An amorphous surface heterogeneous amorphous coating and its preparation method and application

Abstract

The application provides a kind of amorphous surface heterogeneous amorphous coating and its preparation method and application, it is related to amorphous coating preparation technical field.The application provides a kind of preparation method of amorphous surface heterogeneous amorphous coating, comprising the following steps: using heterogeneous amorphous powder is sprayed on the surface of amorphous alloy matrix to form heterogeneous amorphous coating;The chemical composition of the heterogeneous amorphous powder and amorphous alloy matrix is not same.The application uses cold spraying method, and the porosity of heterogeneous amorphous coating prepared on the surface of amorphous alloy is low, shrinkage is small, amorphous rate is high, the thermal influence on zirconium-based amorphous matrix of high strength, high hardness and metastable state is small, which greatly improves the hardness, wear resistance, corrosion resistance and service life of the matrix, and widens its application range.

Description

Technical Field

[0001] The present invention relates to the technical field of amorphous coating preparation, and in particular to a heterogeneous amorphous coating on an amorphous surface, a preparation method and an application thereof. Background Art

[0002] Bulk metallic glasses (BMGs) possess unique atomic arrangements, resulting in mechanical properties several times greater than those of conventional crystalline alloys. Among these, zirconium-based amorphous alloys boast not only strong glass-forming abilities, with critical sizes exceeding 30 mm, but also excellent mechanical properties. These alloys have found applications in military, electronics, medical devices, sporting goods, and space engineering. However, among these amorphous systems, zirconium-based amorphous alloys suffer from relatively poor wear resistance.

[0003] Thermal spraying (supersonic flame spraying, plasma spraying, detonation spraying, arc spraying and electrospark deposition, etc.), laser cladding, laser stereo forming and cold spraying can all be used to prepare amorphous coatings. Among them, thermal spraying and laser cladding require the spraying material to be heated and melted and then rapidly cooled again to become amorphous. Not only is the amorphous content limited, the porosity is high, and the amorphous matrix is ​​easily crystallized. The inevitable remelting of powder and matrix in laser stereo forming causes the interface composition to deviate from any of the amorphous components on both sides to form a transition layer. The dendrites in the transition layer grow perpendicular to the matrix, and cracks are easily formed between the dendrites due to stress. Therefore, the above methods are not suitable for the preparation of heterogeneous amorphous coatings on amorphous surfaces.

[0004] In the past 30 years, the emerging cold spray technology does not require melting of the substrate and powder. The powder is carried by high-pressure gas and sprayed onto the substrate surface, causing both to plastically deform to form a coating. This can maximize the preservation of its amorphous structure and reduce oxidation and phase change of the interface material. The coating has little shrinkage and thermal impact, which is particularly suitable for the preparation of heat-sensitive amorphous coatings. However, this technology is not yet mature. Currently, there are only a few reports on the preparation of amorphous coatings on metal surfaces. Cold spraying amorphous coatings on high-strength, high-hardness and metastable amorphous substrates will face great challenges: (1) Cold spraying mainly relies on the mechanical interlocking caused by the plastic deformation of the substrate and powder to form a bond. However, BMGs have high strength and hardness but poor plasticity. Whether Fe-based amorphous powder can be deposited on the amorphous surface by cold spraying through plastic deformation, its deposition efficiency and mechanism are still unknown; (2) Amorphous alloys have almost no plasticity at room temperature and only have plastic deformation ability within their supercooled liquid phase. The supercooled liquid phase range of general amorphous alloys is only a few tens of degrees. A slightly higher temperature will cause the crystallization of the amorphous material. Therefore, the cold spray process is very demanding. In addition, there are differences in the microstructure of the amorphous coating along the thickness direction. The latter coating has a compacting effect on the previous coating, and may even impact the previous deposited coating to fall off. The changes in porosity, oxidation, and powder microstructure will affect the wear resistance and mechanism of the amorphous coating to varying degrees; (3) The repeated impact and heat accumulation in the cold spray preparation stage and preparation process may affect the microstructure and mechanical properties of the amorphous substrate, causing the crystallization of the amorphous alloy and coating and a sharp deterioration of the mechanical properties of the material.

[0005] Therefore, providing a method for cold spraying heterogeneous amorphous coatings on the surface of a high-strength, high-hardness and metastable amorphous substrate has important application value. Summary of the Invention

[0006] In view of this, the present invention aims to provide a heterogeneous amorphous coating on an amorphous surface, a preparation method, and applications thereof. The heterogeneous amorphous coating prepared by the present invention exhibits minimal shrinkage, low porosity, and a high amorphous fraction. It has minimal thermal impact on the high-strength, high-hardness, metastable amorphous alloy substrate, significantly improving the substrate's hardness, wear resistance, corrosion resistance, and service life, broadening its application range.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a heterogeneous amorphous coating on an amorphous surface, comprising the following steps: cold spraying heterogeneous amorphous powder on the surface of an amorphous alloy substrate to form the heterogeneous amorphous coating; the heterogeneous amorphous powder and the amorphous alloy substrate have different chemical compositions.

[0009] Preferably, the heterogeneous amorphous powder includes iron-based amorphous powder.

[0010] Preferably, the particle size of the heterogeneous amorphous powder is 5 to 50 μm.

[0011] Preferably, the heterogeneous amorphous powder includes iron-based amorphous powder; the chemical composition of the iron-based amorphous powder includes: C 0.7-1.2%, B 2-4%, Si 1-3%, Cr 16-22%, Mo 10-15%, and Fe 54.8-70.3%.

[0012] Preferably, the process parameters of the cold spraying include: spraying gas temperature of 550-750°C, spraying gas pressure of 3.5-5MPa, spraying passes of 1-3 times, gun travel speed of 100-300mm / s, powder feeding rate of 8-10g / min, spraying distance of 5-50mm, and spraying angle of 60-120°.

[0013] Preferably, the thickness of the heterogeneous amorphous coating obtained by a single spraying pass is 20 to 850 μm.

[0014] Preferably, the spraying gas includes nitrogen, argon or helium.

[0015] Preferably, the amorphous alloy matrix comprises a zirconium-based amorphous alloy matrix;

[0016] The amorphous alloy substrate is polished and shot blasted in sequence before use.

[0017] The present invention also provides a heterogeneous amorphous coating prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides the application of the heterogeneous amorphous coating described in the above technical solution in the protective layer, defect repair or 3D printing of amorphous alloy materials.

[0019] The present invention prepares a more wear-resistant and corrosion-resistant heterogeneous amorphous coating on an amorphous alloy substrate, greatly prolongs the service life of the substrate and broadens its application range.

[0020] Due to the high strength, hardness and wear resistance of amorphous alloys, there are very few reports on further improving the wear resistance of amorphous alloys and preparing heterogeneous amorphous coatings on the surface of amorphous alloys. 55 Cu 30 Al 10The deposition of the same amorphous coating on the surface of Ni5BMGs was studied, but due to the high energy of laser stereo forming, crystallization occurred in the heat-affected zone after multiple deposition passes. The cold spraying technology adopted in the present invention mainly relies on mechanical interlocking to form the bonding strength of the coating, which can maintain its amorphous structure to the maximum extent and reduce the oxidation and phase change of the interface material. The heterogeneous amorphous coating prepared on the surface of the amorphous alloy substrate has low porosity, small shrinkage and high amorphous rate. The present invention prepares a more wear-resistant and corrosion-resistant heterogeneous amorphous coating on the surface of the amorphous alloy, greatly improving the service life of the amorphous alloy substrate and broadening its application range. It is particularly suitable for preparing heterogeneous amorphous coatings on heat-sensitive amorphous surfaces and can be used for protective layers, defect repair and 3D printing technologies of amorphous alloy materials.

[0021] The preparation method provided by this invention demonstrates the feasibility of preparing heterogeneous amorphous coatings on the surface of high-strength, high-hardness bulk amorphous alloys. This method combines the excellent mechanical properties and large size of the amorphous alloy substrate with the high wear resistance of the heterogeneous amorphous coating. Furthermore, the residual stress layer formed on the amorphous alloy surface during the cold spraying process and the resulting heterogeneous amorphous coating can significantly improve the room-temperature plasticity of the amorphous alloy. Furthermore, the research results of this invention can also provide a theoretical and experimental basis for cold spray repair of defects in amorphous alloy parts during production and service, and have certain reference significance for the application of cold spray technology to 3D printing additive manufacturing technology, further promoting the industrial application of amorphous materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The cold spray process flow chart of the embodiment and comparative example;

[0023] Figure 2 The XRD patterns of the FeCrMo amorphous powders used in the examples and comparative examples are shown in FIG.

[0024] Figure 3 The DSC spectra of the FeCrMo amorphous powder used in the examples and comparative examples are as follows;

[0025] Figure 4 Zr used in Examples and Comparative Examples 48 Cu 36 XRD pattern of Ag8Al8 amorphous matrix;

[0026] Figure 5 XRD patterns of the iron-based amorphous coatings prepared in Examples 1 to 5;

[0027] Figure 6 The XRD pattern of the iron-based amorphous coating prepared in Comparative Example 1;

[0028] Figure 7This is a cross-sectional SEM image of the composite material prepared in Example 1;

[0029] Figure 8 This is a cross-sectional SEM image of the composite material prepared in Example 5;

[0030] Figure 9 This is a cross-sectional SEM image of the composite material prepared in Comparative Example 2;

[0031] Figure 10 The cross-sectional Vickers hardness variation curves of the composite materials prepared in Examples 1 to 5;

[0032] Figure 11 Zr 48 Cu 36 Friction coefficient results of Ag8Al8 amorphous substrate and iron-based amorphous coatings prepared in Examples 1 to 5;

[0033] Figure 12 Zr 48 Cu 36 Polarization curves of Ag8Al8 amorphous substrate and Fe-based amorphous coatings prepared in Examples 1 to 3 in 3.5 wt% NaCl aqueous solution;

[0034] Figure 13 Zr 48 Cu 36 EDS scan of Ag8Al8 amorphous matrix after corrosion in 3.5wt% NaCl aqueous solution for 20 days;

[0035] Figure 14 This is an EDS scan of the iron-based amorphous coating prepared in Example 1 after being corroded in a 3.5 wt % NaCl aqueous solution for 20 days. DETAILED DESCRIPTION

[0036] The invention provides a method for preparing a heterogeneous amorphous coating on an amorphous surface, comprising the following steps: cold spraying heterogeneous amorphous powder on the surface of an amorphous alloy substrate to form a heterogeneous amorphous coating; the heterogeneous amorphous powder and the amorphous alloy substrate have different chemical compositions.

[0037] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0038] In the present invention, the amorphous alloy substrate preferably includes a zirconium-based amorphous alloy substrate, and the chemical composition of the zirconium-based amorphous alloy plate preferably includes Zr 48 Cu 36 Ag8Al8 (atomic percentage). The zirconium-based amorphous alloy used in the present invention has excellent comprehensive mechanical properties, strong fluidity, good forming ability, and a wide supercooled liquid phase region to ensure a sufficiently wide spraying temperature window.

[0039] In the present invention, the amorphous alloy substrate is sequentially ground and shot peened before use, and then cold sprayed.

[0040] In the present invention, the polishing preferably includes polishing with 60-600# sandpaper. In a specific embodiment, 60#, 120#, 240# and 600# sandpaper are used for polishing in sequence. The single polishing time is preferably 5-10min, and in a specific embodiment it can be 5min, 6min, 7min, 8min, 9min or 10min.

[0041] In the present invention, the shot peening coverage of the surface of the shot peened amorphous alloy substrate obtained after shot peening is preferably 98-100%, and in specific embodiments it can be 98%, 98.5%, 99%, 99.5% or 100%; the shot peening preferably includes steel shots, and the specifications of the steel shots are preferably 0.2-0.25 mm.

[0042] In the present invention, the heterogeneous amorphous powder preferably includes an iron-based amorphous powder, more preferably a FeCrMo amorphous powder. In the present invention, the chemical composition of the iron-based amorphous powder preferably includes, by weight percentage, C 0.7-1.2%, B 2-4%, Si 1-3%, Cr 16-22%, Mo 10-15%, and Fe 54.8-70.3%. The zirconium-based amorphous matrix material Zr used in the present invention is preferably amorphous. 48 Cu 36 Ag8Al8 has a wide supercooled liquid phase range, which can reach above 100K, ensuring that the coating can be deposited within a wide process implementation window. It also has strong thermal stability and is not prone to crystallization during the cold spraying process.

[0043] In the present invention, the particle size of the heterogeneous amorphous powder is preferably 5-50 μm. Too small a particle size can easily clog the spray gun. Due to its small size and large specific surface area, heterogeneous amorphous powder is easily oxidized. Prolonged storage can also cause structural relaxation in the heterogeneous amorphous powder. Therefore, the heterogeneous amorphous powder is preferably stored in a vacuum.

[0044] In the present invention, the process conditions of the cold spraying preferably include: a spraying gas temperature of 550-750°C, and in specific embodiments, it can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C or 750°C; a spraying gas pressure of 3.5-5 MPa, and in specific embodiments, it can be 3.5 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, 4.0 MPa, 5.1 MPa, 5.2 MPa, 5.8 MPa, 5.9 MPa, 6.0 MPa, 6.1 MPa, 6.2 MPa, 6.3 MPa, 6.4 MPa, 6.5 MPa, 6.6 MPa, 6.7 MPa, 6.8 MPa, 6.9 MPa, 7.0 MPa, 7.1 MPa, 7.2 MPa, 7.3 MPa, 7.4 MPa .6MPa, 3.7MPa, 3.8MPa, 3.9MPa, 4MPa, 4.1MPa, 4.2MPa, 4.3MPa, 4.4MPa, 4.5MPa, 4.6MPa, 4.7MPa, 4.8MPa, 4.9MPa or 5MPa; the gun travel speed is 100-500mm / s, and in a specific embodiment can be 100mm / s, 150mm / s, 200mm / s, 250mm / s, 300mm / s, 350mm / s, 400mm / s, 450 mm / s or 500mm / s; the powder feeding rate is 8-10g / min, and in specific embodiments it can be 8g / min, 8.5g / min, 9g / min, 9.5g / min or 10g / min; the spraying distance is 5-50mm, and in specific embodiments it can be 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm or 50mm; the spraying angle is 60-120°, and in specific embodiments it can be 60°, 70°, 80°, 90° , 100°, 110° or 120°; the number of spraying passes is 1 to 3, and in specific embodiments, it can be 1, 2 or 3 passes; the thickness of the heterogeneous amorphous coating obtained by single-pass spraying is 20 to 850 μm, and in specific embodiments, it can be 20 μm, 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 750 μm, 800 μm or 850 μm. In the present invention, the spraying gas preferably includes nitrogen, argon or helium. In the present invention, setting the spraying gas temperature within the supercooled liquid phase region of the heterogeneous amorphous powder can enable better deposition of the heterogeneous amorphous powder. The heterogeneous amorphous powder is accelerated to the deposition speed by high-pressure spraying gas, and the powder is sprayed onto the amorphous alloy substrate through the Lavel nozzle. Relying on the physical deposition of the plastic deformation of the heterogeneous amorphous powder and the amorphous alloy substrate, a heterogeneous amorphous coating is formed on the amorphous surface.

[0045] In the present invention, the process flow chart of preparing heterogeneous amorphous coating on amorphous surface is shown in Figure 1Specifically, the heterogeneous amorphous powder is placed in the powder feeder of the cold spraying equipment, and the amorphous alloy substrate is fixed on the substrate. The spraying angle between the spray gun and the amorphous alloy substrate is maintained by a robotic arm. The cold spraying process parameters are set, and the equipment is preheated for more than 15 minutes before the cold spraying process is carried out. The heterogeneous amorphous powder is injected into the compressed supersonic jet and accelerated to 300-1200m / s. The heterogeneous amorphous powder carried by the spraying gas is sprayed onto the surface of the amorphous substrate by moving the spray gun, and a heterogeneous amorphous coating is formed on the surface of the amorphous substrate by physical deposition.

[0046] Due to the high strength, hardness and wear resistance of amorphous alloys, there are very few reports on further improving the wear resistance of amorphous alloys and preparing heterogeneous amorphous coatings on the surface of amorphous alloys. 55 Cu 30 Al 10 The deposition of the same amorphous coating on the surface of Ni5BMGs was studied, but due to the high energy of laser stereo forming, crystallization occurred in the heat-affected zone after multiple deposition passes. The cold spraying technology adopted in the present invention mainly relies on mechanical interlocking to form the bonding strength of the coating, which can maintain its amorphous structure to the maximum extent and reduce the oxidation and phase change of the interface material. The heterogeneous amorphous coating prepared on the amorphous surface has low porosity, small shrinkage and high amorphous rate. The present invention prepares a more wear-resistant and corrosion-resistant heterogeneous amorphous coating on the amorphous surface, greatly improving the service life of the amorphous substrate and broadening its application range. It is particularly suitable for preparing heterogeneous amorphous coatings as protective layers on heat-sensitive amorphous surfaces. It can also be used for defect repair of amorphous alloy materials and 3D printing technology.

[0047] The present invention also provides a heterogeneous amorphous coating prepared by the preparation method described in the above technical solution. In the present invention, the amorphous ratio of the heterogeneous amorphous coating is preferably ≥83.76%, more preferably 83.76-90.46%. In specific embodiments, it can be 83.76%, 85%, 86.64%, 87%, 88%, 89%, 90%, 90.17%, 90.24%, or 90.46%.

[0048] The present invention also provides the application of the heterogeneous amorphous coating described in the above technical solution in the protective layer, defect repair or 3D printing of amorphous alloy materials.

[0049] In order to further illustrate the present invention, the heterogeneous amorphous coating on an amorphous surface provided by the present invention, its preparation method and application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0050] In the following examples and comparative examples, the chemical composition of the FeCrMo amorphous powder used is shown in Table 1; the XRD patterns are shown in Figure 2The XRD analysis results show that the main feature of the spectrum is the typical amorphous diffuse scattering peak in the 2θ value 40-50° region, indicating that the FeCrMo amorphous alloy powder used for cold spraying maintains a completely amorphous structure and is suitable for cold spray additive manufacturing; the DSC spectrum is shown in Figure 3 , glass transition temperature T g About 560℃, melting temperature T m About 700℃, T g ~T m The temperature of the amorphous powder is adjusted by changing the temperature of the cold spraying gas so that the temperature of the powder is in the supercooled liquid phase during the cold spraying process, so as to obtain higher plasticity and be easier to deposit as a coating.

[0051] Table 1 Chemical composition of FeCrMo amorphous alloy powder

[0052] element C B Si Cr Mo Fe Mass fraction / % 0.7～1.2 2～4 1～3 16～22 10～15 margin

[0053] Zr 48 Cu 36 The XRD pattern of Ag8Al8 amorphous matrix (plate) is shown in Figure 4 The XRD analysis results show that the amorphous alloy used for cold spraying still maintains an amorphous structure after being prepared into a plate by the negative pressure copper mold suction casting method.

[0054] Example 1

[0055] The zirconium-based amorphous alloy matrix (chemical composition Zr 48 Cu 36 Ag8Al8, atomic percentage) was polished with 60#, 120#, 240#, and 600# sandpaper for 5 to 10 minutes respectively until the surface was smooth, and then shot peened with 0.2 mm steel shot at a speed of 30 m / s for 1 minute to achieve a shot peening coverage of nearly 100%, thereby obtaining a pretreated zirconium-based amorphous alloy plate.

[0056] FeCrMo amorphous powder with a particle size of 5 to 50 μm is placed in the powder feeder of the cold spray equipment. The amorphous powder particles are driven by high-pressure gas. Supersonic gas-solid two-phase flow is generated through the Lavel nozzle at the temperature of the powder supercooled liquid phase region. The pretreated zirconium-based amorphous alloy plate is cold sprayed. 48 Cu 36 An iron-based amorphous coating was formed on the surface of the Ag8Al8 amorphous alloy plate, resulting in a composite material. The cold spraying process conditions were: spray gas (argon) temperature of 750°C, spray gas pressure of 5 MPa, one spray pass, gun travel speed of 200 mm / s, powder feed rate of 8 g / min, spray distance of 30 mm, and spray angle of 90°.

[0057] Example 2

[0058] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of an Ag8Al8 amorphous alloy plate. The only difference from Example 1 was that the spraying gas temperature was 650°C.

[0059] Example 3

[0060] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of an Ag8Al8 amorphous alloy plate, and the only difference from Example 1 was that the spraying gas temperature was 550°C.

[0061] Example 4

[0062] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of the Ag8Al8 amorphous alloy plate. The only difference from Example 1 was that the spraying gas pressure was 4.5 MPa.

[0063] Example 5

[0064] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of the Ag8Al8 amorphous alloy plate. The only difference from Example 1 was that the spraying gas pressure was 3.5 MPa.

[0065] Comparative Example 1

[0066] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of an Ag8Al8 amorphous alloy plate. The only difference from Example 1 was that the spraying gas temperature was 850°C.

[0067] Comparative Example 2

[0068] According to the method of Example 1, Zr 48 Cu 36 An iron-based amorphous coating was prepared on the surface of the Ag8Al8 amorphous alloy plate. The only difference from Example 1 was that the spraying gas pressure was 3 MPa.

[0069] Test Example 1

[0070] (1) Amorphous ratio, porosity and thickness

[0071] Figure 5The XRD patterns of the iron-based amorphous coatings prepared in Examples 1 to 5 are analyzed. The main feature of the patterns is a typical amorphous diffuse scattering peak in the 2θ value region of 40 to 50°, indicating that the iron-based amorphous coatings prepared by cold spraying the amorphous alloy powder still contain a relatively high amorphous phase. Figure 6 This is the XRD pattern of the iron-based amorphous coating prepared in Comparative Example 1. Analysis results show that the pattern is primarily characterized by a typical amorphous diffuse scattering peak in the 2θ region of 40-50°. However, compared to the coatings in Examples 1-5, the amorphous fraction is lower. Crystallinity and porosity were calculated for each XRD pattern, and the results are shown in Table 2.

[0072] Table 2 Performance test results of amorphous coatings prepared in Examples and Comparative Examples

[0073]

[0074] Note: “—” in Table 2 indicates that relevant tests were not performed.

[0075] As shown in Table 2, the amorphous coatings prepared according to the present invention exhibited an amorphous ratio exceeding 83.7%, with the amorphous ratio reaching 90.46% when the cold spray process was set at a gas pressure of 5 MPa and a spray gas temperature of 750°C. In contrast, in Comparative Example 1, the iron-based amorphous coating was prepared at an inert gas temperature of 850°C, resulting in severe surface oxidation of the amorphous coating and an amorphous ratio of only 65%, indicating poor coating performance.

[0076] The heat-affected zone, oxidation, and phase transitions produced by thermal spraying remain insurmountable challenges. In contrast, the cold spraying process employed in the present invention is a solid-state process that does not involve powder remelting and virtually eliminates heat-affected zones, oxidation, and phase transitions. Peak analysis of the XRD patterns of the amorphous coatings produced by cold spraying in the present invention revealed only CrB4 and Cr2C3 components; no other components showed significant diffraction peaks, nor were any peaks associated with oxygen-containing elements observed.

[0077] Thermal spraying has higher porosity due to shrinkage during cooling, typically ranging from 1 to 20%. Cold spraying, on the other hand, generally offers higher density than thermal spraying, and cold sprayed amorphous coatings generally have lower porosity, typically ranging from 1 to 10%. In this study, porosity was calculated based on SEM images of cold sprayed coatings. The lowest porosity reached 1.8% when spraying with one pass and a pressure of 5 MPa was achieved.

[0078] Figure 7 This is a cross-sectional SEM image of the composite material prepared in Example 1. Figure 8 This is a cross-sectional SEM image of the composite material prepared in Example 5. Figure 9The cross-section SEM image of the composite material prepared for Comparative Example 2 shows that a dense amorphous coating is prepared on the bulk amorphous alloy by cold spraying. The thickness of the iron-based amorphous coating prepared in Example 1 is about 500 μm, and the thickness of the iron-based amorphous coating prepared in Example 5 is less than 100 μm. The coating thickness can be adjusted by changing the cold spraying process parameters. At the same time, it is calculated that the porosity of the iron-based amorphous coating is as low as about 1%. In Comparative Example 2, the inert gas spraying pressure is only 3 MPa, and the thickness of the prepared iron-based amorphous coating is relatively thin, only about 20 μm.

[0079] (2) Hardness

[0080] The cross-section of each composite material prepared in the examples and comparative examples is tested by a microhardness tester. The loading force is 5 N, and the dwell time is 10 s.

[0081] Figure 10 The cross-section Vickers hardness curve of the composite material prepared in Examples 1-5 shows that the hardness of the amorphous substrate (Zr 48 Cu 36 Ag8Al8) is maintained in the range of 475-550 HV. In the microhardness test experiment, the Vickers hardness of the iron-based amorphous coating prepared in the application is maintained in the range of 700-750 HV, which is due to the physical properties of the iron-based amorphous coating and the zirconium-based amorphous substrate itself. It is shown that the surface hardness of the composite material prepared in the application is obviously improved compared with the original substrate.

[0082] The iron-based amorphous powder used in the application is FeCrMo amorphous powder. The hardness of the iron-based amorphous coating prepared by cold spraying can reach 735.6 HV, and has excellent mechanical properties.

[0083] (3) Wear resistance

[0084] The wear resistance of the sample substrate and coating prepared in Example 1 is measured by a reciprocating friction and wear tester. The friction pair is a Si3N4 ball with a hardness of 1650 HV and a diameter of 3 mm. The friction path is 5 mm, the friction time is 30 min, the load is 5 N, and the reciprocating frequency is 250 t / min.

[0085] Figure 11 The cross-section Vickers hardness curve of the composite material prepared in Examples 1-5 shows that the hardness of the amorphous substrate (Zr 48 Cu 36 Ag8Al8) is maintained in the range of 475-550 HV. In the microhardness test experiment, the Vickers hardness of the iron-based amorphous coating prepared in the application is maintained in the range of 700-750 HV, which is due to the physical properties of the iron-based amorphous coating and the zirconium-based amorphous substrate itself. It is shown that the surface hardness of the composite material prepared in the application is obviously improved compared with the original substrate. -6 ~5.17×10 -6 mm 3 / Nm, the friction coefficient of the iron-based amorphous coating on the amorphous surface is smaller than that of the zirconium-based amorphous substrate and is more stable, indicating that the iron-based amorphous coating prepared on the substrate surface has higher wear resistance.

[0086] (4) Corrosion resistance

[0087] The corrosion resistance of the iron-based amorphous coating and the substrate prepared in Examples 1 to 3 was measured using an electrochemical workstation. The corrosion solution was a 3.5 wt% NaCl aqueous solution and the electrode was Ag / AgCl. The results are shown in Tables 2 and Figure 12 .

[0088] Figure 12 Zr 48 Cu 36 The polarization curves of the Ag8Al8 amorphous substrate and the iron-based amorphous coating prepared in Examples 1 to 3 in 3.5 wt% NaCl aqueous solution are shown in Table 2 and Figure 12 Electrochemical testing of the iron-based amorphous coating revealed a corrosion potential of -0.435 to -0.402 V. During the cold spraying process, the corrosion potential was as low as -0.402 V at a gas temperature of 750°C and a gas pressure of 5 MPa. The corrosion potential of the sprayed iron-based amorphous coating was higher than that of the substrate, indicating that the iron-based amorphous coating prepared by the present invention has higher corrosion resistance.

[0089] Zr 48 Cu 36 After coating treatment, the Ag8Al8 amorphous substrate and the iron-based amorphous coating prepared in Example 1, except for the test surface, were immersed in a 3.5 wt % NaCl aqueous solution for 20 days, and the corrosion morphology of the coating and substrate surface was observed. Figure 13 Zr 48 Cu 36 EDS scan of Ag8Al8 amorphous matrix after immersion corrosion for 20 days. Since Al in the matrix is ​​more active than Cu, Zr, and Ag, it is prone to oxygen absorption corrosion in neutral NaCl aqueous solution. Therefore, the following reaction occurs in the cathode area: Al-3e - →Al 3 +

[0090] Al 3+ With cathode OH - Combined to form Al(OH)3 precipitate, namely Al 3+ +3OH - →Al(OH)3.

[0091] Al(OH)3 can also be expressed as Al2O3·3H2O. The EDS spectrum shows that Al2O3 products are generated in the corrosion pits, while other parts of the substrate surface that remain relatively flat after immersion are enriched in Cu, Zr, and Ag elements. This indicates that the Al-enriched part of the original substrate surface has undergone severe corrosion and generated Al2O3 precipitation.

[0092] Figure 14 This is the EDS scan of the iron-based amorphous coating prepared in Example 1 after being immersed in a 3.5wt% NaCl aqueous solution for 20 days. Due to the presence of Cr, the amorphous coating also undergoes oxygen absorption corrosion when in contact with the neutral 3.5wt% NaCl aqueous solution. The cathode reduction reaction of the iron-based amorphous coating is: O2+2H2O+4e - →4OH - .

[0093] In the iron-based amorphous coating, Cr is more active than Fe, and the anodic oxidation reaction of the coating is: Cr-3e - →Cr 3+ .

[0094] Cr 3+ With cathode OH - Combined to form Cr(OH)3 precipitate, namely Cr 3+ +3OH - →Cr(OH)3.

[0095] Cr(OH)3 can also be expressed as Cr2O3·3H2O. The dense Cr2O3 passivation film effectively prevents further corrosion of the coating and exhibits a certain degree of self-healing ability. Because Mo is less reactive than Fe, the Fe-based amorphous coating also undergoes Cr oxidation. EDS patterns show the enrichment of Cr and O within the corrosion pits, indicating the formation of Cr2O3 precipitation within them. Mo is evenly distributed on the surface of the Fe-based amorphous coating, stabilizing the Cr2O3 passivation film.

[0096] In summary, the present invention adopts a cold spraying method to prepare a Fe-based amorphous coating with better wear resistance and corrosion resistance on the surface of a Zr-based bulk amorphous alloy, and systematically studies the structure and properties of the amorphous coating and the influence of the cold spraying process on the performance of the amorphous coating. The preparation method provided by the present invention proves the feasibility of preparing heterogeneous amorphous coatings on the surface of a high-strength, high-hardness bulk amorphous alloy; on the one hand, it can combine the advantages of excellent mechanical properties and large size of Zr-based amorphous alloys and the advantages of high wear resistance and corrosion resistance of Fe-based amorphous coatings. On the other hand, the residual stress layer formed on the surface of the Zr-based amorphous alloy during the cold spraying process and the Fe-based amorphous coating formed may greatly improve the room temperature plasticity of the amorphous alloy. In addition, the research results of the present invention can also provide a certain theoretical and experimental basis for the cold spray repair of defects generated in the production and service of amorphous alloy parts, and have a certain reference significance for the application of cold spray technology to 3D printing additive manufacturing technology, further promoting the industrial application process of amorphous materials.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a heterogeneous amorphous coating on an amorphous surface, comprising the following steps: A heterogeneous amorphous coating is formed by cold spraying heterogeneous amorphous powder on the surface of an amorphous alloy substrate; the heterogeneous amorphous powder and the amorphous alloy substrate have different chemical compositions; The heterogeneous amorphous powder includes an iron-based amorphous powder; the chemical composition of the iron-based amorphous powder includes: C 0.7-1.2%, B 2-4%, Si 1-3%, Cr 16-22%, Mo 10-15%, and Fe balance; The process parameters of the cold spraying include: spraying gas temperature of 550~750℃, spraying gas pressure of 3.5~5 MPa, spraying passes of 1~3 times, gun travel speed of 100~300 mm / s, powder feeding rate of 8~10 g / min, spraying distance of 5~50 mm, and spraying angle of 60~120°.

2. The preparation method according to claim 1, characterized in that The particle size of the heterogeneous amorphous powder is 5-50 μm.

3. The preparation method according to claim 1, characterized in that The thickness of the heterogeneous amorphous coating obtained by single-pass spraying ranges from 20 to 850 μm.

4. The preparation method according to claim 1, characterized in that The spraying gas includes nitrogen, argon or helium.

5. The preparation method according to claim 1, characterized in that The amorphous alloy substrate includes a zirconium-based amorphous alloy substrate; the amorphous alloy substrate is polished and shot blasted in sequence before use.

6. A heterogeneous amorphous coating obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the heterogeneous amorphous coating according to claim 6 in the protective layer, defect repair or 3D printing of amorphous alloy materials.

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