Low-friction-coefficient high-temperature wear-resistant coating material as well as preparation method and application thereof

Abstract

The invention discloses a low-friction-coefficient high-temperature wear-resistant coating material and a preparation method and application thereof, and relates to a preparation method of a wear-resistant and high-temperature-resistant plasma spraying metal ceramic composite coating, the method comprises the following steps: S1, mixing raw material powder according to the following mass percent: 60-70% of cobalt-based powder, 1-3% of cobalt-based powder, 1-3% of cobalt-based powder, 1-3% of cobalt-based powder, 30-40% of a mixture of hard alloy powder and self-fluxing alloy powder; s2, the surface of the workpiece is pretreated, specifically, a surface oxide layer is removed through polishing, and surface oil stains and dust are wiped away through alcohol; s3, the workpiece is preheated to 200 DEG C to 300 DEG C; s4, preparing a coating on the surface of the preheated workpiece by adopting a laser cladding process; and S5, the obtained coating is subjected to heat treatment, the temperature is higher than 850 DEG C, and the treatment time is longer than 1 hour. According to the high-temperature wear-resistant coating with the low friction coefficient and the preparation method of the high-temperature wear-resistant coating, the compound challenge confronted by parts such as shaft sleeves in hot galvanizing and aluminum plating industries in a high-temperature molten metal environment can be effectively solved, and remarkable technical advantages and application value are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal coating, and specifically to a low-friction coefficient high-temperature wear-resistant coating material and its preparation method and application. Background Art

[0002] With the rapid development of the hot-dip galvanizing and aluminizing industries, components such as bushings work in a molten metal liquid environment for a long time. They not only have to withstand high temperatures above 700 °C, but also resist the corrosion and wear of molten zinc and aluminum liquids. These components are subjected to the combined action of high temperature, corrosion and wear during the production process, posing extremely high requirements for the surface properties of the materials. Currently, high-temperature wear-resistant coating technologies mainly include thermal spraying, physical vapor deposition (PVD), chemical vapor deposition (CVD) and laser cladding, etc. Among them, laser cladding has been tried to be applied to the surface modification of components in a molten metal environment due to its advantages such as high bonding strength with the substrate, high coating density and small heat-affected zone.

[0003] However, the existing high-temperature wear-resistant coatings for the hot-dip galvanizing and aluminizing industries have exposed many problems in practical applications. Traditional coatings are easily corroded and penetrated in a molten metal liquid environment, resulting in coating spalling; at the same time, the friction coefficient increases significantly under high-temperature conditions, accelerating the wear and energy loss of the components. In addition, the microcracks and pores formed during the preparation of the coating not only reduce the mechanical properties of the coating, but also provide channels for the penetration of molten metal liquid, seriously shortening the service life of key components such as bushings, leading to frequent shutdowns and repairs of the production line and causing huge economic losses.

[0004] Therefore, there is an urgent need to develop a coating material and its preparation method that have both low friction coefficient, high-temperature wear-resistant performance and excellent corrosion resistance to molten metal liquid. This coating needs to work stably for a long time in a high-temperature molten zinc and aluminum liquid environment above 700 °C, while maintaining a low friction coefficient and high wear-resistant performance, and the coating needs to be highly dense to prevent the penetration of molten metal liquid. This has important practical significance for improving the production efficiency of the hot-dip galvanizing and aluminizing industries, reducing maintenance costs and extending the service life of equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-friction coefficient high-temperature wear-resistant coating material and its preparation method and application to solve the problems existing in the prior art as mentioned in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions.

[0007] A preparation method of a wear-resistant and high-temperature resistant plasma-sprayed metal ceramic composite coating, the method comprising the following steps:

[0008] S1. Mix raw material powders according to the following mass percentages:

[0009] 60 - 70% cobalt-based powder, 30 - 40% mixture of cemented carbide powder and self-fluxing alloy powder;

[0010] S2. Pretreat the surface of the workpiece, including grinding to remove the surface oxide layer and wiping with alcohol to remove surface oil stains and dust;

[0011] S3. Preheat the workpiece to 200 - 300 °C;

[0012] S4. Prepare a coating on the surface of the preheated workpiece by laser cladding process;

[0013] S5. Heat-treat the obtained coating, with the temperature greater than 850 °C and the treatment time greater than 1 hour.

[0014] Preferably, the raw materials used in the coating include the following components:

[0015] a) Cobalt-based powder, the composition of which is by weight percentage: Co 40 - 60%, Cr 15 - 25%, Ni 10 - 20%, W 10 - 20%, particle size < 100 μm;

[0016] b) Cemented carbide powder, which is WC-Co powder, Co content < 10%, particle size < 100 μm;

[0017] c) Self-fluxing alloy powder, the composition of which is by weight percentage: Co 20 - 30%, Cr 10 - 25%, Mo 30 - 50%, B 5 - 15%, W < 5%.

[0018] Preferably, the laser cladding process in step S4 is carried out using a fiber laser, with a laser power of 3.0 - 5.0 kW and a spot diameter of 2.0 - 3.0 mm.

[0019] Preferably, in the laser cladding process of step S4, the scanning speed is 10 - 40 mm / s and the overlapping rate is 40% - 60%.

[0020] Preferably, the laser cladding process in step S4 adopts a ring coaxial powder feeding method.

[0021] Preferably, the heat treatment in step S5 continues until the microcracks on the coating surface are closed and the porosity is lower than 3%.

[0022] A wear-resistant and high-temperature-resistant plasma spraying metal ceramic composite coating prepared by the above method.

[0023] Application of the low-friction coefficient high-temperature wear-resistant coating on the surface of wear-resistant components under high-temperature working conditions.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1) The low-friction high-temperature wear-resistant coating provided by this application and its preparation method can effectively solve the compound challenges faced by components such as bushings in the hot-dip galvanizing and aluminizing industries in a high-temperature molten metal environment, and have significant technical advantages and application values;

[0026] 2) Through a carefully designed material system and preparation process, a unique composite structure is formed in the coating. The cobalt-based powder provides an excellent high-temperature and corrosion-resistant foundation; the cemented carbide powder (WC-Co) forms a wear-resistant framework, effectively resisting wear; while the self-fluxing alloy powder forms a self-lubricating phase in a high-temperature environment, significantly reducing the friction coefficient. The synergistic effect of the three powders enables the coating to exhibit excellent comprehensive performance in a molten zinc or aluminum liquid environment above 700 °C, with a friction coefficient lower than 0.35 and the corrosion resistance being more than 50% higher than that of traditional coatings;

[0027] 3) The laser cladding process adopted in this application combined with the subsequent heat treatment process ensures the high density and stability of the coating. By controlling process parameters such as laser power, scanning speed, and annular coaxial powder feeding, a metallurgical bond between the coating and the substrate is achieved; while the high-temperature long-term heat treatment promotes the closure of microcracks in the coating and reduces the porosity to less than 3%, effectively blocking the penetration channels of the molten metal liquid. After testing, the service life of the coating of this invention in a simulated molten zinc or aluminum liquid environment is 2-3 times that of traditional coatings, significantly reducing the equipment maintenance frequency and downtime, and bringing significant economic benefits to the hot-dip galvanizing and aluminizing production lines. Description of the Drawings

[0028] Figure 1 It is a flow chart of the preparation method of this application. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] In the description of the invention, it should be noted that the execution order of the steps is not limited by the serial numbers. The order change of some steps, the synchronous execution of steps, the split execution of steps, etc. are all within the protection scope of this application.

[0031] Example 1

[0032] A preparation method of a low-friction high-temperature wear-resistant coating is as follows:

[0033] S1. Mix the raw material powders according to the following mass percentages:

[0034] A mixture of 65% cobalt-based powder (by weight percentage of components: 52% Co, 22% Cr, 15% Ni, 11% W, particle size 75 - 100 μm), 20% cemented carbide powder (components: 95% WC, 5% Co, particle size 45 - 75 μm) and 15% self-fluxing alloy powder (by weight percentage of components: 25% Co, 15% Cr, 45% Mo, 12% B, 3% W).

[0035] S2. Pretreat the surface of the No. 45 steel bushing. First, use a grinding wheel to polish the surface until the metal luster is exposed to remove the surface oxide layer; then wipe and clean it 3 times with acetone, and then wipe it 2 times with anhydrous ethanol to remove surface oil stains and dust; finally, dry it at room temperature for 30 minutes.

[0036] S3. Preheat the bushing to 250 °C using a resistance heating furnace and keep it warm for 15 minutes to make the temperature uniform.

[0037] S4. Laser cladding process parameters: The equipment is an RFL-C4000W fiber laser, the laser power is 3.5 kW, the spot diameter is 2.5 mm, the scanning speed is 25 mm / s, the overlapping rate is 50%, the annular coaxial powder feeding method is adopted, the shielding gas is high-purity argon (purity 99.999%), the flow rate is 15 L / min, and the prepared coating thickness is about 1.8 mm.

[0038] S5. Heat treatment process: Put the clad bushing into a vacuum furnace, heat it to 900 °C at a heating rate of 3 °C / min, keep it warm for 2 hours, and then cool it to room temperature with the furnace.

[0039] As an additional note:

[0040] 1) Microstructure analysis: Use a scanning electron microscope (SEM) and a transmission electron microscope (TEM) to observe the microstructure and phase composition of the coating. Use image analysis software to process the SEM image of the coating cross-section and calculate the porosity. X-ray diffraction (XRD) is used to analyze the phase composition of the coating. Energy dispersive spectroscopy (EDS) is used for elemental distribution analysis to evaluate the interface bonding situation between the coating and the substrate and the elemental diffusion condition. The surface hardness is measured using a Rockwell hardness tester (HRC).

[0041] 2) High-temperature friction and wear test: The UMT-3 high-temperature friction and wear testing machine was used to evaluate the wear resistance and friction coefficient of the coating. The coating specimen was fixed, and the counter material was selected as a ceramic ball (Si3N4, Al2O3, or ZrO2) according to the actual application environment. A load of 10 - 15 N was applied, the sliding speed was 0.2 - 0.3 m / s, and the test time was 2 - 5 hours. The high-temperature test was carried out in an environment of 700 - 750 °C. The specimen was preheated for 30 minutes before the test to ensure uniform temperature. The change in frictional force was recorded in real time through a sensor to calculate the friction coefficient; before and after each test, the mass of the specimen was weighed using a precision electronic balance (accuracy 0.1 mg), and combined with the geometric dimensions of the wear track, the volume wear rate (unit: mm 3 / N·m) was calculated. Each group of samples was tested 3 times, and the average value was taken.

[0042] 3) Molten metal corrosion test: The coating specimen was immersed in molten zinc or aluminum liquid at 450 - 720 °C for 48 - 72 hours, taken out and cooled to room temperature, the residual metal liquid on the surface was cleaned, and the mass loss rate was calculated by weighing with a precision balance. A scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were used to observe the surface and cross-section of the coating to determine the penetration depth of metal elements. In addition, a combined corrosion and wear resistance test was also carried out, that is, the soaked specimen was directly subjected to a high-temperature friction and wear test to evaluate the comprehensive performance of the coating under actual working conditions. Each group of samples was tested with 3 parallel samples, and the average value was taken.

[0043] Performance tests were carried out on the low-friction coefficient high-temperature wear-resistant coating prepared in this example, and the results are as follows:

[0044] 1. Microstructure analysis:

[0045] The cross-section of the coating was observed using a scanning electron microscope. The coating was well bonded to the substrate, and there were no obvious interfacial defects; the coating had a high density, and the porosity was measured to be 2.1%; there were no obvious microcracks.

[0046] 2. High-temperature friction and wear test:

[0047] The test temperature was 700 °C, the counter material was a Si3N4 ball (diameter 6 mm), the load was 10 N, the sliding speed was 0.2 m / s, and the test time was 2 hours.

[0048] Test results: The friction coefficient was 0.28, and the volume wear rate was 4.2×10 -6 mm 3 / Nm.

[0049] 3. Molten zinc corrosion test:

[0050] The coating sample was immersed in molten zinc at 450 °C for 72 hours.

[0051] Test results: There are no obvious corrosion marks on the coating, and the mass loss rate is 0.8%; SEM analysis of the coating surface shows that the penetration depth of zinc element is less than 20 μm.

[0052]

[0053] Therefore, according to the above test results, it can be known that the coating prepared in Example 1 has excellent high-temperature wear resistance and low friction coefficient. The friction coefficient at 700 °C is only 0.28, which is much lower than that of traditional coatings (usually > 0.5). At the same time, the coating shows good corrosion resistance in molten zinc liquid and is suitable as a protective coating for bushings in the hot-dip galvanizing industry.

[0054] Example 2

[0055] A preparation method of a high-temperature wear-resistant coating with low friction coefficient is as follows:

[0056] S1. Mix the raw material powders according to the following mass percentages:

[0057] 60% cobalt-based powder (the composition by weight percentage is: Co 58%, Cr 18%, Ni 12%, W 12%, particle size 50 - 75 μm), 25% cemented carbide powder (composition: WC 93%, Co 7%, particle size 40 - 60 μm) and 15% self-fluxing alloy powder (the composition by weight percentage is: Co 22%, Cr 20%, Mo 40%, B 14%, W 4%).

[0058] S2. Pretreat the surface of the 42CrMo steel guide wheel. First, turn the surface to obtain a roughness of Ra = 3.2 μm; then ultrasonically clean with acetone for 10 minutes, and then ultrasonically clean with absolute ethanol for 5 minutes; finally, dry at 80 °C for 30 minutes.

[0059] S3. Use an induction heating device to preheat the guide wheel to 280 °C and keep it warm for 20 minutes to make the temperature uniform.

[0060] S4. Laser cladding process parameters: The equipment is an RFL-C4000W laser, the laser power is 4.0 kW, the spot diameter is 2.2 mm, the scanning speed is 18 mm / s, the overlapping rate is 55%, the annular coaxial powder feeding method is adopted, the shielding gas is high-purity argon (purity 99.999%), the flow rate is 18 L / min, and the thickness of the prepared coating is about 2.2 mm.

[0061] S5. Heat treatment process: Put the clad guide wheel into an argon protection furnace, heat it to 950 °C at a heating rate of 2 °C / min, keep it warm for 3 hours, and cool it to room temperature at a cooling rate of 5 °C / min.

[0062] The performance of the low-friction coefficient and high-temperature wear-resistant coating prepared in this example was tested, and the results are as follows:

[0063] 1. Microstructural analysis:

[0064] XRD analysis showed that the coating mainly consisted of γ-Co solid solution, WC, Mo2C, and a small amount of CoMoB phase; observing the cross-section of the coating using SEM, the coating and the substrate formed a metallurgical bond, and the width of the transition zone was about 50 μm; the coating had a high density, and the porosity was 1.8%; the hard phases were evenly distributed in the substrate.

[0065] 2. High-temperature friction and wear test:

[0066] The test temperature was 750 °C, the counter material was an Al2O3 ball (diameter 10 mm), the load was 15 N, the sliding speed was 0.25 m / s, and the test time was 3 hours.

[0067] Test results: The friction coefficient was 0.32, and the volumetric wear rate was 3.8×10 -6 mm 3 / Nm.

[0068] 3. Molten aluminum corrosion test:

[0069] The coating sample was immersed in molten aluminum at 720 °C for 48 hours.

[0070] Test results: There were no obvious corrosion marks on the coating, and the mass loss rate was 1.2%; interface analysis showed no obvious penetration of aluminum elements.

[0071]

[0072]

[0073] Therefore, according to the above test results, it can be seen that the coating prepared in Example 2 still maintained a low friction coefficient (0.32) and excellent wear resistance at a high temperature of 750 °C. Compared with Example 1, its performance at a higher temperature decreased slightly, but it was still far better than traditional coatings. This coating showed good resistance to molten aluminum and was suitable for surface protection of guide wheels in the hot-dip aluminum industry.

[0074] Example 3

[0075] A preparation method of a low-friction coefficient and high-temperature wear-resistant coating, the specific steps are as follows:

[0076] S1. Mix the raw material powders according to the following mass percentages:

[0077] A mixture of 70% cobalt-based powder (composition by weight percentage: Co 45%, Cr 24%, Ni 18%, W 13%, particle size 60 - 90 μm), 15% cemented carbide powder (composition: WC 92%, Co 8%, particle size 35 - 70 μm) and 15% self-fluxing alloy powder (composition by weight percentage: Co 28%, Cr 12%, Mo 42%, B 13%, W 5%).

[0078] S2. Pretreat the surface of the H13 die steel conversion roll. First, grind it with a grinding wheel until it shows the metal's natural color; then perform sandblasting until the surface roughness Ra = 4.5 μm; subsequently, wipe it with acetone, and then ultrasonically clean it with absolute ethanol for 5 minutes; finally, dry it at 100 °C for 20 minutes.

[0079] S3. Use an infrared heating device to preheat the conversion roll to 220 °C and keep it at this temperature for 10 minutes to make the temperature uniform.

[0080] S4. Laser cladding process parameters: The equipment is an RFL-C4000W fiber laser, the laser power is 4.8 kW, the spot diameter is 3.0 mm, the scanning speed is 15 mm / s, the overlapping rate is 45%, the annular coaxial powder feeding method is adopted, the shielding gas is high-purity argon (purity 99.999%), the flow rate is 20 L / min, and the thickness of the prepared coating is about 2.5 mm.

[0081] S5. Heat treatment process: Put the clad conversion roll into a vacuum furnace, heat it to 880 °C at a heating rate of 4 °C / min, keep it at this temperature for 4 hours, and then slowly cool it to room temperature with the furnace.

[0082] Perform performance tests on the low-friction coefficient and high-temperature wear-resistant coating prepared in this example. The results are as follows:

[0083] 1. Microstructure analysis:

[0084] TEM analysis shows that nano-scale dispersed phases are formed in the coating, enhancing the matrix strength; there is a metallurgical transition zone of about 30 μm in the bonding area between the coating and the matrix; the coating has a high density, and the porosity is only 1.5%; no obvious microcracks are observed after heat treatment.

[0085] 2. High-temperature friction and wear test:

[0086] Carry out comparative tests at two temperature points of 700 °C and 750 °C. The counter material is a ZrO2 ball (diameter 8 mm), the load is 12 N, the sliding speed is 0.3 m / s, and the test time is 5 hours.

[0087] Test results: The friction coefficient at 700 °C is 0.25, and the volume wear rate is 3.1×10 -6 mm 3 / Nm; The friction coefficient is 0.30 and the volumetric wear rate is 3.9×10 -6 mm 3 / Nm.

[0088] 3. Composite corrosion and wear resistance test:

[0089] Immerse the coated sample in molten zinc-aluminum alloy (55% Zn - 45% Al) at 700°C for 24 hours, and then directly conduct high-temperature friction and wear test (700°C, 12 N, 0.3 m / s, 2 hours) after taking it out.

[0090] Test results: The friction coefficient is 0.33 and the volumetric wear rate is 4.5×10 -6 mm 3 / Nm.

[0091]

[0092] Therefore, according to the above test results, it can be seen that the coating prepared in Example 3 still maintains excellent performance under more severe conditions, especially shows stability in the composite corrosion-wear test, and the friction coefficient only increases from 0.25 to 0.33. The nano-dispersed phase formed in the coating further improves its high-temperature stability and wear resistance. This coating is particularly suitable for components such as transfer rolls that need to withstand both molten metal corrosion and high-temperature wear simultaneously.

[0093] Comparative Example 1

[0094] To verify the role of self-fluxing alloy powder in reducing the friction coefficient of the coating, a coating without self-fluxing alloy powder was prepared in this comparative example.

[0095] The specific steps are as follows:

[0096] S1. Mix the raw material powders according to the following mass percentages:

[0097] 80% cobalt-based powder (composition by weight percentage: Co 52%, Cr 22%, Ni 15%, W 11%, particle size 75 - 100 μm), 20% cemented carbide powder (composition: WC 95%, Co 5%, particle size 45 - 75 μm).

[0098] S2 - S5. The steps are exactly the same as those in Example 1.

[0099] Perform performance tests on the coating prepared in this comparative example, and the results are as follows:

[0100] 1. Microstructure analysis:

[0101] The cross-section of the coating was observed by SEM, and the coating was well bonded to the substrate; the coating had a high density and a porosity of 2.3%; the surface hardness was HRC62, higher than that of Example 1 (HRC58).

[0102] 2. High-temperature friction and wear test:

[0103] The test conditions were the same as those in Example 1.

[0104] Test results: The friction coefficient was 0.58, and the volumetric wear rate was 8.7×10 -6 mm 3 / Nm.

[0105] 3. Molten zinc corrosion test:

[0106] The test conditions were the same as those in Example 1.

[0107] Test results: Slight spalling occurred at the edge of the coating, and the mass loss rate was 2.1%; SEM analysis of the coating surface showed that the penetration depth of zinc element was about 60μm.

[0108]

[0109]

[0110] Thus, according to the above test results, it can be seen that although the hardness of the coating prepared in Comparative Example 1 was slightly higher than that in Example 1, the high-temperature friction coefficient increased significantly, and the volumetric wear rate increased by about 1 times. This proves that the self-fluxing alloy powder played a key role in reducing the friction coefficient of the coating and improving the wear resistance. At the same time, the corrosion resistance of the coating in Comparative Example 1 in molten zinc was also poor, indicating that the self-fluxing alloy powder was also helpful in improving the corrosion resistance of the coating to molten metal.

[0111] Comparative Example 2

[0112] To verify the influence of the heat treatment process on the coating properties, the S5 heat treatment step was omitted in this comparative example.

[0113] The specific steps are as follows:

[0114] S1-S4. The steps were exactly the same as those in Example 1, and the S5 heat treatment step was omitted.

[0115] The coating prepared in this comparative example was tested for its properties, and the results were as follows:

[0116] 1. Microstructure analysis:

[0117] Fine cracks were observed on the coating surface; cross-section analysis showed that the porosity was 5.8%, significantly higher than that in Example 1; there were a small number of microcracks in the bonding area between the coating and the substrate.

[0118] 2. High-temperature friction and wear test:

[0119] The test conditions were the same as those in Example 1.

[0120] Test results: The friction coefficient was 0.35, and the volumetric wear rate was 7.5×10 -6 mm 3 / Nm.

[0121] 3. Molten zinc corrosion test:

[0122] The test conditions were the same as those in Example 1.

[0123] Test results: Obvious corrosion and local spalling occurred on the coating, and the mass loss rate was 5.3%; cross-sectional analysis showed that zinc elements penetrated deep into the coating (>150 μm) through microcracks and pores.

[0124]

[0125]

[0126] Thus, according to the above test results, it can be seen that after omitting the heat treatment process in Comparative Example 2, the microstructure and properties of the coating deteriorated significantly. The porosity increased from 2.1% to 5.8%, and microcracks appeared on the surface, resulting in a significant increase in the friction coefficient and wear rate. More seriously, the corrosion resistance of the coating in molten zinc decreased significantly, and the mass loss rate reached 5.3%, which was 6.6 times that of Example 1. This result fully demonstrates the importance of the heat treatment process for eliminating internal stress in the coating, closing microcracks, and reducing porosity, and it is a key step to obtain a high-performance low-friction coefficient high-temperature wear-resistant coating.

[0127] Comparative Example 3

[0128] To compare the differences between laser cladding and traditional plasma spraying processes, this comparative example used the plasma spraying process to prepare the coating.

[0129] The specific steps are as follows:

[0130] S1. Prepare the mixed powder in the same proportion as in Example 1.

[0131] S2. Pretreat the surface of the workpiece:

[0132] Perform sandblasting treatment until the surface roughness Ra = 6.5 μm; clean with acetone and ethanol; dry at 80°C for 30 minutes.

[0133] S3. Plasma spraying process parameters:

[0134] The equipment is F4 plasma spraying equipment, with a spray gun power of 40kW, a main gas (Ar) flow rate of 45L / min, an auxiliary gas (H2) flow rate of 8L / min, a spraying distance of 120mm, a spraying angle of 90°, a powder feed rate of 40g / min, and a coating thickness of about 1.8mm.

[0135] S4. The heat treatment process is the same as that in Example 1.

[0136] The coating prepared in this comparative example was tested for performance, and the results were as follows:

[0137] 1. Microstructure analysis:

[0138] There are obvious layered structures and oxide packages in the coating; the porosity is 7.2%, which is significantly higher than that in Example 1; the coating is mechanically bonded to the substrate without obvious metallurgical transition zone.

[0139] 2. High temperature friction and wear test:

[0140] The test conditions are the same as those in Example 1.

[0141] Test results: The friction coefficient is 0.42 and the volume wear rate is 12.6×10 -6 mm 3 / Nm.

[0142] 3. Molten zinc corrosion test:

[0143] The test conditions are the same as those in Example 1.

[0144] Test results: The coating peeled off severely, and about 30% of the coating fell off after 48 hours; there was an obvious gap between the remaining coating and the substrate, and the zinc liquid penetrated into the surface of the substrate.

[0145]

[0146] Note: The molten zinc corrosion mass loss rate of Comparative Example 3 is marked as 30*, indicating that about 30% of the coating peeled off and the complete mass loss rate could not be accurately measured.

[0147] Therefore, according to the above test results, the coating prepared by plasma spraying process in comparative example 3 has significantly lower performance despite the same composition as that in example 1. The layered structure and high porosity inside the coating lead to a significant increase in the friction coefficient and wear rate. More seriously, in the molten zinc liquid immersion test, the coating peels off over a large area, which completely fails to meet the actual application requirements. This result shows that the laser cladding process is a key process for preparing high-quality, low-friction, high-temperature and wear-resistant coatings. The dense structure and metallurgical bonding formed by it are the basis for the coating to maintain stable performance in harsh environments.

[0148] It can be seen from the above embodiments and comparative examples that:

[0149] 1. Coating composition: The friction coefficient of the coating containing self-fluxing alloy powder (Examples 1-3) is significantly lower than that of the coating without self-fluxing alloy powder (Comparative Example 1), which indicates that the Mo and B elements in the self-fluxing alloy powder form a self-lubricating phase at high temperatures, effectively reducing the friction coefficient.

[0150] 2. Heat treatment process: The coating after high-temperature long-time heat treatment (Examples 1-3) has a lower porosity and better microstructure, resulting in far better corrosion resistance in molten metal liquid than the coating without heat treatment (Comparative Example 2). The heat treatment process closes the microcracks and reduces the porosity to a state below 3%, effectively blocking the penetration channels of the molten metal liquid.

[0151] 3. Preparation process: Compared with the plasma spraying process (Comparative Example 3), the laser cladding process (Examples 1-3) can form a metallurgical bond with the substrate, and the coating structure is denser, showing significantly superior stability and durability in the molten metal liquid environment.

[0152] 4. Comprehensive performance: Example 3 shows the best performance in high-temperature friction and wear and composite corrosion and wear resistance tests. The friction coefficient at 700 °C is only 0.25, and the volume wear rate is 3.1×10 -6 mm 3 / Nm. Even under more severe composite corrosion-wear conditions, its performance decay is very small, fully demonstrating the excellent comprehensive performance of the coating of the present invention.

[0153] In summary, the low-friction coefficient high-temperature wear-resistant coating of the present invention forms a complete technical solution in terms of material design, preparation process, and post-treatment. The prepared coating has a low friction coefficient, excellent high-temperature wear resistance, and corrosion resistance to molten metal liquid, and is particularly suitable for surface protection of high-temperature components in the hot-dip galvanizing and aluminizing industries.

[0154] Although the present invention has been described in detail with reference to the foregoing embodiments and comparative examples, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a high-temperature wear-resistant coating with a low friction coefficient, characterized in that, The method includes the following steps: S1. Mix the raw material powders according to the following mass percentages: 60 - 70% cobalt-based powder, 30 - 40% mixture of cemented carbide powder and self-fluxing alloy powder; S2. Pretreat the surface of the workpiece, including grinding to remove the surface oxide layer and wiping with alcohol to remove surface oil stains and dust; S3. Preheat the workpiece to 200 - 300 °C; S4. Prepare a coating on the surface of the preheated workpiece by using the laser cladding process; S5. Perform heat treatment on the obtained coating, with the temperature greater than 850 °C and the treatment time greater than 1 hour.

2. The method for preparing a low-friction coefficient high-temperature wear-resistant coating according to claim 1, wherein the raw materials used in the coating include the following components: a) Cobalt-based powder, the composition of which by weight percentage is: Co 40 - 60%, Cr 15 - 25%, Ni 10 - 20%, W 10 - 20%, particle size < 100 μm; b) Cemented carbide powder, which is WC-Co powder, Co content < 10%, particle size < 100 μm; c) Self-fluxing alloy powder, the composition of which by weight percentage is: Co 20 - 30%, Cr 10 - 25%, Mo 30 - 50%, B 5 - 15%, W < 5%.

3. The method for preparing a low-friction coefficient high-temperature wear-resistant coating according to claim 1, wherein the laser cladding process in step S4 is carried out by using a fiber laser, the laser power is 3.0 - 5.0 kW, and the spot diameter is 2.0 - 3.0 mm.

4. The method for preparing a low-friction coefficient high-temperature wear-resistant coating according to claim 1, wherein in the laser cladding process in step S4, the scanning speed is 10 - 40 mm / s, and the overlapping rate is 40% - 60%.

5. The method for preparing a low-friction coefficient high-temperature wear-resistant coating according to claim 1, wherein the laser cladding process in step S4 adopts a ring-shaped coaxial powder feeding method.

6. The method for preparing a low-friction coefficient high-temperature wear-resistant coating according to claim 1, wherein the heat treatment in step S5 continues until the microcracks on the coating surface are closed and the porosity is lower than 3%.

7. A low-friction coefficient high-temperature wear-resistant coating prepared by any one of the methods according to claims 1 to 6.

8. Application of the low-friction coefficient high-temperature wear-resistant coating according to claim 7 on the surface of wear-resistant components under high-temperature working conditions.

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