High-entropy alloy / floating bead composite coating and preparation method thereof

Abstract

The invention belongs to the technical field of surface engineering application, and discloses a high-entropy alloy / floating bead composite coating and a preparation method thereof. The high-entropy alloy material is composed of high-entropy alloy with the volume fraction being 75-95% and floating beads with the volume fraction being 5-25%. The floating beads are promoted to be immersed into the coating through an etching means, the wettability of the floating beads and the high-entropy alloy is improved, and the binding force of the floating beads and the high-entropy alloy is improved; induction heating is utilized to effectively reduce composition segregation through the characteristic of'preheating-heating 'two-step heat cycle, and meanwhile, a high-entropy alloy coating which is relatively uniform and compact, forms metallurgical bonding with a matrix and has a certain thickness can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering application technology, and relates to a high-entropy alloy / flotation ball composite coating and its preparation method. Background Technology

[0002] Part failure often occurs on the surface. Damage to the surface can lead to part scrapping or even complete machine shutdown, severely impacting production efficiency and wasting significant human and material resources. Therefore, adding a protective layer to the material surface can effectively improve its performance, extend its service life, and reduce economic losses. Traditional alloy design theory, after a long period of development and improvement, has reached a bottleneck and is unlikely to achieve significant breakthroughs in the short term. The introduction of high-entropy alloys has opened up a new path for alloy design. These alloys possess both excellent physicochemical and mechanical properties, making them a promising new alloy material. Currently, the preparation of high-entropy alloy coatings mainly employs laser cladding and spraying methods. While laser cladding can achieve metallurgically bonded and dense coatings, its expensive equipment and high operating costs hinder large-scale industrial applications. Spraying, although lower in cost, results in weak bonding strength between the coating and the substrate, and the presence of defects such as pores within the coating, severely affecting its service life. Furthermore, ceramic reinforcing phases are often introduced to improve coating performance. Ceramics possess numerous excellent properties such as high strength and hardness, wear resistance, oxidation resistance, and corrosion resistance. Composite coatings prepared by reinforcing metal matrices with ceramic particles show significant improvements in strength, hardness, and wear resistance. However, traditional reinforcing particles such as carbides and nitrides are costly and have poor wettability with the metal matrix, making interfacial bonding a challenge.

[0003] Fly ash is a waste product emitted after coal combustion. The emission of fly ash from thermal power generation has become the largest single source of industrial solid waste pollution in China. Large amounts of fly ash, if left untreated, will generate dust and pollute the atmosphere; if discharged into water systems, it will cause river siltation and seriously harm the ecological environment. At the same time, the toxic chemicals in fly ash can also harm human beings and organisms.

[0004] In summary, the existing technologies suffer from the following problems: 1) high cost in preparing high-performance coatings; 2) poor adhesion and defects in low-cost coatings; 3) weak interfacial bonding between the reinforcing phase and the substrate; and 4) environmental pollution from fly ash waste. Therefore, the purpose of this invention is to provide a high-entropy alloy composite coating and its preparation method that combines excellent performance with low cost, simple process, and environmental mitigation. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a high-entropy alloy / crystal bead composite coating and its preparation method. The composite coating prepared by this invention has a metallurgical bond with the substrate, exhibiting high bonding strength (Table 1), overcoming the defects of weak bonding and the tendency for >5% porosity within the coating caused by spraying. The wear resistance of this coating is improved by more than 47% compared to pure high-entropy alloy coatings. Figure 5 Simultaneously, the corrosion resistance is significantly enhanced, and the overall performance is comparable to laser cladding coatings. This invention employs induction cladding technology, which reduces equipment investment and operating costs by approximately 40%-60% compared to laser cladding systems. Furthermore, the process is highly efficient, using a two-step "preheating-heating" thermal cycle, with the total processing time controlled within 70-120 seconds, far shorter than the processing cycle of laser cladding, greatly improving production efficiency. This invention uses hydrofluoric acid etching to pretreat the fly ash particles, constructing a micron-nano-scale rough structure on their surface, achieving strong mechanical interlocking with the high-entropy alloy substrate, and enhancing the interfacial bonding strength of the composite coating. This invention creatively uses industrial solid waste: fly ash fly ash particles as the core reinforcing phase, with near-zero cost, achieving "waste-based damage control." This not only gives the invention a significant cost advantage but also aligns with the direction of green and sustainable development, possessing significant environmental significance.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution: A high-entropy alloy / crystal ball composite coating, wherein the composite coating is composed of a CoCrFeNiMn high-entropy alloy with a volume fraction of 75-95% and crystal balls with a volume fraction of 5-25%.

[0007] This invention also claims protection for a method for preparing the above-mentioned high-entropy alloy / flocculent composite coating, comprising the following steps; Step 1: Prepare CoCrFeNiMn high-entropy alloy powder by ball milling metal powders in equal atomic ratios.

[0008] Step 2: Pre-treat the float beads and etch them with hydrofluoric acid.

[0009] Step 3: Mix the CoCrFeNiMn high-entropy alloy powder prepared in Step 1 with the hydrofluoric acid etched beads obtained in Step 2 at a volume percentage of 75-95%: 5-25%.

[0010] Step 4: Use water glass to bond the mixed powder obtained in step 3 and apply it to Q235 with cold.

[0011] Step 5: Using an induction heating device, Q235 with pre-mixed powder from Step 4 is induction cladding in an argon atmosphere to obtain a high-entropy alloy / flotation composite coating.

[0012] In step 1, the CoCrFeNiMn high-entropy alloy powder is prepared by ball milling. Equivalent atomic ratio metal powders are placed in a stainless steel container, and tungsten carbide is used as the grinding balls at a ball-to-powder ratio of 15:1. Dry milling is performed at 400 rpm for 10 h under an argon atmosphere. Then, ethanol is added as a control agent for wet milling for 5 h.

[0013] In step 2, the pretreatment of the cenospheres is as follows: Cleaning: Place the cenospheres in anhydrous ethanol and ultrasonically clean for 15-30 minutes. Filtration: Wash repeatedly with deionized water 2-3 times. Dry the cleaned cenospheres in an oven at 80-120 ℃ for 1-2 hours for later use.

[0014] In step 2, the hydrofluoric acid etching is specifically performed as follows: The pretreated cenospheres are immersed in a 5-20% hydrofluoric acid (HF) aqueous solution, with 0.1-0.5% sodium dodecyl sulfate (SDS) added to reduce the surface tension of the etching solution, allowing it to better wet and penetrate the cenosphere surface, resulting in more uniform etching. Etching is carried out at 30-60℃ for 30-60 min. After etching, the cenospheres are thoroughly washed 3-5 times with deionized water until neutral, and then dried in a vacuum drying oven at 80-120℃ for 2-3 h.

[0015] In step 5, the induction cladding conditions are as follows: the induction cladding current is set in the range of 250-360 A; the preheating time is 30-60 s and the preheating current is 250-290 A; the heating cladding time is 45-60 s and the heating cladding current is 310-360 A; the distance between the coating and the magnetic conductor is 1 mm, and the protective atmosphere is argon.

[0016] The beneficial effects of this invention compared to the prior art are: (1) The induction heating cladding process adopted in this invention uses a two-step thermal cycle of "preheating-heating" to prepare high-entropy alloy / flotation beads as a coating on the surface of a common substrate. This not only improves the surface properties of the material, but also enables the repeated reuse of the substrate. It not only achieves efficient energy saving and low-cost preparation, but also avoids coating defects by gently removing the binder in the preheating stage, promotes densification and metallurgical bonding by electromagnetic stirring in the cladding stage, and effectively suppresses component segregation and refines grains by rapid melting and solidification characteristics. This synergistically optimizes the coating forming quality, interface bonding strength and microstructure.

[0017] (2) Compared with laser cladding, this invention significantly reduces equipment investment and operating costs while ensuring a metallurgical bond between the coating and the substrate, a dense structure, and minimal component segregation. This solves the problem of high application costs caused by expensive equipment in laser cladding and makes it more suitable for surface treatment of mass-produced workpieces. Compared with spraying, this invention utilizes induction heating to achieve complete melting of the coating material, enabling the coating to form a high-strength metallurgical bond with the substrate. This overcomes the drawbacks of insufficient bonding and internal defects in the coating caused by spraying, greatly improving the reliability and service life of the coating.

[0018] (3) Cenospheres were used as reinforcements for the CoCrFeNiMn high-entropy alloy coating. After hydrofluoric acid etching, the surface of the cenospheres became rough, forming a large number of micron-sized pits, which significantly increased their specific surface area. In the subsequent induction cladding process, the molten high-entropy alloy could penetrate into these microstructures, forming a strong metallurgical bond, thereby greatly improving the interfacial bonding strength between the cenospheres and the coating substrate, preventing the detachment of the reinforcing phase, and effectively improving wear resistance and corrosion resistance. On the other hand, as heterogeneous nucleation sites, they reduced the nucleation work and increased the nucleation rate, playing an important role in refining the microstructure and thus further improving the coating performance.

[0019] (4) Cenospheres are hollow ceramic particles contained in fly ash, mainly composed of SiO2 and Al2O3. Cenospheres are a by-product of power plants, with abundant sources and low cost. Introducing them into high-entropy alloys to prepare composite materials can consume some power plant waste, alleviate environmental pressure, and have significant environmental protection significance. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Figure 1 X-ray diffraction image of the high-entropy alloy / bead coating prepared in Example 1 of the present invention.

[0021] Figure 2 The microstructure and energy dispersive spectroscopy (EDS) spectra of the high-entropy alloy / crystal (etched) composite coating prepared in Example 1 of this invention are shown in Figure (a), Figure (b) shows the EDS spectra of O, Figure (c) shows the EDS spectra of Al, Figure (d) shows the EDS spectra of Si, Figure (e) shows the EDS spectra of Cr, Figure (f) shows the EDS spectra of Fe, Figure (g) shows the EDS spectra of Ni, Figure (h) shows the EDS spectra of Co, and Figure (i) shows the EDS spectra of Mn.

[0022] Figure 3The microstructure and energy dispersive spectroscopy (EDS) spectra of the high-entropy alloy / crystal ball (unetched) composite coating prepared for Comparative Example 2 of this invention are shown in Figure (a), Figure (b) shows the EDS spectra of O, Figure (c) shows the EDS spectra of Al, Figure (d) shows the EDS spectra of Si, Figure (e) shows the EDS spectra of Cr, Figure (f) shows the EDS spectra of Fe, Figure (g) shows the EDS spectra of Ni, Figure (h) shows the EDS spectra of Co, and Figure (i) shows the EDS spectra of Mn.

[0023] Figure 4 The images show the wear morphology of the Q235 steel substrate, the high-entropy alloy coating prepared in Comparative Example 1, the high-entropy alloy / crystal composite coating prepared in Comparative Example 2, the high-entropy alloy / crystal composite coating prepared in Example 1, and the high-entropy alloy / crystal composite coating prepared in Example 2. Figure (a) shows the wear morphology of the Q235 steel substrate, Figure (b) shows the wear morphology of the high-entropy alloy coating prepared in Comparative Example 1, Figure (c) shows the wear morphology of the high-entropy alloy / crystal composite coating prepared in Comparative Example 2, Figure (d) shows the wear morphology of the high-entropy alloy / crystal composite coating prepared in Example 1, and Figure (e) shows the wear morphology of the high-entropy alloy / crystal composite coating prepared in Example 2.

[0024] Figure 5 This chart shows the percentage increase in abrasion resistance.

[0025] Figure 6 The figures show the kinetic-chemical polarization test results of Examples 1 and 2, Comparative Examples 1 and 2, and the Q235 steel matrix. Detailed Implementation

[0026] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0027] Example 1: A high-entropy alloy / crystal bead composite coating, wherein the volume fraction of the CoCrFeNiMn high-entropy alloy is 90% and the volume fraction of the crystal beads is 10%, is prepared according to the following method: Step 1: Weigh out Co, Cr, Fe, Ni, and Mn elemental powders in equiatomic ratios. Load the mixed powder into a stainless steel grinding jar of a high-energy ball mill, using tungsten carbide grinding balls at a ball-to-powder mass ratio of 15:1. Pour high-purity argon gas into the grinding jar as a protective atmosphere to prevent powder oxidation. Set the ball mill speed to 400 rpm and perform dry grinding for 10 hours. Then, add anhydrous ethanol as a process control agent and wet grind for 5 hours to effectively suppress cold welding, reduce agglomeration, and obtain a high-entropy alloy powder with more uniform particle size distribution and sphericity. After ball milling, dry the powder in a vacuum drying oven at 90 ℃ for 2 hours for later use.

[0028] Step 2: Take fly ash cenospheres with a particle size range of 80-120 μm. First, ultrasonically clean them in anhydrous ethanol for 30 minutes to remove surface grease and dirt. After filtration, wash them repeatedly three times with deionized water. Place the cleaned cenospheres in a 100 ℃ oven to dry for 2 hours to completely remove moisture. Then, prepare a 10% (volume fraction) hydrofluoric acid (HF) aqueous solution as an etching solution in a polytetrafluoroethylene beaker, and add 0.3% sodium dodecyl sulfate (SDS) as a wetting agent. Add the dried cenospheres to the etching solution at a loading rate of 30 g / L, and etch them for 45 minutes with magnetic stirring at 200 rpm under a constant temperature water bath at 40 ℃. After etching, quickly wash them repeatedly with deionized water until the filtrate is neutral (pH=7). Finally, dry the cenospheres in a vacuum drying oven at 100 ℃ for 3 hours to obtain etched cenospheres with a micro-rough surface structure.

[0029] Step 3: Weigh 90% of the high-entropy alloy powder prepared in Step 1 and 10% of the etched beads obtained in Step 2 by volume. Place both in a mixer and mix at 50 rpm for 2 hours to ensure that the beads are uniformly dispersed in the high-entropy alloy powder.

[0030] Step 4: Take the mixed powder obtained in Step 3 and mix it with sodium silicate water glass adhesive at a mass ratio of 9:1, stirring to form a paste. Then, uniformly coat the paste mixture onto the surface of a Q235 steel substrate treated with 600-grit sandpaper, using a scraper to control the coating thickness to approximately 1.5 mm, forming a pre-coated layer.

[0031] Step 5: Place the Q235 steel substrate with the pre-coated layer on the worktable of the induction heating equipment. Adjust the distance between the induction coil and the coating surface to 1 mm. First, introduce argon gas (flow rate of 10 L / min) to purge the air from the chamber, and perform cladding under this protective atmosphere. The cladding process uses a two-step method: First, apply a current of 280 A to preheat the sample for 40 seconds to fully decompose the binder and raise the overall temperature of the powder layer; then, immediately increase the current to 340 A for rapid cladding for 50 seconds to fully melt the high-entropy alloy powder and the etched bead surface layer and achieve metallurgical bonding with the steel substrate. After cladding, allow it to cool naturally to room temperature under argon protection.

[0032] Figure 1 The X-ray diffraction (XRD) pattern of the high-entropy alloy / crystal bead coating prepared in Example 1 of this invention shows the presence of characteristic peaks of both high-entropy alloy and crystal beads, directly proving that the present invention has successfully prepared a composite coating composed of a metal matrix and crystal beads, with the crystal beads successfully incorporated into the coating.

[0033] Figure 2Microstructure and energy dispersive spectroscopy (EDS) images of the high-entropy alloy / floating bead (etched) composite coating prepared in Example 1 of this invention. Compared with Comparative Example 2 ( Figure 3 The interface gap of ) is compared to Example 1 ( Figure 2 The microstructure of the etching process shows that the interface between the two components is densely bonded. This indicates that the etching process primarily creates a microscopic rough structure at the physical level, strengthening the interfacial bond through an interlocking effect.

[0034] Example 2: A high-entropy alloy / crystal bead composite coating, wherein the volume fraction of the CoCrFeNiMn high-entropy alloy is 80% and the volume fraction of the crystal beads is 20%, is prepared according to the following method: Step 1: Weigh out Co, Cr, Fe, Ni, and Mn elemental powders in equiatomic ratios. Load the mixed powder into a stainless steel grinding jar of a high-energy ball mill, using tungsten carbide grinding balls at a ball-to-powder mass ratio of 15:1. Pour high-purity argon gas into the grinding jar as a protective atmosphere to prevent powder oxidation. Set the ball mill speed to 400 rpm and perform dry grinding for 10 hours. Then, add anhydrous ethanol as a process control agent and wet grind for 5 hours to effectively suppress cold welding, reduce agglomeration, and obtain a high-entropy alloy powder with more uniform particle size distribution and sphericity. After ball milling, dry the powder in a vacuum drying oven at 80 ℃ for 4 hours for later use.

[0035] Step 2: Take fly ash cenospheres with a particle size range of 80-120 μm. First, ultrasonically clean them in anhydrous ethanol for 30 minutes to remove surface grease and dirt. After filtration, wash them repeatedly three times with deionized water. Place the cleaned cenospheres in a 100 ℃ oven to dry for 2 hours to completely remove moisture. Then, prepare a 10% (volume fraction) hydrofluoric acid (HF) aqueous solution as an etching solution in a polytetrafluoroethylene beaker, and add 0.3% sodium dodecyl sulfate (SDS) as a wetting agent. Add the dried cenospheres to the etching solution at a loading rate of 30 g / L, and etch them for 45 minutes with magnetic stirring at 200 rpm under a constant temperature water bath at 40 ℃. After etching, quickly wash them repeatedly with deionized water until the filtrate is neutral (pH=7). Finally, dry the cenospheres in a vacuum drying oven at 100 ℃ for 3 hours to obtain etched cenospheres with a micro-rough surface structure.

[0036] Step 3: Weigh 80% of the high-entropy alloy powder prepared in Step 1 and 20% of the etched beads obtained in Step 2 by volume. Place both in a mixer and mix at 50 rpm for 2 hours to ensure that the beads are uniformly dispersed in the high-entropy alloy powder.

[0037] Step 4: Take the mixed powder obtained in Step 3 and mix it with sodium silicate water glass adhesive at a mass ratio of 9:1, stirring to form a paste. Then, uniformly coat the paste mixture onto the surface of a Q235 steel substrate treated with 600-grit sandpaper, using a scraper to control the coating thickness to approximately 1.5 mm, forming a pre-coated layer.

[0038] Step 5: Place the Q235 steel substrate with the pre-coated layer on the worktable of the induction heating equipment. Adjust the distance between the induction coil and the coating surface to 1 mm. First, introduce argon gas (flow rate of 10 L / min) to purge the air from the chamber, and perform cladding under this protective atmosphere. The cladding process uses a two-step method: First, apply a current of 280 A to preheat the sample for 40 seconds to fully decompose the binder and raise the overall temperature of the powder layer; then, immediately increase the current to 320 A for rapid cladding for 50 seconds, allowing the high-entropy alloy powder and the etched bead surface to fully melt and achieve metallurgical bonding with the steel substrate. After cladding, allow it to cool naturally to room temperature under argon protection.

[0039] Comparative Example 1: A high-entropy alloy coating, wherein the volume fraction of the CoCrFeNiMn high-entropy alloy is 100% and the volume fraction of the cenospheres is 0%, is prepared according to the following method: Step 1: Weigh out Co, Cr, Fe, Ni, and Mn elemental metal powders in equiatomic ratios. Load the mixed powder into a stainless steel grinding jar of a high-energy ball mill, using tungsten carbide grinding balls at a ball-to-powder mass ratio of 15:1. Pour high-purity argon gas into the grinding jar as a protective atmosphere to prevent powder oxidation. Set the ball mill speed to 400 rpm and perform dry grinding for 10 hours. Then, add an appropriate amount of anhydrous ethanol as a process control agent and wet grind for 5 hours to effectively suppress cold welding of the powder, reduce agglomeration, and obtain a high-entropy alloy powder with more uniform particle size distribution and sphericity. After ball milling, dry the powder in a vacuum drying oven at 80 ℃ for 4 hours for later use.

[0040] Step 2: Place the high-entropy alloy powder prepared in Step 1 into a mixer according to the volume fraction, and mix at 50 rpm for 2 hours. The resulting mixed powder is obtained.

[0041] Step 3: Take the mixed powder obtained in Step 2 and mix it with sodium silicate water glass adhesive at a mass ratio of 9:1, stirring to form a paste. Then, uniformly coat the paste mixture onto the surface of a Q235 steel substrate treated with 600-grit sandpaper, using a scraper to control the coating thickness to approximately 1.5 mm, forming a pre-coated layer.

[0042] Step 4: Place the Q235 steel substrate with the pre-coated layer on the worktable of the induction heating equipment. Adjust the distance between the induction coil and the coating surface to 1 mm. First, introduce argon gas (flow rate of 10 L / min) to purge the air from the chamber, and perform cladding under this protective atmosphere. The cladding process uses a two-step method: First, apply a current of 280 A to preheat the sample for 40 seconds to fully decompose the binder and raise the overall temperature of the powder layer; then, immediately increase the current to 320 A for rapid cladding, lasting for 50 seconds, to achieve metallurgical bonding of the high-entropy alloy powder steel substrate. After cladding, allow it to cool naturally to room temperature under argon protection.

[0043] Comparative Example 2: A high-entropy alloy / crystal bead composite coating, wherein the volume fraction of the CoCrFeNiMn high-entropy alloy is 90% and the volume fraction of the crystal beads is 10%, is prepared according to the following method: Step 1: Weigh out Co, Cr, Fe, Ni, and Mn elemental metal powders in equiatomic ratios. Load the mixed powder into a stainless steel grinding jar of a high-energy ball mill, using tungsten carbide grinding balls at a ball-to-powder mass ratio of 15:1. Pour high-purity argon gas into the grinding jar as a protective atmosphere to prevent powder oxidation. Set the ball mill speed to 400 rpm and perform dry grinding for 10 hours. Then, add an appropriate amount of anhydrous ethanol as a process control agent and wet grind for 5 hours to effectively suppress cold welding of the powder, reduce agglomeration, and obtain a high-entropy alloy powder with more uniform particle size distribution and sphericity. After ball milling, dry the powder in a vacuum drying oven at 80 ℃ for 4 hours for later use.

[0044] Step 2: Weigh 90% of the high-entropy alloy powder prepared in Step 1 and 10% of the untreated cenospheres by volume. Place both in a mixer and mix at 50 rpm for 2 hours.

[0045] Step 3: Take the mixed powder obtained in Step 2 and mix it with sodium silicate water glass adhesive at a mass ratio of 9:1, stirring to form a paste. Then, uniformly coat the paste mixture onto the surface of a Q235 steel substrate treated with 600-grit sandpaper, using a scraper to control the coating thickness to approximately 1.5 mm, forming a pre-coated layer.

[0046] Step 4: Place the Q235 steel substrate with the pre-coated layer on the worktable of the induction heating equipment. Adjust the distance between the induction coil and the coating surface to 1 mm. First, introduce argon gas (flow rate of 10 L / min) to purge the air from the chamber, and perform cladding under this protective atmosphere. The cladding process uses a two-step method: First, apply a current of 280 A to preheat the sample for 40 seconds to fully decompose the binder and raise the overall temperature of the powder layer; then, immediately increase the current to 320 A for rapid cladding, lasting for 50 seconds, to achieve metallurgical bonding of the high-entropy alloy powder steel substrate. After cladding, allow it to cool naturally to room temperature under argon protection.

[0047] Figure 3 Microscopic morphology and energy dispersive spectroscopy (EDS) images of the high-entropy alloy / crystal beads (unetched) composite coating prepared for Comparative Example 2 of this invention are shown. Gaps appear at the interface; although the crystal bead structure is preserved, the microscopic morphology indicates slightly poor interfacial bonding.

[0048] Bond strength determination: A universal testing machine (WDW-100E type) was used to test the bond strength between the coatings and the substrate prepared in the examples and comparative examples. The tensile test head was a high-strength steel cylinder with a diameter of 20 mm. A two-component epoxy resin structural adhesive (tensile strength > 80 MPa) was used to bond the test head to the center of the coating surface. After the adhesive cured at room temperature for 24 hours, it was further cured at 60 °C for 2 hours. The experiment was conducted with vertical tension at a constant rate of 1.0 mm / min until the coating separated from the substrate or the coating itself failed, and the maximum load at failure was recorded. Each group of samples was tested 5 times, the average bond strength was calculated, and the cross-sectional failure mode was observed. The test results are shown in Table 1. Comparative Example 1 showed the highest bond strength and cohesive failure, that is, the failure occurred inside the coating material, rather than at the interface between the coating and the substrate. This proves that the induction cladding process used in this invention can form a strong metallurgical bond between the high-entropy alloy coating and the Q235 steel substrate. The bond strength of Comparative Example 2 dropped sharply to 22.7 MPa, and it was an interfacial failure. This indicates that the smooth surface of the cenospheres has poor wettability with the high-entropy alloy substrate, resulting in weak interfacial bonding and becoming a weak point in the coating, severely degrading the overall performance of the coating. The bonding strength of Examples 1 and 2 (55.8 MPa and 52.1 MPa, respectively) is higher than that of Comparative Example 2, and the failure mode is mixed failure, meaning that some damage occurs at the interface, and some occurs inside the coating or within the cenospheres themselves, with strength values ​​comparable to those of pure high-entropy alloy coatings. This indicates that the micro-rough structure created on the cenosphere surface by hydrofluoric acid etching effectively promotes the penetration and anchoring of the molten high-entropy alloy, forming a strong metallurgical bond and greatly improving the interfacial bonding.

[0049] Table 1. Results of the bond strength test Wear Measurement: The wear performance of the coatings prepared in the examples and comparative examples at room temperature was studied using an MDW-02 abrasive wear testing machine. The friction pair was made of YG6 cemented carbide (HV1521) with a diameter of 6.35 mm. The thickness and diameter of the specimens were 3 mm and 20 mm, respectively. The test parameters were: rotational speed 65 r / min, load 40 N, duration 1 h, and radial feed rate 4 mm / s. The test results are shown in Table 2. Wear Resistance: Example 2 > Example 1 > Comparative Example 1 > Comparative Example 2 > Q235 steel substrate. As shown in Table 2, with the increase of hydrofluoric acid etched bead content, the wear resistance of the high-entropy alloy / bead composite coating increased relative to the CoCrFeNiMn high-entropy alloy, while the wear resistance of the high-entropy alloy / bead composite coating with added untreated hydrofluoric acid etched beads decreased relative to the CoCrFeNiMn high-entropy alloy.

[0050] Table 2 Wear Test Results Figure 4 Wear morphology images of the Q235 steel substrate, the high-entropy alloy coating prepared in Comparative Example 1, the high-entropy alloy / crystal composite coating prepared in Comparative Example 2, the high-entropy alloy / crystal composite coating prepared in Example 1, and the high-entropy alloy / crystal composite coating prepared in Example 2. Figure 4 (a) Q235 steel matrix: The surface shows wide and deep furrows and severe material spalling, indicating severe plastic deformation and material loss. Figure 4 (b) Comparative Example 1: The wear morphology was greatly improved, the furrows became shallower and narrower, and the surface was relatively smooth. Figure 4 (c) Comparative example: Obvious spalling pits and deep furrows appear on the surface. This is because the interface between the unetched smooth beads and the high-entropy alloy substrate is weak. During the wear process, the beads are easy to fall off. The hard particles that fall off act as a third-body abrasive, which aggravates the wear of the coating, thus causing its wear resistance to be even lower than that of the pure high-entropy alloy coating. Figure 4 (d) Example 1 and Figure 4 (e) Example 2: The worn surface is the smoothest, with only minor scratches remaining. The hard abrasive particles are firmly embedded in the matrix, effectively bearing the load and hindering the ploughing action of the abrasive, thus exhibiting the best wear resistance. Example 2, containing more hard reinforcing phases, further enhances its wear resistance.

[0051] Figure 5The graph shows the percentage improvement in wear resistance. Compared to the Q235 steel substrate, the wear resistance of Examples 1 and 2 increased by 67.4% and 72.5%, respectively, demonstrating the significant advantages of the composite coating of the present invention. Compared to Comparative Example 1, the wear resistance of Examples 1 and 2 still increased by 47.6% and 55.7%, respectively. The present invention, by introducing hydrofluoric acid-etched cenospheres, not only did not degrade performance but also significantly enhanced the wear resistance of the high-entropy alloy coating.

[0052] Figure 6 The figures show the kinetic-chemical polarization test results of Examples 1 and 2, Comparative Examples 1 and 2, and Q235 steel substrate. Kinetic-chemical polarization test: The corrosion resistance of Examples 1 and 2, Comparative Examples 1 and 2, and Q235 steel was tested using an electrochemical workstation (CHI660D). A three-electrode system was used, including a saturated calomel reference electrode, a platinum auxiliary electrode, and the sample as the working electrode. The test area on the sample surface was 1 cm². 2 The solution was a 3.5 wt.% NaCl solution. The corrosion resistance was as follows: Example 1 > Example 2 > Q235 substrate > Comparative Example 1 > Comparative Example 2. The corrosion resistance increased with the addition of etched cenosphere-treated high-entropy alloy coatings; however, the corrosion resistance of the composite coating decreased with increasing cenosphere content. The corrosion resistance of the unetched cenosphere / high-entropy alloy composite coating was further reduced compared to the etched cenosphere / high-entropy alloy composite coating.

[0053] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A high-entropy alloy / crystal bead composite coating, characterized in that, The composite coating consists of a high-entropy alloy of CoCrFeNiMn with a volume fraction of 75-95% and cenospheres with a volume fraction of 5-25%.

2. The method for preparing a high-entropy alloy / crystal bead composite coating as described in claim 1, characterized in that, Includes the following steps; Step 1: Prepare CoCrFeNiMn high-entropy alloy powder by ball milling metal powders according to equiatomic ratio; Step 2: Pre-treat the cenospheres and etch them with hydrofluoric acid; Step 3: Mix the CoCrFeNiMn high-entropy alloy powder prepared in Step 1 with the hydrofluoric acid etched beads after Step 2 in a volume percentage of 75-95%: 5-25%. Step 4: Use water glass to bond the mixed powder obtained in step 3 and apply it to Q235 with cold compress; Step 5: Using an induction heating device, Q235 with pre-mixed powder from Step 4 is induction cladding in an argon atmosphere to obtain a high-entropy alloy / flotation composite coating.

3. The method for preparing a high-entropy alloy / flotation composite coating as described in claim 2, characterized in that, In step 1, the CoCrFeNiMn high-entropy alloy powder is prepared by ball milling. Equivalent atomic ratio metal powder is placed in a stainless steel container, tungsten carbide is used as the grinding ball, the ball-to-material ratio is 15:1, and the powder is dry-milled at 400 rpm for 10 h under an argon atmosphere. Then, ethanol is added as a control agent for wet milling for 5 h.

4. The method for preparing a high-entropy alloy / flotation composite coating as described in claim 2, characterized in that, In step 2, the pretreatment of the cenospheres is as follows: cleaning, placing the cenospheres in anhydrous ethanol and ultrasonically cleaning for 15-30 minutes; filtration, washing repeatedly with deionized water 2-3 times; drying the cleaned cenospheres in an oven at 80-120 ℃ for 1-2 hours for later use.

5. The method for preparing a high-entropy alloy / flotation composite coating as described in claim 2, characterized in that, In step 2, the hydrofluoric acid etching is specifically performed as follows: the pretreated cenospheres are immersed in a 5-20% hydrofluoric acid aqueous solution, and 0.1-0.5% sodium dodecyl sulfate is added to reduce the surface tension of the etching solution, so as to better wet and penetrate the cenosphere surface and make the etching more uniform. The etching is performed at 30-60 ℃ for 30-60 min. After etching, the cenospheres are thoroughly washed with deionized water 3-5 times until neutral, and then dried in a vacuum drying oven at 80-120 ℃ for 2-3 h.

6. The method for preparing a high-entropy alloy / flotation composite coating as described in claim 2, characterized in that, In step 5, the induction cladding conditions are as follows: the induction cladding current is set in the range of 250-360 A; the preheating time is 30-60 s and the preheating current is 250-290 A; the heating cladding time is 45-60 s and the heating cladding current is 310-360 A; the distance between the coating and the magnetic conductor is 1 mm, and the protective atmosphere is argon.

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