A lubricating coating for high temperature fasteners and method of making and using same

Abstract

The application discloses a lubricating coating for high-temperature fasteners and a preparation method and application thereof. The lubricating coating is prepared by using inorganic phosphate as a binder, nano boron nitride, silver powder, molybdenum disulfide and tungsten disulfide as composite lubricants, antimony trioxide as an antioxidant, nano silicon dioxide as a phosphate binder reinforcing agent, water and anhydrous ethanol as a dispersion medium, and propargyl alcohol as a corrosion inhibitor. The coating is immersed or sprayed on the fastener, and a coating is formed after a certain curing condition. The coating has good adhesion, flexibility and impact resistance, and has no corrosion defects such as pitting, cracking and bubbling after an acetate salt spray test (AASS) for 240 hours. According to the locking torque test in accordance with HB 7687-2001, the locking torque requirement is met after 15 cycles at room temperature and 5 times of warm loading and then air cooling to room temperature. The application has a good application prospect in the field of high-temperature fastener coatings.

Description

Technical Field

[0001] This invention relates to the field of fastener lubrication coating technology, specifically to a lubricating coating for high-temperature fasteners, its preparation method, and its application. Background Technology

[0002] Fasteners, often referred to as the "rice of industry," are diverse, in high demand, and operate under complex and demanding conditions. High-temperature fasteners are crucial connecting components in high-speed rotating compressors and rotors of aerospace engines, between rotors and transmission systems, between casings, and in aircraft wings and fuselages. The excellent and reliable temperature resistance of fasteners ensures the normal operation of aerospace engines. Currently, my country lags behind in product development and technological innovation in high-temperature fasteners. On the one hand, the performance of alloy materials used in high-temperature fasteners is inconsistent across batches; on the other hand, the lubricating coatings used in high-temperature fasteners cannot meet the requirements for stable operation at high temperatures (800℃). After the engine stops operating, the fastener surface coating fails or even jams, making effective engine maintenance impossible. Currently, high-temperature fasteners resistant to 800℃ mainly rely on imports. Developing a lubricating coating for high-temperature fasteners would significantly promote and improve fastener development, engine and other equipment maintenance, and reduce reliance on imports. Summary of the Invention

[0003] The purpose of this invention is to provide a lubricating coating for high-temperature fasteners and its preparation method. Fasteners coated with this coating, when subjected to a tightening torque test according to HB 7687-2001 "Test Method for MJ Threaded Self-Locking Nuts with Operating Temperature Above 425℃", can meet the tightening torque requirements of 15 tightening and unscrewing cycles at room temperature and 5 tightening and unscrewing cycles at 800℃. This invention has good application prospects in the field of high-temperature fastener coatings.

[0004] To achieve the above objectives, the present invention provides a lubricating coating for high-temperature fasteners, which is prepared from phosphate, nano boron nitride, silver powder, molybdenum disulfide, tungsten disulfide, antimony trioxide, nano silica, propynyl alcohol, FS-640, anhydrous ethanol and deionized water.

[0005] Preferably, the coating provided by the present invention is prepared from 25-35% phosphate, 0.5-2% nano boron nitride, 4-8% silver powder, 1-5% molybdenum disulfide, 1-5% tungsten disulfide, 0.1-1% antimony trioxide, 0.1-1% nano silica, 0.1-0.2% propynyl alcohol, 0.1-0.2% FS-640, 25-40% anhydrous ethanol, and the balance being deionized water, wherein the percentages are by weight.

[0006] The lubricating coating provided by this invention can be applied to the surface treatment of high-temperature fasteners.

[0007] The present invention also provides a method for preparing a lubricating coating for high-temperature fasteners, comprising the following steps:

[0008] 1) Weigh each component for later use. Mix the weighed anhydrous ethanol, deionized water, propynyl alcohol, and FS-40 to prepare a mixed solvent.

[0009] 2) Weigh out nano boron nitride, tungsten disulfide, antimony trioxide, and nano silicon dioxide in sequence, add them to the mixed solvent prepared in step 1), and stir thoroughly until completely wetted;

[0010] 3) Add the weighed aluminum dihydrogen phosphate to the mixture obtained in step 2) and stir until well mixed;

[0011] 4) Pour the weighed silver and molybdenum disulfide into a ball mill jar and ball mill for 24 hours. Then pour the mixture obtained in step 3) into the ball mill jar and ball mill again for 20 to 24 hours to obtain a lubricating coating for high-temperature fasteners.

[0012] Preferably, the phosphate in the above preparation method is an inorganic phosphate, preferably an aqueous solution of aluminum dihydrogen phosphate with a concentration of 30-40%.

[0013] Preferably, the boron nitride in the above preparation method is boron nitride nanosheet with a particle size ≤50nm.

[0014] Preferably, in the above preparation method, the silver powder particle size is ≤5μm; the tungsten disulfide particle size is ≤50nm; the silicon dioxide particle size is ≤50nm; and the mass percentage concentration of propynyl alcohol is ≥99%.

[0015] The lubricating coating provided by this invention can be used to prepare lubricating coatings for high-temperature resistant fasteners.

[0016] The present invention also provides a high-temperature resistant lubricating coating for fasteners prepared from the above-mentioned lubricating coating. The lubricating coating is uniformly sprayed or dipped onto the surface of the fastener after rust removal, degreasing, sandblasting, and ultrasonic cleaning, and then allowed to dry rapidly at room temperature to form a film, which is then cured into a coating. The optimal thickness of the coating is 8 to 13 μm.

[0017] Preferably, the curing is carried out in a forced-air drying oven, and the curing conditions are as follows: heat up to 100±5℃ for 30 minutes and hold for 0.5 to 1 hour, then heat up to 300±5℃ for 30 minutes and hold for 1.5 to 2 hours, and then cool to room temperature with the oven.

[0018] The present invention has the following advantages:

[0019] 1. This invention uses aluminum dihydrogen phosphate as a binder, with an operating temperature reaching 1200℃. Boron nitride, commonly known as "white graphite," remains structurally stable at 1100℃. Silver powder and molybdenum disulfide can generate silver molybdate, a high-temperature lubricant, at 800℃. Tungsten disulfide, oxidized to tungsten trioxide at high temperatures, also exhibits good lubrication properties. At medium to low temperatures (≤200℃), molybdenum disulfide and silver with low shear strength provide lubrication; at medium to high temperatures (200~600℃), boron nitride and tungsten disulfide provide lubrication; at high temperatures (600~800℃), the wear surface of the coating "adaptively" generates silver molybdate-like substances with high-temperature lubrication. The presence of liquid silver at the high-temperature interface and the silver molybdate lubricating enamel layer formed under the combined effects of ambient temperature and friction creates a synergistic effect, resulting in excellent lubrication performance of this coating at 800℃.

[0020] 2. The cured coating exhibits good flexibility and impact resistance. After being kept at 800℃ for 6 hours, the coating adhesion is Grade 1. In the acetic acid salt spray test (AASS) for 240 hours, the coating showed no corrosion defects such as pitting, cracking, or blistering. The locking torque test was conducted according to HB 7687-2001 "Test Method for MJ Threaded Self-Locking Nuts with Operating Temperature Above 425℃", meeting the locking torque requirements after 15 cycles at room temperature, including 5 cycles of heating and air cooling to room temperature.

[0021] 3. The components of the high-temperature fastener lubricating coating are environmentally friendly. The coating dries quickly on the fastener surface, making it easy to apply and suitable for large-scale dip coating and spraying of fasteners. Attached Figure Description

[0022] Figure 1 This shows the appearance of the coating in this invention.

[0023] Figure 2 This is a cross-cut test of the coating adhesion in this invention.

[0024] Figure 3 This describes the flexibility of the coating in this invention.

[0025] Figure 4 This describes the impact resistance of the coating in this invention.

[0026] Figure 5 The coating appearance of the present invention after undergoing an acetic acid salt spray test (AASS) for 240 hours. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Note: Unless otherwise specified, the experimental methods in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0029] Example 1

[0030] A method for preparing a lubricating coating for high-temperature fasteners is as follows:

[0031] Weigh out the raw materials by weight percentage, including 30% phosphate, 1% nano boron nitride, 5% silver powder, 2% molybdenum disulfide, 1.5% tungsten disulfide, 0.5% antimony trioxide, 0.3% nano silica, 0.1% propynyl alcohol, 0.1% FS-640, 30% anhydrous ethanol, and the balance being deionized water.

[0032] The phosphate is an aqueous solution of aluminum dihydrogen phosphate with a concentration of 30-40%; the boron nitride is made of nano-boron nitride flakes with a particle size ≤50nm; the silver powder has a particle size ≤5μm; the tungsten disulfide has a particle size ≤50nm; the silicon dioxide has a particle size ≤50nm; and the corrosion inhibitor, propynyl alcohol, has a mass percentage concentration ≥99%.

[0033] This invention uses inorganic phosphates as binders, nano-boron nitride, silver powder, molybdenum disulfide, and tungsten disulfide as composite lubricants, antimony trioxide as antioxidants, nano-silica as phosphate binder reinforcing agents, propynyl alcohol as corrosion inhibitors, FS-640 as surfactants, and anhydrous ethanol and deionized water as dispersion media. The specific preparation steps are as follows:

[0034] 1) Weigh out anhydrous ethanol, deionized water, propynyl alcohol, and FS-40 and mix them to prepare a mixed solvent;

[0035] 2) Weigh out nano boron nitride, tungsten disulfide, antimony trioxide, and nano silicon dioxide in sequence, add them to the mixed solvent prepared in step 1), and stir thoroughly until completely wetted;

[0036] 3) Add the weighed aluminum dihydrogen phosphate to the mixture obtained in step 2) and stir until well mixed;

[0037] 4) Weigh out the silver and molybdenum disulfide and place them in a ball mill jar. Mill for 24 hours. Then, place the mixture obtained in step 3) into the ball mill jar and mill again for 20-24 hours to perform physical mixing, grinding, and dispersion, thereby obtaining a lubricating coating for high-temperature fasteners. The solid content of this lubricating coating is 22±2%.

[0038] The obtained lubricating coating is evenly applied to the surface of fasteners that have undergone rust removal, degreasing, sandblasting, and ultrasonic cleaning by spraying or dipping. It is then allowed to quickly surface dry at room temperature to form a film, followed by curing in a forced-air drying oven. The optimal coating thickness is 8–13 μm. The curing conditions are: heating to 100±5℃ for 30 minutes and holding for 0.5–1 hour, then heating to 300±5℃ for another 30 minutes and holding for 1.5–2 hours, followed by oven cooling to room temperature.

[0039] The properties of the obtained high-temperature fastener lubricating coating were tested, and the results are shown in Table 1.

[0040] Table 1 Performance indicators of a lubricating coating for high-temperature fasteners

[0041]

[0042]

[0043] According to HB7056.1-2004 "Test Method for Appearance of Dry Film Lubricants", the lubricating coating was sprayed onto the surface of a standard test piece. After curing, the coating thickness was 5–15 μm, and the appearance was as follows. Figure 1 As shown, the coating is dark gray, with a smooth and even surface, free from defects such as cracks, pinholes, and bubbles. According to the GB / T 9286-2021 cross-cut adhesion test (1 mm), the coating adhesion is rated as Grade 1. (See results below.) Figure 2 The coating flexibility was tested according to GB / T 1731-2020 (1mm). No cracks, peeling, or other damage were observed in the coating. The coating appearance was as shown. Figure 3 The coating's impact resistance was tested according to GB / T 1732-2020 (1 kg hammer, 50 cm). No cracks, peeling, or other damage were observed in the coating test results. Figure 4 The coating underwent an acetic acid salt spray test (AASS) according to GB / T 10125-2021 for 240 hours. Figure 5 As shown, there are no corrosion defects such as pitting, cracks, or blistering.

[0044] According to HB 7687-2001 "Test Method for MJ Threaded Self-Locking Nuts with Operating Temperature Above 425℃", the locking torque test was carried out. The results of the locking torque test after 15 cycles at room temperature are shown in Table 2. The results of the locking torque after 5 cycles of heating and loading followed by air cooling to room temperature are shown in Table 3.

[0045] Table 2 Locking torque at room temperature for 15 cycles

[0046]

[0047]

[0048] Table 35 shows the locking torque checked after 35 heating and loading cycles followed by air cooling to room temperature.

[0049]

[0050] Example 2

[0051] This embodiment also provides another formulation of the lubricating coating, specifically 30% phosphate, 1% nano boron nitride, 5% silver powder, 2% molybdenum disulfide, 1.5% tungsten disulfide, 0.5% antimony trioxide, 0.3% nano silica, 0.1% propynyl alcohol, 0.1% FS-640, 30% anhydrous ethanol, and the balance being deionized water.

[0052] Using the same preparation process as in Example 1, the solid lubricating coating prepared had a solid content of 24±2%.

[0053] Example 3

[0054] This embodiment also provides another formulation of the lubricating coating, specifically 25% phosphate, 1.5% nano boron nitride, 6% silver powder, 3% molybdenum disulfide, 2.5% tungsten disulfide, 0.5% antimony trioxide, 0.5% nano silica, 0.1% propynyl alcohol, 0.1% FS-640, 30% anhydrous ethanol, and the balance being deionized water.

[0055] Using the same preparation process as in Example 1, the solid lubricating coating prepared had a solid content of 24±2%.

[0056] Example 4

[0057] This embodiment provides another formulation for a lubricating coating, specifically: 25% phosphate, 1% nano boron nitride, 6% silver powder, 3% molybdenum disulfide, 1.5% tungsten disulfide, 0.25% antimony trioxide, 0.25% nano silica, 0.2% propynyl alcohol, 0.2% FS-640, 35% anhydrous ethanol, and the balance being deionized water.

[0058] Using the same preparation process as in Example 1, the solid lubricating coating prepared had a solid content of 22±2%.

[0059] Example 5

[0060] This embodiment provides another formulation for a lubricating coating, specifically: 35% phosphate, 2% nano boron nitride, 4% silver powder, 2% molybdenum disulfide, 4% tungsten disulfide, 1% antimony trioxide, 0.1% nano silica, 0.2% propynyl alcohol, 0.2% FS-640, 25% anhydrous ethanol, and the balance being deionized water.

[0061] Using the same preparation process as in Example 1, the solid lubricating coating prepared had a solid content of 25±2%.

[0062] Example 6

[0063] This embodiment provides another formulation for a lubricating coating, specifically: 35% phosphate, 2% nano boron nitride, 8% silver powder, 2% molybdenum disulfide, 1% tungsten disulfide, 1% antimony trioxide, 1% nano silica, 0.2% propynyl alcohol, 0.2% FS-640, 25% anhydrous ethanol, and the balance being deionized water.

[0064] Using the same preparation process as in Example 1, the solid lubricating coating prepared had a solid content of 26±2%.

[0065] In summary, the coating prepared by the method disclosed in this invention, when sprayed onto high-temperature fasteners, exhibits satisfactory performance in terms of high-temperature resistance, corrosion resistance, and locking properties, demonstrating significant application prospects and value in coatings for high-temperature fasteners.

[0066] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A lubricating coating for high-temperature fasteners, characterized in that, The coating is prepared from the following components by weight percentage: 25-35% phosphate, 0.5-2% nano boron nitride, 4-8% silver powder, 1-5% molybdenum disulfide, 1-5% tungsten disulfide, 0.1-1% antimony trioxide, 0.1-1% nano silica, 0.1-0.2% propynyl alcohol, 0.1-0.2% FS-640, 25-40% anhydrous ethanol, and the balance being deionized water; wherein the particle size of the tungsten disulfide is ≤50nm, and the phosphate is an aqueous solution of aluminum dihydrogen phosphate; the coating is used as a lubricating coating on the surface of fasteners, and a locking torque test is performed according to HB 7687-2001 "Test Method for MJ Threaded Self-Locking Nuts with Operating Temperature Above 425℃", which can form a locking torque that meets the locking torque requirements after at least 5 cycles from room temperature to 800℃.

2. The lubricating coating for high-temperature fasteners according to claim 1, characterized in that, The particle size of the nano-boron nitride is ≤50nm; the particle size of the silver powder is ≤5μm; and the particle size of the nano-silicon dioxide is ≤50nm.

3. A method for preparing a lubricating coating for high-temperature fasteners according to claim 1 or 2, characterized in that, It includes the following steps: 1) Weigh each component for later use. Mix the weighed anhydrous ethanol, deionized water, propynyl alcohol, and FS-640 to prepare a mixed solvent. 2) Weigh out nano boron nitride, tungsten disulfide, antimony trioxide, and nano silicon dioxide in sequence, add them to the mixed solvent prepared in step 1), and stir thoroughly until completely wetted; 3) Add the weighed aluminum dihydrogen phosphate to the mixture obtained in step 2) and stir until well mixed; 4) Pour the weighed silver powder and molybdenum disulfide into a ball mill jar and ball mill for 24 hours. Then pour the mixture obtained in step 3) into the ball mill jar and ball mill again for 20 to 24 hours to obtain a lubricating coating for high-temperature fasteners.

4. The application of the lubricating coating as described in any one of claims 1 to 2 in the preparation of a lubricating coating for high-temperature fasteners.

5. A lubricating coating for high-temperature fasteners prepared from the lubricating coating of claim 1 or 2, characterized in that, The lubricating coating is uniformly sprayed or dipped onto the surface of fasteners that have undergone rust removal, degreasing, sandblasting, and ultrasonic cleaning. It is then allowed to dry rapidly at room temperature to form a film, which is then cured to form a coating with a thickness of 8-13 μm. The curing conditions are as follows: heating to 100±5℃ for 30 minutes and holding for 0.5-1 hour, then heating to 300±5℃ for 30 minutes and holding for 1.5-2 hours, followed by furnace cooling to room temperature.

Images