High-temperature self-lubricating bushing as well as preparation method and application thereof

Abstract

The invention provides a high-temperature self-lubricating bushing as well as a preparation method and application thereof, and relates to the technical field of special sliding bearings. The high-temperature self-lubricating bushing provided by the invention comprises a high-temperature-resistant metal bushing body, a lubricating coating arranged on the surface of a friction surface of the high-temperature-resistant metal bushing body and a plurality of lubricating structures sunken in the friction surface of the high-temperature-resistant metal bushing body, wherein the lubricating structures are filled with a composite solid lubricant; the temperature resistance of the high-temperature-resistant metal lining body is larger than or equal to 300 DEG C, and the hardness ranges from 100 HV to 500 HV. The composite solid lubricant and the lubricating coating comprise a solid lubricant and a binder. The high-temperature self-lubricating bushing provided by the invention has the outstanding characteristics of high temperature resistance, wear resistance, low friction coefficient in a wide temperature range, small wear to matching pair materials, high designability, safety, reliability and the like, and has a good application prospect in high-temperature sliding motion related parts such as high-performance aero-engines, gas turbines, combined cycle engines and the like.

Description

Technical Field

[0001] The invention relates to the technical field of special sliding bearings, and in particular to a high-temperature self-lubricating bushing and a preparation method and application thereof. Background Art

[0002] The adjustable stator vane (VSV) system is commonly used in aero engines, gas turbines, and turbine-based combined cycle engines to control the airflow and pressure of the intake or fuel gas, thereby achieving the regulation of the engine's operating state. The adjustable stator vanes of this type of engine are connected to the casing and the actuator through a self-lubricating bushing. The self-lubricating bushing mainly supports the blades and the rotating shaft of the actuator, reduces friction and wear, and ensures the precise movement of the adjustable stator vanes. The self-lubricating bushing serves in relatively harsh working conditions such as high temperature, vibration, and impact, and is one of the key components for regulating the engine's operating state.

[0003] At present, the actual service temperature of the self-lubricating bushings of conventional engines in service is lower than 300°C. Most of these bushings are made of polymer-based self-lubricating materials, copper alloy-based self-lubricating materials or metal-fluoroplastic double-layer self-lubricating materials. However, with the continuous improvement of performance parameters such as efficiency, thrust and power of the new generation of engines, the engine intake temperature and gas temperature are getting higher and higher, causing the service temperature of the self-lubricating bushings of the VSV system to become higher and higher. At present, the working temperature of the self-lubricating bushings has reached above 400°C. In a high temperature environment above 400°C, polymer-based self-lubricating materials and metal-fluoroplastic double-layer self-lubricating materials will fail such as melting, decomposition, cracking, powdering or burning, while the anti-wear performance and load-bearing capacity of copper alloy-based self-lubricating materials will be sharply reduced, making it difficult to meet the use requirements.

[0004] In order to solve the above problems, powder metallurgy iron-based, nickel-based or cobalt-based metal-based high-temperature self-lubricating composite materials are usually used at home and abroad to manufacture high-temperature self-lubricating bushings above 400°C for engines. These metal-based high-temperature self-lubricating composite materials usually use iron-based, nickel-based or cobalt-based high-temperature resistant material powders as the matrix, add solid lubricant powders, and some also need to add hard wear-resistant phase powders. After mixing evenly, they are sintered into block materials through powder metallurgy technology, and then processed into bushings for use. However, the metal-based self-lubricating composite materials obtained by the above method belong to solid phase diffusion type sintering materials. It is difficult to form high-strength metallurgical bonding between powder particles in the microstructure of this material, and the solid lubricant and wear-resistant phase in its microstructure are randomly distributed, which breaks the continuity of the metal matrix and makes it difficult for the matrix metal to connect to each other to form a high-strength and tough overall structure, resulting in poor plasticity and toughness of this type of material. It is easy to break, break or pulverize in high temperature, high load or impact conditions, and there are high reliability risks and safety hazards. Moreover, in the microstructure of this sintered material, many solid lubricants decompose during the high-temperature sintering process or react chemically with the base metal, making it easy for the components of the final composite material to deviate from the original design, resulting in a high friction coefficient and poor wear resistance. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a high-temperature self-lubricating bushing and its preparation method and application. The high-temperature self-lubricating bushing provided by the present invention has low friction coefficient, good wear resistance, high service temperature, impact resistance, high load-bearing, safety and reliability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a high-temperature self-lubricating bushing, comprising a high-temperature resistant metal bushing body, a lubricating coating arranged on the friction surface of the high-temperature resistant metal bushing body, and a plurality of lubricating structures recessed in the friction surface of the high-temperature resistant metal bushing body, wherein the lubricating structures are filled with a composite solid lubricant;

[0008] The temperature resistance of the high temperature resistant metal bushing body is ≥300°C and the hardness is 100-500HV;

[0009] The composition of the composite solid lubricant and lubricating coating includes a solid lubricant and a binder; the solid lubricant in the composite solid lubricant and lubricating coating includes one or more of graphite, molybdenum disulfide, tungsten disulfide, silver, hexagonal boron nitride, yellow lead oxide, barium difluoride, calcium difluoride, cerium trifluoride, chromium trioxide and nickel monoxide, and the binder in the composite solid lubricant and lubricating coating includes one or more of silica sol, sodium tetraborate, boron trioxide, aluminum dihydrogen phosphate, sodium silicate, aluminum trioxide and silicon dioxide.

[0010] Preferably, the high temperature resistant metal bushing body comprises a high entropy alloy, an iron-based high temperature alloy, a nickel-based high temperature alloy, a cobalt-based high temperature alloy or a titanium alloy.

[0011] Preferably, the sum of the areas of all lubrication structures is 10-70% of the total area of ​​the friction surface of the high temperature resistant metal bushing body.

[0012] Preferably, each lubricating structure is independently shaped as a pit, a hole or a groove, and the hole is a circular hole or a polygonal hole; each lubricating structure independently penetrates or does not penetrate the high temperature resistant metal bushing body.

[0013] Preferably, the lubrication structures are independent of each other or communicated with each other.

[0014] Preferably, the particle size of the solid lubricant in the composite solid lubricant and the lubricating coating is ≤100 μm.

[0015] Preferably, the lubricating coating has a thickness of 2 to 30 μm.

[0016] The present invention provides a method for preparing the high-temperature self-lubricating bushing described in the above technical solution, comprising the following steps:

[0017] Processing the high temperature resistant metal material into a bushing blank having a concave lubrication structure on the friction surface; the processing method includes 3D printing, precision casting or machining;

[0018] Providing a composite solid lubricant slurry, the composite solid lubricant slurry comprising a solid lubricant, a binder and water;

[0019] Filling the composite solid lubricant slurry in the lubrication structure of the bushing blank, and sequentially performing first drying and curing and surface finishing to obtain a bushing body;

[0020] The composite solid lubricant slurry is applied to the friction surface of the bushing body, and after a second drying and curing, the high-temperature self-lubricating bushing is obtained.

[0021] Preferably, the first drying and curing and the second drying and curing are segmented drying and curing or continuous drying and curing; the segmented drying and curing include sequentially performing drying and curing, the drying temperature is 65-95°C, the insulation time is more than 1 hour, the curing temperature is 280-400°C, and the insulation time is more than 1.5 hours; the continuous drying and curing is carried out at 280-400°C, and the insulation time is more than 2 hours.

[0022] The present invention provides the application of the high-temperature self-lubricating bushing described in the above technical solution or the high-temperature self-lubricating bushing prepared by the preparation method described in the above technical solution in high-temperature sliding motion parts.

[0023] The present invention provides a high-temperature self-lubricating bushing, comprising a high-temperature resistant metal bushing body, a lubricating coating disposed on the friction surface of the high-temperature resistant metal bushing body, and a plurality of lubricating structures recessed in the friction surface of the high-temperature resistant metal bushing body, wherein the lubricating structure is filled with a composite solid lubricant; the temperature resistance of the high-temperature resistant metal bushing body is ≥300°C, and the hardness is 100-500HV; the composition of the composite solid lubricant and the lubricating coating includes a solid lubricant and a binder. Compared with the prior art, the present invention has the following beneficial effects:

[0024] Excellent high temperature resistance: The bushing body of the present invention adopts a material with good high temperature resistance, so that the bushing has excellent high temperature resistance; the present invention has excellent bonding strength through compounding of multiple adhesives, and the bonding strength will not change at high temperature, and the tribological properties will not be deteriorated;

[0025] Good anti-wear performance: On the one hand, the present invention adopts a metal material with good high-temperature strength and hardness as the bushing body, which itself has good high-temperature wear resistance; on the other hand, the present invention arranges a lubrication structure filled with solid lubricant on the friction surface of the bushing, and arranges a surface lubrication layer on the friction surface. The present invention adopts a special design of "metal body + lubrication structure + surface lubrication coating", so that the solid lubricant is continuously transferred to the bushing surface during the friction process, which plays a good role in reducing friction and anti-wear, and has good load-bearing capacity and self-lubricating performance, achieving the effect of self-adaptation to working conditions, and effectively improving the service life of the bushing;

[0026] Higher load-bearing capacity and impact resistance: The present invention selects metal materials with good mechanical properties such as high-temperature strength and hardness, so that it has excellent load-bearing capacity and impact resistance at high temperatures; the present invention arranges a lubrication structure on the friction surface of the bushing to fill the solid lubricant, which can avoid stress concentration under high temperature and high load, making it difficult for the bushing to produce defects such as cracks;

[0027] Low friction coefficient: In the present invention, the friction surface of the bushing is provided with a lubrication structure filled with a composite solid lubricant, and a surface lubrication layer is also provided on the friction surface. The lubrication structure can effectively store, release and collect solid lubricants, so that the bushing has a sufficient supply of solid lubricants on the friction surface during the friction process. Therefore, the bushing has an extremely low friction coefficient. The bushing has a low friction coefficient regardless of high temperature, low temperature and wide temperature range, high speed, low speed and wide speed range, and light load, heavy load and variable load environment. The maximum friction coefficient is less than 0.25, and the friction coefficient under some conditions is as low as below 0.1. The embodiment of the present invention still has excellent friction performance under high temperature and heavy load conditions of more than 30000N.

[0028] Less wear on the mating material: Since the present invention uses a relatively low hardness metal material as the bushing body material, and the lubrication structure on the bushing friction surface is set, it has good latent property, compliance and friction reduction during the friction process, and will not cause significant friction damage to the mating material. In practical applications, it can effectively protect the rotating shaft or the bearing seat;

[0029] Strong designability: The lubrication structure and solid lubricant components of the bushing in the present invention are highly designable. The shape, distribution pattern and area ratio of the lubrication structure can be optimized according to the specific working conditions, so that it has good solid lubricant storage, supply and collection functions, as well as good load-bearing and anti-wear effects; the components of the solid lubricant and the ratio with the binder can also be optimized according to the specific working conditions, so that it has both high bonding strength and lubrication performance.

[0030] Since the high-temperature self-lubricating bushing provided by the present invention has the above-mentioned significant beneficial effects, its comprehensive performance such as reliability, safety and service life is superior to the existing high-temperature self-lubricating bushings for engines.

[0031] The present invention provides a method for preparing the high-temperature self-lubricating bushing described in the above technical solution. Since the present invention uses 3D printing, precision casting or machining to process and manufacture the bushing body, the bushing body material has fewer internal defects and is a complete high-strength and tough overall structure with excellent strength, plasticity and toughness, overcoming the problem of poor plasticity and toughness of the bushing body prepared by conventional powder metallurgy and other technical means, so that it will not break or crack under higher operating temperatures and greater loads (such as high temperature shock and severe vibration conditions), and has higher load-bearing capacity and impact resistance at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The process flow chart of preparing a high-temperature self-lubricating bushing according to the present invention;

[0033] Figure 2 This is a schematic structural diagram of a high-temperature self-lubricating bushing and its lubrication structure prepared by 3D printing technology in Example 1;

[0034] Figure 3 It is a structural schematic diagram of a high-temperature self-lubricating bushing and its lubrication structure prepared by precision casting technology in Example 2;

[0035] Figure 4 Schematic diagram of the structure of the high-temperature self-lubricating bushing and its lubrication structure prepared by machining technology in Example 3;

[0036] Figure 5 This is a schematic structural diagram of a high-temperature self-lubricating bushing and its lubrication structure prepared by machining technology in Example 4. DETAILED DESCRIPTION

[0037] The present invention provides a high-temperature self-lubricating bushing, comprising a high-temperature resistant metal bushing body, a lubricating coating arranged on the friction surface of the high-temperature resistant metal bushing body, and a plurality of lubricating structures recessed in the friction surface of the high-temperature resistant metal bushing body, wherein the lubricating structures are filled with a composite solid lubricant;

[0038] The temperature resistance of the high temperature resistant metal bushing body is ≥300°C and the hardness is 100-500HV;

[0039] The composition of the composite solid lubricant and lubricating coating includes a solid lubricant and a binder; the solid lubricant in the composite solid lubricant and lubricating coating includes one or more of graphite, molybdenum disulfide, tungsten disulfide, silver, hexagonal boron nitride, yellow lead oxide, barium difluoride, calcium difluoride, cerium trifluoride, chromium trioxide and nickel monoxide, and the binder in the composite solid lubricant and lubricating coating includes one or more of silica sol, sodium tetraborate, boron trioxide, aluminum dihydrogen phosphate, sodium silicate, aluminum trioxide and silicon dioxide.

[0040] In the present invention, unless otherwise specified, all raw materials involved are commercially available products in the art.

[0041] The high-temperature self-lubricating bushing provided by the present invention comprises a high-temperature resistant metal bushing body.

[0042] In the present invention, the temperature resistance of the high temperature resistant metal bushing body is ≥300°C and the hardness is 100-500HV. In the present invention, the high temperature resistant bushing body preferably comprises a high entropy alloy, an iron-based high temperature alloy, a nickel-based high temperature alloy, a cobalt-based high temperature alloy or a titanium alloy; the high entropy alloy such as CoCrNi, CoFeNi, CoCrFeNi, CoCrFeNiAl 0.2 、CoCrFeNiMo 0.2 、CoCrFeNi 2.1 Al, CoCrFeNiV 0.2High entropy alloys with hardness less than 500HV can be used in harsh working conditions such as high temperature, heavy load, high speed and impact, and the maximum use temperature can reach 800℃; high-temperature alloys with hardness less than 450HV such as iron-based high-temperature alloys, nickel-based high-temperature alloys, and cobalt-based high-temperature alloys such as GH1016, GH2136, GH3536, GH4169, K465, and GH5605 can be used in harsh working conditions such as high temperature, heavy load, high speed and impact, and the maximum use temperature can reach 800℃; titanium alloys such as TC4, TC6, TC11, Ti-6242, IMI-834, Ti60, and Ti600 can be used in working conditions such as high temperature and impact, as well as working conditions with special requirements for density and corrosion resistance, and the maximum use temperature can reach 500℃. In the present invention, the selection of high-temperature resistant metal materials can be carried out according to the different working conditions such as the use temperature, load, and sliding speed of the bushing.

[0043] The high-temperature self-lubricating bushing provided by the present invention comprises a plurality of lubricating structures recessed in the friction surface of the high-temperature resistant metal bushing body (ie the lubricating structures are opened on the friction surface and are lower than the friction surface in the height direction), and the lubricating structures are filled with composite solid lubricants.

[0044] In the present invention, the shape of each lubricating structure is preferably independently a pit, a hole or a groove, and the hole is preferably a circular hole or a polygonal hole, and the polygonal hole is such as a triangular hole, a square hole, a diamond hole or an irregular hole. Each lubricating structure is independent of each other or connected together, and is selected according to the actual application conditions. In the present invention, the equivalent diameter of a single lubricating structure is preferably greater than 0.2 mm and less than 25% of the inner diameter of the bushing; the depth of a single lubricating structure is preferably greater than 0.1 mm, and each lubricating structure can independently penetrate or not penetrate the high temperature resistant metal bushing body (such as the hole can be a through hole or a blind hole). In the present invention, the sum of the areas of all lubricating structures is 10-70% of the total area of ​​the friction surface of the high temperature resistant metal bushing body (i.e., the surface including the lubricating structure and the friction surface without the lubricating structure), which can be 20%, 30%, 40%, 50%, 60% or 70%. In the present invention, the main function of the lubricating structure is to store high temperature resistant solid lubricants, which are continuously supplied to the friction surface during the friction process. The present invention controls the area ratio of the lubrication structure to 10-70%, which can ensure the friction performance of the bushing while ensuring a high load-bearing capacity. The present invention sets a lubrication structure on the friction surface to avoid stress concentration under high temperature and high load, making it difficult for the bushing to produce defects such as cracks, and is relatively easy to process and manufacture.

[0045] In the present invention, the lubricating structure is filled with a composite solid lubricant, and the composite solid lubricant includes a solid lubricant and a binder, that is, the solid lubricant is bonded to the lubricating structure by the binder. In the present invention, the solid lubricant includes one or more of graphite, molybdenum disulfide, tungsten disulfide, silver, hexagonal boron nitride, yellow lead oxide, barium difluoride, calcium difluoride, cerium trifluoride, chromium trioxide and nickel monoxide, and the particle size of the solid lubricant is preferably ≤100μm; the solid lubricant is a high temperature resistant solid lubricant. In the present invention, the binder preferably includes one or more of silica sol, sodium tetraborate, boron trioxide, aluminum dihydrogen phosphate, sodium silicate, aluminum trioxide and silicon dioxide, and the binder is a high temperature resistant binder. Traditional aluminum chromium phosphate or zirconium silicate binders have the following disadvantages: (1) The bonding strength is low, and the composite solid lubricant will fall off under vibration or impact load; (2) After the aluminum chromium phosphate or zirconium silicate binder is added, it will oxidize to form oxides at high temperatures, which will reduce its bonding strength when it is used for a long time at high temperatures, and the formed oxide particles will deteriorate the lubrication performance. The binder of the present invention can be compounded with multiple specific materials to have excellent bonding strength, and the bonding strength will not change at high temperatures, nor will the tribological properties be deteriorated.

[0046] The high-temperature self-lubricating bushing provided by the present invention comprises a lubricating coating arranged on the friction surface of the high-temperature resistant metal bushing body.

[0047] In the present invention, the lubricating coating includes a solid lubricant and a high temperature resistant binder, and the solid lubricant and the high temperature resistant binder are preferably the same as the solid lubricant and the high temperature resistant binder in the above technical solution, and will not be repeated here. In the present invention, the thickness of the lubricating coating is preferably 2 to 30 μm. In the present invention, according to the specific working conditions, the components of the solid lubricant and the binder and the ratio of the solid lubricant and the binder are adjusted to have both high high temperature bonding strength and lubrication performance, which will be described in detail later in the preparation process of the high temperature self-lubricating bushing.

[0048] The present invention provides a lubricating structure filled with a composite solid lubricant on the friction surface of the bushing, and also provides a surface lubricating layer on the friction surface. The lubricating structure is a pit, hole or groove, and the solid lubricant in the lubricating structure can be continuously transferred from the pit to the friction contact surface during the friction process, thereby playing a lubricating and anti-wear role. In the lubricating structure, due to the transfer of the solid lubricant, depressions or holes will be left, and the lubricating coating on the friction surface or the transferred free solid lubricant will be filled in the depressions and holes in the above-mentioned lubricating structure during the friction process. Due to the special design of "lubricating structure + surface lubricating coating" provided by the present invention, the high-temperature resistant solid lubricant on the friction surface can be continuously replenished during the friction process, achieving a dynamic balance process and friction self-adaptive effect, so that it has the characteristics of low friction, high wear resistance and long life. Regardless of various working conditions such as high temperature, heavy load or high speed, or in an environment where the working conditions change sharply, the special design of "metal body + lubricating structure + surface lubricating coating" provided by the present invention can always make it have good load-bearing capacity, self-lubricating performance and anti-wear performance, thereby achieving the effect of working condition self-adaptation. This advantage is difficult to obtain with conventional powder metallurgy self-lubricating materials or other conventional self-lubricating methods.

[0049] Compared with the conventional high-temperature self-lubricating bushings of engines, the high-temperature self-lubricating bushings provided by the present invention have outstanding characteristics such as high temperature resistance, wear resistance, high load-bearing, impact resistance, low friction coefficient in a wide temperature range, small wear on the mating materials, and strong designability. In the high-temperature friction process, the high-temperature resistant metal bushing matrix plays the role of load bearing and wear resistance, the surface lubricating coating and the solid lubricant in the lubricating structure play the role of high-temperature friction reduction and self-lubrication, and the high-temperature resistant solid lubricant in the lubricating structure can be continuously replenished to the friction surface during the friction process, and can have good wear-resistant and self-lubricating properties in a high-temperature environment of up to 800°C.

[0050] The present invention provides a method for preparing the high-temperature self-lubricating bushing described in the above technical solution, comprising the following steps:

[0051] Processing the high temperature resistant metal material into a bushing blank having a concave lubrication structure on the friction surface; the processing method includes 3D printing, precision casting or machining;

[0052] Providing a composite solid lubricant slurry, the composite solid lubricant slurry comprising a solid lubricant, a high temperature resistant binder and water;

[0053] Filling the composite solid lubricant slurry in the lubrication structure of the bushing blank, and sequentially performing first drying and curing and surface finishing to obtain a bushing body;

[0054] The composite solid lubricant slurry is applied to the friction surface of the bushing body, and after a second drying and curing, the high-temperature self-lubricating bushing is obtained.

[0055] The present invention processes a high temperature resistant metal material into a bushing blank having a concave lubrication structure on the friction surface. In the present invention, the high temperature resistant metal material includes a high entropy alloy, an iron-based high temperature alloy, a nickel-based high temperature alloy, a cobalt-based high temperature alloy or a titanium alloy, and the high entropy alloy, the iron-based high temperature alloy, the nickel-based high temperature alloy, the cobalt-based high temperature alloy and the titanium alloy are consistent with the above technical solution and will not be described in detail here.

[0056] In the present invention, the processing methods include 3D printing, precision casting or machining, wherein 3D printing uses selective laser melting (SLM) technology, with high temperature resistant metal material powder as raw material, and is mainly used to prepare bushing matrix with complex lubricating structure shape; precision casting uses investment casting technology, with conventional casting wax as wax mold, and uses high temperature resistant metal material casting master alloy block material as raw material, and is mainly used to prepare bushing matrix with relatively complex lubricating structure shape; machining uses high temperature resistant metal material rods or plates, castings or forgings that need to be finally heat treated, and is mainly used to prepare bushing matrix with relatively simple lubricating structure shape. In actual situations, high temperature resistant metal materials and corresponding processing methods are selected according to specific bushing structures and usage requirements.

[0057] The present invention has no special requirements on the process parameters of the 3D printing, precision casting and machining, and only needs to ensure that the bushing blank without cracks, deformation and high precision can be processed.

[0058] In the present invention, after the 3D printing is completed or the precision casting is performed, the surface of the obtained bushing needs to be machined to improve its dimensional accuracy and reduce its surface roughness.

[0059] The present invention provides a composite solid lubricant slurry, which includes a solid lubricant, a binder and water. In the present invention, the solid lubricant and the binder are consistent with the solid lubricant and the binder described in the above technical solution; the water is preferably distilled water. The present invention has no special requirements for the preparation method of the composite solid lubricant slurry, and the components in the slurry can be mixed evenly, such as preparing the composite solid lubricant slurry by ball milling or stirring; when the ball milling method is adopted, the ball milling is preferably carried out in a planetary ball mill, the speed of the ball mill is preferably 200 to 300 rpm, the ball milling time is preferably 2 to 8h, and the ball-to-material ratio is preferably 1:3; when the stirring method is adopted, the stirring is preferably carried out in a stirrer, the speed of the stirrer is preferably ≥60 rpm, and the stirring time is preferably ≥1h. According to actual application requirements, the viscosity of the slurry can be regulated by adjusting the solid phase content and water content of the composite solid lubricant slurry; and by adjusting the components of the solid lubricant and the binder and the ratio of the solid lubricant and the binder, it has both high high-temperature bonding strength and lubrication performance.

[0060] In the embodiment of the present invention, when preparing a high-temperature self-lubricating bushing that can be used in service at 500°C, the mass percentage of each component in the composite solid lubricant slurry is: solid lubricant 40-50%, binder 25-35%, water 25-30%. The solid lubricant includes the following mass percentage components: graphite 20-30%, molybdenum disulfide 20-30%, tungsten disulfide 10-15%, yellow lead oxide 20-30%, silver 15-20%; the high temperature resistant binder includes the following mass percentage components: silica sol 20-30%, sodium tetraborate 10-15%, sodium silicate 15-20%, boron trioxide 15-20%, aluminum dihydrogen phosphate 25-35%, and the silica sol is preferably an alkaline silica sol with a content of 40wt%.

[0061] In the embodiment of the present invention, when preparing a high-temperature self-lubricating bushing that can be used in service at 600°C, the mass percentage of each component in the composite solid lubricant slurry is: solid lubricant 20-25%, high temperature resistant binder 15-20%, water 60-70%. The solid lubricant includes the following mass percentage components: tungsten disulfide 10-15%, hexagonal boron nitride 15-20%, yellow lead oxide 40-50%, barium difluoride 15-20%, calcium difluoride 10-20%; the high temperature resistant binder includes the following mass percentage components: silica sol 20-30%, sodium tetraborate 15-20%, boron trioxide 15-20%, aluminum dihydrogen phosphate 25-35%, silicon dioxide 10-15%, and the silica sol is preferably an alkaline silica sol with a content of 40wt%.

[0062] In the embodiment of the present invention, when preparing a high-temperature self-lubricating bushing that can be used in service at 750°C, the mass percentage of each component in the composite solid lubricant slurry used is: solid lubricant 40-45%, high temperature resistant binder 25-30%, water 30-35%. The solid lubricant includes the following mass percentage components: hexagonal boron nitride 10-15%, yellow lead oxide 20-25%, silver 10-15%, barium difluoride 40-45%, calcium difluoride 10-20%, cerium trifluoride 3-10%; the high temperature resistant binder includes the following mass percentage components: silica sol 50-60%, sodium tetraborate 20-30%, boron trioxide 15-20%, aluminum trioxide 5-10%, the silica sol is preferably an acidic silica sol with a content of 30wt%, the present invention has no special requirements for the acidic silica sol, and the corresponding commercially available products known in the art can be used.

[0063] In the embodiment of the present invention, when preparing a high-temperature self-lubricating bushing that can be used in service at 800°C, the mass percentage of each component in the composite solid lubricant slurry is: solid lubricant 40-45%, high temperature resistant binder 25-30%, water 30-35%. The solid lubricant includes the following mass percentage components: hexagonal boron nitride 25-30%, yellow lead oxide 30-35%, silver 20-25%, chromium trioxide 10-15%, nickel monoxide 15-20%; the high temperature resistant binder includes the following mass percentage components: silica sol 50-60%, sodium tetraborate 20-30%, boron trioxide 15-20%, aluminum trioxide 5-10%, the silica sol is preferably 40wt% alkaline silica sol, the present invention has no special requirements for the alkaline silica sol, and the corresponding commercially available products known in the art can be used.

[0064] After obtaining the bushing blank and the composite solid lubricant slurry, the present invention fills the composite solid lubricant slurry in the lubrication structure of the bushing blank, and sequentially performs first drying and curing and surface finishing to obtain the bushing body.

[0065] In the present invention, the filling method is preferably vacuum suction injection, spraying or smearing to ensure that the composite solid lubricant slurry is completely filled in the lubricating structure. In the present invention, the vacuum suction injection is to immerse the bushing blank in the composite solid lubricant slurry, and then place it in an environment with a vacuum degree of ≤100Pa for more than 5 minutes to complete the filling, and remove the excess slurry on the bushing surface after the filling is completed. In the present invention, the spraying is to spray the composite solid lubricant slurry into the lubricating structure with a spray gun, and after the pits, grooves or holes of the lubricating structure are filled by spraying, the excess slurry on the bushing surface is removed. In the present invention, the smearing is to fill the composite solid lubricant slurry in the lubricating structure such as pits, grooves or holes by manual smearing, and remove the excess slurry on the surface after the smearing filling is completed. In the present invention, the vacuum suction injection is mainly used to fill lubricating structures with complex shapes, and the spraying and smearing are mainly used to fill lubricating structures with simpler shapes, such as blind holes, through holes, grooves, etc.

[0066] In the present invention, the first drying and curing is preferably staged drying and curing or continuous drying and curing; the staged drying and curing includes sequential drying and curing, the drying temperature is preferably 65-95°C, which can be 65, 70, 80, 90 or 95°C, the holding time is preferably more than 1h, which can be 1.5h, and the heating rate to the drying temperature is preferably ≤5°C / min, which can be 3°C / min; the curing temperature is preferably 280-400°C, which can be 300, 350 or 400°C, the holding time is preferably more than 1.5h, and the heating rate to the curing temperature is preferably ≤15°C / min. In the present invention, the continuous drying and curing is to complete the drying and curing treatment at one time; the continuous drying and curing is preferably carried out at 280-400°C, which can be 310, 350 or 400°C, the holding time is preferably more than 2h, which can be 3, 4 or 6h, and the heating rate to the temperature of continuous drying and curing is preferably ≤5°C / min. In the present invention, the temperature of the first drying and curing can ensure that the solid lubricant will not decompose or react with the metal matrix.

[0067] In the present invention, the surface finishing method is preferably: dry grinding the surface of the dried and solidified bushing material to make its size, shape and position tolerance and surface roughness meet the use requirements; dry grinding is adopted during the dry grinding process, and no grinding fluid, lubricating fluid or coolant in any form can be used to avoid chemical reaction with the solid lubricant, resulting in deterioration of its performance.

[0068] After obtaining the bushing body, the present invention applies the composite solid lubricant slurry on the friction surface of the bushing body, and obtains the high-temperature self-lubricating bushing through a second drying and curing process.

[0069] In the present invention, the application method is preferably spraying with a spray gun. The present invention obtains a slurry viscosity suitable for spraying by controlling the water content in the composite solid lubricant slurry; the spraying thickness is preferably 2 to 30 μm, which can be 2 μm, 5 μm, 10 μm, 20 μm or 30 μm.

[0070] In the present invention, the conditions for the second drying and curing are preferably the same as those for the first drying and curing, and will not be described in detail herein.

[0071] The present invention provides the application of the high-temperature self-lubricating bushing described in the above technical solution or the high-temperature self-lubricating bushing prepared by the preparation method described in the above technical solution in high-temperature sliding motion parts. The high-temperature self-lubricating bushing provided by the present invention can be applied to parts involving high-temperature sliding motion such as aircraft engines, gas turbines, combined cycle engines, etc., and can also prepare medium or large bushings, sleeves or sliding bearings and other parts, which are applied to parts involving high-temperature sliding motion in the fields of metallurgy, energy, chemical industry, material processing, etc.

[0072] Figure 1 The process flow chart of preparing the high-temperature self-lubricating bushing according to the embodiment of the present invention is as follows:

[0073] (1) Select the high-temperature resistant metal material of the bushing body and the properties of the material (powder material, block material or casting master alloy, etc.) according to the actual service conditions of the high-temperature self-lubricating bushing;

[0074] (2) According to the actual service conditions of the high-temperature self-lubricating bushing and the properties of the base material, the main structure of the bushing and the lubrication structure thereon are designed;

[0075] (3) using the bushing body material selected in step (1) to process the bushing blank, and processing the bushing body and the lubrication structure thereon;

[0076] (4) According to the actual service conditions of the high-temperature self-lubricating bushing, the composition of the slurry used for filling in the bushing lubrication structure is designed. The slurry includes a solid lubricant, a binder and water. The slurry is also used for the preparation of the subsequent surface lubrication layer;

[0077] (5) preparing the slurry according to the slurry formula designed in step (4), using a ball milling method or a stirring method to prepare the slurry;

[0078] (6) Filling the slurry prepared in step (5) into the bushing lubrication structure processed in step (3) by vacuum injection, spraying or smearing to ensure that the lubrication structure is completely filled with the slurry;

[0079] (7) After filling, the slurry in the bushing blank is dried and solidified to bond the solid lubricant to the lubrication structure of the bushing;

[0080] (8) After drying and curing, the bushing is ground and processed to ensure that its size, shape and position tolerance and surface finish meet the requirements;

[0081] (9) After finishing, the slurry prepared in step (5) is sprayed on the friction surface of the bushing to prepare a layer of surface lubricating coating. After the surface lubricating coating is dried and solidified, a high-temperature self-lubricating bushing product is obtained.

[0082] In order to further illustrate the present invention, the high-temperature self-lubricating bushing provided by the present invention and its preparation method and application are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present invention.

[0083] Example 1

[0084] This embodiment provides a high-temperature self-lubricating bushing with a very complex lubrication structure (such as Figure 2 As shown in the figure, the overall structure and the lubrication structure of the friction surface are a three-dimensional hollow structure, which has excellent characteristics such as light weight, high strength and low friction, but it is difficult to prepare such a complex structure by conventional precision casting or machining. Therefore, this embodiment uses 3D printing technology to prepare the bushing blank.

[0085] The main dimensions of the bushing are: inner diameter 20mm, outer diameter 30mm, height 30mm, flange outer diameter 36mm, thickness 5mm. The service conditions of the bushing are: maximum service temperature 800℃, maximum radial load 500N, reciprocating swing, swing angle ±30 degrees, maximum swing speed 0.2m / s.

[0086] The specific preparation method of the high temperature self-lubricating bushing is as follows:

[0087] (1) Nickel-based high-temperature alloy GH3536 powder is selected as the base high-temperature resistant metal material for the high-temperature self-lubricating bushing. The maximum operating temperature of GH3536 can reach 900°C, and it has good strength at 800°C, so it can be used as the base material of the bushing that serves at 800°C. When 3D printing the bushing blank, GH3536 powder material is selected, and its particle size distribution is 15 to 53μm. Spherical powder specially used for 3D printing is selected, and the purity requirement is >99.8%, and the proportion of spherical powder is >90%.

[0088] (2) According to the actual service conditions of the high-temperature self-lubricating bushing and the properties of the nickel-based high-temperature alloy GH3536 matrix material, the bushing structure is designed as follows Figure 2As shown. The overall structure and lubrication structure of the bushing both adopt a hollow three-dimensional structure, that is, the main structure and lubrication structure of the bushing are the same, both of which are hollow lattice structures. The parameters of the lattice structure are as follows: the cell is a cube with a side length of 0.5mm, the structure is body-centered cubic, and the connecting rods between the lattices are solid cylinders with a diameter of 0.3mm. The hollow lattice structure is light and high in strength. The pores of the lattice structure are the lubrication structure, which is used to fill solid lubricants. The percentage of the area occupied by the lubrication structure on the friction surface of the bushing is 68.9% of the total friction surface area. The high proportion of the lubrication structure can ensure its excellent lubrication performance.

[0089] (3) The nickel-based high-temperature alloy GH3536 powder material selected in step (1) is used to manufacture the bushing blank using SLM 3D printing technology to manufacture the bushing in one go. High-purity argon is used as a protective gas during the printing process to prevent oxidation of the material and contamination by impurities during the printing process. There are no special requirements for parameters such as laser power, scanning power, and powder thickness during the printing process, as long as various microstructures in the bushing can be printed without deformation. After printing, remove the excess powder and use machining for post-processing to remove burrs and excess materials on the surface so that its size and surface roughness meet the requirements to obtain a bushing blank.

[0090] (4) According to the actual service conditions of the high-temperature self-lubricating bushing, the components of the slurry used for filling in the bushing lubrication structure are designed. Since the bushing requires a service temperature of up to 800°C, a maximum radial load of 500N, and a maximum swing speed of 0.2m / s, it is necessary to design a slurry with excellent high temperature resistance and oxidation resistance. The mass percentage of each component in the slurry used in this embodiment is: 45% of high temperature resistant solid lubricant (particle size ≤100μm), 25% of high temperature resistant binder, and 30% of distilled water; wherein the mass percentage of each component in the high temperature resistant solid lubricant is: 25% hexagonal boron nitride, 30% yellow lead oxide, 20% silver, 10% chromium trioxide, and 15% nickel monoxide; the mass percentage of each component in the high temperature resistant binder is: 50% silica sol (40wt% alkaline silica sol), 20% sodium tetraborate, 20% boron trioxide, and 10% aluminum trioxide. According to the above proportions, the components of the slurry are accurately weighed using a balance.

[0091] (5) After weighing the various components of the slurry according to the slurry formula designed in step (4), the slurry is placed in a stainless steel ball mill and the slurry is prepared by ball milling. The ball-to-material ratio is 1:3, the ball mill speed is 300 rpm, and the ball milling time is 6 to 8 hours. After ensuring that the various components of the slurry are evenly mixed, the slurry is taken out and placed in a beaker for later use.

[0092] (6) Place the 3D printed and post-processed bushing blank in the slurry prepared in step (5) and fill it by vacuum injection. When filling, completely immerse the bushing blank in the slurry, then place the beaker containing the slurry and the bushing in a sealed container that can be vacuumed, and then vacuum the container. The vacuum degree is required to be ≤100Pa. After vacuuming for 10 minutes, the filling is completed. After filling, take out the bushing and remove the excess slurry on its surface.

[0093] (7) Place the filled bushing blank in a box-type resistance furnace to dry and solidify the slurry in the bushing blank. A staged drying and solidification method is used, and the steps are: heating to 95°C at a heating rate of 3°C / min, and then keeping at this temperature for 1.5 hours to complete the drying process; then heating to 400°C at a heating rate of 15°C / min for solidification, the solidification time is 1.5 hours, and it is taken out after solidification.

[0094] (8) After drying and curing, the bushing blank is ground and processed to meet the requirements of size, shape and position tolerance and surface finish. Dry grinding is adopted during the grinding process, and no grinding fluid, lubricant or coolant can be used.

[0095] (9) After finishing, a layer of surface lubricating coating is prepared on the friction surface of the bushing. The surface lubricating coating is prepared by spraying slurry with a spray gun, and the spraying slurry used is the slurry prepared in step (5) and diluted with 40% distilled water. During spraying, the friction surface is sprayed repeatedly with a spray gun to keep its thickness at about 20μm. After spraying, it is dried and cured, and the drying and curing method is the same as step (7). After the surface lubricating coating is dried and cured, a high-temperature self-lubricating bushing product is obtained.

[0096] The friction and wear performance of the finished bushing is tested by a special high-temperature bearing friction tester. During the test, GH4141 alloy is used as the test shaft and bushing seat. The test conditions are as follows: radial load 800N (increase the test load to ensure the safety of the bushing in actual service), the movement form is reciprocating swing, the swing angle is ±30 degrees, the swing speed is 0.2m / s, the test temperature is 750℃, 800℃ and 850℃ respectively, and the reciprocating swing test is stopped after 10,000 times. During the test, the friction coefficient is automatically recorded by the test machine, and the wear amount is measured with a micrometer after the test is completed.

[0097] The test results show that the friction coefficients of the finished bushing at 750℃, 800℃ and 850℃ are ≤0.25, ≤0.23 and ≤0.17 respectively, and the average wear amount is 0.13mm, 0.10mm and 0.15mm respectively. After the test, the bushing structure is intact without deformation, cracking, crushing and other failure phenomena. It can be seen that the bushing has excellent load-bearing capacity and tribological properties at high temperatures.

[0098] Example 2

[0099] This embodiment provides a self-lubricating bushing with a relatively complex lubrication structure. The main dimensions of the bushing are: inner diameter 32mm, outer diameter 48mm, height 56mm, flange outer diameter 64mm, thickness 8mm. The service conditions of the bushing are: maximum service temperature 750℃, maximum radial load 30000N, reciprocating swing, swing angle ±20 degrees, and maximum swing speed 0.1m / s.

[0100] The friction surface of the bushing is its inner and outer surfaces and flange surface. The lubrication structure on the friction surface is a square through hole with a side length of 4mm. The lubrication structure near the edge is a triangular through hole with a right-angle side length of 4mm. The detailed structure is as follows Figure 3 As shown. Since the lubrication structure of the bushing is relatively complex, the present embodiment adopts precision casting technology to prepare the bushing blank. In addition, the precision casting technology can form a large batch of bushing blanks with high precision at one time.

[0101] The specific preparation method of the high temperature self-lubricating bushing is as follows:

[0102] (1) The FCC structured CoCrFeNi high entropy alloy is selected as the high temperature resistant metal material for the high temperature self-lubricating bushing. The CoCrFeNi high entropy alloy has good structural stability, moderate strength and hardness in the range of 700-900°C. It will not cause friction damage to the bushing shaft or shaft seat during use, so it can be used as the bushing matrix material for service at 750°C. The investment casting method is used for precision casting, and the CoCrFeNi high entropy alloy casting block master alloy is used as the raw material, and its impurity content is required to be less than 0.2%.

[0103] (2) According to the actual service conditions of the high-temperature self-lubricating bushing and the material properties of the CoCrFeNi high-entropy alloy, the bushing structure is designed as follows Figure 3As shown. The lubrication structure of the bushing is a square through hole with a side length of 4mm on the friction surface. The lubrication structure near the edge is a triangular through hole with a right-angle side length of 4mm. The lubrication structure is used to fill solid lubricants. The percentage of the area occupied by the lubrication structure on the friction surface of the bushing is 60.3% of the entire friction surface area. The high proportion of the lubrication structure can ensure its excellent lubrication performance.

[0104] (3) The CoCrFeNi high entropy alloy block material for casting selected in step (1) is used to precisely cast a bushing blank in one go using investment casting technology. During the casting process, a wax mold of the bushing blank is made using high-temperature wax for precision casting, and then the CoCrFeNi high entropy alloy bushing blank is obtained after shell making, dewaxing, roasting, casting, and shell removal. There are no special requirements for casting parameters during the precision casting process, as long as a crack-free, deformation-free, and high-precision blank can be cast. After the precision casting is completed, machining is used for post-processing to remove burrs and excess materials on the surface so that its size and surface roughness meet the requirements.

[0105] (4) According to the actual service conditions of the high-temperature self-lubricating bushing, the components of the slurry used for filling in the bushing lubrication structure are designed. Since the bushing requires a service temperature of up to 750°C, a maximum radial load of 30,000N, and a maximum swing speed of 0.1m / s, it is necessary to design a slurry with excellent load-bearing capacity, high temperature resistance, oxidation resistance, self-lubricating performance, and wear resistance. The mass percentage of each component in the slurry used in this embodiment is: 40% of high-temperature resistant solid lubricant (particle size ≤ 100μm), 30% of high-temperature resistant binder, and 30% of distilled water; wherein the mass percentage of each component in the high-temperature resistant solid lubricant is: 10% hexagonal boron nitride, 20% yellow lead oxide, 15% silver, 40% barium difluoride, 10% calcium difluoride, and 5% cerium trifluoride; the mass percentage of each component in the high-temperature resistant binder is: 50% silica sol (30wt% acidic silica sol), 25% sodium tetraborate, 20% boron trioxide, and 5% aluminum trioxide. According to the above ratio, each component of the slurry is accurately weighed using a balance.

[0106] (5) After weighing the various components of the slurry according to the slurry formula designed in step (4), the slurry is placed in a stainless steel ball mill and the slurry is prepared by ball milling. The ball-to-material ratio is 1:3, the ball mill speed is 300 rpm, and the ball milling time is 6 to 8 hours. After ensuring that the various components of the slurry are evenly mixed, the slurry is taken out and placed in a beaker for later use.

[0107] (6) Place the bushing blank that has been precision cast and post-processed into the slurry prepared in step (5) and fill it by vacuum injection. When filling, completely immerse the bushing blank in the slurry, then place the beaker containing the slurry and the bushing in a sealed container that can be evacuated, and then evacuate the container. The vacuum degree is required to be ≤100Pa. After evacuating for 10 minutes, the filling is completed. After filling, take out the bushing and remove the excess slurry on its surface.

[0108] (7) Place the filled bushing blank in a box-type resistance furnace to dry and solidify the slurry in the bushing blank. A continuous drying and solidification method is used, and the process flow is to heat the bushing blank to 350°C at a heating rate of 3°C / min, and then keep the temperature at this temperature for 4 hours to complete the drying and solidification treatment at one time. After drying and solidification, take it out for use.

[0109] (8) After drying and curing, the bushing blank is ground and processed to meet the requirements of size, shape and position tolerance and surface finish. Dry grinding is adopted during the grinding process, and no grinding fluid, lubricant or coolant can be used.

[0110] (9) After finishing, a layer of surface lubricating coating is prepared on the friction surface of the bushing. The surface lubricating coating is prepared by spraying slurry with a spray gun, and the spraying slurry used is the slurry prepared in step (5) and diluted with 40% distilled water. During spraying, the friction surface is sprayed repeatedly with a spray gun to keep its thickness at about 30μm. After spraying, it is dried and cured, and the drying and curing method is the same as step (7). After the surface lubricating coating is dried and cured, a high-temperature self-lubricating bushing product is obtained.

[0111] The friction and wear performance of the finished bushing is tested by a special high-temperature bearing friction tester. During the test, GH4141 alloy is used as the test shaft and bushing seat. The test conditions are as follows: radial load 31000N (increase the test load to ensure the safety of the bushing in actual service), the movement form is reciprocating swing, the swing angle is ±20 degrees, the swing speed is 0.1m / s, the test temperature is 700℃, 750℃ and 800℃ respectively, and the reciprocating swing test is stopped after 10,000 times. During the test, the friction coefficient is automatically recorded by the test machine, and the wear is measured with a micrometer after the test is completed.

[0112] The test results show that the friction coefficient of the bushing at 700℃, 750℃ and 800℃ is ≤0.20, ≤0.18 and ≤0.15 respectively, and the average wear of the bushing at the three temperatures is less than 0.16mm. After the test, the bushing structure is intact, and there is no deformation, cracking, crushing and other failure phenomena. It can be seen that the bushing has excellent load-bearing capacity and tribological properties at high temperatures, especially under extremely harsh conditions such as high temperature and heavy load. It has excellent comprehensive performance.

[0113] Example 3

[0114] This embodiment provides a self-lubricating bushing with a relatively simple lubrication structure (such as Figure 4 The main dimensions of the bushing are: inner diameter 20mm, outer diameter 24mm, height 32mm, flange outer diameter 28mm, single-side thickness 2mm. The service conditions of the bushing are: maximum service temperature 600℃, maximum radial load 20000N, reciprocating swing, swing angle ±12 degrees, maximum swing speed 0.05m / s.

[0115] The friction surface of the bushing is its inner and outer surfaces. The lubrication structure on the friction surface is a circular through hole with a diameter of 1.2 mm. The circular through holes are evenly arranged on the friction surface. The detailed structure is as follows Figure 4 As shown. Since the lubrication structure of the bushing is relatively simple, the bushing blank is prepared by machining technology in this embodiment.

[0116] The specific preparation method of the high temperature self-lubricating bushing is as follows:

[0117] (1) Cobalt-based high-temperature alloy GH5605 is selected as the base high-temperature resistant metal material of the high-temperature self-lubricating bushing. Cobalt-based high-temperature alloy GH5605 has good oxidation resistance, strength and plastic toughness within the range of 1000°C, and its hardness is moderate. It will not cause friction damage to the bushing shaft or shaft seat during use, so it can be used as a bushing base material for service at 600°C. This embodiment uses commercial GH5605 rods as raw materials, and its heat treatment state is a solid solution state after hot rolling, and the rod diameter is greater than 35mm.

[0118] (2) According to the actual service conditions of the high-temperature self-lubricating bushing and the performance of the cobalt-based high-temperature alloy GH5605 material, the bushing structure is designed as follows Figure 4 As shown. The lubrication structure of the bushing is to open a circular through hole with a diameter of 1.2mm on the friction surface, and the circular through holes are all centripetal holes. The percentage of the area occupied by the lubrication structure on the friction surface of the bushing is 49.6% of the entire friction surface area. The high proportion of the lubrication structure can ensure its excellent lubrication performance.

[0119] (3) The cobalt-based high-temperature alloy GH5605 bar selected in step (1) is used to machine the main structure and lubrication structure of the bushing. The machining process uses the existing mature process parameters of GH5605, and after the machining is completed, it is sufficient to ensure that its size and surface roughness meet the requirements.

[0120] (4) According to the actual service conditions of the high-temperature self-lubricating bushing, the components of the slurry used for filling in the bushing lubrication structure are designed. Since the bushing requires a maximum service temperature of 600°C, a maximum radial load of 20,000N, and a maximum swing speed of 0.05m / s, it is necessary to design a slurry with good load-bearing capacity, lubrication performance, high temperature resistance and oxidation resistance. The mass percentage of each component in the slurry used in this embodiment is: 20% high-temperature resistant solid lubricant (particle size ≤ 100μm), 20% high-temperature resistant binder, and 60% distilled water. Among them, the mass percentage content of each component in the high-temperature resistant solid lubricant is: 15% tungsten disulfide, 15% hexagonal boron nitride, 40% yellow lead oxide, 15% barium difluoride, and 15% calcium difluoride; the mass percentage content of each component in the high-temperature resistant binder is: 20% silica sol (40wt% alkaline silica sol), 15% sodium tetraborate, 20% boron trioxide, 30% aluminum dihydrogen phosphate, and 15% silicon dioxide. According to the above ratio, each component of the slurry is accurately weighed out using a balance and then mixed.

[0121] (5) According to the slurry formula designed in step (4), each component of the slurry is weighed and placed in a plastic bucket, and mixed by stirring. A conventional commercial small slurry mixer is used, with a speed of 100 rpm for stirring for 2 hours. After the stirring is completed, the slurry is taken out for use.

[0122] (6) Use a spraying method to spray the slurry prepared above into the lubrication structure of the bushing blank obtained by machining in step (3). Since the bushing lubrication structure prepared in this embodiment is a circular through hole with a diameter of 1.2 mm, the slurry can be directly sprayed and filled into the lubrication structure by a spraying method. There are no special requirements during the spraying process, and it is sufficient to ensure that each circular hole of the lubrication structure is completely filled. After the spraying and filling is completed, the excess slurry on the bushing surface is removed and set aside.

[0123] (7) Place the filled bushing blank in a box-type resistance furnace to dry and solidify the slurry in the bushing blank. A continuous drying and solidification method is used, and the process flow is to heat the bushing blank to 400°C at a heating rate of 5°C / min, and then keep the temperature at this temperature for 3 hours to complete the drying and solidification treatment at one time. After drying and solidification, take it out for use.

[0124] (8) After drying and curing, the bushing blank is ground and processed to meet the requirements of size, shape and position tolerance and surface finish. Dry grinding is adopted during the grinding process, and no grinding fluid, lubricant or coolant can be used.

[0125] (9) After finishing, a layer of surface lubricating coating is prepared on the friction surface of the bushing. The surface lubricating coating is prepared by spraying slurry with a spray gun, and the spraying slurry used is the slurry prepared in step (5) and diluted with 10% distilled water. During spraying, the friction surface is sprayed repeatedly with a spray gun to keep its thickness at about 20μm. After spraying, it is dried and cured, and the drying and curing method is the same as step (7). After the surface lubricating coating is dried and cured, a high-temperature self-lubricating bushing finished product is obtained.

[0126] The friction and wear performance of the finished bushing was tested using a special high-temperature bearing friction tester. During the test, GH4169 alloy was used as the test shaft and bushing seat. The test conditions were as follows: radial load 21000N (increase the test load to ensure the safety of the bushing in actual service), the movement form was reciprocating swing, the swing angle was ±12 degrees, the swing speed was 0.05m / s, the test temperatures were 550℃, 600℃ and 650℃ respectively, and the test was stopped after 25,000 reciprocating swing tests. During the test, the friction coefficient was automatically recorded by the test machine, and the wear was measured with a micrometer after the test was completed.

[0127] The test results show that the friction coefficients of the bushing at 550℃, 600℃ and 650℃ are ≤0.22, ≤0.21 and ≤0.19 respectively, and the average wear of the bushing at the three temperatures is less than 0.12mm. After the test, the bushing structure is intact, and there is no deformation, cracking, crushing and other failure phenomena. It can be seen that the bushing has excellent load-bearing capacity and tribological properties at high temperatures, especially under high temperature and heavy load conditions.

[0128] Example 4

[0129] This embodiment provides a self-lubricating bushing with a relatively simple lubrication structure (such as Figure 5 The main dimensions of the bushing are: inner diameter 14mm, outer diameter 17mm, height 16mm, flange outer diameter 20mm, single-side thickness 1.5mm. The service conditions of the bushing are: maximum service temperature 500℃, maximum radial load 1000N, reciprocating swing, swing angle ±15 degrees, maximum swing speed 0.2m / s.

[0130] The friction surface of the bushing is its inner surface. The lubrication structure on the friction surface is a rectangular groove with a width of 1.0 mm and a depth of 0.5 mm. The groove is a spirally cross-arranged structure around the central axis of the bushing. The detailed structure is as follows: Figure 5 As shown. Since the lubrication structure of the bushing is relatively simple, the bushing blank is prepared by machining technology in this embodiment.

[0131] The specific preparation method and process of the high temperature self-lubricating bushing are as follows:

[0132] (1) High temperature resistant titanium alloy Ti60 is selected as the high temperature resistant metal material of the high temperature self-lubricating bushing. Ti60 alloy has excellent mechanical properties and oxidation resistance in the range below 600°C, so it can be used as the bushing base material for service at 500°C. This embodiment uses commercial Ti60 rods as raw materials, and its heat treatment state is solid solution + aging treatment, and the rod diameter is greater than 22mm.

[0133] (2) According to the actual service conditions of the high-temperature self-lubricating bushing and the performance of Ti60 material, the bushing structure is designed as follows Figure 5 As shown. The lubrication structure of the bushing is a rectangular groove with a width of 1.0mm and a depth of 0.5mm on the friction surface. The groove is a spirally cross-arranged structure around the central axis of the bushing. The percentage of the area occupied by the lubrication structure on the friction surface of the bushing is 27.8% of the entire friction surface area, which can ensure that it has good lubrication performance.

[0134] (3) The Ti60 rod selected in step (1) is used to machine the main structure and lubrication structure of the bushing. The machining process uses the existing mature process parameters of the Ti60 material, and after the machining is completed, it is sufficient to ensure that its size and surface roughness meet the requirements.

[0135] (4) According to the actual service conditions of the high-temperature self-lubricating bushing, the components of the slurry used for filling in the bushing lubrication structure are designed. Since the bushing requires a maximum service temperature of 500°C, a maximum radial load of 1000N, and a maximum swing speed of 0.2m / s, it is necessary to design a slurry with good lubrication performance, high temperature resistance and oxidation resistance. The mass percentage of each component in the slurry used in this embodiment is: 45% of high temperature resistant solid lubricant (particle size ≤ 100μm), 30% of high temperature resistant binder, and 25% of distilled water. Among them, the mass percentage content of each component in the high temperature resistant solid lubricant is: 30% graphite, 20% molybdenum disulfide, 15% tungsten disulfide, 20% yellow lead oxide, and 15% silver; the mass percentage content of each component in the high temperature resistant binder is: 20% silica sol (40wt% alkaline silica sol), 15% sodium tetraborate, 20% sodium silicate, 20% boron trioxide, and 25% aluminum dihydrogen phosphate. According to the above ratio, each component of the slurry is accurately weighed out using a balance and then mixed.

[0136] (5) According to the slurry formula designed in step (4), each component of the slurry is weighed and placed in a plastic bucket, and mixed by stirring. A conventional commercial small slurry mixer is used, with a speed of 200 rpm for stirring for 1 hour. After the stirring is completed, the slurry is taken out for use.

[0137] (6) The slurry prepared above is sprayed into the lubricating structure of the bushing blank obtained by machining in step (3) by manual coating. Since the bushing lubricating structure prepared in this embodiment is a rectangular groove with a width of 1.0 mm and a depth of 0.5 mm, and is on the inner surface of the bushing, it is easy to fill the slurry into the lubricating structure by manual coating. There are no special requirements during the coating and filling process, and it is sufficient to ensure that the lubricating structure is completely filled. After the coating and filling are completed, remove the excess slurry on the bushing surface.

[0138] (7) Place the filled bushing blank in a box-type resistance furnace to dry and solidify the slurry in the bushing blank. A continuous drying and solidification method is used, and the process flow is to heat the bushing blank to 310°C at a heating rate of 3°C / min, and then keep it at this temperature for 6 hours to complete the drying and solidification treatment at one time. After drying and solidification, take it out for use.

[0139] (8) After drying and curing, the bushing blank is ground and processed to meet the requirements of size, shape and position tolerance and surface finish. Dry grinding is adopted during the grinding process, and no grinding fluid, lubricant or coolant can be used.

[0140] (9) After finishing, a layer of surface lubricating coating is prepared on the friction surface of the bushing. The surface lubricating coating is prepared by spraying slurry with a spray gun, and the spraying slurry used is the slurry prepared in step (5) and diluted with 60% distilled water. During spraying, the friction surface is sprayed repeatedly with a spray gun to keep its thickness at about 20μm. After spraying, it is dried and cured, and the drying and curing method is the same as step (7). After the surface lubricating coating is dried and cured, a high-temperature self-lubricating bushing product is obtained.

[0141] The friction and wear performance of the finished bushing was tested using a special high-temperature bearing friction tester. During the test, GH4169 alloy was used as the test shaft and bushing seat. The test conditions were as follows: radial load 1200N (increase the test load to ensure the safety of the bushing in actual service), the movement form was reciprocating swing, the swing angle was ±15 degrees, the swing speed was 0.2m / s, the test temperatures were 450℃, 500℃ and 550℃ respectively, and the test was stopped after 10,000 reciprocating swing tests. During the test, the friction coefficient was automatically recorded by the test machine, and the wear was measured with a micrometer after the test was completed.

[0142] The test results show that the friction coefficients of the bushing at 450℃, 500℃ and 550℃ are ≤0.23, ≤0.21 and ≤0.19 respectively, and the average wear of the bushing at the three temperatures is less than 0.11mm. After the test, the bushing structure is intact without deformation, cracking, crushing and other failure phenomena. It can be seen that the bushing has excellent load-bearing capacity and tribological properties at high temperatures.

[0143] It should be pointed out that: the bushing structures given in the above embodiments are all cylindrical bushings with a flange at one end, but it cannot be understood that the present invention only protects bushings of this structure. The technical solution provided by the present invention can also be applied to cylindrical bushings without flanges or bushings with flanges at both ends, and can also be applied to bushings, sliding bearings, sliding supports and other components with other special structures. In addition, the movement forms of the bushings given in the above embodiments are all reciprocating swing forms, but it cannot be understood that the technical solution provided by the present invention is only applicable to this kind of movement mode. The technical solution provided by the present invention can also be applied to the movement forms of full circle rotation or sliding along the axis of the bushing, and can also be applied to the composite movement forms of both reciprocating swing and sliding along the axis. All sliding parts involving the "metal body + lubrication structure + lubrication coating" structure provided by the present invention in high temperature conditions above 300°C, or improved structures based on this, belong to the protection scope of the present invention.

[0144] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A high temperature self-lubricating bushing, characterized in that: It comprises a high temperature resistant metal bushing body, a lubricating coating arranged on the friction surface of the high temperature resistant metal bushing body, and a plurality of lubricating structures recessed in the friction surface of the high temperature resistant metal bushing body, wherein the lubricating structures are filled with a composite solid lubricant; The temperature resistance of the high temperature resistant metal bushing body is ≥300°C and the hardness is 100-500HV; The composition of the composite solid lubricant and lubricating coating includes a solid lubricant and a binder; the solid lubricant in the composite solid lubricant and lubricating coating includes one or more of graphite, molybdenum disulfide, tungsten disulfide, silver, hexagonal boron nitride, yellow lead oxide, barium difluoride, calcium difluoride, cerium trifluoride, chromium trioxide and nickel monoxide, and the binder in the composite solid lubricant and lubricating coating includes one or more of silica sol, sodium tetraborate, boron trioxide, aluminum dihydrogen phosphate, sodium silicate, aluminum trioxide and silicon dioxide.

2. The high temperature self-lubricating bushing according to claim 1, characterized in that: The high temperature resistant metal bushing body comprises a high entropy alloy, an iron-based high temperature alloy, a nickel-based high temperature alloy, a cobalt-based high temperature alloy or a titanium alloy.

3. The high temperature self-lubricating bushing according to claim 1, characterized in that: The sum of the areas of all lubrication structures is 10 to 70% of the total area of ​​the friction surface of the high temperature resistant metal bushing body.

4. The high temperature self-lubricating bushing according to claim 1 or 3, characterized in that: The shape of each lubricating structure is independently a pit, a hole or a groove, and the hole is a circular hole or a polygonal hole; each lubricating structure independently penetrates or does not penetrate the high temperature resistant metal bushing body.

5. The high temperature self-lubricating bushing according to claim 4, characterized in that: The various lubrication structures are independent of each other or connected together.

6. The high temperature self-lubricating bushing according to claim 1, characterized in that: The particle size of the solid lubricant in the composite solid lubricant and the lubricating coating is ≤100 μm.

7. The high temperature self-lubricating bushing according to claim 1, characterized in that: The thickness of the lubricating coating is 2-30 μm.

8. The method for preparing a high temperature self-lubricating bushing according to any one of claims 1 to 7, characterized in that: The following steps are involved: Processing the high temperature resistant metal material into a bushing blank having a concave lubrication structure on the friction surface; the processing method includes 3D printing, precision casting or machining; Providing a composite solid lubricant slurry, the composite solid lubricant slurry comprising a solid lubricant, a binder and water; Filling the composite solid lubricant slurry in the lubrication structure of the bushing blank, and sequentially performing first drying and curing and surface finishing to obtain a bushing body; The composite solid lubricant slurry is applied to the friction surface of the bushing body, and after a second drying and curing, the high-temperature self-lubricating bushing is obtained.

9. The preparation method according to claim 8, characterized in that: The first drying and curing and the second drying and curing are segmented drying and curing or continuous drying and curing; the segmented drying and curing include sequential drying and curing, the drying temperature is 65-95°C, the insulation time is more than 1 hour, the curing temperature is 280-400°C, and the insulation time is more than 1.5 hours; the continuous drying and curing is carried out at 280-400°C, and the insulation time is more than 2 hours.

10. Use of the high-temperature self-lubricating bushing according to any one of claims 1 to 7 or the high-temperature self-lubricating bushing prepared by the preparation method according to claim 8 or 9 in high-temperature sliding motion parts.

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