Coating particles for rail surface, preparation method and spraying method

Abstract

The present application belongs to the technical field of rail surface protection, and particularly relates to a coating particle for a steel rail surface, a preparation method and a spraying method. The coating particle is composed of NiCr alloy particles and TiB2 ceramic particles; the mass percentage of the NiCr alloy particles is 41% to 60%, and the mass percentage range of the TiB2 ceramic particles is 40% to 59%. In the coating particle, a composite powder of NiCr alloy and TiB2 ceramic is selected as raw material. The NiCr alloy has good shape stability, electrical conductivity and thermal conductivity, excellent wear resistance, corrosion resistance and other characteristics. The TiB2 ceramic has high hardness, high strength, high wear resistance and high modulus characteristics, and can make up for the low hardness and poor wear resistance of the NiCr alloy. The TiB2 ceramic is a conductive ceramic. When it is combined with the NiCr alloy, the advantages of the good plasticity and corrosion resistance of the NiCr alloy and the high hardness and high wear resistance of the TiB2 ceramic can be taken into account, and the conductive ability is also possessed. When the coating particle is used as a coating for the steel rail surface, good technical effects can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of rail surface protection, and in particular relates to coating particles for rail surfaces, a preparation method and a spraying method. Background Art

[0002] A faulty track circuit shunt is commonly known as "unable to crush," "lost train," or "white light band." This occurs when a train enters a certain track section but the corresponding track relay remains engaged or alternately engaged. The corresponding signal lights and control consoles will erroneously display green and white lights, indicating that the track circuit has lost its ability to detect track section occupancy. When this occurs, train drivers and station dispatchers mistakenly believe that no train is occupying the section and proceed with train operation and route entry, potentially leading to serious accidents such as train collisions, crushes, and derailments.

[0003] Currently, the main technologies used in China to directly address poor track circuit shunting on the rail surface include cladding welding, supersonic arc spraying, liquid coating, and plasma coating. The main working principle of cladding welding is to melt the powder and spray it onto the molten rail area, forming a weld on the rail surface. During on-site operations, the process is difficult to implement due to limited environmental and operating conditions. In particular, after welding, the rail is prone to the formation of harmful structures such as martensite, which can lead to cracks inside the rail and the risk of rail breakage. Arc spraying is a thermal spraying method that uses two continuously fed metal electrodes as consumable electrodes, generates an arc at their ends as a heat source, and uses compressed air to atomize the melted wire. The metal is then sprayed onto the workpiece surface at a high speed to form a coating. The sandblasting process for spraying produces a large amount of dust, and the sand is difficult to clean thoroughly. The coating is easily oxidized, has poor bonding strength, and has a very short service life. While liquid coating has significantly improved the coating lifespan, the process and quality are not stable, and the coating construction efficiency is too low, making it very difficult to construct on lines that have already been opened. The coating is thin, has a low rolling resistance life, is prone to rust, and cannot fully meet the actual use needs on site. Plasma coating technology uses a plasma jet as a heat source to melt metal powder or wire and then spray it onto the rail surface, resulting in a high bonding strength coating. However, due to the low hardness of conventional alloy materials, the coating's wear resistance and rolling resistance need to be improved. After a period of service, the coating wears away and needs to be re-coated.

[0004] The above processes have different technical drawbacks. If the coating material is changed, and a wear-resistant conductive layer is applied to the rail surface, while also improving the material hardness and bonding strength, this can not only save users costs, but also reduce the time required for maintenance inspections and on-track coordination by relevant departments, thereby improving overall efficiency and reducing vehicle operation safety accidents.

[0005] Plasma coating can eliminate the hidden dangers of broken rails. The temperature of the rail surface does not change much during the construction process. At the same time, the bonding strength of the coating is improved by optimizing the materials. The anti-rolling life of the plasma-coated alloy coating can reach 80,000 wheel pairs, and the anti-rust period is about three years. In comparison, the anti-rolling life of the traditional supersonic arc spraying is about 8,000 wheel pairs, and the anti-rust period is about one year, while the anti-rolling life of the liquid coating is about 30,000 wheel pairs, and the anti-rust period is about one year.

[0006] Railway authorities' requirements for rectifying poor shunt conditions necessitate plasma coatings with high hardness, excellent wear resistance, good crush resistance, and excellent corrosion resistance. The coating must also exhibit a certain degree of electrical conductivity and meet the requirements of Technical Standard I of the Railway's "Signal Equipment Maintenance Rules." Furthermore, to prevent accidents during service, the worn coating will shed in small particles, preventing red light bands between rails and ensuring safe train operation. Summary of the Invention

[0007] The purpose of the present invention is to provide a coating particle for the surface of a rail, a preparation method and a spraying method to address the drawbacks of the existing technology for rectifying the poor track circuit shunt coating process.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A coating particle for a rail surface is composed of NiCr alloy particles and TiB2 ceramic particles; wherein the mass fraction of the NiCr alloy particles is 41%-60%, the mass fraction of the TiB2 ceramic particles is in the range of 40%-59%, the mass fraction of Ni powder in the NiCr alloy particles is 18.5%-27.5%, and the mass fraction of CrH2 is 22.5%-32.5%.

[0010] The technical solution of the present invention provides a coating particle for the surface of a rail. The coating particle is made of a composite powder of NiCr alloy and TiB2 ceramic. NiCr has excellent shape stability, electrical and thermal conductivity, excellent wear resistance, and corrosion resistance. TiB2 ceramic has high hardness, high strength, high wear resistance, and high modulus, which can compensate for the low hardness and poor wear resistance of NiCr alloy. TiB2 is a conductive ceramic. Combining it with NiCr can combine the advantages of NiCr's good plasticity and corrosion resistance with the high hardness and high wear resistance of TiB2 ceramic, while also maintaining electrical conductivity. Using it as a rail surface coating has excellent technical effects.

[0011] As a preferred technical solution of the present invention, the size range of the coating particles is 145.9±68.3 μm.

[0012] As a preferred technical solution of the present invention, the bonding strength of the coating particles is 73.4±11.6 MPa.

[0013] As a preferred technical solution of the present invention, the microhardness of the coating particles is HV 200gf Range: 580-868.

[0014] The method for preparing the coating particles for the rail surface comprises the following steps:

[0015] Step 1: Prepare raw materials according to the formula of claim 1;

[0016] Step 2: After the raw material powders are evenly mixed, deionized water, a dispersant, and a binder are added to form an intermediate raw material, and the coating particles are prepared from the intermediate raw material.

[0017] As a preferred embodiment of the present invention, in step 1, the raw materials include Ni powder with a mass fraction of 18.5%-27.5%, CrH2 powder with a mass fraction of 22.5%-32.5%, and TiB2 ceramic powder with a mass fraction of 40%-59%.

[0018] During the preparation process of the coating particles of the present invention, physical changes occur, and a uniformly distributed coating material is formed by mixing with deionized water, a dispersant and an adhesive.

[0019] As a preferred embodiment of the present invention, in the raw material powder, the particle size of the TiB2 ceramic powder is 2-8 μm, the particle size of the Ni powder is 3-6 μm, and the particle size of the CrH2 powder is 2-5 μm.

[0020] As a preferred embodiment of the present invention, in step 2, the raw material powders are ball-milled and mixed using a ball mill at a ball milling speed of 240 n / min-280 n / min and a ball milling time of 3.5 h-4 h.

[0021] As a preferred embodiment of the present invention, in step 2, the coating particles are prepared by a spray dryer, the inlet temperature of the spray dryer is in the range of 210°C-230°C, and the outlet temperature of the spray dryer is in the range of 130°C-150°C.

[0022] As a preferred embodiment of the present invention, in step 2, the speed of the peristaltic pump of the spray dryer is 6-6.5 r / min, the gas pressure is 0.45-0.5 MPa, the flow rate is 25 L-30 L / min, and the mixed powder is heat treated under argon.

[0023] As a preferred embodiment of the present invention, the dispersant is ammonium polyacrylate and the adhesive is polyvinyl alcohol (PVA).

[0024] A method for spraying a coating on the surface of a rail adopts coating particles prepared by the above-mentioned preparation method as a spraying material. The specific steps are: placing a plasma spraying device loaded with coating particles above the rail and setting spraying parameters; moving the plasma spraying device along the length of the rail to spray the coating; wherein the spraying parameters include current, voltage, powder feeding speed, spray distance, and cathode and anode types.

[0025] As a more preferred embodiment, the preferred range of the above parameters is: spray distance 90-110mm, argon-hydrogen mixture ratio of 10%:90%-25%:75%, flow rate 30-45L / min, current 200-280A, voltage 60-80V, powder feeding speed 35-50g / min, coating thickness 220μm-300μm.

[0026] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0027] 1. The technical solution of the present invention provides a coating particle for the surface of a rail, wherein the coating particle uses NiCr alloy and TiB2 ceramic composite powder as raw materials, NiCr has good shape stability, electrical conductivity and thermal conductivity, excellent wear resistance, corrosion resistance and other characteristics, TiB2 ceramics have high hardness, high strength, high wear resistance and high modulus characteristics, which can make up for the shortcomings of low hardness and poor wear resistance of NiCr alloy. TiB2 is a conductive ceramic, and compounding it with NiCr can take into account the good plasticity and corrosion resistance of NiCr and the high hardness and high wear resistance of TiB2 ceramics, while having electrical conductivity. Using it as a coating on the surface of a rail has good technical effects. The microhardness of the coating particle is HV 200gf： The coating has a density of 750.7±118.5, a particle size of 145.9±68.3μm, and a coating bonding strength of 73.4±11.6MPa. The coating particles contain elements such as aluminum, titanium, boron, copper, nickel, and chromium, with an aluminum mass ratio of 33.5%, a titanium mass ratio of 10.5%, a boron mass ratio of 4.5%, a copper mass ratio of 2.5%, a nickel mass ratio of 20.5%, and a chromium mass ratio of 15.5%.

[0028] 2. After the coating is applied to the rail, the residual voltage of the coating is tested. The residual voltage of the 25Hz track circuit is 1.2-3V, and the residual voltage of the 2000 track circuit is 30-65mV. The anti-rust performance reaches the national 120-hour neutral salt spray test, and the anti-rust performance of the coating is about three years; the coating hardness is HV 200gf: 750.7±118.5, meeting design requirements, and the coating's rollover resistance is between 80,000 and 100,000. The coating's particle performance is primarily determined by its hardness. The greater the hardness, the greater the rollover resistance. When the coating fails, more powder will fall off, preventing it from flakes being carried by the wheels onto the insulation joint, causing conduction between the rails on both sides of the insulation joint and posing a safety hazard. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a hardness test chart of the coating material of Example 2 of the present invention.

[0030] Figure 2 This is a hardness test chart of the coating material of Example 3 of the present invention.

[0031] Figure 3 1 is a photograph and a schematic diagram of the microstructure of the coating material of Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to more clearly describe the invention purpose, technical solutions and technical effect advantages in the specific implementation cases of the present invention, the solutions in the specific embodiments will be described in detail in conjunction with the drawings of the specification of the present invention. The specific technical solutions involved in the following specific embodiments are only for the purpose of clearly and completely describing the innovative technical solutions of the present invention. They themselves are only part of the specific implementation plans that can be adopted by the present invention, not all embodiments, and should not be understood as limiting the innovative solutions of the present invention. Any solution that adopts the same inventive concept of the present invention should be included in the scope of protection of the present invention.

[0033] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to conventional technical manuals in the field. At the same time, for the places where the above-mentioned terms appear, they can make appropriate understanding or adjustments for reference, and deduce the implementation of the same or similar technical solutions without paying any creative work.

[0034] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the embodiments. The above embodiments and the invention content of the specification only describe the principles or specific cases of the present invention. Without departing from the essence of the innovative ideas of the present invention, the innovative solutions of the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection claimed by the present invention.

[0035] The present invention will be described in detail below with reference to the accompanying drawings.

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing coating particles for rail surfaces, comprising the following steps:

[0039] Step 1: Prepare raw materials according to the formula of claim 1; specifically, the raw materials include Ni powder with a mass fraction of 18.5%-27.5%, CrH2 powder with a mass fraction of 22.5%-32.5%, and TiB2 ceramic powder with a mass fraction of 40%-59%; among the raw material powders, the particle size of the TiB2 ceramic powder is 2-8 μm, the particle size of the Ni powder is 3-6 μm, and the particle size of the CrH2 powder is 2-5 μm;

[0040] Step 2: After the raw material powders are evenly mixed, deionized water, a dispersant, and a binder are added to form an intermediate raw material in a slurry state, and the coating particles are prepared from the intermediate raw material; wherein the dispersant is ammonium polyacrylate and the binder is polyvinyl alcohol (PVA).

[0041] Specifically, in step 2, the raw powder is ball-milled and mixed using a ball mill at a ball milling speed of 250 n / min for 4 h; the coating particles are prepared using a spray dryer, and the inlet temperature range of the spray dryer is 210°C-230°C. In this embodiment, 210°C is preferably selected, and the outlet temperature of the spray dryer is 130°C-150°C; in this embodiment, 150°C is preferred. The peristaltic pump speed of the spray dryer is 6.5 r / min, the gas pressure is 0.5 MPa, and the flow rate is 30 L / min. The mixed powder is heat-treated under argon.

[0042] Example 2

[0043] This embodiment provides a coating particle, which is prepared according to the preparation method of Example 1. Specifically, the parameter information of the coating particle is: microhardness HV 200gf： 750.7±118.5, such as Figure 1 As shown, the particle size is 145.9±68.3μm and the coating bonding strength is 73.4±11.6MPa. TiB2-NiCr ceramic metal powder was prepared by spray drying. The TiB2 mass fraction of the TiB2-NiCr ceramic metal powder is 55%, the Ni powder mass fraction is 18%, and the CrH2 mass fraction is 27%.

[0044] Example 3

[0045] This embodiment provides a coating particle, which is prepared according to the preparation method of Example 1 and has a microhardness of HV 200gf： 643.7±64.1, e.g. Figure 2 As shown, a comparative hardness test was conducted between the developed powder and nickel-chromium-molybdenum. The nickel-chromium-molybdenum hardness test data is annotated on the chart to facilitate comparison with the newly developed powder. In this example, the coating particle size was 145.9 ± 68.3 μm, and the coating bond strength was 62.4 ± 9.8 MPa. The TiB2-NiCr ceramic-metal powder was prepared by spray drying. The TiB2-NiCr ceramic-metal powder contained a TiB2 mass fraction of 45%, a Ni powder mass fraction of 24%, and a CrH2 mass fraction of 31%.

[0046] The hardness of the coating particles in Example 2 was tested using a Vickers microhardness tester to confirm whether it met the design requirements. Figure 1 The figure shows the coating hardness test diagram of Example 2; from the figure, it can be seen that the coating microhardness HV 200gf :750.7±118.5.

[0047] Example 4

[0048] This embodiment provides a method for spraying a rail surface coating, using the coating particles of Example 2, wherein the specific spraying parameters are: spray distance 110 mm, argon-hydrogen mixture ratio 1:9, flow rate 35 L / min, current 210 A, voltage 70 V, powder feeding speed 45 g / min, and coating thickness 250 μm-270 μm.

[0049] Example 5

[0050] This embodiment provides a method for spraying a rail surface coating, using the coating particles of Example 3, such as Figure 3 Shown are pictures of the coating material and a schematic diagram of its microstructure. The coating operation was carried out using existing plasma equipment. Specific spraying parameters were: spray distance 90 mm, argon-hydrogen mixture ratio 1:3, flow rate 40 L / min, current 200 A, voltage 60 V, powder feeding speed 35 g / min, and coating thickness 250 μm-270 μm.

[0051] Use the branch residual pressure test equipment to detect the branch residual pressure of the coating. By rolling the coating, test the number of axes of coating resistance to rolling and observe the shedding status of the coating.

[0052] In Example 4, the coating bonding strength is greater than or equal to 60 MPa through testing; the residual voltage of the 25Hz track circuit is 1.2-3v and the residual voltage of the 2000 track circuit is 30-65mv through residual voltage testing; the rustproof performance reaches the national 120-hour neutral salt spray test, the rustproof performance of the coating lasts for about three years; and the anti-rolling pressure axle number of the coating is between 80000-100000.

[0053] In order to test the effect and applicability of the coating particles as coating materials, representative different railway areas and sections under different use conditions are selected for promotion test. Through feedback from users, the coating conductivity and corrosion resistance are excellent, and the anti-rolling pressure life is significantly improved (the residual voltage of the coating is 1.2-3v for the 25Hz track circuit and 30-65mv for the 2000 track circuit through residual voltage testing, the rustproof performance of the coating lasts for about three years, and the anti-rolling pressure axle number of the coating is between 80000-100000). Subsequently, comprehensive promotion and application are carried out on newly opened lines and existing lines, and so far, plasma coating has been carried out on newly opened lines and existing lines.

[0054] The coating material and spraying method of the technical scheme of the present application are applied to steel rail railways, and the effect of the bad shunting treatment is compared with the effects of the existing three technologies of melting cladding, supersonic arc spraying and liquid coating. The advantages are as follows:

[0055] (1) Eliminate the hidden danger of broken rail and ensure the safe operation of locomotive

[0056] (2) Reduce environmental pollution and meet environmental protection requirements. Arc spraying involves sandblasting, and the liquid coating solution is acidic and cannot be recycled, which causes some pollution to the environment.

[0057] The effect of bad shunting treatment is greatly improved, and the service life and rust prevention period of the coating are significantly improved. The anti-rolling pressure of the supersonic arc sprayed coating is about 8000 wheel pairs, the rust prevention period is about one year, the anti-rolling pressure of the liquid coated coating is about 30000 wheel pairs, the rust prevention period is about one year, and the anti-rolling pressure of the plasma coated coating is about 80000 wheel pairs, the rust prevention period is about three years.

[0058] The above only describes the preferred embodiments of the present application and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for spraying a rail surface coating, characterized in that: The spraying steps are as follows: placing a plasma spraying device loaded with coating particles above the rail and setting the spraying parameters; moving the plasma spraying device along the length of the rail to spray the coating; The spraying parameters include current, voltage, powder feeding speed, spray distance, and anode and cathode types. The coating preparation process parameters are as follows: spray distance 90-110 mm, argon-hydrogen mixture ratio 10%:90%-25%:75%, flow rate 30-45 L / min, current 200-280 A, voltage 60-80 V, powder feeding speed 35-50 g / min, and coating thickness 220 μm-300 μm. The spraying material is a coating particle prepared according to the following method, wherein the coating particles are composed of NiCr alloy particles and TiB2 ceramic particles; the mass proportion of the NiCr alloy particles is 41-60%, and the mass proportion of the TiB2 ceramic particles is in the range of 40-59%; the size range of the coating particles is 145.9±68.3 μm; the preparation method of the coating particles includes: Step 1: Prepare the raw materials; In step 1, the raw materials include Ni powder with a mass fraction of 18.5%-27.5%, CrH2 powder with a mass fraction of 22.5%-32.5%, and TiB2 ceramic powder with a mass fraction of 40-59%; Among the raw materials, the particle size of the TiB2 ceramic powder is 2-8 μm, the particle size of the Ni powder is 3-6 μm, and the particle size of the CrH2 powder is 2-5 μm; Step 2: After the raw material powders are evenly mixed, deionized water, a dispersant, and a binder are added to form an intermediate raw material, and the coating particles are prepared from the intermediate raw material.

2. The rail surface coating spraying method according to claim 1, characterized in that: The bonding strength of the coating was 73.4±11.6 MPa.

3. The rail surface coating spraying method according to claim 1, characterized in that: The microhardness of the coating particles is HV 200gf Range: 580-868.

4. The rail surface coating spraying method according to claim 1, characterized in that: In step 2, the raw powder is ball-milled and mixed using a ball mill at a ball milling speed of 240 n / min-280 n / min and a ball milling time of 3.5 h-4 h; the coated particles are prepared using a spray dryer, the inlet temperature range of the spray dryer is 210°C-230°C, and the outlet temperature of the spray dryer is 130°C-150°C; the peristaltic pump speed of the spray dryer is 6-6.5 r / min, the gas pressure is 0.45-0.5 MPa, and the flow rate is 25-30 L / min, and the mixed powder is heat-treated under argon.

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