Ultra-high-speed laser cladding of full-amorphous crack-free iron-based amorphous coating and preparation method thereof

Abstract

The present application relates to a kind of full amorphous no crack iron-based amorphous coating of ultra-high speed laser cladding and preparation method.To be cladded workpiece is preheated, and the workpiece to be cladded that is preheated is clamped with chuck, and is placed on rotating carrier;Adjust the powder feeding speed of cladding device, carrier gas flow, shielding gas flow;Adjust the distance between cladding head and the workpiece to be cladded, laser focal point, powder flow focal point, set the moving speed of cladding head;Rotating carrier drives the workpiece to be cladded to rotate, and from outside to inside, laser cladding is started, and the full amorphous no crack iron-based amorphous coating of ultra-high speed laser cladding is formed on the surface of the workpiece to be cladded.The present application controls the process parameters of ultra-high speed laser cladding, and selects the parameters suitable for processing amorphous coating, realizes the rapid cooling of coating and defect-free preparation while ensuring the complete amorphous of coating.The coating has high corrosion resistance and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of surface coating preparation technology, and in particular to a fully amorphous, crack-free iron-based amorphous coating prepared by ultra-high-speed laser cladding and its preparation method. Background Technology

[0002] Iron-based amorphous alloys are characterized by long-range disorder, short-range order, and absence of crystal defects, which endow them with many excellent properties such as high corrosion resistance, high wear resistance, and high hardness.

[0003] Currently, amorphous alloy coatings prepared using surface coating technology have been widely applied in practice. Ultra-high-speed laser cladding, as an emerging surface technology, uses a high-energy laser as a heat source to melt alloy powder and deposit it onto the substrate surface to form a coating. Because the energy of the high-energy laser is mainly absorbed by the powder, its thermal impact on the workpiece substrate is minimal. Simultaneously, the high scanning speed leads to a high cooling rate, which is conducive to the formation of metastable amorphous phases. Compared to traditional surface treatment technologies (thermal spraying, magnetron sputtering, conventional laser cladding, etc.), ultra-high-speed laser cladding significantly shortens the cladding time and improves powder utilization. It can achieve the preparation of high-efficiency, high-quality amorphous alloy coatings.

[0004] Chinese patent CN109023351A discloses a method for preparing crack-free amorphous coatings by laser cladding. The method involves pre-melting a substrate, forming a cladding layer through laser cladding, and then remelting the cladding layer to produce a completely crack-free laser-clad amorphous alloy coating with an average micro-Vickers hardness of 807.4 HV. 0.1 However, the amorphous content in laser cladding amorphous coatings is relatively low, only 40%. While the pre-melted substrate eliminates coating defects, it also dilutes the amorphous components of the coating. This solution addresses this by altering the substrate preheating conditions to minimize the impact of the preheating process on the coating preparation process while eliminating residual stress.

[0005] Chinese patent CN113584477A discloses a method for ultra-high-speed laser cladding of amorphous alloy coatings, with a laser power range of 1.0-2.5kW and a scanning speed range of 100-250mm / s. By controlling the cladding parameters, a defect-free surface-protective iron-based amorphous alloy coating at the hundred-micron level is prepared, avoiding the limitations of brittleness and size effects inherent in amorphous alloys. This patent increases the self-corrosion potential of the ultra-high-speed laser cladding iron-based amorphous coating to -0.437V, a 41% increase compared to the substrate. The surface wear rate after amorphous coating protection is 2.99×10⁻⁶. -5 mm 3 N -1 m -1The temperature was reduced by 73% compared to the substrate. However, severe crystallization regions still existed inside the prepared iron-based amorphous alloy coating, and the excessively thick heat-affected zone caused uneven composition within the coating.

[0006] Currently, the preparation of amorphous coatings using ultra-high-speed laser cladding mainly faces the following problems: (1) poor or excessive bonding between the coating and the substrate, and defects such as cracks and pores easily appear on the surface or inside of the amorphous alloy coating; (2) thermal accumulation caused by excessive coating thickness and dilution of the substrate composition caused by high-energy laser during cladding, resulting in changes in the composition of the amorphous alloy coating; (3) obvious overlap marks due to the high scanning rate during high-speed cladding. When preparing amorphous coatings using ultra-high-speed laser cladding, high energy input will cause changes in the coating composition, and various defects and precipitates on the surface and inside of the amorphous coating will provide potential pathways for corrosion. Therefore, how to improve the corrosion resistance and mechanical properties of the amorphous coating by increasing the amorphous content and surface quality is a problem to be solved in this field. Summary of the Invention

[0007] To address the problems of low amorphous phase ratio and internal crystallization in the preparation of amorphous coatings using current high-speed laser cladding technology, this invention provides a fully amorphous, crack-free iron-based amorphous coating prepared by ultra-high-speed laser cladding and its preparation method.

[0008] This invention utilizes ultra-high-speed laser technology to melt amorphous powder. By adjusting process parameters, the amorphous phase content in the coating is increased. Taking advantage of the high energy density, fast laser path scanning speed, and laser action above the workpiece during high-speed cladding, the powder material is directly melted, then adheres to the substrate surface and condenses into a solid, forming a metallurgical bond with the substrate, resulting in a fully amorphous, crack-free iron-based amorphous coating.

[0009] This invention addresses the problems of existing laser cladding processes. Starting from the preparation process, it investigates the relationship between coating thickness and parameters through pretreatment and adjustment of process parameters. Through parameter screening and process optimization, a fully amorphous, crack-free iron-based amorphous coating is obtained. The solution provided in this application can solve problems such as the limitations of amorphous brittleness and size effect, low amorphous phase content in the coating, and susceptibility to cracking.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] This invention provides a method for preparing a fully amorphous, crack-free iron-based amorphous coating by ultra-high-speed laser cladding, comprising the following steps:

[0012] S1. Perform surface treatment on the disc-shaped workpiece to be clad;

[0013] S2. Preheat the workpiece to be clad, clamp the preheated workpiece with a chuck, and place it flat on the rotating carrier.

[0014] S3. Add the alloy powder to the cladding device and adjust the powder feeding speed, carrier gas flow rate, and protective gas flow rate of the cladding device.

[0015] S4. Adjust the distance between the cladding head and the workpiece to be clad, the laser focus, and the powder flow focus to ensure that the laser focus and the powder focus coincide, and that the defocusing range during the ultra-high speed laser cladding process is always 0-10mm above the surface of the workpiece to be clad.

[0016] S5. Set the cladding head moving speed;

[0017] S6. The rotating carrier drives the workpiece to be clad to rotate, and laser cladding begins from the outside to the inside, forming an ultra-high speed laser cladding all-amorphous crack-free iron-based amorphous coating on the surface of the workpiece.

[0018] In one embodiment of the present invention, in step S1, the substrate material of the workpiece to be clad is 316L, 304SS, or Inconel 625.

[0019] In one embodiment of the present invention, step S1, surface treatment of the workpiece to be clad includes: grinding and polishing the surface of the workpiece to be clad to remove oil stains, rust stains, oxide film, etc., to ensure good laser absorption and adhesion of the cladding layer.

[0020] In one embodiment of the present invention, in step S1, the area of ​​the workpiece to be clad is selected according to actual needs, and the thickness of the workpiece to be clad is not less than 5mm.

[0021] In one embodiment of the present invention, in step S2, the temperature at which the workpiece to be clad is preheated is 200-400°C, preferably 200-300°C.

[0022] In one embodiment of the present invention, in step S3, the alloy powder is a sieved and dried powder with a particle size range of 35-75μm, a sphericity ≥90%, and an oxygen content ≤150ppm.

[0023] In one embodiment of the present invention, in step S3, the alloy powder is an iron-based amorphous alloy powder with a particle size of 45μm to 60μm, a sphericity ≥90%, and an oxygen content ≤150ppm.

[0024] In one embodiment of the present invention, in step S3, the powder feeding speed is 15-25 g / min, the carrier gas flow rate is 20-30 L / min, and the protective gas flow rate is 10-15 L / min.

[0025] In one embodiment of the present invention, in step S4, the defocusing amount is 1-10mm, the powder flow focal point is located 0-1mm above the laser focal point, and the spot diameter is 1.5-2.5mm.

[0026] In one embodiment of the present invention, in step S5, the moving speed of the cladding head is set to 1-3 mm / s.

[0027] In one embodiment of the present invention, in step S6, the laser power used in the cladding process is 2-4kW, the rotation speed of the rotating carrier is 0-350rpm, and the corresponding scanning speed is 0-200m / min, wherein neither the rotation speed of the rotating carrier nor the scanning speed is 0. Preferably, the laser power in the cladding process is 3.5-4.5kW, and the carrier rotation speed is 100-1000rpm.

[0028] The equipment used in the cladding process of this invention includes a laser, a laser cladding head, a control terminal, a chuck, and a rotating carrier. The workpiece to be clad is clamped by the chuck and placed on the rotating carrier. The laser cladding head is located at the lower end of the laser. The laser is also connected to the control terminal, which can control the laser feed and cladding-related parameters, and can adjust the rotation speed of the rotating carrier in real time.

[0029] During the laser cladding process, the parameters of the laser cladding are optimized using the following methods:

[0030] The disc-shaped workpiece to be clad for the test is fixed on a chuck on a rotating carrier;

[0031] The preparation method of all-amorphous crack-free iron-based amorphous coating by ultra-high speed laser cladding was followed. The obtained coating was sampled and analyzed. A sample block was taken at 1 cm intervals. The surface quality, coating thickness and coating cross-sectional quality were used to determine whether the cladding parameters were appropriate. The relationship between coating thickness and parameters was plotted to obtain the most suitable process parameters for the alloy powder.

[0032] Readjust the parameters to determine the optimal position for coating quality, and record the radius R at this point. 试验 and rotational speed N 试验 Without changing other parameters such as the feed speed of the cladding head, the rotational speed N of the rotating carrier is made to vary with time; the formula for the gradient variation is as follows (taking a disc-shaped workpiece to be clad as an example, assuming the radius of the disc-shaped workpiece to be clad is R, the moving speed of the cladding head is v, and the time is t):

[0033]

[0034] The rotation speed of the rotating carrier is reset, and cladding begins to prepare a uniform thickness coating of the amorphous material on the target substrate.

[0035] The present invention further provides an all-amorphous, crack-free iron-based amorphous coating obtained by ultra-high-speed laser cladding based on the above method. The thickness of the iron-based amorphous coating is controlled to be 50-100 μm, the porosity is controlled to be less than 1%, and there are no defects such as surface pores and cracks. The width of the heat-affected zone is less than 5 μm.

[0036] This invention provides a method for preparing a fully amorphous iron-based coating using ultra-high-speed laser cladding. Through pretreatment, parameter optimization, and post-treatment, the resulting iron-based amorphous coating exhibits extremely low dilution, with a metallurgical bonding zone of only 2 μm between the coating and the substrate. Furthermore, no overlap marks or nanocrystalline structures were found within the coating. This fully amorphous continuous coating, at the hundreds of micrometer scale and free of significant defects, not only avoids the limitations imposed by amorphous size effects but also prevents service instability caused by component segregation and overlap, significantly increasing the application ceiling of amorphous coatings and broadening their application fields.

[0037] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0038] 1. The laser energy mainly acts on the amorphous alloy powder. The higher laser energy causes the powder to bond with the matrix material in the form of droplets rather than particles. By reasonably setting the position of the laser focus and the powder flow focus, as well as related parameters, the amorphous content of the cladding layer is greatly improved.

[0039] 2. The combination of high rotation speed (cladding speed up to 200m / min) and appropriate laser power not only greatly improves the cladding speed, but also achieves higher bonding strength and surface roughness.

[0040] 3. By optimizing the coordination between powder feed rate, scanning speed, and overlap rate, an optimization law for the rotation speed was derived, thereby improving the thickness and forming quality of the iron-based amorphous coating to the optimal level. While ensuring good metallurgical bonding between the substrate and the coating, the dilution rate of the iron-based amorphous coating by the substrate was minimized. Simultaneously, through specific relationships (reasonable control of laser power, scanning speed, and powder feed rate), a defect-free, fully amorphous coating of uniform thickness was prepared from the iron-based amorphous alloy. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0042] Figure 1 This is a schematic diagram of the ultra-high-speed laser cladding process in Embodiment 1 of the present invention;

[0043] Figure 2 (a)(b)(c) are cross-sectional SEM images of the coating obtained in Example 1 of the present invention at different magnifications. Figure 2 (d) is the process optimization diagram obtained during the parameter adjustment process;

[0044] Figure 3 This is a comparison XRD pattern of the coating and the substrate in Example 1 of the present invention;

[0045] Figure 4 This is a TEM image of the middle part of the coating in Embodiment 1 of the present invention;

[0046] Figure 5 The image shows the corrosion polarization curve of the coating in Example 1 of this invention in a 3.5% NaCl solution.

[0047] Figure 6 The hardness curve of the iron-based fully amorphous coating is shown at a scanning speed of 100.56 m / min.

[0048] The numbers in the diagram are as follows:

[0049] 1. Laser; 2. Laser cladding head; 3. Workpiece to be clad; 4. Control terminal; 5. Chuck; 6. Rotating carrier. Detailed Implementation

[0050] In the description of this invention, it should be understood that the terms "lateral", "thickness", "outer", "inner" and other directional indications are based on the orientation shown in the drawings and are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0051] In one embodiment of the present invention, the amorphous powder is prepared by gas atomization, with a particle size range of 30μm to 75μm, sphericity ≥90%, and oxygen content ≤150ppm; the material is an iron-based amorphous alloy.

[0052] In one embodiment of the present invention, the coating thickness is set as required, and is approximately 54 μm.

[0053] Combination Figures 1-5 The preparation method of the ultra-high speed laser cladding fully amorphous crack-free iron-based amorphous coating according to the embodiments of the present invention is described in detail.

[0054] refer to Figures 1-5 This invention provides a method for preparing a fully amorphous, crack-free iron-based amorphous coating by ultra-high-speed laser cladding, comprising the following steps:

[0055] S1. Perform surface treatment on the disc-shaped workpiece to be clad;

[0056] S2. Preheat the workpiece to be clad, clamp the preheated workpiece with a chuck, and place it flat on the rotating carrier.

[0057] S3. Add the alloy powder to the cladding device and adjust the powder feeding speed, carrier gas flow rate, and protective gas flow rate of the cladding device.

[0058] S4. Adjust the distance between the cladding head and the workpiece to be clad, the laser focus, and the powder flow focus to ensure that the laser focus and the powder focus coincide, and that the defocusing range during the ultra-high speed laser cladding process is always 0-10mm above the surface of the workpiece to be clad.

[0059] S5. Set the cladding head moving speed;

[0060] S6. The rotating carrier drives the workpiece to be clad to rotate, and laser cladding begins from the outside to the inside, forming an ultra-high speed laser cladding all-amorphous crack-free iron-based amorphous coating on the surface of the workpiece.

[0061] In step S1, the substrate material of the workpiece to be clad is a 304SS steel disc with a thickness of 5mm and a diameter of 200mm. Surface treatment of the workpiece to be clad includes grinding and polishing the surface to remove oil, rust, oxide film, etc., to ensure good laser absorption and adhesion of the cladding layer.

[0062] In step S1, the area of ​​the workpiece to be clad is selected according to actual needs, and the thickness of the workpiece to be clad is not less than 5mm.

[0063] In step S2, the temperature for preheating the workpiece to be clad is 200-400℃, preferably 200-300℃.

[0064] In step S3, the alloy powder is a sieved and dried powder with a particle size range of 35-75μm, a sphericity ≥90%, and an oxygen content ≤150ppm.

[0065] After parameter optimization, the laser power in the ultra-high-speed laser cladding process is 1.5kW and the scanning speed is 200mm / s.

[0066] During the pretreatment process, the surface of the disc-shaped workpiece 3 needs to be sanded and polished with sandpaper, cleaned with anhydrous ethanol, and dried at room temperature. The preheating temperature before cladding is 300℃.

[0067] During the cladding process, the ultra-high-speed laser cladding technology uses a laser power of 3.5kW, a workpiece rotation speed of 200rpm, a spot diameter of 2.5mm, and a powder feeding speed of 15 / 20 / 25g / min. The scanning speed is 20-200m / min (the diameter of the disc-shaped substrate used is 200mm); the cladding head feed speed is 1mm / s; the protective gas flow rate is 30L / min; and the carrier gas flow rate is 10L / min.

[0068] The laser focusing position coincides with the powder flow focusing position, with a defocusing amount of 1mm. The defocusing amount is controlled by the control terminal, so that the distance between the cladding head and the substrate is always kept at 10mm.

[0069] After the cladding is completed, the formed workpiece needs to be transferred to an argon-protected chamber to cool at room temperature.

[0070] Preferably, in the ultra-high-speed laser cladding process of the present invention, the optimal laser power is 3.5kW, the scanning speed is 100.56m / min, and the powder feeding speed is 25g / min.

[0071] The equipment used in the cladding process of this invention includes a laser 1, a laser cladding head 2, a control terminal 4, a chuck 5, and a rotating carrier 6. The workpiece 3 to be clad is clamped by the chuck 5 and placed on the rotating carrier 6. The laser cladding head 2 is located at the lower end of the laser 1. The laser 1 is also connected to the control terminal 4. The control terminal can control the laser feed and cladding-related parameters, and can adjust the rotation speed of the rotating carrier 6 in real time.

[0072] During the laser cladding process, the parameters of the laser cladding are optimized using the following methods:

[0073] The disc-shaped workpiece to be clad for the test is fixed on a chuck on a rotating carrier;

[0074] The preparation method of all-amorphous crack-free iron-based amorphous coating by ultra-high speed laser cladding was followed. The obtained coating was sampled and analyzed. A sample block was taken at 1 cm intervals. The surface quality, coating thickness and coating cross-sectional quality were used to determine whether the cladding parameters were appropriate. The relationship between coating thickness and parameters was plotted to obtain the most suitable process parameters for the alloy powder.

[0075] Readjust the parameters to determine the location where the coating quality is optimal, and record the radius R at this point. 试验 and rotational speed N 试验 Without changing other parameters such as the feed speed of the cladding head, the rotational speed N of the rotating carrier is made to vary with time; the formula for the gradient variation is as follows (taking a disc-shaped workpiece to be clad as an example, assuming the radius of the disc-shaped workpiece to be clad is R, the moving speed of the cladding head is v, and the time is t):

[0076]

[0077] The rotation speed of the rotating carrier is reset, and cladding begins to prepare a uniform thickness coating of the amorphous material on the target substrate.

[0078] To better highlight the significant advantages of the ultra-high-speed laser cladding fully amorphous coating obtained by this invention, the following description, in conjunction with the accompanying drawings, further illustrates the iron-based fully amorphous coating under the optimal process of this invention:

[0079] Example 1

[0080] A method for preparing an ultra-high-speed laser cladding fully amorphous crack-free iron-based amorphous coating includes the following steps:

[0081] S1. Perform surface treatment on the disc-shaped workpiece to be clad;

[0082] S2. Preheat the workpiece to be clad, clamp the preheated workpiece with a chuck, and place it flat on the rotating carrier.

[0083] S3. Add the alloy powder to the cladding device and adjust the powder feeding speed, carrier gas flow rate, and protective gas flow rate of the cladding device.

[0084] S4. Adjust the distance between the cladding head and the workpiece to be clad, the laser focus, and the powder flow focus to ensure that the laser focus and the powder focus coincide, and that the defocusing range during the ultra-high speed laser cladding process is always 0-10mm above the surface of the workpiece to be clad.

[0085] S5. Set the cladding head moving speed;

[0086] S6. The rotating carrier drives the workpiece to be clad to rotate, and laser cladding begins from the outside to the inside, forming an ultra-high speed laser cladding all-amorphous crack-free iron-based amorphous coating on the surface of the workpiece.

[0087] In step S1, the substrate material of the workpiece to be clad is a 304S steel disc with a thickness of 5mm and a diameter of 200mm. Surface treatment of the workpiece to be clad includes grinding and polishing the surface to remove oil, rust, oxide film, etc., to ensure good laser absorption and adhesion of the cladding layer.

[0088] After parameter optimization, the laser power in the ultra-high-speed laser cladding process is 1.5kW and the scanning speed is 200mm / s.

[0089] During the pretreatment process, the surface of the disc-shaped workpiece to be clad needs to be polished with sandpaper, cleaned with anhydrous ethanol, and dried at room temperature. The preheating temperature before cladding is 300℃.

[0090] During the cladding process, the laser power of the ultra-high-speed laser cladding process is 3.5kW, the workpiece rotation speed is 200rpm, the spot diameter is 2.5mm, and the powder feeding speed is 15 / 20 / 25g / min. The scanning speed is 100.56m / min (the diameter of the disc substrate used is 200mm); the cladding head feed speed is 1mm / s; the protective gas flow rate is 30L / min; and the carrier gas flow rate is 10L / min.

[0091] The laser focusing position coincides with the powder flow focusing position, with a defocusing amount of 1mm. The defocusing amount is controlled by the control terminal, so that the distance between the cladding head and the substrate is always kept at 10mm.

[0092] After the cladding is completed, the formed workpiece needs to be transferred to an argon-protected chamber to cool at room temperature.

[0093] Before obtaining Example 1, corresponding preliminary tests were conducted. The test parameters are shown in the table below, and the relationship between coating thickness, quality, and process parameters was statistically analyzed. Figure 2 Following d), based on the relationship diagram and experimental experience, it was found that the coating thickness is most affected by the powder feed rate at the same scanning speed. Excessively thick coatings result in surface defects and thermal buildup that are difficult to eliminate. Therefore, the coating thickness needs to be controlled to below 150 μm. Furthermore, generally speaking, when the laser power is above 3kW, powders with a particle size less than 100 μm will be melted. Therefore, minimizing the laser power and appropriately increasing the powder feed rate are the primary considerations in the experiment.

[0094] The 10×5×5mm metallographic sample with coating wire cutting obtained in the embodiment of the present invention is subjected to the following steps: ultrasonic cleaning of surface oil stains, washing with anhydrous ethanol, drying, mounting, grinding of the sample cross section perpendicular to the cladding direction (using 400 / 1500 / 3000 / 4000 / 5000 grit sandpaper in sequence), polishing to mirror finish, and drying.

[0095] The cross-sectional morphology of the amorphous coating was observed using a scanning electron microscope, based on the attached... Figure 2 The cross-sectional morphology of the iron-based amorphous coating is shown. Figure 2 (a) shows the morphology of the coating cross section under low magnification SEM. It can be seen that there are no obvious macroscopic defects inside the coating, and the coating thickness is relatively uniform with a dense internal structure. This is due to the high scanning speed and the parameter optimization in this invention, which fully demonstrates that a uniform coating thickness can be formed on a disc-shaped workpiece through reasonable parameter settings. Figure 2 (b) and Figure 2 (c) Corresponding to regions A and B respectively, it can be seen from... Figure 2 As seen in (b), no obvious crystallized phase or overlap marks were observed inside the coating except in the bonding area with the substrate. This indicates that under these process parameters, the coating and the substrate can achieve good bonding, and the molten pool can also perfectly overlap with the previous trajectory. Figure 2(c) represents the interface state between the coating and the substrate under the optimal process. Under this process, because the cooling rate at the bottom of the molten pool is lower than in other areas, the metallurgical bonding zone with the substrate is cellular, and its growth is perpendicular to the interface. This is because the temperature gradient perpendicular to the cladding coating / interface (metallurgical bonding zone) is the largest, which is conducive to crystallization and growth. Appropriate heat input is beneficial to the formation of a more stable metallurgical bond. The advantage of this invention is that the average bonding zone width of 2.43 μm is much smaller than that of the ultra-high-speed laser cladding coatings prepared in recent studies, and there is no obvious crystallization region inside the coating, maintaining the compositional stability of the amorphous coating.

[0096] The phase composition of the prepared coating was analyzed using X-ray diffraction. Figure 3 The XRD patterns of the fully amorphous coating in Example 1 and the amorphous powder sample of the material are compared. It can be seen that the amorphous coating still has a relatively wide diffuse scattering peak. Although the position of the diffuse scattering peak becomes sharper than that of the powder sample, showing a crystallization trend, this may be due to the local short-range structural changes caused by the overlap.

[0097] To observe the internal microstructure of the coating, a focused ion beam was used to examine the cross-section of the sample. Figure 2 (b) Samples were taken from region B and analyzed by transmission electron microscopy (TEM). Figure 4 (a) is Figure 2 (b) shows the TEM high-resolution spectrum of region B, revealing that the coating obtained by this invention exhibits a typical disordered structure. Furthermore, the corresponding selected electron diffraction pattern ( Figure 4 In (b), the diffraction rings appear as diffuse scattering halos because amorphous alloys have short-range ordered structures, which are almost disordered at the microscopic level.

[0098] The coating prepared by ultra-high speed laser cladding has a finer structure and more uniform composition. In order to better describe the specific performance of the coating obtained in the embodiments of the present invention, the corrosion resistance of the ultra-high speed laser cladding coating is characterized by electrochemical corrosion test.

[0099] An electrochemical corrosion sample measuring 10×5×5mm was cut from the cladding coating. To avoid the influence of uneven cladding coating surface and oxide film, the test sample was ground, polished, cleaned with alcohol, and dried before testing.

[0100] Electrochemical tests were performed on the samples using a three-electrode system at room temperature. The corrosion resistance of the coating was tested using the potentiodynamic polarization method with a potential change rate of 1 mV / s, scanning from a low potential of -0.5 V to a high potential of 1.2 V.

[0101] The electrochemical polarization curves of the examples are as follows: Figure 5As shown, the corrosion potential and corrosion current density of the coating were calculated using the Tafel linear extrapolation method. In this embodiment of the invention, the self-corrosion potential of the coating is -0.266V, and the corrosion current density is 1.25 x 10⁻⁶V. -8 A·cm 2 The corrosion current represents the corrosion rate of the coating under conditions without applied current. The stronger the coating's corrosion resistance, the slower the corrosion rate and the smaller the corrosion current. The corrosion potential primarily indicates the coating's corrosion tendency; a higher corrosion potential indicates a lower corrosion tendency. It can be seen that this coating exhibits excellent corrosion resistance, mainly due to the uniformity of the coating composition and the high surface quality achieved through the optimized ultra-high-speed laser cladding process.

[0102] The hardness curve of the iron-based fully amorphous coating at a scanning speed of 100.56 m / min is shown below. Figure 6 As shown, the microhardness of the ultra-high-speed laser cladding coating is significantly higher than that of the substrate, and decreases rapidly in the metallurgical bonding zone, reflecting the extremely narrow heat-affected zone during ultra-high-speed laser cladding. The average microhardness is approximately 1182.6 HV. 0.2 High scanning speed can reduce fluctuations in coating composition, thereby improving the mechanical properties of the coating.

[0103] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing an ultra-high-speed laser cladding fully amorphous, crack-free iron-based amorphous coating, characterized in that, Includes the following steps: S1. Perform surface treatment on the disc-shaped workpiece to be clad; S2. Preheat the workpiece to be clad at a temperature of 200-400 ℃. Clamp the preheated workpiece with a chuck and place it flat on the rotating carrier. S3. Add the alloy powder to the cladding device and adjust the powder feeding speed, carrier gas flow rate, and protective gas flow rate of the cladding device. S4. Adjust the distance between the cladding head and the workpiece to be clad, the laser focus, and the powder flow focus. The defocusing amount during the ultra-high-speed laser cladding process is 1-10mm, the powder flow focus is 0-1mm above the laser focus, and the spot diameter is 1.5-2.5mm. S5. Set the cladding head moving speed; S6. The rotating carrier drives the workpiece to be clad to rotate, and laser cladding begins from the outside to the inside, forming an ultra-high speed laser cladding all-amorphous crack-free iron-based amorphous coating on the surface of the workpiece. The laser power used in the cladding process is 2-4 kW, the rotation speed of the rotating carrier is 100-350 rpm, and the corresponding scanning speed is 20-200 m / min. During the laser cladding process, the parameters of the laser cladding are optimized using the following methods: The disc-shaped workpiece to be clad for the test is fixed on a chuck on a rotating carrier; The preparation method of all-amorphous crack-free iron-based amorphous coating by ultra-high speed laser cladding was followed. The obtained coating was sampled and analyzed. A sample block was taken at 1 cm intervals. The surface quality, coating thickness and coating cross-sectional quality were used to determine whether the cladding parameters were appropriate. The relationship between coating thickness and parameters was plotted to obtain the most suitable process parameters for the alloy powder. Readjust the parameters to determine the optimal position for coating quality, and record the radius R at this point. 试验 and rotational speed N 试验 Without changing other parameters, the rotational speed N of the rotating carrier is made to vary with time; the gradient formula is as follows, assuming the radius of the target disc-shaped workpiece to be clad is R, the moving speed of the cladding head is v, and the time is t: The rotation speed of the rotating carrier is reset, and cladding begins to prepare a uniform thickness of all-amorphous, crack-free iron-based amorphous coating on the target substrate.

2. The method for preparing an ultra-high-speed laser cladding fully amorphous crack-free iron-based amorphous coating according to claim 1, characterized in that, In step S1, the substrate material of the workpiece to be clad is 316L, 304SS, or Inconel 625; In step S1, the surface treatment of the workpiece to be clad includes: grinding and polishing the surface of the workpiece to be clad to remove oil, rust, and oxide film; In step S1, the thickness of the workpiece to be clad is not less than 5 mm.

3. The method for preparing an ultra-high-speed laser cladding fully amorphous crack-free iron-based amorphous coating according to claim 1, characterized in that, In step S3, the alloy powder is a sieved and dried powder with a particle size range of 35-75 μm, a sphericity ≥90%, and an oxygen content ≤150ppm.

4. The method for preparing an ultra-high-speed laser cladding fully amorphous crack-free iron-based amorphous coating according to claim 1, characterized in that, In step S3, the powder feeding speed is 15-25 g / min, the carrier gas flow rate is 20-30 L / min, and the protective gas flow rate is 10-15 L / min.

5. The method for preparing an ultra-high-speed laser cladding fully amorphous crack-free iron-based amorphous coating according to claim 1, characterized in that, In step S5, the moving speed of the cladding head is set to 1-3 mm / s.

6. A fully amorphous, crack-free iron-based amorphous coating obtained by ultra-high-speed laser cladding according to any one of claims 1-5, characterized in that, The iron-based amorphous coating has a thickness of 50~100μm, a porosity of less than 1%, and is free of surface pores and cracks, with a heat-affected zone width of less than 5μm.

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