In-situ growth MoS2 nanowire self-lubricating composite coating as well as preparation method and application thereof

Abstract

The invention provides an in-situ growth MoS2 nanowire self-lubricating composite coating as well as a preparation method and application thereof, a laser-induced in-situ synthesis technology is adopted, and vertically-oriented molybdenum disulfide MoS2 nanowires are generated on the surface of a steel base in situ. The technology comprises the four steps of steel base pretreatment, molybdenum transition layer formation through laser cladding, MoS2 nanowire generation through in-situ vulcanization reaction and epoxy resin densification treatment. And by combining the cooperative strategy of laser cladding and vulcanization reaction, the wear resistance of the steel material is remarkably improved. Besides, the formed nanowire array has excellent mechanical interlocking and self-lubricating effects, and by combining the interface strengthening effect of epoxy resin, the surface hardness and wear resistance of the material can be remarkably improved, and the friction coefficient is reduced. The process has the advantages of controllable directional growth, high bonding strength, low energy consumption, good environmental friendliness and the like, and an efficient and feasible novel method is provided for in-situ construction and functionalization application of transition metal sulfide on the metal surface.

Description

Technical Field

[0001] This invention belongs to the field of processing and preparation of novel high wear-resistant self-lubricating protective composite materials, specifically involving an in-situ grown MoS2 nanowire self-lubricating composite coating, its preparation method and application. Background Technology

[0002] In modern industry, the demand for wear-resistant materials is increasing, especially in high-intensity, complex working environments where the requirements for wear resistance and self-lubrication are stringent. While traditional wear-resistant coating technologies have extended the service life of mechanical parts to some extent, their performance remains unsatisfactory under high temperature, high load, or extreme friction conditions, particularly in applications requiring both wear resistance and self-lubrication. Therefore, developing novel, functional coatings and composite materials is crucial to solving this problem. Molybdenum disulfide (MoS2) is a typical layered transition metal sulfide, its crystals consisting of stacked sulfur-molybdenum-sulfur (S–Mo–S) triatomic layers. The atoms within each layer are bonded by strong covalent bonds, while the interlayers are governed by weak van der Waals forces. This layered structure allows MoS2 to undergo interlayer slippage during friction, forming a sulfur-rich lubricating film, thereby significantly reducing the coefficient of friction and slowing wear. Simultaneously, MoS2 possesses good chemical stability and high-temperature resistance, maintaining excellent self-lubricating properties and wear resistance even under high temperature, high pressure, and complex working conditions, making it an ideal material for wear protection and lubrication of mechanical parts.

[0003] Currently, MoS2 coatings are mainly prepared using methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), spraying, hot dipping, and electrochemical deposition. While these methods can improve the wear resistance of mechanical parts to some extent, they have significant shortcomings in terms of adhesion, structural controllability, wear resistance, high-temperature stability, cost, and industrial applicability. First, the relationship between the coating and the metal substrate largely relies on physical adsorption or microscopic bonding. Under high loads or high temperatures, the coating is prone to peeling and failure, affecting its long-term stability. Second, existing methods struggle to control the thickness, uniformity, and crystal orientation of MoS2, leading to the presence of pores, cracks, or microstructural inhomogeneities within the coating, thus reducing its wear resistance and self-lubricating properties under extreme friction conditions. Furthermore, at high temperatures, MoS2 is prone to oxidation or desulfurization reactions, resulting in a rapid decline in lubrication performance, further limiting its application under high temperature, high pressure, and harsh operating conditions. Vapor deposition processes such as PVD and CVD involve high investment in equipment, complex operation, and long process cycles. While spraying or hot dipping methods are simple, the density and durability of the coatings are limited, making it difficult to achieve large-area, high-performance coatings for industrial application. Summary of the Invention

[0004] The purpose of this invention is to provide an in-situ grown MoS2 nanowire self-lubricating composite coating, its preparation method and application, which can significantly improve the surface hardness and wear resistance of the material and reduce the coefficient of friction, solving the problems of poor coating adhesion, difficult growth control and poor high temperature stability in the prior art.

[0005] This invention is achieved through the following technical solution: A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating includes the following steps: Step 1: Pre-treatment of the steel disc surface: After ultrasonic cleaning of the alloy steel disc with ethanol, a molybdenum nanoparticle suspension is coated and dried at 70~85 ℃ to form a pre-placed Mo layer with a thickness of 5~8μm. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce H2S / Ar mixed gas for 50-70 min when the temperature rises to 280-320℃ to form MoS2 crystal nuclei; Step 4: Raise the temperature of the tube furnace to 645~655 ℃, introduce sulfur vapor and apply a temperature gradient of 180~220 ℃ / mm perpendicular to the substrate to initiate the sulfidation reaction and induce the MoS2 nanowires to grow perpendicularly along the

[002] crystal direction. Step 5: Use pulsed laser to perform impact strengthening on the steel device with MoS2 nanowires grown on it to achieve surface densification. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor, and then cure it in an environment of 100~120 ℃ to obtain the final self-lubricating composite coating.

[0006] Furthermore, the concentration of the molybdenum nanoparticle suspension in step 1 is 25~35 g / L.

[0007] Furthermore, the volume fraction of H2S in the H2S / Ar mixture described in step 3 is 45% to 55%.

[0008] Furthermore, the vulcanization reaction in step 4 takes 2-3 hours.

[0009] Furthermore, in step 6, the steel device with MoS2 nanowires grown is immersed in epoxy resin for 30-60 minutes, and the curing time is 12-18 hours.

[0010] The present invention also provides an in-situ grown MoS2 nanowire self-lubricating composite coating.

[0011] This invention also provides an application of an in-situ grown MoS2 nanowire self-lubricating composite coating in mechanical parts that combine self-lubrication, corrosion resistance, and impact resistance.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention effectively solves the problems of poor adhesion, difficult growth control, and insufficient high-temperature stability of traditional coatings. Through the synergistic effect of laser cladding and in-situ vulcanization, an Fe–Mo–C alloy transition layer is formed on the steel substrate surface, enabling a tight bond between MoS2 nanowires and the substrate, significantly improving the coating's adhesion and durability. By applying a vertical temperature gradient under high-temperature conditions, the directional growth and self-supporting structure of MoS2 nanowires are achieved, thereby enhancing self-lubricating properties and wear resistance. By combining high-temperature vulcanization and pulsed laser shock peening technology, the coating maintains excellent friction reduction and wear resistance under high-load friction conditions, with overall performance significantly superior to traditional coating systems. Furthermore, introducing an epoxy resin precursor into the gaps between the vertically oriented MoS2 nanowire array and curing it to form a hybrid polymer-based composite structure improves the material's corrosion resistance, impact resistance, and load-bearing capacity. This process has mild preparation conditions, low energy consumption, and controllable cost, allowing for large-scale application on conventional industrial equipment, demonstrating good industrial compatibility and promotional value. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the preparation of the MoS2 nanowire array and self-lubricating composite coating according to the present invention. Figure 2 It is the average friction coefficient of the self-lubricating composite coating prepared in Examples 1-4 of this invention; Figure 3 It is the average wear mark width of the self-lubricating composite coating prepared in Examples 1-4 of this invention; Figure 4 It is the surface contact pressure of the self-lubricating composite coating prepared in Examples 1-4 of this invention. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. These descriptions are intended to explain the invention and not to limit it.

[0015] Example 1: A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating, comprising the following steps: Step 1: Pre-treatment of the steel disc surface: After ultrasonic cleaning of the alloy steel disc with ethanol, a molybdenum nanoparticle suspension with a concentration of 25 g / L is coated and dried at 70 ℃ to form a 5 μm thick pre-placed Mo layer. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser (1064 nm) to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce a mixture of H2S (45 vol%) and Ar for 70 min when the temperature rises to 280℃ to form MoS2 crystal nuclei. Step 4: Raise the temperature of the tube furnace to 645℃, introduce sulfur vapor, and apply a temperature gradient of 180℃ / mm perpendicular to the substrate to induce a sulfidation reaction. The reaction time is 3 h, which induces the MoS2 nanowires to grow perpendicularly along the

[002] crystal direction. Step 5: Use a wavelength of 532 nm and an energy density of 5 J / cm². 2 A pulsed laser with a pulse width of 8 ns was used to perform impact strengthening twice on a steel device with MoS2 nanowires grown on it, thereby achieving densification of the sample surface. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor for 30 min, and then cure it in an environment of 100°C for 18 h to obtain the final self-lubricating composite coating.

[0016] Example 2: A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating, comprising the following steps: Step 1: Pre-treatment of the steel disk surface: After ultrasonic cleaning of the alloy steel disk with ethanol, a 30 g / L molybdenum nanoparticle suspension is coated and dried at 75 °C to form a 6 μm thick pre-placed Mo layer. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser (1064 nm) to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce a mixture of H2S (50 vol%) and Ar for 60 min when the temperature rises to 300℃ to form MoS2 crystal nuclei. Step 4: Raise the temperature of the tube furnace to 650 ℃, introduce sulfur vapor, and apply a temperature gradient of 200 ℃ / mm perpendicular to the substrate to induce a sulfidation reaction. The reaction time is 2.5 h, which induces the MoS2 nanowires to grow perpendicularly along the

[002] crystal direction. Step 5: Use a wavelength of 532 nm and an energy density of 5 J / cm². 2 A pulsed laser with a pulse width of 8 ns was used to perform impact strengthening on a steel device with MoS2 nanowires grown on it three times to achieve densification of the sample surface. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor for 40 min, and then cure it at 110 °C for 16 h to obtain the final self-lubricating composite coating.

[0017] Example 3: A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating, comprising the following steps: Step 1: Pre-treatment of the steel disc surface: After ultrasonic cleaning of the alloy steel disc with ethanol, a molybdenum nanoparticle suspension with a concentration of 35 g / L is coated and dried at 80 °C to form a 7 μm thick pre-placed Mo layer. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser (1064 nm) to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce a mixture of H2S (50 vol%) and Ar for 55 min when the temperature rises to 310℃ to form MoS2 crystal nuclei. Step 4: Raise the temperature of the tube furnace to 655 ℃, introduce sulfur vapor, and apply a temperature gradient of 210 ℃ / mm perpendicular to the substrate to induce a sulfidation reaction. The reaction time is 3 h, which induces the MoS2 nanowires to grow perpendicularly along the

[002] crystal direction. Step 5: Use a wavelength of 532 nm and an energy density of 5 J / cm². 2 A pulsed laser with a pulse width of 8 ns was used to perform impact strengthening on a steel device with MoS2 nanowires grown on it four times to achieve densification of the sample surface. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor for 50 min, and then cure it at 115°C for 14 h to obtain the final self-lubricating composite coating.

[0018] Example 4: A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating, comprising the following steps: Step 1: Pre-treatment of the steel disc surface: After ultrasonic cleaning of the alloy steel disc with ethanol, a molybdenum nanoparticle suspension with a concentration of 35 g / L is coated and dried at 85 °C to form a pre-placed Mo layer with a thickness of 8 μm. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser (1064 nm) to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce a mixture of H2S (55 vol%) and Ar for 50 min when the temperature rises to 320℃ to form MoS2 crystal nuclei. Step 4: Raise the temperature of the tube furnace to 655 ℃, introduce sulfur vapor, and apply a temperature gradient of 220℃ / mm perpendicular to the substrate to induce a sulfidation reaction. The reaction time is 2 h, which induces the MoS2 nanowires to grow perpendicularly along the

[002] crystal direction. Step 5: Use a wavelength of 532 nm and an energy density of 5 J / cm². 2 A pulsed laser with a pulse width of 8 ns was used to perform impact strengthening on a steel device with MoS2 nanowires grown on it four times to achieve densification of the sample surface. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor for 60 min, and then cure it in an environment of 120 °C for 12 h to obtain the final self-lubricating composite coating.

[0019] The preparation process in the embodiments of the present invention is as follows: Figure 1 As shown, the self-lubricating properties of MoS2 nanowires were enhanced through directional growth; simultaneously, high-temperature vulcanization and laser shock peening techniques improved the material's stability at high temperatures. This process is low-cost, easy to apply industrially, and reduces harmful gas emissions, meeting environmental protection requirements. Finally, the combination of MoS2 nanowires with polymer-based composite materials further improved corrosion resistance and impact resistance, expanding the range of applications.

[0020] Reference Figure 2 The self-lubricating composite coatings prepared in Examples 1-4 of this invention have an average friction coefficient of less than 0.09. Compared with epoxy resin-based composite materials modified with lubricating fillers, they exhibit good self-lubricating properties, while the friction coefficient of pure epoxy resin coating is about 0.6.

[0021] The average wear scar width of the self-lubricating composite coatings prepared in Examples 1-4 of this invention is as follows: Figure 3 As shown, the wear mark width of all samples prepared in the embodiments is below 80 μm, which is a low value, indicating that the composite material prepared by the present invention has excellent wear resistance.

[0022] The surface contact pressure of the self-lubricating composite coatings prepared in Examples 1-4 of this invention is as follows: Figure 4 As shown, the surface contact pressure of all samples prepared in the examples during the friction process is above 550 MPa, indicating that the composite material has extremely high load-bearing capacity. The high-temperature vulcanization and pulsed laser shock peening technologies greatly enhance the interfacial bonding strength between the MoS2 nanowires and the matrix, enabling it to maintain excellent lubrication performance and wear resistance even in complex environments.

Claims

1. A method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating, characterized in that, Includes the following steps: Step 1: Pre-treatment of the steel disc surface: After ultrasonic cleaning of the alloy steel disc with ethanol, a molybdenum nanoparticle suspension is coated and dried at 70~85 ℃ to form a pre-placed Mo layer with a thickness of 5~8μm. Step 2: Irradiate the sample obtained in Step 1 with a fiber laser to melt Mo particles into the steel matrix to form an Fe-Mo-C alloy transition layer, and form a nanocrystalline structure after cooling. Step 3: Place the sample obtained in Step 2 in a tube furnace and introduce H2S / Ar mixed gas for 50-70 min when the temperature rises to 280-320℃ to form MoS2 crystal nuclei; Step 4: Raise the temperature of the tube furnace to 645~655 ℃, introduce sulfur vapor and apply a temperature gradient of 180~220 ℃ / mm perpendicular to the substrate to initiate the sulfidation reaction and induce the MoS2 nanowires to grow perpendicularly along the [002] crystal direction. Step 5: Use pulsed laser to perform impact strengthening on the steel device with MoS2 nanowires grown on it to achieve surface densification. Step 6: Immerse the steel device with MoS2 nanowires grown in the epoxy resin precursor, and then cure it in an environment of 100~120 ℃ to obtain the final self-lubricating composite coating.

2. The method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating according to claim 1, characterized in that, The concentration of the molybdenum nanoparticle suspension in step 1 is 25~35 g / L.

3. The method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating according to claim 1, characterized in that, The volume fraction of H2S in the H2S / Ar mixture described in step 3 is 45% to 55%.

4. The method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating according to claim 1, characterized in that, The vulcanization reaction in step 4 takes 2-3 hours.

5. The method for preparing an in-situ grown MoS2 nanowire self-lubricating composite coating according to claim 1, characterized in that, The impregnation time of the steel device with MoS2 nanowires grown in step 6 in epoxy resin is 30-60 min, and the curing time is 12-18 h.

6. An in-situ grown MoS2 nanowire self-lubricating composite coating prepared by the preparation method according to any one of claims 1-5.

7. The application of the in-situ grown MoS2 nanowire self-lubricating composite coating as described in claim 6 in mechanical parts that combine self-lubrication, corrosion resistance, and impact resistance.

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