A high corrosion and wear resistant NiCrCoBSi high-entropy alloy coating layer and a preparation method thereof

Abstract

This invention discloses a high-corrosion-resistant and high-wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method, belonging to the field of high-entropy alloy material preparation technology. First, the polished CrZrCu alloy substrate surface is pretreated by sandblasting. Then, NiCrCoBSi alloy powder prepared by gas atomization is sprayed onto the copper alloy surface using supersonic flame spraying technology. The prepared sample is then subjected to diffusion annealing in a vacuum heat treatment furnace. The transition diffusion layer present at the coating interface / substrate junction improves the coating adhesion. The intense plastic deformation generated during the HVOF preparation process produces a large number of twins and ultrafine grains in the microstructure, improving corrosion resistance, hardness, and wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy alloy material preparation, and more specifically, relates to a high corrosion-resistant and high wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method. Background Technology

[0002] Copper and copper alloys are increasingly in demand in the power, energy, metallurgy, and marine industries due to their excellent machinability and good electrical and thermal conductivity. Particularly in the complex and harsh operating environments of metallurgy and marine sectors, copper alloy wear is becoming increasingly severe. Therefore, research on surface protection of copper and copper alloys is of great significance.

[0003] Ni-based alloys, due to their excellent corrosion resistance and mechanical properties, have been applied to the industrial preparation of HVOF coatings on copper alloy surfaces. Compared with electroplated coatings, Ni-based alloy coatings produced by HVOF generally exhibit better wear resistance. However, the second phases such as borides and carbides in Ni-based alloy coatings are detrimental to further improving corrosion resistance. Due to the difference in self-corrosion potential, the interface between the second phase and the Ni alloy matrix is ​​more susceptible to corrosion.

[0004] Medium-entropy / high-entropy alloys are novel multi-principal element alloys designed based on the concept of entropy regulation, exhibiting structurally ordered but chemically disordered properties. They demonstrate excellent corrosion resistance, mechanical properties, and high-temperature oxidation resistance. Among them, NiCrCo multi-principal element alloys with face-centered cubic structures have great application potential and have become one of the research hotspots in recent years. Due to the low stacking fault energy of NiCrCo alloys, a composite structure with high-density dislocation cells, nanoscale deformation twins, and a large number of stacking faults is formed on the wear surface, thereby reducing the friction coefficient and wear rate. However, medium-entropy / high-entropy alloys suffer from severe oxidation during the HVOF process, which easily leads to problems such as porosity and cracks, affecting the mechanical properties, corrosion resistance, and wear resistance of the alloy, and significantly impacting the performance of the coating.

[0005] A search revealed that patent CN107083502A discloses a wear-resistant and corrosion-resistant cobalt-based alloy powder and its application method. Specifically, it discloses a cobalt-based alloy composition with properties compatible with thermal spraying and sintering technologies. This alloy composition can provide a cladding to various metal substrates with complex geometries, wherein the cladding exhibits the desired density, hardness, wear resistance, and corrosion resistance. In short, the alloy composition described herein comprises 15-25 wt% chromium, 15-20 wt% molybdenum, 0-15 wt% tungsten, 10-20 wt% nickel, 2.5-3.5 wt% boron, 2.5-4.5 wt% silicon, 1-2 wt% carbon, and the balance cobalt, wherein the boron to silicon (B / Si) ratio in the alloy composition is in the range of 0.5 to 1.0. Mo and W elements combine with carbon to form carbides with high hardness, which significantly improves hardness and wear resistance, but they are prone to forming brittle phases. Their microstructure includes metal borides and Co-Mo-Si Reeves brittle phases.

[0006] Patent CN104561877A discloses a thermally sprayed nickel-based self-fluxing alloy amorphous coating. The method involves preparing a nickel-based self-fluxing alloy as a spraying powder and then spraying it onto the surface of a workpiece using a thermal spraying method to form the nickel-based self-fluxing alloy amorphous coating. The elemental composition and weight percentage of the nickel-based self-fluxing alloy, based on a 100% weight percentage, are: Cr 15-20%, B 3.0-5.0%, Si 3.0-5.5%, C 0.5-1.1%, Fe 3-5%, with the balance being Ni. The addition of B and Si can improve the amorphous forming ability of the coating. Furthermore, according to the entropy formula, its entropy value is 1.3R < 1.5R, which is below the standard for high-entropy alloys, therefore it does not belong to the category of high-entropy alloys. Summary of the Invention

[0007] 1. The problem to be solved

[0008] To address the problem of easy oxidation in existing HVOF spray oxidation preparations of high-entropy alloy coatings, this invention provides a highly corrosion-resistant and wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method. The obtained NiCrCoBSi high-entropy alloy coating exhibits high corrosion resistance and high wear resistance.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] This invention draws upon the design concepts of Ni-based self-fluxing alloys and NiCrCo multi-principal element alloys to develop a NiCrCoBSi self-fluxing alloy. The addition of B and Si elements reduces HVOF (High-Voltage-Free) oxidation of the coating, resulting in numerous twins and ultrafine grains, improving the coating's microstructure stability and corrosion resistance. Simultaneously, it generates metal carbides or metal borides, including Cr...23 High-hardness second phases such as C6, CrB, and Ni3B enhance wear resistance. A method for preparing a NiCrCoBSi high-entropy alloy coating on a copper alloy surface is also provided, improving the coating's adhesion, wear resistance, and corrosion resistance.

[0012] In existing technologies, Mo and W elements are often added to form carbides that combine with carbon, resulting in high hardness and significantly improving hardness and wear resistance. However, these carbides are prone to forming brittle phases, which affects the service life of the coating. Therefore, this invention removes Mo and W and introduces B and Si elements. On the one hand, it improves the oxidation phenomenon of HVOF spraying, improves the structural stability and corrosion resistance of the coating. On the other hand, it uses metal carbides or metal borides to increase the hardness of the coating and enhance its wear resistance.

[0013] A method for preparing a highly corrosion-resistant and wear-resistant NiCrCoBSi high-entropy alloy coating includes the following steps:

[0014] Step S1: Cleaning the substrate: The CrZrCu alloy substrate is ground, polished, cleaned, dried, and ready for use.

[0015] In step S1, the sample surface is polished and chemical reagents such as acetone and alcohol are used to remove oil stains and dirt from the substrate surface, so that the cleanliness of the surface to be sprayed meets the requirements.

[0016] Step S2, Sandblasting: Sandblasting is used to treat the cleaned surface into a microscopically uneven surface with a certain degree of roughness. This is to activate the substrate before the spraying operation, increase the overall surface area of ​​the substrate, make the coating easier to adhere, and increase the adhesion. Preferably, the roughness is controlled within the range of Ra 5-7μm.

[0017] In step S2, G25# steel grit is used for surface roughening. During the sandblasting process, the sandblasting pressure is 0.3 to 0.5 MPa, the sandblasting angle is 90°, the sandblasting distance is 120 to 180 mm, and the lateral speed is 0.05 m / s.

[0018] Step S3, Coating Preparation: The sample is preheated with a flame and then HVOF sprayed with a NiCrCoBSi high-entropy alloy coating.

[0019] In step S3, during the NiCrCoBSi high-entropy alloy coating spraying process, the preheating temperature is 100-150℃, the kerosene flow rate is controlled at 5-7 Gal / h, the oxygen flow rate is controlled at 1800-2000 SCFH, and the spraying distance is controlled at 300-400mm.

[0020] During the spraying process, heat source parameters and operating parameters are key factors affecting coating quality, among which oxygen flow rate, kerosene flow rate, and spraying distance are the most significant influencing factors.

[0021] (1) The effect of oxygen and kerosene flow rates on coating quality:

[0022] The supersonic flame spraying technology used in this paper employs aviation kerosene as fuel and oxygen as a combustion accelerant. The heating process of the sprayed powder in the flame is extremely complex. On the one hand, the specific heat capacity and flowability of the powder particles affect their heating and temperature rise in the flame; on the other hand, the particle size and particle size distribution range of the powder also affect its heating time and temperature difference. Therefore, it is necessary to rationally control the flow rates of kerosene and oxygen according to the characteristics of the metal powder to achieve the optimal powder velocity and temperature, thereby improving the coating quality.

[0023] The flow rates and ratios of oxygen and kerosene determine the velocity, temperature, and other characteristics of the supersonic jet, significantly impacting the coating's microstructure. If the kerosene flow rate is too low and oxygen is excessive, the jet will exhibit an "oxidizing" atmosphere, leading to increased powder particle oxidation during flight and a higher oxide inclusion content in the coating. Conversely, if the kerosene flow rate is too high, the flame will produce a low-temperature, oxygen-deficient state, resulting in insufficient powder heating and an increase in unmelted particles and porosity in the coating. When determining spraying parameters, the primary goal is to achieve a neutral flame and reach the spray gun's design power. The flow rates and ratios of oxygen and kerosene are then selected, and adjustments are made based on the matching of the flame temperature with the powder's melting point.

[0024] (2) The effect of spraying distance on coating quality:

[0025] Spraying distance refers to the distance between the spray gun exit and the surface of the substrate to be sprayed, that is, the distance the powder travels in the air after leaving the gun barrel. After leaving the gun barrel, the powder remains within the flame stream and does not immediately escape it; therefore, the powder's velocity undergoes an initial acceleration followed by deceleration. Furthermore, the powder's heating process primarily occurs inside the gun barrel, and its temperature gradually decreases as it travels through the air. If the spraying distance is too long, the kinetic energy and heat from the particles impacting the substrate are insufficient, resulting in inadequate particle deformation and an increase in porosity and other defects within the coating, significantly degrading the coating quality. If the spraying distance is too short, the particles are not sufficiently heated, and their velocity cannot reach the ideal state, leading to an increase in defects within the coating. Therefore, variations in spraying distance have a significant impact on coating quality.

[0026] Supersonic flame spraying offers a wide adjustable spraying distance range, capable of producing coatings between 200 and 400 mm. During the flight of the sprayed powder from the muzzle, the powder temperature gradually decreases with increasing distance, while the particle velocity undergoes an initial acceleration followed by deceleration. Therefore, when determining the spraying distance, the range that maximizes particle velocity should be selected, while also considering factors such as the adverse effects of high-temperature flame heating on the substrate. Based on preliminary explorations, this paper selects a spraying distance range of 320–400 mm.

[0027] (3) The effect of barrel length on coating quality:

[0028] The barrel length affects the powder exit velocity and the effectiveness of heat exchange. During spraying, the heating time of the powder within the barrel depends on the barrel length. The thermal state of the particles is a critical factor in the spraying process; excessively high temperatures can cause powder overheating and adhesion to the inner wall of the spray gun, leading to barrel blockage; excessively low temperatures will prevent the powder from melting sufficiently, resulting in unmelted particles in the coating and severely affecting coating quality. Therefore, it is essential to select an appropriate barrel length during spraying. The JP5000 supersonic spraying system used in this article is equipped with barrels in 4-inch, 6-inch, and 8-inch sizes.

[0029] The NiCrCoBSi high-entropy alloy coating uses alloy powder as a precursor. The precursor composition is as follows: C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.67%, Cr: 20.53%, Si: 2.67%, B: 2.33%, Co: 11.3%, with the balance being Ni. The particle size of the alloy powder is 15-53 μm. The alloy powder can be prepared by aerosol method or other methods.

[0030] Step S4, diffusion annealing: The prepared coating sample is placed in a vacuum heat treatment furnace for diffusion annealing.

[0031] In step S4, the furnace is annealed in a vacuum heat treatment furnace at a temperature of 900–1000°C for 3–10 hours, and then cooled in the furnace.

[0032] The NiCrCoBSi high-entropy alloy coating has the following elemental compositions: C: 0.2%-0.5%, Mo: 1%-3.5%, Cu: 0.5%-3.5%, Fe: 0.5%-3.5%, Cr: 17%-23%, Si: 2%-4%, B: 2%-4%, Co: 10%-13%, with the balance being Ni. The coating porosity is controlled below 1%.

[0033] Porosity is the main forming defect of HVOF. By optimizing the spraying process through orthogonal experiments, the porosity of the coating can be controlled to below 1%.

[0034] During HVOF spraying, the coating forms two types of pores: pores and metal shrinkage cavities. The main factors contributing to their formation are as follows: (1) During spraying, the alloy particles are in an unmelted or semi-melted state. Due to the roughness of the substrate interface, the liquid metal cannot completely fill the gaps in the substrate. (2) The molten alloy solidifies quickly, causing some gas to be unable to escape in time, thus resulting in the formation of pores. (3) During most of the solidification time, the metal layer is in a pasty state. During this period, the liquid metal remains on the surface. At the end of solidification, the liquid metal is absorbed along with the contraction of the inner solidified metal layer, taking away the external gas. Small bubbles are then formed, which transform into pores after solidification. (4) A liquid-solid transition occurs during coating formation. If the amount of liquid metal is small or the fluidity is poor, the pores generated by solidification shrinkage cannot be filled in time, eventually forming shrinkage cavities.

[0035] The coating obtained in this application is a high-entropy alloy coating with an entropy value of 1.6R.

[0036] The mixing entropy of a high-entropy alloy system increases with the number of constituent elements. The higher entropy value of multiple components reduces the free energy required to form a solid solution, promotes the mutual dissolution between elements, and reduces the number of precipitated phases in the high-entropy alloy. At the same time, the lattice potential energy difference of the high-entropy alloy leads to a significant increase in the content of positions with relatively low lattice potential energy. This forms atomic diffusion traps, thereby reducing the diffusion rate and hindering its diffusion behavior. This helps to suppress grain nucleation and growth, thus achieving the effect of refining grains and improving the microstructure stability and corrosion resistance of the coating.

[0037] The interaction between different elements achieves the strengthening of high-entropy alloys. The uniform and irregular atomic arrangement of high-entropy alloys achieves additional alloy strengthening effects, exhibiting a composite effect. In multi-principal alloys, the elements produce a synergistic effect, improving the mechanical properties of the coating.

[0038] The composition and content of the CrZrCu alloy matrix are: Cr: 0.5% to 1.5%, Zr: 0.1% to 0.3%, Cu: balance.

[0039] It generates a 40–50 μm transition diffusion layer at the coating interface / substrate, transforming the bonding between the coating and the substrate from mechanical to metallurgical, significantly improving the coating adhesion. Both the solid solution in the coating and the γ-Cu copper alloy matrix are FCC phases. The solid solution is a substitutional solid solution formed by Co, Cr, and Ni. During diffusion annealing, Ni and Co elements in the coating diffuse into the copper matrix, while Cu elements in the matrix diffuse into the coating, ultimately forming a transition diffusion layer approximately 40–50 μm wide between the coating and the copper matrix. The diffusion layer mainly contains Cu, Ni, and Co elements, with small amounts of Fe and Si elements.

[0040] Compared to the intermediate layer in patent CN1431336A, which is a separate spray coating applied to the material, acting as an adhesive rather than a direct coating, resulting in a compositional difference between the coating and the transition layer, this application directly prepares the coating on the copper alloy surface. The resulting transition layer is formed by diffusion between the coating and the substrate through an annealing process, exhibiting higher adhesion.

[0041] High-velocity flame spraying (HVOF) is one of the most widely used thermal spraying technologies. Due to its high flame velocity, high powder kinetic energy, and low oxidation, it produces coatings with high density and good bonding strength, and allows for a wide range of material selection. The spraying process involves high spraying speeds and temperatures lower than melting. Powder particles are accelerated to speeds exceeding 600 m / s by the spraying flame, causing severe plastic deformation in the coating. Finite element models predict that when 316 stainless steel particles travel at speeds of 520 m / s and 610 m / s, the impact stress on the coating reaches as high as 156 MPa and 277 MPa, respectively. Under this impact force, the sprayed powder induces severe plastic deformation in the coating, generating ultrafine grains and twins of 100–500 nm. The addition of elements such as boron (B) and silicon (Si) reduces coating oxidation and combines with the main components to form CrB, Ni3B, and Cr... 23 The high-hardness second strengthening phase, such as C6, effectively improves the hardness and wear resistance of the coating; it generates a large number of low-ΣCSL grain boundaries, which disrupt the connectivity of the RHABs network, inhibit the occurrence of intergranular corrosion, effectively improve the corrosion resistance of the coating, and enhance the performance of the coating.

[0042] This invention draws upon the design concepts of Ni-based self-fluxing alloys and NiCrCo multi-principal element alloys to develop a NiCrCoBSi self-fluxing high-entropy alloy. The addition of B and Si elements reduces HVOF (High-Voltage-Free) oxidation of the coating. A NiCrCoBSi coating was prepared on the surface of a copper alloy using HVOF technology. During the HVOF process, the strong deoxidizing elements Si and B in the alloy preferentially react with oxygen, and the resulting oxides simultaneously vaporize, thus hindering alloy oxidation. Simultaneously, the HVOF technology promotes the formation of numerous twins and ultrafine grains in the coating, resulting in a highly wear-resistant and corrosion-resistant NiCrCoBSi high-entropy alloy coating. This provides technical support for the surface modification of copper and copper alloys in other fields and promotes the application of multi-principal element alloys in industrial applications.

[0043] 3. Beneficial effects

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) The NiCrCoBSi self-fluxing alloy of the present invention increases B and Si elements, improves HVOF spray oxidation of coating, generates a large number of twins and ultrafine grains, improves the structural stability and corrosion resistance of coating, and generates high hardness second phases such as metal carbides or metal borides, which increases wear resistance.

[0046] (2) The NiCrCoBSi high-entropy alloy coating prepared by HHVOF in this invention generates a 40-50 μm transition diffusion layer at the coating interface / substrate, which changes the bonding method between the coating and the substrate from mechanical bonding to metallurgical bonding, effectively improving the coating bonding force. Attached Figure Description

[0047] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0048] Figure 1 The BSE pattern of the NiCrCoBSi high-entropy alloy coating obtained in Example 1;

[0049] Figure 2 The elemental distribution map of EDS obtained in Example 1;

[0050] Figure 3 Microhardness spectra of the NiCrCoBSi high-entropy alloy coating and the conventional electroplated NiCo coating prepared in Example 1.

[0051] Figure 4 The wear track depth and width spectra of the NiCrCoBSi high-entropy alloy coating prepared in Example 1 and the conventional electroplated NiCo coating in a high-temperature wear test at 450°C.

[0052] Figure 5 The wear resistance spectrum obtained in Example 1;

[0053] Figure 6 The potentiodynamic polarization spectra of the NiCrCoBSi high-entropy alloy coating prepared in Example 1 and the conventional electroplated NiCo coating at room temperature in 3.5 wt.% NaCl solution are shown. Detailed Implementation

[0054] The following detailed description of exemplary embodiments of the invention is taken with reference to the accompanying drawings, which form part of the description and illustrate exemplary embodiments in which the invention may be practiced. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from the spirit and scope thereof. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not restrictive of the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0055] The embodiments of this application use a CrZrCu alloy as the base material, with the following composition and content: Cu: 98.8%, Cr: 1.00%, Zr: 0.20%.

[0056] Microhardness: The microhardness distribution of the coating was measured using an HMV-2T micro Vickers hardness tester with a diamond square pyramid indenter at a diagonal of 136°, a load of 0.1 kgf, and a loading time of 15 s. A 10 × 10 matrix of hardness points with a spacing of 30 μm was created on the coating cross-section using a high-throughput method.

[0057] High-temperature wear: To study the high-temperature wear performance of the coating, an MFT-5000 high-temperature friction and wear testing machine was used. The test temperature was 450℃, the friction pair used was a WC grinding ball with a diameter of 9.525mm, the applied force was 100N, the friction time was 2h, and the friction speed was 60r / min.

[0058] Electrochemical Testing: Electrochemical testing was conducted using a CHI-760E electrochemical workstation with a three-electrode system. The working electrode was the coated sample, and a saturated calomel electrode (SCE) was used as the reference electrode, with a pure platinum sheet as the control electrode. A 3.5 wt.% NaCl solution was used for the electrochemical testing, and the test temperature was room temperature (approximately 25°C). The test sample had a diameter of 13 mm and a thickness of 3 mm. Potentiodynamic polarization was used to obtain the self-corrosion current density and potential. The measurement voltage range was -1.5 to 1 V / CE, and the scan rate was 1 mV / s. To ensure the reliability of the results, each test was performed at least five times.

[0059] Example 1

[0060] A high corrosion-resistant and high wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method, comprising the following steps:

[0061] Step S1: Clean the substrate: Polish the surface of the CrZrCu alloy plate, and use chemical reagents such as acetone and alcohol to remove oil stains and dirt from the surface of the substrate. Then, lock and clamp the experimental plate to fix it.

[0062] Step S2, Sandblasting: The board is sandblasted using a high-efficiency sandblasting machine. The process is as follows: sandblasting pressure 0.5MPa, sandblasting angle 90°, sandblasting distance 150mm, and lateral speed 0.05m / s. After sandblasting is completed, the sandblasting quality is checked as required.

[0063] Step S3: Coating Preparation: After passing quality inspection, spraying is carried out. The process parameters are set, and the powder to be sprayed is sent to the drying oven to dry at 80℃ for 2 hours. Before spraying, the substrate is preheated by the flame of the spray gun without powder feeding. The surface temperature of the substrate is 100℃. After preheating, the coating is prepared by spraying. The spraying process is as follows: kerosene flow rate 5.5 Gal / h, oxygen flow rate controlled at 1900 SCFH, spraying distance 360mm. A NiCrCoBSi high-entropy alloy coating with a thickness of 1mm is obtained on the substrate. The powder to be sprayed is an alloy powder prepared by the aerosol method. Its composition ratio is C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.67%, Cr: 20.53%, Si: 2.67%, B: 2.33%, Co: 11.3%, and the balance is Ni.

[0064] Step S4, Diffusion Annealing: After the spraying is completed, the entire coating is placed in a vacuum heat treatment furnace and held at 940℃ for 3 hours to complete the annealing. The content ratio of each element in the obtained NiCrCoBSi high-entropy alloy coating is as follows: C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.68%, Cr: 20.59%, Si: 2.54%, B: 2.17%, Co: 11.34%, with the balance being Ni.

[0065] The NiCrCoBSi high-entropy alloy coating prepared in Example 1 has a porosity of 0.5%. Its microhardness at room temperature is 467 HV. 0.1 The wear rate is approximately 1.53 × 10⁻⁶. -5 mm·N -1 ·m -1 The potentiodynamic corrosion current density in 3.5 wt.% NaCl at room temperature is 7.83 × 10⁻⁶. -7 A·cm -2 .

[0066] The structure and properties of the coating, such as Figure 1-4As shown, it can be seen that there is obvious diffusion behavior of elements in the coating. The diffusion distance of Co is 31.2 μm, the diffusion distance of Cr is 35.0 μm, the diffusion distance of Cu is 44.1 μm, and the diffusion distance of Ni is 42.0 μm.

[0067] Example 2

[0068] A high corrosion-resistant and high wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method, comprising the following steps:

[0069] Step S1: Clean the substrate: Polish the surface of the CrZrCu alloy plate, and use chemical reagents such as acetone and alcohol to remove oil stains and dirt from the surface of the substrate. Then, lock and clamp the experimental plate to fix it.

[0070] Step S2, Sandblasting: The board is sandblasted using a high-efficiency sandblasting machine. The process is as follows: sandblasting pressure 0.4MPa, sandblasting angle 90°, sandblasting distance 180mm, and lateral speed 0.05m / s. After sandblasting is completed, the sandblasting quality is checked as required.

[0071] Step S3: Coating Preparation: After passing quality inspection, spraying is carried out. The process parameters are set, and the powder to be sprayed is sent to the drying oven to dry at 80℃ for 2 hours. Before spraying, the substrate is preheated by the flame of the spray gun without powder feeding. The surface temperature of the substrate is 100℃. After preheating, the coating is prepared by spraying. The spraying process is as follows: kerosene flow rate 5.5 Gal / h, oxygen flow rate controlled at 1900 SCFH, spraying distance 380mm. A NiCrCoBSi high-entropy alloy coating with a thickness of 1mm is obtained on the substrate. The powder to be sprayed is an alloy powder prepared by the aerosol method. Its composition ratio is C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.67%, Cr: 20.53%, Si: 2.67%, B: 2.33%, Co: 11.3%, and the balance is Ni.

[0072] Step S4, Diffusion Annealing: After spraying, the entire coating is placed in a vacuum heat treatment furnace and held at 940℃ for 4 hours to complete the annealing. The content ratio of each element in the obtained NiCrCoBSi high-entropy alloy coating is as follows: C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.68%, Cr: 20.60%, Si: 2.21%, B: 2.13%, Co: 11.34%, with the balance being Ni.

[0073] The NiCrCoBSi high-entropy alloy coating prepared in Example 2 has a porosity of 0.8%. Its microhardness at room temperature is 453 HV. 0.1 The wear rate is approximately 1.54 × 10⁻⁶. -5 mm·N -1 ·m-1 The potentiodynamic corrosion current density in 3.5 wt.% NaCl at room temperature is 7.86 × 10⁻⁶. -7 A·cm -2 .

[0074] Example 3

[0075] A high corrosion-resistant and high wear-resistant NiCrCoBSi high-entropy alloy coating and its preparation method, comprising the following steps:

[0076] Step S1: Clean the substrate: Polish the surface of the CrZrCu alloy plate, and use chemical reagents such as acetone and alcohol to remove oil stains and dirt from the surface of the substrate. Then, lock and clamp the experimental plate to fix it.

[0077] Step S2, Sandblasting: The board is sandblasted using a high-efficiency sandblasting machine. The process is as follows: sandblasting pressure 0.3MPa, sandblasting angle 90°, sandblasting distance 120mm, and lateral speed 0.05m / s. After sandblasting is completed, the sandblasting quality is checked as required.

[0078] Step S3: Coating Preparation: After passing quality inspection, spraying is performed. Process parameters are set, and the powder to be sprayed is placed in a drying oven at 80℃ for 2 hours. Before spraying, the substrate is preheated using a spray gun flame without powder feeding, with the substrate surface temperature reaching 150℃. After preheating, spraying is performed. The spraying process uses a kerosene flow rate of 6.5 Gal / h, an oxygen flow rate controlled at 2000 SCFH, and a spraying distance of 360mm. A 1mm thick NiCrCoBSi high-entropy alloy coating is obtained on the substrate. The powder to be sprayed is an alloy powder prepared by the aerosol method, comprising the following components in the following proportions: C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.67%, Cr: 20.53%, Si: 2.67%, B: 2.33%, Co: 11.3%, with the balance being Ni.

[0079] Step S4, Diffusion Annealing: After spraying, the entire coating is placed in a vacuum heat treatment furnace and held at 960℃ for 3 hours to complete the annealing. The content ratio of each element in the obtained NiCrCoBSi high-entropy alloy coating is as follows: C: 0.37%, Mo: 2.0%, Cu: 2.0%, Fe: 1.68%, Cr: 20.59%, Si: 2.43%, B: 2.11%, Co: 11.34%, with the balance being Ni.

[0080] The NiCrCoBSi high-entropy alloy coating prepared in Example 3 has a porosity of 0.9%. Its microhardness at room temperature is 452 HV. 0.1 The wear rate is approximately 1.59 × 10⁻⁶. -5 mm·N -1 ·m -1The potentiodynamic corrosion current density in 3.5 wt.% NaCl at room temperature is 7.90 × 10⁻⁶. -7 A·cm -2 .

[0081] Comparative Example 1

[0082] Comparative Example 1 uses a conventional NiCo coating prepared by electroplating. In the coating, Co: 15%, Ni: balance, and the thickness of the coating is 2 mm. The preparation method is the same as that of NiCo coating in [Wang Huiju, Chen Miao, Yang Wu. Corrosion resistance and tribological properties of NiCo / nano-SiO composite coating [J]. Journal of Northwest Normal University: Natural Science Edition, 2007, 43(6): 51-54.].

[0083] The obtained NiCo coating has a microhardness of 284 HV at room temperature. 0.1 The wear rate is approximately 7.91 × 10⁻⁶. -5 mm·N -1 ·m -1 The potentiodynamic corrosion current density in 3.5 wt.% NaCl at room temperature is 1.38 × 10⁻⁶. -5 A·cm -2 .

Claims

1. A high corrosion and wear resistant NiCrCoBSi high-entropy alloy coating, characterized in that, The weight percentage of each element is: C: 0.2%-0.5%, Mo: 1%-3.5%, Cu: 0.5%-3.5%, Fe: 0.5%-3.5%, Cr: 17%-23%, Si: 2%-4%, B: 2%-4%, Co: 10%-13%, and the balance is Ni; A transition diffusion layer of 40-50 mu m is generated at the coating interface and the substrate, and the transition diffusion layer contains a CoCrNi solid solution of FCC phase; The high-entropy alloy coating has a hardness of 450-500 HV 0.1 ; a wear rate of 1.4*10 -5 -1.6*10 - 5 mm*N -1 *m -1 under 450℃; and a corrosion current density of 7*10 -7 -8*10 -7 A*cm -2 in a 3.5wt.% NaCl solution.

2. The NiCrCoBSi high-entropy alloy coating of claim 1, wherein, The porosity of the coating is less than 1%.

3. A method of producing the NiCrCoBSi high-entropy alloy coating according to any one of claims 1-2, characterized in that, The preparation process comprises the following steps: Step S1, cleaning the substrate; Step S2, sand blasting; Step S3, preparing the coating by using a supersonic flame spraying system; Step S4, diffusion annealing.

4. The preparation method according to claim 3, characterized in that, In step S1, the substrate is a CrZrCu alloy substrate, and the components and contents are Cr: 0.5%-1.5%, Zr: 0.1%-0.3%, and Cu: balance.

5. The preparation method according to claim 3, characterized in that, In step S2, G25# steel sand is used for surface roughening treatment, and during the sand blasting process, the sand blasting pressure is 0.3-0.5 MPa, the sand blasting angle is 90°, the sand blasting distance is 120-180 mm, and the transverse speed is 0.05 m / s.

6. The preparation method according to claim 3, characterized in that, In step S3, the preheating temperature is 100-150°C, the kerosene flow rate is 5-7 Gal / h, the oxygen flow rate is 1800-2000 SCFH, and the spraying distance is 300-400 mm.

7. The preparation method according to claim 3, characterized in that, The precursor for preparing the coating is an alloy powder with a particle size of 15-53 mu m, and the weight percentage of each element is: C: 0.2%-0.5%, Mo: 1%-3.5%, Cu: 0.5%-3.5%, Fe: 0.5%-3.5%, Cr: 17%-23%, Si: 2%-4%, B: 2%-4%, Co: 10%-13%, and the balance is Ni.

8. The preparation method according to claim 3, characterized in that, In step S4, annealing is performed in a vacuum heat treatment furnace, the annealing temperature is 900-1000°C, and the annealing time is 3-10 h.

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