Wheel set protective coating and preparation method thereof

Abstract

The invention relates to the technical field of protective coatings, in particular to a wheel set protective coating and a preparation method thereof.The wheel set protective coating comprises a primer and a finish paint, the primer is a single-component epoxy resin coating, the finish paint is a single-component polyurethane coating, the total thickness of the coating is 260-500 microns, nano ceramic particles are added into the finish paint, and the nano ceramic particles are added into the finish paint. The adhesive force grade of the coating is smaller than or equal to 1 grade, the drawing strength is larger than or equal to 4 MPa, the coating passes a flying sand resistance test, the damage grade is smaller than or equal to 4 grade, the coating is not corroded in a salt spray test for more than or equal to 480 hours, and the corrosion phenomenon is avoided within the range of 2 mm around a notch; the wheel set coating has the advantages of high wear resistance, corrosion resistance, high temperature resistance and environmental protection, and can help a railway operator to prolong the service life of wheels through an innovative coating technology, so that the maintenance cost is reduced, and meanwhile, the operation efficiency of a railway system is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of protective coatings, and particularly to a wheel set protective coating and a preparation method thereof. Background Art

[0002] With the rapid development of China's high-speed rail technology, the wheel set, as a key load-bearing component for train operation, its protective coating technology is directly related to the safety, durability and maintenance cost of the vehicle. The wheel set is long-term exposed to complex environments, such as rain, salt spray, mechanical wear and other environments, and is prone to problems such as corrosion and fatigue damage, which in turn affect the operation stability. Traditional painting technologies have problems such as insufficient rust prevention performance, low construction efficiency, and poor weather resistance of the coating. It is necessary to improve the protection effect through material innovation and process optimization. In recent years, the painting technology of railway vehicles has experienced an upgrade from traditional phenolic and alkyd paints to high-performance two-component paints. For example, since 2002, two-component paints have been fully adopted for newly built passenger cars, and thick-film alkyd paints have been promoted for freight cars. At the same time, process equipment such as sandblasting pretreatment and painting manipulators have been introduced, significantly improving the coating quality and operation efficiency. In addition, the formulation of international standards (such as UIC842) and domestic industry standards (such as TB / T2879 series) has provided support for the standardization and systematization of painting technologies.

[0003] Existing coating materials are prone to adhesion failure or peeling under high-frequency mechanical impact and complex loads. For example, the friction, vibration and impact forces endured by the wheel set during operation far exceed those of ordinary rail transit equipment. Traditional epoxy or polyurethane coatings are prone to cracking (such as crocodile cracks) or local peeling due to stress concentration caused by insufficient toughness, exposing the substrate and accelerating corrosion. In addition, the surface of the coating is prone to abrasions or scratches under the impact of particles such as sand, gravel and hail, resulting in a sharp decline in the protection performance. Although some studies have tried to improve the wear resistance by adding nano-fillers (such as silicon carbide, alumina), there are still problems such as increased brittleness of the coating and complex processing technology in practical applications.

[0004] The high-speed rail wheel set needs to adapt to complex environments such as extreme temperature and humidity changes (-40°C to 80°C), high-humidity salt spray (coastal areas) and ultraviolet radiation. Existing coating materials are insufficient in the following aspects: poor temperature cycle tolerance: thermal expansion and contraction cause micro-cracks at the interface between the coating and the metal matrix, accelerating water vapor penetration and corrosion; insufficient moisture resistance: in a high-humidity environment, the adhesion of the coating decreases, and water molecules penetrate to cause hydrolysis reactions, destroying the coating structure; weak anti-ultraviolet aging ability: long-term exposure to outdoor ultraviolet radiation causes the chemical bonds of the coating to break, resulting in powdering, fading and strength attenuation, reducing the protection life.

[0005] The coating of high-speed train wheelsets needs to remain stable under dynamic friction and cyclic loads. However, existing materials lack an intelligent repair mechanism. For example, after local failure of the coating due to mechanical wear or microcracks, the defects cannot be filled through self-repair function, and frequent shutdowns for maintenance are required. Although the academic community has explored self-healing coatings based on microcapsules or shape memory polymers, these technologies have not been scaled up, and the costs are high and the repair efficiency is difficult to match the operating requirements of high-speed trains.

[0006] Current coating materials often rely on solvent-based systems to improve performance, resulting in excessive emissions of volatile organic compounds (VOCs), which conflicts with environmental protection policies. Although waterborne coatings are gradually being promoted, their curing speed is slow and the film-forming compactness is poor, making it difficult to meet the requirements of high-efficiency coating for high-speed train wheelsets. For example, the epoxy alkyd coating developed by a company in Changzhou has good environmental protection performance, but its salt spray resistance performance is about 30% lower than that of solvent-based coatings, and multiple layers of coating need to be applied to make up for the performance loss, increasing the construction complexity.

[0007] Most existing protective coatings follow traditional railway or industrial equipment standards (such as TB / T2879) and are not customized for the "high speed, high load, long cycle" characteristics of high-speed train wheelsets. For example: poor dynamic friction matching: the hardness of the coating does not match well with the wheel-rail materials, resulting in abnormal wear (such as tread bruising) or noise problems; insufficient anti-fatigue performance: under long-term alternating stress, the coating is prone to fatigue spalling and requires frequent repair; compatibility defects: the interfacial bonding force between the multi-layer coating system (primer + topcoat) is insufficient, and delamination failure is prone to occur due to differences in thermal expansion coefficients.

[0008] The material defects of the current protective coatings for high-speed train wheelsets are essentially a concentrated manifestation of the inability of traditional protective technologies to adapt to the extreme service conditions of high-speed trains. In the future, breakthroughs need to be made in the directions of material compounding (such as inorganic-organic hybridization), intelligent functional design (such as self-repair, stress sensing), and green process optimization. At the same time, combined with intelligent monitoring technologies (such as real-time sensing of coating damage), full-life-cycle protection can be achieved.

[0009] To solve the above problems, the present application for a wheelset protective coating and its preparation method is hereby proposed. Summary of the Invention

[0010] To overcome the problem that there is no professional coating protection technology for high-speed train wheelsets in China.

[0011] The technical solution of the present invention is: a wheelset protective coating and its preparation method, including a primer and a topcoat. The primer is a one-component epoxy resin coating, and the topcoat is a one-component polyurethane coating; the total thickness of the coating is 260 - 500 μm.

[0012] Preferably, nano-ceramic particles with a particle size of 20-100 nm are added to the topcoat, and the addition amount is 3-8% of the total mass of the coating. The adhesion grade of the coating under the ISO 2409:2020 standard is ≤1 level, and the pull-out strength is ≥4 MPa. The coating passes the anti-flying sand test in Appendix H of BS EN 13261-2020, and the damage grade is ≤4 levels. The coating has no corrosion in the salt spray test for ≥480 hours, and there is no corrosion phenomenon within 2 mm around the incision. The VOCs content in the coating complies with the GB / T 38597-2020 standard, and the solvent content is ≤150 g / L. A halogen-free flame retardant is added to the topcoat to meet the fire protection grade HL1 / HL2 / HL3 of EN 45545-2:2020R9.

[0013] Preferably, the wheel set protection coating and its preparation method include the following steps:

[0014] Surface pretreatment: The surface of the wheel set is sandblasted to Sa2.5 level, and the roughness Ra = 40-60 μm;

[0015] Primer spraying: Use a high-pressure airless spraying device to spray a single-component epoxy resin primer with a thickness of 80-150 μm and air-dry for 24 hours;

[0016] Topcoat spraying: Use a high-pressure airless spraying device to spray a single-component polyurethane topcoat with a thickness of 180-350 μm, and adopt the wet-on-wet process with a total drying time of ≤72 hours;

[0017] Drying and curing: Naturally dry under the conditions of an ambient temperature of 10-35 °C and a relative humidity of ≤85%, and the total drying time is ≤72 hours.

[0018] Preferably, the spraying is carried out using a high-pressure airless spraying device, with a spraying pressure of 15-25 MPa, a spraying distance of 200-300 mm, and a spraying speed of 0.5-1.0 m / s.

[0019] Preferably, the curing temperature range of the primer and the topcoat is 10-35 °C, and the relative humidity is ≤85%.

[0020] Preferably, the surface pretreatment step includes:

[0021] Cleaning: Use an organic solvent to clean the surface of the wheel set to remove oil stains and dust;

[0022] Sandblasting: Use steel sand or alumina sand for sandblasting, and the sandblasting pressure is 0.6-0.8 MPa;

[0023] Dust removal: Use compressed air to blow the surface of the wheel set to remove residual sand grains and dust.

[0024] Preferably, in the primer spraying step, the VOCs content of the primer is ≤ 150 g / L, the spraying thickness is 80 - 150 μm, and it is naturally dried for 24 hours. In the topcoat spraying step, nano-ceramic particles with a particle size of 20 - 100 nm are added to the topcoat, and the addition amount is 3 - 8% of the total mass of the coating. In the drying and curing step, the total drying time of the coating is ≤ 72 hours, the ambient temperature is 10 - 35 °C, and the relative humidity is ≤ 85%.

[0025] Preferably, the coating needs to be subjected to quality inspection after drying and curing, including:

[0026] Adhesion test: Use the cross-cut method to detect adhesion, ensuring that the grade is ≤ 1;

[0027] Pull-off test: Use a pull-off tester to detect the pull-off strength, ensuring that it is ≥ 4 MPa;

[0028] Thickness detection: Use a coating thickness gauge to detect the coating thickness, ensuring that the total thickness is 260 - 500 μm.

[0029] Preferably, the quality inspection also includes:

[0030] Abrasion resistance test: Use a Taber abrasion tester to test, with the abrasion amount ≤ 0.02 g;

[0031] Salt spray test: Conduct a salt spray test in accordance with the EN ISO 9227 standard, with no corrosion for ≥ 480 hours;

[0032] Anti-flying sand test: Test in accordance with Appendix H of BS EN 13261-2020, with the damage grade ≤ 4;

[0033] Fire resistance test: Test in accordance with the EN 45545-2:2020R9 standard, meeting the HL1 / HL2 / HL3 grades;

[0034] Environmental protection test: Use a gas chromatograph to detect the VOCs content, ensuring that it is ≤ 150 g / L.

[0035] Preferably, the coating is subjected to quality inspection. Use a Taber abrasion tester to test, with the abrasion amount ≤ 0.02 g. Place the coating sample in a salt spray chamber and test for ≥ 480 hours with no corrosion. Use a flying sand test device to test, with the damage grade ≤ 4. Use a fire resistance test device to test, meeting the HL1 / HL2 / HL3 grades. Use a gas chromatograph to detect the VOCs content, ensuring that it is ≤ 150 g / L.

[0036] For the adhesion test, first use a cross cutter to draw 1mm×1mm squares on the coating surface. The depth of the scratches needs to penetrate the coating. Then use tape to stick on the scribed area and quickly tear off the tape. Observe whether the coating peels off. Finally, evaluate the adhesion grade according to the peeled area of the coating. The passing standard is that the grade ≤ 1 level.

[0037] For the pull-off test, first use a pull-off tester to stick a pull-off head on the coating surface to ensure that the pull-off head is in full contact with the coating surface. Then apply a pulling force until the coating is separated from the substrate, and record the pull-off strength. The passing standard is that the pull-off strength ≥ 4MPa.

[0038] For the abrasion resistance test, use a Taber abrasion tester to conduct an abrasion test on the coating surface. Set the load to 1kg, the abrasion wheel to CS-10, set the number of abrasion times to 1000 times, record the abrasion amount. The passing standard is that the abrasion amount ≤ 0.02g.

[0039] For the salt spray test, place the coating sample in a salt spray chamber, set the test time ≥ 480 hours, set the salt spray concentration to 5% NaCl, keep the temperature at 35℃, and observe whether there is corrosion on the coating surface. The passing standard is that there is no corrosion within 2mm around the incision.

[0040] For the anti-fly sand test, set the sand particle size to 0.5 - 1.5mm, the impact speed to 50m / s, use a fly sand test device to conduct a fly sand impact test on the coating surface, set the number of impact times to 1000 times, and observe whether there is damage on the coating surface. The passing standard is that the damage grade ≤ 4 levels.

[0041] For the fire resistance test, use a fire test device to conduct a combustion test on the coating sample. Set the flame temperature to 800 - 1000℃, and observe the combustion time, smoke generation amount and toxic gas release amount of the coating sample. The passing standard is to meet the HL1 / HL2 / HL3 grades.

[0042] For the environmental protection test, use a gas chromatograph to detect the VOCs content in the coating to ensure that the VOCs content ≤ 150g / L, and then use an infrared spectrometer to detect whether there are prohibited substances in the coating.

[0043] The beneficial effects of the present invention:

[0044] 1. This wheel pair coating has high abrasion resistance and can withstand the long-term friction and wear between the wheel pair and the track, extending the service life of the wheel.

[0045] 2. This wheel pair coating can maintain its physical properties and structural stability under high-temperature conditions, preventing the coating from softening, peeling off or cracking.

[0046] 3. This wheel pair coating can effectively prevent damage to the wheel surface caused by oxidation or chemical corrosion, especially showing excellent performance under harsh weather conditions.

[0047] 4. This wheel pair coating has good adhesion, which can ensure that the coating adheres firmly to the wheel surface. Even under strong friction and impact, it can maintain long-term stability. High adhesion helps to improve the durability of the coating and reduce the frequency of maintenance.

[0048] 5. This wheel pair coating has a low coefficient of friction, which helps to reduce the energy consumption of railway vehicles and at the same time reduce the wear between the wheels and the tracks.

[0049] 6. This wheel pair coating provides a quieter driving experience by reducing the noise generated when the wheels contact the tracks, thus enhancing the comfort of passengers.

[0050] 7. This wheel pair coating has strong chemical corrosion resistance and can effectively prevent the damage of these chemicals to the coating.

[0051] 8. This wheel pair coating can reduce the potential hazards to the environment and the human body, and also helps to reduce harmful emissions during the painting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The flowchart shows the wheel pair protective coating and its preparation method of the present invention;

[0053] Figure 2 The flowchart shows the surface pretreatment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0055] The present invention provides an embodiment: a wheel pair protective coating and its preparation method, including a primer and a topcoat. The primer is a one-component epoxy resin coating, and the topcoat is a one-component polyurethane coating; the total thickness of the coating is 260 - 500 μm.

[0056] The topcoat is added with nano-ceramic particles with a particle size of 20 - 100 nm and an addition amount of 3 - 8% of the total mass of the coating. The adhesion grade of the coating under the ISO 2409:2020 standard is ≤ 1 level, and the pull-out strength is ≥ 4 MPa. The coating passes the anti-flying sand test in Appendix H of BS EN 13261-2020, and the damage grade is ≤ 4 levels. The coating has no corrosion in the salt spray test for ≥ 480 hours, and there is no corrosion phenomenon within 2 mm around the incision. The VOCs content in the coating complies with the GB / T 38597-2020 standard, and the solvent content is ≤ 150 g / L. The topcoat is added with a halogen-free flame retardant to meet the fire protection grade HL1 / HL2 / HL3 of EN 45545-2:2020R9.

[0057] The wheel set protection coating and its preparation method include the following steps:

[0058] Surface pretreatment: The surface of the wheel set is sandblasted to Sa2.5 level, and the roughness Ra = 40 - 60 μm;

[0059] Primer spraying: A one-component epoxy resin primer is sprayed using a high-pressure airless spraying device, with a thickness of 80 - 150 μm, and naturally dried for 24 hours;

[0060] Topcoat spraying: A one-component polyurethane topcoat is sprayed using a high-pressure airless spraying device, with a thickness of 180 - 350 μm, and the wet-on-wet process is adopted, and the total drying time is ≤ 72 hours;

[0061] Drying and curing: Naturally dried under the conditions of an ambient temperature of 10 - 35 °C and a relative humidity of ≤ 85%, and the total drying time is ≤ 72 hours.

[0062] The spraying is carried out using a high-pressure airless spraying device, with a spraying pressure of 15 - 25 MPa, a spraying distance of 200 - 300 mm, and a spraying speed of 0.5 - 1.0 m / s.

[0063] The curing temperature range of the primer and the topcoat is 10 - 35 °C, and the relative humidity is ≤ 85%.

[0064] The surface pretreatment step includes:

[0065] Cleaning: The surface of the wheel set is cleaned using an organic solvent to remove oil stains and dust;

[0066] Sandblasting: Sandblasting is carried out using steel sand or alumina sand, and the sandblasting pressure is 0.6 - 0.8 MPa;

[0067] Dust removal: The surface of the wheel set is purged using compressed air to remove residual sand grains and dust.

[0068] In the primer spraying step, the VOCs content of the primer is ≤ 150 g / L, the spraying thickness is 80 - 150 μm, and it is naturally dried for 24 hours. In the topcoat spraying step, nano-ceramic particles are added to the topcoat, with a particle size of 20 - 100 nm and an addition amount of 3 - 8% of the total mass of the coating. In the drying and curing step, the total drying time of the coating is ≤ 72 hours, the ambient temperature is 10 - 35 °C, and the relative humidity is ≤ 85%.

[0069] After drying and curing, the coating needs to be subjected to quality inspection, including:

[0070] Adhesion test: The adhesion is detected using the cross-cut method to ensure that the grade is ≤ 1 level;

[0071] Pull-off test: The pull-off strength is detected using a pull-off tester to ensure that it is ≥ 4 MPa;

[0072] Thickness detection: The coating thickness is detected using a coating thickness gauge to ensure that the total thickness is 260 - 500 μm.

[0073] The quality inspection also includes:

[0074] Abrasion resistance test: It is tested using a Taber abrasion tester, and the abrasion amount is ≤ 0.02 g;

[0075] Salt spray test: The salt spray test is carried out according to the EN ISO 9227 standard, and there is no corrosion for ≥ 480 hours;

[0076] Anti-flying sand test: It is tested according to Appendix H of BS EN 13261 - 2020, and the damage grade is ≤ 4 levels;

[0077] Fire resistance test: It is tested according to the EN 45545 - 2:2020R9 standard and meets the HL1 / HL2 / HL3 grades;

[0078] Environmental protection test: The VOCs content is detected using a gas chromatograph to ensure that it is ≤ 150 g / L.

[0079] The application of the coating on the high-speed rail wheel set can withstand extreme environmental conditions, including a temperature range of -40 °C to 80 °C, a high-humidity salt spray environment, and ultraviolet radiation. The application of the coating on the high-speed rail wheel set can reduce the friction coefficient between the wheel set and the track, reduce energy consumption and noise, and improve the operation efficiency.

[0080] As Figure 1 shown, the detailed steps for the preparation method of the wheel set protection coating are as follows:

[0081] S1, as Figure 2As shown, the surface of the wheel set is pre-treated. Surface pre-treatment is a crucial step in coating preparation, which directly affects the adhesion and durability of the subsequent coating. Its main purpose is to remove contaminants, oxide layers, and impurities on the surface of the wheel set, thereby ensuring good bonding between the coating and the metal matrix.

[0082] In the first step, the surface of the wheel set is cleaned to remove oil stains, dust, and other contaminants on the surface of the wheel set. Ethanol is evenly sprayed on the surface of the wheel set using a high-pressure spray gun to ensure that all areas are covered, and then the residual solvents and dirt on the surface are removed completely.

[0083] In the second step, the surface of the wheel set is sandblasted to increase its surface roughness, improve the adhesion of the coating, and remove the oxide layer on its surface. The medium used for sandblasting is steel sand or alumina sand, with a particle size between 0.5 - 1.5 mm. First, adjust the pressure of the sandblasting equipment to 0.6 - 0.8 MPa, and then use the sandblasting equipment to sandblast the surface of the wheel set. During sandblasting, the surface of the wheel set needs to be evenly covered to ensure that the same roughness is achieved in all areas. After sandblasting, the surface roughness Ra of the wheel set needs to be controlled between 40 - 60 μm, and the cleanliness reaches Sa2.5 level.

[0084] In the third step, the surface of the wheel set is dusted to remove sand grains and dust remaining on the surface after sandblasting. Use high-pressure air to blow the surface of the wheel set to remove the sand grains and dust remaining on the surface.

[0085] S2. Perform the primer spraying operation on the surface of the wheel set to provide a good adhesion foundation and enhance the anti-corrosion performance of the coating.

[0086] In the first step, pour the one-component epoxy paint into the storage tank of the high-pressure airless spraying equipment. Adjust the spraying pressure of the high-pressure airless spraying equipment to be between 15 - 25 MPa. Keep the spraying port perpendicular to the surface of the wheel set and maintain a distance between 200 - 300 mm for spraying. During spraying, use a uniform spraying speed for spraying to ensure that the coating thickness is between 80 - 150 μm.

[0087] In the second step, dry the primer. Set the ambient temperature to 10 - 35 °C, relative humidity ≤ 85%, and dry naturally for 24 hours.

[0088] S3. Spray the topcoat on the wheel set to provide the effects of wear resistance, weather resistance, and resistance to flying sand, and enhance the service life of the coating.

[0089] In the first step, a one-component polyurethane paint is fully mixed with nano-ceramic particles and a halogen-free flame retardant to enhance its wear resistance and weather resistance. When the primer is not completely dry, the topcoat is directly sprayed. The topcoat is poured into the storage tank of a high-pressure airless spraying device. The spraying pressure of the high-pressure airless spraying device is adjusted to be between 15 - 25 MPa. The spraying nozzle is perpendicular to the surface of the wheel set, and spraying is carried out while maintaining a distance between 200 - 300 mm. During spraying, a uniform spraying speed is adopted to ensure that the coating thickness is between 180 - 350 μm;

[0090] In the second step, the topcoat is dried. The ambient temperature is set to 10 - 35 °C, the relative humidity ≤ 85%, and it is naturally dried for 48 hours.

[0091] S4, the coating is dried and cured. The cross-cut method is used to detect the adhesion, ensuring that the grade ≤ 1 level. The pull-off tester is used to detect the pull-off strength, ensuring that it is ≥ 4 MPa. The coating thickness gauge is used to detect the coating thickness, ensuring that the total thickness is 260 - 500 μm.

[0092] S5, the quality of the coating is inspected. The Taber abrasion tester is used for testing, and the abrasion amount ≤ 0.02 g. The coating sample is placed in a salt spray chamber, and no corrosion is detected after testing for ≥ 480 hours. The sandblasting test equipment is used for testing, and the damage grade ≤ 4 levels. The fire protection test equipment is used for testing, meeting the HL1 / HL2 / HL3 grades. The gas chromatograph is used to detect the VOCs content, ensuring that it is ≤ 150 g / L.

[0093] For the adhesion test, first use a cross-cut tool to make 1 mm × 1 mm squares on the coating surface. The depth of the scratches needs to penetrate the coating. Then use tape to stick on the cross-cut area and quickly tear off the tape. Observe whether the coating peels off. Finally, the adhesion grade is evaluated according to the peeling area of the coating. The passing standard is that the grade ≤ 1 level. It should be noted that before the test, it is necessary to ensure that the coating is completely dry, and the force should be kept uniform during cross-cutting to avoid too deep or too shallow scratches affecting the test results.

[0094] For the pull-off test, first use a pull-off tester to stick a pull-off head on the coating surface, ensuring that the pull-off head is in full contact with the coating surface. Then apply a pulling force until the coating is separated from the substrate, and record the pull-off strength. The passing standard is that the pull-off strength ≥ 4 MPa. It should be noted that before the test, it is necessary to ensure that there are no bubbles or voids between the pull-off head and the coating surface, and the pulling force should be kept uniform during the test to avoid suddenly applying too large a pulling force affecting the test results.

[0095] For the abrasion resistance test, a Taber abrasion tester was used to conduct an abrasion test on the coating surface. The load was set at 1 kg, the abrasion wheel was CS-10, the number of abrasion cycles was set at 1000 times, and the abrasion loss was recorded. The acceptance criterion was that the abrasion loss ≤ 0.02 g. It should be noted that before the test, it was necessary to ensure that the coating surface was flat without unevenness, and during the test, the condition of the abrasion wheel needed to be checked regularly to avoid affecting the test results due to damage to the abrasion wheel.

[0096] For the salt spray test, the coated sample was placed in a salt spray chamber. The test time was set ≥ 480 hours, the salt spray concentration was set at 5% NaCl, and the temperature was maintained at 35°C. Whether corrosion occurred on the coating surface was observed. The acceptance criterion was that there was no corrosion within 2 mm around the incision. It should be noted that before the test, an incision needed to be made on the coating surface, and the incision depth should penetrate the coating to the substrate. During the test, the salt spray concentration and temperature in the salt spray chamber needed to be checked regularly to avoid affecting the test results due to changes in the salt spray concentration and temperature.

[0097] For the anti-flying sand property test, the sand particle size was set at 0.5 - 1.5 mm, the impact speed was 50 m / s, and a flying sand test device was used to conduct a flying sand impact test on the coating surface. The number of impact cycles was set at 1000 times. Whether damage occurred on the coating surface was observed. The acceptance criterion was that the damage level ≤ 4. It should be noted that before the test, it was necessary to ensure that the coating surface was flat without unevenness, and during the test, the condition of the sand particles needed to be checked regularly to avoid affecting the test results due to damage to the sand particles.

[0098] For the fire resistance test, a fire resistance test device was used to conduct a combustion test on the coated sample. The flame temperature was set at 800 - 1000°C, and the combustion time, smoke generation amount, and toxic gas release amount of the coated sample were observed. The acceptance criterion was to meet the HL1 / HL2 / HL3 grade. It should be noted that before the test, it was necessary to ensure that the size of the coated sample met the standard requirements, and during the test, protective equipment needed to be worn to avoid inhaling toxic gases.

[0099] For the environmental friendliness test, a gas chromatograph was used to detect the VOCs content in the coating to ensure that the VOCs content ≤ 150 g / L. Then, an infrared spectrometer was used to detect whether there were any prohibited substances in the coating. It should be noted that before the test, it was necessary to ensure that the coated sample was completely dry.

Claims

1. Wheel set protective coating, characterized by: The invention comprises a primer and a topcoat, wherein the primer is a single-component epoxy resin coating, and the topcoat is a single-component polyurethane coating; and the total thickness of the coating is 260-500 μm.

2. The wheelset protective coating according to claim 1, characterized in that: Nano-ceramic particles with a particle size of 20-100nm are added to the topcoat, and the addition amount is 3-8% of the total mass of the coating. The coating has an adhesion grade of ≤1 and a pull-out strength of ≥4MPa under ISO 2409:2020 standard. The coating passes the flying sand resistance test in Appendix H of BS EN 13261-2020, with a damage grade of ≤4. The coating is corrosion-free for ≥480 hours in the salt spray test, and there is no corrosion within 2mm around the incision. The VOCs content in the coating complies with GB / T 38597-2020 standard, and the solvent content is ≤150g / L. A halogen-free flame retardant is added to the topcoat to meet the EN 45545-2:2020R9 fire protection grade HL1 / HL2 / HL3.

3. The wheelset protective coating and preparation method thereof according to claims 1-2, characterized in that: The following steps are involved: Surface pretreatment: The wheelset surface is sandblasted to Sa2.5 level, with a roughness of Ra = 40-60μm; Primer spraying: Use high-pressure airless spray equipment to spray single-component epoxy resin primer with a thickness of 80-150μm and dry naturally for 24 hours; Topcoat spraying: Use high-pressure airless spray equipment to spray single-component polyurethane topcoat with a thickness of 180-350μm, using wet-on-wet process, and the total drying time is ≤72 hours; Drying and curing: Natural drying at an ambient temperature of 10-35°C and relative humidity ≤85%, with a total drying time of ≤72 hours.

4. The preparation method according to claim 3, characterized in that: The spraying adopts high-pressure airless spraying equipment, the spraying pressure is 15-25MPa, the spraying distance is 200-300mm, and the spraying speed is 0.5-1.0m / s.

5. The preparation method according to claim 3, characterized in that: The curing temperature range of the primer and topcoat is 10-35° C., and the relative humidity is ≤85%.

6. The preparation method according to claim 3, characterized in that: The surface pretreatment step comprises: Cleaning: Use organic solvent to clean the surface of the wheelset to remove oil and dust; Sand blasting: Use steel sand or alumina sand for sand blasting, and the sand blasting pressure is 0.6-0.8MPa; Dust removal: Use compressed air to blow the wheelset surface to remove residual sand and dust.

7. The preparation method according to claim 3, characterized in that: In the primer spraying step, the VOCs content of the primer is ≤150g / L, the spraying thickness is 80-150μm, and it is naturally dried for 24 hours. In the topcoat spraying step, nano-ceramic particles are added to the topcoat, the particle size is 20-100nm, and the addition amount is 3-8% of the total mass of the coating. In the drying and curing step, the total drying time of the coating is ≤72 hours, the ambient temperature is 10-35°C, and the relative humidity is ≤85%.

8. The preparation method according to claim 3, characterized in that: The coating needs to be tested for quality after drying and curing, including: Adhesion test: Use the cross-cut method to test adhesion and ensure that the grade is ≤1; Pull-out test: Use a pull-out tester to test the pull-out strength to ensure ≥4MPa; Thickness detection: Use a coating thickness gauge to detect the coating thickness and ensure that the total thickness is 260-500μm.

9. The preparation method according to claim 8, characterized in that: The quality inspection also includes: Wear resistance test: Use Taber abrasion tester to test, wear amount ≤ 0.02g; Salt spray test: Salt spray test according to EN ISO 9227 standard, ≥480 hours without corrosion; Anti-flying sand test: Tested in accordance with BS EN 13261-2020 Appendix H, damage level ≤ 4; Fire performance test: tested according to EN 45545-2:2020R9 standard, meeting HL1 / HL2 / HL3 levels; Environmental testing: Use gas chromatograph to detect VOCs content to ensure ≤150g / L.

10. The preparation method according to claim 8, characterized in that: The coating is quality inspected and tested with a Taber abrasion tester with a wear amount of ≤0.02g. The coating samples are placed in a salt spray chamber and tested for ≥480 hours without corrosion. The flying sand test equipment is used for testing and the damage level is ≤4. The fire protection test equipment is used for testing and meets the HL1 / HL2 / HL3 levels. The VOCs content is tested with a gas chromatograph to ensure that it is ≤150g / L. For adhesion testing, first use a grid marker to scratch 1mm×1mm squares on the coating surface. The depth of the scratches needs to penetrate the coating. Then use tape to stick on the grid area. Quickly tear off the tape and observe whether the coating falls off. Finally, assess the adhesion level based on the area of ​​coating shedding. The qualified standard is level ≤1. For the pull-out test, first use a pull-out tester to stick a pull-out head on the coating surface, ensure that the pull-out head is in full contact with the coating surface, then apply a pulling force until the coating is separated from the substrate, and record the pull-out strength. The qualified standard is a pull-out strength ≥4MPa. For the wear resistance test, the coating surface was tested for wear using a Taber abrasion tester. The load was set to 1 kg, the wear wheel was CS-10, the number of wear times was set to 1000 times, and the wear amount was recorded. The qualified standard was wear amount ≤ 0.02 g. For the salt spray test, the coating sample is placed in a salt spray chamber, the test time is set to ≥ 480 hours, the salt spray concentration is set to 5% NaCl, the temperature is maintained at 35°C, and the coating surface is observed for corrosion. The qualified standard is no corrosion within 2mm around the incision. For the flying sand resistance test, the sand particle size is set to 0.5-1.5mm, the impact speed is 50m / s, and the flying sand testing equipment is used to perform a flying sand impact test on the coating surface. The number of impacts is set to 1000 times, and the coating surface is observed for damage. The qualified standard is damage level ≤4. For the fire resistance test, the coating samples are subjected to a combustion test using fire resistance test equipment. The flame temperature is set at 800-1000°C. The burning time, smoke generation and toxic gas release of the coating samples are observed. The qualification standard is to meet the HL1 / HL2 / HL3 grades. For environmental testing, a gas chromatograph is used to detect the VOCs content in the coating to ensure that the VOCs content is ≤150g / L, and then an infrared spectrometer is used to detect whether the coating contains banned substances.

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