Heterogeneous amorphous coating on amorphous surface as well as preparation method and application of heterogeneous amorphous coating

Abstract

The invention provides an amorphous surface heterogeneous amorphous coating and a preparation method and application thereof, and relates to the technical field of amorphous coating preparation. The invention provides a preparation method of a dissimilar amorphous coating on an amorphous surface. The preparation method comprises the following steps: carrying out cold spraying on the surface of an amorphous alloy matrix by adopting dissimilar amorphous powder to form the dissimilar amorphous coating; the chemical composition of the dissimilar amorphous powder is different from that of the amorphous alloy matrix. The cold spraying method is adopted, the dissimilar amorphous coating prepared on the surface of the amorphous alloy is low in porosity, small in shrinkage, high in amorphous rate and small in heat influence on a zirconium-based amorphous matrix which is high in strength and hardness and is in a metastable state, the hardness, abrasion resistance and corrosion resistance of the matrix are greatly improved, the service life of the matrix is greatly prolonged, and the application range of the matrix is widened.

Description

Technical Field

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

[0002] Bulk metallic glasses (BMGs) have a special atomic arrangement, and their mechanical properties are several times that of traditional crystalline alloys. Among them, zirconium-based amorphous alloys not only have strong glass-forming ability and a critical size of more than 30 mm, but also have excellent mechanical properties. They have been used in military, electronic products, medical equipment, sports equipment, and space engineering. However, among many amorphous systems, the wear resistance of zirconium-based amorphous alloys is relatively poor.

[0003] Thermal spraying (supersonic flame spraying, plasma spraying, explosion 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 quickly 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 component to deviate from any amorphous component on both sides to form a transition layer. The dendrites of 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] The emerging cold spraying technology in the past 30 years does not require melting of substrate and powder. The powder is carried by high-pressure gas and sprayed on the substrate surface, causing both to plastically deform to form a coating. This can maintain its amorphous structure to the greatest extent and reduce oxidation and phase change of interface materials. The coating has little shrinkage and thermal influence, and 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 faces great challenges: (1) Cold spraying mainly relies on the mechanical interlocking caused by 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 region. The supercooled liquid phase region of general amorphous alloys is only a few tens of degrees. Slightly higher temperatures will cause the amorphous material to crystallize. 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 cause 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 object of the present invention is to provide a heterogeneous amorphous coating on an amorphous surface and a preparation method and application thereof. The heterogeneous amorphous coating prepared by the present invention has small shrinkage, low porosity, high amorphous rate, and small thermal influence on a high-strength, high-hardness and metastable amorphous alloy substrate, greatly improving the hardness, wear resistance, corrosion resistance and service life of the substrate, and 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 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.

[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%, Fe54.8-70.3%.

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

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

[0014] Preferably, the spraying gas comprises 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 peened 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 10 Ni 5The deposition of the same amorphous coating on the surface of BMGs has been studied, but due to the high energy of laser stereo forming, crystallization occurs in the heat-affected zone after multiple deposition passes. The cold spraying technology used in the present invention mainly relies on mechanical interlocking to form the bonding strength of the coating, which can maximize the retention of its amorphous structure 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 the present invention proves the feasibility of preparing heterogeneous amorphous coatings on the surface of high-strength and high-hardness bulk amorphous alloys. On the one hand, it can combine the advantages of excellent mechanical properties and large size of the amorphous alloy matrix and the high wear resistance of the heterogeneous amorphous coating. On the other hand, the residual stress layer formed on the surface of the amorphous alloy during the cold spraying process and the heterogeneous amorphous coating formed can 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0024] Figure 3 The DSC spectrum of the FeCrMo amorphous powder used in the examples and comparative examples;

[0025] Figure 4 Zr used in the examples and comparative examples 48 Cu 36 Ag 8 Al 8 XRD pattern of 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 7 This 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] Fig. 9 This is a cross-sectional SEM image of the composite material prepared in Comparative Example 2;

[0031] Fig.10 The Vickers hardness variation curve of the cross section of the composite material prepared in Examples 1 to 5;

[0032] Fig.11 Zr 48 Cu 36 Ag 8 Al 8 The friction coefficient results of the amorphous substrate and the iron-based amorphous coating prepared in Examples 1 to 5 are shown in FIG.

[0033] Fig.12 Zr 48 Cu 36 Ag 8 Al 8 Polarization curves of the amorphous substrate and the iron-based amorphous coating prepared in Examples 1 to 3 in a 3.5 wt % NaCl aqueous solution;

[0034] Fig.13 Zr 48 Cu 36 Ag 8 Al 8 EDS scan of the amorphous substrate after corrosion in 3.5wt% NaCl aqueous solution for 20 days;

[0035] Fig.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 discloses 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 Ag 8 Al8 (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 grinded and shot peened in sequence 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, and more preferably a FeCrMo amorphous powder. In the present invention, the chemical composition of the iron-based amorphous powder preferably includes, by mass 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 48 Cu 36 Ag 8 Al 8 The supercooled liquid phase region is wide, reaching above 100K, which ensures 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 to 50 μm. If the particle size of the heterogeneous amorphous powder is too small, the spray gun is easily blocked. Since the heterogeneous amorphous powder is fine and has a large specific surface area, it is easy to oxidize, and if it is placed for too long, the structure of the heterogeneous amorphous powder will also relax. Therefore, the heterogeneous amorphous powder is preferably stored in a vacuum.

[0044] In the present invention, the process conditions of cold spraying preferably include: a spraying gas temperature of 550-750°C, and in a specific embodiment, 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 3.5-5MPa, and in a specific embodiment, it can be 3.5MPa, 3.5MPa, 3.6MPa or 3.7MPa. .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, it 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 a specific embodiment it can be 8g / min, 8.5g / min, 9g / min, 9.5g / min or 10g / min; the spraying distance is 5-50mm, and in a specific embodiment it can be 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm or 50mm; the spraying angle is 60-120°, and in a specific embodiment it can be 60°, 70°, 80°, 90° , 100°, 110° or 120°; the number of spraying passes is 1 to 3, and in a specific embodiment, 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 a specific embodiment, 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. The present invention sets the spraying gas temperature in the supercooled liquid phase region of the heterogeneous amorphous powder to 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 spray gun is maintained at a spraying angle with the amorphous alloy substrate by a mechanical arm, and the cold spraying process parameters are set. The equipment is preheated for more than 15 minutes before the cold spraying process is performed. The heterogeneous amorphous powder is injected into a 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 Ni 5 The deposition of the same amorphous coating on the surface of BMGs has been studied, but due to the high energy of laser stereo forming, crystallization occurs in the heat-affected zone after multiple deposition passes. The cold spraying technology used 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, and 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 rate of the heterogeneous amorphous coating is preferably ≥83.76%, more preferably 83.76-90.46%, and 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 and its preparation method and application are described in detail below in conjunction with embodiments, but they should not be understood as limiting the protection scope 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 spectrum is 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 spraying 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 to obtain higher plasticity and make it 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 Ag 8 Al 8 XRD spectrum of amorphous matrix (plate) 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 Ag 8 Al 8 , atomic percentage) were polished with 60#, 120#, 240#, and 600# sandpapers for 5 to 10 minutes respectively until the surface was flat, and then shot peened with 0.2mm steel shot at a speed of 30m / s for 1 minute to make the shot peening coverage reach 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 Ag 8 Al 8The surface of the amorphous alloy plate is provided with an iron-based amorphous coating to obtain a composite material. The cold spraying process conditions are as follows: the spraying gas (argon) temperature is 750°C, the spraying gas pressure is 5 MPa, the spraying pass is 1 pass, the gun travel speed is 200 mm / s, the powder feeding rate is 8 g / min, the spraying distance is 30 mm, and the spraying angle is 90°.

[0057] Example 2

[0058] According to the method of Example 1, Zr 48 Cu 36 Ag 8 Al 8 The iron-based amorphous coating is prepared on the surface of the amorphous alloy plate, which is different from Example 1 only in that the spraying gas temperature is 650°C.

[0059] Example 3

[0060] According to the method of Example 1, Zr 48 Cu 36 Ag 8 Al 8 The iron-based amorphous coating was prepared on the surface of the amorphous alloy plate, which was different from Example 1 only in that the spraying gas temperature was 550°C.

[0061] Example 4

[0062] According to the method of Example 1, Zr 48 Cu 36 Ag 8 Al 8 The iron-based amorphous coating was prepared on the surface of the amorphous alloy plate, which was different from Example 1 only in that the spraying gas pressure was 4.5 MPa.

[0063] Example 5

[0064] According to the method of Example 1, Zr 48 Cu 36 Ag 8 Al 8 The iron-based amorphous coating was prepared on the surface of the amorphous alloy plate, which was different from Example 1 only in 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 Ag 8 Al 8 The iron-based amorphous coating is prepared on the surface of the amorphous alloy plate, which is different from Example 1 only in that the spraying gas temperature is 850°C.

[0067] Comparative Example 2

[0068] According to the method of Example 1, Zr 48 Cu 36 Ag 8 Al 8 The iron-based amorphous coating was prepared on the surface of the amorphous alloy plate, which was different from Example 1 only in that the spraying gas pressure was 3 MPa.

[0069] Test Example 1

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

[0071] Figure 5 The XRD patterns of the iron-based amorphous coatings prepared in Examples 1 to 5 show that the main feature of the patterns is the 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 of amorphous alloy powders still contain a relatively high amorphous phase. Figure 6 The XRD spectrum of the iron-based amorphous coating prepared in Comparative Example 1 shows that the main feature of the spectrum is a typical amorphous diffuse scattering peak in the 2θ value 40-50° region, but its amorphous rate is lower than that of the coatings in Examples 1-5. The crystallization rate and porosity of each XRD spectrum are calculated, 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 means no relevant test was conducted.

[0075] As can be seen from Table 2, the amorphous rate of the amorphous coating prepared by the present invention exceeds 83.7%, and the amorphous rate can reach 90.46% when the cold spraying process is set to a gas pressure of 5 MPa and a spraying gas temperature of 750°C. In the process of preparing the iron-based amorphous coating in Comparative Example 1, the inert gas temperature is 850°C, so that the surface of the prepared amorphous coating is severely oxidized, the amorphous rate is only 65%, and the coating performance is poor.

[0076] The heat-affected zone, oxidation and phase change produced in thermal spraying technology are still insurmountable problems. In contrast, the cold spraying used in the present invention is a solid-state process that does not involve remelting of powders and has almost no heat-affected zone, oxidation and phase change. In the present invention, by searching the peaks of the XRD spectrum of the amorphous coating prepared by cold spraying, only CrB 4 and Cr 2 C 3 There are no obvious diffraction peaks for other components, and no peaks for components containing oxygen elements are found.

[0077] In terms of coating porosity, due to the cooling shrinkage of the coating, the porosity of thermal spraying technology is relatively large, usually between 1 and 20%; compared with thermal spraying, the density of cold spraying coatings is usually higher, and the porosity of cold spraying amorphous coatings is generally lower, usually between 1 and 10%. In the present invention, the porosity is calculated by SEM images of the coating after cold spraying. When the spraying pass is 1 and the spraying pressure is 5MPa, the lowest porosity can reach 1.8%.

[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. Fig. 9 The cross-sectional SEM image of the composite material prepared in 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 can be calculated that the porosity of the iron-based amorphous coating can be 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 microhardness test was performed on the cross sections of the matrix, the composite materials prepared in the embodiments and the comparative examples using a microhardness tester, with a loading force of 5 N and a dwell time of 10 s.

[0081] Fig.10 The Vickers hardness curve of the cross section of the composite material prepared in Examples 1 to 5. 48 Cu 36 Ag 8 Al 8 ) The hardness is maintained in the range of 475 to 550 HV. In the microhardness test experiment, the Vickers hardness of the iron-based amorphous coating prepared by the present invention is maintained in the range of 700 to 750 HV. This is due to the physical properties of the iron-based amorphous coating and the zirconium-based amorphous matrix themselves, indicating that the surface hardness of the composite material prepared by the present invention is significantly improved compared with the original matrix.

[0082] The iron-based amorphous powder used in the present invention is FeCrMo amorphous powder. The iron-based amorphous coating prepared by cold spraying has a hardness of up to 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 was measured using a reciprocating friction and wear tester. The friction pair was a Si with a hardness of 1650 HV and a diameter of 3 mm.3 N 4 Small ball, friction path is 5mm, friction time is 30min, load is 5N, and reciprocating frequency is 250t / min.

[0085] Fig.11 Zr 48 Cu 36 Ag 8 Al 8 The friction coefficient results of the amorphous substrate and the iron-based amorphous coating prepared in Examples 1 to 5 show that the friction coefficient of the iron-based amorphous coating prepared in the present invention can be as low as 0.27, and the wear rate is as low as 3.93×10 -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 after the iron-based amorphous coating is prepared on the substrate surface, the present invention 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 Fig.12 .

[0088] Fig.12 Zr 48 Cu 36 Ag 8 Al 8 The polarization curves of the amorphous substrate and the iron-based amorphous coating prepared in Examples 1 to 3 in a 3.5 wt% NaCl aqueous solution are shown in Table 2 and Fig.12 It can be seen that the electrochemical test of the iron-based amorphous coating obtained a corrosion potential of -0.435 to -0.402 V, and the corrosion potential was as low as -0.402 V when the cold spraying process was a gas temperature of 750°C and a gas pressure of 5 MPa. The corrosion potential of the iron-based amorphous coating sprayed on the surface was higher than the corrosion potential of the substrate, indicating that the iron-based amorphous coating prepared by the present invention has higher corrosion resistance.

[0089] Zr 48 Cu 36 Ag 8 Al 8 After the coating treatment, the amorphous substrate and the iron-based amorphous coating prepared in Example 1 were partially immersed in a 3.5 wt % NaCl aqueous solution for 20 days, and the corrosion morphology of the coating and substrate surface was observed. Fig.13 Zr 48 Cu 36 Ag8 Al 8 EDS scan of the amorphous substrate after immersion corrosion for 20 days. Since the Al element in the substrate is more active than Cu, Zr, and Ag, it is easy to absorb oxygen and corrode in a 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, i.e. Al 3+ +3OH - →Al(OH) 3 .

[0091] Al(OH) 3 It can also be expressed as Al 2 O 3 ·3H 2 O, according to the EDS spectrum: there is Al in the corrosion pit 2 O 3 The products were generated, while the other parts of the substrate surface that were still relatively flat after immersion were enriched with Cu, Zr, and Ag elements, indicating that the Al-enriched parts of the original substrate surface were severely corroded and Al was generated. 2 O 3 precipitation.

[0092] Fig.14 The EDS scanning image 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 absorbs oxygen and corrodes when in contact with the neutral 3.5wt% NaCl aqueous solution. The cathode reduction reaction of the iron-based amorphous coating is: 2 +2H 2 O+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 It can also be expressed as Cr 2 O 3 ·3H 2 O, where dense Cr 2 O 3 The passivation film effectively prevents further corrosion of the coating and has a certain self-repair ability. Since the activity of Mo is lower than that of Fe, the iron-based amorphous coating also undergoes Cr oxidation reaction. In the EDS spectrum, Cr and O elements are enriched in the corrosion pits, indicating that Cr is generated in the corrosion pits. 2 O 3 Precipitation, Mo element is evenly distributed on the surface of the Fe-based amorphous coating, which has an impact on the Cr 2 O 3 The passivation film plays a stabilizing role.

[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 performance 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 and 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 spraying 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 principle of the present invention. These improvements and modifications should also be regarded as 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 a heterogeneous amorphous powder on the surface of an amorphous alloy substrate; the heterogeneous amorphous powder and the amorphous alloy substrate have different chemical compositions.

2. The preparation method according to claim 1, characterized in that: The heterogeneous amorphous powder includes iron-based amorphous powder.

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

4. The preparation method according to claim 3, characterized in that: In terms of mass percentage, 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%.

5. The preparation method according to claim 1, 2 or 4, characterized in that: The process parameters of the cold spraying include: a spraying gas temperature of 550 to 750°C, a spraying gas pressure of 3.5 to 5 MPa, 1 to 3 spraying passes, a gun travel speed of 100 to 300 mm / s, a powder feeding rate of 8 to 10 g / min, a spraying distance of 5 to 50 mm, and a spraying angle of 60 to 120°.

6. The preparation method according to claim 5, characterized in that: The thickness of the heterogeneous amorphous coating obtained by single-pass spraying is 20 to 850 μm.

7. The preparation method according to claim 5, characterized in that: The spraying gas includes nitrogen, argon or helium.

8. The preparation method according to claim 1, characterized in that: The amorphous alloy substrate comprises a zirconium-based amorphous alloy substrate; the amorphous alloy substrate is grinded and shot peened in sequence before use.

9. The heterogeneous amorphous coating obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the heterogeneous amorphous coating according to claim 9 in protective layer, defect repair or 3D printing of amorphous alloy materials.

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