1.5 Fe 10 Ni 1 coating. Dislocations appear near the dendrites of the

[0075] Fe Figure 3 Ni Figure 3 coating. Due to the different atomic radii of the five elements of Fe, Co, Ni, Cr, and Al, the lattice distortion effect is caused, resulting in the generation of dislocations near the dendrites. The generation of dislocations will hinder the further slip of the slip plane, thereby improving the strength of the alloy. 0.2 The microhardness test was carried out using a microhardness tester with the model of HVS-1000. The test results are as shown in 8 Fe 3 Ni 8.5 coating, the hardness of each coating is higher than that of the substrate (about 185 HV 2.5 Fe 9 Ni 3 coating, the average hardness is 206.3 HV 0.2 respectively, and the hardness improvement of the0.2 and 230.5 HV 0.2 while Fe 9.5 Ni 2.5 The average hardness of the coating is about 278.5 HV 0.2 while Fe 10 Ni 1 The coating reaches the highest hardness of 306.7 HV 0.2 , which is about 1.66 times the hardness of the substrate, and the wear resistance of the coating is improved accordingly.

[0076] The friction and wear experiments were carried out using an HSR-2M friction and wear testing machine, and the experimental results are as Figure 4 and Figure 5 shown. Figure 4 Among them, a is the wear curve graph, and b is the wear mass loss graph. A detailed analysis Figure 4 shows that the 904L substrate, Fe 8 Ni 3 and Fe 8.5 Ni 2.5 coatings show large fluctuations during the wear process, which may be due to the fact that these coatings are composed of only a single FCC phase and have a low hardness, resulting in a softer matrix and obvious fluctuations in the wear curve. While in the Fe 9 Ni 2 to Fe 10 Ni 1 coatings, in addition to the FCC phase, a BCC phase is formed, and the hardness of the coating gradually increases, so its wear resistance is also enhanced, and the fluctuations of the wear curve become smaller. With the increase of the Fe content in the coating, the wear mass gradually decreases, which also indicates that the wear resistance of the coating has been improved.

[0077] Figure 5 Among them, a and a1 are Fe 8 Ni 3 , b and b1 are Fe 8.5 Ni 2.5 , c and c1 are Fe 9 Ni 2 , d and d1 are Fe 9.5 Ni 1.5 , e and e1 are Fe 10 Ni 1 . A detailed analysis Figure 5 shows that after the friction and wear experiment, large flakes, significant white oxidation areas and small wear debris that did not fall off appeared on the coating surface, mainly showing abrasive wear, adhesive wear and oxidative wear. It can be seen from the three-dimensional wear scar morphology diagrams from a1 to e1 that with the increase of the Fe element content in the coating, the depth of the wear scar gradually becomes shallower, indicating that the wear resistance of the coating has been improved.

[0078] An electrochemical workstation of model CHI660C was used, and 0.5 mol / L H 2 SO 4 solution was used as the electrolyte to conduct the electrochemical corrosion performance test, and the test results are as Figure 6 shown. By analyzing the polarization curve in detail, it can be seen that obvious passivation regions are shown when the substrate and each coating change from the cathode region to the anode region, and the corrosion potentials and corrosion current densities of each coating are not much different. By analyzing the impedance curve, it can be seen that the impedance spectra of each coating present a shape close to a quarter circle, indicating that charge transfer dominates the corrosion process. The impedance arc radius of the substrate is the smallest, and as the content of Fe element increases, the impedance radius gradually increases. Among them, the impedance radius of the Fe 9.5 Ni 1.5 coating is the largest, showing the best corrosion resistance, while the impedance radius of the Fe 10 Ni 1 coating decreases slightly. The above results show that with the increase of the Fe element content, the corrosion resistance of the coating first increases and then decreases, and the Fe 9.5 Ni 1.5 coating has the best corrosion resistance.

[0079] The erosion corrosion experiment was carried out using a DJ1C-120 force-increasing electric stirrer + a DF-101S heating magnetic stirrer with heat collection, and the experimental results are as Figure 7 and Figure 8 shown. Figure 7 In, a is the mass loss curve graph, b is the mass loss bar graph. By analyzing Figure 7 a in detail, it can be seen that the weight loss of each coating continuously increases with the passage of time within 0-14 h, while between 14-24 h, the erosion mass loss of the coating changes little. This may be because the coating is immersed in a strong acid solution for a long time, forming a uniform passivation film, which effectively prevents further corrosion. By analyzing Figure 7 b, it can be seen that with the increase of the Fe element content and the decrease of the Ni element, the weight loss of the coating shows a trend of first decreasing and then increasing, and the Fe 9.5 Ni 1.5 coating has the smallest weight loss. In addition, the mass loss of all coatings is lower than that of the 904L steel substrate.

[0080] Figure 8 In, a is Fe 8 Ni 3 , b is Fe 8.5 Ni 2.5 , c is Fe 9 Ni 2 , d is Fe 9.5 Ni 1.5 , e is Fe 10 Ni 1 , f is the substrate. By analyzing in detailFigure 8 It can be seen that for Fe 8 Ni 3 and Fe 8.5 Ni 2.5 coatings, after erosion-corrosion, coarse grain boundaries appeared, and scratches were clearly visible on the grain boundaries, which may be caused by the continuous impact of particles during the erosion process. For Fe 9 Ni 2 coatings, a finer dendritic structure was exhibited. For Fe 9.5 Ni 1.5 coatings, after erosion, the distribution of dendrites and intercrystals clearly showed a layered structure, forming a river-like morphology. For Fe 10 Ni 1 coatings, the surface was relatively flat, no obvious dendritic and intercrystalline structures were seen, and only a small number of erosion pits appeared. After erosion, more pits and scratches appeared on the surface of the 904L steel substrate.

[0081] The above results prove that the high-entropy alloy coatings of the present invention are superior to traditional metal materials in terms of strength, hardness, thermal stability, and strong acid corrosion resistance, opening up a new direction for the corrosion resistance research of high-entropy alloys in complex corrosion environments and expanding the functional applications of iron-rich high-entropy alloys.

[0082] The above embodiments are only the preferred embodiments of the present invention. Any simple modification, modification, and alternative change made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. A high entropy alloy coating for rail transit repair, characterized in that: The high entropy alloy coating has the following components: iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are mixed, and the high entropy alloy coating is formed on the rail transit substrate by laser cladding; The high entropy alloy coating is a solid solution with a face-centered cubic structure, and the cluster formula of its cluster model is [Al 0.6 Mo 0.4 -Fe 11-x Ni x Cr1]Cr3, x is 1, 1.5, 2, 2.5 or 3.

2. The high entropy alloy coating for rail transit repair according to claim 1, characterized in that: The aluminum powder is 1:1 nickel-coated aluminum powder.

3. The high entropy alloy coating for rail transit repair according to claim 2, characterized in that: In the cluster model, the cluster center is occupied by Al and Mo, the 12 nearest neighbor atoms around the center are occupied by 11-x Fe atoms, x Ni atoms, and 1 Cr atom, respectively, and the connecting gaps between isolated clusters are filled with 3 Cr atoms.

4. The high entropy alloy coating for rail transit repair according to claim 3, characterized in that: The atomic content composition of the high entropy alloy coating is as follows: Fe 50%-70%, Ni 6%-20%, Cr 25%, Mo 2.5%, Al 3.75%, totaling 100%.

5. The high entropy alloy coating for rail transit repair according to claim 4, characterized in that: The cluster formula of the high entropy alloy coating cluster model is [Al 0.6 Mo 0.4 -Fe 10 Ni1Cr1]Cr3.

6. A method for preparing a high entropy alloy coating, characterized in that: The following steps are involved: S1 Based on the cluster model as claimed in claim 1, iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder are weighed in order according to the mass ratio; S2: mixing the weighed metal powders and performing ball milling to obtain mixed powder for later use; S3 performs surface treatment on rail transit substrate; S4 pre-lays a layer of mixed powder on the surface of the rail transit substrate and compacts it, and then uses broadband laser cladding equipment to process it, so that the mixed powder is clad and formed on the rail transit substrate to obtain a high entropy alloy coating.

7. The preparation method according to claim 6, characterized in that: The purity of the iron powder, chromium powder, nickel powder and molybdenum powder is greater than 99.6%, and the powder particle size of the iron powder, chromium powder, nickel powder, molybdenum powder and aluminum powder is no more than 0.075 mm.

8. The preparation method according to claim 7, characterized in that: Based on the atomic content in the cluster formula of the cluster model, the mass content is converted to weigh the corresponding weight of the metal powder. The conversion formula for the mass content is as follows: ； In the above formula, A represents the relative atomic mass, N represents the atomic percentage, and m represents the metal element to be calculated.

9. The preparation method according to claim 8, characterized in that: The rail transit substrate is made of 904L stainless steel; Use a grinding machine and coarse sandpaper to remove the oxide scale on the surface of the rail transit substrate until the surface of the substrate presents a metallic luster, then use alcohol to clean and remove stains on the surface of the substrate. After drying with a hair dryer, store it in a vacuum drying oven for later use.

10. The preparation method according to claim 9, characterized in that: During the laser cladding process, argon gas is introduced for protection; the process parameters of the broadband laser cladding equipment are: laser wavelength 1064nm, cladding power 2.5kW, scanning rate 5mm / s, rectangular spot size 20mm×2mm, defocusing amount 300mm, argon gas flow rate 25L / min.

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