High-wear-resistance and corrosion-resistance sintering machine grate and preparation method thereof

Abstract

The invention discloses a high-wear-resistance and corrosion-resistance sintering machine grate and a preparation method thereof, and belongs to the technical field of metallurgical materials. The method comprises the following steps: selecting polystyrene foam plastic to prepare a foam model; the preparation method comprises the following steps: preparing high-entropy oxide nano powder from ferric nitrate, chromic nitrate, nickel nitrate, manganous nitrate and ammonium molybdate according to a mass ratio, stirring, precipitating, drying, calcining and ball-milling to obtain powder; preparing a water-based binder from polyvinyl alcohol, hydroxypropyl methyl cellulose, lauryl sodium sulfate, p-benzoquinone imine and deionized water according to a mass ratio; preparing an inner-layer coating solution from high-entropy oxide nano powder and a binder in proportion, dip-coating the foam model, and drying to form an inner layer; preparing an outer layer coating solution from nano chromium powder and a binder according to a ratio, and performing dip-coating and drying to form an outer layer; filling refractory sand, pouring high-chromium cast iron alloy melt, and demolding; and tempering at low temperature and strengthening the nano permeation layer. The grate substrate and the double-layer nano coating are cooperated, so that the service life is prolonged, and the cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical materials technology, specifically, it relates to a high wear-resistant and corrosion-resistant sintering machine grate bar and its preparation method. Background Technology

[0002] Sintering machines are key equipment in the metallurgical industry used for sintering mineral powder, and one of their core components is the grate bar. During the sintering process, the grate bar endures extreme conditions such as high temperatures (typically 1000-1300℃), mechanical wear, chemical corrosion, and oxidation. These conditions arise from the heavy pressure of the sintering bed, thermal stress cycles, corrosive gases (such as SO2 and CO2), and friction from particulate materials. The primary function of traditional grate bars is to support the sintering ore and allow hot air circulation, ensuring the uniformity and efficiency of the sintering process. However, due to limitations in material properties, existing sintering machine grate bars have significant shortcomings in terms of service life, maintenance costs, and production efficiency, leading to frequent replacements, increased downtime, and economic losses. According to industry data, sintering processes account for 10-15% of total energy consumption in global steel production, and grate bar failure is one of the main factors affecting the stable operation of sintering machines.

[0003] Traditional sintering machine grate bars mostly use high-chromium cast iron (HCCI) as the matrix material. This material contains 15-30% chromium, which can form a hard chromium carbide phase (Cr7C3 or Cr). 23 C6 provides certain wear resistance and heat resistance. For example, US Patent 3063696A (1962) describes an improved grate design that enhances mechanical strength and corrosion resistance through optimized alloy composition and heat treatment processes. This patent states that adding chromium and nickel can strengthen the anti-oxidation layer, forming a dense Cr2O3 protective film and reducing the high-temperature oxidation rate. However, this technology still faces challenges in practical applications: in high-sulfur environments, the Cr2O3 film is prone to sulfidation, leading to peeling and accelerated corrosion. Similarly, Chinese Patent CN102703820B (2012) discloses a heat-resistant steel for sintering machine grate bars, comprising C 0.3-0.6%, Cr 20-25%, Ni 1-3%, and Mn 0.5-1.0%, obtained through vacuum melting and heat treatment. This material shows a 20% improvement in oxidation resistance at 1100℃, but in wear tests, the wear rate remains as high as 0.15-0.20 mg / cm². 2 The values ​​are far higher than ideal. This reflects the shortcomings of traditional alloys in multiphase synergistic strengthening, which cannot simultaneously meet the requirements of wear resistance, corrosion resistance, and fatigue resistance.

[0004] Further analysis of the limitations of existing technologies reveals that current grate materials are particularly weak in corrosion resistance. During sintering, the grate is exposed to acidic gases and chloride environments, leading to pitting and stress corrosion cracking. According to ASM International's monograph "Sintering and Corrosion Resistance" (2003), the corrosion resistance of sintered stainless steel powder is significantly affected by porosity; high porosity (>5%) promotes the penetration of corrosive media, resulting in a 3-5 fold increase in localized corrosion rates. Similar problems are prevalent in sintering machine grate applications. Chinese patent CN103849819A (2014) proposes a grate production method including smelting, casting, and heat treatment, aiming to simplify the process and improve uniformity; however, this method does not introduce surface modification, resulting in a surface hardness of only HV500-600.

[0005] To overcome these problems, researchers have attempted to improve performance through the addition of alloying elements and improvements in heat treatment processes. For example, adding rare earth elements (such as Ce and La) can refine the grains and improve toughness. Chinese patent CN105588439A (2016) describes a method for detecting grate bars on a sintering machine trolley, indirectly reflecting existing grate bar defects such as cracks and deformation. These defects originate from porosity and shrinkage during the casting process, and the poor fluidity of high-chromium cast iron leads to uneven casting. Despite the progress made in the above technologies, the overall shortcomings of existing technologies are obvious. First, although the traditional high-chromium cast iron matrix is ​​wear-resistant, its corrosion and oxidation resistance are limited, with corrosion rates as high as 50-100 μm / year in acidic environments, resulting in a shortened service life of 3-6 months. Second, surface coating technologies such as thermal spraying HEA are effective, but the metallurgical bond between the coating and the substrate is weak, and it is prone to peeling off under thermal cycling. Third, casting processes such as lost foam casting improve precision, but do not integrate nano-reinforcement, resulting in suboptimal overall performance. Furthermore, the thermodynamic criterion for high-entropy materials is a mixing entropy ≥ 1.5-1.6R. Even if a pentagonal system deviates slightly from equimolarity, it can still reach this level and is considered a "high-entropy" or "multi-principal-element complex solid solution".

[0006] In summary, existing sintering machine grate technology faces bottlenecks in wear resistance, corrosion resistance, and oxidation resistance, failing to meet the demands of modern metallurgical industries for high efficiency and low cost. While alloying optimization of traditional materials has made progress, it is limited by a single mechanism and cannot achieve multi-functional synergy. Surface engineering and advanced casting have introduced new ideas, but the lack of coating peeling, process complexity, and nanoscale control remain obstacles. Therefore, developing a grate preparation method that integrates high-entropy oxide nanocoatings, dual-layer protective design, and optimized lost foam casting has urgent practical significance and broad application prospects. This method can significantly extend service life (expectedly by 2-3 times), reduce replacement frequency, decrease production costs, and improve sintering efficiency, thus promoting the sustainable development of the metallurgical industry. Summary of the Invention

[0007] To address the shortcomings of existing sintering machine grate bars in terms of wear resistance, corrosion resistance, and oxidation resistance, as well as the problems of short service life, frequent replacement leading to increased production costs and reduced efficiency, this invention provides a high-wear-resistant and corrosion-resistant sintering machine grate bar and its preparation method. This invention achieves metallurgical synergistic strengthening of the matrix and coating by introducing a double-layer coating design using high-entropy oxide nanoparticles, optimizing the water-based binder formulation, and combining it with lost foam casting technology, significantly improving the overall performance of the grate bar.

[0008] The present invention adopts the following technical solution: a method for preparing a high wear-resistant and corrosion-resistant sintering machine grate bar, which, by weight, includes the following steps: (1) preparation of foam model: polystyrene foam plastic (CAS No.: 9003-53-6) is selected as the model material, and a sintering machine grate bar foam model is prepared by injection molding; (2) preparation of high entropy oxide nanopowder: ferric nitrate (CAS No.: 10421-48-4), chromium nitrate (CAS No.: 13536-79-3), nickel nitrate (CAS No.: 14216-75-2), manganese nitrate (CAS No.: 10377-66-9), and ammonium molybdate (CAS No.: 12054-85-2) are prepared in a mass ratio of (15-25): (2 0-30): (10-20): (5-15): (5-10) were mixed to obtain a mixture with a total mass of 100 parts. Then, the mixture was stirred and mixed. Then, tannic acid (CAS No.: 1401-55-4) solution with a mass of 15-25 times that of the mixture was added, followed by polyethyleneimine (CAS No.: 9002-98-6) with a mass of 8-12 times that of the mixture was added. The pH was adjusted and the temperature was raised to 70-80℃. The mixture was stirred continuously and then freeze-dried under vacuum. Then, it was calcined under a nitrogen atmosphere to obtain particles and ball milled to obtain high-entropy oxide nanopowder; (3) Preparation of water-based binder: Polyvinyl alcohol (CAS No.: 9002-89-5), hydroxypropyl methylcellulose (CAS No.: 9004- 65-3), sodium dodecyl sulfate (CAS No.: 151-21-3), p-benzoquinone imine (CAS No.: 3009-34-5), and deionized water were mixed in a mass ratio of (4-8): (1-3): (0.5-1.5): (2-6): (30-50) to a total mass of 100 parts. The foam was degassed to obtain a low-VOC water-based adhesive; (4) Preparation and application of the inner coating liquid: The high-entropy oxide nanopowder from step (2) and the water-based adhesive from step (3) were ultrasonically dispersed in a mass ratio of (2-4): 1 to obtain the inner coating liquid; The foam model from step (1) was immersed in the inner coating liquid and dried to obtain a nano-reinforced inner coating; (5) Preparation and application of the outer coating liquid: The purity of the outer coating liquid was... 99.9% nano-chromium powder (average particle size 20-50nm, CAS No.: 7440-47-3) and the water-based binder in step (3) are ultrasonically dispersed at a mass ratio of (3-5):1 to obtain an outer coating liquid; the foam model after step (4) is immersed in the outer coating liquid to obtain a nano-chromium outer coating; (6) Lost foam casting: the foam model after step (5) is placed in a sand box, filled with refractory sand (main component is silica sand, CAS No.: 14808-60-7), vibrated and compacted, and then molten high-chromium cast iron alloy liquid is poured at a pouring temperature of 1450-1550℃. After cooling to room temperature, the mold is demolded; (7) Post-treatment: the casting is subjected to low-temperature tempering, and then surface nano-diffusion layer strengthening is performed.

[0009] Preferably, the surface roughness Ra of the foam model in step (1) is controlled between 0.5 and 2.0 μm; the density of the foam model in step (1) is 15-25 kg / m³. 3 The injection molding temperature is 180-220℃, and the cooling time for injection molding is 5-10 min. The parameters for stirring and mixing in step (2) are as follows: stirring at a temperature of 50-60℃ and a speed of 150-200 rpm until homogeneous. The concentration of tannic acid solution in step (2) is 0.3-0.7 g / L, and the molecular weight of polyethyleneimine is 600-1000. The method for adjusting pH in step (2) is as follows: adjusting pH to 8.5-9.5 using sodium hydroxide (CAS No.: 1310-73-2) solution. The temperature for heating in step (2) is 70-80℃. The parameters for continuous stirring in step (2) are as follows: stirring continuously at a speed of 180-250 rpm for 4-8 h. The parameters for vacuum freeze drying in step (2) are as follows: temperature -50~-40℃, vacuum degree 0.01-0.05 mbar, time 24-48 h.

[0010] Preferably, the calcination parameters in step (2) are as follows: calcination at 850-1000℃ for 16-28h, with a nitrogen flow rate of 0.5-1.0L / min; the ball milling parameters in step (2) are as follows: using zirconia balls (CAS No.: 1314-23-4), with a ball-to-material mass ratio of 8:1-12:1, a ball milling speed of 300-600r / min, a ball milling time of 6-14h, and a specific surface area of ​​50-100m² for the ball-milled nanoparticles. 2 / g; In step (3), the degree of polymerization of polyvinyl alcohol is 1700-2400, and the viscosity of hydroxypropyl methylcellulose is 4000-6000 mPa·s.

[0011] Preferably, the mixing parameters in step (3) are as follows: stirring at 80-100 rpm for 80-120 min; the degassing parameters in step (3) are as follows: degassing at a vacuum of 0.1-0.5 mbar and a temperature of 70-90℃ for 30-50 min; the ultrasonic dispersion parameters in step (4) are as follows: power of 300-500 W, frequency of 25-35 kHz, time of 25-45 min, and temperature of 25-35℃; the solid content of the inner coating liquid in step (4) is 40-60 wt%.

[0012] Preferably, the immersion parameters in step (4) are as follows: time 1-3 min, the foam model is fully submerged during immersion, and hot air circulation drying is used with a wind speed of 2-4 m / s; the drying parameters in step (4) are as follows: drying at 70-90℃ for 2-4 h; the purity test of nano-chromium powder in step (5) is based on ASTM B330 standard, and the viscosity of the outer coating liquid is 500-800 mPa·s; the ultrasonic dispersion parameters in step (5) are as follows: power 300-500 W, frequency 25-35 kHz, time 25-45 min, and temperature 25-35℃.

[0013] Preferably, the surface roughness Ra of the outer coating after drying in step (5) is 0.2-0.8μm; the soaking parameters in step (5) are as follows: time 1-3min, and then drying at 90-110℃ for 3-5h; the particle size of the refractory sand in step (6) is 40-70 mesh, the vibration compaction frequency is 50-60Hz, and the pouring speed is 0.5-1.0kg / s.

[0014] Preferably, in step (6), the high-chromium cast iron alloy is composed of 67-70 parts of iron (CAS No.: 7439-89-6), 25-28 parts of chromium (CAS No.: 7440-47-3), 1.5-2.5 parts of nickel (CAS No.: 7440-02-0), and 0.6-0.8 parts of manganese (CAS No.: 7439-96-5), which belongs to the typical category of high-chromium white cast iron (HCCI); the deoxidizer of the high-chromium cast iron alloy melt in step (6) is aluminum wire (CAS No.: 7429-90-5), with an addition amount of 0.1-0.3wt%; the cooling rate is 10-20℃ / min; the heating rate of the low-temperature tempering in step (7) is 5-10℃ / min, the low-temperature tempering temperature is 350-450℃, and the low-temperature tempering holding time is 3-5h.

[0015] Preferably, in step (7), the surface nano-infiltration layer strengthening is performed under an argon atmosphere, wherein the argon purity is 99.99% and the pressure is 0.1-0.3MPa; the surface nano-infiltration layer strengthening temperature in step (7) is 600-700℃ and the time is 1-2h.

[0016] A high wear-resistant and corrosion-resistant sintering machine grate bar is obtained by the preparation method described above.

[0017] Compared to existing technologies, this invention offers the following advantages: By innovatively integrating a double-layer coating design using high-entropy oxide nanopowder, optimizing the water-based binder formulation, and employing lost foam casting technology, this invention significantly improves the wear resistance, corrosion resistance, and oxidation resistance of sintering machine grate bars. In existing technologies, while traditional high-chromium cast iron grate bars possess basic wear resistance, their overall performance under high-temperature, corrosive, and oxidizing environments is insufficient, resulting in a service life of only 3-6 months. Frequent replacements increase production costs by 20-30% or more. This invention introduces a multi-element synergistic strengthening mechanism through nanotechnology, achieving optimizations of over 60% improvement in wear resistance, over 80% improvement in corrosion resistance, and over 50% improvement in oxidation resistance, extending service life by 2-3 times and significantly reducing maintenance costs and downtime. These advantages stem from the following mechanisms and innovations: First, this invention uses high-entropy oxide nanopowder as the core material for the inner coating, a significant improvement over existing technologies. In existing technologies, sintering machine grate bars often rely on a single alloying element (such as chromium) to provide wear resistance. For example, the high-chromium cast iron described in Chinese patent CN102703820B enhances hardness by forming a Cr7C3 carbide phase. However, this single mechanism is prone to failure under complex damage environments, such as the sulfidation and peeling of the Cr2O3 protective film in high-sulfur gas, leading to a 3-5 times increase in corrosion rate. The high-entropy effect originates from the mixing of multiple elements with equal atomic ratios (such as Fe, Cr, Ni, Mn, Mo), resulting in lattice distortion and enhanced thermodynamic stability, inhibiting phase separation and grain coarsening. In this invention, the preparation of high-entropy oxide nanoparticles employs a sol-gel method combined with vacuum freeze-drying and calcination to obtain nanoparticles with an average particle size of 50-100 nm and a specific surface area of ​​50-100 m². 2 / g. This nanoscale further amplifies the hysteresis diffusion effect: the increased density of nanograin boundaries (grain boundary volume fraction >20%) hinders dislocation movement and diffusion paths, reducing the penetration rate of oxygen ions and corrosive media.

[0018] Regarding the wear resistance mechanism, the inner coating of this invention forms a composite structure of hard phases (such as M23C6 and σ phases) and soft matrix (such as FCC phase) through a cocktail effect (multi-element synergy), achieving a hardness of HV750-850. Existing technologies, such as US Patent 3063696A, only refine carbides through heat treatment, but the wear mechanism is still mainly abrasive wear, with a wear rate of 0.15-0.20 mg / cm². 2 In this invention, nanoparticles form a self-lubricating transfer film during friction, reducing adhesive wear; simultaneously, nanoscale-induced Hall-Petch strengthening increases hardness by over 30%. In the performance tests of this invention, the wear rate of the product in the example was only 0.031-0.058 mg / cm². 2This confirms the effectiveness of this mechanism. Secondly, the introduction of the outer nano-chromium coating further enhances the corrosion and oxidation resistance, a rare dual-layer design in existing technologies. Traditional grate surfaces are often uncoated or treated with a single thermal spray, resulting in weak interfacial bonding and a peeling rate >10% under thermal cycling. In this invention, the outer layer uses 99.9% pure nano-chromium powder with a particle size of 20-50 nm, prepared by vapor deposition to form a dense coating 30-60 μm thick. The nano-chromium of this invention avoids the formation of Cr depletion zones, with an oxidation weight gain of only 0.5 mg / cm³ at high temperatures (1000-1300℃). 2 / h, antioxidant performance improved by 50%. In corrosive environments, nanoscale processes promote the self-healing of the passivation film: Cr 3+ Rapid migration forms a dense film that blocks the penetration of chloride and sulfate ions. The salt spray test time of this invention reaches 1327-1590 hours, far exceeding the 600-800 hours of traditional grate bars.

[0019] The synergistic effect of the dual-layer coating is one of the core mechanisms of this invention. The inner HEA layer provides a multi-element corrosion-resistant buffer, while the outer nano-chromium layer enhances the surface barrier, forming a gradient structure to prevent single-layer coating failure. In existing technologies, coatings are mostly single-layer HEA or Cr. This invention achieves in-situ fusion through lost foam casting: when the foam model evaporates, the coating powder metallurgically bonds with the molten high-chromium cast iron to form a diffusion layer (5-10 μm thick). Adhesion testing achieves grade 0 of GB / T9286-2021, confirming the mechanism.

[0020] The optimization of water-based binders is another key innovation. Existing casting coatings mostly use solvent-based binders, which are high in VOCs and have poor environmental impact. The binder of this invention consists of polyvinyl alcohol, hydroxypropyl methylcellulose, sodium dodecyl sulfate, p-benzoquinone imine, and deionized water, with a total mass of 100 parts. Polyvinyl alcohol provides film-forming properties (degree of polymerization 1700-2400), hydroxypropyl methylcellulose regulates viscosity (4000-6000 mPa·s), sodium dodecyl sulfate acts as a surfactant to reduce surface tension (<30 mN / m), and p-benzoquinone imine acts as a reinforcing agent to promote cross-linking. Mechanism: Ultrasonic dispersion (power 300-500W) forms a stable colloid, which, after drying, forms a network structure, increasing the coating density by >95%. The binder of this invention has high flexibility and thermal stability up to 200℃, ensuring no decomposition during the casting process.

[0021] The use of lost foam casting further amplifies the above advantages. Existing sand casting easily introduces porosity and inclusions, resulting in a density of <95%. This invention uses a polystyrene foam model (density 15-25 kg / m³). 3 The surface roughness Ra is 0.5-2.0μm to ensure uniform coating. Mechanism: During casting (1450-1550℃), the foam pyrolysis generates gas, and the metal quickly fills the gap, forming a casting without a parting line.

[0022] In summary, this invention achieves synergistic optimization through the aforementioned mechanisms: the nano-inner layer provides wear-resistant buffering, the nano-chromium outer layer enhances the corrosion-resistant barrier, the water-based binder ensures uniformity, and lost foam casting achieves high-precision fusion. Compared to existing technologies, this invention offers more comprehensive performance and greater industrialization potential. Test results show a Vickers hardness of 758-846 HV and an adhesion rating of 0, demonstrating its superiority. The inner layer of this invention uses high-entropy oxide nanopowder, providing a multi-element synergistic oxide buffer layer. Due to its high entropy and strong lattice distortion, the high-entropy oxide inhibits the penetration of oxygen ions and corrosive media, amplifying the delayed diffusion effect. Simultaneously, the nanoscale further enhances Hall-Petch strengthening and self-healing passivation capabilities. A dense composite oxide film is formed at high temperatures, exhibiting excellent antioxidant / corrosion resistance. Tannic acid chelates with metal ions at multiple points: Polyphenolic ligands (such as tannic acid / tannic acid, other polyphenols) can form a multinuclear complex network with various transition metal ions through polyphenolic hydroxyl groups, "locking" different metal ions in the same organic framework and maintaining a uniform distribution at both the macroscopic and nanoscale levels. By utilizing polyphenol-metal complex / resin precursors, high-entropy oxides or multi-metal oxides with uniform elemental distribution can be obtained in subsequent calcination. Polyethyleneimine (PEI) regulates charge and spatial dispersion: As a polyamine polymer, PEI, on the one hand, adjusts pH to promote the co-precipitation of multi-metal hydroxides / complexes; on the other hand, it inhibits the regional aggregation of metal species and improves mixing homogeneity through electrostatic and steric hindrance interactions. In the wet chemical synthesis of high-entropy oxides, similar polymers / organic ligands (PVP, PEG, etc.) have been shown to stabilize mixed metal cations at the nanoscale and directly convert them into single-phase HEO in subsequent lower-temperature calcination. Freeze-drying and nitrogen calcination: Maintaining uniform distribution and suppressing phase separation; freeze-drying avoids solute migration and enrichment during ordinary drying processes, significantly reducing the "coffee ring effect," and is used in many high-entropy oxide and multi-metal oxide systems to maintain precursor homogeneity and promote the formation of single-phase HEO. Within the temperature range of 900-950℃, the polymetallic oxide precursors obtained by sol-gel can be transformed into single-phase or near-single-phase high-entropy oxide solid solutions without the need for reduction to metal. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the high-entropy oxide nanopowder prepared in Example 1.

[0024] Figure 2 This is the energy spectrum of the high-entropy oxide nanopowder prepared in Example 1.

[0025] Figure 3 This is the infrared spectrum of the low-VOC water-based binder prepared in Example 1.

[0026] Figure 4 This is a sample image of the high wear-resistant and corrosion-resistant sintering machine grate bar prepared in Example 1. Detailed Implementation

[0027] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of mass is grams (g).

[0028] Example 1

[0029] The preparation method of high wear-resistant and corrosion-resistant sintering machine grate bars includes the following steps: (1) Foam model preparation: polystyrene foam plastic is selected as the model material, and the sintering machine grate bar foam model is prepared by injection molding. The surface roughness Ra of the model is controlled at 1.2μm, and the density of the foam model is 20kg / m³. 3 , Injection temperature 200℃, cooling time 7min. (2) Preparation of high entropy oxide nanopowder: Iron nitrate, chromium nitrate, nickel nitrate, manganese nitrate and ammonium molybdate were mixed in a mass ratio of 20:25:15:10:7.5 (total mass 77.5g, i.e. 20g iron nitrate, 25g chromium nitrate, 15g nickel nitrate, 10g manganese nitrate and 7.5g ammonium molybdate) to obtain a mixed solution. The mixture was stirred evenly at a temperature of 55℃ and a speed of 175rpm. Then, 20 times the mass of the mixed solution of 0.5g / L tannic acid solution was added. After mixing, 10 times the mass of the mixed solution of polyethyleneimine (molecular weight) was added. The sample (800g) was adjusted to pH 9.0 with sodium hydroxide solution, heated to 75℃, and stirred continuously at 215 rpm for 6 hours. It was then subjected to vacuum freeze-drying (temperature -45℃, vacuum degree 0.03 mbar, time 36 hours), followed by calcination at 925℃ for 22 hours under a nitrogen atmosphere (flow rate 0.75 L / min). The resulting particles were then ball-milled using zirconia balls at a ball-to-material mass ratio of 10:1, at a milling speed of 450 rpm for 10 hours, yielding an average particle size of 75 nm and a specific surface area of ​​75 m². 2 / g of high-entropy oxide nanoparticles, the transmission electron microscopy image of which is shown below Figure 1 As shown, its elemental distribution is as follows Figure 2As shown, although not uniformly distributed, all elements are chelated as much as possible. Tannic acid acts as a polyphenol reducing / complexing agent to promote the precipitation of metal ions; polyethyleneimine regulates pH and particle dispersion; nitrogen atmosphere prevents excessive oxidation, but organic residual carbon provides a local reducing atmosphere to form a stable high-entropy oxide phase. (3) Preparation of water-based binder: Polyvinyl alcohol (degree of polymerization 2000), hydroxypropyl methylcellulose (viscosity 5000 mPa·s), sodium dodecyl sulfate, p-benzoquinone imine, and deionized water are mixed in a mass ratio of 6:2:1:4:40 (total mass is 53g, i.e., 6g polyvinyl alcohol, 2g hydroxypropyl methylcellulose, 1g sodium dodecyl sulfate, 4g p-benzoquinone imine, and 40g deionized water), stirred at 92 rpm for 100 min, and then degassed at a vacuum of 0.3 mbar and a temperature of 80℃ for 40 min to obtain a low-VOC water-based binder. Its infrared spectrum is shown in the figure. Figure 3 As shown. (4) Preparation and application of inner coating liquid: The high entropy oxide nanopowder of step (2) and the water-based binder of step (3) are ultrasonically dispersed at a mass ratio of 3:1, with a power of 400W, a frequency of 30kHz, a time of 35min, and a temperature of 30℃, to obtain an inner coating liquid with a solid content of 50wt%; the foam model of step (1) is immersed in the inner coating liquid to ensure uniform coverage, with an immersion time of 2min, and then dried in hot air circulation at 80℃ (wind speed 3m / s) for 3h to obtain a nano-reinforced inner coating with an inner layer thickness of 35μm. (5) Preparation and application of outer coating liquid: 99.9% pure nano-chromium powder (average particle size 35nm, prepared by vapor deposition) and water-based binder from step (3) are ultrasonically dispersed at a mass ratio of 4:1, with the same parameters as in step (4), to obtain an outer coating liquid with a viscosity of 650mPa·s; the foam model treated in step (4) is immersed in the outer coating liquid for 2min, and then dried at 100℃ for 4h to obtain a nano-chromium outer coating with an outer layer thickness of 45μm and a surface roughness Ra of 0.5μm. (6) Lost foam casting: The foam model after step (5) is placed in a sand box, filled with refractory sand (mainly silica sand, particle size 55 mesh), vibrated and compacted (frequency 55Hz), and then molten high-chromium cast iron alloy is poured. The high-chromium cast iron alloy is composed of 68.5 parts iron, 26.5 parts chromium, 2 parts nickel, and 0.7 parts manganese, with 0.2wt% aluminum wire deoxidizer added. The pouring temperature is 1500℃, the pouring speed is 0.75kg / s, the cooling rate is 15℃ / min, and the casting is demolded after cooling to room temperature. (7) Post-treatment: The casting is subjected to low-temperature tempering at 400℃, heating rate 7.5℃ / min, and time 4h. Then, surface nano-diffusion layer strengthening is carried out in an argon atmosphere (purity 99.99%, pressure 0.2MPa) at 650℃ for 1.5h to obtain a high wear-resistant and corrosion-resistant sintering grate bar with a coating hardness of HV800 and an adhesion grade of 0. Figure 4 As shown.

[0030] The specific parameters for Examples 2-8 and Comparative Examples 1-8 are listed in the following tables. The tables are designed according to the progress of the steps, with each table showing different parameter values ​​for the examples / comparative examples, covering all parameter endpoints and intermediate values. Only the parameters that have changed from Example 1 are listed in the tables; the remaining parameters are the same as in Example 1.

[0031] Table 1: Parameters for foam model preparation in step (1)

[0032]

[0033] Table 2: Preparation parameters of high-entropy oxide nanopowder in step (2)

[0034]

[0035] Table 3: Preparation parameters of high-entropy oxide nanopowder in step (2)

[0036]

[0037] Table 4: Preparation parameters of water-based adhesive in step (3)

[0038]

[0039] Table 5: Coating preparation parameters for steps (4) and (5)

[0040]

[0041] Table 6: Casting and post-processing parameters for steps (6) and (7)

[0042]

[0043] Table 7: Differences in parameters for comparative examples (the rest are the same as in Example 1)

[0044]

[0045] To verify the performance of the high wear-resistant and corrosion-resistant sintering machine grate bars described in this invention, multi-dimensional tests were conducted on the products prepared in Examples 1-8 and Comparative Examples 1-8. The tests included Vickers hardness (HV), wear resistance (wear rate), corrosion resistance (salt spray test time), and adhesion (cross-cut test grade). The test methods are as follows: Vickers hardness test: An HV-1000 Vickers hardness tester was used, with a load of 1 kg and a holding time of 15 s. Wear resistance test: According to GB / T3960-2016 standard, an MMW-1 friction and wear testing machine was used, with a GCr15 steel ring as the mating part, a load of 300 N, a rotation speed of 400 r / min, and a time of 60 min. The wear rate (mg / cm²) was calculated. 2Corrosion resistance test: According to GB / T10125-2022 standard, a salt spray test chamber with 5% NaCl solution and a temperature of 35℃ was used. The time (h) until obvious corrosion appeared was recorded. Adhesion test: According to GB / T9286-2021 standard, the cross-cut test was used with a spacing of 2mm. The evaluation level was 0-5, with level 0 being the best.

[0046] Table 8: Performance Test Results

[0047]

[0048] The test results show that the Vickers hardness of the products in the examples ranges from 758.4 to 846.1 HV, and the wear rate ranges from 0.031 to 0.058 mg / cm². 2 The salt spray test results ranged from 1326.9 to 1589.7 hours, with adhesion rated at level 0, demonstrating excellent performance. In contrast, the comparative test results, due to the absence or substitution of key components or parameter deviations, showed a decrease in hardness to 489.1-568.2 HV and an increase in abrasion rate to 0.135-0.191 mg / cm². 2 The salt spray time was reduced to 612.7-812.5 hours, and the adhesion was reduced to level 2-4. This demonstrates the necessity of the key components (such as tannic acid, polyethyleneimine, p-benzoquinone imine, and nanopowder) and parameter range of the present invention, as well as the superiority of combining the double-layer nano-coating with lost foam casting.

[0049] Performance index analysis based on mechanism: Vickers hardness (HV): The average hardness of the examples was 799.5 HV, far higher than the 522.13 HV of the comparative example. This is due to the cocktail effect and nanoscale reinforcement of HEA nanopowder: multi-element (Fe-Cr-Ni-Mn-Mo) synergistically forms a hard phase (such as M23C6) and a soft matrix (FCC phase), combined with the Hall-Petch effect (nanograin boundary density >20%), which hinders dislocation movement and increases hardness by more than 30%. At the same time, the metallurgical bonding between the double coating and the high-chromium cast iron matrix (diffusion layer 5-10μm) further strengthens the surface. The test method (load 1kg, hold for 15s) reflects the overall hardness contribution of the coating. The comparative example lacks key components, resulting in powder particle coarsening or coating unevenness, and a decrease in hardness. Abrasion resistance (wear rate): The average wear rate of the examples was 0.04475mg / cm. 2 The concentration decreased by 72.48% compared to the comparative sample of 0.1626 mg / cm³. 2Mechanistically, the nanoparticles in the inner layer of the HEA form a self-lubricating transfer film during friction, reducing adhesive wear; the high-entropy effect inhibits phase separation and grain coarsening, maintaining structural stability. Test conditions (load 300N, rotation speed 400r / min, 60min, paired part GCr15 steel) simulate the wear environment of a sintering machine. The low wear rate in the example confirms the nanoscale amplified hysteresis diffusion effect, hindering abrasive particle penetration. Deviations in the comparative parameters (such as excessively high calcination temperature) lead to over-sintering of the powder, reducing the specific surface area (normally 50-100m²). 2 / g), thus weakening the strengthening mechanism. Corrosion resistance (salt spray test time): The average salt spray time of the example was 1446.61h, an extension of 105.99% compared to 702.29h of the comparative example. The outer layer of nano-chromium (particle size 20-50nm) forms a dense passivation film (Cr2O3), promoting self-healing and blocking the penetration of chloride and sulfate ions; the inner HEA layer provides a multi-element corrosion-resistant buffer, avoiding Cr depletion zones. The dual-layer gradient structure synergistically resists corrosion, with an oxidation weight gain of only 0.5mg / cm³. 2 / h. The test (5% NaCl, 35℃) simulated a corrosive environment. The long corrosion resistance of the examples stemmed from the coating density >95% and metallurgical bonding. Replacing nano-chromium with micron-sized chromium in the comparative examples resulted in a less dense film, increasing the corrosion rate by 3-5 times. Adhesion (cross-cut grade): All examples were grade 0, while the comparative examples averaged grade 3. The mechanism lies in the optimization of the water-based binder: p-benzoquinone imine promotes cross-linking, forming a network structure; polyvinyl alcohol and hydroxypropyl methylcellulose provide film-forming properties and viscosity; sodium dodecyl sulfate reduces surface tension (<30mN / m). In lost foam casting, foam pyrolysis promotes in-situ fusion of the coating with the melt, achieving an adhesion grade of 0 according to GB / T9286-2021. The test (2mm spacing) showed that the comparative examples lacked reinforcing agents or had parameter deviations, resulting in a coating peeling rate >10%. Comparative examples, by modifying key components or parameters, verified the necessity of the inventive elements: Comparative Example 1 (lacking tannic acid): Tannic acid is crucial as a reducing agent in the preparation of HEA powder using the sol-gel method. Its absence leads to insufficient precipitation of metal ions, uneven powder particles (reduced specific surface area), a hardness of 512.6 HV, and an abrasion rate of 0.168 mg / cm². 2 Salt spray test: 682.4 hours; adhesion rating: 3. Mechanism: No reduction, inhibits high-entropy effect, weakens lattice distortion. Comparative Example 2 (polyethyleneimine replaced with polyvinyl alcohol): Polyethyleneimine (molecular weight 600-1000) acts as a stabilizer to regulate pH and complexation. After replacement, powder agglomeration occurs, nanoscale loss occurs, hardness is 498.3 HV, and abrasion rate is 0.182 mg / cm². 2(Highest) Salt spray test: 651.9 h; Adhesion rating: 4. Mechanism: Stabilizer failure, weakened delayed diffusion effect, and facilitated dislocation movement. Comparative Example 3 (lacking p-benzoquinone imine): p-benzoquinone imine promotes cross-linking in the binder; its absence leads to decreased coating flexibility and thermal stability (200℃), hardness 535.7 HV, and abrasion rate 0.149 mg / cm². 2 Salt spray test: 728.6 hours; adhesion rating: 3. Mechanism: No cross-linking, network structure disintegrates, coating density <95%, easily peeled off. Comparative Example 4 (calcination temperature 1200℃): Exceeding this range leads to excessive powder sintering and grain coarsening (specific surface area <50m²). 2 / g), hardness 489.1HV (lowest), abrasion rate 0.191mg / cm 2 (Highest) Salt spray test: 612.7 h; Adhesion rating: 4. Mechanism: High-entropy stability is disrupted, phase separation is intensified, and the Hall-Petch effect fails. Comparative Example 5 (Inner layer powder: binder 1:1): Insufficient powder ratio leads to inadequate HEA reinforcement; hardness: 521.4 HV; abrasion rate: 0.159 mg / cm². 2 Salt spray test: 705.3 hours; adhesion rating: 3. Mechanism: Weakened cocktail effect, less hard phase formation, unstable self-lubricating film. Comparative Example 6 (outer layer micron-sized chromium powder): Nanoscale (20-50 nm) is key to passivation film self-healing; micron-sized (10 μm) results in porous film; hardness: 547.9 HV; wear rate: 0.142 mg / cm². 2 Salt spray test: 756.8 hours; adhesion rating: 2. Mechanism: Surface barrier failure leads to a 3-5 fold increase in the penetration rate of corrosive media. Comparative Example 7 (reinforced with missing nano-infiltration layer): Post-treatment reinforcement improves metallurgical bonding; the missing layer results in a weak interface; hardness: 568.2 HV; wear rate: 0.135 mg / cm². 2 Salt spray resistance 812.5h (relatively high but still poor), adhesion grade 2. Mechanism: No argon permeation layer (600-700℃), thin diffusion layer, peeling off under thermal cycling. Comparative Example 8 (pouring temperature 1400℃): Too low temperature leads to poor melt fluidity, uneven filling, increased porosity, hardness 503.8HV, wear rate 0.175mg / cm². 2 Salt spray test result: 668.1 hours; adhesion rating: 3. Mechanism: Lost foam casting failure, lack of in-situ fusion, density <95%.

[0050] In summary, the results confirm the necessity of the key components and parameter ranges of this invention. The synergistic mechanism of the double-layer nano-coating and lost foam casting significantly improves the wear resistance and corrosion resistance of the sintering machine grate, extending its service life by 2-3 times.

[0051] The above description, in conjunction with specific 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, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing a high wear-resistant and corrosion-resistant sintering machine grate bar, characterized in that: The process, by weight, includes the following steps: (1) preparing a sintering machine grate foam model by injection molding; (2) mixing ferric nitrate, chromium nitrate, nickel nitrate, manganese nitrate, and ammonium molybdate to obtain a mixed solution, then stirring and mixing, then adding tannic acid solution and polyethyleneimine, adjusting the pH and raising the temperature, stirring continuously, then performing vacuum freeze-drying, calcining to obtain particles, and ball milling to obtain high-entropy oxide nanopowder; (3) mixing polyvinyl alcohol, hydroxypropyl methylcellulose, sodium dodecyl sulfate, p-benzoquinone imine, and deionized water, and degassing to obtain... (4) Disperse the high-entropy oxide nanopowder from step (2) with the water-based binder from step (3) using ultrasonication to obtain an inner coating liquid; immerse the foam model from step (1) in the inner coating liquid and dry it to obtain a nano-reinforced inner coating; (5) Disperse the nano-chromium powder with the water-based binder from step (3) using ultrasonication to obtain an outer coating liquid; immerse the foam model treated in step (4) in the outer coating liquid to obtain a nano-chromium outer coating; (6) Cast the foam model treated in step (5).

2. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: In step (1), polystyrene foam is used to prepare the sintering machine grate foam model by injection molding; the surface roughness Ra of the foam model in step (1) is controlled at 0.5-2.0 μm; the density of the foam model in step (1) is 15-25 kg / m³. 3 The injection molding temperature is 180-220℃, and the cooling time is 5-10 min. In step (2), the mass ratio of ferric nitrate, chromium nitrate, nickel nitrate, manganese nitrate, and ammonium molybdate is (15-25):(20-30):(10-20):(5-15):(5-10). The mixing parameters in step (2) are as follows: the mixture is stirred evenly at a temperature of 50-60℃ and a speed of 150-200 rpm. In step (2), the amount of tannic acid solution is 15-25 times the mass of the mixture, and the amount of polyethyleneimine is 8-12 times the mass of the mixture. In step (2), the concentration of tannic acid solution is 0.3-0.7 g / L, and the molecular weight of polyethyleneimine is 600-1000. In step (2), the pH is adjusted as follows: the pH is adjusted to 8.5-9.5 using sodium hydroxide solution. In step (2), the temperature is 70-80℃. In step (2), the parameters for continuous stirring are as follows: stirring continuously at 180-250 rpm for 4-8 hours. In step (2), the parameters for vacuum freeze drying are as follows: temperature -50~-40℃, vacuum degree 0.01-0.05 mbar, time 24-48 hours.

3. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: The calcination parameters in step (2) are as follows: calcination at 850-1000℃ for 16-28h under a nitrogen atmosphere, with a nitrogen flow rate of 0.5-1.0L / min; the ball milling parameters in step (2) are as follows: using zirconia balls, with a ball-to-material mass ratio of 8:1-12:1, a ball milling speed of 300-600r / min, a ball milling time of 6-14h, and a specific surface area of ​​50-100m² for the ball-milled nanoparticles. 2 / g; In step (3), the degree of polymerization of polyvinyl alcohol is 1700-2400, and the viscosity of hydroxypropyl methylcellulose is 4000-6000 mPa·s.

4. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: The mixing parameters in step (3) are as follows: stirring at 80-100 rpm for 80-120 min; the degassing parameters in step (3) are as follows: degassing at a vacuum of 0.1-0.5 mbar and a temperature of 70-90℃ for 30-50 min; the ultrasonic dispersion parameters in step (4) are as follows: power of 300-500 W, frequency of 25-35 kHz, time of 25-45 min, and temperature of 25-35℃; the solid content of the inner coating liquid in step (4) is 40-60 wt%; the mass ratio between polyvinyl alcohol, hydroxypropyl methylcellulose, sodium dodecyl sulfate, p-benzoquinone imine, and deionized water in step (3) is (4-8):(1-3):(0.5-1.5):(2-6):(30-50); the mass ratio between the high entropy oxide nanopowder in step (2) and the water-based binder in step (3) in step (4) is (2-4):

1.

5. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: The parameters for immersion in step (4) are as follows: time 1-3 min, the foam model is fully submerged during immersion, and hot air circulation drying is used with a wind speed of 2-4 m / s; the parameters for drying in step (4) are as follows: drying at 70-90℃ for 2-4 h; the purity test of nano-chromium powder in step (5) is based on ASTM B330 standard, and the viscosity of the outer coating liquid is 500-800 mPa·s; the parameters for ultrasonic dispersion in step (5) are as follows: power 300-500W, frequency 25-35kHz, time 25-45 min, temperature 25-35℃; the mass ratio between nano-chromium powder and water-based binder in step (3) in step (5) is (3-5):

1.

6. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: The surface roughness Ra of the outer coating after drying in step (5) is 0.2-0.8μm; the soaking parameters in step (5) are as follows: time 1-3min, and then drying at 90-110℃ for 3-5h; the particle size of the refractory sand in the sand box in step (6) is 40-70 mesh, the vibration compaction frequency is 50-60Hz, and the pouring speed is 0.5-1.0kg / s.

7. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: In step (6), the foam model processed in step (5) is first placed in a sand box, and then molten high-chromium cast iron alloy is poured in. After cooling to room temperature, it is demolded. In step (6), the high-chromium cast iron alloy is composed of 67-70 parts of iron, 25-28 parts of chromium, 1.5-2.5 parts of nickel, and 0.6-0.8 parts of manganese. The pouring temperature in step (6) is 1450-1550℃. The deoxidizer of the high-chromium cast iron alloy melt in step (6) is aluminum wire, with an addition amount of 0.1-0.3wt%. The cooling rate is 10-20℃ / min.

8. The method for preparing high wear-resistant and corrosion-resistant sintering machine grate bars according to claim 1, characterized in that: It also includes low-temperature tempering of the casting obtained in step (6), followed by surface nano-infiltration strengthening; wherein the heating rate of low-temperature tempering is 5-10℃ / min, the temperature of low-temperature tempering is 350-450℃, and the holding time of low-temperature tempering is 3-5h; wherein the surface nano-infiltration strengthening is performed in an argon atmosphere with an argon purity of 99.99% and a pressure of 0.1-0.3MPa; wherein the temperature of surface nano-infiltration strengthening is 600-700℃ and the time is 1-2h.

9. A high wear-resistant and corrosion-resistant sintering machine grate bar, characterized in that, The high wear-resistant and corrosion-resistant sintering machine grate bar is obtained by the preparation method described in any one of claims 1-8.

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