Multi-field coupling laser cladding FeCoCrNiCu high-entropy alloy coating as well as preparation method and application thereof

Abstract

According to the method for preparing the FeCoCrNiCu high-entropy alloy coating through multi-field coupling laser cladding, dynamic desulfurization is conducted through a Na2CO3 pre-laying layer, slag formers (CaO, CaF2, B2O3 and CeO2) are added into composite powder, and ultrasonic-magnetic field cooperative regulation and control are conducted, so that the problems of Cu segregation, impurity residues, molten pool defects and the like are solved. In the laser cladding process, Na2CO3 is decomposed to achieve in-situ desulfurization, slag former combination synergistic deoxidation and molten pool liquidity improvement, grains are refined through an ultrasonic field to promote floating of impurities, Cu segregation is inhibited through a magnetic field, and finally the coating high in density and uniform in component is obtained. Through the multi-mechanism synergistic effect, effective control over the quality of the high-entropy alloy coating is achieved, the prepared FeCoCrNiCu high-entropy alloy coating has excellent electrical conductivity, corrosion resistance and mechanical performance and is suitable for surface protection of inert anodes and other extreme working conditions, and the service life of the FeCoCrNiCu high-entropy alloy coating is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology of metallic materials, specifically relating to a multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating and its preparation method, and also relating to the application of the above-mentioned high-entropy alloy coating in the surface protection of inert anode materials. Background Technology

[0002] Inert anodes, as key components in electrolytic metallurgy and the chlor-alkali industry, are subjected to high-temperature, highly corrosive, and highly oxidizing environments for extended periods, facing severe material challenges. Traditionally used nickel / copper-based alloys and metal oxide coatings suffer from conductivity degradation, surface corrosion, and structural failure under extreme conditions, severely limiting the efficiency of electrolytic processes and equipment lifespan. For example, while metal oxide ceramics (such as NiFe2O4 and SnO2) exhibit good corrosion resistance, they suffer from poor conductivity, high brittleness, and poor thermal shock resistance, making them prone to cracking and spalling at high temperatures. Furthermore, the high-temperature sintering required and the difficulty in processing complex shapes result in high manufacturing costs and a service life typically less than two years.

[0003] Laser cladding technology, as an advanced surface modification method, rapidly melts and solidifies alloy powder and substrate surfaces using a high-energy laser beam to form a coating with excellent properties, providing a new technical approach for surface strengthening of inert anode materials. The FeCoCrNiCu high-entropy alloy, with its unique multi-principal element solid solution effect and excellent comprehensive properties, offers a new solution for the innovation of inert anode materials. The introduction of Cu significantly improves the conductivity of this alloy system, making it an ideal candidate material for inert anode surface modification.

[0004] However, several key technical bottlenecks still exist in the process of preparing FeCoCrNiCu high-entropy alloy coatings by laser cladding: On the one hand, the enthalpy of mixing of Cu with other components (such as Cr and Fe) is quite different. During solidification, Cu tends to accumulate at the grain boundaries due to solubility limitations, agglomerating into a copper-rich phase and forming obvious compositional segregation bands. These bands have low potentials and are preferentially corroded in high-temperature corrosive environments, greatly reducing the corrosion resistance of the material. At the same time, this segregation not only directly leads to fluctuations in the conductivity of the coating and affects the conductivity stability of the coating, but also causes defects such as poor molten pool fluidity, porosity, and cracks, directly affecting the compositional uniformity, density, and bonding strength of the coating. On the other hand, impurities such as sulfur and oxygen in the molten pool tend to form low-melting-point eutectic phases with Cu, such as Cu2S and Cu2O, which reduce the corrosion resistance of the coating and can also cause localized corrosion during the corrosion process.

[0005] In existing technologies, conventional slag-forming agents (such as CaF2-CaO slag systems) can improve the fluidity of the molten pool, but their desulfurization efficiency is insufficient and they may introduce new impurities. Patent CN117431421A discloses a production process for high-performance copper alloy materials. Although this method reduces oxygen and hydrogen impurities through slag-forming agents and helium blowing, it does not suppress the segregation of Cu with other elements (such as Ni and Cr), which easily leads to uneven copper alloy composition and affects conductivity and corrosion resistance. In addition, the preparation process of the slag-forming agent in this method is complex, involving more than ten raw materials, requiring multiple steps of mixing, granulation, and calcination, resulting in high costs and low production efficiency. Patent CN103060797A discloses a method for preparing a plasma-clad high-entropy alloy coating, producing a FeCoCrNiMnCu high-entropy alloy. The slag-forming agents are rutile, fluorite, and mica. However, this method cannot effectively suppress Cu segregation, easily leading to uneven coating composition and affecting conductivity and corrosion resistance. Furthermore, the slag-forming agent in this method is mainly rutile (TiO2), lacking a dynamic desulfurization mechanism, resulting in a high risk of sulfur residue and easy formation of low-melting-point Cu2S, further reducing the material's corrosion resistance. Patent CN119553114A discloses a nickel-copper alloy and its preparation method. Although this method refines the grains using rare earth elements, it does not clearly define how to suppress Cu and Ni segregation, leading to uneven alloy composition and consequently affecting the material's conductivity and corrosion resistance.

[0006] Meanwhile, to ensure that FeCoCrNiCu high-entropy alloy coatings meet the stringent requirements of inert anode applications, higher standards have been set for the cladding process. Some studies have shown that introducing magnetic or ultrasonic fields during laser cladding can partially improve cladding quality, but these methods still cannot effectively solve the aforementioned problems. For example, while simply applying a magnetic field can suppress Cu segregation, its effect on deoxidation and desulfurization of the molten pool is limited. Furthermore, Cu-containing high-entropy alloys applied to inert anodes operate in an electrolytic metallurgical environment characterized by strong corrosion and oxidation. Sulfur forms a low-melting-point eutectic phase with Cu, which not only reduces the coating's corrosion resistance but also induces localized corrosion during electrolysis, severely impacting the performance and lifespan of the inert anode. In addition, Cu has a strong affinity for sulfur, easily forming a low-melting-point eutectic phase, exacerbating coating defects and affecting conductivity and corrosion resistance. Moreover, current research on molten pool behavior and control mechanisms under multi-field coupling conditions remains insufficient, and the correlation between process parameters and material properties requires further investigation.

[0007] Based on this, an innovative multi-field coupled laser cladding process is provided to achieve high-quality preparation of FeCoCrNiCu high-entropy alloy coatings. This has important engineering application value for improving the service performance of inert anodes in extreme environments and is also a technical problem that urgently needs to be solved. Summary of the Invention

[0008] One of the objectives of this invention is to provide a method for preparing a high-density, high-conductivity, and corrosion-resistant FeCoCrNiCu high-entropy alloy coating that can solve the problems of Cu element segregation, impurity residue, and molten pool defects.

[0009] The second objective of this invention is to provide a high-density, high-conductivity, and corrosion-resistant FeCoCrNiCu high-entropy alloy coating prepared by multi-field coupled laser cladding technology.

[0010] The third objective of this invention is to provide an application of FeCoCrNiCu high-entropy alloy coating in the surface protection of inert anode materials.

[0011] One of the technical solutions adopted to achieve the objective of this invention is: to provide a method for preparing a FeCoCrNiCu high-entropy alloy coating by multi-field coupled laser cladding, comprising the following steps: A layer of Na2CO3 powder is pre-laid on the substrate surface; a high-entropy alloy coating is prepared on the substrate surface with Na2CO3 powder by laser cladding under the combined assistance of ultrasonic field and magnetic field, consisting of FeCoCrNiCu high-entropy alloy powder and slag-forming agent. The composite powder contains a slag-forming agent content of 2wt.%-4wt.%; the slag-forming agent is composed of CaO, CaF2, B2O3, and CeO2.

[0012] The overall concept and inventive principle of this invention are as follows: To address issues such as Cu segregation, residual impurities, and molten pool defects, and to prepare high-quality, high-performance inert anodic protective coatings, this invention makes the following improvements to existing methods for preparing high-entropy alloy coatings using laser cladding: First, before laser cladding, a Na2CO3 powder pre-layer is laid on the substrate surface to achieve efficient dynamic desulfurization. During the laser cladding process, the Na2CO3 powder decomposes to generate Na2O, which reacts with sulfur in the molten pool through the reaction S + Na2O → Na2S↑ to achieve in-situ desulfurization, effectively avoiding the formation of the low-melting-point Cu2S eutectic phase.

[0013] Secondly, a small amount of slag-forming agent is added to the composite powder used for cladding. CaO in the slag-forming agent is used for deoxidation, B2O3 generates BO gas to assist in deoxidation, CeO2 refines the grains and improves the material's strength, and CaF2 lowers the melting point of the slag and improves its fluidity. The addition of the slag-forming agent is suitable for the rapid solidification process of laser cladding, comprehensively reducing the oxygen content of the molten pool and reducing oxide inclusions, thus simultaneously achieving deoxidation and strengthening of the coating during coating preparation. Furthermore, the amount of slag-forming agent added needs to be controlled within the range of 2wt.%-4wt.%. When the slag-forming agent content is below 2wt.%, its deoxidation and desulfurization effects in the molten pool will be significantly weakened, resulting in poor improvement in molten pool fluidity, and the slag will also have difficulty effectively encapsulating impurities, hindering impurity flotation and removal. When the slag-forming agent content exceeds 4wt.%, excessive slag phases will be introduced. These excess slag phases remain in the coating after the molten pool solidifies, forming slag inclusion defects and disrupting the continuity and uniformity of the coating.

[0014] Finally, during the laser cladding process, ultrasonic and magnetic fields are simultaneously applied for combined auxiliary operation. The magnetic field can regulate the flow direction of the molten pool, suppress the segregation of Cu during solidification, and ensure a uniform distribution of coating composition. The ultrasonic field can refine the grains, promote the flotation of pores and slag, and reduce defects in the coating. The synergistic effect of both further improves the fluidity of the molten pool and the coating quality.

[0015] The preparation method provided by this invention achieves high-quality preparation of FeCoCrNiCu high-entropy alloy coating by optimizing the slag-forming agent composition and introducing a dynamic desulfurization mechanism of Na2CO3 pre-lay layer, combined with the synergistic regulation of ultrasonic field and magnetic field, thereby improving the service performance of inert anode in extreme environments.

[0016] Furthermore, in the FeCoCrNiCu high-entropy alloy powder, the atomic percentages of each element are: Fe: 15%-25%, Co: 15%-25%, Cr: 15%-25%, Ni: 15%-25%, Cu: 10%-30%, and the particle size of the FeCoCrNiCu high-entropy alloy powder is 48-75μm.

[0017] Further, the slagging agent, by weight percentage, comprises: CaO: 50%-65%; CaF2: 20%-30%; B2O3: 14%-18.5%; CeO2: 1.0%-2.0%, and the particle size of the slagging agent is 38-45 μm. The CaO in the slagging agent reacts in the high-temperature molten pool via the reaction CaO + [O] → Ca 2+ + O 2-The addition of CaF2 lowers the melting point of the slag-forming agent and improves the fluidity of the slag. B2O3 has the function of assisting deoxidation, and the generation of gas through B2O3 + [O] → 2BO↑ further reduces the oxygen content in the molten pool. In addition, its low viscosity promotes convection in the molten pool, reduces the local aggregation of Cu elements in the molten pool, and improves the uniformity of Cu distribution. The addition of a small amount of CeO2 can refine the grains. During solidification, CeO2 can act as a nucleation core, increasing the nucleation rate and refining the grains. The refined grains can also effectively suppress Cu segregation. Furthermore, CeO2 can also purify the grain boundaries by adsorbing impurities, weaken the driving force for the formation of low-melting-point eutectic phases such as Cu2S at the grain boundaries, improve the strength and toughness of the coating, and enhance the corrosion resistance and conductivity of the coating.

[0018] Furthermore, the FeCoCrNiCu high-entropy alloy powder and slag-forming agent are combined into a powder by ball milling or mechanical mixing for 2-8 hours.

[0019] Furthermore, the thickness of the Na2CO3 powder layer on the substrate surface is 30-80 μm, and the amount of Na2CO3 powder layered is 1%-2% of the weight of the composite powder; preferably, the particle size of the Na2CO3 powder is 500-800 mesh (18-25 μm), and the purity is higher than 99%. The substrate is pretreated, and the pretreatment method includes one or more combinations of shot peening, laser cleaning, and mechanical polishing.

[0020] In this invention, a pre-lay thickness of 30-80 μm for the Na2CO3 powder ensures that the Na2O generated from the decomposition of Na2CO3 reacts fully with the sulfur in the molten pool during laser cladding to achieve desulfurization. This thickness range provides sufficient Na2O to capture sulfur without leaving excessive impurities in the coating due to excessive thickness. When the Na2CO3 pre-lay thickness is too small, desulfurization is incomplete; while when the thickness is too large, it not only introduces excessive sodium, potentially forming new impurity phases in the coating and affecting the uniformity and conductivity of the coating, but also the excess gas generated from the decomposition of Na2CO3 may form defects such as pores in the coating. Furthermore, this invention limits the amount of Na2CO3 powder to 1%-2% of the weight of the composite powder, calculated based on the approximately 0.15% S content in the system (including the inert anode substrate, metal powder raw materials, and other potential sources of sulfur), with a molar mass ratio of Na2CO3 to S of approximately 7:1, ensuring effective desulfurization.

[0021] Furthermore, the laser cladding process parameters include: laser power of 0.6-1.5kW, spot diameter of 1-3mm, scanning speed of 8-15mm / s, and overlap rate of 30%-60%.

[0022] Furthermore, the ultrasonic field acts on the back side of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 25-35kHz and the amplitude is 5-20μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool.

[0023] Furthermore, the magnetic field is an electromagnetic coil or permanent magnet array, which applies a transverse alternating magnetic field to the molten pool region. The magnetic field strength is 50-200mT, the frequency is 5-20Hz, and the magnetic field action time covers the entire solidification process of the molten pool.

[0024] Furthermore, the preparation method also includes post-processing: after the laser cladding is completed, the slag on the surface of the high-entropy alloy coating is removed by mechanical brushing or ultrasonic cleaning.

[0025] The second objective of this invention is achieved by providing a multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating, which is prepared by the preparation method described in one of the objectives of this invention.

[0026] The third objective of this invention is to provide an application of multi-field coupled laser cladding of FeCoCrNiCu high-entropy alloy coating.

[0027] Furthermore, the multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating is used for surface protection of inert anode materials, which can effectively suppress Cu element segregation, reduce impurity inclusions and molten pool defects, and significantly improve the conductivity stability and service life of inert anodes in high-temperature and strong corrosion environments.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a method for preparing a high-entropy alloy coating of FeCoCrNiCu by multi-field coupled laser cladding. A Na2CO3 pre-lay is used, which decomposes to generate Na2O during the laser cladding process. This Na2O reacts with sulfur in the molten pool to achieve in-situ desulfurization, effectively avoiding the formation of a low-melting-point Cu2S eutectic phase. A slag-forming agent composed of CaO, CaF2, B2O3, and CeO2 is added to the composite powder. CaO is used for deoxidation, B2O3 generates BO gas to assist deoxidation, CeO2 refines the grains and improves the strength of the material, and CaF2 lowers the melting point of the slag and improves its fluidity, making it suitable for the rapid solidification process of laser cladding. This comprehensively reduces the oxygen content in the molten pool and decreases oxide inclusions. Furthermore, this preparation method simultaneously applies ultrasonic and magnetic fields during the laser cladding process for combined assistance. The magnetic field controls the flow direction of the molten pool, suppressing Cu segregation during solidification and ensuring uniform coating composition. The ultrasonic field refines the grains, promoting the floating of pores and slag, and reducing defects in the coating.

[0029] (2) The present invention provides a method for preparing a high-entropy FeCoCrNiCu alloy coating by multi-field coupled laser cladding. By optimizing the slag-forming agent composition and introducing a dynamic desulfurization mechanism of Na2CO3 pre-lay layer, combined with the synergistic regulation of ultrasonic field and magnetic field, the problems of Cu element segregation, impurity residue and molten pool defects are solved, and a high-density, high-conductivity and corrosion-resistant FeCoCrNiCu high-entropy alloy coating is obtained. It is particularly suitable for surface protection under extreme working conditions such as inert anodes, and can significantly improve the service performance of inert anodes in extreme environments, and has important engineering application value. Attached Figure Description

[0030] Figure 1 This is a microstructure diagram of the coating obtained in Example 1 of the present invention; Figure 2 This is a microstructure diagram of the coating obtained in Comparative Example 1 of the present invention; Figure 3 The results of the oxidation weight gain experiments of the coatings obtained in Examples 1-3 and Comparative Examples 1-3 of this invention are shown. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0033] This invention provides a method for preparing a FeCoCrNiCu high-entropy alloy coating by multi-field coupled laser cladding, comprising the following steps: Step 1: Pre-treat the substrate surface using methods such as shot peening, laser cleaning, and mechanical polishing; pre-lay a 50-80 μm thick layer of Na2CO3 powder on the substrate surface; the Na2CO3 powder has a particle size of 500-800 mesh (18-25 μm) and a purity higher than 99%; Step 2: Mix five metal powders of Fe, Co, Cr, Ni and Cu according to the atomic percentage of each metal element as follows: Fe: 15%-25%, Co: 15%-25%, Cr: 15%-25%, Ni: 15%-25%, Cu: 10%-30%, and ball mill for 2-8 hours to obtain FeCoCrNiCu high-entropy alloy powder. Step 3: Mechanically mix FeCoCrNiCu high-entropy alloy powder and slag-forming agent at a mass ratio of 96:4-98:2, and dry under vacuum at 50-70℃ for 1-4 hours to obtain composite powder; the composition of the slag-forming agent, by weight percentage, includes: CaO: 50%-65%; CaF2: 20%-30%; B2O3: 14%-18.5%; CeO2: 1.0%-2.0%; in the composite powder, the particle size of FeCoCrNiCu high-entropy alloy powder is 48-75μm; the particle size of the slag-forming agent is 38-45μm; Step 4: Using laser cladding, a high-entropy alloy coating is prepared on the surface of the substrate under the combined assistance of an ultrasonic field and a magnetic field. In laser cladding, the laser power is 0.6-1.5kW, the spot diameter is 1-3mm, the scanning speed is 8-15mm / s, and the overlap rate is 30%-60%. The ultrasonic field acts on the back of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 25-35kHz, and the amplitude is 5-20μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool. The magnetic field uses an electromagnetic coil or permanent magnet array to apply a transverse alternating magnetic field to the molten pool area. The magnetic field strength is 50-200mT, the frequency is 5-20Hz, and the magnetic field action time covers the entire solidification process of the molten pool. Step 5: After the laser cladding is completed, remove the slag on the surface of the high-entropy alloy coating by mechanical brushing or ultrasonic cleaning.

[0034] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0035] In the various embodiments and comparative examples of the present invention, the atomic percentage (at.%) of each metal element in the high-entropy alloy is shown in Table 1 below; the composition and content (mass percentage wt.%) of the slag-forming agent in the composite powder and the amount of Na2CO3 added (mass percentage wt.%) are shown in Table 2; the main parameters of laser cladding are shown in Table 3.

[0036] Table 1

[0037] Table 2

[0038] Table 3

[0039] Example 1 This embodiment provides a method for preparing a FeCoCrNiCu high-entropy alloy coating by multi-field coupled laser cladding, including the following steps: Step 1: The surface of the Q235 substrate is pretreated by methods such as shot peening, laser cleaning, and mechanical polishing; a 50μm thick layer of Na2CO3 powder is pre-laid on the substrate surface; Step 2: Mix five metal powders of Fe, Co, Cr, Ni and Cu according to the atomic percentage of each metal element as Fe:20%, Co:20%, Cr:20%, Ni:20% and Cu:20%, and ball mill for 4 hours to obtain FeCoCrNiCu high-entropy alloy powder. Step 3: The FeCoCrNiCu high-entropy alloy powder and the slag-forming agent are mechanically mixed at a mass ratio of 97:3 and vacuum dried at 60℃ and -0.1MPa for 2 hours to obtain the composite powder. The composition of the slag-forming agent, by weight percentage, includes: CaO: 55%; CaF2: 25%; B2O3: 18.5%; CeO2: 1.5%.

[0040] Step 4: A high-entropy alloy coating is prepared on the surface of the substrate using laser cladding under the combined assistance of an ultrasonic field and a magnetic field. In laser cladding, the laser power is 600W, the spot diameter is 2mm, the scanning speed is 8mm / s, and the overlap rate is 50%. The ultrasonic field acts on the back of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 35kHz, and the amplitude is 15μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool. The magnetic field uses an electromagnetic coil or permanent magnet array to apply a transverse alternating magnetic field to the molten pool area. The magnetic field strength is 100mT, the frequency is 10Hz, and the magnetic field action time covers the entire solidification process of the molten pool. Step 5: After the laser cladding is completed, remove the slag on the surface of the high-entropy alloy coating by mechanical brushing or ultrasonic cleaning.

[0041] Figure 1 This is a microstructure diagram of the FeCoCrNiCu high-entropy alloy coating obtained in Example 1. Figure 1 As can be seen, the overall structure of the coating is dense, and no obvious cracks, pores, or other defects in the molten pool were observed. This indicates that the density of the coating was significantly improved under the combined effects of dynamic desulfurization with Na2CO3 pre-laying, synergistic deoxidation with slag-forming agents, and ultrasound-magnetic field. The coating microstructure is dominated by uniformly distributed dendrites with clear and continuous grain boundaries. No Cu-rich phase agglomerates or compositional segregation bands were observed, confirming the inhibitory effect of the magnetic field on Cu element segregation and the synergistic effect of the ultrasonic field in refining grains. The uniformly distributed microstructure also provides a foundation for the comprehensive performance of the coating, demonstrating the significant advantages of this invention in solving problems such as Cu segregation, impurity residues, and molten pool defects.

[0042] Example 2 This embodiment provides a method for preparing a FeCoCrNiCu high-entropy alloy coating by multi-field coupled laser cladding, including the following steps: Step 1: The surface of the Q235 substrate is pretreated by methods such as shot peening, laser cleaning, and mechanical polishing; a 30μm thick layer of Na2CO3 powder is pre-laid on the substrate surface; Step 2: Mix five metal powders of Fe, Co, Cr, Ni and Cu according to the atomic percentage of each metal element as Fe: 25%, Co: 25%, Cr: 25%, Ni: 15% and Cu: 10%, and ball mill for 5 hours to obtain FeCoCrNiCu high entropy alloy powder. Step 3: The FeCoCrNiCu high-entropy alloy powder and the slag-forming agent were mechanically mixed at a mass ratio of 98:2, and then vacuum dried at 65℃ and -0.1MPa for 3 hours to obtain the composite powder. The composition of the slag-forming agent, by weight percentage, includes: CaO: 65%; CaF2: 20%; B2O3: 14%; CeO2: 1%. Step 4: A high-entropy alloy coating is prepared on the surface of the substrate using laser cladding under the combined assistance of an ultrasonic field and a magnetic field. In laser cladding, the laser power is 1500W, the spot diameter is 2mm, the scanning speed is 15mm / s, and the overlap rate is 30%. The ultrasonic field acts on the back of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 35kHz, and the amplitude is 5μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool. The magnetic field uses an electromagnetic coil or permanent magnet array to apply a transverse alternating magnetic field to the molten pool area. The magnetic field strength is 50mT, the frequency is 20Hz, and the magnetic field action time covers the entire solidification process of the molten pool. Step 5: After the laser cladding is completed, remove the slag on the surface of the high-entropy alloy coating by mechanical brushing or ultrasonic cleaning.

[0043] Example 3 This embodiment provides a method for preparing a FeCoCrNiCu high-entropy alloy coating by multi-field coupled laser cladding, including the following steps: Step 1: The surface of the Q235 substrate is pretreated by methods such as shot peening, laser cleaning, and mechanical polishing; Na2CO3 powder with a thickness of 80μm is pre-laid on the substrate surface; Step 2: Mix five metal powders of Fe, Co, Cr, Ni and Cu according to the atomic percentage of each metal element as Fe:15%, Co:15%, Cr:15%, Ni:25% and Cu:30%, and ball mill for 3 hours to obtain FeCoCrNiCu high entropy alloy powder. Step 3: The FeCoCrNiCu high-entropy alloy powder and the slagging agent were mechanically mixed at a mass ratio of 96:4, and then vacuum dried at 55℃ and -0.1MPa for 2.5h to obtain the composite powder. The composition of the slagging agent, by weight percentage, includes: CaO: 50%; CaF2: 30%; B2O3: 18%; CeO2: 2%. Step 4: A high-entropy alloy coating is prepared on the surface of the substrate using laser cladding under the combined assistance of an ultrasonic field and a magnetic field. In laser cladding, the laser power is 1000W, the spot diameter is 2mm, the scanning speed is 10mm / s, and the overlap rate is 50%. The ultrasonic field acts on the back of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 25kHz, and the amplitude is 20μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool. The magnetic field uses an electromagnetic coil or permanent magnet array to apply a transverse alternating magnetic field to the molten pool area. The magnetic field strength is 200mT, the frequency is 5Hz, and the magnetic field action time covers the entire solidification process of the molten pool. Step 5: After the laser cladding is completed, remove the slag on the surface of the high-entropy alloy coating by mechanical brushing or ultrasonic cleaning.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that no slag-forming agent is added during the preparation of the composite powder. The other operations, conditions and parameters remain unchanged. The FeCoCrNiCu high-entropy alloy powder is directly used to perform laser cladding on the surface of a substrate with a Na2CO3 powder pre-lay. The laser cladding is carried out under the combined assistance of an ultrasonic field and a magnetic field.

[0045] Figure 2 This is a microstructure diagram of the FeCoCrNiCu high-entropy alloy coating prepared in Comparative Example 1. Figure 2 It can be seen that there are obvious defects in its microstructure: a large number of copper-rich phases appear in the microstructure. Due to the lack of slag-forming agent, the lack of the synergistic effect of B2O3 to improve molten pool convection and CeO2 to refine grains leads to Cu elements existing in a free state during solidification; at the same time, there are many black inclusion particles distributed in the coating. These inclusions are mainly unremoved oxides or sulfides (such as Cu2O, Cu2S). Due to insufficient deoxidation and desulfurization, impurities form defects in the molten pool.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that no Na2CO3 pre-lay layer is set, while the other operations, conditions and parameters remain unchanged. The composite powder (FeCoCrNiCu high-entropy alloy powder + slag-forming agent) is directly used to perform laser cladding on the pretreated substrate surface. The laser cladding is carried out under the combined assistance of ultrasonic field and magnetic field.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that no ultrasonic field or magnetic field is used for assistance during the laser cladding process, while the other operations, conditions and parameters remain unchanged.

[0048] Performance testing The FeCoCrNiCu high-entropy alloy coatings obtained in Examples 1-3 and Comparative Examples 1-3 were tested for hardness, high-temperature oxidation weight gain rate, electrical conductivity, and Cu element segregation degree. The oxidation weight gain experiment involved exposing the samples to air at 800℃, weighing them every 20 hours, and plotting the weight gain curves (e.g., ...). Figure 3 (As shown in the figure) and the high-temperature weight gain oxidation rate of the sample was calculated. The relevant test results are shown in Table 4 below.

[0049] Table 4

[0050] As can be seen from the above table, In Comparative Example 1, no slag-forming agent was added to the composite powder. Compared with Example 1, the coating obtained had a 22% lower hardness, indicating that the addition of the slag-forming agent (CaO / CaF2 / B2O3 / CeO2) significantly improved the coating density by deoxidizing, refining grains, and encapsulating impurities in the slag. The coating conductivity decreased by 26%, confirming that the slag-forming agent can reduce the obstruction of electron transport by oxide inclusions. The Cu segregation degree was as high as 4 times that of Example 1, indicating that the low viscosity of B2O3 and the grain boundary purification effect of CeO2 in the slag-forming agent effectively inhibited the segregation of Cu elements.

[0051] Comparative Example 2, which did not have a Na2CO3 pre-lay layer on the substrate surface, showed a coating with a 61% higher high-temperature oxidation weight gain rate than Example 1. This confirms that the Na2O generated from the decomposition of Na2CO3 effectively eliminates the low-melting-point eutectic phase of Cu2S through the reaction S + Na2O → Na2S↑, thereby improving the coating's oxidation resistance. Furthermore, Comparative Example 2 still exhibited a relatively high Cu segregation degree, confirming that the dynamic desulfurization mechanism of Na2CO3 can reduce brittle phases at grain boundaries and indirectly improve the uniformity of elemental distribution.

[0052] In the laser cladding process of Comparative Document 3, no combined assistance of ultrasonic and magnetic fields was introduced. Compared with Example 1, the hardness and conductivity of the resulting coating were not ideal, and the Cu segregation was also higher. This indicates that relying solely on the optimization of material composition cannot effectively compensate for defects in the molten pool. The synergistic assistance of magnetic and ultrasonic fields plays a positive role in the uniformity of composition.

[0053] Examples 1-3 of this invention systematically solve the problems of Cu segregation, impurity residue, and molten pool defects in high-entropy alloy coatings by optimizing the composition of the slag-forming agent, utilizing dynamic desulfurization through Na2CO3 pre-laying, and employing a laser cladding method assisted by a combination of ultrasound and magnetic fields. Comparative data fully demonstrate that the absence of any single technical step leads to a significant performance degradation. The excellent performance of Examples 1-3 verifies the integrity and synergistic innovation of the technical solution of this invention, making it particularly suitable for inert anode protection scenarios with stringent requirements for density, conductivity, and corrosion resistance.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and scope of protection of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a multi-field coupling laser cladding FeCoCrNiCu high-entropy alloy coating, characterized in that, Includes the following steps: A layer of Na2CO3 powder is pre-laid on the substrate surface; a high-entropy alloy coating is prepared on the substrate surface with Na2CO3 powder by laser cladding under the combined assistance of ultrasonic field and magnetic field, consisting of FeCoCrNiCu high-entropy alloy powder and slag-forming agent. The composite powder contains a slag-forming agent content of 2wt.%-4wt.%; the slag-forming agent is composed of CaO, CaF2, B2O3, and CeO2.

2. The production method according to claim 1, characterized by, The atomic percentages of each element in the FeCoCrNiCu high-entropy alloy powder are as follows: Fe: 15%-25%, Co: 15%-25%, Cr: 15%-25%, Ni: 15%-25%, Cu: 10%-30%.

3. The preparation method according to claim 1, characterized in that, The composition of the slag-forming agent, by weight percentage, includes: CaO: 50%-65%; CaF2: 20%-30%; B2O3: 14%-18.5%; CeO2: 1.0%-2.0%.

4. The preparation method according to claim 1, characterized in that, The thickness of the Na2CO3 powder on the substrate surface is 30-80 μm, and the amount of Na2CO3 powder is 1%-2% of the weight of the composite powder; the substrate is pretreated, and the pretreatment method includes one or more combinations of shot peening, laser cleaning, and mechanical polishing.

5. The preparation method according to claim 1, characterized in that, The laser cladding process parameters include: laser power of 0.6-1.5kW, spot diameter of 1-3mm, scanning speed of 8-15mm / s, and overlap rate of 30%-60%.

6. The preparation method according to claim 1, characterized in that, The ultrasonic field acts on the back of the substrate and is transmitted to the substrate through a piezoelectric ceramic transducer. The ultrasonic vibration frequency is 25-35kHz and the amplitude is 5-20μm. The ultrasonic vibration direction is perpendicular to the laser scanning direction, and the vibration time covers the entire solidification process of the molten pool.

7. The preparation method according to claim 1, characterized in that, The magnetic field is applied to the molten pool region by means of electromagnetic coils or permanent magnet arrays. The magnetic field strength is 50-200mT and the frequency is 5-20Hz. The magnetic field action time covers the entire solidification process of the molten pool.

8. The preparation method according to claim 1, characterized in that, The preparation method also includes post-processing: after the laser cladding is completed, the slag on the surface of the high-entropy alloy coating is removed by mechanical brushing or ultrasonic cleaning.

9. A multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating, characterized in that, It is prepared by any one of the preparation methods according to claims 1-8.

10. The application of the multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating according to claim 9, characterized in that, The multi-field coupled laser cladding FeCoCrNiCu high-entropy alloy coating is used for surface protection of inert anode materials.

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