A composite self-lubricating coating for medium and low carbon steel materials and its preparation method

Abstract

This invention relates to a composite self-lubricating coating for low- and medium-carbon steel materials and its preparation method. The coating comprises a wear-resistant deposited layer on the surface of the low- and medium-carbon steel material and a self-lubricating layer sprayed onto the surface of the deposited layer. The wear-resistant deposited layer is a tungsten carbide deposited layer, and the self-lubricating layer is a molybdenum disulfide self-lubricating layer. A scaly tungsten carbide deposited layer is formed on the surface of the low- and medium-carbon steel material using electrical discharge deposition (EDD) technology. Then, molybdenum disulfide is sprayed onto the tungsten carbide deposited layer using a spraying technique to form the self-lubricating layer. After baking and cooling, the composite self-lubricating layer is formed. The combination of tungsten carbide and molybdenum disulfide significantly improves the wear resistance and hardness of the material, especially in applications under abrasive wear environments, effectively extending the service life of the workpiece. Furthermore, the process provided by this invention is simple, easy to operate, has low equipment costs, and is easily achievable for large-scale mass production.

Description

Technical Field

[0001] This invention relates to the field of metal coating technology, specifically to a composite self-lubricating coating for medium and low carbon steel materials and its preparation method. Background Technology

[0002] Medium and low carbon steel generally refers to non-alloy steel with a carbon content of less than 0.6%. It is commonly used to manufacture gears, bearings, hammers, plowshares, and other working parts for agricultural machinery, and is widely used in industrial and agricultural engineering fields. However, these workpieces are frequently subjected to friction and impact during use, resulting in significant wear and tear, often leading to severe vibrations and noise during machine operation. This not only reduces the workpiece's efficiency but also increases energy consumption, reduces work quality, and the frequent replacement of workpieces significantly increases production costs. Therefore, employing appropriate surface strengthening techniques to treat medium and low carbon steel workpieces to improve their wear resistance and fatigue resistance is crucial for extending their service life.

[0003] Currently, most common methods for improving the surface properties of low- and medium-carbon steel materials involve altering the overall microstructure and composition of the material surface. These include various surface heat treatments and strengthening coatings, primarily traditional surface modification methods such as surface induction hardening, laser hardening, carburizing hardening, and nitriding, as well as surface strengthening coatings using surface deposition, spraying, and welding techniques to prepare various compositional systems. Carburizing significantly improves the overall hardness of the material and allows for millimeter-level control of the carburized layer thickness, resulting in a tougher interior and a harder exterior, significantly improving wear resistance. However, the equipment used for carburizing is expensive, making it unaffordable for some small and micro-enterprises, especially in agricultural engineering. Compared to carburizing, strengthening coatings prepared using surface deposition and spraying techniques allow for the selection of appropriate coating composition systems based on the workpiece's operating environment, offering better specialization. However, coatings prepared using these techniques are relatively thin and brittle, exhibiting peeling under impact loads. Therefore, these strengthening techniques are not entirely suitable for certain components.

[0004] Electrical discharge deposition (EDD) technology has a relatively early development and is quite mature. It boasts advantages such as high efficiency, energy saving, material saving, and environmental friendliness, and is widely used in surface strengthening treatment of parts in industries such as automotive and mining. During EDD, an electrode rod rotates at high speed on the workpiece surface. The high-density current instantaneously passing through a tiny area in contact with the workpiece generates localized high temperatures, causing the material in that area to ionize at high energy. Under the influence of the electric field, the ionized material rapidly transfers to the workpiece surface and gradually diffuses into the surface layer, forming a metallurgically bonded deposition layer. Furthermore, this method allows for adjustment of the composition and thickness of the deposition layer according to the different performance requirements of the workpiece, enabling the workpiece to possess special properties such as high wear resistance, high fatigue strength, high temperature resistance, and ablation resistance. In addition, this process involves relatively low heat input to the substrate, preventing workpiece deformation and meeting workpiece precision requirements. However, the surface roughness of the deposition layer prepared by this technology is relatively high, making it difficult to meet the good lubricity requirements of the workpiece. Summary of the Invention

[0005] This invention provides a composite self-lubricating coating for medium and low carbon steel materials and its preparation method. It effectively combines the electric spark deposition process and the spraying process to solve the problem of thermal deformation of components when heat treatment is performed on medium and low carbon steel workpieces to improve surface wear resistance. This allows medium and low carbon steel workpieces to meet the requirements of high hardness and high wear resistance on the surface while maintaining the strength and toughness of the core.

[0006] The solution of the present invention to solve the above technical problems is as follows: a composite self-lubricating coating for medium and low carbon steel materials, the coating comprising a deposition layer deposited on the surface of the medium and low carbon steel materials and a self-lubricating layer sprayed on the surface of the deposition layer;

[0007] The deposition layer is a tungsten carbide deposition layer;

[0008] The self-lubricating layer is a molybdenum disulfide self-lubricating layer.

[0009] Preferably, the tungsten carbide deposition layer comprises a multilayer flake-type tungsten carbide coating, wherein the flake-type tungsten carbide coating is formed by multiple groups of single-row flake-type tungsten carbide units arranged longitudinally in a molten state; the thickness of the tungsten carbide deposition layer is 10-30 μm, and the row spacing between two adjacent groups of single-row flake-type tungsten carbide units is 0.1-3 mm (this row spacing is based on the distance between two adjacent groups of single-row flake-type tungsten carbide units during the preparation process).

[0010] The hardness of the tungsten carbide deposit varies with its thickness. If the thickness is too low, it will not meet the hardness requirements of the specimen. If the thickness is too high, it will generate excessive residual stress inside the deposit, leading to cracking of the deposit.

[0011] Preferably, the single-row flake-type tungsten carbide unit is formed by partially stacking multiple circular tungsten carbide units in a transverse direction in a molten state. The circular tungsten carbide unit is a pit-shaped pulsed tungsten carbide molten pool with a radius of 0.3-2 mm and a depth of 0.1-1.8 mm. The distance between two adjacent circular tungsten carbide units is -0.2-2 mm (this distance is based on the distance between two adjacent circular tungsten carbide units during the preparation process; a negative distance indicates overlap).

[0012] Preferably, the thickness of the molybdenum disulfide self-lubricating layer is 20-30 μm.

[0013] The method for preparing the composite self-lubricating coating of low-carbon steel as described above includes the following steps:

[0014] Step 1) Pre-treat the surface of the low-carbon steel material;

[0015] Step 2) Using a tungsten carbide electrode, multiple circular tungsten carbide units are partially stacked in the transverse direction on the surface of low-carbon steel to form a single row of flake-type tungsten carbide units through electrical discharge deposition (EDD). The spacing between two adjacent circular tungsten carbide units is -0.2 to 2 mm (negative spacing indicates overlap). Then, the single rows of flake-type tungsten carbide units are arranged in the longitudinal direction to form a flake-type tungsten carbide coating. The row spacing between two adjacent sets of single rows of flake-type tungsten carbide units is 0.1 to 3 mm.

[0016] Specifically, tungsten carbide is used as the positive electrode and placed at a certain distance from the surface of the substrate. Then, a high-voltage pulse current is applied between the two using a pulse power supply. When the electric field strength is sufficient to ionize and break down the gas medium between the two, the electrode can generate an electric spark discharge with the surface of the substrate in a very short time, producing a special environment with high temperature and high pressure. This causes the electrode tip to melt with the micro-area on the surface of the substrate, forming a small molten pool. The molten metal is directed to impact the surface of the substrate under the action of heat, electromagnetic force and mechanical force, leaving arc spots and depositing scaly tungsten carbide units on the surface of the substrate.

[0017] Step 3) After the first layer of flake-type tungsten carbide coating is completed, deposit multiple layers of flake-type tungsten carbide coating according to the method in Step 2); keep it at a temperature for a period of time, cool it naturally, and then clean it to form a tungsten carbide deposition layer;

[0018] Step 4) Molybdenum disulfide is uniformly sprayed onto the surface of the tungsten carbide deposition layer using a spraying technique to form a composite self-lubricating coating.

[0019] Preferably, step 1) includes pretreatment processes such as grinding, polishing, cleaning, and drying performed sequentially.

[0020] Preferably, step 3) specifically includes: after the first layer of flake-type tungsten carbide coating is completed, the medium and low carbon steel material is horizontally rotated in a preset direction, and then the second layer of flake-type tungsten carbide coating is deposited according to the method in step 2). Then the medium and low carbon steel material is horizontally rotated in a preset direction and the third layer of flake-type tungsten carbide coating is deposited. After repeating this operation multiple times, the material is kept at a certain temperature for a period of time, and then cleaned after natural cooling to form a tungsten carbide deposition layer.

[0021] Preferably, step 5) specifically includes: spraying a layer of molybdenum disulfide onto the surface of the tungsten carbide deposition layer using spraying technology, rotating the medium-low carbon steel material horizontally in a preset direction, then spraying a second layer of molybdenum disulfide, heating and holding the temperature for a period of time, and then naturally cooling to form a composite self-lubricating coating on the surface of the medium-low carbon steel material.

[0022] Furthermore, step 5) specifically includes: spraying a layer of molybdenum disulfide onto the surface of the tungsten carbide deposition layer using a spraying technique, and surface drying at 80-100℃ for 10 minutes; then rotating the medium-low carbon steel material horizontally by 90° clockwise, and then spraying a second layer of molybdenum disulfide, heating to 180-220℃ and holding at that temperature for 20-40 minutes, followed by natural cooling, thus forming a composite self-lubricating coating on the surface of the medium-low carbon steel material. During the surface drying process of molybdenum disulfide, excessively high temperatures can cause the lubricating layer to crack, while excessively low temperatures can lead to a slow drying speed.

[0023] Preferably, in step 2), the diameter of the tungsten carbide electrode is 2.0-5.0 mm, the tip angle of the tungsten carbide electrode is 30-60°, the welding torch deflection angle is 50-70°, and the distance from the tip of the tungsten carbide electrode to the surface of the medium and low carbon steel material is 0.3-1.0 mm.

[0024] Further preferred, in step 2), the tungsten carbide electrode has a diameter of 4 mm, a sharp angle of 50°, a welding torch deflection angle of 60°, and a distance of 0.5 mm from the tip of the tungsten carbide electrode to the surface of the medium and low carbon steel material.

[0025] Preferably, in step 2), during the spark deposition process, the pulse voltage is 50-150V, the pulse frequency is 50-500Hz, the output power is 1000W, the tungsten carbide electrode rotation speed is 1300r / min, and the deposition rate is 5min / cm. 2 .

[0026] Further preferably, in step 2), during the electric spark deposition process, the pulse voltage is 100V, the pulse frequency is 300Hz, the output power is 1000W, the tungsten carbide electrode rotation speed is 1300r / min, and the deposition rate is 5min / cm. 2 ...

[0027] The working principle of this invention is as follows: When using tungsten carbide electrodes in electrical discharge deposition, the resulting reinforcement layer can form a shallow carburized layer on the substrate, which helps improve the interfacial adhesion between the coating and the substrate, enabling it to withstand certain impact loads. Furthermore, the tungsten carbide deposition layer has a scaly biomimetic structure on its surface, which helps to store more molybdenum disulfide during subsequent self-lubricating layer spraying, thereby improving the self-lubricating properties of the workpiece surface and further enhancing the material's anti-sticking, anti-drag, and anti-wear properties.

[0028] The beneficial effects of this invention are: compared with existing metal workpiece surface strengthening technology, this invention has the advantages of small heat input to the substrate material and small substrate deformation, giving the workpiece good properties of internal toughness and external hardness; in addition, this invention also has the advantages of low cost, flexible and convenient operation, and strong applicability, making it easy to promote and apply, and can effectively improve the surface roughness of electrical discharge deposition coatings, giving the workpiece good wear resistance and friction reduction properties.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0031] Figure 1 This is a cross-sectional topography diagram of the tungsten carbide deposit layer in Example 1;

[0032] Figure 2 This is a cross-sectional topography diagram of the tungsten carbide deposition layer in Example 2;

[0033] Figure 3 This is a cross-sectional topography diagram of the tungsten carbide deposition layer in Example 3;

[0034] Figure 4 The images show the surface morphology of the tungsten carbide deposited layer in Example 1 at different magnifications.

[0035] Figure 5 The friction coefficient diagram is shown for medium and low carbon steel and Comparative Example 1.

[0036] Figure 6 The friction coefficient diagrams are for Example 1 and Comparative Example 1. Detailed Implementation

[0037] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0038] Example 1

[0039] This embodiment provides a composite self-lubricating coating for medium and low carbon steel materials and its preparation method, as detailed below:

[0040] (1) Use 400, 800 and 1000 grit sandpaper to polish and remove oxides or foreign matter from the surface of medium and low carbon steel materials, and clean with acetone to remove surface oil stains and then blow dry for later use.

[0041] (2) Electrospark Deposition of Substrate Coating: In this example, a tungsten carbide rod was selected as the electrode, with a diameter of 4 mm. A tungsten carbide deposition layer was prepared on the substrate surface using a rotating electrode electrospark deposition system. Simultaneously, a thin carburized layer was formed on the substrate surface, taking advantage of the stronger bonding between carbon and chromium atoms. Argon was used as the protective gas during the deposition process. The process parameters were adjusted as follows: operating voltage: 60 V, output power: 1000 W, pulse frequency: 70 Hz, protective gas flow rate: 8 L / min, electrode extension length: 10 mm, electrode rotation speed: 1300 r / min, and deposition rate: 5 min / cm². 2 With the above parameters set, multiple circular tungsten carbide units are stacked and arranged laterally on the surface of a low-carbon steel substrate to form a single row of flake-type tungsten carbide units. Each circular tungsten carbide unit is a pit-shaped pulsed tungsten carbide molten pool with a radius of 0.3-2 mm and a depth of 0.1-1.8 mm. The spacing between two adjacent circular tungsten carbide units is -0.2-2 mm. Then, single rows of flake-type tungsten carbide units are arranged longitudinally to form a flake-type tungsten carbide coating. The row spacing between two adjacent sets of single rows of flake-type tungsten carbide units is 0.1-3 mm.

[0042] (3) After the first layer of flake-type WC coating is completed, rotate the workpiece horizontally by 90 degrees clockwise and repeat step (2) to form the second layer of flake-type tungsten carbide coating; then rotate the workpiece horizontally by 90 degrees clockwise and repeat step (2) to form the third layer of flake-type tungsten carbide coating; a tungsten carbide deposition layer formed by 3 layers of flake-type tungsten carbide coating is prepared; the thickness of the tungsten carbide deposition layer is 10 μm;

[0043] (4) Place the medium and low carbon steel material matrix completed in step (3) into sand for heat preservation for 20 minutes, and let it cool naturally.

[0044] (5) Using a reciprocating machine, a molybdenum disulfide self-lubricating layer is formed on the surface of the medium-low carbon steel substrate with tungsten carbide deposition layer prepared in step (4). Two coats are applied to each side, and the thickness of each coat is controlled at 10-15 μm. The specific process is as follows: after the first coat is applied, the workpiece is surface dried at 80-100℃ for 10 min; then the workpiece is rotated 90 degrees clockwise and a second coat of molybdenum disulfide is applied; the workpiece is then moved to an oven, heated to 180-220℃ and held for 30 min. After natural cooling, a molybdenum disulfide self-lubricating layer is formed on the tungsten carbide deposition layer of the medium-low carbon steel substrate. The thickness of the molybdenum disulfide self-lubricating layer is 20 μm.

[0045] Example 2

[0046] This embodiment provides a composite self-lubricating coating for medium and low carbon steel materials and its preparation method. The specific steps are basically the same as those in Embodiment 1, except that in step (3), a 6-layer flake-type tungsten carbide coating is prepared to form a tungsten carbide deposition layer; the thickness of the tungsten carbide deposition layer is 20 μm.

[0047] Example 3

[0048] This embodiment provides a composite self-lubricating coating for medium and low carbon steel materials and its preparation method. The specific steps are basically the same as those in Embodiment 1, except that in step (3), a 9-layer flake-type tungsten carbide coating is prepared to form a tungsten carbide deposition layer; the thickness of the tungsten carbide deposition layer is 30 μm.

[0049] Comparative Example 1

[0050] This embodiment provides a tungsten carbide deposition coating for medium and low carbon steel materials and its preparation method. The specific steps are basically the same as those in Embodiment 1, except that step (5) of spraying molybdenum disulfide to form a self-lubricating layer is not performed.

[0051] The HV1000B microhardness tester manufactured by Huayin Company was used to test the microhardness of different thicknesses of the tungsten carbide deposited layer to the low carbon steel material substrate in Examples 1-3. The test load was 1.962 N, the load holding time was 15 s, the measurement interval from the surface of the deposited layer to the inside was 5 μm, and 3 test points were taken on the same thickness horizontal line. The results are shown in Tables 1-3.

[0052] Table 1 shows the hardness distribution (Hv) of the tungsten carbide deposition layer to the substrate section of low-carbon steel material provided in Example 1.

[0053] Thickness (μm) Test point 1 Test point 2 Test point 3 5 381.2 383.2 385.7 10 356.7 354.2 353.1 15 235.3 254.2 254.2 20 225.0 230.7 227.3

[0054] Table 2 shows the hardness distribution (Hv) of the tungsten carbide deposition layer to the substrate section of low-carbon steel material provided in Example 2.

[0055] Thickness (μm) Test point 1 Test point 2 Test point 3 5 657.1 809.9 773.7 10 522.6 263.8 266.6 15 382.1 254.2 254.2 20 332.1 230.7 227.3 25 231.8 212.3 220.7 30 226.1 245.1 240.2

[0056] Table 3 shows the hardness distribution (Hv) of the tungsten carbide deposition layer to the substrate section of low-carbon steel material provided in Example 3.

[0057] Thickness (μm) Test point 1 Test point 2 Test point 3 5 1149.7 809.9 773.7 10 985.4 263.8 266.6 15 658.9 254.2 254.2 20 401.2 230.7 227.3 25 382.5 375.5 360.6 30 301.3 299.2 280.2 35 266.6 272.4 259.6 40 263.8 265.2 251.6

[0058] As shown in Table 1-3, after preparing a tungsten carbide deposition layer on the surface of a low-carbon steel substrate, the hardness of the deposition layer is highest at the surface. The hardness gradually decreases with increasing test distance. Furthermore, the test results indicate that the surface hardness of the wear-resistant deposition layer gradually increases with the number of deposition layers, with the maximum surface hardness of the deposition layer around 1150 Hv. In summary, this technology only forms a high-hardness layer on the workpiece surface, having little impact on the overall hardness of the substrate. It can improve the hardness and wear resistance of the workpiece while ensuring its overall toughness.

[0059] Depend on Figure 1-3 As shown, through ultra-depth-of-field cross-sectional morphology testing, it can be seen that the tungsten carbide deposition layer is uniform and dense overall, and a thin carburized layer is formed between it and the substrate, which can form a good metallurgical bond with the substrate. The thicknesses of the tungsten carbide deposition layers in Examples 1-3 are 11.14 μm, 19.93 μm, and 29.71 μm, respectively, indicating that the thickness gradually increases with the increase of the number of tungsten carbide deposition layers. Figure 4 As shown, the surface structure of the tungsten carbide deposit is an irregular bumpy spot structure. By overlapping the spots, a strip-like scale structure can be obtained. When molybdenum disulfide is sprayed on this surface, it helps to store more lubricating medium, making its self-lubricating effect better and increasing the lubrication time.

[0060] The wear resistance of the samples was tested using an Rtec MFT-5000 friction and wear testing machine. Figure 5 As shown, after depositing a tungsten carbide layer on the surface of a medium-low carbon steel (45 steel) substrate, the surface hardness of the workpiece is improved, and the surface friction coefficient is reduced, thus fully utilizing its wear-resistant properties; Figure 6 It can be seen that the surface friction coefficient was low in the first half of the experiment in Example 1, indicating that molybdenum disulfide has good self-lubricating properties. However, as the experiment progressed, the surface friction coefficient gradually increased, eventually reaching a level comparable to that of molybdenum disulfide. Figure 5 The results were consistent, indicating that the lubricating layer gradually breaks down during the test, at which point the deposited layer and the substrate are gradually exposed. Furthermore, in comparison... Figure 6 The significant increase in the friction coefficient curve indicates that the self-lubricating layer coated on the tungsten carbide deposit surface has a longer wear resistance time, suggesting better adhesion between it and the tungsten carbide deposit substrate. In summary, the above experimental results demonstrate that the composite self-lubricating coating exhibits better wear resistance, and this method can be effectively applied to surface strengthening of medium and low carbon steel workpieces.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A composite self-lubricating coating for medium and low carbon steel materials, characterized in that, The coating comprises a deposited layer deposited on the surface of low-carbon steel and a self-lubricating layer sprayed onto the surface of the deposited layer. The deposition layer is a tungsten carbide deposition layer; The self-lubricating layer is a molybdenum disulfide self-lubricating layer; The tungsten carbide deposition layer comprises a multilayer flake-type tungsten carbide coating, wherein the flake-type tungsten carbide coating is formed by multiple groups of single-row flake-type tungsten carbide units arranged longitudinally in a molten state; the thickness of the tungsten carbide deposition layer is 10-30 μm. The single-row flake-type tungsten carbide unit is formed by multiple circular tungsten carbide units arranged in a transversely stacked manner in a molten state. The circular tungsten carbide unit is a pit-shaped pulsed tungsten carbide molten pool with a radius of 0.3-2 mm and a depth of 0.1-1.8 mm.

2. The composite self-lubricating coating for medium and low carbon steel materials according to claim 1, characterized in that, The thickness of the molybdenum disulfide self-lubricating layer is 20-30 μm.

3. A method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to any one of claims 1-2, characterized in that, Includes the following steps: Step 1) Pre-treat the surface of the low-carbon steel material; Step 2) Using tungsten carbide electrodes, multiple circular tungsten carbide units are partially stacked in the transverse direction on the surface of medium and low carbon steel to form a single row of scaly tungsten carbide units through electrical discharge deposition technology. Then, each single row of scaly tungsten carbide units is arranged in the longitudinal direction to form a scaly tungsten carbide coating. Step 3) After the first layer of flake-type tungsten carbide coating is completed, deposit multiple layers of flake-type tungsten carbide coating according to the method in Step 2) to form a tungsten carbide deposition layer; Step 4) Molybdenum disulfide is uniformly sprayed onto the surface of the tungsten carbide deposition layer using a spraying technique to form a composite self-lubricating coating.

4. The method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to claim 3, characterized in that, The pretreatment process in step 1 includes grinding, polishing, cleaning, and drying in sequence.

5. The method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to claim 3, characterized in that, Step 3) specifically includes: after the first layer of flake-type tungsten carbide coating is completed, the medium and low carbon steel material is horizontally rotated in a preset direction, and then the second layer of flake-type tungsten carbide coating is deposited according to the method in step 2). Then the medium and low carbon steel material is horizontally rotated in a preset direction and the third layer of flake-type tungsten carbide coating is deposited. After repeating this operation multiple times, the material is kept at a certain temperature for a period of time, and then cleaned after natural cooling to form a tungsten carbide deposition layer.

6. The method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to claim 3, characterized in that, Step 4) specifically includes: spraying a layer of molybdenum disulfide onto the surface of the tungsten carbide deposition layer using spraying technology, rotating the medium and low carbon steel material horizontally in a preset direction, then spraying a second layer of molybdenum disulfide, heating and holding the temperature for a period of time, and then naturally cooling to form a composite self-lubricating coating on the surface of the medium and low carbon steel material.

7. The method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to claim 3, characterized in that, In step 2), the diameter of the tungsten carbide electrode is 2.0-5.0 mm, the tip angle of the tungsten carbide electrode is 30-60°, the welding torch deflection angle is 50-70°, and the distance from the tip of the tungsten carbide electrode to the surface of the medium and low carbon steel material is 0.3-1.0 mm.

8. The method for preparing a composite self-lubricating coating for medium and low carbon steel materials according to claim 6, characterized in that, In step 4), a layer of molybdenum disulfide is sprayed onto the surface of the tungsten carbide deposition layer using a spraying technique, and surface dried at 80-100℃ for 10 min. The medium-low carbon steel material is then rotated horizontally by 90° clockwise, and a second layer of molybdenum disulfide is sprayed on. The temperature is raised to 180-220℃ and held for 20-40 min. After natural cooling, a composite self-lubricating coating is formed on the surface of the medium-low carbon steel material.

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