High wear-resistant railway turnout coating and preparation method thereof

Abstract

The application discloses a preparation method of a high-wear-resistance railway turnout coating and relates to the technical field of railway turnout coatings. A surface grafted modified nano tungsten carbide reinforcing phase is formed; a nano composite pre-alloy powder is obtained; a spherical high-entropy alloy composite spraying powder with high fluidity is obtained; a rough anchoring surface with a micron-level staggered grid structure is constructed on the surface of a base material; a base coating substrate with a thermal expansion gradient buffer feature is obtained; an initial cladding coating workpiece is obtained; and the high-wear-resistance railway turnout coating is prepared. The application excludes closed pores in the powder, and significantly improves the density and fluidity of the powder.

Description

Technical Field

[0001] This invention relates to the field of railway turnout coating technology, and in particular to a high wear-resistant railway turnout coating and its preparation method. Background Technology

[0002] With the rapid development of high-speed rail and heavy-haul transportation technologies, train speeds and axle loads are constantly increasing. As a crucial component guiding train wheels to switch tracks, railway turnouts face increasingly severe transient impacts, high-frequency shearing, and complex rolling contact friction at the wheel-rail contact interface. Preparing high-performance composite coatings on the turnout substrate surface has become a standard protective measure to extend turnout service life and ensure train operation safety. However, the preparation and interface control of high-wear-resistant railway turnout coatings face numerous challenges in the wheel-rail contact environment subjected to multi-dimensional, broadband loads.

[0003] Traditional composite coating powder preparation methods typically rely on simple mechanical mixing or conventional ball milling. Nanoscale hard phases readily aggregate within the metal matrix and easily introduce exogenous carbon and oxygen impurities, resulting in porous powders with poor macroscopic flowability. This not only makes it difficult to form a dense structure during subsequent coating processes but also creates localized brittle fracture sources due to the agglomeration of the hard phase.

[0004] With increasing train impact loads, ensuring a high-strength bond between the coating and the turnout steel substrate, as well as mitigating interfacial thermal stress, becomes increasingly difficult. Traditional substrate pretreatment methods not only have environmental drawbacks but also provide extremely limited surface anchoring force. In the absence of an effective thermal expansion gradient buffering mechanism, the coating and substrate are highly susceptible to large-area peeling due to interfacial shear stress and thermal stress mismatch.

[0005] Traditional laser cladding film formation and post-processing mechanisms often fail to simultaneously achieve microstructure uniformity and macroscopic stress control. Conventional Gaussian beam heat sources easily lead to excessively high temperatures at the center of the molten pool and the burning off of alloying elements. Simultaneously, gravity causes severe sedimentation and agglomeration of hard phases at the bottom of the molten pool. The extremely high cooling rate accompanying the cladding process inevitably introduces significant residual tensile stress within the coating. Traditional stress-relief annealing or shot peening cannot effectively reverse this stress field without damaging surface roughness or inducing grain coarsening, making the coating highly susceptible to rolling contact fatigue cracking during actual service. Summary of the Invention

[0006] One objective of this invention is to provide a method for preparing a high wear-resistant railway turnout coating. This invention eliminates closed pores inside the powder, significantly improving the density and flowability of the powder.

[0007] A method for preparing a high wear-resistant railway turnout coating according to an embodiment of the present invention, the method comprising: Nano-tungsten carbide particles and silane coupling agent were ultrasonically dispersed and cross-linked in anhydrous ethanol solvent, and then dried to form a surface-grafted modified nano-tungsten carbide reinforced phase. The surface-grafted modified nano-tungsten carbide reinforcing phase was mixed with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio and placed in a high-energy ball mill for mechanical alloying under inert gas protection to obtain nano-composite pre-alloyed powder. Radio frequency plasma spheroidization treatment was performed on the nanocomposite pre-alloyed powder to eliminate internal pores and promote surface melting and densification, resulting in a spherical high-entropy alloy composite spray powder with high fluidity. The surface of the railway turnout substrate is subjected to surface degreasing, ultrasonic cleaning and nanosecond laser microtexturing treatment in sequence to construct a rough anchoring surface with a micron-level interlaced grid structure on the substrate surface; On a rough anchoring surface, a nickel-chromium-aluminum-yttrium base powder is deposited using supersonic flame spraying technology to obtain a base coating substrate with thermal expansion gradient buffering characteristics. Using wide-beam laser cladding technology, spherical high-entropy alloy composite spray powder is deposited layer by layer on the substrate with the base coating. The deep melting effect is controlled by the laser heat source, so that the powder and the base coating form a metallurgical bond to obtain the initial cladding coating workpiece. The initial cladding coating workpiece is subjected to ultrasonic surface rolling strengthening treatment, which induces severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and introduces a residual compressive stress field with a depth of 0.5mm-1.0mm into the interior, finally obtaining a high wear-resistant railway turnout coating.

[0008] Optionally, the step of ultrasonically dispersing and crosslinking the nano-tungsten carbide particles with a silane coupling agent in anhydrous ethanol solvent, and then drying them to form a surface-grafted modified nano-tungsten carbide reinforcing phase, includes: Deionized water and anhydrous ethanol were mixed and the pH value was adjusted. A silane coupling agent containing epoxy and amino groups was added for hydrolysis to form a two-component synergistic hydrolysis precursor solution. Surface-activated tungsten carbide nanoparticles were obtained by in-situ polar excitation treatment of the surface of tungsten carbide nanoparticles using hydrogen peroxide aqueous solution. Surface-activated nano-tungsten carbide was added to the two-component synergistic hydrolysis precursor solution, and ultrasonic dispersion and in-situ ring-opening crosslinking reaction were performed under a dual-frequency alternating ultrasonic field to form an organic-inorganic hybrid coated precursor. The organic-inorganic hybrid coating precursor was subjected to freeze-drying to obtain a surface-grafted modified nano-tungsten carbide reinforced phase.

[0009] Optionally, the step of mixing the surface-grafted modified nano-tungsten carbide reinforcing phase with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio, and then subjecting the mixture to mechanical alloying treatment under inert gas protection in a high-energy ball mill to obtain nano-composite pre-alloyed powder includes: Cobalt-chromium-iron-nickel high-entropy alloy powder, the surface-grafted modified nano-tungsten carbide reinforcing phase, and transient volatile grinding aid are mixed and loaded into a high-energy ball mill to form a mixed grinding system. Under inert gas protection, the mixed grinding system is subjected to cryogenic ball milling by liquid nitrogen cooling to obtain a pre-ground powder that undergoes low-temperature embrittlement and grain refinement. Stop cooling and allow the system to naturally warm up. Perform a mild diffusion ball milling process on the initial milled powder to allow the tungsten carbide core to diffuse along the grain boundaries in a short distance, and obtain intermediate diffusion powder. Increasing the ball mill speed and performing high-energy intercalation ball milling on the intermediate-state diffused powder forces the nano-hard phase into the high-entropy alloy matrix, resulting in a highly dense nano-composite pre-alloyed powder.

[0010] Optionally, the radio frequency plasma spheroidization treatment performed on the nanocomposite pre-alloyed powder to eliminate internal pores and promote surface melting and densification, resulting in a highly fluid spherical high-entropy alloy composite spray powder, includes: A plasma high-temperature thermal field with a wide and gentle stepped enthalpy distribution was constructed by using a mixed gas supply mode of argon, hydrogen and helium. Nanocomposite pre-alloyed powder is injected at a constant rate into a plasma high-temperature thermal field for transient surface melting, causing it to condense and expel internal pores under the action of surface tension, forming molten spherical droplets; The molten spherical droplets were subjected to extreme rapid cooling using a forced supersonic cryogenic argon jet to suppress grain growth, ultimately resulting in a highly fluid spherical high-entropy alloy composite spray powder.

[0011] Optionally, the process of sequentially performing surface degreasing, ultrasonic cleaning, and nanosecond laser microtexturing on the surface of the railway turnout substrate to construct a rough anchoring surface with a micron-level interlaced grid structure includes: A biodegradable water-based cleaning agent was used to perform surface degreasing treatment on the railway turnout substrate to obtain a degreased substrate. The degreased substrate was placed in anhydrous ethanol and subjected to high-frequency ultrasonic cleaning to obtain a clean turnout substrate. A nanosecond pulsed laser was used to perform a biomimetic textured two-dimensional scanning on the clean turnout substrate, ablation to form micron-level interlaced grid grooves; By utilizing the vaporization and recoil effect during the transient laser ablation process, a mushroom-shaped recast layer is generated in situ at the edge of the micron-level interlaced grid groove, thus constructing a rough anchoring surface with a micron-level interlaced grid structure on the substrate surface.

[0012] Optionally, the deposition of nickel-chromium-aluminum-yttrium primer powder on the rough anchoring surface using supersonic flame spraying technology to obtain a primer-coated substrate with thermal expansion gradient buffering characteristics includes: Low-pressure radio frequency plasma etching modification treatment was performed on nickel-chromium-aluminum-yttrium base powder using a fluorine-oxygen mixed gas to obtain a modified base powder with highly active nanoscale pits on the surface. By adjusting the spraying oxygen-fuel ratio parameters and accelerating with a retractable Laval nozzle, a supersonic flame stream with a slightly reducing atmosphere is constructed. The modified primer powder is melted and accelerated by a micro-reducible supersonic flame, causing it to impact the rough anchoring surface at high speed for flattening, spreading and composite mechanical interlocking, thus depositing a substrate with a primer coating that has thermal expansion gradient buffering characteristics.

[0013] Optionally, the method of using wide-beam laser cladding technology to deposit spherical high-entropy alloy composite spraying powder layer by layer onto the substrate with a base coating, and controlling the deep melting effect through a laser heat source to form a metallurgical bond between the powder and the base coating to obtain an initial cladding coating workpiece, includes: Microlens array technology is used to shape the laser heat source beam to obtain a broadband rectangular flat-top beam with uniform energy distribution. Using a broadband rectangular flat-top beam, the spherical high-entropy alloy composite spray powder is melted onto the substrate with a base coating under controlled specific energy to form a liquid molten pool with controlled dilution rate; A mixed protective gas containing highly active nitrogen atoms is continuously introduced into the liquid molten pool to interfere with and reverse the Marangoni convection direction inside the molten pool, so that the tungsten carbide hard phase is uniformly suspended and completes diffusionless solidification, thus obtaining the initial cladding coating workpiece.

[0014] Optionally, the initial cladding coating workpiece undergoes ultrasonic surface rolling strengthening treatment to induce severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and a residual compressive stress field with a depth of 0.5mm-1.0mm is introduced into the interior, ultimately producing a high wear-resistant railway turnout coating, comprising: Under the dual physical field coupling of static pressure load and high-frequency dynamic ultrasonic impact, the surface of the initial cladding coating workpiece is subjected to ultrasonic surface rolling strengthening treatment, which induces severe plastic deformation of the surface and generates high-density dislocation cells. Through the subgrain boundary rotation and dynamic recrystallization mechanism of high-density dislocation cells, a dense equiaxed nanocrystalline structure with extremely low surface roughness is generated in situ on the coating surface. By utilizing the elastic recovery resistance transmitted from the surface plastic deformation to the interior of the matrix, a deep residual compressive stress field with a gradient distribution is constructed beneath the dense nanocrystalline layer, ultimately resulting in a high wear-resistant railway turnout coating.

[0015] A high wear-resistant railway turnout coating, wherein the high wear-resistant railway turnout coating has a multi-level gradient composite structure from the substrate to the surface.

[0016] The beneficial effects of this invention are: This invention overcomes the problem of easy agglomeration of nanoparticles by introducing a dual-frequency alternating ultrasonic field combined with a specific ratio of a two-component silane coupling agent precursor solution and a three-stage variable-temperature ball milling mechanism with a transiently volatile grinding aid. This allows for adaptive control of the interfacial energy and dispersibility of the nano-hard phase at both the molecular and lattice levels. Furthermore, this invention constructs a robust chemical bond coating network on the tungsten carbide surface through hydrolysis and in-situ ring-opening crosslinking of the two-component coupling agent within an extremely narrow pH range. Combined with subsequent spheroidization and reshaping using a ternary mixed gas via radio frequency plasma, this eliminates closed pores within the powder, significantly improving the powder's density and flowability.

[0017] This invention utilizes two-dimensional scanning ablation of a specific depth on the railway turnout substrate and in-situ generation of a mushroom-shaped recast layer through vaporization backlash. Simultaneously, it incorporates nickel-chromium-aluminum-yttrium (NiCh-A) base powder modified by plasma etching with a fluorine-oxygen mixture, creating a three-dimensional mechanical interlocking and micro-metallurgical composite anchoring at the coating-substrate interface. By introducing micron-level staggered mesh grooves and barbed structures, the actual anchoring surface area is significantly expanded. Furthermore, the micro-reducing flame flow constructed through precise control of the oxygen-fuel ratio protects the integrity of the buffer layer elements, establishing a smooth thermal expansion gradient buffer zone. This significantly enhances the coating's resistance to spalling under the high-frequency shearing of heavy-load trains.

[0018] This invention combines broadband rectangular flat-top laser cladding with multidimensional ultrasonic surface rolling strengthening technology. It uses a nitrogen-doped mixed protective gas to intervene in the surface tension and temperature gradient of liquid metal, and leverages the dual physical field coupling of high-frequency dynamic ultrasonic impact and static pressure to dynamically reshape the entire chain of melt deposition and solidification phase transformation processes. By using trace amounts of active nitrogen atoms to reverse the Marangoni convection direction, the nano-hard phase achieves uniform suspension and solidification under gentle inward convection. Combined with ultrasonic rolling to induce severe plastic deformation and dynamic recrystallization of the surface layer, not only are coarse grains thoroughly refined into equiaxed nanocrystals of 15nm to 25nm, but a high-amplitude residual compressive stress field with peak values ​​reaching -600MPa to -800MPa is successfully constructed deep within the coating. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a method for preparing a high wear-resistant railway turnout coating proposed in this invention. Detailed Implementation

[0020] Example 1: Reference Figure 1 A method for preparing a high wear-resistant railway turnout coating, the method comprising: Nano-tungsten carbide particles and silane coupling agent were ultrasonically dispersed and cross-linked in anhydrous ethanol solvent, and then dried to form a surface-grafted modified nano-tungsten carbide reinforced phase. In this embodiment, nano-tungsten carbide particles and a silane coupling agent are ultrasonically dispersed and crosslinked in anhydrous ethanol solvent. After drying, a surface-grafted modified nano-tungsten carbide reinforced phase is formed, comprising: In terms of raw material pretreatment and green solvent substitution, the traditional highly toxic toluene or xylene reflux modification process is abandoned. Instead, a green polar co-solvent system is constructed by mixing deionized water and anhydrous ethanol at a volume ratio of 1:3.8 to 1:4.2. In this system, 0.5% to 0.8% glacial acetic acid is added by mass percentage as a hydrolysis catalyst to precisely control the pH value of the system to an extremely narrow critical range of 4.2 to 4.5. Within this critical pH range, silane coupling agent KH-560 containing epoxy groups and silane coupling agent KH-550 containing amino groups are added at a mass ratio of 1:1. The hydrolysis reaction is carried out at a constant temperature of 25°C with low-speed magnetic stirring for 45 to 50 minutes, allowing the methoxy and ethoxy groups of the coupling agents to be completely hydrolyzed into highly active silanol groups, forming a two-component synergistic hydrolysis precursor solution. Surface hydroxylation polarization treatment was performed on tungsten carbide nanoparticles with an original purity of not less than 99.9% and an average particle size of 40 nm to 60 nm: The tungsten carbide nanoparticles were placed in a 2.5 mol / L hydrogen peroxide aqueous solution and treated with gentle boiling at 60 °C for 2 hours. High-density surface hydroxyl groups were generated on the particle surface in situ without destroying the WC lattice, utilizing the strong oxidizing property. The particles were washed with deionized water until neutral and dried in a vacuum drying oven at 80 °C for 12 hours to obtain surface-activated tungsten carbide nanoparticles. A variable-frequency ultrasonic dispersion and cross-linking reaction, breaking with conventional conditions, was performed: Surface-activated nano-tungsten carbide was slowly added at a mass-volume fraction of 5% to 8% to a two-component synergistic hydrolysis precursor solution, and placed in a closed ultrasonic reactor with a temperature dynamic feedback system. Irradiation was carried out using alternating dual-frequency ultrasonic fields of 20kHz and 40kHz. The ultrasonic power density was set to a specific critical range of 0.8W / cm² to 1.0W / cm², and the ultrasonic time was 1.5 hours to 2 hours. Under this specific dual-frequency cavitation effect, not only was monodispersity of nano-tungsten carbide achieved, but also the local extreme high pressure and micro-region high temperature generated by the instantaneous collapse of cavitation bubbles overcame the steric hindrance and activation energy barrier for the condensation reaction between silanol groups and hydroxyl groups on the tungsten carbide surface. This allowed KH-560 and KH-550 molecules to be firmly grafted onto the tungsten carbide surface in the form of chemical bonds, and epoxy groups and amino groups to undergo in-situ ring-opening cross-linking, forming a dense organic-inorganic hybrid coating network with a thickness of 2nm to 5nm on the tungsten carbide surface. To avoid secondary hard agglomeration caused by conventional hot air drying, a freeze-vacuum drying process was adopted. After pre-freezing at -50℃ for 4 hours, the particles were heated and dried under 10Pa absolute pressure for 24 hours to obtain a surface-grafted modified nano-tungsten carbide reinforcing phase. The modification process significantly reduced the surface energy of the nanoparticles. When subsequently mixed with high-entropy alloy powder, the wetting angle was sharply reduced from the original 115° to below 35°. This completely solved the technical bias that nano-scale hard phases are prone to agglomeration in metal matrices, forming defect sources, and provided the coating with unexpected dispersion strengthening and toughness improvement effects.

[0021] The surface-grafted modified nano-tungsten carbide reinforcing phase was mixed with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio and placed in a high-energy ball mill for mechanical alloying under inert gas protection to obtain nano-composite pre-alloyed powder. In this embodiment, the surface-grafted modified nano-tungsten carbide reinforcing phase is mixed with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio, and then subjected to mechanical alloying treatment under inert gas protection in a high-energy ball mill to obtain nano-composite pre-alloyed powder, comprising: In terms of the innovative selection of raw material ratios and milling media, the cobalt-chromium-iron-nickel high-entropy alloy powder is a spherical powder prepared by gas atomization, with a particle size range of 15μm to 30μm. Surface-grafted modified nano-tungsten carbide reinforcing phase is precisely compounded with the high-entropy alloy powder at a mass ratio of 1.5:8.5 to 2.0:8.0. In this process, the technical barrier of easily introducing exogenous carbon and oxygen impurities leading to coating embrittlement when using stearic acid or anhydrous ethanol as process control agents is broken. Instead, a transient volatile grinding aid—a mixed gas-liquid phase fluid of high-purity liquid nitrogen and trace amounts of perfluorohexanone—is creatively introduced. The mixed powder is loaded into a stainless steel ball mill jar along with three-stage graded cemented carbide grinding balls with a diameter ratio of 8mm:5mm:2mm and a mass ratio of 1:3:1, with the ball-to-material ratio strictly controlled within an extremely narrow range of 12:1 to 15:1.

[0022] The breakthrough change in process parameters is reflected in the setting of the nonlinear temperature and pressure high-energy ball milling program: traditional ball milling usually operates at a constant speed, while this invention adopts a novel three-stage temperature-controlled variable speed mechanical alloying route of deep cryogenic stimulation, mild diffusion, and high-energy intercalation. In the first stage, liquid nitrogen is introduced into the jacket of the ball mill to control the ambient temperature of the ball milling system between -80°C and -100°C, and ball milling is carried out at a speed of 250 rpm to 300 rpm for 4 to 6 hours. At extremely low temperatures, the high-entropy alloy powder undergoes low-temperature embrittlement, and rapidly undergoes a cycle of intense plastic deformation, cold welding, and breakage under the collision of the grinding balls, resulting in a rapid refinement of the grain size to the nanoscale, while simultaneously introducing a large number of crystal defects such as dislocations and vacancies. In the second stage, liquid nitrogen cooling is stopped, allowing the system to naturally warm to room temperature, and the speed is reduced to 150 rpm to 180 rpm, with ball milling continuing for 8 to 10 hours. In this stage, the organic graft layer on the tungsten carbide surface partially degrades under the action of mechanical energy, exposing a highly active nano-tungsten carbide core, which then diffuses short-range along dislocation lines and grain boundary networks generated within the high-entropy alloy powder. In the third stage, the ball mill speed is rapidly increased to 450 to 500 rpm, and ball milling continues for 2 to 3 hours. Driven by the intense plastic deformation generated by high-energy collisions, the nano-tungsten carbide particles are forced to uniformly embed into the high-entropy alloy FCC solid solution matrix, which has already undergone severe lattice distortion, forming a microscopic intrinsic dispersion reinforcement structure.

[0023] By employing nonlinear mechanical alloying within an extremely narrow critical parameter range, the traditional long-term high-temperature sintering and solution treatment steps for powders are eliminated. A one-pot method is used to directly prepare nanocomposite pre-alloyed powders with highly dense internal structure, uniformly dispersed nano-hard phases, and an oxygen content below 0.05 wt%. The grain size of the CoCrFeNi matrix in the powder is stably controlled between 20 nm and 35 nm. The synergistic effect of solid solution strengthening and grain refinement brought about by severe lattice distortion lays the foundation for a microscopic phase transformation that achieves high wear resistance.

[0024] Radio frequency plasma spheroidization treatment was performed on the nanocomposite pre-alloyed powder to eliminate internal pores and promote surface melting and densification, resulting in a spherical high-entropy alloy composite spray powder with high fluidity. In this embodiment, the nanocomposite pre-alloyed powder is subjected to radio frequency plasma spheroidization treatment to eliminate internal pores and promote surface melting and densification, resulting in a highly fluid spherical high-entropy alloy composite spray powder, comprising: Mechanically alloyed products are typically irregularly shaped flakes or polygons, containing micropores left by mechanical interlocking. Direct application to spray coatings results in high porosity and poor adhesion. A breakthrough improvement was achieved by using radio frequency inductively coupled plasma technology for powder reshaping, which significantly improved the conventional plasma gas ratio and thermal field distribution.

[0025] In terms of plasma gas selection and ratio improvement, a dynamic coordinated gas supply mode of three gases—center gas, sheath gas, and carrier gas—is adopted. High-purity argon is used as the center gas, with a flow rate set at 20 L / min to 25 L / min, to maintain a stable plasma torch. This overcomes the drawback of traditional sheath gas use of pure hydrogen or pure helium, which easily leads to excessive droplet vaporization. Innovatively, a ternary mixture of argon, hydrogen, and a trace amount of helium is used as the sheath gas. The argon flow rate is 60 L / min to 70 L / min, the hydrogen flow rate is precisely controlled at 3.5 L / min to 4.5 L / min, and the helium flow rate is set at 1.0 L / min to 1.5 L / min, forming a broad, gently sloping high-temperature plasma thermal field with a stepped enthalpy distribution. Argon is used as the carrier gas, with a flow rate of 3 L / min to 5 L / min.

[0026] In terms of breakthrough control of process parameters, the radio frequency power supply frequency is set in a specific range of 2.0MHz to 3.0MHz to increase the plasma penetration depth. The system power is precisely locked between 15kW and 18kW, and the operating pressure of the reaction chamber is maintained at a slight negative pressure of 85kPa to 90kPa. Using a specially designed ultrasonic micro-vibration powder feeder, nanocomposite pre-alloyed powder is injected into the central high-temperature zone with a temperature as high as 10000K along the axis of the plasma torch at a constant rate of 10g / min to 15g / min. In terms of reshaping mechanism and thermodynamic critical process control, after the irregular pre-alloyed powder enters the high-temperature zone, due to the enhanced thermal conductivity effect of trace amounts of helium gas, the powder rapidly absorbs a large amount of heat and melts on the surface and near the surface within an extremely short residence time of a few milliseconds to tens of milliseconds. However, the nano-tungsten carbide particles inside the powder, due to their extremely high melting point, do not decompose and lose carbon under the specific power parameters set at 15kW to 18kW. Under the spontaneous contraction of extremely high surface tension, the molten high-entropy alloy matrix instantly condenses into perfect spherical droplets, expelling the closed pores generated by the mechanical interlocking inside the powder.

[0027] The critical cooling stage employed a self-designed forced supersonic quenching ring device. As the molten, spherical high-entropy alloy composite droplets exited the high-temperature plasma zone, they were immediately subjected to powerful quenching by a low-temperature argon jet with a jet velocity of Mach 2 to Mach 3. This extreme, unconventional quenching rate completely suppressed the grain growth trend of the high-entropy alloy and the high-temperature precipitation phase transformation of tungsten carbide, instantly freezing its nanocrystalline and even amorphous mixed structure. The collected spherical high-entropy alloy composite spray powder exhibited unexpectedly high physical properties: a sphericity exceeding 98%, an internal density approaching 100% of the theoretical density, a Hall flow rate between 12 s / 50 g and 15 s / 50 g, and a uniform three-dimensional distribution of the nano-tungsten carbide reinforcing phase within the spherical particles, effectively avoiding the localized brittle fracture problem caused by the segregation of hard phases in conventional spray powders.

[0028] The surface of the railway turnout substrate is subjected to surface degreasing, ultrasonic cleaning and nanosecond laser microtexturing treatment in sequence to construct a rough anchoring surface with a micron-level interlaced grid structure on the substrate surface; In this embodiment, the railway turnout substrate surface is sequentially subjected to surface degreasing, ultrasonic cleaning, and nanosecond laser microtexturing treatment to construct a rough anchoring surface with a micron-level interlaced grid structure. Addressing the core challenge of the coating interface, the specific parameter settings and structural innovations implemented are as follows: In optimizing the pretreatment process for railway turnout substrates, the traditional methods of strong acid and alkali immersion cleaning and sandblasting roughening, which are highly prone to environmental pollution and hydrogen embrittlement, were abandoned. Instead, a biodegradable water-based cleaning agent, composed of sodium citrate, cocamidopropyl betaine, and deionized water, was used for surface degreasing at 60°C to 70°C, followed by ultrasonic cleaning at 28kHz in anhydrous ethanol for 20 minutes to completely remove surface oil and loose oxide scale.

[0029] To address the world-class industry challenge of coating peeling from the turnout substrate due to massive transient impacts and high-frequency shear stresses on high-speed, heavy-load train wheels, a groundbreaking nanosecond laser-inspired biomimetic textured design was implemented in the substrate surface treatment process. A 1064nm wavelength, ytterbium-doped fiber nanosecond pulse laser with a beam quality factor was used to process the substrate. Instead of conventional full remelting or simple unidirectional scribing, the laser processing employed a micrometer-scale biomimetic staggered mesh structure with critical spacing characteristics.

[0030] The breakthrough changes in process parameters and structure are limited to: an extremely narrow laser pulse width of 80ns to 100ns, a pulse repetition frequency of 50kHz to 80kHz, an average power of 20W to 30W, a focused spot diameter precisely adjusted to 40μm to 50μm, and a laser scanning speed of 500mm / s to 800mm / s. Through high-speed scanning control using a two-dimensional galvanometer, crisscrossing grid-like microgrooves are fabricated on the surface of the turnout substrate. The depth of the microgrooves is strictly controlled within the critical range of 30μm to 45μm, and the spacing between adjacent parallel microgrooves is set to 150μm to 200μm, ensuring that the center of the grid retains a tiny square platform that is not ablated by the laser. Under the transient ablation of the high energy density of the nanosecond pulsed laser, the steel substrate material at the bottom and sidewalls of the microgrooves undergoes rapid melting and vaporization explosion. The molten metal expelled by the vaporization back pressure rapidly cools and solidifies at the edge of the microgrooves, spontaneously forming a nanoscale recast layer with a height of 5μm to 10μm and a mushroom-shaped curled edge morphology. This multi-level rough anchoring surface, composed of macroscopic interlaced mesh grooves and microscopic mushroom-shaped barbs, increases the actual specific surface area of ​​the substrate by more than 3 to 4 times.

[0031] During the subsequent deposition of the underlying powder, the high-speed powder particles not only deeply penetrate the microgrooves to form macroscopic mechanical interlocks, but the molten droplets are also tightly linked by the microscopic barb structure. This changes the traditional two-dimensional planar bonding mode of spray coatings, which relies solely on weak van der Waals forces or limited mechanical interlocking, and constructs a novel composite interface with three-dimensional gripping force. After this process, the bonding strength between the coating and the railway turnout substrate increases exponentially from less than 40 MPa in the traditional method to over 120 MPa, producing an extremely significant and unexpected effect in resisting impact detachment.

[0032] On a rough anchoring surface, a nickel-chromium-aluminum-yttrium base powder is deposited using supersonic flame spraying technology to obtain a base coating substrate with thermal expansion gradient buffering characteristics. In this embodiment, a nickel-chromium-aluminum-yttrium primer powder is deposited on the rough anchoring surface using supersonic flame spraying technology to obtain a substrate with a primer coating that has thermal expansion gradient buffering characteristics, including: Regarding the selection of raw materials and special pretreatment of the deposited base powder, the nickel-chromium-aluminum-yttrium (NiCrAlY) base powder used is not a commercially available conventional powder, but a micro-nano-scale powder that has undergone specific asymmetric plasma etching modification treatment. Pure NiCrAlY powder with an average particle size of 10μm to 20μm was placed in a low-pressure radio frequency plasma reaction chamber, and a mixed etching gas of Freon and oxygen at a volume ratio of 1:5 was introduced. The process was carried out for 10 to 15 minutes at a power of 300W to 400W. The high-energy fluorine radicals and oxygen free radicals in the plasma were used to roughen the powder surface at the nanoscale, removing the natural passivation oxide film on the powder surface and forming a large number of highly active nanoscale pits on the powder surface, greatly improving the heat absorption efficiency and melting uniformity of the powder during flight. In terms of groundbreaking changes to the process parameters of supersonic flame spraying, the conventional, crude approach of relying solely on increasing flame temperature to enhance adhesion has been abandoned. Kerosene is used as fuel, and high-purity oxygen as a combustion aid, but the oxygen-fuel ratio is precisely controlled within an extremely narrow range: the kerosene flow rate is strictly controlled between 22 L / h and 24 L / h, and the oxygen flow rate is set between 850 L / min and 880 L / min. Under this critical oxygen-fuel ratio, the flame in the combustion chamber not only reaches a high temperature of 2800℃ to 3000℃, but more importantly, it forms a unique micro-reducing flame atmosphere. This micro-reducing atmosphere completely overcomes the technical bias of traditional spraying processes where active elements yttrium and aluminum are easily oxidized and burned off, leading to a significant decrease in the coating's resistance to high-temperature oxidation, thus ensuring the complete deposition of alloying elements. In the simplified design integrating spraying dynamics and spraying path, a retractable Laval nozzle is used to supersonic accelerate the airflow. The spraying distance is precisely locked within a narrow range of 180mm to 200mm, and the carrier gas flow rate is set to 18L / min to 20L / min. This allows the modified NiCrAlY powder particles to achieve an unprecedented Mach number of 800m / s to 950m / s before contacting the substrate. The molten and semi-molten powder particles, carrying enormous kinetic energy, impact the rough, anchoring surface with microscopic mushroom-shaped barbs with extremely high impulse. In constructing the interface interlocking and gradient buffering mechanism, due to the extremely high kinetic energy, the molten droplets undergo violent lateral flattening and spreading upon impact. This not only completely fills the microgrooves generated by nanosecond laser processing, avoiding the residue of micropores at the interface, but also, under the obstruction and tearing effect of the micro-barb structure, the droplets and the substrate achieve a composite anchoring of local mechanical interlocking and micro-metallurgical bonding. By controlling the spray gun movement speed and spray passes, a dense base coating with a thickness strictly controlled between 80μm and 120μm is prepared. Perfectly positioned between the railway turnout substrate and the outer high-entropy alloy coating, a smooth transition thermal expansion gradient buffer zone is established, completely blocking the abrupt transmission of internal stress caused by the extremely high temperature gradient to the substrate interface during subsequent laser cladding, resulting in unexpectedly high interfacial shear fatigue life.

[0033] Using wide-beam laser cladding technology, spherical high-entropy alloy composite spray powder is deposited layer by layer on a substrate with a base coating. The deep melting effect is controlled by the laser heat source, so that the powder and the base coating form a metallurgical bond, and the initial cladding coating workpiece is obtained. In this embodiment, wide-beam laser cladding technology is used to deposit spherical high-entropy alloy composite spray powder layer by layer onto a substrate with a base coating. The deep-melting effect is controlled by a laser heat source, enabling the powder and the base coating to form a metallurgical bond, thus obtaining an initial cladding coating workpiece, including: In terms of improving the heat source and innovatively reshaping the beam geometry, the circular beam with Gaussian energy distribution characteristics used in traditional laser cladding has been abandoned. A beam shaping technique based on a microlens array has been introduced to modulate the original beam of the high-power semiconductor laser into a broadband rectangular flat-top beam with dimensions of 12mm × 2mm. The flat-top beam achieves an energy distribution uniformity of over 95% across its entire 12mm width, fundamentally eliminating localized hot spots within the molten pool and realizing a large-area, uniform, co-directional solidification process. In achieving breakthrough control over process parameters and critical energy density, an extremely stringent parameter matching system was established to ensure that the high-entropy alloy coating forms a strong metallurgical bond with the base coating without excessive dilution leading to a decrease in hardness and wear resistance. This system included: laser output power set precisely within the range of 4500W to 4800W; laser scanning speed controlled between 8mm / s and 12mm / s; powder feed rate set between 18g / min and 22g / min; and overlap rate set between 40% and 45%. Through precise parameter coupling, the laser specific energy was strictly limited to a selected critical value between 60J / mm² and 75J / mm². At this energy density, the depth of the molten pool is precisely sufficient to penetrate the newly deposited high-entropy alloy powder, creating a micro-melting zone of 15μm to 25μm thickness only on the underlying NiCrAlY base coating. This precisely controlled deep-melting effect keeps the coating dilution rate firmly within an extremely narrow range of 2% to 5%, ensuring atomic-level metal bonding while completely avoiding the destruction of the high-entropy alloy single-phase solid solution structure by the large-scale floating of iron elements in the matrix. In terms of groundbreaking improvements to molten pool dynamics and protective gas, a coaxial wide-band powder feeding nozzle was adopted, and an innovative argon-nitrogen mixture with a volume ratio of 98:2 was used as both the powder feeding carrier gas and the molten pool protective gas, with a total gas flow rate of 15 L / min to 18 L / min. The introduced trace amounts of highly reactive nitrogen dissociate into nitrogen atoms at the high temperature of the molten pool, dissolving into the liquid metal. This not only plays a role in interstitial solid solution strengthening, but more importantly, the introduction of trace nitrogen significantly alters the surface tension temperature gradient of the molten high-entropy alloy, intervening in and reversing the Marangoni convection direction within the molten pool. The originally strong outward divergent convection from the center to the edge is transformed into a gentle inward converging convection from the edge to the center. This qualitative change in hydrodynamics allows the nano-tungsten carbide hard phase, which would normally sink easily under gravity, to be uniformly suspended and solidified throughout the entire coating thickness range under the support of gentle convection. Regarding the transformation of the solidification and crystallization mechanism, the uniform heat input and subsequent rapid cooling provided by the flat-top wide-beam laser effectively suppressed the precipitation of brittle Laves phase and σ intermetallic compounds in the CoCrFeNi high-entropy alloy. The liquid metal underwent rapid diffusionless solidification, retaining a highly tough single-face-centered cubic solid solution structure. Furthermore, the residual carbon-silicon framework of the silane coupling agent grafted onto the tungsten carbide surface transformed in situ into nanoscale silicon carbide particles at high temperatures, significantly refining the high-entropy alloy grains. Initial cladding coatings with thicknesses ranging from 1.5 mm to 2.0 mm, free of internal cracks and pores, and with a uniformly dispersed distribution of hard phases were obtained.

[0034] The initial cladding coating workpiece is subjected to ultrasonic surface rolling strengthening treatment, which induces severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and introduces a residual compressive stress field with a depth of 0.5mm-1.0mm into the interior, finally obtaining a high wear-resistant railway turnout coating.

[0035] In this embodiment, the initial cladding coating workpiece undergoes ultrasonic surface rolling strengthening treatment to induce severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and a residual compressive stress field with a depth of 0.5mm-1.0mm is introduced into the interior, ultimately producing a high wear-resistant railway turnout coating, including: In the innovative integration of surface strengthening process routes, traditional processes typically employ shot peening or prolonged stress-relief annealing to eliminate the high residual tensile stress caused by laser cladding. However, shot peening tends to increase surface roughness, while annealing can lead to grain coarsening and reduced hardness. Introducing multidimensional ultrasonic surface rolling strengthening technology as the final modification step for the coating integrates surface polishing, stress relief, and nano-modification into a single step, significantly simplifying the post-processing flow. In setting the breakthrough core parameters for ultrasonic rolling, tungsten carbide cemented carbide rollers with a front radius of 3mm to 5mm were used as the execution end. To balance the ultra-high hardness of the high-entropy alloy coating with the extremely complex curved surface profile of railway turnouts, a dual physical field coupling parameter critical model of high-frequency dynamic ultrasonic impact and constant static pressure was constructed: the static pressure load was precisely set between 800N and 1100N, the output frequency of the ultrasonic generator was locked in the resonance range of 28kHz to 32kHz, and the ultrasonic amplitude was extremely precisely controlled within an extremely narrow range of 15μm to 25μm; the rolling feed rate was set to 0.05mm / r to 0.1mm / r, and the rolling linear speed was controlled between 1.5m / min and 2.0m / min. During the processing, a synthetic grease-based micro-lubricating coolant with extreme pressure additives was sprayed simultaneously to eliminate the adverse effects of rolling heat generation on the microstructure. In the in-depth analysis of microstructure evolution and dislocation multiplication, the coating surface underwent severe plastic deformation with extremely high strain rates under the synergistic effect of ultra-high frequency strong impact kinetic energy and high hydrostatic potential energy. According to the mechanism of metal physics, the acoustic softening effect of ultrasound significantly lowers the yield threshold of plastic deformation, resulting in a large number of dislocation sources inside the originally coarse columnar grains on the surface of the high-entropy alloy. With the continuation of ultrasonic impact, the dislocation density increases sharply and they entangle to form high-density dislocation walls, which then evolve into dislocation cells. When the plastic strain accumulates to the critical point, the dislocation cell walls absorb more dislocations and undergo subgrain boundary rotation. Finally, in situ, complete dynamic recrystallization is induced in the coating surface to a depth of about 50 μm to 100 μm from the surface, which completely breaks down the coarse grains and refines them into a dense layer of equiaxed nanocrystalline structure with an average size of 15 nm to 25 nm. This nanocrystalline layer greatly improves the microhardness of the coating surface and reduces the surface roughness Ra from more than 8.0 μm after laser cladding to a mirror level of 0.15 μm to 0.2 μm, significantly reducing the friction coefficient between the turnout and the wheel. In terms of macroscopic stress field reversal and unexpected technical effects, the intense surface plastic deformation not only eliminates the harmful tensile stress introduced by laser thermal cycling, but also generates a huge elastic recovery resistance on the coating surface and transmits it deep into the material matrix. This allows for the successful construction of a gradient-distributed high-amplitude residual compressive stress field within an astonishing depth range of 0.5 mm to 1.0 mm from the coating surface, with the peak value of the maximum residual compressive stress reaching a breakthrough of -600 MPa to -800 MPa. This deep compressive stress field acts like an invisible armor, effectively closing potential microcracks within the coating under the enormous alternating shear stress generated when heavy-load railway trains pass through turnouts, greatly delaying the initiation and propagation of fatigue cracks. This resulted in the preparation of a high-wear-resistant railway turnout coating.

[0036] Example 2: During a certain R&D cycle, the implementation team officially launched the trial production of a full-size high-wear-resistant turnout composite coating. In the initial powder surface modification stage, the online pH meter of the chemical monitoring system issued a slight fluctuation alarm, indicating that the pH of the polar co-solvent system deviated from the preset range. The experimenter immediately intervened, precisely pumping glacial acetic acid into the system using a micro-titration pump to lock the pH value at an extremely narrow critical value of 4.3. Feedback panels from the online viscometer and ultrasonic generator showed that when activated by alternating 20kHz and 40kHz dual-frequency ultrasonic fields, the cavitation noise in the reactor reached its peak decibel level, and the local pressure sensor recorded microsecond-level extreme high-pressure pulses. After two hours of reaction, a contact angle meter performed a water droplet test on the dried sample. The optical angle measurement system captured that the contact angle of the untreated nano-tungsten carbide water droplet was as high as 115°, while after chemical bonding with the coupling agent, the automatically calculated contact angle on the screen dropped sharply to 34.2°. The system automatically generated a quality inspection report confirming that the powder surface activation met the standards.

[0037] With this activated and modified reinforcing phase, the team moved to the mechanical alloying workshop. A sensor network meticulously recorded every change in the high-energy ball mill's state. After the cryogenic intensification stage began, the liquid nitrogen flow meter was fully open, and the jacket temperature sensor data plummeted within 15 minutes, stabilizing at -92°C. At this point, a significant step change appeared in the load torque feedback from the spindle motor, indicating that the high-entropy alloy powder had become embrittled at extremely low temperatures and was forcefully crushed by the grinding balls. After 5 hours of cryogenic ball milling, the operator shut off the liquid nitrogen, and an infrared thermometer recorded that the tank temperature slowly rose to 22°C during natural rewarming. In the final high-energy bonding stage, the tachometer reading soared to 480 rpm. After discharge, the report issued by the oxygen, nitrogen and hydrogen analyzer showed that, thanks to the protection of transient volatile grinding aids and high-purity argon, the oxygen content of the powder was extremely suppressed to 0.03 wt%. The X-ray diffraction analysis software automatically calculated, according to the Scherrer formula, that the average grain size of the high-entropy alloy had been refined to 28 nanometers, and the nano-hard phase had been completely embedded in the metal lattice.

[0038] Irregularly shaped pre-alloyed powder was fed into the plasma reshaping station. On the control panel, the operator closely monitored the flow meter of the ternary mixed gas: argon was maintained at 65 L / min, hydrogen at 4.0 L / min, and helium, which plays a crucial role in heat conduction, was set at 1.2 L / min. The plasma generator power meter remained stable at 16.5 kW. A high-speed camera, under a strong light-blocking filter, captured the moment the powder flew across the center of a thermal field reaching tens of thousands of degrees Celsius; the microsecond-level flash proved that surface melting occurred. At the collection end, the operator poured the product into a funnel of a standard Hall flow meter for physical calibration. A stopwatch recorded the time for 50 grams of powder to completely flow out at 13.8 seconds, far superior to the more than 40 seconds required for traditional powders. The three-dimensional morphology analysis algorithm obtained from scanning electron microscopy showed that the powder sphericity reached 98.5%, and the system determined that the batch of sprayed powder had excellent flowability, meeting the requirements of the next process.

[0039] In the substrate pretreatment area, a high-manganese steel turnout specimen was placed on a three-dimensional moving platform. On the monitoring interface of the laser control system, the parameters of the nanosecond pulse laser were set to a pulse width of 90 ns and a frequency of 65 kHz. A continuous blue-white plasma plume erupted inside the protective chamber, and a laser rangefinder and confocal microscope performed a real-time three-dimensional morphological scan of the area that had just been scanned. The data analysis module of the morphological cloud map popped up a green pass indicator: the average depth of the microgrooves was 38 micrometers, the adjacent spacing was 180 micrometers, and at the edge of the grooves, the system identified a recast layer protrusion with a height of approximately 6.5 micrometers. This three-dimensional barbed structure at the microscopic level provides a perfect geometric basis for subsequent mechanical anchoring.

[0040] The substrate with barbed structure was transferred to the thermal spraying chamber. The screen of the supersonic flame spraying control cabinet continuously displayed the combustion chamber pressure and flow parameters: kerosene flow rate remained stable at 23 L / h, and oxygen flow rate at 865 L / min. The optical particle velocimeter transmitted exciting telemetry data: accelerated by the micro-reducing flame, the primer powder particles, after plasma etching to remove the oxide film, achieved a flight speed exceeding 880 m / s, and the particle surface temperature reached a molten state of 2910℃. After spraying, an ultrasonic thickness gauge performed multi-point array sampling at different coordinate points on the substrate, reporting an average thickness of 95 micrometers.

[0041] In the core laser cladding stage, all focus was on the real-time monitoring of the molten pool dynamics. A beam quality analyzer confirmed that the laser output was a 12mm × 2mm rectangular flat-topped spot with 95.5% energy uniformity. When 4650W of laser power was applied to the coating, a coaxial gas supply system injected an argon-nitrogen mixture at a ratio of 98:2. In the pseudo-color molten pool dynamic video transmitted from a high-speed infrared thermal imager mounted on the side of the nozzle, the operator observed a crucial hydrodynamic reversal phenomenon: the red, high-temperature flow that would have rolled outwards due to the temperature gradient in traditional processes clearly exhibited a convection pattern converging towards the center of the molten pool under the intervention of trace amounts of nitrogen atoms. After cladding, wire-cut cross-section analysis of the specimen was performed. Metallurgical microscopy combined with energy dispersive spectroscopy showed that the tungsten element distribution pattern exhibited uniform, dense bright spots throughout the entire coating thickness, completely eliminating bottom settling. Through a dilution rate calculation model, the upward flotation of iron elements in the matrix was strictly limited to an extremely low level of 3.2%.

[0042] In the final stage of construction, the specimen was clamped in a large ultrasonic surface rolling CNC machine. A pressure sensor provided real-time feedback that the constant static pressure applied by the rollers was 950 N, and the ultrasonic generator frequency was locked at 30 kHz. As the rollers advanced, the real-time reading of the online surface roughness meter mounted beside the tool holder experienced a precipitous drop, decreasing from an initial Ra of 8.5 micrometers and stabilizing at Ra 0.18 micrometers, causing the coating surface to instantly exhibit a mirror-like reflective finish. After removal from the machine, the operator used an X-ray residual stress diffractometer to perform deep delamination non-destructive testing on the coating. The stress-depth distribution curve on the computer screen showed that the +400 MPa tensile stress originally left by the laser cladding was not only completely smoothed out, but the system also detected a compressive stress valley with a peak value of -710 MPa at a depth of 0.6 mm from the surface. Simultaneously, the nanoindentation test report indicated that the surface microhardness reached 845 HV. Based on comprehensive remote sensing data and test reports, the system finally generated an overall evaluation conclusion: the high wear-resistant railway turnout coating has broken through the physical limits of existing processes in terms of microstructure dispersion, macroscopic interface bonding force, and fatigue stress field distribution, completely eliminating the hidden dangers of easy brittle peeling and excessive wear of the coating in the existing technology.

[0043] The above description is only 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 method for preparing a high wear-resistant railway turnout coating, characterized in that, The preparation method includes: Nano-tungsten carbide particles and silane coupling agent were ultrasonically dispersed and cross-linked in anhydrous ethanol solvent, and then dried to form a surface-grafted modified nano-tungsten carbide reinforced phase. The surface-grafted modified nano-tungsten carbide reinforcing phase was mixed with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio and placed in a high-energy ball mill for mechanical alloying under inert gas protection to obtain nano-composite pre-alloyed powder. Radio frequency plasma spheroidization treatment was performed on the nanocomposite pre-alloyed powder to eliminate internal pores and promote surface melting and densification, resulting in a spherical high-entropy alloy composite spray powder with high fluidity. The surface of the railway turnout substrate is subjected to surface degreasing, ultrasonic cleaning and nanosecond laser microtexturing treatment in sequence to construct a rough anchoring surface with a micron-level interlaced grid structure on the substrate surface; On a rough anchoring surface, a nickel-chromium-aluminum-yttrium base powder is deposited using supersonic flame spraying technology to obtain a base coating substrate with thermal expansion gradient buffering characteristics. Using wide-beam laser cladding technology, spherical high-entropy alloy composite spray powder is deposited layer by layer on the substrate with the base coating. The deep melting effect is controlled by the laser heat source, so that the powder and the base coating form a metallurgical bond to obtain the initial cladding coating workpiece. The initial cladding coating workpiece is subjected to ultrasonic surface rolling strengthening treatment, which induces severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and introduces a residual compressive stress field with a depth of 0.5mm-1.0mm into the interior, finally obtaining a high wear-resistant railway turnout coating.

2. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process of ultrasonically dispersing and crosslinking tungsten carbide nanoparticles with a silane coupling agent in anhydrous ethanol solvent, followed by drying to form a surface-grafted modified tungsten carbide nanoparticle reinforced phase, includes: Deionized water and anhydrous ethanol were mixed and the pH value was adjusted. A silane coupling agent containing epoxy and amino groups was added for hydrolysis to form a two-component synergistic hydrolysis precursor solution. Surface-activated tungsten carbide nanoparticles were obtained by in-situ polar excitation treatment of the surface of tungsten carbide nanoparticles using hydrogen peroxide aqueous solution. Surface-activated nano-tungsten carbide was added to the two-component synergistic hydrolysis precursor solution, and ultrasonic dispersion and in-situ ring-opening crosslinking reaction were performed under a dual-frequency alternating ultrasonic field to form an organic-inorganic hybrid coated precursor. The organic-inorganic hybrid coating precursor was subjected to freeze-drying to obtain a surface-grafted modified nano-tungsten carbide reinforced phase.

3. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process involves mixing surface-grafted modified nano-tungsten carbide reinforcing phase with cobalt-chromium-iron-nickel high-entropy alloy powder at a preset mass ratio, and then subjecting the mixture to mechanical alloying treatment under inert gas protection in a high-energy ball mill to obtain nano-composite pre-alloyed powder, comprising: Cobalt-chromium-iron-nickel high-entropy alloy powder, the surface-grafted modified nano-tungsten carbide reinforcing phase, and transient volatile grinding aid are mixed and loaded into a high-energy ball mill to form a mixed grinding system. Under inert gas protection, the mixed grinding system is subjected to cryogenic ball milling by liquid nitrogen cooling to obtain a pre-ground powder that undergoes low-temperature embrittlement and grain refinement. Stop cooling and allow the system to naturally warm up. Perform a mild diffusion ball milling process on the initial milled powder to allow the tungsten carbide core to diffuse along the grain boundaries in a short distance, and obtain intermediate diffusion powder. Increasing the ball mill speed and performing high-energy intercalation ball milling on the intermediate-state diffused powder forces the nano-hard phase into the high-entropy alloy matrix, resulting in a highly dense nano-composite pre-alloyed powder.

4. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The radio frequency plasma spheroidization treatment performed on the nanocomposite pre-alloyed powder eliminates internal pores and promotes surface melting and densification to obtain a highly fluid spherical high-entropy alloy composite spraying powder, comprising: A plasma high-temperature thermal field with a wide and gentle stepped enthalpy distribution was constructed by using a mixed gas supply mode of argon, hydrogen and helium. Nanocomposite pre-alloyed powder is injected at a constant rate into a plasma high-temperature thermal field for transient surface melting, causing it to condense and expel internal pores under the action of surface tension, forming molten spherical droplets; The molten spherical droplets were subjected to extreme rapid cooling using a forced supersonic cryogenic argon jet to suppress grain growth, ultimately resulting in a highly fluid spherical high-entropy alloy composite spray powder.

5. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process of sequentially performing surface degreasing, ultrasonic cleaning, and nanosecond laser microtexturing on the surface of the railway turnout substrate to construct a rough anchoring surface with a micron-level interlaced grid structure includes: A biodegradable water-based cleaning agent was used to perform surface degreasing treatment on the railway turnout substrate to obtain a degreased substrate. The degreased substrate was placed in anhydrous ethanol and subjected to high-frequency ultrasonic cleaning to obtain a clean turnout substrate. A nanosecond pulsed laser was used to perform a biomimetic textured two-dimensional scanning on the clean turnout substrate, ablation to form micron-level interlaced grid grooves; By utilizing the vaporization and recoil effect during the transient laser ablation process, a mushroom-shaped recast layer is generated in situ at the edge of the micron-level interlaced grid groove, thus constructing a rough anchoring surface with a micron-level interlaced grid structure on the substrate surface.

6. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process involves depositing nickel-chromium-aluminum-yttrium primer powder on a rough anchoring surface using supersonic flame spraying technology to obtain a primer-coated substrate with thermal expansion gradient buffering characteristics, including: Low-pressure radio frequency plasma etching modification treatment was performed on nickel-chromium-aluminum-yttrium base powder using a fluorine-oxygen mixed gas to obtain a modified base powder with highly active nanoscale pits on the surface. By adjusting the spraying oxygen-fuel ratio parameters and accelerating with a retractable Laval nozzle, a supersonic flame stream with a slightly reducing atmosphere is constructed. The modified primer powder is melted and accelerated by a micro-reducible supersonic flame, causing it to impact the rough anchoring surface at high speed for flattening, spreading and composite mechanical interlocking, thus depositing a substrate with a primer coating that has thermal expansion gradient buffering characteristics.

7. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process utilizes wide-beam laser cladding technology to deposit spherical high-entropy alloy composite spray powder layer by layer onto the substrate with a base coating. By controlling the deep-melting effect through a laser heat source, the powder and the base coating form a metallurgical bond, resulting in an initial cladding coating workpiece. This includes: Microlens array technology is used to shape the laser heat source beam to obtain a broadband rectangular flat-top beam with uniform energy distribution. Using a broadband rectangular flat-top beam, the spherical high-entropy alloy composite spray powder is melted onto the substrate with a base coating under controlled specific energy to form a liquid molten pool with controlled dilution rate; A mixed protective gas containing highly active nitrogen atoms is continuously introduced into the liquid molten pool to interfere with and reverse the Marangoni convection direction inside the molten pool, so that the tungsten carbide hard phase is uniformly suspended and completes diffusionless solidification, thus obtaining the initial cladding coating workpiece.

8. The method for preparing a high wear-resistant railway turnout coating according to claim 1, characterized in that, The process involves performing ultrasonic surface rolling strengthening treatment on the initial cladding coating workpiece to induce severe plastic deformation of the coating surface to form a dense nanocrystalline layer, and introducing a residual compressive stress field with a depth of 0.5mm-1.0mm into the interior, ultimately producing a high wear-resistant railway turnout coating, comprising: Under the dual physical field coupling of static pressure load and high-frequency dynamic ultrasonic impact, the surface of the initial cladding coating workpiece is subjected to ultrasonic surface rolling strengthening treatment, which induces severe plastic deformation of the surface and generates high-density dislocation cells. Through the subgrain boundary rotation and dynamic recrystallization mechanism of high-density dislocation cells, a dense equiaxed nanocrystalline structure with extremely low surface roughness is generated in situ on the coating surface. By utilizing the elastic recovery resistance transmitted from the surface plastic deformation to the interior of the matrix, a deep residual compressive stress field with a gradient distribution is constructed beneath the dense nanocrystalline layer, ultimately resulting in a high wear-resistant railway turnout coating.

9. A high wear-resistant railway turnout coating, characterized in that, The high wear-resistant railway turnout coating has a multi-level gradient composite structure from the substrate to the surface.

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