Preparation method of high-temperature-resistant, corrosion-resistant and oxidation-resistant solid lubricant and internal thread fastener

Abstract

The application discloses a preparation method of a high-temperature-resistant, corrosion-resistant and oxidation-resistant solid lubricant and an internally threaded fastener, and the solid lubricant comprises, in percentage by mass, 5-10% of Ni powder, 10-30% of graphite, 25-15% of MoTe, 3-10% of barium salt, 2-5% of corrosion inhibitor, 1-5% of dispersant, phosphate binder and 20-40% of mixed solvent; the a agent and the b agent are prepared step by step, then mixed, ball milled and homogenized to obtain the finished product; and the application further discloses a method for preparing a lubricating coating of the internally threaded fastener by using the solid lubricant, which comprises the following steps: pretreatment, dip coating, centrifugal uniform distribution, step-by-step solidification and the like, so that a uniform and controllable coating is formed on the surface of the fastener. The coating prepared by the application has excellent high-temperature resistance, corrosion resistance and oxidation resistance, and simultaneously has low friction coefficient, good wear resistance and locking performance, and can be widely applied to the fields of fasteners matched with hot working parts of aero-engines and gas turbines.

Description

Technical Field

[0001] This invention belongs to the field of fastener coating technology, specifically relating to a high-temperature resistant, corrosion-resistant and oxidation-resistant solid lubricant and a method for preparing internal thread fasteners. Background Technology

[0002] With the rapid development of science and technology and the increasing attention paid to aerospace technology by various countries, people are paying more and more attention to the friction and wear of components in service in the aerospace field. For example, the operating environment of aero-engine components is harsh, and the connection parts are required to have characteristics such as high temperature resistance and high strength. Its moving parts need to have good wear resistance and lubrication characteristics at service temperatures above 760℃.

[0003] Existing coatings (such as solid lubricating films, silver layers, etc.) often exhibit poor adhesion, severe coating peeling, bolt breakage and head deformation, and nut deformation, adhesion, or seizing during routine maintenance and disassembly. For rapidly developing aero-engine component materials, especially those used in aerospace, gas turbines, and extreme conditions, higher requirements are placed on their service temperatures. This also presents a severe test to the oxidation resistance and wear resistance of component surface coatings under ultra-high temperature environments.

[0004] Currently available high-temperature coatings struggle to simultaneously possess excellent oxidation resistance, wear resistance, and lubrication under ultra-high temperature conditions. For example, in high-speed combat aircraft operating at high temperatures for extended periods, coatings often exhibit widespread blistering, peeling, and oxidation failure, failing to meet the requirements for repeatable and long-life applications. The rapid deterioration of coating protective performance further exacerbates the issue. Therefore, there is an urgent need to develop ultra-high temperature resistant lubricating materials to improve the oxidation resistance and wear resistance of ultra-high temperature moving parts. These materials can replace existing coatings, addressing issues such as coating peeling, blistering, and high-temperature adhesion, thus achieving temperature resistance, wear resistance, and lubrication. This is crucial for improving product quality and reliability.

[0005] Currently, there are no mature products in China that can be directly applied to the surfaces of ultra-high temperature components in aero-engines and gas turbines for high-temperature resistance, corrosion resistance, and oxidation protection. The main approach is to use silver plating to address these issues. However, silver plating has significant limitations in its service life: the highest temperature it can withstand is only 760℃, and this effect is short-term. Above 760℃, adhesion and seizing occur, leading to wear, seizing, and fretting wear on the assembly contact surfaces. Therefore, developing a solid lubricant that can withstand 760℃ high temperatures, has 96 hours of corrosion resistance, and also possesses oxidation resistance, for use in fasteners on high-temperature components of aero-engines, is the core objective of domestic production in this field. Summary of the Invention

[0006] To address the above problems, the present invention aims to provide a high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant, as well as a method for preparing a coating for internal thread fasteners.

[0007] This invention is achieved through the following technical solution: A high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant, comprising the following components by mass percentage: 5-10% Ni powder, 10-30% graphite, 25-15% MoTe, 3-10% barium salt, 2-5% corrosion inhibitor, 1-5% dispersant, 20-40% mixed solvent, and phosphate binder; the total mass percentage of each component is 100%, with the balance being phosphate binder; the phosphate binder, by mass percentage, comprises 10-20% H3PO4, 5-10% Al(OH)3, and 1-5% CrO3; the mixed solvent is one or a mixture of two of xylene and ethylene glycol monoethyl ether in any proportion.

[0008] Furthermore, by mass percentage, it consists of 7% Ni powder, 20% graphite, 10% MoTe2, 6% barium salt, 4% resist, 3% dispersant, phosphate binder, and 30% mixed solvent.

[0009] Furthermore, the phosphate binder, by mass percentage, consists of 18% H3PO4, 39% Al(OH)3, and 33% CrO3.

[0010] A method for preparing a high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant includes the following steps: Preparation of S1 and a agent: Ni powder, graphite, MoTe2, barium salt, corrosion inhibitor and dispersant are weighed and mixed according to the corresponding ratio, and placed in a cylindrical ball mill for 3-4 hours at a speed of 200 r / min to ball mill until the particle size is ≤5μm to obtain agent a; Preparation of S2 and agent b: Weigh and mix H3PO4, Al(OH)3 and CrO3 according to the corresponding ratio, heat to dissolve, cool to 80-100℃, add 1%-3% of methylformaldehyde (methylformaldehyde) according to the total mass of agent b, heat to boiling again and keep warm for 30 minutes to obtain agent b; S3. Preparation of the mixed finished product: Mix agent a, agent b and mixed solvent, pour into a cylindrical ball mill and process for 6-8 hours at a speed of 500 r / min until the particle size is ≤5μm.

[0011] Furthermore, in step S3, the mass percentage of the mixed solvent is 30%.

[0012] Furthermore, after ball milling in step S3, a homogenization process is also included: homogenization is performed for 8 to 10 minutes under conditions of 10 to 15 MPa pressure, 5000 to 10000 r / min rotation speed, and 80 to 100℃, and the finished product is obtained after cooling.

[0013] A method for preparing a high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricating coating for internally threaded fasteners includes the following steps: A. Inspection before coating: Ensure that the surface of the fasteners to be coated is free of defects such as oil stains, rust, and deformation; B. Pretreatment: Surface treatment of internal threaded fasteners to improve coating adhesion; C. Dip coating: Mix solid lubricant and anhydrous ethanol at a mass ratio of 1:1.5 until homogeneous. Dip the fastener to be coated into the coating solution and repeat the dipping process until the required thickness is met. D. Centrifugation and mixing: Place the coated fasteners into a centrifuge to remove excess coating liquid; E. Curing: The fasteners are cured by step-by-step heating, and the coating is completed after cooling.

[0014] Furthermore, the pretreatment described in step B specifically involves: sequentially performing degreasing, sandblasting, pickling, and passivation treatments on the internally threaded fasteners to remove surface oxides and oxidation colors.

[0015] Furthermore, the process parameters for centrifugation in step D are: rotation speed 400-500 r / min, single processing time 2 min, and the number of centrifugations matching the number of dip coatings.

[0016] Further, the specific process of the stepped curing in step E is as follows: place the fastener in an oven at a temperature not exceeding 60°C, raise the temperature to 100±5°C at a rate of 4-6°C / min, and hold for 30 min; then raise the temperature to 200±5°C and hold for 30 min; continue to raise the temperature to 300±10°C and hold for 2 h.

[0017] The beneficial effects of this invention are: 1. This invention has developed a novel high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant formula. Through the synergistic lubrication of Ni powder, graphite, and MoTe2, combined with the film-forming protective effect of phosphate binder, the product simultaneously possesses long-term high-temperature resistance at 760℃, 96h resistance to neutral salt spray corrosion, and excellent oxidation resistance, filling the gap in related mature products in the domestic aerospace field.

[0018] 2. This invention achieves uniform dispersion of lubricating functional components and adhesive film-forming components through a stepwise preparation process of agent A and agent B. By controlling the process of graded ball milling and homogenization treatment, the particle size of the material is guaranteed to be ≤5μm, which lays the foundation for subsequent uniform coating and solves the problems of easy sedimentation and poor coating stability of solid lubricants.

[0019] 3. This invention optimizes the coating process for internal thread fasteners. By improving coating adhesion through pretreatment, and by using a combination of dip coating and centrifugal spinning to precisely control the uniformity of coating thickness at the internal thread, this invention solves the problems of material accumulation, uneven thickness, and thread fit failure that easily occur when coating internal thread fasteners, thus adapting to the needs of industrial mass production.

[0020] 4. This invention avoids the problems of pinholes, cracking, and peeling that occur when the coating is cured rapidly by using a stepped curing process, and further improves the adhesion between the coating and the substrate. The resulting coating has a stable coefficient of friction of 0.08 to 0.12, and has excellent wear resistance, locking performance, and repeated disassembly and assembly performance. It solves the industry pain points of existing silver plating layers that are prone to sticking, seizing, and severe wear at high temperatures, and can be stably applied to extreme working conditions such as fasteners for thermal components of aero engines and gas turbines. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0022] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Example 1

[0023] The specific steps for preparing high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricants are as follows: Preparation of Agent Aa: Weigh out 7% Ni powder, 20% graphite, 10% MoTe2, 6% barium chloride, 4% zinc chromate, and 3% stearic acid by mass percentage. Add all the above materials into a cylindrical ball mill, seal it, start the ball mill, set the speed to 200 r / min, and ball mill for 3.5 h. After stopping the machine, check that the particle size of the material is ≤5 μm, take it out, seal it, and set it aside for later use to obtain Agent A.

[0024] Preparation of Agent Bb: Weigh 15% H3PO4, 37% Al(OH)3, and 33% CrO3 by mass percentage. Add the above materials to a corrosion-resistant beaker, heat slowly and stir continuously until the materials are completely dissolved. After stopping the heating, let it cool naturally to 90°C. Add 2% of the total mass of Agent B, formaldehyde, and stir evenly. Heat again until the solution boils, keep it at boiling for 30 minutes, let it cool naturally to room temperature, and then seal it for later use to obtain Agent B.

[0025] C. Mixed ball milling: Add the prepared agent a, agent b, and 25% by mass of the mixed solvent into a cylindrical ball mill, seal it, start the ball mill, set the speed to 500 r / min, and ball mill for 7 hours. After stopping the machine, check that the particle size of the material is ≤5μm and take it out for later use.

[0026] D. Homogenization: Transfer the mixed ball-milled material into a homogenizer, set the pressure to 12MPa, the rotation speed to 8000r / min, and the temperature to 90℃, and homogenize for 9 minutes to ensure uniform material dispersion and system stability.

[0027] E. Cooling and Packaging: The homogenized material is naturally cooled to room temperature and then filled into a sealed container to obtain the finished solid lubricant of this embodiment.

[0028] The specific steps for preparing a high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricating coating for internally threaded fasteners are as follows: A. Pre-coating acceptance: Select M10 internal thread nuts for aircraft engines as the workpieces to be coated, and check the surface condition of each piece to ensure that there are no surface defects such as oil stains, rust, oxides, paint, coloring, spots, nodules, burrs, deformation, bumps and scratches. After passing the acceptance, proceed to the next process.

[0029] B. Pretreatment: For the accepted workpieces, degreasing, sandblasting, pickling and passivation are carried out in sequence to thoroughly remove oil, oxides and oxide color from the surface of the workpieces. The surface roughness of the workpieces is adjusted to Ra6.3-12.5. After the treatment is completed, the workpieces are rinsed with anhydrous ethanol and dried for later use.

[0030] C. Preparation of dipping solution: Weigh the solid lubricant and anhydrous ethanol prepared in this example at a mass ratio of 1:1.5, add them to a beaker, place it on a magnetic stirrer, and stir continuously for 30 minutes until the solution is completely mixed and homogeneous. Keep stirring at a low speed until ready for use.

[0031] D. Dip Coating Operation: Place the pretreated workpiece neatly into a stainless steel wire mesh basket, immerse it completely in the coating solution, and shake it up and down and left and right 3 times to ensure that the internal thread tooth profile is completely wetted with the coating solution; then take out the workpiece and shake it for 15 seconds to remove the surface liquid, and repeat the dip coating operation 2 times to ensure that the coating thickness reaches the preset range.

[0032] E. Centrifugal Spinning: After dipping and coating, the workpiece is dried at room temperature until it is surface dry, then hung on a special centrifugal fixture and placed in a centrifugal spinner. The speed is set to 450 r / min, the single processing time is 2 min, and the centrifugation is performed twice to completely remove excess coating liquid from the surface and internal threads of the workpiece.

[0033] F. Stepped curing: The workpiece after centrifugation and mixing is transferred to an oven at 40°C and heated to 100°C at a heating rate of 5°C / min, and held for 30 min; then heated to 200°C at the same rate and held for 30 min; then heated to 300°C and held for 2 h. After the holding period, the workpiece is cooled to room temperature in the oven to complete the curing process and obtain the coated fastener product of this embodiment. Example 2

[0034] The only difference between this embodiment and Embodiment 1 is that: Differences in solid lubricant preparation: Aa agent preparation: ball milling time is 4h; Bb agent preparation: weigh 18% H3PO4, 39% Al(OH)3, and 33% CrO3 by mass percentage, dissolve the materials, cool to 85℃, add 2% of the total mass of b agent with formaldehyde, and stir evenly; C. Mixed ball milling: the mass percentage of mixed solvent is 30%, and the ball milling time is 8h; D. Homogenization treatment: set the pressure to 15MPa, the speed to 10000r / min, and the temperature to 100℃, and homogenize for 10 minutes.

[0035] The coating preparation was no different, and all other steps, parameters, and raw material specifications were completely consistent with those in Example 1. Example 3

[0036] The only difference between this embodiment and Embodiment 1 is that: Differences in solid lubricant preparation: Aa agent preparation: Weigh 5% Ni powder, 10% graphite, 25% MoTe, 3% barium chloride, 2% zinc chromate, and 1% stearic acid by mass percentage, and ball mill for 3 hours; Bb agent preparation: Weigh 10% H3PO4, 35% Al(OH)3, and 1% CrO3 by mass percentage, dissolve the materials, cool to 80℃, add 1% of formaldehyde (by mass of agent b), and stir evenly; C. Mixed ball milling: Mixed solvent mass percentage is 40%, and ball milling time is 6 hours; D. Homogenization treatment: Set pressure 10MPa, speed 5000r / min, temperature 80℃, and homogenize for 8 minutes.

[0037] Differences in coating preparation: The centrifugal spinning step is set with a rotation speed of 400 r / min, a single treatment time of 2 min, and two centrifugation treatments; the step-curing step starts with an oven temperature of 60℃, a heating rate of 4℃ / min, and holding temperatures of 100±5℃, 200±5℃, and 300±10℃ for each temperature zone.

[0038] All other steps, parameters, and raw material specifications are completely consistent with those in Example 1. Example 4

[0039] The only difference between this embodiment and Embodiment 1 is that: Differences in solid lubricant preparation: Aa agent preparation: Weigh 10% Ni powder, 30% graphite, 15% MoTe2, 10% barium chloride, 5% zinc chromate, and 5% stearic acid by mass percentage, and ball mill for 4 hours; Bb agent preparation: Weigh 20% H3PO4, 10% Al(OH)3, and 35% CrO by mass percentage, dissolve the materials, cool to 100℃, add 4% of the total mass of b agent with formaldehyde, and stir evenly; C. Mixed ball milling: Mixed solvent mass percentage is 20%, and ball milling time is 8 hours; D. Homogenization treatment: Set pressure 15MPa, speed 10000r / min, temperature 100℃, and homogenize for 10 minutes.

[0040] Differences in coating preparation: In the dip coating operation, the workpiece is removed and shaken for 20 seconds, and the dip coating operation is repeated 3 times; in the centrifugal spinning step, the speed is set to 500 r / min, the single processing time is 2 min, and the centrifugation is performed 3 times; in the stepped curing step, the starting oven temperature is 50℃, the heating rate is 6℃ / min, and the holding temperature of each temperature zone is 100±5℃, 200±5℃, and 300±10℃.

[0041] All other steps, parameters, and raw material specifications are completely consistent with those in Example 1.

[0042] Comparative Example 1 shows a silver-plated fastener from the prior art. Select an M10 internal thread nut of the same specification as in Examples 1-4, and prepare a silver plating layer using a conventional silver plating process in the aerospace field. The silver layer thickness is 8-12μm.

[0043] Comparative Example 2 shows solid lubricants and coatings lacking MoTe2. Except for the absence of MoTe2 in agent a, the other components, proportions, and solid lubricant preparation methods in this comparative example are completely consistent with those in Example 2, and a comparative solid lubricant is obtained. Then, the coating preparation process is completely consistent with that in Example 2 to prepare a coating for internal thread fasteners.

[0044] The coated fasteners obtained in Examples 1-4 and the samples in Comparative Examples 1-2 were subjected to full performance testing according to the testing methods described in this specification. The test results are shown in the table below:

[0045] As shown in the table above, the solid lubricants and matching coatings prepared in Examples 1-4 of this invention can all achieve long-term high-temperature resistance at 760℃, 96h resistance to neutral salt spray corrosion, excellent oxidation resistance, and low-friction lubrication performance, fully meeting the extreme operating conditions required for fasteners used in aero-engines and gas turbines. Among them, the preferred formulation in Example 2 has the best overall performance and is the optimal solution. In contrast, Comparative Example 1 of the prior art exhibits adhesion and seizing at 760℃, failing to meet the requirements for long-term high-temperature service. Comparative Example 2, lacking the core functional component MoTe2, shows a significant decrease in high-temperature resistance, corrosion resistance, adhesion, and lubrication performance, fully demonstrating the outstanding substantive features and significant progress of the technical solution of this invention.

[0046] The scope of protection of this invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this invention shall fall within the scope of protection of this invention.

Claims

1. A high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant, characterized in that: The product comprises, by mass percentage, the following components: 5-10% Ni powder, 10-30% graphite, 25-15% MoTe, 3-10% barium salt, 2-5% resist, 1-5% dispersant, 20-40% mixed solvent, and phosphate binder; the phosphate binder comprises, by mass percentage of its total mass, 10-20% H3PO4, 5-10% Al(OH)3, 1-5% CrO3, with the balance being deionized water; the mixed solvent is one or a mixture of two of xylene and ethylene glycol monoethyl ether in any proportion.

2. The high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant according to claim 1, characterized in that: By mass percentage, it consists of 7% Ni powder, 20% graphite, 10% MoTe, 6% barium salt, 4% corrosion resist, 3% dispersant, 20% phosphate binder, and 30% mixed solvent.

3. The high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant according to claim 1, characterized in that: The phosphate binder, by mass percentage, consists of 18% H3PO4, 39% Al(OH)3, and 33% CrO3.

4. The method for preparing the high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricant according to any one of claims 1-3, characterized in that: Includes the following steps: Preparation of S1 and a agent: Ni powder, graphite, MoTe2, barium salt, corrosion inhibitor and dispersant are weighed and mixed according to the corresponding ratio, and placed in a cylindrical ball mill for 3-4 hours at a speed of 200 r / min to ball mill until the particle size is ≤5μm to obtain agent a; Preparation of S2 and agent b: Weigh and mix H3PO4, Al(OH)3, and CrO3 according to the corresponding ratio, heat to dissolve, cool to 80-100℃, add methylformaldehyde, heat again to boiling and keep warm for 30 minutes to obtain agent b, wherein the amount of methylformaldehyde added accounts for 1%-3% of the total mass of agent b; S3. Preparation of the mixed finished product: Mix agent a, agent b and mixed solvent, pour into a cylindrical ball mill and process for 6-8 hours at a speed of 500 r / min until the particle size is ≤5μm.

5. The preparation method according to claim 4, characterized in that: In step S3, the mass percentage of the mixed solvent is 30%.

6. The preparation method according to claim 4, characterized in that: After ball milling in step S3, a homogenization process is also included: homogenization is performed for 8 to 10 minutes under a pressure of 10 to 15 MPa, a rotation speed of 5000 to 10000 r / min, and a temperature of 80 to 100°C, and the finished product is obtained after cooling.

7. A method for preparing a high-temperature resistant, corrosion-resistant, and oxidation-resistant solid lubricating coating for internally threaded fasteners, characterized in that: Includes the following steps: A. Inspection before coating: Ensure that the surface of the fasteners to be coated is free of defects such as oil stains, rust, and deformation; B. Pretreatment: Surface treatment of internal threaded fasteners to improve coating adhesion; C. Dip coating: Mix solid lubricant and anhydrous ethanol at a mass ratio of 1:1.5 until homogeneous. Dip the fastener to be coated into the coating solution and repeat the dipping process until the required thickness is met. D. Centrifugation and mixing: Place the coated fasteners into a centrifuge to remove excess coating liquid; E. Curing: The fasteners are cured by step-by-step heating, and the coating is completed after cooling.

8. The preparation method according to claim 7, characterized in that: The pretreatment described in step B specifically involves sequentially performing degreasing, sandblasting, pickling, and passivation treatments on the internally threaded fasteners to remove surface oxides and oxidation colors.

9. The preparation method according to claim 7, characterized in that: The process parameters for centrifugation in step D are: rotation speed 400-500 r / min, single processing time 2 min, and the number of centrifugations matched with the number of dip coatings.

10. The preparation method according to claim 7, characterized in that: The specific process of the stepped curing in step E is as follows: place the fastener in an oven at a temperature not exceeding 60°C, raise the temperature to 100±5°C at a rate of 4-6°C / min, and hold for 30 minutes; then raise the temperature to 200±5°C and hold for 30 minutes; continue to raise the temperature to 300±10°C and hold for 2 hours.

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