A device and method for modifying laser cladding coating under ultra-high pressure environment with magnetic field assisted plasma

Abstract

This invention provides a device and method for magnetic field-assisted plasma modification of laser cladding coatings under ultra-high pressure. A nickel-based alloy substrate is placed in a sealed working chamber. Inert gas is continuously injected into the sealed working chamber to maintain an ultra-high pressure environment. A molten pool is formed by laser irradiation of nickel-based alloy powder deposited on the surface of the substrate. Simultaneously, metal plasma is used as an element dopant in the nickel-based alloy coating. The metal plasma is sprayed onto the surface of the nickel-based alloy substrate, and the plasma-state active element dopant accumulates on the surface of the molten pool under the control of a magnetic field. Under the synergistic effect of the ultra-high pressure environment and the alternating magnetic field, the metal plasma penetrates into the molten pool and reacts with the molten material, resulting in a nickel-based alloy cladding coating with uniform active element doping. This invention achieves effective doping of the active element Hf into the nickel-based alloy coating, improving the coating's high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of laser cladding technology, specifically to a device and method for magnetic field-assisted plasma modification of laser cladding coatings under ultra-high pressure conditions. Background Technology

[0002] Nickel-based alloys are widely used in nuclear power, petrochemicals, shipbuilding, ground-based gas turbines, and aerospace due to their high-temperature resistance, oxidation resistance, and excellent high-temperature mechanical properties. Representative applications include the manufacture of high-temperature components such as turbine disks, combustion chambers, and blades for aero engines. In recent years, with the continuous development of national technology and defense, and the increasing demands for energy conservation and emission reduction, the intake air temperature inside aero engines has been rising. Key components such as turbopumps and turbine blades are beginning to experience oxidation, corrosion, and fatigue fracture under high-temperature loads.

[0003] Nickel-based superalloy parts are expensive to manufacture, making periodic inspection and repair essential for extending their service life. Applying a modified coating with high-temperature oxidation resistance to the alloy substrate surface has become an effective repair method to improve engine operating temperatures. In high-temperature operating environments, the dense oxide film formed on the modified coating surface effectively isolates the alloy substrate material from the environment, enhancing the alloy's oxidation resistance and extending the service life of high-temperature components. Current methods for preparing surface modified layers include electroplating, plasma spraying, casting alloying, and vapor deposition. However, coatings prepared by these methods typically have drawbacks such as thinness (<100μm), poor microstructure density, and low bonding strength with the substrate. Laser cladding technology effectively overcomes these shortcomings, allowing for coating thickness adjustment within the micrometer to millimeter range to obtain a dense cladding structure and achieve a good metallurgical bond between the coating and the substrate. Furthermore, due to its versatility and heating (cooling) rate of up to 106 K / s, laser cladding technology can achieve precise control of surface properties while preserving the overall mechanical properties of the material, thus producing a surface-modified layer with excellent performance.

[0004] Considering that the coating composition plays a decisive role in the growth rate, composition, and interfacial bonding strength of the oxide film on the coating surface under high-temperature conditions, selecting a suitable coating material is also an important factor in improving the service life of the coating. Studies have found that adding trace amounts of active elements (0.05–0.5 at.%) to nickel-based alloy coatings can effectively promote the formation of a dense oxide film and the precipitation of beneficial phases on the coating surface, reduce the coating oxidation rate, and significantly improve the high-temperature oxidation performance of the coating. However, in the traditional laser cladding composite coating preparation process, the composite powder is usually obtained by mechanical mixing. During the mixing process, the active elements doped are prone to agglomeration due to their small particle size and strong adhesion. The prepared composite powder also adheres to the conveying tube wall during coaxial powder feeding, making it difficult to control the distribution and solubility of the added trace elements in the coating, thus affecting the coating's forming quality and high-temperature oxidation resistance. Current laser cladding processes struggle to achieve effective and uniform doping of trace active elements in nickel-based alloy coatings, thus hindering the preparation of active element-modified coatings with excellent forming quality and high-temperature performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a magnetic field-assisted plasma modification device and method for laser cladding coating under ultra-high pressure. Based on existing laser cladding nickel-based alloy coating processes, a microwave plasma source system ionizes the active element Hf into low-temperature plasma. The low-temperature plasma is confined by a magnetic field and transported above the molten pool. Under continuous laser irradiation, active Hf atoms are dissociated. Influenced by the energy clusters inside the plasma, the high-kinetic-energy active Hf atoms penetrate into the molten pool under the assistance of the magnetic field and ultra-high pressure, and violently stir with the molten material. The active element Hf is dispersed and uniformly distributed in the nickel-based alloy coating, significantly improving the coating's resistance to high-temperature oxidation. The application of a homing magnetic field increases the energy fluctuations of the melt in the molten pool, providing additional energy for crystal nucleation and thus improving the nucleation rate. Furthermore, the magnetic field generates periodically varying magnetic forces in the molten pool, causing internal vibrations and forced convection, promoting the redistribution of the solute, refining the grain structure, and reducing segregation in the solidification structure. On the other hand, the plasma, constrained by the homing magnetic field, condenses into energy clusters and consistently acts above the molten pool, achieving effective doping of the active element Hf into the nickel-based alloy coating, further enhancing its high-temperature resistance. Using ultra-high pressure technology with magnetic field assistance reduces the free energy at the crystal-melt interface, increases the number of nucleation sites, further refines the coating's grain structure, and suppresses cracking. Compared to conventional high-pressure environments, ultra-high pressure technology not only improves the surface smoothness of the formed sample but also increases the wetting ability between phases in the melt, enhances the solid solubility of the active element in the coating, and strengthens the interfacial bonding strength, enabling the nickel-based alloy coating to achieve both grain refinement and solid solution strengthening effects. This effectively improves the coating's high-temperature performance and mechanical stability.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment includes the following steps:

[0008] The nickel-based alloy substrate is placed in a sealed working chamber; inert gas is continuously injected into the sealed working chamber to maintain an ultra-high pressure environment.

[0009] A molten pool is formed by laser irradiation of nickel-based alloy powder deposited on the surface of a nickel-based alloy substrate. At the same time, metal plasma is used as an element dopant in the nickel-based alloy coating. The metal plasma is sprayed onto the surface of the nickel-based alloy substrate, and the plasma-state active element dopant accumulates on the surface of the molten pool under the control of a magnetic field. Under the synergistic effect of ultra-high pressure environment and alternating magnetic field, metal plasma penetrates into the molten pool and reacts with the molten material to obtain a nickel-based alloy cladding coating with uniform active element doping.

[0010] Furthermore, by controlling the magnetic field strength applied during the cladding process, the magnetic field strength during the cladding process is maintained at 20–40 mT.

[0011] Furthermore, a pressure pump is used to maintain an ultra-high pressure of 100-120 MPa inside the working chamber.

[0012] Furthermore, the metal plasma is hafnium plasma, which is generated by a microwave plasma source system and emitted coaxially with the laser beam through a laser cladding head.

[0013] Furthermore, the flow rate of the metal plasma jet was adjusted to 1.5 L / min to 2.5 L / min using a microwave plasma source system.

[0014] Furthermore, the diameter of the nickel-based alloy powder ranges from 53 to 150 μm, and the thickness of the powder layer ranges from 0.8 to 1.2 mm.

[0015] Furthermore, the parameters of the continuous laser used in the laser irradiation process are as follows: wavelength 1070nm, laser power ≤2000W, spot diameter ≥0.4mm; laser power 800~1000W, scanning speed 500mm / s, scanning spacing 100~150μm, and cladding scanning path is bow-shaped.

[0016] An apparatus for a magnetic field-assisted plasma modification laser cladding coating method under ultra-high pressure environment includes a working chamber, a microwave plasma source system, a laser cladding head, an AC magnetic field device, and a pressure holding system. A nickel-based alloy substrate is placed inside the working chamber. The microwave plasma source system is used to generate metallic plasma. The microwave plasma source system is connected to the laser cladding head to ensure that the metallic plasma is emitted coaxially with the laser beam. An AC magnetic field device is provided at the bottom of the nickel-based alloy substrate to generate an alternating magnetic field. The pressure holding system is connected to the working chamber to create an ultra-high pressure environment within the working chamber.

[0017] Furthermore, the AC magnetic field device includes an excitation coil, a silicon steel core, an isolation voltage regulator, and a worktable; the excitation coil is fitted over the silicon steel core, and the excitation coil is connected to the isolation voltage regulator for adjusting the magnetic field strength; the silicon steel core is mounted on a movable worktable, and the worktable is used to move the silicon steel core synchronously with the laser beam.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. The magnetic field-assisted plasma modification laser cladding coating method under ultra-high pressure environment described in this invention uses Hf plasma as an element dopant in nickel-based alloy coatings. The Hf plasma is stably excited by a microwave plasma source system and discharged coaxially with the laser beam through the cladding head. Under the constraint of a follow-up magnetic field, it is always kept above the high-temperature molten pool. Compared with traditional metal powder doping, plasma-state Hf element is a laser-state material containing abundant energy and contains a large number of uniform Hf atomic clusters at the nanoscale. These high-kinetic-energy particles are violently stirred with the molten material inside the molten pool under the synergistic effect of magnetic field assistance and ultra-high pressure. The distribution of active element Hf in the nickel-based coating becomes diffuse and uniform, and the high-temperature oxidation resistance of the coating is significantly improved.

[0020] 2. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment described in this invention uses a follow-up alternating magnetic field to assist in the preparation of laser cladding coating. On the one hand, under the action of induced current induced by electromagnetic field, the number of relatively stable atomic clusters in the melt increases. During solidification, these atomic clusters form a large number of stable preforms, and the number of nuclei in the molten pool increases significantly, thereby achieving the effect of grain refinement. In addition, the periodically changing magnetic field force accelerates the vibration and convection inside the molten pool, promotes the uniform dispersion of new nuclei in the molten pool, and effectively reduces elemental segregation inside the coating. On the other hand, under the control of the servo magnetic field, the plasma jet angle distribution is improved. Guided by magnetic field lines, the plasma is transported above the molten pool and rapidly condenses into an energy cluster within the magnetic field's influence area. Subsequently, under the further confinement of the servo magnetic field, it consistently acts on the high-temperature molten pool, stabilizing the effective contact area between the plasma and the molten pool and ensuring the effectiveness of active element doping within the coating. Furthermore, under the influence of the induced electric field generated by the alternating magnetic field, the energy distribution within the plasma cluster changes. After further absorbing laser irradiation energy, more active Hf atoms are ionized and participate in the molten pool modulation process, increasing the solubility of active elements in the coating and further reducing the oxidation rate of the coating at high temperatures. The alternating magnetic field-assisted microstructure of the coating is refined and homogenized, while simultaneously promoting the effective and uniform doping of active elements within the coating, significantly improving both the mechanical and high-temperature properties of the nickel-based alloy coating.

[0021] 3. The magnetic field-assisted plasma modification laser cladding coating method under ultra-high pressure environment described in this invention, through ultra-high pressure environment-assisted laser cladding coating formation, significantly reduces the free energy of the crystal-melt interface, decreases the critical nucleation radius, and increases the number of nucleation sites, thereby further refining the coating solidification structure based on the magnetic field-assisted process. Although melt flow is suppressed to some extent under ultra-high pressure conditions, under the real-time stirring induced by the alternating magnetic field and the coupling effect of high-kinetic-energy metal plasma dopants, significant convection is still maintained inside the molten pool, the solute is uniformly dispersed, and the coating microstructure maintains a uniform and refined effect. Compared with conventional high-pressure environment, ultra-high pressure technology not only reduces the degree of molecular force asymmetry on the surface of high-temperature melt and significantly improves the surface smoothness of the coating, but also allows phases that are not mutually wettable under normal pressure to begin to diffuse into each other through solid solution, increasing the solid solubility of active elements in the nickel-based alloy coating, and intensifying element diffusion between the cladding layer and the substrate. This allows the nickel-based alloy coating to achieve solid solution strengthening gain while also significantly enhancing the interfacial bonding strength between the coating and the substrate, further strengthening the mechanical stability and high-temperature performance of the coating.

[0022] 4. The magnetic field-assisted plasma modification laser cladding coating method under ultra-high pressure environment described in this invention allows all process parameters, including laser parameters, servo-alternating magnetic field parameters, ultra-high pressure and microwave plasma parameters, to be controlled by algorithms. It has the advantages of simple operation, low cost, and high efficiency, and is easy to implement in industrial applications. It is geared towards the service environment of nickel-based alloys for key aerospace components and has broad application prospects. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the magnetic field-assisted plasma modification laser cladding coating device under ultra-high pressure environment described in this invention.

[0025] Figure 2 The image shows a comparison of the macroscopic morphology of the untreated coating and the nickel-based alloy coating prepared in Example 1 of this invention.

[0026] Figure 3 The image shows a comparison of the cross-sectional microstructure of the untreated coating and the coating prepared in Example 1 of this invention.

[0027] Figure 4 The image shows a comparison of the XRD patterns of the untreated coating and the coating prepared in Example 1 of this invention.

[0028] Figure 5 This is a comparison of the oxidation kinetics curves of the untreated coating and the coating prepared in Example 1 of this invention.

[0029] Figure 6 This is a comparison diagram of the microhardness of the coating surfaces prepared in various embodiments of the present invention.

[0030] In the picture:

[0031] 1-Nickel-based alloy substrate; 2-Working box; 3-Microwave plasma source system; 4-Laser cladding head; 5-Excitation coil; 6-Silicon steel core; 7-Isolation voltage regulator; 8-Worktable; 9-Clamp; 10-Pressure pump; 11-Pressure gauge; 12-Gas flow meter. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not 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 the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] like Figure 1 As shown, the magnetic field-assisted plasma modification laser cladding coating device under ultra-high pressure environment of the present invention includes a working box 2, a microwave plasma source system 3, a laser cladding head 4, an AC magnetic field device, and a pressure holding system. A nickel-based alloy substrate 1 is fixed in the working box 2 by a clamp 9, and nickel-based alloy powder can be deposited on the nickel-based alloy substrate 1. The microwave plasma source system 3 is used to generate metallic plasma; the laser emitter is used to generate a laser beam, which is emitted from the center of the laser cladding head 4. The microwave plasma source system 3 is connected to the laser cladding head 4 to ensure that the metallic plasma and the laser beam are emitted coaxially, with the metallic plasma located outside the laser beam. This can be understood as the laser beam being emitted from the center of the laser cladding head 4, with the metallic plasma surrounding the laser beam.

[0036] The nickel-based alloy substrate 1 has an alternating magnetic field device at its bottom for generating an alternating magnetic field. This device includes an excitation coil 5, a silicon steel core 6, an isolation voltage regulator 7, and a worktable 8. The excitation coil 5 is fitted over the silicon steel core 6 and connected to the isolation voltage regulator 7 to adjust the magnetic field strength. The silicon steel core 6 is mounted on a movable worktable 8, which allows the silicon steel core 6 to move synchronously with the laser beam, ensuring that the direction of the alternating magnetic field movement remains consistent with the cladding trajectory during the forming process. A silicon steel core with high permeability can enhance the magnetic field strength at the center of the coil and reduce magnetic losses.

[0037] The pressure-holding system is connected to the working chamber 2 and is used to generate an ultra-high pressure environment in the working chamber 2. The pressure-holding system includes a pressurizing pump 10 and a pressure gauge 11. The pressurizing pump 10 is connected to the working chamber 2, and the pressure gauge 11 is installed on the working chamber 2 to measure the pressure inside the working chamber 2. A gas flow meter 12 is installed between the microwave plasma source system 3 and the laser cladding head 4 to detect the metal plasma flow rate.

[0038] The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment described in this invention includes the following steps:

[0039] The surface of the nickel-based alloy substrate 1 was rough ground, and the treated surface was ultrasonically cleaned and dried with anhydrous ethanol.

[0040] Mix 2-3 ml of 3 wt.% polyvinyl alcohol aqueous solution with 5-8 g of nickel-based alloy powder evenly, then spread the mixture evenly on the pretreated surface of the substrate and let it stand until it dries and solidifies. The nickel-based alloy powder with a diameter range of 53-150 μm has a pre-placed thickness of 0.8-1.2 mm.

[0041] The nickel-based alloy substrate 1 is placed in a sealed working chamber 2; argon gas is continuously injected into the sealed working chamber 2 to maintain an ultra-high pressure environment in the working chamber 1, and a pressure pump is used to maintain the ultra-high pressure environment in the working chamber, with an ultra-high pressure of 100-120 MPa.

[0042] A molten pool is formed by laser irradiation of nickel-based alloy powder deposited on the surface of a nickel-based alloy substrate 1. Simultaneously, metal plasma is used as an element dopant in the nickel-based alloy coating. The metal plasma is sprayed onto the surface of the nickel-based alloy substrate 1, and the plasma-state active element dopant accumulates on the surface of the molten pool under the control of a magnetic field. Under the synergistic effect of an ultra-high pressure environment and an alternating magnetic field, the metal plasma penetrates into the molten pool and reacts with the molten material, resulting in a nickel-based alloy cladding coating with uniform active element doping. The magnetic field strength applied during the cladding process is controlled to maintain a value between 20 and 40 mT. The metal plasma used in this invention is hafnium (Hf) plasma.

[0043] The experiment revealed a linear relationship between the voltage (x / V) and magnetic induction intensity (y / mT) of the isolation voltage regulator 7: y = 0.85x + c, where c is a correction coefficient and its value is 5 to 6. Generally, the applied voltage is adjusted to be in the range of 17 to 41V so that the magnetic field intensity during the cladding process is maintained at 20 to 40mT.

[0044] The present invention describes a magnetic field-assisted plasma-modified laser cladding coating method under ultra-high pressure environment. In this method, metal plasma is used as an active element dopant to prepare a nickel-based alloy Hf-doped coating under ultra-high pressure environment. During the forming process, the plasma is constrained by a follow-up magnetic field and transmitted to the top of the molten pool. Under the influence of working pressure and magnetic field, the plasma penetrates into the molten pool and is uniformly distributed in the molten pool, thereby achieving effective and uniform doping of trace active elements in the nickel-based alloy coating. Hf plasma was used as an element dopant in laser cladding. Under the influence of laser irradiation energy, a large number of high-energy nanoscale Hf atom clusters dissociated within the plasma. These high-energy particles, under the synergistic effect of ultra-high pressure and electromagnetic stirring, stirred and modulated the molten material in the molten pool, achieving a uniform and dispersed distribution of active elements in the coating, effectively improving the high-temperature oxidation resistance of the nickel-based alloy coating. Using a servo-driven alternating magnetic field to assist in the forming of the cladding sample not only increased the number of nuclei in the molten pool and intensified internal vibration and convection, resulting in a refined and homogenized coating solidification structure, but also improved the plasma jet angle, ensuring effective contact between the plasma and the laser molten pool during the forming process. Furthermore, the internal energy of the plasma increased under the influence of the induced electric field excited by the magnetic field, leading to the formation of more active Hf atoms. Ionization participates in the molten pool stirring reaction, increasing the solubility of active elements in the coating and effectively enhancing its high-temperature performance. Laser cladding under extremely high pressure promotes increased nucleation rate in the molten pool, further refines the grain structure with magnetic field assistance, and improves the surface forming quality of the coating. Ultra-high pressure technology also promotes solid solution diffusion between phases, increasing the solid solubility of active elements in the coating and strengthening the bond between the coating and the substrate. This significantly improves the high-temperature oxidation resistance and mechanical properties of the nickel-based alloy coating. By optimizing parameters such as ultra-high pressure, plasma jet flow rate, and magnetic field strength, this invention allows for the control of the macroscopic morphology of the Hf-doped nickel-based alloy coating prepared by laser cladding. This effectively reduces macroscopic cracks, pores, and other defects, improving the overall forming quality of the coating.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, IN718 nickel-based alloy is selected as the research object below, and the invention will be described in detail with reference to specific embodiments.

[0046] Example 1:

[0047] The method for modifying laser cladding coatings with magnetic field-assisted plasma under ultra-high pressure environment as described in Example 1 includes the following steps:

[0048] Before the cladding operation, the IN718 substrate was sanded with sandpaper of 800# and 1000# grit. Then, the treated surface was ultrasonically cleaned with anhydrous ethanol and dried.

[0049] 3 ml of 3 wt.% polyvinyl alcohol aqueous solution was uniformly mixed with 8 g of IN718 powder. The mixture was then spread evenly on the pretreated surface of the substrate and left to stand for 30 minutes. The IN718 powder with a diameter range of 95 μm was pre-placed to a thickness of 1.0 mm.

[0050] An alternating magnetic field device that can move with the cladding direction is installed under the IN718 substrate. The two-axis linkage stage control system in the device is connected to the laser cladding system to ensure that the direction of movement of the alternating magnetic field during the sample forming process is consistent with the cladding trajectory.

[0051] Adjust the voltage of the isolation voltage regulator to 17.5V to keep the magnetic field strength at 20mT during the cladding process;

[0052] Argon gas was injected into the working chamber, and a pressure pump was used to maintain the ultra-high pressure environment inside the working chamber. A pressure gauge was installed inside the working chamber to monitor and ensure that the pressure during the cladding process was within the range of 100 MPa.

[0053] The microwave plasma source system was connected to the laser cladding head. Metal dopant Hf was placed in the plasma generator to prepare Hf plasma. The plasma jet flow rate was monitored by a gas flow meter at the outlet of the microwave plasma generator, which was 1.5 L / min.

[0054] An IPG-YLS-2000-TR fiber laser was selected, with continuous mode modulation. The specific processing parameters were: wavelength 1070 nm, spot diameter 3 mm. The specific process parameters for laser cladding were: laser power 800 W, scanning speed 500 mm / s, scanning spacing 150 μm, and a bow-shaped scanning path for single-layer cladding. Based on these processing parameters, plasma-doped laser cladding with a servo magnetic field-assisted process was performed in an ultra-high pressure environment to prepare a nickel-based alloy Hf-doped coating exhibiting excellent high-temperature performance and mechanical properties.

[0055] A molten pool is formed by laser irradiation of nickel-based alloy powder deposited on the surface of nickel-based alloy substrate 1. At the same time, Hf plasma is used as an element dopant in the nickel-based alloy coating. Hf plasma is sprayed onto the surface of nickel-based alloy substrate 1. Under the control of a magnetic field, the Hf plasma-state active element dopant accumulates on the surface of the molten pool. Under the synergistic effect of ultra-high pressure environment and alternating magnetic field, metal plasma penetrates into the molten pool and reacts with the molten material to obtain a nickel-based alloy cladding coating with uniform active element doping.

[0056] The macroscopic morphology of the nickel-based alloy coating prepared in Example 1 is as follows: Figure 2 As shown, compared to coatings prepared by traditional laser cladding processes, the sample surface exhibits lower waviness and no obvious defects such as cracks, demonstrating excellent surface forming quality; Figure 3 As shown, in the cross-sectional morphology of the coating prepared in Example 1, the proportion of equiaxed crystals and fine dendrites is relatively large. The grain structure of the nickel-based alloy cladding layer prepared under ultra-high pressure environment and alternating magnetic field is further refined. In addition, from Figure 4 The XRD results show that a new HfC phase appeared in the IN718 Hf-doped coating, proving the effective doping of the IN718 cladding layer by Hf plasma. High-temperature oxidation experiments at 850℃ / 100h were conducted on the conventional cladding layer and the coating prepared in Example 1, and the oxidation results are as follows: Figure 5 As shown, the oxidation weight gain of the traditional cladding layer is 2.598 mg / cm³. 2 The oxidative weight gain of the coating prepared in Example 1 was 1.443 mg / cm³. 2 Compared to traditional cladding layers, the oxidation rate was reduced by 44.5%, indicating that under the synergistic mechanism of extremely high pressure, magnetic field stirring, and plasma element doping, the Hf element inside the nickel-based alloy coating is uniformly distributed, and the oxidation rate of the coating is significantly reduced. Furthermore, as... Figure 6 As shown, ultra-high pressure conditions promote the mutual solid solution diffusion between phases in the melt. Some Hf reacts with the molten material in the molten pool to form a beneficial phase with high hardness and high melting point, which improves the surface hardness of the coating. The microhardness value of the coating in Example 1 reached 269.8 HV, which is 3.2% higher than the average hardness value of 261.5 HV of the traditional cladding layer surface. This is of great significance for improving the high temperature oxidation resistance and wear resistance of laser cladding nickel-based alloy coatings in a low-cost and efficient manner.

[0057] Example 2

[0058] Based on Example 1, in Example 2 the plasma flow rate is 2.0 L / min, the magnetic field strength is maintained at 40 mT, and the ultra-high pressure environment in the working chamber is maintained at 110 MPa.

[0059] The coating obtained in Example 2 exhibits lower macroscopic surface waviness and a smoother surface, demonstrating excellent surface forming quality. Compared to the coating prepared in Example 1, Example 2 utilizes a higher pressure environment, a higher magnetic field strength, and plasma flow rate-assisted laser cladding to form the sample. This results in a finer grain structure in the coating, leading to a more uniform distribution of Hf atoms within the coating. The reaction efficiency between the molten material and the active element is improved, enhancing the stirring effect within the molten pool. The size of the Hf atom clusters segregated at the grain boundaries and their solid solubility in the coating increase, effectively improving the strengthening effect. Under a high-temperature oxidation environment of 850℃ / 100h, the oxidation weight gain of the coating prepared in this example is 0.96 mg / cm³. 2 Compared to traditional cladding layers, the oxidation weight gain is 2.598 mg / cm³. 2 The oxidation weight gain was reduced by 63%, compared to 1.443 mg / cm³ after treatment in Example 1. 2 It decreased by 33.5%, and in addition, Figure 6 As shown, the microhardness value of the nickel-based alloy coating prepared in this embodiment is 282 HV, which is 7.8% higher than the average hardness value of 261.5 HV of the sample surface prepared by traditional laser cladding, and 4.5% higher than the average hardness value of 269.8 HV of the sample surface after treatment in Example 1. Appropriately increasing the pressure and magnetic field strength and increasing the plasma jet flow rate increases the content of active Hf atoms in the doping, and the stirring reaction with the molten material in the molten pool is more complete, further improving the high-temperature performance and mechanical properties of the nickel-based alloy coating.

[0060] Example 3

[0061] Based on Example 1, in Example 3 the plasma flow rate is 2.5 L / min, the magnetic field strength is maintained at 30 mT, and the ultra-high pressure environment in the working chamber is maintained at 120 MPa.

[0062] The sample treated in Example 3 had a relatively smooth macroscopic surface, and the coating cross-sectional morphology showed a large proportion of fine dendrites. The prepared nickel-based alloy coating also exhibited excellent forming quality and a uniform, fine grain structure. The oxidation weight gain of the coating prepared in this example at 850℃ / 100h was 1.02 mg / cm³. 2 Compared to traditional cladding layers, the oxidation weight gain is 2.598 mg / cm³. 2 The hardness was reduced by 60.7%. In addition, the microhardness value of the coating surface in this embodiment was 275.1 HV, which is 5.2% higher than the average hardness of 261.5 HV of the traditional cladding layer surface. It achieves the simultaneous preparation of laser cladding nickel-based alloy coatings with optimized macroscopic forming, refined microstructure, and improved high-temperature and mechanical properties.

[0063] Table 1 shows the characterization results of samples processed by different methods according to the present invention.

[0064]

[0065]

[0066] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0067] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modifying laser cladding coatings using magnetic field-assisted plasma under ultra-high pressure conditions, characterized in that, Includes the following steps: The nickel-based alloy substrate (1) is placed in a sealed working chamber (2); inert gas is continuously injected into the sealed working chamber (2) to maintain an ultra-high pressure environment in the working chamber (2), with the pressure of the ultra-high pressure environment being 100~120MPa; A molten pool is formed by laser irradiation of nickel-based alloy powder deposited on the surface of a nickel-based alloy substrate (1). At the same time, metal plasma is used as an element dopant in the nickel-based alloy coating. The metal plasma is sprayed onto the surface of the nickel-based alloy substrate (1). The plasma-state active element dopant accumulates on the surface of the molten pool under the control of a magnetic field. Under the synergistic effect of ultra-high pressure environment and alternating magnetic field, metal plasma penetrates into the molten pool and reacts with the molten material to obtain a nickel-based alloy cladding coating with uniform active element dopant.

2. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, By controlling the magnetic field strength applied during the cladding process, the magnetic field strength during the cladding process is maintained at 20~40mT.

3. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, The pressure is maintained at ultra-high pressure inside the working box (2) by a pressure pump (10).

4. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, The metal plasma is hafnium plasma, which is generated by a microwave plasma source system (3) and emitted coaxially with the laser beam through a laser cladding head (4).

5. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, The flow rate of the metal plasma jet is adjusted to 1.5 L / min to 2.5 L / min by the microwave plasma source system (3).

6. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, The diameter of the nickel-based alloy powder ranges from 53 to 150 μm, and the thickness of a single layer of powder ranges from 0.8 to 1.2 mm.

7. The method for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 1, characterized in that, The parameters of the continuous laser used in the laser irradiation process are as follows: wavelength 1070nm, laser power ≤2000W, spot diameter ≥0.4mm; laser power 800~1000W, scanning speed 500mm / s, scanning spacing 100~150μm, and cladding scanning path is bow-shaped.

8. An apparatus for a method of magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to any one of claims 1-7, characterized in that, The system includes a working chamber (2), a microwave plasma source system (3), a laser cladding head (4), an AC magnetic field device, and a pressure holding system. A nickel-based alloy substrate (1) is placed inside the working chamber (2). The microwave plasma source system (3) is used to generate metal plasma. The microwave plasma source system (3) is connected to the laser cladding head (4) to make the metal plasma and the laser beam coaxially emitted. An AC magnetic field device is provided at the bottom of the nickel-based alloy substrate (1) to generate an alternating magnetic field. The pressure holding system is connected to the working chamber (2) to generate an ultra-high pressure environment in the working chamber (2).

9. The apparatus for magnetic field-assisted plasma modification of laser cladding coating under ultra-high pressure environment according to claim 8, characterized in that, The AC magnetic field device includes an excitation coil (5), a silicon steel core (6), an isolation voltage regulator (7), and a worktable (8); the excitation coil (5) is fitted over the silicon steel core (6), and the excitation coil (5) is connected to the isolation voltage regulator (7) to adjust the magnetic field strength; the silicon steel core (6) is mounted on a movable worktable (8), and the worktable (8) is used to make the silicon steel core (6) move synchronously with the laser beam.

Images