High-entropy amorphous coating based on thermal spraying and preparation process

Abstract

The application discloses a high-entropy amorphous coating based on thermal spraying and a preparation process, relates to the field of amorphous alloy new materials, and comprises an alloy system and a transition group metal system; the alloy system accounts for 67wt%-75wt% of the total mass of the coating, and the transition group metal system accounts for 25wt%-33wt% of the total mass of the coating; the alloy system comprises the following components: Cr, B, Si, and the balance is Fe. According to the application, the mass proportion of the alloy system and the transition group metal system is accurately controlled, the specific contents of Cr, B, Si and the Fe matrix are matched, the transition group metal system is composed of transition group metals such as Ni, Co and Mo which are not repeated, meanwhile, the coating corresponding to the alloy system can form a bulk amorphous alloy with an amorphous forming critical size not less than 1mm, the amorphous forming capacity and the structural stability of the coating are effectively improved, and a component basis is laid for excellent performance of the subsequent coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of amorphous alloy new materials, and particularly relates to a high-entropy amorphous coating based on thermal spraying and a preparation process. BACKGROUND

[0002] Since the concept of high-entropy alloy was proposed, breakthroughs have been continuously made in this field in the past 20 years, showing strong technical vitality and broad application prospects. As a typical representative of multi-component alloys, high-entropy alloys are characterized by the combination of five or more elements, and the atomic percentage of each element is basically controlled within the range of 5%-35%. This new system, which breaks the traditional single / dual main component alloy design paradigm, endows the material with unique physical-chemical-mechanical properties through the synergistic effect of multiple components.

[0003] Studies have shown that under certain thermal spraying process conditions, some high-entropy alloys can spontaneously form amorphous structures, i.e., high-entropy amorphous coatings. This coating not only inherits the composition characteristics of multi-component non-main elements of high-entropy alloys, but also has excellent properties of amorphous alloys, including high strength, high hardness, excellent wear resistance and corrosion resistance, thus showing revolutionary application value in the field of high-end equipment protection.

[0004] Amorphous alloys are a kind of metallic materials with short-range order and long-range disordered atomic arrangement, which are usually formed under high cooling rate (10 5 -10 6 K / s). Its microstructure without crystal defects (dislocations, grain boundaries, precipitates, etc.) endows the material with excellent mechanical properties, wear resistance and corrosion resistance. Among them, iron-based amorphous alloys have an important position in industrial applications due to their low cost and excellent performance. However, the large-scale application of iron-based metallic glasses still faces two technical bottlenecks:

[0005] Firstly, its formation requires extremely high cooling rate, limiting the choice of forming process;

[0006] Secondly, it is easy to undergo crystallization transformation during the manufacturing process or in high-temperature service environment, leading to performance degradation or even failure. SUMMARY

[0007] To solve the above technical problems, the present application provides a high-entropy amorphous coating based on thermal spraying and a preparation process. The following technical solutions are adopted:

[0008] The high-entropy amorphous coating based on thermal spraying includes an alloy system and a transition metal system;

[0009] The alloy system accounts for 67wt%-75wt% of the total mass of the coating, and the transition metal system accounts for 25wt%-33wt% of the total mass of the coating;

[0010] The alloy system comprises the following components: Cr 28wt%-35wt%, B 3wt%-6wt%, Si 1wt%-2wt%, with the balance being Fe;

[0011] The transition metal system comprises the following components: 15wt%-18wt% of transition metal A, 9wt%-12wt% of transition metal D, and 1wt%-3wt% of transition metal C;

[0012] The alloy system corresponding to the coating forms a bulk amorphous alloy, and the coating, after being prepared by thermal spraying, exhibits typical amorphous peak characteristics when detected by XRD.

[0013] Optionally, the A-group metal, D-group metal, and C-group metal are all selected from Ni, Co, Mo, Nb, and Cu, and the three transition metals are not repeated.

[0014] Optionally, when the alloy system corresponding to the coating forms a bulk amorphous alloy, the critical size Dc for amorphous formation is greater than or equal to 1 mm.

[0015] Optionally, the thermal spraying process for preparing the coating is selected from atmospheric plasma spraying or supersonic flame spraying.

[0016] A process for preparing a high-entropy amorphous coating based on thermal spraying, comprising the following steps:

[0017] Step 1: Select Fe, Cr, B, Si powders and A, B, C transition metal powders with a purity of ≥99.5% according to the composition ratio of the coating to prepare a uniformly mixed raw material powder.

[0018] Step 2: Place the raw material powder from Step 1 in an inert atmosphere and prepare the master alloy ingot using an electric arc melting method. During the melting process, repeatedly turn the ingot over 4-5 times to ensure that the composition of the master alloy ingot is uniform.

[0019] Step 3: Prepare alloy powder from the master alloy ingot of Step 2 using gas atomization powder making technology;

[0020] Step 4: Using atmospheric plasma spraying or supersonic flame spraying, the alloy powder from Step 3 is sprayed onto the pretreated substrate surface to form a coating.

[0021] Step 5: Perform XRD analysis on the coating obtained in Step 4 until XRD is detected. The presence of typical amorphous steamed bun peaks with a full width at half maximum (FWHM) greater than or equal to 5° within the range, without obvious crystallization impurity peaks, indicates the formation of a high-entropy amorphous coating based on thermal spraying. The angle between the incident X-rays and the surface of the high-entropy amorphous coating sample to be tested in XRD detection;

[0022] Optionally, in step 1, after removing impurities by passing all powders through a 100-120 mesh sieve, they are placed in a planetary ball mill and mixed for 2-3 hours with anhydrous ethanol as the dispersant, a ball-to-material ratio of (8-10):1, and a rotation speed of 200-250 r / min. Subsequently, they are dried in a vacuum drying oven at 60-80℃ for 1-1.5 hours to obtain uniformly mixed raw material powder.

[0023] Optionally, step 2 includes the following detailed steps:

[0024] The dried raw material powder from step 1 is placed into a water-cooled copper crucible, and argon gas is introduced as a protective atmosphere. The raw material is then melted in a non-consumable arc furnace. During the melting process, the raw material is first pre-melted with a current of 300A-400A for 1-2 minutes to remove adsorbed gas on the surface. Then, it is mainly melted with a current of 500A-600A for 3-5 minutes. After each melting, the alloy ingot is rotated 180° and the melting process is repeated 4-5 times to ensure uniform composition. After cooling, the master alloy ingot is obtained.

[0025] Optionally, step 3 includes the following detailed steps:

[0026] The master alloy ingot from step 2 is crushed into 5mm-10mm particles and fed into a gas atomization powder-making device; argon is used as the atomizing gas, and the atomization pressure is controlled at 4MPa-6MPa, the molten metal droplet falling height is 800mm-1000mm, and the cooling rate is greater than or equal to 10. 4 K / s, prepare alloy powder; then screen through a three-layer vibrating screen, the upper, middle and lower layers of the three-layer vibrating screen are respectively made of 45μm, 15μm and 10μm mesh, to collect powder of 15μm-45μm, and place it in a vacuum drying oven at 100℃-120℃ for 2-2.5h to obtain powder for spraying.

[0027] Optionally, step 4 includes the following detailed steps:

[0028] Select the thermal spraying process according to the coating performance requirements: If atmospheric plasma spraying is used, set the working gas to be a mixture of argon and hydrogen, the spraying power to be 28kW-32kW, the spraying distance to be 100-120mm, and the powder feeding rate to be 30g / min-40g / min.

[0029] If supersonic flame spraying is used, set the fuel flow rate to 20L / h-25L / h, the oxygen flow rate to 80L / h-90L / h, the spraying distance to 250mm-280mm, and the powder feeding rate to 25g / min-35g / min. During the spraying process, monitor the substrate temperature in real time with an infrared thermometer and control the substrate temperature to be less than or equal to 200℃ to avoid coating crystallization. Place the sprayed coating in a vacuum annealing furnace with a vacuum degree of less than or equal to 10⁻³Pa, heat it to 300℃-350℃ at a rate of 5K / min-8K / min, hold it at that temperature for 1.5-2 hours, and then cool it to room temperature with the furnace to complete stress release and form the coating.

[0030] Optionally, if atmospheric plasma spraying is used in step 4, the spray gun should be preheated before spraying: heat the spray gun to 150℃-200℃ with an argon flow rate of 10L / min-15L / min and keep it at that temperature for 20min-30min to prevent the powder from condensing and clogging inside the spray gun in the early stage of spraying.

[0031] In summary, the present invention has at least one of the following beneficial technical effects:

[0032] This invention provides a high-entropy amorphous coating and its preparation process based on thermal spraying. By precisely controlling the mass ratio of the alloy system and the transition metal system, and combining specific contents of Cr, B, Si and Fe matrix, and selecting non-overlapping transition metals such as Ni, Co and Mo to form the transition metal system, it ensures that the corresponding alloy system of the coating can form a bulk amorphous alloy with a critical amorphous formation size of not less than 1 mm. This effectively improves the amorphous formation ability and structural stability of the coating, laying the compositional foundation for the excellent performance of the coating.

[0033] In the raw material pretreatment stage, sieving, planetary ball milling, and vacuum drying are used to ensure uniform mixing of raw material powder with low impurity content. The master alloy ingot preparation adopts non-consumable arc melting under argon protection, combined with pre-melting degassing and repeated turning melting to ensure the uniformity of composition of the master alloy ingot. The gas atomization powder making process controls the atomization pressure, droplet fall height, and cooling rate, combined with screening with a vibrating screen of a specific aperture and vacuum drying, to obtain a powder with suitable particle size and good flowability for spraying. All stages work together to improve the quality of raw materials and intermediate products and reduce defects in subsequent coatings.

[0034] During thermal spraying and post-treatment, atmospheric plasma spraying or supersonic flame spraying can be flexibly selected according to performance requirements. By optimizing parameters such as working gas ratio, spraying power, distance, and powder feeding rate, and combining infrared thermography to control the substrate temperature in real time to not exceed 200℃, crystallization of the coating is avoided during the spraying process. Subsequent vacuum annealing further releases the internal stress of the coating and improves the bonding strength between the coating and the substrate. The final prepared coating, as detected by XRD, exhibits a typical amorphous peak with a half-width of not less than 5° in the range of 2θ=40°−50°, without obvious crystallization impurity peaks. It combines high hardness, excellent corrosion resistance, and structural stability, meeting the usage requirements of high-end equipment protection and other scenarios, and has good industrial application value. Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of the high-entropy amorphous coating preparation process based on thermal spraying according to the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings.

[0037] This invention discloses a high-entropy amorphous coating based on thermal spraying and its preparation process.

[0038] Reference Figure 1 Example 1: A high-entropy amorphous coating based on thermal spraying, including alloy systems and transition metal systems;

[0039] The alloy system accounts for 67wt%-75wt% of the total coating mass, and the transition metal system accounts for 25wt%-33wt% of the total coating mass.

[0040] The alloy system comprises the following components: Cr 28wt%-35wt%, B 3wt%-6wt%, Si 1wt%-2wt%, with the balance being Fe;

[0041] The transition metal system comprises the following components: 15wt%-18wt% of transition metal A, 9wt%-12wt% of transition metal D, and 1wt%-3wt% of transition metal C;

[0042] The alloy system corresponding to the coating forms a bulk amorphous alloy, and the coating, after being prepared by thermal spraying, exhibits typical amorphous peak characteristics when detected by XRD.

[0043] In Example 2, the A, D, and C transition metals are all selected from any one of Ni, Co, Mo, Nb, and Cu, and the three transition metals are not repeated.

[0044] In Example 3, when the alloy system corresponding to the coating forms a bulk amorphous alloy, the critical size Dc for amorphous formation is greater than or equal to 1 mm.

[0045] Example 4: The thermal spraying process for preparing the coating is selected from atmospheric plasma spraying or supersonic flame spraying.

[0046] By adopting the above technical solutions, from the perspective of amorphous formation, Cr, as a key element in the alloy system, has a good atomic structure compatibility with Fe, which can not only improve the corrosion resistance of the coating, but also enhance the amorphous formation capability by adjusting the atomic arrangement environment; B is a typical glass-forming element, which can significantly reduce the critical cooling rate of the alloy and reduce the tendency of amorphous to crystalline state transformation; Si further optimizes the stability of the amorphous system by refining the atomic-scale structure; Fe, as a matrix element, provides basic mechanical property support for the coating, and its compatibility with other elements ensures compositional uniformity. The design of the content range of the transition metal system is to precisely control the mixing entropy of the system: 15wt%-18wt% of A transition metals are used as the main additives, 9wt%-12wt% of D transition metals are used for auxiliary control, and 1wt%-3wt% of C transition metals are used for trace modification. The three components work together to increase the mixing entropy of the system, making it easier for atoms to form long-range disordered amorphous structures. The mass ratio of the alloy system (67wt%-75wt%) and the transition metal system (25wt%-33wt%) is balanced, which avoids the compositional segregation caused by the excess of a single system and ensures that the synergistic effect of multiple components is fully utilized. Furthermore, the alloy system corresponding to the coating is limited to forming bulk amorphous alloys because the formation of bulk amorphous materials depends on strong glass-forming ability, which can be extended to the coating preparation process. Even if there are local cooling rate fluctuations in thermal spraying, the system with bulk amorphous formation ability can maintain the amorphous structure. The typical amorphous peaks observed in XRD detection are essentially a manifestation of the long-range disorder and short-range order of atoms in the amorphous structure. The absence of sharp crystallization peaks proves that the coating has not crystallized, ensuring core properties such as high strength and high corrosion resistance.

[0047] From the perspective of atomic structure compatibility, Ni, Co, Mo, Nb, and Cu are all transition metals with similar outer electron configurations and small differences in atomic radii (all within the range of 120-145 pm). This characteristic can reduce lattice distortion during multi-component mixing, lower the crystallization driving force, and facilitate the formation of a uniform solid solution structure, laying the foundation for the formation of amorphous states. From the perspective of performance synergy, different transition metals complement each other: Ni can improve the toughness and fatigue resistance of the coating, Co enhances high-temperature stability, Mo increases hardness and wear resistance, Nb further strengthens glass-forming ability, and Cu optimizes resistance to localized corrosion. The restriction of "non-repetition" is to avoid the overemphasis of a single transition metal—if the proportion of a certain element is too high, it is easy to break the mixing entropy balance of the system and induce localized crystallization. Multi-element synergy can maximize the mixing entropy effect, while covering multiple performance requirements such as wear resistance, corrosion resistance, and high-temperature resistance, ensuring that the coating is suitable for high-end equipment protection scenarios.

[0048] The critical amorphous formation size (Dc) is a key indicator for measuring the glass-forming ability of alloys: the larger the Dc, the more likely the alloy can avoid crystallization and form an amorphous structure even at a lower cooling rate, indicating a stronger glass-forming ability. For thermal spraying, although the cooling rate is relatively high after the molten powder impacts the substrate during spraying, different areas of the coating (such as the interface between the surface and the substrate) exhibit varying cooling rates. If the Dc of the alloy system is small (e.g., <1 mm), crystallization may occur when the local cooling rate is slightly lower, leading to uneven coating performance. However, for systems with Dc ≥ 1 mm, the glass-forming ability is sufficient to adapt to the fluctuations in the cooling rate of thermal spraying. Even with slightly slower local cooling, the amorphous structure can still be maintained, ensuring the continuity of the overall amorphous state of the coating and thus stably exhibiting high strength and high corrosion resistance.

[0049] From the perspective of atmospheric plasma spraying, this process can generate a high-temperature plasma arc (temperatures can reach over 10,000℃), ensuring that the high-entropy amorphous alloy powder of this invention (containing high-melting-point elements such as Cr, Mo, and Nb) is fully melted, avoiding coating defects caused by unmelted powder; at the same time, its working gas (such as argon or hydrogen) can isolate air, preventing oxidation during powder melting and ensuring component purity; and during the spraying process, the molten particles rapidly cool after impacting the substrate (cooling rate can reach 10). 4 -10 5 The K / s ratio matches the glass-forming ability of this alloy system, suppressing crystallization and promoting the formation of amorphous structures. From the perspective of supersonic flame spraying, this process has extremely high particle ejection velocities (up to 2000 m / s or more). The kinetic energy of molten particles impacting the substrate is converted into bonding force, significantly improving the bonding strength between the coating and the substrate. By controlling the flame temperature through adjusting the fuel-to-oxygen flow ratio, excessive temperature can be avoided, preventing crystallization of the alloy system. Simultaneously, the high-speed cooling process further ensures the amorphous structure. Furthermore, this process results in a highly dense coating, reducing porosity, which is highly compatible with the excellent wear resistance and corrosion resistance requirements of the coating in this invention. Both processes can adapt to the preparation requirements of high-entropy amorphous composition systems through the control of temperature, cooling rate, and protective atmosphere, ensuring the formation of a stable amorphous structure and the performance of core properties in the coating.

[0050] Example 5: A process for preparing a high-entropy amorphous coating based on thermal spraying, comprising the following steps:

[0051] Step 1: Select Fe, Cr, B, Si powders and A, B, C transition metal powders with a purity of ≥99.5% according to the composition ratio of the coating to prepare a uniformly mixed raw material powder.

[0052] Step 2: Place the raw material powder from Step 1 in an inert atmosphere and prepare the master alloy ingot using an electric arc melting method. During the melting process, repeatedly turn the ingot over 4-5 times to ensure that the composition of the master alloy ingot is uniform.

[0053] Step 3: Prepare alloy powder from the master alloy ingot of Step 2 using gas atomization powder making technology;

[0054] Step 4: Using atmospheric plasma spraying or supersonic flame spraying, the alloy powder from Step 3 is sprayed onto the pretreated substrate surface to form a coating.

[0055] Step 5: Perform XRD analysis on the coating obtained in Step 4 until XRD is detected. The presence of typical amorphous steamed bun peaks with a full width at half maximum (FWHM) greater than or equal to 5° within the range, without obvious crystallization impurity peaks, indicates the formation of a high-entropy amorphous coating based on thermal spraying.

[0056] It is the angle between the incident X-rays and the surface of the high-entropy amorphous coating sample to be tested in XRD detection;

[0057] In Example 6, in step 1, all powders were passed through a 100-120 mesh sieve to remove impurities, and then placed in a planetary ball mill. Anhydrous ethanol was used as the dispersant, and the ball-to-powder ratio was (8-10):1. The mixture was carried out at a speed of 200-250 r / min for 2-3 hours. Subsequently, the powders were dried in a vacuum drying oven at 60-80℃ for 1-1.5 hours to obtain a uniformly mixed raw material powder.

[0058] Example 7, step 2 includes the following detailed steps:

[0059] The dried raw material powder from step 1 is placed into a water-cooled copper crucible, and argon gas is introduced as a protective atmosphere. The raw material is then melted in a non-consumable arc furnace. During the melting process, the raw material is first pre-melted with a current of 300A-400A for 1-2 minutes to remove adsorbed gas on the surface. Then, it is mainly melted with a current of 500A-600A for 3-5 minutes. After each melting, the alloy ingot is rotated 180° and the melting process is repeated 4-5 times to ensure uniform composition. After cooling, the master alloy ingot is obtained.

[0060] Example 8, step 3 includes the following detailed steps:

[0061] The master alloy ingot from step 2 is crushed into 5mm-10mm particles and fed into a gas atomization powder-making device; argon is used as the atomizing gas, and the atomization pressure is controlled at 4MPa-6MPa, the molten metal droplet falling height is 800mm-1000mm, and the cooling rate is greater than or equal to 10. 4K / s, prepare alloy powder; then screen through a three-layer vibrating screen, the upper, middle and lower layers of the three-layer vibrating screen are respectively made of 45μm, 15μm and 10μm mesh, to collect powder of 15μm-45μm, and place it in a vacuum drying oven at 100℃-120℃ for 2-2.5h to obtain powder for spraying.

[0062] Example 9, step 4 includes the following detailed steps:

[0063] Select the thermal spraying process according to the coating performance requirements: If atmospheric plasma spraying is used, set the working gas to be a mixture of argon and hydrogen, the spraying power to be 28kW-32kW, the spraying distance to be 100-120mm, and the powder feeding rate to be 30g / min-40g / min.

[0064] If supersonic flame spraying is used, set the fuel flow rate to 20L / h-25L / h, the oxygen flow rate to 80L / h-90L / h, the spraying distance to 250mm-280mm, and the powder feeding rate to 25g / min-35g / min. During the spraying process, monitor the substrate temperature in real time with an infrared thermometer and control the substrate temperature to be less than or equal to 200℃ to avoid coating crystallization. Place the sprayed coating in a vacuum annealing furnace with a vacuum degree of less than or equal to 10⁻³Pa, heat it to 300℃-350℃ at a rate of 5K / min-8K / min, hold it at that temperature for 1.5-2 hours, and then cool it to room temperature with the furnace to complete stress release and form the coating.

[0065] In Example 10, if atmospheric plasma spraying is used in step 4, the spray gun is preheated before spraying: the spray gun is heated to 150℃-200℃ with an argon flow rate of 10L / min-15L / min and kept at that temperature for 20min-30min to prevent the powder from condensing and clogging inside the spray gun in the early stage of spraying.

[0066] By adopting the above technical solutions, raw materials with a purity of ≥99.5% can reduce the impurity content, avoid impurities from inducing local crystallization during subsequent smelting or spraying, and eliminate interference for the formation of amorphous structures; proportional ingredient proportioning is based on the previous composition system design to ensure that the mass ratio of the alloy system and the transition metal system, as well as the content of each element, meet the requirements for the mixing entropy control of amorphous formation.

[0067] Step 2 involves preparing a master alloy ingot using electric arc melting and repeatedly turning it over during melting. The principle is that electric arc melting provides a high-temperature environment, allowing the multi-component powder to fully melt and breaking down interfacial barriers between elements. Repeated turning 4-5 times can counteract the component segregation caused by gravity, ensuring a uniform distribution of Fe, Cr, B, and transition metals, preventing local element enrichment that could lead to crystallization, and providing a uniform master alloy base for subsequent powder preparation. Step 3 involves gas atomization powdering, which uses a high-speed airflow to break the molten master alloy into fine powder. This process allows for rapid cooling, initially suppressing the tendency to crystallize, and the prepared powder particle size is easily controllable, adapting to the powder morphology requirements of subsequent thermal spraying. Step 4 selects atmospheric plasma spraying or supersonic flame spraying because both processes can meet the amorphous formation conditions of "high-temperature melting of powder and rapid cooling for shaping." High temperature ensures that high-melting-point elements (such as Cr and Mo) are fully melted, avoiding coating defects caused by unmelted powder. Rapid cooling after molten particles impact the substrate reaches the critical cooling rate required for amorphous formation, suppressing the long-range ordered arrangement of atoms. The XRD detection in step 5 is based on the diffraction characteristics of amorphous structures; the bun-shaped peaks in the range of 2θ=40°−50° are a direct manifestation of long-range atomic disorder and short-range order. The full width at half maximum (FWHM) is ≥5° and there are no crystallization impurity peaks, which proves that the coating has not crystallized. This ensures that the coating has core properties such as high strength and high corrosion resistance, and is a key basis for judging whether the product is qualified.

[0068] The 100-120 mesh sieve is used to remove large particles or foreign objects that may be present in the raw materials. If these impurities enter the subsequent processes, they will cause uneven melting during smelting or form pores in the coating during spraying, affecting the continuity of the amorphous structure. Planetary ball milling uses mechanical force to break up powder agglomerates. Anhydrous ethanol is used as a dispersant to prevent powder from agglomerating due to electrostatics. At the same time, ethanol is volatile and leaves no residue, so it will not introduce new impurities. The ball-to-material ratio (8-10): 1. The parameter design of the rotation speed of 200r / min-250r / min ensures the mixing effect while avoiding excessive ball-to-material ratio or rotation speed that would cause wear of the grinding balls and introduce additional impurities. Mixing for 2-3 hours can ensure that the powder of each element reaches microscopic uniformity and avoid local component deviation. Vacuum drying at 60℃-80℃ is used to remove ethanol solvent and adsorbed moisture from the mixed powder. Moisture will vaporize when heated during electric arc melting, forming bubbles that cause pores in the master alloy ingot. Ethanol residue may decompose at high temperatures, affecting the purity of the alloy composition. The vacuum environment can prevent powder oxidation during the drying process, further ensuring the purity of the raw materials.

[0069] The water-cooled copper crucible serves to achieve rapid cooling. When the molten metal comes into contact with the crucible, the water cooling system quickly removes heat, causing the molten metal to solidify rapidly and preventing crystallization caused by slow cooling. Argon gas acts as a protective atmosphere, isolating the metal from air and preventing oxidation of metallic elements (such as Fe and Cr) at high temperatures. Oxidation products would become crystallization nuclei, disrupting the conditions for amorphous formation. The pre-melting stage involves heating with a current of 300A-400A for 1-2 minutes to remove gases (such as oxygen and water vapor) adsorbed on the surface of the raw materials. If these gases remain, they will form bubbles during the main melting, leading to porosity defects in the master alloy ingot. The main melting stage involves heating with a current of 500A-600A for 3-5 minutes because the higher current provides sufficient heat to ensure that high-melting-point transition metals (such as Mo and Nb) are fully melted, preventing unmelted particles from causing compositional inhomogeneity. Each melting cycle involves rotating the crucible 180° and repeating this process 4-5 times, allowing the molten metal to flow fully under gravity, eliminating compositional differences between the bottom and top, and ultimately obtaining a uniform, defect-free master alloy ingot.

[0070] The master alloy ingot is crushed to 5mm-10mm because this particle size range is easily heated and melted, and the increased surface area after crushing allows for thorough atomization by the airflow, preventing large pieces of master alloy from being difficult to atomize and resulting in uneven powder particle size. Argon, as the atomizing gas, protects the molten metal from oxidation, and its moderate density provides sufficient impact force to break the molten metal into fine droplets, while simultaneously achieving rapid cooling (cooling rate ≥10). 4 Rapid cooling (K / s) inhibits crystallization of molten metal droplets during solidification, maintaining an amorphous tendency. The atomization pressure of 4MPa-6MPa and droplet fall height of 800mm-1000mm are designed to balance powder particle size and cooling effect: excessive pressure leads to overly fine powder (<10μm), which is easily carried away by the airflow during spraying; insufficient pressure results in overly coarse powder (>45μm), making full melting difficult during spraying; the fall height, combined with the cooling rate, ensures that the droplets solidify before landing, preventing particle adhesion. A three-layer vibrating screen filters powder from 15μm to 45μm because powder in this size range has good flowability and uniform heating area, allowing for stable delivery and full melting during spraying; vacuum drying at 100℃-120℃ removes adsorbed moisture from the powder surface, preventing moisture evaporation during spraying and the formation of coating pores. Simultaneously, the vacuum environment prevents powder oxidation, ensuring powder activity.

[0071] In atmospheric plasma spraying, argon and hydrogen are mixed as the working gas. Argon provides a stable protective atmosphere, while hydrogen increases the plasma arc temperature, ensuring the complete melting of high-melting-point elements. The combination of spraying power of 28kW-32kW, distance of 100-120mm, and powder feed rate of 30g / min-40g / min ensures that the powder is completely melted before reaching the substrate, and that the molten particles cool rapidly after impacting the substrate (avoiding heat accumulation in the substrate that leads to a decrease in the cooling rate), meeting the critical cooling rate requirements for amorphous formation. In supersonic flame spraying, the setting of fuel and oxygen flow rates controls the flame temperature and particle injection velocity. High temperature ensures powder melting, and the kinetic energy of high-speed particles impacting the substrate is converted into bonding force, improving the bonding strength between the coating and the substrate. The coordination of spraying distance and powder feed rate is also to balance the degree of melting and the cooling rate, avoiding overheating or insufficient cooling of the particles. The substrate temperature is controlled to be ≤200℃ because excessively high substrate temperatures reduce the cooling rate of molten particles. When the cooling rate is below the critical value for amorphous formation, atoms have enough time to arrange themselves into an ordered crystalline state, leading to coating crystallization. Vacuum annealing is used to release the internal stress generated during the spraying process. Rapid solidification of the coating during thermal spraying easily generates internal stress, which may cause the coating to crack or peel off. A heating rate of 5K / min-8K / min and a holding temperature of 300℃-350℃ can slowly release stress without triggering crystallization. The vacuum environment prevents coating oxidation during annealing, further ensuring the stability of the amorphous structure.

[0072] In the initial stage of spraying, the spray gun temperature is low. If powder is directly introduced, it is prone to condensation and adhesion upon contact with the low-temperature gun wall, leading to blockage of the internal channels of the spray gun. Blockage will cause interruption of powder delivery, resulting in uneven coating thickness or missed spraying defects. Heating the spray gun to 150℃-200℃ can bring the gun wall temperature close to the initial preheating temperature of the powder, avoiding powder condensation upon contact with cold air. An argon flow rate of 10L / min-15L / min serves two purposes: firstly, it acts as a heating medium, uniformly transferring heat to stabilize the spray gun temperature; secondly, it isolates the spray gun from air, preventing internal oxidation and rust. Holding the spray gun at this temperature for 20-30 minutes allows the overall temperature of the spray gun to reach a stable state, avoiding the risk of condensation due to excessively low local temperatures. This ensures continuous and uniform powder delivery during subsequent spraying, ultimately forming a uniform, defect-free amorphous coating.

[0073] The following specific embodiments illustrate the implementation principle of the present invention: Specific Implementation Example 1:

[0075] Raw material preparation: Fe, Cr, B, and Si powders with a purity ≥99.5% were selected according to the coating component ratio, as well as Ni, Co, and Mo transition metal powders with a purity ≥99.5%. The alloy system accounted for 70 wt% of the total coating mass (Cr 32.2 wt%, B 4.5 wt%, Si 1.2 wt%, Fe 32.1 wt%), and the transition metal system accounted for 30 wt% (Ni 17.5 wt%, Co 10.2 wt%, Mo 2.3 wt%). All powders were passed through a 100-mesh sieve to remove impurities and placed in a planetary ball mill. Anhydrous ethanol was used as the dispersant, and the mixture was stirred for 2.5 h at a ball-to-powder ratio of 9:1 and a rotation speed of 220 r / min. Subsequently, the mixture was dried in a vacuum drying oven at 70℃ for 1.2 h to obtain a uniformly mixed raw material powder.

[0076] To prepare the master alloy ingot, the dried raw material powder was placed into a water-cooled copper crucible and protected with argon gas of ≥99.99% purity. A non-consumable arc melting furnace was used. First, the raw material was pre-melted with a current of 350A for 1.5 minutes to remove the adsorbed gas on the surface. Then, it was mainly melted with a current of 550A for 4 minutes. The alloy ingot was rotated 180° after each melting, and this process was repeated 5 times. After cooling, a master alloy ingot with uniform composition was obtained.

[0077] Alloy powder preparation involves crushing the master alloy ingot into 8mm particles and feeding them into a gas atomization powder-making device; argon is used as the atomizing gas, and the atomization pressure is controlled at 5MPa, the molten metal droplet falling height at 900mm, and the cooling rate at ≥10. 4 K / s, prepare alloy powder; through a three-layer vibrating sieve (upper layer 45μm, middle layer 15μm, lower layer 10μm), collect 15-45μm powder, dry in a vacuum drying oven at 110℃ for 2.2h to obtain powder for spraying.

[0078] For thermal spraying and post-treatment, atmospheric plasma spraying was selected. Before spraying, the spray gun was heated to 180℃ with argon gas at a flow rate of 12L / min and held at that temperature for 25min. The working gases were set as argon (45L / min) and hydrogen (7L / min), with a spraying power of 30kW, a spraying distance of 110mm, and a powder feeding rate of 35g / min. The substrate was 1×1cm 316L stainless steel, which was ultrasonically cleaned for 18min, then sandblasted with 80-mesh white corundum abrasive (pressure 0.7MPa, distance 180mm, angle 50°), and then dried at 130℃ for 35min. During the spraying process, the substrate temperature was monitored in real time with an infrared thermometer and controlled at 180℃. After spraying, the coating was placed in a vacuum annealing furnace with a vacuum degree ≤10⁻³Pa, heated to 320℃ at a rate of 6K / min, held at that temperature for 1.8h, and then cooled with the furnace to complete stress release.

[0079] The coating was tested by XRD, and a typical amorphous peak with a full width at half maximum (FWHM) of 6.2° appeared in the range of 2θ = 40°-50°. There were no crystallization impurity peaks, which indicates that the coating is a high-entropy amorphous coating. Specific Implementation Example 2:

[0081] Raw material preparation: Fe, Cr, B, and Si powders with a purity ≥99.5% were selected according to the coating component ratio, as well as A transition metal (Nb), D transition metal (Cu), and C transition metal (Mo) powders with a purity ≥99.5%. The alloy system accounted for 68 wt% of the total coating mass (Cr 31.3 wt%, B 4.7 wt%, Si 1.2 wt%, Fe 30.8 wt%), and the transition metal system accounted for 32 wt% (Nb 16.7 wt%, Cu 10.5 wt%, Mo 4.8 wt%). All powders were passed through a 120-mesh sieve to remove impurities and then placed in a planetary ball mill. Anhydrous ethanol was used as the dispersant, and the mixture was held at a ball-to-powder ratio of 8:1 and a speed of 240 r / min for 2 hours. Subsequently, the mixture was dried in a vacuum drying oven at 65℃ for 1.5 hours to obtain a uniformly mixed raw material powder.

[0082] To prepare the master alloy ingot, the dried raw material powder was placed into a water-cooled copper crucible and protected with argon gas of ≥99.99% purity. A non-consumable arc melting furnace was used. First, the raw material was pre-melted with a current of 380A for 1.2 minutes to remove the adsorbed gas on the surface. Then, it was mainly melted with a current of 580A for 3.5 minutes. The alloy ingot was rotated 180° after each melting, and this process was repeated 4 times. After cooling, a master alloy ingot with uniform composition was obtained.

[0083] Alloy powder preparation involves crushing the master alloy ingot into 6mm particles and feeding them into a gas atomization powder-making device; argon is used as the atomizing gas, and the atomization pressure is controlled at 4.5MPa, the molten metal droplet falling height at 850mm, and the cooling rate at ≥10. 4 K / s, prepare alloy powder; through a three-layer vibrating sieve (upper layer 45μm, middle layer 15μm, lower layer 10μm), collect 15-45μm powder, dry in a vacuum drying oven at 105℃ for 2.5h to obtain powder for spraying.

[0084] Supersonic flame spraying was selected for thermal spraying and post-treatment. The fuel (kerosene) flow rate was set at 22 L / h, the oxygen flow rate at 85 L / h, the spraying distance at 260 mm, and the powder feed rate at 30 g / min. The substrate was 1×1 cm 45# steel, ultrasonically cleaned for 15 min, then sandblasted with 100-mesh white corundum abrasive (pressure 0.6 MPa, distance 160 mm, angle 55°), and then dried at 120℃ for 40 min. During the spraying process, the substrate temperature was monitored in real-time using an infrared thermometer and controlled at 190℃. After spraying, the coating was placed in a vacuum annealing furnace with a vacuum degree ≤10⁻³ Pa, heated to 340℃ at a rate of 7 K / min, held at that temperature for 1.5 h, and then cooled in the furnace to complete stress release.

[0085] The coating was tested by XRD, and a typical amorphous peak with a full width at half maximum (FWHM) of 5.8° appeared in the range of 2θ = 40°-50°. There were no crystallization impurity peaks, which indicates that the coating is a high-entropy amorphous coating.

[0086] The performance test results of the high-entropy amorphous coating are shown in Table 1:

[0087] Table 1

[0088] Test item Specific embodiment 1 Specific embodiment 2 Test item XRD characteristic (2θ range / full width at half maximum) 40°-50° / 6.2° 40°-50° / 5.8° Cu target X-ray was used, scanning range 20°-80°, scanning rate 5° / min, peak shape and full width at half maximum in the range of 2θ=40°-50° were recorded Microhardness (HV) 1150 1080 Three different measuring points were selected on the coating surface, Vickers hardness tester was used, load 200g, pressure maintaining time 15s, and average value was taken Coating and substrate bonding strength (MPa) 58 55 Sample size 10mmx50mm, tensile test was used to test the maximum load when the coating and substrate were separated, and the strength was calculated based on the bonding area Neutral salt spray resistance time (h) 1200 1150 5wt% NaCl solution was prepared, temperature 35℃±2℃, continuous spraying, and the time when the first corrosion point appeared on the coating was observed Corrosion rate (mm / a) 0.0035 0.0042 After salt spray test, the mass change of the coating sample before and after weighing was calculated combined with the coating density, exposed area and test time Crystallization temperature (℃) 645 536 Differential scanning calorimeter (DSC) was used, the temperature was raised to 1273K at a rate of 10K / min, and the temperature corresponding to the crystallization peak of the coating was recorded Coating thickness (μm) 220 200 Along the cross section of the coating, after polishing and polishing, metallographic microscope was used to observe and measure the average value of three measuring points Porosity (%) 0.8 1.0 The cross section of the coating was taken, metallographic sample was prepared, and the percentage of pore area to total coating area was calculated by image analysis method

[0089] Table 2 shows the performance comparison results between high-entropy amorphous coatings and traditional coatings:

[0090] Table 2

[0091] Test item Specific embodiment 1 Specific embodiment 2 Traditional iron-based amorphous coating 316L stainless steel coating Traditional WC-Co coating Test item Microhardness (HV) 1150 1080 850-950 250-300 1200-1300 Microhardness (HV) Coating and substrate bonding strength (MPa) 58 55 40-50 30-40 50-60 Coating and substrate bonding strength (MPa) Neutral salt spray resistance time (h) 1200 1150 600-800 300-400 800-900 Neutral salt spray resistance time (h) Corrosion rate (mm / a) 0.0035 0.0042 0.008-0.012 0.015-0.020 0.005-0.007 Corrosion rate (mm / a) Crystallization temperature (℃) 645 536 500-550 Crystalline 600-650 Crystallization temperature (℃) Coating thickness (μm) 220 200 150-250 100-200 150-250 Coating thickness (μm) Porosity (%) 0.8 1.0 1.5-2.0 0.5-1.0 0.5-1.0 Porosity (%) Preparation process adaptability Atmospheric plasma / hypersonic flame spraying Atmospheric plasma / hypersonic flame spraying High cooling rate process is required Conventional spraying Hypersonic flame spraying Preparation process adaptability

[0092] Therefore, it can be seen that the high-entropy amorphous coating of the present invention has significant advantages over traditional coatings in terms of performance stability, corrosion and wear resistance, and process adaptability. From the perspective of structural and performance stability, this coating can stably maintain its amorphous state after thermal spraying, with a high crystallization temperature. This avoids the problem of crystallization during the preparation or high-temperature service of traditional iron-based amorphous coatings, which leads to degradation of strength and corrosion resistance. From the perspective of corrosion resistance and mechanical properties, relying on the multi-component synergistic design, the corrosion resistance (such as salt spray resistance) of this coating is superior to that of traditional iron-based amorphous coatings and conventional metal coatings (such as 316L stainless steel coatings). Its hardness and wear resistance are also more outstanding, which can meet the requirements of high-end equipment protection for harsh environmental tolerance. From the perspective of process adaptability, this coating can be prepared by conventional processes such as atmospheric plasma spraying and supersonic flame spraying. It does not require the extremely high cooling rate required by traditional amorphous coatings, making the process operation simpler. Although the hardness of traditional hard coatings (such as WC-Co coatings) is close to that of this coating, this coating is superior in terms of overall corrosion resistance and conventional process adaptability, making it easier to achieve industrial application.

[0093] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-entropy amorphous coating based on thermal spraying, characterized in that: Including alloy systems and transition metal systems; The alloy system accounts for 67wt%-75wt% of the total coating mass, and the transition metal system accounts for 25wt%-33wt% of the total coating mass. The alloy system comprises the following components: Cr 28wt%-35wt%, B 3wt%-6wt%, Si 1wt%-2wt%, with the balance being Fe; The transition metal system comprises the following components: 15wt%-18wt% of transition metal A, 9wt%-12wt% of transition metal D, and 1wt%-3wt% of transition metal C; In the transition metal system, the A transition metal is Ni, the D transition metal is Co, and the C transition metal is Mo; or the A transition metal is Nb, the D transition metal is Cu, and the C transition metal is Mo. The alloy system corresponding to the coating forms a bulk amorphous alloy, and the coating, after being prepared by thermal spraying, exhibits typical amorphous peak characteristics when detected by XRD.

2. The high-entropy amorphous coating based on thermal spraying according to claim 1, characterized in that: When the alloy system corresponding to the coating forms a bulk amorphous alloy, the critical amorphous formation size Dc is greater than or equal to 1 mm.

3. The high-entropy amorphous coating based on thermal spraying according to claim 2, characterized in that: The thermal spraying process for preparing the coating is selected from atmospheric plasma spraying or supersonic flame spraying.

4. A preparation process for a high-entropy amorphous coating based on thermal spraying, characterized in that, The method for preparing the high-entropy amorphous coating based on thermal spraying as described in claim 3 includes the following steps: Step 1: Select Fe, Cr, B, Si powders and A, B, C transition metal powders with a purity of ≥99.5% according to the composition ratio of the coating to prepare a uniformly mixed raw material powder. Step 2: Place the raw material powder from Step 1 in an inert atmosphere and prepare the master alloy ingot using an electric arc melting method. During the melting process, repeatedly turn the ingot over 4-5 times to ensure that the composition of the master alloy ingot is uniform. Step 3: Prepare alloy powder from the master alloy ingot of Step 2 using gas atomization powder making technology; Step 4: Using atmospheric plasma spraying or supersonic flame spraying, the alloy powder from Step 3 is sprayed onto the pretreated substrate surface to form a coating. Step 5: Perform XRD analysis on the coating obtained in Step 4 until XRD is detected. The presence of typical amorphous peaks with a full width at half maximum (FWHM) greater than or equal to 5° within the specified range, without any obvious crystallization impurity peaks, indicates the formation of a high-entropy amorphous coating based on thermal spraying.

5. The preparation process of a high-entropy amorphous coating based on thermal spraying according to claim 4, characterized in that: In step 1, after removing impurities by passing all powders through a 100-120 mesh sieve, they are placed in a planetary ball mill and mixed for 2-3 hours at a ball-to-powder ratio of (8-10):1 and a speed of 200-250 r / min. Then, they are dried in a vacuum drying oven at 60-80℃ for 1-1.5 hours to obtain uniformly mixed raw material powder.

6. The preparation process of a high-entropy amorphous coating based on thermal spraying according to claim 5, characterized in that: Step 2 includes the following detailed steps: The dried raw material powder from step 1 is placed into a water-cooled copper crucible, and argon gas is introduced as a protective atmosphere. The raw material is then melted in a non-consumable arc furnace. During the melting process, the raw material is first pre-melted with a current of 300A-400A for 1-2 minutes to remove adsorbed gas on the surface. Then, it is mainly melted with a current of 500A-600A for 3-5 minutes. After each melting, the alloy ingot is rotated 180° and the melting process is repeated 4-5 times to ensure uniform composition. After cooling, the master alloy ingot is obtained.

7. The preparation process of a high-entropy amorphous coating based on thermal spraying according to claim 6, characterized in that: Step 3 includes the following detailed steps: The master alloy ingot from step 2 is crushed into 5mm-10mm particles and fed into a gas atomization powder-making device; argon is used as the atomizing gas, and the atomization pressure is controlled at 4MPa-6MPa, the molten metal droplet falling height is 800mm-1000mm, and the cooling rate is greater than or equal to 10. 4 K / s, prepare alloy powder; then screen through a three-layer vibrating screen, the upper, middle and lower layers of the three-layer vibrating screen are respectively made of 45μm, 15μm and 10μm mesh, to collect powder of 15μm-45μm, and place it in a vacuum drying oven at 100℃-120℃ for 2-2.5h to obtain powder for spraying.

8. The preparation process of a high-entropy amorphous coating based on thermal spraying according to claim 7, characterized in that: Step 4 includes the following detailed steps: Select the thermal spraying process according to the coating performance requirements: If atmospheric plasma spraying is used, set the working gas to be a mixture of argon and hydrogen, the spraying power to be 28kW-32kW, the spraying distance to be 100-120mm, and the powder feeding rate to be 30g / min-40g / min. If supersonic flame spraying is used, set the fuel flow rate to 20L / h-25L / h, the oxygen flow rate to 80L / h-90L / h, the spraying distance to 250mm-280mm, and the powder feeding rate to 25g / min-35g / min. During the spraying process, monitor the substrate temperature in real time with an infrared thermometer and control the substrate temperature to be less than or equal to 200℃ to avoid coating crystallization. Place the sprayed coating in a vacuum annealing furnace with a vacuum degree of less than or equal to 10⁻³Pa, heat it to 300℃-350℃ at a rate of 5K / min-8K / min, hold it at that temperature for 1.5-2 hours, and then cool it to room temperature with the furnace to complete stress release and form the coating.

9. The preparation process of a high-entropy amorphous coating based on thermal spraying according to claim 8, characterized in that: If atmospheric plasma spraying is used in step 4, the spray gun should be preheated before spraying: heat the spray gun to 150℃-200℃ with argon gas at a flow rate of 10L / min-15L / min and keep it at that temperature for 20min-30min to prevent the powder from condensing and clogging inside the spray gun in the early stage of spraying.

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