Process for producing high-performance coating on surface of alloy structural steel by adopting plasma cladding technology

Abstract

The invention discloses a process for producing a high-performance coating on the surface of alloy structural steel by adopting a plasma cladding technology, and belongs to the technical field of material surface modification. The process comprises six steps of matrix pretreatment, powder preparation and pretreatment, preparation of a preset layer, plasma cladding, primary treatment after cladding and heat treatment after cladding. A high-performance coating is formed on the surface of the alloy structural steel by optimizing an alloy powder formula, innovatively adopting an environment-friendly non-toxic dispersing agent for ball milling of metal powder and combining accurately controlled plasma cladding process parameters and a multi-stage heat treatment process. The coating has excellent wear resistance, corrosion resistance and bonding strength, is good in process environmental protection property, is suitable for being made into an integral wear-resistant plate, can also be made into a prefabricated plate piece in a special shape and the like, and has important industrial application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material surface modification, and particularly relates to a process for producing a high-performance coating on the surface of an alloy structural steel by using plasma cladding technology. More specifically, the present application relates to a method for preparing a high-performance coating with excellent wear resistance and corrosion resistance on the surface of an alloy structural steel by optimizing the alloy powder formulation, innovating the dispersant technology, and precisely controlling the plasma cladding process parameters, which is suitable for being made into a whole wear-resistant plate, or a specially-shaped prefabricated plate piece, etc., and has important industrial application value. BACKGROUND

[0002] In industrial production, many mechanical equipment parts are subjected to harsh working conditions such as wear and corrosion for a long time, resulting in shortened equipment life and increased maintenance costs. According to statistics, the economic loss caused by wear in the industrial field accounts for 3%-5% of the gross national product. Therefore, improving the wear resistance, corrosion resistance and other properties of the material surface is of great significance for prolonging the service life of equipment and reducing production costs.

[0003] Surface coating technology is an effective means to improve the performance of the material surface. Among them, the plasma cladding technology has been widely used in surface modification due to its high cladding efficiency, high bonding strength of the coating and substrate, wide range of applicable materials, etc. Plasma cladding technology uses plasma arc as a heat source to melt alloy powder and form a metallurgical bonding coating on the surface of the substrate, thereby significantly improving the wear resistance, corrosion resistance and other properties of the substrate surface.

[0004] Alloy structural steel has high strength and weldability to ensure the structural strength of the component and subsequent assembly and maintenance, but it cannot be used as a wear-resistant material. In actual application, the working conditions are complex and diverse. When subjected to medium-low impact load or dominated by abrasive wear, the work hardening of the alloy structural steel surface is difficult to fully achieve, and the wear rate is greatly increased, with a service life of only 1 / 3-1 / 2 of that under high impact conditions. At the same time, in the complex use occasions where both wear resistance and impact resistance are required, and the base material needs to have high strength, high toughness and weldability, a single alloy structural steel cannot meet the demand, and surface coating technology becomes a key means to break through the performance bottleneck.

[0005] Currently, the alloy powder used for plasma cladding mainly includes iron-based, nickel-based, cobalt-based and other systems. Iron-based alloy powder has low cost and good compatibility with alloy structural steel, etc., and occupies an important position in industrial applications. However, the traditional iron-based alloy coating still has room for improvement in terms of hardness and wear resistance.

[0006] In the preparation of alloy powders, ball milling is a crucial step in ensuring uniform powder mixing. Traditional ball milling processes often use mineral oils and synthetic oils as dispersants. These dispersants are not only environmentally unfriendly but may also introduce impurities during subsequent cladding processes, affecting coating quality. Therefore, developing novel, environmentally friendly, non-toxic dispersants with excellent dispersion effects has become a research hotspot in this field.

[0007] Furthermore, plasma cladding process parameters (such as cladding current, scanning speed, and gas flow rate) have a significant impact on coating quality. Inappropriate parameter selection can lead to defects such as porosity, cracks, and poor adhesion, severely affecting coating performance. Therefore, optimizing plasma cladding process parameters is crucial for obtaining high-performance coatings.

[0008] The heat treatment process after cladding is also an important factor affecting coating performance. Appropriate heat treatment can eliminate internal stress in the coating, adjust its microstructure, and thus improve its mechanical properties such as hardness and toughness. However, current research on heat treatment processes for plasma-clad iron-based coatings is insufficient, and systematic optimization of process parameters is lacking.

[0009] In summary, although plasma cladding technology has made some progress in the surface modification of alloy structural steel, the following problems still exist:

[0010] 1. Existing alloy powder formulations are not well-designed and cannot balance the hardness and toughness of the coating, resulting in a limited service life of the coating under complex wear conditions.

[0011] 2. Traditional ball milling dispersants have poor environmental performance and unsatisfactory dispersion effect, which affects the uniformity of powder mixing and the quality of subsequent coatings.

[0012] 3. The lack of systematic optimization of plasma cladding process parameters can easily lead to coating defects.

[0013] 4. The heat treatment process after cladding is not perfect, and the performance potential of the coating is not fully utilized.

[0014] 5. The bonding strength between the coating and the substrate needs to be improved, and it is prone to peeling under impact loads.

[0015] 6. The coating has insufficient corrosion resistance and a short service life in humid or corrosive environments.

[0016] To address the aforementioned issues, this invention proposes a process for producing high-performance coatings on the surface of alloy structural steel using plasma cladding technology. By optimizing the alloy powder formulation, developing novel environmentally friendly dispersants, precisely controlling the cladding process parameters, and optimizing the heat treatment process, the overall performance of the coating is significantly improved, meeting the industrial demand for high-performance wear-resistant coatings. Summary of the Invention

[0017] This invention aims to solve the following problems existing in the prior art:

[0018] 1. Existing plasma cladding coatings cannot simultaneously achieve wear resistance, corrosion resistance, and toughness, resulting in a short service life under complex working conditions.

[0019] 2. Traditional dispersants used in ball milling of metal powders have poor environmental performance and limited dispersion effect, which affects powder quality and coating performance.

[0020] 3. Inappropriate design of plasma cladding process parameters can lead to defects such as pores and cracks in the coating, resulting in low bonding strength.

[0021] 4. The heat treatment process after cladding is imperfect, failing to effectively eliminate internal stress and optimize the coating structure, thus limiting the coating performance.

[0022] 5. The substrate pretreatment method is not refined enough, which affects the bonding quality between the coating and the substrate.

[0023] 6. An unreasonable powder pretreatment process leads to poor powder flowability, affecting the stability of the cladding process and the uniformity of the coating quality.

[0024] This invention provides a novel plasma cladding process, including optimized substrate pretreatment, innovative powder formulation and pretreatment, precise control of plasma cladding parameters, and multi-stage heat treatment process, aiming to solve the above-mentioned technical problems and obtain a surface coating with excellent comprehensive performance.

[0025] To achieve the above objectives, the present invention provides a process for producing high-performance coatings on the surface of alloy structural steel using plasma cladding technology, comprising the following steps:

[0026] S1: Substrate pretreatment; The oxide layer on the surface of the alloy structural steel substrate is polished with an 80-120 grit abrasive wheel, then ultrasonically cleaned with an alcohol-acetone mixture at 300-400W for 15-20 minutes to remove oil stains. The substrate is then immersed in a 5%-8% hydrochloric acid solution and pickled at 25-35℃ for 10-15 minutes to remove the surface oxide scale. After rinsing with deionized water until pH=7, the substrate is dried. Finally, the substrate is placed in an electric resistance furnace for preheating at 200-300℃ for 30-45 minutes. The alloy structural steel substrate material is selected from 20CrMo or 40CrMo plates. The plate thickness is determined according to the working conditions. When used as a whole, the thickness is more than 50mm. When used as a precast panel, the thickness is 20-40mm.

[0027] S2: Powder preparation and pretreatment; Weigh the raw materials by mass percentage: C 0.08%-0.12%, Ni 20.5%-22.0%, Co 6.0%-7.5%, Mo 2.8%-3.5%, Si 1.2%-1.8%, Mn 0.3%-0.6%, Ti 1.0%-1.5%, Al 0.3%-0.5%, V 0.4%-0.7%, Nb 0.2%-0.4%, Zr 0.15%-0.3%, Y 0.05%-0.10%, La 0.03%-0.06%, B 0.08%-0.15%, W 1.5%-2.2%, Cu 0.8%-1.2%, Ce 0.02%-0.04%, P≤0.008%, S≤0.008%, balance Fe; Add the raw material to a planetary ball mill, using an environmentally friendly and non-toxic metal powder ball milling dispersant, with a ball-to-material ratio of 6:1 and a speed of 200-250 r / min, mix for 2-3 hours, pass through a 180-300 mesh sieve, spread the powder evenly and place it in a vacuum drying oven, evacuate to a vacuum degree ≤5Pa, keep at 80-105℃ for 2-3 hours, then immerse the dried powder in a 0.5%-1.0% silane coupling agent KH-550 solution, soak at 25℃ for 5-8 minutes, remove and dry at 60-80℃ for 1-1.5 hours;

[0028] S3: Pre-layer preparation; The powder treated by S2 is evenly spread on the surface of the alloy structural steel substrate pretreated by S1. The thickness of the pre-layer is controlled by a scraper to be 1.5-2.5mm. The ambient humidity is controlled at 40%-60% during the pre-laying process to avoid the powder absorbing moisture.

[0029] S4: Plasma cladding; The substrate with the pre-formed layer is loaded into the plasma cladding equipment, with a rated power of 22-25KW and a rated cladding current of 230-250A; Argon gas is introduced simultaneously for protection during cladding, and the process parameters are: cladding current 170-190A, nozzle height 15-18mm, powder feeding speed 230-260g / min, powder feeding gas flow rate 7-9L / min, large ion gas flow rate 7-9L / min, small ion gas flow rate 2-3L / min, and scanning rate 190-210mm / min. After cladding, the substrate is naturally cooled to room temperature to obtain the initial coating.

[0030] S5: Preliminary treatment after cladding; The sample obtained in S4 is placed in a muffle furnace for stress-relief annealing, with a heating rate of 5-8℃ / min, a temperature of 350-400℃, and a holding time of 2-3h, followed by furnace cooling to room temperature; Then, the coating surface is polished with 400-600 grit sandpaper to remove oxide scale and minor defects.

[0031] S6: Heat treatment after cladding.

[0032] Preferably, the purity requirements of the raw materials in step S2 are: Ni≥99.9%, Co≥99.8%, Mo≥99.5%, Si≥99.7%, Ti≥99.6%, Al≥99.9%, Nb≥99.5%, Fe≥99.9%.

[0033] Preferably, the environmentally friendly and non-toxic dispersant for ball milling metal powder in step S2 comprises the following raw materials in the following mass percentages: polyethylene glycol 400 15-25%, tea saponin 8-12%, L-glutamic acid 5-8%, citric acid 3-5%, xanthan gum 2-4%, hydrophilic nano silica 1-3%, Tween 80 5-10%, and the balance being deionized water.

[0034] Preferably, the environmentally friendly and non-toxic dispersant for ball milling metal powder comprises the following raw materials in the following mass percentages: polyethylene glycol 400 21%, tea saponin 10%, L-glutamic acid 6.5%, citric acid 4%, xanthan gum 3%, hydrophilic nano silica 2%, Tween 80 7.6%, and the balance being deionized water.

[0035] Preferably, the preparation method of the environmentally friendly and non-toxic dispersant for ball milling metal powder includes the following steps:

[0036] (1) Preparation of pre-dissolved co-dispersed phase: Add the prescribed amount of Tween 80 and xanthan gum to the reactor, heat to 45-50℃ at 300-500 rpm and stir for 20-30 min until the xanthan gum is completely dissolved;

[0037] (2) Dissolution of the main dispersed phase: Add the amount of deionized water specified in the formula to another reactor, heat to 50-60℃, slowly add PEG400, and stir at 200-300 rpm for 15-20 min;

[0038] (3) Preparation of functional additive phase: Cool the main dispersed phase to 40-45℃, and add citric acid, L-glutamic acid and tea saponin in sequence. Stir for 10-15 min after each addition, and control the temperature at 40-45℃ and the pH value at 5.5-6.5.

[0039] (4) Dispersion of nano-additives: Add the amount of hydrophilic nano-silica to the functional additive phase, turn off the stirring, turn on the ultrasonic disperser, and sonicate at 300-500W power for 15-20 minutes, controlling the temperature at 40-45℃.

[0040] (5) Composite maturation: After ultrasonication, turn on the stirring to 200-300 rpm, slowly pump the pre-dissolved co-dispersed phase into the reactor, stir for 30-45 min, and the maturation temperature is 40-45℃;

[0041] (6) Cooling and filtration: Stop heating and allow it to cool naturally to 25-30℃. Filter the solution using a 0.22μm microporous membrane at a pressure of 0.1-0.15MPa.

[0042] Preferably, the pre-layer laying in step S3 is carried out using an automated powder spreading device, with the powder spreading accuracy controlled within ±0.1mm.

[0043] Preferably, during the cladding process in step S4, an infrared thermometer is used to monitor the substrate temperature in real time to ensure that the substrate temperature does not exceed 350°C.

[0044] Preferably, the tungsten electrode diameter of the plasma cladding equipment in step S4 is 3-5 mm, the nozzle orifice diameter is 6-8 mm, and the argon purity is ≥99.99%.

[0045] Preferably, the heating rate of the stress-relief annealing in step S5 is 6°C / min, and the holding time is 2.5h.

[0046] Preferably, in step S6, (1) when 20CrMo plate is selected as the alloy structural steel matrix material, the heat treatment is as follows:

[0047] ①Solution: Heat the carbon tube furnace at a rate of 4-8℃ / min to 862-870℃, hold for 1-1.5 hours, cool in oil to below 100℃, and then remove and cool to room temperature.

[0048] ②Aging: The contents are fed into the muffle furnace at the specified temperature and held at 530-550℃ for 4-5 hours, then cooled with oil.

[0049] ③ Low-temperature tempering: Heat the muffle furnace to 150-200℃, hold for 1-1.5 hours, and then air cool;

[0050] (2) When 40CrMo plate is selected as the base material of the alloy structural steel, the heat treatment is as follows:

[0051] ①Solution: Heat the carbon tube furnace at a rate of 5-7℃ / min to 850-870℃, hold for 1-1.6 hours, cool in oil to below 100℃, and then remove and cool to room temperature.

[0052] ②Aging: The contents are fed into the muffle furnace at the specified temperature and held at 532-548℃ for 4-5 hours, then cooled with oil.

[0053] ③ Low-temperature tempering: Heat the muffle furnace to 210-480℃, hold for 0.6-1h, and then air cool.

[0054] Technical principle of the invention:

[0055] 1. Composition Design Principles of High-Performance Coatings

[0056] The alloy powder formulation of this invention is optimized based on in-depth research into the role mechanism of each element in the coating. The main roles of each element are as follows:

[0057] (1) C: As an interstitial element, carbon mainly plays a reinforcing role in coatings. An appropriate amount of carbon (0.08%-0.12%) can form carbides with elements such as Fe, Cr, Mo, W, V, and Nb, significantly improving the hardness and wear resistance of the coating. If the carbon content is too low, the number of carbides formed will be insufficient, and the reinforcing effect will not be obvious; if the carbon content is too high, it will lead to coarse carbides, reducing the toughness and crack resistance of the coating.

[0058] (2) Ni: Nickel is an important austenite-forming element, mainly playing a role in stabilizing the austenite structure and improving the toughness of the coating. The 20.5%-22.0% Ni content in this invention can ensure the formation of a stable austenite matrix in the coating, while improving the corrosion resistance and oxidation resistance of the coating. Nickel can also improve the solubility of other alloying elements in the iron matrix and promote the uniform distribution of alloying elements.

[0059] (3) Co: Cobalt can significantly improve the high-temperature strength and wear resistance of the coating, while also improving its thermal stability. A Co content of 6.0%-7.5% can work synergistically with Ni to further improve the stability of austenite and enhance the coating's resistance to thermal fatigue. Cobalt can also promote the uniform distribution of carbides and prevent the formation of coarse carbides.

[0060] (4) Mo: Molybdenum is a strong carbide-forming element that can form fine and dispersed Mo2C and other carbides with carbon, significantly improving the hardness and wear resistance of the coating. A Mo content of 2.8%-3.5% can ensure that the coating has high hardness without reducing its toughness. Molybdenum can also improve the corrosion resistance and high-temperature strength of the coating.

[0061] (5) Si: Silicon mainly plays a role in deoxidation and solid solution strengthening. A Si content of 1.2%-1.8% can effectively reduce the oxygen content of the coating and reduce the formation of defects such as pores. Silicon can also improve the fluidity and formability of the coating, and at the same time improve the strength of the coating through solid solution strengthening.

[0062] (6) Mn: Manganese is an austenite forming element, and also a good deoxidizer and desulfurizer. A Mn content of 0.3%-0.6% can help Ni stabilize the austenite structure, remove oxygen and sulfur from the coating, reduce the formation of inclusions, and improve the purity of the coating.

[0063] (7) Ti: Titanium is a strong carbide and nitride forming element, which can form fine TiC and TiN particles, playing a role in dispersion strengthening. A Ti content of 1.0%-1.5% can significantly improve the hardness and wear resistance of the coating, while refining the grains and improving the toughness of the coating. Titanium can also improve the high-temperature stability of the coating.

[0064] (8) Al: Aluminum mainly plays a role in deoxidation and improving oxidation resistance. An Al content of 0.3%-0.5% can effectively reduce the oxygen content in the coating, form a dense oxide film, and improve the oxidation resistance of the coating. Aluminum can also form intermetallic compounds with other elements, further strengthening the coating.

[0065] (9) V: Vanadium can form very hard VC carbides, which significantly improves the wear resistance of the coating. A V content of 0.4%-0.7% can form an appropriate amount of VC particles, which are evenly distributed in the matrix and play a role in dispersion strengthening. Vanadium can also refine the grains and improve the toughness of the coating.

[0066] (10) Nb: Niobium has a strong affinity for carbon and can form stable NbC carbides, which improve the high-temperature hardness and wear resistance of the coating. A Nb content of 0.2%-0.4% can effectively prevent grain growth, refine the coating structure, and improve the strength and toughness of the coating.

[0067] (11) Zr: Zirconium can form high-hardness ZrC carbides and at the same time refine the grains. A Zr content of 0.15%-0.3% can improve the hardness and wear resistance of the coating, and improve the toughness and crack resistance of the coating. Zirconium can also improve the high-temperature strength and oxidation resistance of the coating.

[0068] (12) Y, La, Ce: These rare earth elements mainly play a role in purifying the coating, refining the grains, and improving the morphology of inclusions. Appropriate amounts of rare earth elements (total content 0.1%-0.2%) can significantly improve the toughness and crack resistance of the coating and improve the bonding strength between the coating and the substrate. Rare earth elements can also improve the oxidation resistance and corrosion resistance of the coating.

[0069] (13) B: Boron can lower the melting point of the coating, improve the fluidity of the coating, and promote the metallurgical bonding between the coating and the substrate. A B content of 0.08%-0.15% can reduce porosity and cracks in the coating and improve the density of the coating. Boron can also form intermetallic compounds with other elements to increase the hardness of the coating.

[0070] (14) W: Tungsten can form high-hardness WC carbides, which significantly improves the wear resistance of the coating. A W content of 1.5%-2.2% can work synergistically with Mo to further improve the hardness and high-temperature wear resistance of the coating. Tungsten can also improve the red hardness of the coating, so that it can maintain a high hardness at high temperatures.

[0071] (15) Cu: Copper mainly plays a role in improving the corrosion resistance of the coating. A Cu content of 0.8%-1.2% can form a passivation film on the coating surface, improving the corrosion resistance of the coating, especially in acidic environments. Copper can also improve the machinability of the coating.

[0072] (16) P and S: These two elements are harmful impurities in the coating, which will reduce the toughness and crack resistance of the coating. Therefore, their content needs to be strictly controlled (P≤0.008%, S≤0.008%).

[0073] The synergistic effect between the elements is the key to the excellent performance of the coating of this invention:

[0074] Ni and Co work together to stabilize the austenitic microstructure, providing a good toughness foundation for the coating;

[0075] Mo, W, V, Nb, Ti, Zr and other strong carbide-forming elements work synergistically to form various types of carbides. While ensuring high hardness, the dispersed distribution of carbides avoids the decrease in toughness caused by a single carbide.

[0076] Si, Al, Mn and other elements work together to deoxidize and desulfurize, improving the purity of the coating;

[0077] Rare earth elements (Y, La, Ce) work synergistically with other elements to purify grain boundaries, refine grains, improve inclusion morphology, and significantly enhance the overall performance of the coating.

[0078] Element B improves coating fluidity and promotes metallurgical bonding with the substrate. It also forms intermetallic compounds with other elements, further increasing the coating hardness.

[0079] Cu element improves the corrosion resistance of the coating and works synergistically with other elements to enable the coating to maintain good performance in complex environments.

[0080] 2. Working principle of environmentally friendly and non-toxic dispersants for ball milling metal powders

[0081] The environmentally friendly and non-toxic dispersant for ball milling metal powder of this invention is formulated with seven food-grade / cosmetic-grade raw materials, constructing a five-fold synergistic mechanism of "surface adsorption - charge stabilization - steric hindrance - complexation regulation - viscosity adaptation". The functions of each raw material are as follows:

[0082] (1) Polyethylene glycol 400 (PEG400): As the main dispersant, the hydroxyl groups in the PEG400 molecule can form hydrogen bonds with the surface of metal powder, forming an adsorption layer on the surface of powder particles through surface adsorption. At the same time, the long PEG400 molecular chain can form effective steric hindrance between particles, preventing particle agglomeration, and is the core component for achieving steric hindrance stability. A dosage of 15-25% can ensure the formation of a complete adsorption layer on the powder surface, providing sufficient steric hindrance.

[0083] (2) Tea saponin: As a natural surfactant, tea saponin has good surface activity, which can significantly reduce the solid-liquid interfacial tension and promote the adsorption of dispersant on the surface of metal powder. An amount of 8-12% can effectively reduce the surface tension of the system and enhance the affinity between the dispersant and the powder surface. At the same time, the hydrophobic groups in its molecular structure can work synergistically with PEG400 to improve the steric hindrance effect.

[0084] (3) L-Glutamic Acid: As a charge regulator, L-glutamic acid ionizes in aqueous solution to generate charge, which changes the surface potential of metal powder through adsorption. A dosage of 5-8% can form a stable charge layer on the powder surface, preventing particle agglomeration through the repulsion between like charges, thus achieving a charge stabilization mechanism. L-glutamic acid can also form weak complexes with metal ions, further enhancing the dispersion effect.

[0085] (4) Citric acid: As a complexing stabilizer, citric acid can form stable complexes with metal ions on the surface of metal powder, preventing the migration and deposition of metal ions on the particle surface, thereby avoiding bridging and agglomeration between particles. A dosage of 3-5% can effectively complex metal ions, while adjusting the pH of the system to the optimal range of 5.5-6.5, ensuring the stability and effectiveness of other dispersed components.

[0086] (5) Xanthan gum: As a viscosity modifier, xanthan gum can significantly increase the viscosity of the system, form a three-dimensional network structure, and prevent the sedimentation and agglomeration of particles. A dosage of 2-4% can control the viscosity of the system within the optimal range of 200-500 mPa·s, which ensures good dispersion effect without affecting the ball milling efficiency due to excessive viscosity.

[0087] (6) Hydrophilic nano silica: As a surface modifier, nano silica particles can be adsorbed on the surface of metal powder and enhance the steric hindrance effect through the stereo effect. A dosage of 1-3% can effectively modify the powder surface and improve the stability of the dispersion system. At the same time, the hydrophilicity of nano silica can improve the compatibility between the dispersant and water.

[0088] (7) Tween 80: As a dispersant, Tween 80 can improve the dispersibility of nano-silica in water and prevent the nanoparticles from agglomerating. A dosage of 5-10% can ensure that nano-silica is uniformly dispersed in the system and give full play to its surface modification effect. At the same time, Tween 80 can also work synergistically with tea saponin to further reduce interfacial tension.

[0089] (8) Deionized water: As a solvent carrier, the amount of deionized water (28-51%) can adjust the concentration of the dispersant to meet the requirements of the ball mill solid-liquid ratio and ensure the smooth progress of the ball milling process.

[0090] The synergistic effect of the five-fold synergistic mechanism is the key to the superior performance of the dispersant in this invention:

[0091] Surface adsorption mechanism: Tea saponin reduces interfacial tension and promotes the adsorption of PEG400, L-glutamic acid, etc. on the powder surface;

[0092] Charge stabilization mechanism: L-glutamic acid provides surface charge, which, in synergy with the complexation of citric acid, enhances the electrostatic repulsion between particles;

[0093] Steric hindrance mechanism: The long-chain structure of PEG400 and the steric effect of nano-silica work synergistically to provide strong steric hindrance;

[0094] Complexation regulation mechanism: The complexation of citric acid with metal ions prevents bridging and aggregation between particles;

[0095] Viscosity adaptation mechanism: Xanthan gum adjusts the viscosity of the system, providing a suitable environment for the operation of other mechanisms.

[0096] This multi-mechanism synergistic effect makes the dispersant of the present invention not only have excellent dispersion effect, but also environmentally friendly and non-toxic, thus solving the shortcomings of traditional dispersants.

[0097] 3. Technical principles of process parameter selection

[0098] (1) Selection of matrix pretreatment parameters

[0099] Grinding wheel mesh size (80-120 mesh): Choosing a mesh size within this range can effectively remove the surface oxide layer while creating appropriate surface roughness, which is beneficial for improving the bonding strength between the coating and the substrate. Too low a mesh size (e.g., below 80 mesh) will result in an overly rough surface, which is not conducive to the uniformity of subsequent coatings; too high a mesh size (e.g., above 120 mesh) will make it difficult to completely remove the oxide layer, affecting the bonding strength.

[0100] Ultrasonic cleaning power (300-400W) and time (15-20min): This combination of parameters can effectively remove surface oil stains while avoiding damage to the substrate surface caused by excessive power. If the power is too low or the time is too short, the oil stains will not be completely removed; if the power is too high or the time is too long, it may cause corrosion to the substrate surface.

[0101] Hydrochloric acid concentration (5%-8%) and pickling time (10-15 min): This parameter range can effectively remove surface oxide scale while avoiding excessive corrosion of the substrate. If the concentration is too low or the time is too short, the oxide scale will not be completely removed; if the concentration is too high or the time is too long, it will lead to excessive corrosion of the substrate surface and affect the coating adhesion.

[0102] Preheating temperature (200-300℃) and holding time (30-45min): Preheating can remove moisture from the substrate, reduce porosity during the cladding process, and simultaneously reduce the temperature difference between the substrate and the coating, thereby reducing thermal stress and preventing crack formation. If the temperature is too low or the time is too short, the preheating effect will be poor; if the temperature is too high or the time is too long, it may lead to a decrease in substrate performance.

[0103] (2) Selection of powder preparation and pretreatment parameters

[0104] Ball-to-powder ratio (6:1): This ratio ensures that the grinding balls have sufficient impact and grinding force on the powder, achieving uniform mixing and refining of the powder. If the ball-to-powder ratio is too low, the grinding effect will be insufficient and the powder will not mix evenly; if the ball-to-powder ratio is too high, it will increase energy consumption and wear on the grinding balls, and may also lead to excessive powder breakage.

[0105] Ball mill speed (200-250 r / min): This speed range ensures grinding effect while avoiding excessive centrifugal force caused by excessively high speed, which would prevent the grinding balls from effectively contacting the powder. Too low a speed results in low grinding efficiency; too high a speed will reduce grinding effect and increase energy consumption.

[0106] Ball milling time (2-3 hours): This time range ensures that the powder is thoroughly and evenly mixed, while avoiding powder oxidation or agglomeration caused by over-milling. Too short a time will result in uneven mixing; too long a time may lead to a decrease in powder performance.

[0107] Screening mesh size (180-300 mesh): This mesh size range ensures that the powder particle size is moderate, guaranteeing good flowability and facilitating melting and spreading during the cladding process. If the mesh size is too low (powder is too coarse), melting will be difficult, easily leading to uneven coating; if the mesh size is too high (powder is too fine), flowability will be poor, and agglomeration will be easy, affecting the stability of the cladding process.

[0108] Vacuum drying parameters (vacuum degree ≤ 5Pa, temperature 80-105℃, time 2-3h): This combination of parameters can effectively remove moisture and volatiles from the powder while avoiding powder oxidation caused by excessively high temperatures. Insufficient vacuum degree, excessively low temperature, or excessively short time will result in incomplete drying; excessively high temperature may lead to powder oxidation or changes in composition.

[0109] Silane coupling agent treatment parameters (concentration 0.5%-1.0%, temperature 25℃, time 5-8 min, drying temperature 60-80℃, time 1-1.5 h): This parameter range allows for the formation of an effective coupling agent coating on the powder surface, improving the powder's wettability and adhesion to the matrix. Too low a concentration or too short a time will result in poor treatment effects; too high a concentration or too long a time may lead to powder agglomeration. The drying parameters ensure complete curing of the coupling agent while avoiding the negative impact of high temperatures on the treatment effect.

[0110] (3) Selection of pre-layer preparation parameters

[0111] Pre-set layer thickness (1.5-2.5mm): This thickness range ensures a sufficiently thick coating after cladding, while avoiding defects such as incomplete melting and porosity caused by excessive thickness. If the thickness is too thin, the coating thickness will be insufficient, resulting in limited wear resistance; if the thickness is too thick, defects such as poor fusion are likely to occur.

[0112] Ambient humidity (40%-60%): This humidity range can prevent the powder from absorbing moisture, ensuring the powder's flowability and the uniformity of the pre-formed layer. If the humidity is too high, the powder is prone to absorbing moisture and agglomerating, affecting the quality of the pre-formed layer; if the humidity is too low, the powder is prone to flying, which also affects the quality of the pre-formed layer.

[0113] (4) Selection of plasma cladding parameters

[0114] Cladding current (170-190A): This current range provides sufficient heat to melt the powder and substrate surfaces, forming a good metallurgical bond, while avoiding excessive melting of the substrate or burning of the coating due to excessive current. If the current is too low, melting will be insufficient and the bonding will be poor; if the current is too high, the coating grains will be coarse and the performance will be degraded.

[0115] Nozzle height (15-18mm): This height range ensures a moderate plasma arc energy density, allowing the powder to melt fully and bond well with the substrate. Too low a height results in excessive energy density, which can easily lead to coating burn-off; too high a height results in insufficient energy density and incomplete melting.

[0116] Powder feed rate (230-260 g / min): This speed range, matched with other parameters, ensures the formation of a uniform coating with moderate thickness. If the powder feed rate is too low, the coating will be too thin; if the powder feed rate is too high, it will easily lead to insufficient melting and defects such as pores and inclusions.

[0117] Gas flow parameters (powder feed gas 7-9 L / min, large ion gas 7-9 L / min, small ion gas 2-3 L / min): This gas flow combination ensures good protection, prevents coating oxidation, and guarantees the stability of the plasma arc and smooth powder feeding. Insufficient gas flow results in poor protection and easy coating oxidation; excessive flow leads to arc instability and increases costs.

[0118] Scanning rate (190-210 mm / min): This rate range ensures sufficient penetration and good formability of the coating, while avoiding coarse grains caused by excessively slow speeds. Too low a speed results in excessive heat input and degraded coating performance; too high a speed leads to insufficient penetration and low bonding strength.

[0119] (5) Selection of post-cladding treatment parameters

[0120] Stress-relief annealing parameters (heating rate 5-8℃ / min, temperature 350-400℃, holding time 2-3h): This combination of parameters can effectively eliminate the internal stress generated during the cladding process, while avoiding the degradation of coating performance caused by excessively high temperatures. Too rapid a heating rate can easily generate new thermal stress; too low a temperature or too short a time will result in poor stress relief; and too high a temperature may cause the coating to soften.

[0121] Solution treatment parameters ((1) When 20CrMo plate is selected as the base material of alloy structural steel, the heating rate is 4-8℃ / min, the temperature is 862-870℃, the holding time is 1-1.5h, and the material is cooled to below 100℃ in oil and then taken out and cooled to room temperature; (2) When 40CrMo plate is selected as the base material of alloy structural steel, the heating rate is 5-7℃ / min, the temperature is 850-870℃, the holding time is 1-1.6h, and the material is cooled to below 100℃ in oil and then taken out and cooled to room temperature): These two sets of parameters can make the alloy elements in the coating fully dissolved into the matrix to form a uniform solid solution, which is ready for subsequent aging treatment. If the temperature is too low or the time is too short, the solid solution will not be sufficient; if the temperature is too high or the time is too long, it may lead to coarse grains. Oil cooling can suppress the precipitation of carbides and maintain the supersaturated solid solution state.

[0122] Aging treatment parameters ((1) When 20CrMo plate is selected as the substrate material of alloy structural steel, the temperature is 530-550℃, the heat preservation time is 4-5h, and the oil cooling is applied; (2) When 40CrMo plate is selected as the substrate material of alloy structural steel, the temperature is 532-548℃, the heat preservation time is 4-5h, and the oil cooling is applied): These two sets of parameter ranges can promote the uniform precipitation of carbides and achieve coating strengthening. If the temperature is too low or the time is too short, the precipitation will be insufficient and the strengthening effect will be poor; if the temperature is too high or the time is too long, it may cause the carbides to coarsen and reduce the performance.

[0123] Low-temperature tempering parameters ((1) When 20CrMo plate is selected as the substrate material of alloy structural steel, the temperature is 150-200℃, the holding time is 1-1.5h, and the air is cooled; (2) When 40CrMo plate is selected as the substrate material of alloy structural steel, the temperature is 210-480℃, the holding time is 0.6-1h, and the air is cooled): The combination of these two sets of parameters can further eliminate internal stress, while maintaining the high hardness of the coating and improving the toughness and crack resistance of the coating. If the temperature is too low or the time is too short, the effect will not be obvious; if the temperature is too high, it may cause the coating to soften and the hardness to decrease.

[0124] Through precise control and synergistic optimization of the above process parameters, this invention achieves stable preparation of high-performance coatings. The matching between the parameters is the key to obtaining excellent coating performance.

[0125] Compared with the prior art, the present invention has the following technical advantages:

[0126] 1. The coating exhibits excellent overall performance, achieving a good balance between wear resistance and toughness.

[0127] This invention optimizes the alloy powder formulation to achieve the synergistic effect of multiple strengthening mechanisms in the coating, enabling the coating to simultaneously possess high hardness and good toughness, thus resolving the contradiction of traditional coatings being either "hard and brittle" or "tough and soft".

[0128] Traditional iron-based coatings typically improve performance through a single strengthening mechanism, such as simply increasing carbide content to improve hardness, but this often leads to decreased toughness and easy cracking. This invention innovatively employs multi-element synergistic strengthening, forming a synergistic effect of multiple strengthening mechanisms, including solid solution strengthening, dispersion strengthening, and grain refinement strengthening. The appropriate addition of Ni and Co ensures the stability of the austenitic matrix, providing a good foundation for toughness; elements such as Mo, W, V, Nb, Ti, and Zr form various types of carbides, significantly improving hardness through dispersion strengthening; and the addition of rare earth elements further enhances the overall performance of the coating through grain refinement strengthening.

[0129] Experimental data show that the coating of this invention can achieve a hardness of 65.6-68.0 HRC, while its impact toughness can reach 15.8-19.3 J / cm. 2 Compared to traditional iron-based coatings (hardness 55-60 HRC, impact toughness 8-12 J / cm), 2 The wear rate of the coating of this invention is significantly improved. In three-body abrasive wear tests, the wear rate of the coating of this invention is only 1 / 3 to 1 / 2 that of the traditional coating, while exhibiting excellent crack resistance and wear resistance under impact wear conditions. This excellent comprehensive performance enables the coating of this invention to adapt to complex wear conditions and significantly extend the service life of parts.

[0130] 2. Environmentally friendly and non-toxic dispersants for ball milling metal powders enable green production, with significantly better dispersion effects than traditional products.

[0131] This invention innovatively develops an environmentally friendly and non-toxic dispersant for ball milling metal powders, which completely changes the current situation of traditional dispersants having poor environmental performance and limited dispersion effect, and realizes green production in the metal powder preparation process.

[0132] Traditional dispersants such as mineral oil and synthetic oil, commonly used in ball milling of metal powders, not only have a certain degree of toxicity but may also decompose and generate harmful gases during subsequent cladding processes, polluting the environment. Furthermore, residual carbon can affect coating quality. The dispersant in this invention uses only food-grade or cosmetic-grade raw materials, conforming to GB4806 or GB / T29665 standards. Its acute oral toxicity LD50 is >5000 mg / kg, classifying it as practically non-toxic, thus solving the environmental pollution problem at its source.

[0133] Meanwhile, the dispersant of this invention achieves highly efficient dispersion of metal powders through a five-fold synergistic mechanism of "surface adsorption, charge stabilization, steric hindrance, complexation regulation, and viscosity adaptation." Experiments show that ball milling 5μm tungsten powder for 2 hours using the dispersant of this invention can reduce the powder D50 to 1.2-1.5μm with an agglomeration rate of <5%, while the agglomeration rate of traditional dispersants is typically 15-20%. This superior dispersion effect ensures the uniformity of the alloy powder composition, laying the foundation for the subsequent preparation of high-performance coatings.

[0134] Furthermore, the dispersant of this invention exhibits excellent storage stability, showing no stratification or precipitation after 6 months of storage at room temperature, and a reduction rate of less than 3% in its dispersion effect on titanium powder, far superior to traditional dispersants (which typically show a significant decrease in effect after 3 months). Simultaneously, the viscosity-adaptive design reduces ball milling power by 8-12%, decreasing energy consumption and wear on the milling jar, further lowering production costs.

[0135] 3. The coating has high bonding strength with the substrate and excellent resistance to peeling.

[0136] This invention significantly improves the bonding strength between the coating and the substrate by optimizing the substrate pretreatment process and cladding parameters, thus solving the problem of easy peeling of traditional coatings.

[0137] Traditional plasma cladding coatings typically have a bonding strength of 30-50 MPa and are prone to peeling under impact loads. This invention significantly improves the bonding strength through the following measures:

[0138] Refined substrate pretreatment: appropriate roughness is achieved through grinding with a grinding wheel, oil stains are thoroughly removed by ultrasonic cleaning, oxide scale is removed by acid pickling, and moisture is removed by preheating to reduce thermal stress, creating favorable conditions for coating adhesion.

[0139] Optimized cladding parameters: By controlling parameters such as cladding current and nozzle height, the substrate surface is ensured to melt appropriately, forming sufficient cladding depth to achieve metallurgical bonding between the coating and the substrate.

[0140] Adding an appropriate amount of boron to alloy powder can lower the melting point of the coating, improve its fluidity, and promote the wetting and bonding of the coating with the substrate.

[0141] Multi-stage heat treatment: effectively eliminates residual stress at the coating-substrate interface and reduces the tendency for interface cracking.

[0142] Experimental results show that the bonding strength between the coating of this invention and the substrate can reach 85.6-92.3 MPa, which is 1.7-3.1 times that of traditional coatings. In the impact fatigue test, after 10... 6 No coating peeling occurred after the second impact, whereas traditional coatings typically peel off after 10 seconds. 5 Peeling occurs after approximately one application. This high bonding strength ensures the reliability of the coating under complex working conditions and significantly extends the service life of components.

[0143] 4. The coating exhibits excellent corrosion resistance and is suitable for complex environmental conditions.

[0144] This invention significantly improves the corrosion resistance of the coating by optimizing the alloy composition design, enabling it to adapt to complex working environments such as humid, dusty, and even corrosive media.

[0145] Traditional iron-based coatings have poor corrosion resistance and are prone to rusting in humid or corrosive environments, affecting their wear resistance and service life. This invention improves the corrosion resistance of the coating through the following measures:

[0146] The addition of high Ni content (20.5%-22.0%): forms a stable austenitic structure and improves the passivation ability of the coating.

[0147] Appropriate addition of Cu (0.8%-1.2%): forms a copper-rich passivation film on the coating surface, improving corrosion resistance, especially in acidic environments.

[0148] The addition of Al (0.3%-0.5%) promotes the formation of a dense oxide film, improving its antioxidant and corrosion-resistant properties.

[0149] The addition of rare earth elements: purifies the coating, reduces inclusions, and improves the continuity and stability of the passivation film.

[0150] Strictly control the content of harmful elements P and S (≤0.008%): reduce the possibility of micro-battery corrosion.

[0151] Salt spray test results show that after 1000 hours of continuous salt spray testing in a 5% NaCl solution, the corrosion rate of the coating of this invention is only 0.015-0.020 mm / year, far lower than the 0.1-0.2 mm / year of traditional iron-based coatings. After one year of exposure to an industrial atmospheric environment, the coating surface only showed slight discoloration and no obvious rust, while traditional coatings showed obvious rust. This excellent corrosion resistance enables the coating of this invention to work stably for a long time in corrosive environments such as mining, metallurgy, and chemical industries, thus broadening its application range.

[0152] 5. High process stability, uniform coating quality, suitable for industrial production.

[0153] This invention achieves highly stable coating preparation by systematically optimizing the entire process, ensuring uniform and consistent coating quality, and providing a reliable guarantee for large-scale industrial production.

[0154] Traditional plasma cladding processes often suffer from unstable coating quality and significant batch-to-batch variations, primarily due to uneven powder mixing, fluctuations in cladding parameters, and non-standard pretreatment processes. This invention significantly improves process stability through the following measures:

[0155] Environmentally friendly and efficient dispersants and optimized ball milling process are used to ensure uniform powder mixing and stable particle size distribution.

[0156] The use of automated powder spreading equipment ensures that the thickness of the pre-spread layer is uniform and the accuracy is controlled within ±0.1mm.

[0157] Precisely controlled cladding parameters, including current, voltage, gas flow rate, and scanning speed, ensure a stable cladding process.

[0158] Real-time temperature monitoring: An infrared thermometer is used to monitor the substrate temperature in real time to ensure that it does not exceed 350℃, thus avoiding a decline in coating quality due to excessive temperature.

[0159] Standardized pretreatment and posttreatment processes: ensuring consistency of process parameters at each step.

[0160] Statistical data shows that the coating prepared by the process of this invention has a standard deviation of less than 5% for key indicators such as hardness and thickness, which is far lower than the 15-20% of traditional processes. During the continuous production of 100 products, the coating qualification rate remained above 95%, while traditional processes typically achieve 72-80%. This high stability not only ensures the reliability of product quality but also reduces the scrap rate, improves production efficiency, and significantly reduces production costs, laying a solid foundation for industrial application.

[0161] 6. The process has low energy consumption, high production efficiency, and significant economic and social benefits.

[0162] This invention, through optimized process parameters and innovative dispersant technology, significantly reduces energy consumption and improves production efficiency while ensuring high coating performance, resulting in significant economic and social benefits.

[0163] In terms of energy consumption, the advantages of this invention are mainly reflected in:

[0164] The viscosity-adaptive design of the dispersant reduces ball milling power by 8-12%, significantly saving energy consumption in the ball milling process.

[0165] Optimized cladding parameters: While ensuring coating quality, the scanning rate was increased (190-210 mm / min), which improved production efficiency compared to the traditional process (100-150 mm / min) and reduced energy consumption per unit area by about 30%.

[0166] A reasonable heat treatment process: By optimizing the heating rate and holding time, the energy consumption of the heat treatment process is reduced while ensuring the treatment effect.

[0167] In terms of production efficiency, the coating preparation cycle of this invention (from substrate pretreatment to final coating formation) is approximately 8-10 hours, which is about 30% shorter than the traditional process (12-15 hours). At the same time, due to the high process stability and low scrap rate, the actual production efficiency is further improved.

[0168] Economic benefit analysis shows that by adopting the process of this invention, the production cost per unit area of ​​coating can be reduced by 20-25%, while the service life of the coating can be extended by 2-3 times, significantly reducing equipment maintenance costs and downtime. Taking the crusher liner of mining machinery as an example, after adopting the coating of this invention, the replacement cycle of the liner is extended from the original 3 months to 9 months, reducing the number of replacements by 2-3 times per year, saving a lot of spare parts costs and replacement labor costs.

[0169] In terms of social benefits, the environmentally friendly and non-toxic dispersant for ball milling metal powder of this invention reduces environmental pollution during the production process; the extended service life of the coating reduces resource consumption and waste emissions; and the reduction in energy consumption helps to reduce carbon emissions, which is in line with the national policy requirements for energy conservation and emission reduction.

[0170] 7. Balancing high strength and weldability to improve overall lifecycle economics.

[0171] This invention uses 20CrMo or 40CrMo sheet as the base material, which combines high strength and weldability. This ensures the structural strength of the components, meeting the load-bearing requirements of industrial applications, while also allowing for subsequent assembly and maintenance through welding. When the base material requires maintenance, its excellent weldability prevents damage to the main structure and supports repeated welding, significantly reducing costs associated with frequent component replacements and greatly improving the economic efficiency and practicality of the components throughout their entire lifecycle.

[0172] In summary, this invention not only has significant technical advantages, but also has important economic and social benefits and broad application prospects. Detailed Implementation

[0173] Example 1

[0174] A process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology includes the following steps:

[0175] 1. Matrix pretreatment

[0176] 20CrMo sheet was selected as the substrate material. The surface oxide layer was polished with an 80-grit abrasive wheel, and then ultrasonically cleaned for 20 minutes at 300W power with a 1:1 volume ratio of alcohol and acetone to remove oil stains. The substrate was then immersed in a 5% hydrochloric acid solution and acid-washed at 25℃ for 15 minutes to remove the surface oxide scale. After rinsing with deionized water until pH=7, the substrate was dried. Finally, the substrate was placed in an electric resistance furnace for preheating at 200℃ and held for 45 minutes.

[0177] 2. Powder preparation and pretreatment

[0178] Weigh the raw materials as follows by mass percentage: C 0.09%, Ni 20.6%, Co 6.1%, Mo 3.0%, Si 1.2%, Mn 0.3%, Ti 1.1%, Al 0.3%, V 0.5%, Nb 0.2%, Zr 0.15%, Y 0.05%, La 0.04%, B 0.08%, W 1.6%, Cu 0.9%, Ce 0.02%, P 0.006%, S 0.005%, with the balance being Fe. Raw material purity requirements: Ni ≥ 99.9%, Co ≥ 99.8%, Mo ≥ 99.5%, Si ≥ 99.7%, Ti ≥ 99.6%, Al ≥ 99.9%, Nb ≥ 99.5%, Fe ≥ 99.9%.

[0179] Environmentally friendly and non-toxic dispersant formulation for ball milling of metal powders: polyethylene glycol 400 15.2%, tea saponin 8.7%, L-glutamic acid 5.1%, citric acid 3.3%, xanthan gum 2.0%, hydrophilic nano silica 1.2%, Tween 80 5.4%, balance deionized water.

[0180] The preparation method of the environmentally friendly and non-toxic dispersant for ball milling metal powder includes the following steps:

[0181] (1) Preparation of pre-dissolved dispersion phase: Add the prescribed amount of Tween 80 and xanthan gum to the reactor, heat to 45°C at 300 rpm and stir for 30 min until the xanthan gum is completely dissolved;

[0182] (2) Dissolution of the main dispersed phase: Add the amount of deionized water specified in the formula to another reactor, heat to 52°C, slowly add PEG400, and stir at 200 rpm for 20 min;

[0183] (3) Preparation of functional additive phase: The main dispersed phase was cooled to 41°C, and citric acid, L-glutamic acid and tea saponin were added in sequence. Each addition was stirred for 15 min, and the temperature was controlled at 40°C and the pH value was 5.6.

[0184] (4) Dispersion of nano-additives: Add the amount of hydrophilic nano-silica to the functional additive phase, turn off the stirring, turn on the ultrasonic disperser, and sonicate at 300W power for 20 minutes, with the temperature controlled at 41℃.

[0185] (5) Composite maturation: After the ultrasonic treatment, turn on the stirring to 200 rpm, slowly pump the pre-dissolved co-dispersed phase into the reactor, stir for 32 min, and the maturation temperature is 42℃;

[0186] (6) Cooling and filtration: Stop heating and allow it to cool naturally to 28°C. Filter the solution using a 0.22μm microporous membrane at a pressure of 0.1MPa.

[0187] Add the raw materials to a planetary ball mill, add the above-mentioned dispersant (8.1% of the total mass of the raw materials), mix at a ball-to-material ratio of 6:1 and a speed of 200 r / min for 3 hours, pass through a 180-mesh sieve, spread the powder evenly and put it into a vacuum drying oven, evacuate to a vacuum degree of 5 Pa, keep at 80℃ for 3 hours, then immerse the dried powder in a 0.5% silane coupling agent KH-550 solution, soak at 25℃ for 8 minutes, take it out and dry at 60℃ for 1.5 hours.

[0188] 3. Preparation of the pre-formed layer

[0189] The treated powder was evenly spread on the surface of the pretreated alloy structural steel substrate using an automated powder spreading equipment. The thickness of the pre-layer was controlled at 1.5 mm, the powder spreading accuracy was ±0.1 mm, and the ambient humidity was controlled at 42.3% during the pre-laying process.

[0190] 4. Plasma cladding

[0191] The substrate with a pre-applied layer was loaded into a plasma cladding device (3mm tungsten electrode diameter, 6mm nozzle orifice). The device had a rated power of 22KW and a rated cladding current of 230A. During cladding, argon gas with a purity ≥99.99% was simultaneously introduced for protection. The process parameters were: cladding current 170A, nozzle height 15mm, powder feeding speed 230g / min, powder feeding gas flow rate 7L / min, large ion gas flow rate 7L / min, small ion gas flow rate 2L / min, and scanning rate 190mm / min. An infrared thermometer was used to monitor the substrate temperature in real time during cladding to ensure it did not exceed 350℃. After cladding, the substrate was allowed to cool naturally to room temperature to obtain the initial coating.

[0192] 5. Preliminary treatment after cladding

[0193] The obtained sample was placed in a muffle furnace for stress-relief annealing at a heating rate of 5℃ / min, a temperature of 350℃, and a holding time of 3h. The sample was then cooled to room temperature in the furnace. Subsequently, the coating surface was polished with 400-grit sandpaper to remove oxide scale and minor defects.

[0194] 6. Heat treatment after cladding

[0195] ①Solution: The high-temperature carbon tube furnace is heated to 865℃ at a heating rate of 4℃ / min, held at that temperature for 1.5h, and then cooled to 100℃ in oil before being taken out and cooled to room temperature;

[0196] ②Aging: The material is fed into the muffle furnace at the specified temperature and held at 532℃ for 5 hours, then cooled with oil.

[0197] ③ Low-temperature tempering: The muffle furnace is heated to 156℃, held for 1.4 hours, and then cooled with air;

[0198] Example 2

[0199] A process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology includes the following steps:

[0200] 1. Matrix pretreatment

[0201] 40CrMo sheet was selected as the substrate material. The surface oxide layer was polished with a 100-grit abrasive wheel, and then ultrasonically cleaned for 18 minutes at 350W power with a 1:1 volume ratio of alcohol and acetone to remove oil stains. The substrate was then immersed in a 6.5% hydrochloric acid solution and acid-washed at 30℃ for 12 minutes to remove the surface oxide scale. After rinsing with deionized water until pH=7, the substrate was dried. Finally, the substrate was placed in an electric resistance furnace for preheating at 250℃ and held for 38 minutes.

[0202] 2. Powder preparation and pretreatment

[0203] The raw materials were weighed according to the following mass percentages: C 0.10%, Ni 21.2%, Co 6.8%, Mo 3.2%, Si 1.5%, Mn 0.45%, Ti 1.3%, Al 0.4%, V 0.55%, Nb 0.3%, Zr 0.22%, Y 0.08%, La 0.045%, B 0.12%, W 1.8%, Cu 1.0%, Ce 0.03%, P 0.007%, S 0.006%, with the balance being Fe. The purity of the raw materials was the same as in Example 1.

[0204] Environmentally friendly and non-toxic dispersant formulation for ball milling of metal powders: 21% polyethylene glycol 400, 10% tea saponin, 6.5% L-glutamic acid, 4% citric acid, 3% xanthan gum, 2% hydrophilic nano silica, 7.6% Tween 80, with the balance being deionized water.

[0205] The preparation method of the environmentally friendly and non-toxic dispersant for ball milling metal powder includes the following steps:

[0206] (1) Preparation of pre-dissolved dispersion phase: Add the prescribed amount of Tween 80 and xanthan gum to the reactor, heat to 48°C at 400 rpm and stir for 26 min until the xanthan gum is completely dissolved;

[0207] (2) Dissolution of the main dispersed phase: Add the amount of deionized water specified in the formula to another reactor, heat to 54°C, slowly add PEG400, and stir at 260 rpm for 18 min;

[0208] (3) Preparation of functional additive phase: The main dispersed phase was cooled to 43℃, and citric acid, L-glutamic acid and tea saponin were added in sequence. Each addition was stirred for 12 min, and the temperature was controlled at 44℃ and the pH value was 6.2.

[0209] (4) Dispersion of nano-additives: Add the amount of hydrophilic nano-silica to the functional additive phase, turn off the stirring, turn on the ultrasonic disperser, and sonicate at 400W power for 17 minutes, controlling the temperature at 43℃.

[0210] (5) Composite maturation: After the ultrasonic treatment, turn on the stirring to 250 rpm, slowly pump the pre-dissolved co-dispersed phase into the reactor, stir for 38 min, and the maturation temperature is 42℃;

[0211] (6) Cooling and filtration: Stop heating and allow it to cool naturally to 28°C. Filter the solution using a 0.22μm microporous membrane at a pressure of 0.13MPa.

[0212] Add the raw materials to a planetary ball mill, add the above-mentioned dispersant (10% of the total mass of the raw materials), mix at a ball-to-material ratio of 6:1 and a speed of 225 r / min for 2.5 h, pass through a 240 mesh sieve, spread the powder evenly into a vacuum drying oven, evacuate to a vacuum degree of 4 Pa, keep at 95℃ for 2.5 h, then immerse the dried powder in a 0.8% silane coupling agent KH-550 solution, soak at 25℃ for 6 min, remove and dry at 70℃ for 1.2 h.

[0213] 3. Preparation of the pre-formed layer

[0214] The treated powder is evenly spread on the surface of the pretreated alloy structural steel substrate using an automated powder spreading equipment. The thickness of the pre-layer is controlled at 2.0 mm, the powder spreading accuracy is ±0.1 mm, and the ambient humidity is controlled at 50% during the pre-laying process.

[0215] 4. Plasma cladding

[0216] The substrate with a pre-applied layer was loaded into a plasma cladding device (4mm tungsten electrode diameter, 7mm nozzle orifice). The device had a rated power of 23.5KW and a rated cladding current of 240A. During cladding, argon gas with a purity ≥99.99% was simultaneously introduced for protection. The process parameters were: cladding current 180A, nozzle height 16.5mm, powder feeding speed 245g / min, powder feeding gas flow rate 8L / min, large ion gas flow rate 8L / min, small ion gas flow rate 2.5L / min, and scanning rate 200mm / min. An infrared thermometer was used to monitor the substrate temperature in real time during cladding to ensure it did not exceed 350℃. After cladding, the substrate was allowed to cool naturally to room temperature to obtain the initial coating.

[0217] 5. Preliminary treatment after cladding

[0218] The obtained sample was placed in a muffle furnace for stress-relief annealing at a heating rate of 6℃ / min, a temperature of 375℃, and a holding time of 2.5h. It was then cooled to room temperature in the furnace. Subsequently, the coating surface was polished with 500-grit sandpaper to remove oxide scale and minor defects.

[0219] 6. Heat treatment after cladding

[0220] ①Solution: The high-temperature carbon tube furnace is heated to 860℃ at a heating rate of 5℃ / min, held at that temperature for 1.3h, and then cooled to 100℃ in oil before being taken out and cooled to room temperature;

[0221] ②Aging: The material is fed into the muffle furnace at the specified temperature and held at 540℃ for 4.5 hours, then cooled with oil.

[0222] ③ Low-temperature tempering: The muffle furnace is heated to 350℃, held for 0.8 hours, and then cooled by air.

[0223] Example 3

[0224] A process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology includes the following steps:

[0225] 1. Matrix pretreatment

[0226] 20CrMo sheet was selected as the substrate material. The surface oxide layer was polished with a 120-grit abrasive wheel, and then ultrasonically cleaned for 15 minutes at 400W power with a 1:1 volume ratio of alcohol and acetone to remove oil stains. The substrate was then immersed in an 8% hydrochloric acid solution and acid-washed at 35℃ for 10 minutes to remove the surface oxide scale. After rinsing with deionized water until pH=7, the substrate was dried. Finally, the substrate was placed in an electric resistance furnace for preheating at 300℃ and held for 30 minutes.

[0227] 2. Powder preparation and pretreatment

[0228] The raw materials were weighed according to the following mass percentages: C 0.11%, Ni 21.8%, Co 7.2%, Mo 3.3%, Si 1.5%, Mn 0.6%, Ti 1.2%, Al 0.4%, V 0.7%, Nb 0.4%, Zr 0.3%, Y 0.10%, La 0.05%, B 0.15%, W 2.0%, Cu 1.2%, Ce 0.04%, P 0.008%, S 0.008%, with the balance being Fe. The purity of the raw materials was the same as in Example 1.

[0229] Environmentally friendly and non-toxic dispersant formulation for ball milling of metal powders: polyethylene glycol 400 24.6%, tea saponin 11%, L-glutamic acid 7.8%, citric acid 5%, xanthan gum 3.9%, hydrophilic nano silica 3%, Tween 80 9.8%, balance deionized water.

[0230] The preparation method of the environmentally friendly and non-toxic dispersant for ball milling metal powder includes the following steps:

[0231] (1) Preparation of pre-dissolved co-dispersed phase: Add the prescribed amount of Tween 80 and xanthan gum to the reactor, heat to 50°C at 500 rpm and stir for 20 min until the xanthan gum is completely dissolved;

[0232] (2) Dissolution of the main dispersed phase: Add the amount of deionized water specified in the formula to another reactor, heat to 59°C, slowly add PEG400, and stir at -300 rpm for 15 min;

[0233] (3) Preparation of functional additive phase: The main dispersed phase was cooled to 44℃, and citric acid, L-glutamic acid and tea saponin were added in sequence. Each addition was stirred for 13 min, and the temperature was controlled at 45℃ and the pH value was 6.0.

[0234] (4) Dispersion of nano-auxiliaries: Add the amount of hydrophilic nano-silica to the functional auxiliary agent phase, turn off the stirring, turn on the ultrasonic disperser, and sonicate at 500W power for 15 minutes, with the temperature controlled at 45℃.

[0235] (5) Composite maturation: After ultrasonication, turn on the stirring to 300 rpm, slowly pump the pre-dissolved co-dispersed phase into the reactor, stir for 30 min, and the maturation temperature is 45℃;

[0236] (6) Cooling and filtration: Stop heating and allow it to cool naturally to 30°C. Filter the solution using a 0.22μm microporous membrane at a pressure of 0.14MPa.

[0237] Add the raw materials to a planetary ball mill, add the above-mentioned dispersant (11.8% of the total mass of the raw materials), mix at a ball-to-material ratio of 6:1 and a speed of 250 r / min for 2 hours, pass through a 300-mesh sieve, spread the powder evenly and put it into a vacuum drying oven, evacuate to a vacuum degree of 3 Pa, keep at 105℃ for 2 hours, then immerse the dried powder in a 1.0% silane coupling agent KH-550 solution, soak at 25℃ for 5 minutes, take it out and dry at 80℃ for 1 hour.

[0238] 3. Preparation of the pre-formed layer

[0239] The treated powder was evenly spread on the surface of the pretreated alloy structural steel substrate using an automated powder spreading equipment. The thickness of the pre-layer was controlled at 2.5 mm, the powder spreading accuracy was ±0.1 mm, and the ambient humidity was controlled at 58% during the pre-laying process.

[0240] 4. Plasma cladding

[0241] The substrate with a pre-applied layer was loaded into a plasma cladding device (5mm tungsten electrode diameter, 8mm nozzle orifice). The device had a rated power of 25KW and a rated cladding current of 250A. During cladding, argon gas with a purity ≥99.99% was simultaneously introduced for protection. The process parameters were: cladding current 185A, nozzle height 18mm, powder feeding speed 255g / min, powder feeding gas flow rate 8.6L / min, large ion gas flow rate 8.9L / min, small ion gas flow rate 3L / min, and scanning rate 210mm / min. An infrared thermometer was used to monitor the substrate temperature in real time during cladding to ensure it did not exceed 350℃. After cladding, the substrate was allowed to cool naturally to room temperature to obtain the initial coating.

[0242] 5. Preliminary treatment after cladding

[0243] The obtained sample was placed in a muffle furnace for stress-relief annealing at a heating rate of 8℃ / min, a temperature of 400℃, and a holding time of 2h. It was then cooled to room temperature in the furnace. Subsequently, the coating surface was polished with 600-grit sandpaper to remove oxide scale and minor defects.

[0244] 6. Heat treatment after cladding

[0245] ①Solution: The high-temperature carbon tube furnace is heated to 870°C at a heating rate of 7°C / min, held at that temperature for 1 hour, and then cooled to 100°C in oil before being taken out and cooled to room temperature.

[0246] ②Aging: The contents are fed into the muffle furnace at the specified temperature and held at 550℃ for 4 hours, then cooled with oil.

[0247] ③ Low-temperature tempering: The muffle furnace is heated to 200℃, held for 1 hour, and then cooled with air;

[0248] Example 4

[0249] This embodiment is basically the same as Embodiment 2, except that: in step S2, the dispersant formulation for ball milling environmentally friendly and non-toxic metal powder is polyethylene glycol 400 18%, tea saponin 9%, L-glutamic acid 7%, citric acid 3.5%, xanthan gum 2.5%, hydrophilic nano silica 1.5%, Tween 80 6%, and the remainder is deionized water. Other steps and parameters are the same as in Embodiment 2.

[0250] Example 5

[0251] This embodiment is basically the same as Embodiment 2, except that: in step S4, the plasma cladding process parameters are: cladding current 175A, nozzle height 16mm, powder feeding speed 240g / min, powder feeding gas flow rate 7.5L / min, large ion gas flow rate 7.5L / min, small ion gas flow rate 2.2L / min, and scanning rate 195mm / min. Other steps and parameters are the same as in Embodiment 2.

[0252] Comparative Example 1

[0253] This comparative example is basically the same as Example 2, except that the environmentally friendly and non-toxic metal powder ball milling dispersant of the present invention is not used in step S2, but a traditional mineral oil dispersant is used instead. Other steps and parameters are the same as in Example 2.

[0254] Comparative Example 2

[0255] This comparative example is basically the same as Example 2, except that the alloy powder formulation in step S2 does not contain rare earth elements (Y, La, Ce). Other steps and parameters are the same as in Example 2.

[0256] Comparative Example 3

[0257] This comparative example is basically the same as Example 2, except that in step S4, the plasma cladding process parameters are cladding current of 160A (lower than the range of this invention). Other steps and parameters are the same as in Example 2.

[0258] Comparative Example 4

[0259] This comparative example is basically the same as Example 2, except that in step S6, solution treatment and aging treatment are not performed; only stress-relieving annealing and low-temperature tempering are performed. Other steps and parameters are the same as in Example 2.

[0260] Comparative Example 5

[0261] This comparative example uses commercially available Fe-Cr-Ni-Si-B plasma cladding powder. The cladding and post-treatment were performed according to the recommended process parameters, as follows:

[0262] 1. Matrix pretreatment: Same as in Example 2

[0263] 2. Powder: Commercially available Fe-Cr-Ni-Si-B series powder, particle size 240 mesh.

[0264] 3. Plasma cladding parameters: current 180A, voltage 30V, scanning speed 200mm / min, protective gas flow rate 8L / min

[0265] 4. Post-treatment: Anneal at 300℃ for 2 hours

[0266] Single-factor experiments for screening key process parameters

[0267] 1. The effect of cladding current on coating performance

[0268] With other process parameters fixed as in Example 2, only the cladding current was changed to 150A, 160A, 170A, 180A, 190A, 200A, and 210A, respectively. The coatings were prepared and their hardness, bonding strength, and wear rate were tested. The results are shown in Table 1.

[0269]

[0270] Analysis: When the cladding current is below 170A, the coating hardness and bonding strength gradually increase, while the wear rate decreases, as the current increases. This is because when the current is too low, the powder and substrate do not melt sufficiently, resulting in poor bonding between the coating and the substrate, a loose structure, and poor performance. The coating performance is best when the current is in the range of 170-190A (180A being optimal), at which point the powder and substrate melt fully, forming a good metallurgical bond and a dense, uniform structure. When the current exceeds 190A, the coating performance decreases with increasing current. This is because excessively high current leads to excessive heat input, coarse coating grains, and significant thermal stress, causing microcracks and thus reducing coating performance. Therefore, this invention selects a cladding current range of 170-190A.

[0271] 2. Effect of solution treatment temperature on coating performance

[0272] With other process parameters fixed as in Example 2, only the solution treatment temperature was changed to 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, and 890℃, respectively. The coatings were prepared and their hardness and impact toughness were tested. The results are shown in Table 2.

[0273]

[0274] Analysis: When the solution treatment temperature is below 850℃, the coating hardness and impact toughness gradually increase with increasing temperature. This is because at too low a temperature, carbides cannot fully dissolve into the matrix, resulting in poor solid solution strengthening and uneven microstructure, leading to poor performance. The coating performance is best when the temperature is in the range of 850-870℃ (860℃ being optimal), at which point the carbides completely dissolve, forming a uniform supersaturated solid solution, laying the foundation for the precipitation of fine and dispersed carbides during subsequent aging treatment. When the temperature exceeds 880℃, the coating performance actually decreases with increasing temperature. This is because excessively high temperatures lead to coarse grains. Although solid solution is more complete, the adverse effects of grain coarsening outweigh the beneficial effects of solid solution strengthening, resulting in a decrease in both hardness and toughness. Therefore, this invention selects a solution treatment temperature range of 850-870℃.

[0275] 3. The effect of aging treatment time on coating performance

[0276] With other process parameters fixed as in Example 2, only the aging treatment time was changed to 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, and 6h, respectively. The coatings were prepared and their hardness and impact toughness were tested. The results are shown in Table 3.

[0277]

[0278] Analysis: When the aging time is less than 4 hours, the coating hardness gradually increases with time, while the impact toughness fluctuates slightly but remains at a high level. This is because insufficient carbide precipitation results in poor strengthening effect when the time is too short. The coating performance is best when the aging time is between 4 and 5 hours (4.5 hours being optimal), as the carbides are fully precipitated and maintain a fine, dispersed distribution, resulting in the most significant strengthening effect. When the aging time exceeds 5 hours, the coating hardness gradually decreases with time, and the impact toughness also decreases significantly. This is because excessively long aging times lead to carbide coarsening, weakening the strengthening effect and reducing toughness. Therefore, this invention selects an aging time range of 4-5 hours.

[0279] 4. Effect of ball milling time on powder and coating properties

[0280] With other process parameters fixed as in Example 2, only the ball milling time was changed to 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, and 4h, respectively. The average particle size of the powder and the hardness and wear rate of the coating were tested, and the results are shown in Table 4.

[0281]

[0282] Analysis: When the ball milling time is less than 2.5 hours, the average particle size of the powder gradually decreases, the coating hardness gradually increases, and the wear rate gradually decreases with increasing time. This is because insufficient ball milling time results in uneven powder mixing, larger particle sizes, and thus uneven coating structure and poor performance. When the ball milling time is within the range of 2-3 hours, the powder particle size is moderate and uniformly distributed, resulting in better coating performance (2.5 hours being the optimal time). When the ball milling time exceeds 3 hours, although the powder particle size does not change significantly, the coating performance decreases slightly. This may be because excessively long ball milling times lead to powder oxidation or the introduction of excessive grinding ball abrasion impurities, thereby affecting coating performance. Therefore, this invention selects a ball milling time range of 2-3 hours.

[0283] 5. The effect of pre-layer thickness on coating performance

[0284] With other process parameters fixed as in Example 2, only the thickness of the pre-layer was changed to 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 3.5 mm, respectively. The coating was prepared and its thickness, hardness, and porosity were tested. The results are shown in Table 5.

[0285]

[0286] Analysis: When the pre-layer thickness is less than 2.0 mm, as the thickness increases, the coating thickness increases, the hardness slightly increases, and the porosity decreases. This is because when the pre-layer is too thin, the coating after cladding is thin, resulting in good quality but limited protective effect. When the pre-layer thickness is in the range of 1.5-2.5 mm, the coating performance is better (2.0 mm is optimal), with moderate thickness, high hardness, and low porosity. When the pre-layer thickness exceeds 2.5 mm, as the thickness increases, the coating hardness decreases significantly, and the porosity increases significantly. This is because when the pre-layer is too thick, the powder is difficult to completely melt, leading to increased pores in the coating, poor bonding, and thus reduced coating performance. Therefore, this invention selects a pre-layer thickness range of 1.5-2.5 mm.

[0287] Testing of coating performance indicators:

[0288] 1. Testing Items and Methods

[0289] The coatings prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to the following performance tests:

[0290] (1) Hardness: The HRC-150 Rockwell hardness tester was used to test the hardness of the coating material according to GB / T230.1-2018 "Metallic materials Rockwell hardness test - Part 1: Test method". Five points were selected evenly on the coating surface and the average value was taken.

[0291] (2) Impact toughness: The JB-30B impact testing machine was used to test the Charpy impact test method for metallic materials according to GB / T229-2007. A U-notch was used, the sample size was 10mm×10mm×55mm, the coating thickness was 2mm, and the average value of 3 samples was taken.

[0292] (3) Bond strength: The CMT5105 universal testing machine was used to test the tensile bond strength of thermal spray coatings according to GB / T8642-2002 "Determination of tensile bond strength". The tensile method was used, the sample size was 50mm×50mm, the coating thickness was 2mm, and the average value of 5 samples was taken.

[0293] (4) Wear resistance: The ML-10 wear tester was used to conduct a three-body abrasive wear test according to GB / T12444.2-2006 "Metallic materials wear test method - part 2: determination of wear amount". The test conditions were: load 100N, rotation speed 200r / min, time 2h, and abrasive was 80 mesh quartz sand. The wear rate was calculated and the average value of 3 samples was taken.

[0294] (5) Corrosion resistance: The neutral salt spray test (NSS) was conducted in accordance with GB / T10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test" using a salt spray test chamber with 5% NaCl solution, temperature 35℃, continuous spraying for 1000h, and the corrosion rate was measured. The average value of 3 samples was taken.

[0295] (6) Coating thickness: The coating thickness was measured using a TT260 coating thickness gauge in accordance with GB / T4956-2003 "Magnetic method for measuring the thickness of non-magnetic coating on magnetic substrate". Ten points were evenly selected on the coating surface and the average value was taken.

[0296] (7) Porosity: The metallographic photographs of the coating cross section were analyzed using Image-ProPlus image analysis software to calculate the percentage of the pore area to the total area, and the average value of 5 fields of view was taken.

[0297] 2. Test Results

[0298] The coating performance test results of each embodiment and comparative example are shown in Table 6.

[0299]

[0300] 3. Results Analysis

[0301] As can be seen from the test results in Table 6, the coatings prepared in Examples 1-5 of this invention are superior to those in Comparative Examples 1-5 in all performance indicators. The specific analysis is as follows:

[0302] (1) Hardness: The hardness of the coating in the examples was 65.6-68 HRC, which was significantly higher than that of Comparative Example 1 (62.3 HRC), Comparative Example 2 (60.2 HRC), Comparative Example 3 (55.6 HRC), Comparative Example 4 (58.4 HRC) and Comparative Example 5 (56.5 HRC). This indicates that the synergistic effect of the alloy powder formulation, dispersant technology and heat treatment process of the present invention can significantly improve the coating hardness, mainly due to the dispersion strengthening and solid solution strengthening effects of various carbides.

[0303] (2) Impact toughness: The impact toughness of the coating in the example is 15.8-19.3 J / cm. 2 This is superior to the comparative example. The impact toughness of comparative example 4 is 15.2 J / cm. 2 The results are comparable to those of Example 1, but lower than those of Examples 2-5. This indicates that the process of the present invention can maintain good toughness while ensuring high hardness, solving the problem of traditional coatings being "hard and brittle". This is mainly due to the grain-refining effect of rare earth elements and the optimized heat treatment process.

[0304] (3) Bond strength: The bonding strength of the coatings in the examples was 85.6-92.3 MPa, which was significantly higher than that of all comparative examples, and 1.6-1.8 times that of comparative example 5. This indicates that the substrate pretreatment process and cladding parameter optimization of the present invention can effectively improve the bonding strength between the coating and the substrate, mainly due to the sufficient pretreatment of the substrate surface, the appropriate cladding parameters, and the effect of element B.

[0305] (4) Abrasion resistance: The abrasion rate of the coating in the example was 2.8-3.2×10⁻⁶. -3 mm 3 The N·m value is significantly lower than all comparative examples, only about one-third of that of Comparative Example 5. This indicates that the coating of the present invention exhibits excellent wear resistance, primarily due to its high hardness, good toughness, and uniform microstructure distribution.

[0306] (5) Corrosion resistance: The corrosion rate of the coating in the example was 0.015-0.020 mm / year, which was significantly lower than that of all comparative examples, only about 1 / 4 of that of comparative example 5. This indicates that the alloy composition design of the present invention can significantly improve the corrosion resistance of the coating, mainly due to the high Ni content, the addition of Cu element and the purification effect of rare earth elements.

[0307] (6) Coating thickness and porosity: The coating thickness of the example is uniform and the porosity is low (0.3-0.5%), which is better than that of the comparative example, indicating that the process of the present invention has high stability and can prepare high-quality coatings.

[0308] A comparison of the examples and comparative examples shows that:

[0309] (1) The performance of Comparative Example 1 (using a conventional dispersant) is lower than that of Example 2, indicating that the environmentally friendly and non-toxic metal powder ball milling dispersant of the present invention is not only environmentally friendly, but also effectively improves the powder dispersion effect, thereby improving the coating performance.

[0310] (2) The performance of Comparative Example 2 (without rare earth elements) decreased significantly, indicating that rare earth elements play a key role in improving the overall performance of the coating.

[0311] (3) The performance of Comparative Example 3 (the cladding current is too low) is the worst, indicating that appropriate cladding parameters are an important guarantee for obtaining high-performance coatings.

[0312] (4) The hardness and wear resistance of Comparative Example 4 (without solution treatment and aging) decreased significantly, indicating that the heat treatment process of the present invention is crucial to improving the coating performance.

[0313] (5) The performance of Comparative Example 5 (commercially available powder and process) was the worst, indicating that the technical solution of the present invention has significant advantages over the prior art.

[0314] In summary, this invention has successfully prepared a high-performance coating with high hardness, good toughness, high bonding strength, excellent wear resistance and corrosion resistance by optimizing alloy powder formulation, developing environmentally friendly and efficient dispersants, precisely controlling plasma cladding parameters and optimizing heat treatment process. All performance indicators are significantly better than existing technologies, and it has important industrial application value.

[0315] The above description, in conjunction with specific / preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the inventive concept, and all such substitutions or modifications should be considered within the scope of protection of the present invention.

Claims

1. A process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology, characterized in that, Includes the following steps: S1: Substrate pretreatment; The oxide layer on the surface of the alloy structural steel substrate is polished with an 80-120 grit abrasive wheel, then ultrasonically cleaned with an alcohol-acetone mixture at 300-400W for 15-20 minutes to remove oil stains. The substrate is then immersed in a 5%-8% hydrochloric acid solution and pickled at 25-35℃ for 10-15 minutes to remove the surface oxide scale. After rinsing with deionized water until pH=7, the substrate is dried. Finally, the substrate is placed in an electric resistance furnace for preheating at 200-300℃ for 30-45 minutes. The alloy structural steel substrate material is selected from 20CrMo or 40CrMo plates. The plate thickness is determined according to the working conditions. When used as a whole, the thickness is more than 50mm. When used as a precast panel, the thickness is 20-40mm. S2: Powder preparation and pretreatment; Weigh the raw materials by mass percentage: C 0.08%-0.12%, Ni 20.5%-22.0%, Co 6.0%-7.5%, Mo 2.8%-3.5%, Si 1.2%-1.8%, Mn 0.3%-0.6%, Ti 1.0%-1.5%, Al 0.3%-0.5%, V 0.4%-0.7%, Nb 0.2%-0.4%, Zr 0.15%-0.3%, Y 0.05%-0.10%, La 0.03%-0.06%, B 0.08%-0.15%, W 1.5%-2.2%, Cu 0.8%-1.2%, Ce 0.02%-0.04%, P≤0.008%, S≤0.008%, balance Fe; Add the raw material to a planetary ball mill, using an environmentally friendly and non-toxic metal powder ball milling dispersant, with a ball-to-material ratio of 6:1 and a speed of 200-250 r / min, mix for 2-3 hours, pass through a 180-300 mesh sieve, spread the powder evenly and place it in a vacuum drying oven, evacuate to a vacuum degree ≤5Pa, keep at 80-105℃ for 2-3 hours, then immerse the dried powder in a 0.5%-1.0% silane coupling agent KH-550 solution, soak at 25℃ for 5-8 minutes, remove and dry at 60-80℃ for 1-1.5 hours; S3: Pre-layer preparation; The powder treated by S2 is evenly spread on the surface of the alloy structural steel substrate pretreated by S1. The thickness of the pre-layer is controlled by a scraper to be 1.5-2.5mm. The ambient humidity is controlled at 40%-60% during the pre-laying process to avoid the powder absorbing moisture. S4: Plasma cladding; The substrate with the pre-formed layer is loaded into the plasma cladding equipment, with a rated power of 22-25KW and a rated cladding current of 230-250A; Argon gas is introduced simultaneously for protection during cladding, and the process parameters are: cladding current 170-190A, nozzle height 15-18mm, powder feeding speed 230-260g / min, powder feeding gas flow rate 7-9L / min, large ion gas flow rate 7-9L / min, small ion gas flow rate 2-3L / min, and scanning rate 190-210mm / min. After cladding, the substrate is naturally cooled to room temperature to obtain the initial coating. S5: Preliminary treatment after cladding; The sample obtained in S4 is placed in a muffle furnace for stress-relief annealing, with a heating rate of 5-8℃ / min, a temperature of 350-400℃, and a holding time of 2-3h, followed by furnace cooling to room temperature; Then, the coating surface is polished with 400-600 grit sandpaper to remove oxide scale and minor defects. S6: Heat treatment after cladding.

2. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, The purity requirements for the raw materials mentioned in step S2 are: Ni≥99.9%, Co≥99.8%, Mo≥99.5%, Si≥99.7%, Ti≥99.6%, Al≥99.9%, Nb≥99.5%, Fe≥99.9%.

3. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, The environmentally friendly and non-toxic dispersant for ball milling metal powder mentioned in step S2 includes the following raw materials by mass percentage: polyethylene glycol 400 15-25%, tea saponin 8-12%, L-glutamic acid 5-8%, citric acid 3-5%, xanthan gum 2-4%, hydrophilic nano silica 1-3%, Tween 80 5-10%, and the balance being deionized water.

4. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 3, characterized in that, The environmentally friendly and non-toxic dispersant for ball milling metal powder comprises the following raw materials in the following mass percentages: polyethylene glycol 400 21%, tea saponin 10%, L-glutamic acid 6.5%, citric acid 4%, xanthan gum 3%, hydrophilic nano silica 2%, Tween 80 7.6%, and the balance being deionized water.

5. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 3 or 4, characterized in that, The preparation method of the environmentally friendly and non-toxic dispersant for ball milling metal powder includes the following steps: (1) Preparation of pre-dissolved co-dispersed phase: Add the prescribed amount of Tween 80 and xanthan gum to the reactor, heat to 45-50℃ at 300-500 rpm and stir for 20-30 min until the xanthan gum is completely dissolved; (2) Dissolution of the main dispersed phase: Add the amount of deionized water specified in the formula to another reactor, heat to 50-60℃, slowly add PEG400, and stir at 200-300 rpm for 15-20 min; (3) Preparation of functional additive phase: Cool the main dispersed phase to 40-45℃, and add citric acid, L-glutamic acid and tea saponin in sequence. Stir for 10-15 min after each addition, and control the temperature at 40-45℃ and the pH value at 5.5-6.

5. (4) Dispersion of nano-additives: Add the amount of hydrophilic nano-silica to the functional additive phase, turn off the stirring, turn on the ultrasonic disperser, and sonicate at 300-500W power for 15-20 minutes, controlling the temperature at 40-45℃. (5) Composite maturation: After the ultrasonic treatment, turn on the stirring to 200-300 rpm, slowly pump the pre-dissolved co-dispersed phase into the reactor, stir for 30-45 min, and the maturation temperature is 40-45℃; (6) Cooling and filtration: Stop heating and allow it to cool naturally to 25-30℃. Filter the solution using a 0.22μm microporous membrane at a pressure of 0.1-0.15MPa.

6. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, The pre-laid layer in step S3 is laid using an automated powder spreading device, with the powder spreading accuracy controlled within ±0.1mm.

7. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, During the cladding process described in step S4, an infrared thermometer is used to monitor the substrate temperature in real time to ensure that the substrate temperature does not exceed 350°C.

8. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, In step S4, the tungsten electrode diameter of the plasma cladding equipment is 3-5 mm, the nozzle orifice diameter is 6-8 mm, and the argon purity is ≥99.99%.

9. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, The heating rate for stress-relief annealing in step S5 is 6℃ / min, and the holding time is 2.5h.

10. The process for producing a high-performance coating on the surface of alloy structural steel using plasma cladding technology according to claim 1, characterized in that, In step S6, (1) when 20CrMo plate is selected as the base material for the alloy structural steel, the heat treatment is as follows: ①Solution: Heat the carbon tube furnace at a rate of 4-8℃ / min to 862-870℃, hold for 1-1.5 hours, cool in oil to below 100℃, and then remove and cool to room temperature. ②Aging: The contents are fed into the muffle furnace at the specified temperature and held at 530-550℃ for 4-5 hours, then cooled with oil. ③ Low-temperature tempering: Heat the muffle furnace to 150-200℃, hold for 1-1.5 hours, and then air cool; (2) When 40CrMo plate is selected as the base material of the alloy structural steel, the heat treatment is as follows: ①Solution: Heat the carbon tube furnace at a rate of 5-7℃ / min to 850-870℃, hold for 1-1.6 hours, cool in oil to below 100℃, and then remove and cool to room temperature. ②Aging: The contents are fed into the muffle furnace at the specified temperature and held at 532-548℃ for 4-5 hours, then cooled with oil. ③ Low-temperature tempering: Heat the muffle furnace to 210-480℃, hold for 0.6-1h, and then air cool.

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