An ultrahigh-hardness anti-cavitation high-entropy alloy coating and a preparation method thereof

Abstract

The application discloses a kind of superhard anti-cavitation high-entropy alloy coating and preparation method thereof.The atom percentage of the superhard high-entropy alloy coating described herein is: Al 20%~26%, Cr 30%~34%, Co 30%~34%, Ni 16%~22%.The high-entropy alloy coating of the application can maintain solid solution stability under the condition of higher Al content, and will not appear element desorption and heterogeneous nucleation during powdering and spraying process.The crystal structure is single body-centered cubic phase (BCC), and can have very high hardness without any post-processing process: nano-hardness can reach 9.1~11.4 GPa, and microhardness is 858~881 HV 0.1 , which is the maximum value of high-entropy alloy coating prepared by the same process reported in China at present, and is suitable for popularization and application as anti-cavitation coating on the surface of various flow mechanical components.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced metal materials and surface protection, and particularly relates to an ultra-high hardness cavitation-resistant high-entropy alloy coating and a preparation method thereof. Background Art

[0002] Cavitation erosion is the most common threat to the safe operation of flow-through components, such as propellers and turbine blades, operating in hydrodynamic environments. Cavitation damage to materials primarily stems from the mechanical damage to the material surface caused by the high-pressure shock waves and high-speed microjets (cavitation loading) generated by the collapse of cavitation bubbles. Therefore, the search for high-strength and high-hardness materials has long been a research priority in cavitation erosion prevention. Since cavitation erosion originates from the component surface, coating the flow-through components with cavitation-resistant materials through advanced surface engineering techniques such as thermal spraying is undoubtedly a cost-effective and practical approach.

[0003] Metal-ceramic coatings, such as WC-CoCr and Cr3C2-NiCr (Wear, 2016, 364-365, 201-210), are among the earliest surface protective coatings used on flow-passing components due to their high hardness and excellent resistance to cavitation loads. However, the actual service life of these coatings is often significantly shorter than their initial design life. Research and analysis have revealed that while the hard WC and Cr3C2 phases are resistant to cavitation loads, the bonding metal Co or NiCr alloys are the first to be debonded due to their low hardness. Subsequently, the unbonded WC or Cr3C2 particles also rapidly debond under the load. Furthermore, carbide phases such as WC and Cr3C2 are extremely sensitive to high temperatures and oxygen. They are easily oxidized and decomposed during coating preparation using industrial techniques such as high-velocity flame spraying or atmospheric plasma spraying, significantly reducing the coating's toughness. Consequently, the cavitation protection capabilities of these coatings fall far short of expectations.

[0004] High entropy alloys (HEAs) often exhibit mechanical strength that is difficult to match with traditional metal materials due to their inherent high entropy effect, lattice distortion effect, delayed diffusion effect, and cocktail effect. They also tend to form simple solid solution structures, making them a research hotspot for new cavitation protection coatings. The invention patent with publication number CN115418595B, "A high entropy alloy coating resistant to cavitation corrosion and its preparation method," discloses a high entropy alloy powder and coating based on a face-centered cubic phase (FCC). The coating exhibits a high work hardening index and good impact energy absorption capability, but its hardness is still relatively low. Under repeated impacts of high-pressure shock waves or high-speed microjets, the surface layer will inevitably enrich structural defects such as dislocations due to plastic deformation, leading to fatigue delamination and accelerated cavitation damage (ACS Applied Materials & Interfaces, 2023, 15(2), 3651-3663).

[0005] To date, people have not yet developed a high-entropy alloy coating with a hardness close to that of metal-ceramic coatings and a uniform structure, resulting in the current practical application of this type of coating is still limited. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides an ultra-high hardness high-entropy alloy coating and its preparation method, which can not only obtain a single face-centered cubic structure (BCC) spherical spray powder and a high-density coating through the vacuum induction atomization powder making technology and supersonic flame spraying technology that are convenient for industrial production, but also has extremely high nanohardness (9.1~11.4 GPa) and microhardness (858~881 HV) without any post-processing process. 0.1 ), which is the maximum value of high entropy alloy coatings prepared by the same process reported in China, and even exceeds the Cr3C2-NiCr metal ceramic coating (780±40 HV 0.1 ) (Tribology Letters, 2010, 37, 463-475), thus showing excellent cavitation protection ability and having great application potential as a cavitation-resistant coating on the surface of flow-through components such as turbines, propellers, and thrust bearings.

[0007] 1. Preparation of ultra-high hardness high entropy alloy coating

[0008] Disclosed is an ultra-high hardness cavitation-resistant high-entropy alloy coating. Calculated by atomic percentage, the high-entropy alloy coating comprises the following components (at.%): Al 20%-26%, Cr 30%-34%, Co 30%-34%, and Ni 16%-22%.

[0009] The preparation method is as follows:

[0010] (1) Prepare pure metal raw materials containing Al, Cr, Co, and Ni according to the atomic percentage of the high entropy alloy coating converted into mass percentage, clean the crucible at the same time, and then place the prepared raw materials into the crucible of the induction heating furnace;

[0011] (2) Vacuum to ensure the vacuum degree is ≤1×10 -1 Pa, the raw material is heated to 1250~1750℃ through an induction coil, melted and flowed into the atomization zone, and the metal liquid is impacted and broken by high-speed and high-pressure inert gas, atomized into fine metal droplets, which are then cooled and solidified into high-entropy alloy powder in the atomization chamber. After screening, the powder with a particle size range of 15~70 μm suitable for use in supersonic flame spraying technology is obtained;

[0012] (3) The surface of the metal substrate is sandblasted and cleaned, and then fixed on a spraying table. After setting the spraying process parameters, the supersonic flame spraying equipment is started, and the powder obtained in step (2) is sent into the flame flow and sprayed and deposited on the surface of the metal substrate to obtain an ultra-high hardness cavitation-resistant high-entropy alloy coating.

[0013] In step (1), the purity of the pure metal raw materials of Al, Cr, Co and Ni is above 99.9 wt.%.

[0014] In step (2), the inert gas is any one of nitrogen, argon and helium, with a pressure of 0.5~5 MPa and a flow rate of 900~1500 m 3 / h.

[0015] In step (3), the metal substrate is one of copper alloy, titanium alloy, aluminum alloy, stainless steel, nickel aluminum bronze, manganese aluminum bronze, aluminum bronze, L907A steel, and cast steel, and the roughness of the metal substrate surface after sandblasting is Ra ≥ 1 μm.

[0016] In step (3), the fuel gas used by the supersonic flame spraying equipment is natural gas, propane or aviation kerosene, the supporting gas is oxygen or air, and the carrier gas is nitrogen, argon or helium.

[0017] The spraying parameters in step (3) are oxygen flow rate 50~56 m 3 / h, gas flow rate 20~25 L / h, powder feeder speed 20~25 rpm, spray gun moving speed 200~1000 mm / s, spraying distance 25~40 cm, pass spacing 1~4mm, compressed air pressure 100~120MPa, compressed air flow 18~22 m 3 / h.

[0018] The coating thickness deposited in step (3) is 100~800 μm, and the phase structure is a single BCC phase.

[0019] 2. Morphology and structure of high entropy alloy powder

[0020] Figure 1 The SEM image of the high-entropy alloy powder of the present invention is shown. The powder exhibits good sphericity and a smooth surface, demonstrating that the optimized metal element formulation system of the present invention, particularly the optimized melting temperature, atomizing gas pressure, and flow rate, is well suited for producing spherical high-entropy alloy powders via vacuum induction atomization industrial powder production technology, which is extremely beneficial for improving powder flowability. Furthermore, the image shows that the powder particle size ranges primarily between 15 and 53 μm, indicating that the sieved high-entropy alloy powder falls within the particle size range most suitable for use in supersonic flame spraying technology.

[0021] Figure 2 The XRD pattern of the high-entropy alloy powder of the present invention is presented. It is readily apparent that the powder exhibits only diffraction peaks characteristic of the BCC phase, devoid of any other impurity peaks. This indicates that the optimized atomic ratio of Al, Cr, Co, and Ni in the present invention does not result in elemental dissolution or heterogeneous nucleation during the atomization process due to differences in solubility and electronegativity among the four elements. Despite the significantly higher Al content than previously disclosed high-entropy alloys such as CN115418595B, the simple solid solution phase remains stable, resulting in a novel high-entropy alloy powder material with a phase structure significantly different from that of the conventional single BCC phase. This is highly advantageous for fully utilizing the strong lattice distortion and concentration fluctuations brought about by the differences in atomic size and electronegativity between Al and the other three elements to significantly enhance the mechanical strength and load-resistance of the high-entropy alloy.

[0022] 3. Microstructure of high entropy alloy coating

[0023] Figure 3 A SEM image of a polished cross-section of the high-entropy alloy coating of the present invention is provided. As can be seen, the coating's structure is very dense, with virtually no pores observed within the coating. Furthermore, the coating's interface with the metal substrate is extremely tight, with no obvious defects. This demonstrates that the optimized powder feed composition, morphology, and particle size range, particularly the HVOF process parameters, are well-suited for producing highly bonded and dense high-entropy alloy coatings, facilitating their application on various metal component surfaces.

[0024] Figure 4The XRD pattern of the high-entropy alloy coating of the present invention is presented. It can be found that the coating still perfectly retains the single BCC phase crystal structure of its sprayed powder, without any diffraction peaks of other crystal structures, intermetallic compounds, or oxides. This further proves that the optimized powder composition and high-velocity flame spraying parameters of the present invention can effectively maintain the stability of this new solid solution during the high-temperature spraying process, which is crucial for ultimately achieving a high-entropy alloy coating with ultra-high strength and excellent cavitation resistance.

[0025] 4. Performance test of high entropy alloy coating

[0026] In order to better study the performance of the high entropy alloy coating of the present invention, a series of mechanical properties tests were carried out using a nanoindenter and a microhardness tester. The results are as follows: Figure 5 and 6 As shown. It can be seen that the nanohardness of the high entropy alloy coating of the present invention is as high as 9.1~11.4 GPa, and the microhardness is also 858~881 HV 0.1 These data are not only significantly higher than those of the Al2O3 prepared in Comparative Example 1, which is mainly composed of FCC phase. 10 Cr 28 Co 28 Ni 34 The high entropy alloy coating is also higher than the traditional AlCrCoFeNi high entropy alloy coating with BCC phase prepared in Comparative Example 2, and even higher than the Cr3C2-NiCr metal ceramic coating (780±40 HV 0.1 ) (Tribology Letters, 2010, 37, 463-475). Among them, the Al 10 Cr 28 Co 28 Ni 34 The nanohardness and microhardness of the high entropy alloy coating are only 4.7 GPa and 516 HV respectively. 0.1 , while the nanohardness and microhardness of the AlCrCoFeNi high entropy alloy coating dominated by BCC phase are only 7.7 GPa and 705 HV respectively. 0.1 , which are respectively reduced by about 10% to 60% compared with the high-entropy alloy of the present invention. This indicates that the present invention has successfully developed a new high-entropy alloy coating with a single BCC phase that can match the hardness of traditional metal ceramic coatings.

[0027] An ultrasonic vibration cavitation tester was used to conduct cavitation experiments on the high entropy alloy coating prepared by the present invention, the high entropy alloy coating prepared in Comparative Examples 1 and 2, and L907A steel, a commonly used metal material for flow-through components, in deionized water in accordance with the GB / T 6383-2009 standard. The test conditions were as follows: the temperature of the deionized water was (25±2)°C, the vibration frequency of the amplitude rod was 20 kHz, the amplitude was 50 μm (peak-to-peak), the distance between the lower end of the amplitude rod and the coating surface was 0.5 mm, and the distance between the sample surface and the liquid surface was 12 mm. The surface SEM morphology of the high entropy alloy coating of the present invention and the high entropy alloy coating prepared in Comparative Example 1 after cavitation for 3 h was observed using SEM. Figure 7 As shown, the cavitation damage of the coating surface material in Comparative Example 1 is more serious, while the degree of peeling of the surface of the high entropy alloy coating of the present invention is much milder, indicating that the ultra-high hardness high entropy alloy coating of the present invention can better resist the mechanical impact caused by cavitation collapse and effectively prevent the peeling of the material. The cumulative mass loss of the samples after different cavitation times was weighed using a 1 / 10,000 balance. The results are shown in Figure 8 It is not difficult to find that after 10 hours of cavitation, the cumulative mass losses of the high-entropy alloy coatings prepared in Examples 1-3 were 6.6 mg, 7.2 mg, and 6.9 mg, respectively, significantly lower than those of metal-ceramic coatings such as WC-CoCr and Cr3C2-NiCr (Wear, 2016, 364-365, 201-210). The cumulative mass losses of the high-entropy alloy coating in Comparative Example 1 and Comparative Example 2 were 11.2 mg, 20.1 mg, and 69.7 mg for L907A steel, respectively, significantly higher than those of the coatings of the present invention. This demonstrates that the ultra-high-hardness high-entropy alloy coatings with a single BCC phase prepared in the present invention exhibit extremely superior cavitation resistance. Under cavitation loads, they exhibit more consistent deformation or resistance to deformation, avoiding the selective destruction of individual phases that accelerates overall material damage. These coatings are more suitable for use as cavitation-resistant coatings than other existing metal or cermet coatings.

[0028] In summary, the present invention has the following advantages compared with the prior art:

[0029] The present invention optimizes the atomic ratio of the four metal components Al, Cr, Co and Ni, as well as the process parameters of vacuum induction atomization powder making and supersonic flame spraying. On the basis of ensuring the stability of the high-entropy solid solution structure, the content of Al, which has obvious differences in atomic size, electronegativity and solubility from the other three elements, is significantly increased. The strengthening effect brought about by the lattice distortion and concentration fluctuation caused by this component is greatly amplified. As a result, the coating exhibits a nanohardness of 9.1-11.4 GPa and a microhardness of 858-881 HV without any post-processing process. 0.1The ultra-high hardness is not only the maximum value of high-entropy alloy coatings prepared by the same process currently reported in China, but even exceeds the Cr3C2-NiCr metal ceramic coating prepared by supersonic flame spraying technology, and can effectively resist damage from external forces. More importantly, the high-entropy alloy system of the present invention can produce spherical powders and dense coatings of a single BCC phase through very mature industrial production technologies such as vacuum induction atomization powder making and supersonic flame spraying. It can also effectively prevent the coating from selective spalling damage caused by uneven phase structure under cavitation load impact, demonstrating cavitation resistance that is far superior to other existing metal or metal ceramic coatings. Therefore, it is very suitable for promotion and application on the surfaces of various complex and special-shaped flow-through components such as turbines, propellers, and thrust bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the SEM morphology of the high entropy alloy powder of Example 1 of the present invention.

[0031] Figure 2 This is the XRD pattern of the high entropy alloy powder of Example 1 of the present invention.

[0032] Figure 3 This is the SEM cross-sectional morphology of the high entropy alloy coating of Example 1 of the present invention.

[0033] Figure 4 This is the XRD pattern of the high entropy alloy coating of Example 1 of the present invention.

[0034] Figure 5 The nanohardness of the high entropy alloy coatings of the embodiments of the present invention and the comparative example.

[0035] Figure 6 The microhardness of the high entropy alloy coatings of the embodiments of the present invention and the comparative example.

[0036] Figure 7 Surface SEM morphologies of the high entropy alloy coatings of Example 1 of the present invention and Comparative Example 1 after cavitation in deionized water for 3 h.

[0037] Figure 8 The cavitation cumulative mass loss curves of the high entropy alloy coating and L907A steel in deionized water in the examples and comparative examples of the present invention are shown. DETAILED DESCRIPTION

[0038] The present invention will be further explained below with reference to specific embodiments.

[0039] Example 1

[0040] (1) Select pure metals with a purity of more than 99.9 wt.% of Al, Cr, Co and Ni as raw materials, and mix them according to the atomic percentage: Al 22%; Cr 30%; Co 30%; Ni 18%. Before mixing, clean the oxide film and impurities on the surface of the raw materials. When mixing, convert the atomic ratio into the percentage of the mass of each element in the total mass, weigh them, and put them into the crucible.

[0041] (2) Place the crucible into the vacuum induction atomization powder making furnace, cover the furnace door, and start vacuuming. Wait until the vacuum degree reaches 5×10 -2 After Pa, the raw materials in the crucible are heated to 1400~1600 ℃ through the induction coil to melt, and the molten metal flows into the atomizing nozzle through the guide hole.

[0042] (3) Use argon gas with a pressure of 1~2 MPa at 800~1500 m 3 The flow rate of / h is passed through the atomizing nozzle to impact and break the molten metal falling into the atomizing area, making it atomized into fine metal droplets, which are then cooled and solidified into high entropy alloy powder in the atomizing chamber. After screening, spherical Al2O3 with a particle size range of 15~53 μm is obtained. 22 Cr 30 Co 30 Ni 18 powder.

[0043] (4) Using supersonic flame spraying technology to spray and deposit Al on the surface of 316L stainless steel substrate after sandblasting roughening 22 Cr 30 Co 30 Ni 18 The corresponding coating material can be obtained by high entropy alloy powder. The spraying process is an oxygen flow rate of 52.3 m 3 / h, kerosene flow rate 22.7 L / h, powder feeder speed 21 rpm, spray gun moving speed 600 mm / s, spraying distance 38.0 cm, pass spacing 2 mm, compressed air pressure 110 MPa, compressed air flow rate 19 m 3 / h, and the coating thickness is about 320 μm.

[0044] (5) Phase structure and properties of high entropy alloy coating: The crystal structure is a single BCC phase, the nanohardness is 11.4GPa, and the microhardness is 881HV 0.1 The cumulative mass loss after cavitation in deionized water for 10 h is only 6.6 mg, showing the characteristics of typical ultra-high hardness and extremely excellent cavitation resistance.

[0045] Example 2

[0046] (1) Select pure metals with a purity of more than 99.9 wt.% of Al, Cr, Co and Ni as raw materials, and mix them according to the atomic percentage: Al 22%; Cr 30%; Co 30%; Ni 18%. Before mixing, clean the oxide film and impurities on the surface of the raw materials. When mixing, convert the atomic ratio into the percentage of the mass of each element in the total mass, weigh them, and put them into the crucible.

[0047] (2) Place the crucible into the vacuum induction atomization powder making furnace, cover the furnace door, and start vacuuming. Wait until the vacuum degree reaches 5×10 -2 After Pa, the raw materials in the crucible are heated to 1400~1600 ℃ through the induction coil to melt, and the molten metal flows into the atomizing nozzle through the guide hole.

[0048] (3) Use argon gas with a pressure of 1~2 MPa at 800~1500 m 3 The flow rate of / h is passed through the atomizing nozzle to impact and break the molten metal falling into the atomizing area, making it atomized into fine metal droplets, which are then cooled and solidified into high entropy alloy powder in the atomizing chamber. After screening, spherical Al2O3 with a particle size range of 15~53 μm is obtained. 22 Cr 30 Co 30 Ni 18 powder.

[0049] (4) Using supersonic flame spraying technology to spray deposit Al on the surface of the nickel-aluminum bronze substrate after sandblasting roughening 22 Cr 30 Co 30 Ni 18 The corresponding coating material can be obtained by high entropy alloy powder. The spraying process is an oxygen flow rate of 54.5 m 3 / h, kerosene flow rate of 23.4 L / h, powder feeder speed of 23 rpm, spray gun moving speed of 500 mm / s, spraying distance of 38.0 cm, pass spacing of 2 mm, compressed air pressure of 110 MPa, compressed air flow rate of 19 m 3 / h, the coating thickness is about 450 μm.

[0050] (5) Phase structure and properties of high entropy alloy coating: The crystal structure is a single BCC phase, the nanohardness is 9.7GPa, and the microhardness is 858 HV 0.1 The cumulative mass loss after cavitation in deionized water for 10 h is only 7.2 mg, showing the characteristics of typical ultra-high hardness and extremely excellent cavitation resistance.

[0051] Example 3

[0052] (1) Select pure metals with a purity of more than 99.9 wt.% of Al, Cr, Co and Ni as raw materials, and mix them according to the atomic percentage: Al 22%; Cr 30%; Co 30%; Ni 18%. Before mixing, clean the oxide film and impurities on the surface of the raw materials. When mixing, convert the atomic ratio into the percentage of the mass of each element in the total mass, weigh them, and put them into the crucible.

[0053] (2) Place the crucible into the vacuum induction atomization powder making furnace, cover the furnace door, and start vacuuming. Wait until the vacuum degree reaches 5×10 -2 After Pa, the raw materials in the crucible are heated to 1400~1600 ℃ through the induction coil to melt, and the molten metal flows into the atomizing nozzle through the guide hole.

[0054] (3) Use argon gas with a pressure of 1~2 MPa at 800~1500 m 3 The flow rate of / h is passed through the atomizing nozzle to impact and break the molten metal falling into the atomizing area, making it atomized into fine metal droplets, which are then cooled and solidified into high entropy alloy powder in the atomizing chamber. After screening, spherical Al2O3 with a particle size range of 15~53 μm is obtained. 22 Cr 30 Co 30 Ni 18 powder.

[0055] (4) Using supersonic flame spraying technology to spray deposit Al on the surface of TC4 titanium alloy substrate after sandblasting roughening 22 Cr 30 Co 30 Ni 18 The corresponding coating material can be obtained by spraying high entropy alloy powder. The spraying process is oxygen flow rate 50.2 m 3 / h, kerosene flow rate 21.5 L / h, powder feeder speed 22 rpm, spray gun moving speed 800 mm / s, spraying distance 38.0 cm, pass spacing 2 mm, compressed air pressure 110 MPa, compressed air flow rate 19 m 3 / h, and the coating thickness is about 400 μm.

[0056] (5) Phase structure and properties of high entropy alloy coating: The crystal structure is a single BCC phase, the nanohardness is 9.1GPa, and the microhardness is 860 HV 0.1 The cumulative mass loss after cavitation in deionized water for 10 h is only 6.9 mg, showing the characteristics of typical ultra-high hardness and extremely excellent cavitation resistance.

[0057] Comparative Example 1

[0058] (1) High entropy alloy powder with a particle size range of 15-53 μm and an atomic percentage of Al 10%, Cr 28%, Co 28%, and Ni 34% (not within the atomic percentage range specified in the claims of the present invention) prepared by vacuum induction atomization powder making technology was selected as the spray feed.

[0059] (2) Using supersonic flame spraying technology to spray deposit Al on the surface of 316L stainless steel substrate after sandblasting roughening 10 Cr 28 Co 28 Ni 34 The corresponding coating material can be obtained by high entropy alloy powder. The spraying process is an oxygen flow rate of 52.3 m 3 / h, kerosene flow rate 22.7 L / h, powder feeder speed 21 rpm, spray gun moving speed 600 mm / s, spraying distance 38.0 cm, pass spacing 2 mm, compressed air pressure 110 MPa, compressed air flow rate 19 m 3 / h, the coating thickness is about 500 μm.

[0060] (3) Al 10 Cr 28 Co 28 Ni 34 Phase structure and properties of high entropy alloy coating: The crystal structure is a single FCC phase, the nanohardness is 4.7 GPa, and the microhardness is 516 HV 0.1 The cumulative mass loss after 10 h of cavitation in deionized water was 11.2 mg, indicating that the hardness and cavitation resistance of this coating were inferior to those of the coating of the present invention. This indicates that even if the type of metal components, powder particle size, and spraying process are consistent with those of the present invention, it is impossible to prepare an ultra-high-hardness, cavitation-resistant high-entropy alloy coating as long as the atomic ratio of the metal components is not within the range specified in the claims of the present invention.

[0061] Comparative Example 2

[0062] (1) High entropy alloy powder (not within the range of component types and atomic percentages specified in the claims of the present invention) with a particle size range of 15-53 μm and an atomic percentage of Al 20%, Cr 20%, Co 20%, Fe 20%, and Ni 20% prepared by vacuum induction atomization powder making technology is selected as spray feed.

[0063] (2) The corresponding coating material can be obtained by spraying and depositing AlCrCoFeNi high entropy alloy powder on the surface of 316L stainless steel substrate after sandblasting roughening using supersonic flame spraying technology. The spraying process is an oxygen flow rate of 20.4 m 3 / h, natural gas flow rate 16.6 m 3 / h, powder feeding rate is 25 g / min, spray gun moving speed is 800 mm / s, spraying distance is 27.5 cm, pass spacing is 2 mm, compressed air pressure is 110 MPa, compressed air flow rate is 19 m 3 / h, the coating thickness is about 450 μm.

[0064] (3) Phase structure and properties of AlCrCoFeNi high entropy alloy coating: The crystal structure is a single BCC phase, the nanohardness is 7.7 GPa, and the microhardness is 705 HV 0.1 The cumulative mass loss after 10 h of cavitation in deionized water was 20.1 mg. This indicates that while the coating's hardness is higher than that of Comparative Example 1, its cavitation resistance is worse. This indicates that even if the coating's crystal structure is consistent with that of the present invention, it is impossible to produce an ultra-high-hardness, cavitation-resistant high-entropy alloy coating unless the types, atomic ratios, and spraying parameters of the metal components fall within the ranges specified in the claims.

[0065] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating, characterized in that: The following steps are involved: (1) Prepare corresponding amounts of pure metal raw materials containing Al, Cr, Co, and Ni according to the atomic percentages of Al 20% to 26%, Cr 30% to 34%, Co 30% to 34%, and Ni 16% to 22%. Clean the crucible at the same time, and then place the prepared raw materials into the crucible of the induction heating furnace. (2) Vacuum to ensure the vacuum degree is ≤1×10 -1 Pa, the raw material is heated to 1250~1750℃ through an induction coil, melted and flowed into the atomization zone, and the metal liquid is impacted and broken by high-speed and high-pressure inert gas, atomized into fine metal droplets, which are then cooled and solidified into high-entropy alloy powder in the atomization chamber. After screening, the powder with a particle size range of 15~70 μm suitable for use in supersonic flame spraying technology is obtained; (3) The surface of the metal substrate is sandblasted and cleaned, and then fixed on a spraying table. After setting the spraying process parameters, the supersonic flame spraying equipment is started, and the powder obtained in step (2) is sent into the flame flow and sprayed and deposited on the surface of the metal substrate to obtain an ultra-high hardness cavitation-resistant high-entropy alloy coating.

2. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, characterized in that: The purity of the pure metal raw materials of Al, Cr, Co and Ni in step (1) is above 99.9 wt.%.

3. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, wherein: In step (2), the inert gas is any one of nitrogen, argon and helium, the pressure of the inert gas is 0.5~5 MPa, and the flow rate of the inert gas is 900~1500 m 3 / h.

4. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, wherein: In step (3), the metal substrate is one of copper alloy, titanium alloy, aluminum alloy, stainless steel, nickel aluminum bronze, manganese aluminum bronze, aluminum bronze, L907A steel, and cast steel, and the roughness of the metal substrate surface after sandblasting is Ra≥1μm.

5. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, wherein: In step (3), the fuel gas used by the supersonic flame spraying equipment is natural gas, propane or aviation kerosene, the supporting gas is oxygen or air, and the carrier gas is nitrogen, argon or helium.

6. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, wherein: The spraying parameters in step (3) are oxygen flow rate 50~56 m 3 / h, gas flow rate 20~25 L / h, powder feeder speed 20~25 rpm, spray gun moving speed 200~1000 mm / s, spraying distance 25~40 cm, pass spacing 1~4 mm, compressed air pressure 100~120MPa, compressed air flow 18~22 m 3 / h.

7. The method for preparing an ultra-high hardness cavitation-resistant high-entropy alloy coating according to claim 1, wherein: The thickness of the ultra-high hardness cavitation-resistant high-entropy alloy coating deposited in step (3) is 100~800 μm, and the coating phase structure is a single BCC phase.

8. An ultra-high hardness cavitation-resistant high-entropy alloy coating prepared by the preparation method according to any one of claims 1 to 7.

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