An iron-based alloy powder, an iron-based alloy coating, and a production method and applications thereof

Abstract

The present application belongs to the technical field of coating materials, and particularly relates to an iron-based alloy powder, an iron-based alloy coating, and a preparation method and application thereof. The iron-based alloy powder provided by the present application is added with high-content Cr3C2 powder, or simultaneously added with a certain amount of Y2O3 powder. Through a laser cladding process with specific parameters, the iron-based alloy coating prepared has a uniform surface tissue distribution, no cracks, higher hardness and resistance, and the highest hardness can reach above 1110 Hv, and can be used for surface repair of worn metal parts or surface protection of easily-worn metal parts.

Description

Technical Field

[0001] This invention belongs to the field of coating materials technology, specifically relating to an iron-based alloy powder, an iron-based alloy coating, its preparation method, and its application. Background Technology

[0002] In the operation of excavators and other heavy machinery, the bucket, as the main component in direct contact with materials, frequently faces a high-wear, high-impact working environment. Wear on the inner wall of the bucket not only affects work efficiency but also increases maintenance costs and replacement frequency, significantly impacting the overall operating cost and service life of the machinery. Therefore, developing wear-resistant coatings to enhance the wear resistance of the bucket's inner wall has become an important means of improving the bucket's mechanical performance and extending its service life. In existing bucket wear-resistant technologies, wear-resistant steel plates such as NM360, NM400, NM450, and NM500 are often used as materials for bucket manufacturing. By adjusting the alloy element content in the steel and employing appropriate heat treatment processes, the wear resistance, impact resistance, and fatigue resistance of the steel can be improved. These steel plates have been widely used in excavator bucket manufacturing with good results, but they still suffer from high manufacturing costs, difficult welding processes, and poor performance in bulk material handling, leading to increased operating costs and decreased operating efficiency.

[0003] Laser cladding is a surface modification technology that involves adding external materials, such as iron-based alloy powder, to a substrate after laser irradiation, forming a molten pool. The two materials then rapidly solidify together to form a cladding layer, thereby improving the surface properties of the substrate. Cr3C2 has a moderate melting point, high hardness, and good wear resistance, and exhibits good compatibility with iron-based self-fluxing alloy powders. It is often used in conjunction with these powders to prepare iron-based alloy powders, which are then used to modify the substrate surface through laser cladding. The addition of Cr3C2 can effectively improve the wear resistance and hardness of the cladding layer to a certain extent. However, when the Cr3C2 content increases to a certain level, eutectic crystallization occurs in the coating, leading to a decrease in coating toughness and making the coating surface prone to cracking, thus affecting the coating's performance. Summary of the Invention

[0004] In view of this, the present invention provides an iron-based alloy powder, an iron-based alloy coating, a preparation method thereof, and an application thereof. The iron-based alloy coating prepared using the iron-based alloy powder has a uniform surface microstructure distribution, is free of cracks, and has higher hardness and toughness. It can be used for surface repair of worn metal parts or surface protection of easily worn metal parts.

[0005] To solve the above technical problems, the present invention provides an iron-based alloy powder, comprising, by weight percentage: 40wt%~60wt% Fe-based self-fluxing alloy powder and 40wt%~60wt% Cr3C2 powder; wherein the Fe-based self-fluxing alloy powder comprises the following elements by weight percentage: C 0.4wt%~1.2wt%, Si 1wt%~3wt%, Cr 5wt%~10wt%, Ni 25wt%~40wt%, B 2wt%~6wt%, with the balance being Fe.

[0006] The iron-based alloy powder provided by this invention contains 40wt%~60wt% Cr3C2 powder. Cr3C2 is a ceramic material with high hardness and high wear resistance. When the iron-based alloy powder is clad onto the surface of a metal substrate using laser cladding, in the early stage of solidification, Cr3C2 reacts with Fe in the molten pool to form (Fe,Cr)7C3 phase and Cr7C3 phase. The (Fe,Cr)7C3 phase and Cr7C3 phase have high melting points and can serve as preferential nucleation materials, significantly increasing the nucleation rate and promoting grain refinement. As a result, a large number of Cr3C2 particles are generated in the cladding layer. Cr3C2 particles have the high hardness and high wear resistance characteristic of ceramic materials. Therefore, its high content can significantly improve the hardness and wear resistance of the iron-based alloy cladding layer, reduce wear, and improve the overall performance of the cladding layer.

[0007] A second aspect of the present invention provides an iron-based alloy powder, characterized in that, by weight percentage, it comprises: 38wt%~60wt% Fe-based self-fluxing alloy powder, 39wt%~61wt% Cr3C2 powder, and 0.5wt%~1.25wt% Y2O3 powder; wherein the Fe-based self-fluxing alloy powder comprises the following elements by weight percentage: C 0.4wt%~1.2wt%, Si 1wt%~3wt%, Cr 5wt%~10wt%, Ni 25wt%~40wt%, B 2wt%~6wt%, with the balance being Fe.

[0008] Although adding 40wt%~60wt% Cr3C2 powder can improve the wear resistance and hardness of the final cladding layer, the hardness and wear resistance of this coating layer are insufficient to meet the actual application requirements under high-wear conditions such as heavy machinery. The inventors discovered that adding a certain amount of rare earth metal Y2O3 can refine the grain and reduce the initiation of cracks in the cladding coating, thereby further improving the wear resistance and hardness of the cladding layer, even enabling the hardness of the cladding layer to reach over 1000 HV. This is because Y2O3 decomposes into active yttrium atoms in the high-temperature environment of laser cladding and diffuses into the cladding layer. Yttrium atoms have a large atomic radius and easily form intermetallic compounds with nickel. Especially when the nickel content is high, the Ni2Y phase is preferentially formed. Ni2Y can form a solid solution or a dispersed second phase with the hard phase, which improves the hardness and compressive strength by pinning dislocations and hindering crack propagation.

[0009] Preferably, the particle size of the Y2O3 powder is 100~150μm.

[0010] Preferably, the Fe-based self-fluxing alloy powder has a particle size of 100-150 μm, and the Cr3C2 powder has a particle size of 130-220 μm.

[0011] The raw materials selected in this invention have a high degree of particle size matching, making them easier to mix evenly, thereby ensuring that the powder can be fully melted and improving the utilization rate of the powder. At the same time, the uniform mixing of each component is conducive to the uniform distribution of yttrium oxide or chromium carbide in the matrix, thereby ensuring that the surface of the obtained cladding layer has good density, high hardness, and good wear resistance.

[0012] The third aspect of the present invention provides a method for preparing iron-based alloy powder, wherein each raw material is weighed according to the above-mentioned formula for iron-based alloy powder, the raw materials are mixed and then ball-milled and dried to obtain the iron-based alloy powder.

[0013] Preferably, the ball milling speed is 150~180 r / min, the ball milling time is 2~3 h; the drying temperature is 150~155℃, and the drying time is 2~3 h.

[0014] The ball milling speed and time selected in this invention ensure that the raw materials are fully milled, resulting in finer and more uniform particle size distribution of the obtained iron-based alloy powder, thereby obtaining a cladding coating with excellent overall performance. The drying conditions described above remove moisture from the iron-based alloy powder, preventing defects such as pores from appearing in the cladding layer.

[0015] A fourth aspect of the present invention provides an iron-based alloy coating, wherein the coating is obtained by laser cladding of the aforementioned iron-based alloy powder onto the surface of a metal substrate.

[0016] The fifth aspect of this invention provides a method for preparing an iron-based alloy coating, comprising the following steps: The surface of the metal substrate to be clad is cleaned, polished and dried, and then placed on the laser action platform. The distance between the metal substrate and the laser head is adjusted so that the upper surface of the substrate is located on the focal plane. The laser processing parameters and the laser path code are set, and the iron-based alloy powder is fed into the laser action area by synchronous powder feeding method, and laser cladding is performed with the metal substrate to obtain the iron-based alloy coating. The laser processing parameters include: laser power of 1400~1600W, spot diameter of 4.5~5mm, scanning speed of 410~430mm / min, and powder feeding rate of 4~6g / min.

[0017] While the addition of Cr3C2 to iron-based alloy powders can improve the hardness and wear resistance of the coating to some extent, it still cannot meet the requirements of certain harsh environments. However, research has found that further increasing the Cr3C2 content leads to defects such as cracks on the surface of the cladding layer. This invention, by adjusting the laser cladding process parameters, obtains a laser cladding process that can match high Cr3C2 addition levels. This laser cladding process is also applicable to iron-based alloy powders with further added Y2O3 powder. During laser cladding, the iron-based alloy powder is directly fed into the laser action zone, simultaneously melting both the metal substrate surface and the iron-based alloy powder. Under specific laser parameter conditions, a cladding layer is prepared, resulting in a cladding layer with significantly improved hardness and wear resistance while being crack-free. This is of great significance for the production of heavy machinery in high-wear operating conditions.

[0018] This invention employs a synchronous powder feeding method for laser cladding. Under the action of a laser, iron-based alloy powder and a thin layer on the surface of a metal substrate are simultaneously melted to obtain a dense and uniform cladding layer. To further improve the performance of the cladding layer, the metal substrate to be clad is preheated to 280~320℃ to eliminate the internal stress of the iron-based alloy cladding layer, thereby obtaining a uniform and dense cladding layer, improving its toughness, hardness, and durability, ensuring that the cladding layer is crack-free, and ultimately obtaining an iron-based alloy coating with good adhesion to the metal substrate, no surface cracks, and superior overall performance.

[0019] Preferably, a CZ-6000-A laser cladding machine can be used for laser cladding. This laser cladding machine has a maximum power of 6000W and a maximum spot diameter of 5mm. It is also equipped with a robotic arm, a computer, a water-cooled box, and a powder feeder. The iron-based alloy powder is placed in the powder feeder, and the cladding layer can be prepared using the synchronous powder feeding method.

[0020] Preferably, the laser heat source used is a Gaussian heat source, which can make the single-pass cladding layer exhibit a semi-elliptical morphology with low sides and high center. When it is necessary to repair a large area of ​​the damaged surface of the metal substrate, continuous processing and multi-pass overlapping can be carried out on the basis of single-pass cladding to prepare a large-area coating.

[0021] Preferably, the laser cladding includes single-pass cladding and multi-pass cladding, and the overlap rate of the multi-pass cladding is 45% to 55%. This overlap rate can obtain a cladding layer with good surface flatness, no cracks, and uniform and dense structure.

[0022] More preferably, the overlap rate of the multi-layer cladding is 50%.

[0023] Preferably, the overlap rate of the multi-layer cladding is expressed as: η = (K / W) × 100%; where η is the overlap rate, K is the overlap width between two adjacent cladding layers, and W is the width of a single cladding layer. For example, when using a CZ-6000-A laser cladding machine, if K is 1.0 mm and W is 2.0 mm, the overlap rate is 50%, and the path code for 20 overlaps is: G201 Y30 U1.7 D20.

[0024] Preferably, the path code for the single-pass cladding is: start G01 X0 Y0, end G01 X0 Y30, which means traveling 30mm along the Y-axis.

[0025] Preferably, the powder feeding gas flow rate is 14~16L / min, and the protective gas flow rate is 0.8~1L / min; wherein, the powder feeding gas or protective gas is high-purity argon.

[0026] The present invention also provides the application of the above-mentioned iron-based alloy coating or the iron-based alloy coating prepared according to the above-mentioned iron-based alloy coating preparation method in the surface repair of worn metal parts or the surface protection of easily worn metal parts.

[0027] Preferably, the metal component can be an excavator bucket liner, an army equipment ball bearing, a 40Cr steel road wheel, etc. Attached Figure Description

[0028] Figure 1 These are macroscopic morphology images of the iron-based alloy coatings obtained in Examples 8-10, wherein... Figure 1 (a) is a macroscopic morphology diagram of the iron-based alloy coating obtained in Example 8. Figure 1 (b) is a macroscopic morphology diagram of the iron-based alloy coating obtained in Example 9. Figure 1 (c) is a macroscopic morphology diagram of the iron-based alloy coating obtained in Example 10.

[0029] Figure 2 The images show the microstructure of the iron-based alloy coatings obtained in Examples 8-10. Figure 2 (a) is a microstructure diagram of the iron-based alloy coating obtained in Example 8. Figure 2 (b) is a microstructure diagram of the iron-based alloy coating obtained in Example 9. Figure 2 (c) is a microscopic morphology diagram of the iron-based alloy coating obtained in Example 10.

[0030] Figure 3 The XRD diffraction patterns are those of the iron-based alloy coatings obtained in Examples 8-10.

[0031] Figure 4 The image shows the average microhardness of the iron-based alloy coatings obtained in Examples 8-10.

[0032] Figure 5 The images show the wear of the iron-based alloy coating and the bucket substrate obtained in Examples 8-10.

[0033] Figure 6 These are microscopic morphology images of the iron-based alloy coatings obtained in Examples 8-10 after wear. Figure 6 (a) is a microscopic morphology image of the iron-based alloy coating obtained in Example 8 after wear. Figure 6 (b) is a microscopic morphology image of the iron-based alloy coating obtained in Example 9 after wear. Figure 6 (c) is a microscopic morphology diagram of the iron-based alloy coating obtained in Example 10 after wear.

[0034] Figure 7 The images show the microstructure of the iron-based alloy coatings obtained in Examples 11-14, where... Figure 7 (a) is a microstructure diagram of the iron-based alloy coating obtained in Example 11. Figure 7 (b) is a microstructure diagram of the iron-based alloy coating obtained in Example 12. Figure 7 (c) is a microstructure diagram of the iron-based alloy coating obtained in Example 13. Figure 7 (d) is a microscopic morphology diagram of the iron-based alloy coating obtained in Example 14.

[0035] Figure 8 The XRD diffraction patterns are those of the iron-based alloy coatings obtained in Examples 11-14.

[0036] Figure 9 The image shows the average microhardness of the iron-based alloy coatings obtained in Examples 11-14.

[0037] Figure 10 The friction coefficient curves of the iron-based alloy coatings obtained in Examples 11-14 are shown.

[0038] Figure 11 The wear diagrams are for the iron-based alloy coatings obtained in Examples 11-14.

[0039] Figure 12These are microscopic morphology images of the iron-based alloy coatings obtained in Examples 11-14 after wear. Figure 12 (a) is a microscopic morphology image of the iron-based alloy coating obtained in Example 11 after wear. Figure 12 (b) is a microscopic morphology image of the iron-based alloy coating obtained in Example 12 after wear. Figure 12 (c) is a microscopic morphology image of the iron-based alloy coating obtained in Example 13 after wear. Figure 12 (d) is a microscopic morphology diagram of the iron-based alloy coating obtained in Example 14 after wear.

[0040] Figure 13 The images show the microstructures of the iron-based alloy coatings obtained in Example 9 and Comparative Examples 1-2. Figure 13 (a) is a microstructure diagram of the iron-based alloy coating obtained in Comparative Example 2. Figure 13 (b) is a microstructure diagram of the iron-based alloy coating obtained in Comparative Example 1. Figure 13 (c) is a microscopic morphology diagram of the iron-based alloy coating obtained in Example 9. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0042] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0043] Unless otherwise specified, the raw materials, reagents and equipment used in this invention are all conventional commercially available reagents and equipment.

[0044] Cr3C2 has a moderate melting point, high hardness, and good wear resistance. It is often mixed with iron-based self-fluxing alloy powders and then used in laser cladding to modify the surface of the substrate, thereby improving the wear resistance and hardness of the cladding layer. Although the addition of Cr3C2 can improve the wear resistance and hardness of the cladding layer to some extent, the wear resistance of the resulting cladding layer still cannot meet the requirements of use in harsh environments. Some studies have attempted to further increase the Cr3C2 content to improve the hardness and wear resistance of the cladding layer, but it has been found that when the Cr3C2 content increases to a certain extent, it leads to excessive internal stress in the cladding layer. This is mainly due to the high hardness and brittleness of chromium carbide, and its tendency to form hard phase particles during the cladding process, resulting in a decrease in the toughness of the cladding layer. When the internal stress exceeds the bearing capacity of the cladding layer, cracks will occur, thus affecting the overall performance of the coating.

[0045] In view of this, the present invention provides an iron-based alloy powder, an iron-based alloy coating, a preparation method thereon, and applications. The iron-based alloy powder provided by the present invention contains a high content of Cr3C2 powder, or simultaneously contains Y2O3 powder. The iron-based alloy coating prepared from this iron-based alloy powder using a specific laser cladding process not only has higher hardness and wear resistance, but also exhibits good surface density and is free of cracks. This is of great significance for the surface repair and protection of metal instruments used in high-wear conditions.

[0046] The following detailed description of the iron-based alloy powder, iron-based alloy coating, and preparation method provided by the present invention is provided through specific embodiments.

[0047] The Cr3C2 powder used in the following embodiments and comparative examples of this invention was purchased from Zhuoyue Alloy Powder, with a purity of 99.99% and a particle size of 130~220μm; the Fe-based self-fluxing alloy powder was purchased from Shanghai Xinzuan Alloy Materials Co., Ltd. (of which, C 0.8wt%, Si 2wt%, Cr 7.5wt%, Ni 32wt%, B 4%wt., balance Fe), with a particle size of 100~150μm; the Y2O3 powder was purchased from China Metallurgical New Materials, with a purity of 99.99% and a particle size of 100~150μm.

[0048] The following embodiments and comparative examples of the present invention use the CZ-6000-A laser cladding machine, which has a maximum power of 6000W and a spot diameter of 5mm, and is equipped with a robotic arm, a computer, a water-cooled box and a powder feeder.

[0049] Example 1 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 60 wt% Fe-based self-fluxing alloy powder and 40 wt% Cr3C2 powder. Its preparation method is as follows: Weigh out Fe-based self-fluxing alloy powder and Cr3C2 powder according to the above proportions, mix them, and then ball mill them using a BXQI-4L planetary ball mill. Shake the mixed powder evenly at a speed of 150 r / min for 2 hours. Place the evenly mixed alloy powder into an R-F1200 vacuum drying oven and dry it at 150°C for 2 hours.

[0050] Example 2 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 50 wt% Fe-based self-fluxing alloy powder and 50 wt% Cr3C2 powder. Its preparation method is as follows: Weigh out Fe-based self-fluxing alloy powder and Cr3C2 powder according to the above proportions, mix them, and then ball mill them using a BXQI-4L planetary ball mill. Shake the mixed powder evenly at a speed of 165 r / min for 2.5 h. Place the evenly mixed alloy powder into an R-F1200 vacuum drying oven and dry it at 153℃ for 2.5 h.

[0051] Example 3 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 40 wt% Fe-based self-fluxing alloy powder and 60 wt% Cr3C2 powder. Its preparation method is as follows: Weigh out Fe-based self-fluxing alloy powder and Cr3C2 powder according to the above proportions, mix them, and then ball mill them using a BXQI-4L planetary ball mill. Shake the mixed powder evenly at a speed of 180 r / min for 3 hours. Place the evenly mixed alloy powder into an R-F1200 vacuum drying oven and dry it at 155℃ for 3 hours.

[0052] Example 4 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 39.5 wt% Fe-based self-fluxing alloy powder, 60 wt% Cr3C2 powder, and 0.5 wt% Y2O3 powder. Its preparation method is as follows: Weigh out Fe-based self-fluxing alloy powder, Cr3C2 powder and Y2O3 powder according to the above proportions, mix them, and then ball mill them using a BXQI-4L planetary ball mill. Shake the mixed powder evenly at a speed of 180 r / min for 3 hours. Place the evenly mixed alloy powder into an R-F1200 vacuum drying oven and dry it at 155℃ for 3 hours.

[0053] Example 5 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 39.25 wt% Fe-based self-fluxing alloy powder, 60 wt% Cr3C2 powder, and 0.75 wt% Y2O3 powder. Its preparation method is the same as in Example 4 and will not be repeated here.

[0054] Example 6 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 39.0 wt% Fe-based self-fluxing alloy powder, 60 wt% Cr3C2 powder, and 1.0 wt% Y2O3 powder. Its preparation method is the same as in Example 4 and will not be repeated here.

[0055] Example 7 This embodiment provides an iron-based alloy powder, comprising, by weight percentage: 38.75 wt% Fe-based self-fluxing alloy powder, 60 wt% Cr3C2 powder, and 1.25 wt% Y2O3 powder. Its preparation method is the same as in Example 4 and will not be repeated here.

[0056] Example 8 This embodiment provides a metal-based alloy coating, which is prepared by laser cladding of the metal-based alloy powder in Example 1 onto the surface of a bucket substrate. The specific preparation method is as follows: Pre-treat the bucket base: Use sandpaper to polish the surface of the bucket base, and simultaneously clean it with alcohol and acetone to remove residual oil, oxides, and other impurities. Place the pre-treated bucket base on the laser platform, and adjust the distance between the base and the laser head so that the upper surface of the base is located on the focal plane.

[0057] The laser processing parameters and laser path codes were set on the computer equipped with the laser. The surface temperature of the bucket substrate was preheated to 300℃. Iron-based alloy powder was fed into the laser action area using a synchronous powder feeding method for laser cladding with the bucket substrate. The laser processing parameters used were as follows: laser power 1400W, spot diameter 5mm, scanning speed 410mm / min, powder feeding gas flow rate 14L / min, protective gas flow rate 0.8L / min, and powder feed rate 4 g / min. A single-pass cladding layer was prepared, with argon as both the carrier and protective gas. The path code for a single-pass cladding layer was: start G01 X0 Y0, end G01 X0 Y30, i.e., traveling 30mm along the Y-axis. For multi-pass cladding, an overlap rate of 50% was used. The path code for 20 overlaps was: G201 Y30 U1.7 D20 F410, resulting in a rectangular cladding layer of 30×340mm.

[0058] Example 9 This embodiment provides a metal-based alloy coating, which is prepared by laser cladding of the metal-based alloy powder in Example 2 onto the surface of the bucket substrate. The specific preparation method is as follows: Pre-treat the bucket base: Use sandpaper to polish the surface of the bucket base, and simultaneously clean it with alcohol and acetone to remove residual oil, oxides, and other impurities. Place the pre-treated bucket base on the laser platform, and adjust the distance between the base and the laser head so that the upper surface of the base is located on the focal plane.

[0059] The laser processing parameters and laser path codes were set on the computer equipped with the laser. The surface temperature of the bucket substrate was preheated to 280℃. Iron-based alloy powder was fed into the laser action area using a synchronous powder feeding method for laser cladding with the bucket substrate. The laser processing parameters used were as follows: laser power 1500W, spot diameter 5mm, scanning speed 420mm / min, powder feeding gas flow rate 15L / min, protective gas flow rate 0.9L / min, and powder feed rate 4 g / min. A single-pass cladding layer was prepared, with argon as both the carrier and protective gas. The path code for a single-pass cladding layer was: start G01 X0 Y0, end G01 X0 Y30, i.e., traveling 30mm along the Y-axis. For multi-pass cladding, an overlap rate of 50% was used. The path code for 20 overlaps was: G201 Y30 U1.7 D20 F420, resulting in a rectangular cladding layer of 30×340mm.

[0060] Example 10 This embodiment provides a metal-based alloy coating, which is prepared by laser cladding of the metal-based alloy powder in Example 3 onto the surface of the bucket substrate. The specific preparation method is as follows: Pre-treat the bucket base: Use sandpaper to polish the surface of the bucket base, and simultaneously clean it with alcohol and acetone to remove residual oil, oxides, and other impurities. Place the pre-treated bucket base on the laser platform, and adjust the distance between the base and the laser head so that the upper surface of the base is located on the focal plane.

[0061] The laser processing parameters and laser path codes were set on the computer equipped with the laser. The surface temperature of the bucket substrate was preheated to 320℃. Iron-based alloy powder was fed into the laser action area using a synchronous powder feeding method for laser cladding with the bucket substrate. The laser processing parameters used were as follows: laser power 1600W, spot diameter 5mm, scanning speed 430mm / min, powder feeding gas flow rate 16L / min, protective gas flow rate 1.0L / min, and powder feed rate 4 g / min. A single-pass cladding layer was prepared, with argon as both the carrier and protective gas. The path code for a single-pass cladding layer was: start G01 X0 Y0, end G01 X0 Y30, i.e., traveling 30mm along the Y-axis. For multi-pass cladding, an overlap rate of 50% was used. The path code for 20 overlaps was: G201 Y30 U1.7 D20 F430, resulting in a rectangular cladding layer of 30×340mm.

[0062] Example 11 This embodiment provides an iron-based alloy coating, which is prepared by laser cladding of the iron-based alloy powder in Example 4 onto the surface of the bucket substrate. The specific preparation method is the same as in Example 10, and will not be repeated here.

[0063] Example 12 This embodiment provides an iron-based alloy coating, which is prepared by laser cladding of the iron-based alloy powder in Example 5 onto the surface of the bucket substrate. The specific preparation method is the same as in Example 10, and will not be repeated here.

[0064] Example 13 This embodiment provides an iron-based alloy coating, which is prepared by laser cladding of the iron-based alloy powder in Example 6 onto the surface of the bucket substrate. The specific preparation method is the same as in Example 10, and will not be repeated here.

[0065] Example 14 This embodiment provides an iron-based alloy coating, which is prepared by laser cladding of the iron-based alloy powder in Example 7 onto the surface of the bucket substrate. The specific preparation method is the same as in Example 10, and will not be repeated here.

[0066] Comparative Example 1 This comparative example provides an iron-based alloy coating, which is obtained by laser cladding of the iron-based alloy powder in Example 2 onto the surface of the bucket substrate. The specific preparation method is similar to that in Example 9, except that the powder feeding rate of the powder feeder is 8g / min, and the other laser process parameters are the same.

[0067] Comparative Example 2 This comparative example provides an iron-based alloy coating, which is obtained by laser cladding of the iron-based alloy powder in Example 2 onto the surface of the bucket substrate. The specific preparation method is similar to that in Example 9, except that the powder feeding rate of the powder feeder is 12g / min, and the other laser process parameters are the same.

[0068] Test Example 1 The performance of the iron-based alloy coatings (i.e., cladding layers) obtained in Examples 8-10 were tested respectively: The cross-section of the cladding layer after laser cladding was obtained along the direction perpendicular to the laser scanning direction. After polishing, aqua regia (HCl:HNO3, volume ratio = 3:1) was used as the etchant for 10 seconds. The macroscopic and microscopic morphology and microstructure of the cladding layer were then observed using an Axiovert-A1 optical metallographic microscope, a VEGA3 scanning electron microscope (SEM), and X-ray diffraction (XRD). The results are as follows: Figure 1 (a) ~ (c) Figure 2 (a)~(c) and Figure 3 As shown.

[0069] Depend on Figure 1 It can be seen that the surface smoothness of the cladding layer obtained in Examples 8-10 is good. Figure 2 It can be seen that, Figure 2 (a) The white block is an inlaid state of chromium carbide, surrounded by fine grains, which are fine chromium carbide particles broken by a high-energy laser beam. Figure 2 (b) and (c) contain a large number of cellular and equiaxed crystals, which are the strengthening phases, and Figure 2 (c) The strengthening effect of breaking chromium carbide particles into equiaxed crystals is better, thus its hardness and wear resistance are superior. Figure 3 It can be seen that γ-(Fe,Ni), Cr7C3, and CFe15.1 diffraction peaks were detected in the cladding layer after laser cladding; at the same time, the compound (Cr,Fe)7C3 of Fe and Cr7C3 was formed. Moreover, with the increase of chromium carbide addition, the contents of (Cr,Fe)7C3 and Cr7C3 in the iron-based chromium carbide wear-resistant coating on the surface of the cladding layer both showed an increasing trend, which also confirmed that the cladding layer obtained in Example 10 had the highest Cr content.

[0070] The surface hardness and cross-sectional hardness distribution of the cladding layer were tested using a TIVS-1 Vickers hardness tester. To minimize measurement error, three points were marked on the same horizontal direction, and the average value was taken. The load was 0.2 kg, and the loading time was 10 s. The test results are as follows: Figure 4 As shown.

[0071] Depend on Figure 4It can be seen that the hardness of the coating gradually increases with the increase of Cr3C2 powder addition. Since the hard phase Cr7C3 is formed in the coating, and the Cr3C7 content in the coating of Example 10 is the highest, its average hardness is the highest, with an average hardness of 1000 HV. 0.2 The maximum surface microhardness of the cladding layer after laser cladding can reach 1103 HV. 0.2 .

[0072] The wear resistance of the cladding layer and bucket substrate in Examples 8-10 was tested using a UMT TriboLab tribo-wear testing machine. The SI3N4 friction pair sample size was 15mm × 20mm × 10mm. During the wear process, the friction pair was fixed, and the sample was embedded in the grinding disc with slight contact with the friction pair. The test parameters were: wear time 120min, load 100N, wear area 5mm. After wear, the worn surface was rinsed with ethanol and dried. The sample was weighed using an electronic balance (accuracy 0.1mg), and the wear morphology of the sample after wear was observed using SEM. The results are as follows: Figure 5 and Figure 6 As shown in (a) to (c).

[0073] Depend on Figure 5 It can be seen that the wear amount of the coatings in Examples 8-10 is significantly lower than that of the bucket substrate, indicating that the cladding coating can significantly improve the wear resistance of the bucket surface. Furthermore, with the increase of Cr3C2 powder addition, the wear amount of the resulting cladding coating shows a decreasing trend. Figure 6 As can be seen from (a) to (c), after the wear test, the surface of the cladding layer showed ploughing grooves and wear debris of varying sizes. The microscopic morphology of the worn surface of the coating was relatively smooth, which is typical of abrasive wear. Moreover, the abrasive wear was significantly reduced compared to the pure Fe-based wear-resistant coating, which further proves that the introduction of the ceramic phase Cr3C2 can effectively improve the abrasive wear resistance of the Fe-based wear-resistant coating. The increased hardness of the cladding layer and the wear-resistant effect of the unmelted Cr3C2 particles are the main reasons for the improved abrasive wear resistance of the obtained cladding layer.

[0074] Test Example 2 The performance of the iron-based alloy coatings (i.e. cladding layers) obtained in Examples 11 to 14 was tested according to the test methods in Example 1.

[0075] The test results of the microstructure and microstructure of the iron-based alloy coatings obtained in Examples 11-14 are as follows: Figure 7 (a) ~ (d) and Figure 8 As shown.

[0076] Depend on Figure 7It can be seen that the cladding layers obtained in Examples 11-14 contain a large number of regularly growing dendrites, growing perpendicularly from the substrate towards the cladding layer. Some parts of the cladding layer appear blackish, indicating pores. This is due to the rapid melting and solidification characteristics during laser cladding, where trace amounts of gas in the coating are not promptly expelled, resulting in pores. It can also be seen that the cladding layer contains a large number of regularly growing columnar and equiaxed crystals, exhibiting elongated polygonal shapes, which significantly improve the mechanical properties of the material. Moreover, as the Y₂O₃ content increases from 0.5 wt% to 1.25 wt%, the number of equiaxed crystals in the cladding layer gradually decreases, and the growth morphology changes from regular to disordered until it almost disappears. The number of columnar crystals continuously increases, gradually becoming dominant from a dispersed distribution, resulting in a more uniform and dense distribution and a more consistent microstructure. Simultaneously, the increase in the number of columnar crystals and the refinement of the grains significantly improve the hardness and wear resistance of the cladding layer.

[0077] Depend on Figure 8 It can be seen that diffraction peaks such as γ-(Fe,Ni), Ni-Cr-Fe, Fe-Cr, Cr7C3, and Ni2Y were detected in the cladding layers obtained in Examples 11-14 with added yttrium oxide. The diffraction peaks of coatings with different Y2O3 contents were similar, and the diffraction peaks of most phases such as γ-(Fe,Ni), Ni-Cr-Fe, Fe-Cr, and Cr7C3 overlapped. The reason for this phenomenon is mainly due to the solid solution formed during the solidification process of the laser cladding molten pool, which disrupts the equilibrium state between atoms, causing lattice distortion. As the Y2O3 content increases, the diffraction peak of Ni2Y gradually strengthens. Yttrium oxide decomposes into active yttrium atoms in the high-temperature environment of laser cladding and diffuses into the cladding layer. Yttrium atoms have a large radius and easily form intermetallic compounds with nickel, especially when the nickel content is high, preferentially forming the Ni2Y phase. Ni2Y can form a solid solution or a diffusely distributed second phase with the hard phase, which can improve hardness and compressive strength by pinning dislocations and hindering crack propagation.

[0078] The average microhardness of the iron-based alloy coatings obtained in Examples 11-14 is as follows: Figure 9 As shown (the cladding layer extends from its surface to 1.0 mm, the heat-affected zone extends from 1.0 mm to 1.1 mm, and the substrate extends beyond 1.1 mm), the hardness distribution of the cladding layer is uniform. Furthermore, the average hardness of the cladding layer surfaces with yttrium oxide contents of 0.5 wt.%, 0.75 wt.%, 1.0 wt.%, and 1.25 wt.% (corresponding to Examples 11-14, respectively) reached 1013 HV. 0.2 1055HV 0.2 1070HV 0.2 and 1112HV 0.2It can be seen that the hardness of the cladding layer gradually increases with the increase of yttrium oxide content. The average hardness of the cladding layer corresponding to 1.25 wt.% Y₂O₃+Cr₃C₂+Fe-based self-fluxing powder reaches 1112 HV. 0.2 It is the matrix hardness (330HV) 0.2 The hardness is 3.6 times that of the coating. This is because the microstructure of the coating is more dense and uniform after the addition of yttrium oxide. Furthermore, the content of the Ni2Y phase increases with the increase of yttrium oxide content. Ni2Y can form a solid solution or a dispersed second phase with the hard phase Cr7C3, which can improve hardness and compressive strength by pinning dislocations and hindering crack propagation. This also confirms that the addition of Y2O3 can significantly improve the hardness of the coating, thereby enhancing its wear resistance.

[0079] The friction coefficient curves and wear diagrams of the iron-based alloy coatings obtained in Examples 11-14 are shown below. Figure 10 and Figure 11 As shown, the wear weight loss of the coating gradually decreases as the Y₂O₃ content increases from 0.5 wt.% to 1.25 wt.%. The coating with 1.25 wt.% Y₂O₃ content exhibits the best wear resistance, with a 30% reduction in wear weight loss and a 0.26 reduction in average friction coefficient compared to the 0.5 wt.% content. During wear tests, the friction coefficient shows a rapid increase followed by a stable state. However, some coatings still exhibit high peak friction coefficients because the inclusion of hard phase particles such as Cr₃C₂ and Cr₇C₃ in the wear process causes unstable changes in the friction coefficient. The addition of yttrium oxide increases the melting tendency of chromium carbide, reduces the content of unmelted chromium carbide, and decreases the number of chromium carbide particles that detach and participate in the wear process, thus reducing both wear weight loss and friction coefficient. Furthermore, the addition of yttrium oxide can promote the flow of molten metal in the molten pool during cladding, helping to remove gases and inclusions, reducing defects in the cladding layer, and improving the smoothness of the cladding layer surface.

[0080] The microstructure images of the iron-based alloy coatings obtained in Examples 11-14 after wear are shown below. Figure 12 As shown in (a) to (d), it can be seen that furrows appear on the surface of the cladding layer, and wear debris of varying sizes is detected. The microstructure of the wear surface of the coating is relatively smooth, which is typical of abrasive wear. Moreover, the abrasive wear is significantly reduced compared to the wear-resistant coating without yttrium oxide. This further proves that the introduction of yttrium oxide can effectively improve the abrasive wear resistance of Fe-based wear-resistant coatings.

[0081] Test Example 3 The surface morphology of the iron-based alloy coatings obtained in Example 9 and Comparative Examples 1-2 were observed, and the results are as follows: Figure 13As shown, the iron-based alloy coating obtained in Example 9 has a dense surface without cracks, while the iron-based alloy coatings obtained in Comparative Examples 1 and 2, which have higher powder feeding rates, both show obvious cracks on their surfaces. This indicates that the powder feeding rate selected in this invention can be synergistically matched with the composition of the iron-based alloy powder to obtain a high-quality iron-based alloy coating.

[0082] In summary, this invention improves the composition of iron-based alloy powder and employs specific laser cladding process parameters. Under the action of a laser, the iron-based alloy powder and a thin layer on the surface of the metal substrate are simultaneously melted to obtain a uniform and dense cladding layer. This significantly improves the toughness, hardness, and wear resistance of the cladding layer, ensures that the cladding layer is crack-free, and ultimately obtains an iron-based alloy coating that is well bonded to the metal substrate, crack-free, and has superior performance.

[0083] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A type of iron-based alloy powder, characterized in that, The composition, by weight percentage, comprises: 40wt%~60wt% Fe-based self-fluxing alloy powder and 40wt%~60wt% Cr3C2 powder; wherein the Fe-based self-fluxing alloy powder comprises the following elements by weight percentage: C 0.4wt%~1.2wt%, Si 1wt%~3wt%, Cr 5wt%~10wt%, Ni 25wt%~40wt%, B 2wt%~6wt%, with the balance being Fe.

2. A type of iron-based alloy powder, characterized in that, The composition, by weight percentage, comprises: 38wt%~60wt% Fe-based self-fluxing alloy powder, 39wt%~61wt% Cr3C2 powder, and 0.5wt%~1.25wt% Y2O3 powder; wherein the Fe-based self-fluxing alloy powder comprises the following elements by weight percentage: C 0.4wt%~1.2wt%, Si 1wt%~3wt%, Cr 5wt%~10wt%, Ni 25wt%~40wt%, B 2wt%~6wt%, with the balance being Fe.

3. The iron-based alloy powder as described in claim 2, characterized in that, The particle size of the Y2O3 powder is 100~150μm.

4. The iron-based alloy powder as described in claim 1 or 2, characterized in that, The Fe-based self-fluxing alloy powder has a particle size of 80~150μm, and the Cr3C2 powder has a particle size of 130~220μm.

5. A method for preparing iron-based alloy powder, characterized in that, According to the iron-based alloy powder formula of claim 1 or 2, each raw material is weighed, the raw materials are mixed, and then ball-milled and dried to obtain the iron-based alloy powder.

6. The method for preparing iron-based alloy powder as described in claim 5, characterized in that, The ball milling speed is 150~180 r / min, and the ball milling time is 2~3 h; the drying temperature is 150~155℃, and the drying time is 2~3 h.

7. A type of iron-based alloy coating, characterized in that, The coating is obtained by laser cladding of the iron-based alloy powder described in claim 1 or 2 onto the surface of a metal substrate.

8. A method for preparing the iron-based alloy coating according to claim 7, characterized in that, The steps include: The surface of the metal substrate to be clad is cleaned, polished and dried, and then placed on the laser action platform. The distance between the metal substrate and the laser head is adjusted so that the upper surface of the substrate is located on the focal plane. The laser processing parameters and the laser path code are set, and the iron-based alloy powder is fed into the laser action area by synchronous powder feeding method, and laser cladding is performed with the metal substrate to obtain the iron-based alloy coating. The laser processing parameters include: laser power of 1400~1600W, spot diameter of 4.5~5mm, scanning speed of 410~430mm / min, and powder feeding rate of 4~6g / min.

9. The method for preparing the iron-based alloy coating as described in claim 8, characterized in that, The laser cladding includes single-pass cladding and multi-pass cladding, and the overlap rate of the multi-pass cladding is 45%~55%.

10. The application of the iron-based alloy coating of claim 7 or the iron-based alloy coating prepared by the preparation method of any one of claims 8 to 9 in the surface repair of worn metal parts or the surface protection of easily worn metal parts.

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