A high entropy alloy slurry for vacuum cladding and a method for preparing the high entropy alloy coating

Abstract

The present invention discloses a high entropy alloy slurry for vacuum cladding and a method for preparing the high entropy alloy coating thereof. By utilizing the four major effects of high entropy alloys and adopting a slurry sintering process, a uniform and dense thermal protective high entropy alloy coating can be formed on the surface of titanium and titanium alloys, thereby significantly improving their service life and reliability in high temperature and corrosive environments. The high entropy alloy slurry is composed of Mo, Cr, Fe, Co, Ni and B powder, and is mixed with polyethylene glycol, acetylated hydroxypropyl cellulose, epoxy resin and anhydrous ethanol as a binder. The specific preparation method includes the steps of configuring powder and binder in proportion, mixing alloy powder with the binder after ball milling, sandblasting the sample, slurrying, drying and vacuum cladding sintering. The process is simple and easy to implement, has low equipment requirements, controllable coating thickness, strong bonding force, good mechanical properties and corrosion resistance, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of titanium metal and titanium alloy materials, and particularly relates to a method for preparing a high-entropy alloy slurry for vacuum cladding and a high-entropy alloy coating thereof. Background Art

[0002] Titanium alloys are widely used in the aerospace industry, primarily due to their high corrosion resistance, high strength, and high-temperature resistance. These properties make them ideal materials for manufacturing aircraft and spacecraft components. Overall, the aviation industry has a decisive influence on the titanium market, and the application of titanium alloys has driven advancements in aviation technology.

[0003] Titanium alloys have an extremely high strength-to-weight ratio, rivaling steel in strength at approximately half the weight. They exhibit excellent corrosion resistance in a variety of harsh environments, particularly seawater, salt spray, and fuel. This corrosion resistance extends the service life of aircraft and spacecraft, reducing maintenance costs and frequency. In the aerospace field, titanium alloys have a low coefficient of thermal expansion and good compatibility with composites and other high-performance materials, helping to reduce stress and deformation caused by thermal expansion and ensuring the stability and reliability of aircraft structures. Furthermore, titanium alloys' biocompatibility makes them non-toxic both inside and outside the human body, making them suitable for use in astronaut equipment and life support systems.

[0004] However, titanium alloys face challenges in their use, including insufficient oxidation resistance, wear resistance, and corrosion resistance. Titanium alloys lack the oxidation resistance of some other high-temperature alloys at high temperatures. Although they can form a dense oxide film in air to protect the underlying material, this film can break down at high temperatures, making them susceptible to further oxidative corrosion. This limits their application in extreme high-temperature conditions. Titanium alloys have relatively low hardness and wear resistance, making them susceptible to wear from friction and impact. While surface treatments such as nitriding, oxidation, and coatings can improve their wear resistance, these treatments increase manufacturing and maintenance costs. In high-stress or high-wear environments, such as gears and bearings, titanium alloys may need to be combined with other materials to compensate for their lack of wear resistance. Furthermore, in certain corrosive environments (such as those containing chlorides), titanium alloys exhibit stress corrosion cracking (SCC) and hydrogen embrittlement.

[0005] Therefore, surface modification research—the preparation of coatings or surface protective films on titanium and titanium alloys—has become a current research hotspot. High-entropy alloys (HEAs) possess unique elemental compositions, arrangements, and interaction potential fields. Scholars have summarized their properties as "four major effects": the thermodynamic high entropy effect, the structural lattice distortion effect, the kinetic hysteresis diffusion effect, and the "cocktail" effect. HEAs exhibit exceptional corrosion resistance due to their unique multi-element composition and solid solution structure. The intersolubility of different elements and the high mixing entropy effect help inhibit the formation of intermetallic compounds, resulting in a more uniform and stable chemical composition and, consequently, improved corrosion resistance in corrosive media. HEA coatings contain a variety of high-temperature-resistant elements, such as chromium (Cr), nickel (Ni), and aluminum (Al). These elements form a stable oxide film at high temperatures, significantly enhancing the coating's oxidation resistance. The high entropy effect and slow diffusion effect contribute to the coating's excellent thermal stability and uniformity. The coating undergoes no significant phase transformation or element segregation at high temperatures, ensuring its stable performance in complex environments.

[0006] Currently, common methods for preparing high-entropy alloy coatings include thermal spraying, laser cladding, magnetron sputtering, electrodeposition, and plasma cladding. These technologies all have limitations: magnetron sputtering is inefficient and takes a long time to prepare; thermal spraying has high porosity and may have weak bonding; and electrodeposition is difficult to control compositionally, resulting in uneven coatings and limited thickness.

[0007] Chinese patents CN 117344306 A, CN 108103494 A, CN 118531393 A, and CN 106319513 A all utilize laser cladding to produce high-entropy alloy coatings of various systems. Laser cladding has the following disadvantages: 1. High equipment cost: Laser cladding systems typically require a high-performance laser, a precision motion platform, and supporting powder feeding equipment, all of which are relatively expensive to purchase and maintain. 2. Risk of cracking: During the laser cladding process, rapid cooling due to high energy density can generate thermal stress within the coating. This stress is more pronounced when the coating is thick, and can easily lead to cracking or fissures, affecting the coating's performance and service life. 3. Limited coating thickness: Laser cladding is suitable for producing thin coatings, typically ranging from a few hundred microns to a few millimeters. Overly thick coatings can cause substrate deformation due to concentrated thermal stress, affecting the overall quality of the coating and reducing its effectiveness. 4. Difficulty controlling the melt pool: During the laser cladding process, melt pool stability is crucial. The temperature, shape, and flow state of the molten pool need to be precisely controlled. Any instability will lead to defects such as uneven coating thickness, pores, or inclusions. Using this process, it is difficult to control the porosity of the coating and it is difficult to ensure the quality of the coating.

[0008] Chinese patent CN 103556146 A mixes an organic solvent with 200-mesh metal powders of Fe, Cr, Cu, Ni, Co, Mn, and Mo. The alloy powder is then clad onto the substrate surface using gas tungsten arc welding (TIG). While TIG cladding offers good quality, it also has disadvantages: 1. Slow cladding speed: TIG welding has a relatively low welding speed, which can reduce production efficiency, especially when large cladding thicknesses are required. 2. High heat input: Due to the long dwell time required during welding, the heat input is relatively high, which can cause overheating, deformation, and structural changes in the heat-affected zone (HAZ). 3. High operational requirements: TIG welding requires high operator skill and requires experienced welders to ensure weld quality, especially in controlling welding parameters during the cladding process. 4. High material cost: TIG welding often uses expensive welding materials (such as high-purity tungsten electrodes and specialized welding wire), increasing overall material costs. This method is difficult to meet large-scale product demand and is subject to process instability.

[0009] How to simply and efficiently prepare a coating with high hardness, corrosion resistance, wear resistance and high-temperature oxidation resistance on the surface of complex titanium and titanium alloy workpieces is the technical problem to be solved by the present invention. Summary of the Invention

[0010] The purpose of the present invention is to provide a high entropy alloy slurry for vacuum cladding and a method for preparing a high entropy alloy coating on the surface of titanium or titanium alloy in response to the problems existing in the prior art. By utilizing the four major effects of high entropy alloys and applying slurry followed by vacuum cladding and sintering, a uniform and dense thermal protective high entropy alloy coating can be prepared on the surface of complex workpieces of titanium and titanium alloys, thereby significantly improving its service life and reliability in high temperature and corrosive environments and significantly reducing production costs. The method also has the advantages of being easy to operate, simple in required equipment, reliable and stable in process, and capable of realizing industrial production. The coating obtained by this method has high hardness, uniform structure, low porosity and controllable coating thickness.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] The present invention first provides a high-entropy alloy slurry for vacuum cladding, comprising a high-entropy alloy powder and a binder. The high-entropy alloy powder comprises, by atomic percentage, 3-4 at.% B, 22-24 at.% Cr, 23-25 ​​at.% Fe, 2.5-3.5 at.% Mo, 11-13 at.% Co, with the remainder being Ni. The binder comprises, by mass percentage, 1-5 wt.% polyethylene glycol, 1-5 wt.% acetylated hydroxypropyl cellulose, 1-2 wt.% epoxy resin, with the remainder being anhydrous ethanol.

[0013] In the above technical solution, B, Cr, Fe, Mo, Co, and Ni in the high-entropy alloy powder are provided by B, Cr, Fe, Mo, Co, and Ni metal element powders, wherein the purity of Mo, Cr, Fe, B, Co, and Ni powders are all analytically pure, and the powder particle size is all less than 100 microns.

[0014] In the above technical solution, the number average molecular weight Mn of the polyethylene glycol in the binder is 6000-20000, preferably Mn is 20000; the epoxy equivalent weight of the epoxy resin is 180-200 g / eq.

[0015] Furthermore, the slurry composition is: 85 wt.% high entropy alloy powder and 15 wt.% binder.

[0016] The present invention further provides a method for preparing the high entropy alloy slurry for vacuum cladding, comprising the following steps:

[0017] (1) Weighing Mo, Cr, Fe, Co, Ni, and B metal powders according to atomic ratio, placing the powders in a ball mill for 15 h at a speed of 350-420 rpm, and then pouring out for later use to obtain high entropy alloy powder;

[0018] (2) polyethylene glycol, acetylated hydroxypropyl cellulose, epoxy resin, and anhydrous ethanol were weighed and mixed according to the binder formulation, and then ball milled in a ball mill for 1 h at a ball milling speed of 300 rpm to obtain a binder;

[0019] (3) The high entropy alloy powder and the binder are mixed in proportion and mechanically stirred to obtain a high entropy alloy slurry.

[0020] The present invention also provides a method for preparing a high entropy alloy coating on a titanium / titanium alloy surface by vacuum cladding using the high entropy alloy slurry. The method comprises the following steps:

[0021] (1) Sample pretreatment: The titanium / titanium alloy samples were sandblasted to remove surface impurities and increase surface roughness to promote coating adhesion; the sandblasted samples were cleaned with anhydrous ethanol and dried to ensure that the surface was clean and free of oil.

[0022] (2) Slurry coating: Immerse the sample pretreated in step (1) into the prepared high entropy alloy slurry and stir it gently for 10-15 seconds to ensure that the sample surface is evenly coated with slurry; in order to increase the coating thickness, the sample after slurry coating can be uniformly dried in a vacuum drying oven at 500°C for 70-80 minutes and then cooled to 50°C; the binder ratio remains unchanged, and secondary slurry coating or repeated slurry coating is performed, with a slurry coating thickness of 1.5-2.2 mm, preferably a slurry coating thickness of 2 mm.

[0023] (3) Drying: Place the sample after coating in a drying oven and keep it at 500℃ for 70 minutes to make the coating fully dry and the residual gas after thermal decomposition of organic matter in the coating completely overflow.

[0024] (4) Vacuum cladding sintering: Place the dried sample in a vacuum sintering furnace and keep it at 1320-1360℃ for 40-60min. This step helps to form a good metallurgical bond between the coating and the substrate, improving the mechanical properties and corrosion resistance of the coating. Subsequently, the sample is cooled in the furnace. After the vacuum sintering furnace is cooled to 50℃, the sample is taken out and the residue on the surface of the sample is rinsed with running water, then cleaned again with anhydrous ethanol, and finally dried to obtain the final high-entropy alloy coating.

[0025] Furthermore, the vacuum degree of the vacuum cladding sintering is 10 -4 Below Pa.

[0026] Furthermore, the heating rate of the vacuum cladding sintering is 5-10°C / min, specifically, the heating rate is 10°C / min within the temperature range of 50-500°C, the heating rate is 8°C / min within the temperature range of 500-1000°C, and the heating rate is 5°C / min above 1000°C.

[0027] Beneficial effects of the present invention:

[0028] The present invention first designs a MoCrFeCoNiB high entropy alloy powder, and improves the corrosion resistance and wear resistance of the coating by adjusting the element dosage.

[0029] As the Cr content gradually increases from a low content (such as 5%), the corrosion resistance will be significantly improved. This is because Cr can form a stable passivation film (such as Cr2O3), which effectively prevents matrix corrosion. At the same time, the high-temperature strength usually increases gradually, and Cr can enhance the stability of the alloy at high temperatures. After reaching a certain Cr content (usually between 15% and 25%), the corrosion resistance will tend to saturate, and the effect of further increasing the Cr content will weaken. At extremely high Cr contents, the structure of the alloy may become brittle, affecting the corrosion resistance, and the high-temperature strength will also decrease.

[0030] The presence of Fe helps stabilize the formation of FCC or BCC phases, improving the alloy's structural stability. The recommended range is 15-25%. When the Fe content is gradually increased from a low level (e.g., 10%), the alloy's structural stability generally improves. Within the moderate range of 15-30%, increasing Fe continues to improve structural stability, enhancing the alloy's durability and deformation resistance. Once the iron content exceeds the threshold of 30%, the alloy may experience phase transformation or increased brittleness, resulting in a decrease in structural stability.

[0031] Co maintains strength and hardness in high-temperature environments and is an important element in high-temperature alloys. As the Co content gradually increases from a low content (such as 5%), the strength and hardness of the alloy generally increase significantly. Co can enhance the high-temperature strength and toughness of the alloy and improve its mechanical properties. In the medium range of 5-15%, the strength and hardness generally continue to increase, and the increase in Co helps to improve the structural stability of the alloy. When the Co content reaches a certain threshold (usually between 15% and 20%), the strength and hardness may reach a peak, at which point the effect of further increasing the Co content on performance improvement is weakened. At extremely high Co contents (such as more than 20%), increased brittleness or phase transformation may occur, resulting in a decrease in strength and hardness.

[0032] When the Ni content is gradually increased from a low content (such as 10%), ductility significantly improves. This is because Ni stabilizes the FCC structure and enhances the toughness of the alloy. Ductility may reach a peak in the 15-20% content range. At this point, the alloy's microstructure has been optimized, and toughness and ductility have been significantly enhanced. When the content exceeds 20%, ductility may begin to decline. This is because excessive Ni may cause phase transformation, lattice distortion, or interactions in the alloy, affecting the overall mechanical properties of the alloy.

[0033] B can significantly refine the grains and improve the comprehensive mechanical properties of the alloy. As the B content increases from 0.5% to 4%, the grain size of the alloy usually decreases significantly. The addition of B can promote the formation of crystal nuclei, thereby effectively refining the grains. In the range of 0.5%-4%, the grain refining effect is most obvious. At this time, the refined grains can improve the mechanical properties of the alloy, such as strength and toughness. When the B content is further increased to more than 4%, the grain refining effect may tend to saturation, and the degree of refinement will no longer be significantly improved. At very high B contents (more than 5%), it may cause grain growth or the production of other phases, which in turn affects the microstructural stability of the alloy.

[0034] The addition of Mo can refine the microstructure of the alloy, forming a mixed phase structure of FCC phase and σ phase. As the Mo content increases from 5% to 15%, the microstructure of the alloy is generally significantly refined. Mo can promote phase transformation and nucleation, which helps to improve the uniformity and refinement of grains. When the Mo content is increased in the initial stage, the hardness of the alloy is generally also significantly improved. When the Mo content reaches between 15-20%, the refinement effect and hardness improvement may tend to saturate, and the effect of further increasing the Mo content on performance improvement will weaken. However, excessive Mo may cause Cr precipitation, affecting the overall performance of the alloy. Excessive Mo may cause microstructure inhomogeneity, affecting the phase stability of Fe, and thus affecting the toughness of the alloy. In addition, excessive Mo may interfere with the solid solution strengthening effect of B, affecting the overall structural stability of the alloy. To achieve better results, we control the Mo content within 5-10%.

[0035] Combining the chemical composition of high-entropy alloy powder and substrate, the present invention designs a binder, in which polyethylene glycol has good lubricating properties, can reduce friction between materials, improve the processing performance of materials during the preparation process, and can give the material a certain flexibility, thereby enhancing the toughness and crack resistance of the coating. Acetylated hydroxypropyl cellulose is a commonly used thickener that can significantly increase the viscosity of the slurry and prevent the sedimentation of dispersed particles. It has good film-forming properties and can form a uniform film layer after the coating dries, thereby enhancing the density and durability of the coating. Varnish has good adhesion and can form a protective film on the surface to prevent the external environment from eroding the coating and improve corrosion resistance. Acetylated hydroxypropyl cellulose as a thickener, combined with polyethylene glycol, can prevent particle sedimentation and maintain a uniform distribution of the slurry; at the same time, the adhesion of the varnish ensures that the coating is firmly adhered to the substrate. The combination of the three can provide better adhesion and ensure the stability and uniformity of the coating during the preparation process.

[0036] The present invention mixes MoCrFeCoNiB high-entropy alloy powder with a specific binder to form a slurry. The method of using the high-entropy alloy slurry to prepare a coating on the complex surface of titanium and titanium alloys through slurry sintering has significant advantages in terms of equipment cost, process simplicity, coating quality, and bonding strength. The required equipment is relatively simple and does not require expensive lasers or vacuum systems, which greatly reduces operating and maintenance costs. It is easy to mass produce, the coating thickness is controllable, and the production efficiency is high. The preparation efficiency of the high-entropy alloy coating is significantly improved, and the utilization efficiency of the powder is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The surface morphology of the coating after drying (left) and vacuum cladding (right) in Example 4;

[0038] Figure 2The surface morphology of the coating after drying (left) and vacuum cladding (right) in Example 5;

[0039] Figure 3 The surface morphology of the coating after drying (left) and vacuum cladding (right) in Example 6;

[0040] Figure 4 This is the EDS characterization spectrum of the high entropy alloy coating prepared in Example 4;

[0041] Figure 5 This is the EDS characterization spectrum of the high entropy alloy coating prepared in Example 5;

[0042] Figure 6 This is the EDS characterization spectrum of the high entropy alloy coating prepared in Example 6;

[0043] Figure 7 This is the morphology of the interface area of ​​the high entropy alloy coating prepared in Example 6;

[0044] Figure 8 This is the XRD characterization spectrum of the high entropy alloy coating prepared in Example 6. DETAILED DESCRIPTION

[0045] The present invention is described in detail below with reference to the embodiments.

[0046] The raw materials used in the following specific examples of the present invention are as follows:

[0047] The substrate material is Ti-6Al-4V (Grade 5).

[0048] Cobalt (Co) powder (99.9%), with a particle size of <10 μm, was purchased from Sigma-Aldrich.

[0049] Chromium (Cr) powder (99.5%), particle size <20 μm, was purchased from Alfa Aesar.

[0050] Iron (Fe) powder (99.9%), particle size <10 μm, was purchased from Merck.

[0051] Molybdenum (Mo) powder (99.5%), particle size <15 μm, was purchased from Alfa Aesar.

[0052] Nickel (Ni) powder (99.8%), particle size <30 μm, was purchased from Alfa Aesar.

[0053] Boron (B) powder (99.5%), particle size <48 μm, was purchased from Alfa Aesar.

[0054] Polyethylene glycol (Mn 20000) was purchased from aladdin.

[0055] Epoxy resin (EPON Resin 828), viscosity 110-150 P, purchased from Hexion.

[0056] All raw materials and reagents not otherwise specified in the present invention can be obtained commercially. Example 1

[0057] The high entropy alloy powder composition is: 3at.% B powder, 22at.% Cr powder, 23at.% Fe powder, 2.5at.% Mo powder, 11at.% Co powder, 38.5at.% Ni powder.

[0058] The metal powder was milled in a ball mill with a ball-to-powder ratio of 15:1. Zirconia ceramic balls were used, with a ratio of large, medium, and small balls of 3:5:2. The milling speed was 450 r / min, and the milling time was 13 hours. The milled powder was pressed into 10 x 10 x 10 mm blocks, and metallographic microscopy was performed on the samples. The resulting high-entropy alloy powder exhibited good uniformity, with the crystal phase primarily remaining in its initial state and a small particle size, showing no significant phase transition. Example 2

[0059] The difference between this embodiment and embodiment 1 is that the ball mill speed is 300 r / min and the ball milling time is 18 h. Metallographic microscopic observation shows that the powder particle size is reduced and some crystal phases are transformed into unstable phases, resulting in a decrease in material performance. Example 3

[0060] This example differs from Example 1 in that the ball mill speed was 330 r / min and the milling time was 15 h. Metallographic microscopy revealed a moderate powder particle size, a stable crystal phase, and excellent physical and chemical properties. Further increasing the ball mill speed within this milling time can yield a smaller powder particle size while maintaining the crystal phase. Example 4

[0061] (1) Sample pretreatment: The sample was sandblasted and then cleaned and dried with anhydrous ethanol;

[0062] (2) Preparation of slurry: The high entropy alloy powder composition is: 3at.% B powder, 22at.% Cr powder, 23at.% Fe powder, 2.5at.% Mo powder, 11at.% Co powder, 38.5at.% Ni powder. The prepared powder is placed in a ball mill and ground for 15 hours at a speed of 350 r / min. Then it is removed and set aside. The binder composition is: 3wt.% polyethylene glycol, 1% acetylated hydroxypropyl cellulose, 1% epoxy resin, and the remainder is anhydrous ethanol. The prepared binder is placed in a ball mill and ground for 1 hour at a speed of 300 r / min. Then it is removed and set aside. The slurry composition is: 85wt.% high entropy alloy powder, 15wt.% binder.

[0063] (3) Slurry coating: immerse the titanium alloy in the slurry, stir it slightly, and take it out after 10 seconds. The slurry coating thickness is 1.5 mm;

[0064] (4) Drying: Place the coated sample in a vacuum drying oven and keep it at 500°C for 70 min to fully dry the coating and prevent bubbles during the sintering process;

[0065] (5) Vacuum cladding sintering: The dried sample is placed in a vacuum sintering furnace and kept at 1320 °C for 40 min. The sample is cooled with the furnace. After the vacuum sintering furnace is cooled to 50 °C, the sample is taken out and washed with anhydrous ethanol, and then dried to obtain a high-entropy alloy coating. Example 5

[0066] (1) Sample pretreatment: The sample was sandblasted and then cleaned with anhydrous ethanol and dried;

[0067] (2) Preparation of slurry: The high-entropy alloy powder composition is: 3 at. % B powder, 23 at. % Cr powder, 24 at. % Fe powder, 3% Mo powder, 12 at. % Co powder, and 35 at. % Ni powder. The prepared powder is placed in a ball mill and ground for 15 h at a speed of 390 r / min. Then, it is removed and set aside. The binder composition is: 4% polyethylene glycol, 3% acetylated hydroxypropyl cellulose, 1% epoxy resin, and the remainder is anhydrous ethanol. The prepared binder is placed in a ball mill and ground for 1 h at a speed of 300 r / min. Then, it is removed and set aside. The slurry composition is: 85 wt. % high-entropy alloy powder, 15 wt. % binder.

[0068] (3) Slurry coating: immerse the titanium alloy in the slurry, stir it slightly, and take it out after 13 seconds. The slurry coating thickness is 1.8 mm.

[0069] (4) Drying: Place the coated sample in a vacuum drying oven and keep it at 500°C for 70 min to fully dry the coating and prevent bubbles during the sintering process;

[0070] (5) Vacuum cladding sintering: The dried sample is placed in a vacuum sintering furnace and kept at 1340°C for 50 minutes. The sample is cooled with the furnace. After the vacuum sintering furnace is cooled to 50°C, the sample is taken out and washed with anhydrous ethanol, and then dried to obtain a high-entropy alloy coating. Example 6

[0071] (1) Sample pretreatment: The sample was sandblasted and then cleaned with anhydrous ethanol and dried;

[0072] (2) Preparation of slurry: The high-entropy alloy powder composition is: 4 at. % B powder, 24 at. % Cr powder, 25 at. % Fe powder, 3.5 at. % Mo powder, 13 at. % Co powder, and the balance is Ni powder. The prepared powder is placed in a ball mill and ground for 15 h at a speed of 420 r / min, then removed and set aside. The binder composition is: 4% polyethylene glycol, 5% acetylated hydroxypropyl cellulose, 2% epoxy resin, and the balance is anhydrous ethanol. The prepared binder is placed in a ball mill and ground for 1 h at a speed of 300 r / min, then removed and set aside. The slurry composition is: 85 wt. % high-entropy alloy powder, 15 wt. % binder.

[0073] (3) Slurry coating: immerse the titanium alloy in the slurry, stir it slightly, and take it out after 15 seconds. The slurry coating thickness is about 2.1 mm;

[0074] (4) Drying: Place the coated sample in a vacuum drying oven and keep it at 500°C for 70 minutes to fully dry the coating and prevent bubbles during the sintering process;

[0075] (5) Vacuum cladding sintering: The dried sample is placed in a vacuum sintering furnace and kept at 1360°C for 60 minutes. The sample is cooled with the furnace. After the vacuum sintering furnace is cooled to 50°C, the sample is taken out and washed with anhydrous ethanol, and then dried to obtain a high-entropy alloy coating.

[0076] Performance indicators and specific testing methods of the product of the present invention:

[0077] The high-entropy alloy coating prepared by the present invention has few micropores and no cracks, and the coating thickness after vacuum cladding and sintering is ≥1 mm. Taking Example 6 as an example, the cross-section was cut and observed, and 10 different areas at the interface and the coating were observed. The porosity of the coating was calculated using Image J software. The maximum and minimum values ​​were removed, and the remaining data were averaged to obtain a coating porosity of 1.86%, which is significantly lower than the coating porosity of the laser cladding process and the tungsten inert gas welding cladding process.

[0078] The high-entropy alloy coating prepared by this invention primarily consists of FCC and σ phases. Nanoindentation hardness testing revealed that the FCC phase has a hardness between 3.94 and 4.07 GPa, while the σ phase region reaches a hardness of 7.35 GPa, and the FCC + σ phase region reaches a hardness of 5.82 to 6.23 GPa, resulting in an overall hardness of 7.79 to 8.14 GPa. This is significantly higher than the hardness of titanium and titanium alloys. The coating's hardness increases with increasing Mo content, which is related to the increased area of ​​the σ phase.

[0079] High-temperature oxidation resistance is tested using a muffle furnace. The coating and substrate samples are cleaned to remove surface contaminants (such as grease, dust, etc.). Sample dimensions are measured, ensuring that each sample's initial condition is recorded. The sample is placed in the muffle furnace and heated at an 8°C / min ramp rate. The temperature is monitored to ensure a steady rise to 800°C. The oxidation treatment is maintained at 800°C for 12 hours, with temperature monitored regularly to ensure stability. After treatment, the sample is cooled in the muffle furnace. Once the furnace cools to room temperature, the sample is removed and cross-sectionally analyzed to investigate any failure behaviors such as cracking or flaking in the coating, which are then compared to the substrate.

[0080] Corrosion resistance was tested comparatively using 3.5% NaCl solution and 4% HF solution. Prepare coating samples (2 × 2 cm), ensuring their surfaces are smooth and clean, and record the initial mass. Sample size should be consistent to ensure comparability across experiments. Completely immerse the samples in both the NaCl solution and the HF solution, recording the time of immersion start. Set the immersion time to 48 hours and remove the samples after the time is up. After removing the samples, rinse them with deionized water to remove surface salt and gently dry them. Measure the mass of each sample using a precision balance, recording the mass change before and after immersion. Weight loss = initial mass − mass after immersion.

[0081] Table 1 High entropy alloy coating performance test results

[0082] .

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A high entropy alloy slurry for vacuum cladding, characterized in that: The high-entropy alloy slurry comprises, by mass percentage, 85 wt.% of a high-entropy alloy powder and 15 wt.% of a binder; the high-entropy alloy powder comprises, by atomic percentage, 3-4 at.% B, 22-24 at.% Cr, 23-25 ​​at.% Fe, 2.5-3.5 at.% Mo, 11-13 at.% Co, and the remainder Ni; the binder comprises, by mass percentage, 1%-5% polyethylene glycol, 1%-5% acetylated hydroxypropyl cellulose, 1-2% epoxy resin, and the remainder anhydrous ethanol.

2. The high entropy alloy slurry for vacuum cladding according to claim 1, characterized in that: The Mo, Cr, Fe, B, Co and Ni elements in the high entropy alloy powder are provided by Mo, Cr, Fe, B, Co and Ni metal single substance powders respectively. The purity of the metal single substance powders is analytically pure and the powder particle size is less than 100 microns.

3. The high entropy alloy slurry for vacuum cladding according to claim 1, characterized in that: In the binder, the number average molecular weight of the polyethylene glycol is 6000-20000; and the epoxy equivalent weight of the epoxy resin is 180-200 g / eq.

4. The method for preparing a high entropy alloy slurry for vacuum cladding according to any one of claims 1 to 3, characterized in that: The steps include: (1) Weighing Mo, Cr, Fe, Co, Ni, and B metal powders according to the atomic percentages, placing them in a ball mill and milling them for 15 hours at a speed of 350-420 rpm to obtain high entropy alloy powder; (2) Weighing raw materials according to the mass percentage of the binder, mixing, placing in a ball mill for 1 hour at a ball milling speed of 300 rpm to obtain a binder; (3) The high entropy alloy powder and the binder are mixed in proportion and mechanically stirred to obtain the high entropy alloy slurry for vacuum cladding.

5. A method for preparing a high entropy alloy coating, characterized in that: The steps include: (1) Sample pretreatment: sandblast the sample, clean and dry it; (2) Slurry coating: immerse the sample pretreated in step (1) in the high entropy alloy slurry for vacuum cladding according to any one of claims 1 to 3, and stir slightly to make the surface of the sample evenly coated with slurry; (3) Drying: Place the sample after slurry coating in a drying oven and keep it at 500℃ for 70-80min; (4) Vacuum cladding sintering: Place the dried sample in a vacuum sintering furnace and keep it at 1320-1360℃ for 40-60min; the sample is cooled with the furnace, and after the temperature drops to 50℃, the sample is taken out, cleaned, and dried to obtain a high-entropy alloy coating.

6. The method for preparing a high entropy alloy coating according to claim 5, wherein: The thickness of the slurry in step (2) is 1.5-2.2 mm.

7. The method for preparing a high entropy alloy coating according to claim 5, wherein: The slurrying described in step (2) also includes drying the sample at 500°C for 70-80 minutes after slurrying, cooling it to below 50°C, and then repeatedly slurrying to increase the slurrying thickness.

8. The method for preparing a high entropy alloy coating according to claim 5, wherein: The vacuum degree of the vacuum cladding sintering is less than 10 -4 Pa, the heating rate of the vacuum cladding sintering is 5-10°C / min.

9. The method for preparing a high entropy alloy coating according to claim 8, wherein: The vacuum cladding sintering has a heating rate of 10°C / min at a temperature of 50-500°C; a heating rate of 8°C / min at a temperature of 500-1000°C; and a heating rate of 5°C / min at a temperature above 1000°C.

10. The method for preparing a high entropy alloy coating according to claim 5, wherein: The material of the sample is titanium or titanium alloy.

Images