A silver-free high temperature lubricating coating and its method of manufacture and use

Abstract

The application discloses a silver-free high-temperature lubricating coating and a preparation method and application thereof, and comprises the following steps: S1: stirring and mixing an aluminum source, a magnesium source, a chromium source and a phosphoric acid aqueous solution to obtain a mixed solution; S2: mixing the mixed solution with a tellurium source, a molybdenum source and a cobalt source, and obtaining a silver-free high-temperature lubricating coating after ball milling; and coating the silver-free high-temperature lubricating coating on a base material, and obtaining a silver-free high-temperature lubricating coating after solidification. The application provides the high-temperature lubricating coating which is applied to high-temperature alloy fasteners and adopts a telluride to replace silver as a high-temperature lubricating material, and the high-temperature lubricating coating has better high-temperature resistance and stronger stability compared with other coatings; the telluride can maintain the original structure and performance under 600-800 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of aerospace technology, and in particular relates to a silver-free high-temperature lubricating coating, its preparation method, and its application. Background Technology

[0002] With the rapid development of modern aerospace technology and high-end manufacturing, the friction and wear problems of key mechanical components under high-temperature and heavy-load conditions are becoming increasingly prominent. Under the combined effects of continuous high temperature (usually exceeding 600℃) and extreme loads, traditional organic lubricants fail due to thermal decomposition, oxidation, volatilization, or carbonization, leading to lubrication failure at the friction interface, which in turn causes abnormal wear of parts or even system failure. Of particular concern is the significant friction between the threaded contact surface and the supporting surface during the assembly of threaded fasteners such as bolts and nuts, which can easily lead to torque dispersion, unstable preload, and even thread seizing and jamming. Therefore, applying a lubricating coating to the threaded pair before assembly can effectively reduce the coefficient of friction, stabilize the torque coefficient, ensure uniform and controllable assembly preload, reduce thread wear, inhibit fretting corrosion and high-temperature seizing, and improve the reliability and service life of the connection. This technical bottleneck has spurred the innovative development of new high-temperature solid lubricating coatings, among which phosphate-based inorganic high-temperature resistant coatings have become a research hotspot due to their unique performance advantages. This material system exhibits multi-dimensional technical advantages: First, its matrix material can form a dense coating through low-temperature curing (400~550℃), demonstrating excellent substrate adhesion; second, it can maintain structural stability above 600℃, and its coefficient of thermal expansion matches well with the metal substrate; furthermore, compared with traditional precious metal-based coatings, the phosphate system has significant advantages in terms of readily available raw materials and low preparation costs, thus achieving large-scale application in refractory materials, high-temperature molds, and other fields. The invention patent "A Lubricating Coating for High-Temperature Fasteners and Its Preparation Method" by Cui Xiaohui of the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, uses inorganic phosphate as a binder and selects nano-boron nitride, silver powder, molybdenum disulfide, and tungsten disulfide as composite lubricants to prepare a lubricating coating for high-temperature fasteners. The cured coating exhibits good adhesion, flexibility, and impact resistance. After a 240-hour acetic acid salt spray test (AASS), it showed no pitting, cracking, blistering, or other corrosion defects. According to HB76872001, the locking torque requirement was met after 15 cycles at room temperature and 5 cycles of heating followed by air cooling to room temperature. Xu Haiyan's invention patent, "A High-Temperature Resistant Solid Lubricating Coating and Its Preparation and Application," from the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, uses phosphate resin as a binder and sulfides, silver powder, and rare earth fluorides as lubricants to create a lubricating coating. After curing, the coating adheres well to the metal substrate and exhibits excellent tribological properties at high temperatures, effectively solving the lubrication, seizing, and adhesion problems between the contact surfaces of self-locking nuts at high temperatures. However, according to SAEAS 1701F-2022, the addition of silver (Ag) as a solid lubricant component is explicitly prohibited for high-temperature coatings, especially Class IV coatings (maximum operating temperature up to 760℃), and this restriction applies to all categories of high-temperature coatings. Silver has a melting point of 961℃. At 760℃, it is close to softening or even melting, which can easily lead to softening, dripping, and peeling of the coating, thus causing lubrication failure.Furthermore, in high-temperature environments, silver readily reacts with sulfur, oxygen, and halogens to form brittle compounds, causing coating cracking and reduced adhesion, severely impacting the coating's reliability and service life. Therefore, the aforementioned coating system has significant shortcomings in meeting aviation high-temperature lubrication standards. Summary of the Invention

[0003] In view of this, the present invention aims to provide a silver-free high-temperature lubricating coating, its preparation method and application, in order to solve at least one technical problem in the background art.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for preparing a silver-free high-temperature lubricating coating includes the following steps: S1: Mix aluminum source, magnesium source, chromium source and phosphoric acid aqueous solution to obtain a mixed solution; S2: The mixed solution is mixed with tellurium source, molybdenum source and cobalt source, and ball milled to obtain a silver-free high-temperature lubricating coating. The silver-free high-temperature lubricating coating is applied to the substrate and cured to obtain a silver-free high-temperature lubricating coating layer.

[0005] Further, the aluminum source in step S1 includes one or more of aluminum oxide, aluminum hydroxide, and aluminum nitrate; preferably, the aluminum source is aluminum hydroxide.

[0006] And / or, the magnesium source in step S1 includes one or more of magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium oxide, magnesium hydroxide, and magnesium carbonate; preferably, the magnesium source is magnesium oxide.

[0007] And / or, the chromium source in step S1 includes one or more of chromium trioxide, chromium trichloride, chromium sulfate, chromic anhydride, and chromium nitrate. Preferably, the chromium source is chromium trioxide. Further, the tellurium source in step S2 includes one or more of lead telluride, bismuth telluride, molybdenum telluride, copper telluride, sodium telluride, tellurium dioxide, tellurium trioxide, barium telluride, calcium telluride, and magnesium telluride. Preferably, the tellurium source is tellurium trioxide. And / or, the molybdenum source in step S2 includes one or more of molybdenum oxide, molybdenum sulfide, molybdenum dioxide, molybdenum tetroxide, and calcium molybdate, preferably, the molybdenum source is molybdenum dioxide.

[0008] Further, the cobalt source in step S2 includes one or more of cobalt chloride, cobalt nitrate, cobalt oxide, cobalt acetate, cobalt sulfate, cobalt carbonate, and cobalt hydroxide. Preferably, the cobalt source is cobalt carbonate.

[0009] Furthermore, the molar ratio of phosphoric acid: aluminum source: magnesium source: chromium source: tellurium source: molybdenum source: cobalt source is 3~8:0.8~1.2:1~2.5:1~1.5:0.8~1.2:0.2~2:0.5~3.

[0010] Furthermore, the stirring and mixing in step S1 is performed using a heat-collecting constant-temperature magnetic stirrer with a rotation speed of 400~1000 r / min and a temperature of 80~100℃.

[0011] Furthermore, in step S2, the mechanical ball milling time is 2 hours, the ball milling medium is the prepared mixed coating, the ball milling speed is 1500~2600 r / min, and the ball-to-material ratio is 5:1~3.

[0012] Further, the silver-free high-temperature lubricating coating from step S2 is applied to the substrate and cured at 400~550℃ for 0.5~1h to obtain a silver-free high-temperature lubricating coating.

[0013] The silver-free high-temperature lubricating coating prepared by the above-mentioned method is a silver-free high-temperature lubricating coating.

[0014] The aforementioned silver-free high-temperature lubricating coating is applied to high-temperature alloy fasteners.

[0015] Compared with existing technologies, the silver-free high-temperature lubricating coating, its preparation method, and its application described in this invention have the following advantages: 1. The high-temperature lubricating coating provided by this invention uses telluride instead of silver as a high-temperature lubricating material for high-temperature alloy fasteners. Compared with other coatings, it has better high-temperature resistance and stronger stability. Telluride can maintain its original structure and performance at 600~800℃.

[0016] 2. The high-temperature lubricating coating for high-temperature alloy fasteners without silver provided by the present invention can form a lubricating film during friction due to the special structure of telluride, thereby reducing friction and wear and thus having excellent lubrication performance.

[0017] 3. The high-temperature lubricating coating for high-temperature alloy fasteners without silver provided by this invention has excellent lubrication and protection performance at high temperatures of 600~800℃.

[0018] 4. The method for preparing a silver-free high-temperature lubricating coating for high-temperature alloy fasteners provided by this invention is simple to operate and easy to mass-produce. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a rendering of Embodiment 1 of the present invention; Figure 2 This is a rendering of Embodiment 2 of the present invention; Figure 3This is a rendering of Embodiment 3 of the present invention; Figure 4 This is a rendering of Embodiment 4 of the present invention; Figure 5 This is a rendering of Embodiment 5 of the present invention. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] Example 1: In this embodiment, the method for preparing the high-temperature lubricating coating for high-temperature alloy fasteners that does not contain silver is as follows: Preparation of Component A: Dissolve 15g of phosphoric acid in 50g of water, heat to 90℃ using a heat-collecting constant temperature magnetic stirrer, stir at 800r / min for 10min to obtain a clear phosphoric acid aqueous solution, add 3g of aluminum hydroxide and 2g of magnesium oxide, stir for 3 hours until the solution is clear, then add 11g of chromium trioxide and stir for 1 hour to obtain a clear and transparent Component A.

[0023] The prepared component A was mixed with 9g of barium telluride, 5g of molybdenum oxide, and 5g of cobalt oxide, and then mechanically ball-milled for 2 hours to obtain a silver-free high-temperature lubricating coating. This coating was applied to a substrate and cured at 450℃ for 0.5 hours to obtain a uniform and continuous silver-free high-temperature lubricating coating with no adverse effects on the substrate. This coating exhibits excellent lubrication and protective properties at high temperatures of 600~800℃. The coefficient of friction after curing is 0.108. After holding at 800℃ for 30 hours, as... Figure 1 As shown, the surface condition remained intact with no significant changes, and the coefficient of friction decreased slightly to 0.100. The change in the coefficient of friction before and after high-temperature treatment was minimal, indicating that the coating has excellent stability under high-temperature conditions.

[0024] Example 2: In this embodiment, the method for preparing the high-temperature lubricating coating for high-temperature alloy fasteners that does not contain silver is as follows: Preparation of Component A: Dissolve 19g of phosphoric acid in 40g of water, heat to 90℃ using a heat-collecting constant temperature magnetic stirrer, stir at 800r / min for 10min to obtain a clear phosphoric acid aqueous solution, add 3g of aluminum hydroxide and 2g of magnesium oxide and stir for 3 hours until the solution is clear, then add 7g of chromium trioxide and stir for 1 hour to obtain a clear and transparent Component A.

[0025] The prepared component A was mixed with 10g of calcium telluride, 10g of molybdenum oxide, and 9g of cobalt oxide, and then mechanically ball-milled for 2 hours to obtain a silver-free high-temperature lubricating coating. This coating was then applied to a substrate and cured at 450℃ for 0.5 hours to obtain a uniform and continuous silver-free high-temperature lubricating coating with no adverse effects on the substrate. This coating exhibits excellent lubrication and protective properties at high temperatures of 600~800℃. The coefficient of friction after curing is 0.101. After holding at 800℃ for 30 hours, as... Figure 2 As shown, the surface condition remained intact with no significant changes, and the coefficient of friction decreased slightly to 0.092. The change in the coefficient of friction before and after high-temperature treatment was minimal, indicating that the coating has excellent stability under high-temperature conditions.

[0026] Example 3: In this embodiment, the method for preparing the high-temperature lubricating coating for high-temperature alloy fasteners that does not contain silver is as follows: Preparation of Component A: Dissolve 15g of phosphoric acid in 40g of water, heat to 90℃ using a heat-collecting constant temperature magnetic stirrer, stir at 800r / min for 10min to obtain a clear phosphoric acid aqueous solution, add 3g of aluminum oxide and 2g of magnesium oxide and stir for 3 hours until the solution is clear, then add 10g of chromium trioxide and stir for 1 hour to obtain a clear and transparent Component A.

[0027] The prepared component A was mixed with 10g magnesium telluride, 10g molybdenum dioxide, and 10g cobalt carbonate, and then mechanically ball-milled for 2 hours to obtain a silver-free high-temperature lubricating coating. This coating was applied to a substrate and cured at 450℃ for 0.5 hours to obtain a uniform and continuous silver-free high-temperature lubricating coating with no adverse effects on the substrate. This coating exhibits excellent lubrication and protective properties at high temperatures of 600~800℃. The coefficient of friction after curing is 0.098. After holding at 800℃ for 30 hours, as... Figure 3 As shown, the surface condition remained intact with no significant changes, and the coefficient of friction decreased slightly to 0.092. The change in the coefficient of friction before and after high-temperature treatment was minimal, indicating that the coating has excellent stability under high-temperature conditions.

[0028] Example 4: In this embodiment, the method for preparing the high-temperature lubricating coating for high-temperature alloy fasteners that does not contain silver is as follows: Preparation of component A: Dissolve 20g of phosphoric acid in 50g of water, heat to 90℃ using a heat-collecting constant temperature magnetic stirrer, stir at 800r / min for 10min to obtain a clear phosphoric acid aqueous solution, add 2g of aluminum hydroxide and 2g of magnesium oxide, stir for 3 hours until the solution is clear, then add 7g of chromium trioxide and stir for 1h to obtain a clear and transparent component A.

[0029] The prepared component A was mixed with 10g tellurium dioxide, 5g molybdenum oxide, and 4g cobalt oxide, and then mechanically ball-milled for 2 hours to obtain a silver-free high-temperature lubricating coating. This coating was applied to a substrate and cured at 450℃ for 0.5 hours to obtain a uniform and continuous silver-free high-temperature lubricating coating with no adverse effects on the substrate. This coating exhibits excellent lubrication and protective properties at high temperatures of 600~800℃. The coefficient of friction after curing is 0.096. After holding at 800℃ for 30 hours, as... Figure 4 As shown, the surface condition remained intact with no significant changes, and the coefficient of friction decreased slightly to 0.082. The change in the coefficient of friction before and after high-temperature treatment was minimal, indicating that the coating has excellent stability under high-temperature conditions.

[0030] Example 5: In this embodiment, the method for preparing the high-temperature lubricating coating for high-temperature alloy fasteners that does not contain silver is as follows: Preparation of component A: Dissolve 20g of phosphoric acid in 50g of water, heat to 90℃ using a heat-collecting constant temperature magnetic stirrer, stir at 800r / min for 10min to obtain a clear phosphoric acid aqueous solution, add 2g of aluminum hydroxide and 2g of magnesium oxide and stir for 3 hours until the solution is clear, then add 7g of chromium trioxide and stir for 1 hour to obtain a clear and transparent component A.

[0031] The prepared component A was mixed with 10g tellurium trioxide, 5g molybdenum dioxide, and 4g cobalt carbonate, and then mechanically ball-milled for 2 hours to obtain a silver-free high-temperature lubricating coating. This coating was applied to a substrate and cured at 450℃ for 0.5 hours to obtain a uniform and continuous silver-free high-temperature lubricating coating with no adverse effects on the substrate. This coating exhibits excellent lubrication and protective properties at high temperatures of 600~800℃. The coefficient of friction after curing is 0.094. After holding at 800℃ for 30 hours, as... Figure 5 As shown, the surface condition remained intact with no significant changes, and the coefficient of friction decreased slightly to 0.091. The change in the coefficient of friction before and after high-temperature treatment was minimal, indicating that the coating has excellent stability under high-temperature conditions.

[0032] Comparative Example 1 The difference from Example 1 is that barium telluride was not added; The coating of Comparative Example 1 was applied to a substrate and cured at 450℃ for 0.5 h to obtain a uniform, continuous, silver-free, barium telluride-free high-temperature lubricating coating with no adverse effects on the substrate. The lubrication and protective properties of this coating significantly decreased at high temperatures of 600–800℃. The coefficient of friction after curing was 0.370. After being held at 800℃ for 30 h, the entire coating surface oxidized and turned white, losing its lubricating effect.

[0033] Comparative Example 2 The difference from Example 2 is that calcium telluride was not added.

[0034] The coating from Comparative Example 2 was applied to a substrate and cured at 450℃ for 0.5 hours, resulting in a uniform, continuous, silver-free, and calcium telluride-free high-temperature lubricating coating with no adverse effects on the substrate. However, the lubrication and protective properties of this coating significantly decreased at high temperatures of 600–800℃. The coefficient of friction after curing was 0.364. After being held at 800℃ for 30 hours, the entire coating surface oxidized and turned white, losing its lubricating effect.

[0035] Comparative Example 3 The difference from Example 3 is that magnesium telluride was not added.

[0036] The coating of Comparative Example 3 was applied to a substrate and cured at 450℃ for 0.5 h to obtain a high-temperature lubricating coating that was free of silver and magnesium telluride. This coating exhibited a high coefficient of friction, poor wear resistance, and weak interfacial adhesion. The lubrication and protective properties of this coating significantly decreased at high temperatures of 600–800℃. After being held at 800℃ for 30 h, the coating surface oxidized and peeled off, losing its protective and lubricating function. Comparative Example 4 The difference from Example 4 is that tellurium dioxide was not added.

[0037] The coating of Comparative Example 4 was applied to a substrate and cured at 450℃ for 0.5 hours to obtain a high-temperature lubricating coating that is free of silver and tellurium dioxide. This coating exhibits a high coefficient of friction with large fluctuations and poor wear resistance stability, as well as weak interfacial adhesion. The lubrication and protective properties of this coating significantly decrease at high temperatures of 600–800℃. After being held at 800℃ for 30 hours, the coating surface becomes porous and easily peels off, exhibiting poor continuity and losing its protective and lubricating effects.

[0038] Comparative Example 5 The difference from Example 5 is that tellurium trioxide was not added.

[0039] The coating of Comparative Example 5 was applied to a substrate and cured at 450℃ for 0.5 h to obtain a high-temperature lubricating coating that is free of silver and tellurium trioxide. This coating exhibits a high coefficient of friction with large fluctuations and poor wear resistance stability, as well as weak interfacial adhesion. The lubrication and protective properties of this coating significantly decrease at high temperatures of 600–800℃. After being held at 800℃ for 30 h, the coating surface becomes porous and cracked, exhibiting poor continuity and losing its protective and lubricating effects.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a silver-free high-temperature lubricating coating, characterized in that: Includes the following steps: S1: Mix aluminum source, magnesium source, chromium source and phosphoric acid aqueous solution to obtain a mixed solution; S2: The mixed solution is mixed with tellurium source, molybdenum source and cobalt source, and ball milled to obtain a silver-free high-temperature lubricating coating. The silver-free high-temperature lubricating coating is applied to the substrate and cured to obtain a silver-free high-temperature lubricating coating layer.

2. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The aluminum source in step S1 includes one or more of aluminum oxide, aluminum hydroxide, and aluminum nitrate; And / or, the magnesium source in step S1 includes one or more of magnesium nitrate, magnesium chloride, magnesium sulfate, magnesium oxide, magnesium hydroxide, and magnesium carbonate; And / or, the chromium source in step S1 includes one or more of chromium trioxide, chromium trichloride, chromium sulfate, chromic anhydride, and chromium nitrate.

3. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The tellurium source in step S2 includes one or more of lead telluride, bismuth telluride, molybdenum telluride, copper telluride, sodium telluride, tellurium dioxide, tellurium trioxide, barium telluride, calcium telluride, and magnesium telluride. And / or, the molybdenum source in step S2 includes one or more of molybdenum oxide, molybdenum sulfide, molybdenum dioxide, molybdenum tetroxide, and calcium molybdate.

4. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The cobalt source in step S2 includes one or more of cobalt chloride, cobalt nitrate, cobalt oxide, cobalt acetate, cobalt sulfate, cobalt carbonate, and cobalt hydroxide.

5. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The molar ratio of phosphoric acid: aluminum source: magnesium source: chromium source: tellurium source: molybdenum source: cobalt source is 3~8: 0.8~1.2: 1~2.5: 1~1.5: 0.8~1.2: 0.2~2: 0.5~3.

6. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The mixing in step S1 is performed using a heat-collecting, constant-temperature magnetic stirrer with a rotation speed of 400~1000 r / min and a temperature of 80~100℃.

7. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: The mechanical ball milling time in step S2 is 2 hours. The ball milling medium is the prepared mixed coating. The ball milling speed is 1500~2600 r / min. The ball-to-material ratio is 5:1~3.

8. The method for preparing a silver-free high-temperature lubricating coating according to claim 1, characterized in that: In step S2, the silver-free high-temperature lubricating coating is applied to the substrate and cured at 400~550℃ for 0.5~1h to obtain a silver-free high-temperature lubricating coating.

9. The silver-free high-temperature lubricating coating prepared by the method for preparing a silver-free high-temperature lubricating coating according to any one of claims 1-8.

10. The silver-free high-temperature lubricating coating of claim 9 is applied to high-temperature alloy fasteners.

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