A surface coating for high manganese rail steel and its preparation method and use method

Abstract

The present invention relates to the field of coating technology, and in particular to a surface coating for high-manganese rail steel, its preparation method, and its use. The surface coating comprises a composite powder, a binder, and water, with the mass ratio of the composite powder to the combined mass of the binder and water being 1:0.8-1.2, and the mass ratio of the binder to water being 2-8:92-98. The composite powder comprises 15-25 parts SiO2 / Al composite powder, 10-20 parts alumina, 10-18 parts talc fine powder, 3-8 parts chromium oxide powder, 15-20 parts mullite powder, 20-30 parts zircon sand, and 6-10 parts boron oxide powder. Spherical aluminum powder is mixed with SiO2 fine powder and ball-milled to form an intercalated SiO2 / Al composite powder. The present invention achieves highly effective protection for high-manganese steel substrates in extremely high-temperature environments, significantly improving the coating's oxidation resistance, thermal stability, and service life, and has broad engineering application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a surface coating for high manganese rail steel and a preparation method and a use method thereof. Background Art

[0002] Rail steel is an austenitic steel alloyed with elements such as manganese and vanadium. It exhibits excellent wear resistance, high impact toughness, and work-hardening capabilities. Existing grades include 50, 60, 75, U71Mn, and U71VH. With the development of my country's rail transportation and the continuous improvement of infrastructure such as high-speed rail and subways, the quality requirements for rail steel are also increasing. To maintain a stable single austenitic structure and avoid the formation of ferrite or carbides, manganese-based rail steels typically require heat treatment temperatures between 1050 and 1250°C to ensure sufficient solution of manganese. Furthermore, the diffusion rates of elements such as manganese and carbon in high-manganese rail steels are relatively low. Therefore, a longer heat treatment time is required to ensure sufficient diffusion and uniform distribution of these elements in the austenite matrix and to promote the solution and re-solution of metastable phases such as carbides (Mn3C and Fe3C) or inclusions. Furthermore, for large-scale castings, it is crucial to maintain a roughly uniform temperature profile throughout the casting to avoid uneven heat-treated structures. Therefore, the heat treatment time of high manganese rail steel is usually 4 to 6 hours.

[0003] However, during high-temperature heat treatment of rail steel, due to its high chemical activity and affinity for oxygen at high temperatures, it is highly susceptible to oxidation and decarburization, leading to performance degradation. For example, in high-manganese rail steel, Mn readily reacts with oxygen to form oxides such as MnO or Mn3O4, leading to oxidation and release of Mn from the surface. This loss of manganese disrupts the chemical stability of the austenite, inducing a microstructure transformation to pearlite or ferrite, severely impacting fatigue performance. Furthermore, in heat treatment environments with high oxygen partial pressures, carbon in the steel readily diffuses to the surface and reacts with oxygen to form CO or CO2, ultimately resulting in significant decarburization. High-manganese steel, a core material for railway track and other key components such as turnouts and switches, suffers from surface decarburization, which can significantly reduce fatigue strength (by 30%-40%) and accelerate stress crack initiation under alternating loads, seriously threatening the safe service life of the rails. Such problems are particularly prominent during the hot processing, heat treatment and high-temperature service of rail steel, becoming a major bottleneck restricting its production and use.

[0004] In existing research and industrial applications, the following strategies are mainly used to address the high-temperature oxidation and decarburization problems of rail steel:

[0005] (1) Protective atmosphere heat treatment: For example, heating in a furnace using a vacuum, hydrogen, or inert gas atmosphere to suppress oxidation and decarburization reactions. However, this method has high equipment costs, complex operations, and is not suitable for large components or continuous heating production lines, which limits its large-scale industrial promotion.

[0006] (2) Carburizing, siliconizing or nitriding modification: By performing element diffusion treatment on the surface of rail steel at high temperature, its oxidation resistance and hardness are improved. However, this type of method generally has problems such as long processing cycle, high cost, and uneven processing thickness, and is not suitable for complex shapes or large-sized parts.

[0007] (3) Surface coating technology: In recent years, surface coating with inorganic materials that are resistant to high-temperature oxidation and penetration has become a research hotspot. For example, the use of silicon-containing coatings, aluminum oxide coatings, ceramic coatings, and other methods to form a dense barrier layer on the surface of rail steel can effectively block the diffusion path of oxygen and carbon atoms, thereby delaying the oxidation and decarburization process. This technology has good application prospects in metallurgical heat treatment, glass kilns, mold protection, and other fields.

[0008] Existing patents such as CN115260806B utilize a thick, multi-layer coating method, resulting in a high SiO2 content and complex application. Furthermore, silicon dioxide easily reacts with manganese oxide to form a low-melting-point manganese silicate compound. While the coating composition of CN118359948A offers good protective properties, its binder preparation is complex, highly corrosive to alkalis, and its high cost makes it unsuitable for large-scale industrial application. While CN104845416B effectively improves oxidation resistance, its protection is short-lived, maintaining decarburization protection for only three hours, making it unsuitable for use in the actual heat treatment of rail steel during processing (4-6 hours). Therefore, there is an urgent need to develop a surface protective coating that can maintain excellent decarburization and oxidation resistance even under high-temperature conditions, thereby enhancing the structural stability and service life of rail steel under high-temperature conditions. Summary of the Invention

[0009] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a surface coating for high manganese rail steel and a preparation method and a use method thereof.

[0010] A first object of the present invention is to provide a surface coating for high-manganese rail steel, the surface coating comprising a composite powder, a binder, and water, wherein the mass ratio of the composite powder to the sum of the masses of the binder and water is 1:0.8-1.2, and the mass ratio of the binder to water is 2-8:92-98; the composite powder comprises the following raw materials in mass fractions: 15-25 parts of SiO2 / Al composite powder, 10-20 parts of alumina, 10-18 parts of talc fine powder, 3-8 parts of chromium oxide powder, 15-20 parts of mullite powder, 20-30 parts of zircon sand, and 6-10 parts of boron oxide powder;

[0011] The SiO2 / Al composite powder is prepared by a high-energy ball milling method: spherical metal aluminum powder and SiO2 micropowder are mixed and ball milled to form an embedded SiO2 / Al composite powder.

[0012] Furthermore, the initial particle size of the spherical metal aluminum powder is less than 50 μm, and the initial particle size of the SiO2 powder is less than 2 μm.

[0013] Furthermore, in the SiO2 / Al composite powder, the mass ratio of SiO2:Al is (4~5):1, wherein the D50 particle size of the composite powder is <50 μm.

[0014] Furthermore, during ball milling, the ball-to-material ratio is 10:1 to 20:1, the rotation speed is 300 to 600 rpm, and the ball milling is continued for 4 to 6 h.

[0015] Furthermore, the binder is potassium metasilicate.

[0016] Furthermore, the bauxite is high-alumina bauxite, wherein the Al2O3 content is ≥85%, the SiO2 content is 10-15%, the Fe2O3 and TiO2 contents are ≤1.5%, and the CaO, MgO, K2O, and Na2O are ≤0.5%; the particle size of the bauxite is <5 μm.

[0017] Furthermore, the SiO2 content in the talc fine powder is ≥60%, and the MgO content is ≥30%; and the particle size of the talc fine powder is <5 μm.

[0018] Furthermore, the Cr2O3 content in the chromium oxide powder is ≥99%; and the particle size of the chromium oxide powder is <5 μm.

[0019] Furthermore, the Al2O3 content of the mullite powder is ≥70%, and the SiO2 content is ≥25%; and the particle size of the mullite powder is <10 μm.

[0020] Furthermore, the ZrO2 content of the zircon sand is ≥65%, and the SiO2 content is ≥34%; the particle size of the zircon sand is <45 μm;

[0021] The B2O3 content in the boron oxide powder is ≥99%, and the particle size of the boron oxide powder is <10 μm.

[0022] A second object of the present invention is to provide a method for preparing a surface coating for high manganese rail steel as described above, wherein a binder is mixed with water to prepare a binder solution, and then the composite powder and the binder solution are stirred and mixed in a water bath to form a surface coating for high manganese rail steel.

[0023] A third object of the present invention is to provide a method for using the above-mentioned surface coating for high manganese rail steel, wherein the obtained surface coating is evenly applied to the surface of the rail steel by brushing or spraying, with a coating thickness of 200 to 500 μm; and dried and pre-cured at room temperature to obtain the surface protective coating.

[0024] In the present invention, the SiO2 / Al composite powder is a composite powder with aluminum as the matrix and silicon dioxide flake structures embedded on the surface. The composite powder is prepared by high-energy ball milling and has excellent anti-oxidation, anti-decarburization and coating self-healing properties. The average particle size D of the powder is 50 The particle size distribution is controlled within 50 μm, with a narrow particle size distribution and good dispersibility. The composite powder is prepared by high-energy ball milling. Since SiO2 has a Mohs hardness of approximately 6.5 and Al has a Mohs hardness of approximately 2.7, there is a large hardness difference between the two. Under the action of high-speed collision and shear, the harder SiO2 particles gradually embed into the relatively soft aluminum powder surface, forming a stable mechanical interlocking interface, thus constructing a uniformly distributed and densely structured embedded composite powder.

[0025] Compared with ordinary mixed powders, this structure can avoid component separation, SiO2 agglomeration or interface cracking caused by mismatched thermal expansion of particles during heat treatment, and can effectively improve the distribution uniformity and interface stability of the powder in the coating. Since the heat treatment process of rail steel often involves a long period of time (4 to 6 hours) and is in a high temperature environment of 1100 to 1250 ° C, more stringent requirements are placed on the thermal stability, antioxidant durability and structural integrity of the coating material. In the SiO2 / Al composite powder described in the present invention, at the initial stage of heating, Al preferentially reacts with oxygen in the environment to quickly form a dense and continuous aluminum oxide (Al2O3) film. The reaction formula is as follows:

[0026]

[0027] This aluminum oxide film has an extremely low oxygen diffusion coefficient and a high melting point (approximately 2050°C), effectively building a highly dense physical isolation barrier on the coating surface, significantly reducing the oxygen permeation rate in the coating while also lowering the local oxygen partial pressure. By first forming this dense Al2O3 protective layer, not only is the diffusion of oxygen into the rail steel substrate effectively inhibited, but the protective film also wraps around the SiO2 particles, causing mullite formation and forming an indirect shielding layer that blocks contact between the Fe and Mn elements in the steel matrix and the exposed SiO2, preventing the following harmful reactions from occurring in high-temperature environments:

[0028]

[0029] The aforementioned iron silicate (FeSiO4) and manganese silicate (MnSiO4) are low-melting-point brittle oxides. These brittle phases are typically porous, providing diffusion pathways for oxygen penetration and carbon escape. The use of SiO2 / Al composite powder effectively blocks the formation of silicate brittle phases, maintaining the integrity of the interface between the coating and the substrate. Furthermore, due to the effective suppression of oxygen diffusion, the local ambient oxygen partial pressure on the coating surface decreases, significantly reducing the reaction rate of carbon and oxygen within the substrate. This effectively suppresses carbon escape, slows the formation of a decarburized layer, and significantly improves the structural stability and service life of high-manganese steel in high-temperature environments.

[0030] As the temperature rises, the SiO₂ particles embedded in the aluminum surface react with B₂O₃ in a eutectic reaction between 600°C and 800°C, forming a low-viscosity borosilicate glass phase. This glass phase exhibits excellent fluidity and wettability at high temperatures, rapidly penetrating and filling microcracks, pores, and interfacial defects within the coating, acting as a self-healing and hermetic seal, effectively blocking the diffusion pathways of corrosive media such as oxygen and water vapor. This composite structure enables the overall coating system's protective mechanism to transition from rapid aluminum oxidation barrier formation to the slow release of SiO₂ to form a glass-sealing layer, creating a dual-layer protection system that "first seals oxygen, then seals cracks." This sequential response mechanism not only ensures rapid protection of the rail steel during the initial heating phase, but also provides continuous structural stability and crack repair during the prolonged heat treatment process, significantly improving overall service life and oxidation stability.

[0031] In the coating of the present invention, mullite (3Al2O3·2SiO2), zircon sand (ZrSiO4) and alumina (Al2O3) serve as high-melting-point skeleton phases, forming a stable three-dimensional interlocking ceramic framework structure under high-temperature environments. This can significantly enhance the overall thermomechanical properties of the coating, resist thermal expansion stress and external impact, and improve the thermal shock resistance and structural integrity of the coating.

[0032] The talc fine powder introduced into the coating (main component Mg3Si4O 10 (OH)2) partially decomposes at high temperatures, releasing MgO and SiO2. MgO participates in the high-temperature sintering process, promotes the neck connection between ceramic particles, forms a sintering support phase, and further improves the density, strength and heat resistance of the coating. The addition of MgO can also increase the melting temperature of the material, making the coating inert to the steel substrate, which helps the coating to peel off after the billet is removed from the furnace. MgAl 0.6 Fe 1.4 O4 and other spinel structures enhance the density of the oxide layer and inhibit the oxidation process of steel.

[0033] In addition, chromium oxide (Cr2O3) is preferentially enriched on the surface during the high-temperature reaction of the coating, and reacts with oxygen to form a dense chromium oxide film with an extremely low oxygen ion diffusion coefficient, which can significantly enhance the coating surface's barrier ability to oxygen penetration and delay the oxidation and carbon escape of the high-manganese steel substrate.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) Through structural design, the time-delayed release and multi-stage coordinated response of the protective function are achieved, so that the coating system has the triple functions of immediate barrier, late healing, and structural stability, breaking through the technical bottlenecks of chaotic reactions, functional interference, and unsustainable protection in the traditional mixed powder heat treatment process.

[0036] (2) The coating has excellent anti-oxidation and anti-decarburization properties at a high temperature of 1250°C and is easy to descale. It is suitable for high manganese rail steel heat treatment, high temperature forging and high temperature processing.

[0037] (3) The coating still has excellent adhesion, anti-peeling and thermal stability at high temperatures of 1250℃ and above;

[0038] (4) The introduction of SiO2 / Al composite powder effectively optimizes the oxygen diffusion blocking mechanism of the coating. After high manganese steel is protected by the coating, the thickness of the decarburized layer (<150 μm) and the oxidation weight gain (less than 5%) are significantly reduced under the condition of 6 h holding time at 1250°C.

[0039] (5) The coating can be prepared at room temperature without the need for high-temperature sintering or special pretreatment. The process is simple and suitable for industrial promotion;

[0040] (6) The coating system is non-toxic and environmentally friendly, avoiding the use of Cr 6+ Class components, in line with the development direction of green manufacturing.

[0041] In summary, the present invention achieves efficient protection of high-manganese steel substrates in extreme high-temperature environments through the synergistic effects of multiple mechanisms, including aluminum oxidation and oxygen reduction mechanism, glass phase melting and densification mechanism, ceramic skeleton support mechanism, and crack self-healing mechanism, significantly improving the oxidation resistance, thermal stability, and service life of the coating, and has broad engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The high-temperature protective coating for preventing decarburization and oxidation on the surface of rail steel prepared in accordance with the present invention is applied to Examples 1 to 3, and the cross-sectional metallographic structure diagrams of Comparative Examples 1 to 3 after high-temperature heat treatment;

[0043] Figure 2 Schematic diagram of the SiO2 / Al composite powder structure. DETAILED DESCRIPTION

[0044] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0045] The raw materials used in the embodiment are as follows:

[0046] Preparation of SiO2 / Al composite powder

[0047] The high-energy ball milling method was used for preparation: spherical aluminum powder (initial particle size <50 μm) and SiO2 fine powder (initial particle size <2 μm) were mixed at a mass ratio of SiO2:Al of 4:1, and then placed in a high-energy planetary ball mill with a ball-to-material ratio of 20:1. The speed was controlled at 300-600 rpm and the ball milling was continued for 4 h to obtain SiO2 / Al composite powder. Its structural diagram is shown in the figure. Figure 2 shown.

[0048] The bauxite is high-alumina bauxite, in which the Al2O3 content is ≥85%, the SiO2 content is 10-15%, the Fe2O3 and TiO2 contents are ≤1.5%, and the CaO, MgO, K2O, and Na2O are ≤0.5%; the particle size of the bauxite is <5 μm.

[0049] The SiO2 content in the talc fine powder is ≥60%, and the MgO content is ≥30%; the particle size of the talc fine powder is <5 μm.

[0050] The Cr2O3 content in the chromium oxide powder is ≥99%; the particle size of the chromium oxide powder is <5 μm.

[0051] The Al2O3 content in the mullite powder is ≥70%, and the SiO2 content is ≥25%; the particle size of the mullite powder is <10 μm.

[0052] The ZrO2 content in zircon sand is ≥65%, and the SiO2 content is ≥34%; the particle size of zircon sand is <45 μm;

[0053] The B2O3 content in the boron oxide powder is ≥99%, and the particle size of the boron oxide powder is <10 μm.

[0054] Example 1

[0055] The powder composition is: 15% alumina, 12% talc fine powder, 4% chromium oxide powder, 18% mullite powder, 24% SiO2 / Al composite powder, 22% zircon sand, 5% boron oxide powder, and the total mass fraction is 100%.

[0056] The binder is an aqueous solution composed of 5% potassium metasilicate (K2SiO3) and deionized water, with the total liquid mass being 100%.

[0057] The powder and binder solution were mixed in a 1:1 mass ratio and stirred in a 50°C water bath for 60 minutes to prepare a uniform slurry. The slurry was evenly applied to the surface of high-manganese steel by brushing, with a coating thickness of approximately 300 μm. The coating was dried in a 100°C drying oven for 2 hours. The coating prepared in this example was smooth and intact. The sample was then placed in an electric furnace and heated at 1250°C for 6 hours before cooling.

[0058] The high manganese steel sample after heat treatment with the coating of this embodiment was tested for the decarburization layer depth according to GB / T224-2019, and the decarburization layer depth was less than 100 μm; the oxidation weight gain rate was tested according to GB / T38430-2019, and the oxidation weight gain rate was 4.38%; the high-pressure water descaling method was used, and the high-pressure nozzle impact force IF value was 2.0 N / mm 2 The oxide scale coverage was measured to be 4.8%, which is easier to remove scale.

[0059] Example 2

[0060] The powder composition is: 12% alumina, 10% talc fine powder, 6% chromium oxide powder, 20% mullite powder, 22% SiO2 / Al composite powder, 28% zircon sand, and 2% boron oxide powder, with a total mass fraction of 100%.

[0061] The remaining components, coating preparation method and sample heat treatment method are the same as those in Example 1.

[0062] The testing method of the samples obtained after heat treatment in this embodiment is the same as that in Example 1.

[0063] The test results show that the depth of the decarburized layer is less than 50 μm, the oxidation weight gain rate is 3.82%, the oxide scale coverage rate is 2.5%, and the descaling is easy.

[0064] Example 3

[0065] The powder composition is: 10% alumina, 15% talc fine powder, 5% chromium oxide powder, 15% mullite powder, 27.5% SiO2 / Al composite powder, 25% zircon sand, and 2.5% boron oxide powder, with a total mass fraction of 100%.

[0066] The remaining components, coating preparation method and sample heat treatment method are the same as those in Example 1.

[0067] The test method of the sample obtained after heat treatment in this embodiment is the same as that in Example 1. The test results show that the decarburized layer depth is less than 150 μm, the oxidation weight gain rate is 5.13%, and the oxide scale coverage rate is 5.4%, indicating that descaling is relatively easy.

[0068] Comparative Example 1

[0069] The high manganese steel sample of Comparative Example 1 was not coated.

[0070] The test method for the sample obtained after heat treatment in Comparative Example 1 was the same as that in Example 1. The test results showed that the surface of the sample was severely oxidized, forming a reddish-brown oxide scale that was flaking. The thickness of the decarburized layer was greater than 2000 μm, indicating complete decarburization. The oxidation weight gain was 16.62%, the oxide scale coverage was 22.9%, and the sample was difficult to descale.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 2 is that SiO2 / Al composite powder is not added, and silicon powder of equal mass is used as a substitute. The remaining components, coating preparation method and sample heat treatment method are the same as Example 2.

[0073] The test method of the sample obtained after heat treatment in Comparative Example 2 was the same as that in Example 2. The test results showed that the decarburized layer depth was less than 650 μm, the oxidation weight gain rate was 8.35%, and the oxide scale coverage rate was 12.4%, indicating that descaling was difficult.

[0074] Comparative Example 3

[0075] The difference between Comparative Example 3 and Example 2 is that no SiO2 / Al composite powder is added, and 20% silicon powder and 2% aluminum powder are used instead. The remaining components, coating preparation method and sample heat treatment method are the same as Example 2.

[0076] The test method of the sample obtained after heat treatment in Comparative Example 3 was the same as that in Example 2. The test results showed that the decarburized layer depth was less than 250 μm, the oxidation weight gain rate was 6.51%, and the oxide scale coverage rate was 9.7%, indicating that descaling was difficult.

[0077] Table 1 below shows the decarburization depth, oxidation weight gain rate, and scale coverage of high manganese steel protected by the coatings of Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 after heat treatment at 1250° C. for 6 hours.

[0078] Table 1

[0079]

[0080] It can be seen that the coating provided by the present invention achieves efficient protection of high manganese steel substrates in extremely high temperature environments, significantly improves the oxidation resistance, thermal stability and service life of the coating, and has broad engineering application prospects.

[0081] Figure 1Figures 1-3 (ac) and 1-3 (df) show the cross-sectional microstructures of rail steel coated with the high-temperature protective coating prepared according to the present invention to prevent decarburization and oxidation, respectively, and comparative examples 1-3 (df) after high-temperature heat treatment. The figures show that the coatings in the examples bond well to the substrate, the decarburized layer is significantly thinner, and the austenite grains within the substrate are uniform with distinct interfaces. In contrast, the decarburized layer in the comparative example is thicker, and the interior of the substrate exhibits a noticeable reddish-brown coloration, indicating significant decarburization and oxidation during the high-temperature heat treatment. This destabilizes the austenite structure and makes it more susceptible to pearlite or ferritic transformation.

[0082] Any matters not mentioned above shall be subject to the existing technology.

[0083] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A surface coating for high manganese rail steel, characterized in that: The surface coating is composed of composite powder, binder and water, wherein the mass ratio of the composite powder to the sum of the mass of the binder and water is 1:0.8-1.2, and the mass ratio of the binder to water is 2-8:92-98; the composite powder comprises the following raw materials in mass fractions: 15-25 parts of SiO2 / Al composite powder, 10-20 parts of alumina, 10-18 parts of talc fine powder, 3-8 parts of chromium oxide powder, 15-20 parts of mullite powder, 20-30 parts of zircon sand, and 6-10 parts of boron oxide powder; The SiO2 / Al composite powder is prepared by a high-energy ball milling method: spherical metal aluminum powder and SiO2 micropowder are mixed and ball milled to form an embedded SiO2 / Al composite powder.

2. The surface coating for high manganese rail steel according to claim 1, characterized in that: The initial particle size of the spherical aluminum powder is less than 50 μm, and the initial particle size of the SiO2 powder is less than 2 μm.

3. The surface coating for high manganese rail steel according to claim 1, characterized in that: In the SiO2 / Al composite powder, the mass ratio of SiO2:Al is (4~5):1, and the D50 particle size of the composite powder is <50 μm.

4. The surface coating for high manganese rail steel according to claim 1, characterized in that: During ball milling, the ball-to-material ratio is 10:1 to 20:1, the rotation speed is 300 to 600 rpm, and the ball milling is continued for 4 to 6 hours.

5. The surface coating for high manganese rail steel according to claim 1, characterized in that: The binder is potassium metasilicate.

6. The surface coating for high manganese rail steel according to claim 1, characterized in that: The bauxite is high-alumina bauxite, wherein the Al2O3 content is ≥85%, the SiO2 content is 10-15%, the Fe2O3 and TiO2 contents are ≤1.5%, and the CaO, MgO, K2O, and Na2O contents are ≤0.5%; the particle size of the bauxite is <5 μm; The SiO2 content of the talc fine powder is ≥60%, and the MgO content is ≥30%; the particle size of the talc fine powder is <5 μm.

7. The surface coating for high manganese rail steel according to claim 1, characterized in that: The Cr2O3 content in the chromium oxide powder is ≥99%; the particle size of the chromium oxide powder is <5 μm; The Al2O3 content of the mullite powder is ≥70%, and the SiO2 content is ≥25%; the particle size of the mullite powder is <10 μm.

8. The surface coating for high manganese rail steel according to claim 1, characterized in that: The zircon sand has a ZrO2 content of ≥65% and a SiO2 content of ≥34%; and a particle size of the zircon sand is <45 μm; The B2O3 content in the boron oxide powder is ≥99%, and the particle size of the boron oxide powder is <10 μm.

9. A method for preparing a surface coating for high manganese rail steel according to any one of claims 1 to 8, characterized in that: The binder is mixed with water to prepare a binder solution, and then the composite powder and the binder solution are stirred and mixed in a water bath to form a surface coating for high manganese rail steel.

10. A method for using the surface coating for high manganese rail steel according to any one of claims 1 to 8, characterized in that: The obtained surface coating is evenly applied to the rail steel surface by brushing or spraying, with a coating thickness of 200 to 500 μm; and dried and pre-cured at room temperature to obtain the surface protective coating.

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