Preparation method of wear-resistant self-lubricating composite material for robot joint

Abstract

The application discloses a preparation method of a wear-resistant self-lubricating composite material for a robot joint and relates to the technical field of self-lubricating composite materials, and comprises the following steps: performing surface activation treatment on short carbon fibers to form an interface anchoring layer on the surfaces of the short carbon fibers; mixing the short carbon fibers with the interface anchoring layer with a layered solid lubricating phase dispersion liquid to form a layered lubricating layer outside the interface anchoring layer; forming a polyaryletherketone compatible confinement layer outside the layered lubricating layer to obtain a load / lubricating composite unit; preparing a surface layer material, a transition layer material and a core layer material with different mass contents of the load / lubricating composite unit; and sequentially laying the surface layer material, the transition layer material and the core layer material to obtain the wear-resistant self-lubricating composite material for the robot joint after hot pressing. The application can improve the spatial synergistic effect of the reinforcing phase and the lubricating phase, reduce the migration and agglomeration of the lubricating phase, and enhance the continuous lubricating supply capacity of the friction surface, so that the wear-resistant self-lubricating property and the overall load-bearing strength of the composite material are considered.

Description

Technical Field

[0001] This invention relates to the field of self-lubricating composite materials technology, and specifically to a method for preparing a wear-resistant self-lubricating composite material for robot joints. Background Technology

[0002] Components such as bushings, bushings, gaskets, and sliding supports in robot joints are typically subjected to frictional conditions during operation, including reciprocating oscillation, low-speed heavy loads, and intermittent start-stop cycles. Therefore, materials must possess good wear resistance, self-lubrication, mechanical load-bearing capacity, and long-term frictional stability. Poly(etheretherketone) materials, such as poly(etheretherketone) and poly(etherketoneketone) ketones, are often used as matrix materials for wear-resistant and self-lubricating composite materials for robot joints due to their good heat resistance, wear resistance, and mechanical properties.

[0003] In existing technologies, to improve the tribological properties of polyaryletherketone (PAEK)-based composites, short-cut carbon fibers, ceramic particles, and other reinforcing phases are typically added to the matrix to enhance load-bearing capacity. Simultaneously, solid lubricating phases such as molybdenum disulfide, tungsten disulfide, hexagonal boron nitride, graphite, or graphene are added to reduce the coefficient of friction. However, these reinforcing and lubricating phases are often added to the PAEK matrix through direct blending or random dispersion, resulting in a lack of stable spatial bonding. This makes it difficult for the load-bearing capacity of the reinforcing phase and the low-shear friction-reducing effect of the lubricating phase to synergistically exert their effects at the friction interface. Furthermore, the solid lubricating phase is prone to migration, agglomeration, or random redispersibility during mixing and hot pressing. When the lubricating phase content is low, the lubrication supply to the friction surface is insufficient; when the lubricating phase content is high, it easily disrupts the continuity of the PAEK matrix and forms weak interfaces, thus affecting the material's mechanical strength and long-term wear resistance stability. Therefore, existing PAEK-based wear-resistant self-lubricating composites typically suffer from the problem of simultaneously achieving friction reduction, wear resistance, and load-bearing strength.

[0004] Furthermore, wear on the friction components of robot joints primarily occurs in areas close to the friction surface, while areas farther away bear more of the support and load-bearing functions. Existing composite materials with uniformly distributed fillers are difficult to adjust in terms of material structure according to the functional requirements of different regions along the thickness direction, easily leading to problems such as insufficient surface lubrication supply or excessive overall filler causing a decrease in material strength. Summary of the Invention

[0005] One objective of this invention is to provide a method for preparing wear-resistant self-lubricating composite materials for robot joints, thereby solving the technical problems in the prior art where the reinforcing phase and lubricating phase in polyarylether ketone-based wear-resistant self-lubricating composite materials are mostly randomly dispersed and lack spatial coordination, resulting in easy migration and aggregation of the lubricating phase, unstable long-term lubrication supply to the friction surface, and difficulty in simultaneously achieving wear-resistant self-lubricating performance and overall load-bearing strength.

[0006] Another objective of this invention is to create a layered gradient distribution of load-bearing / lubricating composite units in the composite material along a direction away from the friction surface, thereby achieving a balance between surface lubrication supply, transition layer stress buffering, and core layer load-bearing support.

[0007] According to the purpose of this invention, a method for preparing a wear-resistant self-lubricating composite material for robot joints is provided, comprising the following steps: Surface activation treatment of short-cut carbon fibers; The surface-activated short carbon fibers are mixed with an interface modification solution, and after solid-liquid separation, washing and drying, an interface anchoring layer is formed on the surface of the short carbon fibers. Short carbon fibers with the interface anchoring layer formed thereon are mixed with a layered solid lubricating phase dispersion, so that the layered solid lubricating phase is attached to the outer peripheral surface of the short carbon fibers through the interface anchoring layer, thereby forming a layered lubricating layer on the outside of the interface anchoring layer. The short-cut carbon fibers with the layered lubricating layer are coated in a polyaryletherketone compatible confinement liquid to form a polyaryletherketone compatible confinement layer on the outside of the layered lubricating layer, thereby obtaining a load-bearing / lubricating composite unit. The load-bearing / lubricating composite unit is mixed with a polyaryletherketone matrix to prepare surface materials, transition layer materials, and core layer materials with different mass contents of load-bearing / lubricating composite units. The surface layer material, the transition layer material, and the core layer material are sequentially laid out from the side closest to the friction surface to the side furthest from the friction surface. After hot pressing, a wear-resistant self-lubricating composite material for robot joints with a layered gradient distribution of load-bearing / lubricating composite units along a direction perpendicular to the friction surface is obtained; wherein... The mass content of the load-bearing / lubricating composite unit in the surface layer material is higher than that in the transition layer material, and the difference between the two mass contents is any value between 6% and 12%. The mass content of the load-bearing / lubricating composite unit in the transition layer material is higher than that in the core layer material, and the difference between the two mass contents is any value between 5% and 10%.

[0008] Optionally, the surface layer material contains 22%-32% by mass of the load-bearing / lubrication composite unit, the transition layer material contains 14%-23% by mass of the load-bearing / lubrication composite unit, and the core layer material contains 7%-15% by mass of the load-bearing / lubrication composite unit.

[0009] Optionally, the thickness ratio of the surface material, the transition layer material, and the core material is any value in the range of 1:(1-3):(2-6).

[0010] Optionally, the thickness of the layered lubricating layer is 80 nm-2 μm, the thickness of the polyaryletherketone compatibility confinement layer is 50 nm-1 μm, and the thickness of the polyaryletherketone compatibility confinement layer is less than or equal to the thickness of the layered lubricating layer.

[0011] Optionally, the mass ratio of the layered solid lubricating phase to the short-cut carbon fiber on which the interface anchoring layer is formed is (0.08-0.45):1; The mass ratio of the polyaryletherketone compatible confinement layer forming material to the short-cut carbon fibers on which the layered lubricating layer is formed is (0.03-0.30):1.

[0012] Optionally, the coating treatment is carried out at a temperature of 40℃-90℃ for a time of 0.5h-6h.

[0013] Optionally, the polyaryletherketone matrix includes one or more of polyetheretherketone, polyetherketoneketone, polyetherketone, polyetheretherketoneketone, or copolymers thereof; The layered solid lubricating phase includes one or more of molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride.

[0014] Optionally, the chopped carbon fibers have a length of 50μm-300μm and a diameter of 5μm-15μm.

[0015] Optionally, the surface activation treatment includes one or more of plasma treatment, ozone treatment, acidification treatment, alkalization treatment, or silanization pretreatment; The interface-modifying components in the interface-modifying solution are dopamine and / or silane coupling agents; The polyaryletherketone compatible confined layer forming material includes one or more of sulfonated polyaryletherketone, polyaryletherketone oligomers, or sizing agents containing aryletherketone structures.

[0016] Optionally, the hot pressing temperature is 10°C-40°C above the melting point of the polyaryletherketone matrix and below its thermal decomposition temperature, the pressure is 8MPa-20MPa, and the holding time is 10min-45min.

[0017] This invention integrates and coordinates the surface activation degree of chopped carbon fibers, the adhesion ability of the interface anchoring layer, the peripheral fixation state of the layered lubricating layer, the encapsulation and confinement effect of the polyaryletherketone (PAEK) compatibility confinement layer, and the gradient content design of the load-bearing / lubricating composite units in the surface layer, transition layer, and core layer materials to form a strong coupling relationship between each step: the surface activation treatment provides active adhesion sites for the stable formation of the interface anchoring layer, the interface anchoring layer further provides a fixed foundation for the layered solid lubricating phase, transforming the layered solid lubricating phase from the traditional random dispersion in the matrix to directional adhesion around the chopped carbon fibers, while the PAEK compatibility confinement layer confines and compatibly connects the layered lubricating layer on the outside, so that the load-bearing / lubricating composite units can still maintain the spatial binding relationship between the reinforcing phase and the lubricating phase during subsequent mixing and hot pressing, reducing the migration, shedding, and aggregation of the lubricating phase. Based on this, by distributing the load-bearing / lubricating composite units in a specific gradient decreasing direction away from the friction surface, the surface layer obtains continuous lubrication supply and transfer film formation capability, the transition layer buffers component differences and stress concentration, and the core layer maintains matrix continuity and load-bearing strength. This enables wear-resistant self-lubricating composite materials for robot joints to simultaneously achieve a low coefficient of friction, a low wear rate, high mechanical strength, and good long-term friction stability.

[0018] Furthermore, the surface material of the present invention contains 22%-32% by mass of the load-bearing / lubrication composite unit, the transition layer material contains 14%-23% by mass of the load-bearing / lubrication composite unit, and the core material contains 7%-15% by mass of the load-bearing / lubrication composite unit. This enables the composite material to form a layered gradient distribution of the load-bearing / lubrication composite unit from high to low along the direction away from the friction surface, thereby achieving a balance between surface lubrication supply, transition layer stress buffering, and core layer load-bearing support.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing a wear-resistant self-lubricating composite material for robot joints according to an embodiment of the present invention; Figure 2 This is a transmission electron microscope image of the load-bearing / lubricating composite unit according to Embodiment 1 of the present invention; Figure 3The image shows the Raman spectrum of the wear-resistant self-lubricating composite material for robot joints according to the present invention (MoS2) and Example 1. Figure 4 These are Raman spectra of wear-resistant self-lubricating composite materials for robot joints according to Embodiment 1 and Comparative Examples 4-5 of the present invention; Figure 5 This is a graph showing the friction coefficient of the wear-resistant self-lubricating composite material for robot joints according to Embodiment 1 and Comparative Examples 4-5 of the present invention. Figure 6 These are SEM images of the wear-resistant self-lubricating composite materials for robot joints according to Embodiment 1 and Comparative Examples 4-5 after friction testing. Figure 7 This is a cross-sectional SEM image of the wear-resistant self-lubricating composite material for robot joints according to Embodiment 1 and Comparative Example 6 of the present invention, along the direction perpendicular to the friction surface. Figure 8 This is a cross-sectional SEM image of the wear-resistant self-lubricating composite material for robot joints according to Comparative Examples 7-8 of the present invention, along the direction perpendicular to the friction surface. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0023] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] Figure 1 This is a schematic flowchart illustrating a method for preparing a wear-resistant, self-lubricating composite material for robot joints according to an embodiment of the present invention.

[0026] like Figure 1 As shown, the present invention provides a method for preparing a wear-resistant self-lubricating composite material for robot joints, comprising the following steps: Step S100: Perform surface activation treatment on the short-cut carbon fibers; Step S200: The surface-activated short carbon fibers are mixed with the interface modification solution, and after solid-liquid separation, washing and drying, an interface anchoring layer is formed on the surface of the short carbon fibers. Step S300: The short carbon fiber with the interface anchoring layer is mixed with the layered solid lubricating phase dispersion, so that the layered solid lubricating phase is attached to the outer peripheral surface of the short carbon fiber through the interface anchoring layer, so as to form a layered lubricating layer on the outside of the interface anchoring layer. Step S400: The short carbon fibers with the layered lubricating layer are placed in a polyaryletherketone compatible confinement liquid for coating treatment, so as to form a polyaryletherketone compatible confinement layer on the outside of the layered lubricating layer, and thus obtain a load-bearing / lubricating composite unit. Step S500: Mix the carrier / lubricant composite unit with the polyaryletherketone matrix to prepare surface material, transition layer material and core material with different mass contents of carrier / lubricant composite unit; Step S600: The surface layer, transition layer, and core layer are laid sequentially from the side closest to the friction surface to the side furthest from the friction surface. After hot pressing, a wear-resistant self-lubricating composite material for robot joints with a layered gradient distribution of load-bearing / lubricating composite units along a direction perpendicular to the friction surface is obtained. Specifically, the mass content of load-bearing / lubricating composite units in the surface layer is higher than that in the transition layer, and the difference between the two mass contents is any value between 6% and 12%. The mass content of load-bearing / lubricating composite units in the transition layer is higher than that in the core layer, and the difference between the two mass contents is any value between 5% and 10%. Here, the mass content difference between the surface layer and the transition layer can be 6%, 7%, 8%, 9%, 10%, 11%, or 12%, or any other value between 6% and 12%. The mass content difference between the transition layer and the core layer can be 5%, 6%, 7%, 8%, 9%, or 10%, or any other value between 5% and 10%. The layered lubricating layer is a continuous or discontinuous coating structure formed by the attachment, overlapping or local stacking of lamellar solid lubricating phases on the outer periphery of chopped carbon fibers.

[0027] In this embodiment, the preparation method of wear-resistant self-lubricating composite material for robot joints firstly involves surface activation treatment of chopped carbon fibers to improve the adhesion of the chopped carbon fiber surface to the interface modification components. Then, the surface-activated chopped carbon fibers are mixed with an interface modification solution to form an interface anchoring layer on the surface of the chopped carbon fibers. Subsequently, the chopped carbon fibers with the interface anchoring layer are mixed with a layered solid lubricating phase dispersion, allowing the layered solid lubricating phase to adhere and fix to the outer peripheral surface of the chopped carbon fibers through the interface anchoring layer, forming a layered lubricating layer on the outside of the interface anchoring layer. Furthermore, the chopped carbon fibers with the layered lubricating layer are placed in a polyaryletherketone (PAEK) compatibility confinement solution for coating treatment, forming a PAEK compatibility confinement layer on the outside of the layered lubricating layer. This results in a load-bearing / lubricating composite unit having, from the inside out, chopped carbon fibers, an interface anchoring layer, a layered lubricating layer, and a PAEK compatibility confinement layer. The load-bearing / lubricating composite unit was then mixed with a polyaryletherketone (PAK) matrix to prepare surface, transition, and core layers with different PAD contents. These layers were then laid sequentially from the side closest to the friction surface to the side furthest away from it and hot-pressed. The surface layer had a higher PAD content than the transition layer (6%-12%), while the transition layer had a higher PAD content than the core layer (5%-10%). This resulted in a wear-resistant, self-lubricating composite material for robot joints with a layered gradient distribution of PADs perpendicular to the friction surface. The PAK compatibility confinement fluid was a solution containing PAK compatibility confinement layer forming material.

[0028] In this embodiment, the surface activation degree of chopped carbon fibers, the adhesion ability of the interface anchoring layer, the peripheral fixation state of the layered lubricating layer, the encapsulation and confinement effect of the polyaryletherketone compatibility confinement layer, and the gradient content design of the load-bearing / lubricating composite units in the surface layer, transition layer, and core layer are integrated and synergistically controlled to form a strong coupling relationship between each step: the surface activation treatment provides active adhesion sites for the stable formation of the interface anchoring layer, the interface anchoring layer further provides a fixed foundation for the layered solid lubricating phase, so that the lubricating phase changes from the traditional random dispersion in the matrix to directional adhesion around the chopped carbon fibers, while the polyaryletherketone compatibility confinement layer confines and compatibly connects the layered lubricating layer on the outside, so that the load-bearing / lubricating composite units can still maintain the spatial binding relationship between the reinforcing phase and the lubricating phase during subsequent mixing and hot pressing, reducing the migration, shedding, and aggregation of the lubricating phase. Based on this, by distributing the load-bearing / lubricating composite units in a specific gradient decreasing direction away from the friction surface, the surface layer obtains continuous lubrication supply and transfer film formation capability, the transition layer buffers component differences and stress concentration, and the core layer maintains matrix continuity and load-bearing strength. This enables wear-resistant self-lubricating composite materials for robot joints to simultaneously achieve a low coefficient of friction, a low wear rate, high mechanical strength, and good long-term friction stability.

[0029] In this embodiment, by gradually decreasing the mass content of the load-bearing / lubricating composite unit in the surface layer, transition layer, and core layer materials away from the friction surface, and controlling the mass content difference between the surface layer and transition layer materials to 6%-12% and between the transition layer and core layer materials to 5%-10%, it is possible to avoid insufficient surface lubrication enrichment due to excessively small differences, and to avoid an increase in interlayer interface defects due to excessively large differences. This results in a composite material with good self-lubricating properties, wear resistance, interlayer bonding stability, and mechanical load-bearing capacity. Specifically, the higher content of the load-bearing / lubricating composite unit in the surface layer material can improve the supply capacity of the layered solid lubricating phase on the friction surface, which is beneficial for the formation of a stable lubricating film or transfer film during friction, thereby reducing the friction coefficient and wear rate. The intermediate content in the transition layer material can mitigate the component differences between the surface layer and core layer materials, reducing the risk of interlayer stress concentration, cracking, and delamination caused by abrupt changes in filler content. The lower content of the load-bearing / lubricating composite unit in the core layer material helps maintain the continuity of the polyaryletherketone matrix and the overall load-bearing strength.

[0030] In step S100, the length of the chopped carbon fiber is 50μm-300μm and the diameter is 5μm-15μm. That is, the length of the chopped carbon fiber can be 50μm, 100μm, 150μm, 200μm, 250μm or 300μm, or any other value among 50μm-300μm. The diameter can be 5μm, 7μm, 10μm, 12μm or 15μm, or any other value among 5μm-15μm. This enables the chopped carbon fiber to achieve a synergistic match between aspect ratio, surface modifiable area, dispersion stability and load transfer capability. Specifically, the 50μm-300μm length of chopped carbon fibers provides sufficient overlap load-bearing and crack deflection capabilities, enabling the formation of an effective local support structure within the polyaryletherketone (PAEK) matrix. This provides a continuous load-bearing skeleton for the fixation of the layered solid lubricating phase on its periphery. The 5μm-15μm diameter provides a suitable specific surface area, facilitating the formation of a sufficient number of active sites such as hydroxyl, carboxyl, or carbonyl groups after surface activation. This promotes the stable formation of the interfacial anchoring layer, the layered lubricating layer, and the PAEK compatibility confinement layer, while also preventing agglomeration, entanglement, or increased viscosity due to excessively fine fibers. Therefore, chopped carbon fibers maintain good dispersibility and interfacial bonding stability during subsequent coating, mixing, and hot pressing processes, allowing for a stable gradient distribution of the load-bearing / lubricating composite unit in the surface layer, transition layer, and core layer.

[0031] The surface activation treatment in step S100 includes the following steps: First, the chopped carbon fibers are ultrasonically cleaned in ethanol or an ethanol / deionized water mixture for 10-30 minutes to remove floating dust, sizing agent residue, or weakly attached impurities from the surface of the chopped carbon fibers. Then, after filtration or centrifugation, the fibers are dried. Next, the dried chopped carbon fibers are placed in a plasma cleaner and subjected to plasma surface activation treatment in an oxygen, air, or oxygen / argon mixed atmosphere. The treatment power is 50W-200W, and the treatment time is 1-15 minutes, to introduce active groups onto the surface of the reinforcing core. Here, the ultrasound time can be 10 min, 15 min, 20 min, 25 min or 30 min, or any other value between 10 min and 30 min; the processing power can be 50 W, 100 W, 150 W or 200 W, or any other value between 50 W and 200 W; and the processing time can be 1 min, 3 min, 5 min, 7 min, 10 min, 12 min or 15 min, or any other value between 1 min and 15 min.

[0032] In step S300, the concentration of the layered solid lubricating phase in the dispersion can be any value between 2 mg / mL and 10 mg / mL, for example, 2 mg / mL, 3 mg / mL, 5 mg / mL, 8 mg / mL, or 10 mg / mL, or any other value between 2 mg / mL and 10 mg / mL. By controlling the concentration of the layered solid lubricating phase dispersion within the above range, the layered solid lubricating phase can remain dispersible within the time required for subsequent mixing treatment, and its contact and adhesion efficiency with the short-cut carbon fibers with the interfacial anchoring layer can be improved. Here, dispersibility can be improved by adjusting the pH, adding removable dispersing agents, hydroxylating or surface modifying the layered solid lubricating phase, or using high-speed shearing / probe ultrasonic methods.

[0033] In this embodiment, the specific process for attaching the layered solid lubricating phase to the outer peripheral surface of the chopped carbon fiber through the interface anchoring layer may include the following steps: First, the layered solid lubricating phase material is added to ethanol, deionized water, or a mixture of ethanol and deionized water, and ultrasonically dispersed for 20-40 minutes to obtain a layered solid lubricating phase dispersion; then, the chopped carbon fiber with the interface anchoring layer is added to the layered solid lubricating phase dispersion, and stirred at room temperature to 60°C for 0.5-4 hours to ensure that the layered solid lubricating phase and the interface anchoring layer are in full contact, and the phase is attached to the outer peripheral surface of the chopped carbon fiber through hydrogen bonding, coordination, π-π interaction, electrostatic adsorption, or physical adsorption by the polar groups, catechol groups, amine groups, or silane coupling groups on the interface anchoring layer. After treatment, the resulting mixture was subjected to low-speed centrifugation or differential sedimentation to preferentially settle the short-cut carbon fibers loaded with the layered solid lubricating phase. The proportion of free layered solid lubricating phase was reduced by low-speed centrifugation or differential sedimentation. The washing endpoint was defined as the turbidity, UV absorption, solid content, or elemental content of the supernatant stabilizing. Subsequently, the precipitate was redispersed with an ethanol / deionized water mixture, and the centrifugation, supernatant removal, and redispersing process was repeated 3-5 times until no significant layered solid lubricating phase suspension was found in the supernatant. Finally, the precipitate was vacuum-dried at 50℃-80℃ for 6-10 hours to form a layered lubricating layer on the outside of the interfacial anchoring layer.

[0034] In step S400, the mass concentration of the polyaryletherketone (PAEK) compatibility confinement layer forming material in the PAEK compatibility confinement solution can be any value between 1 wt% and 5 wt%, specifically 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%, or any other value between 1 wt% and 5 wt%. By controlling the mass concentration of the PAEK compatibility confinement solution within the above range, the solution can possess suitable viscosity, wetting ability, and film-forming ability, thereby forming a continuous or semi-continuous PAEK compatibility confinement layer of appropriate thickness on the outer side of the layered lubricating layer. Here, the PAEK compatibility confinement solution is a solution, dispersion, or suspension containing soluble PAEK oligomers, sulfonated PAEK, or PAEK-containing sizing agents.

[0035] In this embodiment, the coating process may specifically include the following steps: dissolving or dispersing the polyaryletherketone (PAK) compatibility confinement layer forming material in N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, or dimethyl sulfoxide to prepare a PAK compatibility confinement solution; adding short-cut carbon fibers with a layered lubricating layer to the PAK compatibility confinement solution, and stirring and coating at 40℃-90℃ for 1h-4h to allow the PAK compatibility confinement layer forming material to fully wet the layered lubricating layer, and to adsorb, deposit, and form a film on the outside of the layered lubricating layer. After the coating process is completed, the solid product is collected by vacuum filtration or centrifugation and then rapidly washed with ethanol or an ethanol / water mixture to remove the uncoated free polyaryletherketone compatibility confinement layer forming material. Subsequently, the obtained solid product is placed in a vacuum drying oven at 60℃-100℃ for 8h-14h to allow the polyaryletherketone compatibility confinement layer forming material to be stably filmed on the outside of the layered lubricating layer, thereby forming a polyaryletherketone compatibility confinement layer on the outside of the layered lubricating layer, thus obtaining the load-bearing / lubricating composite unit.

[0036] In a further embodiment, the surface layer material contains 22%-32% by mass of the load-bearing / lubricating composite unit, the transition layer material contains 14%-23% by mass of the load-bearing / lubricating composite unit, and the core layer material contains 7%-15% by mass of the load-bearing / lubricating composite unit. This allows the composite material to form a layered gradient distribution of the load-bearing / lubricating composite unit from high to low along the direction away from the friction surface, thereby achieving a balance between surface lubrication supply, transition layer stress buffering, and core layer load-bearing support. Specifically, the higher content of load-bearing / lubricating composite units in the surface layer material can improve the supply capacity of the layered solid lubricating phase on the friction surface, which is beneficial to the formation of a continuous or semi-continuous lubricating film or transfer film during friction, thereby reducing the coefficient of friction and wear rate. The moderate content of load-bearing / lubricating composite units in the transition layer material can mitigate the compositional differences between the surface layer material and the core layer material, reducing the risk of interlayer stress concentration, crack propagation, and interface delamination. The lower content of load-bearing / lubricating composite units in the core layer material can maintain the continuity and overall mechanical strength of the polyaryletherketone matrix, avoiding material embrittlement or decreased load-bearing capacity due to excessive filler content. Here, the mass content of the load-bearing / lubricating composite unit in the surface layer material can be 22%, 24%, 26%, 28%, 30%, or 32%, or any other value between 22% and 32%. The mass content of the load-bearing / lubricating composite unit in the transition layer material can be 14%, 16%, 18%, 20%, or 23%, or any other value between 14% and 23%. The mass content of the load-bearing / lubricating composite unit in the core layer material can be 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or any other value between 7% and 15%.

[0037] In other embodiments, when the content of the load-bearing / lubricating composite unit in the surface material is less than 22%, the supply of lubricating phase to the friction surface is insufficient, making it difficult to form a stable lubricating film. When it is higher than 32%, the content of surface filler is too high, which can easily lead to a decrease in matrix continuity and local agglomeration.

[0038] In a further embodiment, the thickness ratio of the surface layer, transition layer, and core layer is any value in the range of 1:(1-3):(2-6). That is, the thickness ratio of the surface layer, transition layer, and core layer in the wear-resistant self-lubricating composite material for robot joints can be 1:1:2, 1:2:2, 1:3:2, 1:1:3, 1:2:4, or 1:3:6, or any other value in the range of 1:(1-3):(2-6). This allows the composite material to form a reasonable functional layer thickness matching relationship in the thickness direction, thereby achieving a balance between lubrication supply to the friction surface, interlayer transition buffering, and overall load-bearing support. Specifically, the surface layer is located on the side closest to the friction surface, and its thickness serves as a reference layer. This ensures that sufficient load-bearing / lubricating composite units participate in the running-in and transfer film formation during the friction process, while avoiding an excessively thick surface layer that leads to an excessively large high-filler content area and a decrease in the overall toughness of the material. The transition layer, with a thickness 1-3 times that of the surface layer, ensures a sufficient transition of components and stress buffer between the high-content load-bearing / lubricating composite unit regions on the surface and the low-content load-bearing / lubricating composite unit regions in the core layer, reducing the risk of interlaminar cracks, voids, or delamination caused by abrupt changes in material composition. The core layer, with a thickness 2-6 times that of the surface layer, provides the main structural support and dimensional stability for the composite material, enabling it to maintain good overall load-bearing strength in load-bearing components such as robot joint bushings, bushings, or gaskets.

[0039] In other embodiments, when the thickness of the transition layer or the core layer is too small, the compositional differences between the surface layer and the core layer are difficult to buffer sufficiently, and the overall load-bearing capacity of the composite material is insufficient. When the thickness of the transition layer or the core layer is too large, the proportion of the effective lubrication functional area near the friction surface decreases, and the continuous supply capacity of the layered solid lubrication interface to the opposing friction surfaces declines.

[0040] In a further embodiment, the thickness of the layered lubricating layer is 80 nm-2 μm, the thickness of the polyaryletherketone compatibility confinement layer is 50 nm-1 μm, and the thickness of the polyaryletherketone compatibility confinement layer is less than or equal to the thickness of the layered lubricating layer. That is, the thickness of the layered lubricating layer can be 80 nm, 100 nm, 500 nm, 1 μm, 1.5 μm or 2 μm, or any value among 80 nm-2 μm. The thickness of the polyaryletherketone compatibility confinement layer can be 50 nm, 100 nm, 200 nm, 500 nm, 700 nm or 1 μm, or any other value among 50 nm-1 μm. This achieves a balance between the lubrication supply capacity of the layered solid lubricating phase, the interfacial stability of the load-bearing / lubricating composite unit, and the ability of the exposed lubricating phase to participate in friction. Specifically, when the thickness of the layered lubricating layer is in the range of 80 nm to 2 μm, the layered solid lubricating phase can form a continuous or semi-continuous low-shear lubricating structure on the periphery of the chopped carbon fibers. This allows it to continuously participate in the formation of the transfer film or lubricating film during friction, thereby reducing the friction coefficient and wear rate. Simultaneously, controlling the thickness of the polyaryletherketone (PAK) compatibility confinement layer within the range of 50 nm to 1 μm facilitates the formation of a moderately compatible coating structure on the outside of the layered lubricating layer. This ensures good interfacial compatibility between the load-bearing / lubricating composite unit and the PAK matrix during mixing and hot pressing, and restricts the migration, detachment, and random redispersion of the layered solid lubricating phase within the layered lubricating layer. Here, the thickness of the layered lubricating layer refers to the maximum apparent thickness measured in the local stacked region.

[0041] Furthermore, by limiting the thickness of the polyaryletherketone compatibility confinement layer to less than or equal to the thickness of the layered lubricating layer, it is possible to avoid the compatibility confinement layer being too thick and weakening the exposed supply capacity of the low-shear lubricating layer. This allows the composite unit to have both good matrix compatibility and anti-migration ability, while maintaining the effective supply of the layered solid lubricating phase during the friction process, thereby improving the long-term self-lubricating properties, wear resistance, and interfacial bonding stability of the composite material.

[0042] In other embodiments, if the layered lubricating layer is too thin, the supply of the layered solid lubricating phase will be insufficient, making it difficult to form a stable lubricating film. If the layered lubricating layer is too thick, it will easily lead to the accumulation and peeling of the lubricating phase or weaken the load transfer capability between the chopped carbon fibers and the polyaryletherketone matrix. If the polyaryletherketone compatibility confinement layer is too thin, its confinement and interfacial compatibility effects on the layered lubricating layer will be insufficient. If the polyaryletherketone compatibility confinement layer is too thick, it will easily excessively obscure the layered solid lubricating phase, making it difficult for it to be exposed in time and participate in the lubrication of the friction interface.

[0043] In a further embodiment, the mass ratio of the layered solid lubricating phase to the chopped carbon fibers with the interface anchoring layer is (0.08-0.45):1, and the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the chopped carbon fibers with the layered lubricating layer is (0.03-0.30):1. That is, the mass ratio of the layered solid lubricating phase to the chopped carbon fibers with the interface anchoring layer can be 0.08:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, or 0.45:1, or it can be (0.08-0.45):1. For any other value in 45):1, the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the short-cut carbon fiber with the layered lubricating layer can be 0.03:1, 0.05:1, 0.1:1, 0.2:1 or 0.3:1, or any other value in (0.03-0.30):1, which can make the loading amount of the layered solid lubricating phase match the coating amount of the polyaryletherketone compatibility confinement layer, thereby achieving a balance between low-shear lubricating phase supply, enhanced phase load transfer, interfacial compatibility and lubricating phase anti-migration ability.

[0044] Specifically, when the mass ratio of the layered solid lubricating phase to the chopped carbon fibers with the interfacial anchoring layer is within the range of (0.08-0.45):1, the layered solid lubricating phase can form a relatively sufficient layered lubricating layer on the outer periphery of the chopped carbon fibers. This allows the load-bearing / lubricating composite unit to continuously supply the layered solid lubricating phase and form a lubricating film or transfer film during friction. Simultaneously, controlling the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the chopped carbon fibers with the layered lubricating layer to (0.03-0.30):1 allows the compatibility confinement layer to form a moderate coating on the outside of the layered lubricating layer. This not only improves the interfacial compatibility between the load-bearing / lubricating composite unit and the polyaryletherketone matrix, making it easier for the composite unit to melt-bond, form chain segment entanglements, or interfacial interdiffusion with the matrix during hot pressing, but also restricts the migration, detachment, and random redispersion of the layered solid lubricating phase during mixing and hot pressing, thereby maintaining the local enrichment of the layered lubricating phase around the chopped carbon fibers.

[0045] In other embodiments, if the mass ratio of the layered solid lubricating phase to the chopped carbon fibers with the interface anchoring layer is too low, the layered solid lubricating phase will not be adequately loaded and it will be difficult to form a stable low-shear lubrication interface. If the mass ratio is too high, the excessive layered solid lubricating phase will easily accumulate on the periphery of the chopped carbon fibers or agglomerate in the matrix, weakening the load transfer between the chopped carbon fibers and the polyaryletherketone matrix, and may lead to local peeling or an increase in third-body abrasive particles during wear.

[0046] In other embodiments, if the mass ratio of the polyaryletherketone (PAEK) compatibility confinement layer forming material to the chopped carbon fibers with the layered lubricating layer is too low, the compatibility confinement layer will not form sufficiently, resulting in insufficient confinement of the layered lubricating layer and inadequate compatibility with the PAEK matrix. If the mass ratio is too high, an excessively thick coating layer may form, obscuring the layered solid lubricating phase and reducing its ability to be exposed to the friction interface and participate in the formation of the lubricating film.

[0047] In a further embodiment, the coating treatment temperature is 40°C-90°C. The short-cut carbon fibers with the layered lubricating layer are placed in a polyaryletherketone (PAK) compatible confinement solution for coating treatment. The treatment temperature can be 40°C, 50°C, 60°C, 70°C, 80°C, or 90°C, or any other value within the 40°C-90°C range. The treatment time is 1 hour-4 hours, meaning the coating treatment time can be 1 hour, 2 hours, 3 hours, or 4 hours, or any other value within the 1 hour-4 hour range. This allows the PAK compatible confinement layer forming material to achieve sufficient wetting, moderate diffusion, and stable adhesion on the outside of the layered lubricating layer, thereby forming a continuous or semi-continuous compatible confinement layer. The aforementioned treatment temperature and treatment time work synergistically to coordinate the film-forming sufficiency of the PAK compatible confinement layer and the exposure supply capacity of the layered solid lubricating phase. When the processing temperature is within the range of 40℃-90℃, the polyaryletherketone compatibility confinement liquid has good fluidity and wetting ability, and can enter the interlayer gaps or surface irregularities on the outer side of the layered lubricating layer, thereby improving the bonding stability between the polyaryletherketone compatibility confinement layer and the layered lubricating layer. At the same time, this temperature range will not cause the solvent to evaporate too quickly or cause the polyaryletherketone compatibility confinement layer to be deposited too thickly in some areas, thus avoiding the compatibility confinement layer from over-coating and obscuring the layered solid lubricating phase.

[0048] In a further embodiment, the polyaryletherketone matrix includes one or more of polyetheretherketone, polyetherketoneketone, polyetherketone, polyetherketone, or copolymers thereof. This allows the use of the heat resistance, wear resistance, chemical resistance, dimensional stability, and high mechanical strength of such polyaryletherketone materials to provide a stable load-bearing matrix for wear-resistant self-lubricating composite materials for robot joints. During hot pressing, the aforementioned polyaryletherketone matrix can melt and flow to encapsulate the load-bearing / lubricating composite unit. Simultaneously, it exhibits good structural compatibility with the polyaryletherketone compatibility confinement layer, which facilitates melt bonding, chain segment entanglement, or interfacial interdiffusion between the load-bearing / lubricating composite unit and the matrix, thereby improving the interfacial bonding strength and overall load-bearing stability of the composite material.

[0049] In this embodiment, by selecting one or more of molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride as the layered solid lubricating phase, the lamellar structure and low interlayer shear characteristics of these materials can be utilized to facilitate interlayer slippage during friction, forming a lubricating film or transfer film at the friction interface, thereby reducing the coefficient of friction and wear rate. After the aforementioned layered solid lubricating phase is fixed to the periphery of the chopped carbon fibers by the interface anchoring layer, it is no longer dispersed in the polyaryletherketone matrix as a random filler, but forms a load-bearing / lubricating composite unit with the chopped carbon fibers, spatially coupling the load-bearing effect of the reinforcing phase with the friction-reducing effect of the layered solid lubricating phase.

[0050] In a further embodiment, the surface activation treatment includes one or more of plasma treatment, ozone treatment, acidification treatment, alkalization treatment, or silanization pretreatment. Depending on the material type and surface chemical state of the chopped carbon fibers, active sites such as hydroxyl, carboxyl, carbonyl, silanol, or coupling groups can be introduced to improve the adhesion of the interface modification components to the surface of the chopped carbon fibers. This allows the subsequent interface anchoring layer to form more stably on the surface of the chopped carbon fibers, reducing the risk of the interface anchoring layer falling off during mixing, washing, or hot pressing, and providing a stable basis for the fixation of the layered solid lubricating phase on the periphery of the chopped carbon fibers.

[0051] In this embodiment, the interface-modifying components in the interface-modifying solution are dopamine and / or silane coupling agents, which can form an interface anchoring layer with adhesiveness and reactivity on the surface of chopped carbon fibers. Dopamine can adhere to the surface of chopped carbon fibers through catechol groups, amino groups, or hydroxyl groups, and provide hydrogen bonds, coordination, π-π interactions, or physical adsorption sites for layered lubricating materials such as molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride. The silane coupling agent can form a coupling layer on the surface of chopped carbon fibers with hydroxyl or polar groups, improving the interfacial bonding stability between the chopped carbon fibers and the layered solid lubricating phase.

[0052] In this embodiment, the polyaryletherketone (PAE) compatibility confinement layer forming material includes one or more of sulfonated PAEs, PAE oligomers, or sizing agents containing PAEs structures. This material can form a confinement layer with good compatibility or interfacial bonding ability with the PAE matrix on the outer side of the layered lubricating layer. Specifically, the PAE compatibility confinement layer not only provides physical confinement and interfacial protection for the layered solid lubricating phase during subsequent mixing and hot pressing, reducing the migration, shedding, and random redispersion of the layered solid lubricating phase, but also improves the interfacial compatibility between the load-bearing / lubricating composite unit and the PAE matrix, making it easier for the unit to melt-bond, form chain entanglements, or interfacial interdiffusion with the PAE matrix during hot pressing.

[0053] It should be noted that the above-mentioned surface activation methods, interface modification components, and polyaryletherketone compatibility confinement layer forming materials can be adapted and selected according to the type and surface properties of the short-cut carbon fibers. It is not required that all materials, when combined arbitrarily, adopt the same reaction mechanism.

[0054] In a further embodiment, the hot-pressing temperature is 10°C-40°C above the melting point of the polyaryletherketone matrix and below its thermal decomposition temperature; the pressure is 8MPa-20MPa; and the holding time is 10min-45min. That is, the hot-pressing temperature can be 10°C, 20°C, 30°C, or 40°C above the melting point of the polyaryletherketone matrix, or any other value above the melting point of 10°C-40°C, but must be below the thermal decomposition temperature of the polyaryletherketone matrix. The pressure can be 8MPa, 10MPa, 15MPa, or 20MPa, or 8MPa-2... Any other value within 0 MPa, with a holding time of 10 min, 20 min, 30 min, 40 min, or 45 min, or any other value between 10 min and 45 min, allows the polyaryletherketone matrix to fully melt and flow while simultaneously undergoing melt bonding, chain segment entanglement, or interfacial interdiffusion with the polyaryletherketone compatibility confinement layer outside the support / lubrication composite unit. This improves the interfacial bonding strength between the support / lubrication composite unit and the polyaryletherketone matrix, and creates a good interlayer fusion structure between the surface layer, transition layer, and core layer materials. In a preferred embodiment, when the polyaryletherketone matrix is ​​polyetheretherketone, the hot-pressing temperature is 360℃-390℃.

[0055] The technical solution of this application will be further described below with reference to specific embodiments.

[0056] Example 1 The preparation method of wear-resistant and self-lubricating composite material for robot joints includes the following steps: Step S100: Select chopped carbon fibers as chopped carbon fibers. The length of the chopped carbon fibers is 150μm and the diameter is 7μm. Perform oxygen plasma surface activation treatment on the chopped carbon fibers. The treatment power is 100W and the treatment time is 5min.

[0057] Step S200: The surface-activated chopped carbon fibers were added to a dopamine interface modification solution with a concentration of 2 mg / mL, and the mixture was stirred and reacted for 6 h under weakly alkaline conditions at pH 8.5. After the reaction was completed, solid-liquid separation was performed by vacuum filtration, and the solid product was collected. The solid product was then washed sequentially with deionized water and ethanol until the washing solution was essentially colorless and the pH was close to neutral. Subsequently, the washed solid product was dried at 60 °C for 8 h to form a polydopamine interface anchoring layer on the surface of the chopped carbon fibers.

[0058] Step S300: Short-cut carbon fibers with an interface anchoring layer are added to a molybdenum disulfide dispersion with a concentration of 5 mg / mL and mixed, wherein the mass ratio of molybdenum disulfide to the short-cut carbon fibers with the interface anchoring layer is 0.25:1. The resulting mixture is then centrifuged at 3000 rpm for 5 min to allow the molybdenum disulfide-loaded short-cut carbon fibers to settle preferentially. The supernatant containing free molybdenum disulfide sheets is removed. The precipitate is then redispersed using an ethanol / deionized water mixture, and the centrifugation, supernatant removal, and redispersing process is repeated three times until no obvious black molybdenum disulfide suspensions are found in the supernatant. The resulting precipitate is then vacuum-dried at 60 °C for 6 h, forming a locally stacked layered lubricating layer on the outer periphery of the short-cut carbon fibers.

[0059] Step S400: Short carbon fibers with a layered lubricating layer are placed in a 2wt% sulfonated polyether ether ketone solution for coating treatment. The mass ratio of sulfonated polyether ether ketone to the short carbon fibers with a layered lubricating layer is 0.12:1. The coating temperature is 60℃ and the coating time is 2h. After drying, a polyarylether ketone compatibility confinement layer is formed on the outside of the layered lubricating layer. The thickness of the polyarylether ketone compatibility confinement layer is 200nm.

[0060] Step S500: Mix the obtained carrier / lubricant composite unit with polyether ether ketone powder to prepare surface material, transition layer material and core material respectively. The surface material contains 28% carrier / lubricant composite unit by mass, the transition layer material contains 19% carrier / lubricant composite unit by mass, and the core material contains 11% carrier / lubricant composite unit by mass.

[0061] Step S600: Core layer material, transition layer material and surface layer material are laid sequentially from the side close to the friction surface to the side away from the friction surface, wherein the thickness ratio of the surface layer material, transition layer material and core layer material is 1:2:4. Hot pressing is performed under the conditions of temperature 375℃, pressure 15MPa and holding time 25min. After cooling, wear-resistant self-lubricating composite material for robot joints is obtained.

[0062] Example 2 The only difference between Example 2 and Example 1 is that the layered solid lubricating phase is tungsten disulfide, the mass ratio of tungsten disulfide to the short-cut carbon fiber with the interface anchoring layer is 0.20:1, and the local stacking thickness of the layered lubricating layer is 400 nm. The mass content of the load-bearing / lubricating composite unit in the surface layer, transition layer, and core layer is 26%, 18%, and 10%, respectively.

[0063] Example 3 The difference between Example 3 and Example 1 is only that the layered solid lubricating phase is hexagonal boron nitride, the mass ratio of hexagonal boron nitride to the short carbon fiber with the interface anchoring layer is 0.30:1, and the polyaryletherketone compatibility confinement layer forming material is polyaryletherketone oligomer with a number average molecular weight of about 5000 and an average degree of polymerization of about 15. The mass content of the load-bearing / lubricating composite unit in the surface layer, transition layer, and core layer is 30%, 21%, and 13%, respectively.

[0064] Example 4 The only difference between Example 4 and Example 1 is that the mass ratio of the layered solid lubricating phase to the short-cut carbon fiber with the interface anchoring layer is 0.08:1, the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the short-cut carbon fiber with the layered lubricating layer is 0.03:1, the local stacking thickness of the layered lubricating layer is 100 nm, the thickness of the polyaryletherketone compatibility confinement layer is 50 nm, the coating treatment temperature is 45 °C, and the coating treatment time is 0.5 h. The mass content of the load-bearing / lubricating composite unit in the surface layer, transition layer, and core layer is 22%, 16%, and 11%, respectively.

[0065] Example 5 The only difference between Example 5 and Example 1 is that the mass ratio of the layered solid lubricating phase to the chopped carbon fibers with the interface anchoring layer is 0.45:1, the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the chopped carbon fibers with the layered lubricating layer is 0.30:1, the local stacking thickness in the layered lubricating layer is 1.5 μm, the thickness of the polyaryletherketone compatibility confinement layer is 1.0 μm, the coating treatment temperature is 85°C, the coating treatment time is 6 h, and the mass content of the load-bearing / lubricating composite unit in the surface material, transition layer material, and core layer material is 32%, 22%, and 14%, respectively. The difference between the surface layer material and the transition layer material is 10%, and the difference between the transition layer material and the core layer material is 8%.

[0066] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the short-cut carbon fibers were directly added to the dopamine interface modification solution, without plasma surface activation treatment of the short-cut carbon fibers.

[0067] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the surface-activated short-cut carbon fibers were directly compounded with the molybdenum disulfide dispersion, without being mixed with the dopamine interface modification solution.

[0068] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that after the interface anchoring layer is formed on the surface of the short-cut carbon fiber, the polyaryletherketone compatibility confinement layer coating treatment is performed directly.

[0069] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that after forming the layered lubricating layer, the short-cut carbon fibers with the layered lubricating layer formed are directly mixed with the polyether ether ketone matrix.

[0070] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the short-cut carbon fibers, molybdenum disulfide and polyetheretherketone powder are directly mixed.

[0071] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the mass content of the load-bearing / lubricating composite unit in the surface material, transition layer material and core material is 19%.

[0072] Comparative Example 7 The only difference between Comparative Example 7 and Example 1 is that the mass content of the load-bearing / lubricating composite unit in the surface layer material is 22%, in the transition layer material it is 19%, and in the core layer material it is 16%. Specifically, the difference in mass content of the load-bearing / lubricating composite unit between the surface layer material and the transition layer material is 3%, and the difference in mass content between the transition layer material and the core layer material is also 3%.

[0073] Comparative Example 8 The only difference between Comparative Example 8 and Example 1 is that the surface layer material contains 36% load-bearing / lubricating composite units by mass, the transition layer material contains 20% load-bearing / lubricating composite units by mass, and the core layer material contains 8% load-bearing / lubricating composite units by mass. Specifically, the difference in the load-bearing / lubricating composite unit mass content between the surface layer material and the transition layer material is 16%, and the difference between the transition layer material and the core layer material is 12%.

[0074] Comparative Example 9 The only difference between Comparative Example 9 and Example 1 is that the mass ratio of molybdenum disulfide to chopped carbon fibers with an interface anchoring layer is 0.03:1, and the local stacking thickness of the layered lubricating layer is 30 nm.

[0075] Comparative Example 10 The only difference between Comparative Example 10 and Example 1 is that the mass ratio of molybdenum disulfide to chopped carbon fibers with an interface anchoring layer is 0.60:1, and the local stacking thickness of the layered lubricating layer is 3 μm.

[0076] Comparative Example 11 The only difference between Comparative Example 11 and Example 1 is that the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the short-cut carbon fiber with the layered lubricating layer is 0.01:1, and the thickness of the polyaryletherketone compatibility confinement layer is 20 nm.

[0077] Comparative Example 12 The only difference between Comparative Example 12 and Example 1 is that the mass ratio of the polyaryletherketone compatibility confinement layer forming material to the short-cut carbon fiber with the layered lubricating layer is 0.45:1, and the thickness of the polyaryletherketone compatibility confinement layer is 1.5 μm.

[0078] Figure 2 This is a transmission electron microscope image of the load-bearing / lubricating composite unit according to Embodiment 1 of the present invention. Figure 3 This is the Raman spectrum of the wear-resistant self-lubricating composite material for robot joints according to the present invention (MoS2) and Example 1. Figure 4 These are Raman spectra of the wear-resistant, self-lubricating composite materials for robot joints according to Embodiment 1 and Comparative Examples 4-5 of the present invention. Figure 5 This is a graph showing the coefficient of friction of the wear-resistant, self-lubricating composite material for robot joints according to Embodiment 1 and Comparative Examples 4-5 of the present invention. Figure 6 These are SEM images of the wear-resistant self-lubricating composite materials for robot joints according to Embodiment 1 and Comparative Examples 4-5 after friction testing. Figure 7 This is a cross-sectional SEM image of the wear-resistant self-lubricating composite material for robot joints according to Embodiment 1 and Comparative Example 6 of the present invention, along the direction perpendicular to the friction surface. Figure 8 This is a cross-sectional SEM image of the wear-resistant self-lubricating composite material for robot joints according to Comparative Examples 7-8 of the present invention, along the direction perpendicular to the friction surface.

[0079] First, the load-bearing / lubricating composite unit prepared in Example 1 was characterized by transmission electron microscopy, and the results were as follows: Figure 2 The test results are shown.

[0080] like Figure 2 As shown, the load-bearing / lubricating composite unit obtained in Example 1 exhibits a core-shell structure with chopped carbon fibers as the core and a progressively distributed outer cladding layer. Figure 2 As shown in (a), the chopped carbon fiber core in the low-magnification transmission scanning electron microscope image is continuous and has a clear outline. A relatively uniform coating area is formed around its periphery, indicating that after interface anchoring, molybdenum disulfide composite coating, and polyaryletherketone compatibility confinement treatment, the lamellar lubricating material can stably adhere to the surface of the chopped carbon fiber, rather than being randomly dispersed as free particles. (See enlarged view of region A for reference.) Figure 2 (b) shows a locally stacked layered coating region with a thickness of approximately 500 nm on the outer side of the chopped carbon fibers. This region corresponds to a low-shear layered lubricating layer of molybdenum disulfide, indicating that molybdenum disulfide can form a continuous or semi-continuous layered lubricating structure on the fiber periphery. Further, a lighter-colored outer coating region with a thickness of approximately 200 nm is visible outside this layered lubricating layer, corresponding to a polyaryletherketone compatibility confinement layer. This indicates that the compatibility confinement layer can coat the outer side of the layered lubricating layer and form external protection and compatibility bonding. (See enlarged view of region B for reference.) Figure 2(c) Further, it is shown that there is a thin layer region of about 10nm-20nm between the chopped carbon fiber core and the layered lubricating layer, corresponding to the polydopamine interface anchoring layer, indicating that the surface-activated chopped carbon fiber can establish a stable bond with the molybdenum disulfide lubricating layer through the interface anchoring layer.

[0081] Next, Raman spectroscopy characterization was performed on the wear-resistant self-lubricating composite materials for robot joints in Examples 1, 4, and 5 after hot pressing, and before hot pressing in Example 1, yielding the following results: Figure 3 and Figure 4 The test results are shown.

[0082] like Figure 3 As shown, the MoS2 feedstock is at approximately 383 cm⁻¹ -1 Approximately 408cm -1 Appearing in different places Peak and A 1g The peak indicates that it has a typical molybdenum disulfide lamellar structure. In Example 1, the same characteristic peak of MoS2 was observed before hot pressing, indicating that molybdenum disulfide had been successfully introduced into the load-bearing / lubricating composite unit; simultaneously, at approximately 1350 cm⁻¹... -1 Approximately 1580cm -1 The presence of D and G peaks of carbon materials nearby indicates that chopped carbon fibers exist as chopped carbon fibers within the composite unit. Furthermore, in Example 1, approximately 383 cm⁻¹ can still be observed after hot pressing. -1 Approximately 408cm -1 The presence of the characteristic MoS2 peaks nearby, with no significant shift in peak position, indicates that the low-shear lubricating phase of molybdenum disulfide was not destroyed during hot pressing and retains its lamellar lubricating structure. Simultaneously, the D and G peaks corresponding to the carbon fibers remain, demonstrating good structural retention of the load-bearing / lubricating composite unit after hot pressing. Therefore, the polyaryletherketone compatibility confinement layer can provide some protection and confinement for the lamellar lubricating layer during hot pressing, allowing the molybdenum disulfide lubricating phase to maintain its identifiable characteristic structure after high-temperature hot pressing, providing a structural basis for the formation of a lubricating film or transfer film during subsequent friction processes.

[0083] like Figure 4 As shown, Raman spectra of the samples after hot pressing in Example 1, Comparative Example 4, and Comparative Example 5 were compared. The Raman spectra of Example 1 were observed at approximately 383 cm⁻¹. -1 Approximately 408cm -1 It still exhibits clear and high-intensity MoS2 characteristic peaks at approximately 1350 cm⁻¹. -1 Approximately 1580cm -1The D and G peaks of the carbon fibers were observed nearby, indicating that molybdenum disulfide in Example 1 remained relatively stable in the region near the chopped carbon fibers after hot pressing. In contrast, in Comparative Example 4, the MoS2 characteristic peak was still detectable due to the absence of a polyaryletherketone (PAK) compatibility confinement layer, but the peak intensity was significantly weaker than in Example 1. This indicates that without a compatibility confinement layer, molybdenum disulfide is more prone to migration, shedding, or dispersion during hot pressing, leading to a decrease in the retention of molybdenum disulfide in the test area. Comparative Example 5 used a random mixture of chopped carbon fibers, molybdenum disulfide, and PAK matrix. The MoS2 characteristic peak signal in its Raman curve was unstable, with large fluctuations in peak shape and intensity, indicating that molybdenum disulfide was randomly distributed and accompanied by local agglomeration after hot pressing, making it difficult to form a stable spatial correspondence with the chopped carbon fibers. The results show that the load-bearing / lubricating composite unit constructed by the interface anchoring layer and the PAK compatibility confinement layer in Example 1 can improve the structural retention and distribution stability of molybdenum disulfide after hot pressing, thereby improving the long-term self-lubricating stability of the material.

[0084] The friction coefficient of the wear-resistant self-lubricating composite material used for robot joints in Example 1 and Comparative Examples 4-5 was tested, and the results were as follows: Figure 5 The test results are shown.

[0085] like Figure 5 As shown, in Example 1, after a brief break-in period at the beginning of the test, the coefficient of friction rapidly decreased from approximately 0.20 to approximately 0.16, and remained relatively stable within the range of 0.15-0.18 during the subsequent 10-hour test. The curve showed minimal fluctuation and no obvious continuous upward trend, indicating that the load-bearing / lubricating composite unit in Example 1 could continuously provide stable low-shear lubrication during long-term friction. In contrast, although the coefficient of friction in Comparative Example 4 decreased initially, it gradually increased with the extension of the test time, rising from approximately 0.18 to over 0.30, and the fluctuations increased significantly in the later stages. This indicates that in the absence of a polyaryletherketone compatibility confinement layer, the layered solid lubricating phase is prone to migration, detachment, or local depletion during hot pressing and friction, leading to a decrease in the formation and maintenance capacity of the lubricating film. The coefficient of friction of Comparative Example 5 was the highest overall. It remained at a high level after the initial break-in period and continued to rise to about 0.35-0.40 in subsequent tests. At the same time, the fluctuation range was large, indicating that there was a lack of stable spatial bonding between the layered solid lubricating phase and the reinforcing phase under random mixing. The lubricating phase was prone to agglomeration, local depletion or formation of unstable third-body abrasive particles, making it difficult to achieve long-term stable lubrication.

[0086] To further verify the wear morphology differences corresponding to the aforementioned friction coefficient variation trends, and to analyze the influence of different structures on the wear mechanism of the friction interface, SEM observation was performed on the wear tracks of Example 1, Comparative Example 4, and Comparative Example 5 after long-term friction testing. The results are as follows: Figure 6 As shown.

[0087] like Figure 6 As shown, the surface of the wear track in Example 1 is generally smooth, with only a small amount of shallow furrows and fine wear debris distributed along the sliding direction. No obvious large-area peeling, deep grooves, or holes were observed, indicating that Example 1 experienced relatively light wear during friction, and the friction interface maintained a relatively stable surface state. This is consistent with... Figure 5 The results of Example 1 show a low and relatively stable coefficient of friction. In contrast, Comparative Example 4 exhibits more pronounced parallel furrows, localized flaking, and wear debris adhesion on the wear surface. This indicates that in the absence of a polyaryletherketone (PAK) compatibility confinement layer, the layered solid lubricant phase is more prone to migration, detachment, or local depletion during hot pressing and friction. This makes it difficult for the friction interface to maintain a stable lubrication protection structure, thereby exacerbating abrasive wear and localized detachment. Comparative Example 5 shows the most significant wear surface damage, with deeper furrows, more wear debris accumulation, localized agglomerated particles, and a small number of holes or pull-out marks. This indicates that under random mixing, there is a lack of stable spatial bonding between the short-cut carbon fibers, the layered solid lubricant phase, and the PAK matrix. The layered solid lubricant phase is prone to localized agglomeration or uneven distribution, making it difficult to form a continuous and stable lubrication protection structure during friction. Furthermore, localized agglomerates or detached particles may transform into third-body abrasive particles, further aggravating wear. The above results further illustrate that the friction reduction and wear resistance effect of this application does not simply come from the addition of layered solid lubricating phase, but from the multi-layered structure of the load-bearing / lubricating composite unit and its stable spatial bonding relationship.

[0088] Furthermore, to investigate whether the layered gradient distribution of the surface layer, transition layer, and core layer can simultaneously achieve both surface functionalization and interlayer bonding stability, cross-sectional SEM observations were performed on Example 1 and comparative examples 6-8 with different gradient settings. The results are as follows: Figure 7 and Figure 8 As shown.

[0089] like Figure 7 As shown in Example 1, the surface region near the friction surface has a relatively high distribution of load-bearing / lubricating composite units, the number of load-bearing / lubricating composite units gradually decreases in the transition layer, and the number of load-bearing / lubricating composite units further decreases in the core layer, exhibiting a relatively obvious and continuous layered gradient distribution characteristic. Meanwhile, no obvious continuous cracks or interlayer delamination were observed between the surface layer, transition layer, and core layer, indicating that Example 1 can maintain a good interlayer fusion state while achieving functional enrichment of the surface layer. In Comparative Example 6, the distribution of load-bearing / lubricating composite units in each layer is relatively uniform, and the gradient difference in the thickness direction is not obvious, indicating that without a gradient setting, it is difficult to form effective lubrication function enrichment in the region near the friction surface.

[0090] like Figure 8As shown in Comparative Example 7, although the load-bearing / lubricating composite units show a certain decreasing trend along the thickness direction, the difference between the surface layer, transition layer, and core layer is weak, and the enrichment degree of the surface layer is insufficient. This indicates that when the gradient difference is too small, it is difficult to fully improve the lubricating phase supply capacity of the friction surface. Further observation of Comparative Example 8 reveals that the load-bearing / lubricating composite units in its surface region are excessively enriched, and there are relatively obvious interface cracks, pores, and local interlayer defects between the surface layer and the transition layer. This indicates that when the difference in the content of load-bearing / lubricating composite units between adjacent layers is too large, it is easy to cause abrupt changes in interlayer composition, differences in melt flow, and local stress concentration, thereby weakening the interlayer bonding stability. Therefore, this application controls the mass content difference of the load-bearing / lubricating composite unit in the surface layer material and the transition layer material to 6%-12%, and the mass content difference of the load-bearing / lubricating composite unit in the transition layer material and the core layer material to 5%-10%. This can form a good matching relationship between the enrichment of surface lubrication function, the buffering of the transition layer and the load-bearing support of the core layer. It avoids insufficient surface lubrication supply due to too small gradient difference, and avoids interlayer cracks and pore defects due to too large gradient difference. This is beneficial to improving the wear resistance stability and overall mechanical reliability of wear-resistant self-lubricating composite materials for robot joints.

[0091] Based on the above results regarding microstructure, structure retention after hot pressing, friction coefficient variation, wear track morphology, and interlayer cross-sectional morphology, it can be seen that the multilayer load-bearing / lubricating composite unit and its layered gradient distribution structure of this application have a significant impact on the friction reduction, wear resistance, and mechanical properties of the composite material. To further quantitatively evaluate the comprehensive performance of each embodiment and comparative example, the average friction coefficient, wear rate, and flexural strength of Examples 1-5 and Comparative Examples 1-12 were tested, and the results are shown in Table 1. Specifically, the wear-resistant self-lubricating composite materials for robot joints obtained in Examples 1-5 and Comparative Examples 1-12 were subjected to friction and wear performance tests. The test method followed GB / T 3960-2016 "Test Method for Sliding Friction and Wear of Plastics"; the test conditions were dry friction at room temperature, a load of 50 N, a sliding speed of 0.10 m / s, a test time of 10 h, and a GCr15 steel ball as the grinding object. The curve of friction coefficient change over time was recorded during the test, and the average friction coefficient was calculated. After the test, the cross-section or wear volume of the wear track was measured using a 3D profilometer, and the wear rate was calculated by dividing the wear volume by the load and sliding distance. The wear rate was expressed in mm. 3 / (N·m). The composite materials obtained in Examples 1-5 and Comparative Examples 1-12 were subjected to flexural strength tests. The test methods were in accordance with GB / T 9341-2008 "Determination of Flexural Properties of Plastics". The three-point bending test method was adopted, and each group of samples had no less than 3 parallel samples.

[0092] Table 1. Performance test results of composite materials in Examples 1-5 and Comparative Examples 1-12

[0093] The data in Table 1 are the average values ​​of at least three parallel samples.

[0094] As shown in Table 1, the average coefficient of friction in Examples 1-5 remained within the range of 0.18-0.22, and the wear rate was no higher than 2.5 × 10⁻⁶. -6 mm 3 ·N -1 ·m -1 Furthermore, the flexural strength remained above 172 MPa, indicating that the composite material obtained by the preparation method according to the embodiments of this application can simultaneously achieve good friction reduction, wear resistance, and mechanical load-bearing properties. Among them, Example 1 exhibited the lowest average coefficient of friction and wear rate, while maintaining a high level of flexural strength, indicating that the interface anchoring layer, layered lubrication layer, polyaryletherketone compatible confinement layer, and layered gradient distribution structure can form a superior synergistic effect.

[0095] In contrast, Comparative Examples 1-5, lacking surface activation, interface anchoring layers, layered lubricating layers, compatibility confinement layers, or employing random mixing methods, all resulted in significantly increased friction coefficients and wear rates. This indicates that the technical effect of this application does not stem from simply adding reinforcing or lubricating phases, but rather from the multi-layered structure of the load-bearing / lubricating composite unit. Comparative Examples 6-8 show that both excessively small and excessively large differences in the mass content of the layered gradient distribution are detrimental to overall performance improvement. When the gradient difference is too small, the surface lubrication supply is insufficient; when the gradient difference is too large, interlayer defects and strength reduction are more pronounced. Comparative Examples 9-12 further illustrate that both the layered lubricating layer and the polyaryletherketone compatibility confinement layer have suitable thicknesses and coverage ranges. If the layer is too thin, it is difficult to provide sufficient lubrication or confinement; if the layer is too thick, it will weaken load transfer or obscure the lubricating phase.

[0096] In summary, this application, through the synergistic design of multi-layer load-bearing / lubricating composite units and layered gradient distribution in the thickness direction, can significantly improve the long-term friction reduction, wear resistance, and load-bearing stability of wear-resistant self-lubricating composite materials for robot joints.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a wear-resistant, self-lubricating composite material for robot joints, characterized in that, Includes the following steps: Surface activation treatment of short-cut carbon fibers; The surface-activated short carbon fibers are mixed with an interface modification solution, and after solid-liquid separation, washing and drying, an interface anchoring layer is formed on the surface of the short carbon fibers. Short carbon fibers with the interface anchoring layer formed thereon are mixed with a layered solid lubricating phase dispersion, so that the layered solid lubricating phase is attached to the outer peripheral surface of the short carbon fibers through the interface anchoring layer, thereby forming a layered lubricating layer on the outside of the interface anchoring layer. The short-cut carbon fibers with the layered lubricating layer are coated in a polyaryletherketone compatible confinement liquid to form a polyaryletherketone compatible confinement layer on the outside of the layered lubricating layer, thereby obtaining a load-bearing / lubricating composite unit. The load-bearing / lubricating composite unit is mixed with a polyaryletherketone matrix to prepare surface material, transition layer material and core layer material with different mass contents of the load-bearing / lubricating composite unit; The surface layer material, the transition layer material, and the core layer material are sequentially laid out from the side closest to the friction surface to the side furthest from the friction surface. After hot pressing, a wear-resistant self-lubricating composite material for robot joints with a layered gradient distribution of load-bearing / lubricating composite units along a direction perpendicular to the friction surface is obtained; wherein... The mass content of the load-bearing / lubricating composite unit in the surface layer material is higher than that in the transition layer material, and the difference between the two mass contents is any value between 6% and 12%. The mass content of the load-bearing / lubricating composite unit in the transition layer material is higher than that in the core layer material, and the difference between the two mass contents is any value between 5% and 10%.

2. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 1, characterized in that, The surface layer material contains 22%-32% by mass of the load-bearing / lubrication composite unit, the transition layer material contains 14%-23% by mass of the load-bearing / lubrication composite unit, and the core layer material contains 7%-15% by mass of the load-bearing / lubrication composite unit.

3. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 2, characterized in that, The thickness ratio of the surface material, the transition layer material, and the core material is any value in the range of 1:(1-3):(2-6).

4. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 2, characterized in that, The thickness of the layered lubricating layer is 80 nm-2 μm, the thickness of the polyaryletherketone compatibility confinement layer is 50 nm-1 μm, and the thickness of the polyaryletherketone compatibility confinement layer is less than or equal to the thickness of the layered lubricating layer.

5. The method for preparing wear-resistant self-lubricating composite material for robot joints according to any one of claims 1-4, characterized in that, The mass ratio of the layered solid lubricating phase to the short-cut carbon fiber on which the interface anchoring layer is formed is (0.08-0.45):1; The mass ratio of the polyaryletherketone compatibility confinement layer forming material to the short-cut carbon fibers on which the layered lubricating layer is formed is (0.03-0.30):

1.

6. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 5, characterized in that, The coating process is carried out at a temperature of 40℃-90℃ for a duration of 0.5h-6h.

7. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 6, characterized in that, The polyaryletherketone matrix includes one or more of polyetheretherketone, polyetherketoneketone, polyetherketone, polyetheretherketoneketone, or copolymers thereof; The layered solid lubricating phase includes one or more of molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride.

8. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 7, characterized in that, The chopped carbon fibers have a length of 50μm-300μm and a diameter of 5μm-15μm.

9. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 8, characterized in that, The surface activation treatment includes one or more of plasma treatment, ozone treatment, acidification treatment, alkalization treatment or silanization pretreatment; The interface-modifying components in the interface-modifying solution are dopamine and / or silane coupling agents; The polyaryletherketone compatible confined layer forming material includes one or more of sulfonated polyaryletherketone, polyaryletherketone oligomers, or sizing agents containing aryletherketone structures.

10. The method for preparing the wear-resistant self-lubricating composite material for robot joints according to claim 9, characterized in that, The hot pressing temperature is 10°C-40°C above the melting point of the polyaryletherketone matrix and below its thermal decomposition temperature, the pressure is 8MPa-20MPa, and the holding time is 10min-45min.

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